A method for the separation and resource utilization of thiocyanate ions in industrial wastewater

Abstract

This invention discloses a method for the separation and resource recovery of thiocyanate ions from industrial wastewater, belonging to the field of industrial wastewater treatment and resource recovery technology. The invention first pre-treats industrial wastewater containing thiocyanate ions to remove particulate matter; then, it introduces the wastewater into an electrodialysis system to separate thiocyanate ions from organic matter and other salt ions; next, it undergoes concentration treatment to obtain a highly concentrated thiocyanate ion concentrate, which is then reused in the production stage after ultrafiltration / UV disinfection; or it can be cooled and crystallized to obtain thiocyanate products. This invention solves the problem of separating and recovering thiocyanate ions from industrial wastewater containing thiocyanate ions, achieving a thiocyanate ion separation and recovery rate of over 90%, a concentration efficiency of 10-40%, and yielding industrial-grade pure products. This invention achieves full resource utilization of solid thiocyanate compounds, with zero pollution emissions throughout the entire process, promoting near-zero discharge of industrial wastewater containing thiocyanate ions.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment and resource recovery technology containing thiocyanate ions, specifically to a method for separating and recovering thiocyanate ions from industrial wastewater. Background Technology

[0002] In recent years, the increasing severity of global climate change and environmental problems has made green industrial transformation and the development of green, low-carbon, and circular economies crucial pathways to achieving sustainable economic and social development and overcoming resource and environmental constraints. Industrial wastewater containing thiocyanate ions typically exhibits high salt content, high organic matter concentration, high suspended solids content, high color, strong odor, high ammonia nitrogen concentration, and high salt content. Current mainstream treatment methods for thiocyanate-containing industrial wastewater, 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. 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.

[0003] Industrial efforts to treat thiocyanate ions primarily focus on promoting recovery and reuse methods, or applying degradation technologies to break down thiocyanate in wastewater into harmless substances. Various methods and technologies have been applied to the separation and recovery of thiocyanate ions, 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 thiocyanate 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 thiocyanate ions and realize resource utilization. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the separation and resource recovery of thiocyanate ions in industrial wastewater. The method uses electrodialysis technology to separate and recover thiocyanate ions, effectively removing particulate matter, organic matter and miscellaneous salt ions from industrial wastewater, thereby achieving the separation and recovery of thiocyanate ions.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] A method for separating and recovering thiocyanate ions from industrial wastewater includes: firstly, pretreating the industrial wastewater containing thiocyanate ions using an ultrafiltration membrane; then, passing the pretreated wastewater through an electrodialysis system for electrodialysis to separate and recover the thiocyanate ion-containing product. The ultrafiltration membrane is a polysulfone ultrafiltration membrane, which is formed by reacting bis(4-chlorophenyl)sulfone with bisphenol A and then with polyvinylpyrrolidone. The pore size of the polysulfone ultrafiltration membrane is 0.2-100 μm. This invention first pretreats the industrial wastewater containing thiocyanate ions to initially remove particulate matter and impurity salt ions. Then, the wastewater is passed through an electrodialysis system to separate thiocyanate ions from organic matter and impurity salt ions. Finally, the thiocyanate product obtained after RO reverse osmosis and cooling crystallization achieves the resource utilization of thiocyanate ions.

[0007] Preferably, the mass ratio of bis(4-chlorophenyl) sulfone to bisphenol A is 1:1-2.

[0008] Preferably, the mass ratio of polyvinylpyrrolidone to bis(4-chlorophenyl)sulfone is 1:3-10.

[0009] Preferably, the ultrafiltration membrane is a modified polysulfone ultrafiltration membrane with a pore size of 0.2-100 μm.

[0010] More preferably, in the preparation of the modified polysulfone ultrafiltration membrane, bis(4-chlorophenyl)sulfone is first reacted with a dihydroxy derivative at high temperature, and then reacted with polyvinylpyrrolidone to form a membrane. The dihydroxy derivative includes at least 4,4'-cyclohexylenebisphenol and 2,2-bis(4-hydroxy-3-aminophenyl)propane. This invention introduces 4,4'-cyclohexylenebisphenol and 2,2-bis(4-hydroxy-3-aminophenyl)propane, containing hydrophilic groups, into the molecular framework of the polysulfone ultrafiltration membrane to obtain a polar modified polysulfone ultrafiltration membrane. This modified polysulfone ultrafiltration membrane is then used to pretreat industrial wastewater, removing particulate matter while initially retaining thiosulfate ions. The pretreated wastewater is then passed into an electrodialysis system for further treatment, achieving the separation of thiocyanate ions from organic matter and other salt ions in the industrial wastewater. This effectively improves the removal efficiency of thiosulfate ions in thiocyanate wastewater, thereby increasing the separation and recovery rate of thiocyanate ions.

[0011] More preferably, the mass ratio of bis(4-chlorophenyl) sulfone and 4,4'-cyclohexylbisphenol is 1:0.5-1.

[0012] More preferably, the mass ratio of bis(4-chlorophenyl) sulfone and 2,2-bis(4-hydroxy-3-aminophenyl)propane is 1:0.5-1.

[0013] More preferably, the mass ratio of polyvinylpyrrolidone to bis(4-chlorophenyl)sulfone is 1:3-10.

[0014] More preferably, in the high-temperature reaction, the reaction temperature is 140-160℃.

[0015] More preferably, in the high-temperature reaction, the reaction time is 6-15 hours.

[0016] Preferably, the ultrafiltration membrane includes a polysulfone ultrafiltration membrane or a modified polysulfone ultrafiltration membrane.

