A high-concentration copper-containing wastewater evaporation concentration pretreatment process

Abstract

This invention discloses a pretreatment process for high-concentration copper-containing wastewater through evaporation and concentration. The process sequentially involves homogenization and impurity removal, primary membrane concentration and separation, and deep concentration coupled with evaporation. Physicochemical pretreatment is completed through pH adjustment, coagulation and flocculation, and pressure filtration. Ultrafiltration and reverse osmosis are then used for tiered reuse of the purified water. Finally, disc-tube reverse osmosis is used for deep concentration in conjunction with an MVR evaporator to complete evaporation and crystallization. This invention reduces the amount of water entering the evaporation system by 60%-80% through multi-stage membrane gradient reduction, significantly lowering energy consumption. The pre-treatment structure effectively inhibits scaling on the membrane and evaporator, extending equipment lifespan and reducing cleaning frequency. The system can stably remove copper and hardness ions, allowing for the reuse of condensate and the resource utilization of crystallized salts. Overall, it achieves high efficiency, low consumption, and stable operation, solving the problems of high energy consumption, easy scaling, and poor treatment effect of traditional processes. It is suitable for the industrial pretreatment of high-concentration, high-hardness, and high-salt copper-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of copper-containing wastewater treatment technology, specifically to a pretreatment process for high-concentration copper-containing wastewater by evaporation and concentration. Background Technology

[0002] High-concentration copper-containing wastewater generated in industrial production is characterized by high pollutant concentration, high salinity, high hardness, and stable complexed heavy metals, making it difficult for conventional treatment processes to achieve stable compliance and resource recovery. Existing copper-containing wastewater treatment methods often employ direct chemical precipitation, single membrane separation, or direct evaporation concentration. However, these methods generally suffer from high operating costs, severe equipment scaling, and low treatment efficiency. Because copper ions in wastewater often form stable complexes with EDTA, ammonia nitrogen, and organic acids, simple chemical precipitation is insufficient to completely remove them, leading to excessive heavy metal levels in the effluent. Furthermore, scaling precursors such as calcium, magnesium, and silicon are not effectively removed, easily adhering to the membrane surface and evaporator inner wall during membrane concentration and evaporation. This causes rapid decline in membrane flux and reduced evaporator heat transfer efficiency, significantly increasing cleaning and maintenance costs and shortening equipment lifespan. Furthermore, traditional processes do not employ gradient reduction treatment for concentrated wastewater, resulting in a large influx of clean water into the evaporation system. This leads to persistently high steam consumption, with operating energy consumption accounting for a major portion of the total treatment cost. Moreover, the evaporation crystallization products are mostly mixed salts, difficult to utilize as resources, and largely require disposal as hazardous waste, further increasing the environmental burden on enterprises. These combined shortcomings make it difficult for existing technologies to simultaneously meet the industrial demands of high-efficiency treatment, low-consumption operation, and resource recovery, thus hindering the large-scale promotion and long-term stable operation of copper-containing wastewater treatment technologies.

[0003] For the reasons mentioned above, it is necessary to propose a high-concentration copper-containing wastewater evaporation and concentration pretreatment process to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a high-concentration copper-containing wastewater evaporation and concentration pretreatment process to address the deficiencies in the existing technology.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A pretreatment process for high-concentration copper-containing wastewater by evaporation and concentration includes the following steps: S10, Impurity Removal and Homogenization Adjustment: The copper-containing wastewater is collected in the equalization tank and subjected to preliminary homogenization treatment of water quality and quantity. The copper-containing wastewater is then subjected to pH adjustment and flocculation processes to soften the water quality. After flocculation treatment, it is sent to a filter press for solid-liquid separation to separate the copper-containing sludge from the liquid. S20, primary membrane concentration and separation, performs series-stage fractionation on the filtrate separated in step S10. The series-stage fractionation includes ultrafiltration and primary reverse osmosis. Ultrafiltration separates colloids and macromolecular organic matter in the liquid, and primary reverse osmosis separates the liquid into clear liquid and concentrated water. S30, deep concentration and evaporation coupling, performs secondary reverse osmosis and evaporation crystallization on the concentrate from step S20. The secondary reverse osmosis further concentrates the concentrate and separates it to form deep concentrated water (high concentration brine). The deep concentrated water is then evaporated and crystallized, and after evaporation separation, condensate and crystalline salt are formed.

[0006] Furthermore, S10 includes an equalization tank, a wastewater lift pump, a reaction tank, a flocculation tank, a first intermediate tank, a filter press pump, and a filter press. The equalization tank is used to collect copper-containing wastewater. The inlet end of the wastewater lift pump is connected to the equalization tank, and the outlet end is connected to the reaction tank. The reaction tank is connected to the flocculation tank through a conveying pipe, and the effluent from the flocculation tank is connected to the first intermediate tank. The inlet end of the filter press pump is connected to the first intermediate tank, and the outlet end is connected to the filter press. The filter press separates copper-containing sludge and filter liquid.

