A method for treating nickel plating rinse water

Abstract

This invention belongs to the field of wastewater treatment technology, specifically relating to a method for treating nickel plating rinse water. The method for treating nickel plating rinse water provided by this invention includes the following steps: adjusting the pH value of the nickel plating rinse water to 5-6.5, performing flocculation and sedimentation, followed by solid-liquid separation to obtain a liquid phase; sequentially subjecting the liquid phase to ultrafiltration, nanofiltration, and electrostatic desalination to obtain a concentrated solution; subjecting the concentrated solution to electrowinning to remove impurities to obtain a purified concentrated solution; and subjecting the purified concentrated solution to membrane electrowinning to obtain elemental nickel. This invention utilizes a combined process of chemical precipitation + membrane separation + electrowinning to first separate nickel from small amounts of impurities such as copper, zinc, iron, and aluminum, producing only a small amount of sludge; subsequently, membrane separation technology is used to concentrate nickel ions, and finally, electrowinning is used to achieve the resource recovery of nickel. The treatment method provided by this invention has a high nickel recovery rate, and the separation membrane used is less prone to fouling.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and specifically relates to a method for treating nickel plating rinsing water. Background Technology

[0002] Nickel electroplating is an electrochemical process, also a redox process. It involves immersing the workpiece in a nickel salt solution as the cathode and a metallic nickel plate as the anode, then applying a direct current power supply to deposit a metallic nickel plating layer onto the workpiece. Due to its fine-grained, smooth, and bright coating, low internal stress, and strong adhesion to ceramic metallization layers, nickel electroplating has become one of the most important plating methods in the electroplating industry. However, the nickel electroplating process generates a large amount of rinsing water.

[0003] Nickel plating rinse water originates from pre-plating cleaning and post-plating rinsing of the workpieces. The main components of the rinse water are nickel ions, sulfate ions, chloride ions, and boric acid, along with small amounts of copper, zinc, iron, and aluminum ions. Currently, the main treatment processes for nickel plating rinse water are precipitation, ion exchange, and membrane separation. Precipitation involves adding a precipitant to adjust the pH of the wastewater, causing metal ions to precipitate as hydroxides. Commonly used precipitants include NaOH and CaO. While this method effectively removes nickel ions from the wastewater, it produces a large amount of sludge, resulting in resource waste and additional solid waste. Ion exchange uses ion exchange resins to selectively adsorb metal ions from the wastewater, reducing heavy metal ions while also achieving metal recovery. However, ion exchange resins have high water quality requirements, are easily contaminated, and the wastewater contains multiple metal ions. Currently, resins that preferentially adsorb nickel in a mixed system of copper, zinc, iron, aluminum, and nickel are scarce and expensive. Membrane separation is widely used in wastewater treatment due to its simple operation and good treatment effect. However, membrane separation alone is difficult to recover metals from wastewater, and the membrane is easily fouled during the treatment process.

[0004] Therefore, providing an efficient and environmentally friendly method for recycling nickel plating rinse water is an urgent technical problem that needs to be solved. Summary of the Invention

[0005] In view of this, the present invention provides a method for treating nickel plating rinse water. The method provided by the present invention can efficiently recover nickel from the wastewater, and no solid waste or liquid waste is generated during the treatment process.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for treating nickel plating rinsing water, comprising the following steps:

[0007] After adjusting the pH of the nickel plating rinse water to 5-6.5, flocculation and sedimentation are carried out, followed by solid-liquid separation to obtain the liquid phase;

[0008] The liquid phase was subjected to ultrafiltration, nanofiltration and electro-desalination in sequence to obtain a concentrated solution;

[0009] The concentrate is subjected to electrowinning to remove impurities, resulting in a purified concentrate.

[0010] The purified concentrate is subjected to membrane electrowinning to obtain elemental nickel.

[0011] Preferably, before adjusting the pH value of the nickel plating rinse water, the process further includes: oxidizing the nickel plating rinse water.

[0012] Preferably, the pH adjuster used to adjust the pH value of the nickel plating rinsing water includes sodium hydroxide, sodium carbonate, or sodium bicarbonate.

[0013] Preferably, the ultrafiltration process further includes sterilizing the liquid phase.

[0014] Preferably, the nanofiltration process further includes: mixing the nanofiltration-obtained freshwater with resin for ion exchange, followed by sequential first reverse osmosis and second reverse osmosis to obtain reclaimed water.

