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WO2025233969A1 - Procédé à basse température pour la récupération d'alumine à partir de différentes sources - Google Patents

Procédé à basse température pour la récupération d'alumine à partir de différentes sources

Info

Publication number
WO2025233969A1
WO2025233969A1 PCT/IN2025/050726 IN2025050726W WO2025233969A1 WO 2025233969 A1 WO2025233969 A1 WO 2025233969A1 IN 2025050726 W IN2025050726 W IN 2025050726W WO 2025233969 A1 WO2025233969 A1 WO 2025233969A1
Authority
WO
WIPO (PCT)
Prior art keywords
alumina
temperature
water
naoh
sodium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/IN2025/050726
Other languages
English (en)
Inventor
Prof. Chenna Rao BORRA
Dr. Prasanta JANA
Gautam Behera
Gutti Chinna Chandrudu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Indian Institute of Technology Kharagpur
Original Assignee
Indian Institute of Technology Kharagpur
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Indian Institute of Technology Kharagpur filed Critical Indian Institute of Technology Kharagpur
Publication of WO2025233969A1 publication Critical patent/WO2025233969A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
    • C01F7/0606—Making-up the alkali hydroxide solution from recycled spent liquor
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
    • C01F7/0646—Separation of the insoluble residue, e.g. of red mud
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/14—Aluminium oxide or hydroxide from alkali metal aluminates

