Treatment method of gold reduction post-solution

Abstract

The invention belongs to the field of smelting, and particularly relates to a method for treating an intermediate product after-gold-reduction liquid in the copper anode slime treatment process, the volume of the after-gold-reduction liquid is greatly reduced while the after-gold-reduction liquid is subjected to concentration treatment and hydrochloric acid recovery, the technological process for recovering platinum and palladium in the after-gold-reduction liquid is shortened, and the working efficiency is improved. When platinum and palladium are precipitated in the concentrated solution, silver can be attached to precipitates to be separated out, most of silver and platinum are left in residues together when palladium is dissolved, at the moment, platinum-containing filter residues are leached out with ammonia water to remove silver, it is avoided that silver chloride influences dissolution and filtration of platinum in the subsequent platinum treatment process, and the recovery rate of platinum is increased. According to the treatment scheme of the gold reduced liquid, the process is short, the cost is low, the efficiency is high, the recovery rate of platinum and palladium is increased, and objective economic benefits are brought to smelting enterprises.

Description

Technical Field

[0001] The invention belongs to the field of smelting, and in particular relates to a method for treating an intermediate product, gold-reduced liquid, in a copper anode mud treatment process. Background Art

[0002] The treatment of copper anode mud is a hazardous waste produced during the copper smelting process. It contains a variety of precious metals and the treatment steps are relatively complicated. The treatment process is roughly as follows: copper anode mud decoppering, Kaldo furnace smelting to produce gold-silver alloy, silver electrolysis, production of silver anode mud, gold chlorination, gold reduction, and recovery of platinum and palladium. The waste liquid produced in the "gold reduction" stage is the gold reduction liquid.

[0003] The components in the solution after gold reduction generally include Au: 1-4 mg / L, Ag: 10-100 mg / L, Cu: 400-800 mg / L, Pt: 200-400 mg / L, Pd: 1000-3000 mg / L, and hydrochloric acid: 90-100 g / L.

[0004] In the prior art, the gold reduction liquid is treated by first replacing it with a copper plate at a temperature of 50-60°C for about 16 hours, then adding 6-8 kg of copper powder, and continuously stirring with compressed air to increase the copper replacement reaction rate to produce a platinum-palladium concentrate rich in Au, Ag, Pt, and Pd; the platinum-palladium concentrate is added to 2-4 mol / L hydrochloric acid and heated to 70-80°C, sodium chlorate is added in batches, gold, platinum, and palladium enter the chlorinated liquid, and silver enters the chlorinated slag, and then ammonium chloride is used to precipitate platinum and palladium to generate a mixture of ammonium chloroplatinate and ammonium chloropalladate. After the mixture is slurried with water, ammonia water is added in a stirring state, palladium enters the liquid phase, and platinum remains in the slag, which is called platinum concentrate and is used for platinum extraction; the palladium-containing filtrate is acidified with hydrochloric acid to produce dichlorodiamine palladium precipitate, cooled and filtered, and dichlorodiamine palladium is refined by ammoniation to produce sponge palladium (containing more than 99.9% palladium). The platinum concentrate is slurried with water, and hydrazine hydrate is added to reduce ammonium chloroplatinate to crude platinum. The crude platinum is refined into sponge platinum (containing more than 99.9% platinum) by aqua regia dissolution and ammonium chloride precipitation method.

[0005] The above solutions mainly have the following problems:

[0006] (1) The precious metals in the solution after gold reduction are replaced by copper. The replacement time of copper plate / copper powder is long, but the replacement is still not complete. The solution after copper replacement reduction contains Au 0.05-1mg / L, Ag 2-20mg / L, Pt2-20mg / L, and Pd 2-10mg / L, causing the precious metals to move back into the wastewater treatment system and dispersed and lost;

[0007] (2) Using copper to replace the precious metals in the gold reduction solution to produce platinum-palladium concentrate, and then chlorinating the platinum-palladium concentrate with sodium chlorate to allow the platinum-palladium to enter the solution for platinum-palladium refining, resulting in a waste of copper plates, copper powder, and sodium chlorate;

[0008] (3) The copper plate / copper powder is oxidized and enters the solution, which is neutralized with sodium hydroxide and the copper is recovered as copper hydroxide. This causes the copper hydroxide to be further refined into metallic copper, which also results in a waste of sodium hydroxide;

[0009] (4) The hydrochloric acid in the solution after gold reduction is not recycled, and sodium hydroxide is consumed in the sodium hydroxide and copper precipitation process, resulting in a waste of hydrochloric acid and sodium hydroxide;

[0010] (5) The precious metals in the liquid after gold reduction are replaced by copper to produce platinum-palladium concentrate, which is then chlorinated with sodium chlorate to allow platinum-palladium to enter the solution for platinum-palladium refining. The process for recovering platinum-palladium from the liquid after gold reduction is long and labor-intensive for workers.

