Process method for producing superfine copper powder through combined recovery of waste copper materials and acid etching liquid

Abstract

The invention particularly relates to a process method for producing superfine copper powder through combined recovery of a waste copper material and an acid etching solution. The process method comprises the following steps that the waste copper material is dissolved into the acid etching solution of a first-stage reaction kettle to form a uniform solution; discharging into a second-stage reaction kettle, and adding liquid caustic soda to react to obtain a turbid solution; transferring into a heating kettle after membrane separation; sulfuric acid is added into the heating kettle for heating reaction, and a superfine copper powder primary product is separated out from the solution; separating the solution containing the ultrafine copper powder primary product to obtain ultrafine copper powder and a copper sulfate solution, and drying the ultrafine copper powder at low temperature to obtain an ultrafine copper powder product; and discharging the copper sulfate solution into a three-stage reaction kettle, adding sulfuric acid for pretreatment, transferring into a crystallization kettle for freezing treatment, centrifuging, cleaning, separating, drying and the like to obtain the copper sulfate pentahydrate. The method is high in yield and low in energy consumption, wastewater discharge is reduced, and a sustainable raw material route is provided for production of superfine copper powder and copper sulfate pentahydrate.

Description

Technical Field

[0001] The invention relates to the technical field of recycling of waste copper materials, and in particular to a process for producing ultrafine copper powder by jointly recycling waste copper materials and acidic etching solution. Background Art

[0002] In the electronics manufacturing industry, copper plate processing generates a large amount of copper scrap (such as scraps and drilling shavings) and acidic etching solutions (primarily containing Cu²⁺, Cl⁻, and H⁺). Currently, there are two main methods for recycling copper scrap: pyrometallurgy and hydrometallurgy. Pyrometallurgy involves oxidizing and removing impurities from the scrap copper through high-temperature smelting. This method is energy-intensive, produces large amounts of waste gas, and significantly pollutes the environment. Furthermore, the copper recovery rate is limited. Hydrometallurgy typically uses chemical solvents to dissolve the scrap copper, but this process involves the use of large amounts of chemical reagents, resulting in highly polluting wastewater. It also presents complex processes and high costs. Acidic etching solutions, on the other hand, are primarily treated through neutralization precipitation. Neutralization precipitation uses alkaline substances to precipitate copper ions. However, this method produces coarse precipitates with high levels of residual chloride ions, making them difficult to directly use in high-value-added products. Consequently, these methods for treating both scrap copper and acidic etching solutions suffer from low resource efficiency, high risk of secondary pollution, and low product value.

[0003] To this end, by combining scrap copper and acidic etching solution to produce ultrafine copper powder, the acidic etching solution can not only dissolve the scrap copper, achieving the goal of "treating waste with waste and turning waste into treasure", but also significantly improve the copper recovery rate and produce high-value-added ultrafine copper powder products. Therefore, this application proposes a process for combining scrap copper and acidic etching solution to produce ultrafine copper powder. Summary of the Invention

[0004] The purpose of the present invention is to solve the above-mentioned deficiencies in the prior art and to provide a process for producing ultrafine copper powder by jointly recovering waste copper and acid etching solution.

[0005] The object of the present invention is achieved by the following technical solution: The present invention provides a process for producing ultrafine copper powder by jointly recovering waste copper and acid etching solution, comprising the following steps: S1. The acidic etching solution used in the production line is discharged into a primary reactor, and waste copper is added thereto to completely dissolve the waste copper to form a uniform solution; S2, the uniform solution is discharged into the secondary reaction kettle, and liquid alkali is added to the secondary reaction to obtain a turbid solution; S3, after the turbid solution is separated by membrane, it is transferred to a heating kettle; S4, adding sulfuric acid to the heating kettle and raising the temperature to react, and the initial product of ultrafine copper powder is precipitated in the solution; S5, subjecting the solution containing the ultrafine copper powder primary product to solid-liquid separation by a high-speed centrifuge to obtain ultrafine copper powder and copper sulfate solution, respectively, and drying the ultrafine copper powder at a low temperature under an inert gas atmosphere to obtain an ultrafine copper powder product; S6, the copper sulfate solution is discharged into the three-stage reactor, and sulfuric acid is added thereto for pretreatment, and the resulting solution is passed through a precision filter and then enters a crystallization kettle; S7, lowering the temperature of the crystallization kettle to freeze the copper sulfate solution, and then separating it through a high-speed centrifuge to obtain copper sulfate pentahydrate crystals, and recovering the permeate to the mother liquor tank for recycling; S8. Using a saturated copper sulfate solution, the copper sulfate pentahydrate crystals obtained in step S7 are cleaned and subjected to a secondary centrifugal separation. After the separated copper sulfate pentahydrate crystals are dried, electroplating-grade superior copper sulfate pentahydrate is obtained.

