A system and method for resource recovery of industrial wastewater

Abstract

The application provides a system for producing acid and alkali by coupling a resin packed bed with a bipolar membrane electrodialysis and a method for resourceful treatment of industrial wastewater. The system for producing acid and alkali by coupling a resin packed bed with a bipolar membrane electrodialysis comprises a bipolar membrane electrodialysis device and a resin packed bed arranged in a salt chamber of the bipolar membrane electrodialysis device, wherein the resin packed bed is filled with at least two selected from chelating resin, macroporous resin and weak acid cation ion exchange resin. The system for producing acid and alkali by coupling a resin packed bed with a bipolar membrane electrodialysis can be operated stably for a long time, promotes engineering application of the technology for producing acid and alkali by bipolar membrane electrodialysis to resourceful treatment of high-salt industrial wastewater, and has dual benefits of environment and economy.

Description

Technical Field

[0001] This invention relates to systems and methods for the resource recovery treatment of industrial wastewater, and more particularly to systems and methods for the resource recovery treatment of industrial wastewater using a bipolar membrane electrodialysis apparatus comprising a coupled resin packed bed. Background Technology

[0002] The resource utilization of high-salinity industrial wastewater has become an increasingly popular trend. This can not only minimize the amount of wastewater discharged and environmental risks, but also reduce the pressure on ecosystems caused by freshwater extraction.

[0003] The salts in high-salinity industrial wastewater are mostly composed of Cl. - SO4 2- Na + Ca 2+ This type of wastewater is composed of various components, including soluble inorganic salts (>1%) and small amounts of recalcitrant organic matter. Its complex composition, high concentrations of recalcitrant organic matter and toxic pollutants, not only causes environmental pollution and equipment corrosion but also leads to soil salinization. Furthermore, it is difficult and costly to treat. This type of wastewater primarily originates from industries such as coal-fired power plants, chemicals, metallurgy, pharmaceuticals, printing and dyeing, papermaking, food processing, and seawater desalination.

[0004] The main methods for treating high-salinity industrial wastewater include thermal methods and membrane concentration technologies. Thermal methods include multi-stage flash evaporation (MSF), multi-effect evaporation (MED), and mechanical vapor recompression (MVR), while membrane concentration technologies include nanofiltration (NF), reverse osmosis (RO), electrodialysis (ED), membrane distillation (MD), and forward osmosis (FO). Current treatment methods mainly involve highly concentrated or further evaporated and crystallized high-salinity industrial wastewater to form industrial salt. For example, patent application CN201910277700.8 provides a complete set of equipment for external circulation evaporation and separation of high-salinity industrial wastewater, which can effectively improve the concentration ratio during the heating and evaporation of high-salinity wastewater. Patent application CN201921425937.8 discloses a high-salinity industrial wastewater and greywater reuse treatment device, which features strong adaptability to raw water, high freshwater recovery rate, high concentration ratio of concentrated water, and good effluent quality. Patent application CN201920906761.1 provides a high-salinity industrial wastewater resource utilization and reuse device that combines evaporation and concentration with condensation and sedimentation, enabling rapid recovery and utilization of waste salt. However, existing high-salinity industrial wastewater treatment methods not only have high investment and operating costs but also generate large amounts of low-value industrial waste salt and pose a risk of secondary pollution.

[0005] Bipolar membranes (BPMs) are a novel type of ion-exchange composite membrane, composed of a cation exchange layer, an interfacial hydrophilic layer (catalytic layer), and an anion exchange layer. Under the influence of a DC electric field, the bipolar membrane can dissociate water molecules, yielding H+ on both sides of the membrane. + Ions and OH - Ions. Utilizing this characteristic, a bipolar membrane electrodialysis system, which combines bipolar membranes with other anion and cation exchange membranes, can convert salts in aqueous solutions into their corresponding acids and bases without introducing new components. This method is called bipolar membrane electrodialysis (BMED). Currently, researchers have attempted to apply bipolar membrane electrodialysis technology to the resource recovery and treatment of high-salinity industrial wastewater. For example, patent application CN202021224132.X provides a high-salinity industrial wastewater resource recovery and treatment system, including a reverse osmosis device and a bipolar membrane electrodialysis device. Its feature is that an induced crystallization device is set between the two to remove hard ions and heavy metal ions in the wastewater, and the bipolar membrane electrodialysis is used to convert the salt in the wastewater into high-value acids and alkalis. Patent application CN202010307007.3 proposes a high-salinity wastewater bipolar membrane electrodialysis device, treatment system and method, which adopts multi-salt chamber operation to achieve resource recovery treatment of high-salinity wastewater. Patent application CN201510851548.1 integrates Fenton technology and bipolar membrane technology into a treatment device, which can remove salt and reduce the COD of wastewater, and generate corresponding acids and alkalis for recycling. Because bipolar membrane electrodialysis systems require very low concentrations (<1 mg / L) of calcium, magnesium, and high-valence metal ions in the influent to prevent scaling and membrane fouling, some existing treatment technologies have proposed incorporating induced crystallization or combining with Fenton technology. However, these technologies still cannot ensure that the residual concentrations of calcium, magnesium, and other high-valence metal ions, as well as the content of organic impurities in high-salt industrial wastewater, meet the influent requirements of bipolar membrane electrodialysis systems.

