WO2024147160A1

WO2024147160A1 - Method of conversion of combustion wastes and refuse derived fuel into value-added products

Info

Publication number: WO2024147160A1
Application number: PCT/IN2024/050010
Authority: WO
Inventors: Kaushik Palicha; Harinipriya Seshadri
Original assignee: Individual
Current assignee: Individual
Priority date: 2023-01-03
Filing date: 2024-01-03
Publication date: 2024-07-11
Anticipated expiration: 2025-07-03

Abstract

A method of recovery of value-added products (VAP) such as native metals, metal alloys, and compounds from combustion wastes (CW) or Refuse derived fuels (RDF) The method includes acid digestion of CW or RDF to form acid digested solution (ADS) and precipitate; ADS is separated from the precipitate by filtration, and diluted with water to form water dissolved salt solution (WDS), wherein the WDS is transferred to an Electrochemical Cell (EC). The precipitate is washed with water repeatedly to separate remaining WDS; WDS is transferred to the EC. In the EC, VAPs are isolated from WDS on the working electrode (graphite) surface employing linear sweep voltammetry (LSV). The precipitate after WDS removal was centrifuged to isolate different Water-insoluble salts (WINS), the WINS are recrystallised; the sludge from the precipitate is subjected to CCVD to form carbon nanotubes or graphene; rare-earths in the sludge are separated by magnetic separation.

