CN1132946C

CN1132946C - Noble metal smelting slag wet metallurgical process

Info

Publication number: CN1132946C
Application number: CN00101543A
Authority: CN
Inventors: 韩英东
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-01-11
Filing date: 2000-01-11
Publication date: 2003-12-31
Anticipated expiration: 2020-01-11
Also published as: CN1268580A

Abstract

The present invention relates to a hydrometallurgical technique for noble metal smelting slag, and a chemical metallurgical method for noble metals. The technique of the present invention can extract gold, silver, copper, lead and borax from gold and silver smelting slag and smoke dust by different reagents according to certain sequence in a selection way. The present invention is characterized in that raw materials are crushed and finely ground, and are leached by water, and borax is recovered; the recovered copper is leached by the diluted sulfuric acid; the recovered silver and the lead are leached by nitric acid-ferric nitrate; the gold is recovered from the silver leaching slag by any method, and the residues are discarded. The present invention carries out the leaching process at normal temperature, and each valent component can be respectively recovered and utilized.

Description

Hydrometallurgical process for precious metal smelting slag

The method is a chemical metallurgymethod for recovering gold, silver, copper, lead and borax fluxes from smelting slag (commonly called as 'borax slag') and smoke dust produced in the gold and silver smelting process. In the high-temperature smelting of gold and silver, borax, soda ash, silicon dioxide, fluorite and the like are almost used as slagging fluxes without exception to produce precious metal smelting slag and smoke dust, the main components of the slagging fluxes are decomposition products of the fluxes, base metals such as oxides of copper, lead, zinc, iron and the like, and matte (the main component is Cu)₂S, FeS) toAnd the noble metals gold and silver lost in the alloy due to mechanical impurities. The content of gold and silver in the slag materials fluctuates greatly and is different from several grams to several kilograms per ton, and most of gold and silver exist in the form of silver-gold alloy or alloy formed by the silver and the base metal copper and lead, which causes difficulty for the conventional hydrometallurgy process (such as cyaniding).

For many years, the slag materials are treated by a classical fire process at home and abroad, namely, the slag materials are remelted, molten lead is used as a gold and silver collecting agent, noble lead enriched with gold and silver is obtained through smelting, then the noble lead is subjected to oxidation refining, namely ash blowing operation, and gold and silver are separated and recovered from gold and silver alloy obtained through ash blowing (see south Africa gold metallurgy). The process produces a large amount of lead smoke, seriously pollutes the environment, damages the health of operators, has long production period, causes secondary loss of gold and silver (loss in cupel materials) in the ash blowing process, reduces the direct recovery rate, consumes more fuel and is difficult to recover the added lead.

In addition, according to the gold reported in 1994, 1 st, some foreign factories use fine grinding of slag, mercury mixing, and then return to the cyanidation process. The smelting slag is treated by adopting a gravity separation method, and the defects that the recovery rate of gold and silver is low, particularly, a large amount of silver is difficult to recover, and the obtained gravity separation product is an intermediate product and still needs to be further treated by a smelting plant.

Because gold and silver are mostly present in an alloy state, generally, the ratio of silver to gold in the materials is not less than 10: 1, so that the materials cannot be directly treated by the existing hydrometallurgical processes such as cyanidation, aqueous solution chlorination and the like.

The invention aims to provide a continuously operated hydrometallurgical process for selectively recovering gold, silver, copper, lead and borax fluxes from precious metal smelting slag and smoke dust in a certain sequence, and the process has high gold and silver recovery rate.

It is another object of the present invention to provide a process for recovering silver from a silver-containing material.

The present invention relates to a new hydrometallurgical process for recovering gold, silver, copper, lead and borax flux from noble metal smelting slag and smoke dust. In this process, gold, silver, copper, lead and borax are selectively extracted in a certain order by different reagents. The method is characterized in that smelting slag is firstly crushed and ground, then is leached by water, and borax is recovered from a solution; leaching the water leaching residue with dilute sulfuric acid, and recovering the kettle from the solution; the acid leaching residue is leached out silver by nitric acid-ferric nitrate, which can ensure high yield of gold and silver, and the method is difficult to realize by the prior art. And finally, treating the silver separating residue enriched with gold by using the existing gold extraction method, and recovering the gold in the silver separating residue. The whole process consists of the following procedures:

1. crushing, grinding and sieving the smelting slag, wherein the grinding fineness is less than 20 meshes, preferably 60 to 120 meshes, namely the grain diameter is less than 0.9 mm, preferably 0.28 to 0.125 mm.

