Method and device system for recovering and treating electroplating gold wastewater

Abstract

The present application relates to a kind of electroplating gold wastewater recovery processing method and its device system, the method includes: electroplating gold wastewater is sequentially carried out solid-liquid separation treatment, cyanide breakage treatment, pH adjustment treatment and reverse osmosis concentration treatment, and reverse osmosis concentrated solution is obtained;Reverse osmosis concentrated solution is carried out distillation concentration treatment, and distillation concentrated solution is obtained;Distillation concentrated solution is used as electrolyte, and targeted electrochemical recovery treatment is carried out, and crude gold is obtained;Crude gold is carried out smelting purification treatment, and purified gold is obtained.The present application can realize the full-component recovery of precious metal gold and water resources, and recovery purity and efficiency are higher, energy consumption and cost are lower.

Description

Technical Field

[0001] This invention relates to the field of electroplating wastewater treatment technology, specifically to a method and apparatus system for recycling and treating electroplating gold wastewater. Background Technology

[0002] In the electroplating industry, traditional gold electroplating technology plays a vital role, but the resulting wastewater is difficult to recycle and utilize. Gold electroplating wastewater has a complex composition, containing cyanide, trace metal ions, and various complexes. Direct discharge of this wastewater would pose a serious threat to the ecological environment and human health.

[0003] Currently, the industry commonly uses chemical precipitation, ion exchange membrane, or membrane separation methods to treat electroplating gold wastewater. However, these traditional treatment processes generally have many problems: (1) the water recovery rate is low, usually less than 80%, resulting in a large amount of water being lost and wasted during the treatment process, making it difficult to meet the demand for efficient water utilization; (2) the recovery efficiency of precious metal gold is low, resulting in the loss of precious metals along with the wastewater treatment process, which not only wastes resources but also increases the cost of enterprises; (3) the energy consumption in the treatment process is high and highly dependent on fossil energy, resulting in high costs in the wastewater treatment process.

[0004] Therefore, how to achieve zero wastewater discharge, efficient recovery of precious metals, and improved energy utilization are the technical problems that need to be solved in this field. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method and apparatus system for recycling and treating electroplating gold wastewater. Compared with the existing technology, this invention can achieve full-component recovery of precious metal gold and water resources, and has higher recovery purity and efficiency, and lower energy consumption and cost.

[0006] To achieve this objective, the present invention employs the following technical solution:

[0007] In a first aspect, a method for recycling and treating electroplating wastewater, the method comprising the following steps:

[0008] (1) The electroplating wastewater is subjected to solid-liquid separation treatment to obtain separated water;

[0009] (2) The separated water obtained in step (1) is subjected to cyanide complex-breaking treatment to obtain complex-breaking water;

[0010] (3) The water obtained in step (2) after breaking the complex is subjected to pH adjustment treatment and reverse osmosis concentration treatment in sequence to obtain reverse osmosis concentrate;

[0011] (4) The reverse osmosis concentrate obtained in step (3) is concentrated by distillation to obtain a distilled concentrate;

[0012] (5) The distillation concentrate obtained in step (4) is used as an electrolyte for targeted electrochemical recovery treatment to obtain crude gold.

[0013] (6) The crude gold obtained in step (5) is smelted and purified to obtain purified gold.

[0014] In this invention, the electroplating wastewater is first subjected to solid-liquid separation treatment, primarily to remove suspended solids and large molecular organic matter, providing protection for subsequent reverse osmosis concentration treatment. Then, cyanide complex-breaking treatment is performed, mainly because cyanide in the wastewater forms complexes with metal ions; this complex-breaking treatment releases the gold ions from the complexes for subsequent recovery and removal. Finally, pH adjustment treatment is performed, serving two main purposes: firstly, to enhance the effectiveness of subsequent reverse osmosis concentration; and secondly, to pre-adjust the pH of the system to prevent subsequent targeted electroplating. In the chemical recycling process, the electrodes oxidize and fail. Then, reverse osmosis concentration is used to retain gold ions, and the gold concentration is increased before distillation concentration is carried out to further increase the gold concentration. Then, the distillation concentrate is used as an electrolyte for targeted electrochemical recycling. Gold ions are selectively reduced to nano-gold particles (50-80nm in diameter) on a specific cathode surface by pulsed current, and the co-precipitation of impurities such as copper and nickel in the electroplating wastewater is reduced. The gold mud is scraped off the cathode plate to obtain crude gold, which can be recycled for the gold plating process after smelting and purification.

[0015] Preferably, the solid-liquid separation process in step (1) includes ultrafiltration.

[0016] Preferably, the molecular weight cutoff of the ultrafiltration is 5-20 kDa, for example, it can be 5 kDa, 6 kDa, 8 kDa, 10 kDa, 12 kDa, 14 kDa, 16 kDa, 18 kDa or 20 kDa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the turbidity after ultrafiltration is <1 NTU, for example, it can be 0.8 NTU, 0.5 NTU, 0.3 NTU, 0.2 NTU or 0.1 NTU, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] In this invention, the preferred method for controlling solid-liquid separation treatment includes ultrafiltration, which can further remove suspended solids and large molecular organic matter, reduce the turbidity of the separated water, and provide protection for reverse osmosis concentration treatment.

[0019] Preferably, the cyanide complex-breaking treatment in step (2) includes adding persulfate and thiourea to the separated water.