[0007] Furthermore, the reaction tank is equipped with an alkali addition tank and a PAC addition tank; the pH value of the wastewater is adjusted in the reaction tank.

[0008] Furthermore, the flocculation tank is equipped with a PAM dosing tank to perform sedimentation or co-precipitation treatment on the wastewater to separate heavy metal impurities.

[0009] Furthermore, S20 includes a second intermediate tank, a first booster pump, a first fine filter, an ultrafiltration device, a first reverse osmosis device, a reclaimed water tank, and a second booster pump. The filtrate is sent to the second intermediate tank for pretreatment and water quality stabilization, then sent to the first fine filter by the first booster pump to remove suspended impurities, and then sequentially processed by the ultrafiltration device and the first reverse osmosis device. The ultrafiltration device removes colloids and macromolecular organic matter from the wastewater. The first reverse osmosis treatment separates the water into a clear liquid and a concentrated liquid through membrane separation. The clear liquid is sent to the reclaimed water tank, and the inlet end of the second booster pump is connected to the reclaimed water tank, while the outlet end is used for reuse.

[0010] Furthermore, the filtration accuracy of the first fine filter is 5-10 μm; the ultrafiltration equipment adopts a tubular or hollow fiber ultrafiltration membrane with a molecular weight cutoff of 10,000-50,000 Da; the first reverse osmosis equipment is a brackish water reverse osmosis membrane or an anti-fouling reverse osmosis membrane.

[0011] Furthermore, S30 includes a third intermediate tank, a third booster pump, a second fine filter, a second reverse osmosis device, and an MVR evaporator; the concentrated water is sent into the third intermediate tank and then filtered by the second fine filter via the third booster pump before entering the second reverse osmosis device, where it is separated into deeply concentrated water and fresh water. The deeply concentrated water is sent into the MVR evaporator, which is linked to a steam heat pump to recover and utilize waste heat from evaporation. The condensate is sent to a recycled water tank.

[0012] Furthermore, the total dissolved solids (TDS) of the deeply concentrated water separated by the second reverse osmosis unit is concentrated to 8%-15%; the second reverse osmosis unit adopts a high-salt-resistant and fouling-resistant disc tube reverse osmosis membrane module.

[0013] Furthermore, in step S10, a low-frequency ultrasonic synergistic complex-breaking device is set between the reaction tank and the flocculation tank, and a modified nano-iron-based coagulant is added to the device. The low-frequency ultrasonic synergistic complex-breaking device is equipped with a low-frequency ultrasonic generator. It also includes a MOF (Metal-Organic Framework) mesoporous adsorption tower, in which the filtrate is fed to the MOF for selective adsorption to remove scaling precursors and recalcitrant organic matter.

[0014] Furthermore, the nano-iron-based coagulant adopts a composite modified formula of nano-zero-valent iron (nZVI) and polyaluminum ferric chloride (PAFC), and the mass fraction ratio of its components is: nano-zero-valent iron 5%-12%, polyaluminum ferric chloride 20%-35%, modified bentonite carrier 8%-15%, anhydrous sodium sulfate dispersant 2%-5%, and the remainder is deionized water; the nano-iron-based coagulant has a particle size of 20-80 nm and a specific surface area ≥40 m². 2 / g, pH 7.5-10.5; The MOF metal-organic framework mesoporous adsorption tower is filled with MOF adsorption packing material, which is an amino-modified MIL-53(Fe) mesoporous MOF material with a specific surface area ≥1200 m². 2 / g, pore size 2-8nm, selectively adsorbs Cu 2 +、Ca 2 +, Mg 2 +, SiO2, adsorption capacity ≥65mg / g.

[0015] The advantages and beneficial effects of this invention are as follows: The high-concentration copper-containing wastewater evaporation and concentration pretreatment process of this invention ensures the stability of the influent and removes scale and pollutants through homogenization and physicochemical impurity removal structures. The multi-stage membrane combination structure of ultrafiltration + reverse osmosis + disc tube reverse osmosis achieves the tiered reuse of clean water through gradient concentration, reducing the amount of water entering the MVR evaporator by 60%-80%, thereby reducing the steam consumption and operating costs of the evaporation system from the source. The pre-treatment structure for removing impurities and hardness protects the membrane system and evaporator equipment throughout the process, reducing the frequency of equipment cleaning and extending its service life. Ultimately, the entire process is adaptable to special working conditions such as high-concentration copper-containing wastewater and high-hardness wastewater, while achieving multiple technical effects such as energy saving, stable operation, and resource reuse, perfectly solving the core problems of high energy consumption, easy scaling, and unstable operation of traditional processes. Attached Figure Description