Definitions

  • Alumina Al 2 O 3
  • bauxite Primary ore of aluminium
  • alumina there are other areas of application of alumina such as ceramics, abrasive, catalyst flame retardant, and high- performance materials in electronics and aerospace.
  • Primary source of alumina is bauxite (30 – 40% alumina) and there are a lot of secondary resources of alumina such as Bauxite residue (Red Mud), low-grade iron ore, aluminium dross, overburden.
  • Bauxite residue contains 15 – 20% alumina, Low-grade iron ore 4 – 8% alumina, aluminium dross 50 – 75% and overburden and iron ore tailings have 5-10% alumina.
  • Bauxite residue contains 15 – 20% alumina
  • Low-grade iron ore 4 – 8% alumina aluminium dross 50 – 75% and overburden and iron ore tailings have 5-10% alumina.
  • Global alumina production reached approximately to 140 million metric tons in 2022.
  • Bayer process Conventional and current alumina production in world is mostly done by the Bayer process, developed in the late 19 th century, which involves refining bauxite through digestion, precipitation, and calcination.
  • Bayers process utilizes a temperature of around 150-270 degrees centigrade depending upon the types of alumina rich phase present in bauxite ore and also a pressure of around 25 atm is used.
  • Another limitation of this process is that it is not suitable for all the alumina resources such as aluminum dross and diasporic bauxite and low-grade ore or ore containing high silica due to the formation of sodium alumino silicate phase leading to loss of sodium hydroxide as well as alumina leading to less recovery.
  • Other conventional process for lean bauxite ore or ore with high silica content are soda sintering or lime soda sintering process which involves refining bauxite through sintering/roasting, leaching, and carbonizing. This process utilized a temperature of around 950-1050 °C which is extremely high so it is an energy-intensive process.
  • IN202021022813 discloses a method to selectively enriching and separating alumina and silica from clay minerals and alumino- siliceous industrial rejects using acid, which generates huge volumes of effluents. The reagents are consumed in this process.
  • US730952 discloses a method to recover the caustic and alumina values from Bayer Red mud. However, it’s worth noting that this process utilized a temperature of around 1050° C which is significantly high. And use of both lime stone (calcium carbonate) and NaOH and coke.
  • the present invention is directed to a low-temperature (T ⁇ 200° C) method of recovery of alumina from various alumina-containing resources.
  • the method comprises the steps of treating an alumina-containing resource with Sodium Hydroxide (NaOH) at a predefined temperature in presence of small amount (5-50%) of water, which helps in better reaction between alumina containing phases and NaOH, and leaching the treated alumina- containing resource with water to dissolve Sodium Aluminate (NaAlO2) and produce leachate.
  • the method includes performing filtration/clarification for separating the solid residues from the leachate.
  • the method further comprises causing precipitation of Aluminium Hydroxide (Al(OH)3) by reacting the leachate with CO2 so as to convert the Sodium Aluminate (NaAlO2) to Aluminium Hydroxide (Al(OH) 3 ), and performing calcination of the precipitated Aluminium Hydroxide (Al(OH)3) at a pre-defined temperature to obtain alumina.
  • the sodium carbonate generated after alumina is regenerated by treating the solution with lime/slaked lime (CaO/Ca(OH) 2 ) to convert sodium carbonate to sodium hydroxide. After solid/liquid separation, NaOH solution is evaporated and the solution or crystals containing NaOH.H2O is send back for the reuse in the treatment.
  • Figure 1 illustrates a flowchart for workflow a low-temperature method of recovery of alumina from various alumina-containing resources, in accordance with an embodiment of the present disclosure
  • Figure 2 illustrates exemplary XRD pattern of aluminum hydroxide produced from dross, in accordance with an embodiment of the present disclosure
  • Figure 3 illustrates exemplary XRD pattern of sodium aluminate, formed upon NaOH treatment with red mud at different low temperature with 20% water, in accordance with an embodiment of the present disclosure.
  • Alumina a versatile compound derived mostly from bauxite, finds wide-ranging applications, including as the main constituent for aluminium production and in ceramics, abrasives, catalysts, flame retardants, and high-performance materials in electronics and aerospace. While bauxite is the primary source of alumina, there are numerous secondary resources available, such as bauxite residue (red mud), low-grade iron ore, aluminium dross, and overburden.
  • Embodiments of the present disclosure provide a method for recovery of alumina from various alumina-containing resources as illustrated in Figure 1.
  • the various alumina-containing resources include but not limited to red mud, dross, iron ore slime, overburden, low-grade iron ore any industrial waste or natural source.
  • the size and configuration of the required set of machinery for accomplishing the method (100) may be variable in accordance with the requirement of the different types of installation environment. Any such variation/modification shall be construed to be within the scope of the present disclosure.
  • the method (100) comprises one or more blocks to be performed for recovery of alumina from various alumina containing resources.
  • an alumina-containing resource is treated with Sodium Hydroxide (NaOH).
  • the alumina-containing resource is treated with Sodium Hydroxide (NaOH) at a predefined temperature in the presence of water preferably below 1:1 ratio of the NaOH to water and most preferably below 1:0.5.
  • the amount of water can be in a range of 5% to 50% and the critical amount of water can be in a range of 10% – 20%.
  • Critical amount of water 10 – 20% relative to weight of alumina containing sources is beneficial for maximizing the alumina recovery at this low temperature treatment.
  • the alumina-containing resource can also be treated with other alkali hydroxides such as KOH, LiOH etc.
  • the predefined temperature for treating the alumina-containing resource is in a range of 60 – 200°C, most preferably below 150°C. Further, the alumina containing resource and the sodium hydroxide is in a ratio ranging from 1:0.1 to 1:2.
  • the alumina-containing resource is mixed with NaOH and treated at temperatures between 80- 140°C to convert the alumina into sodium aluminate, as depicted in equation 1: Al2O3+NaOH + H2O ⁇ 2NaAlO2.H2O (1) [0022]
  • the treated alumina-containing resource is leached with water.
  • the treated alumina-containing resource is leached with water to dissolve Sodium Aluminate (NaAlO2.xH2O) and produce leachate.
  • leaching the treated alumina-containing resource with water is carried out in temperature between room temperature to 100°C i.e., in a range of 25oC – 100oC.
  • filtration is carried out to separate NaAlO2.xH2O from the leached residue.
  • Aluminium Hydroxide (Al(OH) 3 ) is precipitated from the leachate using CO 2 gas.
  • the Aluminium Hydroxide (Al(OH) 3 ) is precipitated by reacting the leachate with CO2 gas so as to convert the Sodium Aluminate (NaAlO2) to Aluminium Hydroxide (Al(OH)3).
  • Al(OH)3 is precipitated by introducing CO2 into the sodium aluminate solution, as shown in equation 2.
  • filtration is performed. In an embodiment, filtration is performed for effectively separating the Al(OH) 3 from Na 2 CO 3 solution produced upon CO 2 purging.
  • calcination of the precipitated Aluminium Hydroxide (Al(OH) 3 ) is performed and Sodium Hydroxide is regenerated. In an embodiment, calcination of the precipitated Aluminium Hydroxide (Al(OH) 3 ) is performed at a pre-defined temperature to obtain alumina. Further, Alumina hydroxide is separated from sodium carbonate solution by solid liquid separation followed by conventional calcination to obtain alumina.
  • the subsequent controlled treatment phase conducted within an oven or reactor, is calibrated to optimize reaction conditions. Following low temperature treatment, the samples undergo leaching with distilled water. [0028] Subsequent to leaching, the filtration process, effectively separating the solid residues from the leachate. To ensure the removal of residual sodium aluminate, water washing is performed. [0029] In conjunction with these procedures, X-ray fluorescence spectrometer (XRF) analysis is carried out on both the as-received sample and the leach residues obtained from the experiment. This analytical step or other techniques enables the precise quantification of the elemental composition, providing crucial data for subsequent calculations as illustrated in Figure 2. Primarily, Al(OH) 3 is characterized by three phases: gibbsite, bayerite and nordstrandite.