[0011] Therefore, optimizing the processing flow of gold reduction liquid, improving processing efficiency, increasing the recovery rate of precious metal resources, and reducing processing cost investment are the long-term work content that technical personnel are committed to. Summary of the invention

[0012] The purpose of the present invention is to provide a method for treating a gold reduction liquid, which directly concentrates the gold reduction liquid and precipitates platinum and palladium to simplify the treatment process and omit the step of replacing precious metals with copper to avoid difficulties in copper recovery.

[0013] To achieve the above object, the technical solution adopted by the present invention is: a method for treating a gold reduction solution, comprising the following steps:

[0014] (1) The gold reduction solution is heated to 70-100°C for concentration, and the generated volatile gas is recycled into hydrochloric acid through a hydrochloric acid recovery system, and the tail gas is discharged;

[0015] (2) adding ammonium chloride to the concentrated solution obtained in step (1), and performing solid-liquid separation after the reaction to obtain filtrate A1 and residue B1;

[0016] (3) Dissolving the filter residue B1 with aqueous ammonia, filtering to obtain a filtrate A2 and a filter residue B2, acidifying the filtrate A2 with hydrochloric acid to obtain a precipitate of dichlorodiammine palladium, and refining the dichlorodiammine palladium by an ammoniation method to produce sponge palladium; after the filter residue B2 is leached with aqueous ammonia, it is successively reduced with hydrazine hydrate, oxidized with aqua regia, and refined by an ammonium chloride precipitation method to produce sponge platinum.

[0017] The above scheme concentrates the gold reduction liquid, recovers hydrochloric acid, and also greatly reduces the volume of the gold reduction liquid, shortens the process flow of platinum and palladium recovery, and improves work efficiency; when the concentrated liquid precipitates platinum and palladium, silver enters the platinum and palladium slag in the form of silver chloride and silver chloride complex ions, and most of it remains in the slag together with platinum when dissolving palladium. At this time, the platinum-containing filter residue is leached with ammonia water to remove silver, avoiding the silver chloride affecting the dissolution and filtration of platinum in the subsequent platinum treatment process, and improving the recovery rate of platinum. The treatment scheme of the gold reduction liquid of the present invention not only has a short process, low cost, and high efficiency, but also improves the recovery rate of platinum and palladium, bringing objective economic benefits to smelting enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a processing flow chart of the gold reduction liquid in the prior art;

[0019] Figure 2 The present invention is a process flow chart of the gold reduction liquid. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0021] A method for treating a gold reduction solution comprises the following steps:

[0022] (1) The gold reduction solution is heated to 70-100°C for concentration, and the generated volatile gas is recycled into hydrochloric acid through a hydrochloric acid recovery system, and the tail gas is discharged;

[0023] (2) adding ammonium chloride to the concentrated solution obtained in step (1), and performing solid-liquid separation after the reaction to obtain filtrate A1 and filter residue B1;

[0024] (3) Dissolving the filter residue B1 with aqueous ammonia, filtering to obtain a filtrate A2 and a filter residue B2, acidifying the filtrate A2 with hydrochloric acid to obtain a precipitate of dichlorodiammine palladium, and refining the dichlorodiammine palladium by an ammoniation method to produce sponge palladium; after the filter residue B2 is leached with aqueous ammonia, it is successively reduced with hydrazine hydrate, oxidized with aqua regia, and refined by an ammonium chloride precipitation method to produce sponge platinum.

[0025] Specifically, the gold reduction solution contains Au: 1-4 mg / L, Ag: 10-100 mg / L, Cu: 400-800 mg / L, Pt: 200-400 mg / L, Pd: 1000-3000 mg / L, and hydrochloric acid: 90-100 g / L.

[0026] In the step (1), the hydrochloric acid recovery system comprises a graphite tube-in-tube condenser, a jet vacuum unit, and an acid mist purification tower which are connected in sequence, and the treated tail gas is discharged; the liquid after gold reduction is concentrated to 1 / 4 to 1 / 5 of the volume.

[0027] In the step (2), ammonium chloride is added to the concentrated solution at a temperature of 60 to 70° C. to react and generate a mixed precipitate of ammonium chloroplatinate and ammonium chloropalladate.

[0028] In the step (3), the filter residue A is dissolved with ammonia water having a mass concentration of 10% to 15%; the filter residue B is leached with ammonia water having a mass concentration of 5% to 10%, and the solid-liquid ratio of the filter residue B to the ammonia water during leaching is 1:(8-10). The ammonia water and the filter residue B are mixed and stirred at room temperature for 2 to 4 hours. After solid-liquid separation, the filter residue is subjected to a hydrazine hydrate reduction step.

