Method and device system for recycling and treating electrogilding wastewater

Abstract

The invention relates to a method and a device system for recycling and treating electrogilding wastewater, and the method comprises the following steps: sequentially carrying out solid-liquid separation treatment, cyanide complex breaking treatment, pH value adjusting treatment and reverse osmosis concentration treatment on the electrogilding wastewater to obtain a reverse osmosis concentrated solution; distilling and concentrating the reverse osmosis concentrated solution to obtain a distilled concentrated solution; carrying out targeted electrochemical recovery treatment by taking the distilled concentrated solution as an electrolyte to obtain crude gold; and the crude gold product is subjected to smelting purification treatment, and purified gold is obtained. All-component recovery of precious metal gold and water resources can be achieved, the recovery purity and efficiency are high, and energy consumption and cost are low.

Description

Technical Field

[0001] The present invention relates to the technical field of electroplating wastewater treatment, and particularly to a method and an apparatus system for recycling and treating electroplating gold wastewater. Background Art

[0002] In the electroplating industry, the traditional electroplating gold process occupies an important position, but the electroplating wastewater generated by it is difficult to recycle and utilize. The electroplating gold wastewater has a complex composition, containing cyanides, trace metal ions and various complexes. If it is directly discharged, it will pose a serious threat to the ecological environment and human health.

[0003] At present, the industry generally uses chemical precipitation method, ion exchange membrane method or membrane separation method to treat electroplating gold wastewater. However, these traditional treatment processes generally have many problems: (1) The water resource recovery rate is relatively low, usually less than 80%, resulting in a large amount of water resources being lost and wasted during the treatment process, which is difficult to meet the demand for efficient utilization of water resources; (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 causes resource waste but also increases the cost of enterprises; (3) The energy consumption during the treatment process is relatively high, and it highly depends on fossil energy, resulting in a relatively high cost of the wastewater treatment link.

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

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method and an apparatus system for recycling and treating electroplating gold wastewater. Compared with the existing technology, the present invention can achieve the full-component recovery of precious metal gold and water resources, and has a relatively high recovery purity and efficiency, as well as relatively low energy consumption and cost.

[0006] To achieve the purpose of this invention, the following technical solutions are adopted:

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

[0008] (1) Perform solid-liquid separation treatment on the electroplating gold wastewater to obtain separated water;

[0009] (2) Perform cyanide complex-breaking treatment on the separated water obtained in step (1) to obtain complex-broken water;

[0010] (3) Perform pH value adjustment treatment and reverse osmosis concentration treatment on the complex-broken water obtained in step (2) in sequence to obtain a reverse osmosis concentrate;

[0011] (4) Perform distillation concentration treatment on the reverse osmosis concentrate obtained in step (3) to obtain a distillation concentrate;

[0012] (5) Use the distillation and concentration liquid obtained in step (4) as the electrolyte, and perform targeted electrochemical recovery treatment to obtain crude gold.

[0013] (6) Perform smelting and purification treatment on the crude gold obtained in step (5) to obtain purified gold.

[0014] In the present invention, first, the electroplating gold wastewater is subjected to solid-liquid separation treatment. The main purpose is to remove suspended solids and macromolecular organic matters to provide protection for subsequent reverse osmosis concentration treatment. Then, cyanide complex-breaking treatment is carried out. This is mainly because the cyanide in the electroplating wastewater forms complexes with metal ions. Through complex-breaking treatment, gold ions are released from the complexes for subsequent recovery and removal. After that, pH adjustment treatment is carried out. Its functions mainly include two aspects: on the one hand, it improves the effect of subsequent reverse osmosis concentration, and on the other hand, it pre-adjusts the pH value of the system to avoid electrode oxidation failure in subsequent targeted electrochemical recovery treatment. Then, gold ions are intercepted through reverse osmosis concentration treatment. After the gold concentration is increased, distillation and concentration treatment are carried out to further increase the gold concentration through distillation and concentration. After that, the distillation and concentration liquid is used as the electrolyte for targeted electrochemical recovery treatment. Through pulsed current, gold ions are selectively reduced to nano-gold particles (particle size: 50 - 80 nm) on the surface of a specific cathode, and the coprecipitation of impurities such as copper and nickel in the electroplating wastewater is reduced. The crude gold is obtained by scraping the gold mud on the cathode plate. The obtained crude gold can be recycled for the electroplating gold process after smelting and purification.

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

[0016] Preferably, the cut-off molecular weight 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 numerical range are equally applicable.

[0017] Preferably, the turbidity after ultrafiltration < 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 numerical range are equally applicable.