  • Figure 2 shows Bayerite phase which is one form of aluminium hydroxide, which is produced from dross.
  • Figure 3 illustrates exemplary XRD pattern of sodium aluminate, formed upon NaOH treatment with red mud at different low temperature with 20% water.
  • Figure 3 shows XRD analysis of heat-treated red mud mass with NaOH to red mud mass ratio of 1 and 20% water addition which revealed the formation of sodium aluminate at different temperatures below 150 degrees Celsius.
  • the present invention introduces a novel and simple process that eliminates the need for high temperature or acids as disclosed by the conventional techniques.
  • the method of the present invention represents a significant advancement in alumina production.
  • this innovative technique operates at low temperatures without the need for elevated temperature/pressure conditions.
  • the proposed method By directly treating alumina-containing resources with NaOH, the proposed method generates a water-soluble sodium aluminate phase, a crucial step in the production of alumina. Addition of small amount of water in the raw materials during low temperature process make the alumina recovery efficiency highly significant. This water makes the reaction more effective to form NaAlO 2 .
  • One of the key benefits of the proposed method is its sustainability. By eliminating or significantly reducing the reliance on chemicals like acids or temperature or pressure, the proposed method minimizes the environmental impact associated with alumina production.
  • the proposed method conserves energy, addressing one of the primary challenges of conventional alumina production. Energy-intensive processes often contribute to greenhouse gas emissions and are costly to operate.
  • the present invention offers a promising solution by significantly reducing energy requirements, thus contributing to a more sustainable and cost-effective production process.
  • the present invention represents a significant leap forward in the field of alumina production from different resources. Its ability to produce alumina sustainably, while overcoming the challenges associated with energy-intensive processes, makes it a promising solution for the industry's future.
  • Example 2 This experiment was conducted to assess the influence of treatment & leaching duration on the recovery percentage of alumina from 5 g portions of red mud. Each sample was placed with varying NaOH concentrations, (specifically 0.5 and 1 to NaOH to red mud mass including 10% water). A homogenized mixture was prepared meticulously using a glass rod and spatula to ensure uniform distribution of components.
  • Example 3 The objective of this experiment was to examine the impact of water percentage on the recovery of alumina from 5 g portions of red mud.
  • each sample was placed in nickel crucibles with a NaOH concentration of 100% relative to the weight of red mud, supplemented with no water and 10%, 20%, 30%, 40% water.
  • a homogenized mixture was meticulously prepared.
  • these homogenized mixtures were subjected to low temperature treatment in an oven at varying temperatures, specifically 80, 100, 120, and 140 degrees Celsius, each for a duration of 4 hours.
  • Post-treatment the samples underwent leaching with water in a glass beaker positioned on a hot plate equipped with a magnetic stirrer, maintaining a temperature of 60 degrees Celsius. Following the leaching process, the filtrate was subjected to filtration, accompanied by three rounds of washing with ambient water to eliminate any residual impurities.
  • the resulting residue was dried in an oven, and the subsequent weight was accurately recorded.
  • the recovery percentage of alumina demonstrates an increasing trend with no water to water addition.
  • the disparity in recovery percentages between 10% and 20% water content is minimal, only 1%.
  • the disparity becomes markedly significant when comparing treatment processes with and without water.
  • the alumina recovery percentages at 140°C are 37%, 71.5%, and 72.5% respectively for processes without water, with 10% water, and with 20% water.
  • the recovery decreased further with water addition beyond 20%, yielding 66% and 59.3% recovery for 30% and 40% water addition, respectively.
  • Example 4 5 gm dross was milled in a planetary ball mill with a ball to powder ration of 1:10 for 1 hour to convert the dross to 90 microns. The milled dross was leached with water with 1:2 ratio at 95 °C for 4 hours to dissolve the salt and convert most of the AlN to Al(OH) 3 and ammonia gas. The slurry was filtered, and the solution was evaporated to produce the salt (NaCl+KCl), which is about 0.6 g. After drying, the solid was mixed with NaOH with 1:1 wt ratio in a mortar pestle. Then it was roasted at 80-140 °C for 4 h followed by water leaching at 60 °C for 1 h.
  • Example 5 Each 5 g portion of low-grade iron ore was mixed with varying NaOH concentrations: 0.50, and 1 NaOH to low grade iron ore mass ratio, each comprising 20% water relative to the iron ore weight. A homogenized mixture was prepared Subsequently, these homogenized mixtures underwent low temperature treatment in an oven at different temperature settings (80, 100, and 120 degrees Celsius) for a standardized duration of 4 hours. Following treatment process, the samples were subjected to leaching with water at 80 degrees Celsius. Post-leaching, filtration was carried out followed by three rounds of washing with ambient water to remove any residual sodium aluminate.
  • the resulting residue was then dried in an oven, and the subsequent weight was accurately recorded.
  • the maximum alumina recovery achieved is at both 100 & 120 degrees Celsius, reaching 81% when utilizing 1 NaOH to low grade iron ore mass ratio concentration. Specifically, at 120°C with a 50% NaOH concentration, the alumina recovery stands out at 76%. In contrast, at 100°C, the recovery percentage slightly decreases to 71%. Notably, the recovery percentage appears to increase with a higher concentration of NaOH, particularly evident at 0.5 NaOH to low grade iron ore mass ratio concentration compared to 1 NaOH to low grade iron ore mass ratio. Interestingly, even at a relatively low temperature of 80°C, significant differences in alumina recovery percentages are observed between varying NaOH concentrations.
  • Example 6 Each 5 g portion of low-grade iron ore homogenized with varying NaOH concentrations: 0.5, and 1NaOH to low grade iron ore mass ratio, each comprising 10% water relative to the iron ore weight.
  • these homogenized mixtures underwent treatment in an oven at settings temperature of (140 degrees Celsius) for a standardized duration of 4 hours. Following the treatment process, the samples were subjected to leaching with water at 80 degrees Celsius. Post-leaching, filtration was carried out, followed by three rounds of washing with ambient water to remove any residual sodium aluminate. The resulting residue was then dried in an oven, and the subsequent weight was accurately recorded.
  • the alumina recovery percentage stands at 73%, while at 1 NaOH to low grade iron ore mass ratio concentration, it rises to 79%. Remarkably, these recovery percentages are similar to those observed at 80 degrees Celsius.
  • the present invention applies to all kinds of alumina-containing sources both primary and secondary. This way we can increase alumina production as well as minimize or eliminate the waste generated from mining (overburdens) and metallurgy (tailings, residues, dross). [0046]
  • the present invention is significantly energy efficient since the operating temperature for the process is in the range of 80 – 140°C and no use of pressure is involved.
  • the present invention is free of the use of acids and free of more steps making it easy to control and since the main chemical reagent NaOH is regenerated in this process so making the process more economical and environmentally friendly.
  • the present invention for the production of alumina is indigenous technology which can have significant implications for a society's technological advancement, economic development.
  • the present invention also incurs cost of alumina production that is significantly lower than the conventional route and also no use of expensive vessels or equipment is required.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

