Method for recovering metal copper powder through cuprous chloride slag reduction leaching

Abstract

The invention discloses a method for recovering metal copper powder through reduction leaching of cuprous chloride slag, which comprises the following steps: washing the cuprous chloride slag with clear water, putting the washed cuprous chloride slag in a mixed solution of Na0H and hydrazine, and leaching for more than 2 hours at 50-60 DEG C to obtain the metal copper powder and a NaCl leaching solution; filtering the metal copper powder, washing the metal copper powder with an H2S04 aqueous solution with the pH value of 2-4 until the pH value is 6-7, then leaching the metal copper powder with clear water, drying and packaging the metal copper powder for sale or returning the metal copper powder to a copper slag dechlorination process for use; and after alkali and hydrazine are supplemented to the NaCl-containing leachate, returning to reduction leaching for use, stopping returning for use until the content of NaCl in the leachate is greater than or equal to 5O g / L, removing the concentrated and crystallized NaCl, and returning the crystallized mother liquor for use. The method has the beneficial effects that the cuprous chloride slag can be subjected to wet-process low-temperature reduction leaching, metal copper powder with high economic value is directly recycled, and the method has the characteristics of few three wastes, low energy consumption and low cost.

Description

Technical Field

[0001] The invention belongs to the field of hydrometallurgy and comprehensive recovery, and specifically relates to a chlorine-containing zinc sulfate solution and other chlorine-containing metallurgical and chemical wastewater Cu 2+ The invention discloses a method for recovering metallic copper powder by reducing and leaching the cuprous chloride slag obtained by dechlorination with a reducing agent using a mixed solution of NaOH and hydrazine. Background Art

[0002] Cu 2+ It is the main method for industrial dechlorination at present. It can remove chlorine from chlorine-containing zinc sulfate solution or other chlorine-containing metallurgical and chemical wastewater by using copper powder (slag) or zinc powder or other reducing agents. It has a shorter process flow, higher dechlorination efficiency, lower cost and less waste than extraction or ion exchange. 3 Chlorine-containing wastewater can produce about 0.5 to 1 kg of cuprous chloride slag. At present, my country's electrolytic zinc production is 6 to 7 million tons / year, and the output of chlorine-containing wastewater is 1 million m3. 3 / year or more. If cuprous chloride is used for chlorination, more than 10,000 tons of cuprous chloride slag can be produced per year.

[0003] The current recovery technology of cuprous chloride slag is mainly to recycle with CuS04.5H20. This method mainly includes, as disclosed in Chinese patent CN105177309B, alkali boiling cuprous chloride slag to obtain cupric hydroxide, then leaching with H2S04 to obtain copper sulfate solution for return or concentrated crystallization of 5-water copper sulfate for recovery. Another example is disclosed in Chinese patent CN117486400A, mixing cuprous chloride slag with H2S04, sulphating and roasting in air to obtain copper sulfate solid and HCL waste gas, and copper sulfate is returned for use. Cuprous chloride is recovered in the form of copper sulfate. Whether it is using wet alkali boiling and then acid leaching, or using pyrosulfating and roasting, there are long process flow and large pollution of three wastes, and the purity of the obtained copper sulfate liquid or solid is not high, so it can only be returned for use by the enterprise.

[0004] Cuprous chloride is recovered as metallic copper powder. Currently, there is only a technical process disclosed in Chinese patent CN108526490B. The patented technology is to wash cuprous chloride with water and place it in a microwave vacuum furnace to decompose it at 900-1000°C to obtain metallic copper powder and chlorine. The purity of the obtained metallic copper powder reaches more than 98%. Although the process is short and the purity of the metallic copper powder is high, the current microwave vacuum furnace equipment is still only laboratory-scale. There is still some distance to go before building a large-scale microwave vacuum furnace suitable for industrial scale. At the same time, it requires a high temperature of more than 900°C to decompose, so the energy consumption is relatively high. Summary of the invention

[0005] The invention adopts a wet method of reducing and leaching cuprous chloride slag with a mixed solution of NaOH and hydrazine at low temperature to recover the metallic copper powder, which overcomes the disadvantages of the above methods, does not require investment in the research and development of special equipment, simplifies the technical process, reduces the discharge of three wastes, reduces energy consumption and production costs, and improves the economic value of the recovered products.