[0016] Figure 1 This is a flow chart of the copper-containing wastewater evaporation and concentration pretreatment process according to Embodiment 1 of the present invention; Figure 2 This is a flow chart of the copper-containing wastewater evaporation and concentration pretreatment process according to Embodiment 2 of the present invention; In the diagram: 1. Equalization tank; 2. Wastewater lift pump; 3. Reaction tank; 4. Flocculation tank; 5. First intermediate tank; 6. Filter press pump; 7. Filter press; 8. Copper-containing sludge; 9. Filtrate; 10. Alkali dosing tank; 11. PAC dosing tank; 12. PAM dosing tank; 13. Second intermediate tank; 14. First booster pump; 15. First fine filter; 16. Ultrafiltration equipment; 17. First reverse osmosis equipment; 18. Reclaimed water tank; 19. Second booster pump; 20. Clear liquid; 21. Concentrate; 22. Third intermediate tank; 23. Third booster pump; 24. Second fine filter; 25. Second reverse osmosis equipment; 26. MVR evaporator; 27. Low-frequency ultrasonic synergistic complex breaking device; 28. Coagulant dosing tank; 29. ​​Low-frequency ultrasonic generator; 30. MOF metal-organic framework mesoporous adsorption tower. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0018] Example 1: A high-concentration copper-containing wastewater evaporation and concentration pretreatment process is proposed. The core of this process is an integrated process route of physicochemical pretreatment, membrane concentration, and MVR evaporation. This process optimizes the traditional copper-containing wastewater treatment method in terms of structure and process, and specifically solves the industry problems of high evaporation energy consumption and easy scaling of equipment. The overall process proceeds in sequence according to the logic of water quality homogenization and impurity removal, staged membrane volume reduction, and deep evaporation crystallization. The structure of each unit is interconnected and the functions are complementary.

[0019] Includes the following steps: S10, Impurity Removal and Homogenization Adjustment: The copper-containing wastewater is collected in the equalization tank 1 and subjected to preliminary homogenization treatment of water quality and quantity. The copper-containing wastewater is then subjected to pH adjustment and flocculation processes to soften the water quality. After flocculation treatment, it is sent to the filter press 7 for solid-liquid separation to separate the copper-containing sludge 8 from the liquid. Specifically, such as Figure 1 As shown, the system includes an equalization tank 1, a wastewater lift pump 2, a reaction tank 3, a flocculation tank 4, a first intermediate tank 5, a filter press pump 6, and a filter press 7. The equalization tank 1 is used to collect copper-containing wastewater. The inlet end of the wastewater lift pump 2 is connected to the equalization tank 1, and the outlet end is connected to the reaction tank 3. The reaction tank 3 is connected to the flocculation tank 4 through a conveying pipe, and the effluent from the flocculation tank 4 is connected to the first intermediate tank 5. The inlet end of the filter press pump 6 is connected to the first intermediate tank 5, and the outlet end is connected to the filter press 7. The filter press 7 separates copper-containing sludge 8 and filtrate 9.

[0020] In the initial stage of the process, a homogenization and equalization structure consisting of equalization tank 1 is first set up to collect high-concentration copper-containing wastewater and complete the equalization and equalization of water quality and quantity, so as to avoid the impact of water quality fluctuations and uneven water quantity on subsequent treatment units. This structure provides stable water inlet conditions for the entire process.

[0021] Subsequently, a physicochemical impurity removal system is constructed based on the reaction tank 3, flocculation tank 4, first intermediate tank 5 and filter press 7. The pH value of the wastewater is adjusted by adding coagulants such as NaOH and PAC in the reaction tank 3. Specifically, the reaction tank 3 is equipped with an alkali addition tank 10 and a PAC addition tank 11. In actual use, sodium carbonate solution or sodium hydroxide solution can be used in the alkali addition tank 10, and the pH value of the wastewater is adjusted in the reaction tank 3.