[0017] Preferably, the preparation of the ultrafiltration membrane specifically involves,

[0018] A dihydroxy compound and bis(4-chlorophenyl)sulfone are mixed, and N,N-dimethylacetamide is added and stirred to dissolve. Potassium carbonate and toluene are then added, and the mixture is reacted at 140-160℃ for 6-15 hours. The mixture is then cooled to room temperature, and polyvinylpyrrolidone is added. The mixture is stirred at 70-90℃ until completely dissolved, and the mixture is degassed under vacuum to obtain a casting solution. The casting solution is poured onto a glass plate at room temperature, and a flat sheet membrane is prepared using a scraper with a gap of 0.2-1 μm. The glass plate is then immersed in pure water for 20-40 seconds, and the flat sheet membrane is peeled off the glass plate. The flat sheet membrane is washed with pure water 2-5 times to obtain an ultrafiltration membrane.

[0019] More preferably, the dihydroxy compound includes at least one selected from bisphenol A, 4,4'-cyclohexylbisphenol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, and 2-quinolinediol. The present invention further incorporates 2-quinolinediol into the molecular framework of the polysulfone ultrafiltration membrane to obtain a modified polysulfone ultrafiltration membrane. Using this modified polysulfone ultrafiltration membrane to separate and recover thiocyanate ions from industrial wastewater containing thiocyanate ions helps to further improve the removal efficiency of thiosulfate ions in thiocyanate wastewater and increase the separation and recovery rate of thiocyanate ions.

[0020] More preferably, the mass ratio of bis(4-chlorophenyl) sulfone to bisphenol A is 1:1-2.

[0021] More preferably, the mass ratio of bis(4-chlorophenyl) sulfone and 4,4'-cyclohexylbisphenol is 1:0.5-1.

[0022] More preferably, the mass ratio of bis(4-chlorophenyl) sulfone and 2,2-bis(4-hydroxy-3-aminophenyl)propane is 1:0.5-1.

[0023] More preferably, the mass ratio of bis(4-chlorophenyl) sulfone and 2-quinolindiol is 1:0.5-1.

[0024] More preferably, the ratio of bis(4-chlorophenyl) sulfone to N,N-dimethylacetamide is 1 g: 5-10 mL.

[0025] More preferably, the mass ratio of bis(4-chlorophenyl)sulfone to potassium carbonate is 1:0.2-0.7.

[0026] More preferably, the volume ratio of toluene to N,N-dimethylacetamide is 1:2-10.

[0027] More preferably, the mass ratio of polyvinylpyrrolidone to bis(4-chlorophenyl)sulfone is 1:3-10.

[0028] Preferably, the electrodialysis system includes a power supply, a flow meter, a membrane stack, a circulating pump, and a water tank.

[0029] More preferably, the membrane stack includes an anode plate, an anode separator, a cathode separator, a cathode plate, and membrane units. The separator is a separator commonly used in the field of electrodialysis. The anode plate and cathode plate are respectively disposed at both ends of the membrane stack, with the anode plate connected to the positive terminal of the power supply and the cathode plate connected to the negative terminal. The membrane units are located between the anode plate and the cathode plate, and sequentially include anion exchange membranes and repeating unit membranes from the anode plate to the cathode plate; in the repeating unit membranes, unit membranes formed by cation exchange membranes and anion exchange membranes are repeatedly arranged, with the number of repeating unit membranes ranging from 2 to 20. The anode plate, membrane stack, and cathode plate are arranged alternately to form the membrane stack anode chamber, repeating unit chamber, and membrane stack cathode chamber. The repeating unit chamber is a repeating unit chamber formed by dilute and concentrated chambers, and the number of repeating unit chambers corresponds to the number of repeating unit membranes.

[0030] More preferably, the membrane resistance of the membrane unit is 3-6 Ω / cm. 2 It has an exchange capacity greater than 1.3 mol / kg and a pH range of 2-10 for acid and alkali tolerance.

[0031] More preferably, the membrane stack voltage is 5-50V and the membrane stack flow rate is 1000-10000mL / min.

[0032] More preferably, the water tank includes an electrode chamber tank, a concentrate chamber tank, and a distillation chamber tank. The electrode chamber tank stores the electrode solution and is connected via conduits to the cathode and anode chambers of the membrane stack located at both ends of the membrane stack. The concentrate chamber tank stores the separated thiocyanate solution and is connected via conduits to the inlet and outlet of the concentrate chamber located on the membrane stack. The distillation chamber tank stores a mixed solution containing thiocyanate ions, as well as miscellaneous salts and organic matter, and is connected via conduits to the inlet and outlet of the distillation chamber of the membrane stack, so that the mixed solution flows from the distillation chamber tank into the membrane stack and then back into the distillation chamber tank.

[0033] More preferably, the electrode liquid is a sodium sulfate solution with a concentration of 0.05-0.1 mol / L.

[0034] Preferably, a method for separating and recycling thiocyanate ions from industrial wastewater specifically includes:

[0035] S1. Pretreatment of industrial wastewater containing thiocyanate ions: Before pretreatment, the ultrafiltration membrane is pre-pressurized with pure water at 0.1-0.15 MPa for 20-40 minutes, then the pressure is adjusted to 0.05-0.1 MPa for 1 hour. The industrial wastewater containing thiocyanate ions is then passed through a polysulfone ultrafiltration membrane under 0.05-0.1 MPa conditions to obtain pretreated wastewater. The ultrafiltration membrane is a polysulfone ultrafiltration membrane or a modified polysulfone ultrafiltration membrane.

