A method for preparing cadmium phosphide using copper-cadmium slag

Abstract

The present invention relates to a method for preparing cadmium phosphide using copper-cadmium slag, and the method comprises the following steps: (1) Oxidative acid leaching: Mix copper-cadmium slag, ammonium dichromate and water, stir and react, and control the end point pH to be 5-5.2. After solid-liquid separation, a mixed solution of zinc sulfate and chromium sulfate and a solid phase are obtained respectively; (2) Separation of zinc and chromium: In the mixed solution of zinc sulfate and chromium sulfate, add ammonia water for chromium precipitation reaction to obtain [Zn(NH3)4](OH)2 solution, and a mixed precipitate of chromium hydroxide and chromium oxysulfate respectively; (3) Separation of copper and cadmium: Add sulfuric acid solution and water to the solid phase for acid leaching reaction to obtain cadmium sulfate solution and copper slag with copper content > 90% respectively; (4) Preparation of cadmium phosphide: Pump the cadmium sulfate solution into a reaction kettle, first add ammonia water to make the pH of the solution 9-12 and then seal it, then remove the oxygen in the reactor, and then introduce phosphine gas for reaction. After the reaction is completed, cool to room temperature, filter, wash and dry to obtain cadmium phosphide product with purity > 98%. The process of the present invention is short, the operation is simple, and the cost is low.

Description

Technical Field

[0001] The invention relates to a hydrometallurgical process in the field of metallurgy, and in particular to a method for preparing cadmium phosphide by utilizing copper-cadmium slag. Background Art

[0002] Copper-cadmium slag is the leaching slag produced by the wet zinc smelting purification process. Every 10,000 tons of cathode zinc produced produces 300 tons of copper-cadmium slag, of which Zn 45~50%, Cd 8~12%, Cu 6~10%, S 9~11%, O 20~32%, and others 1~3%, with high content of zinc, cadmium and copper.

[0003] At present, the copper-cadmium slag recovery and treatment processes are mainly divided into two types: pyrometallurgical process and hydrometallurgical process. The pyrometallurgical process is mature, but it has high energy consumption and strict equipment requirements; the hydrometallurgical process is simple and has low energy consumption. The industrial treatment of copper-cadmium slag is mainly carried out for the recovery of cadmium. The grade of sponge cadmium obtained by replacement is only controlled by controlling the proportion of zinc powder added during the two-stage replacement. It cannot effectively remove impurities and improve the grade of sponge cadmium, and the economic benefits are low.

[0004] Therefore, there is an urgent need to develop a high-value comprehensive recycling process for copper-cadmium slag that is simpler, faster, lower-cost, and environmentally friendly. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing cadmium phosphide by using copper-cadmium slag, which has the advantages of short process, simple operation and low cost.

[0006] To solve the above problems, a method for preparing cadmium phosphide using copper-cadmium slag according to the present invention comprises the following steps:

[0007] ⑴ Oxidative acid leaching:

[0008] The copper-cadmium slag, ammonium dichromate and water are mixed and stirred for reaction, and the endpoint pH is controlled to be 5-5.2, and a mixed solution of zinc sulfate and chromium sulfate and a solid phase are obtained by solid-liquid separation, respectively; the mass ratio of the ammonium dichromate to the copper-cadmium slag is 0.6-0.68:1; the ratio of the copper-cadmium slag to the water is 1kg:10L;

[0009] ⑵Separation of zinc and chromium:

[0010] Ammonia water is added to the mixed solution of zinc sulfate and chromium sulfate to carry out chromium precipitation reaction, the ratio of the copper-cadmium slag to the ammonia water is 1 kg: 4-8 L, and the endpoint pH is controlled to be 8-12, and solid-liquid separation is performed to obtain [Zn(NH 3 ) 4 ](OH) 2 solution, chromium hydroxide and chromium oxysulfate mixed precipitation; the [Zn(NH 3 ) 4](OH) 2 The solution enters the electrolysis process after being acidified; the mixed precipitate of chromium hydroxide and chromium oxysulfate is returned to the oxidation acid leaching process after being oxidized;

[0011] ⑶Separation of copper and cadmium:

[0012] A sulfuric acid solution and water with a concentration of 90-180 g / L are added to the solid phase at a liquid-solid ratio of 3-6 L:1 kg to carry out an acid leaching reaction, and the end point pH is controlled to be 3-5, and after solid-liquid separation, a cadmium sulfate solution and a copper slag with a copper content of more than 90% are obtained respectively; the copper slag is used for refining and recovering copper;

[0013] ⑷ Preparation of cadmium phosphide:

[0014] The cadmium sulfate solution is pumped into a reactor, and ammonia water is first added to make the pH value of the solution = 9-12 and then sealed, and then nitrogen is filled into the solution for 3-5 minutes to remove oxygen in the reactor, and then phosphine gas is introduced for reaction. After the reaction is completed, it is cooled to room temperature and then filtered, washed and dried to obtain a cadmium phosphide product with a purity of more than 98%; the consumption of the phosphine gas is determined according to the cadmium content.

