RU2244760C1 - Method for metal recovery from technologically proof raw materials - Google Patents

Abstract

FIELD: metal recovery, in particular noble metals from technologically proof raw materials.

SUBSTANCE: method includes raw grinding to 0.2 mm; blending with batch containing halogen salts and/or oxygen-containing salts, and mixture opening: cake cooling, leaching with simultaneous reaction pulp agitation with hot water, and metal recovery from solution and insoluble residue. Opening is carried out in electrical furnace at 100-120^oC preferably at redox potential of 1.8-2.6 V, by elevating of temperature up to 450-560^oC at rate of 8-10^oC/min and holding for 1-7 h at highest mixture redox potential. Opened and cooled cake is grinded and leached in opened agitator.

EFFECT: environmentally friendly method with increased yield; utilization of unconventional noble and non-iron metal sources.

1 cl, 2 tbl

Description

The invention relates to the metallurgy of non-ferrous and rare metals, physically and chemically strongly associated with natural or man-made raw materials. In particular, it relates to methods for the extraction of metals from technologically refractory raw materials, especially precious metals.

The closest in technical essence to the claimed is a method of extracting metals from technologically resistant raw materials (RU 2113526 C1, publ. 06/20/1998). In the known method, the ore and (or) its concentrate are heat treated in the presence of a reagent of aqueous magnesium chlorides. The blending of crushed ore and (or) its concentrate with a reagent is carried out in a certain ratio, and heat treatment at 400-600 ° C for 20-40 minutes.

The disadvantages of this method include the insufficiently high degree of metal extraction.

The objective of the invention is the creation of a thermoelectrochemical technological process for the opening of raw materials to increase the recovery rate and profitability of the production of precious metals, reduce costs, reduce harmful emissions into the environment, increase reserves, and hence capitalize minerals, involve unprofitable and non-traditional sources of noble and non-ferrous metals.

The problem is solved in that the method of extracting metals from technologically resistant raw materials includes grinding the raw materials, mixing with the mixture from the salts and opening the mixture in an electric furnace when heated, cooling the cake, leaching it with stirring the reaction pulp with hot water, separating the solution from the undissolved part and extracting metals from the solution and undissolved part, while the grinding of the feedstock is carried out to -0.2 mm, mixing is carried out with a mixture of salts of halides and / or oxygen-containing salts, the remainder of which is calculated based on the chemical and mineralogical composition of the feedstock, the autopsy is carried out by placing the mixture in an electric furnace at a temperature of 100-120 ° C, setting at a speed of 8-10 ° C per minute in an automatic mode of temperature 450-560 ° C and holding for 1-7 hours at the maximum redox potential of the mixture obtained by opening and cooling the cake is crushed and leaching is carried out in an open propaganda apparatus.

It is advisable that the redox potential of the mixture was 1.8-2.6 V, the autopsy was carried out when oxygen was supplied, and the gases, steam and dust that were discharged during the autopsy from the furnace were captured by bubblers with the extraction of easily sublimated noble metal compounds.

It is advisable that when opening a magnetic field was created, and the cake was ground to -0.1 mm.

Preferably, when the leaching is observed, the ratio of the cake and the volume of the capacity of the agitation apparatus is 3:10.

Preferably, the temperature of the hot water is 80-90 ° C, and the ratio of cake to water is 1: (2-3), the pH of the pulp during leaching was in the range of 1-2, which is achieved by a rush of hydrochloric or sulfuric acid.

It is also advisable when the solution is separated from the insoluble part by filtration at a temperature of 40-60 ° C and noble and non-ferrous metals are separated from them, and after their separation from the solution, halide salts are recovered, which are reused for the preparation of a new portion of the charge.

Existing methods do not always achieve the full opening of the resistant part of the ore matrix. And so part of the noble metals is irretrievably lost. For example, during oxidative firing, the autopsy is not ensured, and it can also lead to the loss of noble metals with dust, gases, and vapors. Hydrometallurgical and pyrometallurgical processes do not provide a sufficient level of electrochemical reduction potential and do not transform most components of refractory ore components.

When recovering such components of the matrix of raw materials as oxides of silicon, aluminum, manganese, magnesium, various carbon compounds, it is necessary to have an oxidizing potential in the range of 1.3-2.6 V. For example, the gold-aluminum complex has a reduction potential of 1.3 V, with titanium - 1.9 V, with silicon - 2.6 V.

However, cyanidation achieves - 0.9 V, hypochlorite - 1.3 V, lead litharge - 1.69 V. These values of oxidation potentials do not provide complete opening of the ore and, accordingly, the completeness of extraction of precious metals included in such components.