2. And (5) soaking in water. And (3) leaching the qualified material by stirring with water at normal temperature, wherein the liquid-solid ratio is 3-5: 1, the time is 1 hour, liquid-solid separation is carried out after leaching is finished, borax flux is recovered from the solution, and the water leaching residue enters an acid leaching process.

3. And (4) leaching with dilute acid. Leaching the water leaching residue at normal temperature by stirring with dilute sulfuric acid with concentration of 10-20 wt% to remove most of acid soluble substances and recover copper in the raw material; further enriching gold and silver. The leaching time is 1-2 hours, the liquid-solid separation is finished after the leaching, copper is recovered from the solution, and the acid leaching residue is treated by a silver separation process.

4. And (4) leaching silver. Leaching the acid leaching residue with a mixed solvent of nitric acid and ferric nitrate to obtain silver and HNO at normal temperature₃Concentration of (2) - (15%), Fe (NO)₃)₃The concentration of the silver is 2-10 percent, the time is 1-2 hours, after the leaching is finished, liquid-solid separation is carried out, silver and lead are recovered from the solution, and the silver leaching residue is sent to the gold recovery process.

5.And (6) recovering gold. The gold in the silver leaching residue can be recovered by any conventional method. The existing method for recovering gold comprises the following steps: 5.1 cyanidation; 5.2 chlorination methods, including aqueous solution chlorination method and chlorination volatilization method; 5.3 aqua regia dissolving-reducing method; 5.4 pyrogenic lead enrichment.

The attached drawing is a process flow chart for treating the smelting slag and the smoke dust produced in the smelting process in the precious metal smelting process.

The invention is described in detail with reference to the attached figures and specific examples. The results of treating gold and silver smelting slag are described below, but the process can also be used for treating the smoke produced in the precious metal smelting process, and other silver-containing materials containing natural silver or silver alloys.

The raw material used by the method is typical borax-silicon oxide binary system smelting slag which contains Au, Ag, Cu, Pb, Fe and SiO₂、B₂O₃、Na₂O, and the like. In the gold cyanide mud smelting process, the alloy gold smelting slag and the crude silver smelting slag are produced, the alloy gold smelting slag and the crude silver smelting slag are preferably mixed, melted and precipitated to obtain a small amount of gold and silver, the operation is called 'slag returning' operation to reduce the grade of the gold and the silver in the slag, because the silver content in the smelting slag for smelting the crude silver is very high, and after the smelting slag is mixed and melted with the alloy gold smelting slag, the melted silver particles have the trapping effect on the gold, so that the loss of the gold in the smelting operation can be reduced, and the obtained precious metal smelting slag is treated by the process.

It has been found that by the method of the invention, finely ground raw materials can be leached with water and dilute acid at ambient temperature to remove more than 90% of impurities, even up to 97%, to which gold and silver are greatly enriched, and the silver is leached with a mixed solvent to separate gold from silver, recovering silver from the solution, and the gold in the leached silver residue is recovered by any of the methods known in the art.

As shown in the attached drawing, the precious metal smelting slag is firstly crushed, and various ore crushing equipment such as jaw crushing can be selected; the grinding equipment can be ball mill, rod mill or gravel mill, and the grinding fineness is 20-120 meshes, namely the grain diameter is 0.125-0.9 mm. It is noted that, in the grinding, the particle size of the nonmetallic minerals becomes small, while the particle size of metals such as gold, silver and alloys thereof becomes large and flakes are formed, and therefore, the coarse particles of gold and silver in the slag can be recovered by a simple grinding and screening process. Tests prove that after the 20-mesh sieve is subjected to water leaching and acid leaching, about 63 percent of the-200-mesh sieve is used, so that the subsequent gold and silver leaching is facilitated.