[0006] The technical solution of the present invention:

[0007] A method for recovering metallic copper powder by reduction leaching of cuprous chloride slag, characterized by being implemented according to the following steps:

[0008] Step 1. Wash the cuprous chloride slag with clean water at 70-80°C until the total amount of impurity ions is ≤1g / L, and the pH is 6-7; the impurity ions include one or more of sulfate or chloride ions of Zn, Cd, Fe, Al, As, Sb, Bi, Ni, and Co;

[0009] Step 2. The cuprous chloride residue washed in step 1 is subjected to reduction leaching with a mixed solution of NaOH and hydrazine until the CuCl content in the leached and filtered metallic copper powder is less than 0.1%, thereby obtaining metallic copper powder and NaCl leaching solution;

[0010] Step 3. Wash the metal copper powder in step 2 with a H2SO4 aqueous solution of pH=2-4 at room temperature until the pH is 6-7, and then rinse with clean water 1-2 times to obtain a metal copper powder free of acid and alkali ions;

[0011] Step 4. Drying and packaging the metal copper powder washed in step 3 for sale or returning it to the copper slag dechlorination process for use;

[0012] Step 5. The NaOH and hydrazine mixed leaching filtrate of step 2 is supplemented with NaOH and hydrazine and then returned for reduction leaching of cuprous chloride slag until the leachate contains NaCl ≥ 50 g / L and stops returning for use, removes the concentrated crystallized NaCl, and returns the crystallization mother liquor for leaching.

[0013] Furthermore, the cuprous chloride slag in step 1 is cuprous chloride slag obtained by dechlorinating a chlorine-containing zinc sulfate solution or other chlorine-containing metallurgical wastewater or chlorine-containing industrial wastewater using copper sulfate and metallic copper powder or metallic zinc powder or other reducing agents.

[0014] Furthermore, in the mixed solution of NaOH and hydrazine in step 2, the mass percentage of NaOH is 20-30%, and the volume percentage of hydrazine is 10-20%; the reduction leaching conditions are liquid / solid = 2-3, the leaching temperature is 50-60° C., and the leaching time is more than 2 hours, until the CuCl content in the metallic copper powder after leaching and filtration is less than 0.1%.

[0015] The invention has the beneficial effects that cuprous chloride slag can be leached by low-temperature reduction in a wet process to directly recover metal copper powder with high economic value, and has the characteristics of less three wastes, low energy consumption and low cost.

[0016] Working principle of the present invention:

[0017] 1. Cuprous chloride (CuCl) is insoluble in dilute acid and alkali solution, but when the mass percentage of NaOH is ≥5%, it will react with NaOH to dechlorinate: CuCl + NaOH = CuOH + NaCl. In addition to forming relatively stable compounds with halogen ions, the compounds formed by the reaction of monovalent copper ions with other non-metallic ions are unstable due to disproportionation. Cuprous hydroxide is prone to hydrolysis to form Cu(OH)2: CuOH + H2O = Cu(OH)2 + H + .

[0018] 2. Hydrazine (N2H4) is a strong reducing agent in alkaline solution, and its reducing power increases with the increase of alkalinity. It can reduce metal ions and compounds whose electrode potential is ranked after hydrogen to metal, that is, it can take away 0H in Cu(0H)2 and Cu0H. - Generate H20 to make Cu + Cu 2 + is reduced to metallic copper powder. The reducing property of N2H4 at this time actually reflects the reducing effect of hydrogen. Using a mixture of 20-30% NaOH and 10-20% hydrazine at 50-60°C can not only perform alkaline elution and dechlorination well, but also make hydrazine have strong reducing properties. Therefore, the cuprous hydroxide generated when cuprous chloride reacts with alkali to dechlorinate is reduced to metallic copper powder by hydrazine in the mixture before it has time to react with water for hydrolysis. The chemical reaction equation is 4Cu0H+N2H4=4Cu↓+4H20+N2↑. In the presence of a strong reducing agent, even if cuprous hydroxide is hydrolyzed, the newly generated Cu(0H)2 will gradually be reduced to Cu0H, and further reduced to metallic copper powder. Therefore, the overall chemical reaction equation is 4CuCl+4Na0H+N2H4=4Cu↓+4NaCl+4H20+N2↑.