[0022] The flocculation tank 4 is equipped with a PAM dosing tank 12 for sedimentation or co-precipitation treatment of wastewater to separate heavy metal impurities. After adapting to the reaction conditions for heavy metal removal, PAM flocculant is added to the flocculation tank 4. Through coagulation and flocculation reactions, heavy metal impurities are removed through sedimentation or co-precipitation. For special conditions with high calcium and magnesium ion content in the wastewater, sodium carbonate or sodium hydroxide can be added in an alkaline environment to soften the water, removing hardness ions prone to scaling at the source. This structural improvement not only separates and removes target pollutants such as copper ions but also blocks scaling factors in subsequent membrane modules and evaporators. The treated mixture is sent to a filter press 7 via a filter pump 6 for solid-liquid separation. Copper-containing sludge 8 is disposed of safely as solid waste, while the clarified liquid 20 enters the next treatment stage, achieving solid-liquid separation and targeted pollutant reduction. After physicochemical pretreatment, it is sent to the second intermediate tank 13. S20, primary membrane concentration and separation, performs series-stage fractionation on the filtrate 9 separated in step S10. The series-stage fractionation includes ultrafiltration and primary reverse osmosis. Ultrafiltration separates colloids and macromolecular organic matter in the liquid, and primary reverse osmosis separates the liquid into clear liquid 20 and concentrated water 21. After completing the physicochemical pretreatment, the process enters the primary membrane concentration and separation structure, which consists of the second intermediate tank 13, the first booster pump 14, the first fine filter 15, the ultrafiltration equipment 16, the first reverse osmosis equipment 17, and the recycled water tank 18. This is the core unit for the process to achieve early reuse of clean water.

[0023] Specifically, such as Figure 1 As shown, this step includes a second intermediate tank 13, a first booster pump 14, a first fine filter 15, an ultrafiltration device 16, a first reverse osmosis device 17, a reclaimed water tank 18, and a second booster pump 19. The filtrate 9 is sent to the second intermediate tank 13 for pretreatment and water quality stabilization. It is then sent to the first fine filter 15 via the first booster pump 14 to remove suspended impurities, and then sequentially processed through the ultrafiltration device 16 and the first reverse osmosis device 17. The pretreated clarified liquid 20 is first stored in the second intermediate tank 13 to stabilize the water quality, and then transported by the first booster pump 14 and passed through the first fine filter 15 to remove minute suspended impurities, protecting subsequent membrane elements. The ultrafiltration device 16 removes colloids and large molecular organic matter from the wastewater, and then sequentially processes it through ultrafiltration (UF) and reverse osmosis (RO) membrane modules. The ultrafiltration device 16 can retain... Colloidal and macromolecular organic matter in the wastewater further purifies the water quality and protects the reverse osmosis membrane. The reverse osmosis equipment separates the clarified liquid 20 and concentrated water 21 through membrane separation. The first reverse osmosis treatment separates the clarified liquid 20 and concentrated water 21 through membrane separation. The produced clarified liquid 20 is directly sent to the recycled water tank 18. The inlet end of the second booster pump 19 is connected to the recycled water tank 18, and the outlet end is sent out for reuse. It can be reused in the production process to realize water resource recycling. The concentrated water 21, which is rich in dissolved salts such as sodium ions, sulfate ions, and chloride ions, flows into the third intermediate tank 22 to prepare for deep concentration. This membrane structure achieves a large amount of clean water reuse before evaporation through staged filtration and separation, reducing the amount of water entering the evaporation unit from the process perspective and laying the foundation for subsequent energy saving and consumption reduction.

[0024] In step S20, a series-connected, staged treatment structure combining ultrafiltration and the first reverse osmosis unit 17 is used. The ultrafiltration unit 16 serves as a pre-protection unit for the reverse osmosis unit, forming a fixed process sequence of ultrafiltration removing colloids followed by reverse osmosis desalination. Secondly, the second intermediate tank 13 buffers and stabilizes the influent flow rate and pressure, while limiting the output pressure range of the first booster pump 14, further stabilizing the operating pressure of ultrafiltration and reverse osmosis at 0.8-1.6 MPa to prevent damage to membrane elements from excessive pressure or a decrease in separation efficiency from excessively low pressure. The first fine filter 15 is a 5-10 μm precision security filter used to intercept residual micro-suspended matter from the pretreatment process, preventing scratches and clogging of the ultrafiltration membrane.

[0025] The type and molecular weight cutoff of the ultrafiltration equipment 16 need to be specifically defined, and a tubular or hollow fiber ultrafiltration membrane should be used, with a molecular weight cutoff of 10,000-50,000 Da, to ensure effective removal of colloids, suspended solids, and large organic molecules, providing permeate that meets the feed water requirements for reverse osmosis. The first reverse osmosis equipment 17 is a brackish water reverse osmosis membrane or an anti-fouling reverse osmosis membrane, with an operating pressure limited to 1.2-2.0 MPa, a desalination rate of not less than 98%, and a permeate rate of 50%-75% for the first-stage reverse osmosis, ensuring a balance between the reuse ratio of clarified liquid 20 and the concentration factor of concentrated water 21. The effluent characteristics of step S20 are as follows: In this step, the clarified liquid 20 from the first reverse osmosis unit directly enters the recycled water tank 18, and the water quality meets the requirements for production reuse, with TDS ≤ 500 mg / L and copper ion concentration ≤ 0.1 mg / L; the concentrated water 21 produced by reverse osmosis is 2-4 times the TDS of the raw water, and contains only dissolved salts and a small amount of unremoved heavy metals, without suspended solids and colloids, and is used as the feed liquid for deep concentration in step 30.