[0036] S2. Thiocyanate ion separation: Pretreated wastewater is introduced into the electrodialysis system. This wastewater is placed in the dilute chamber tank as the dilute solution, ultrapure water enters the concentrate tank as the concentrate solution, and a 0.05-0.1 mol / L sodium sulfate solution enters the electrode tank as the electrode solution. The volumes of the dilute, concentrate, and electrode solutions are kept consistent. The circulation pump is turned on, transferring the electrode solution, concentrate solution, and dilute solution from each tank to their respective compartments within the membrane stack. The DC power supply is turned on, and the solutions entering the membrane stack undergo electrodialysis and ion migration under a constant voltage of 10-30V and a speed of 600-800 rpm. The solutions then flow out from their respective compartments within the membrane stack and return to their respective tanks. The electrode solution, concentrate solution, and dilute solution circulate repeatedly between the tanks and the membrane stack, carrying out the electrodialysis reaction until the conductivity of the electrolyte solution in the concentrate tank decreases to a constant level. The reaction is then stopped, the power is turned off, and the first-stage electrodialysis concentrate effluent is obtained. Then, the effluent from the primary separation concentrate chamber of the electrodialysis system is introduced into the electrodialysis system, and the effluent from the primary separation concentrate chamber of the electrodialysis system is placed in the dilute chamber water tank as a dilute chamber solution. This step is repeated to obtain thiocyanate wastewater.

[0037] S3. Preliminary concentration of thiocyanate ions: The thiocyanate wastewater obtained in step S2 is introduced into the electrodialysis system. The thiocyanate wastewater is placed in the dilute chamber water tank as the dilute solution, and ultrapure water is placed in the concentrate chamber water tank as the concentrate solution. Sodium sulfate solution with a concentration of 0.05-0.1 mol / L is placed in the electrode chamber water tank as the electrode solution. The volumes of the dilute solution, concentrate solution and electrode solution are kept consistent. Turn on the circulation pump to deliver the electrode solution, concentrate solution, and dilute solution stored in each water tank to their respective compartments within the membrane stack. Turn on the DC power supply, and the solutions entering the membrane stack undergo electrodialysis and ion migration under a constant voltage of 10-30V and a speed of 600-800r / min. Then, they flow out from their respective compartments within the membrane stack and return to their respective water tanks. The electrode solution, concentrate solution, and dilute solution circulate back and forth between the water tanks and the membrane stack, carrying out the electrodialysis reaction until the conductivity of the electrolyte solution in the concentrate tank decreases to a constant level. Stop the reaction, turn off the power supply, and obtain a preliminary concentrated solution of thiocyanate ions.

[0038] S4. High concentration of thiocyanate ions and recovery of thiocyanate products: The initial concentrated solution of thiocyanate ions is subjected to RO reverse osmosis treatment using spiral wound membrane elements. The particle size of the separation sieve is 0.1-0.9 nm, and the membrane flux is 10-20 LMH. After RO reverse osmosis treatment, highly concentrated water is obtained. The concentrated water is then cooled and crystallized at a temperature of 0-10℃, a stirring rate of 500-2000 rpm, and a residence time of 1-2 h. The thiocyanate product is obtained after the treatment.

[0039] This invention utilizes a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, 2-quinolinediol, and bis(4-chlorophenyl)sulfone to pretreat industrial wastewater. The wastewater is then treated via electrodialysis, reverse osmosis (RO), and cooling crystallization to obtain thiocyanate. This process yields the following beneficial effects: The modified polysulfone ultrafiltration membrane pretreats the industrial wastewater, removing particulate matter while initially retaining thiosulfate ions. The pretreated wastewater is then passed through an electrodialysis system, effectively improving the removal efficiency of thiosulfate ions in the thiocyanate wastewater and thus increasing the separation and recovery rate of thiocyanate ions. Finally, thiocyanate is obtained through preliminary concentration via electrodialysis, RO reverse osmosis, and cooling crystallization. The method of this invention solves the problem of separating and recovering thiocyanate ions from industrial wastewater containing thiocyanate ions, realizes the full utilization of solid thiocyanate compounds, and achieves zero pollution discharge throughout the entire process, thus promoting the near-zero discharge of industrial wastewater containing thiocyanate ions. Attached Figure Description

[0040] Figure 1 This is a process flow diagram for the separation and resource utilization of thiocyanate ions in industrial wastewater.

[0041] Figure 2 This is a structural diagram of an electrodialysis system.

[0042] Figure 3 A schematic diagram illustrating the principle of separating and recovering thiocyanate ions.

[0043] Figure 4 The concentration of thiocyanate ions in the thiocyanate wastewater is given. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0045] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0046] Example 1:

[0047] The preparation of polysulfone ultrafiltration membranes includes,

[0048] Bisphenol A and bis(4-chlorophenyl)sulfone were mixed, and N,N-dimethylacetamide was added and stirred to dissolve. Potassium carbonate and toluene were then added, and the mixture was reacted at 150°C for 12 hours. The mixture was then cooled to room temperature, and polyvinylpyrrolidone was added. The mixture was stirred at 80°C until completely dissolved, and the solution was degassed under vacuum to obtain the casting solution. The casting solution was poured onto a glass plate at room temperature, and a flat sheet membrane was prepared using a doctor blade with a 0.3 μm gap. The glass plate was then immersed in pure water for 30 seconds, and the flat sheet membrane was peeled off the glass plate. The membrane was washed three times with pure water to obtain a polysulfone ultrafiltration membrane. The mass ratio of bis(4-chlorophenyl)sulfone to bisphenol A was 1:1; the volume ratio of bis(4-chlorophenyl)sulfone to N,N-dimethylacetamide was 1 g:7 mL; the mass ratio of bis(4-chlorophenyl)sulfone to potassium carbonate was 1:0.5; the volume ratio of toluene to N,N-dimethylacetamide was 1:5; and the mass ratio of polyvinylpyrrolidone to bis(4-chlorophenyl)sulfone was 1:6.