Abstract

La présente invention concerne un procédé à basse température de récupération d'alumine à partir de diverses ressources contenant de l'alumine. Le procédé comprend les étapes consistant à traiter une ressource contenant de l'alumine avec de l'hydroxyde de sodium (NaOH) à une basse température prédéfinie en présence d'eau (5 à 50 %), et à lixivier la ressource contenant de l'alumine traitée avec de l'eau chaude pour dissoudre l'aluminate de sodium (NaAlO₂) et produire un lixiviat. Le procédé consiste en outre à provoquer la précipitation d'hydroxyde d'aluminium (Al(OH)3) par réaction du lixiviat avec du CO2 de façon à convertir l'aluminate de sodium (NaAlO₂) en hydroxyde d'aluminium (Al(OH)3). Le procédé comprend la réalisation d'une filtration pour séparer efficacement les résidus solides du lixiviat ; et la réalisation d'une calcination de l'hydroxyde d'aluminium précipité (Al(OH)3) à une température prédéfinie pour obtenir de l'alumine. En outre, la solution de carbonate de sodium est traitée avec de la chaux ou de la chaux éteinte pour régénérer l'hydroxyde de sodium.
PCT/IN2025/050726 2024-05-10 2025-05-08 Procédé à basse température pour la récupération d'alumine à partir de différentes sources Pending WO2025233969A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IN202431037174 2024-05-10
IN202431037174 2024-05-10

Publications (1)

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WO2025233969A1 true WO2025233969A1 (fr) 2025-11-13

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Country Link
WO (1) WO2025233969A1 (fr)

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