[0006] Furthermore, the acidic etching solution contains the following components: 90-120 g / L of copper ions, 220-240 g / L of chloride ions, and 2-3 g / L of hydrogen ions.

[0007] Furthermore, in step S1, the mass ratio of the scrap copper material to the acidic etching solution is 1:10-15.

[0008] Furthermore, in step S1, hydrogen peroxide and a catalyst are added to the primary reactor, wherein the amount of hydrogen peroxide is 0.3-0.6 vol%, and the amount of the catalyst is an iron-based catalyst and / or a copper-based catalyst, and the amount of the catalyst is 0.01-0.05 mol / L. The temperature of the primary reactor is 35-40°C, and the dissolution time is 0.5-1 hour.

[0009] In the present invention, the waste copper material is catalytically oxidized and dissolved by adding hydrogen peroxide and an iron-based catalyst, which can significantly shorten the dissolution time of the waste copper material, increase the reaction rate, and avoid the precipitation of cuprous chloride.

[0010] Furthermore, in step S2, the liquid alkali is any one of sodium hydroxide, potassium hydroxide, and ammonia water.

[0011] Furthermore, in step S2, sodium citrate is also added to the secondary reaction, and the liquid alkali is added intermittently.

[0012] Furthermore, the pH of the solution in the secondary reactor is controlled to be 3.5-4.0 by the amount of liquid alkali added, the amount of sodium citrate added is 0.05-0.1 mol / L, the temperature is 25-40° C., the mechanical stirring speed is 200-300 rpm, and the reaction time is 30-60 min.

[0013] In the present invention, by introducing sodium citrate and intermittently adding liquid caustic soda, the reaction is made more uniform, avoiding excessively high alkali concentration in the secondary reactor, which leads to excessively large or uneven precipitate particles, and facilitating the production of copper hydroxide colloid with uniform particle size. Specifically, the liquid caustic soda can be added in three steps, with each step separated by 5-10 minutes. By adding the liquid caustic soda in steps, the reaction is made more uniform, and the precipitate particles in the resulting turbid solution are finer and more uniform.

[0014] Furthermore, in step S3, the membrane used for the membrane separation is an ultrafiltration ceramic membrane, the operating pressure of the membrane separation is 0.25-0.35 MPa, the pore size of the ultrafiltration membrane is 50-100 nm, and the initial temperature of the heating kettle is 25-40°C.

[0015] Furthermore, in step S3, a portion of the concentrated liquid after membrane separation is piped back to the secondary reactor for reuse. The return volume of the concentrated liquid is controlled to maintain the copper ion concentration of the solution in the secondary reactor at 80-90% of the initial concentration. In the present invention, by reusing the concentrated liquid after membrane separation back to the secondary reactor, raw material and energy consumption are reduced, while also reducing wastewater discharge.

[0016] Furthermore, in step S4, a surfactant is added to the heating kettle, wherein the surfactant is any one of sodium lauryl sulfate, polyvinyl pyrrolidone, and hexadecyltrimethylammonium bromide, and the amount of the surfactant is 0.05-0.5 wt%.

[0017] Furthermore, in step S4, a reducing agent is added to the heating kettle, and the reducing agent is at least one of ethylene glycol, ascorbic acid, and hydrazine hydrate, and the molar ratio of the reducing agent to the copper content in the heating kettle solution is 1-1.2:1.

[0018] Furthermore, in step S4, the temperature of the heating kettle is increased to 40-60°C, the heating rate is 1-3°C / min, the holding time is 20-40min, the sulfuric acid concentration is 0.5-1mol / L, and the mechanical stirring rate is 200-400rpm.

[0019] In the present invention, the addition of a surfactant can prevent the agglomeration of copper powder particles, so that the generated ultrafine copper powder can maintain a small particle size and good dispersibility. Furthermore, the addition of a reducing agent can effectively increase the reaction rate and improve the yield of ultrafine copper powder. In addition, in order to prevent oxidation of the copper powder in step S4, the heating kettle can also be protected by an inert gas, which is generally nitrogen or argon.