[0026] Furthermore, the material flow in step S20 is a unidirectional continuous process: second intermediate tank 13 → first booster pump 14 → first fine filter 15 → ultrafiltration equipment 16 → first reverse osmosis. All ultrafiltration permeate enters the reverse osmosis system, all reverse osmosis permeate is reused, and concentrate 21 enters the third intermediate tank 22, forming a split flow. For special operating conditions such as high salt and high hardness, step S20 can also be equipped with switchable anti-fouling membrane modules and a timed online flushing program to ensure long-term stable operation of the membrane system.

[0027] S30 involves deep concentration and evaporation coupling. The concentrated water 21 from step S20 undergoes secondary reverse osmosis and evaporation crystallization. The secondary reverse osmosis further concentrates the concentrated water 21 and separates it into deeply concentrated water (high-concentration brine). The deeply concentrated water is then evaporated and crystallized, resulting in condensate and crystalline salt. Specifically, S30 includes a third intermediate tank 22, a third booster pump 23, a second fine filter 24, a second reverse osmosis unit 25, and an MVR evaporator 26. The concentrated water 21 is fed into the third intermediate tank 22 and then filtered by the third booster pump 23 to the second fine filter 24 before entering the second reverse osmosis unit 25. The second reverse osmosis unit 25 separates the concentrated water into deeply concentrated water and fresh water. The deeply concentrated water is then fed into the MVR evaporator 26, which is linked to a steam heat pump to recover and utilize waste heat from evaporation (and improve steam efficiency). The condensate is sent to the recycled water tank 18.

[0028] This deep concentration and evaporation coupling step is the final reduction and crystallization unit of the process. It consists of the third intermediate tank 22, the second booster pump 19, the second fine filter 24, the disc tube reverse osmosis equipment, the MVR evaporator 26, the recycled water tank 18, and the crystallization salt treatment structure. It is an optimized structure for the deep treatment of high-concentration brine. The concentrated water 21 in the third intermediate tank 22 is pretreated by the third booster pump 23 and the second fine filter 24, and then enters the second reverse osmosis equipment 25 (disc tube reverse osmosis DTRO) for deep concentration. The second reverse osmosis equipment 25 adopts a high-salt-resistant and fouling-resistant disc tube reverse osmosis membrane module. This membrane module is suitable for the special working conditions of high-salt and high-pollution wastewater, and has stronger fouling resistance and anti-scaling ability. It can concentrate the TDS of the concentrated water 21 to 8%-15% (total dissolved solids, which refers to the total amount of all ions, salts, metals, minerals and other solid substances dissolved in water. In this embodiment, in the copper wastewater process, TDS mainly refers to: copper ions, sodium ions, calcium and magnesium ions, sulfate ions, chloride ions and other dissolved salts). The concentrated water 21 is further reduced, and the separated clear liquid 20 is returned to the equalization tank 1 for recycling, further improving the water resource recovery rate. The highly concentrated brine after deep concentration is sent to the mechanical vapor recompression (MVR) evaporator 26. Since the copper ions and hardness ions have been removed by the front-end physicochemical pretreatment, the tendency of scaling inside the evaporator is greatly reduced. The problem of easy scaling and frequent cleaning of traditional evaporators is solved from the perspective of equipment operation structure. The MVR evaporator 26 realizes the recycling of heat energy through vapor recompression technology. The condensate produced by evaporation is sent to the recycled water tank 18 for reuse after meeting the standards. The sodium sulfate, sodium chloride and other crystalline salts produced by the crystallizer can be recycled or safely disposed of according to the purity, realizing the resource utilization or harmless treatment of salt resources.

[0029] The second fine filter 24 has a filtration accuracy of 1-5μm and is used to further remove small particles and colloidal impurities from the concentrate 21 to prevent clogging of the disc tube reverse osmosis membrane. The disc tube reverse osmosis equipment uses high-salt-resistant and fouling-resistant disc tube reverse osmosis membrane modules, with an operating pressure of 3-6MPa. Its core function is to deeply reduce and concentrate the first-stage reverse osmosis concentrate 21. After treatment by this equipment, the TDS of the concentrate 21 can be stably controlled at 8%-15%, and the TDS of the clarified liquid 20 is not higher than 1000mg / L. This clarified liquid 20 can be returned to the front-end equalization tank 1 for recycling. The concentrated concentrate 21 with a TDS of 8%-15% needs to be fed into the MVR evaporator 26. The copper ion concentration and TDS of the condensate produced by the evaporator are ≤0.1mg / L and ≤500mg / L, respectively. After meeting the production reuse standards, it is sent to the recycled water tank 18. In addition, the S30 step uses a disc tube reverse osmosis and MVR evaporator 26 in a series coupled structure to form a continuous process of deep volume reduction and final evaporation. The front-end membrane method significantly reduces the amount of evaporated water, so that the steam consumption of the MVR evaporator 26 system is reduced by more than 60% compared with direct evaporation. At the same time, due to the pre-removal of hardness and heavy metals, the scaling rate inside the evaporator is reduced by more than 80%, and the cleaning cycle is extended to more than 6 months.