[0020] Preferably, the amount of persulfate added is 0.05-0.3 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L or 0.3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the amount of thiourea added is 0.1-1.0 g / L, for example, it can be 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L or 1.0 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In this invention, persulfate and thiourea are preferably used in the cyanide complexation treatment, forming a highly efficient synergistic oxidation system. The free radicals (SO4) generated by persulfate... - · / ·OH) decomposes potassium gold cyanide (KAu(CN)2) into free gold ions (Au) 3+ The general complex-breaking rate is ≥98%; thiourea reacts with Au in the decomposition products of potassium gold cyanide via the -SH group. 3+ Specific binding forms a stable thiourea-gold complex (e.g., Au(SC(NH2)2)3). 3+ ), to prevent Au 3+ Reconnect with CN - This forms stable complexes, improving the selectivity of subsequent recovery processes (such as targeted electrochemical recovery treatment).

[0023] In this invention, the persulfate is a commonly used persulfate in the art, such as sodium persulfate, ammonium persulfate, etc.

[0024] Preferably, the endpoint pH value of the pH adjustment treatment in step (3) is 3.3-3.7, for example, it can be 3.3, 3.4, 3.5, 3.6 or 3.7, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] In this invention, by preferably controlling the pH value of the pH adjustment treatment to be within a specific range, the effect of reverse osmosis concentration treatment can be improved, while avoiding cathode oxidation failure in subsequent targeted electrochemical recovery treatment.

[0026] Preferably, the operating pressure of the reverse osmosis concentration treatment is 2.5-4.5 MPa, for example, it can be 2.5 MPa, 2.6 MPa, 2.8 MPa, 3 MPa, 3.2 MPa, 3.4 MPa, 3.6 MPa, 3.8 MPa, 4 MPa, 4.2 MPa, 4.4 MPa or 4.5 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] In this invention, by optimizing the control of the operating pressure of the reverse osmosis concentration process, the retention effect of gold ions can be further improved, the conductivity of the permeate can be reduced, and the concentration of the concentrate can be increased.

[0028] Preferably, the reverse osmosis concentration treatment also yields reverse osmosis permeate.

[0029] Preferably, the conductivity of the reverse osmosis permeate is ≤50μS / cm, for example, it can be 50μS / cm, 40μS / cm, 30μS / cm, 20μS / cm or 10μS / cm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the reverse osmosis permeate is reused in the gold plating tank of the electroplating gold process.

[0031] In this invention, the reverse osmosis product water has a low content of metal ions or impurities. Reusing it in the gold plating tank of the electroplating gold process can improve the utilization rate of water resources. That is, the method provided by this invention can not only realize the recovery of precious metal gold, but also realize the recovery and efficient utilization of water resources, achieving "zero liquid discharge".

[0032] Preferably, the concentration of the reverse osmosis concentrate is ≥2200ppm, for example, it can be 2200ppm, 2300ppm, 2400ppm, 2500ppm, 2600ppm, 2700ppm, 2800ppm, 2900ppm or 3000ppm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0033] Preferably, the distillation and concentration process in step (4) includes spiral multi-effect distillation.

[0034] Preferably, the heat exchange area of ​​the distillation and concentration process is 20-100 m². 2 For example, it could be 20m 2 30m 2 40m 2 50m 2 60m 2 70m 2 80m 2 90m 2 or 100m2 However, this does not limit the listed values; other unlisted values ​​within the range are also applicable.

[0035] Preferably, the temperature of the distillation and concentration process is 80-95℃, for example, it can be 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, 92℃, 94℃ or 95℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the concentration of the distillation concentrate is ≥5000ppm, for example, it can be 5000ppm, 5500ppm, 6000ppm, 6500ppm or 7000ppm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0037] Preferably, the steam obtained from the distillation and concentration process is cooled to obtain condensate.

[0038] Preferably, the conductivity of the condensate is ≤8.5μS / cm, for example, it can be 8.5μS / cm, 8μS / cm, 7.5μS / cm, 7μS / cm, 6.5μS / cm or 6μS / cm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the condensate is treated with ultraviolet light for sterilization and then reused in the post-gold plating rinsing tank of the electroplating gold process.

[0040] In this invention, by optimally controlling the heat exchange area and temperature of the distillation concentration process within a specific range, the concentration of the concentrate can be further increased. Furthermore, the obtained steam is condensed to obtain condensate, which has a lower conductivity. Recycling the condensate in the washing tank after gold plating can further improve the utilization rate of water resources, reduce the amount of fresh water used, reduce wastewater discharge, and lower treatment costs.

[0041] Preferably, the pulse current for the targeted electrochemical recovery treatment in step (5) is 10-25 mA / cm. 2 For example, it could be 10mA / cm 2 12mA / cm 2 14mA / cm 2 16mA / cm 2 18mA / cm 2 20mA / cm 2 22mA / cm 2 24mA / cm 2 Or 25mA / cm 2 However, this does not limit the listed values; other unlisted values ​​within the range are also applicable.

[0042] Preferably, the pulse duty cycle of the targeted electrochemical recovery treatment is 20-50%, for example, it can be 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, or 50%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] In this invention, by preferably controlling the pulse current and pulse duty cycle of the targeted electrochemical recovery process within a specific range, the recovery rate and purity of gold can be further improved.

[0044] Preferably, the cathode used in the targeted electrochemical recovery process includes a thiourea / graphene composite electrode.

[0045] In this invention, by modifying thiourea, the -SH (thiol group) and -NH2 (amino group) in the thiourea molecule can undergo a condensation reaction with the oxygen-containing functional groups (such as -COOH, -OH) of graphene oxide through high-temperature sintering, forming stable CS bonds and CN bonds, thereby enhancing the bonding strength at the interface between the two phases. Furthermore, during the high-temperature sintering process, the S and N elements released by thiourea can be doped into the graphene lattice, forming sulfur-nitrogen co-doped active sites, improving the electrode's resistance to noble metal ions Au. 3+ The selective adsorption capacity of thiourea; the gases such as NH3 and H2S produced by the decomposition of thiourea at high temperature can be used as pore-forming agents to induce the formation of uniformly distributed submicron-sized pores (porosity 35-40%) in the thiourea / graphene composite layer, thereby increasing the specific surface area and optimizing the mass transfer channels.

