Method for recovering copper from composite copper containing sludge

Abstract

The present invention relates to a method for recovering copper from composite copper sludge, and more specifically, comprises a copper ion leaching step in which copper ions are leached by mixing an aqueous sulfuric acid solution and an aqueous hydrogen peroxide solution with the composite copper sludge; a filtration step in which the mixture from which copper ions have been leached through the copper ion leaching step is filtered to separate solid residue and copper-containing liquid; an iron substitution step in which copper is precipitated by mixing iron powder with the copper-containing liquid separated through the filtration step; and a copper recovery step in which the copper leached through the iron substitution step is recovered. The copper recovery method including the above process can recover copper contained in complex copper sludge with excellent purity and yield, and since iron sulfate can be produced from the filtrate generated during the copper recovery process, it is not only environmentally friendly but also exhibits excellent economic efficiency by enabling the resource utilization of waste.

Description

Technology Field

[0001] The present invention relates to a method for recovering copper from composite copper sludge, and more specifically, to a method for recovering copper from composite copper sludge that is not only environmentally friendly but also economically efficient, as it enables the recovery of copper contained in the composite copper sludge with excellent purity and yield, and allows for the production of iron sulfate from the liquid generated during the copper recovery process, thereby enabling the resource utilization of waste. Background Technology

[0003] Complex copper sludge contains not only copper but also other metals such as zinc, iron, nickel, and lead, as well as organic matter, solids, and moisture, and is mainly generated in the electronics and semiconductor industries, metal plating industries, and industrial wastewater treatment processes.

[0004] A representative source of complex copper sludge is the semiconductor power device manufacturing process, where large amounts of copper-containing sludge are generated during wafer processing, cleaning, patterning, and plating processes. This sludge contains fine copper particles, organic and inorganic contaminants, combined oxides, and matrix materials, and if not properly treated, it leads to serious environmental and economic problems such as heavy metal contamination and increased waste disposal costs.

[0005] In general, there is an increasing demand in industrial sites to recover and recycle copper from sludge due to the resource value and economic value of copper. Due to this increasing demand, various copper recovery methods have been proposed in the past, such as dry calcination and reduction treatment of sludge, leaching using acidic or alkaline solvents, chemical precipitation, and electrolytic refining.

[0006] However, dry calcination methods entail disadvantages such as high energy consumption, equipment investment costs, and secondary pollution (air emissions, etc.) generated during the calcination process. In addition, chemical leaching and precipitation methods face limitations in industrial application due to low recovery rates, lack of selectivity, issues with precipitation sludge treatment, and process complexity. In particular, micro and complex waste generated in semiconductor processes is difficult to treat efficiently using traditional methods, and there is a significant disadvantage in terms of residual contaminants regarding the high purity required for semiconductor manufacturing.

[0007] Therefore, recently, active research is being conducted on copper recovery methods that can simultaneously achieve leaching efficiency, control of residual oxidizers and impurities, activation of substitution reactions, high-efficiency separation, and resource recovery of the remaining liquid while overcoming the disadvantages listed above. Prior art literature

[0009] Korean Registered Publication No. 10-1658323 (2016.09.09.) Korean Registered Publication No. 10-1892098 (2018.08.21.) The problem to be solved

[0010] The objective of the present invention is to provide a method for recovering copper from complex copper sludge that is not only environmentally friendly but also highly economical, as it enables the recovery of copper contained in the complex copper sludge with excellent purity and yield, and allows for the production of iron sulfate from the filtrate generated during the copper recovery process, thereby enabling the resource utilization of waste. means of solving the problem

[0012] The objective of the present invention can be achieved by providing a method for recovering copper from a complex copper sludge, comprising: a copper ion leaching step in which copper ions are leached by mixing an aqueous sulfuric acid solution and an aqueous hydrogen peroxide solution with the complex copper sludge; a filtration step in which the mixture from which copper ions have been leached through the copper ion leaching step is filtered to separate solid residue from copper-containing liquid; an iron substitution step in which copper is precipitated by mixing iron powder with the copper-containing liquid separated through the filtration step; and a copper recovery step in which the copper leached through the iron substitution step is recovered.

