A complete set of equipment and methods for efficient stepwise recovery of valuable substances from industrial wastewater.

Abstract

This invention provides a complete set of equipment and methods for the efficient stepwise recovery of valuable substances from industrial wastewater. The equipment includes a multi-chamber electrodialysis system, a high-concentration system, a distillation extraction system, and a cooling crystallization system. Under the influence of an electric field, the multi-chamber electrodialysis system separates valuable substances from organic matter using multilayer anion and cation exchange membranes. The composite multi-walled carbon nanotube anion exchange membrane is used, formed by the polymerization reaction of 2-acrylamido-2-methylpropanesulfonic acid and 1-butyl-3-vinyl-1H-imidazolium-3-onium bromide with multi-walled carbon nanotubes. The concentrated liquid after separation undergoes high-concentration, distillation extraction, and cooling crystallization to achieve efficient stepwise recovery of various valuable substances. This invention features a simple and safe separation process, high salt recovery rate, and the ability to reuse the recovered salt in the production process. The entire process is pollution-free, promoting near-zero discharge of industrial wastewater and possessing significant environmental and economic value.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a complete set of equipment and methods for the efficient stepwise recovery of valuable substances from industrial wastewater. Background Technology

[0002] Industrial wastewater is typically characterized by high salt content, high organic matter concentration, high suspended solids content, high color, strong odor, high ammonia nitrogen concentration, and high salt content.

[0003] Currently, mainstream industrial wastewater treatment methods, such as physical, biological, and chemical methods, mostly aim to directly eliminate or remove substances from the wastewater, neglecting the presence of valuable usable substances such as thiocyanate and acetate. Thiocyanate can be used to produce thiocyanates, esters, various thiocyanates, and cyanides, and is widely used in chemical and pharmaceutical industries, possessing significant industrial value. Acetate is commonly used in the food industry as a food additive for sodium biacetate, providing acidification and preservative functions. Acetate also has applications in the dye and pharmaceutical industries.

[0004] Industrial efforts to treat thiocyanate and acetate ions primarily focus on promoting recovery and reuse methods, or applying degradation technologies to decompose thiocyanate in wastewater into harmless substances. Various methods and technologies have been applied to the separation and recovery of thiocyanate, such as adsorption, photodegradation, membrane extraction, coagulation and precipitation, and advanced oxidation methods. However, these methods suffer from drawbacks such as high implementation costs, the generation of other pollutants, and low purity of the recovered ions, resulting in significant waste. Therefore, it is necessary to develop an efficient and cost-effective treatment process to achieve the separation and recovery of valuable ions and realize resource utilization. Summary of the Invention

[0005] The purpose of this invention is to provide a complete set of equipment and methods for the efficient stepwise recovery of valuable substances in industrial wastewater from pharmaceutical wastewater containing high-value salt residues and its reuse in the production process.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0007] A complete set of equipment for efficient stepwise recovery of valuable substances from industrial wastewater includes a multi-chamber electrodialysis system, a high-concentration system, a distillation extraction system, and a cooling crystallization system. The multi-chamber electrodialysis system includes a pretreatment unit and an electrodialysis unit to separate organic matter and valuable substances from the wastewater. The high-concentration system highly concentrates the separated valuable substances. The distillation extraction system is used to separate specific ions. The cooling crystallization system further separates the remaining ions.

[0008] The pretreatment unit includes microfiltration and ultrafiltration systems.

[0009] Preferably, the filtration mode includes immersion filtration, MBR membrane tank filtration, or vibrating membrane filtration.

[0010] Preferably, the pore size of the filter membrane is 0.2-100 μm.

[0011] Preferably, the filter membrane material includes hollow fiber, polysulfone, polyamide, or ceramic.

[0012] The electrodialysis unit includes an electrodialysis membrane stack, a DC regulated power supply, a flow meter, a circulating pump, and a water tank. The electrodialysis membrane stack has an anode plate and a cathode plate at both ends. The anode plate and an adjacent partition form an anode chamber, and the cathode plate and an adjacent partition form a cathode chamber. At least one membrane unit is located between the anode chamber and the cathode chamber. Each membrane unit contains multiple ion exchange membranes, with a concentration chamber or a dilute chamber formed between two ion exchange membranes. A membrane unit may have one concentration chamber and 2-5 dilute chambers, or one dilute chamber and 2-5 concentration chambers. The concentration and dilute chambers can be freely combined according to the target ion recovery principle and efficiency optimization. The water tank includes an electrode chamber water tank for storing the electrolytic solution, a concentration chamber water tank for storing the separated thiocyanate solution, and a dilute chamber water tank for storing a mixed solution containing thiocyanate ions, miscellaneous salts, and organic matter.

[0013] Preferably, the solute in the polar liquid of the polar chamber water tank includes sodium sulfate, sodium chloride, and sodium nitrate, and the concentration of the solute is 0.05-0.2 mol / L.

[0014] Preferably, the number of membrane units is 1-50.

[0015] Preferably, the voltage of the electrodialysis membrane stack is 5-50V, and the flow rate of the electrodialysis membrane stack is 1000-10000mL / min.

[0016] Preferably, the ion exchange membrane includes heterogeneous membranes, homogeneous membranes, and alloy membranes, with a membrane resistance of 0-10 Ω / cm. 2 Its exchange capacity is 1.3-3 mol / Kg, and its acid and alkali resistance is pH 2-10.

[0017] Ion exchange membranes also include composite multi-walled carbon nanotube anion exchange membranes. The preparation steps of the composite multi-walled carbon nanotube anion exchange membrane are as follows: acidifying, amination, and vinylating multi-walled carbon nanotubes to obtain vinyl-functionalized multi-walled carbon nanotubes; performing polymerization grafting reaction between the vinyl-functionalized multi-walled carbon nanotubes and a modifier to obtain composite multi-walled carbon nanotubes; and performing film-forming treatment on the composite multi-walled carbon nanotubes to obtain the composite multi-walled carbon nanotube anion exchange membrane.

[0018] Preferably, the modifier includes 2-acrylamido-2-methylpropanesulfonic acid and 1-butyl-3-vinyl-1H-imidazolium-3-onium bromide, with a mass ratio of vinyl-functionalized multi-walled carbon nanotubes to 2-acrylamido-2-methylpropanesulfonic acid of 20-200:100-1000, and a mass ratio of vinyl-functionalized multi-walled carbon nanotubes to 1-butyl-3-vinyl-1H-imidazolium-3-onium bromide of 20-200:60-600. The two form copolymer chains on the multi-walled carbon nanotubes. The sulfonic acid group and the imidazolium cation cation synergistically form a continuous ion conduction channel, improving the selective transport capability for specific anions. The copolymer structure enhances the cohesion of the membrane through intermolecular interactions, improving the membrane's thermal stability and mechanical properties, and enhancing its chemical stability, enabling it to maintain stable performance in different environments.