[0020] Furthermore, in step S5, deionized water is used for multiple centrifugal washing, with the high-speed centrifuge speed being 8000-12000 rpm for 10-15 minutes; the separated ultrafine copper powder is then washed with a mixed solution of 0.1M dilute sulfuric acid and ethanol at a mass ratio of 1:1. In the present invention, washing with a mixed solution of dilute sulfuric acid and ethanol can improve the dispersibility of the ultrafine copper powder, avoid agglomeration, and prevent oxidation.

[0021] Furthermore, in step S6, 98% sulfuric acid is added to make the hydrogen ion concentration of the solution in the tertiary reactor reach 4.3-4.5 mol / L.

[0022] Furthermore, in step S7, the crystallization temperature of the crystallization kettle is 0-5°C, and the crystallization freezing time is 3-5h; a three-stage gradient cooling is adopted, the first stage is reduced from room temperature to about 15°C, the cooling rate is 1-2°C / min, and the temperature is kept for 1h; the second stage is reduced from 15°C to about 5°C, and the temperature is kept for 1-2h, and the cooling rate is 0.5-1°C / min; the third stage is reduced from 5°C to 0-5°C, and the temperature is kept for 1-2h, and the cooling rate is 0.2-0.5°C / min.

[0023] Furthermore, in step S7, 0.1 wt% of copper sulfate pentahydrate microcrystals are added to the crystallization kettle.

[0024] Furthermore, in step S7, the permeate obtained by separation in the high-speed centrifuge is transported to a mother liquid tank via a pipeline, and the copper ion concentration in the solution is monitored in real time in the mother liquid tank. When the copper ion concentration is greater than 10 g / L, the permeate is passed through an ion exchange resin column at a flow rate ratio of 10-20% to remove impurity ions and then returned to the primary reactor for use.

[0025] In the present invention, impurities such as iron ions in the permeate are removed through an ion exchange resin column, and the uncrystallized copper ions in the permeate are returned to the primary reactor to participate in the reaction again, thereby achieving efficient recycling of materials, reducing wastewater discharge, and lowering production costs.

[0026] The present invention provides a process for producing ultrafine copper powder by combining waste copper and acidic etching solutions. By recycling and reprocessing the waste copper and acidic etching solutions generated during copper plate processing, the process achieves efficient resource recovery and utilization, producing high-value-added ultrafine copper powder and copper sulfate pentahydrate. The ultrafine copper powder obtained by this method has a small particle size and is uniformly distributed; the copper sulfate pentahydrate is of high purity, reaching electroplating grade standards. Catalytic oxidative dissolution reduces energy consumption and improves the dissolution efficiency of waste copper. The use of membrane separation and ion exchange technologies allows for the reuse of mother liquor, significantly reducing wastewater discharge. DETAILED DESCRIPTION

[0027] In order to facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the embodiments. The contents mentioned in the embodiments are not intended to limit the present invention.

[0028] Example 1 This embodiment provides a process for producing ultrafine copper powder by jointly recovering waste copper and acidic etching solution, comprising the following steps: S1. The acidic etching solution used in the production line is discharged into a primary reactor, and waste copper is added thereto to completely dissolve the waste copper to form a uniform solution; S2, the uniform solution is discharged into the secondary reaction kettle, and liquid alkali is added to the secondary reaction to obtain a turbid solution; S3, after the turbid solution is separated by membrane, it is transferred to a heating kettle; S4, adding sulfuric acid to the heating kettle and raising the temperature to react, and the initial product of ultrafine copper powder is precipitated in the solution; S5, subjecting the solution containing the ultrafine copper powder primary product to solid-liquid separation by a high-speed centrifuge to obtain ultrafine copper powder and copper sulfate solution, respectively, and drying the ultrafine copper powder at a low temperature under an inert gas atmosphere to obtain an ultrafine copper powder product; S6, the copper sulfate solution is discharged into the three-stage reactor, and sulfuric acid is added thereto for pretreatment, and the resulting solution is passed through a precision filter and then enters a crystallization kettle; S7, lowering the temperature of the crystallization kettle to freeze the copper sulfate solution, and then separating it through a high-speed centrifuge to obtain copper sulfate pentahydrate crystals, and recovering the permeate to the mother liquor tank for recycling; S8. Using a saturated copper sulfate solution, the copper sulfate pentahydrate crystals obtained in step S7 are cleaned and subjected to a secondary centrifugal separation. After the separated copper sulfate pentahydrate crystals are dried, electroplating-grade superior copper sulfate pentahydrate is obtained.

[0029] Furthermore, the acidic etching solution contains the following components: 90 g / L copper ions, 220 g / L chloride ions, and 2 g / L hydrogen ions.