[0013] According to a preferred feature of the present invention, the copper ion leaching step is performed by mixing 10 to 20 parts by weight of an aqueous sulfuric acid solution and 2 to 5 parts by weight of an aqueous hydrogen peroxide solution with 100 parts by weight of a composite copper sludge, wherein the aqueous sulfuric acid solution has a mass concentration of 1 to 2 weight% and the aqueous hydrogen peroxide solution has a mass concentration of 30 to 40 weight%, the iron substitution step is performed by mixing 5 to 20 parts by weight of iron powder with 100 parts by weight of the copper-containing filtrate separated through the filtration step, and then performing the step at a temperature of 55 to 65°C for 8 to 10 hours, wherein the iron powder has a particle size of 50 to 300 micrometers, and the oxide film is removed through a deoxidation process, wherein the deoxidation process is performed by immersing the iron powder in an aqueous solution of a reducing agent, and the reducing agent may be ascorbic acid or sodium borohydride.

[0014] According to a more preferred feature of the present invention, after the copper recovery step, an iron sulfate recovery step is further performed to recover iron ions contained in the filtrate remaining through the copper recovery step as iron sulfate. The iron sulfate recovery step may be carried out by mixing sulfuric acid into the filtrate remaining through the copper recovery step to adjust the acid concentration to 10 to 25 weight%, then injecting nitrogen or mixing a reducing agent, and then crystallizing and filtering. Effects of the invention

[0016] The method for recovering copper from composite copper sludge according to the present invention can recover copper contained in the composite copper sludge with excellent purity and yield, and since iron sulfate can be produced from the filtrate generated during the copper recovery process, it exhibits an excellent effect of providing a copper recovery method that is not only environmentally friendly but also exhibits excellent economic efficiency by enabling the resource utilization of waste. Brief explanation of the drawing

[0018] FIG. 1 is a flowchart illustrating a method for recovering copper from composite copper sludge according to one embodiment of the present invention. FIG. 2 is a flowchart illustrating a method for recovering copper from composite copper sludge according to another embodiment of the present invention. Specific details for implementing the invention

[0019] Hereinafter, preferred embodiments of the present invention and the physical properties of each component are described in detail. This description is intended to be sufficient for a person skilled in the art to easily practice the invention, and does not imply that the technical scope and concept of the present invention are limited thereby.

[0021] The method for recovering copper from composite copper sludge according to the present invention comprises a copper ion leaching step (S101) in which copper ions are leached by mixing an aqueous sulfuric acid solution and an aqueous hydrogen peroxide solution with the composite copper sludge; a filtration step (S103) in which the mixture from which copper ions have been leached through the copper ion leaching step (S101) is filtered to separate solid residue and copper-containing liquid; an iron substitution step (S105) in which copper is precipitated by mixing iron powder with the copper-containing liquid separated through the filtration step (S103); and a copper recovery step (S107) in which the copper leached through the iron substitution step (S105) is recovered.

[0022] The copper ion leaching step (S101) above is a step of leaching copper ions by mixing an aqueous sulfuric acid solution and an aqueous hydrogen peroxide solution with a composite copper sludge, and preferably comprises mixing 10 to 20 parts by weight of an aqueous sulfuric acid solution and 2 to 5 parts by weight of an aqueous hydrogen peroxide solution with 100 parts by weight of the composite copper sludge and stirring at a speed of 100 to 300 rpm for 1 to 3 hours.

[0023] At this time, the composite copper sludge contains 5 to 45 weight percent of copper. In particular, plating waste sludge generated in the electroplating process contains a large amount of residue in the form of metallic copper or copper oxide, exhibiting a high copper content of about 20 to 45 weight percent, whereas sludge generated in the CMP and cleaning processes contains silicon oxide, organic matter, and slurry components, exhibiting a relatively low copper content of 5 to 15 weight percent.

[0024] It is preferable to use the above aqueous sulfuric acid solution containing 10 to 20 parts by weight and having a mass concentration of 1 to 2% by weight, and it serves to convert metallic copper and copper oxide in the sludge into water-soluble copper ions, promote oxidation reactions with hydrogen peroxide to improve the copper leaching rate and efficiency, stably disperse sludge particles, and prevent sedimentation and aggregation to provide a uniform leaching environment.

[0025] If the content of the above aqueous sulfuric acid solution is less than 10 parts by weight, copper leaching may be incomplete and the recovery rate may decrease, and if the content of the above aqueous sulfuric acid solution exceeds 20 parts by weight, it is undesirable because unnecessary acid consumption and inhibition of the reaction in the iron substitution step may occur.