[0006] Therefore, even after pretreatment and impurity removal, high-salt industrial wastewater still contains small amounts of calcium, magnesium, and other heavy metal high-valence ions, as well as recalcitrant organic matter. Conventional bipolar membrane electrodialysis treatment of high-salt industrial wastewater easily leads to membrane fouling, affecting the lifespan of all ion-binding membranes, including the bipolar membrane, and preventing the bipolar membrane electrodialysis system from operating stably for extended periods. After reviewing extensive literature and conducting in-depth research, the inventors of this invention have developed a bipolar membrane electrodialysis salt-to-acid / alkali production device and method with a coupled resin-filled bed. The device utilizes the selectivity of ion exchange resin to adsorb and intercept residual small amounts of calcium, magnesium, and other heavy metal high-valence ions, as well as recalcitrant organic matter, in the pretreated high-salt industrial wastewater, inhibiting the adsorption of high-valence ions and other impurities on the ion exchange membrane surface, thus preventing membrane fouling. Furthermore, when the salt concentration in the salt chamber is low, the resin-filled bed can enhance the transmembrane migration of target ions through "resin channels," improving the current efficiency and operational stability of the bipolar membrane electrodialysis salt-to-acid / alkali production process. This invention solves the problems of scaling and severe membrane fouling in conventional bipolar membrane electrodialysis treatment of high-salt industrial wastewater, and the difficulty in long-term stable operation of the system, and promotes the engineering application of bipolar membrane electrodialysis salt-to-acid and alkali technology in the resource-based treatment of high-salt industrial wastewater. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a bipolar membrane electrodialysis salt production device and method with a coupled resin-packed bed. The device utilizes the selectivity of the resin in the resin-packed bed to adsorb and intercept residual trace amounts of calcium, magnesium, and other heavy metal high-valence ions, as well as recalcitrant organic matter, in high-salt industrial wastewater after impurity pretreatment. This inhibits the adsorption of high-valence ions and other impurities on the ion exchange membrane surface, thus preventing membrane fouling. Furthermore, when the salt concentration in the salt chamber is low, the resin-packed bed can enhance the transmembrane migration of target ions through "resin channels," improving the current efficiency and operational stability of the bipolar membrane electrodialysis salt production process. This invention solves the problems of scaling, severe membrane fouling, and difficulty in long-term stable operation of conventional bipolar membrane electrodialysis for treating high-salt industrial wastewater. It promotes the engineering application of bipolar membrane electrodialysis salt production technology in the resource-based treatment of high-salt industrial wastewater, offering both environmental and economic benefits.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] According to a first aspect of the present invention, a system for producing acid and alkali from salts using a bipolar membrane electrodialysis bed coupled with a resin-packed bed is provided, wherein the system comprises:

[0010] Bipolar membrane electrodialysis device; and

[0011] A resin-packed bed is disposed in the salt chamber of a bipolar membrane electrodialysis device, wherein the resin-packed bed is filled with at least two of the following: chelating resin, macroporous resin, and weakly acidic cation exchange resin; preferably, the resin-packed bed is simultaneously filled with chelating resin, macroporous resin, and weakly acidic cation exchange resin.

[0012] Preferably, the resin-filled bed is filled in layers or mixed evenly before filling.

[0013] Preferably, when filling after mixing, the volume ratio of chelating resin, macroporous resin and weakly acidic cation exchange resin is 1:0.5-1.5:0.5-1.5; or when filling in layers, the layer thickness ratio of chelating resin, macroporous resin and weakly acidic cation exchange resin is 1:0.8-1.3:0.8-1.3.

[0014] Chelating resins are a class of resins that selectively adsorb and chelate metal ions such as copper, lead, zinc, tin, nickel, cobalt, manganese, nickel, antimony, mercury, cadmium, and bismuth in industrial wastewater.

