Epoxy resin wastewater desalination method through cooperation of reverse electrodialysis and membrane capacitive deionization

Abstract

The invention relates to an epoxy resin wastewater desalination method by cooperating reverse electrodialysis with membrane capacitive deionization, which comprises the following steps: adjusting the pH value of pretreated epoxy resin wastewater to 8.0-9.0 in a wastewater buffer pool, and heating to 40-45 DEG C; the adjusted waste water is introduced into a waste water buffer pool, clear water flows back into the waste water buffer pool from the clear water pool, the volume ratio of the waste water to the clear water is 1: 2-1: 3, and the flow speed is the same. According to the epoxy resin waste water desalting method with the cooperation of reverse electrodialysis and membrane capacitive deionization, salinity difference energy in the waste water is recycled through reverse electrodialysis, electric energy is directly provided for operation of the membrane capacitive deionization device and heating of the waste water, only a small amount of energy of auxiliary equipment such as a water pump needs to be consumed, and the operation cost of epoxy resin waste water desalting is remarkably reduced. Meanwhile, the process design is simple and adapts to an industrial treatment scene, the problems that a traditional process is high in cost and difficult to popularize on a large scale are solved, and an economical and feasible technical path is provided for epoxy resin wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of interdisciplinary technology of environmental protection technology and new energy technology, specifically a method for desalination of epoxy resin wastewater by reverse electrodialysis combined with membrane capacitor deionization. Background Technology

[0002] Epoxy resins are widely used in coatings, adhesives, and electronic packaging, and are an important chemical product in my country. Bisphenol A type epoxy resin, due to its high production volume and wide application, is known as a general-purpose epoxy resin. However, its production process generates toxic industrial wastewater with high salinity and high organic matter content (i.e., epoxy resin wastewater), which contains high concentrations of sodium. + Cl - It contains inorganic ions, as well as highly toxic organic pollutants such as toluene, epichlorohydrin, and unreacted bisphenol A. Once it enters the environment, it will cause serious and lasting damage to water bodies and soil.

[0003] Currently, epoxy resin wastewater presents significant challenges for treatment due to its high salt content and high levels of recalcitrant organic matter. Biodegradation and chemical oxidation processes are hampered by high concentrations of inorganic salts, hindering effective degradation of organic matter. Evaporation processes are not only costly but also prone to clogging due to organic matter, and the crystallized salts can become mixed with organic matter, resulting in difficult-to-treat industrial waste salt. Pressure-driven membrane processes such as reverse osmosis and nanofiltration are limited by membrane fouling and processing capacity, making them ill-suited for handling this type of high-salt, high-organic wastewater. Furthermore, national policies restrict the discharge of high-salt wastewater and encourage the recycling of inorganic salts. Therefore, there is an urgent need for novel processes to achieve low-cost separation of salts and organic matter, and to recover salts to prevent the generation of industrial waste salt.

[0004] Reverse electrodialysis technology converts the chemical potential difference between salt solutions of different concentrations into electrical energy. Traditional applications focus on generating electricity from salinity gradients, such as seawater and river water, or concentrated brine and freshwater. For example, the invention patent "A seawater desalination method coupled with reverse electrodialysis and electrodialysis (201510439862.9)" uses electrodialysis to desalinate seawater, and then uses the concentrated seawater to balance the salt concentration through reverse electrodialysis to generate electricity. The invention patent "A reverse electrodialysis reactor, wastewater treatment device and its application (202010067739.X)" generates electricity through the salinity difference between high-salt and low-salt wastewater, driving electro-Fenton degradation of organic matter. However, these methods cannot solve the core needs of epoxy resin wastewater desalination and efficient retention of organic matter. Another invention patent, "Reverse electrodialysis and electrochemical wastewater treatment method for nitrogen-containing compounds (200680021098.2)," although mentioning reverse electrodialysis in the title, actually discusses the function of electrodialysis in concentrating salt, which is a technical description deviation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for desalinating epoxy resin wastewater using reverse electrodialysis combined with membrane capacitance deionization, thus solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for desalinating epoxy resin wastewater by reverse electrodialysis combined with membrane capacitance deionization, comprising the following steps: S1: Adjust the pH of the pretreated epoxy resin wastewater to 8.0-9.0 in the wastewater buffer tank and heat it to 40℃-45℃; S2: The adjusted wastewater is introduced into the wastewater buffer tank, while the clean water flows counter-currently from the clean water tank into the wastewater buffer tank. The volume ratio of the wastewater to the clean water is 1:2 to 1:3, and the flow rates are the same. Desalination is achieved through spontaneous migration of salinity gradient energy and electricity is generated. S3: Adjust the pH of the wastewater after reverse electrodialysis desalination to 4.0-5.0 in the pH adjustment tank, and adjust the temperature to 35℃-40℃; S4: The re-adjusted wastewater is fed into the membrane capacitor deionization device, and the electrical energy generated by the reverse electrodialysis is used for deep desalination until the conductivity of the effluent is lower than 0.5 mS / cm. Among them, the salt solution from the wastewater buffer tank is recycled to the salt recovery tank, with a conductivity greater than 80 mS / cm and an organic matter content of less than 30 mg / L.