[0026] In addition, if the mass concentration of the above-mentioned aqueous sulfuric acid solution is less than 1 weight%, the acidity of the solution is low, so the copper leaching reaction becomes incomplete and the recovery rate may decrease, and the removal of oxides from the surface of the sludge and copper ionization are not sufficiently achieved, which may hinder the activation of the subsequent iron substitution reaction. If the mass concentration of the above-mentioned aqueous sulfuric acid solution exceeds 2 weight%, unnecessary acid consumption increases, and the acidity in the solution increases excessively, which may adversely affect the reaction rate and efficiency with the iron powder in the iron substitution step (S105), and is undesirable because it may cause equipment corrosion and safety problems.

[0027] In addition, it is preferable to use an aqueous hydrogen peroxide solution mixed in an amount of 2 to 5 parts by weight with a mass concentration of 30 to 40% by weight, which serves to more effectively convert metallic copper and copper oxide in the sludge into water-soluble copper ions.

[0028] To explain in more detail, an aqueous hydrogen peroxide solution acts as a powerful oxidizing agent, converting copper metal into copper ions (Cu 2+ By oxidizing to ) and promoting the dissolution of copper oxide (CuO, Cu2O), it not only improves the copper leaching rate and efficiency, but also removes oxides from the sludge surface and provides a uniform copper leaching environment, thereby exhibiting the effect of activating the reaction with iron in the iron substitution step (S105).

[0029] If the content of the above-mentioned aqueous hydrogen peroxide solution is less than 2 parts by weight, the oxidizing power is insufficient, so copper leaching is incomplete and the recovery rate may decrease; and if the content of the above-mentioned aqueous hydrogen peroxide solution exceeds 5 parts by weight, it is undesirable because the excessive oxidation of hydrogen peroxide affects other metals in the sludge or the iron substitution step (S105), thereby impairing process efficiency and safety.

[0030] In addition, if the mass concentration of the aqueous hydrogen peroxide solution is less than 30 weight%, sufficient oxidizing power is not secured, resulting in a slow elution rate, and if the mass concentration of the aqueous hydrogen peroxide solution exceeds 40 weight%, the reaction rate becomes excessively fast, which is undesirable as it may cause local peroxidation and difficulties in process control.

[0032] The above filtration step (S103) is a step of separating solid residue and copper-containing liquid by filtering the mixture from which copper ions have been leached through the copper ion leaching step (S101). It is preferable that the process of separating solid residue and copper-containing liquid by filtering the mixture from which copper ions have been leached through the copper ion leaching step (S101) using a filtration device such as filter paper, a processable ceramic filter, and a metal mesh is performed.

[0033] The above mixture from which copper ions have been leached contains sludge residue, metal oxides, and additive residues, and these solids must be effectively removed through the above filtration device to recover a clear and uniform copper-containing liquid.

[0034] At this time, if the solid is not properly removed in the filtration step (S103), the reaction activation of the iron powder surface in the iron substitution step (S105) is inhibited, and accordingly, the copper recovery rate may decrease.

[0035] In addition, since the solid residue separated through the filtration step (S103) contains a large amount of aluminum components, aluminum sulfate can be separated by mixing with a low concentration aqueous sulfuric acid solution (0.2 to 0.4 mol) and filtering, and it is preferable to dispose of the solid residue from which aluminum sulfate has been separated.

[0036] The iron substitution step (S105) above is a step of precipitating copper by mixing iron powder into the copper-containing liquid separated through the filtration step (S103), and it is preferable that 5 to 20 parts by weight of iron powder be mixed with 100 parts by weight of the copper-containing liquid separated through the filtration step (S103), and then carried out for 8 to 10 hours at a temperature of 55 to 65°C.

[0037] When the iron substitution step (S105) is performed through the above process, copper ions are reduced to metallic copper by iron powder and precipitated, and at the same time, iron is dissolved in the solution in the form of iron ions, thereby efficiently recovering copper ions and enabling the recovery of high-purity copper in the copper recovery step (S107).

[0038] In the above iron substitution step (S105), if the iron powder content is less than 5 parts by weight, the surface area of ​​the iron powder in contact with copper ions is excessively reduced, resulting in incomplete copper precipitation and a reduced recovery rate; and if the iron powder content exceeds 20 parts by weight, the concentration of iron ions increases excessively due to the dissolution of unnecessary iron powder, which increases the burden of processing the solution and can make the recovery and separation process of the precipitate excessively complex, which is undesirable.