[0046] In this invention, graphene oxide can be partially reduced during the sintering process, restoring sp. 2 The hybrid conjugated structure forms a three-dimensional conductive network, significantly reducing electrode resistivity (by more than 70% compared to pure thiourea coatings); and graphene oxide exhibits high electron mobility (>1000 cm⁻¹). 2 / V·s) ensures rapid charge transfer, supporting high current efficiency (over 99%) for targeted electrochemical recovery processing.

[0047] In this invention, by preferentially controlling the cathode to use a thiourea / graphene composite electrode, the chemical activity regulation of thiourea can be combined with the physical structural support of graphene oxide, achieving the dual functions of high conductivity and high adsorption. The -SH group of thiourea and Au 3+ Coordination bonds are formed, and the graphene network ensures rapid electron injection into reaction sites; the hydrophobic regions of graphene oxide repel polar impurities. Therefore, gold nanoparticles selectively deposit within the coating pores, with a particle size distribution of 50-80 nm, suppressing co-deposition of other metals. The current efficiency of gold recovery reaches over 99%, the coverage of copper and nickel impurities on the electrode surface is <0.3%, and the co-deposition inhibition rate of copper and nickel is >98%.

[0048] Preferably, the anode used in the targeted electrochemical recovery process comprises a stainless steel plate.

[0049] Preferably, the cathode of the targeted electrochemical recovery treatment yields deposited crude gold.

[0050] Preferably, the purity of the crude gold is ≥99.92%, for example, it can be 99.92%, 99.93% or 99.94%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Preferably, the preparation method of the thiourea / graphene composite electrode in step (5) includes the following steps: spraying a mixture of thiourea and graphene oxide onto a substrate electrode, and then sintering it at high temperature to obtain a thiourea / graphene composite electrode, wherein the surface of the thiourea / graphene composite electrode contains a thiourea / graphene composite layer.

[0052] Preferably, the solvent of the mixture includes deionized water.

[0053] Preferably, the concentration of thiourea in the mixture is 80-130 g / L, for example, it can be 80 g / L, 85 g / L, 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L, 115 g / L, 120 g / L, 125 g / L or 130 g / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0054] Preferably, the concentration of graphene oxide in the mixture is 10-50 g / L, for example, it can be 10 g / L, 12 g / L, 15 g / L, 18 g / L, 20 g / L, 22 g / L, 25 g / L, 28 g / L, 30 g / L, 32 g / L, 35 g / L, 38 g / L, 40 g / L, 42 g / L, 45 g / L, 48 g / L or 50 g / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0055] Preferably, the high-temperature sintering temperature is 400-500℃, for example, it can be 400℃, 420℃, 440℃, 460℃, 480℃ or 500℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] Preferably, the substrate electrode comprises a titanium mesh.

[0057] In this invention, the purity of the titanium mesh is generally ≥99.6%. Before spraying, the titanium mesh generally needs to undergo sandblasting roughening treatment to control Ra to 5.8-6.8μm.

[0058] Preferably, the pore size of the thiourea / graphene composite electrode is 0.4-0.6 mm, for example, it can be 0.4 mm, 0.42 mm, 0.44 mm, 0.46 mm, 0.48 mm, 0.5 mm, 0.52 mm, 0.54 mm, 0.56 mm, 0.58 mm or 0.6 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] In this invention, the titanium mesh itself has pores, and after spraying and high-temperature sintering, the resulting electrode still has a porous structure with pore sizes basically consistent with those of the titanium mesh, and a surface thiol group density of 4.2 mmol / m. 2 .

[0060] Preferably, the porosity of the thiourea / graphene composite electrode is 35-40%, for example, it can be 35%, 36%, 37%, 38%, 39% or 40%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] In this invention, the porosity refers to the porosity of the thiourea / graphene composite layer formed by the NH3, H2S, and other gases produced by the decomposition of thiourea at high temperatures, which act as pore-forming agents and induce the formation of uniformly distributed submicron-sized pores. The thiourea molecules interact with Au through the -SH group. 3+ Stable coordination bonds are formed, and gold nanoparticles are selectively deposited in the pores of the coating.

[0062] Preferably, the thickness of the thiourea / graphene composite layer on the thiourea / graphene composite electrode is 45-55 μm, for example, it can be 45 μm, 46 μm, 47 μm, 48 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm or 55 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0063] Preferably, the purity of the refined gold obtained by the smelting and refining process in step (6) is ≥99.95%, for example, it can be 99.95%, 99.96%, 99.97%, 99.98% or 99.99%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] Preferably, the refined gold is reused in the gold plating tank of the electroplating gold process.

[0065] In this invention, the purified gold is reused in the gold plating tank of the electroplating gold process, which can realize the recycling of metal resources and reduce the generation of hazardous waste.

[0066] In this invention, the smelting and purification process is a conventional process in the field, and the parameters used are conventional parameters in the field. It generally includes a melting stage and a refining stage performed sequentially. The temperature of the melting stage is 1100-1200℃ and the time is 30-45 min. The temperature of the refining stage is 1300-1350℃ and the time is 60-90 min.

[0067] As a preferred embodiment of the first aspect of the present invention, the method includes the following steps:

[0068] (1) The electroplating wastewater was subjected to ultrafiltration to obtain separated water with a molecular weight cutoff of 5-20 kDa and turbidity <1 NTU.

