Method for recycling copper and nickel through resourceful treatment of copper electrolyte

Abstract

The invention discloses a method for recycling copper and nickel through copper electrolyte resourceful treatment. The method comprises the process steps that copper electrolyte waste liquid is subjected to evaporation concentration and cooling crystallization to produce copper sulfate; the concentrated liquid is subjected to two-stage electrodeposition to produce copper, black copper slag and nickel-containing electrodeposition liquid; the black copper slag is subjected to ball milling, synergistic oxidation acid leaching and metal cascade precipitation to realize arsenic-copper separation; and carrying out evaporation concentration, freezing crystallization and refining purification on the nickel-containing electrodeposition liquid to finally obtain a nickel product. The invention provides a whole set of treatment process for the waste liquid produced by copper electrolysis, is suitable for industrial treatment of the waste electrolyte of a copper electrolysis system, and particularly has higher applicability for high-copper-content acidic waste liquid; and meanwhile, arsenic and copper in the produced black copper slag material are separated, nickel in the nickel-containing electrodeposition liquid is recycled, and a process scheme is provided for realizing productization of nickel. The method disclosed by the invention is wide in application range, simple and effective in process and easy to realize large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrometallurgy processes, and specifically relates to a method for resource treatment and recovery of copper and nickel from copper electrolyte. Background Art

[0002] In the copper electrolytic refining industry, copper anodes of a certain specification are produced by casting using fire-refined blister copper as the raw material as the anode, and stainless steel plates as the cathode. Electrolytic refining is carried out in a sulfuric acid - copper sulfate mixed system to produce cathode copper and anode slime rich in precious metals. During the electrolysis process, under the action of direct current, the copper anode plates dissolve into ions and precipitate at the cathode. However, during the process, the composition of the electrolyte will continuously change, the copper ion concentration increases, the sulfuric acid concentration decreases, and impurities continuously accumulate. Since the oxidation potentials of nickel ions and iron ions are relatively low, -0.257V and -0.441V respectively, they cannot obtain electrons during the electrolysis process and can only continuously accumulate in the solution; however, the oxidation potential of arsenic ions is close to that of copper ions, +0.248V. When the arsenic ion concentration in the solution is low, it cannot obtain electrons and continuously accumulates in the solution. When the arsenic ion concentration accumulates to a relatively high concentration, arsenic may also obtain electrons and discharge and precipitate at the cathode, resulting in the arsenic content of the final copper product exceeding the standard. To ensure a normal electrolysis process, part of the electrolyte needs to be purified and adjusted, and the one containing high arsenic, nickel, and iron impurities is called copper electrolysis waste liquid.

[0003] Most domestic copper smelting enterprises purify copper electrolysis waste liquid through copper removal and impurity removal processes. The copper removal and impurity removal processes are generally divided into two categories. One is to use single-stage or two-stage electrowinning for copper removal and impurity removal, which generally includes the following steps: First, the waste electrolyte is treated by vacuum evaporation, freeze crystallization, and vacuum belt filter to obtain crude copper sulfate, heavy solution, and crystallization mother liquor; the crude copper sulfate contains about 23% copper and can be directly sold; the heavy solution can be remixed with the waste electrolyte for treatment or used to produce crude nickel sulfate; the crystallization mother liquor can continue to be electrolytically de-coppered by the continuous de-copper and de-arsenic method, and electrodeposited copper, black copper powder, black copper mud, etc. are obtained in the electrolytic cell in turn. The final solution after electrolytic de-copperization is used to produce nickel sulfate. When the crystallization mother liquor is electrolytically de-coppered by the continuous de-copper and de-arsenic method, generally an insoluble anode is used as the anode and the electrolytic residue is used as the cathode for electrolysis, and electrodeposited copper, black copper powder, black copper mud, etc. can be obtained. This process is the current mainstream process and is used by most copper smelting enterprises. The other is to use the sulfide precipitation process to purify the copper electrolysis waste liquid. The general process is to dissolve sodium sulfide into a sodium sulfide solution, then add it to the copper electrolysis waste liquid, and strictly control the addition amount of the sodium sulfide solution according to the reaction requirement. The copper ions in the copper electrolysis waste liquid have a strong binding force with sulfur anions and preferentially combine with sulfur anions to form copper sulfide with very low solubility, achieving the purpose of removing copper ions. During this process, due to the limited addition amount of the sodium sulfide solution, arsenic ions do not combine with sulfur anions and continue to exist in the solution; the filtered liquid after removing copper ions and arsenic ions is evaporated and concentrated, and the concentrated liquid is then cooled and crystallized to obtain nickel sulfate hexahydrate products and mother liquor, and the mother liquor is returned to the electrolysis process for liquid preparation. The main disadvantage of this process is that the sulfide precipitation slag is a mixed slag of copper sulfide and arsenic sulfide, and copper and arsenic are not separated, increasing the burden of subsequent precipitation slag treatment. At the same time, the direct recovery rate of nickel is low, and only a small number of enterprises use this process to treat copper electrolysis waste liquid.