[0039] At this time, it is preferable to use iron powder having a particle size of 50 to 300 micrometers. If the particle size of the iron powder is less than 50 micrometers, the surface area increases, and although the copper precipitation rate is fast, it may be difficult to separate and recover the precipitate as it mixes with the precipitated copper. If the particle size of the iron powder exceeds 300 micrometers, the surface area is reduced excessively, which limits contact with copper ions, slows down the precipitation reaction rate, and reduces the recovery rate, so it is not desirable.

[0040] In addition, it is preferable to use iron powder from which the oxide film has been removed through a deoxidation process, wherein the deoxidation process is carried out by immersing the iron powder in an aqueous solution of a reducing agent having a mass concentration of 0.5 to 2 weight% for 30 to 120 minutes, and it is even more preferable that the reducing agent be ascorbic acid or sodium borohydride.

[0041] Through the above process, the oxide film removed from the iron powder activates the metal surface, thereby improving the contact area and reactivity between the iron powder and copper ions, which further increases the copper precipitation rate and recovery rate in the iron substitution step (S105).

[0042] In addition, if the temperature of the iron substitution step (S105) is less than 55℃, the reaction rate between the iron powder and copper ions slows down, resulting in incomplete precipitation and a decrease in copper recovery rate. If the temperature of the iron substitution step (S105) exceeds 65℃, excessive iron dissolution may occur or side reactions may develop, which is undesirable as it may impair process efficiency and stability.

[0043] In addition, if the reaction time of the iron substitution step (S105) is less than 8 hours, copper precipitation is not sufficiently achieved, and if the reaction time of the iron substitution step (S105) exceeds 10 hours, the above effect is not significantly improved, and unnecessary energy consumption and the possibility of side reactions increase, so it is undesirable.

[0044] The copper recovery step (S107) above is a step for recovering copper leached through the iron substitution step (S105), and it is preferable that the copper is recovered by filtering or centrifuging the liquid containing copper leached through the iron substitution step (S105).

[0045] It is more preferable to wash the copper recovered through the copper recovery step (S107) with purified water to remove residual iron ions, sulfuric acid, and other impurities on the surface of the copper, and then proceed with the drying process.

[0046] In addition, after the copper recovery step (S107), an iron sulfate recovery step (S109) is further performed to recover iron ions contained in the filtrate remaining through the copper recovery step (S107) as iron sulfate. The iron sulfate recovery step (S109) preferably consists of mixing sulfuric acid into the filtrate remaining through the copper recovery step (S107) to adjust the acid concentration to 10 to 25 weight%, then injecting nitrogen or mixing a reducing agent, and then crystallizing and filtering.

[0047] If the iron sulfate recovery step (S109) performed by the above process is further carried out, the iron component remaining in the filtrate after copper recovery can be efficiently recovered and secured in the form of iron sulfate. In particular, in the iron sulfate recovery step (S109), sulfuric acid is mixed into the filtrate to adjust the acid concentration to 10 to 25 weight%, and iron ions are stabilized by injecting nitrogen or mixing a reducing agent, and then crystallization and filtration are performed, thereby recovering high-purity iron sulfate as a solid.

[0048] This process removes iron components from the filtrate, reducing the burden of subsequent wastewater treatment and enabling the recycling of iron resources. Furthermore, it not only improves the resource utilization efficiency and economic viability of the entire copper recovery process but also demonstrates eco-friendly effects.

[0049] If the acid concentration of the above liquid is less than 10%, the solubility of iron ions is low, so crystallization may occur unevenly or the precipitation rate may be slowed, which may reduce the recovery rate; and if the acid concentration of the above liquid exceeds 25%, it is undesirable because the excessive acid concentration may cause side reactions in the solution or have an adverse effect on the growth and purity of iron sulfate crystals.

[0050] At this time, it is preferable that the nitrogen injection rate be 0.1 to 0.5 L / min based on 1 L of liquid, and it is preferable to use sodium borohydride, zinc, zinc sulfate, etc. as the reducing agent.

[0052] Hereinafter, the method for recovering copper from composite copper sludge according to the present invention and the physical properties of the copper recovered by the recovery method will be explained with reference to examples.

[0054] <Preparation Example 1> Preparation of iron powder with oxide film removed

[0055] Iron powder with the oxide film removed was prepared by impregnating iron powder (particle size 50 to 300 micrometers) in an aqueous ascorbic acid solution with a mass concentration of 1 wt% for 60 minutes through a deoxidation process.