[0029] Take the gold reduction liquid produced during the treatment of copper anode mud in a copper smelting enterprise as an example, where Au: 2.1mg / L, Ag: 55.2mg / L, Cu: 606mg / L, Pt: 318mg / L, Pd: 2250mg / L, hydrochloric acid: 95.2g / L. The gold reduction liquid is treated as follows:

[0030] Comparative Example (Prior Art)

[0031] 1000L of the gold reduction liquid is heated to 50-60°C in a reactor, and after being replaced with a copper plate for about 16 hours, 6-8 kg of copper powder is added, and compressed air is used for continuous stirring to increase the copper replacement reaction rate to produce a platinum-palladium concentrate rich in Au, Ag, Pt, and Pd; the platinum-palladium concentrate is heated to 70-80°C in 3 mol / L hydrochloric acid, and sodium chlorate is added in batches, gold, platinum, and palladium enter the chlorinated liquid, and silver enters the chlorinated slag, and then ammonium chloride is used to precipitate platinum and palladium to generate a mixture of ammonium chloroplatinate and ammonium chloropalladate. After the mixture is put into a reactor and slurried with water, ammonia water is added in a stirring state, palladium enters the liquid phase, and platinum remains in the slag, which is called platinum concentrate and is used for platinum extraction; the palladium-containing filtrate is acidified with hydrochloric acid to produce dichlorodiamine palladium precipitate, cooled and filtered, and dichlorodiamine palladium is refined by ammoniation method to produce sponge palladium 1980g (containing more than 99.9% palladium). Platinum concentrate was slurried with water, and hydrazine hydrate was added to reduce ammonium chloroplatinate to crude platinum. The crude platinum was dissolved and oxidized three times with aqua regia, and then refined into 252g of sponge platinum (containing more than 99.9% platinum) by ammonium chloride precipitation method. The liquid components after replacement were detected: Au 0.08mg / L, Ag 10mg / L, Pt15mg / L, Pd 5mg / L.

[0032] Embodiment (Solution of the present invention)

[0033] 1. Pump 1000L of the gold-reduced liquid into the concentration kettle in batches, heat it to 85°C and keep it constant, and concentrate it to a volume of about 200L. The tail gas is treated once by a graphite tube-and-tube condenser, a jet vacuum unit, and an acid mist purification tower before being discharged. The hydrochloric acid and water vapor in the tail gas are condensed and recovered by a graphite tube-and-tube condenser, enter the dilute hydrochloric acid storage tank, and return to the gold chlorination process of the copper anode mud treatment system for recycling.

[0034] 2. Stop heating the concentration kettle, add 10 kg of ammonium chloride in batches to the obtained concentrated solution at the current temperature (about 60-70°C) to generate a mixed precipitate of ammonium chloroplatinate and ammonium chloropalladate (silver generates silver chloride precipitate), and filter to obtain the mixed precipitate.

[0035] 3. Add 10% ammonia water to the mixed precipitate to dissolve it, palladium enters the solution, and platinum remains in the slag (most of the silver also remains in the slag with the platinum), filter to obtain palladium-containing filtrate and platinum-containing filter residue, acidify the palladium-containing filtrate with hydrochloric acid to produce dichlorodiamine palladium precipitate, and refine the dichlorodiamine palladium by ammoniation method to produce sponge palladium 2095g (containing more than 99.9% palladium);

[0036] The platinum-containing precipitate was stirred at room temperature for 3 hours with 5% ammonia water (solid-liquid ratio 1:10), and silver chloride formed silver ammine complex ions and entered the solution. The platinum-containing precipitate was filtered and successively reduced with hydrazine hydrate, oxidized with aqua regia, and refined with ammonium chloride precipitation to produce 292g of sponge platinum (containing more than 99.9% platinum). The technology for producing sponge palladium and sponge platinum in the prior art is relatively mature and will not be described here.

[0037] The technicians have found in the long-term production practice that in the prior art (comparative example), silver chloride generates elemental silver when reduced by hydrazine hydrate, and elemental silver forms silver chloride when dissolved in aqua regia, which wraps platinum, making platinum difficult to dissolve in aqua regia, resulting in difficulty in dissolving platinum in aqua regia and difficulty in filtering with silver chloride blocking the filter cloth. Therefore, the step of leaching silver with ammonia water is designed. Practice has proved that the filtration time is shortened to 1 / 4, and there is no clogging of the filter cloth.