[0019] More preferably, the modifier includes 2-acrylamido-2-methylpropanesulfonic acid, 1-butyl-3-vinyl-1H-imidazolium-3-onium bromide, and polyethylene glycol dimethacrylate, with a mass ratio of vinyl-functionalized multi-walled carbon nanotubes to polyethylene glycol dimethacrylate of 20-200:10-100. Polyethylene glycol dimethacrylate has double bonds at both ends of its molecule, allowing it to simultaneously connect with two or more polymer chains to form covalent bonds, linking the originally relatively independent polymer chains together to construct a three-dimensional cross-linked network structure. This restricts the relative movement of the polymer chains, giving the anion exchange membrane better mechanical strength and stability. Optimizing the membrane's microstructure and adjusting the pore size and porosity makes its selective transport of different ions more effective, thereby improving the membrane's ion selectivity.

[0020] The high-concentration system uses RO reverse osmosis for mid-stage concentration and includes a base plate, protective blocks, sleeves, connecting rods, springs, columns, and a top frame. The base plate has a reverse osmosis treatment structure. The protective blocks surround the base plate and are connected to it via sleeves and connecting rods, with springs between the connecting rods and sleeves. Columns are vertically fixed at the four corners of the base plate, and the top of the columns is connected to the top frame. The reverse osmosis treatment structure includes a booster pump, a quartz sand filter, an activated carbon filter, a softening resin filter, reverse osmosis tubing, and a precision filter. The RO reverse osmosis system is multi-stage, and the RO membrane elements are spiral wound membrane elements.

[0021] Preferably, the particle size of the separated particles is 0.1-0.9 nm.

[0022] Preferably, the membrane flux is designed to be 10-20 LMH.

[0023] The distillation extraction system includes a distillation column, an extractant addition device, a reflux system, a collection device, and a temperature and pressure control system. The distillation column has multiple distillation zones, each with different temperatures and pressures. The extractant addition device includes a metering pump and an adjustable nozzle for adding extractant to the distillation zones.

[0024] The cooling crystallization system includes a vertical cylindrical container-shaped shell, a flat cover, a material distribution device, a scraping device, a conical head, cooling coils, and a cooling medium distribution pipe. Multiple sets of cooling coils inside the shell are connected to the cooling medium distribution pipe, forming multiple individual crystallizers connected in sequence. Each layer of cooling coils is hexagonal and is installed on a multi-functional lifting pipe connected to the hydraulic lifting device.

[0025] A method for efficient stepwise recovery of valuable substances from industrial wastewater includes the following steps: pre-treating the industrial wastewater in a pre-treatment unit; introducing the pre-treated wastewater into a multi-chamber electrodialysis system to separate salts and organic matter; and sequentially introducing the effluent from the electrodialysis concentration chamber into a high-concentration system, a distillation extraction system, and a cooling crystallization system for treatment to recover the valuable substances.

[0026] The present invention also provides a multi-chamber electrodialysis system, including a pretreatment unit and an electrodialysis unit.

[0027] The pretreatment unit includes microfiltration and ultrafiltration systems. The filter membrane is placed flat into the membrane mounting cavity, and its edges are sealed with sealing strips. The inlet of the pretreatment equipment is connected to the wastewater source, and the outlet is connected to the inlet of the electrodialysis unit. Pipe clamps are used to secure the pipe connections firmly.

[0028] Preferably, the filtration mode includes immersion filtration, MBR membrane tank filtration, or vibrating membrane filtration.

[0029] Preferably, the pore size of the filter membrane is 0.2-100 μm.

[0030] Preferably, the filter membrane material includes hollow fiber, polysulfone, polyamide, or ceramic.

[0031] The electrodialysis unit includes an electrodialysis membrane stack, a DC regulated power supply, a flow meter, a circulating pump, and a water tank. The membrane stack has a positive electrode plate and a negative electrode plate at both ends. The anode plate and the adjacent partition plate form the anode chamber, and the cathode plate and the adjacent partition plate form the cathode chamber. Membrane units are arranged between the anode chamber and the cathode chamber. When there are multiple repeated membrane units, they are arranged closely together. Each membrane unit contains multiple ion exchange membranes, including cation exchange membranes and anion exchange membranes. A concentration chamber or a dilute chamber is formed between two ion exchange membranes. Each membrane unit has one concentration chamber and 2-5 dilute chambers, or one dilute chamber and 2-5 concentration chambers. The concentration chambers and dilute chambers can be freely combined according to the target ion recovery principle and efficiency optimization, such as concentrated-concentrated-dilute, dilute-dilute-concentrated, concentrated-concentrated-concentrated-dilute, etc. The anode chamber has an anolyte inlet and an anolyte outlet, the cathode chamber has a cathode inlet and a cathode outlet, the concentration chamber has a concentrate inlet and a concentrate outlet, and the dilute chamber has a desalination inlet and a desalination outlet. The partition plates are the commonly used partition plates in the field of electrodialysis. The water tank system includes an electrode chamber water tank for storing the electrode solution, a concentration chamber water tank for storing the separated thiocyanate solution, and a dilute chamber water tank for storing a mixed solution containing thiocyanate ions, miscellaneous salts, and organic matter. The electrode chamber water tanks are connected to both sides of the electrode plates via conduits, and a circulating pump establishes an electrode solution circulation loop. The concentration chamber water tank is connected to the concentrate inlet and outlet via conduits, allowing concentrate to flow sequentially from the concentration chamber water tank into the membrane stack and then back to the concentration chamber water tank. The dilute chamber water tank is connected to the dilute water inlet and outlet via conduits, allowing the mixed solution to flow sequentially from the dilute chamber water tank into the membrane stack and then back to the dilute chamber water tank. The negative terminal of the DC regulated power supply is connected to the cathode of the membrane stack, and the positive terminal is connected to the anode of the membrane stack.

[0032] Preferably, the number of membrane units is 1-50.

[0033] More preferably, the number of membrane units is 5-20.

[0034] Preferably, the ion exchange membrane includes heterogeneous membranes, homogeneous membranes, and alloy membranes, wherein the membrane resistance is 0-10 Ω / cm. 2 Its exchange capacity is 1.3-3 mol / Kg, and its acid and alkali resistance is pH 2-10.

[0035] The present invention also provides a high-concentration system, including a base plate, a protective block, a sleeve, a connecting rod, a spring, a column, and a top frame.

[0036] Install the booster pump and quartz sand filter sequentially on the base plate, connecting each component with pipes according to the process flow, ensuring tight and leak-free connections. Install protective blocks around the base plate, connecting them to the base plate via sleeves and connecting rods, with springs installed between the connecting rods and sleeves. Vertically fix columns at the four corners of the base plate, connecting the top to the top frame, and install retaining strips between adjacent columns. Install rollers at the four corners of the lower surface of the base plate, and install a receiving tray at the bottom, ensuring that the edge plate of the receiving tray fits snugly against the base plate support strips. Install the control panel on the columns and connect the wiring for each component.