[0015] Preferably, the chelating resin is selected from one or more of CH-90a, D110, D152, D401, D403, D418 and D564.

[0016] Weakly acidic cation exchange resins are a class of resins containing weakly acidic exchange groups such as carboxylic acid groups (—COOH), phosphate groups (—PO2H2), and phenolic groups. They are used to selectively adsorb and remove calcium, magnesium, and some high-valence metal ions from wastewater.

[0017] Preferably, the weakly acidic cation exchange resin is selected from one or more of styrene-based, acrylic-based, and phenolic-based resins. As an example, weakly acidic cation exchange resin D113 can be used.

[0018] Preferably, the macroporous resin is selected from strongly acidic cation exchange resins and strongly basic anion exchange resins. Its role in the bipolar membrane electrodialysis wastewater treatment process is to form "resin channels" at low concentrations to promote the exchange of Na+. + and Cl - Transmembrane migration of monovalent ions.

[0019] Preferably, the strongly acidic cation exchange resin is selected from one or more of styrene-based, acrylic-based, and phenolic-based resins.

[0020] Preferably, the strongly basic anion exchange resin is selected from one or more of styrene-based, acrylic-based, and epoxy-based resins.

[0021] As an example, macroporous resin D101-II can be used.

[0022] Preferably, the height of the filling bed is the same as the height of the salt chamber partition; more preferably, the height of the resin filling bed is 3 to 100 mm, for example, 3 mm, 8 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm or 100 mm.

[0023] Preferably, the length and width of the resin-filled bed are the same as the length and width of the ion exchange membrane in the bipolar membrane electrodialysis device.

[0024] Preferably, the bipolar membrane electrodialysis device includes an anode, a bipolar membrane (BPM), an anion exchange membrane (AM), a cation exchange membrane (CM), a bipolar membrane (BPM), and a cathode arranged sequentially, as well as a waterproof, leak-proof, and current-preventing partition for supporting the bipolar membrane, anion exchange membrane, cation exchange membrane, and bipolar membrane and for forming acid chambers, salt chambers, and alkali chambers. A salt chamber is formed between the cation exchange membrane and the anion exchange membrane, an acid chamber is formed between the anion exchange membrane and the bipolar membrane, an alkali chamber is formed between the cation exchange membrane and the bipolar membrane, and electrode chambers are formed between the cathode and the bipolar membrane, and between the anode and the bipolar membrane.

[0025] Waterproof, leak-proof, and electrical leakage-proof partitions can prevent water from seeping into and leaking electricity between different compartments.

[0026] Preferably, the cation exchange membrane (CM) is a low-permeability, fouling-resistant cation exchange membrane, which is effective against water molecules and OH-. - Ions have low permeability.

[0027] Preferably, the anion exchange membrane (AM) is a low-permeability, fouling-resistant anion exchange membrane (AM), which is effective against water molecules and H+. + Ions have low permeability.

[0028] Preferably, the bipolar membrane in the bipolar membrane electrodialysis device is composed of a cation exchange layer, an interfacial hydrophilic layer (catalytic layer), and an anion exchange layer. Water molecules diffuse into the catalytically active interfacial hydrophilic layer and are dissociated into OH- under the influence of an electric field. - Ions and H + Ions, under the influence of an electric field, pass through the anion exchange layer and cation exchange layer of the bipolar membrane and then enter the alkaline or acidic chamber.

[0029] Preferably, the anion exchange membrane (AM), cation exchange membrane (CM), and bipolar membrane (BPM), as well as the salt chamber, acid chamber, and alkali chamber located therein, constitute a membrane repeating unit. The bipolar membrane electrodialysis device includes multiple membrane repeating units, more preferably 2 to 100, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 units.

[0030] Preferably, the cathode is a titanium-based electrode, more preferably a titanium plate electrode or a titanium mesh electrode.

[0031] Preferably, the anode is a titanium-based electrode with a corrosion-resistant coating. More preferably, the corrosion-resistant coating of the titanium-based electrode is a coating comprising a metal oxide or a composite metal oxide selected from ruthenium, iridium, niobium, and tantalum, and further subjected to platinum plating. This anode has a low hydrogen and oxygen evolution overpotential; preferably, the titanium-based electrode is a titanium plate or titanium mesh.

[0032] Preferably, the effective areas of the cathode and anode are the same as the effective area of ​​a single ion exchange membrane.

[0033] Preferably, the cathode and anode are fixed in the electrode frame, forming an electrode chamber together with the adjacent waterproof and leak-proof partition and bipolar membrane.