[0015] The main chemical components of the copper-cadmium slag in step (1) are: Zn 45-50%, Cd 8-12%, Cu 6-8%, S 9-11%, O2 1-26%, and others 1-4%.

[0016] The stirring reaction conditions in step (1) are that the reaction temperature is 70-85° C., the stirring speed is 200 rpm, and the reaction time is 2-3 h.

[0017] The conditions for the chromium precipitation reaction in step (2) are that the reaction temperature is 100-120° C., the stirring speed is 200 rpm, and the reaction time is 1-2 h.

[0018] The conditions for the acid leaching reaction in step (3) are that the reaction temperature is 75-90° C., the stirring speed is 150 rpm, and the reaction time is 3-6 h.

[0019] The reaction conditions in step (4) refer to the pressure in the reactor being 0.3-0.6 MPa, the reaction temperature being 60-80° C., the stirring speed being 200 rpm, and the reaction time being 1.5-3 h.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The present invention utilizes ammonium dichromate solution to perform oxidation acid leaching on the copper-cadmium slag produced in the purification process of wet zinc smelting to separate zinc from copper and cadmium, then utilizes oxidation alkali leaching to separate zinc and chromium and atmospheric pressure acid leaching to separate copper and cadmium, and finally introduces phosphine gas into the liquid after the copper-cadmium separation to prepare a cadmium phosphide product. The process is short and the operation is simple, and there is no secondary pollution. The purpose of high-value utilization of valuable metals such as zinc and copper and cadmium in the copper-cadmium slag can be achieved by efficiently recovering the valuable metals and cadmium in the copper-cadmium slag, and the invention has important promotion value in industry.

[0022] 2. The present invention adopts ammonium dichromate oxidation acid leaching of copper-cadmium slag, which can realize efficient separation of zinc from copper and cadmium; the chromium-containing precipitate after zinc-chromium separation can be recycled, which reduces the cost, and the chromium and cadmium content in the final zinc sulfate solution is less than 10 mg / L, which meets the requirements of zinc electrowinning. At the same time, the purity of cadmium phosphide prepared by passing phosphine gas into the cadmium sulfate solution after copper-cadmium separation can reach more than 98%, which has higher economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0024] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0025] like Figure 1 As shown, a method for preparing cadmium phosphide using copper-cadmium slag comprises the following steps:

[0026] ⑴ Oxidative acid leaching:

[0027] Copper-cadmium slag, ammonium dichromate and water are mixed, the mass ratio (kg / kg) of ammonium dichromate to copper-cadmium slag is 0.6-0.68:1, and the ratio of copper-cadmium slag to water is 1kg:10 L. Stir the reaction at 70-85°C and 200rpm for 2-3h, and control the end point pH to 5-5.2. After solid-liquid separation, a mixed solution of zinc sulfate and chromium sulfate and a solid phase are obtained respectively.

[0028] Among them: the main chemical components of copper-cadmium slag are: Zn 45~50%, Cd 8~12%, Cu 6~8%, S 9~11%, O 21~26%, and others 1~4%.

[0029] ⑵Separation of zinc and chromium:

[0030] Ammonia water is added to the mixed solution of zinc sulfate and chromium sulfate to carry out chromium precipitation reaction. The ratio of copper-cadmium slag to ammonia water is 1 kg: 4-8 L, the reaction temperature is 100-120 ° C, the stirring speed is 200 rpm, the reaction time is 1-2 hours, and the end point pH is controlled to be 8-12, so that Cr (III) generates chromium hydroxide and chromium sulfate precipitation, and zinc and ammonia are complexed to generate [Zn (NH3 ) 4 ](OH) 2 After solid-liquid separation, [Zn(NH 3 ) 4 ](OH) 2 solution, chromium hydroxide and chromium oxysulfate mixed precipitation. [Zn(NH 3 ) 4 ](OH) 2 After the solution is acidified, it enters the electrolysis process; the mixed precipitation of chromium hydroxide and chromium oxysulfate is oxidized and then returns to the oxidation acid leaching process.

