Water treatment method and system

Abstract

The present invention relates to a water treatment method and system, wherein the water is an aqueous system containing organic substances, and chlorinated compounds are present in the aqueous system. The method comprises: an electrochemical treatment step and a photochemical treatment step, wherein in the electrochemical treatment step, the aqueous system flows from a cathode toward an anode, the aqueous system passes through the cathode and the anode in the flow direction, and the aqueous system flowing out from the anode generates hypochlorite via an anodic electrochemical reaction; in the photochemical treatment step, the aqueous system flowing out from the anode is subjected to ultraviolet light irradiation, so that chlorine free radicals are generated within the aqueous system and chemically react with the organic substances, and the aqueous system that has completed the photochemical treatment step is at least partially returned to flow toward the cathode in the electrochemical treatment step; and at least a portion of the aqueous system undergoes one or more cycles of treatment comprising the electrochemical treatment step and the photochemical treatment step.

Description

Water treatment methods and systems Technical Field The present invention belongs to the field of environment and relates to a method and system for purifying a water system containing organic matter and salt. More specifically, the present invention relates to a method and system for purifying a water system containing organic matter and salt, especially such industrial or domestic wastewater system. Background Art With industrial development and water resource scarcity, some industries are generating increasingly high-salinity organic wastewater (or simply, high-salinity wastewater) with increasing concentrations and complex compositions, placing increasing pressure on the environment. For example, chemical agents are used in various industries, including pesticides, pharmaceuticals, textiles, papermaking, printing and dyeing, and chemicals, generating large amounts of high-salinity organic wastewater during their production and use. High-salt organic wastewater usually contains a large amount of inorganic salts and organic matter. Some literature defines it as wastewater with an organic COD value greater than 200 mg / L and a dissolved solids (TDS) of more than 3.5%. In addition, the salt content is expressed as the amount of sodium chloride, and the salt mass fraction is not less than 1%. High-salinity organic wastewater has long been characterized by high salinity, high COD values, strong acidity and alkalinity, high toxicity, complex chemical composition, and poor biodegradability. Because high-salinity organic wastewater contains high concentrations of soluble inorganic salts, recalcitrant organic matter, and oils, direct treatment using biological or physicochemical methods is costly and difficult to achieve the desired purification effect. Furthermore, if the wastewater is directly discharged, the soluble inorganic salts and recalcitrant toxic organic matter in it will severely impact soil and water bodies, causing irreversible damage to the environment. Reference 1 summarizes the treatment technology of high-salt organic wastewater, focusing on the research and application status of various processes. The high concentration of soluble inorganic salts and organic matter in high-salt organic wastewater will inhibit the degradation process of microorganisms, affect the growth and metabolism of microorganisms themselves, and cause toxicity to microorganisms. Therefore, there are certain advantages in using physical and chemical methods to treat this wastewater. Commonly used physical and chemical methods include: electrochemical method, incineration method, evaporation method, ion exchange method, adsorption method, membrane separation method, and advanced oxidation method. In addition, biological methods can be used to treat high-salt organic wastewater. The principle behind biological wastewater treatment is to utilize halophilic and halotolerant bacteria, which thrive in high-salt environments, to utilize organic pollutants in wastewater as nutrients for their growth and metabolism. Under specific conditions, these pollutants are converted into small molecules, even CO2 and H2O. Although, as mentioned above, high-salt wastewater inhibits and toxics microbial growth and metabolism, significantly reducing the effectiveness of biological methods for treating high-salt organic wastewater, biological methods remain a key research focus for treating high-salt organic wastewater due to their low operating costs and lack of secondary pollution. Reference 2 discloses a method for treating high-salinity, recalcitrant organic wastewater. Specifically, it involves applying a triple-effect evaporation, membrane bioreactor, security filtration, and reverse osmosis process to the treatment of high-salinity, recalcitrant organic wastewater. Compared with using a membrane bioreactor alone, this method is suitable for treating recalcitrant organic wastewater with higher salinity and can essentially achieve zero wastewater discharge. Reference 3 discloses a method for treating high-salt, high-concentration dye wastewater. Using a plastic sheet (CeO2 / C)-β-PbO2-PTFE electrode as the anode and a steel sheet as the cathode, NaCl is added to the dye wastewater for electrolytic treatment. The 20% (CeO2 / C)-β-PbO2-PTFE electrode synergistically acts with chloride ions to treat the dye wastewater, significantly improving the decolorization rate and COD removal rate. It is also known that in some other ultrapure water treatments containing urea, there are also schemes of using chlorine oxidizing agents in conjunction with ultraviolet treatment, such as Reference 4 and Reference 5. Although numerous studies have been conducted on wastewater treatment, especially the treatment of high-salt organic wastewater, there is still room for further exploration in terms of treatment effectiveness and economy. References: Reference 1: Cao Meiling et al., Treatment and research progress of high-salt organic wastewater[J]. Nonferrous Metals Science and Engineering, 2019, 10(3): 92-98. Reference 2: CN102267781A Reference 3: CN105776449A Reference 4: CN114890605A Reference 5: CN115925037A Summary of the Invention Problems to be solved by the invention The biological toxicity and rapid quenching of oxygen-containing free radicals caused by high-salinity environments pose severe challenges to traditional organic pollutant treatment methods such as biological methods, ozone, or Fenton methods. This makes the unit organic matter treatment cost several or even hundreds of times higher than that of general wastewater. To achieve the water treatment industry's critical need for "synergistic efficiency in