[0030] Furthermore, in step S1, the mass ratio of the scrap copper material to the acidic etching solution is 1:10.

[0031] Furthermore, in step S1, hydrogen peroxide and a catalyst were added to the primary reactor, wherein the amount of hydrogen peroxide was 0.3 vol%, the amount of the catalyst was an iron-based catalyst, and the amount of the catalyst was 0.02 mol / L. The temperature of the primary reactor was 35° C., and the dissolution time was 1 hour.

[0032] Furthermore, in step S2, the liquid alkali is potassium hydroxide.

[0033] Furthermore, in step S2, sodium citrate is also added to the secondary reaction, and liquid alkali is added intermittently. The liquid alkali can be added three times, with an interval of 10 minutes between each addition.

[0034] Furthermore, the pH of the solution in the secondary reactor was controlled to be 3.5 by the amount of liquid alkali added, the amount of sodium citrate added was 0.06 mol / L, the temperature was 30° C., the mechanical stirring speed was 200 rpm, and the reaction time was 50 min.

[0035] Furthermore, in step S3, the membrane used for the membrane separation is an ultrafiltration ceramic membrane, the operating pressure of the membrane separation is 0.25 MPa, the pore size of the ultrafiltration membrane is 100 nm, and the initial temperature of the heating kettle is 30°C.

[0036] Furthermore, in step S3, part of the concentrated liquid after membrane separation is transported back to the secondary reactor through a pipeline, and the return amount of the concentrated liquid is controlled so that the copper ion concentration of the solution in the secondary reactor is maintained at 90% of the initial concentration.

[0037] Furthermore, in step S4, a surfactant is added to the heating kettle. The surfactant is hexadecyltrimethylammonium bromide, and the amount of the surfactant is 0.1 wt%.

[0038] Furthermore, in step S4, a reducing agent is added to the heating kettle, and the reducing agent is ascorbic acid, and the molar ratio of the reducing agent to the copper in the heating kettle solution is 1:1.

[0039] Furthermore, in step S4, the temperature of the heating kettle is increased to 40°C at a heating rate of 2°C / min, the holding time is 30 minutes, the sulfuric acid concentration is 0.5 mol / L, and the mechanical stirring rate is 200 rpm. In step S4, to prevent oxidation of the copper powder, the heating kettle can also be ventilated with nitrogen.

[0040] Furthermore, in step S5, deionized water is used for multiple centrifugal washing, the speed of the high-speed centrifuge is 8000 rpm, and the time is 15 minutes; then the separated ultrafine copper powder is washed with a mixed solution of 0.1M dilute sulfuric acid and ethanol with a mass ratio of 1:1.

[0041] Furthermore, in step S6, 98% sulfuric acid is added to make the hydrogen ion concentration of the solution in the tertiary reactor reach 4.3 mol / L.

[0042] Furthermore, in step S7, the crystallization temperature of the crystallization kettle is 0°C, and the crystallization freezing time is 4h; a three-stage gradient cooling is adopted, the first stage is reduced from room temperature to about 15°C, the cooling rate is 2°C / min, and the temperature is kept for 1h; the second stage is reduced from 15°C to about 5°C, and the temperature is kept for 1h, and the cooling rate is 1°C / min; the third stage is reduced from 5°C to 0°C, and the temperature is kept for 2h, and the cooling rate is 0.5°C / min.

[0043] Furthermore, in step S7, 0.1 wt% of copper sulfate pentahydrate microcrystals are added to the crystallization kettle.

[0044] Furthermore, in step S7, the permeate obtained by separation in the high-speed centrifuge is transported to a mother liquid tank via a pipeline, and the copper ion concentration in the solution is monitored in real time in the mother liquid tank. When the copper ion concentration is greater than 10 g / L, the permeate is passed through an ion exchange resin column at a flow rate ratio of 10% to remove impurity ions and then returned to the primary reactor for use.

[0045] In this embodiment, the copper conversion rate is 99.2%, the yield of the ultrafine copper powder is 98.5%, the average particle size of the ultrafine copper powder is 100 nm, the yield of copper sulfate pentahydrate is 97%, the purity of copper sulfate pentahydrate is 99.93%, and the wastewater discharge is 0.5 L / kg copper.