Description

TITLE METHOD OF CONVERSION OF COMBUSTION WASTES AND REFUSE DERIVED FUEL INTO VALUE-ADDED PRODUCTS CROSS REFERENCE TO RELATED APPLICATIONS The present application is based upon and claims priority to India complete patent application number 202341000490 filed on January 03, 2024, which claims priority to India provisional patent application number 202341000490 filed on January 03, 2023. The entire contents of all are herein incorporated by reference. FIELD The present invention relates to method of conversion of combustion wastes (CW), and refuse derived fuels (RDF) into useful value-added products (VAP). DEFINITION As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise. As used herein, the term “combustion wastes” or “CW” includes: − industrial combustion wastes that are generated in various industries from combustion of fuels, wherein the fuels include fossil fuels such as coal, lignite, oil and gas, and biomass fuels. − furnace wastes such as steel slag generated from steel making processes. As used herein, the term “Refuse derived fuels” or “RDF” is the fuel material created from Municipal Solid Wastes (MSW). “RDF” includes “RDF ash” i.e., the ash generated from combustion of RDF as a Combustion waste (CW). BACKGROUND Effective utilisation of combustion wastes (CW) that arise from burning of fuels such as coal, oil, natural gas, or the Refuse derived fuels (RDF) is minimum. When coal is combusted in coal fired power plants, the residue generated is fly ash. In general, 90% of the fly ash is burnt to produce electricity. The non- combustible part of the coal is often utilized to create by-products useful to the chemical industries. Annually, about 120 million tons of coal/lignite waste (fly ash, bottom ash, slag, and flue gas) were desulfurized to form useful products. During the combustion of coal, all minerals associated with it are fluidized due to very high temperature (usually 1400 ºC (2500 ºF)) and then upon cooling forms solid slag or waste. At such high temperatures, the mineral trapped in the coal undergoes different processes such as oxidization, decomposition, fusion, disintegration or agglomeration and upon rapid cooling results in the formation of spherical, amorphous (non-crystalline) particles. Presence of volatile substances in the coal results in the expansion of the minerals to form a hollow cenosphere. Such heating and cooling have significant effect on the composition and morphology of every particle of coal combustion waste. Several utility of the coal waste had been in practice such as fly ash as a construction material, fertilizer to develop mineral composition of soil, precursor for synthesis of mineral, among others. But these are not the correct practice and applications of fly ash or coal combustion waste. Globally, coal based thermal power plants contribute to approximately 39 % of the total electricity generated. The rationale behind this higher contribution by coal fired thermal power plants are due to the abundancy and cost-effective nature of Coal compared to oil and natural gas. The major bottleneck of usage of higher coal in power plants is the formation and accumulation of humongous “waste”, known as coal/lignite fly ash. The coal/lignite fly ash is quite common in countries like China, USA and India. Annually, around 750 million tonnes of coal/lignite ash is produced world-wide, and this is expected to grow further due to increased power requirement in the near future. This increased production of coal/lignite ash is an issue of grave environmental and health concern. The issues related to safe disposal or recycling of the coal/lignite ash is yet to be addressed completely and hence is a matter of threat to public health and potential damage to soil, agriculture and bio-diversity in the nature. Coal/lignite ash is capable of leaching into the sub-soil thereby contaminating the ground water table with heavy metals such as Pb, As, Cr, Mo, Sr, Cd, Ni, Ti etc. Thus, recycling and reutilization of coal/lignite ash by safely removing these heavy metals and other minerals of interest becomes inevitable before putting them into use in cement and construction industries. Presently, coal/lignite ash had been utilized in concrete production, paving roads, mine fillings, building material production, land reclamation, soil stabilization, toxic element immobilization, and synthesis of polymers and agriculture etc. The increased amount of coal/lignite ash left unattended and dumped in man- made ponds and lakes as disposable wastes possess serious environmental, public health and heavy metal contamination problems in the region of coal mining and coal/lignite fired thermal power plants and its vicinity. Any accidental ingestion of the lignite ash by human may cause accumulation of heavy metals in the blood and in long run can affect vital organs such as kidney and liver, pulmonological diseases such as wheezing, chronic bronchitis and ultimately lung cancer. The presence of heavy metals such as Pb, As, Cd etc can lead to skin related diseases and skin cancer in long time exposure. Presence of Lanthanides and actinides in the samples indicate the exposure risk to these minerals or elemental that >1 µg/l exposure leads to severe genetic mutations and organ specific uncontrollable cell growth with cancer risk. Although Ca and Mg minerals lead to accelerated growth of plants and crops, presence of Li, Na, K, Sr etc leads to contamination of the food crops and also carcinogenic material intake by the plants and in turn the humans consuming them. The water body is completely contaminated with heavy metals and is useless for utility purposes, these water bodies affect the fauna and flora thriving around these water resources, by utilizing these heavy metals contaminated water resources for the material recovery from lignite source, it will serve dual purpose of not allowing further contamination of the water bodies and the living systems around them. US4475993A discloses a process for recovering silver, gallium and/or other trace metals from a fine grained industrial fly ash associated with a process for producing phosphorous, the fly ash having a silicate base and containing surface deposits of the trace metals as oxides, chlorides or the like, with the process being carried out by contacting the fly ash with AlCl3 in an alkali halide melt to react the trace metals with the AlCl3 to form compositions soluble in the melt and a residue containing the silicate and aluminum oxide or other aluminum precipitate, and separating the desired trace metal or metals from the melt by electrolysis or other separation techniques. US4652433A discloses a process for recovery of valuable minerals and chemicals such as cenospheres (hollow microspheres), carbon, magnetite (Fe3O4), alumina (Al2O3), iron oxide (Fe2O3) and iron chloride (FeCl3). US4319988A discloses a process for recovering magnetite from fly ash. At present, coal or lignite ash is absolutely considered as an alternative source of various value-added materials such as metals, minerals, ores, and metal salts of interest, among others. This is mainly due to the general composition of the coal/lignite fly ash. The broad chemical composition of the coal/lignite fly ash is a mixed oxides of alkali, alkaline earth, transition, inner transition metals, lanthanides and actinides, such as Na₂O, K₂O, SiO₂, Al₂O₃, MgO, Mn₂O₃, ZnO, NiO, CO₂O₃, Mo₂O₃, CaO, SrO, Fe₂O₃, TiO₂, Pb₂O₃, CdO, U₂O₃, ThO₂, Y₂O₃, Nd2O3, etc., with smaller amounts of trace elements depending on the mineral resource in the coal mining area or region under consideration. These chemicals present in these combustion wastes or in the RDF can be separated, purified, and used as energy storage materials, as catalyst for several organic, inorganic reactions, hydrogen by water splitting as well as water purification purposes. As there is a great demand for metals, metal oxide resources in the field of energy and energy storage devices applications, recovery of metals, minerals and ores from coal/lignite fly ash not only assist in supply chain sustenance and circular economy, reduces the burden on the mining sites, obviates the environmental and public safety protocol avoidance in the mining sites, it also reduces environmental risks associated with disposal and leaching of heavy metals to surface and subsurface waters, reduces the factors that affects bio-diversity restoration, reduce the risk of accidental and involuntary intake of the coal/lignite ash by public residing near to the mining and disposal or dumping area and the health hazards associated with such intake. In developing countries like India, as the coal/lignite fired thermal power plants are owned by Government of India majorly, the public sector involved in coal mining and firing to produce electricity, would earn profit from the recycling and reutilization of coal/lignite fly ash leading to the financial sustenance of the public sector and a value addition to the tax-payers contribution on the public sector. Based on the moisture, ash & minerals, volatile compounds, and fixed carbon content, RDF is categorized in to 12 types as shown in Table 1. Table 1 indicates the approximate content of the different components in RDF and its classification Table 1 LHV Ash & HHV C H N S O Cl (MJ/Kg); Minerals (MJ/kg) Raw RDF1 40.83 5.36 1.18 0.29 37.08 0.34 14.92 19.15 14.4 RDF2 57.02 8.36 1.2 0.48 17.68 0.64 14.62 24.46 16.41 RDF3 46.91 6.22 1.23 0.29 36.85 0.43 8.07 19.28 12.47 RDF4 50.89 6.28 0.51 0.17 30.33 0.49 11.33 20.39 13.97 RDF5 46.95 6.01 1.89 0.11 34.53 0.49 10.02 21.49 11.17 RDF6 50.63 6.63 1.87 0.36 30.8 0.24 9.47 23.99 14.61 RDF7 51.79 6.47 1.22 0.07 30.05 0.18 10.22 19.74 12.29 RDF8 46.2 5.66 0.31 0 34.67 0.21 12.95 17.13 12.17 RDF9 55.22 9.12 0.68 0.64 22.32 1.02 11 22.33 14.91 RDF10 49.34 7.5 0.95 0.37 28.13 0.73 12.98 18.49 10.85 RDF11 51.61 8.33 0.83 0.58 24.96 0.63 13.06 20.33 12.73 RDF12 57.41 8.99 1 0.53 21.42 0.74 9.91 22.73 15.39 The chemical composition had classified the RDF into 12 categories, whereas the surface morphology based on ASTM E38.01 standards, RDFs have been classified into 7 types as shown in Table 2. Table 2 shows the ASTM E 38.01 based classification of RDFs. Table 2 Type Surface morphology Composition Remarks or Nature RDF1 Municipal Solid Waste Unprocessed or Raw Minimal processing had (MSW) been done to separate large sized particles or bulky wastes RDF2 Coarse size MSW processed to Includes iron waste as coarse particle size well, 95% of the RDF is that can pass expected to pass through through 6 square the specified mesh, also inch mesh screen labelled as c-RDF RDF3 Fluffy material Shredded MSW. Removal of metal, glass, Criteria is should minerals or mineral pass through 2 waste (inorganics) from square inch mesh MSW 95% of the RDF is expected to pass through the specified mesh, also labelled as f-RDF RDF4 Powder and Combustible Mostly oxides of metals, amorphous fraction processed to metalloids in a definite powder and passes proportion and through 0.035 stoichiometric square inch mesh composition. 95% of the RDF is expected to pass through the specified mesh, also labelled as p-RDF RDF5 Densified solid Combustible Mostly oxides of metals, material material compressed metalloids in a definite in the form of proportion and pellets, slugs, stoichiometric cubettes, briquettes composition, also etc labelled as d-RDF RDF6 Liquid The combustible Organic and plastic waste fraction is content is converted to processed in liquid liquid fuel of HHV fuel RDF7 Gas The combustible The gaseous fuel can be waste fraction is utilized for electricity processed in production or household, gaseous fuel automotive utility The present inventors envisaged conversion or separation of the minerals of interest from the combustion wastes (CW) or from Refuse derived fuels (RDF) via proprietary acid digestion, chemical precipitation, magnetic separation, and linear sweep voltammetry (LSV) techniques. SUMMARY The present disclosure provides a method of recovery of value-added products (VAP) such as native metals, metal alloys, and compounds from combustion wastes (CW) or from Refuse derived fuels (RDF). The method includes the following steps. Acid digestion of CW or RDF to form acid digested solution (ADS), and formation of water dissolved salt solution (WDS) and transfer to Electrochemical Cell (EC): − Combustion wastes (CW) or Refuse derived fuels (RDF) (from dispenser D1) are digested in a First reactor (R1) with concentrated inorganic acid (from dispenser D2) at 10⁰C and 1 atm pressure with continuous stirring to form an acid digested solution (ADS) that contains water soluble salts of the metallic components present in the CW or RDF with the anion of the acid used, and a precipitate, wherein the concentrated inorganic acid can be selected from HCl, H₂SO₄, HNO₃, H₃PO₄; − The acid digested solution (ADS) is separated from the precipitate by filtration to Tank T1; − The ADS is added to distilled water in Tank T2 at 20⁰C and 1 atm pressure with constant stirring for one hour to form water dissolved salt solution (WDS), wherein the dilution is done in a ratio of 1:3 to 1:5 based on the strength of the concentrated inorganic acid used. For strong acid as H2SO4, the dilution is done in a ratio of 1:5, whereas for acids such as HCl, HNO3, the dilution is done in a ratio of 1:4, and for H3PO4 the dilution is done in a ratio of 1:3; − The WDS is transferred to the electrochemical cell (EC) for electrochemical reaction; Precipitate Handling: washing with water, separation of water dissolved salt solution (WDS), separation of water-insoluble salts (WINS), and separation of sludge: − the precipitate from the First reactor (R1) is transferred to a second Reactor (R2), where the precipitate is washed with distilled water at 20⁰C and 1 atm pressure with constant stirring for one hour to separate any remaining water-soluble salts as water dissolved salt solution (WDS) by filtration, wherein the WDS is transferred to the electrochemical cell (EC) for electrochemical reaction, wherein this process of washing with distilled water, filtration, and transferring the WDS to the electrochemical cell is repeated several times until all the water-soluble salts are separated as WDS; − the precipitate after removal of the WDS is dried in vacuum at 100⁰C, and optionally ground to form a fine precipitate powder; − the precipitate or the fine precipitate powder is dissolved in a suitable solvent to form a precipitate mass, wherein the solvent is selected from any non-polar organic solvents such as chloroform, carbon tetrachloride, and aromatic alcohols; − The precipitate was subjected to centrifugation, where the water-insoluble salts (WINS) such as salts of Ag present in the precipitate were removed separately by their density gradients, wherein the water-insoluble salts (WINS) of differing density are separated at different revolutions per minute (RPM), one by one based on their density difference, and are transferred to tank T4. − The separated WINS are individually, separately dried in a vacuum oven at 100⁰C, and the individual WINS are ground to form each a fine powder; − The individual WINS fine powders are subjected to High Resolution – Scanning Electron Microscopy and Energy Dispersive Spectroscopy (HR- SEM-EDS) for surface morphology and elemental composition; − Based on their elemental composition, the WINS were subjected to recrystallisation by seeding pure crystal; − Sludge: After removal of the water-insoluble salts, the reactor 2 is left behind with sludge, wherein the sludge is transferred to a separate tank T5; − The sludge is dried in a vacuum oven at 100⁰C; − If the sludge is rich in carbon, it is subjected to continuous chemical vapour deposition (CCVD) to form carbon nanotubes and/or graphene; − Rare earth elements, and other minerals present in the dried sludge are separated by magnetic separation processes. Linear Sweep Voltammetry (LSV) for the water dissolved salt solution (WDS): − The WDS is subjected to electrochemical process to isolate the elements as native metals or alloys or compounds at appropriate potential and current window on the working electrode (graphite) surface employing linear sweep voltammetry (LSV) technique. Effluent Handling: Transfer of the WINS, and alkali metal WDS: − After the electrochemical action, the effluent from the electrochemical cell, which includes water insoluble salts (WINS) such as salts of Ag, which were transferred to the tank T4 through effluent tank T3. − The effluent also includes the water-soluble Alkali metal salts (a portion of WDS) such as Li, Na, K salts, which were not recovered in the electrochemical process, as the electrochemical separation is not deliberately performed in the desired potential window. This is because as the electrochemical cell operates in an aqueous environment, the alkali metal salts on reduction will form highly water reactive alkali metals on graphite surface. These water-soluble alkali metal salts also are transferred from the electrochemical cell to the tank T4 through the effluent tank T3. Linear sweep voltametric (LSV) technique is carried out in the range of -3 to 3V potential window and at 50 mV/s scan rate in a three-electrode assembly electrochemical cell that includes: − the water dissolved salt solution (WDS) extracted from the acid digested solution (ADS) is used as the electrolyte; − graphite rod as working electrode; − Pt wire counter electrode; and − Ag/AgCl as reference electrode. Wherein, LSV is done in Cathode stripping mode involving reduction of ions into elemental deposition on the working electrode (graphite) surface. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig. 1 illustrates the process flow of separation or conversion of combustion wastes (CW) and Refuse derived fuels (RDF) into value-added products (VAP). Fig. 2 illustrates a three-electrode assembly electrochemical cell for Linear sweep voltametric (LSV) technique of the water dissolved salt solution (WDS). Fig. 3 illustrates linear sweep voltammetry (LSV) of the elements separated from the lignite ash samples. Fig. 4 illustrates Field Emission Scanning Electron Microscopy (FESEM) of Sr and Ba deposition on graphite surface, and cross-sectional area and thickness of the deposition. Fig. 5 illustrates Energy Dispersive Spectroscopy (EDS) spectra and elemental composition of the Sr and Ba deposition on graphite surface. Fig. 6 illustrates FESEM image of Mg deposition on graphite surface, and cross- sectional area and thickness of the deposition. Fig. 7 illustrates EDS spectra and elemental composition of Mg deposition on graphite surface. Fig. 8 illustrates FESEM of Al and Be deposition on graphite surface, and cross- sectional area and thickness of the deposition. Fig. 9 illustrates EDS spectra and elemental composition of Be and Al deposited on the graphite surface. Fig.10 illustrates FESEM of V and Mn deposition on graphite surface, and cross- sectional area and thickness of the deposition. Fig. 11 illustrates EDS spectra and elemental composition of V and Mn deposited on graphite surface. Fig. 12 illustrates FESEM of Fe, Co, Ni, Sn and Pb deposition on graphite surface, and cross-sectional area and thickness of the deposition. Fig. 13 illustrates EDS spectra and elemental composition of Fe, Co, Ni, Sn and Pb deposited on graphite surface. Fig.14 illustrates FESEM of Ag and Sb deposition on graphite surface, and cross- sectional area and thickness of the deposition. Fig.15 illustrates EDS spectra and elemental composition of Ag and Sb deposited on graphite surface. Fig.16 illustrates linear sweep voltammetry (LSV) of the elements separated from the steel slag sample. Fig.17 illustrates linear sweep voltammetry (LSV) of the elements separated from the RDF sample. DETAILED DESCRIPTION The subject matter of the present disclosure is described in detail with reference to the accompanying drawings. Unless otherwise specified, all the technical and scientific terms used herein have the same meaning as is generally understood by a person skilled in the art pertaining to the present disclosure. Headings are used solely for organizational purposes, and are not intended to limit the disclosure in any way. The use of the singular includes the plural unless specifically stated otherwise. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well. The use of “or” means “and/or” unless stated otherwise. Unless otherwise indicated, all numbers used herein to express quantities, dimensions, and so forth used should be understood as being modified in all instances by the term "about." It is to be understood that wherein a numerical range is recited, it includes all values within that range, and all narrower ranges within that range, whether specifically recited or not. As used herein, "including," "containing" and like terms are understood to be synonymous with "comprising" and are therefore open-ended and do not exclude the presence of additional undescribed or unrecited elements, materials, phases or method steps. In addition, it should be appreciated that any figures are provided herewith, they are for explanation purposes to persons ordinarily skilled in the art and that the drawings of them are not necessarily drawn to scale. Any method/process steps and/or operations and/or instructions used in this disclosure, are for illustrative purposes in a particular order and/or grouping. Other orders and/or grouping of the process steps or its portions and/or operations or its portions and/or instructions or its portions are possible and, one or more of the process steps and/or operations and/or instructions can be combined and/or deleted. The present disclosure provides a method of recovery of value-added products (VAP) such as native metals, metal alloys, and compounds from combustion wastes (CW) or from Refuse derived fuels (RDF). Fig. 1 illustrates the process flow of separation or conversion of combustion wastes (CW) and Refuse derived fuels (RDF) into value-added products (VAP). The method includes the following steps. Acid digestion of CW or RDF to form acid digested solution (ADS), and formation of water dissolved salt solution (WDS) and transfer to Electrochemical Cell (EC): − Combustion wastes (CW) or Refuse derived fuels (RDF) (from dispenser D1) are digested in a First reactor (R1) with concentrated inorganic acid (from dispenser D2) at 10⁰C and 1 atm pressure with continuous stirring to form an acid digested solution (ADS) that contains water soluble salts of the metallic components present in the CW or RDF with the anion of the acid used, and a precipitate, wherein the concentrated inorganic acid can be selected from HCl, H₂SO₄, HNO₃, H₃PO₄; − The acid digested solution (ADS) is separated from the precipitate by filtration to Tank T1; − The ADS is added to distilled water in Tank T2 at 20⁰C and 1 atm pressure with constant stirring for one hour to form water dissolved salt solution (WDS), wherein the dilution is done in a ratio of 1:3 to 1:5 based on the strength of the concentrated inorganic acid used. For strong acid as H2SO4, the dilution is done in a ratio of 1:5, whereas for acids such as HCl, HNO3, the dilution is done in a ratio of 1:4, and for H3PO4 the dilution is done in a ratio of 1:3; − The WDS is transferred to the electrochemical cell (EC) for electrochemical reaction; The rationale behind the dilution ratio is based on two primary factors, first, to bring the salts into an aqueous solution, as well as when the ADS is subjected to electrochemical action it needs to be in an aqueous phase to act as electrolyte, and second, at the same time the dilution should not be so much that the elements/salts available in the ppm level do not get further reduced in size. With this rationale in mind, H₂SO₄ being a strong acid needs more dilution, whereas, HCl, HNO3, H3PO4 are diluted lesser. Nevertheless, a person skilled in the art may modulate the dilution levels with consideration of the above two primary factors. Precipitate Handling: washing with water, separation of water dissolved salt solution (WDS), separation of water-insoluble salts (WINS), and separation of sludge: − the precipitate from the First reactor (R1) is transferred to a second Reactor (R2), where the precipitate is washed with distilled water at 20⁰C and 1 atm pressure with constant stirring for one hour to separate any remaining water-soluble salts as water dissolved salt solution (WDS) by filtration, wherein the WDS is transferred to the electrochemical cell (EC) for electrochemical reaction, wherein this process of washing with distilled water, filtration, and transferring the WDS to the electrochemical cell is repeated several times until all the water-soluble salts are separated as WDS. The completion of separation of all the water-soluble salts is indicated by no change in weight of the precipitates after water washing. − the precipitate after removal of the WDS is dried in vacuum at 100⁰C, and optionally ground to form a fine precipitate