[0037] Preferably, the reverse osmosis membrane is a single-stage or multi-stage type.

[0038] Preferably, the RO membrane element is a spiral wound membrane element.

[0039] Preferably, the particle size of the separation sieve is 0.1-0.9 nm, and the designed membrane flux is 10-20 LMH.

[0040] The present invention also provides a distillation extraction system, including a distillation column, an extractant addition device, a reflux system, a collection device, and a temperature and pressure control system.

[0041] Construct a distillation column, set up a distillation zone, and open inlet and outlet ports; install an extractant addition device, connect the metering pump and nozzle and fix them in the middle of the distillation column; connect the reflux system, connect the top and bottom collection devices of the distillation column with pipelines, and install relevant valves; install a temperature and pressure control system, and connect all sensors and control equipment; set up an extractant storage tank, extractant regeneration device and extractant circulation pump, connect them with pipelines to form a recovery system, and connect it to the distillation column.

[0042] The present invention also provides a cooling crystallization system, comprising: a vertical cylindrical container-shaped shell, a flat cover, a material distribution device, a material scraping device, a conical end cap, a cooling coil, and a cooling medium distribution pipe.

[0043] Install a vertical cylindrical container-shaped shell, install cooling coils inside the shell, connect the cooling coils to the cooling medium distribution pipe, making each layer of cooling coils hexagonal and fixed on the multi-functional lifting pipe; install a flat cover on the top of the shell and install a material distribution device; install a conical end cap and a scraper at the bottom; install a hydraulic lifting device on the flat cover and connect it to the multi-functional lifting pipe, the hydraulic lifting device includes a rigid connecting frame, a hydraulic cylinder, and a hydraulic pump station; connect a seed crystal circulation pipeline outside the shell.

[0044] This invention also provides a method for preparing a composite multi-walled carbon nanotube anion exchange membrane, comprising:

[0045] Preparation of carboxylated multi-walled carbon nanotubes: MWNTs were dispersed in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, stirred and refluxed at 85-95℃ for 6-8h, cooled to room temperature, vacuum filtered, and washed with deionized water until the pH of the washing solution was 6.9-7.1. The solution was then vacuum dried at 85-95℃ for 8-12h to obtain MWNT-COOH.

[0046] Preferably, in the mixed acid solution, the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 6-60:2-20.

[0047] Preferably, the mass-to-volume ratio of MWNT to mixed acid is 20-200 mg: 8-80 mL.

[0048] Preparation of amino-functionalized multi-walled carbon nanotubes: MWNT-COOH was dispersed in DMF, ethylenediamine, EDC and DMAP were added, and the mixture was ultrasonically mixed for 15-45 min. After reacting at 85-95℃ for 18-30 h, the mixture was cooled to room temperature, vacuum filtered, washed with deionized water, and vacuum dried at 50-70℃ for 8-12 h to obtain MWNT-NH2.

[0049] Preferably, the mass-to-volume ratio of MWNT-COOH to DMF is 20-200 mg: 25-250 mL.

[0050] Preferably, the mass-to-volume ratio of MWNT-COOH to ethylenediamine is 20-200 mg: 10-100 mL.

[0051] Preferably, the mass ratio of MWNT-COOH to EDC is 20-200:30-300.

[0052] Preferably, the mass ratio of MWNT-COOH to DMAP is 20-200:30-300.

[0053] Preparation of vinyl-functionalized multi-walled carbon nanotubes: MWNT-NH2 was dispersed in DMF, and acrylic acid, EDC, and DMAP were added. The mixture was ultrasonically mixed for 10-30 min and reacted at 45-55℃ with stirring for 18-30 h. After cooling to room temperature, the mixture was vacuum filtered, washed with deionized water, and vacuum dried at 45-55℃ for 8-12 h to obtain MWNT-CH=CH2, i.e., vinyl-functionalized multi-walled carbon nanotubes.

[0054] Preferably, the mass-to-volume ratio of MWNT-NH2 to DMF is 20-200 mg: 25-250 mL.

[0055] Preferably, the mass-to-volume ratio of MWNT-NH2 to acrylic acid is 20-200 mg: 10-100 mL.

[0056] Preferably, the mass ratio of MWNT-NH2 to EDC is 20-200:30-300.

[0057] Preferably, the mass ratio of MWNT-NH2 to DMAP is 20-200:30-300.

[0058] Preparation of composite multi-walled carbon nanotubes: MWNT-CH=CH2 was dispersed in deionized water to form a MWNT-CH=CH2 dispersion. Under nitrogen protection at 45-55℃, potassium persulfate was added and stirred for 10-30 min. Modifiers AMPS and BVImBr were added and stirred until homogeneous. The temperature was raised to 75-85℃ and reacted for 8-12 h under stirring and nitrogen protection. After cooling to room temperature, the mixture was vacuum filtered and washed alternately with deionized water and ethanol. It was then dried at 65-75℃ for 8-12 h to obtain P(AMPS-BVImBr)-g-MWCNTs, i.e., composite multi-walled carbon nanotubes.

[0059] Preferably, in the MWNT-CH=CH2 dispersion, the mass-to-volume ratio of MWNT-CH=CH2 to deionized water is 20-200 mg: 10-100 mL.

[0060] Preferably, the mass ratio of MWNT-CH=CH2 to potassium persulfate is 20-200:20-200.

[0061] Preferably, the modifier includes AMPS and BVImBr, with the mass ratio of MWNT-CH=CH2 to AMPS being 20-200:100-1000 and the mass ratio of MWNT-CH=CH2 to BVImBr being 20-200:60-600.

[0062] More preferably, the modifier includes AMPS, BVImBr, and PEGDMA, with the mass ratio of MWNT-CH=CH2 to AMPS being 20-200:100-1000, the mass ratio of MWNT-CH=CH2 to BVImBr being 20-200:60-600, and the mass ratio of MWNT-CH=CH2 to PEGDMA being 20-200:10-100.

[0063] Preparation of composite multi-walled carbon nanotube anion exchange membrane: Composite multi-walled carbon nanotubes were dispersed in DMF and sonicated for 45-90 min to obtain a uniform dispersion. Polyvinyl alcohol was added and sonicated for 15 min. Glutaraldehyde was added and sonicated for 15-45 min. The mixture was then uniformly coated onto a glass plate to form a liquid membrane. The membrane was vacuum dried at 65-75℃ for 8-12 h to obtain a solid membrane. After peeling, the membrane was soaked in deionized water for 18-30 h and then vacuum dried for 10-12 h to obtain the composite multi-walled carbon nanotube anion exchange membrane.

[0064] Preferably, the mass-to-volume ratio of composite multi-walled carbon nanotubes to DMF is 20-200:2-20mL.

[0065] Preferably, the mass ratio of composite multi-walled carbon nanotubes to polyvinyl alcohol is 20-200:10-100.

[0066] Preferably, the mass ratio of composite multi-walled carbon nanotubes to glutaraldehyde is 20-200:1-10.