[0015] Preferably, the ultrafiltration membrane is a cellulose acetate tubular membrane;

[0016] The nanofiltration membrane is a cellulose acetate tubular membrane.

[0017] Preferably, the current density for the electrodeposition impurity removal is 25–75 A / m. 2 .

[0018] Preferably, the pH value of the diaphragm electrodeposition solution is 2.5 to 4; and the concentration of nickel ions in the diaphragm electrodeposition solution is 3 g / L or higher.

[0019] Preferably, the current density of the diaphragm electrodeposition is 150–300 A / m. 2 .

[0020] Preferably, after the diaphragm is electrowinning, it further includes:

[0021] After the diaphragm electrodeposition liquid is subjected to nickel precipitation, it is mixed with sodium carbonate to carry out a precipitation reaction, resulting in nickel carbonate sludge.

[0022] The nickel carbonate sludge is further subjected to diaphragm electrodeposition to obtain elemental nickel.

[0023] This invention provides a method for treating nickel plating rinse water, comprising the following steps: adjusting the pH of the nickel plating rinse water to 5-6.5, performing flocculation and sedimentation, followed by solid-liquid separation to obtain a liquid phase; subjecting the liquid phase to ultrafiltration, nanofiltration, and electrostatic desalination sequentially to obtain a concentrated solution; subjecting the concentrated solution to electrowinning to remove impurities to obtain a purified concentrated solution; and subjecting the purified concentrated solution to membrane electrowinning to obtain elemental nickel. This invention utilizes a combined process of chemical precipitation + membrane separation + electrowinning to first separate nickel from small amounts of impurities such as copper, zinc, iron, and aluminum, generating only a small amount of sludge; subsequently, membrane separation technology is used to concentrate nickel ions, and finally, electrowinning is used to achieve the resource recovery of nickel. The treatment method provided by this invention achieves a high nickel recovery rate, and the separation membrane used is less prone to fouling. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process for treating nickel plating rinse water in an example. Detailed Implementation

[0025] This invention provides a method for treating nickel plating rinse water, comprising the following steps:

[0026] After adjusting the pH of the nickel plating rinse water to 5-6.5, flocculation and sedimentation are carried out, followed by solid-liquid separation to obtain the liquid phase;

[0027] The liquid phase was subjected to ultrafiltration, nanofiltration and electro-desalination in sequence to obtain a concentrated solution;

[0028] The concentrate is subjected to electrowinning to remove impurities, resulting in a purified concentrate.

[0029] The purified concentrate is subjected to membrane electrowinning to obtain elemental nickel.

[0030] This invention adjusts the pH of the nickel plating rinsing water to 5-6.5, performs flocculation and sedimentation, and then separates the solid and liquid phases to obtain a liquid phase. In this invention, preferably before adjusting the pH of the nickel plating rinsing water, the process further includes oxidizing the nickel plating rinsing water. In this invention, the nickel plating rinsing water preferably contains the following impurities at the following mass concentrations: 1000-3000 mg / L nickel ions, less than 50 mg / L copper ions, less than 50 mg / L zinc ions, and less than 100 mg / L iron ions; the pH of the nickel plating rinsing water is preferably 0.5-2.5, more preferably 1.0-2.0; the conductivity of the nickel plating rinsing water is preferably 8000-13000 μS / cm, more preferably 9000-12000 μS / cm; the COD of the nickel plating rinsing water is preferably 100-500 mg / L, more preferably 150-300 mg / L. In this invention, the oxidation treatment preferably includes one or more of electrocatalytic oxidation, photocatalytic oxidation, Fenton oxidation, permanganate oxidation, persulfate oxidation, and hydrogen peroxide oxidation; more preferably, it is one of these three methods; and even more preferably, it is electrocatalytic oxidation. In this invention, the current for the electrocatalytic oxidation is preferably 180–220 A / m. 2 More preferably 200A / m 2 The electrocatalytic oxidation time is preferably 25-35 min, more preferably 30 min.

[0031] This invention reduces the organic matter content and COD in nickel plating rinse water through oxidation treatment.