[0018] In the present invention, preferably, the method of the solid-liquid separation treatment includes ultrafiltration, which can further remove suspended solids and macromolecular organic matters, 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 added amount of the persulfate 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, and other values not listed within the numerical range are also applicable.

[0021] Preferably, the added amount of thiourea 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, and other unlisted values within the numerical range are also applicable.

[0022] In the present invention, it is preferred to use persulfate and thiourea in the cyanide decomposition treatment, which form an efficient synergistic oxidation system. The free radicals (SO4 - · / ·OH) decomposes potassium aurous cyanide (KAu(CN)2) into free gold ions (Au 3+ ), the general decomposition rate is ≥98%; thiourea reacts with Au in the decomposition product of potassium cyanide through -SH group 3+ Specific binding to form a stable thiourea-gold complex (such as Au(SC(NH2)2)3 3+ ), to prevent Au 3+ Reconnect with CN - The formation of stable complexes improves the selectivity of subsequent recovery processes (such as targeted electrochemical recovery treatment).

[0023] In the present invention, the persulfate is a persulfate commonly used in the art, for example, 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, 3.3, 3.4, 3.5, 3.6 or 3.7, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0025] In the present invention, by preferably controlling the end point pH value of the pH adjustment treatment within a specific range, the effect of the reverse osmosis concentration treatment can be improved, while avoiding cathode oxidation failure in the 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. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0027] In the present invention, by preferably controlling the operating pressure of the reverse osmosis concentration treatment, the retention effect on gold ions can be further improved, the conductivity of the produced water can be reduced, and the concentration of the concentrated solution can be increased.

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

[0029] Preferably, the conductivity of the reverse osmosis permeate water ≤ 50 μS / cm. For example, it can be 50 μS / cm, 40 μS / cm, 30 μS / cm, 20 μS / cm or 10 μS / cm. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0030] Preferably, the reverse osmosis permeate water is recycled and used in the gold plating bath of the gold plating process.

[0031] In the present invention, the content of metal ions or impurities in the reverse osmosis permeate water is relatively low. Recycling it and using it in the gold plating bath of the gold plating process can improve the utilization rate of water resources. That is, the method provided by the present 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 ≥ 2200 ppm. For example, it can be 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm or 3000 ppm. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

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

[0034] Preferably, the heat exchange area of the distillation concentration treatment is 20 - 100 m 2 , for example, it can be 20 m 2 , 30 m 2 , 40 m 2 , 50 m 2 , 60 m 2 , 70 m 2 , 80 m 2 , 90 m 2 or 100 m2 , but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0035] Preferably, the temperature of the distillation and concentration treatment is 80 - 95 °C. For example, it can be 80 °C, 82 °C, 84 °C, 86 °C, 88 °C, 90 °C, 92 °C, 94 °C or 95 °C, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0036] Preferably, the concentration of the distillation and concentrated solution ≥ 5000 ppm. For example, it can be 5000 ppm, 5500 ppm, 6000 ppm, 6500 ppm or 7000 ppm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0037] Preferably, the steam obtained from the distillation and concentration treatment is cooled to obtain condensed water.

[0038] Preferably, the conductivity of the condensed water ≤ 8.5 μS / cm. For example, it can be 8.5 μS / cm, 8 μS / cm, 7.5 μS / cm, 7 μS / cm, 6.5 μS / cm or 6 μS / cm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0039] Preferably, the condensed water is reused in the post - plating water - washing tank for the gold - plating process after being treated by ultraviolet sterilization.

[0040] In the present invention, by preferably controlling the heat - exchange area and temperature of the distillation and concentration treatment within a specific range, the concentration of the concentrated solution can be further increased, and the obtained steam is condensed to obtain condensed water with lower conductivity. Recycling the condensed water for use in the post - plating water - washing tank can further improve the utilization rate of water resources, reduce the consumption of fresh water, reduce the discharge of wastewater, and lower the treatment cost.

[0041] Preferably, the pulsed current for the targeted electrochemical recovery treatment in step (5) is 10 - 25 mA / cm 2 , for example, it can be 10 mA / cm 2 , 12 mA / cm 2 , 14 mA / cm 2 , 16 mA / cm 2 , 18 mA / cm 2 , 20 mA / cm 2 , 22 mA / cm 2 , 24 mA / cm 2 or 25 mA / cm 2 , but not limited to the listed values, and other unlisted values within the numerical range are equally 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 not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0043] In the present invention, by preferably controlling the pulse current and pulse duty cycle of the targeted electrochemical recovery treatment 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 treatment includes a thiourea / graphene composite electrode.