[0069] (2) Add 0.05-0.3 mol / L of persulfate and 0.1-1.0 g / L of thiourea to the separated water obtained in step (1) to perform cyanide complex-breaking treatment to obtain complex-breaking water;

[0070] (3) The pH value of the water obtained in step (2) after breaking the complex is adjusted to the final pH value of 3.3-3.7. Then, the operating pressure is controlled at 2.5-4.5MPa for reverse osmosis concentration treatment to obtain reverse osmosis concentrate with a concentration ≥2200ppm and reverse osmosis permeate with a conductivity ≤50μS / cm. The reverse osmosis permeate is recycled for the gold plating tank in the electroplating process.

[0071] (4) The reverse osmosis concentrate obtained in step (3) is subjected to distillation concentration treatment, wherein the heat exchange area of ​​the distillation concentration treatment is 20-100m². 2 The distillation and concentration process is carried out at a temperature of 80-95℃ to obtain a distillation concentrate with a concentration of ≥5000ppm and steam. The steam is cooled to obtain condensate with a conductivity of ≤8.5μS / cm. The condensate is then sterilized by ultraviolet light and reused in the post-gold plating water washing tank of the electroplating process.

[0072] (5) Using the distilled concentrate obtained in step (4) as the electrolyte, with a thiourea / graphene composite electrode as the cathode and a stainless steel plate as the anode, an electrolytic current of 10-25 mA / cm² is applied. 2 Targeted electrochemical recovery treatment was carried out under pulse duty cycle of 20-50%, and crude gold with a purity of ≥99.92% was obtained from the cathode;

[0073] The preparation method of the thiourea / graphene composite electrode includes the following steps:

[0074] A mixture of thiourea and graphene oxide is sprayed onto a titanium mesh. The concentration of thiourea in the mixture is 80-130 g / L, and the concentration of graphene oxide is 10-50 g / L. Then, it is sintered at a high temperature of 400-500℃ to obtain a thiourea / graphene composite electrode. The surface of the thiourea / graphene composite electrode contains a thiourea / graphene composite layer with a thickness of 45-55 μm.

[0075] (6) The crude gold obtained in step (5) is smelted and purified to obtain purified gold with a purity of ≥99.95%, and the purified gold is reused in the gold plating tank of the electroplating process.

[0076] In a second aspect, the present invention provides an apparatus system for recycling and treating electroplating wastewater, the apparatus system being used for the method of recycling and treating electroplating wastewater as described in the first aspect of the present invention.

[0077] The device system includes a solid-liquid separation device, a cyanide complex breaking device, a pH adjustment device, and a reverse osmosis concentration device connected in sequence along the gold enrichment direction.

[0078] The concentrated liquid outlet of the reverse osmosis concentration unit is connected to the distillation concentration unit, and the concentrated liquid outlet of the distillation concentration unit is connected to the electrolyte tank of the electrochemical unit.

[0079] The cathode deposit collection outlet of the electrochemical device is connected to the smelting and purification device.

[0080] The device system provided by this invention is a method for recycling and treating electroplating wastewater, which can realize the dual resource recovery of water and gold resources, shorten the process path, improve the treatment efficiency, and reduce the generation of hazardous waste.

[0081] Preferably, the solid-liquid separation device includes an ultrafiltration device.

[0082] Preferably, the gold purification outlet of the smelting and refining device is connected to the gold plating tank.

[0083] Preferably, the product water outlet of the reverse osmosis concentration device is connected to the gold plating tank.

[0084] Preferably, the condensate outlet of the distillation and concentration device is connected to the gold-plated washing tank via an ultraviolet sterilization device.

[0085] Preferably, the distillation and concentration apparatus includes a drive power supply system and a heating system.

[0086] Preferably, the drive power supply system includes a solar collector, a photovoltaic panel, a flow battery energy storage module, and a shunt controller.

[0087] Preferably, the heat source outlet of the solar collector is connected to the heating system via a diversion controller.

[0088] Preferably, the photovoltaic panel is connected to the flow battery energy storage module circuit via a shunt controller.

[0089] Preferably, the flow battery energy storage module is connected to the heating system.

[0090] It should be noted that this invention, through the optimized control and drive power supply system including a solar collector, photovoltaic panels, a flow battery energy storage module, and a shunt controller, can achieve synergistic energy supply and dynamic regulation of the heating system of the distillation and concentration apparatus by combining solar thermal and photovoltaic power. Specifically, during the day, the solar collector converts solar energy into thermal energy of the heating medium, with a photothermal conversion efficiency of ≥65%. The resulting heating medium provides energy to the heating system of the distillation and concentration apparatus via the shunt controller. Simultaneously, during the day, the photovoltaic panels convert solar energy into electrical energy and store the electrical energy in the flow battery energy storage module via the shunt controller, with a photoelectric efficiency of 18-24%. At night, when the solar collector is not working, the flow battery energy storage module directly provides electrical energy to the heating system of the distillation and concentration apparatus for electric heating, thereby meeting the temperature requirements of the distillation and concentration apparatus.

[0091] In this invention, energy is supplied to the heating system through solar collectors or flow batteries, and the output power is controlled to match the system's energy consumption demand, so that the self-sufficiency rate is ≥85% and the grid dependence is reduced.

[0092] Compared with the prior art, the present invention has the following beneficial effects:

[0093] (1) The method and apparatus system provided by the present invention can realize a dual resource recovery path of water resources and precious metal gold resources, which can reduce the amount of hazardous waste generated by more than 95%. This zero-emission closed-loop recycling and treatment mode can improve the utilization rate of resources and the process is green and environmentally friendly.

[0094] (2) In the method provided by the present invention, the use of a thiourea / graphene composite electrode in the targeted electrochemical recovery process can achieve selective deposition of gold. Under optimal conditions, the gold yield reaches more than 98.9% and the purity reaches more than 99.1%, which improves the gold recovery rate and purity and inhibits the co-precipitation of impurities such as copper and nickel.