[0046] Example 2 This embodiment provides a process for producing ultrafine copper powder by jointly recovering waste copper and acidic etching solution, comprising the following steps: S1. The acidic etching solution used in the production line is discharged into a primary reactor, and waste copper is added thereto to completely dissolve the waste copper to form a uniform solution; S2, the uniform solution is discharged into the secondary reaction kettle, and liquid alkali is added to the secondary reaction to obtain a turbid solution; S3, after the turbid solution is separated by membrane, it is transferred to a heating kettle; S4, adding sulfuric acid to the heating kettle and raising the temperature to react, and the initial product of ultrafine copper powder is precipitated in the solution; S5, subjecting the solution containing the ultrafine copper powder primary product to solid-liquid separation by a high-speed centrifuge to obtain ultrafine copper powder and copper sulfate solution, respectively, and drying the ultrafine copper powder at a low temperature under an inert gas atmosphere to obtain an ultrafine copper powder product; S6, the copper sulfate solution is discharged into the three-stage reactor, and sulfuric acid is added thereto for pretreatment, and the resulting solution is passed through a precision filter and then enters a crystallization kettle; S7, lowering the temperature of the crystallization kettle to freeze the copper sulfate solution, and then separating it through a high-speed centrifuge to obtain copper sulfate pentahydrate crystals, and recovering the permeate to the mother liquor tank for recycling; S8. Using a saturated copper sulfate solution, the copper sulfate pentahydrate crystals obtained in step S7 are cleaned and subjected to a secondary centrifugal separation. After the separated copper sulfate pentahydrate crystals are dried, electroplating-grade superior copper sulfate pentahydrate is obtained.

[0047] Furthermore, the acidic etching solution contains the following components: 100 g / L copper ions, 230 g / L chloride ions, and 2 g / L hydrogen ions.

[0048] Furthermore, in step S1, the mass ratio of the scrap copper material to the acidic etching solution is 1:12.

[0049] Furthermore, in step S1, hydrogen peroxide and a catalyst were added to the primary reactor. The hydrogen peroxide was used in an amount of 0.4 vol%. The catalyst was composed of an iron-based catalyst and a copper-based catalyst in a mass ratio of 1:1, and the catalyst was used in an amount of 0.03 mol / L. The temperature of the primary reactor was 35°C, and the dissolution time was 0.5 h.

[0050] Furthermore, in step S2, the liquid alkali is sodium hydroxide.

[0051] Furthermore, in step S2, sodium citrate is also added to the secondary reaction, and liquid alkali is added intermittently. The liquid alkali can be added three times, with an interval of 8 minutes between each addition.

[0052] Furthermore, the pH of the solution in the secondary reactor was controlled to be 3.8 by the amount of liquid alkali added, the amount of sodium citrate added was 0.08 mol / L, the temperature was 35° C., the mechanical stirring speed was 200 rpm, and the reaction time was 40 min.

[0053] Furthermore, in step S3, the membrane used for the membrane separation is an ultrafiltration ceramic membrane, the operating pressure of the membrane separation is 0.3 MPa, the pore size of the ultrafiltration membrane is 100 nm, and the initial temperature of the heating kettle is 35°C.

[0054] Furthermore, in step S3, part of the concentrated liquid after membrane separation is transported back to the secondary reactor through a pipeline, and the return amount of the concentrated liquid is controlled so that the copper ion concentration of the solution in the secondary reactor is maintained at 90% of the initial concentration.

[0055] Furthermore, in step S4, a surfactant is added into the heating kettle. The surfactant is polyvinyl pyrrolidone, and the amount of the surfactant is 0.2 wt%.

[0056] Furthermore, in step S4, a reducing agent is added to the heating kettle, and the reducing agent is ascorbic acid, and the molar ratio of the reducing agent to the copper in the heating kettle solution is 1:1.

[0057] Furthermore, in step S4, the temperature of the heating kettle is increased to 50°C at a heating rate of 2°C / min, the holding time is 30 minutes, the sulfuric acid concentration is 0.6 mol / L, and the mechanical stirring rate is 400 rpm. In step S4, to prevent oxidation of the copper powder, the heating kettle can also be ventilated with nitrogen.

[0058] Furthermore, in step S5, deionized water is used for multiple centrifugal washing, the speed of the high-speed centrifuge is 10000 rpm, and the time is 10 minutes; then the separated ultrafine copper powder is washed with a mixed solution of 0.1M dilute sulfuric acid and ethanol with a mass ratio of 1:1.

[0059] Furthermore, in step S6, 98% sulfuric acid is added to make the hydrogen ion concentration of the solution in the tertiary reactor reach 4.5 mol / L.