[0004] A method and device for treating waste electrolyte proposed by Wang Yamin et al. of Yanggu Xiangguang Copper Co., Ltd. (CN104694978A) includes the following steps: a) Treat the waste electrolyte to obtain a primary copper removal final solution, where the copper ion concentration in the primary copper removal solution is 35 g / L to 45 g / L; b) Use an insoluble anode as the anode and a stainless steel cathode as the cathode, and treat the primary copper removal final solution by continuous electrowinning to obtain grade A copper and a secondary copper removal final solution; c) Use an insoluble anode as the anode and an electrolytic anode residue as the cathode, and treat the secondary copper removal final solution by continuous electrowinning to obtain electrowon copper, black copper plates, black copper powder, and black copper mud. A method for treating copper electrolysis waste liquid proposed by Tao Zhengxiu et al. of Zhuzhou Sante Environmental Protection and Energy Saving Co., Ltd. (CN104694978A) includes the following steps: S1. Copper recovery: Use hydrogen sulfide as a sulfiding agent and introduce it into the copper electrolysis waste liquid to precipitate copper ions; after solid-liquid separation, obtain a copper-containing filter residue and a copper-removed filtrate; S2. Arsenic recovery: Use hydrogen sulfide as a sulfiding agent and introduce it into the copper-removed filtrate to precipitate arsenic ions; after solid-liquid separation, obtain an arsenic-containing filter residue and an arsenic-removed filtrate; S3. Sulfuric acid recovery: Use nickel hydroxide or nickel carbonate as a neutralizing agent and add it to the arsenic-removed filtrate to recover sulfuric acid; S4. Nickel recovery: The nickel sulfate solution is evaporated and concentrated to obtain a concentrated solution with a high nickel ion concentration; after the concentrated solution cools, a crystal liquid mixture is produced, and nickel sulfate hexahydrate crystals and mother liquor are obtained by centrifugal separation, and the mother liquor continues to be recycled for evaporation and concentration. A method for extracting copper from copper electrolysis waste liquid proposed by Guan Xin et al. of Jinchuan Group Co., Ltd. (CN114808031A) includes using a new electrowinning copper removal technology to adjust the solution flow rate, current density, and final copper ion concentration to make the three match for production to achieve the purpose of removing copper from the electrolyte.

[0005] In summary, the existing copper electrolysis waste liquid treatment processes mainly focus on how to remove copper from the copper electrolysis waste liquid. The copper-arsenic mixture produced after removal has not been resourcefully treated, and at the same time, no further product treatment has been done for the produced crude nickel sulfate. Therefore, it is urgent to develop a new method that can efficiently recover copper and nickel, realize the harmlessness of the waste liquid, and improve the resource utilization rate. Summary of the Invention

[0006] To solve the above problems, the present invention provides a method for resourcefully treating copper electrolysis waste liquid to recover copper and nickel.