[0049] An electrodialysis system includes a power supply, a flow meter, a membrane stack, a circulating pump, and a water tank. The membrane stack comprises an anode plate, a separator, an anion plate, and membrane units. The separator is a commonly used type in electrodialysis. The anode and anion plates are located at opposite ends of the membrane stack; the anode plate is connected to the positive terminal of the power supply, and the anion plate is connected to the negative terminal. Membrane units are located between the anode and anion plates, and from the anode to the anion plate, they sequentially include anion exchange membranes and repeating unit membranes. In the repeating unit membranes, unit membranes formed by cation exchange membranes and anion exchange membranes are arranged repeatedly, with two repeating unit membranes in total. The anode plate, membrane stack, and anion plate alternately form the anode chamber, repeating unit chamber, and cathode chamber of the membrane stack. The repeating unit chambers are repeating unit chambers formed by dilute and concentrated chambers, and the number of repeating unit chambers corresponds to the number of repeating unit membranes. The membrane unit has a membrane resistance of 5 Ω / cm², an exchange capacity of 1.3 mol / kg, and a pH value of 2. The membrane stack voltage is 20V, and the membrane stack flow rate is 2000mL / min. The water tanks include an electrode chamber tank, a concentrate chamber tank, and a distillation chamber tank. The electrode chamber tank stores the electrode solution and is connected via conduits to the cathode and anode chambers of the membrane stack located at both ends of the membrane stack. The concentrate chamber tank stores the separated thiocyanate solution and is connected via conduits to the inlet and outlet of the concentrate chamber located on the membrane stack. The distillation chamber tank stores a mixed solution containing thiocyanate ions, as well as miscellaneous salts and organic matter, and is connected via conduits to the inlet and outlet of the distillation chamber of the membrane stack.

[0050] A method for separating and recycling thiocyanate ions from industrial wastewater, comprising,

[0051] S1. Pretreatment of industrial wastewater containing thiocyanate ions: Before pretreatment, the polysulfone ultrafiltration membrane is pre-pressurized with pure water at 0.15 MPa for 30 min, and then the pressure is adjusted to 0.1 MPa for 1 h. The industrial wastewater containing thiocyanate ions is then passed through the polysulfone ultrafiltration membrane under 0.1 MPa conditions to obtain pretreated industrial wastewater containing thiocyanate ions.

[0052] S2. Thiocyanate ion separation: Pretreated wastewater is introduced into the electrodialysis system. This wastewater is placed in the dilute chamber tank as the dilute solution, ultrapure water enters the concentrate tank as the concentrate solution, and a 0.1 mol / L sodium sulfate solution enters the electrode tank as the electrode solution. The volumes of the dilute, concentrate, and electrode solutions are kept consistent. The circulation pump is turned on, transferring the electrode solution, concentrate solution, and dilute solution from each tank to their respective compartments within the membrane stack. The DC power supply is turned on, and the solutions entering the membrane stack undergo electrodialysis and ion migration under a constant voltage of 20V and a speed of 700 rpm. The solutions then flow out from their respective compartments within the membrane stack and return to their respective tanks. The electrode solution, concentrate solution, and dilute solution circulate repeatedly between the tanks and the membrane stack, carrying out the electrodialysis reaction until the conductivity of the electrolyte solution in the concentrate tank decreases to a constant level. The reaction is then stopped, the power is turned off, and the concentrated effluent from the first-stage electrodialysis separation is obtained. Then, the effluent from the primary separation concentrate chamber of the electrodialysis system is introduced into the electrodialysis system, and the effluent from the primary separation concentrate chamber of the electrodialysis system is placed in the dilute chamber water tank as a dilute chamber solution. This step is repeated to obtain thiocyanate wastewater.

[0053] S3. Preliminary Concentration of Thiocyanate Ions: The thiocyanate wastewater obtained in step S2 is introduced into the electrodialysis system. The thiocyanate wastewater is placed in the dilute chamber water tank as the dilute solution, ultrapure water is placed in the concentrate chamber water tank as the concentrate solution, and a 0.1 mol / L sodium sulfate solution is placed in the electrode chamber water tank as the electrode solution. The volumes of the dilute, concentrate, and electrode solutions are kept consistent. The circulation pump is turned on, transferring the electrode solution, concentrate solution, and dilute solution stored in each water tank to their respective compartments within the membrane stack. The DC power supply is turned on, and the solutions entering the membrane stack undergo electrodialysis and ion migration under a constant voltage of 230V and a speed of 700 r / min. The solutions then flow out from their respective compartments within the membrane stack and return to their respective water tanks. The electrode solution, concentrate solution, and dilute solution circulate repeatedly between the water tanks and the membrane stack, carrying out the electrodialysis reaction until the conductivity of the electrolyte solution in the concentrate chamber water tank decreases to a constant level. The reaction is then stopped, the power supply is turned off, and a preliminary concentrated solution of thiocyanate ions is obtained.

[0054] S4. High concentration of thiocyanate ions and recovery of thiocyanate products: The initial concentrated solution of thiocyanate ions is subjected to RO reverse osmosis treatment using spiral wound membrane elements. The particle size of the separation sieve is 0.45 nm, and the membrane flux is 15 LMH. After RO reverse osmosis treatment, highly concentrated water is obtained. The concentrated water is then cooled and crystallized at a temperature of 5°C, a stirring rate of 1000 rpm, and a residence time of 1 h. The resulting product contains thiocyanate ions.