[0032] In this invention, the pH adjuster used to adjust the pH value of the nickel plating rinsing water preferably includes sodium hydroxide, sodium carbonate, or sodium bicarbonate, more preferably sodium hydroxide. In this invention, the adjusted pH value of the nickel plating rinsing water is 5-6.5, preferably 5.5-6. This invention limits the pH value of the nickel plating rinsing water to within the above range to remove the vast majority of Al. 3+ Fe 3+ and some Cu 2+ and Zn 2+ This causes it to precipitate as hydroxides, which then flocculate and settle.

[0033] In this invention, the flocculation and sedimentation time is preferably 2.5 to 3.5 hours, and more preferably 3 hours.

[0034] In this invention, the solid-liquid separation is preferably performed by filtration.

[0035] The solid obtained by solid-liquid separation in this invention is a mixture of aluminum hydroxide, iron hydroxide, copper hydroxide and zinc hydroxide; preferably, the mixture obtained by solid-liquid separation is sent to an electroplating sludge collection point for further processing.

[0036] After obtaining the liquid phase, the present invention sequentially performs ultrafiltration, nanofiltration, and electro-desalination on the liquid phase to obtain a concentrated solution. In the present invention, the liquid phase is preferably further subjected to disinfection treatment before ultrafiltration (UF). In the present invention, the disinfection treatment preferably includes ozone disinfection, ultraviolet light disinfection, or hypochlorite disinfection, more preferably ultraviolet light disinfection or hypochlorite disinfection. In the present invention, the hypochlorite disinfection is preferably achieved by adding a hypochlorite solution to the liquid phase. In the present invention, the hypochlorite solution is preferably a sodium hypochlorite solution; the mass concentration of the hypochlorite solution is preferably 5–10 mg / L, more preferably 6–8 mg / L. In the present invention, the disinfection treatment time is preferably 1–2 hours, more preferably 1.5–2 hours. The disinfection treatment of the present invention can reduce fouling of membrane materials used for ultrafiltration and nanofiltration.

[0037] In this invention, the ultrafiltration membrane is preferably a cellulose acetate tubular membrane. Ultrafiltration in this invention can further remove large organic molecules and fine particles.

[0038] In this invention, the nanofiltration (NF) membrane is preferably a cellulose acetate tubular membrane. In this invention, the molecular weight cutoff of the nanofiltration membrane is preferably 100 Da; the water yield of the nanofiltration is preferably 70% or more, more preferably 75-80%; and the conductivity of the nanofiltration concentrate effluent is preferably ≥30000 μS / cm.

[0039] In this invention, the nanofiltration process preferably further includes: mixing the nanofiltration-obtained desalinated water and resin for ion exchange, followed by sequential first reverse osmosis (RO1) and second reverse osmosis (RO2) to obtain recycled water. In this invention, the resin is preferably a weakly acidic cation exchange resin, and the weakly acidic cation exchange resin is preferably D100 resin. In this invention, the ion exchange is preferably a two-stage ion exchange; the flow rate of the nanofiltration desalinated water during the ion exchange is preferably 10 BV / h. This invention utilizes the resin and nickel ions in the nanofiltration desalinated water for ion exchange. When the resin is saturated, this invention preferably uses sulfuric acid to desorb the saturated resin. In this invention, resin saturation is indicated when the nickel ion concentration in the ion-exchanged water is greater than or equal to 0.5 mg / L. In this invention, the mass concentration of the sulfuric acid is preferably 4-6%, more preferably 5%. This invention preferably mixes the desorbed solution and the concentrated solution for electrowinning to remove impurities.

[0040] In this invention, the pressure of the first reverse osmosis is preferably 1.5–2 MPa, more preferably 1.6–1.8 MPa. In this invention, the desalinated water from the first reverse osmosis can be reused in the production line of an electroplating enterprise in the industrial park. Preferably, the concentrated water from the first reverse osmosis is subjected to a second reverse osmosis. In this invention, the pressure of the second reverse osmosis is preferably 3–4.2 MPa, more preferably 3.5–4 MPa. In this invention, the desalinated water from the second reverse osmosis can be used in the production line of an electroplating enterprise in the industrial park or in a resin treatment system; the concentrated water from the second reverse osmosis can be evaporated to recover sodium chloride byproduct salt.