powder; − the precipitate or the fine precipitate powder is dissolved in a suitable solvent to form a precipitate mass, wherein the solvent is selected from any non-polar organic solvents such as chloroform, carbon tetrachloride, and aromatic alcohols; − The precipitate was subjected to centrifugation, where the water-insoluble salts (WINS) such as salts of Ag present in the precipitate were removed separately by their density gradients, wherein the water-insoluble salts (WINS) of differing density are separated at different revolutions per minute (RPM), one by one based on their density difference, and are transferred to tank T4. − The separated WINS are individually, separately dried in a vacuum oven at 100⁰C, and the individual WINS are ground to form each a fine powder; − The individual WINS fine powders are subjected to High Resolution – Scanning Electron Microscopy and Energy Dispersive Spectroscopy (HR- SEM-EDS) for surface morphology and elemental composition; − Based on their elemental composition, the WINS were subjected to recrystallisation by seeding pure crystal; − Sludge: After removal of the water-insoluble salts from the precipitate in Reactor 2, the Reactor 2 is left behind with sludge, wherein the sludge is transferred to a separate tank T5; − The sludge is dried in a vacuum oven at 100⁰C; − If the sludge is rich in carbon, it is subjected to continuous chemical vapour deposition (CCVD) to form carbon nanotubes and/or graphene; − Rare earth elements, and other minerals present in the dried sludge are separated by magnetic separation processes. After removing any rare earth elements and other minerals including carbon, the dried sludge is utilized in pavement industries and blocks for cement industries due to its chemical inertness. Linear Sweep Voltammetry (LSV) for the water dissolved salt solution (WDS): − The WDS is subjected to electrochemical process to isolate the elements as native metals or alloys or compounds at appropriate potential and current window on the working electrode (graphite) surface employing linear sweep voltammetry (LSV) technique. Effluent Handling: Transfer of the WINS, and alkali metal WDS: − After the electrochemical action, the effluent from the electrochemical cell, which includes water insoluble salts (WINS) such as salts of Ag, which were transferred to the tank T4 through effluent tank T3. − The effluent also includes the water-soluble Alkali metal salts (a portion of WDS) such as Li, Na, K salts, which were not recovered in the electrochemical process, as the electrochemical separation is not deliberately performed in the desired potential window. This is because as the electrochemical cell operates in an aqueous environment, the alkali metal salts on reduction will form highly water reactive alkali metals on graphite surface. These water-soluble alkali metal salts also are transferred from the electrochemical cell to the tank T4 through the effluent tank T3. Fig. 2 represents the three-electrode assembly electrochemical cell for the Linear sweep voltametric (LSV). Linear sweep voltametric (LSV) technique is carried out in the range of -3 to 3V potential window and at 50 mV/s scan rate in a three-electrode assembly electrochemical cell that includes: − the water dissolved salt solution (WDS) extracted from the acid digested solution (ADS) is used as the electrolyte; − graphite rod as working electrode; − Pt wire counter electrode; and − Ag/AgCl as reference electrode. Wherein, LSV is done in Cathode stripping mode involving reduction of ions into elemental deposition on the working electrode (graphite) surface. The electrochemical cell is connected to Zahner Zennium E4 electrochemical workstation. Lignite ash In an embodiment of the present disclosure, lignite ash is used as the waste material to recover the VAPs from it. Samples of Lignite ash from coal mining were collected from lignite fired thermal power plant, South India. Samples of coal ash from coal fired power plants were collected from chennai, South India A random sample (Sample 0) of the Lignite ash collected from these coal mining and coal fired power plants is done to obtain the broad chemical composition by Energy-Dispersive X-ray Fluorescence (ED-XRF) technique, by Ram Charan Co Pvt Ltd. (RCPL), Entity1 Group. The Broad chemical composition of Lignite ash employing ED-XRF technique is as provided in Table 3. Table 3 S. No. Chemical composition Weight % 1. Silicon dioxide 44.00 2. Magnesium Oxide 2.51 3. Copper Oxide 0.015 4. Phosphorous Pentoxide 0.077 5. Sulphur trioxide 1.90 6. Calcium Oxide 9.53 7. Nickel Oxide 0.014 8. Chromium Oxide 0.053 9. Aluminium Oxide 36.40 10. Zirconium Oxide 0.086 11. Zinc Oxide 0.019 12. Iron Oxide 3.51 13. Titanium Oxide 1.77 As evident from Table 3, the major composition of the lignite ash comprises of silica and alumina amounting to 44% and 36.4% respectively. The minor composition of the lignite ash includes alkaline earth metal oxides of Mg, Ca as well as Ferrite & Titania in the percentage of 2.51, 9.53, 3.51 & 1.77 respectively. Traces involve Copper oxide, Nickel Oxide, Chromium Oxide, Zirconium Oxide and Zinc Oxide, Based on the above broad chemical composition, the lignite ash sample (Sample 0) is further subjected to elemental analysis via Inductively coupled plasma mass spectrometry (ICP-MS) revealing the enriched elemental presence in the lignite ash. The elements range from alkali to alkaline earth to transition, inner transition and rare earths. The detailed elemental composition of the lignite ash sample employing ICP-MS technique is as provided in Table 4. Table 4 S. No. Elements ppm Alkali Metals 1. Sodium (Na) 500.0 2. Potassium (K) 71.5 Alkaline Earth Metals 3. Beryllium (Be) 5.31 4. Magnesium (Mg) 5446.05 5. Calcium (Ca) 33428.4 6. Strontium (Sr) 253.86 7. Barium (Ba) 206.03 Inner transition or rare earth metals 8. Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Less than Samarium (Sm), Europium (Eu), Promethium (Pm), 0.1 ppm Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm) 9. Thorium (Th) 3.544 10. Uranium (U) 13.44 Transition Metals 11. Titanium (Ti) 642.52 12. Zinc (Zn) 11.06 13. Cadmium (Cd) 0.131 Metalloids 14. Silicon (Si) 12.50 15. Boron (B) 45.27 For the lignite ash Sample 0, ICP-MS confirms the presence of metals and elements as reported by ED-XRF. In addition, ICP-MS analysis shows the presence of heavy metals such as B, Pb, As, Cr, Cd, Se, U and Th at significant levels above the threshold of the environment. With the support of the above analysis of the lignite ash Sample 0, eight more samples of the lignite ash (fresh) and those dumped in the pond as pond ash for several decades, those lignite ashes currently sold to cement and construction industry were collected by the RCPL–Entity1 scientist and management team that had visited the coal mining and thermal power plant sites. The eight samples (Sample 1-8) of Lignite ash (or from the site of lignite ash) collected for analysis are: Sample 1: Lignite ash (combustible); Sample 2: Sand from lignite ash sample site for out loading to consumption and cement industries; Sample 3: Black & Grey lignite ash from pond ash; Sample 4: Black lignite ash in pond ash; Sample 5: Grey lignite ash from pond ash; Sample 6: Layered-pond ash on the surface; Sample 7: Ball clay from the surface; Sample 8: Ball clay detailed from site. The eight samples of lignite ash (Sample 1-8) collected were subjected to extensive chemical composition analysis via ICP-MS. The matrix of elements present in these eight samples of the lignite ash as identified through ICP-MS analysis is provided in Table 5, and Table 5.1. Table 5 (Samples 1-4) S. Element / Sample 1 Sample 2 Sample 3 Sample 4 No metal (mg/kg) (mg/kg) (mg/kg) (mg/kg) 1. Be 5.311 0.204 3.071 6.195 2. B 45.27 1.388 18.892 24.860 3. Na 500.05 122.506 496.595 939.035 4. Mg 5446.08 128.781 3382.897 6509.353 5. Al 17165.78 4944.188 5394.305 10715.213 6. K 71.52 32.915 92.874 131.884 7. Ca 33482.40 856.691 19519.191 27412.408 8. V 144.14 12.199 17.684 21.861 9. Cr 37.77 7.974 12.63 13.39 10. Mn 17.88 14.095 41.259 65.233 11. Fe 22.23 423.161 541.989 519.602 12. Co 35.47 11.091 19.281 10.577 13. Ni 7.52 16.129 38.150 21.834 14. Cu 56.49 5.345 9.578 9.531 15. Zn 11.06 59.766 59.350 58.350 16. As 7.94 0.850 2.275 3.745 17. Se 22.23 0.816 2.804 4.240 18. Sr 253.89 6.236 117.009 175.477 19. Mo 5.45 0.943 1.444 1.855 20. Ag 2.556 0.316 0.156 - 21. Cd 0.131 < 0.1 < 0.1 - 22. Sn 2.68 < 0.1 < 0.1 92.773 23. Sb 0.56 < 0.1 < 0.1 - 24. Ba 206.03 17.166 182.760 255.735 25. Pb 5.172 2.045 2.906 3.117 26. U 13.44 < 0.1 2.124 2.146 27. Ti 642.52 62.98 311.650 485.754 28. Th 3.54 4.883 4.454 4.154 29. Hg < 0.1 0.703 0.515 0.319 30. Nb < 0.1 1.191 1.925 1.254 31. Ce < 0.1 6.951 86.429 107.127 32. Y < 0.1 2.192 31.945 46.401 33. Li - - 1.698 1.711 34. Na - - 496.595 939.045 35. K - - 92.874 131.884 36. Si - - 54.546 67.687 37. Sr - - - 175.477 38. Nd - - - - 39. Sc - - - - Table 5.1 (Samples 5-8) S. Element / Sample 5 Sample 6 Sample 7 Sample 8 No metal (mg/kg) (mg/kg) (mg/kg) (mg/kg) 1. Be 3.643 12.406 2. B 9.868 24.251 0.707 0.771 3. Na 661.173 887.619 197.509 209.309 4. Mg 2652.264 10408.466 322.832 374.499 5. Al 4442.628 19776.432 1580.706 1585.439 6. K 58.908 147.309 23.935 27.548 7. Ca 14362.037 59358.330 1355.139 1591.441 8. V 11.577 48.889 13.378 11.791 9. Cr 17.401 29.313 12.931 13.588 10. Mn 34.290 123.679 1.012 1.579 11. Fe 487.872 379.613 435.119 444.298 12. Co 2.947 4.773 0.483 0.446 13. Ni 9.651 18.434 2.777 4.846 14. Cu 4.793 9.180 11.971 12.547 15. Zn 50.604 79.632 5.492 12.686 16. As 1.552 9.133 - - 17. Se 2.423 6.430 8.087 18. Sr 88.513 341.932 0.405 8.882 19. Mo 1.324 2.066 0.217 0.453 20. Ag 0.198 - - 0.322 21. Cd - - - - 22. Sn - - 105.314 17.205 23. Sb - - - - 24. Ba 137.820 598.738 5.713 7.320 25. Pb 1.60 4.017 2.095 2.977 26. U 0.761 2.310 - - 27. Ti 282.415 154.552 22.164 18.98 28. Th 3.057 6.115 2.913 4.244 29. Hg 0.230 0.880 0.410 0.543 30. Nb 1.126 0.720 0.704 0.659 31. Ce 75.112 178.652 1.616 1.382 32. Y 31.937 100.596 0.469 0.40 33. Li 1.109 3.541 0.32 0.316 34. Na 661.173 887.619 197.509 209.306 35. K 58.908 147.309 23.935 27.548 36. Si 25.007 22.118 190.260 87.438 37. Sr 88.513 341.932 0.405 - 38. Nd 75.112 - - - 39. Sc 31.937 - - - ICP-MS analysis of the lignite ash samples revealed the presence of all the above listed elements and their concentration in the sample without any error. Thus, confirming the chemical composition and the elemental composition of the lignite ash. Steel slag In another embodiment of the present disclosure, Steel slag is used as the waste material to recover the VAPs from it. The following five samples were collected by RCPL Entity1 scientists from Jamshedpur, India, from different operations of a steel plant such as (i) Coal Ash- 1, (ii) Coal Ash-2, (iii) Coal Rejects, (iv) Steel Slag-1 and (v) Steel Slag-2. The energy dispersive X-ray Fluorescence (XRF) studies of the above mentioned five samples were carried out to understand the mineral composition of the same and listed in Table 6 to Table 10. Table 6 ED-XRF chemical composition of Coal Ash-1 S. Minerals % Remarks No analysed composition 1. Al2O3 28.1 Large variety of products like cans, foils, kitchen utensils, window forums, beer kegs, and aeroplane parts. Recovery by proposed process is 100% 2. CaO 0.753 Binder agents, cement, aggregates, Recovery by proposed process is 100% 3. CuO 0.01 Electrical wires, current collectors, electrodes, utensils etc. Recovery by proposed process is 100% 4. Fe₂O₃ 3.59 The manufacturing of body parts of ubiquitous machine tools, automobile components, ships hulls, and buildings. Can also be put back in steel production. Recovery by proposed process is > 95% 5. Mn2O3 0.03 Produce a variety of different alloys, dry cell batteries, and black-brown pigment in paint. Recovery by proposed process is > 90% 6. NiO 0.008 Pesticides, baking powder, incendiary bombs, and light-emitting diodes. Recovery by proposed process > 75% 7. SiO₂ 63.10 Semiconductor in computers and microelectronics industries, used as fertilizer, and in the production of glass and other ceramics. Recovery by proposed process is > 75% 8. K₂O 2.04 fertilizer. Recovery by proposed process is > 70% 9. TiO₂ 2.26 Aerospace, aircraft, and engines. Pharma grade as pigment. Drug delivery systems etc. Recovery by proposed process is > 90% 10. ZnO 0.012 Semiconductors, optoelectronics, drug delivery systems Recovery by proposed process is> 90% Table 7 ED-XRF chemical composition of Coal Ash-2 S. Minerals % Remarks No analysed composition 1. Al₂O₃ 23.10 Large variety of products like cans, foils, kitchen utensils, window forums, beer kegs, and aeroplane parts. Recovery by proposed process is 100% Binder agents, cement, aggregates, Recovery by proposed process is 100% Electrical wires, current collectors, electrodes, utensils etc. Recovery by proposed process is 100% Nano-oxide anodes, pigments. Recovery by proposed process > 85% The manufacturing of body parts of ubiquitous machine tools, automobile components, ships hulls, and buildings. Can also be put back in steel production. Recovery by proposed process is > 95% Produce a variety of different alloys, dry cell batteries, and black-brown pigment in paint. Recovery by proposed process is > 90% Pesticides, baking powder, incendiary bombs, and light-emitting diodes. Recovery by proposed process > 75% fertilizer. Recovery by proposed process is > 70% Semiconductor in computers and microelectronics industries, used as fertilizer, and in the production of glass and other ceramics. Recovery by proposed process is > 75% Semiconductors, optoelectronics, drug delivery systems Recovery by proposed process is> 90% Table 8 ED-XRF chemical composition of Coal-Rejects S. Minerals % Remarks No analysed composition 1. Al2O3 19.60 Large variety of products like cans, foils, kitchen utensils, window forums, beer kegs, and aeroplane parts. Recovery by proposed process is 100% 2. CaO 4.28 Binder agents, cement, aggregates, Recovery by proposed process is 100% 3. CuO 0.012 Electrical wires, current collectors, electrodes, utensils etc. Recovery by proposed process is 100% 4. P2O5 2.31 Pesticides, baking powder, incendiary bombs, and light-emitting diodes. Recovery by proposed process > 85% 5. Fe₂O₃ 8.30 The manufacturing of body parts of ubiquitous machine tools, automobile components, ships hulls, and buildings. Can also be put back in steel production. Recovery by proposed process is > 95% 6. Mn₂O₃ 0.095 Produce a variety of different alloys, dry cell batteries, and black-brown pigment in paint. Recovery by proposed process is > 90% 7. NiO 0.012 Pesticides, baking powder, incendiary bombs, and light-emitting diodes. Recovery by proposed process > 75% 8. K2O 3.19 fertilizer. Recovery by proposed process is > 70% 9. SiO₂ 51.90 Semiconductor in computers and microelectronics industries, used as fertilizer, and in the production of glass and other ceramics. Recovery by proposed process is > 75% 10. TiO2 3.38 Aerospace, aircraft, and engines. Pharma grade as pigment. Drug delivery systems etc. Recovery by proposed process is > 90% Table 9 ED-XRF chemical composition of Steel Slag-1 S. Minerals % Remarks No analysed composition 1. Al₂O₃ 15.40 Large variety of products like cans, foils, kitchen utensils, window forums, beer kegs, and aeroplane parts. Recovery by proposed process is 100% 2. CaO 41.80 Binder agents, cement, aggregates, Recovery by proposed process is 100% 3. MgO 7.50 Semiconductor, drug delivery systems. Recovery by proposed process is 100% 4. Fe₂O₃ 2.10 The manufacturing of body parts of ubiquitous machine tools, automobile components, ships hulls, and buildings. Can also be put back in steel production. Recovery by proposed process is > 95% 5. Mn2O3 0.091 Produce a variety of different alloys, dry cell batteries, and black-brown pigment in paint. Recovery by proposed process is > 90% 6. ZnO 0.034 Semiconductors, optoelectronics, drug delivery systems Recovery by proposed process is> 90% 7. SiO2 31.20 Semiconductor in computers and microelectronics industries, used as fertilizer, and in the production of glass and other ceramics. Recovery by proposed process is > 75% 8. S₂O₆ 1.71 Anodes for Li-S batteries, gypsum. Recovery by proposed process is > 90% Table 10 ED-XRF chemical composition of Steel Slag-2 S. Minerals % Remarks No analysed composition 1. Al2O3 1.53 Large variety of products like cans, foils, kitchen utensils, window forums, beer kegs, and aeroplane parts. Recovery by proposed process is 100% 2. CaO 57.40 Binder agents, cement, aggregates, Recovery by proposed process is 100% 3. CuO 0.235 Electrical wires, current collectors, electrodes, utensils etc. Recovery by proposed process is 100% 4. P2O5 1.80 Pesticides, baking powder, incendiary bombs, and light-emitting diodes. Recovery by proposed process > 85% 5. Fe₂O₃ 22.80 The manufacturing of body parts of ubiquitous machine tools, automobile components, ships hulls, and buildings. Can also be put back in steel production. Recovery by proposed process is > 95% 6. Mn2O3 0.744 Produce a variety of different alloys, dry cell batteries, and black-brown pigment in paint. Recovery by proposed process is > 90% 7. S2O6 0.363 Anodes for Li-S batteries, gypsum. Recovery by proposed process is > 90% 8. SiO₂ 14.20 Semiconductor in computers and microelectronics industries, used as fertilizer, and in the production of glass and other ceramics. Recovery by proposed process is > 75% 9. TiO2 0.92 Aerospace, aircraft, and engines. Pharma grade as pigment. Drug delivery systems etc. Recovery by proposed process is > 90% The ICP-MS elemental composition of the sample Slag was carried out to confirm the presence of metals and elements and listed in Table 11. Table 11 ICP-MS elemental composition of Slag 1 S. Element/metal mg/kg Remarks No 1. Be 4.275 ICP-MS confirms the presence of metals and 2. B 41.176 elements as reported by ED-XRF. In addition, 3. Na 1851.507 heavy metals such as B, Pb, As, Cr, Cd, Se, U 4. Mg 47751.536 and Th at significant levels above the 5. Al 3581.233 threshold of the environment. 6. K 3645.354 7. Ca 236980.368 When all the other elements are separated by 8. V 35.431 electrochemical method, lanthanides and 9. Cr 51.271 actinides can be separated as salts by acid 10. Mn 407.062 digestion process. 11. Fe 539.055 12. Co 0.139 13. Ni 5.748 14. Cu 35.349 15. Zn 147.555 16. As 0.799 17. Se 2.98 18. Sr 53.042 19. Mo 0.84 20. Ag < 0.1 21. Cd < 0.1 22. Sn 1.959 23. Sb 0.358 24. Ba 352.003 25. Pb 6.835 26. U 4.083 27. Ti 1113.13 28. Nb 3.255 29. Th 21.98 30. Ce < 0.1 Even at ppm or ppb level the rare earth metals 31. Y < 0.1 can be separated by magnetic separation process Refuse Derived Fuel (RDF) In yet another embodiment of the present disclosure, Refuse Derived Fuel (RDF) is used as the waste material to recover the VAPs from it. Refuse Derived Fuel (RDF) samples were collected by RCPL Entity1 scientists from Municipal Solid Waste (MSW) collection yard at Kota, Rajasthan, India. Ten different RDF samples were collected. The nature of the RDF samples was amorphous, hygroscopic and light weight powder, yellow to grey in colour. These RDF samples were analyzed by X-ray Fluorescence (XRF) technique, and the following composition are observed as shown in Table 12, and Table 12.1. XRF Experimental Conditions for analysis of the RDF samples: Ignition at 250⁰C to identify the alkali & alkaline earth metal compounds, then further increased to 650⁰C to identify other metal oxides. The temperature was still further increased upto 950⁰C to identify metalloids and related compounds. The loss on ignition is approximately 2 to 5%. Table 12 (Samples 1-5) S. Composition of Sample Sample Sample Sample Sample No. the RDF 1 2 3 4 5 1. Manganese oxide 0.114 0.099 0.10 0.114 0.105 2. Zinc oxide 0.124 0.113 0.106 0.122 0.116 3. Aluminium oxide 13.90 12.10 15.30 12.10 13.60 4. Phosphorous 2.05 1.65 2.26 1.61 1.77 pentoxide 5. Titanium oxide 1.67 1.52 1.09 1.15 1.01 6. Iron oxide 7.71 7.45 8.15 7.28 7.15 7. Magnesium oxide 2.06 1.29 2.15 1.41 1.94 8. Silicon dioxide 51.40 54.0 52.70 46.10 46.40 9. Barium oxide 0.0334 0.0517 0.0436 0.027 0.0338 10. Sulphur trioxide 3.50 3.78 2.51 4.00 3.68 11. Potassium oxide 2.30 2.47 1.89 2.31 2.05 12. Calcium oxide 14.90 15.30 13.20 14.60 12.90 13. Copper oxide 0.0948 0.0979 0.0741 0.0666 0.113 14. Chromium oxide 0.637 0.0428 0.0437 0.0355 0.035 15. Zirconium oxide 0.0623 0.0444 0.0366 0.0313 0.0391 16. Nickel oxide 0.0169 0.0148 0.0097 0.0135 0.0129 17. Sodium oxide - - - 9.02 9.06 18. Cobalt oxide - - - - 0.0359 Table 12.1 (Samples 6-10) S. Composition of Sample Sample Sample Sample Sample No. the RDF 6 7 8 9 10 1. Manganese oxide 0.118 0.115 0.122 0.120 0.164 2. Zinc oxide 0.118 0.156 0.118 0.137 0.162 3. Aluminium oxide 13.0 13.70 12.30 14.10 11.80 4. Phosphorous 1.67 2.13 1.65 2.30 1.81 pentoxide 5. Titanium oxide 1.23 1.39 1.87 1.48 1.77 6. Iron oxide 8.14 8.47 8.77 8.46 10.70 7. Magnesium oxide 1.48 2.05 1.82 1.84 1.54 8. Silicon dioxide 50.80 49.60 48.80 50.60 47.30 9. Barium oxide 0.0497 0.0315 0.0747 0.0448 0.0497 10. Sulphur trioxide 4.38 4.53 4.73 2.82 4.32 11. Potassium oxide 2.54 2.49 2.64 1.97 2.75 12. Calcium oxide 16.30 15.10 16.90 15.90 17.30 13. Copper oxide 0.0964 0.111 0.0848 0.134 0.139 14. Chromium oxide 0.0390 0.0581 0.0582 0.0466 0.0801 15. Zirconium oxide 0.0481 0.043 0.0278 0.0704 0.0786 16. Nickel oxide 0.0135 0.0185 0.0205 0.0151 0.0206 17. Sodium oxide - - - - - 18. Cobalt oxide - - - - - Based on the above analysis, it is observed that the RDF sample possess transition metals and alkali and alkaline metal oxides along with silica, Alumina and iron oxide as major content. The metals weight proportion in these samples are above the threshold limit of the environmental acceptance by competent pollution board applicable in India and hence if used as such for repurposing or reusing such as pavement blocks or road laying material may leach into the soil and water in the area the material is deployed. While the embodiments of the invention include lignite ash, Steel slag, and RDF, as the process involves an Acid digestion step, a person skilled in the art may use the process/method of the present disclosure to recover the VAPs such as native metals, metal alloys, and compounds from any other potential starting material that inherently includes such VAPs. Examples: The present disclosure will now be explained in further detail by the following examples. These examples are illustrative of certain embodiments of the disclosure without limiting the scope of the present disclosure. As discussed, the method of the present disclosure broadly includes the following steps: − Acid digestion of CW or RDF to form acid digested solution (ADS), and formation of water dissolved salt solution (WDS) and transfer to Electrochemical Cell (EC) − Precipitate Handling: washing with water, separation of water dissolved salt solution (WDS), separation of water-insoluble salts (WINS), and separation of sludge − Linear Sweep Voltammetry (LSV) for the water dissolved salt solution (WDS) − Effluent Handling: Transfer of the WINS, and alkali metal WDS Example 1: Recovery of VAPs from Lignite ash samples The Eight Lignite ash samples (Sample 1-8) that were subjected to extensive chemical composition analysis via ICP-MS to understand the matrix of elements present in them is provided in Table 5, and Table 5.1, now subjected to the process of the present disclosure in order to recover the value-added products (VAP) such as native metals, metal alloys, and compounds. The acid used for the acid digestion step for formation of the acid digested solution (ADS) is HCl. It is to be noted that as HCl is used, the metallic components present in the lignite ash samples form chloride salts. The individual water-insoluble salts (WINS) were subjected to High Resolution – Scanning Electron Microscopy and Energy Dispersive Spectroscopy (HR-SEM- EDS) for surface morphology and elemental composition. Linear Sweep Voltammetric (LSV) deposition of elements from the water dissolved salt solutions (WDS) extracted from the Acid digested solution (ADS) of the ash samples 1 to 8. As shown in Fig. 2 Linear sweep voltametric (LSV) technique is carried out (for the water dissolved salts (WDS) from the lignite ash samples 1 to 8) in the range of -3 to 3V potential window and at 50 mV/s scan rate in a three-electrode assembly electrochemical cell that includes: − the water dissolved salt solution (WDS) extracted from the acid digested solution (ADS) is used as the electrolyte; − graphite rod as working electrode; − Pt wire counter electrode; and − Ag/AgCl as reference electrode. The WDS electrolyte consists of different concentrations of BeCl₂, MgCl₂, AlCl₃, VCl3, CrCl2, MnCl2, FeCl3, CoCl2, NiCl2, CuCl2, ZnCl2, Se2Cl2 (hydrolysed as Se₂(OH)₂), SrCl₂, CdCl₂, SnCl₂, SbCl₂, BaCl₂, PbCl₂, TiCl₃, SiCl₄, AgCl. Electrochemical reactions involved 1. Beryllium: BeCl₂ + 2e + 2H⁺ ^ Be(s) + 2HCl E = -1.99 V vs SHE So with respect to Ag/AgCl reference electrode E = - 1.75 V