[0034] Preferably, the partition between the alkali chamber and the acid chamber of the bipolar membrane electrodialysis device is provided with a mesh to promote turbulence and uniform water distribution in the solution in the alkali chamber and the acid chamber; the partition in the salt chamber does not have a mesh and is directly filled with a resin packed bed.

[0035] Preferably, the industrial wastewater is coal chemical wastewater.

[0036] According to a second aspect of the present invention, a method for the resource-based treatment of industrial wastewater is provided, comprising the following steps:

[0037] 1) Pre-treat industrial wastewater to reduce the concentration of organic matter to less than or equal to 40 mg / L, the total concentration of calcium and magnesium ions and other heavy metal ions to less than or equal to 20 mg / L, and the pH value to 6-8.

[0038] 2) The industrial wastewater pretreated in step 1) is electrolyzed using a bipolar membrane electrodialysis salt-to-alkali system with a coupled resin packed bed as described in this invention to obtain alkali and acid.

[0039] Preferably, the acid obtained is selected from HCl, HNO3 or H2SO4.

[0040] Preferably, the prepared alkali is selected from NaOH, KOH or ammonia.

[0041] Preferably, the pretreatment is selected from one or more of chemical precipitation, membrane separation, activated carbon adsorption, electrodeposition, electrodialysis and electroadsorption.

[0042] In this invention, when pretreated industrial wastewater flows through the resin-packed bed in a bipolar membrane electrodialysis membrane stack, residual calcium and magnesium ions or other high-valence heavy metal ions, recalcitrant organic matter and other impurities in the industrial wastewater can be selectively adsorbed by the ion exchange resin, and the concentration of calcium and magnesium ions or other high-valence heavy metal ions in the effluent drops to below 20 mg / L, and the concentration of organic matter is below 40 mg / L.

[0043] The bipolar membrane electrodialysis salt-to-alkali system with coupled resin packed bed according to the present invention can treat not only industrial wastewater with high salt concentration, but also industrial wastewater with low salt concentration.

[0044] When the salt concentration of wastewater in the salt chamber drops to 50 g / L or lower, the resistance of the salt chamber solution increases, making it difficult for the system to continue operating. However, in this invention, because the ion exchange resins in the resin-packed bed are tightly connected, they can form "resin channels," which can promote the migration and transfer of target ions in the salt chamber solution, thereby improving the current efficiency and operational stability of bipolar membrane electrodialysis for acid and alkali production.

[0045] Preferably, the salt concentration in the industrial wastewater is 20–200 g / L, more preferably 50–200 g / L.

[0046] Preferably, when the resin in the resin-filled bed is saturated with adsorption, the prepared acid and alkali are used to perform cyclic chemical cleaning of the resin-filled bed until the performance of the ion exchange resin-filled bed is restored.

[0047] Preferably, the waste liquid generated from the chemical cleaning of the resin-filled bed is returned to the industrial wastewater for pretreatment to remove calcium and magnesium ions, high-valence heavy metal ions, and other impurities before entering the bipolar membrane electrodialysis salt-to-alkali system with coupled resin-filled bed according to the present invention.

[0048] Preferably, the industrial wastewater is coal chemical wastewater.

[0049] Beneficial effects

[0050] The present invention has at least the following beneficial effects:

[0051] (1) The bipolar membrane electrodialysis salt production system with coupled resin packed bed described in this invention realizes the coupling and integration of resin packed bed and bipolar membrane electrodialysis device, which can suppress membrane fouling caused by heavy metal ions and recalcitrant organic matter in industrial wastewater, improve the tolerance of bipolar membrane electrodialysis system to calcium and magnesium in high-salt industrial wastewater and impurities such as high-valence heavy metal ions and recalcitrant organic matter, and improve the operational stability of bipolar membrane electrodialysis salt production unit;

[0052] (2) The bipolar membrane electrodialysis salt acid and alkali production system of the coupled resin packed bed described in this invention can realize that the unit energy consumption of converting salt into corresponding acid and alkali in the bipolar membrane electrodialysis salt acid and alkali production device of the coupled resin packed bed is less than 2.5 kWh / kg alkali, and the continuous stable operation time is extended by more than 1 times.

[0053] (3) The bipolar membrane electrodialysis salt production system with coupled resin packed bed described in this invention solves the problems of easy scaling and serious membrane fouling when using conventional bipolar membrane electrodialysis to treat high-salt industrial wastewater, and the difficulty in long-term stable operation of the system. It can promote the engineering application of bipolar membrane electrodialysis salt production technology in the resource-based treatment of high-salt industrial wastewater.