[0041] This invention does not have special requirements for the electro-desalination (ED) process; conventional methods in the art can be used. In this invention, the conductivity of the concentrated effluent obtained from the electro-desalination is preferably ≥100,000 μS / cm. Preferably, the desalinated water obtained from the electro-desalination is further subjected to nanofiltration.

[0042] The present invention concentrates nickel ions in nickel plating rinse water through nanofiltration and electro-desalination. In the present invention, the mass concentration of nickel ions in the concentrated solution is preferably greater than 30 g / L, more preferably 30-40 g / L.

[0043] After obtaining the concentrate, the present invention performs electrowinning to remove impurities, resulting in a purified concentrate. In this invention, the preferred current density for electrowinning is 25–75 A / m. 2 More preferably 50-70 A / m 2 This invention uses electrowinning to remove impurities, which first separates and precipitates copper and zinc ions in the concentrate, reducing their concentration to below 30 mg / L.

[0044] After obtaining the purified concentrate, the present invention performs diaphragm electrowinning on the purified concentrate to obtain elemental nickel. In the present invention, the pH value of the diaphragm electrowinning solution is preferably 2.5–4, more preferably 3–4. The present invention preferably adds an alkaline substance to the purified concentrate to adjust its pH value; the alkaline substance is preferably sodium hydroxide or sodium carbonate, more preferably sodium hydroxide. The present invention preferably adds borate buffer to the purified concentrate to maintain its pH value within the above range, which is beneficial for diaphragm electrowinning. In the present invention, the mass concentration of the borate buffer is preferably 10–20 g / L, more preferably 15–18 g / L. In the present invention, the concentration of nickel ions in the diaphragm electrowinning solution is preferably 3 g / L or higher. The present invention preferably introduces the diaphragm electrowinning solution into the cathode region of the diaphragm electrowinning cell in a bottom-in, top-out manner. In this invention, the diaphragm used for diaphragm electrowinning is preferably an anion exchange membrane; the anode material used for diaphragm electrowinning is preferably titanium-coated tantalum-iridium or titanium-coated lead dioxide; and the cathode material used for diaphragm electrowinning is preferably stainless steel, nickel plate, or nickel foam, more preferably nickel plate.

[0045] In this invention, the current density of the diaphragm electrodeposition is preferably 150–300 A / m. 2 More preferably 200–260 A / m 2 The present invention preferably maintains the nickel ion concentration in the diaphragm electrodeposition cathode cell at above 3 g / L by controlling the replenishment rate of the new electrodeposition solution. The present invention also preferably maintains the pH value of the electrodeposition solution in the diaphragm electrodeposition cathode cell at 2.5–4 by adding an alkaline substance to the diaphragm electrodeposition cathode cell during the diaphragm electrodeposition process.

[0046] In this invention, the electrodeposition of the diaphragm preferably further includes:

[0047] After the diaphragm electrodeposition liquid is subjected to nickel precipitation, it is mixed with sodium carbonate solution to carry out a precipitation reaction, resulting in nickel carbonate sludge.

[0048] The nickel carbonate sludge is further subjected to diaphragm electrodeposition to obtain elemental nickel.

[0049] This invention involves mixing the liquid obtained after diaphragm electrowinning with a sodium carbonate solution to undergo a precipitation reaction, yielding nickel carbonate sludge. In this invention, the mass concentration of nickel ions in the liquid obtained after diaphragm electrowinning is preferably below 3 g / L; the mass concentration of sodium ions in the liquid obtained after diaphragm electrowinning is preferably above 15 g / L, more preferably 15–20 g / L.

[0050] In this invention, the mass concentration of the sodium carbonate solution is preferably 18-22%, more preferably 20%. In this invention, the pH value of the mixed system is preferably 7-8. This invention does not have special requirements on the amount of sodium carbonate solution used, as long as the pH value of the mixed system meets the requirements.

[0051] In this invention, the precipitation reaction is preferably accompanied by stirring, and the stirring time is preferably 0.5 to 2 hours, more preferably 1 to 18 hours. This invention does not have special requirements for the stirring speed, as long as it allows for a complete reaction.

[0052] In this invention, the precipitation reaction is followed by: solid-liquid separation of the nickel-precipitated system, and rinsing of the solid obtained from the solid-liquid separation to obtain nickel carbonate sludge. In this invention, the solid-liquid separation is preferably filtration, and the filtration is preferably pressure filtration. In this invention, the filtrate obtained from the filtration contains a large amount of salt, and it is preferable to evaporate the filtrate to recover the salt. In this invention, the rinsing solvent is preferably water. This invention can remove sodium ions from the nickel carbonate sludge through rinsing. In this invention, the rinsing solution contains salt and nickel ions, and it is preferable to return the rinsing solution to nanofiltration for secondary recovery.