2. Magnesium: MgCl2 + 2e + 2H⁺ ^ Mg(s) + 2HCl E = -2.356 V vs SHE and in the on graphite at E = -2.116 V vs Ag/AgCl

3. Aluminum: AlCl₃ + 3e + 3H⁺ ^ Al + 3HCl E = -1.676V vs SHE On graphite Al deposits at – 1.436 V

4. Vanadium: VCl3 + 3e + 3H⁺ ^ V + 3HCl E = - 1.385 V vs SHE whereas in surface V gets deposited at -1.145 V

vs Ag/AgCl 5. Chromium: CrCl2 + 2e + 2H⁺ ^ Cr + 2HCl E = - 0.9 V vs SHE With respect to Ag/AgCl reference electrode on graphite surface, Cr is deposited at – 0.66 V 6. Manganese: MnCl2 + 2e + 2H⁺ ^ Mn + 2HCl E = - 1.17 V vs SHE For Ag/AgCl reference, Mn deposits on graphite at – 0.93 V 7. Iron: FeCl3 + 3e + 3H⁺ ^ Fe + 3HCl E = - 0.037 V vs SHE In the

graphite electrode at 0.203 V vs Ag/AgCl reference electrode 8. Cobalt: CoCl2 + 2e + 2H⁺ ^ Co + 2HCl E = - 0.277 V vs SHE and E = -