[0038] In ammonia water, silver chloride forms silver ammine complex ions and enters the solution, further removing silver chloride and silver ammine complex ions in the ammoniation slag, and the silver content in the platinum-containing filter residue is reduced from 5-10% to 0.5-1%. The reaction formula of ammonia water dissolving silver chloride is:

[0039] AgCl+2NH3.H2O=Ag(NH3)2Cl+2H2O

[0040] Silver chloride hydrazine hydrate reduction reaction formula:

[0041] 4AgCl+5N2H4·H2O=4Ag+4N2H5Cl+N2↑+5H2O

[0042] Silver ammine ion hydrazine hydrate reduction reaction formula:

[0043] 4Ag(NH3)2Cl+5N2H4.H2O+3H2O→4Ag+4N2H5Cl+8NH3.H2O+N2↑

[0044] Reaction formula of silver dissolving in aqua regia:

[0045] Ag+HNO3+HCl=AgCl+NO2+H2O, AgCl is insoluble in aqua regia

[0046] The reaction formula of platinum dissolving in aqua regia:

[0047] 3Pt+4HNO3+18HCl=3H2[PtCl6]+4NO↑+8H2O

[0048] After adding the ammonia leaching and washing process for the ammoniated slag, the primary dissolution rate of platinum in aqua regia increased from 50% to 98%.

[0049] The beneficial effects of the present invention are as follows: it avoids the waste of copper plates, copper powder and sodium chlorate caused by replacing precious metals in the liquid after gold reduction to produce platinum-palladium concentrate, and then chlorinating the platinum-palladium concentrate with sodium chlorate to allow platinum-palladium to enter the solution for platinum-palladium refining. The problem of copper recovery caused by copper replacement into the solution is avoided. The volatilized hydrochloric acid is condensed and returned to the gold chlorination for repeated recycling. The silver in the ammoniation slag is removed by leaching with ammonia water, which reduces the number of platinum dissolving processes in aqua regia due to platinum wrapped with silver chloride. After the concentrated solution is refined with the ammonium chloroplatinate and ammonium chloropalladate mixture produced by ammonium chloride precipitation, the main grades of sponge palladium and sponge platinum reach more than 99.9%. The present invention simplifies the process of recovering platinum-palladium from the liquid after gold reduction, improves the recovery rate of platinum-palladium and reduces the waste of auxiliary material resources.

Claims

1. A method for treating a gold reduction solution, comprising the following steps: (1) The gold reduction solution is heated to 70-100°C for concentration, and the generated volatile gas is recycled into hydrochloric acid through a hydrochloric acid recovery system, and the tail gas is discharged; (2) adding ammonium chloride to the concentrated solution obtained in step (1), and performing solid-liquid separation after the reaction to obtain filtrate A1 and filter residue B1; (3) Dissolving the filter residue B1 with aqueous ammonia, filtering to obtain a filtrate A2 and a filter residue B2, acidifying the filtrate A2 with hydrochloric acid to obtain a precipitate of dichlorodiammine palladium, and refining the dichlorodiammine palladium by an ammoniation method to produce sponge palladium; after the filter residue B2 is leached with aqueous ammonia, it is successively reduced with hydrazine hydrate, oxidized with aqua regia, and refined by an ammonium chloride precipitation method to produce sponge platinum.

2. The method for treating the gold reduction liquid according to claim 1, characterized in that: The gold reduction solution contains Au: 1-4 mg / L, Ag: 10-100 mg / L, Cu: 400-800 mg / L, Pt: 200-400 mg / L, Pd: 1000-3000 mg / L, and hydrochloric acid: 90-100 g / L.

3. The method for treating the gold reduction liquid according to claim 1, characterized in that: In the step (1), the hydrochloric acid recovery system includes a graphite tube-in-tube condenser, a jet vacuum unit, and an acid mist purification tower which are connected in sequence, and the treated tail gas is discharged.

4. The method for treating the gold-reduced liquid according to claim 1, characterized in that: In the step (1), the liquid after gold reduction is concentrated to 1 / 4 to 1 / 5 of its volume.

5. The method for treating the gold-reduced liquid according to claim 1, characterized in that: In the step (2), ammonium chloride is added to the concentrated solution at a temperature of 60 to 70° C. to react and generate a mixed precipitate of ammonium chloroplatinate and ammonium chloropalladate.

6. The method for treating the gold-reduced liquid according to claim 1, characterized in that: In the step (3), the filter residue B1 is dissolved with aqueous ammonia having a mass concentration of 10% to 15%.

7. The method for treating gold-reduced liquid according to claim 1, characterized in that: In the step (3), the filter residue B2 is leached with ammonia water having a mass concentration of 5 to 10%, and the solid-liquid ratio of the filter residue B2 to the ammonia water is 1:(8-10) during the leaching. The ammonia water and the filter residue B2 are mixed and stirred at room temperature for 2 to 4 hours. After the solid-liquid separation, the filter residue is subjected to a hydrazine hydrate reduction step.

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