[0057] <Example 1>

[0058] 100 parts by weight of composite copper sludge (generated in the electroplating process, containing about 30% copper) were mixed with 15 parts by weight of an aqueous sulfuric acid solution (mass concentration of 1.5 wt%) and 3.5 parts by weight of an aqueous hydrogen peroxide solution (mass concentration of 35 wt%), stirred at a speed of 200 rpm for 2 hours to leach copper ions, and the mixture from which copper ions were leached was filtered through a processable ceramic filter to separate solid residue and copper-containing filtrate, 100 parts by weight of the separated copper-containing filtrate were mixed with 12.5 parts by weight of iron powder (particle size of 50 to 300 micrometers), and reacted at a temperature of 60°C for 9 hours to precipitate copper, and the copper was recovered by centrifuging the leached copper-containing filtrate.

[0060] <Example 2>

[0061] The process was carried out in the same manner as in Example 1 above, but 10 parts by weight of an aqueous sulfuric acid solution and 2 parts by weight of an aqueous hydrogen peroxide solution were mixed, and 5 parts by weight of iron powder were mixed to recover copper.

[0063] <Example 3>

[0064] The procedure was carried out in the same manner as in Example 1 above, but 20 parts by weight of an aqueous sulfuric acid solution and 5 parts by weight of an aqueous hydrogen peroxide solution were mixed, and 20 parts by weight of iron powder were mixed to recover copper.

[0066] <Example 4>

[0067] The process was carried out in the same manner as in Example 1 above, but copper was recovered by mixing the iron powder with the oxide film removed prepared through Manufacturing Example 1 above.

[0069] <Example 5>

[0070] The process was carried out in the same manner as in Example 2 above, but copper was recovered by mixing the iron powder with the oxide film removed prepared through Manufacturing Example 1 above.

[0072] <Example 6>

[0073] The process was carried out in the same manner as in Example 3 above, but copper was recovered by mixing the iron powder with the oxide film removed prepared through Manufacturing Example 1 above.

[0075] <Example 7>

[0076] In the above Example 1, sulfuric acid was mixed with 100 parts by weight of the remaining liquid after copper was recovered to adjust the acid concentration to 12.5% ​​by weight, then nitrogen was injected at a rate of 0.3 L / min, and after crystallization by cooling to a temperature of 20°C, iron sulfate was recovered by filtering with a Plate & Frame compression filter.

[0078] <Comparative Example 1>

[0079] 15 parts by weight of an aqueous sulfuric acid solution (mass concentration of 1.5 wt%) was mixed with 100 parts by weight of a composite copper sludge (generated in the electroplating process, containing about 30% copper) and stirred at a speed of 200 rpm for 2 hours to leach copper ions, the mixture from which copper ions were leached was filtered through a processable ceramic filter to separate solid residue and copper-containing liquid, 2 parts by weight of a precipitating agent (hydrogen sulfide) was mixed with 100 parts by weight of the separated copper-containing liquid and stirred at a stirring speed of 100 rpm at a temperature of 50°C for 60 minutes to precipitate copper, and the copper was recovered by centrifuging the leached copper-containing liquid.

[0081] <Comparative Example 2>

[0082] The procedure was carried out in the same manner as in Example 1 above, but 5 parts by weight of an aqueous sulfuric acid solution and 1 part by weight of an aqueous hydrogen peroxide solution were mixed, and 3 parts by weight of iron powder were mixed to recover copper.

[0084] <Comparative Example 3>

[0085] The process was carried out in the same manner as in Example 1 above, but 30 parts by weight of an aqueous sulfuric acid solution and 10 parts by weight of an aqueous hydrogen peroxide solution were mixed, and 30 parts by weight of iron powder were mixed to recover copper.

[0087] <Comparative Example 4>

[0088] 30 parts by weight of hydrogen sulfide were mixed with 100 parts by weight of the remaining liquid after copper was recovered through Example 1 above, and after crystallization by cooling to a temperature of 20°C, iron sulfate was recovered by filtering with a Plate & Frame press filter.

[0090] <Experimental Example 1> Component Analysis of Solid Residue and Copper-Containing Filter

[0091] The components contained in the solid residue separated through the process of filtration with a ceramic filter in Example 1 above and the copper-containing liquid were analyzed by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) and are shown in Table 1 below.

[0092]

[0093]

[0095] As shown in Table 1 above, it can be seen that the copper-containing liquid separated through the process of filtration with a ceramic filter in Example 1 contains a large amount of copper compared to the solid residue.

[0097] <Experimental Example 2> Component Analysis of Recovered Copper

[0098] The components of the copper recovered through Example 1 above were analyzed and are shown in Table 2 below. The components of the recovered copper were confirmed through X-ray fluorescence analysis (XRF).

