A method for recovering high-purity nano copper from electroplating wastewater

Abstract

This invention belongs to the field of resource recycling, specifically relating to a method for recovering high-purity nano-copper from electroplating wastewater. The method involves heating the copper electroplating wastewater to 50-60°C and maintaining this temperature, adding a mixed solution of NaOH and FeCl2 while stirring, and then adding Na2S2O4. The total molar amount of NaOH is equal to the amount of Cu in the copper electroplating wastewater. 2+ The total molar amount of FeCl2 is 4.4–5.9 times that of Cu. 2+ The total molar amount is 0.1-0.15% of the total molar amount, and the total molar amount of Na₂S₂O₄ is Cu. 2+ The total molar volume is 1.1-1.2 times the volume of the copper nanoparticles. After continuous stirring and reaction, centrifugation is performed. The supernatant is discharged after meeting the standards, and the precipitate is washed with deionized water and then vacuum dried to obtain high-purity nano-copper. This method constructs a microenvironment through NaOH dissolution, Fe... 2+ Under alkaline conditions, a disproportionation reaction occurs, producing Fe. 3+ and Fe 0 Using Na2S2O4 to reduce Cu in electroplating wastewater 2+ Fe 0 Catalytic reduction of Cu by Na2S2O4 2+ It accelerates the reaction, recovers and fixes the product, the raw materials are readily available, the product has high purity and good uniformity, the operation is simple, there is no secondary pollution, and it can be used directly or stored for a long time in dry air.

Description

Technical Field

[0001] The invention belongs to the field of resource recycling, and in particular relates to a method for recovering high-purity nano copper from electroplating wastewater. Background Art

[0002] As the electroplating industry develops, the problem of electroplating pollution is becoming more and more apparent. Electroplating wastewater has become one of the typical representatives of industrial wastewater that is difficult to treat. If it is directly discharged without reasonable treatment, it will cause environmental pollution. At the same time, electroplating wastewater itself is also a cheap renewable secondary resource. Among electroplating wastewater, copper-containing wastewater is ubiquitous. This part of wastewater has high copper content and is difficult to treat. At present, the main methods for treating copper-containing wastewater include chemical precipitation, oxidation-reduction method, solvent extraction separation method, adsorption method, liquid membrane separation method, etc.

[0003] The Chinese patent document with publication number CN108529789A discloses a method for treating copper-containing electroplating wastewater and recovering copper by sulfide precipitation, wherein sulfide is added in batches and stirred to treat the copper-containing electroplating wastewater to obtain copper sulfide precipitation, a flocculant is added, the pH is adjusted to 7.0-8.0, and solid-liquid separation is performed to obtain a supernatant and mixed heavy metal sulfides that meet the discharge standards. However, further treatment is required to obtain copper products with higher added value.

[0004] Literature (Synthesis of nanosized copper plates by reduction of copper withhydrazine hydrate in the presence of an ethoxylated carboxylic acid.<Materials Today> , 2020, Vol. 31, Part 3, pp. 548-550) reported the use of hydrazine hydrate as a reducing agent to reduce copper ions. The total molar amount of hydrazine hydrate is Cu 2+ At 60°C, a copper sheet with a size of 300-500 nanometers and a thickness of 50-70 nanometers was synthesized. The produced nano copper sheets can be used to manufacture printed electronic products and conductive pastes and inks. However, the hydrazine hydrate itself is highly toxic in the report, and a large amount is used to reduce copper ions, which limits its large-scale application.

[0005] Therefore, it is a very important task to find a reducing agent that can replace hydrazine hydrate for efficient reduction and has ecological compatibility to extract copper from copper-containing electroplating wastewater and make the entire treatment process ecological and harmless. It will be conducive to promoting the ecological treatment and green recycling of copper-containing wastewater and promoting the sustainable development of the environment. Summary of the invention

[0006] One of the purposes of the present invention is to treat traditional copper-containing electroplating wastewater, especially the plated parts rinsing wastewater generated in the electroplating process, which has the problems of high copper content, difficulty in treatment, high cost and low efficiency, and to propose a method for recovering high-purity nano copper particles with low cost and high efficiency.

