A method for directly reducing and recovering copper from complexed copper wastewater

Abstract

The application discloses a method for directly reducing and decomplexing and recovering copper from complex copper wastewater, which comprises the following steps: firstly, putting aluminum-carbon composite material into complex copper wastewater, continuously stirring, and making the composite material adsorb complex copper, so that electrons are directly reduced to Cu(II) and decomplexing is completed to remove the complex copper; Cu(II) is reduced to Cu 0 , and adhered to the surface of the material, and copper can be efficiently recovered through suction filtration. The application has the advantages of convenience, quickness and secondary pollution avoidance, solves the deficiency of traditional technologies, and achieves the pollutant removal rate of more than 95% and the copper recovery rate of more than 90%, so it is a new complex copper wastewater treatment method which is efficient, green, convenient, safe and practical.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water pollution treatment and resource utilization, and particularly relates to a method for directly reducing and decomplexing and recycling copper from complex copper wastewater. BACKGROUND

[0002] With the development of industrialization and informationization, electronic products are more and more widely used, and accordingly, electroplating and chemical plating metal processes are massively put into production. However, in the actual metal plating process, only 30-40% of the metal is effectively utilized and fixed on the plated part. Therefore, in order to improve product quality and stabilize the electroplating solution, in the process of copper plating, in addition to copper salt and reducing agent, various additives are added to the plating solution, including complexing agents for preventing metal ions from precipitating and stabilizers for improving the quality of the plated layer, among which the complexing agents used more include pyrophosphoric acid, tartaric acid, citric acid, ethylenediaminetetraacetic acid, etc. The complex copper in wastewater has stable chemical properties, and the traditional metal ion removal methods including adsorption, ion exchange and neutralization precipitation are difficult to effectively treat it. The free copper ions in the aqueous solution can be removed in the form of precipitation by adding alkali to increase the pH. However, the complex copper is still in a stable complex state under alkaline pH, and is difficult to be removed by precipitation.

[0003] In order to meet the increasingly stringent standards of heavy metal treatment and control, it is urgent to develop efficient, green and environmentally friendly complex copper wastewater treatment technology. At present, the removal of complex copper by using advanced oxidation technology and displacement substitution method has been studied more, which promotes the development of new treatment technology, each has its own advantages and disadvantages: the advanced oxidation technology pays more attention to the oxidation of organic ligand, and easily ignores the more toxic copper ions; the displacement substitution method often relies on iron-based materials to achieve, and the amount of mud produced is large.

[0004] Therefore, it is necessary to develop a method for efficiently decomplexing and simultaneously recycling metal copper which is simple to operate and does not need additional pretreatment and post-treatment. Most of the current research focuses on the oxidation of organic ligand, and there is no literature report and engineering case of direct reduction method at home and abroad. The present application focuses on Cu(II) which is more toxic and has more recycling value, and if it can be reduced, it will achieve two goals at once. Zero-valent aluminum (E0 = -1.66 V) with strong reducing ability is expected to achieve direct reduction of complex copper. However, due to the steric hindrance effect of organic ligand, the electrons provided by metal aluminum are difficult to reach Cu(II), so the metal aluminum modified by carbon material can transmit the electrons of zero-valent aluminum to Cu(II) as an electron transmission medium. Based on this, the present application uses one-step method of aluminum-carbon composite material, which is the first to realize efficient reduction and decomplexing of complex copper in wastewater at home and abroad, and can recycle Cu 0 . SUMMARY

[0005] The purpose of the present application is to use aluminum-carbon composite material, simple one-step addition, to realize the direct reduction and decomplexation of complex copper, Cu(II) is directly reduced on the surface of the material in the form of Cu 0 , and high-efficiency recovery is achieved. The present application is achieved in this way:

[0006] A method for directly reducing and decomplexing and recovering copper from complex copper wastewater, the specific steps are as follows:

[0007] (1) Take 0.5 ~ 4 g / L of aluminum-carbon composite material (the amount depends on the content of complex copper in the wastewater, calculated in terms of copper element);

[0008] (2) If the pH of the complex copper wastewater exceeds the optimal range (pH > 3.00), the pH needs to be adjusted to the appropriate range (the complex copper wastewater is usually strongly acidic, so there is no need to adjust the pH).

[0009] (3) Use inert gas (nitrogen, argon, helium, etc.) to deoxygenate the wastewater obtained in step (2) (continuous inert gas or inert gas for a certain period of time, then isolate air), keep the dissolved oxygen concentration < 0.5 mg / L;

[0010] (4) Add the material in step (1) to the wastewater obtained in step (3), continuously stir to maintain the suspended state, and carry out decomplexation reaction;

[0011] (5) After the reaction is completed, stop stirring the wastewater after step (4) reaction, carry out solid-liquid separation by suction filtration, and freeze-dry the powder containing Cu 0 for recovery;

[0012] As above, the detailed preparation method of the aluminum-carbon composite material in step (1) is referred to the "Preparation method of aluminum-carbon nanotube composite material" disclosed in patent CN113603204A.