[0030] From the perspective of overall process structural improvements and operating principles, the homogenization and physicochemical impurity removal structure ensures the stability of the influent and removes scale and contaminants. The multi-stage membrane combination structure of ultrafiltration + reverse osmosis + disc tube reverse osmosis achieves the tiered reuse of clean water through gradient concentration, reducing the amount of water entering the MVR evaporator 26 by 60%-80%, thereby reducing the steam consumption and operating costs of the evaporation system from the source. The pre-treatment structure for impurity and hardness removal protects the membrane system and evaporator equipment throughout the process, reducing the frequency of equipment cleaning and extending its service life. Ultimately, the entire process can adapt to special working conditions such as high-concentration copper-containing wastewater and high-hardness wastewater, while achieving multiple technical effects such as energy saving, stable operation, and resource reuse, perfectly solving the core problems of high energy consumption, easy scaling, and unstable operation of traditional processes.

[0031] Example 2: This embodiment is a structural improvement based on the aforementioned Embodiment 1. The difference lies in the following: Figure 2 As shown, in step S10, a low-frequency ultrasonic synergistic complex-breaking device 27 is set between the reaction tank 3 and the flocculation tank 4, and a modified nano-iron-based coagulant is added to the device. The low-frequency ultrasonic synergistic complex-breaking device 27 is equipped with a low-frequency ultrasonic generator 29. In the original process's impurity removal and homogenization adjustment stages, the basic structure of wastewater collection, homogenization adjustment, pH adjustment, coagulation and flocculation, and pressure filtration separation is retained. Specifically, a low-frequency ultrasonic synergistic complex-breaking device 27 is added, and a modified nano-iron-based coagulant is added. The ultrasonic cavitation effect is used to powerfully break the stable complexes formed by EDTA, ammonia, citric acid, etc. with copper, converting the complexed copper into free copper ions, which are then deeply removed through coagulation and co-precipitation. This improvement, together with the pH adjustment and coagulation and precipitation steps in Example 1, is used to solve the pain point of the original process's inefficient removal of complexed copper and significantly reduce sludge production. At the same time, it avoids the pollution of subsequent membrane modules by organic complexes. Compared with the original process, the copper ion removal rate is increased from about 85% to over 97%, providing extremely clean feed water conditions for subsequent membrane concentration and evaporation.

[0032] Furthermore, it also includes a MOF (Metal-Organic Framework) mesoporous adsorption tower 30. After ultrasonic complex breaking and coagulation sedimentation, before entering the first-stage membrane concentration in the original process, in this embodiment, the MOF mesoporous adsorption tower 30 can be set after the filter press 7 to treat the filtrate 9. The filtrate 9 is sent to the MOF mesoporous adsorption tower 30 for selective adsorption to remove scaling precursors and recalcitrant organic matter.

[0033] The newly added MOF (Metal-Organic Framework) mesoporous adsorption tower 30 is a deep purification unit. MOF materials have high specific surface area and selective adsorption characteristics, which can accurately adsorb residual trace heavy metals, silicon, phosphorus, calcium and magnesium scaling precursors and recalcitrant organic matter. It complements the original softening and hardening steps of the process, completely blocking the scaling causes of membrane system and evaporator from the source, realizing the synergy of pretreatment, membrane protection and anti-scaling, reducing the subsequent membrane flux decay rate by more than 70%, and basically eliminating the tendency of evaporator to scale.

[0034] Furthermore, in the original process's first-stage membrane concentration and separation stage, the core structures of the ultrafiltration unit 16 and the first reverse osmosis unit 17 are retained. The clarified liquid 20 is still recycled into the reclaimed water tank 18, and the concentrated water 21 is sent to the subsequent deep treatment. However, between the RO concentrated water 21 outlet and the DTRO disc tube reverse osmosis, a new selective electrodialysis (SED) high-end salt separation unit is added. This unit uses selective ion exchange membranes to accurately separate and grade sodium chloride and sodium sulfate, diverting the mixed salt concentrated water 21 in the original process into single-component concentrated brine, which is then sent to the subsequent second reverse osmosis unit 25 (disc tube reverse osmosis DTRO) for further volume reduction. This forms a synergistic effect of "graded concentration - precise salt separation - deep volume reduction" with the original membrane concentration system. This not only solves the problems of complex salt composition, easy scaling, and mixed salt hazardous waste in the original process's concentrated water 21, but also makes the membrane system more stable, further reduces the DTRO treatment load, and achieves simultaneous improvement in membrane concentration efficiency and salt resource utilization potential.