[0060] Furthermore, in step S7, the crystallization temperature of the crystallization kettle is -5°C, and the crystallization freezing time is 5h; a three-stage gradient cooling is adopted, the first stage is reduced from room temperature to about 15°C, the cooling rate is 1°C / min, and the temperature is kept for 1h; the second stage is reduced from 15°C to about 5°C, and the temperature is kept for 2h, and the cooling rate is 0.5°C / min; the third stage is reduced from 5°C to 0°C, and the temperature is kept for 2h, and the cooling rate is 0.2°C / min.

[0061] Furthermore, in step S7, 0.1 wt% of copper sulfate pentahydrate microcrystals are added to the crystallization kettle.

[0062] Furthermore, in step S7, the permeate obtained by separation in the high-speed centrifuge is transported to a mother liquid tank via a pipeline, and the copper ion concentration in the solution is monitored in real time in the mother liquid tank. When the copper ion concentration is greater than 10 g / L, the permeate is passed through an ion exchange resin column at a flow rate ratio of 15% to remove impurity ions and then returned to the primary reactor for use.

[0063] In this embodiment, the copper conversion rate is 99.5%, the yield of the ultrafine copper powder is 98.5%, the average particle size of the ultrafine copper powder is 90 nm, the yield of the copper sulfate pentahydrate is 98%, the purity of the copper sulfate pentahydrate is 99.95%, and the wastewater discharge is 0.5 L / kg copper.

[0064] Example 3 This embodiment provides a process for producing ultrafine copper powder by jointly recovering waste copper and acidic etching solution, comprising the following steps: S1. The acidic etching solution used in the production line is discharged into a primary reactor, and waste copper is added thereto to completely dissolve the waste copper to form a uniform solution; S2, the uniform solution is discharged into the secondary reaction kettle, and liquid alkali is added to the secondary reaction to obtain a turbid solution; S3, after the turbid solution is separated by membrane, it is transferred to a heating kettle; S4, adding sulfuric acid to the heating kettle and raising the temperature to react, and the initial product of ultrafine copper powder is precipitated in the solution; S5, subjecting the solution containing the ultrafine copper powder primary product to solid-liquid separation by a high-speed centrifuge to obtain ultrafine copper powder and copper sulfate solution, respectively, and drying the ultrafine copper powder at a low temperature under an inert gas atmosphere to obtain an ultrafine copper powder product; S6, the copper sulfate solution is discharged into the three-stage reactor, and sulfuric acid is added thereto for pretreatment, and the resulting solution is passed through a precision filter and then enters a crystallization kettle; S7, lowering the temperature of the crystallization kettle to freeze the copper sulfate solution, and then separating it through a high-speed centrifuge to obtain copper sulfate pentahydrate crystals, and recovering the permeate to the mother liquor tank for recycling; S8. Using a saturated copper sulfate solution, the copper sulfate pentahydrate crystals obtained in step S7 are cleaned and subjected to a secondary centrifugal separation. After the separated copper sulfate pentahydrate crystals are dried, electroplating-grade superior copper sulfate pentahydrate is obtained.

[0065] Furthermore, the acidic etching solution contains the following components: 120 g / L copper ions, 240 g / L chloride ions, and 3 g / L hydrogen ions.

[0066] Furthermore, in step S1, the mass ratio of the scrap copper material to the acidic etching solution is 1:13.

[0067] Furthermore, in step S1, hydrogen peroxide and a catalyst were added to the primary reactor. The amount of hydrogen peroxide was 0.5 vol%. The catalyst was composed of an iron-based catalyst and a copper-based catalyst in a mass ratio of 1:1, and the amount of the catalyst was 0.05 mol / L. The temperature of the primary reactor was 40° C., and the dissolution time was 0.5 h.

[0068] Furthermore, in step S2, the liquid alkali is sodium hydroxide.

[0069] Furthermore, in step S2, sodium citrate is also added to the secondary reaction, and liquid alkali is added intermittently. The liquid alkali can be added three times, with an interval of 5 minutes between each addition.

[0070] Furthermore, the pH of the solution in the secondary reactor was controlled to be 4.0 by the amount of liquid alkali added, the amount of sodium citrate added was 0.1 mol / L, the temperature was 40° C., the mechanical stirring speed was 200 rpm, and the reaction time was 50 min.

[0071] Furthermore, in step S3, the membrane used for the membrane separation is an ultrafiltration ceramic membrane, the operating pressure of the membrane separation is 0.35 MPa, the pore size of the ultrafiltration membrane is 50 nm, and the initial temperature of the heating kettle is 40°C.