[0007] To achieve the above object, the present invention adopts the following technical solution: A method for recovering high-purity nano copper from electroplating wastewater, comprising the following steps:

[0008] S1. Measurement of Cu in electroplating copper waste liquid 2+ The total molar amount is adjusted to pH ≥ 5, and the electroplating copper waste liquid is heated to 50-60° C. and kept warm;

[0009] S2, NaOH, FeCl 2 Add deionized water, stir to produce a white solid, then add Na 2 S 2 O 4 , stirring to completely dissolve it, to obtain a mixed solution, in which the total molar amount of NaOH is the Cu in the electroplating copper waste liquid. 2+ 4.4-5.9 times the total molar amount, FeCl 2 The total molar amount of Cu in the electroplating copper waste liquid 2+ 0.1-0.15 of the total molar amount, Na 2 S 2 O 4 The total molar amount of Cu in the electroplating copper waste liquid 2+ 1.1-1.2 times the total molar amount;

[0010] S3, slowly adding the mixed solution of step S2 to the electroplating copper waste liquid, continuously stirring until fully reacted, rapidly centrifuging the reaction solution, discharging the supernatant in compliance with the standards, washing the precipitate with deionized water and then vacuum drying, thereby obtaining high-purity nano copper.

[0011] As a further improvement of the method for recovering high-purity nano copper from electroplating wastewater:

[0012] Preferably, the copper electroplating waste liquid in step S1 contains Cu 2+ The molar concentration is 0.002mol / L-0.1mol / L.

[0013] Preferably, the stirring speed in step S2 is 150-200 r / min.

[0014] Preferably, the deionized water added in step S2 does not exceed 1% of the wastewater to be treated.

[0015] Preferably, in step S3, stirring is performed at a speed of 300-500 r / min for 20-30 min until the reaction is fully achieved.

[0016] Preferably, the vacuum drying temperature in step S3 is 60-105° C. and the time is 4-10 h.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The invention provides a method for recovering high-purity nano copper from electroplating wastewater, wherein a microenvironment is constructed by dissolving NaOH, Fe 2+ Under alkaline conditions, a disproportionation reaction occurs to generate Fe 3+ and Fe 0 , using Na 2 S 2 O 4 Reduction of Cu in electroplating wastewater 2+ , Fe 0 Provide catalytic conditions to accelerate Na 2 S 2 O 4 Reduction of Cu 2+ , while Na 2 S 2 O 4 Reduction of Fe 3+ Become Fe 2+ , making Fe 2+ Recycling, continuously generating Fe 0 The copper element is catalytically reduced to prepare pure copper powder. When the appropriate process parameters are controlled, the particle size of the copper powder can reach the nanometer level. The reaction equations are shown in equations (1), (2), (3), (4) and (5).

[0019] Fe 2+ +2OH - =Fe(OH) 2 (1)

[0020] 3Fe(OH) 2 =2Fe(OH) 3 +Fe 0 (2)

[0021] Fe(OH) 3 +S 2 O 4 2– +3OH – =Fe(OH) 2 +2SO 3 2– +2H 2 O (3)

[0022] Cu 2+ +2OH – =Cu(OH) 2 (4)

[0023] Cu(OH) 2 +S 2 O 4 2– +2OH – =Cu+2SO 3 2– +2H 2 O (5)

[0024] The present invention adopts cheap Na 2 S 2 O 4 As a reducing agent, it is more ecological, non-toxic, and does not produce toxic substances compared to the traditional hydrazine hydrate reducing agent. In addition, in the present invention, a recyclable catalyst FeCl is added. 2 , promotes the efficient occurrence of the entire reaction, the product is fixed, the raw materials are easily obtained, the product has high purity, good uniformity, simple operation, no secondary pollution, and can be used directly or stored for a long time in dry air.

[0025] The method for recovering high-purity nano copper from electroplating wastewater of the present invention has a nanometer-level copper particle size and a purity of more than 95%. After copper is recovered, the wastewater meets the "Electroplating Pollutant Emission Standard" (GB21900-2008), and the wastewater is discharged safely up to the standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a flow chart of preparing nano copper by recycling electroplating copper-containing wastewater.

[0027] Figure 2 It is an X-ray diffraction diagram of the nano copper particles prepared by the present invention.