[0095] (3) In the device system provided by the present invention, by adopting the mode of complementary solar thermal and photovoltaic power generation, the energy consumption cost can be reduced by more than 40% compared with the power grid supply, and the energy utilization rate is improved. Attached Figure Description

[0096] Figure 1 This is a schematic diagram of the device system provided in Embodiment 1 of the present invention;

[0097] Figure 2This is a schematic diagram of the drive power supply system and heating system provided in Embodiment 1 of the present invention;

[0098] Among them, 1-ultrafiltration device; 2-cyanide complex breaking device; 3-pH adjustment device; 4-reverse osmosis concentration device; 5-distillation concentration device; 6-electrochemical device; 7-smelting and purification device; 8-gold plating tank; 9-ultraviolet sterilization device; 10-gold plating post-washing tank.

[0099] 501-Solar collector; 502-Photovoltaic panel; 503-Flow battery energy storage module; 504-Shunting controller; 505-Heating system. Detailed Implementation

[0100] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0101] Example 1

[0102] This embodiment provides a method for recycling and treating electroplating wastewater, the method comprising the following steps:

[0103] (1) The electroplating wastewater was subjected to ultrafiltration to obtain separated water with a molecular weight cutoff of 12kDa and turbidity <1NTU.

[0104] (2) Add 0.15 mol / L sodium persulfate and 0.5 g / L thiourea to the separated water obtained in step (1) to perform cyanide complex-breaking treatment to obtain complex-breaking water;

[0105] (3) The pH value of the water obtained in step (2) after breaking the complex is adjusted to the final pH value of 3.5. Then, the operating pressure is controlled at 3.5MPa for reverse osmosis concentration treatment to obtain reverse osmosis concentrate and reverse osmosis permeate. The reverse osmosis permeate is recycled for the gold plating tank of the electroplating gold process.

[0106] (4) The reverse osmosis concentrate obtained in step (3) is subjected to distillation concentration treatment. The distillation concentration treatment adopts a spiral multi-effect distillation with a heat exchange area of ​​60m². 2 The distillation and concentration process is carried out at a temperature of 87°C to obtain distillate concentrate and steam. The steam is cooled to obtain condensate, which is then treated with ultraviolet light and reused in the post-plating water washing tank of the electroplating process.

[0107] (5) Using the distilled concentrate obtained in step (4) as the electrolyte, with a thiourea / graphene composite electrode as the cathode and a stainless steel plate as the anode, a pulse current of 17 mA / cm² is applied. 2Targeted electrochemical recovery was performed under a pulse duty cycle of 35%, and crude gold with a particle size of 50-80 nm was obtained at the cathode.

[0108] The preparation method of the thiourea / graphene composite electrode includes the following steps:

[0109] A mixture of thiourea and graphene oxide was sprayed onto a titanium mesh (pore size 0.5 mm, purity ≥99.6%). The concentration of thiourea in the mixture was 100 g / L, and the concentration of graphene oxide was 30 g / L. Then, it was sintered at 450 °C to obtain a thiourea / graphene composite electrode. The surface of the thiourea / graphene composite electrode contained a thiourea / graphene composite layer with a thickness of 50 μm. The pore size of the thiourea / graphene composite electrode was 0.5 mm, and the porosity was 38%.

[0110] (6) The crude gold obtained in step (5) is hung from the cathode plate and then subjected to smelting and purification treatment. The smelting and purification treatment includes a melting stage and a refining stage performed sequentially. The temperature of the melting stage is 1150°C and the time is 40 min. The temperature of the refining stage is 1330°C and the time is 80 min, so as to obtain purified gold with a purity of ≥99.95%. The purified gold is reused in the gold plating tank of the electroplating gold process.

[0111] This embodiment also provides a device system used in the above method, such as Figure 1 As shown, the device system includes an ultrafiltration device 1, a cyanide complex-breaking device 2, a pH adjustment device 3, and a reverse osmosis concentration device 4 connected sequentially along the gold enrichment direction. The concentrated liquid outlet of the reverse osmosis concentration device 4 is connected to a distillation concentration device 5, the product water outlet of the reverse osmosis concentration device 4 is connected to a gold plating tank 8, the concentrated liquid outlet of the distillation concentration device 5 is connected to an electrolyte tank of an electrochemical device 6, the condensate outlet of the distillation concentration device 5 is connected to a post-gold plating water washing tank 10 via an ultraviolet sterilization device 9, the cathode deposit collection outlet of the electrochemical device 6 is connected to a smelting and purification device 7, and the purified gold outlet of the smelting and purification device 7 is connected to the gold plating tank 8.

[0112] like Figure 2As shown, the distillation and concentration device 5 includes a drive power supply system and a heating system 505. The drive power supply system includes a solar collector 501, a photovoltaic panel 502, a flow battery energy storage module 503, and a flow controller 504. The heat source outlet of the solar collector 501 is connected to the heating system 505 via the flow controller 504. The photovoltaic panel 502 is electrically connected to the flow battery energy storage module 503 via the flow controller 504. The flow battery energy storage module 503 is connected to the heating system 505. During the day, the solar collector 501 converts solar energy into thermal energy for the heating medium. The resulting heating medium provides energy to the heating system 505 of the distillation and concentration device 5 via the shunt controller 504, with a photothermal conversion efficiency of 65%. Simultaneously, during the day, the photovoltaic panel 502 converts solar energy into electrical energy and stores the electrical energy in the flow battery energy storage module 503 via the shunt controller 504, with a photoelectric efficiency of 22%. At night, when the solar collector 501 cannot work, the flow battery energy storage module 503 directly provides electrical energy to the heating system 505 of the distillation and concentration device 5 for electric heating, thereby meeting the temperature requirements of the distillation and concentration device 5.