[0035] In the original process of deep concentration and evaporation coupling stage, the main structure of DTRO deep concentration and MVR evaporation crystallization is retained, but the MVR system is upgraded with heat pump coupling and online anti-scaling. The MVR evaporator 26 is linked with the steam heat pump to recover the waste heat of evaporation and improve steam energy efficiency. At the same time, an online ultrasonic anti-scaling module is installed inside the evaporator to form a full-process anti-scaling synergy with the front-end pretreatment steps of hardening, impurity removal and salt separation. The condensate produced by evaporation is still reused. The crystallized salt is no longer simply judged for recycling or disposal according to the original process. Instead, a new short-range melting crystallization in-situ purification unit is added to melt, recrystallize and separate the crude salt produced by MVR at high temperature, directly purifying the industrial by-product salt to a purity of more than 99%. This works in synergy with the front-end selective electrodialysis salt separation, transforming the mixed crystallized salt, which was originally hazardous waste, into marketable first-grade industrial salt, realizing a revolutionary transformation from "hazardous waste disposal" to "resource production".

[0036] Furthermore, in this embodiment, the nano-iron-based coagulant adopts a modified formulation of nano-zero-valent iron (nZVI) and polyaluminum ferric chloride (PAFC), with the following mass fraction ratio of components: 5%-12% nano-zero-valent iron, 20%-35% polyaluminum ferric chloride, 8%-15% modified bentonite carrier, 2%-5% anhydrous sodium sulfate dispersant, and the remainder being deionized water; the nano-iron-based coagulant has a particle size of 20-80 nm and a specific surface area ≥40 m². 2 / g, maintaining high activity in the pH range of 7.5-10.5, can remove free copper through coagulation and precipitation, and can also remove heavy metals and organic complexes simultaneously by reducing and breaking the complex using nano iron. The dosage is 50-200mg / L, and the copper removal rate can reach more than 97% when combined with low-frequency ultrasound. The low-frequency ultrasonic synergistic chelation device 27 in this embodiment includes an internally installed ultrasonic transducer assembly, a flow guide baffle, a pH online monitoring probe, a stirring paddle, a temperature control sensor, a reagent dosing port, and a water inlet distributor.

[0037] Low-frequency ultrasonic generator 29: frequency 20-28kHz, power density 0.8-1.5W / cm³ 2 The device employs a double-sided vibrating plate embedded installation to ensure full coverage of the cavitation field without any blind spots.

[0038] The MOF metal-organic framework mesoporous adsorption tower 30 is filled with MOF adsorption packing material, which is an amino-modified MIL-53(Fe) mesoporous MOF material with a specific surface area ≥1200 m². 2 / g, pore size 2-8nm, with strong selective adsorption capacity, adsorption capacity ≥65mg / g.

[0039] The MOF (Metal-Organic Framework) mesoporous adsorption tower 30 is a vertical fixed-bed dual-tower parallel structure, with one tower in use and one on standby or operating simultaneously. It is used for deep pre-membrane treatment to remove trace heavy metals, silicon, phosphorus, calcium, magnesium, and organic matter.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A pretreatment process for high-concentration copper-containing wastewater by evaporation and concentration, characterized in that, Includes the following steps: S10, Impurity Removal and Homogenization Adjustment: The copper-containing wastewater is collected in the equalization tank and subjected to preliminary homogenization treatment of water quality and quantity. The copper-containing wastewater is then subjected to pH adjustment and flocculation processes to soften the water quality. After flocculation treatment, it is sent to a filter press for solid-liquid separation to separate the copper-containing sludge from the liquid. S20, primary membrane concentration and separation, performs series-stage fractionation on the filtrate separated in step S10. The series-stage fractionation includes ultrafiltration and primary reverse osmosis. Ultrafiltration separates colloids and macromolecular organic matter in the liquid, and primary reverse osmosis separates the liquid into clear liquid and concentrated water. S30, deep concentration and evaporation coupling, performs secondary reverse osmosis and evaporation crystallization on the concentrate from step S20. The secondary reverse osmosis further concentrates the concentrate and separates it into deep concentrated water. The deep concentrated water is then evaporated and crystallized, and after evaporation separation, condensate and crystalline salt are formed.