[0053] After obtaining nickel carbonate sludge, the nickel carbonate sludge of the present invention is further subjected to diaphragm electrowinning to obtain elemental nickel. Preferably, the nickel carbonate sludge and the impurity removal concentrate are mixed for diaphragm electrowinning.

[0054] This invention only requires adjusting the pH of wastewater to 5.5–6.5 to separate nickel from iron and aluminum ions, saving on reagent usage and reducing sludge volume. Through combined membrane treatment (ultrafiltration, nanofiltration, and electro-desalination), it enables wastewater reuse, reduces the possibility of membrane fouling, and concentrates valuable metal ions such as nickel, copper, and zinc for efficient resource recovery. The introduction of highly selective nanofiltration membranes improves nickel recovery while separating monovalent chloride and sodium ions, effectively mitigating chlorine generation and sodium sulfate precipitation during nickel electrowinning. The use of membrane treatment combined with ion exchange overcomes the difficulty of nickel adsorption in mixed metal ion systems, while simultaneously treating various wastewater streams, essentially achieving zero discharge. The resource recovery product is nickel plates, which have a broader market than industrial by-product salt production, thus creating more direct economic value.

[0055] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0056] according to Figure 1 The process shown is used to treat the nickel plating rinse water.

[0057] Example 1

[0058] The rinsing water from the bright nickel plating process is a light green and transparent liquid with no visible suspended particles and a pH of 1.8. The treatment steps are as follows:

[0059] 1) Raw water is fed into the electrocatalytic oxidation system. The electrocatalytic anode is a titanium-coated ruthenium-iridium plate, and the cathode is stainless steel. The current density is controlled at 200 A / m³. 2 The relative residence time of the water is 30 minutes;

[0060] 2) After electrocatalytic oxidation, the solution is passed into a sedimentation tank, and the pH value is adjusted to 5.0 with liquid alkali for flocculation and sedimentation for 3 hours. Then, it is filtered and separated to obtain liquid and solid phases.

[0061] 3) Transfer the liquid phase to the disinfection raw water tank and add 10 mg / L NaClO solution for disinfection for 1 hour;

[0062] 4) After disinfection, the solution is sent to ultrafiltration, using a cellulose acetate tubular membrane. The concentrated water from ultrafiltration is sent to nanofiltration, using a cellulose acetate tubular membrane with a molecular weight cutoff of 100 DaL. The water yield of the nanofiltration membrane is 70%, and the conductivity of the nanofiltration concentrate is 30,000 μS / cm. The nanofiltration concentrate is then subjected to electro-desalination and concentration, and the conductivity of the electro-desalination concentrate (concentrate) is 100,000 μS / cm. The electro-desalination concentrate is then subjected to electrowinning to remove impurities.

[0063] 5) Two-stage ion exchange of nanofiltration desalinated water was carried out using 100# weakly acidic cation exchange resin with a feed flow rate of 10 BV / h. When the nickel ion concentration in the resin effluent was higher than 0.5 mg / L, the adsorption-protected resin was desorbed using 5% sulfuric acid. The nickel ion concentration in the desorbate was 35 g / L.

[0064] 6) The desorbed solution is subjected to first-stage reverse osmosis at a pressure of 1.5 MPa. The conductivity of the first-stage reverse osmosis desalinated water is below 100 μS / cm and is returned to the production line for reuse. The first-stage reverse osmosis concentrate is subjected to second-stage reverse osmosis at a pressure of 3.0 MPa. The conductivity of the second-stage reverse osmosis desalinated water is below 200 μS / cm and is used for reuse. The second-stage reverse osmosis concentrate is sent to evaporation.

[0065] 7) The concentrated water from the electro-deionization process is heated at a current density of 50 A / m³. 2 Electrowinning was performed for 1 hour under the specified conditions to obtain a concentrated solution; the anode for electrowinning was titanium-coated lead dioxide, and the cathode was a copper plate.