[0113] Example 2

[0114] This embodiment provides a method for recycling and treating electroplating wastewater, the method comprising the following steps:

[0115] (1) The electroplating wastewater was subjected to ultrafiltration to obtain separated water with a molecular weight cutoff of 8kDa and turbidity <1NTU.

[0116] (2) Add 0.08 mol / L sodium persulfate and 1.0 g / L thiourea to the separated water obtained in step (1) to perform cyanide complex-breaking treatment to obtain complex-breaking water;

[0117] (3) The pH value of the water obtained in step (2) after breaking the complex is adjusted to the final pH value of 3.3. Then, the operating pressure is controlled at 4.5MPa for reverse osmosis concentration treatment to obtain reverse osmosis concentrate and reverse osmosis permeate. The reverse osmosis permeate is recycled for the gold plating tank of the electroplating gold process.

[0118] (4) The reverse osmosis concentrate obtained in step (3) is subjected to distillation concentration treatment. The distillation concentration treatment adopts a spiral multi-effect distillation with a heat exchange area of ​​30m². 2 The distillation and concentration process is carried out at a temperature of 95°C to obtain distillate concentrate and steam. The steam is cooled to obtain condensate, which is then treated with ultraviolet light and reused in the post-plating water washing tank of the electroplating process.

[0119] (5) Using the distilled concentrate obtained in step (4) as the electrolyte, with a thiourea / graphene composite electrode as the cathode and a stainless steel plate as the anode, a pulse current of 25 mA / cm² is applied. 2 Targeted electrochemical recovery was performed under a pulse duty cycle of 20%, and crude gold with a particle size of 50-80 nm was obtained at the cathode.

[0120] The preparation method of the thiourea / graphene composite electrode includes the following steps:

[0121] A mixture of thiourea and graphene oxide was sprayed onto a titanium mesh (pore size 0.5 mm, purity ≥99.6%). The concentration of thiourea in the mixture was 80 g / L, and the concentration of graphene oxide was 20 g / L. Then, it was sintered at 400 °C to obtain a thiourea / graphene composite electrode. The surface of the thiourea / graphene composite electrode contained a thiourea / graphene composite layer with a thickness of 45 μm. The pore size of the thiourea / graphene composite electrode was 0.5 mm, and the porosity was 38%.

[0122] (6) The crude gold obtained in step (5) is hung from the cathode plate and then subjected to smelting and purification treatment. The smelting and purification treatment includes a melting stage and a refining stage performed sequentially. The temperature of the melting stage is 1150°C and the time is 40 min. The temperature of the refining stage is 1330°C and the time is 80 min, so as to obtain purified gold with a purity of ≥99.95%. The purified gold is reused in the gold plating tank of the electroplating gold process.

[0123] This embodiment also provides a device system used in the above method, which is the same as that in Embodiment 1.

[0124] Example 3

[0125] This embodiment provides a method for recycling and treating electroplating wastewater, the method comprising the following steps:

[0126] (1) The electroplating wastewater was subjected to ultrafiltration to obtain separated water with a molecular weight cutoff of 18kDa and turbidity <1NTU.

[0127] (2) Add 0.3 mol / L sodium persulfate and 0.4 g / L thiourea to the separated water obtained in step (1) to perform cyanide complex-breaking treatment to obtain complex-breaking water;

[0128] (3) The pH value of the water obtained in step (2) after breaking the complex is adjusted to the final pH value of 3.7, and then the operating pressure is controlled at 2.5MPa for reverse osmosis concentration treatment to obtain reverse osmosis concentrate and reverse osmosis permeate. The reverse osmosis permeate is recycled for the gold plating tank of the electroplating gold process.

[0129] (4) The reverse osmosis concentrate obtained in step (3) is subjected to distillation concentration treatment. The distillation concentration treatment adopts a spiral multi-effect distillation with a heat exchange area of ​​98m². 2 The distillation and concentration process is carried out at a temperature of 80°C to obtain distillate concentrate and steam. The steam is cooled to obtain condensate, which is then treated with ultraviolet sterilization and reused in the post-plating water washing tank of the electroplating process.

[0130] (5) Using the distilled concentrate obtained in step (4) as the electrolyte, with a thiourea / graphene composite electrode as the cathode and a stainless steel plate as the anode, a pulse current of 10 mA / cm² is applied. 2 Targeted electrochemical recovery was performed under a pulse duty cycle of 50%, and crude gold with a particle size of 50-80 nm was obtained at the cathode.

[0131] The preparation method of the thiourea / graphene composite electrode includes the following steps:

[0132] A mixture of thiourea and graphene oxide was sprayed onto a titanium mesh (pore size 0.5 mm, purity ≥99.6%). The concentration of thiourea in the mixture was 130 g / L, and the concentration of graphene oxide was 50 g / L. Then, it was sintered at 500 °C to obtain a thiourea / graphene composite electrode. The surface of the thiourea / graphene composite electrode contained a thiourea / graphene composite layer with a thickness of 55 μm. The pore size of the thiourea / graphene composite electrode was 0.5 mm, and the porosity was 38%.

[0133] (6) The crude gold obtained in step (5) is hung from the cathode plate and then subjected to smelting and purification treatment. The smelting and purification treatment includes a melting stage and a refining stage performed sequentially. The temperature of the melting stage is 1150°C and the time is 40 min. The temperature of the refining stage is 1330°C and the time is 80 min, so as to obtain purified gold with a purity of ≥99.95%. The purified gold is reused in the gold plating tank of the electroplating process.

[0134] This embodiment also provides a device system used in the above method, which is the same as that in Embodiment 1.