[0072] Furthermore, in step S3, part of the concentrated liquid after membrane separation is transported back to the secondary reactor through a pipeline, and the return amount of the concentrated liquid is controlled so that the copper ion concentration of the solution in the secondary reactor is maintained at 80% of the initial concentration.

[0073] Furthermore, in step S4, a surfactant is added to the heating kettle. The surfactant is sodium lauryl sulfate, and the amount of the surfactant is 0.2 wt%.

[0074] Furthermore, in step S4, a reducing agent is added to the heating kettle, wherein the reducing agent is ethylene glycol, and the molar ratio of the reducing agent to the copper content in the heating kettle solution is 1.2:1.

[0075] Furthermore, in step S4, the temperature of the heating kettle is increased to 60°C at a heating rate of 2°C / min, the holding time is 30 minutes, the sulfuric acid concentration is 1 mol / L, and the mechanical stirring rate is 400 rpm. In step S4, to prevent oxidation of the copper powder, the heating kettle can also be ventilated with nitrogen.

[0076] Furthermore, in step S5, deionized water is used for multiple centrifugal washing, the speed of the high-speed centrifuge is 12000 rpm, and the time is 10 minutes; then the separated ultrafine copper powder is washed with a mixed solution of 0.1M dilute sulfuric acid and ethanol with a mass ratio of 1:1.

[0077] Furthermore, in step S6, 98% sulfuric acid is added to make the hydrogen ion concentration of the solution in the tertiary reactor reach 4.5 mol / L.

[0078] Furthermore, in step S7, the crystallization temperature of the crystallization kettle is 0°C, and the crystallization freezing time is 4h; a three-stage gradient cooling is adopted, the first stage is reduced from room temperature to about 15°C, the cooling rate is 1°C / min, and the temperature is kept for 1h; the second stage is reduced from 15°C to about 5°C, and the temperature is kept for 1h, and the cooling rate is 1°C / min; the third stage is reduced from 5°C to 0°C, and the temperature is kept for 2h, and the cooling rate is 0.5°C / min.

[0079] Furthermore, in step S7, 0.1 wt% of copper sulfate pentahydrate microcrystals are added to the crystallization kettle.

[0080] Furthermore, in step S7, the permeate obtained by separation in the high-speed centrifuge is transported to a mother liquid tank via a pipeline, and the copper ion concentration in the solution is monitored in real time in the mother liquid tank. When the copper ion concentration is greater than 10 g / L, the permeate is passed through an ion exchange resin column at a flow rate ratio of 20% to remove impurity ions and then returned to the primary reactor for use.

[0081] In this embodiment, the copper conversion rate is 99.1%, the yield of the ultrafine copper powder is 98.3%, the average particle size of the ultrafine copper powder is 90 nm, the yield of the copper sulfate pentahydrate is 96.8%, the purity of the copper sulfate pentahydrate is 99.92%, and the wastewater discharge is 0.6 L / kg copper.

[0082] Comparative Example 1 The difference between this comparative example and Example 2 is: In step S1, the acidic etching solution used in the production line is discharged into the primary reactor, and waste copper is added thereto to completely dissolve the waste copper to form a uniform solution. The temperature of the primary reactor is 80°C and the stirring rate is 80 rpm.

[0083] In step S2, the liquid alkali is 3 mol / L sodium hydroxide, the volume ratio of the acidic etching solution to the liquid alkali is 1:2, the reaction temperature is 70° C., and the stirring rate is 120 rpm.

[0084] In step S4, 50% sulfuric acid was added to the heating kettle, and the temperature was raised to 65° C., and the stirring rate was 100 rpm, and the primary product of ultrafine copper powder was precipitated in the solution.

[0085] The rest of the content is similar to that of Example 2 and will not be repeated here.

[0086] In this comparative example, the above method achieved complete dissolution of the copper scrap in step S1 of 4 hours, and a 2-hour alkali reaction in step S2. The copper conversion rate was 85%, the yield of ultrafine copper powder was 82%, and the particle size of the resulting ultrafine copper powder was 1-10 μm. The yield of copper sulfate pentahydrate was 80.5%, the purity of copper sulfate pentahydrate was 99.5%, and the wastewater discharge was 3 L / kg of copper.