[0054] (4) The bipolar membrane electrodialysis salt production method of the coupling resin packed bed described in this invention can not only treat industrial wastewater with high salt concentration, but also industrial wastewater with low salt concentration, and has wide applicability.

[0055] (5) This invention solves the problem that conventional bipolar membrane electrodialysis treatment of high-salt industrial wastewater is prone to scaling, resulting in serious membrane fouling and difficulty in long-term stable operation of the system. It can promote the engineering application of bipolar membrane electrodialysis salt to acid and alkali technology in the resource-based treatment of high-salt industrial wastewater, and has dual environmental and economic benefits. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of a bipolar membrane electrodialysis salt production system with a coupled resin packed bed according to the present invention. Detailed Implementation

[0057] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0058] like Figure 1 As shown, the bipolar membrane electrodialysis salt production system with coupled resin-packed bed according to the present invention includes a cation exchange membrane (CM), an anion exchange membrane (AM), a bipolar membrane (BPM), a waterproof and leak-proof separator, and two titanium-based electrodes with low hydrogen and oxygen evolution overpotentials and corrosion-resistant coatings located on both sides. A salt chamber is formed between the cation exchange membrane and the anion exchange membrane, an acid chamber is formed between the anion exchange membrane and the bipolar membrane, an alkali chamber is formed between the cation exchange membrane and the bipolar membrane, and an electrode chamber is formed between the titanium-based electrode with the corrosion-resistant coating and the bipolar membrane. The salt chamber is filled with a resin-packed bed composed of resin. The waterproof and leak-proof separator serves as the system frame for fixing the cation exchange membrane, anion exchange membrane, and bipolar membrane. The bipolar membrane electrodialysis salt production system with coupled resin-packed bed according to the present invention may include multiple membrane repeating units (e.g., anion exchange membrane, cation exchange membrane, and bipolar membrane) composed of anion exchange membrane, cation exchange membrane, and bipolar membrane. Figure 1(As shown by the dotted lines in the diagram). The salt chamber, alkali chamber, acid chamber, and electrode chamber are connected to the brine tank, alkali tank, acid tank, and electrode water tank respectively via pipelines, so that pretreated industrial brine, dilute alkali solution, dilute acid solution, and electrode water can be pumped into the salt chamber, alkali chamber, and acid chamber respectively by a delivery pump.

[0059] The titanium-based electrode with a corrosion-resistant coating is connected to a regulated DC power supply via a circuit.

[0060] Cation exchange membranes (CM) are low-permeability, fouling-resistant cation exchange membranes, and anion exchange membranes (AM) are low-permeability, fouling-resistant anion exchange membranes. Low-permeability, fouling-resistant cation exchange membranes (CM) are effective against water molecules and OH-. - Ions have low permeability characteristics; low permeability and fouling-resistant anion exchange membranes (AM) can effectively absorb water molecules and H+. + Ions have low permeability.

[0061] The bipolar membrane is composed of a cation exchange layer, an interfacial hydrophilic layer (catalytic layer), and an anion exchange layer. Water molecules diffuse into the catalytically active interfacial hydrophilic layer and are dissociated into OH- under the influence of an electric field. - Ions and H + Ions, under the influence of an electric field, pass through the anion exchange layer and cation exchange layer of the bipolar membrane and then enter the alkaline or acidic chamber.

[0062] Waterproof, leak-proof, and anti-electric leakage partitions can prevent water from seeping between different compartments and prevent membrane stack leakage; the partitions between the alkali and acid compartments have a mesh to promote turbulence and uniform water distribution in the solutions in the alkali and acid compartments; the partitions in the salt compartment do not have a mesh and are directly filled with resin-filled beds.

[0063] A titanium-based electrode with a corrosion-resistant coating is fixed within an electrode frame, forming an electrode chamber together with an adjacent waterproof and leak-proof partition and a bipolar membrane. The coating of the corrosion-resistant titanium-based electrode is a composite metal oxide coating of ruthenium, iridium, and niobium. The oxide-coated electrode is further plating platinum to reduce the hydrogen evolution and oxygen evolution overpotentials of the electrode.

[0064] The titanium-based electrode is a titanium plate, and the effective area of ​​the electrode is the same as the effective area of ​​the ion exchange membrane.