The invention uses the properties of molten electrolytes.

The electrolyte is selected from the following compositions: KCl - NaCl, KCl - NaCl - MgCl ₂ , KCl - NaCl - ZnCl ₂ , KCl - NaCl - FeCl ₃ , LiCl - KCl, KCl - NaCl - CaCl ₂ , other halides or oxygen-containing salts.

The melting point of eutectic mixtures in two- and three-component systems should be in the range of 300 - 450 ° C.

For example, the most low-melting MgCl ₂ - KCl mixtures melt at a temperature of ≈ 425 ° C. Adding NaCI to the mixture, we obtain a mixture that already has a melting point of 396 ° C. The electrical conductivity of this ternary mixture at 500 ° C is from 1.3 to 1.9 Ohm ^-1 cm ^-1 . It increases with increasing NaCl and decreases with increasing MgCl ₂ .

в расплавленных галогенидах должны быть выбраны таким образом, чтобы они были достаточны для термоэлектрохимического вскрытия сырья и были в пределах от 1,8 до 2,6 В.Conditional Standard Potentials

in molten halides should be selected so that they are sufficient for thermoelectrochemical opening of raw materials and were in the range from 1.8 to 2.6 V.

Electrochemical series of metals in molten NaCl-KCl media; NaCl-KCl-MgCl ₂ ; LiCl-KCl (see table 1)

Table 1 Solvents Temperature ° С NaCl-KCl 700 Mg, Th, U, Mn, Hf, Al, Zr, Ti, Zn, Tb, Cr, Gd, Fe, Pb, Sn, Co, Cn, Ni, Ag, Pd, Pt, Au. NaCl-KCl-MgClz 450 Na, Be, Al, Mn, Zn, Cd, Fe, Pb, Cr, Sn, Co, Ni, Ag, Cu, Pd, Pt, Au. LiCl-KCl 450 Li, La, Nb, Ce, Gd, Mg, Th, Sc, Hf, Mn, U, Zr, Al, Be, Ta, Ti, Zn, Te, W, Cd, Mo, V, Ga, In, Co, Ni, Ag, Sb, Bi, Hg, Cu, Pd, Pt.

Electrochemical series of metals in molten media make it possible to judge the sequence of their separation from molten electrolytes.

In ionic melts, oxidation and reduction processes occur in various salt mixtures - solvents. The highest electrode potentials of metals in the molten eutectic LiCl-KCl mixture at 450 ° C are lithium, magnesium, aluminum, uranium, manganese, and zinc.

All electrochemical processes are heterogeneous processes occurring at the separation of two phases. Such two-phase systems are called electrodes. They are solid or liquid materials with electronic conductivity of a metallic or semiconductor nature, which are in direct contact with liquid or solid electrolytes having ionic conductivity. The thermoelectrochemical process taking place in an electric furnace represents, as it were, unfolded halves of redox reactions: either only reduction (at the cathode) or oxidation (at the anode).

The role of the reducing agent (electron donor) or oxidizing agent (acceptor) is an electric current passing through the electrode. In this case, either the ionization of the substance at the electrode (for example, metal at the anode or chlorine at the cathode) or the discharge or recharge of ions in the electrolyte occurs. In the absence of an external current on the electrode, a dynamic equilibrium is established between simultaneously running mutually opposite oxidation and reduction processes:

Me↔ Me $\genfrac{}{}{0ex}{}{\text{n +}}{\text{(spread)}}$ + ne ^-

At high temperatures, in the ion exchange between halide melts and metals, ions of not one but two different valencies participate in commensurate quantities:

Me↔ xMe $\genfrac{}{}{0ex}{}{\text{m +}}{\text{(spread)}}$ + (1-x) Me $\genfrac{}{}{0ex}{}{\text{n +}}{\text{(spread)}}$ + [xm + (1-x) n] e ^-

The ratio of the concentrations of the lowest and highest valencies (n> m), passing into the electrolyte, satisfies the reaction equilibrium condition:

Me $\genfrac{}{}{0ex}{}{\text{n +}}{\text{(spread)}}$ + [(nm) / m] Me↔ (n / m) Me $\genfrac{}{}{0ex}{}{\text{m +}}{\text{(spread)}}$

The metals that make up the alloy of which the electrode is made exchange their ions with the electrolyte. In this case, to each electrode composition at equilibrium there corresponds a strictly defined ratio of cation activities in the salt melt.