[0031] ⑶Separation of copper and cadmium:

[0032] A sulfuric acid solution with a concentration of 90-180 g / L is added to the solid phase at a liquid-solid ratio of 3-6 L:1 kg to carry out acid leaching reaction, the reaction temperature is 75-90 ° C, the stirring speed is 150 rpm, the reaction time is 3-6 hours, and the end point pH is controlled to be 3-5. After solid-liquid separation, cadmium sulfate solution and copper slag with a copper content of more than 90% are obtained respectively; the copper slag is used for refining and recovery of copper.

[0033] ⑷ Preparation of cadmium phosphide:

[0034] The cadmium sulfate solution is pumped into the reactor, and ammonia water is first added to make the pH of the solution 9-12 and then sealed. Then nitrogen is filled into the solution for 3-5 minutes to remove the oxygen in the reactor, and then phosphine gas is introduced. The consumption of phosphine gas is determined according to the cadmium content. After the pressure in the reactor reaches 0.3-0.6MPa, the ventilation is stopped, and the reaction is carried out at 60-80℃ and 200rpm for 1.5-3h. After the reaction is completed, the solution is cooled to room temperature, filtered, washed, and dried to obtain a cadmium phosphide product with a purity of >98%.

[0035] Ammonia water, ammonium dichromate, phosphine gas and sulfuric acid are all of industrial grade.

[0036] Example 1 A method for preparing cadmium phosphide using copper-cadmium slag comprises the following steps:

[0037] ⑴ Oxidative acid leaching:

[0038] 1 kg of copper-cadmium slag (Zn 45%, Cd 12%, Cu 6%, S 10%, O 26%, other 1%) ground to a particle size of -100 mesh was placed in a reactor, 0.6 kg of ammonium dichromate was added and mixed with 3 L of water, and the reaction was stirred at 70°C and 200 rpm for 2 h, and the endpoint pH was controlled to be 5-5.2. After solid-liquid separation, 2.93 L of a mixed solution of zinc sulfate and chromium sulfate and 401 g of a solid phase were obtained respectively.

[0039] ⑵Separation of zinc and chromium:

[0040] 4.8 L of ammonia water was added to the mixed solution of zinc sulfate and chromium sulfate for chromium precipitation reaction. The reaction temperature was 100 °C, the stirring speed was 200 rpm, the reaction time was 2 h, and the end point pH was controlled to be 12. After solid-liquid separation, 4.7 L [Zn(NH 3 ) 4 ](OH) 2 solution, 430 g of chromium hydroxide and chromium oxysulfate as a mixed precipitate. [Zn(NH 3 ) 4 ](OH) 2 After the solution is acidified, it enters the electrolysis process; the mixed precipitation of chromium hydroxide and chromium oxysulfate is oxidized and then returns to the oxidation acid leaching process.

[0041] ⑶Separation of copper and cadmium:

[0042] 0.56 L of 180 g / L sulfuric acid solution was added to the solid phase, and then 0.7 L of water was added for acid leaching reaction. The reaction temperature was 75 ° C, the stirring speed was 150 rpm, the reaction time was 3 h, and the endpoint pH was controlled to be 3. After solid-liquid separation, 1.25 L of cadmium sulfate solution with a cadmium content of 90 g / L and 226 g of copper slag with a copper content of > 90% were obtained respectively; the copper slag was used for refining and recovery of copper.

[0043] ⑷ Preparation of cadmium phosphide:

[0044] The cadmium sulfate solution was pumped into the reactor, and ammonia water was first added to make the pH of the solution = 9 and then sealed, and then nitrogen was filled into the solution for 3-5 minutes to remove the oxygen in the reactor, and then 25L of phosphine gas was introduced to stop the ventilation after the pressure in the reactor reached 0.3MPa, and the reaction was carried out at 80°C and a speed of 200rpm for 1.5h. After the reaction was completed, the excess phosphine gas was introduced into the copper sulfate solution through the exhaust port for recovery, and the slurry was filtered, washed, and dried after cooling to room temperature to obtain 120g of cadmium phosphide product with a purity of 98.5%.