[0045] In the present invention, through the modification of thiourea, the -SH (mercapto) and -NH2 (amino) in the thiourea molecule can be utilized. Through high-temperature sintering, they undergo a condensation reaction with the oxygen-containing functional groups (such as -COOH, -OH) of graphene oxide to form stable C-S bonds and C-N bonds, enhancing the binding strength of the two-phase interface. And during the high-temperature sintering process, the S and N elements released by thiourea can be doped into the graphene lattice to form sulfur-nitrogen co-doped active sites, improving the selective adsorption ability of the electrode for precious metal ions Au 3+ ; The gases such as NH3 and H2S generated 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, increasing the specific surface area and optimizing the mass transfer channels.

[0046] In the present invention, graphene oxide can be partially reduced during the sintering process to restore the sp 2 hybrid conjugated structure, forming a three-dimensional conductive network, significantly reducing the electrode resistivity (the reduction can reach more than 70% compared with the pure thiourea coating); and the high electron mobility (>1000 cm 2 / V·s) of graphene oxide ensures rapid charge transfer, supporting a high current efficiency (more than 99%) of the targeted electrochemical recovery treatment.

[0047] In the present invention, by preferably controlling the cathode to use a thiourea / graphene composite electrode, the combination of the chemical activity regulation of thiourea and the physical structure support of graphene oxide can be realized, achieving the dual functions of high conductivity and high adsorption. The -SH group of thiourea forms a coordination bond with Au 3+ ; while the graphene network ensures rapid electron injection into the reaction site; the hydrophobic region of graphene oxide repels polar impurities. Therefore, gold nanoparticles are selectively deposited in the pores of the coating, with a particle size distribution of 50-80 nm, inhibiting the co-deposition of other metals. The current efficiency of gold recovery reaches more than 99%, the coverage rate of copper and nickel impurities on the electrode surface <0.3%, and the co-deposition inhibition rate of copper and nickel >98%.

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

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

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

[0051] Preferably, the preparation method of the thiourea / graphene composite electrode in step (5) comprises the following steps: spraying the mixed solution of thiourea and graphene oxide onto the substrate electrode, and then performing high-temperature sintering to obtain the thiourea / graphene composite electrode, and the surface of the thiourea / graphene composite electrode contains a thiourea / graphene composite layer.

[0052] Preferably, the solvent of the mixed solution comprises deionized water.

[0053] Preferably, the concentration of thiourea in the mixed solution 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 numerical range are equally applicable.

[0054] Preferably, the concentration of graphene oxide in the mixed solution 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 numerical range are equally applicable.

[0055] Preferably, the temperature of the high-temperature sintering is 400 - 500 °C, for example, it can be 400 °C, 420 °C, 440 °C, 460 °C, 480 °C or 500 °C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

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

[0057] In the present invention, the purity of the titanium mesh is generally ≥ 99.6%. Before spraying the titanium mesh, it generally needs to be subjected to sandblasting roughening treatment, and Ra is controlled to be 5.8 - 6.8 μm.

[0058] Preferably, the pore diameter 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. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0059] In the present invention, the titanium mesh itself has pores, and after spraying and high-temperature sintering, the obtained electrode is still a porous structure. The pore diameter is basically the same as that of the titanium mesh, and the surface mercapto density reaches 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%. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0061] In the present invention, the porosity refers to the porosity in which gases such as NH3 and H2S generated by the decomposition of thiourea at high temperature act as pore-forming agents to induce the formation of uniformly distributed submicron-sized pores in the thiourea / graphene composite layer. Thiourea molecules form stable coordination bonds with Au through -SH groups 3+ 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. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0063] Preferably, the purity of the purified gold obtained by the melting and purification treatment in step (6) ≥ 99.95%, for example, it can be 99.95%, 99.96%, 99.97%, 99.98% or 99.99%. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0064] Preferably, the purified gold is recycled and used in the gold plating bath of the gold plating process.

[0065] In the present invention, recycling the purified gold and using it in the gold plating bath of the gold plating process can achieve the recycling of metal resources and reduce the generation of hazardous waste.

[0066] In the present invention, the smelting and purification treatment is a conventional process in the art, and the parameters used are conventional parameters in the art, generally including a melting stage and a refining stage carried out in sequence. The temperature in the melting stage is 1100 - 1200 °C, and the time is 30 - 45 min. The temperature in the refining stage is 1300 - 1350 °C, and the time is 60 - 90 min.