[0013] As above, the concentration of complex copper in step (2) can be as high as ~ 1200 mg / L (calculated in terms of copper element).

[0014] As above, the types of complex copper wastewater in step (2) include copper pyrophosphate, copper tartrate, copper citrate and EDTA-copper, etc.

[0015] The advantages of the present application are as follows:

[0016] (1) The present application first proposes a new idea and method for one-step direct reduction and decomplexation removal of complex copper in wastewater.

[0017] (2) The removal method described in the present application is simple, and the composite material can be directly added without other pretreatment and repeated pH adjustment, which is convenient and fast.

[0018] (3) The whole reaction is carried out at normal temperature and pressure, without special equipment, with mild reaction conditions, energy saving, and suitable for industrial application.

[0019] (4) The method can efficiently remove pollutants and simultaneously efficiently reduce and recover Cu 0 , realizes resource utilization of wastewater treatment, and turns waste into treasure. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 EDTA-copper removal effect diagram of aluminum-carbon composite material, single micron aluminum, single carbon nanotube, single ball-milled micron aluminum, and single ball-milled carbon nanotube.

[0021] Figure 2 EDTA-copper decomplexation of aluminum-carbon composite material under different pH conditions.

[0022] Figure 3 EDTA-copper decomplexation of aluminum-carbon composite material under different dissolved oxygen concentrations.

[0023] Figure 4 EDTA-copper decomplexation of aluminum-carbon composite material under different concentrations.

[0024] Figure 5 EDTA-copper decomplexation of aluminum-carbon composite material on copper pyrophosphate, copper tartrate, copper citrate, and EDTA-copper.

[0025] Figure 6 EDTA-copper decomplexation of aluminum-carbon composite material on actual copper pyrophosphate and EDTA-copper industrial wastewater.

[0026] Figure 7 Cu 0 recovery after decomplexing complex copper by aluminum-carbon composite material. DETAILED DESCRIPTION

[0027] The application will be further described below in combination with specific implementation cases, and the specific implementation cases described are only used to explain the application and do not limit the application.

[0028] Example 1: Comparison of effects of different materials on removal of EDTA-copper in water

[0029] Under room temperature conditions, the initial pH of EDTA-copper simulated wastewater was adjusted to 3.00, nitrogen gas was bubbled for 15 minutes to remove dissolved oxygen in the wastewater and isolate air, then 4 g / L of aluminum-carbon composite material was directly added and oscillated to mix uniformly and maintain a suspended state to maintain the reduction reaction, and the remaining EDTA-copper in the water was analyzed by sampling and filtering at a fixed time. At the same time, commercial micron zero-valent aluminum, single ball-milled micron zero-valent aluminum, commercial carbon nanotube, and single ball-milled carbon nanotube were used as controls. As shown inFigure 1 As shown in the figure, the commercial micron-sized zero-valent aluminum, the separately ball-milled micron-sized zero-valent aluminum, the commercial carbon nanotubes, and the separately ball-milled carbon nanotubes can only remove a small amount of EDTA-copper, but the method of the present application can efficiently decomplex and remove EDTA-copper by more than 95%, proving the feasibility of the method for removing EDTA-copper.

[0030] Example 2: Decomplexing of EDTA-copper by aluminum-carbon composite at different pH values

[0031] At room temperature, the initial pH of the EDTA-copper simulated wastewater was adjusted to 1.50, 2.00, 3.00, and 4.00, respectively. Nitrogen gas was bubbled for 15 minutes to remove dissolved oxygen in the wastewater and isolate air. Then, 2 g / L of aluminum-carbon composite was directly added to the wastewater and shaken to mix uniformly and maintain a suspended state to maintain the reduction reaction. Samples were taken at regular intervals and filtered to analyze the remaining EDTA-copper in the water. As shown in the figure, the aluminum-carbon composite can only effectively decomplex EDTA-copper under strong acidic conditions with pH ≤ 3. Figure 2

[0032] Example 3: Decomplexing of EDTA-copper by aluminum-carbon composite at different dissolved oxygen concentrations

[0033] At room temperature, the initial pH of the EDTA-copper simulated wastewater was adjusted to 3.00. The wastewater was treated in three ways: nitrogen gas was bubbled for 15 minutes; no treatment was performed; and oxygen gas was bubbled for 15 minutes to significantly distinguish the initial dissolved oxygen content of the wastewater, and air was isolated. Then, 4 g / L of aluminum-carbon composite was directly added to the wastewater and shaken to mix uniformly and maintain a suspended state to maintain the reduction reaction. Samples were taken at regular intervals and filtered to analyze the remaining EDTA-copper in the water. As shown in the figure, the method must be carried out under deoxygenated conditions to efficiently reduce and decomplex EDTA-copper. Figure 3