[0055] Example 2:

[0056] Preparation of modified polysulfone ultrafiltration membranes, including,

[0057] 4,4'-cyclohexylbisphenol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, and bis(4-chlorophenyl)sulfone were mixed and N,N-dimethylacetamide was added and stirred to dissolve. Potassium carbonate and toluene were then added, and the mixture was reacted at 150°C for 12 hours. The mixture was then cooled to room temperature, and polyvinylpyrrolidone was added. The mixture was stirred at 80°C until completely dissolved, and the solution was degassed under vacuum to obtain a casting solution. The casting solution was poured onto a glass plate at room temperature, and a flat sheet membrane was prepared using a scraper with a gap of 0.3 μm. The glass plate was then immersed in pure water for 30 seconds, and the flat sheet membrane was peeled off the glass plate. The flat sheet membrane was washed three times with pure water to obtain a modified polysulfone ultrafiltration membrane. The mass ratio of bis(4-chlorophenyl) sulfone to 4,4'-cyclohexylbisphenol is 1:1; the mass ratio of bis(4-chlorophenyl) sulfone to 2,2-bis(4-hydroxy-3-aminophenyl)propane is 1:1; the volume ratio of bis(4-chlorophenyl) sulfone to N,N-dimethylacetamide is 1 g: 7 mL; the mass ratio of bis(4-chlorophenyl) sulfone to potassium carbonate is 1:0.5; the volume ratio of toluene to N,N-dimethylacetamide is 1:5; and the mass ratio of polyvinylpyrrolidone to bis(4-chlorophenyl) sulfone is 1:6.

[0058] The electrodialysis system is the same as in Example 1.

[0059] A method for separating and recycling thiocyanate ions from industrial wastewater, compared with Example 1, except that the polysulfone ultrafiltration membrane is replaced with the modified polysulfone ultrafiltration membrane prepared in this example, all other conditions are the same as in Example 1.

[0060] Example 3:

[0061] The preparation of the modified polysulfone ultrafiltration membrane was the same as in Example 2, except that the mass ratio of bis(4-chlorophenyl)sulfone and 4,4'-cyclohexylbisphenol was replaced with 1:0.5.

[0062] The electrodialysis system is the same as in Example 1.

[0063] A method for separating and recycling thiocyanate ions from industrial wastewater, compared with Example 1, except that the polysulfone ultrafiltration membrane is replaced with the modified polysulfone ultrafiltration membrane prepared in this example, all other conditions are the same as in Example 1.

[0064] Example 4:

[0065] The preparation of the modified polysulfone ultrafiltration membrane was the same as in Example 2, except that the mass ratio of bis(4-chlorophenyl)sulfone and 2,2-bis(4-hydroxy-3-aminophenyl)propane was replaced with 1:0.5.

[0066] The electrodialysis system is the same as in Example 1.

[0067] A method for separating and recycling thiocyanate ions from industrial wastewater, compared with Example 1, except that the polysulfone ultrafiltration membrane is replaced with the modified polysulfone ultrafiltration membrane prepared in this example, all other conditions are the same as in Example 1.

[0068] Example 5:

[0069] Preparation of modified polysulfone ultrafiltration membranes, including,

[0070] 4,4'-cyclohexylbisphenol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, 2-quinolinediol, and bis(4-chlorophenyl)sulfone were mixed and N,N-dimethylacetamide was added and stirred to dissolve. Potassium carbonate and toluene were then added, and the mixture was reacted at 150°C for 12 hours. The mixture was then cooled to room temperature, and polyvinylpyrrolidone was added. The mixture was stirred at 80°C until completely dissolved, and the solution was degassed under vacuum to obtain a casting solution. The casting solution was poured onto a glass plate at room temperature, and a flat sheet membrane was prepared using a scraper with a gap of 0.3 μm. The glass plate was then immersed in pure water for 30 seconds, and the flat sheet membrane was peeled off the glass plate. The flat sheet membrane was washed three times with pure water to obtain a modified polysulfone ultrafiltration membrane. The mass ratio of bis(4-chlorophenyl) sulfone to 4,4'-cyclohexylbisphenol is 1:1; the mass ratio of bis(4-chlorophenyl) sulfone to 2,2-bis(4-hydroxy-3-aminophenyl)propane is 1:1; the mass ratio of bis(4-chlorophenyl) sulfone to 2-quinolinediol is 1:1; the volume ratio of bis(4-chlorophenyl) sulfone to N,N-dimethylacetamide is 1 g: 7 mL; the mass ratio of bis(4-chlorophenyl) sulfone to potassium carbonate is 1:0.5; the volume ratio of toluene to N,N-dimethylacetamide is 1:5; and the mass ratio of polyvinylpyrrolidone to bis(4-chlorophenyl) sulfone is 1:6.

[0071] The electrodialysis system is the same as in Example 1.

[0072] A method for separating and recycling thiocyanate ions from industrial wastewater, compared with Example 1, except that the polysulfone ultrafiltration membrane is replaced with the modified polysulfone ultrafiltration membrane prepared in this example, all other conditions are the same as in Example 1.

[0073] Example 6:

[0074] The preparation of the modified polysulfone ultrafiltration membrane was the same as in Example 5, except that the mass ratio of bis(4-chlorophenyl)sulfone and 2-quinolinediol was changed to 1:0.5.

[0075] The electrodialysis system is the same as in Example 1.

[0076] A method for separating and recycling thiocyanate ions from industrial wastewater, compared with Example 1, except that the polysulfone ultrafiltration membrane is replaced with the modified polysulfone ultrafiltration membrane prepared in this example, all other conditions are the same as in Example 1.

[0077] Comparative Example 1:

[0078] Preparation of modified polysulfone ultrafiltration membranes, including,

[0079] 4,4'-cyclohexylbisphenol and bis(4-chlorophenyl)sulfone were mixed, and N,N-dimethylacetamide was added and stirred to dissolve. Potassium carbonate and toluene were then added, and the mixture was reacted at 150°C for 12 hours. The mixture was then cooled to room temperature, and polyvinylpyrrolidone was added. The mixture was stirred at 80°C until completely dissolved, and the mixture was degassed under vacuum to obtain a casting solution. The casting solution was poured onto a glass plate at room temperature, and a flat sheet membrane was prepared using a scraper with a gap of 0.3 μm. The glass plate was then immersed in pure water for 30 seconds, and the flat sheet membrane was peeled off the glass plate. The flat sheet membrane was washed three times with pure water to obtain a modified polysulfone ultrafiltration membrane. The mass ratio of bis(4-chlorophenyl) sulfone to 4,4'-cyclohexylbisphenol was 1:1; the volume ratio of bis(4-chlorophenyl) sulfone to N,N-dimethylacetamide was 1 g:7 mL; the mass ratio of bis(4-chlorophenyl) sulfone to potassium carbonate was 1:0.5; the volume ratio of toluene to N,N-dimethylacetamide was 1:5; and the mass ratio of polyvinylpyrrolidone to bis(4-chlorophenyl) sulfone was 1:6.