[0065] The bipolar membrane electrodialysis salt-to-alkali device with coupled resin packed bed described in this invention is used to realize the resource-based treatment of industrial wastewater. The method includes the following steps: (1) The industrial wastewater is first pretreated by conventional physicochemical methods to significantly reduce the impurities such as organic matter, calcium, magnesium and other heavy metal ions in the industrial wastewater; (2) When the pretreated and impurity-removed industrial wastewater passes through the salt chamber, the monovalent cations in the wastewater, such as M + or anion A n-Each substance enters the alkaline or acidic chamber through a cation exchange membrane or an anion exchange membrane, and reacts with the OH- generated by the hydrolysis of the bipolar membrane in this invention. - and H + Ions combine to form MOH and H. n A. Residual calcium and magnesium ions, high-valence heavy metal ions, and other impurities in wastewater can be adsorbed and intercepted by the resin in the packed resin bed, reducing the concentration of calcium and magnesium ions or other high-valence heavy metal ions in the effluent to <1 mg / L and the organic matter concentration to <10 mg / L. This significantly inhibits the adsorption of high-valence ions and other impurities on the ion exchange membrane surface, thus preventing membrane fouling. When most of the ions in the industrial wastewater have transferred to the alkali or acid chamber, resulting in a low salt concentration in the salt chamber (<50 g / L or lower), the packed resin bed can enhance the transmembrane migration of target ions in the wastewater through "resin channels," improving the current efficiency and operational stability of bipolar membrane electrodialysis for acid and alkali production. When the ion exchange resin packed bed in this invention becomes saturated with adsorption of heavy metals and impurities in high-salt industrial wastewater, the resin packed bed is chemically cleaned alternately with the acid and alkali prepared by the device of this invention until the performance of the ion exchange resin packed bed is restored. The waste liquid generated from the chemical cleaning of the ion exchange resin packed bed is returned to the physicochemical treatment unit for high-salt industrial wastewater for reprocessing, so that calcium and magnesium ions, high-valence heavy metal ions and other impurities are removed from the high-salt wastewater.

[0066] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Therefore, the following detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0067] Example 1

[0068] A method for producing acids and alkalis from bipolar membrane electrodialysis salts using a coupled resin packed bed includes the following steps:

[0069] (1) The industrial wastewater comes from the coal chemical industry. After conventional impurity removal pretreatment, the industrial wastewater is then desalinated by membrane filtration using ultrafiltration + nanofiltration. The nanofiltration permeate is then concentrated by conventional electrodialysis, thereby obtaining the industrial wastewater further treated by this invention. The soluble inorganic salts in this pretreated industrial wastewater are mainly NaCl salts, with a salt content of approximately 136 g / L. The residual organic matter COD value in the wastewater is 35 mg / L, the calcium and magnesium hardness and other heavy metal ion concentrations are 17 mg / L, and the pH is 7.5.

[0070] (2) The pretreated industrial wastewater is pumped into the salt chamber of a bipolar membrane electrodialysis salt production system with a coupled resin-packed bed having the above-described structure. The resin-packed bed is constructed by mixing three resins—Tulsimer chelating resin CH-90Na, weakly acidic cation exchange resin D113, and macroporous resin D101-II—in equal volume ratio and filling them into the bipolar membrane electrodialysis salt chamber, thus forming a composite resin-packed bed with a thickness of 10 mm. This coupled resin-packed bed bipolar membrane electrodialysis salt production system includes 10 membrane repeating units; the effective area of ​​a single ion exchange membrane is 50 cm². 2 The voltage of the regulated DC power supply is controlled at 40V. The solutions in the salt, alkali and acid chambers are driven by a pump and the flow rate is controlled at 50L / h. They circulate through different compartments. The volume ratio of the industrial wastewater tank to the alkali and acid tanks is controlled at 3:1. The bipolar membrane electrodialysis anode uses a titanium-based electrode with a ruthenium-iridium oxide coating, and the cathode uses a common titanium plate electrode.

[0071] After continuous operation for 120 minutes, the concentration of NaOH generated in the alkali chamber of this coupled resin packed bed bipolar membrane electrodialysis salt production system is >2.5 mol / L, and the concentration of HCl generated in the acid chamber is about 1.98 mol / L. The unit energy consumption for converting NaCl salt in industrial wastewater into the corresponding acid and alkali is 2.1 kWh / kg salt. Moreover, after continuous operation for more than 24 hours, the salt conversion efficiency, current efficiency, and unit energy consumption of this coupled resin packed bed bipolar membrane electrodialysis salt production system remain almost unchanged.

[0072] Example 2

[0073] Except that the acid and base were prepared in the same manner as in Example 1, except that the Tulsimer chelating resin CH-90Na, the domestic weak acid cation exchange resin D113 and the domestic macroporous resin D101-II were uniformly filled into the salt chamber of the bipolar membrane electrodialysis device in a layered manner with each layer having the same thickness.