[0066] 8) The purified concentrate is sent to the raw water tank of the diaphragm electrodeposition cell. Nickel carbonate is added to adjust the pH to 4.0, followed by the addition of 20 g / L boric acid buffer. After mixing and dissolving, the solution is sent to the cathode area of ​​the diaphragm electrodeposition cell for diaphragm electrodeposition. Titanium-coated iridium-tantalum plates are used as anodes and titanium plates as cathodes within the cell. The diaphragm is a homogeneous anion exchange membrane. The feed solution is fed from bottom to top. The current density during the diaphragm electrodeposition process is controlled at 200 A / m³. 2 Meanwhile, soda ash solution is added to maintain the pH value at around 4.0. The nickel plate obtained after electrowinning is dense and has a purity of 99.4%.

[0067] 9) The electrolyte solution produced in step 8) is discharged into the sedimentation tank, 20% soda ash solution is added, the pH value is adjusted to 7.0, and the precipitation reaction is carried out with stirring for 1 hour. After the reaction is complete, the solution is filtered by pressure, and the filtrate is sent to the evaporator. After evaporation, sodium sulfate solid salt is obtained and sold as an industrial by-product salt. The nickel carbonate sludge obtained by pressure filtration is washed with water to remove sodium. The washed nickel carbonate is returned to the electrolyte tank to adjust the pH value of the electrolyte, and the nickel carbonate washing water is sent to the nanofiltration tank.

[0068] The indicators of water samples from each process in Example 1 are listed in Table 1.

[0069] Table 1. Overview of Water Quality for Each Process

[0070]

[0071] Example 2

[0072] The rinsing water from the bright nickel plating process is a light green and transparent liquid with no visible suspended particles and a pH of 1.6. The treatment process is as follows:

[0073] 1) Raw water is fed into the electrocatalytic oxidation system. The electrocatalytic anode is a titanium-coated ruthenium-iridium plate, and the cathode is stainless steel. The current density is controlled at 200 A / m³. 2 The relative residence time of the water is 60 minutes;

[0074] 2) After electrocatalytic oxidation, the solution is passed into a sedimentation tank, and the pH value is adjusted to 6.0 with liquid alkali for flocculation and sedimentation for 3 hours. Then, it is filtered and separated to obtain liquid and solid phases.

[0075] 3) Transfer the liquid phase to the disinfection raw water tank and disinfect it with ultraviolet light for 2 hours;

[0076] 4) After disinfection, the solution is sent to ultrafiltration, using a cellulose acetate tubular membrane. The concentrated water from ultrafiltration is sent to nanofiltration, using a cellulose acetate tubular membrane with a molecular weight cutoff of 100 DaL. The water yield of the nanofiltration membrane is 70%, and the conductivity of the nanofiltration concentrate is 30,000 μS / cm. The nanofiltration concentrate is then subjected to electro-desalination and concentration, and the conductivity of the electro-desalination concentrate (concentrate) is 100,000 μS / cm. The electro-desalination concentrate is then subjected to electrowinning to remove impurities.

[0077] 5) Two-stage ion exchange of nanofiltration desalinated water was carried out using 100# weakly acidic cation exchange resin with a feed flow rate of 10 BV / h. When the nickel ion concentration in the resin effluent was higher than 0.5 mg / L, the adsorption-protected resin was desorbed using 5% sulfuric acid. The nickel ion concentration in the desorbate was 35 g / L.

[0078] 6) The desorbed solution is subjected to first-stage reverse osmosis at a pressure of 1.5 MPa. The conductivity of the first-stage reverse osmosis desalinated water is below 100 μS / cm and is returned to the production line for reuse. The first-stage reverse osmosis concentrate is subjected to second-stage reverse osmosis at a pressure of 3.5 MPa. The conductivity of the second-stage reverse osmosis desalinated water is below 200 μS / cm and is used for reuse. The second-stage reverse osmosis concentrate is sent to evaporation.

[0079] 7) The concentrated water from the electro-deionization process is heated at a current density of 50 A / m³. 2 Electrowinning was performed for 1 hour under the specified conditions to obtain a concentrated solution; the anode for electrowinning was titanium-coated lead dioxide, and the cathode was a copper plate.