So, for example, chlorine adsorbed on a lining exchanges its ions with an electrolyte:

Cl _(hell) + e ^- ↔ Cl $\genfrac{}{}{0ex}{}{\text{-}}{\text{(spread)}}$

In a medium of molten halides at high temperatures, the materials of the electrodes that would be directly involved in the electrode reactions can be sulfides, silicides, borides, hydrides, and other compounds that make up the raw material matrix with sufficiently high electronic conductivity.

If the electrolyte in the dissolved state simultaneously contains both the oxidized and reduced forms, then reactions occur on any electrode with electronic conductivity immersed in it

Me $\genfrac{}{}{0ex}{}{\text{n +}}{\text{2 (spread)}}$ + (nm) e ^- ↔ Me $\genfrac{}{}{0ex}{}{\text{m +}}{\text{(spread)}}$

Cl _{2 (spread)} + 2e ^- ↔ 2Cl $\genfrac{}{}{0ex}{}{\text{-}}{\text{(spread)}}$

Na $\genfrac{}{}{0ex}{}{\text{+}}{\text{2 (spread)}}$ ↔ Na $\genfrac{}{}{0ex}{}{\text{+}}{\text{(spread)}}$ + e ^-

Here, at the electrode-electrolyte interface, a jump in the electric potential occurs, which is called the redox or redox potential of the system Me ^{n +} / Me ^{m +} , Cl ₂ / Cl, Na ⁺ / Na $\genfrac{}{}{0ex}{}{\text{+}}{\text{2}}$ etc. He is equal

,

,

The redox potential in halide melts is determined by the state of the oxidized and reduced forms of chemical elements.

The potential of any metal electrode with respect to its ions upon reaching equilibrium becomes equal to the redox potential of the surrounding electrolyte. Therefore, during the establishment of the equilibrium potential, metals restore the oxidized forms of the electrolyte, in particular, their ions of higher valency, i.e. dissolve or, as they say, correlate. The equilibrium potential of a metal electrode exchanging cations of different valencies (M ^{m +} and M ^{n +} ) with a halide melt satisfies the equality:

where α is the equilibrium activity of these ions in the electrolyte.

From this it follows that between the formal redox potential of the system of ions M ^{m +} / M ^{n +} and the standard electrode potential of the metal with respect to these ions, there is a relation

The interaction of metals with ionic melts occurs spontaneously due to the dissolution of metals in these environments.

Two types of corrosion occur in ionic melts: chemical and electrochemical.

Chemical corrosion occurs due to:

- Interactions of metals with galloids with the formation of halides;

- Interactions of metals with oxygen dissolved in the ionic melt and oxygen in the air due to the dissolution of new portions of oxygen in the ionic melt;

- Thermal decomposition of oxygen-containing salts;

- Water dissolved in an ionic melt.

Electrochemical corrosion depends on the properties of the metal and ion melt. In halide melts, oxidizing agents can be metal ions, including alkaline ones, which are capable of passing into subions. In this case, metal corrosion can be expressed by the following reaction:

Me + 4Na ⁺ = Me ²⁺ + 2Na $\genfrac{}{}{0ex}{}{\text{+}}{\text{2}}$

at the cathode 4Na ⁺ + 2e → 2Na $\genfrac{}{}{0ex}{}{\text{+}}{\text{2}}$

on the anode Me → Me ²⁺ +2 e

In such a melt, the redox potential is established

where Me is an alkali metal (Li, Na, K, etc.).

At the first moment after immersion of a metal (Ti, Cu, Fe, Ni, Pt, Co, Au, Pd, Ag, etc.) in a salt melt, while the equilibrium has not yet been established, the metal potential has a more negative value than the redox potential of the medium . Therefore, alkali metal ions are reduced to subions due to the oxidation (dissolution) of the metal immersed in the melt, i.e. there is a corrosion process.

As ions of a dissolving metal accumulate in the electrode layer, its electrode potential shifts toward more positive values. At the same time, the value of the redox potential shifts toward more negative values. When both potentials become equal, balance will come. Further, metal corrosion continues at a constant rate due to diffusion. Electrochemical corrosion contributes to the presence of water. Hydrogen ions, as well as alkali metal ions, can be considered as oxidizing agents.

Some metals exchange ions of not one but several valencies with molten salts. Such a salt melt can interact with ions of more electropositive metals with which the correlating metal forms alloys.