The screened fine materials are stirred and leached by water at normal temperature, the liquid-solid ratio is 3-5: 1, the time is 1 hour, the leaching is finished, the fine materials are filtered in a centrifuge, the filtrate is further processed to produce borax fluxing agent, and the borax fluxing agent can be directly used as fluxing agent for smelting noble metals or sold as products. In the process, most of the water soluble matters in the raw materials are dissolved, the precious metals of metal, silver and valuable metals of copper and lead are enriched for the first time, and the water leaching slag is about 20-30% of the raw materials.

It is known that the base metal oxides and copper matte in the slag can be dissolved out with various mineral acids, where sulfuric acid is used, which has the advantage of being very cheap and even directly using the low-concentration waste acid discharged from the acid plant of the nonferrous smelting plant. The purpose of dilute sulphuric acid leaching is to remove most of the acid-soluble impurities, including the ice kettle, to destroy the original structure, to fully dissociate gold and silver, and to recover copper. The acid leaching slag is about 3-7% of the raw material, gold and silver are enriched for the second time, and the subsequent material processing amount and workload are greatly reduced. In order to accelerate the reaction speed and improve the leaching rate of copper during acid leaching, ammonium nitrate can be added into the leaching solution, and the concentration of the ammonium nitrate is not lower than 30 g/L. Leaching with 10-20% sulfuric acid at a liquid-solid ratio of 3-6: 1, mechanically stirring at normal temperature for 1-2 hr, filtering, recovering copper from the filtrate, and treating the acid leaching residue in silver separating process. It is worth noting that when dilute acid is leached, the silicon oxide in the raw material can be partially dissolved to generate silicic acid, and the silicon oxide is in a colloid state along with the increase of the pH value of the solution, so that slurry is thickened, and the filtration is influenced. During leaching, the concentration of acid is controlled to ensure that the silicon oxide is dissolved out as little as possible and prevent colloidal slurry. The optimum concentration of sulfuric acid in the leachate is determined by the solid content in the pulp and the content of various impurities, and the theoretical amount required for the reaction of the excess amount of sulfuric acid with various compounds and metal impurities in the raw materials is ensured.

After the acid leaching is finished, the filter residue is stirred at normal temperature by nitric acid-ferric nitrate to leach silver. As mentioned above, silver in the slag forms an alloy with gold, copper and lead, so that the effect of leaching silver with nitric acid alone is poor, while ferric nitrate is a good solvent for silver and can dissolve other base metal impurities, and the reaction formula is:

the added nitric acid also takes part in the reaction and can adjust the pH value of the solution to prevent the ferric iron from being hydrolyzed. The concentration of nitric acid is 2-15%, the concentration of ferric nitrate is 2-10%, liquid-solid ratio is 2-3: 1, leaching time is 1-2 hr, and silver leaching process can be implemented at normal temp., preferably at 50-80 deg.C. The mixed solvent of nitric acid and ferric nitrate can ensure high leaching rate of silver, which is unique to the process of the invention. And after leaching, liquid-solid separation is finished, silver and lead are recovered from the filtrate, and filter residue is sent to a gold extraction process for treatment.

The gold in the silver separating slag can be recovered by any conventional method. The existing method for recovering gold comprises the following steps: 1) a cyanidation process; 2) chlorination processes, including aqueous chlorination and chlorination volatilization; 3) aqua regia dissolving-reducing method; 4) pyrogenic lead enrichment.

And (4) selecting a proper solvent for secondary treatment to recover residual gold and silver from the residues after gold recovery according to the content of gold and silver. The final residue was discarded.

The process has the obvious advantages that according to the results of small tests, the leaching rate of gold can reach more than 98 percent, the leaching rate of silver can reach more than 96 percent, and higher leaching rate can be reached after repeated treatment; secondly, valuable components in the raw materials, such as borax, copper, lead and the like, can be comprehensively recovered; the process has the advantage of being more economical, and the method adopts step-by-step leaching to remove impurities, so that the processing ore amount of the precious metal raw material is reduced as much as possible, the dosage of the medicament is reduced, and the processing cost of the precious metal smelting slag raw material is greatly reduced.

The process of the present invention is illustrated in detail by the following examples, but the present invention is not limited thereto.