9. Nickel: NiCl₂ + 2e + 2H⁺ ^ Ni + 2HCl E = - 0.257 V vs SHE and –

on graphite surface. 10. Copper: CuCl₂ + 2e + 2H⁺ ^ Cu + 2HCl E = 0.159 V vs SHE whereas versus Ag/AgCl on graphite surface Cu deposits at 0.399 V 11. Zinc: ZnCl2 + 2e + 2H⁺ ^ Zn + 2HCl E = - 0.7618 V vs SHE, - 0.5218 V vs

12. Selenium: Se₂(OH)₂ + 2e ^ 2Se + 2OH- E = -0.67 V vs SHE and -0.43 V

13. Strontium: SrCl₂ + 2e + 2H+ ^ Sr + 2HCl E = - 2.89 V vs SHE and – 2.65 V

14. Cadmium: CdCl2 + 2e + 2H⁺ ^ Cd + 2HCl E = - 0.403 V vs SHE and – 0.163

15. Tin: SnCl₂ + 2e + 2H⁺ ^ Sn + 2HCl E = - 0.14 V vs SHE

16. Antimony: SbCl3 + 3e + 3H⁺ ^ Sb + 3HCl E = 0.212V vs SHE and 0.452 V

17. Barium: BaCl2 + 2e + 2H⁺ ^ Ba + 2HCl E = - 2.91 V vs SHE and – 2.65 V vs Ag/AgCl 18. Lead: PbCl₂ + 2e + 2H⁺ ^ Pb + 2HCl E = - 0.126 V vs SHE and