Below are the results of technological testing of samples by thermoelectrochemical method. The experiments were carried out on samples of at least 100 g (table 2)

1. Standard samples of copper-nickel ores and their tailings were taken:

table 2 Samples G / t Au Pt Pd Rh Ore №1 Passport Content 0.1 1,1 4.9 0.5 Extracted in a new way 0.557 2.1 8.45 0.88 Ore №1 Passport Content 0.18 1,02 3.6 0.18 Extracted in a new way 0.276 0.724 9,588 0,092 Tails Passport Content 0,039 0.493 0.847 0,078 Extracted in a new way 0.155 1,648 3,335 0,076

In addition to precious metals, more than 90% of copper, nickel, cobalt, 76-81% of sulfur are converted into a solution. In total, 70 elements passed into the solutions, including 14 lanthanides, uranium, and thorium.

2. A sample was taken with a total copper content of 1.86, Fe ₂ O ₃ - 4.05, SiO ₂ - 67.88, Al ₂ O ₃ - 10.35, MgO - 6.36, CaO - 1.32, K ₂ O - 2.90, Na ₂ O - 2.67. Silver is determined - 14.59 g / t, gold - 0.27 g / t.

The sample was processed by thermoelectrochemical method. From water-acid leaching extracted: 91% copper; 21.1 g / t silver; 0.93 g / t gold.

3. Samples were taken from the tailings of the metallurgical mining and processing enterprise with the content of components in%: TiO ₂ - 0.79, Fe - 6.29, V ₂ O ₅ - 0.049, SiO ₂ - 46.90, Al ₂ O ₃ - 7.55, CaO - 19.4, MgO - 13.6 . The content of noble metals in g / t: Au <0.1, Ag = 10-20, Pt = 0.03-0.1, Pd = 0.1-0.05.

Samples were mixed with the charge and subjected to thermoelectrochemical processing. Extracted: 0.3-0.4 g / t of gold, 0.9-1.025 g / t of platinum, 0.35-0.4 g / t of palladium, 0.176-0.190 g / t of rhodium.

The technical result of the invention:

- noble, non-ferrous metals and other elements are comprehensively extracted, more than 70 elements in total, including lanthanides, uranium, thorium;

- precious metals are extracted into a marketable product that is 1.5-10 times or more higher than the initial content;

- useful components are extracted from sulfide, pirate, pyrite, clay, granite, black shale and other refractory ores and anthropogenic raw materials - tailings of GOKs, clinker of zinc production, ashes of coal and oil shale, ephels, etc .;

- used in the analysis when determining the content of precious metals in geological prospecting, geological and other works, when approving and reapproving the reserves of mineral deposits;

- reduces harmful emissions into the environment;

- reduces energy consumption, especially in the production of non-ferrous metals;

- reduces the unit investment for the production of a unit of output.

Claims (11)

1. The method of extracting metals from technologically resistant raw materials, including grinding the raw materials, mixing with a mixture of salts and opening the mixture in an electric furnace when heated, cooling the cake, leaching it with stirring the reaction pulp with hot water, separating the solution from the undissolved part and extracting metals from the solution and undissolved part, characterized in that the grinding of the feedstock is carried out to -0.2 mm, mixing is carried out with a mixture of salts of halides and / or oxygen-containing salts, the composition of which is calculated According to the chemical and mineralogical composition of the feedstock, autopsy is carried out by placing the mixture in an electric furnace at a temperature of 100-120 ° C, setting at a speed of 8-10 ° C per minute in automatic mode, the temperature is 450-560 ° C and holding for 1 -7 hours at the maximum redox potential of the mixture obtained by opening and cooling the cake is crushed and leaching is carried out in an open propaganda apparatus. 2. The method according to claim 1, characterized in that the redox potential of the mixture is 1.8-2.6 V. 3. The method according to claim 1, characterized in that the autopsy is carried out when oxygen is supplied. 4. The method according to claim 1, characterized in that the exhaust gases from the furnace, gases and steam and dust are captured by bubblers with the extraction of easily sublimated noble metal compounds from them. 5. The method according to claim 1, characterized in that upon opening they create a magnetic field. 6. The method according to claim 1, characterized in that the cake is crushed to -0.1 mm 7. The method according to claim 6, characterized in that when leaching, the ratio of the cake to the capacity of the agitation apparatus is maintained at 3:10. 8. The method according to claim 1, characterized in that the temperature of the hot water is 80-90 ° C, and the ratio of cake to water is 1: (2-3). 9. The method according to claim 8, characterized in that the pH of the pulp during leaching is in the range of 1-2, which is achieved by a rush of hydrochloric or sulfuric acid. 10. The method according to claim 1, characterized in that the separation of the solution from the insoluble part is carried out by filtration at a temperature of 40-60 ° C and separate from them noble and non-ferrous metals. 11. The method according to claim 10, characterized in that after the separation of these metals from the solution, the halide salts are recovered, which are reused for the preparation of a new portion of the charge.