Method for recovering gold, silver, platinum and palladium from chelating agent precipitation precious metal residues

Abstract

The invention relates to a method for recovering gold, silver, platinum and palladium from chelating agent precipitated noble metal slag, which specifically comprises the following steps of: reducing the noble metal slag precipitated by using a chelating agent into simple substance alloy by using a reducing agent by using a medium-frequency reduction roasting method; the alloy is put into a vacuum furnace, specific temperature and negative pressure are set, and effective separation of gold, platinum, palladium and silver is achieved; the obtained gold-platinum-palladium alloy is dissolved with aqua regia, and gold, platinum and palladium are recycled step by step; and casting the anode plate with the silver alloy to produce a 1 # silver ingot. According to the method, for the gold-platinum-palladium material with the high silver content, phase conversion of gold, silver, platinum and palladium in the material is achieved through reduction roasting, then separation of silver from gold, platinum and palladium is achieved through a vacuum separation method, and the process has the advantages of being easy to operate, high in precious metal recovery rate, little in waste water generation, little in nitric oxide generation and low in production cost; the popularization and application prospects are good.

Description

Technical Field

[0001] The present invention belongs to the technical field of smelting processes, and particularly relates to a method for recovering gold, silver, platinum, and palladium from precious metal slag precipitated by chelating agents. Background Art

[0002] In the production of precious metal smelting enterprises for recovering precious metals (mainly platinum group metals such as platinum and palladium), chelating agents are added to nitric acid leaching solutions or aqua regia solutions to achieve the recovery of platinum group metals. These chelating agents include sodium sulfide, butyl xanthate, dimethylglyoxime, etc. For the precious metal slag precipitated by chelation, the common treatment methods are usually divided into two types: one is to directly treat the enriched precious metal slag with aqua regia; the other is to put the precious metal slag material into a calcination furnace for calcination, and then crush the obtained material for nitric acid leaching or aqua regia leaching to achieve the recovery of precious metals.

[0003] Currently, the main problems in treating precious metal slag precipitated by chelating agents are as follows: (1) When directly using aqua regia, the leaching rate of precious metals is not high, and multiple aqua regia treatments are required, increasing production costs and the generation of nitrogen oxides; (2) Although the slag produced by the calcination method has a high leaching rate, there are mainly problems such as the oxidation and volatilization of precious metals during the calcination process and the entrainment in the separation of silver and palladium by nitric acid leaching, and the amount of nitrogen oxides generated during the leaching process is relatively large, increasing the waste gas treatment cost. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for recovering gold, silver, platinum, and palladium from precious metal slag precipitated by chelating agents. Using the precious metal slag precipitated by chelating agents as the recovery object, through reduction roasting - vacuum separation - aqua regia dissolution - stepwise recovery, the effective separation and recovery of precious metals are realized.

[0005] The technical solution of the present invention is realized as follows: A method for recovering gold, silver, platinum, and palladium from precious metal slag precipitated by chelating agents, including the following technological steps:

[0006] a Mix the precious metal enriched slag precipitated by chelating agents with sodium carbonate and coke, and the mixing ratio is 100:1 - 2:1 - 3. Then put it into an intermediate frequency furnace, control the temperature at 950 - 1150 °C, reduce and roast the precious metal enriched slag, and fish out a small amount of scum on the surface of the molten alloy;

[0007] b Put the precious metal alloy obtained in a into a vacuum furnace, control the temperature at 1450 °C - 1600 °C, the negative pressure at 0 - 30 Pa, and the separation time at 3 - 5 hours to obtain a gold, platinum, and palladium alloy residue and a silver alloy volatile;

[0008] c The gold-platinum-palladium alloy residue obtained in b is melted by a punching machine and then centrifuged to make a film. The feeding and dissolution are carried out according to the mass ratio of flaky alloy: hydrochloric acid: nitric acid: water of 1:4-5:1:6-8. The reaction temperature is 85-95 °C, and the reaction time is 1.5-2 hours. After the reaction ends, solid-liquid separation is carried out, and the solid slag is reserved as the raw material for extracting other platinum group metals except gold, platinum and palladium;

[0009] d The filtrate obtained by filtration in c is added with ammonium chloride, sodium chlorate and sodium sulfite step by step to obtain platinum slag, palladium slag and crude gold powder, and then sponge platinum with a purity of more than 99.95, sponge palladium with a purity of more than 99.95 and No. 1 gold powder are obtained through refining and purification;

[0010] e The silver alloy volatiles obtained in b are put into a silver separating furnace for oxidative refining to produce silver anode plates, and qualified No. 1 silver powder is obtained through an electrolysis process;

[0011] Preferably, the mixing ratio of the precious metal enrichment slag precipitated by the chelating agent in step a, sodium carbonate and coke is 100:1.5:2, and the temperature of the intermediate frequency furnace is controlled at 1050 °C.