[0028] Figure 3 The SEM and EDS spectra of the nano copper particles prepared in the present invention are shown in FIG. 1 , wherein (a) is the SEM image of the recovered product, (b) is the element energy spectrum, (c) is the EDS surface scanning O element distribution map, and (d) is the EDS surface scanning Cu element distribution map. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] This embodiment provides a method for recovering high-purity nano copper from electroplating wastewater. Figure 1 , specifically including the following steps:

[0032] S1. The wastewater to be treated is the rinsing wastewater of plated parts from a certain electroplating plant in East China, with a pH of 5.7. The copper ion concentration of the electroplating copper waste liquid is measured to be 0.008 mol / L. 50L of the electroplating copper waste liquid is placed in a container, heated to 50-60°C for insulation, and stirred at a speed of 500r / min.

[0033] S2, 1.8 mol NaOH and 0.05 mol FeCl 2 Add 100mL of deionized water and then add 0.45molNa 2 S 2 O 4 , stirring at 180 r / min to completely dissolve it to obtain a mixed solution;

[0034] S3. Slowly drip the mixed solution into the copper-containing electroplating wastewater, stir at a speed of 300-500r / min for 20min, stop heating and stirring, quickly centrifuge the reaction product, wash the precipitate with deionized water for 3 times, and place the product in a vacuum drying oven at 80°C for 6h to obtain nano copper powder; after testing, the copper ion concentration of the solution in the treated supernatant is 0.13mg / L, which meets the "Electroplating Pollutant Emission Standard" (GB21900-2008), and achieves safe discharge of wastewater in compliance with the standards.

[0035] Figure 2 is the X-ray diffraction pattern of the nano copper particles obtained above, Figure 2 It can be seen that there are three obvious diffraction peaks at diffraction angles 2θ = 43.05°, 50.19° and 73.91°, corresponding to the (111), (200) and (220) crystal planes of the copper phase in the face-centered cubic system. No other impurities were detected in the diffraction peaks, indicating that the reaction product under this condition is pure copper in cubic form. Figure 3 The SEM and EDS spectra of the nano copper particles obtained above are shown in Figure 1, where (a) is the SEM image of the recovered product, (b) is the element spectrum, (c) is the EDS surface scanning O element distribution map, and (d) is the EDS surface scanning Cu element distribution map. Figure 3 It can be seen that the recovered product is a spherical particle with uniform particles and an average particle size of 96nm. After testing, the purity of the nano copper powder prepared above is above 95%.

[0036] Example 2

[0037] This embodiment provides a method for recovering high-purity nano copper from electroplating wastewater. Figure 1 , specifically including the following steps:

[0038] S1. The wastewater to be treated is acidic copper-containing wastewater from an electroplating plant in East China. The pH is measured to be 2.3, adjusted to 5, and the copper ion concentration of the electroplating copper waste liquid is measured to be 0.072 mol / L. 10L of the electroplating copper waste liquid is taken from the water tank and placed in a container, heated to 55°C for insulation, and stirred at a speed of 500r / min;

[0039] S2, 3.2 mol NaOH and 0.08 mol FeCl 2 Add 80mL of deionized water and then add 0.864molNa 2 S 2 O 4 , stirring at 150 r / min to completely dissolve it to obtain a mixed solution;

[0040] S3. Slowly drip the mixed solution into the copper-containing electroplating wastewater, stir at a speed of 450r / min for 25min, stop heating and stirring, quickly centrifuge the reaction product, wash the precipitate with deionized water for 3 times, and place the product in a vacuum drying oven at 65°C for 10h to obtain nano copper powder.

[0041] After testing, the copper ion concentration of the supernatant is 0.28 mg / L, which meets the "Electroplating Pollutant Emission Standard" (GB21900-2008), achieving safe discharge of wastewater in compliance with the standards, and the purity of the nano copper powder prepared above is above 95%.

[0042] Example 3

[0043] This embodiment provides a method for recovering high-purity nano copper from electroplating wastewater. Figure 1 , specifically including the following steps:

[0044] S1. The wastewater to be treated is copper-containing electroplating wastewater from Wuhu Fanchang Electroplating Center. The pH value is 8.2, and the copper ion concentration of the electroplating copper waste liquid is 0.045 mol / L. 10L of the electroplating copper waste liquid is taken from the water storage tank and placed in a container. The wastewater is heated to 55°C and stirred at a speed of 500 r / min.