[0074] After 120 minutes of continuous operation, the concentration of NaOH generated in the alkali chamber was >2.43 mol / L, and the concentration of HCl generated in the acid chamber was approximately 1.97 mol / L. The unit energy consumption for converting NaCl salt in industrial wastewater into the corresponding acid and alkali was 2.2 kWh / kg salt. Furthermore, after more than 24 hours of continuous operation, the salt conversion efficiency, current efficiency, and unit energy consumption of this coupled resin-filled bipolar membrane electrodialysis salt acid and alkali production system showed almost no change. This indicates that whether the resin in the packed bed is uniformly or layered has no significant impact on the performance of the bipolar membrane electrodialysis salt acid and alkali production system.

[0075] Example 3

[0076] Acids and bases were prepared in the same manner as in Example 1, except that macroporous resin D101-II was used to fill the salt chamber of the bipolar membrane electrodialysis device.

[0077] After 120 minutes of continuous operation, the concentration of NaOH generated in the alkali chamber was >2.01 mol / L, and the concentration of HCl generated in the acid chamber was approximately 1.83 mol / L. The unit energy consumption for converting NaCl salt in industrial wastewater into the corresponding acid and alkali was 2.39 kWh / kg salt. Furthermore, after 20 hours of continuous operation, the salt conversion efficiency, current efficiency, and unit energy consumption of this bipolar membrane electrodialysis system with coupled resin packed bed significantly decreased. A possible reason is that the single ion exchange resin was not effective in removing impurities from high-salt industrial wastewater. Calcium, magnesium, and other high-valence heavy metal ions in high-salt wastewater can form scale and cause membrane fouling on the ion exchange membrane surface, thus leading to a significant decline in the performance of the bipolar membrane electrodialysis system for acid and alkali production.

[0078] Comparative Example 1

[0079] The acid and base were prepared in the same manner as in Example 1, except that the salt chamber in the bipolar membrane electrodialysis device was not filled with resin.

[0080] After 120 minutes of continuous operation, the concentration of NaOH generated in the alkali chamber was >1.94 mol / L, and the concentration of HCl generated in the acid chamber was approximately 1.76 mol / L. The unit energy consumption for converting NaCl salt in industrial wastewater into the corresponding acid and alkali was 2.72 kWh / kg salt. Moreover, after 10 hours of continuous operation, the salt conversion efficiency, current efficiency, and unit energy consumption of the bipolar membrane electrodialysis acid and alkali production system decreased significantly. It is speculated that this is due to the adsorption of calcium, magnesium, and other heavy metal ions, as well as recalcitrant organic matter, on the surface of the ion exchange membrane in high-salt industrial wastewater, forming scale and causing membrane fouling. Therefore, it has a significant impact on the performance of bipolar membrane electrodialysis acid and alkali production, especially the operational stability of the bipolar membrane electrodialysis acid and alkali production system.

[0081] Example 4

[0082] Except for the use of pretreated industrial wastewater with the following parameters in the bipolar membrane electrodialysis salt production system using a coupled resin packed bed, the acid and alkali are prepared by the same method as in Example 1, wherein the soluble inorganic salts in the pretreated industrial wastewater are mainly NaCl salts with a salt content of approximately 123 g / L, while the residual organic matter COD value in the wastewater is 17 mg / L, the calcium and magnesium hardness and other heavy metal ion concentrations are 0.8 mg / L, and the pH is 6.9.

[0083] After 120 minutes of continuous operation, the concentration of NaOH generated in the alkali chamber was 2.19 mol / L, and the concentration of HCl generated in the acid chamber was approximately 1.98 mol / L. The unit energy consumption for converting NaCl salt in industrial wastewater into the corresponding acid and alkali was 2.05 kWh / kg NaOH. Moreover, the bipolar membrane electrodialysis salt acid and alkali production system of this coupled resin packed bed operated continuously for more than 24 hours, and the performance of the system, such as salt conversion efficiency, current efficiency, and unit energy consumption, remained almost unchanged.

[0084] Comparative Example 2

[0085] The acid and base were prepared in the same manner as in Example 4, except that the salt chamber in the bipolar membrane electrodialysis device was not filled with resin.

[0086] After 120 minutes of continuous operation, the concentration of NaOH generated in the alkali chamber was 1.91 mol / L, and the concentration of HCl generated in the acid chamber was approximately 1.78 mol / L. The unit energy consumption for converting NaCl salt in industrial wastewater into the corresponding acid and alkali was 3.26 kWh / kg NaOH. Moreover, after the bipolar membrane electrodialysis salt acid and alkali production system of this coupled resin packed bed had been running continuously for more than 24 hours, the salt conversion efficiency, current efficiency, and unit energy consumption of the system showed a gradual downward trend.