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

[0068] (1) Ultrafilter the electroplated gold wastewater to obtain separated water. After ultrafiltration, the molecular weight cut-off is 5 - 20 kDa, and the turbidity is <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) for cyanide complex-breaking treatment to obtain complex-breaking water;

[0070] (3) Adjust the pH value of the complex-breaking water obtained in step (2) to an end-point pH value of 3.3 - 3.7, and then control the operating pressure at 2.5 - 4.5 MPa for reverse osmosis concentration treatment to obtain a reverse osmosis concentrate with a concentration ≥2200 ppm and reverse osmosis product water with a conductivity ≤50 μS / cm. The reverse osmosis product water is recycled to the gold plating bath in the electroplated gold process;

[0071] (4) Perform distillation concentration treatment on the reverse osmosis concentrate obtained in step (3). The heat exchange area of the distillation concentration treatment is 20 - 100 m 2 , and the temperature of the distillation concentration treatment is 80 - 95 °C to obtain a distillation concentrate with a concentration ≥5000 ppm and steam. The steam is cooled to obtain condensed water with a conductivity ≤8.5 μS / cm. The condensed water is recycled to the post-gold plating washing bath in the electroplated gold process after ultraviolet sterilization treatment;

[0072] (5) Use the distillation concentrate obtained in step (4) as the electrolyte, use a thiourea / graphene composite electrode as the cathode, and a stainless steel plate as the anode to carry out targeted electrochemical recovery treatment under the conditions of a pulsed current of 10 - 25 mA / cm 2 , and a pulse duty cycle of 20 - 50%. Crude gold with a purity ≥99.92% is obtained at the cathode;

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

[0074] The mixed solution of thiourea and graphene oxide is sprayed onto a titanium mesh. The concentration of thiourea in the mixed solution is 80 - 130 g / L, and the concentration of graphene oxide is 10 - 50 g / L. Then, high-temperature sintering is carried out at 400 - 500 °C 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 subjected to smelting and purification treatment to obtain purified gold with a purity ≥99.95%. The purified gold is recycled to the gold plating bath for the gold plating process.

[0076] Second, the present invention provides a device system for the recovery and treatment of gold plating wastewater, and the device system is used for the method of recovering and treating gold plating 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 value adjustment device, and a reverse osmosis concentration device connected in sequence along the direction of gold element enrichment;

[0078] The concentrated liquid outlet of the reverse osmosis concentration device is connected to a distillation concentration device, and the concentrated liquid outlet of the distillation concentration device is connected to the electrolyte tank of an electrochemical device;

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

[0080] The device system provided by the present invention for the method of recovering and treating gold plating wastewater can achieve the dual resource recovery of water resources 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 purified gold outlet of the smelting and purification device is connected to the gold plating bath.

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

[0084] Preferably, the condensed water outlet of the distillation concentration device is connected to the post-gold plating washing tank through an ultraviolet sterilization device.

[0085] Preferably, the distillation concentration device includes a driving energy supply system and a heating system.

[0086] Preferably, the driving energy 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 through a shunt controller.

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

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

[0090] It should be noted that by preferably controlling the driving energy supply system including a solar collector, a photovoltaic panel, a flow battery energy storage module, a shunt controller and other structures, the present invention can realize the coordinated supply of solar thermal and photovoltaic energy to provide energy for the heating system of the distillation and concentration device and dynamically regulate it. Specifically, during the day, the solar collector converts solar energy into the thermal energy of the heating medium, and the solar - thermal conversion efficiency is ≥65%. The obtained heating medium provides energy for the heating system of the distillation and concentration device through the shunt controller. At the same time, during the day, the photovoltaic panel converts solar energy into electrical energy and stores the electrical energy in the flow battery energy storage module through the shunt controller, and the photovoltaic efficiency is 18 - 24%; when night comes and the solar collector cannot work, the flow battery energy storage module directly provides electrical energy for the heating system of the distillation and concentration device for electric heating, so as to meet the temperature requirements of the distillation and concentration device.

[0091] In the present invention, the heating system is powered by the solar collector or the flow battery energy storage, and the output power is controlled to match the energy consumption demand of the system, so that the self - support rate is ≥85%, reducing the dependence on the power grid.

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

[0093] (1) In the method and device system provided by the present invention, a dual resource recovery path for water resources and precious metal gold resources can be realized, and the generation amount of hazardous waste can be reduced by more than 95%. This zero - emission closed - loop recovery and treatment mode can improve the resource utilization rate, and the process is green and environmentally friendly.

[0094] (2) In the method provided by the present invention, a thiourea / graphene composite electrode is used in the targeted electrochemical recovery treatment, which can realize the selective deposition of gold. Under relatively optimal conditions, the recovery rate of gold reaches more than 98.9%, and the purity reaches more than 99.1%, improving the recovery rate and purity of gold and inhibiting the coprecipitation of impurities such as copper and nickel.