[0045] S2, 2 mol NaOH and 0.05 mol FeCl 2 Add 80 mL of deionized water and then add 0.54 mol Na 2 S 2 O 4 , stirring at 200 r / min to completely dissolve it to obtain a mixed solution;

[0046] S3. Slowly drip the mixed solution into the copper-containing electroplating wastewater, stir at a speed of 450r / min for 30min, stop heating and stirring, quickly centrifuge the reaction product, wash the precipitate with deionized water for 3 times, and place the product in a vacuum drying oven at 65°C for 10h to obtain nano copper powder.

[0047] After testing, the copper ion concentration of the supernatant is 0.25 mg / L, which meets the "Electroplating Pollutant Emission Standard" (GB21900-2008) and achieves safe discharge of wastewater in compliance with the standards; the purity of the nano copper powder obtained above is 96%.

[0048] Example 4

[0049] This embodiment provides a method for recovering high-purity nano copper from electroplating wastewater. Figure 1 , specifically including the following steps:

[0050] S1. The wastewater to be treated is copper-containing wastewater from an electroplating process in East China. The pH value is 7.9, and the copper ion concentration of the electroplating copper waste liquid is 0.022 mol / L. 10L of the electroplating copper waste liquid is taken from the water storage tank and placed in a container, heated to 55°C for insulation, and stirred at a speed of 500 r / min.

[0051] S2, 1 mol NaOH and 0.025 mol FeCl 2 Add 100mL of deionized water and then add 0.0264molNa 2 S 2 O 4 , stirring at 150 r / min to completely dissolve it to obtain a mixed solution;

[0052] S3. Slowly drip the mixed solution into the copper-containing electroplating wastewater, stir at a speed of 450r / min for 25min, stop heating and stirring, quickly centrifuge the reaction product, wash the precipitate with deionized water for 3 times, and place the product in a vacuum drying oven at 60°C and dry it for 12h to obtain nano copper powder.

[0053] After testing, the copper ion concentration of the supernatant is 0.24 mg / L, which meets the "Electroplating Pollutant Emission Standard" (GB21900-2008), and achieves safe discharge of wastewater in compliance with the standards. The purity of the nano copper powder obtained above is 96%.

[0054] Those skilled in the art should understand that the above are only some specific embodiments of the present invention, rather than all embodiments. It should be noted that for those of ordinary skill in the art, many modifications and improvements can be made, and all modifications or improvements that do not exceed the scope of protection of the present invention should be regarded as the scope of protection of the present invention.

Claims

1. A method for recovering high-purity nano copper from electroplating wastewater, characterized in that: The steps include: S1. Measurement of Cu in electroplating copper waste liquid 2+ The total molar amount is adjusted to pH ≥ 5, and the electroplating copper waste liquid is heated to 50-60° C. and kept warm; S2. Add NaOH and FeCl2 into deionized water and stir to produce a white solid. Then add Na2S2O4 and stir to completely dissolve it to obtain a mixed solution, in which the total molar amount of NaOH is equal to the Cu in the electroplating copper waste liquid. 2+ The total molar amount of FeCl2 is 4.4-5.9 times that of Cu in electroplating copper waste liquid. 2+ The total molar amount of Na2S2O4 is 0.1-0.15 of the total molar amount of Cu in the electroplating copper waste liquid. 2+ 1.1-1.2 times the total molar amount; S3, slowly dropping the mixed solution of step S2 into the electroplating copper waste liquid, continuously stirring until fully reacted, rapidly centrifuging the reaction liquid, discharging the supernatant in compliance with the standards, washing the precipitate with deionized water and then vacuum drying, thus obtaining high-purity nano copper.

2. The method for recovering high-purity nano copper from electroplating wastewater according to claim 1, characterized in that: The copper in the electroplating waste liquid in step S1 2+ The molar concentration is 0.002mol / L-0.1mol / L.

3. The method for recovering high-purity nano copper from electroplating wastewater according to claim 2, characterized in that: The stirring speed in step S2 is 150-200 r / min.

4. The method for recovering high-purity nano copper from electroplating wastewater according to claim 2, characterized in that: The deionized water added in step S2 does not exceed 1% of the wastewater to be treated.

5. The method for recovering high-purity nano copper from electroplating wastewater according to claim 1, characterized in that: In step S3, the mixture is stirred at a speed of 300-500 r / min for 20-30 min until the reaction is fully completed.

6. The method for recovering high-purity nano copper from electroplating wastewater according to claim 1, characterized in that: The vacuum drying temperature in step S3 is 60-105° C. and the time is 4-10 h.

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