[0067] This invention also provides a method for the efficient distribution and recovery of valuable substances in industrial wastewater, comprising:

[0068] Wastewater pretreatment: Wastewater generated in the production process of pharmaceutical companies is taken and removed from particulate matter and suspended solids through a microfiltration pretreatment unit to obtain pretreated wastewater.

[0069] Electrodialysis separation: Add the corresponding solutions to each tank of the apparatus, specifically: add electrode solution to the electrode chamber tank; pass pure water into the concentrate chamber tank; and pass pretreated wastewater into the dilute chamber tank. Next, start the corresponding circulation pump for each tank, i.e., start the circulation pump installed on the conduit connecting each tank to its corresponding compartment in the membrane stack, and adjust the corresponding circulation flow rate. Then, turn on the DC power supply. When the conductivity tends to stabilize, it is considered the reaction endpoint; stop the process and turn off the power.

[0070] Preferably, the solute in the polar liquid of the polar chamber water tank includes sodium sulfate, sodium chloride, and sodium nitrate, and the concentration of the solute is 0.05-0.2 mol / L.

[0071] More preferably, the solute is sodium sulfate with a concentration of 0.05-0.1 mol / L.

[0072] Preferably, the volume of the polar chamber water tank, the concentrate water tank, and the dilute water tank is 5L.

[0073] Preferably, the voltage of the electrodialysis membrane stack is 5-50V, and the flow rate of the electrodialysis membrane stack is 1000-10000mL / min.

[0074] Preferably, the speed of the circulating pump is maintained at 600-800 rpm.

[0075] Electrodialysis concentration: The effluent from the concentrated chamber of electrodialysis separation is introduced into the electrodialysis concentration system for concentration. The operation steps are the same as those of the primary electrodialysis separation system.

[0076] Preferably, electrodialysis concentration includes multi-stage intermittent, multi-stage semi-intermittent, or volume difference concentration.

[0077] High concentration: The concentrated water from the electrodialysis concentration chamber is introduced into the RO reverse osmosis unit, and the booster pump is turned on so that the wastewater passes through each filter device and reverse osmosis tube in sequence for high concentration.

[0078] Preferably, the RO reverse osmosis system adopts a multi-stage design.

[0079] Preferably, the RO membrane element is a spiral wound membrane element.

[0080] Preferably, the particle size of the separated particles is 0.1-0.9 nm.

[0081] Preferably, the membrane flux is designed to be 10-20 LMH;

[0082] Distillation and extraction: The highly concentrated RO reverse osmosis solution is introduced into the distillation and extraction system and extracted and distilled under normal pressure; the mixture of extractant and water is piped to a water distillation kettle for distillation, the extractant is recovered, and high-purity glacial acetic acid is collected.

[0083] Preferably, the reflux ratio is controlled to be 1-8.

[0084] Preferably, the temperature at the top of the column is 60-80℃, and the temperature at the bottom of the column is 110-130℃.

[0085] Preferably, the molar ratio of extractant to feed liquid is 1-10:10-100.

[0086] Preferably, the extractant includes acetophenone, N-methylacetamide, methylpyrrolidone, tributyl phosphate, and isopropyl acetate.

[0087] Cooling crystallization: The separated liquid after extraction is introduced into a cooling crystallization system, and sodium thiocyanate is obtained by cooling crystallization.

[0088] Preferably, the crystallizer temperature is controlled at 0-20℃ and the stirring speed is 500-3000rpm.

[0089] More preferably, the crystallizer temperature is controlled at 0-10℃ and the stirring speed is controlled at 500-2000rpm.

[0090] Preferably, the wastewater retention time is 1-2 hours.

[0091] This invention employs a multi-chamber electrodialysis system, a high-concentration system, a distillation extraction system, and a cooling crystallization system to form a complete set of equipment for the efficient stepwise recovery of valuable substances from industrial wastewater. It utilizes a composite multi-walled carbon nanotube anion exchange membrane, where 2-acrylamido-2-methylpropanesulfonic acid and 1-butyl-3-vinyl-1H-imidazolium-3-onium bromide undergo a polymerization reaction with the multi-walled carbon nanotubes. Therefore, it offers the following advantages: the device and method provided by this invention can achieve efficient stepwise recovery of multiple valuable substances from industrial wastewater. The separation process is simple and safe, solving the problem of separating and recovering valuable substances from industrial wastewater. It achieves high separation and recovery rates of multiple valuable substances, fully utilizes salt resources, and the entire process is pollution-free, promoting near-zero discharge of industrial wastewater. Therefore, this invention is a highly efficient and pollution-free complete set of equipment and method for the efficient stepwise recovery of valuable substances from industrial wastewater. Attached Figure Description

[0092] Figure 1 This is a process flow diagram of a complete set of equipment and methods for the efficient stepwise recovery of valuable substances from industrial wastewater.

[0093] Figure 2 This is a structural diagram of a multi-chamber electrodialysis unit in a complete set of equipment for the efficient stepwise recovery of valuable substances from industrial wastewater.

[0094] Figure 3 This is a schematic diagram illustrating the principle of ion separation and recovery using an electrodialysis membrane stack in a specific embodiment of the present invention.

[0095] Figure 4 This is a schematic diagram showing the treatment effect of electrodialysis on different salt concentrations of actual industrial wastewater. Detailed Implementation

[0096] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0097] The concepts involved in this application will first be described with reference to the accompanying drawings. It should be noted that the following descriptions of various concepts are only for the purpose of making the content of this application easier to understand and do not constitute a limitation on the scope of protection of this application; furthermore, the embodiments and features in the embodiments of this application can be combined with each other unless otherwise specified. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0098] Table 1. Chinese meanings of abbreviations

[0099]

[0100] The multi-chamber electrodialysis device used in this invention, such as Figure 2 As shown, 1 is the electrodialysis power supply, 2 is the electrodialysis membrane stack, 3 is the membrane stack inlet, 4 is the membrane stack outlet, 5 is the electrode plate, 6 is the ion exchange membrane, 7 is the power cord, 8 is the conduit, 9 is the discharge tank, 10 is the feed tank, 11 is the electrode liquid tank, 12 is the positive electrode, and 13 is the negative electrode. This schematic diagram illustrates one specific embodiment and is intended to aid understanding; it does not constitute a limitation of the invention.

[0101] The electrodialysis membrane stack used in this invention is as follows: Figure 3 As shown, it consists of one anode and one cathode, and includes a cation exchange membrane and an anion exchange membrane, as well as chambers separated by ion exchange membranes. The schematic diagram is a specific embodiment to aid understanding and does not constitute a limitation of the invention.

[0102] Example 1

[0103] A complete set of equipment for efficient stepwise recovery of valuable substances from industrial wastewater includes: a multi-chamber electrodialysis system, a high-concentration system, a distillation extraction system, and a cooling crystallization system; wherein the multi-chamber electrodialysis system includes a pretreatment unit and an electrodialysis unit.