[0034] Example 4: Decomplexing of EDTA-copper by aluminum-carbon composite at different concentrations

[0035] At room temperature, the initial pH of the EDTA-copper simulated wastewater was adjusted to 3.00. The wastewater was treated in three ways: nitrogen gas was bubbled for 15 minutes; no treatment was performed; and oxygen gas was bubbled for 15 minutes to significantly distinguish the initial dissolved oxygen content of the wastewater, and air was isolated. Then, 4 g / L of aluminum-carbon composite was directly added to the wastewater and shaken to mix uniformly and maintain a suspended state to maintain the reduction reaction. Samples were taken at regular intervals and filtered to analyze the remaining EDTA-copper in the water. As shown in the figure, the method must be carried out under deoxygenated conditions to efficiently reduce and decomplex EDTA-copper. Figure 3 Figure 4 As shown in the figure, the aluminum-carbon composite can almost completely decomplex and degrade 20 ~ 200 mg / L of EDTA-copper within a certain time. As the concentration of the pollutant increases, the degradation rate of EDTA-copper gradually decreases.

[0036] ​Example 5: Effect of aluminum-carbon composite on the decomplexation of copper pyrophosphate, copper tartrate, copper citrate and EDTA-copper

[0037] At room temperature, 50 mg / L (in terms of copper element) of copper pyrophosphate, copper tartrate, copper citrate and EDTA-copper simulated wastewater was taken, nitrogen was bubbled for 15 minutes to remove dissolved oxygen in the wastewater and isolate air, then 2 g / L of aluminum-carbon composite was directly added and oscillated to mix uniformly and keep in a suspended state to maintain the reduction reaction, and the remaining complex copper in the water was analyzed by sampling and filtering at regular intervals. As shown in Figure 5 , the aluminum-carbon composite can efficiently decomplex and degrade copper pyrophosphate, copper tartrate, copper citrate and EDTA-copper, and the decomplexing rate is more than 90%, proving the universality and high efficiency of the method for removing complex copper.

[0038] Example 6: Effect of aluminum-carbon composite on the decomplexation of actual copper pyrophosphate and EDTA-copper industrial wastewater

[0039] The pH value of EDTA-copper wastewater is 0.96, the total copper concentration is 290 ± 30 mg / L, and the COD is 28000 ± 2000 mg / L; the total copper content of copper pyrophosphate wastewater is 1050 ± 100 mg / L, and the initial pH is 9.49, which needs to be adjusted to 3.00 in advance. At room temperature, take the actual wastewater, bubble nitrogen for 15 minutes to remove dissolved oxygen in the wastewater and isolate air, then directly add 2 g / L of aluminum-carbon composite and oscillate to mix uniformly and keep in a suspended state to maintain the reduction reaction, and the remaining total copper in the water is analyzed by sampling and filtering at regular intervals. As shown in Figure 6 , the method can reduce 98% of the total copper in the actual wastewater, realize decomplexation, and recover Cu 0 .

[0040] Example 7: Cu 0

[0041] After the reaction, the serum bottle was removed from the shaker, and the solid-liquid separation was performed by suction filtration. The filter paper containing the solid powder was placed in a petri dish, and after freeze-drying, the surface of the powder was red and had a metallic luster, which was the recovered Cu Figure 7 . 0 .

Claims

1. A method for directly reducing, decomposing, and recovering copper from complexed copper wastewater, characterized in that, The complexed copper wastewater includes copper pyrophosphate, copper tartrate, copper citrate, and EDTA-copper, etc., and the specific steps are as follows: (1) Adjust the pH value of the actual wastewater to a strongly acidic condition of pH ≤ 3; (2) Use inert gas to remove dissolved oxygen from the wastewater obtained in (1) and maintain the concentration of dissolved oxygen in the wastewater < 0.5 mg / L; (3) Add 0.5 ~ 4 g / L of aluminum-carbon composite material to the wastewater obtained in step (2); (4) Stir the wastewater obtained in step (3) continuously to maintain the suspension state of the composite material and carry out the decomplexation reaction; (5) The inert gas mentioned in step (2) includes nitrogen, argon, helium, etc.; (6) After the reaction is complete, stop stirring the wastewater from step (3), perform solid-liquid separation by filtration, and Cu can be recovered. 0 .

2. The method according to claim 1, characterized in that, The concentration of copper in the wastewater can be as high as ~1200 mg / L.

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