[0007] Furthermore, the wastewater buffer tank consists of five isomorphic devices operating in series, with adjacent units connected by pipelines. The wastewater flows sequentially through each membrane stack unit, while the clean water flows in the opposite direction to the wastewater.

[0008] Furthermore, the water in the clear water tank is tap water, deionized water, or a low-salt aqueous solution with a conductivity of less than 0.5 mS / cm.

[0009] Furthermore, the electrical energy generated by the reverse electrodialysis is stored in an energy storage device and used to drive the membrane capacitor deionization device and provide energy for heating the wastewater buffer tank or pH adjustment tank.

[0010] Furthermore, the membrane capacitor deionization device uses a conventional ion exchange membrane, and its operating voltage is 1.0V to 1.2V.

[0011] Furthermore, the electrode material of the membrane capacitor deionization device is a commercially available carbon electrode.

[0012] Furthermore, the heating in both the wastewater buffer tank and the pH adjustment tank is achieved using the electrical energy generated by the reverse electrodialysis.

[0013] Furthermore, in the wastewater buffer tank, wastewater and clean water flow counter-currently in opposite directions.

[0014] Furthermore, the feature is that it also includes a water storage tank for storing the final effluent, and the water storage tank is connected to the membrane capacitor deionization device through a pipeline, and its conductivity is less than 0.5 mS / cm.

[0015] Compared with the prior art, the technical solution of this application has the following beneficial effects: 1. This method for desalinating epoxy resin wastewater using reverse electrodialysis combined with membrane capacitive deionization recovers the salinity gradient energy from the wastewater through reverse electrodialysis, directly providing power for the operation of the membrane capacitive deionization unit and wastewater heating. It requires only a small amount of energy from auxiliary equipment such as water pumps, significantly reducing the operating cost of epoxy resin wastewater desalination. Furthermore, the process design is simple and adaptable to industrial treatment scenarios, solving the problems of high costs and difficulty in large-scale promotion of traditional processes, and providing an economically feasible technical path for epoxy resin wastewater treatment.

[0016] 2. This reverse electrodialysis synergistic membrane capacitance deionization method for desalination of epoxy resin wastewater is based on the characteristics of organic molecules in epoxy resin wastewater. By precisely controlling pH and temperature, it promotes the folding and polymerization of organic molecules or weakens their electro-driven properties, making them unable to pass through the separation membrane. The final recovered salt solution has a conductivity greater than 80 mS / cm and an organic matter content of less than 30 mg / L. This avoids the problem of crystalline salt mixed with organic matter forming difficult-to-treat industrial waste salt in traditional processes, and truly realizes the resource utilization of inorganic salts.

[0017] 3. This method of desalinating epoxy resin wastewater using reverse electrodialysis combined with membrane capacitance deionization can reduce the conductivity of the wastewater to below 0.5 mS / cm after treatment. It also effectively retains toxic and harmful organic compounds such as toluene, epichlorohydrin, and bisphenol A. This not only solves the problem of high-salt environment inhibiting traditional processes such as biodegradation and chemical oxidation, but also creates favorable conditions for subsequent degradation of organic matter using conventional methods. It forms a complete treatment chain of desalination and organic matter degradation, achieving efficient purification and pollutant reduction of epoxy resin wastewater. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention.

[0019] In the diagram: 1. Wastewater buffer tank; 2. Reverse electrodialysis; 3. pH adjustment tank; 4. Membrane capacitor deionization; 5. Water storage tank; 6. Clear water tank; 7. Salt recovery tank; 8. Energy storage device. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 1 This invention provides a method for desalinating epoxy resin wastewater using reverse electrodialysis combined with membrane capacitive deionization. The system mainly comprises a wastewater buffer tank 1, a reverse electrodialysis device 2, a pH adjustment tank 3, a membrane capacitive deionization device 4, and a water storage tank 5, connected sequentially by pipelines. The system also includes a clear water tank 6, a salt recovery tank 7, and an energy storage device 8. A pumping system facilitates the directional transport of wastewater and clear water between the various devices.