Example one

A sample of precious metal slag containing 156 g/ton gold and 1700 g/ton silver was crushed by a jaw crusher, grinding in a rod mill, sieving through a 60 mesh sieve, in a test series consisting of 5 leaching processes, each sample is 500 g, the mixture is stirred and leached by water at normal temperature according to the weight ratio of liquid-solid ratio of 3: 1 which is more than the weight ratio, the rotating speed of a stirrer is 360 revolutions per minute, the time is 1 hour, filtering after water leaching, leaching filter residue with 15% (weight) dilute sulfuric acid under stirring at normal temperature at a stirring speed of 360 r/min and a liquid-solid ratio of 6: 1 for 1 hour, filtering, washing, drying and weighing, calculating the acid leaching residue to be 3.2 percent of the raw material, leaching the silver of the acid leaching residue by using 5 percent nitric acid-8 percent ferric nitrate, wherein the liquid-solid ratio is 2: 1, the time is 2hours, and finally, filtering and washing, recovering silver and lead from the filtrate, and enabling filter residues to enter a gold recovery process. Recovering gold from the gold by an aqueous solution chlorination method, wherein the operating conditions of the aqueous solution chlorination method are as follows: the dosage of sodium chlorate is 20 percent of the feeding amount, the liquid-solid ratio is 3: 1, the temperature is 85 to 90 ℃, the time is 4 hours, the concentration of hydrochloric acid is 3N, and the concentration of sodium chloride is 80 g/L. The following technical indexes are obtained: the gold leaching rate is 98.3 percent, and the silver leaching rate is 97.5 percent. And finally, carrying out secondary treatment on the residue to recover residual gold and silver, and then discarding the residual gold and silver.

Example two

The precious metal slag sample contained 35 g/ton gold and 387 g/ton silver, and the test procedure was the same as in example one. The concentration of sulfuric acid is 20 percent during acid leaching, the liquid-solid ratio is 4: 1, silver leaching residue is leached by 3 percent nitric acid-5 percent ferric nitrate, the liquid-solid ratio is 2: 1, the time is 1 hour, the leaching is finished, the filtration and the washing are finished, silver is recovered from filtrate, the silver leaching residue is heated and dissolved by 1: 1 (volume ratio) of dilute aqua regia, and the obtained technical indexes are as follows: the gold leaching rate is 99 percent, and the silver leaching rate is 98 percent.

Claims

1. A hydrometallurgical process for recovering gold, silver, copper, lead and borax fluxes from precious metal smelting slag and smoke dust comprises fine grinding of raw materials and fractional leaching by adopting proper solvents to separate and recover gold, silver and valuable components, and is characterized in that: 1.1 crushing, grinding and screening the smelting slag; 1.2 mixing the sieved material and the smoke dust, then carrying out water leaching operation at normal temperature and filtering, wherein the liquid-solid weight ratio is 3-5: 1, and recovering borax from the filtrate; 1.3 leaching the water leached filter cake with a dilute sulfuric acid solution at normal temperature, wherein the weight percentage concentration of sulfuric acid in the solution is 10-20%, and the solid-to-solid weight ratio of the leaching solution is 3-6: 1; 1.4 leaching the acid leaching residue by using a diluted nitric acid-ferric nitrate mixed solvent at normal temperature or in a heating state, filtering, wherein the weight percentage concentration of nitric acid and ferric nitrate in the mixed solvent is 2-15% and 2-10%, the solid-to-solid weight ratio of a leaching solution is 1-2: 1, and recovering silver and lead from the filtrate; 1.5 the silver leaching residue is used for recovering the gold in the silver leaching residue by any one of the existing methods.

2. As set forth in claim 1, the raw material of the noble metal slag is a silver-containing material in which the natural silver, silver oxide or silver alloy state of silver is present, such as a gold-containing slag produced in a gold or silver smelting process, a raw silver slag, or a slag, soot and silver produced by melting a mixture of the two.

3. As set forth in claim 1, the slag has a fineness of less than 0.9 mm.

4. The method according to claim 1, wherein the molten slag has a fineness of 0.125 to 0.28 mm.

5. As described in claim 1, the time of three liquid-solid leaching operations is 1 to 2 hours, respectively.

6. As described in claim 1, the existing methods for gold recovery are: a cyanidation process; chlorination processes, including aqueous chlorination and chlorination volatilization; aqua regia dissolving-reducing method; pyrogenic lead enrichment.