[0095] (3) In the device system provided by the present invention, by adopting the complementary mode of solar thermal and photovoltaic energy, compared with grid power supply, the energy consumption cost can be reduced by more than 40%, improving the energy utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0097] Figure 2It is a schematic structural diagram of the driving energy supply system and the heating system provided by Embodiment 1 of the present invention;

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

[0099] 501 - solar collector; 502 - photovoltaic panel; 503 - flow battery energy storage module; 504 - shunt controller; 505 - heating system. Specific Embodiments

[0100] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0101] Embodiment 1

[0102] This embodiment provides a method for recycling and treating electroplated gold wastewater, and the method includes the following steps:

[0103] (1) Ultrafilter the electroplated gold wastewater to obtain separated water. The molecular weight cut-off after ultrafiltration is 12 kDa, and the turbidity is <1 NTU;

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

[0105] (3) Adjust the pH value of the complex-breaking treated water obtained in step (2) to an end pH value of 3.5, and then control the operating pressure to be 3.5 MPa for reverse osmosis concentration treatment to obtain reverse osmosis concentrate and reverse osmosis product water. The reverse osmosis product water is recycled to the gold plating bath of the electroplated gold process;

[0106] (4) Perform distillation concentration treatment on the reverse osmosis concentrate obtained in step (3). The distillation concentration treatment uses spiral multi-effect distillation, and the heat exchange area is 60 m 2 , the temperature of the distillation concentration treatment is 87 °C, to obtain distillation concentrate and steam. The steam is cooled to obtain condensed water, and the condensed water is recycled to the post-gold plating water washing bath of the electroplated gold process after ultraviolet sterilization treatment;

[0107] (5) Use the distillation concentrate obtained in step (4) as the electrolyte, use a thiourea / graphene composite electrode as the cathode, and a stainless steel plate as the anode. At a pulsed current of 17 mA / cm 2, under the condition that the pulse duty cycle is 35%, targeted electrochemical recovery treatment is carried out, and crude gold with a particle size of 50 - 80 nm is obtained at the cathode;

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

[0109] The mixed solution of thiourea and graphene oxide is sprayed onto a titanium mesh (pore size 0.5 mm, purity ≥ 99.6%), the concentration of thiourea in the mixed solution is 100 g / L, and the concentration of graphene oxide is 30 g / L. Then, high-temperature sintering is carried out at 450 °C 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 50 μm. The pore size of the thiourea / graphene composite electrode is 0.5 mm, and the porosity is 38%;

[0110] (6) After the crude gold obtained in step (5) is scraped from the cathode plate, it is subjected to smelting and purification treatment. The smelting and purification treatment includes a melting stage and a refining stage in sequence. 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. Purified gold with a purity ≥ 99.95% is obtained, and the purified gold is recycled to the gold plating bath in the gold plating process.

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

[0112] As Figure 2As shown, the distillation and concentration device 5 includes a driving energy supply system and a heating system 505. The driving energy supply system includes a solar collector 501, a photovoltaic panel 502, a flow battery energy storage module 503, and a shunt controller 504. The heat source outlet of the solar collector 501 is connected to the heating system 505 through the shunt controller 504. The photovoltaic panel 502 is electrically connected to the flow battery energy storage module 503 through the shunt controller 504, and 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 the thermal energy of the heating medium. The obtained heating medium provides energy for the heating system 505 of the distillation and concentration device 5 through the shunt controller 504, and the photothermal conversion efficiency is 65%. At the same time, 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 through the shunt controller 504, and the photoelectric efficiency is 22%. When night falls and the solar collector 501 cannot work, the flow battery energy storage module 503 directly provides electrical energy for the heating system 505 of the distillation and concentration device 5 for electric heating, so as to meet the temperature requirements of the distillation and concentration device 5.

[0113] Example 2

[0114] This embodiment provides a method for recycling and treating electroplated gold wastewater. The method includes the following steps:

[0115] (1) Ultrafilter the electroplated gold wastewater to obtain separated water. After ultrafiltration, the retention molecular weight is 8 kDa and the turbidity is <1 NTU;

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

[0117] (3) Adjust the pH value of the complex-breaking water obtained in step (2) to the end point pH value of 3.3, and then control the operating pressure to be 4.5 MPa for reverse osmosis concentration treatment to obtain reverse osmosis concentrate and reverse osmosis product water. The reverse osmosis product water is reused in the gold plating tank of the electroplated gold process;