[0012] Preferably, the temperature of the vacuum furnace in step b is controlled at 1550 °C, the negative pressure is 15 Pa, and the separation time is 4 hours.

[0013] Preferably, the mass ratio of the flaky alloy: hydrochloric acid: nitric acid: water in step c is 1:4.5:1:7, the reaction temperature is 90 °C, and the reaction time is 1.8 hours.

[0014] The technical problem solved by the present invention is as follows: for the recovery of gold, silver, platinum and palladium in the precious metal slag precipitated by the chelating agent, reduction roasting is carried out in an intermediate frequency furnace to convert the precious metals such as gold, silver, platinum and palladium in the precious metal slag into elemental alloys, and then the separation of silver in the alloy is realized by means of vacuum separation, so as to avoid a large amount of nitrogen oxides generated by wet treatment. The produced silver volatiles can be directly cast into silver anode plates for electrolytic production of No. 1 silver powder, avoiding the problems of entrainment and incomplete separation during the separation of silver and palladium in the wet process. The present invention is easy to realize industrialization, which is proposed for the first time, has simple operation and high recovery rates of gold, silver, platinum and palladium.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1. The present invention mainly aims at the precious metal slag material precipitated by the chelating agent, and through reduction roasting in an intermediate frequency furnace, the precious metals gold, silver, platinum and palladium in the slag material are converted into elemental alloys, avoiding the volatilization of precious metals into the soot during conventional calcination.

[0017] 2. It is innovatively proposed to use vacuum separation technology to separate gold, platinum and palladium from silver in the precious metal alloy, avoiding the entrainment of palladium during the silver recovery process caused by conventional nitric acid leaching, resulting in a low direct recovery rate of palladium, and at the same time reducing the generation of nitrogen oxides during the nitric acid leaching process.

[0018] 3. Compared with other precious metal recovery technologies, the method of the present invention is advanced. The recovery rates of gold, silver, platinum, and palladium are all above 99%, realizing the separation and recovery of gold, silver, platinum, and palladium in precious metal slag. The method is environmentally friendly during the implementation process and can be promoted in industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] In order to better understand the present invention, the content of the present invention will be elaborated in detail below in conjunction with embodiments. The content of the present invention is not limited to the following embodiments.

[0021] The content of each element in the precious metal slag is shown in Table 1:

[0022] Table 1 Content of main elements in precious metal slag %

[0023]

[0024] Note: The grade of the element with * is g / t

[0025] Example 1:

[0026] A method for recovering gold, silver, platinum, and palladium from chelating agent-precipitated precious metal slag, comprising the following steps: Mix 30 kg of precious metal enriched slag precipitated by chelating agent with sodium carbonate and coke at a mixing ratio of 100:1.5:2, then put it into an intermediate frequency furnace, control the temperature at 980 °C, and reductively roast the precious metal enriched slag. Skim off a small amount of scum on the surface of the molten alloy. Put the obtained precious metal alloy into a vacuum furnace, control the temperature at 1500 °C, the negative pressure at 25 Pa, and the separation time at 3.5 hours to obtain a gold-platinum-palladium alloy residue and a silver alloy volatile. Melt the obtained gold-platinum-palladium alloy residue through a punching machine and then centrifuge it into tablets. Feed and dissolve it according to the mass ratio of tablet alloy: hydrochloric acid: nitric acid: water of 1:4:1:6, control the reaction temperature at 85 °C, and the reaction time at 2 hours. After the reaction ends, perform solid-liquid separation. Add ammonium chloride, sodium chlorate, and sodium sulfite to the obtained filtrate step by step to obtain platinum slag, palladium slag, and crude gold powder, and then obtain sponge platinum with a purity above 99.95, sponge palladium with a purity above 99.95, and No. 1 gold powder through refining and purification. Put the obtained silver alloy volatile into a silver separating furnace for oxidative refining to produce a silver anode plate, and obtain qualified No. 1 silver powder through an electrolysis process. The implementation indexes are shown in Table 2 and Table 3.