[0080] 8) The purified concentrate is sent to the raw water tank of the diaphragm electrodeposition cell. Sodium carbonate is added to adjust the pH to 4.0, followed by the addition of 20 g / L boric acid buffer. After mixing and dissolving, the solution is sent to the cathode area of ​​the diaphragm electrodeposition cell for diaphragm electrodeposition. Titanium-coated iridium-tantalum plates are used as anodes and titanium plates as cathodes within the cell. The diaphragm is a homogeneous anion exchange membrane. The feed solution is fed from bottom to top. The current density during the diaphragm electrodeposition process is controlled at 200 A / m³. 2 Meanwhile, soda ash solution is added to maintain the pH value at around 4.0. The nickel plate obtained after electrowinning is dense and has a purity of 99.7%.

[0081] 9) The electrolyte solution produced in step 8) is discharged into the sedimentation tank, 20% soda ash solution is added, the pH value is adjusted to 8.0, and the precipitation reaction is carried out with stirring for 0.5 hours. After the reaction is complete, the solution is filtered by pressure, and the filtrate is sent to evaporate. After evaporation, sodium sulfate solid salt is obtained and sold as an industrial by-product salt. The nickel carbonate sludge obtained by pressure filtration is washed with water to remove sodium. The washed nickel carbonate is returned to the electrolyte tank to adjust the pH value of the electrolyte, and the nickel carbonate washing water is sent to nanofiltration.

[0082] The indicators of water samples from each process in Example 2 are listed in Table 2.

[0083] Table 2. Water Quality Overview for Each Process

[0084]

[0085]

[0086] As can be seen from the treatment results of Examples 1 and 2, the nickel recovered from the nickel plating rinsing water treatment provided by this invention has a purity of 99.4%–99.7%, produces less sludge, has lower costs, and is environmentally friendly. The treated wastewater can meet wastewater discharge standards. After treatment, the nickel plating rinsing water has less impurity pollution and meets the requirements for recycled water influent. If conditions permit, it can be incorporated into a recycled water process.

[0087] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for treating nickel plating rinse water, comprising the following steps: The pH of the nickel plating rinsing water is adjusted to 5-6.5, followed by flocculation and sedimentation, and then solid-liquid separation is performed to obtain the liquid phase. The nickel plating rinsing water contains impurities with the following mass concentrations: 1000-3000 mg / L nickel ions, less than 50 mg / L copper ions, less than 50 mg / L zinc ions, and less than 100 mg / L iron ions. Before adjusting the pH of the nickel plating rinsing water, the process further includes oxidizing the nickel plating rinsing water. The liquid phase is subjected to ultrafiltration, nanofiltration and electro-desalination in sequence to obtain a concentrated solution; the ultrafiltration membrane is a cellulose acetate tubular membrane; the nanofiltration membrane is a cellulose acetate tubular membrane. The concentrate is subjected to electrowinning to remove impurities, resulting in a purified concentrate; the current density for electrowinning is 25~75 A / m. 2 ; The purified concentrate is subjected to diaphragm electrowinning to obtain elemental nickel.

2. The method for treating nickel plating rinse water according to claim 1, characterized in that, The pH adjuster used to adjust the pH value of the nickel plating rinse water includes sodium hydroxide, sodium carbonate, or sodium bicarbonate.

3. The method for treating nickel plating rinse water according to claim 1, characterized in that, The process before ultrafiltration also includes sterilizing the liquid phase.

4. The method for treating nickel plating rinse water according to claim 1, characterized in that, The process after nanofiltration also includes: mixing the nanofiltration-obtained freshwater with resin for ion exchange, followed by sequential first and second reverse osmosis to obtain reclaimed water.

5. The method for treating nickel plating rinse water according to claim 1, characterized in that, The pH value of the diaphragm electrodeposition solution is 2.5~4; the concentration of nickel ions in the diaphragm electrodeposition solution is above 3g / L.

6. The method for treating nickel plating rinse water according to claim 1 or 5, characterized in that, The current density of the diaphragm electrodeposition is 150~300A / m. 2 .

7. The method for treating nickel plating rinse water according to claim 6, characterized in that, After the diaphragm is electrolyzed, it also includes: After the diaphragm electrodeposition liquid is subjected to nickel precipitation, it is mixed with sodium carbonate to carry out a precipitation reaction, resulting in nickel carbonate sludge. The nickel carbonate sludge is further subjected to diaphragm electrodeposition to obtain elemental nickel.

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