[0104] The pretreatment unit includes microfiltration and ultrafiltration systems. The filter membrane is placed flat into the membrane mounting cavity, and its edges are sealed with sealing strips. The inlet of the pretreatment equipment is connected to the wastewater source, and the outlet is connected to the inlet of the electrodialysis unit. Pipe clamps are used to secure the pipe connections firmly. The filter membrane is made of hollow fiber with a pore size of 0.32 μm.

[0105] The electrodialysis unit includes an electrodialysis membrane stack, a DC regulated power supply, a flow meter, a circulating pump, and a water tank. In this embodiment, the electrodialysis membrane stack comprises one membrane unit, which includes one anion exchange membrane, four cation exchange membranes, one dilute chamber, and four concentrate chambers. Using the anode plate as a reference plane, the following layers are stacked sequentially: anode plate, homogeneous anion exchange membrane, separator, anion exchange membrane, separator, homogeneous anion exchange membrane, separator, cation exchange membrane, separator, and anion exchange membrane, finally covering the cathode plate to form the membrane stack structure. The separator is a commonly used separator in the field of electrodialysis. The water tank includes an electrode chamber water tank for storing the electrode solution, a concentrate chamber water tank for storing the separated thiocyanate solution, and a dilute chamber water tank for storing a mixed solution containing thiocyanate ions, miscellaneous salts, and organic matter. The membrane consists of two interconnected tanks: an anion exchange membrane and a cation exchange membrane. The anion exchange membrane is connected to both sides of the electrode plate via conduits, and a circulating pump establishes an electrode liquid circulation loop. The concentrate exchange membrane is connected to the concentrate inlet and outlet via conduits, allowing concentrate to flow sequentially from the concentrate exchange membrane into the membrane stack and then back to the concentrate exchange membrane. The dilute exchange membrane is connected to the dilute inlet and outlet via conduits, allowing the mixed solution to flow sequentially from the dilute exchange membrane into the membrane stack and then back to the dilute exchange membrane. The negative terminal of the DC regulated power supply is connected to the cathode of the membrane stack, and the positive terminal is connected to the anode of the membrane stack. Both the anion exchange membrane and the cation exchange membrane are homogeneous membranes with a membrane resistance of 8 Ω / cm. 2 Its exchange capacity is 1.5 mol / Kg, and its acid and alkali resistance is pH 2-10.

[0106] The high-concentration system includes a base plate, protective blocks, sleeves, connecting rods, springs, columns, and a top frame. The booster pump, quartz sand filter, activated carbon filter, softening resin filter, reverse osmosis tubing, and precision filter are sequentially installed on the base plate. All components are connected by pipes to ensure tight, leak-free connections. A control panel is installed on one of the columns. Rollers are installed at the four corners of the base plate's lower surface, and a receiving tray with flanges at both ends fits snugly against the support strips at the bottom of the base plate. Protective blocks are installed around the base plate and connected to it via sleeves and connecting rods, with springs installed between the connecting rods and sleeves. Columns are vertically fixed at the four corners of the base plate, connected to the top frame, and baffles are installed between adjacent columns. The control panel is installed on the columns, and the wiring for each component is connected. The reverse osmosis membrane is multi-segmented, using spiral wound membrane elements with a separation particle size of 0.45 nm and a designed membrane flux of 15 LMH.

[0107] The distillation extraction system includes a distillation column, an extractant addition device, a reflux system, a collection device, and a temperature and pressure control system. The distillation column has three distillation zones. The metering pump and nozzles of the extractant addition device are installed in the middle of the column. The nozzles are adjustable in angle and direction to ensure uniform spraying of the extractant into the distillation zones. The reflux system connects the top and bottom of the distillation column. The collection device is located at the bottom of the distillation column, and the temperature and pressure control system is connected to the column. The extractant recovery system includes an extractant storage tank, an extractant regeneration device, and an extractant circulation pump, all installed and connected.

[0108] The cooling crystallization system includes a shell, a flat cover, a material distribution device, a scraping device, a conical head, cooling coils, and a cooling medium distribution pipe. The shell is a vertical cylindrical container with multiple sets of cooling coils inside. Each layer of cooling coils is hexagonal and mounted on a multi-functional lifting pipe. The multi-functional lifting pipe is connected to a hydraulic lifting device on the flat cover, forming multiple individual crystallizers connected sequentially from top to bottom. Each crystallizer is a multi-layered polygonal cooling coil made of straight pipes. The pipes between layers are connected by three-dimensional elbows and are staggered. The hydraulic lifting device consists of a rigid connecting frame, a hydraulic cylinder, and a hydraulic pump station. The cooling coils are connected to the cooling medium distribution pipe. A seed crystal circulation pipeline is set outside the shell. The material distribution device, scraping device, and conical head are installed in place.

[0109] A method for the efficient distribution and recovery of valuable substances in industrial wastewater:

[0110] Wastewater pretreatment: Antibiotic wastewater generated in the pharmaceutical production process is taken and removed from particulate matter and suspended solids by a microfiltration pretreatment unit to obtain pretreated wastewater; the wastewater contains 7000 mg / L thiocyanate, 10000 mg / L chloride, and 8000 mg / L acetate.

[0111] Electrodialysis separation: Add the corresponding solutions to each water tank of the apparatus. Specifically: add 5L of 0.1mol / L sodium sulfate solution to the electrode chamber tank; introduce 5L of pure water into the concentrate tank; and introduce 5L of pretreated wastewater into the dilute tank. Then, turn on the corresponding circulation pump for each tank, i.e., turn on the circulation pump located on the conduit connecting each tank to its corresponding compartment in the membrane stack, and adjust the corresponding circulation flow rate. The membrane stack flow rate is controlled at 3L / min. Next, turn on the DC power supply, maintaining a constant voltage of 20V, and set the circulation pump speed to 700rpm. When the conductivity tends to stabilize, the reaction is considered to have reached its endpoint; stop the process and turn off the power.

[0112] High concentration: The effluent from the electrodialysis concentration chamber is introduced into the RO reverse osmosis unit, and the booster pump is turned on so that the wastewater passes through each filter device and reverse osmosis tube in sequence to obtain a high concentration solution.

[0113] Distillation and extraction: The highly concentrated liquid is introduced into the distillation and extraction system for extraction and distillation under normal pressure, with a reflux ratio of 4, a top temperature of 70°C, and a bottom temperature of 120°C. Acetophenone is selected as the extractant, and the molar ratio of extractant to feed liquid is 5:1. The mixture of extractant and water is piped to a water distillation kettle for distillation to recover the extractant and collect high-purity glacial acetic acid. The concentrated water after extraction is subjected to ultrafiltration and UV disinfection before entering the biological treatment system for biological treatment.