[0045] Example 2 A method for preparing cadmium phosphide using copper-cadmium slag comprises the following steps:

[0046] ⑴ Oxidative acid leaching:

[0047] 1 kg of copper-cadmium slag (Zn 48%, Cd 10%, Cu 7%, S 11%, O 23%, other 1%) ground to a particle size of -120 mesh was placed in a reactor, 0.68 kg of ammonium dichromate was added and mixed with 5 L of water, and the reaction was stirred at 80 ° C and 200 rpm for 2.5 h, and the endpoint pH was controlled to be 5-5.2. After solid-liquid separation, 4.93 L of a mixed solution of zinc sulfate and chromium sulfate and 384 g of a solid phase were obtained respectively.

[0048] ⑵Separation of zinc and chromium:

[0049] 5.17 L of ammonia water was added to the mixed solution of zinc sulfate and chromium sulfate for chromium precipitation reaction. The reaction temperature was 110 ° C, the stirring speed was 200 rpm, the reaction time was 1.5 h, and the end point pH was controlled to be 10. After solid-liquid separation, 5.09 L [Zn(NH 3 ) 4 ](OH) 2 solution, 488 g of chromium hydroxide and chromium oxysulfate as a mixed precipitate. [Zn(NH 3 ) 4 ](OH) 2 After the solution is acidified, it enters the electrolysis process; the mixed precipitation of chromium hydroxide and chromium oxysulfate is oxidized and then returns to the oxidation acid leaching process.

[0050] ⑶Separation of copper and cadmium:

[0051] 0.65 L of 130 g / L sulfuric acid solution was added to the solid phase, and then 1.27 L of water was added for acid leaching reaction. The reaction temperature was 80 ° C, the stirring speed was 150 rpm, the reaction time was 4.5 h, and the endpoint pH was controlled to be 5. After solid-liquid separation, 1.20 L of cadmium sulfate solution with a cadmium content of 78 g / L and 214 g of copper slag with a copper content of > 90% were obtained respectively; the copper slag was used for refining and recovery of copper.

[0052] ⑷ Preparation of cadmium phosphide:

[0053] The cadmium sulfate solution was pumped into the reactor, and ammonia water was first added to make the pH of the solution = 11 and then sealed, and then nitrogen was filled into the solution for 3-5 minutes to remove the oxygen in the reactor, and then 20L of phosphine gas was introduced to stop the ventilation after the pressure in the reactor reached 0.4MPa, and the reaction was carried out at 70°C and a speed of 200rpm for 2.5h. After the reaction was completed, the excess phosphine gas was introduced into the copper sulfate solution through the exhaust port for recovery, and the slurry was filtered, washed, and dried after cooling to room temperature to obtain 100g of cadmium phosphide product with a purity of 98.3%.

[0054] Example 3 A method for preparing cadmium phosphide using copper-cadmium slag comprises the following steps:

[0055] ⑴ Oxidative acid leaching:

[0056] 1 kg of copper-cadmium slag (Zn 50%, Cd 8%, Cu 8%, S 9%, O 21%, other 4%) ground to a particle size of -100 mesh was placed in a reactor, 0.65 kg of ammonium dichromate was added and mixed with 9.9 L of water, and the reaction was stirred at 85 ° C and 200 rpm for 3 h, and the endpoint pH was controlled to be 5-5.2. After solid-liquid separation, 5.93 L of a mixed solution of zinc sulfate and chromium sulfate and 376 g of a solid phase were obtained respectively.

[0057] ⑵Separation of zinc and chromium:

[0058] 5.35L of ammonia water was added to the mixed solution of zinc sulfate and chromium sulfate for chromium precipitation reaction. The reaction temperature was 120°C, the stirring speed was 200rpm, the reaction time was 1h, and the end point pH was controlled to be 8. After solid-liquid separation, 5.27L [Zn(NH 3 ) 4 ](OH) 2 solution, 466g of chromium hydroxide and chromium oxysulfate as a mixed precipitate. [Zn(NH 3 ) 4 ](OH) 2 After the solution is acidified, it enters the electrolysis process; the mixed precipitation of chromium hydroxide and chromium oxysulfate is oxidized and then returns to the oxidation acid leaching process.

[0059] ⑶Separation of copper and cadmium:

[0060] 0.75 L of 90 g / L sulfuric acid solution was added to the solid phase, and then 1.47 L of water was added for acid leaching reaction. The reaction temperature was 85 ° C, the stirring speed was 150 rpm, the reaction time was 6 h, and the endpoint pH was controlled to be 5. After solid-liquid separation, 145 L of cadmium sulfate solution with a cadmium content of 31 g / L and 152 g of copper slag with a copper content of > 90% were obtained respectively; the copper slag was used for refining and recovery of copper.