[0135] Example 4

[0136] This embodiment provides a method for recycling and treating electroplating wastewater. The only difference from Embodiment 1 is that thiourea is not added in the cyanide complex-breaking treatment in step (2).

[0137] Example 5

[0138] This embodiment provides a method for recycling and treating electroplating wastewater. The only difference from Embodiment 1 is that the amount of thiourea added in the cyanide complex-breaking treatment in step (2) is 2.0 g / L.

[0139] Example 6

[0140] This embodiment provides a method for recycling and treating electroplating wastewater. The only difference between this embodiment and the one in Embodiment 1 is that the final pH value of the pH adjustment treatment in step (3) is 2.8.

[0141] Example 7

[0142] This embodiment provides a method for recycling and treating electroplating wastewater. The only difference between this embodiment and the one in embodiment 1 is that the final pH value of the pH adjustment treatment in step (3) is 4.2.

[0143] Example 8

[0144] This embodiment provides a method for recycling and treating electroplating wastewater. The only difference from Embodiment 1 is that the cathode electrode in the targeted electrochemical recycling process described in step (5) is replaced with a commonly used graphite electrode.

[0145] Example 9

[0146] This embodiment provides a method for recycling and treating electroplating wastewater. The only difference from Embodiment 1 is that the thiourea / graphene composite electrode in step (5) is replaced with a graphene oxide modified electrode. The preparation method of the graphene oxide modified electrode differs from the preparation method of the thiourea / graphene composite electrode in Embodiment 1 only in that thiourea is not added to the mixture.

[0147] Example 10

[0148] This embodiment provides a method for recycling and treating electroplating wastewater. The only difference from Embodiment 1 is that the thiourea / graphene composite electrode in step (5) is replaced with a thiourea modified electrode. The preparation method of the thiourea modified electrode differs from the preparation method of the thiourea / graphene composite electrode in Embodiment 1 only in that graphene oxide is not added to the mixture.

[0149] Example 11

[0150] This embodiment provides a device system for recycling and treating electroplating wastewater. The only difference from Embodiment 1 is that no drive power supply system is set up, and the heating system 505 is directly powered by the power grid for electric heating.

[0151] Compared to this embodiment, Example 1 uses an energy-saving method that can save 40% of energy costs.

[0152] Comparative Example 1

[0153] This comparative example provides a method for recycling and treating electroplating wastewater. The only difference from Example 1 is that cyanide complex breaking treatment is not performed, and the resulting separated water is directly subjected to pH adjustment treatment.

[0154] Comparative Example 2

[0155] This comparative example provides a method for recycling and treating electroplating wastewater. The only difference from Example 1 is that pH adjustment is not performed, and the obtained broken complex water is directly subjected to reverse osmosis concentration treatment.

[0156] The yield and purity of crude gold in Examples 1-10 and Comparative Examples 1-2 were tested, and the results are shown in Table 1.

[0157] Table 1

[0158] Yield / % purity / % Example 1 99.9 99.9 Example 2 99.2 99.3 Example 3 98.9 99.1 Example 4 84.6 96.7 Example 5 90.2 97.3 Example 6 86.4 95.8 Example 7 89.7 97.1 Example 8 78.5 93.4 Example 9 81.2 94.6 Example 10 83.7 95.3 Comparative Example 1 69.8 80.3 Comparative Example 2 75.4 85.7

[0159] The following points can be observed from the data in Table 1:

[0160] (1) As can be seen from the data of Examples 1-3, the method provided by the present invention can achieve a gold yield of more than 98.9% and a purity of more than 99.1% under better conditions.

[0161] (2) As can be seen from the comparison between Example 1 and Examples 4-5, the present invention can further improve the purity and yield of gold by adding thiourea in the cyanide complexation treatment and preferably controlling the amount of thiourea added.

[0162] (3) As can be seen from the comparison between Example 1 and Examples 6-7, the present invention can further improve the purity and yield of gold by preferentially controlling the pH value to adjust the final pH value of the treatment.

[0163] (4) As can be seen from the comparison between Example 1 and Examples 8-10, the present invention can improve the purity and yield of gold by using a thiourea / graphene composite electrode, compared with the use of commonly used graphite electrodes and electrodes modified by thiourea or graphite alone.

[0164] (5) As can be seen from the comparison between Example 1 and Comparative Examples 1-2, the present invention can achieve a high recovery rate and recovery purity by performing cyanide complex breaking treatment and pH adjustment treatment, which can work synergistically with solid-liquid separation treatment, reverse osmosis concentration treatment and targeted electrochemical recovery treatment.

[0165] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for recycling and treating electroplating wastewater, characterized in that, The method includes the following steps: (1) The electroplating wastewater was subjected to solid-liquid separation treatment to obtain separated water; (2) The separated water obtained in step (1) is subjected to cyanide complex-breaking treatment to obtain complex-breaking water; the cyanide complex-breaking treatment includes: adding persulfate and thiourea to the separated water; (3) The water obtained in step (2) after breaking the complex is subjected to pH adjustment treatment and reverse osmosis concentration treatment in sequence to obtain reverse osmosis concentrate; (4) The reverse osmosis concentrate obtained in step (3) is concentrated by distillation to obtain a distilled concentrate; (5) The distillation concentrate obtained in step (4) is used as an electrolyte for targeted electrochemical recovery treatment to obtain crude gold; (6) The crude gold obtained in step (5) is smelted and purified to obtain purified gold.

2. The method according to claim 1, characterized in that, The solid-liquid separation process described in step (1) includes ultrafiltration.

3. The method according to claim 2, characterized in that, The ultrafiltration has a molecular weight cutoff of 5-20 kDa.