[0114] Cooling crystallization: The separated liquid after extraction is introduced into the cooling crystallization system, the crystallizer temperature is controlled at 5℃, the stirring speed is 1000rpm, the wastewater retention time is 1.5h, and sodium thiocyanate is obtained by cooling crystallization.

[0115] Example 2: The only difference between this example and Example 1 is that the anion exchange membrane in the electrodialysis unit is a composite multi-walled carbon nanotube anion exchange membrane.

[0116] The preparation of composite multi-walled carbon nanotube anion exchange membranes includes:

[0117] Preparation of carboxylated multi-walled carbon nanotubes: MWNTs were dispersed in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid. The solution was stirred and refluxed at 90°C for 7 hours, then cooled to room temperature. After vacuum filtration, the solution was washed with deionized water until the pH of the washing solution reached 7.0. The solution was then vacuum dried at 90°C for 10 hours to obtain MWNT-COOH, i.e., carboxylated multi-walled carbon nanotubes. In the mixed acid solution, the volume ratio of concentrated nitric acid to concentrated sulfuric acid was 30:10; the mass-to-volume ratio of MWNTs to the mixed acid was 100 mg:40 mL.

[0118] Preparation of amino-functionalized multi-walled carbon nanotubes: MWNT-COOH was dispersed in DMF, and ethylenediamine, EDC, and DMAP were added. The mixture was ultrasonically mixed for 30 min, reacted at 90 °C for 24 h, cooled to room temperature, vacuum filtered, washed with deionized water, and vacuum dried at 60 °C for 10 h to obtain MWNT-NH2, i.e., amino-functionalized multi-walled carbon nanotubes. The mass-to-volume ratio of MWNT-COOH to DMF was 40 mg:50 mL; the mass-to-volume ratio of MWNT-COOH to ethylenediamine was 40 mg:20 mL; the mass ratio of MWNT-COOH to EDC was 40:60; and the mass ratio of MWNT-COOH to DMAP was 40:60.

[0119] Preparation of vinyl-functionalized multi-walled carbon nanotubes: MWNT-NH2 was dispersed in DMF, and acrylic acid, EDC, and DMAP were added. The mixture was ultrasonically mixed for 15 min and reacted at 50 °C with stirring for 24 h. After cooling to room temperature, the mixture was vacuum filtered, washed with deionized water, and vacuum dried at 50 °C for 10 h to obtain MWNT-CH=CH2, i.e., vinyl-functionalized multi-walled carbon nanotubes. The mass-to-volume ratio of MWNT-NH2 to DMF was 40 mg:50 mL; the mass-to-volume ratio of MWNT-NH2 to acrylic acid was 40 mg:20 mL; the mass ratio of MWNT-NH2 to EDC was 40:60; and the mass ratio of MWNT-NH2 to DMAP was 40:60.

[0120] Preparation of composite multi-walled carbon nanotubes: MWNT-CH=CH2 was dispersed in deionized water to form a MWNT-CH=CH2 dispersion. Potassium persulfate was added at 50℃ under nitrogen protection, and the mixture was stirred for 15 min. AMPS and BVImBr were then added and stirred until homogeneous. The temperature was raised to 80℃, and the reaction was carried out for 10 h under stirring and nitrogen protection. After cooling to room temperature, the mixture was vacuum filtered and washed alternately with deionized water and ethanol. It was then dried at 70℃ for 10 h to obtain P(AMPS-BVImBr)-g-MWCNTs, i.e., composite multi-walled carbon nanotubes. In the MWNT-CH=CH2 dispersion, the mass-to-volume ratio of MWNT-CH=CH2 to deionized water was 40 mg:20 mL; the mass ratio of MWNT-CH=CH2 to potassium persulfate was 40:40; the mass ratio of MWNT-CH=CH2 to AMPS was 40:200; and the mass ratio of MWNT-CH=CH2 to BVImBr was 40:120.

[0121] Preparation of composite multi-walled carbon nanotube anion exchange membrane: Composite multi-walled carbon nanotubes were dispersed in DMF and sonicated for 1 h to obtain a uniform dispersion. Polyvinyl alcohol was added and sonicated for 15 min. Glutaraldehyde was added and sonicated for 30 min. The mixture was then uniformly coated onto a glass plate to form a liquid film. The liquid film was vacuum dried at 70 °C for 10 h to obtain a solid film. After peeling, the film was soaked in deionized water for 24 h and then vacuum dried for 8 h to obtain the composite multi-walled carbon nanotube anion exchange membrane. The mass-to-volume ratio of composite multi-walled carbon nanotubes to DMF was 100:10 mL, the mass ratio of composite multi-walled carbon nanotubes to polyvinyl alcohol was 100:50, and the mass ratio of composite multi-walled carbon nanotubes to glutaraldehyde was 100:5.

[0122] Example 3: The only difference between this example and Example 2 is the preparation of the composite multi-walled carbon nanotubes.

[0123] Preparation of composite multi-walled carbon nanotubes: MWNT-CH=CH2 was dispersed in deionized water to form a MWNT-CH=CH2 dispersion. Under nitrogen protection at 50℃, potassium persulfate was added and stirred for 15 min. AMPS and BVImBr were then added and stirred until homogeneous. The temperature was raised to 80℃, and the reaction was carried out for 10 h under stirring and nitrogen protection. After cooling to room temperature, the mixture was vacuum filtered and washed alternately with deionized water and ethanol. It was then dried at 70℃ for 10 h to obtain P(AMPS-BVImBr)-g-MWCNTs, i.e., composite multi-walled carbon nanotubes. In the MWNT-CH=CH2 dispersion, the mass-to-volume ratio of MWNT-CH=CH2 to deionized water was 40 mg:20 mL; the mass ratio of MWNT-CH=CH2 to potassium persulfate was 40:40; the mass ratio of MWNT-CH=CH2 to AMPS was 40:200; and the mass ratio of MWNT-CH=CH2 to BVImBr was 40:200.

[0124] Example 4: The only difference between this example and Example 2 is the preparation of the composite multi-walled carbon nanotubes.

[0125] Preparation of composite multi-walled carbon nanotubes: MWNT-CH=CH2 was dispersed in deionized water to form a MWNT-CH=CH2 dispersion. Potassium persulfate was added at 50℃ under nitrogen protection and stirred for 15 min. AMPS, BVImBr, and PEGDMA were added and stirred until homogeneous. The temperature was raised to 80℃ and reacted for 10 h under stirring and nitrogen protection. After cooling to room temperature, the mixture was vacuum filtered and washed alternately with deionized water and ethanol. It was then dried at 70℃ for 10 h to obtain P(AMPS-BVImBr)-g-MWCNTs, i.e., composite multi-walled carbon nanotubes. In the MWNT-CH=CH2 dispersion, the mass-to-volume ratio of MWNT-CH=CH2 to deionized water was 40 mg:20 mL; the mass ratio of MWNT-CH=CH2 to potassium persulfate was 40:40; the mass ratio of MWNT-CH=CH2 to AMPS was 40:200; the mass ratio of MWNT-CH=CH2 to BVImBr was 40:120; and the mass ratio of MWNT-CH=CH2 to PEGDMA was 40:40.