[0022] In detail, from Figure 1 It can be clearly seen that the basic process flow of this invention is as follows: After simple pretreatment, the epoxy resin wastewater enters the wastewater buffer tank 1. In the wastewater buffer tank 1, specific pH and specific temperature are adjusted. The electrical energy required for temperature adjustment comes from the electrical energy generated by the reverse electrodialysis 2 itself. After the pH and temperature are set, the wastewater enters the series reverse electrodialysis 2 system. The clear water flows countercurrently from the clear water tank 6 into the reverse electrodialysis 2 system. Most of the inorganic ions spontaneously transfer to the clear water. The resulting saline solution enters the salt recovery tank 7. The electrical energy generated by the reverse electrodialysis 2 system is collected and reused by the energy storage device 8. The wastewater enters the pH adjustment tank 3 to adjust the pH to a specific range again and maintains it at a specific temperature. After passing through the membrane capacitor deionization 4, inorganic salt ions are separated again. After the separation of inorganic salts is achieved, the wastewater enters the water storage tank 5, thus achieving the objective of this invention patent.

[0023] Furthermore, the specific pH and temperature, combined with reverse electrodialysis 2 and membrane capacitor deionization 4, to carry out a countercurrent series desalination process is a proprietary discovery of this invention in conjunction with the organic matter in epoxy resin wastewater, and is an important feature protected by this invention's patent.

[0024] Furthermore, the reverse electrodialysis 2 system in a countercurrent mode is a beneficial enhancement of the present invention. As long as the pH and temperature set by the present invention are within the limits of the present invention, other operating modes such as cocurrent mode do not fundamentally change the inventive discovery of the present invention. That is, under specific conditions, the reverse electrodialysis 2 and membrane capacitor deionization 4 greatly enhance the retention effect of organic molecules, realize the separation and purification of inorganic salts, and lay the foundation for the resource utilization of inorganic salts.

[0025] Furthermore, the membrane capacitive deionization 4, combined with epoxy resin wastewater, a specific pH and a specific temperature, utilizes the electrical energy generated by reverse electrodialysis 2 to achieve deep separation of inorganic salt ions from complex wastewater. Therefore, the differences in the membrane capacitive deionization 4 equipment do not change the inventiveness of this invention. Example

[0026] The generated typical high-salt organic wastewater, after pretreatment to remove suspended particulate matter, enters this system for further treatment. First, the wastewater is introduced into wastewater buffer tank 1, and the pH of the wastewater is precisely adjusted to 8.5 by adding an appropriate amount of alkaline regulator. At the same time, the temperature of the wastewater is stably maintained at 42 degrees Celsius using an electric heating device integrated into the tank.

[0027] Subsequently, the wastewater is pumped into a reverse electrodialysis unit 2, which consists of five identical membrane stack units connected in series. At the same time, deionized water from the clear water tank 6 flows counter-currently into the unit in the opposite direction to the wastewater flow. The control system precisely maintains the volumetric flow rate ratio of wastewater to deionized water at 1:2.5 and ensures that the flow rates of the two are consistent. During the flow through the reverse electrodialysis unit 2, the significant salt concentration difference between the high-salt wastewater and the low-salt clear water drives sodium ions and chloride ions to spontaneously migrate from the wastewater side to the clear water side through the selective ion exchange membrane. This not only achieves the initial desalination of the wastewater, but more importantly, it directly converts the salinity difference energy in the wastewater into electrical energy. The generated electrical energy is collected in real time and stored in the connected energy storage device 8.

[0028] Furthermore, after desalination via reverse electrodialysis, the wastewater with significantly reduced salinity is introduced into pH adjustment tank 3. In this section, the pH of the wastewater is precisely adjusted to 4.5 by adding dilute hydrochloric acid to create a weakly acidic environment most suitable for subsequent advanced treatment. At the same time, the wastewater temperature is controlled at 38 degrees Celsius using the system's self-generated electricity.

[0029] Furthermore, the wastewater, after pH and temperature adjustment, then enters the membrane capacitor deionization unit 4 for deep desalination. This unit is directly powered by the energy storage device 8, with an operating voltage set at 1.1 volts. Under the action of the electric field, residual ions in the wastewater are efficiently adsorbed onto the electrode surface, thereby achieving deep salt removal. The treatment process continues until the online conductivity meter detects that the conductivity of the effluent has dropped below 0.5 mS / cm. The treated water is then temporarily stored in the storage tank 5.

[0030] Furthermore, on the concentrate side of the reverse electrodialysis unit 2, salts migrating from the wastewater are collected, forming a high-concentration brine. This concentrated brine is then directed to the salt recovery tank 7. The resulting concentrated salt solution is clear and transparent, with a conductivity exceeding 80 mS / cm, while the key indicator, dissolved organic matter content, is successfully controlled below 30 mg / L, meeting the requirements for industrial reuse or further resource recovery. Example

[0031] Using the same epoxy resin wastewater raw water and water treatment system configuration as in Example 1, the adaptability and stability of this method were verified by adjusting key process parameters.