[0118] (4) Perform distillation and concentration treatment on the reverse osmosis concentrate obtained in step (3). The distillation and concentration treatment adopts spiral multi-effect distillation, and the heat exchange area is 30 m 2 , the temperature of the distillation and concentration treatment is 95 °C to obtain distillation concentrate and steam. The steam is cooled to obtain condensed water. The condensed water is reused in the post-gold plating water washing tank of the electroplated gold process after ultraviolet sterilization treatment;

[0119] (5) Use the distillation and concentration liquid obtained in step (4) as the electrolyte, use the thiourea / graphene composite electrode as the cathode, and use the stainless steel plate as the anode. Perform targeted electrochemical recovery treatment under the conditions of a pulsed current of 25 mA / cm 2 , and a pulse duty cycle of 20%. The cathode obtains crude gold with a particle size of 50 - 80 nm;

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

[0121] Spray the mixed solution of thiourea and graphene oxide onto a titanium mesh (pore size 0.5 mm, purity ≥ 99.6%). The concentration of thiourea in the mixed solution is 80 g / L, and the concentration of graphene oxide is 20 g / L. Then, perform high-temperature sintering at 400 °C to obtain the thiourea / graphene composite electrode. The surface of the thiourea / graphene composite electrode contains a thiourea / graphene composite layer with a thickness of 45 μm. The pore size of the thiourea / graphene composite electrode is 0.5 mm, and the porosity is 38%;

[0122] (6) After scraping the crude gold obtained in step (5) from the cathode plate, perform melting and purification treatment. The melting and purification treatment includes a melting stage and a refining stage carried out in sequence. 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. Obtain purified gold with a purity ≥ 99.95%, and the purified gold is reused in the gold plating bath of the gold plating process.

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

[0124] Example 3

[0125] This embodiment provides a method for recovering and treating electroplated gold wastewater. The method includes the following steps:

[0126] (1) Ultrafilter the electroplated gold wastewater to obtain separated water. The molecular weight cut-off after ultrafiltration is 18 kDa, and the turbidity < 1 NTU;

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

[0128] (3) Adjust the pH value of the complex broken water obtained in step (2) to the end point pH value of 3.7, and then control the operating pressure to be 2.5 MPa for reverse osmosis concentration treatment to obtain reverse osmosis concentrated liquid and reverse osmosis product water. The reverse osmosis product water is reused in the gold plating bath of the gold plating process;

[0129] (4) The reverse osmosis concentrate obtained in step (3) is subjected to distillation and concentration treatment, and the distillation and concentration treatment adopts spiral multi-effect distillation with a heat exchange area of 98 m 2 , the temperature of the distillation and concentration treatment is 80 °C, a distillation concentrate and steam are obtained, the steam is cooled to obtain condensed water, and the condensed water is reused in the post-gold-plating washing tank of the gold plating process after ultraviolet sterilization treatment;

[0130] (5) The distillation concentrate obtained in step (4) is used as an electrolyte, a thiourea / graphene composite electrode is used as the cathode, and a stainless steel plate is used as the anode. Under the conditions of a pulse current of 10 mA / cm 2 and a pulse duty cycle of 50%, targeted electrochemical recovery treatment is carried out, and crude gold with a particle size of 50 - 80 nm is obtained at the cathode;

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

[0132] The mixed solution of thiourea and graphene oxide is sprayed onto a titanium mesh (pore size 0.5 mm, purity ≥ 99.6%), the concentration of thiourea in the mixed solution is 130 g / L, and the concentration of graphene oxide is 50 g / L. Then, high-temperature sintering is carried out at 500 °C 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 55 μm, the pore size of the thiourea / graphene composite electrode is 0.5 mm, and the porosity is 38%;

[0133] (6) The crude gold obtained in step (5) is scraped from the cathode plate and then subjected to melting and purification treatment. The melting and purification treatment includes a melting stage and a refining stage carried out in sequence. 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 to obtain purified gold with a purity ≥ 99.95%. The purified gold is reused in the gold plating tank of the gold plating process.

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

[0135] Example 4

[0136] This embodiment provides a method for recovering and treating gold plating wastewater, which is only different from that in Example 1 in that thiourea is not added in the cyanide complex-breaking treatment in step (2).

[0137] Example 5

[0138] This embodiment provides a method for recovering and treating gold plating wastewater, which is only different from that in Example 1 in that the addition amount of thiourea in the cyanide complex-breaking treatment in step (2) is 2.0 g / L.

[0139] Example 6

[0140] This example provides a method for the recovery and treatment of electroplated gold wastewater. The only difference compared with Example 1 is that the end pH value of the pH adjustment treatment in step (3) is 2.8.