[0087] The above specific embodiments are further explanations of the technical solutions and beneficial effects of the present invention, and are not intended to limit the implementation methods. For those skilled in the art, any obvious substitutions that do not depart from the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A process for producing ultrafine copper powder by combining waste copper and acidic etching solution, characterized in that: The steps include: S1. The acidic etching solution used in the production line is discharged into a primary reactor, and waste copper is added thereto to completely dissolve the waste copper to form a uniform solution; S2, the uniform solution is discharged into the secondary reaction kettle, and liquid alkali is added to the secondary reaction to obtain a turbid solution; S3, after the turbid solution is separated by membrane, it is transferred to a heating kettle; S4, adding sulfuric acid to the heating kettle and raising the temperature to react, and the initial product of ultrafine copper powder is precipitated in the solution; S5, subjecting the solution containing the ultrafine copper powder primary product to solid-liquid separation by a high-speed centrifuge to obtain ultrafine copper powder and copper sulfate solution, respectively, and drying the ultrafine copper powder at a low temperature under an inert gas atmosphere to obtain an ultrafine copper powder product; S6, the copper sulfate solution is discharged into the three-stage reactor, and sulfuric acid is added thereto for pretreatment, and the resulting solution is passed through a precision filter and then enters a crystallization kettle; S7, lowering the temperature of the crystallization kettle to freeze the copper sulfate solution, and then separating it through a high-speed centrifuge to obtain copper sulfate pentahydrate crystals, and recovering the permeate to the mother liquor tank for recycling; S8. Using a saturated copper sulfate solution, the copper sulfate pentahydrate crystals obtained in step S7 are cleaned and subjected to a secondary centrifugal separation. After the separated copper sulfate pentahydrate crystals are dried, electroplating-grade superior copper sulfate pentahydrate is obtained.

2. The process for producing ultrafine copper powder by combining waste copper and acidic etching solution according to claim 1, characterized in that: The acidic etching solution contains the following components: 90-120 g / L of copper ions, 220-240 g / L of chloride ions, and 2-3 g / L of hydrogen ions.

3. The process for producing ultrafine copper powder by combining waste copper and acidic etching solution according to claim 1, characterized in that: In step S2, the liquid alkali is any one of sodium hydroxide, potassium hydroxide, and ammonia water.

4. The process for producing ultrafine copper powder by combining waste copper and acidic etching solution according to claim 1, characterized in that: In step S3, the membrane used for membrane separation is an ultrafiltration ceramic membrane, the operating pressure of the membrane separation is 0.25-0.35 MPa, the pore size of the ultrafiltration membrane is 50-100 nm, and the initial temperature of the heating kettle is 25-40°C.

5. The process for producing ultrafine copper powder by combining waste copper and acidic etching solution according to claim 1, characterized in that: In step S4, a surfactant is added into the heating kettle, and the surfactant is any one of sodium lauryl sulfate, polyvinyl pyrrolidone, and hexadecyltrimethylammonium bromide.

6. The process for producing ultrafine copper powder by combining waste copper and acidic etching solution according to claim 5, characterized in that: In step S4, a reducing agent is further added into the heating kettle, and the reducing agent is at least one of ethylene glycol, ascorbic acid, and hydrazine hydrate.

7. The process for producing ultrafine copper powder by combining waste copper and acidic etching solution according to claim 1, characterized in that: In step S6, sulfuric acid is added to make the hydrogen ion concentration of the solution in the tertiary reactor reach 4.3-4.5 mol / L.

8. The process for producing ultrafine copper powder by combining waste copper and acidic etching solution according to claim 1, characterized in that: In step S7, the crystallization temperature of the crystallization kettle is 0-5°C, and the crystallization freezing time is 3-5h.

9. The process for producing ultrafine copper powder by combining waste copper and acidic etching solution according to claim 1, characterized in that: In step S7, the crystallization kettle adopts a three-stage gradient cooling method, wherein the first stage is cooled from room temperature to about 15°C, the cooling rate is 1-2°C / min, and the temperature is kept for 1 hour; the second stage is cooled from 15°C to about 5°C, and the temperature is kept for 1-2 hours, and the cooling rate is 0.5-1°C / min; the third stage is cooled from 5°C to 0-5°C, and the temperature is kept for 1-2 hours, and the cooling rate is 0.2-0.5°C / min.

10. The process for producing ultrafine copper powder by combining waste copper and acidic etching solution according to claim 1, characterized in that: In step S7, the permeate obtained by separation in the high-speed centrifuge is transported to a mother liquid tank via a pipeline, and the copper ion concentration in the solution is monitored in real time in the mother liquid tank. When the copper ion concentration is greater than 10 g / L, the permeate is passed through an ion exchange resin column at a flow rate ratio of 10-20% to remove impurity ions and then returned to the primary reactor for use.