4. The method according to claim 2, characterized in that, The turbidity after ultrafiltration is <1 NTU.

5. The method according to claim 1, characterized in that, The amount of persulfate added is 0.05-0.3 mol / L.

6. The method according to claim 1, characterized in that, The amount of thiourea added is 0.1-1.0 g / L.

7. The method according to claim 1, characterized in that, The final pH value of the pH adjustment treatment in step (3) is 3.3-3.

7.

8. The method according to claim 1, characterized in that, The operating pressure for the reverse osmosis concentration process is 2.5-4.5 MPa.

9. The method according to claim 1, characterized in that, The reverse osmosis concentration process also yields reverse osmosis permeate.

10. The method according to claim 9, characterized in that, The conductivity of the reverse osmosis permeate is ≤50μS / cm.

11. The method according to claim 9, characterized in that, The reverse osmosis permeate is reused in the gold plating tank of the electroplating gold process.

12. The method according to claim 1, characterized in that, The concentration of the reverse osmosis concentrate is ≥2200ppm.

13. The method according to claim 1, characterized in that, The distillation and concentration process in step (4) includes spiral multi-effect distillation.

14. The method according to claim 1, characterized in that, The heat exchange area of the distillation concentration treatment is 20-100 m 2 .

15. The method according to claim 1, characterized in that, The distillation and concentration process is carried out at a temperature of 80-95℃.

16. The method according to claim 1, characterized in that, The concentration of the distillation concentrate is ≥5000ppm.

17. The method according to claim 1, characterized in that, The steam obtained from the distillation and concentration process is cooled to obtain condensate.

18. The method according to claim 17, characterized in that, The conductivity of the condensate is ≤8.5μS / cm.

19. The method according to claim 17, characterized in that, The condensate is treated with ultraviolet light for sterilization and then reused in the post-plating rinsing tank of the electroplating gold process.

20. The method according to claim 1, characterized in that, The pulse current for the targeted electrochemical recovery treatment in step (5) is 10-25 mA / cm. 2 .

21. The method according to claim 1, characterized in that, The pulse duty cycle of the targeted electrochemical recovery process is 20-50%.

22. The method according to claim 1, characterized in that, The cathode used in the targeted electrochemical recovery process includes a thiourea / graphene composite electrode.

23. The method according to claim 1, characterized in that, The anode used in the targeted electrochemical recovery process includes a stainless steel plate.

24. The method according to claim 1, characterized in that, The cathode of the targeted electrochemical recovery treatment yields deposited crude gold.

25. The method according to claim 24, characterized in that, The purity of the crude gold is ≥99.92%.

26. The method according to claim 22, characterized in that, The preparation method of the thiourea / graphene composite electrode in step (5) includes the following steps: A mixture of thiourea and graphene oxide is sprayed onto a substrate electrode and then sintered at high temperature to obtain a thiourea / graphene composite electrode, wherein the surface of the thiourea / graphene composite electrode contains a thiourea / graphene composite layer.

27. The method according to claim 26, characterized in that, The solvent for the mixture includes deionized water.

28. The method according to claim 26, characterized in that, The concentration of thiourea in the mixture is 80-130 g / L.

29. The method according to claim 26, characterized in that, The concentration of graphene oxide in the mixture is 10-50 g / L.

30. The method according to claim 26, characterized in that, The high-temperature sintering temperature is 400-500℃.

31. The method according to claim 26, characterized in that, The substrate electrode includes a titanium mesh.

32. The method according to claim 26, characterized in that, The thiourea / graphene composite electrode has a pore size of 0.4-0.6 mm.

33. The method according to claim 26, characterized in that, The porosity of the thiourea / graphene composite electrode is 35-40%.

34. The method according to claim 26, characterized in that, The thickness of the thiourea / graphene composite layer on the thiourea / graphene composite electrode is 45-55 μm.

35. The method according to claim 1, characterized in that, The purity of the refined gold obtained by the smelting and refining process in step (6) is ≥99.95%.

36. The method according to claim 1, characterized in that, The refined gold is reused in the gold plating tank of the electroplating process.

37. A device system for recycling and treating electroplating wastewater, characterized in that, The device system is used in the method for recycling and treating electroplating wastewater as described in any one of claims 1-36; The device system includes a solid-liquid separation device, a cyanide complex breaking device, a pH adjustment device, and a reverse osmosis concentration device connected in sequence along the gold enrichment direction. The concentrated liquid outlet of the reverse osmosis concentration unit is connected to the distillation concentration unit, and the concentrated liquid outlet of the distillation concentration unit is connected to the electrolyte tank of the electrochemical unit. The cathode deposit collection outlet of the electrochemical device is connected to the smelting and purification device.

38. The apparatus system according to claim 37, characterized in that, The solid-liquid separation device includes an ultrafiltration device.

39. The apparatus system according to claim 37, characterized in that, The gold purification outlet of the smelting and refining device is connected to the gold plating tank.

40. The apparatus system according to claim 37, characterized in that, The product water outlet of the reverse osmosis concentration unit is connected to the gold plating tank.

41. The apparatus system according to claim 37, characterized in that, The condensate outlet of the distillation and concentration device is connected to the gold-plated washing tank via an ultraviolet sterilization device.

42. The apparatus system according to claim 37, characterized in that, The distillation and concentration apparatus includes a drive power supply system and a heating system.

43. The apparatus system according to claim 42, characterized in that, The drive power supply system includes a solar collector, photovoltaic panels, a flow battery energy storage module, and a shunt controller.

44. The apparatus system according to claim 43, characterized in that, The heat source outlet of the solar collector is connected to the heating system via a diversion controller.

45. The apparatus system according to claim 43, characterized in that, The photovoltaic panel is connected to the flow battery energy storage module circuit via a shunt controller.

46. ​​The apparatus system according to claim 43, characterized in that, The flow battery energy storage module is connected to the heating system.

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