19. Titanium: TiCl3 + 3e + 3H+ ^ Ti + 3HCl E = - 0.533 V vs SHE and – 0.293

20. Silver: AgCl + e + H⁺ ^ Ag + HCl E = 0.2223 V vs SHE and 0.4623 V vs Ag/AgCl

21. Silicon: SiCl4 + 4e + 4H⁺ ^ Si + 4HCl E = - 0.909 V vs SHE and – 0.669 V vs

Fig. 3 illustrates linear sweep voltammetry (LSV) of the elements separated from the samples 1-8. The LSV of Fig. 3 shows the combined and/or individual reduction peaks of the elements listed above from all the samples into consideration. As can be seen from Fig. 3 the individual elements deposit at appropriate potential on the graphite surface. The elements that possess closer deposition potential or reduction potential with respect to the Ag/AgCl reference electrode, deposit one over the other leading to alloys or layered materials. From Fig. 3, it is clear that elements like Sr, Ba deposit together with Mg sequentially, Be, Al sequentially, V and Mn together, Si, Cr, Cu, Zn, Se & Ti deposit together, Ag& Sb sequentially, Fe, Co, Ni, Sn & Pb deposit together at appropriate reduction potential when the three-electrode assembly cell is scanned with potential in the window of -3 to 3 V vs Ag/AgCl reference electrode. The elemental composition present in the water dissolved salt solution (WDS), and the water-insoluble salts (WINS), obtained from each of the lignite ash samples 1-8 were evaluated and have been presented in the Table 13 to Table 20. Table 13 The elemental composition of the Sample 1 S. Element Sample1 Remarks No / Metal (mg/kg) 1. Be 5.311 Beryllium Chloride is a yellowish, crystalline, inorganic compound with a sharp odor formed on acid digestion of BeO present in the lignite ash. BeCl2 is soluble in water and is extracted as supernatant liquid from the acid digested lignite ash. The supernatant liquid is subjected to electrochemical separation of Be by linear sweep voltametric technique. Boron results in BCl3 after acid digestion process. Hydrolysed by water but soluble in CCl4 or ethanol. Hence extracted in ethanol. Ethanol is evaporated by drying the precipitate in oven at 100^oC. Sodium precipitates as NaCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain NaCl salt. Magnesium precipitates as MgCl₂ and is highly soluble in water. The supernatant solution of MgCl₂ is filtered and used as electrolyte in linear sweep voltammetry to deposit Mg on graphite surface. Aluminium precipitates as AlCl₃ and is soluble in water. The supernatant solution is filtered and used as electrolyte in linear sweep voltammetry to deposit Al on graphite surface. Potassium precipitates as KCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain KCl salt. Calcium precipitates as CaCl2 and is soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain CaCl2 salt. Vanadium precipitates as VCl3, green solution in water as supernatant and filtered, used as electrolyte in linear sweep voltammetry to deposit V on graphite surface. Chromium precipitates as CrCl₂ and is soluble in water (585g/l). Thus the amount of Cr in the sample 1 is very less and highly soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cr on graphite surface. Manganese precipitates as MnCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Mn on graphite surface. Iron precipitates as FeCl₃ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Fe on graphite surface. Cobalt precipitates as CoCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Co on graphite surface. Nickel precipitates as NiCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ni on graphite surface. Copper precipitates as CuCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cu on graphite surface. Zinc precipitates as ZnCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Zn on graphite surface. Forms As(OH)3 precipitate with water and can be filtered, dried in oven at 100^oC and removed as As₂O₃. Forms Se2Cl2 and decomposes in water as Se2(OH)2. The hydroxide is removed as supernatant liquid and used as electrolyte in linear sweep voltammetry to deposit Se on graphite surface. Forms SrCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Sr on graphite surface. Forms Mo(OH)₅ precipitate with water and can be filtered, dried in oven at 100^oC and removed as MoO₃. Forms AgCl precipitate that can be filtered and removed. It is sparingly soluble in water, the amount present in the sample 1 is within the solubility limit and hence the supernatant is filtered and used as electrolyte to deposit Ag on graphite surface by linear sweep voltammetry. Forms CdCl2 and soluble in water at the level present in the sample 1 of the lignite ash. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms SnCl2 and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Sn on graphite surface. 23. Sb 0.56 Forms SbCl₃ and hydrolyses to SbOCl in water. Antimony oxy chloride is used as electrolyte in linear sweep voltammetry to deposit Sb on graphite surface. 24. Ba 206.03 Forms BaCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ba on graphite surface. 25. Pb 5.172 Forms PbCl₂ and upto 9.9g/l is the solubility in water. As the concentration of Pb here is 5.172mg, the PbCl₂ formed is soluble at this concentration in water and the supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Pb on graphite surface. 26. U 13.44 Forms UCl₃ which is soluble in water. The supernatant is filtered and dried in oven to obtain UCl₃ salt. 27. Ti 642.52 Forms TiCl3 which is soluble in dil.HCl. The supernatant is filtered and used as electrolyte in linear sweep voltammetry to deposit Ti on graphite surface. 28. Th 3.54 Forms ThCl₄ which is soluble in water. The supernatant is filtered and dried in oven to obtain ThCl4 salt. Table 14 The elemental composition of the Sample 2 S. Element Sample 2 Remarks No / Metal (mg/kg) 1. Be 0.204 Beryllium Chloride is a yellowish, crystalline, inorganic compound with a sharp odor formed on acid digestion of BeO present in the lignite ash. BeCl2 is soluble in water and is extracted as supernatant liquid from the acid digested lignite ash. The supernatant liquid is subjected to electrochemical separation of Be by linear sweep voltametric technique. 2. B 1.388 Boron results in BCl3 after acid digestion process. Hydrolysed by water but soluble in CCl₄ or ethanol. Hence extracted in ethanol. Ethanol is evaporated by drying the precipitate in oven at 100^oC. 3. Na 122.506 Sodium precipitates as NaCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain NaCl salt. Magnesium precipitates as MgCl₂ and is highly soluble in water. The supernatant solution of MgCl2 is filtered and used as electrolyte in linear sweep voltammetry to deposit Mg on graphite surface. Aluminium precipitates as AlCl₃ and is soluble in water. The supernatant solution is filtered and used as electrolyte in linear sweep voltammetry to deposit Al on graphite surface. Potassium precipitates as KCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain KCl salt. Calcium precipitates as CaCl2 and is soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain CaCl₂ salt. Vanadium precipitates as VCl3, green solution in water as supernatant and filtered, used as electrolyte in linear sweep voltammetry to deposit V on graphite surface. Chromium precipitates as CrCl₂ and is soluble in water (585g/l). Thus the amount of Cr in the sample 1 is very less and highly soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cr on graphite surface. Manganese precipitates as MgCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Mn on graphite surface. Iron precipitates as FeCl₃ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Fe on graphite surface. Cobalt precipitates as CoCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Co on graphite surface. Nickel precipitates as NiCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ni on graphite surface. Copper precipitates as CuCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cu on graphite surface. Zinc precipitates as ZnCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Zn on graphite surface. Forms As(OH)₃ precipitate with water and can be filtered, dried in oven at 100^oC and removed as As₂O₃. Forms Se2Cl2 and decomposes in water as Se2(OH)2. The hydroxide is removed as supernatant liquid and used as electrolyte in linear sweep voltammetry to deposit Se on graphite surface. Forms SrCl2 and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Sr on graphite surface. Forms Mo(OH)₅ precipitate with water and can be filtered, dried in oven at 100^oC and removed as MoO₃. Forms AgCl precipitate that can be filtered and removed. It is sparingly soluble in water, the amount present in the sample 2 is within the solubility limit and hence the supernatant is filtered and used as electrolyte to deposit Ag on graphite surface by linear sweep voltammetry. Forms CdCl₂ and soluble in water at the level present in the sample 1 of the lignite ash. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms SnCl2 and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms SbCl3 and hydrolyses to SbOCl in water. Antimony oxy chloride is used as electrolyte in linear sweep voltammetry to deposit Sb on graphite surface. Forms BaCl2 and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ba on graphite surface. Forms PbCl₂ and upto 9.9g/l is the solubility in water. As the concentration of Pb here is 5.172mg, the PbCl2 formed is soluble at this concentration in water and the supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Pb on graphite surface. 26. U < 0.1 Forms UCl3 which is soluble in water. The supernatant is filtered and dried in oven to obtain UCl3 salt. 27. Ti 62.98 Forms TiCl₃ which is soluble in dil.HCl. The supernatant is filtered and used as electrolyte in linear sweep voltammetry to deposit Ti on graphite surface. 28. Th 4.883 Forms ThCl₄ which is soluble in water. The supernatant is filtered and dried in oven to obtain ThCl₄ salt. 29. Hg 0.703 Forms HgCl2 which is soluble in water. The supernatant is filtered and dried in oven to obtain HgCl₂ salt. 30. Nb 1.191 Forms NbCl5 which is soluble in water. The supernatant is filtered and dried in oven to obtain NbCl5 salt. 31. Ce 6.951 Rare earth elements or compounds in sample 2 are 32. Y 2.192 Cerium oxide and yittrium oxide. They are separated by magnetic process before acid digestion as minerals Table 15 The elemental composition of the Sample 3 S. Element Sample3 Remarks No / Metal (mg/kg) 1. Be 3.071 Beryllium Chloride is a yellowish, crystalline, inorganic compound with a sharp odor formed on acid digestion of BeO present in the lignite ash. BeCl₂ is soluble in water and is extracted as supernatant liquid from the acid digested lignite ash. The supernatant liquid is subjected to electrochemical separation of Be by linear sweep voltametric technique. 2. B 18.892 Boron results in BCl₃ after acid digestion process. Hydrolysed by water but soluble in CCl₄ or ethanol. Hence extracted in ethanol. Ethanol is evaporated by drying the precipitate in oven at 100^oC. Sodium precipitates as NaCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain NaCl salt. Magnesium precipitates as MgCl2 and is highly soluble in water. The supernatant solution of MgCl2 is filtered and used as electrolyte in linear sweep voltammetry to deposit Mg on graphite surface. Aluminium precipitates as AlCl₃ and is soluble in water. The supernatant solution is filtered and used as electrolyte in linear sweep voltammetry to deposit Al on graphite surface. Potassium precipitates as KCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain KCl salt. Calcium precipitates as CaCl₂ and is soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain CaCl₂ salt. Vanadium precipitates as VCl3, green solution in water as supernatant and filtered, used as electrolyte in linear sweep voltammetry to deposit V on graphite surface. Chromium precipitates as CrCl2 and is soluble in water (585g/l). Thus the amount of Cr in the sample 1 is very less and highly soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cr on graphite surface. Manganese precipitates as MgCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Mn on graphite surface. Iron precipitates as FeCl3 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Fe on graphite surface. Cobalt precipitates as CoCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Co on graphite surface. Nickel precipitates as NiCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ni on graphite surface. Copper precipitates as CuCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cu on graphite surface. Zinc precipitates as ZnCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Zn on graphite surface. Forms As(OH)₃ precipitate with water and can be filtered, dried in oven at 100^oC and removed as As₂O₃. Forms Se₂Cl₂ and decomposes in water as Se₂(OH)₂. The hydroxide is removed as supernatant liquid and used as electrolyte in linear sweep voltammetry to deposit Se on graphite surface. Forms SrCl2 and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Sr on graphite surface. Forms Mo(OH)5 precipitate with water and can be filtered, dried in oven at 100^oC and removed as MoO3. Forms AgCl precipitate that can be filtered and removed. It is sparingly soluble in water, the amount present in the sample 3 is within the solubility limit and hence the supernatant is filtered and used as electrolyte to deposit Ag on graphite surface by linear sweep voltammetry. Forms CdCl₂ and soluble in water at the level present in the sample 1 of the lignite ash. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms SnCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms SbCl₃ and hydrolyses to SbOCl in water. Antimony oxy chloride is used as electrolyte in linear sweep voltammetry to deposit Sb on graphite surface. Forms BaCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ba on graphite surface. Forms PbCl₂ and upto 9.9g/l is the solubility in water. As the concentration of Pb here is 5.172mg, the PbCl2 formed is soluble at this concentration in water and the supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Pb on graphite surface. Forms UCl₃ which is soluble in water. The supernatant is filtered and dried in oven to obtain UCl3 salt. Forms TiCl₃ which is soluble in dil.HCl. The supernatant is filtered and used as electrolyte in linear sweep voltammetry to deposit Ti on graphite surface. Forms ThCl₄ which is soluble in water. The supernatant is filtered and dried in oven to obtain ThCl₄ salt. Forms HgCl2 which is soluble in water. The supernatant is filtered and dried in oven to obtain HgCl2 salt. Forms NbCl5 which is soluble in water. The supernatant is filtered and dried in oven to obtain NbCl5 salt. Rare earth elements or compounds in sample 3 are Cerium oxide and yittrium oxide. They are separated by magnetic process before acid digestion as minerals LiCl is formed which is highly soluble in water that can be recrystallized by seeding pure crystal NaCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal KCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal SiCl₄ is formed. Soluble in CHCl3 and hence extracted in chloroform and used as electrolyte to form Si on graphite surface by linear sweep voltammetry. Table 16 The elemental composition of the Sample 4 S. Element Sample 4 Remarks No / Metal (mg/kg) 1. Be 6.195 Beryllium Chloride is a yellowish, crystalline, inorganic compound with a sharp odor formed on acid digestion of BeO present in the lignite ash. BeCl₂ is soluble in water and is extracted as supernatant liquid from the acid digested lignite ash. The supernatant liquid is subjected to electrochemical separation of Be by linear sweep voltametric technique. 2. B 24.860 Boron results in BCl₃ after acid digestion process. Hydrolysed by water but soluble in CCl₄ or ethanol. Hence extracted in ethanol. Ethanol is evaporated by drying the precipitate in oven at 100^oC. 3. Na 939.035 Sodium precipitates as NaCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain NaCl salt. 4. Mg 6509.353 Magnesium precipitates as MgCl2 and is highly soluble in water. The supernatant solution of MgCl2 is filtered and used as electrolyte in linear sweep voltammetry to deposit Mg on graphite surface. 5. Al 10715.213 Aluminium precipitates as AlCl3 and is soluble in water. The supernatant solution is filtered and used as electrolyte in linear sweep voltammetry to deposit Al on graphite surface. 6. K 131.884 Potassium precipitates as KCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain KCl salt. 7. Ca 27412.408 Calcium precipitates as CaCl₂ and is soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain CaCl2 salt. 8. V 21.861 Vanadium precipitates as VCl_3, green solution in water as supernatant and filtered, used as electrolyte in linear sweep voltammetry to deposit V on graphite surface. Chromium precipitates as CrCl₂ and is soluble in water (585g/l). Thus the amount of Cr in the sample 1 is very less and highly soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cr on graphite surface. Manganese precipitates as MgCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Mn on graphite surface. Iron precipitates as FeCl₃ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Fe on graphite surface. Cobalt precipitates as CoCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Co on graphite surface. Nickel precipitates as NiCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ni on graphite surface. Copper precipitates as CuCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cu on graphite surface. Zinc precipitates as ZnCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Zn on graphite surface. Forms As(OH)3 precipitate with water and can be filtered, dried in oven at 100^oC and removed as As2O3. Forms Se₂Cl₂ and decomposes in water as Se₂(OH)₂. The hydroxide is removed as supernatant liquid and used as electrolyte in linear sweep voltammetry to deposit Se on graphite surface. Forms SrCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Sr on graphite surface. Forms Mo(OH)₅ precipitate with water and can be filtered, dried in oven at 100^oC and removed as MoO3. Forms AgCl precipitate that can be filtered and removed. It is highly insoluble in water, hence the precipitate is dried and separated as salt. Forms CdCl2 and soluble in water at the level present in the sample 1 of the lignite ash. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms SnCl2 and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms SbCl3 and hydrolyses to SbOCl in water. Antimony oxy chloride is used as electrolyte in linear sweep voltammetry to deposit Sb on graphite surface. Forms BaCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ba on graphite surface. Forms PbCl₂ and upto 9.9g/l is the solubility in water. As the concentration of Pb here is 5.172mg, the PbCl2 formed is soluble at this concentration in water and the supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Pb on graphite surface. Forms UCl₃ which is soluble in water. The supernatant is filtered and dried in oven to obtain UCl3 salt. Forms TiCl₃ which is soluble in dil.HCl. The supernatant is filtered and used as electrolyte in linear sweep voltammetry to deposit Ti on graphite surface. Forms ThCl₄ which is soluble in water. The supernatant is filtered and dried in oven to obtain ThCl₄ salt. Forms HgCl2 which is soluble in water. The supernatant is filtered and dried in oven to obtain HgCl2 salt. 30. Nb 1.254 Forms NbCl₅ which is soluble in water. The supernatant is filtered and dried in oven to obtain NbCl5 salt. 31. Ce 107.127 Rare earth elements or compounds in sample 4 are 32. Y 46.401 Cerium oxide and yittrium oxide. They are separated by magnetic process before acid digestion as minerals 33. Li 1.711 LiCl is formed which is highly soluble in water that can be recrystallized by seeding pure crystal 34. Na 939.045 NaCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal 35. K 131.884 KCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal 36. Si 67.687 SiCl₄ is formed. Soluble in CHCl₃ and hence extracted in chloroform and used as electrolyte to form Si on graphite surface by linear sweep voltammetry. Table 17 The elemental composition of the Sample 5 S. Element Sample 5 Remarks No / Metal 1 (mg/kg) 1. Be 3.643 Beryllium Chloride is a yellowish, crystalline, inorganic compound with a sharp odor formed on acid digestion of BeO present in the lignite ash. BeCl2 is soluble in water and is extracted as supernatant liquid from the acid digested lignite ash. The supernatant liquid is subjected to electrochemical separation of Be by linear sweep voltametric technique. 2. B 9.868 Boron results in BCl3 after acid digestion process. Hydrolysed by water but soluble in CCl4 or ethanol. Hence extracted in ethanol. Ethanol is evaporated by drying the precipitate in oven at 100^oC. 3. Na 661.173 Sodium precipitates as NaCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain NaCl salt. Magnesium precipitates as MgCl2 and is highly soluble in water. The supernatant solution of MgCl2 is filtered and used as electrolyte in linear sweep voltammetry to deposit Mg on graphite surface. Aluminium precipitates as AlCl3 and is soluble in water. The supernatant solution is filtered and used as electrolyte in linear sweep voltammetry to deposit Al on graphite surface. Potassium precipitates as KCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain KCl salt. Calcium precipitates as CaCl₂ and is soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain CaCl₂ salt. Vanadium precipitates as VCl_3, green solution in water as supernatant and filtered, used as electrolyte in linear sweep voltammetry to deposit V on graphite surface. Chromium precipitates as CrCl2 and is soluble in water (585g/l). Thus the amount of Cr in the sample 1 is very less and highly soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cr on graphite surface. Manganese precipitates as MgCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Mn on graphite surface. Iron precipitates as FeCl3 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Fe on graphite surface. Cobalt precipitates as CoCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Co on graphite surface. Nickel precipitates as NiCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ni on graphite surface. Copper precipitates as CuCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cu on graphite surface. Zinc precipitates as ZnCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Zn on graphite surface. Forms As(OH)3 precipitate with water and can be filtered, dried in oven at 100^oC and removed as As2O3. Forms Se₂Cl₂ and decomposes in water as Se₂(OH)₂. The hydroxide is removed as supernatant liquid and used as electrolyte in linear sweep voltammetry to deposit Se on graphite surface. Forms SrCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Sr on graphite surface. Forms Mo(OH)5 precipitate with water and can be filtered, dried in oven at 100^oC and removed as MoO₃. Forms AgCl precipitate that can be filtered and removed. It is highly insoluble in water, hence the precipitate is dried and separated as salt. Forms CdCl₂ and soluble in water at the level present in the sample 1 of the lignite ash. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms SnCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms SbCl₃ and hydrolyses to SbOCl in water. Antimony oxy chloride is used as electrolyte in linear sweep voltammetry to deposit Sb on graphite surface. Forms BaCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ba on graphite surface. Forms PbCl2 and upto 9.9g/l is the solubility in water. As the concentration of Pb here is 5.172mg, the PbCl2 formed is soluble at this concentration in water and the supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Pb on graphite surface. Forms UCl3 which is soluble in water. The supernatant is filtered and dried in oven to obtain UCl3 salt. Forms TiCl3 which is soluble in dil.HCl. The supernatant is filtered and used as electrolyte in linear sweep voltammetry to deposit Ti on graphite surface. Forms ThCl₄ which is soluble in water. The supernatant is filtered and dried in oven to obtain ThCl4 salt. Forms HgCl₂ which is soluble in water. The supernatant is filtered and dried in oven to obtain HgCl₂ salt. Forms NbCl₅ which is soluble in water. The supernatant is filtered and dried in oven to obtain NbCl₅ salt. Rare earth elements or compounds in sample 5 are Cerium oxide and yittrium oxide. They are separated by magnetic process before acid digestion as minerals LiCl is formed which is highly soluble in water that can be recrystallized by seeding pure crystal NaCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal KCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal SiCl4 is formed. Soluble in CHCl3 and hence extracted in chloroform and used as electrolyte to form Si on graphite surface by linear sweep voltammetry. Rare earth elements or compounds in sample 5 are Neodymium oxide and Scandium oxide. They are separated by magnetic process before acid digestion as minerals Table 18 The elemental composition of the Sample 6 S. Element Sample 6 Remarks No / Metal (mg/kg) 1. Be 12.406 Beryllium Chloride is a yellowish, crystalline, inorganic compound with a sharp odor formed on acid digestion of BeO present in the lignite ash. BeCl2 is soluble in water and is extracted as supernatant liquid from the acid digested lignite ash. The supernatant liquid is subjected to electrochemical separation of Be by linear sweep voltametric technique. 2. B 24.251 Boron results in BCl3 after acid digestion process. Hydrolysed by water but soluble in CCl4 or ethanol. Hence extracted in ethanol. Ethanol is evaporated by drying the precipitate in oven at 100^oC. 3. Na 887.619 Sodium precipitates as NaCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain NaCl salt. 4. Mg 10408.466 Magnesium precipitates as MgCl2 and is highly soluble in water. The supernatant solution of MgCl2 is filtered and used as electrolyte in linear sweep voltammetry to deposit Mg on graphite surface. 5. Al 19776.432 Aluminium precipitates as AlCl₃ and is soluble in water. The supernatant solution is filtered and used as electrolyte in linear sweep voltammetry to deposit Al on graphite surface. 6. K 147.309 Potassium precipitates as KCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain KCl salt. 7. Ca 59358.330 Calcium precipitates as CaCl2 and is soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain CaCl₂ salt. 8. V 48.889 Vanadium precipitates as VCl3, green solution in water as supernatant and filtered, used as electrolyte in linear sweep voltammetry to deposit V on graphite surface. 9. Cr 29.313 Chromium precipitates as CrCl2 and is soluble in water (585g/l). Thus the amount of Cr in the sample 1 is very less and highly soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cr on graphite surface. Manganese precipitates as MgCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Mn on graphite surface. Iron precipitates as FeCl3 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Fe on graphite surface. Cobalt precipitates as CoCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Co on graphite surface. Nickel precipitates as NiCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ni on graphite surface. Copper precipitates as CuCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cu on graphite surface. Zinc precipitates as ZnCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Zn on graphite surface. Forms As(OH)3 precipitate with water and can be filtered, dried in oven at 100^oC and removed as As2O3. Forms Se2Cl2 and decomposes in water as Se2(OH)2. The hydroxide is removed as supernatant liquid and used as electrolyte in linear sweep voltammetry to deposit Se on graphite surface. Forms SrCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Sr on graphite surface. Forms Mo(OH)₅ precipitate with water and can be filtered, dried in oven at 100^oC and removed as MoO3. Forms BaCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ba on graphite surface. Forms PbCl₂ and upto 9.9g/l is the solubility in water. As the concentration of Pb here is 5.172mg, the PbCl₂ formed is soluble at this concentration in water and the supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Pb on graphite surface. Forms UCl₃ which is soluble in water. The supernatant is filtered and dried in oven to obtain UCl₃ salt. Forms TiCl₃ which is soluble in dil.HCl. The supernatant is filtered and used as electrolyte in linear sweep voltammetry to deposit Ti on graphite surface. Forms ThCl4 which is soluble in water. The supernatant is filtered and dried in oven to obtain ThCl₄ salt. Forms HgCl2 which is soluble in water. The supernatant is filtered and dried in oven to obtain HgCl2 salt. Forms NbCl₅ which is soluble in water. The supernatant is filtered and dried in oven to obtain NbCl5 salt. Rare earth elements or compounds in sample 6 are Cerium oxide and yittrium oxide. They are separated by magnetic process before acid digestion as minerals LiCl is formed which is highly soluble in water that can be recrystallized by seeding pure crystal NaCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal KCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal SiCl₄ is formed. Soluble in CHCl₃ and hence extracted in chloroform and used as electrolyte to form Si on graphite surface by linear sweep voltammetry. Table 19 The elemental composition of the Sample 7 S. Element Sample 7 Remarks No / Metal (mg/kg) 1. B 0.707 Boron results in BCl3 after acid digestion process. Hydrolysed by water but soluble in CCl₄ or ethanol. Hence extracted in ethanol. Ethanol is evaporated by drying the precipitate in oven at 100^oC. 2. Na 197.509 Sodium precipitates as NaCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain NaCl salt. 3. Mg 322.832 Magnesium precipitates as MgCl2 and is highly soluble in water. The supernatant solution of MgCl2 is filtered and used as electrolyte in linear sweep voltammetry to deposit Mg on graphite surface. 4. Al 1580.706 Aluminium precipitates as AlCl₃ and is soluble in water. The supernatant solution is filtered and used as electrolyte in linear sweep voltammetry to deposit Al on graphite surface. 5. K 23.935 Potassium precipitates as KCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain KCl salt. 6. Ca 1355.139 Calcium precipitates as CaCl₂ and is soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain CaCl₂ salt. 7. V 13.378 Vanadium precipitates as VCl3, green solution in water as supernatant and filtered, used as electrolyte in linear sweep voltammetry to deposit V on graphite surface. 8. Cr 12.931 Chromium precipitates as CrCl2 and is soluble in water (585g/l). Thus the amount of Cr in the sample 1 is very less and highly soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cr on graphite surface. 9. Mn 1.012 Manganese precipitates as MgCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Mn on graphite surface. Iron precipitates as FeCl₃ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Fe on graphite surface. Cobalt precipitates as CoCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Co on graphite surface. Nickel precipitates as NiCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ni on graphite surface. Copper precipitates as CuCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cu on graphite surface. Zinc precipitates as ZnCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Zn on graphite surface. Forms Se2Cl2 and decomposes in water as Se2(OH)2. The hydroxide is removed as supernatant liquid and used as electrolyte in linear sweep voltammetry to deposit Se on graphite surface. Forms SrCl2 and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Sr on graphite surface. Forms Mo(OH)₅ precipitate with water and can be filtered, dried in oven at 100^oC and removed as MoO₃. Forms SnCl2 and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms BaCl2 and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ba on graphite surface. Forms PbCl2 and upto 9.9g/l is the solubility in water. As the concentration of Pb here is 5.172mg, the PbCl2 formed is soluble at this concentration in water and the supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Pb on graphite surface. 21. Ti 22.164 Forms TiCl₃ which is soluble in dil.HCl. The supernatant is filtered and used as electrolyte in linear sweep voltammetry to deposit Ti on graphite surface. 22. Th 2.913 Forms ThCl₄ which is soluble in water. The supernatant is filtered and dried in oven to obtain ThCl₄ salt. 23. Hg 0.410 Forms HgCl₂ which is soluble in water. The supernatant is filtered and dried in oven to obtain HgCl₂ salt. 24. Nb 0.704 Forms NbCl5 which is soluble in water. The supernatant is filtered and dried in oven to obtain NbCl5 salt. 25. Ce 1.616 Rare earth elements or compounds in sample 7 are 26. Y 0.469 Cerium oxide and yttrium oxide. They are separated by magnetic process before acid digestion as minerals 27. Li 0.32 LiCl is formed which is highly soluble in water that can be recrystallized by seeding pure crystal 28. Na 197.509 NaCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal 29. K 23.935 KCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal 30. Si 190.260 SiCl₄ is formed. Soluble in CHCl₃ and hence extracted in chloroform and used as electrolyte to form Si on graphite surface by linear sweep voltammetry. Table 20 The elemental composition of the Sample 8 S. Element Sample 8 Remarks No / Metal (mg/kg) 1. B 0.771 Boron results in BCl3 after acid digestion process. Hydrolysed by water but soluble in CCl4 or ethanol. Hence extracted in ethanol. Ethanol is evaporated by drying the precipitate in oven at 100^oC. 2. Na 209.309 Sodium precipitates as NaCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain NaCl salt. 3. Mg 374.499 Magnesium precipitates as MgCl₂ and is highly soluble in water. The supernatant solution of MgCl2 is filtered and used as electrolyte in linear sweep voltammetry to deposit Mg on graphite surface. Aluminium precipitates as AlCl3 and is soluble in water. The supernatant solution is filtered and used as electrolyte in linear sweep voltammetry to deposit Al on graphite surface. Potassium precipitates as KCl and is highly soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain KCl salt. Calcium precipitates as CaCl₂ and is soluble in water. The supernatant solution is filtered and water dried in oven at 60^oC to obtain CaCl₂ salt. Vanadium precipitates as VCl3, green solution in water as supernatant and filtered, used as electrolyte in linear sweep voltammetry to deposit V on graphite surface. Chromium precipitates as CrCl2 and is soluble in water (585g/l). Thus the amount of Cr in the sample 1 is very less and highly soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cr on graphite surface. Manganese precipitates as MgCl2 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Mn on graphite surface. Iron precipitates as FeCl3 and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Fe on graphite surface. Cobalt precipitates as CoCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Co on graphite surface. Nickel precipitates as NiCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ni on graphite surface. Copper precipitates as CuCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cu on graphite surface. Zinc precipitates as ZnCl₂ and is soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Zn on graphite surface. Forms SrCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Sr on graphite surface. Forms Mo(OH)₅ precipitate with water and can be filtered, dried in oven at 100^oC and removed as MoO₃. Forms AgCl precipitate that can be filtered and removed. It is highly insoluble in water, hence the precipitate is dried and separated as salt. Forms SnCl2 and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Cd on graphite surface. Forms BaCl₂ and soluble in water. The supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Ba on graphite surface. Forms PbCl₂ and upto 9.9g/l is the solubility in water. As the concentration of Pb here is 5.172mg, the PbCl₂ formed is soluble at this concentration in water and the supernatant liquid is filtered and used as electrolyte in linear sweep voltammetry to deposit Pb on graphite surface. Forms TiCl₃ which is soluble in dil.HCl. The supernatant is filtered and used as electrolyte in linear sweep voltammetry to deposit Ti on graphite surface. Forms ThCl4 which is soluble in water. The supernatant is filtered and dried in oven to obtain ThCl₄ salt. Forms HgCl2 which is soluble in water. The supernatant is filtered and dried in oven to obtain HgCl2 salt. Forms NbCl5 which is soluble in water. The supernatant is filtered and dried in oven to obtain NbCl5 salt. Rare earth elements or compounds in sample 8 is Cerium oxide. It is separated by magnetic process before acid digestion as minerals 26. Li 0.316 LiCl is formed which is highly soluble in water that can be recrystallized by seeding pure crystal 27. Na 209.306 NaCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal 28. K 27.548 KCl is formed which is highly soluble in water and can be recrystallized by seeding pure crystal 29. Si 87.438 SiCl4 is formed. Soluble in CHCl3 and hence extracted in chloroform and used as electrolyte to form Si on graphite surface by linear sweep voltammetry. Through the Linear sweep voltametric (LSV) technique, the elements deposited at appropriate potential on the graphite surface as layers are then removed and separated from the graphite surface. The deposited layers are subjected to FESEM analysis to understand the surface morphology and thickness of the layers. Fig. 4 illustrates FESEM of Sr and Ba deposition on graphite surface, and cross- sectional area and thickness of the deposition. Fig 4 (a) represents 10 microns magnification of the deposited Sr and Ba on graphite surface. Fig 4 (b) represents 3 microns magnification of the deposited Sr and Ba on graphite surface. Fig 4 (c) indicates the cross-sectional image and the thickness of the Sr and Ba layers were measured to be 7.236µm and 8.621 µm respectively. Fig. 5 illustrates Energy Dispersive Spectroscopy (EDS) spectra and elemental composition of the Sr and Ba deposition on graphite surface. Fig. 6 illustrates FESEM image of Mg deposition on graphite surface, and cross- sectional area and thickness of the deposition. The thickness of Mg deposition layer on graphite as obtained from the cross sectional FESEM image is 9.525 µm. Fig. 7 illustrates EDS spectra and elemental composition of Mg deposition on graphite surface. Fig. 8 illustrates FESEM of Be and Al deposition on graphite surface, and cross- sectional area and thickness of the deposition. The electrodeposition of Be and Al on graphite surface happens sequentially. The thickness of the Be and Al layers are respectively 14.61 & 12.91µm on graphite surface Fig. 9 illustrates EDS spectra and elemental composition of Be and Al deposited on the graphite surface. On continuing the potential scan, set of elements V and Mn get deposited together on graphite surface. Fig.10 illustrates FESEM of V and Mn deposition on graphite surface, and cross- sectional area and thickness of the deposition. The thickness of the V & Mn deposited is found to be 25.28 and 33.99 µm respectively from the cross section of the image. Fig. 11 illustrates EDS spectra and elemental composition of V and Mn deposited on graphite surface. With further potential swapping, set of elements such as Fe, Co, Ni, Sn and Pb get deposited together on graphite surface. Fig. 12 illustrates FESEM of Fe, Co, Ni, Sn and Pb deposition on graphite surface, and cross-sectional area and thickness of the deposition. The thickness of the Fe, Co, Ni, Sn & Pb deposited is found to be 8.621 µm cumulatively from the cross section of the image. Fig. 13 illustrates EDS spectra and elemental composition of Fe, Co, Ni, Sn and Pb deposited on graphite surface. When the potential is scanned further upto 3V with respect to Ag/AgCl, the remaining two elements such as Ag and Sb gets deposited in sequential manner on the graphite electrode surface. Fig.14 illustrates FESEM of Ag and Sb deposition on graphite surface, and cross- sectional area and thickness of the deposition. The thickness of the Ag & Sb deposited is found to be 12.91 & 14.61 µm respectively from the cross section of the image. Fig.15 illustrates EDS spectra and elemental composition of Ag and Sb deposited on graphite surface. Example 2 Recovery of VAPs from Steel Slag sample The process was carried out with the teaching of the present disclosure, where Steel slag sample (Steel Slag-1) was digested in HCl as the concentrated inorganic acid, and the WDS were transferred to the electrochemical cell, where linear sweep voltammetry (LSV) with the method as shown in Fig.2. Fig.16 illustrates linear sweep voltammetry (LSV) of the elements separated from the steel slag sample. As all elements possess unique finger print in the electrochemical series with respect to their redox chemistry and the reference electrode employed, the elements such as Mg, Mn, Cr, Al, Ti, Ni, Ca, Zn can be electrochemically deposited on electrode surface as metals or alloys, leaving behind Fe, Si in the slag in its ore or salt form. According to the electrochemical series, the following are the redox potentials of the elements under consideration. 1. Magnesium – all of its oxidation states from +2 to native metal lies in the potential of -2.37 and hence can be deposited on the electrode surface MgO ⇌ Mg²⁺ + 2e⁻ 2.37 V 2. Manganese – MnO2(s) + 4H⁺ + 2e⁻ ⇌ Mn²⁺ + 2H2O(l) 1.23 V - 1.17 V ⇌ Mn + 2H₂O(l) 0.06 V (SHE)