[0141] Example 7

[0142] This example provides a method for the recovery and treatment of electroplated gold wastewater. The only difference compared with Example 1 is that the end pH value of the pH adjustment treatment in step (3) is 4.2.

[0143] Example 8

[0144] This example provides a method for the recovery and treatment of electroplated gold wastewater. The only difference compared with Example 1 is that in the targeted electrochemical recovery treatment in step (5), the cathode electrode is replaced with a commonly used graphite electrode.

[0145] Example 9

[0146] This example provides a method for the recovery and treatment of electroplated gold wastewater. The only difference compared with Example 1 is that in step (5), the thiourea / graphene composite electrode is replaced with a graphene oxide modified electrode. The preparation method of the graphene oxide modified electrode is only different from the preparation method of the thiourea / graphene composite electrode in Example 1 in that thiourea is not added to the mixed solution.

[0147] Example 10

[0148] This example provides a method for the recovery and treatment of electroplated gold wastewater. The only difference compared with Example 1 is that in step (5), the thiourea / graphene composite electrode is replaced with a thiourea modified electrode. The preparation method of the thiourea modified electrode is only different from the preparation method of the thiourea / graphene composite electrode in Example 1 in that graphene oxide is not added to the mixed solution.

[0149] Example 11

[0150] This example provides a device system for the recovery and treatment of electroplated gold wastewater. The only difference compared with Example 1 is that the driving energy supply system is not set, and the power grid is directly used to supply power to the heating system 505 for electric heating.

[0151] Compared with this example, Example 1 can save 40% of the energy consumption cost.

[0152] Comparative Example 1

[0153] This comparative example provides a method for the recovery and treatment of electroplated gold wastewater. The only difference compared with Example 1 is that the cyanide breaking complexing treatment is not carried out, and the separated water obtained is directly subjected to pH adjustment treatment.

[0154] Comparative Example 2

[0155] This comparative example provides a method for the recovery and treatment of electroplated gold wastewater. The only difference compared with Example 1 is that no pH adjustment treatment is carried out, and the water after complex breaking is directly subjected to reverse osmosis concentration treatment.

[0156] The yields and purities of the crude gold in Examples 1-10 and Comparative Examples 1-2 were detected, 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] It can be seen from the data in Table 1 as follows:

[0160] (1) It can be seen from the data of Examples 1-3 that the method provided by the present invention can achieve a gold recovery rate of more than 98.9% and a purity of more than 99.1% under relatively optimal conditions.

[0161] (2) It can be seen from the comparison between Example 1 and Examples 4-5 that by adding thiourea and preferably controlling the addition amount of thiourea in the cyanide complex breaking treatment, the present invention can further improve the purity and recovery rate of gold.

[0162] (3) It can be seen from the comparison between Example 1 and Examples 6-7 that by preferably controlling the end pH value of the pH adjustment treatment, the present invention can further improve the purity and recovery rate of gold.

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

[0164] (5) It can be seen from the comparison between Example 1 and Comparative Examples 1-2 that by carrying out cyanide complex breaking treatment and pH adjustment treatment, the present invention can cooperate with solid-liquid separation treatment, reverse osmosis concentration treatment, targeted electrochemical recovery treatment, etc. to achieve a relatively high recovery rate and recovery purity.

[0165] The applicant declares that the above is only the specific implementation manner 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 thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for recovering and treating electroplated gold wastewater, characterized in that The method includes the following steps: (1) Perform solid-liquid separation on the electroplating gold wastewater to obtain separated water; (2) Perform cyanide complex-breaking treatment on the separated water obtained in step (1) to obtain complex-broken water; (3) Sequentially perform pH adjustment treatment and reverse osmosis concentration treatment on the complex-broken water obtained in step (2) to obtain reverse osmosis concentrate; (4) Perform distillation concentration treatment on the reverse osmosis concentrate obtained in step (3) to obtain distillation concentrate; (5) Use the distillation concentrate obtained in step (4) as an electrolyte and perform targeted electrochemical recovery treatment to obtain crude gold; (6) Perform smelting and purification treatment on the crude gold obtained in step (5) to obtain purified gold.

2. The method according to claim 1, wherein The method of the solid-liquid separation treatment in step (1) includes ultrafiltration; Preferably, the cut-off molecular weight of the ultrafiltration is 5-20 kDa; Preferably, the turbidity after ultrafiltration < 1 NTU.

3. The method according to claim 1 or 2, characterized in that, The cyanide complex-breaking treatment in step (2) includes: adding persulfate and thiourea to the separated water; Preferably, the addition amount of the persulfate is 0.05-0.3 mol / L; Preferably, the addition amount of the thiourea is 0.1-1.0 g / L.