[0032] In actual use, the wastewater is adjusted to a more alkaline pH of 9.0 in the wastewater buffer tank 1, and the temperature is raised to 45 degrees Celsius. It then enters the reverse electrodialysis unit 2, which consists of five membrane stacks connected in series. Low-conductivity tap water from the clear water tank 6 comes into countercurrent contact with the wastewater at a volume ratio of 1:3. The salinity gradient power generation process is stable, and the electrical energy is effectively collected by the energy storage device 8.

[0033] Furthermore, the desalinated wastewater is adjusted to pH 5.0 in pH adjustment tank 3, with the temperature set at 40 degrees Celsius, before entering the membrane capacitor deionization unit 4. The unit operates at a working voltage of 1.2 volts, and the final effluent conductivity stabilizes below the threshold of 0.5 mS / cm before entering the storage tank 5. The concentrated brine produced by the reverse electrodialysis unit 2 is collected in the salt recovery tank 7, with a conductivity exceeding 80 mS / cm and a dissolved organic matter content far below 30 mg / L, further demonstrating the high purity of the recovered salt.

[0034] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for desalinating epoxy resin wastewater using reverse electrodialysis combined with membrane capacitance deionization, characterized in that: Includes the following steps: S1: Adjust the pH of the pretreated epoxy resin wastewater to 8.0-9.0 in the wastewater buffer tank (1) and heat it to 40℃-45℃; S2: The adjusted wastewater is fed into the reverse electrodialysis device (2), and at the same time, the clean water is fed into the reverse electrodialysis device (2) from the clean water tank (6) in a countercurrent manner. The volume ratio of the wastewater to the clean water is 1:2 to 1:3, and the flow rates are the same. Desalination is carried out by spontaneous migration through the salt gradient and electricity is generated. S3: Adjust the pH of the wastewater after reverse electrodialysis desalination to 4.0-5.0 in pH adjustment tank (3) and adjust the temperature to 35℃-40℃; S4: The re-adjusted wastewater is fed into the membrane capacitor deionization device (4) and the electrical energy generated by the reverse electrodialysis is used for deep desalination until the conductivity of the effluent is lower than 0.5 mS / cm. Among them, the salt solution from the reverse electrodialysis unit (2) is recycled to the salt recovery tank (7), which has a conductivity greater than 80 mS / cm and an organic content less than 30 mg / L.

2. The method for desalination of epoxy resin wastewater by reverse electrodialysis combined with membrane capacitance deionization according to claim 1, characterized in that: The reverse electrodialysis device (2) consists of five isomorphic devices connected in series, and adjacent units are connected by pipelines. The wastewater flows through each membrane stack unit in sequence, while the clean water flows in the opposite direction to the wastewater.

3. The method for desalination of epoxy resin wastewater by reverse electrodialysis synergistic membrane capacitance deionization according to claim 1, characterized in that: The clear water in the clear water tank (6) is tap water, deionized water, or a low-salt aqueous solution with a conductivity of less than 0.5 mS / cm.

4. The method for desalination of epoxy resin wastewater by reverse electrodialysis synergistic membrane capacitance deionization according to claim 1, characterized in that: The electrical energy generated by the reverse electrodialysis is stored in the energy storage device (8) and used to drive the membrane capacitor deionization device (4) and to provide energy for heating the wastewater buffer tank (1) or pH adjustment tank (3).

5. The method for desalination of epoxy resin wastewater by reverse electrodialysis synergistic membrane capacitance deionization according to claim 1, characterized in that: The membrane capacitor deionization device (4) uses a conventional ion exchange membrane and its operating voltage is 1.0V to 1.2V.

6. The method for desalination of epoxy resin wastewater by reverse electrodialysis synergistic membrane capacitance deionization according to claim 5, characterized in that: The electrode material of the membrane capacitor deionization device (4) is a commercially available carbon electrode.

7. The method for desalination of epoxy resin wastewater by reverse electrodialysis synergistic membrane capacitance deionization according to claim 1, characterized in that: The heating in the wastewater buffer tank (1) and the pH adjustment tank (3) is achieved by the electrical energy generated by the reverse electrodialysis.

8. The method for desalination of epoxy resin wastewater by reverse electrodialysis synergistic membrane capacitance deionization according to claim 1, characterized in that: In the reverse electrodialysis device (2), wastewater and clean water flow in opposite directions.

9. The method for desalination of epoxy resin wastewater by reverse electrodialysis synergistic membrane capacitance deionization according to claim 1, characterized in that: It also includes a water storage tank (5) for storing the final effluent, and the water storage tank (5) is connected to the membrane capacitor deionization device (4) through a pipeline, and its conductivity is less than 0.5 mS / cm.

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