Hence Mn can be deposited on electrode surface at near zero potential of just 60 mV 3. Phosphorous – P₂O₅ can be converted to phosphoric acid in acidic medium as follows P₂O₅ +6H⁺+6e−⇌2PH₃(g) + 5/2 O₂ 0.06V 2PH₃(g) + 4H₂O(l) ⇌ 2H₃PO₂ + 8H⁺ + 8e⁻ -0.5 V 2H₃PO₂ + 2H₂O (l) ⇌ 2H₃PO₃+ 4H⁺ + 4e⁻ -0.5 V 2H3PO3 + 2H2O (l) ⇌ 2H3PO4+ 4H⁺ + 4e⁻ -0.28 V Overall reaction: P2O5 + 3H2O(l) ⇌ 2H3PO4 -1.34 V Hence phosphorous is removed electrochemically at -1.34 V as phosphoric acid 4. Chromium – Chromium Oxide exists in +3 oxidation state and would involve the following electrochemical reaction Cr₂O₃ + e⁻ ⇌ 2CrO + ½ O₂ - 0.424 V 2CrO + 4e⁻ ⇌ 2Cr + O₂ - 0.9 V Overall reaction: Cr2O3 + 5e⁻ ⇌ 2Cr + 1½ O₂ - 1.324 V Thus, at – 1.324 V Cr can be deposited on the electrode surface in metallic state 5. Aluminium – Electrochemically Al can be recovered from steel slag as below Al(OH)₄ ⁻ + 3e⁻ ⇌⇌ Al(s) + 4OH⁻ - 2.31 V Specifically at -2.31V, Al can be deposited on the electrode surface from the slag. 6. Titanium – TiO2 + e⁻ ⇌ Ti³⁺ + O2 - 0.7 V Ti³⁺ + e⁻ ⇌ Ti²⁺ - 0.37 V Ti²⁺ + 2e⁻ ⇌ Ti - 0.163 V Overall reaction TiO2 + 4e⁻ ⇌ Ti + O2 -1.233 V Thus, at -1.233 V, Ti can be extracted electrochemically from the slag to metallic state and deposited on the electrode surface. 7. Nickel – Ni exists mostly as hydrated oxides or hydroxides and can be easily reduced to metallic Ni electrochemically at – 0.72V Ni(OH)₂ + 2e⁻ ⇌ Ni(s) + 2OH⁻ - 0.72 V 8. Calcium – Calcium Oxide is extracted as Ca on electrode surface at – 2.84V CaO + 2e⁻ ⇌⇌ Ca(s) + ½ O2 - 2.84 V 9. Carbon – If the steel slag is rich in carbonas well, it can be electrochemically oxidized or reduced to CO2⇌CO cycle at specific potential as shown below C + 2H₂O + 2e⁻ ⇌ CO₂ + 2H₂ - 1.15 V CO₂(g) + 2H⁺ + 2e⁻ ⇌ CO(g) + H₂O(l) - 0.106 V Overall reaction C + H₂O(l) + 2H⁺ + 4e⁻ ⇌ CO + 2H₂ - 1.256 V 10. Silica – being a source material for any semiconductor industry, electrochemically SiO2 can be reduced to Si and deposited on graphite surface at – 0.909 V. SiO2(s) + 4H⁺ + 4e⁻ ⇌ Si(s) + 2H2O(l) - 0.909V The deposited Si is then sintered at very high temperature to form SiC in a muffle furnace. The obtained SiC would be of semiconductor grade and possess high thermal conductivity and hence can be utilized in semiconductor as well as thermal insulation applications. 11. Sulphur – sulphur trioxide is electrochemically reduced or converted to suplhites as follows S2O6²⁻ + 4H⁺ + 2e⁻ ⇌ 2H2SO3 0.569 V 12. Potassium – Potassium exists as oxide and can be converted to elemental K at -2.93 V and deposited on electrode surface. This is a good source of K metal anode in K-ion batteries. K⁺ + e- ⇌ K - 2.93 V 13. Copper – Copper existing as oxide, can be recovered electrochemically as metallic copper and deposited on electrode surface at Cu²⁺ + e⁻ ⇌ Cu⁺ 0.159 V Cu⁺ + e⁻ ⇌ Cu(s) 0.52 V Overall reaction: Cu²⁺ + 2e- ⇌ Cu 0.3419 V 14. Zinc – In slightly acidic solution, ZnO froms metallic Zn as follows: ZnO + 2H⁺ + 2e⁻ ⇌⇌ Zn(s) + 2H₂O 1.473 V Thus, after electrochemically removing all the other minerals of the steel slag and/or ash either simultaneously or sequentially and then the slag would contain iron oxide as the only constituent. This solution is then centrifuged to higher rpm ca. 10000 rpm, will result in agglomeration of iron oxide at the bottom of the centrifuge tube. These settled solid matter are then filtered with Whatman filter paper of appropriate mesh size and dried in vacuum oven at 150⁰C. The resultant dry powder will be Fe₂O₃ in agglomerated state. This agglomerated iron ore from the steel slag can be further broken down into smaller particles of appropriate size by ball milling with proper solvent. The material or elements recovered as indicated in above points can be upscaled to appropriate industry as they will be in their purest form. Example 3 Recovery of VAPs from RDF sample The process was carried out with the teaching of the present disclosure, where RDF sample (Sample 5) was digested in HCl as the concentrated inorganic acid, and the WDS were transferred to the electrochemical cell, where linear sweep voltammetry (LSV) with the method as shown in Fig.2. Fig.17 illustrates linear sweep voltammetry (LSV) of the elements separated from the RDF sample. As evident from Fig. 17, the following elements were deposited depending upon their redox potentials as follows: I. Magnesium and Alumnium at 2.37 and - 2.31 V respectively II. Strontium and Barium at 2.865 and – 2.65 V respectively III. Beryllium at – 1.75 V IV. Vanadium and Manganese at 1.51 and 1.25 V respectively V. Iron, Cobalt, Nickel, Tin and Lead in the range of 0.7 to 0.8 V VI. Silver and Antimony around 1.75 and 1.9 V respectively Advantages: The method of conversion of combustion wastes and refuse derived fuel into value-added products of the present disclosure has the following non-limiting advantages. − Recovery of metals, minerals and or ores help in restoration of the bio- diversity, agricultural soil rejuvenation, eliminates seepage of heavy metals in surface and sub-surface water table, soil contamination, public health, environmental safety, among others. − Eliminates or at least alleviates the chances of any accidental ingestion of the combustion wastes such as lignite ash, RDF, or steel slag by human may cause accumulation of heavy metals in the blood and in long run can affect vital organs such as kidney and liver, may cause pulmonological diseases such as wheezing, chronic bronchitis and ultimately lung cancer. − Reduces the possibilities of human/animal ingestion of heavy metals such as Pb, As, Cd, etc., that can lead to skin related diseases and skin cancer in long time exposure. − Recovery of lanthanides and actinides assuages the risk of exposure to these minerals or elements, where >1 µg/l exposure leads to severe genetic mutations and organ specific uncontrollable cell growth with cancer risk. − Although Ca and Mg minerals lead to accelerated growth of plants and crops, the process of the present disclosure reduces the presence of Li, Na, K, Sr etc. in the wastes, which otherwise leads to contamination of the food crops and also carcinogenic material intake by the plants and in turn the humans consuming them. − Saves the water bodies from getting contaminated with heavy metals, which otherwise affect the fauna and flora thriving around these water resources, by utilizing these heavy metals contaminated water resources for the material recovery from lignite source. − Separation and purification of the elements can add value to the market and supply chain with good revenue. − Be, Sr and Ba are less abundant elements and of applications in chemical, pharmaceutical and other industries. Hence even in ppm these elements add value and revenue to the system on separation or precipitation as salts. − As rare earth metals are scarce in the earth’s crust, its recycling from the waste products can cater to the circular economy. − Rare earths can cater to nuclear energy industry. − Ti, Zn and B can be extracted as elements of appropriate salts for supply chain to raw material industry, whereas Si as silica (sand) can be sold to pavement construction industry and cement industries. Applications: The method of conversion of combustion wastes and refuse derived fuel into value-added products of the present disclosure has the following non-limiting industrial applications. − Recovery of value-added products (VAP) such as native metals, metal alloys, and compounds from combustion wastes (CW) or Refuse derived fuels (RDF). Although the present disclosure is described in terms one or more embodiments, it is to be understood that they have been presented by way of example, and are not limiting. Thus, the present disclosure should not be limited by any of the above- described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