[0126] Example 5: The only difference between this example and Example 2 is the preparation of the composite multi-walled carbon nanotubes.

[0127] Preparation of composite multi-walled carbon nanotubes: MWNT-CH=CH2 was dispersed in deionized water to form a MWNT-CH=CH2 dispersion. Potassium persulfate was added at 50℃ under nitrogen protection and stirred for 15 min. AMPS, BVImBr, and PEGDMA were added and stirred until homogeneous. The temperature was raised to 80℃ and reacted for 10 h under stirring and nitrogen protection. After cooling to room temperature, the mixture was vacuum filtered and washed alternately with deionized water and ethanol. It was then dried at 70℃ for 10 h to obtain P(AMPS-BVImBr)-g-MWCNTs, i.e., composite multi-walled carbon nanotubes. In the MWNT-CH=CH2 dispersion, the mass-to-volume ratio of MWNT-CH=CH2 to deionized water was 40 mg:20 mL; the mass ratio of MWNT-CH=CH2 to potassium persulfate was 40:40; the mass ratio of MWNT-CH=CH2 to AMPS was 40:200; the mass ratio of MWNT-CH=CH2 to BVImBr was 40:120; and the mass ratio of MWNT-CH=CH2 to PEGDMA was 40:80.

[0128] Comparative Example 1: The only difference between this comparative example and Example 2 is that AMPS was not used in the preparation of the composite multi-walled carbon nanotubes.

[0129] Comparative Example 2: The only difference between this comparative example and Example 2 is that BVImBr was not used in the preparation of the composite multi-walled carbon nanotubes.

[0130] Experimental Example 1: Test on the treatment effect of different salt concentrations of actual industrial wastewater after electrodialysis treatment.

[0131] Test sample: Concentrate effluent from the electrodialysis chamber in Example 1.

[0132] Test method: Water samples were collected from the concentrate chamber outlet every 15 minutes after the start of the electrodialysis reaction, for a total of 60 minutes; thiocyanate ions and iron ions were complexed and the results were determined by ultraviolet spectrophotometry, and the separation efficiency and selectivity were evaluated based on the thiocyanate ion concentration; the ion concentration changes of sulfate ions, phosphate ions, chloride ions and acetate ions were detected by ion chromatography, and the TOC content was determined by a total organic carbon molecular analyzer.

[0133] The treatment effects of electrodialysis on different salt concentrations in actual industrial wastewater are as follows: Figure 4 As shown, the electrodialysis system has a good separation and concentration effect on thiocyanate ions, phosphate ions, chloride ions, acetate ions and organic pollutants in wastewater, and can effectively reduce the content of related ions and organic matter in the desalination chamber wastewater.

[0134] Experimental Example 2: Ion exchange capacity test of anion exchange membrane.

[0135] Test samples: anion exchange membranes prepared in Examples 2-5 and Comparative Examples 1-2.

[0136] Test method: Cut the anion exchange membrane into squares of the same size, weigh them, and immerse the anion exchange membrane in a certain volume of 1 mol / L sodium chloride solution for 24 h at 25℃ with stirring. Then rinse with deionized water, take the supernatant, and determine the concentration of the remaining sodium ions in the solution using an ion chromatograph.

[0137] Ion exchange capacity is calculated as follows:

[0138]

[0139] In the formula:

[0140] Q Ion exchange capacity, c 1 represents the initial sodium ion concentration. c 2 represents the remaining sodium ion concentration, V represents the volume of the sodium chloride solution, and m represents the mass of the anion exchange membrane.

[0141] The ion exchange capacity test results of the anion exchange membrane prepared by this invention are shown in Table 2:

[0142] Table 2. Ion exchange capacity test results of anion exchange membranes

[0143]

[0144] Compared to Comparative Examples 1-2, Examples 2-3 used composite multi-walled carbon nanotube anion exchange membranes obtained by polymerizing 2-acrylamido-2-methylpropanesulfonic acid, 1-butyl-3-vinyl-1H-imidazolium-3-onium bromide, and multi-walled carbon nanotubes. These membranes exhibited ion exchange capacities of 3.2-3.5 mmol / g, significantly higher than Comparative Examples 1-2. This demonstrates that both the sulfonic acid group and the imidazolium cation exchange group are indispensable and work synergistically to form continuous ion conduction channels, improving the selective transport capability for specific anions and thus facilitating ion exchange and increasing the ion exchange capacity. In Examples 4-5, polyethylene glycol dimethacrylate was introduced during the preparation of the composite multi-walled carbon nanotubes, further increasing the ion exchange capacity. This indicates that the addition of polyethylene glycol dimethacrylate altered the membrane's chemical structure and interchain interactions, optimizing the membrane structure and enhancing its hydrophilicity, making it easier for ions to diffuse and exchange within the membrane, thereby improving the ion exchange capacity.

[0145] Experimental Example 3: Average desalination rate test of anion exchange membrane.

[0146] Test samples: anion exchange membranes prepared in Examples 2-5 and Comparative Examples 1-2.

[0147] Test Method: Anion exchange membranes were cut to the same size and installed in an electrodialysis apparatus. A certain volume of 0.1 mol / L sodium chloride solution was added to the desalination chamber of the electrodialysis apparatus. Simultaneously, appropriate amounts of deionized water were added to the anode and cathode chambers. Under stirring conditions, a DC power supply was connected to begin the electrodialysis desalination experiment. Every 10 minutes, 5 mL of solution was taken from the desalination chamber, and its conductivity was measured using a conductivity meter. This process was continued for 60 minutes, and the average desalination rate of the entire experiment was calculated.

[0148] The desalination rate at each time point is calculated as follows:

[0149]

[0150] In the formula:

[0151] R For desalination rate, C 0 represents the initial concentration of the sodium chloride solution. C t Let t be the concentration of the sodium chloride solution in the desalination chamber at time t.

[0152] The ion exchange capacity test results of the anion exchange membrane prepared by this invention are shown in Table 3:

[0153] Table 3. Average desalination rate test results of anion exchange membranes

[0154]

[0155] The average desalination rates of Examples 2-3 were significantly higher than those of Comparative Examples 1-2, indicating that the synergistic effect of the sulfonic acid groups and the imidazolium cation exchange groups created a more ideal ion transport environment. This environment more effectively blocked the passage of anions from the salt, improving the selective repulsion of specific anions and thus facilitating the desalination process and increasing the average desalination rate. In Examples 4-5, the introduction of polyethylene glycol dimethacrylate (PEG) during the preparation of the composite multi-walled carbon nanotubes further increased the average desalination rate. This demonstrates that the addition of PEG altered the chemical structure and interchain interactions of the membrane, optimizing its overall performance. It may have enhanced the membrane's hydrophilicity, making it easier for water molecules to transport within the membrane. Simultaneously, it further adjusted the structure and properties of the ion channels, making it more difficult for salt ions to pass through the membrane, resulting in a more orderly and efficient ion transport process within the membrane. This significantly improved the average desalination rate, leading to better membrane performance during the desalination process.