[0007] The technical solution of the present invention is realized as follows: A method for resourcefully treating copper electrolysis waste liquid to recover copper and nickel includes the following process steps: a. The copper electrolysis waste liquid undergoes evaporation and concentration - cooling crystallization to produce crude copper sulfate. b. The post-crystallization liquid undergoes two-stage electrowinning to produce copper, black copper slag, and nickel-containing electrowinning solution. c. After the black copper slag undergoes the processes of ball milling - synergistic oxidation acid leaching - metal cascade precipitation, copper hydroxide and calcium arsenate are produced; d. The nickel - containing electrolyte solution is evaporated and concentrated - freeze - crystallized to obtain crude nickel sulfate; e. The crude nickel sulfate undergoes sulfide conversion - nitric acid dissolution - purification and impurity removal - single precipitation - calcination decomposition - reduction, and finally a nickel product is obtained; Preferably, in the synergistic oxidation acid leaching process in step c, the oxidant used is sodium persulfate, and the acidic reagent used is sulfuric acid. Before ball milling, the black copper slag and sodium persulfate are mixed or sodium persulfate is added while ball milling. Sodium persulfate and the black copper slag are added in a ratio of 0.5 - 1 mol / L. After ball milling, the slurry is pumped into the reaction kettle and sulfuric acid is added. Sulfuric acid and the slurry are added in a ratio of 1 - 3 mol / L; Preferably, in the metal cascade precipitation process in step c, the pH is adjusted in a step - by - step manner. The regulator is calcium hydroxide. The pH for arsenic precipitation is 2 - 4, and the pH for copper precipitation is 5 - 6; Preferably, in the sulfide conversion process in step e, the sulfide used is any one or a mixture of two or more of sodium sulfide, hydrogen sulfide, and sodium bisulfide; Preferably, the impurity remover used in step e is hydrogen sulfide. For purification and impurity removal, first adjust the pH to 4 - 5, then heat and boil for 5 - 10 min, and then let it stand for 1 - 1.5 h; Preferably, the precipitant used in the single precipitation process in step e is C4H8N2O2. Ni is 2+ converted and precipitated to form a bright red precipitate of C8H 14 N4O4Ni, and it is calcined at 700 - 800 °C for 1 - 2 h to obtain NiO; Preferably, the reducing agent used in the reduction process in step e is hydrogen or hydrazine hydrate.

[0008] The beneficial effects of the present invention are as follows: The present invention proposes a complete set of treatment processes for the waste liquid produced by copper electrolysis, which is applicable to the industrial treatment of the waste electrolyte in the copper electrolysis system, especially more applicable to the highly copper - containing acidic waste liquid. Through metal cascade precipitation, the separation of arsenic and copper in the black copper slag is realized. A process scheme is proposed for the separation of arsenic and copper in the produced black copper slag material and the recovery of nickel in the nickel - containing electrolyte solution and the realization of nickel productization. The method of the present invention has a wide application range, simple and effective process, and is easy to realize large - scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] For a better understanding of the present invention, the following is combined with the attached Figure 1The content of the present invention is elaborated, and the content of the present invention is not limited to the following embodiments.

[0011] Example 1: A method for resource treatment and recovery of copper and nickel from copper electrolyte, comprising the following steps: a. The copper electrolysis waste liquid is subjected to evaporation concentration - cooling crystallization to produce crude copper sulfate: Evaporation concentration: The copper electrolysis waste liquid is pumped into the waste liquid storage tank, and steam is turned on for evaporation concentration until the specific gravity reaches 1.4.

[0012] Cooling crystallization: The concentrated waste electrolyte is pumped into a water - cooled crystallization tank for cooling to precipitate copper sulfate, and then a centrifuge is used to filter the copper sulfate to obtain crude copper sulfate.

[0013] b. Two - stage electrowinning: The copper sulfate crystallization mother liquor produced in step a first passes through a first - stage electrowinning cell for electrowinning to produce copper and a first - stage copper - removed mother liquor, with a circulation rate of 20 L / min, a temperature of 45 °C, and a current density of 200 A / m 2 ; The first - stage copper - removed mother liquor passes through a second - stage electrowinning cell for secondary copper removal to produce black copper slag and nickel - containing electrowinning solution, with a circulation rate of 10 L / min, a temperature of 54 °C, and a current density of 180 A / m 2 .

[0014] c. Ball milling - synergistic oxidation acid leaching - metal cascade precipitation: The black copper slag produced in step b is taken for ball milling, and sodium persulfate is added at 0.6 mol / L during the ball milling process. The ball - milled slurry is pumped into a reaction kettle, and sulfuric acid is added at 2 mol / L for leaching; after solid - liquid separation, calcium hydroxide is added to the leaching solution for cascade pH adjustment. First, the pH is adjusted to 3 to precipitate calcium arsenate, and after solid - liquid separation, the pH is adjusted again to 5 to precipitate copper hydroxide and return it to the large system. Cascade precipitation uses calcium hydroxide to adjust the pH to ensure that copper and arsenic precipitate in the form of copper hydroxide and calcium arsenate respectively within different pH ranges, realizing the separation of arsenic and copper in the black copper slag.

[0015] d. The nickel - containing electrowinning solution obtained in step c is subjected to evaporation concentration - freeze crystallization to obtain crude nickel sulfate: Evaporation concentration: The secondary copper - removed mother liquor is pumped into an evaporation kettle and steam is turned on for evaporation concentration; Freeze crystallization: The concentrated nickel sulfate crystallization solution is pumped into a nickel sulfate crystallization tank, and a brine unit is turned on to produce refrigerant liquid. At low temperature, nickel sulfate crystallizes out to produce crude nickel sulfate.