[0080] The electrodialysis system is the same as in Example 1.

[0081] A method for separating and recycling thiocyanate ions from industrial wastewater, compared with Example 1, except that the polysulfone ultrafiltration membrane is replaced with the modified polysulfone ultrafiltration membrane prepared in this example, all other conditions are the same as in Example 1.

[0082] Comparative Example 2:

[0083] Preparation of modified polysulfone ultrafiltration membranes, including,

[0084] 2,2-bis(4-hydroxy-3-aminophenyl)propane and bis(4-chlorophenyl)sulfone were mixed, and N,N-dimethylacetamide was added and stirred to dissolve. Potassium carbonate and toluene were then added, and the mixture was reacted at 150°C for 12 hours. The mixture was then cooled to room temperature, and polyvinylpyrrolidone was added. The mixture was stirred at 80°C until completely dissolved, and the mixture was degassed under vacuum to obtain a casting solution. The casting solution was poured onto a glass plate at room temperature, and a flat sheet membrane was prepared using a scraper with a gap of 0.3 μm. The glass plate was then immersed in pure water for 30 seconds, and the flat sheet membrane was peeled off the glass plate. The flat sheet membrane was washed three times with pure water to obtain a modified polysulfone ultrafiltration membrane. The mass ratio of bis(4-chlorophenyl) sulfone to 2,2-bis(4-hydroxy-3-aminophenyl)propane is 1:1; the volume ratio of bis(4-chlorophenyl) sulfone to N,N-dimethylacetamide is 1 g: 7 mL; the mass ratio of bis(4-chlorophenyl) sulfone to potassium carbonate is 1:0.5; the volume ratio of toluene to N,N-dimethylacetamide is 1:5; and the mass ratio of polyvinylpyrrolidone to bis(4-chlorophenyl) sulfone is 1:6.

[0085] The electrodialysis system is the same as in Example 1.

[0086] A method for separating and recycling thiocyanate ions from industrial wastewater, compared with Example 1, except that the polysulfone ultrafiltration membrane is replaced with the modified polysulfone ultrafiltration membrane prepared in this example, all other conditions are the same as in Example 1.

[0087] Comparative Example 3:

[0088] Preparation of modified polysulfone ultrafiltration membranes, including,

[0089] 2-Quinolinediol and bis(4-chlorophenyl)sulfone were mixed, and N,N-dimethylacetamide was added and stirred to dissolve. Potassium carbonate and toluene were then added, and the mixture was reacted at 150°C for 12 hours. The mixture was then cooled to room temperature, and polyvinylpyrrolidone was added. The mixture was stirred at 80°C until completely dissolved, and the solution was degassed under vacuum to obtain a casting solution. The casting solution was poured onto a glass plate at room temperature, and a flat sheet membrane was prepared using a scraper with a gap of 0.3 μm. The glass plate was then immersed in pure water for 30 seconds, and the flat sheet membrane was peeled off the glass plate. The flat sheet membrane was washed three times with pure water to obtain a modified polysulfone ultrafiltration membrane. The mass ratio of bis(4-chlorophenyl) sulfone to 2-quinolinediol is 1:1; the volume ratio of bis(4-chlorophenyl) sulfone to N,N-dimethylacetamide is 1 g: 7 mL; the mass ratio of bis(4-chlorophenyl) sulfone to potassium carbonate is 1:0.5; the volume ratio of toluene to N,N-dimethylacetamide is 1:5; and the mass ratio of polyvinylpyrrolidone to bis(4-chlorophenyl) sulfone is 1:6.

[0090] The electrodialysis system is the same as in Example 1.

[0091] A method for separating and recycling thiocyanate ions from industrial wastewater, compared with Example 1, except that the polysulfone ultrafiltration membrane is replaced with the modified polysulfone ultrafiltration membrane prepared in this example, all other conditions are the same as in Example 1.

[0092] Experimental example:

[0093] 1. Detection of thiocyanate ion concentration

[0094] The industrial wastewater from coke oven gas desulfurization was treated according to the method in Example 1, and the concentration of thiocyanate ions in the wastewater was 2300 mg / L. Figure 1 The process flow diagram for the separation and resource utilization of thiocyanate ions in industrial wastewater is as follows: First, the industrial wastewater is pretreated to remove particulate matter and thiosulfate ions, achieving preliminary separation of thiocyanate ions and obtaining pretreated wastewater. Then, the pretreated wastewater is passed into an electrodialysis system to separate thiocyanate ions from organic matter and miscellaneous salt ions, obtaining thiocyanate-containing wastewater. The thiocyanate-containing wastewater is then subjected to RO reverse osmosis and cooling crystallization to achieve the separation and recovery of thiocyanate ions, obtaining thiocyanate products.

[0095] Figure 2 This is a structural diagram of an electrodialysis system, where 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. Figure 3 This is a schematic diagram illustrating the principle of an electrodialysis system for separating and recovering thiocyanate ions. The AEM is an anion exchange membrane, and the CEM is a cation exchange membrane. Under the influence of an electric field, the solutions in the electrode chamber, dilute chamber, and concentrated chamber circulate repeatedly, undergoing electrodialysis and ion migration, thereby separating thiocyanate ions.