[0156] The embodiments and / or implementation methods described above are merely preferred embodiments and / or implementation methods for implementing the technology of the present invention, and are not intended to limit the implementation methods of the technology of the present invention in any way. Any person skilled in the art can make some modifications or alterations to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as the technology or embodiments that are substantially the same as the present invention.

[0157] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A complete set of equipment for the efficient stepwise recovery of valuable substances from industrial wastewater, comprising a multi-chamber electrodialysis system, a high-concentration system, a distillation extraction system, and a cooling crystallization system; wherein, The multi-chamber electrodialysis system includes a pretreatment unit and an electrodialysis unit to separate organic matter and valuable substances from wastewater; the high-concentration system highly concentrates the separated valuable substances; the distillation extraction system is used to separate specific ions; and the cooling crystallization system further separates residual ions. The electrodialysis unit includes an electrodialysis membrane stack, with an anode plate and a cathode plate at both ends. The anode plate and an adjacent partition form an anode chamber, and the cathode plate and an adjacent partition form a cathode chamber. At least one membrane unit is provided between the anode chamber and the cathode chamber. The membrane unit is provided with multiple ion exchange membranes, and a concentration chamber or a dilute chamber is formed between two ion exchange membranes. The ion exchange membrane includes a composite multi-walled carbon nanotube anion exchange membrane, wherein the preparation steps of the composite multi-walled carbon nanotube anion exchange membrane are as follows: acidification, amination and vinylation treatment of multi-walled carbon nanotubes to obtain vinyl-functionalized multi-walled carbon nanotubes. Vinyl functionalized multi-walled carbon nanotubes were polymerized and grafted with a modifier to obtain composite multi-walled carbon nanotubes; the composite multi-walled carbon nanotubes were then subjected to film-forming treatment to obtain a composite multi-walled carbon nanotube anion exchange membrane. The modifiers include 2-acrylamido-2-methylpropanesulfonic acid and 1-butyl-3-vinyl-1H-imidazol-3-onium bromide.

2. The complete set of equipment for efficient stepwise recovery of valuable substances in industrial wastewater according to claim 1, characterized in that, The pretreatment unit includes microfiltration and ultrafiltration systems. The filtration modes include immersion, MBR membrane pool, or vibrating membrane. The membrane pore size is 0.2-100μm, and the membrane material includes hollow fiber, polysulfone, polyamide, or ceramic.

3. The complete set of equipment for efficient stepwise recovery of valuable substances in industrial wastewater according to claim 1, characterized in that, The electrodialysis unit includes a DC regulated power supply, a flow meter, a circulating pump, and a water tank; the membrane unit is provided with one concentration chamber and 2-5 dilute chambers, or one dilute chamber and 2-5 concentration chambers, and the concentration chambers and dilute chambers are freely combined according to the target ion recovery principle and efficiency optimization; the water tank includes an electrode chamber water tank for storing the electrode solution, a concentration chamber water tank for storing the separated thiocyanate solution, and a dilute chamber water tank for storing a mixed solution containing thiocyanate ions, as well as miscellaneous salts and organic matter.

4. The complete set of equipment for efficient stepwise recovery of valuable substances in industrial wastewater according to claim 3, characterized in that, The solute in the electrode solution of the electrode chamber includes sodium sulfate, sodium chloride, and sodium nitrate, with a solute concentration of 0.05-0.2 mol / L; the number of membrane units is 1-50; the electrodialysis membrane stack voltage is 5-50V, and the electrodialysis membrane stack flow rate is 1000-10000 mL / min; the ion exchange membrane includes heterogeneous membranes, homogeneous membranes, and alloy membranes, wherein the membrane resistance is 0-10 Ω / cm. 2 Its exchange capacity is 1.3-3 mol / Kg, and its acid and alkali resistance is pH 2-10.

5. The complete set of equipment for efficient stepwise recovery of valuable substances in industrial wastewater according to claim 1, characterized in that, The mass ratio of the vinyl-functionalized multi-walled carbon nanotubes to 2-acrylamido-2-methylpropanesulfonic acid is 2-100:10-500; the mass ratio of the vinyl-functionalized multi-walled carbon nanotubes to 1-butyl-3-vinyl-1H-imidazol-3-onium bromide is 2-100:6-300.

6. The complete set of equipment for efficient stepwise recovery of valuable substances in industrial wastewater according to claim 1, characterized in that, The high-concentration system employs RO reverse osmosis for mid-stage concentration and includes a base plate, protective blocks, sleeves, connecting rods, springs, columns, and a top frame. The base plate has a reverse osmosis treatment structure. The protective blocks surround the base plate and are connected to it via sleeves and connecting rods, with springs between the connecting rods and sleeves. Columns are vertically fixed at the four corners of the base plate, with the top of each column connected to the top frame. A baffle strip connects adjacent columns, flush with the outer surface of the column. The reverse osmosis treatment structure includes a booster pump, a quartz sand filter, an activated carbon filter, a softening resin filter, reverse osmosis tubing, and a precision filter. The reverse osmosis membrane is either single-stage or multi-stage, and the RO membrane element is a spiral wound membrane element. The particle size to be separated is 0.1-0.9 nm, and the designed membrane flux is 10-20 LMH.

7. The complete set of equipment for efficient stepwise recovery of valuable substances in industrial wastewater according to claim 1, characterized in that, The distillation and extraction system includes a distillation column, an extractant addition device, a reflux system, a collection device, and a temperature and pressure control system. The distillation column has multiple distillation zones, each with different temperatures and pressures. The extractant addition device includes a metering pump and an adjustable nozzle for adding extractant to the distillation zones.

8. A complete set of equipment for efficient stepwise recovery of valuable substances from industrial wastewater according to claim 1, characterized in that, The cooling crystallization system includes a vertical cylindrical container-shaped shell, a flat cover, a material distribution device, a scraping device, a conical head, cooling coils, and a cooling medium distribution pipe. Multiple sets of cooling coils inside the shell are connected to the cooling medium distribution pipe, forming multiple individual crystallizers connected in sequence. Each layer of cooling coils is hexagonal and is set on a multi-functional lifting pipe connected to a hydraulic lifting device.

9. A method for efficient stepwise recovery of valuable substances from industrial wastewater, carried out by a complete set of equipment for efficient stepwise recovery of valuable substances from industrial wastewater as described in any one of claims 1-8, comprising the following steps: Industrial wastewater is pretreated in a pretreatment unit. The pretreated wastewater is introduced into a multi-chamber electrodialysis system to separate salts and organic matter; The effluent from the electrodialysis concentration chamber is sequentially introduced into a high-concentration system, a distillation extraction system, and a cooling crystallization system for treatment to recover valuable substances.

Images