[0016] e. The crude nickel sulfate obtained in step d is subjected to sulfide conversion - nitric acid dissolution - purification and impurity removal - single precipitation - calcination decomposition - reduction to finally obtain a single - element nickel product: Sulfide conversion: Take crude nickel sulfate and slurry it at a solid-liquid ratio of 1:4 and a temperature of 60 °C. Use sodium sulfide as the sulfiding reagent. Calculate the theoretical amount according to NiSO4 + Na2S = NiS↓ + Na2SO4, and add sodium sulfide at 2 times the theoretical amount. After 2 hours of conversion, nickel sulfide is obtained.

[0017] Nitric acid dissolution: Take nickel sulfide and slurry it at a solid-liquid ratio of 1:4 and a temperature of 70 °C. Add nitric acid at 2 mol / L to dissolve the nickel sulfide.

[0018] Purification and impurity removal: Adjust the pH of the nickel sulfide nitric acid dissolution solution to 4. After heating and boiling for 8 minutes, let it stand for 1 hour for solid-liquid separation to obtain a pure nickel sulfide nitric acid leaching solution. Pass hydrogen sulfide for final purification until no obvious black impurities are produced as the end point.

[0019] Single precipitation: Add C4H8N2O2 to the purified nickel sulfide solution to form a bright red precipitate of C8H 14 N4O4Ni, and stop when no obvious bright red precipitate is produced as the end point.

[0020] Calcination decomposition - reduction: Wash C8H 14 N4O4Ni with pure water multiple times, heat it at 750 °C for 2 hours. After calcination, NiO is obtained, and Ni is obtained by reduction with hydrazine hydrate.

[0021] Example 2: A method for resource treatment and recovery of copper and nickel from copper electrolyte, comprising the following steps: a. The copper electrolysis waste liquid undergoes evaporation concentration - cooling crystallization to produce crude copper sulfate: Evaporation concentration: Pump the copper electrolysis waste liquid into the waste liquid storage tank, turn on the steam for evaporation concentration until the specific gravity reaches 1.4.

[0022] Cooling crystallization: Pump the concentrated waste electrolyte into a water-cooled crystallization tank for cooling to precipitate copper sulfate, and then use a centrifuge to filter the copper sulfate to obtain crude copper sulfate.

[0023] b. Two-stage electrowinning: The copper sulfate crystallization mother liquor produced in step a first passes through a first-stage electrowinning cell for electrowinning to produce copper and a first-stage copper-depleted mother liquor, with a circulation rate of 20 L / min, a temperature of 45 °C, and a current density of 200 A / m 2 ; The first-stage copper-depleted mother liquor passes through a second-stage electrowinning cell for secondary copper removal to produce black copper slag and nickel-containing electrowinning solution, with a circulation rate of 10 L / min, a temperature of 54 °C, and a current density of 180 A / m 2 .

[0024] c Ball milling - synergistic oxidation acid leaching - metal cascade precipitation: Take the black copper slag produced in step b for ball milling. Before ball milling, mix the black copper slag and sodium persulfate, with a mixing ratio of 100:6. After mixing evenly, conduct ball milling. The ball-milled slurry is pumped into a reaction kettle, and sulfuric acid is added for leaching at a concentration of 2 mol / L. After solid-liquid separation, calcium hydroxide is added to the leachate to adjust the pH stepwise. First, adjust the pH to 3 to precipitate calcium arsenate, and after solid-liquid separation, adjust the pH to 5 again to precipitate copper hydroxide and return it to the large system. The cascade precipitation uses calcium hydroxide to adjust the pH to ensure that copper and arsenic precipitate in the forms of copper hydroxide and calcium arsenate respectively within different pH ranges, realizing the separation of arsenic and copper in the black copper slag.

[0025] d Take the nickel-containing electrolyte solution obtained in step c and obtain crude nickel sulfate through evaporation concentration - freeze crystallization: Evaporation concentration: Pump the secondary copper-removed solution into an evaporation kettle and start the steam for evaporation concentration; Freeze crystallization: Pump the concentrated nickel sulfate crystallization solution into a nickel sulfate crystallization tank, start the brine unit to produce refrigerant liquid, and nickel sulfate crystallizes out at low temperature to obtain crude nickel sulfate.