[0096] The pretreated wastewater was fed into an electrodialysis system for further treatment to obtain the effluent from the primary separation chamber of the electrodialysis system. The effluent from the primary separation chamber of the electrodialysis system was then fed into the electrodialysis system for further treatment. Thiocyanate wastewater was collected at 0, 5, 15, 30, 60 and 90 minutes of treatment, and ferric chloride was added for complexation. After the reaction was completed, the concentration of thiocyanate ions was determined by ultraviolet spectrophotometry. Figure 4 The concentration of thiocyanate ions in the thiocyanate wastewater is determined by... Figure 4 It can be seen that the thiocyanate concentration increases with the increase of the electrodialysis system treatment time. At the 90-minute treatment, the thiocyanate ion concentration in the obtained thiocyanate wastewater was 1800 mg / L. This indicates that the present invention, by passing the pretreated wastewater into the electrodialysis system, can effectively separate and recover thiocyanate ions.

[0097] 2. Separation and recovery rate of thiocyanate ions

[0098] First, the polysulfone ultrafiltration membrane prepared in Example 1, and the modified polysulfone ultrafiltration membranes prepared in Examples 2-6 and Comparative Examples 1-3 were used to pretreat the industrial wastewater from coke oven gas desulfurization, obtaining pretreated wastewater for the corresponding treatment groups. Then, the pretreated wastewater from each group was passed into an electrodialysis system for further treatment, obtaining the effluent from the first-stage electrodialysis concentration chamber. The effluent from the first-stage electrodialysis concentration chamber was then passed into the electrodialysis system for 90 minutes to obtain the corresponding thiocyanate wastewater. The concentration of thiocyanate ions in the coke oven gas desulfurization industrial wastewater was 2300 mg / L. The separation recovery rate was determined as follows: ferric chloride was added to the thiocyanate wastewater for complexation. After the reaction, the concentration of thiocyanate ions was determined by ultraviolet spectrophotometry, and the thiocyanate ion separation recovery rate was calculated. Thiocyanate ion separation recovery rate (%) = (thiocyanate ion concentration in thiocyanate wastewater / thiocyanate ion concentration in coke oven gas desulfurization industrial wastewater) × 100%. The measurement results are shown in Table 1.

[0099] Table 1. Recovery rate of thiocyanate ions (%)

[0100]

[0101] As shown in Table 1, the thiocyanate ion separation recovery rate of Examples 2-4 of this invention is higher than that of Example 1. This is because in the separation and resource recovery of thiocyanate ions in industrial wastewater, Example 2 first uses a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, and bis(4-chlorophenyl)sulfone to treat the industrial wastewater, followed by electrodialysis. In contrast, Example 1 first uses a polysulfone ultrafiltration membrane prepared by reacting bisphenol A and bis(4-chlorophenyl)sulfone to pretreat the industrial wastewater. The thiocyanate ion separation recovery rate of Example 2 is higher than that of Examples 3-4 because the amounts of 4,4'-cyclohexanediol and 2,2-bis(4-hydroxy-3-aminophenyl)propane used in the preparation of the modified polysulfone ultrafiltration membrane are different. The thiocyanate ion separation and recovery rate in Example 2 was higher than that in Comparative Examples 1-2. This is because, in the separation and resource recovery of thiocyanate ions in industrial wastewater, Comparative Example 1 used only a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol and bis(4-chlorophenyl)sulfone for pretreatment of industrial wastewater, while Comparative Example 2 used only a modified polysulfone ultrafiltration membrane prepared by reacting 2,2-bis(4-hydroxy-3-aminophenyl)propane and bis(4-chlorophenyl)sulfone for pretreatment of industrial wastewater. This demonstrates that the present invention, by synergistically using a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol and 2,2-bis(4-hydroxy-3-aminophenyl)propane for pretreatment of industrial wastewater, followed by electrodialysis, can improve the separation and recovery rate of thiocyanate ions in thiocyanate wastewater.

[0102] The thiocyanate ion separation recovery rate of Examples 5-6 of this invention is higher than that of Example 2 because, in the separation and resource recovery of thiocyanate ions in industrial wastewater, Examples 5-6 used a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, 2-quinolinediol, and bis(4-chlorophenyl)sulfone to pretreat the industrial wastewater before electrodialysis. The thiocyanate ion separation recovery rate of Example 5 is higher than that of Example 6 because the amount of 2-quinolinediol used in the preparation of the modified polysulfone ultrafiltration membrane is different. The thiocyanate ion separation recovery rate of Examples 5-6 is higher than that of Comparative Example 3 because, in the separation and resource recovery of thiocyanate ions in industrial wastewater, Comparative Example 3 only used a modified polysulfone ultrafiltration membrane prepared by reacting 2-quinolinediol and bis(4-chlorophenyl)sulfone to pretreat the industrial wastewater. This indicates that using a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, 2-quinolindiol, and bis(4-chlorophenyl)sulfone for pretreatment of industrial wastewater, followed by electrodialysis, can further improve the separation and recovery rate of thiocyanate ions in thiocyanate wastewater.

[0103] 3. Removal efficiency of thiosulfate ions

[0104] Industrial wastewater containing thiocyanate ions contains a large amount of sulfur-containing impurities, such as thiosulfate ions. These sulfur-containing impurities are generated as byproducts during industrial wastewater treatment, thus affecting the separation and recovery of thiocyanate ions. Therefore, it is necessary to remove sulfur-containing impurities from industrial wastewater containing thiocyanate ions.