4. The method according to any one of claims 1 to 3, characterized in that The end pH value of the pH adjustment treatment in step (3) is 3.3-3.7; Preferably, the operating pressure of the reverse osmosis concentration treatment is 2.5-4.5 MPa; Preferably, the reverse osmosis concentration treatment also obtains reverse osmosis product water; Preferably, the conductivity of the reverse osmosis product water ≤ 50 μS / cm; Preferably, the reverse osmosis product water is recycled to the gold plating tank of the electroplating gold process; Preferably, the concentration of the reverse osmosis concentrate ≥ 2200 ppm.

5. The method according to any one of claims 1 to 4, characterized in that, The distillation concentration treatment in step (4) includes spiral multi-effect distillation; Preferably, the heat exchange area for the distillation and concentration treatment is 20-100 m 2 ; Preferably, the temperature of the distillation concentration treatment is 80-95 °C; Preferably, the concentration of the distillation concentrate ≥ 5000 ppm; Preferably, the steam obtained by the distillation concentration treatment is cooled to obtain condensed water; Preferably, the conductivity of the condensed water ≤ 8.5 μS / cm; Preferably, the condensed water is recycled to the post-gold plating washing tank of the electroplating gold process after ultraviolet sterilization treatment.

6. The method according to any one of claims 1-5, characterized in that, The pulsed current for the targeted electrochemical recovery treatment described in step (5) is 10 - 25 mA / cm 2 ; Preferably, the pulse duty cycle of the targeted electrochemical recovery treatment is 20-50%; Preferably, the cathode used in the targeted electrochemical recovery treatment includes a thiourea / graphene composite electrode; Preferably, the anode used in the targeted electrochemical recovery treatment includes a stainless steel plate; Preferably, the cathode of the targeted electrochemical recovery treatment obtains deposited crude gold; Preferably, the purity of the crude gold ≥ 99.92%.

7. The method according to claim 6, characterized in that, The preparation method of the thiourea / graphene composite electrode in step (5) includes the following steps: Spray the mixed solution of thiourea and graphene oxide onto the substrate electrode, and then perform high-temperature sintering to obtain a thiourea / graphene composite electrode, and the surface of the thiourea / graphene composite electrode contains a thiourea / graphene composite layer; Preferably, the solvent of the mixed solution includes deionized water; Preferably, the concentration of thiourea in the mixed solution is 80-130 g / L; Preferably, the concentration of graphene oxide in the mixed solution is 10-50 g / L; Preferably, the temperature of the high-temperature sintering is 400-500 °C; Preferably, the matrix electrode includes a titanium mesh; Preferably, the pore size of the thiourea / graphene composite electrode is 0.4-0.6 mm; Preferably, the porosity of the thiourea / graphene composite electrode is 35-40%; Preferably, the thickness of the thiourea / graphene composite layer on the thiourea / graphene composite electrode is 45-55 μm.

8. The method according to any one of claims 1-7, characterized in that, The purity of the purified gold obtained by the melting and purification treatment in step (6) is ≥99.95%; Preferably, the purified gold is recycled to the gold plating bath in the gold plating process.

9. An apparatus system for the recovery and treatment of electroplating gold wastewater, characterized in that, The device system is used for the method for recovering and treating electroplating gold wastewater as described in any one of claims 1-8; The device system includes a solid-liquid separation device, a cyanide complex-breaking device, a pH value adjustment device, and a reverse osmosis concentration device connected in sequence along the gold element enrichment direction; The concentrated liquid outlet of the reverse osmosis concentration device is connected to the distillation concentration device, and the concentrated liquid outlet of the distillation concentration device is connected to the electrolyte tank of the electrochemical device; The cathode deposit collection outlet of the electrochemical device is connected to the melting and purification device.

10. The device system according to claim 9, characterized in that, The solid-liquid separation device includes an ultrafiltration device; Preferably, the purified gold outlet of the melting and purification device is connected to the gold plating bath; Preferably, the water production outlet of the reverse osmosis concentration device is connected to the gold plating bath; Preferably, the condensed water outlet of the distillation concentration device is connected to the post-gold plating washing tank through an ultraviolet sterilization device; Preferably, the distillation concentration device includes a driving energy supply system and a heating system; Preferably, the driving energy supply system includes a solar collector, a photovoltaic panel, a flow battery energy storage module, and a shunt controller; Preferably, the heat source outlet of the solar collector is connected to the heating system through the shunt controller; Preferably, the photovoltaic panel is electrically connected to the flow battery energy storage module through the shunt controller; Preferably, the flow battery energy storage module is connected to the heating system.

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