2. The high-concentration copper-containing wastewater evaporation and concentration pretreatment process according to claim 1, characterized in that, S10 includes an equalization tank, a wastewater lift pump, a reaction tank, a flocculation tank, a first intermediate tank, a filter press pump, and a filter press. The equalization tank is used to collect copper-containing wastewater. The inlet end of the wastewater lift pump is connected to the equalization tank, and the outlet end is connected to the reaction tank. The reaction tank is connected to the flocculation tank through a conveying pipe, and the effluent from the flocculation tank is connected to the first intermediate tank. The inlet end of the filter press pump is connected to the first intermediate tank, and the outlet end is connected to the filter press. The filter press separates copper-containing sludge and filtrate.

3. The high-concentration copper-containing wastewater evaporation and concentration pretreatment process according to claim 2, characterized in that, The reaction tank is equipped with an alkali addition tank and a PAC addition tank; the pH value of the wastewater is adjusted in the reaction tank.

4. The high-concentration copper-containing wastewater evaporation and concentration pretreatment process according to claim 2, characterized in that, The flocculation tank is equipped with a PAM dosing tank to treat wastewater by sedimentation or co-precipitation to separate heavy metal impurities.

5. The high-concentration copper-containing wastewater evaporation and concentration pretreatment process according to claim 1, characterized in that, The S20 includes a second intermediate tank, a first booster pump, a first fine filter, an ultrafiltration device, a first reverse osmosis device, a reclaimed water tank, and a second booster pump. The filtrate is sent to the second intermediate tank for pretreatment and water quality stabilization. It is then sent to the first fine filter by the first booster pump to remove suspended impurities. It then passes through the ultrafiltration device and the first reverse osmosis device in sequence. The ultrafiltration device removes colloids and macromolecular organic matter from the wastewater. The first reverse osmosis treatment separates the wastewater into a clear liquid and a concentrated liquid through membrane separation. The clear liquid is sent to the reclaimed water tank. The inlet of the second booster pump is connected to the reclaimed water tank, and the outlet is used for reuse.

6. The high-concentration copper-containing wastewater evaporation and concentration pretreatment process according to claim 5, characterized in that, The first fine filter has a filtration accuracy of 5-10 μm; the ultrafiltration equipment uses a tubular or hollow fiber ultrafiltration membrane with a molecular weight cutoff of 10,000-50,000 Da; the first reverse osmosis equipment is a brackish water reverse osmosis membrane or an anti-fouling reverse osmosis membrane.

7. The high-concentration copper-containing wastewater evaporation and concentration pretreatment process according to claim 1, characterized in that, The S30 includes a third intermediate tank, a third booster pump, a second fine filter, a second reverse osmosis device, and an MVR evaporator. The concentrated water is sent to the third intermediate tank and then to the second fine filter via the third booster pump. After filtration, it enters the second reverse osmosis device, where it is separated into highly concentrated water and fresh water. The highly concentrated water is sent to the MVR evaporator, which is linked to a steam heat pump to recover and utilize waste heat from evaporation. The condensate is sent to a recycled water tank.

8. The high-concentration copper-containing wastewater evaporation and concentration pretreatment process according to claim 7, characterized in that, The total dissolved solids of the deeply concentrated water separated by the second reverse osmosis unit are concentrated to 8%-15%; the second reverse osmosis unit adopts a high-salt-resistant and fouling-resistant disc tube reverse osmosis membrane module.

9. The high-concentration copper-containing wastewater evaporation and concentration pretreatment process according to claim 2, characterized in that, In step S10, a low-frequency ultrasonic synergistic complex-breaking device is set between the reaction tank and the flocculation tank, and a modified nano-iron-based coagulant is added to the device. The low-frequency ultrasonic synergistic complex-breaking device is equipped with a low-frequency ultrasonic generator. It also includes a MOF (Metal-Organic Framework) mesoporous adsorption tower, in which the filtrate is fed to the MOF for selective adsorption to remove scaling precursors and recalcitrant organic matter.

10. The high-concentration copper-containing wastewater evaporation and concentration pretreatment process according to claim 9, characterized in that, The nano-iron-based coagulant uses a modified formulation of nano-zero-valent iron and polyaluminum ferric chloride. The mass fraction of its components is as follows: 5%-12% nano-zero-valent iron, 20%-35% polyaluminum ferric chloride, 8%-15% modified bentonite carrier, 2%-5% anhydrous sodium sulfate dispersant, and the remainder is deionized water. The nano-iron-based coagulant has a particle size of 20-80 nm and a specific surface area ≥40 m². 2 / g, pH 7.5-10.5; The MOF metal-organic framework mesoporous adsorption tower is filled with MOF adsorption packing material, which is an amino-modified MIL-53(Fe) mesoporous MOF material with a specific surface area ≥1200 m². 2 / g, pore size 2-8nm, selectively adsorbs Cu 2 +、Ca 2 +, Mg 2 +, SiO2, adsorption capacity ≥65mg / g.

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