[0105] First, the polysulfone ultrafiltration membrane prepared in Example 1, and the modified polysulfone ultrafiltration membranes prepared in Examples 2-6 and Comparative Examples 1-3 were used to pretreat the industrial wastewater from coke oven gas desulfurization, obtaining pretreated wastewater for the corresponding treatment groups. Then, the pretreated wastewater from each group was passed into an electrodialysis system for further treatment, obtaining the effluent from the primary separation chamber of the electrodialysis system. The effluent from the primary separation chamber of the electrodialysis system was then passed into the electrodialysis system for 90 minutes to obtain the corresponding thiocyanate wastewater. The concentration of thiosulfate ions in the coke oven gas desulfurization industrial wastewater was 1128 mg / L. The determination procedure for the thiosulfate ion concentration was as follows: dilute hydrochloric acid was added to the thiocyanate wastewater to adjust the pH to acidic, then sodium tetrachloromercurate, formaldehyde, and pararosaniline hydrochloride were added to react and generate a purple-red complex. The thiosulfate ion concentration (g / L) was determined using a colorimetric method. Thiosulfate ion removal efficiency (%) = (thiosulfate ion concentration in coke oven gas desulfurization industrial wastewater - thiosulfate ion concentration in thiocyanate wastewater) × 100%. The test results are shown in Table 2.

[0106] Table 2. Thiosulfate ion removal efficiency (%)

[0107]

[0108] As shown in Table 2, the thiosulfate ion removal efficiency of Examples 2-4 of this invention is higher than that of Example 1. This is because in the separation and resource utilization of thiocyanate ions in industrial wastewater, Example 2 first uses a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, and bis(4-chlorophenyl)sulfone to treat the industrial wastewater, followed by electrodialysis. In contrast, Example 1 first uses a polysulfone ultrafiltration membrane prepared by reacting bisphenol A and bis(4-chlorophenyl)sulfone to pretreat the industrial wastewater. The thiosulfate ion removal efficiency of Example 2 is higher than that of Examples 3-4 because the amounts of 4,4'-cyclohexanediol and 2,2-bis(4-hydroxy-3-aminophenyl)propane used in the preparation of the modified polysulfone ultrafiltration membrane are different. The thiosulfate ion removal efficiency of Example 2 is higher than that of Comparative Examples 1-2. This is because, in the separation and resource recovery of thiocyanate ions in industrial wastewater, Comparative Example 1 only used a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol and bis(4-chlorophenyl)sulfone for pretreatment of industrial wastewater, while Comparative Example 2 only used a modified polysulfone ultrafiltration membrane prepared by reacting 2,2-bis(4-hydroxy-3-aminophenyl)propane and bis(4-chlorophenyl)sulfone for pretreatment of industrial wastewater. This demonstrates that the present invention, by synergistically using a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol and 2,2-bis(4-hydroxy-3-aminophenyl)propane for pretreatment of industrial wastewater, followed by electrodialysis, can improve the thiosulfate ion removal efficiency in thiocyanate wastewater.

[0109] The thiosulfate ion removal efficiency of Examples 5-6 of this invention is higher than that of Example 2 because, in the separation and resource recovery of thiocyanate ions in industrial wastewater, Examples 5-6 used a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, 2-quinolinediol, and bis(4-chlorophenyl)sulfone to pretreat the industrial wastewater before electrodialysis. The thiosulfate ion removal efficiency of Example 5 is higher than that of Example 6 because the amount of 2-quinolinediol used in the preparation of the modified polysulfone ultrafiltration membrane is different. The thiosulfate ion removal efficiency of Examples 5-6 is higher than that of Comparative Example 3 because, in the separation and resource recovery of thiocyanate ions in industrial wastewater, Comparative Example 3 only used a modified polysulfone ultrafiltration membrane prepared by reacting 2-quinolinediol and bis(4-chlorophenyl)sulfone to pretreat the industrial wastewater. This indicates that using a modified polysulfone ultrafiltration membrane prepared by reacting 4,4'-cyclohexanediol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, 2-quinolindiol, and bis(4-chlorophenyl)sulfone to pretreat industrial wastewater before electrodialysis can further improve the removal efficiency of thiosulfate ions in thiocyanate wastewater.

[0110] The conventional operations in the operation steps of this invention are well known to those skilled in the art and will not be described in detail here.

[0111] The embodiments described above provide a detailed explanation of the technical solution of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for separating and utilizing thiocyanate ions in industrial wastewater, comprising: First, industrial wastewater containing thiocyanate ions is pretreated using an ultrafiltration membrane. Then, the pretreated wastewater is passed into an electrodialysis system for electrodialysis to separate and recover the thiocyanate ion-containing product. The ultrafiltration membrane is a modified polysulfone ultrafiltration membrane. In the preparation of the modified polysulfone ultrafiltration membrane, bis(4-chlorophenyl) sulfone is first reacted with a dihydroxy derivative at high temperature, and then reacted with polyvinylpyrrolidone to form a membrane. The dihydroxy derivative is 4,4'-cyclohexylbisphenol, 2,2-bis(4-hydroxy-3-aminophenyl)propane, and 2-quinolinediol. The mass ratio of bis(4-chlorophenyl) sulfone to 4,4'-cyclohexylbisphenol is 1:0.5-1; the mass ratio of bis(4-chlorophenyl) sulfone to 2,2-bis(4-hydroxy-3-aminophenyl)propane is 1:0.5-1; and the mass ratio of bis(4-chlorophenyl) sulfone to 2-quinolinediol is 1:0.5-1.

2. The method for separating and utilizing thiocyanate ions in industrial wastewater according to claim 1, characterized in that, The mass ratio of polyvinylpyrrolidone to bis(4-chlorophenyl)sulfone is 1:3-10.

3. The method for separating and utilizing thiocyanate ions in industrial wastewater according to claim 1, characterized in that, The modified polysulfone ultrafiltration membrane has a pore size of 0.2-100 μm.

4. The method for separating and utilizing thiocyanate ions in industrial wastewater according to claim 1, characterized in that, In the high-temperature reaction, the reaction temperature is 140-160℃.

5. The method for separating and resource-based treatment of thiocyanate ions in industrial wastewater according to claim 1, characterized in that, In the high-temperature reaction, the reaction time is 6-15 hours.

Images