[0061] ⑷ Preparation of cadmium phosphide:

[0062] The cadmium sulfate solution was pumped into the reactor, and ammonia water was first added to make the pH of the solution = 12 and then sealed, and then nitrogen was filled into the solution for 3-5 minutes to remove the oxygen in the reactor, and then 18L of phosphine gas was introduced to stop the ventilation after the pressure in the reactor reached 0.6MPa, and the reaction was carried out at 60°C and 200rpm for 3h. After the reaction was completed, the excess phosphine gas was introduced into the copper sulfate solution through the exhaust port for recovery, and the slurry was filtered, washed and dried after cooling to room temperature to obtain 80g of cadmium phosphide product with a purity of 98.7%.

Claims

1. A method for preparing cadmium phosphide using copper-cadmium slag, The following steps are involved: ⑴ Oxidative acid leaching: The copper-cadmium slag, ammonium dichromate and water are mixed and stirred for reaction, and the endpoint pH is controlled to be 5-5.2, and a mixed solution of zinc sulfate and chromium sulfate and a solid phase are obtained by solid-liquid separation, respectively; the mass ratio of the ammonium dichromate to the copper-cadmium slag is 0.6-0.68:1; the ratio of the copper-cadmium slag to the water is 1kg:10L; ⑵Separation of zinc and chromium: Ammonia water is added to the mixed solution of zinc sulfate and chromium sulfate to carry out chromium precipitation reaction, the ratio of the copper-cadmium slag to the ammonia water is 1 kg: 4-8 L, and the endpoint pH is controlled to be 8-12, and solid-liquid separation is performed to obtain [Zn(NH 3 ) 4 ](OH) 2 solution, chromium hydroxide and chromium oxysulfate mixed precipitation; the [Zn(NH 3 ) 4 ](OH) 2 The solution enters the electrolysis process after being acidified; the mixed precipitate of chromium hydroxide and chromium oxysulfate is returned to the oxidation acid leaching process after being oxidized; ⑶Separation of copper and cadmium: A sulfuric acid solution and water with a concentration of 90-180 g / L are added to the solid phase at a liquid-solid ratio of 3-6 L:1 kg to carry out an acid leaching reaction, and the end point pH is controlled to be 3-5, and after solid-liquid separation, a cadmium sulfate solution and a copper slag with a copper content of more than 90% are obtained respectively; the copper slag is used for refining and recovering copper; ⑷ Preparation of cadmium phosphide: The cadmium sulfate solution is pumped into a reactor, and ammonia water is first added to make the pH value of the solution = 9-12 and then sealed, and then nitrogen is filled into the solution for 3-5 minutes to remove oxygen in the reactor, and then phosphine gas is introduced for reaction. After the reaction is completed, it is cooled to room temperature and then filtered, washed and dried to obtain a cadmium phosphide product with a purity of more than 98%; the consumption of the phosphine gas is determined according to the cadmium content.

2. A method for preparing cadmium phosphide using copper-cadmium slag as claimed in claim 1, Features: The main chemical components of the copper-cadmium slag in step (1) are: Zn 45-50%, Cd 8-12%, Cu 6-8%, S 9-11%, O 21-26%, and others 1-4%.

3. A method for preparing cadmium phosphide using copper-cadmium slag according to claim 1, Features: The stirring reaction conditions in step (1) are that the reaction temperature is 70-85° C., the stirring speed is 200 rpm, and the reaction time is 2-3 h.

4. A method for preparing cadmium phosphide using copper-cadmium slag as claimed in claim 1, Features: The conditions for the chromium precipitation reaction in step (2) are that the reaction temperature is 100-120° C., the stirring speed is 200 rpm, and the reaction time is 1-2 h.

5. A method for preparing cadmium phosphide using copper-cadmium slag as claimed in claim 1, Features: The conditions for the acid leaching reaction in step (3) are that the reaction temperature is 75-90° C., the stirring speed is 150 rpm, and the reaction time is 3-6 h.

6. A method for preparing cadmium phosphide using copper-cadmium slag as claimed in claim 1, Features: The reaction conditions in step (4) refer to the pressure in the reactor being 0.3-0.6 MPa, the reaction temperature being 60-80° C., the stirring speed being 200 rpm, and the reaction time being 1.5-3 h.

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