[0019] 3. Hydrazine (N2H4) is an alkaline liquid at room temperature and does not react with strong bases such as NaOH. Its freezing point is 2°C and boiling point is 113.5°C. At the reaction temperature of 50-60°C of the present invention, it can be fully mixed with the NaOH solution without a large amount of evaporation and decomposition. This not only ensures the effect of dechlorination of the mixed solution by alkali washing of cuprous chloride, but also maintains the concentration of hydrazine in the mixed solution and the effectiveness of reducing cuprous chloride to metallic copper powder. After filtering the metallic copper powder, as long as the alkali and hydrazine consumed in the reaction are supplemented and the sodium chloride in the solution is guaranteed not to produce crystals, it can be returned for use, thereby reducing costs and reducing waste liquid discharge. Due to the large mass fraction of NaOH in the reaction system, the metallic copper powder obtained by reduction must be washed with weak acid water to wash NaOH before it can be dried, packaged and sold or returned to the copper slag dechlorination process for use. DETAILED DESCRIPTION

[0020] The present invention will be further described below by way of examples.

[0021] Embodiment: A method for recovering metallic copper powder by reduction leaching of cuprous chloride slag, the specific implementation steps are as follows:

[0022] Step 1. Wash the cuprous chloride (CuCl) slag with clean water at 70-80°C until the total amount of impurity ions contained is ≤1g / L, and the pH is 6-7; the impurity ions are one or more of the sulfate or chloride ions of Zn, Cd, Fe, Al, As, Sb, Bi, Ni, and Co;

[0023] Step 2. The cuprous chloride slag washed in step 1 is subjected to reduction leaching with a mixed solution of NaOH and hydrazine (N2H4) for more than 2 hours until CuCl<0.1% in the metallic copper powder obtained by filtering and reducing leaching, thereby obtaining metallic copper powder and NaCl leaching solution; the mixed solution of NaOH and hydrazine is a mixed solution containing 20-30% by mass of NaOH and 10-20% by volume of hydrazine; the reduction leaching conditions are leaching temperature of 50-60°C, leaching solution / solid=2-3, and leaching end point of CuCl<0.1%;

[0024] Step 3. Wash the metal copper powder in step 2 with a sulfuric acid aqueous solution with a pH of 2 to 4 at room temperature until the pH is 6 to 7, and then rinse with clean water for 1 to 2 times to obtain a metal copper powder free of acid, alkali and other impurity ions;

[0025] Step 4. Dry and package the metal copper powder washed in step 3 for sale, or directly return it to the copper slag dechlorination process after leaching;

[0026] Step 5. After filtering the metallic copper powder from the mixed leachate of NaOH and hydrazine in step 2, the mixed leachate is supplemented with NaOH and hydrazine and then returned for reduction leaching of cuprous chloride slag until the NaCl in the returned mixed solution is ≥50 g / L, then the return is stopped, the NaCl is removed for concentrated crystallization, and the crystallization mother liquor is returned for leaching.

[0027] Example 1. Take the cuprous chloride slag obtained by removing chlorine by replacing copper slag (powder) with metallic zinc powder during hydrometallurgy of a certain enterprise, first wash it twice with sulfuric acid solution of pH=2 at 40-50°C, and obtain cuprous chloride slag containing about 0.1% zinc. Then add the cuprous chloride slag to a mixed solution containing 20% ​​mass percentage of NaOH and 10% volume percentage of hydrazine at liquid / solid=2, and carry out reduction leaching for more than 2 hours at 50±5°C until the reduction leaching slag contains CuCl≤0.1%, and obtain metallic copper powder and alkaline leaching solution containing NaCl, NaOH, and N2H4. After filtering, the metallic copper powder is eluted at room temperature with H2S04 aqueous solution of pH=3 to about pH=6, and then eluted at room temperature with clean water to about pH=7, and the quality of the metallic copper powder is 95.3% after drying and testing.