[0026] e Take the crude nickel sulfate obtained in step d and obtain elemental nickel products through sulfidation conversion - nitric acid dissolution - purification and impurity removal - single precipitation - calcination decomposition - reduction: Sulfidation conversion: Take the crude nickel sulfate and slurry it at a solid-liquid ratio of 1:4 and a temperature of 60 °C. The sulfiding reagent is a mixture of sodium sulfide and hydrogen sulfide, with a mixing ratio of 1:1. Calculate the theoretical amount according to NiSO4 + Na2S = NiS↓ + Na2SO4, and add the sulfiding agent mixture at 2 times the theoretical amount. After conversion for 2 h, nickel sulfide is obtained.

[0027] Nitric acid dissolution: Take nickel sulfide and slurry it at a solid-liquid ratio of 1:4 and a temperature of 70 °C, and add nitric acid at a concentration of 2 mol / L to dissolve the nickel sulfide.

[0028] Purification and impurity removal: Adjust the pH of the nickel sulfide nitric acid dissolution solution to 5, heat it to boiling for 10 min, then let it stand for 1.5 h for solid-liquid separation to obtain a pure nickel sulfide nitric acid leaching solution, and pass hydrogen sulfide for final purification until no obvious black impurities are produced as the end point.

[0029] Single precipitation: Add C4H8N2O2 to the purified nickel sulfide solution to form a bright red precipitate of C8H 14 N4O4Ni, with no obvious bright red precipitate being produced as the end point.

[0030] Calcination decomposition - reduction: Wash C8H 14 N4O4Ni with pure water multiple times, heat it at 750 °C for 2 h, obtain NiO after calcination, and reduce it with hydrogen to obtain Ni.

Claims

1. A method for resource treatment and recovery of copper and nickel from copper electrolyte, characterized in that It includes the following technological steps: a. The copper electrolysis waste liquid undergoes evaporation concentration - cooling crystallization to produce crude copper sulfate; b. After crystallization, the liquid is subjected to two - stage electrowinning to produce copper, black copper slag, and nickel - containing electrowinning solution; c. The black copper slag undergoes ball milling - synergistic oxidative acid leaching - metal cascade precipitation process to produce copper hydroxide and calcium arsenate; d. The nickel - containing electrowinning solution undergoes evaporation concentration - freeze crystallization to obtain crude nickel sulfate; e. The crude nickel sulfate undergoes sulfide conversion - nitric acid dissolution - purification and impurity removal - single precipitation - calcination decomposition - reduction to finally obtain elemental nickel products.

2. The method for resource treatment and recovery of copper and nickel from copper electrolyte as claimed in claim 1, wherein In the synergistic oxidative acid leaching process in step c, the oxidant used is sodium persulfate, and the acidic reagent used is sulfuric acid. Before ball milling, the black copper slag and sodium persulfate are mixed or sodium persulfate is added while ball milling. The sodium persulfate is added to the black copper slag at a ratio of 0.5 - 1 mol / L. After ball milling, the slurry is pumped into the reaction kettle and sulfuric acid is added. The sulfuric acid is added to the slurry at a ratio of 1 - 3 mol / L.

3. A method for resource treatment and recovery of copper and nickel from copper electrolyte as claimed in claim 1 or 2, characterized in that In the metal cascade precipitation process in step c, the pH is adjusted in a step - by - step manner. The regulator is calcium hydroxide. The pH for arsenic precipitation is 2 - 4, and the pH for copper precipitation is 5 - 6.

4. A method for resource treatment and recovery of copper and nickel from copper electrolyte as claimed in claim 1 or 2, characterized in that In the sulfide conversion process in step e, the sulfide used is any one or a mixture of two or more of sodium sulfide, hydrogen sulfide, and sodium bisulfide.

5. A method for resource treatment and recovery of copper and nickel from copper electrolyte as claimed in claim 1 or 2, characterized in that In step e, the impurity remover used is hydrogen sulfide. For purification and impurity removal, the pH is first adjusted to 4 - 5, then heated and boiled for 5 - 10 min, and then left to stand for 1 - 1.5 h.

6. A method for resource treatment and recovery of copper and nickel from copper electrolyte as claimed in claim 1 or 2, characterized in that In the single precipitation process in step e, the precipitant used is C4H8N2O2, and Ni 2+ is converted and precipitated to form a bright red precipitate of C8H 14 N4O4Ni. After calcining at 700-800 °C for 1-2 h, NiO is obtained.

7. A method for resource treatment and recovery of copper and nickel from copper electrolyte as claimed in claim 1 or 2, characterized in that In the reduction process in step e, the reducing agent used is hydrogen or hydrazine hydrate.

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