[0099] Table 2

[0100]

[0102] As shown in Table 2 above, it can be seen that the copper recovered through Example 1 of the present invention has excellent purity.

[0104] <Experimental Example 3> Measurement of Purity and Yield of Recovered Copper

[0105] The purity and yield of the copper recovered through the above Examples 1 to 6 and Comparative Examples 1 to 3 were measured and are shown in Table 3 below. The purity of the recovered copper was measured using X-ray fluorescence analysis, and the yield of the recovered copper was calculated using the following formula after measuring the amount of copper contained in the composite copper sludge and the amount of recovered copper using ICP.

[0107] Yield (%) = (Amount of recovered copper / Amount of copper contained in sludge) × 100

[0109] Table 3

[0110]

[0112] As shown in Table 3 above, the copper recovered through Examples 1 to 6 of the present invention exhibits superior purity and yield compared to the copper recovered through Comparative Examples 1 to 2, and in particular, it can be seen that the purity and yield of the recovered copper are further improved when iron powder from which the oxide film has been removed through a deoxidation process as in Examples 4 to 6 is used.

[0113] On the other hand, as in Comparative Example 3, when an excessive amount of aqueous sulfuric acid solution, aqueous hydrogen peroxide solution, and iron powder are mixed, the yield is slightly improved, but it can be seen that the purity of the recovered copper is excessively reduced due to an increase in impurities.

[0115] <Experimental Example 4> Measurement of Purity and Yield of Recovered Iron Sulfate

[0116] The purity and yield of the iron sulfate recovered through Example 7 and Comparative Example 4 above were measured and are shown in Table 4 below. The purity of the recovered iron sulfate was measured using X-ray fluorescence analysis, and the yield of the recovered iron sulfate was calculated using the following formula after measuring the amount of iron contained in the filtrate and the amount of recovered iron sulfate using ICP.

[0118] Yield (%) = (Amount of iron contained in recovered iron sulfate / Amount of iron contained in filtrate) × 100

[0120] Table 4

[0121]

[0123] As shown in Table 4 above, it can be seen that the iron sulfate recovered through Example 7 of the present invention exhibits higher purity and yield compared to the iron sulfate recovered through Comparative Example 4.

[0125] Accordingly, the method for recovering copper from composite copper sludge according to the present invention can recover copper contained in the composite copper sludge with excellent purity and yield, and since iron sulfate can be produced from the filtrate generated during the copper recovery process, it is not only environmentally friendly as waste is utilized as a resource, but also exhibits excellent economic efficiency. Explanation of the symbols

[0127] S101 ; Copper ion leaching step S103 ; Filtration stage S105 ; Iron substitution step S107 ; Copper recovery stage S109 ; Iron sulfate recovery stage

Claims

Claim 1 A copper ion leaching step of leaching copper ions by mixing 10 to 20 parts by weight of an aqueous sulfuric acid solution and 2 to 5 parts by weight of an aqueous hydrogen peroxide solution with 100 parts by weight of a composite copper sludge; a filtration step of separating a solid residue and a copper-containing filtrate by filtering the mixture from which copper ions have been leached through the copper ion leaching step; an iron substitution step of mixing 5 to 20 parts by weight of iron powder with 100 parts by weight of the copper-containing filtrate separated through the filtration step, and then precipitating copper at a temperature of 55 to 65°C for 8 to 10 hours; and a copper recovery step of recovering the copper leached through the iron substitution step. A method for recovering copper from composite copper sludge, comprising: an aqueous sulfuric acid solution having a mass concentration of 1 to 2 weight%; an aqueous hydrogen peroxide solution having a mass concentration of 30 to 40 weight%; an iron powder having a particle size of 50 to 300 micrometers; an oxide film being removed through a deoxidation process; the deoxidation process being performed by immersing the iron powder in an aqueous reducing agent solution; and the reducing agent being ascorbic acid or sodium borohydride. Claim 2 delete Claim 3 A method for recovering copper from composite copper sludge according to claim 1, wherein, after the copper recovery step, an iron sulfate recovery step is further performed to recover iron ions contained in the filtrate remaining through the copper recovery step as iron sulfate, and the iron sulfate recovery step is performed by mixing sulfuric acid with the filtrate remaining through the copper recovery step to adjust the acid concentration to 10 to 25 weight%, then injecting nitrogen or mixing a reducing agent, and crystallizing and filtering.

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