[0028] Example 2. Take the cuprous chloride slag obtained by a chemical enterprise from removing chlorine from chlorine-containing wastewater using copper sulfate and sodium sulfite reducing agents, wash it twice with H2S04 water at 40-50°C and pH=3, and then wash it once with clean water to obtain cuprous chloride slag containing 0.06% sodium sulfite. Then add the cuprous chloride slag to a mixed solution containing 30% mass percentage of NaOH and 15% volume percentage of hydrazine at a liquid / solid ratio of 3, stir and leach it at 60±2°C for more than 2 hours until the copper metal powder contains CuCl<0.05%. After filtering, wash it with sulfuric acid water at 30±5°C and pH=2 to about pH=7, rinse it with clean water once, and dry it to detect that the quality of the copper metal powder is 98.5%.

[0029] Example 3. The NaOH and hydrazine mixed solution of the cuprous chloride slag of Example 2 was tested for reduction leaching of the filtered metallic copper powder, and the concentration of NaOH was 18.3%, the concentration of hydrazine was 8.5%, and the concentration of NaCl was 13.2g / L. Then NaOH was supplemented to 20%, hydrazine was supplemented to 10%, and the reduction leaching test of the cuprous chloride slag of Example 2 was carried out again. The test conditions were liquid / solid=3, reduction leaching temperature 60±2°C, leaching time 3 hours, and the metallic copper powder obtained by reduction leaching was detected to contain 0.56% CuCl. The leaching time was extended to 4 hours, and the metallic copper powder was detected to contain 0.12% CuCl. After filtering the metallic copper powder, it was washed and dried using the method of Example 2, and the quality of the metallic copper powder obtained was 98.2%.

[0030] The invention has the beneficial effects that cuprous chloride slag can be leached by low-temperature reduction in a wet process to directly recover metal copper powder with high economic value, and has the characteristics of less three wastes, low energy consumption and low cost.

[0031] The above examples are only used to further illustrate the present invention, and the present invention is not limited thereto.

Claims

1. A method for recovering metallic copper powder by reduction leaching of cuprous chloride slag, characterized in that: Follow these steps to implement: Step 1. Wash the cuprous chloride slag with clean water at 70-80°C until the total amount of impurity ions is ≤1g / L, and the pH is 6-7; the impurity ions include one or more of sulfate or chloride ions of Zn, Cd, Fe, Al, As, Sb, Bi, Ni, and Co; Step 2. The cuprous chloride residue washed in step 1 is subjected to reduction leaching with a mixed solution of NaOH and hydrazine until the CuCl content in the leached and filtered metallic copper powder is less than 0.1%, thereby obtaining metallic copper powder and NaCl leaching solution; Step 3. Wash the metal copper powder in step 2 with a H2SO4 aqueous solution of pH=2-4 at room temperature until the pH is 6-7, and then rinse with clean water 1-2 times to obtain a metal copper powder free of acid and alkali ions; Step 4. Drying and packaging the metal copper powder washed in step 3 for sale or returning it to the copper slag dechlorination process for use; Step 5. The NaOH and hydrazine mixed leaching filtrate of step 2 is supplemented with NaOH and hydrazine and then returned for reduction leaching of cuprous chloride slag until the leachate contains NaCl ≥ 50 g / L and stops returning for use, removes the concentrated crystallized NaCl, and returns the crystallization mother liquor for leaching.

2. The method for recovering metallic copper powder by reduction leaching of cuprous chloride slag as claimed in claim 1, characterized in that: The cuprous chloride slag in step 1 is obtained by removing chlorine from a chlorine-containing zinc sulfate solution or other chlorine-containing metallurgical wastewater or chlorine-containing industrial wastewater by using copper sulfate and metal copper powder or metal zinc powder.

3. The method for recovering metallic copper powder by reduction leaching of cuprous chloride slag as claimed in claim 1, characterized in that: In the mixed solution of NaOH and hydrazine in step 2, the mass percentage of NaOH is 20-30%, and the volume percentage of hydrazine is 10-20%; the reduction leaching conditions are liquid / solid=2-3, the leaching temperature is 50-60°C, and the leaching time is more than 2 hours, until the CuCl content in the metal copper powder after leaching and filtration is less than 0.1%.