Claims

1. A bipolar membrane electrodialysis system for producing acids and alkalis using a coupled resin-packed bed, wherein, The system includes: Bipolar membrane electrodialysis device; and A resin-packed bed is installed in the salt chamber of a bipolar membrane electrodialysis device, wherein the resin-packed bed is simultaneously filled with chelating resin, macroporous resin, and weakly acidic cation exchange resin. When filling the mixture, the volume ratio of chelating resin, macroporous resin, and weakly acidic cation exchange resin is 1:0.5~1.5:0.5~1.5; or When performing layered filling, the layer thickness ratio of chelating resin, macroporous resin and weakly acidic cation exchange resin is 1:0.8~1.3:0.8~1.

3.

2. The bipolar membrane electrodialysis salt-to-alkali system with a coupled resin packed bed according to claim 1, wherein, The bipolar membrane electrodialysis device includes an anode, a bipolar membrane (BPM), an anion exchange membrane (AM), a cation exchange membrane (CM), a bipolar membrane (BPM), and a cathode arranged sequentially, as well as a waterproof and leak-proof partition for supporting the bipolar membrane, anion exchange membrane, cation exchange membrane, and bipolar membrane and for forming acid chambers, salt chambers, and alkali chambers. A salt chamber is formed between the cation exchange membrane and the anion exchange membrane, an acid chamber is formed between the anion exchange membrane and the bipolar membrane, an alkali chamber is formed between the cation exchange membrane and the bipolar membrane, and electrode chambers are formed between the cathode and the bipolar membrane, and between the anode and the bipolar membrane.

3. The bipolar membrane electrodialysis salt-to-alkali system with a coupled resin packed bed according to claim 2, wherein, Anion exchange membranes (AM), cation exchange membranes (CM), and bipolar membranes (BPM), along with salt, acid, and alkali chambers located within them, constitute membrane repeating units. A bipolar membrane electrodialysis device includes multiple membrane repeating units.

4. The bipolar membrane electrodialysis salt-to-alkali system with a coupled resin packed bed according to claim 3, wherein, Electrodialysis devices consist of 2 to 100 membrane repeating units.

5. The bipolar membrane electrodialysis salt-to-alkali system with a coupled resin packed bed according to claim 2, wherein, The cathode is a titanium-based electrode; or The anode is a titanium-based electrode with a corrosion-resistant coating.

6. The bipolar membrane electrodialysis salt-to-alkali system with a coupled resin packed bed according to claim 5, wherein, The cathode is a titanium plate electrode or a titanium mesh electrode; or In the anode, the corrosion-resistant coating of the titanium-based electrode is a coating containing a metal oxide or a composite metal oxide selected from ruthenium, iridium, niobium and tantalum and further subjected to platinum plating.

7. The bipolar membrane electrodialysis salt-to-alkali system with a coupled resin packed bed according to any one of claims 1 to 6, wherein, The alkali chamber of the bipolar membrane electrodialysis device has a mesh screen installed in the middle of the partition, and the acid chamber has a mesh screen installed in the middle of the partition.

8. A method for the resource-based treatment of industrial wastewater, comprising the following steps: 1) Pre-treat industrial wastewater to reduce the concentration of organic matter to less than or equal to 40 mg / L, the total concentration of calcium and magnesium ions and other heavy metal ions to less than or equal to 20 mg / L, and the pH value to 6-8. 2) The industrial wastewater pretreated in step 1) is electrolyzed using a bipolar membrane electrodialysis salt-to-alkali system with a coupled resin packed bed as described in any one of claims 1 to 7 to obtain alkali and acid.

9. The method for resource-based treatment of industrial wastewater according to claim 8, wherein, The acid obtained is selected from HCl, HNO3, or H2SO4; The prepared alkali is selected from NaOH, KOH or ammonia.

10. The method for resource-based treatment of industrial wastewater according to claim 8 or 9, wherein, The pretreatment is selected from one or more of the following: chemical precipitation, membrane separation, activated carbon adsorption, electrodeposition, electrodialysis, and electroadsorption.

11. The method for resource-based treatment of industrial wastewater according to claim 10, wherein, The salt concentration of industrial wastewater is 20~200g / L.

12. The method for resource-based treatment of industrial wastewater according to claim 10, wherein, The salt concentration of industrial wastewater is 50~200 g / L.

13. The method for resource-based treatment of industrial wastewater according to claim 8 or 9, wherein, The industrial wastewater is coal chemical wastewater.

Images