[0027] Table 2 Indexes of Example 1 %

[0028]

[0029] Note: The grade of the element with * is g / t

[0030] Table 3 Recovery rates of gold, silver, platinum and palladium in Example 1 (%)

[0031]

[0032] Example 2:

[0033] A method for recovering gold, silver, platinum and palladium from the precious metal slag precipitated by chelating agent, which adopts the following steps: Mix 35 kg of the precious metal enriched slag precipitated by chelating agent with sodium carbonate and coke, and the mixing ratio is 100:1:2.5. Then put it into an intermediate frequency furnace, control the temperature at 1100 °C, and reduce and roast the precious metal enriched slag. Scoop out a small amount of dross on the surface of the molten alloy. Put the obtained precious metal alloy into a vacuum furnace, control the temperature at 1550 °C, the negative pressure at 20 Pa, and the separation time at 4 hours to obtain the gold-platinum-palladium alloy residue and the silver alloy volatiles. Melt the obtained gold-platinum-palladium alloy residue through a punching machine and then perform centrifugal sheet making. Feed and dissolve according to the mass ratio of sheet alloy: hydrochloric acid: nitric acid: water of 1:5:1:8. The reaction temperature is 92 °C, and the reaction time is 1.5 hours. After the reaction ends, perform solid-liquid separation. Add ammonium chloride, sodium chlorate and sodium sulfite to the obtained filtrate step by step to obtain platinum slag, palladium slag and crude gold powder, and then obtain sponge platinum with a purity of more than 99.95, sponge palladium with a purity of more than 99.95 and No. 1 gold powder through refining and purification. Put the obtained silver alloy volatiles into a silver separating furnace for oxidative refining to produce silver anode plates, and obtain qualified No. 1 silver powder through electrolysis process. The implementation indexes are shown in Table 4 and Table 5.

[0034] Table 4 Indexes of Example 2 (%)

[0035]

[0036] Note: The grade of the element with * is g / t

[0037] Table 5 Recovery rates of gold, silver, platinum and palladium in Example 2 (%)

[0038]

Claims

1. A method for recovering gold, silver, platinum and palladium from precious metal slag precipitated by a chelating agent, characterized in that The process steps include: a. Mix the precious metal-enriched slag precipitated by the chelating agent with sodium carbonate and coke in a mixing ratio of 100:1-2:1-3, and then put it into a medium frequency furnace, control the temperature at 950-1150°C, reduce and roast the precious metal-enriched slag, and remove a small amount of scum on the surface of the molten alloy; b. Putting the precious metal alloy obtained in a into a vacuum furnace, controlling the temperature at 1450°C to 1600°C, the negative pressure at 0 to 30 Pa, and the separation time at 3 to 5 hours to obtain gold, platinum, palladium alloy residues and silver alloy volatiles; c. Melting the gold, platinum and palladium alloy residue obtained in step b through a sheet puncher and then centrifugally preparing sheets, feeding and dissolving the sheet alloy: hydrochloric acid: nitric acid: water in a mass ratio of 1:4-5:1:6-8, reacting at a temperature of 85-95° C. for 1.5-2 hours, and performing solid-liquid separation after the reaction is completed, and retaining the solid residue as a raw material for extracting other platinum group metals except gold, platinum and palladium; d. The filtrate obtained by filtering in c. is added with ammonium chloride, sodium chlorate and sodium sulfite step by step to obtain platinum slag, palladium slag and coarse gold powder, and then refined and purified to obtain sponge platinum with a purity of more than 99.95%, sponge palladium with a purity of more than 99.95% and 1# gold powder; e. The silver alloy volatiles obtained in b are put into a silver separation furnace for oxidation refining to produce silver anode plates, and qualified 1# silver powder is obtained through an electrolytic process.

2. A method for recovering gold, silver, platinum and palladium from chelating agent precipitated precious metal slag as claimed in claim 1, characterized in that In step a, the precious metal-enriched slag precipitated by the chelating agent is mixed with sodium carbonate and coke in a ratio of 100:1.5:2, and the temperature of the medium frequency furnace is controlled at 1050°C.

3. A method for recovering gold, silver, platinum and palladium from chelating agent precipitated precious metal slag as claimed in claim 1 or 2, characterized in that In step b, the temperature of the vacuum furnace is controlled at 1550° C., the negative pressure is 15 Pa, and the separation time is 4 hours.

4. A method for recovering gold, silver, platinum and palladium from chelating agent precipitated precious metal slag as claimed in claim 1 or 2, characterized in that In step c, the mass ratio of the flaky alloy: hydrochloric acid: nitric acid: water is 1:4.5:1:7, the reaction temperature is 90° C., and the reaction time is 1.8 hours.

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