CLAIMS 1. A method of recovery of value-added products (VAP) from combustion wastes (CW) or Refuse derived fuels (RDF) comprising the steps of: − digesting Combustion wastes (CW) or Refuse derived fuels (RDF) in a First reactor (R1) with concentrated inorganic acid at 10⁰C and 1 atm pressure with continuous stirring to form an acid digested solution (ADS) that contains water soluble salts of the metallic components present in the CW or RDF, and a precipitate; − separating the acid digested solution (ADS) from the precipitate by filtration to Tank T1; − diluting the ADS by adding the ADS to distilled water in Tank T2 at 20⁰C and 1 atm pressure with constant stirring to form water dissolved salt solution (WDS), − transferring the WDS to the electrochemical cell (EC) for electrochemical reaction; − transferring the precipitate from the First reactor (R1) to a second Reactor (R2), where the precipitate is washed with distilled water at 20⁰C and 1 atm pressure with constant stirring to separate any remaining water-soluble salts as water dissolved salt solution (WDS) by filtration, wherein the WDS is transferred to the electrochemical cell (EC) for electrochemical reaction, wherein this process of washing with distilled water, filtration, and transferring the WDS to the electrochemical cell is repeated several times until all the water-soluble salts are separated as WDS; − after removal of the WDS, drying the precipitate in vacuum at 100⁰C; − dissolving the precipitate in a non-polar solvent to form a precipitate mass; − subjecting the precipitate to centrifugation, where the water-insoluble salts (WINS) present in the precipitate were removed separately by their density gradients, wherein the water-insoluble salts (WINS) of differing density are separated at different revolutions per minute (RPM), one by one based on their density difference, and are transferred to tank T4; − drying the separated WINS individually in a vacuum oven at 100⁰C, and the individual WINS are ground to form each a fine powder; − recrystallising the WINS based on their elemental composition by seeding pure crystal; − transferring the sludge to a separate tank T5, wherein the sludge is the left over material after the WINS are separated from Reactor 2 by centrifugation; − drying the sludge in a vacuum oven at 100⁰C; − separating the rare earth elements, and other minerals present in the dried sludge by magnetic separation; − subjecting the WDS in the electrochemical cell (EC) to electrochemical process to isolate the elements as native metals or alloys or compounds at appropriate potential and current window on the working electrode (graphite) surface employing linear sweep voltammetry (LSV) technique, wherein the electrochemical cell is a three-electrode assembly electrochemical cell that includes: i. the water dissolved salt solution (WDS) extracted from the acid digested solution (ADS) is used as the electrolyte, ii. graphite rod as working electrode, iii. Pt wire counter electrode, and iv. Ag/AgCl as reference electrode, − after the electrochemical action, transferring the the effluent from the electrochemical cell, which includes water insoluble salts (WINS) to tank T4 through effluent tank T3; − transferring the water-soluble alkali metal salts (a portion of WDS) (that were not recovered in the electrochemical process) from the electrochemical cell to the tank T4 through the effluent tank T3.

2. The method as claimed in claim 1, wherein the concentrated inorganic acid is selected from HCl, H2SO4, HNO3, H3PO4.

3. The method as claimed in claim 1, wherein the dilution of the ADS in distilled water is done in a ratio of 1:3 to 1:5 based on the strength of the concentrated inorganic acid used, wherein when the concentrated inorganic acid is H2SO4, the dilution is done in a ratio of 1:5, when the concentrated inorganic acid is HCl, HNO3, the dilution is done in a ratio of 1:4, and when the concentrated inorganic acid is H₃PO₄ the dilution is done in a ratio of 1:3.

4. The method as claimed in claim 1, wherein the water dissolved salt solution (WDS) is formed by the reaction of the metallic components present in the CW or RDF with the anion of the acid used, and a precipitate, wherein the concentrated inorganic acid can be selected from HCl, H2SO4, HNO3, H3PO4.

5. The method as claimed in claim 1, wherein the VAP include native metals, metal alloys, and compounds.

6. The method as claimed in claim 1, wherein after the step of removal of the WDS from the precipitate and after drying the precipitate in vacuum at 100⁰C, the dried precipitate is ground to form a fine precipitate powder.

7. The method as claimed in claim 1, wherein the non-polar solvent for dissolving the precipitate to form a precipitate mass is selected from chloroform, carbon tetrachloride, and aromatic alcohols.

8. The method as claimed in claim 1, wherein the water-insoluble salt (WINS) are salts of Ag.

9. The method as claimed in claim 1, wherein when the sludge is rich in carbon, it is subjected to continuous chemical vapour deposition (CCVD) to form carbon nanotubes and/or graphene.

10. The method as claimed in claim 1, wherein after removal of any rare earth elements and other minerals including carbon, the dried sludge is utilized in pavement industries and blocks for cement industries.

11. The method as claimed in claim 1, wherein Linear sweep voltametric (LSV) technique is carried out in the range of -3 to 3V potential window and at 50 mV/s scan rate in the three-electrode assembly electrochemical cell.