pollution reduction and carbon reduction," it is imperative to develop low-carbon treatment technologies for organic pollutants in high-salinity wastewater. In extensive industrial practice, it has been found that the solution in Reference 2 is still not convenient. Reference 3 requires the additional use of chloride salts, and therefore requires additional supplementation, control or regulation measures. Moreover, the removal of many organic substances by the oxidation effect of high-valent chlorine alone is also limited. In addition, although cited documents 4 and 5 verify that the coordinated use of chlorination and ultraviolet light can effectively treat ultrapure water containing urea, they cannot be considered suitable for the treatment of high-salt organic wastewater. At the same time, in the above documents, chlorination treatment and ultraviolet light treatment occur almost at the same time and in the same location. Therefore, the accumulation of thermal effects caused by this cannot be said to be beneficial for the continuity and stability of industrial production. Based on various practices of the existing technology, the present invention discovered that the photoelectrochemical technology of reduction dechlorination and enhanced free radical oxidation decontamination is an effective means to treat organic matter in high-salt wastewater, which can well solve the problems of high energy consumption, low efficiency, and incomplete mineralization of organic matter in the existing high-salt wastewater treatment process. Therefore, the present invention provides a treatment method and a treatment system for a water-containing system containing organic matter that can be circulated. By creatively coupling an electrochemical treatment unit that can penetrate the cathode and anode with a photochemical treatment unit of ultraviolet light, and through one or more cyclic treatments, organic matter in high-salt wastewater can be effectively removed, and no additional oxidizing reagents are required. Solutions for solving problems It has been found that the above technical problems can be solved by implementing the following technical solutions: [1] The present invention first provides a method for treating an aqueous system containing organic matter, wherein a chlorine-containing compound is present in the aqueous system, the method comprising: electrochemical treatment steps and photochemical treatment steps, in, In the electrochemical treatment step, the aqueous system flows from the cathode toward the anode. In the moving direction, the aqueous system passes through the cathode and the anode, and the aqueous system flowing out of the anode generates hypochlorite through the anode electrochemical reaction. In the photochemical treatment step, the aqueous system flowing out of the anode is irradiated with ultraviolet light to generate chlorine free radicals in the aqueous system, and the free radicals react chemically with the organic matter. In addition, the aqueous system that has completed the photochemical treatment step is at least partially returned to the cathode in the electrochemical treatment step. At least part of the aqueous system is subjected to one or more cycles comprising an electrochemical treatment step and a photochemical treatment step. [2] The method according to [1], wherein the aqueous system produces monatomic hydrogen via a cathode electrochemical reaction; The aqueous system flowing out of the anode is irradiated with ultraviolet light so that hydroxyl radicals are generated in the aqueous system, and the free radicals also produce photochemical reactions with the organic matter. [3] The method according to [1] or [2], wherein the anode comprises ruthenium oxide; the cathode comprises metallic palladium; and during the electrochemical treatment step, a direct current is passed between the anode and the cathode. [4] The method according to any one of [1] to [3], wherein in the photochemical treatment step, the light in the ultraviolet band includes one or more types of light with a wavelength of less than 260 nm. [5] The method according to any one of [1] to [4], wherein at least part of the chlorine element in the aqueous system that completes the photochemical treatment step forms non-aromatic organic matter in the form of covalent bonds. [6] The method according to any one of [1] to [5], wherein the aqueous system returned to the cathode in the electrochemical treatment step after the photochemical treatment step is converted at least partially into chloride ions under the action of the cathode. [7]. Furthermore, the present invention also provides a treatment system for an aqueous system containing organic matter, wherein chlorine-containing compounds are present in the aqueous system. The system includes an electrochemical cell, a photochemical cell, a driving unit, and a connecting unit, wherein the connecting unit connects the electrochemical cell, the photochemical cell, and the driving unit. The driving unit provides the flow force of the aqueous system in the treatment system. The electrochemical unit comprises a power source, an inlet, an outlet, an anode and a cathode, wherein the anode and the cathode is disposed between the inlet and the outlet and has a fluid-permeable structure, the aqueous system flows from the cathode toward the anode, and in the flow direction, the aqueous system penetrates the cathode and the anode, The photochemical cell comprises an inlet, an outlet and an ultraviolet light source, and the ultraviolet light source irradiates the aqueous system flowing out of the anode of the electrochemical cell with ultraviolet radiation. Furthermore, the outlet of the photochemical cell is in communication with the inlet of the electrochemical cell, so that at least a portion of the aqueous system flowing out of the photochemical cell is returned to the electrochemical cell. [8] The system according to [7], wherein the electrochemical cell is configured so that the aqueous system flowing out of the electrochemical cell outlet includes hypochlorite. [9] The system according to [8], wherein at least part of the hypochlorite is derived from an electrochemical reaction at the anode of the electrochemical cell; and at least part of the hydroxide is derived from an electrochemical reaction at the cathode of the electrochemical cell.

[0010] .A system according to any one of [7] to [9], wherein, in the electrochemical unit, the anode comprises a metal ruthenium oxide; the cathode comprises a metal palladium; and the power supply is a direct current power supply.

[0011] .A system according to any one of [7] to

[0010] , wherein the photochemical unit is configured to generate chlorine radicals, and optionally also hydroxyl radicals, in an aqueous system irradiated by the ultraviolet light source.

[0012] .A system according to any one of [7] to

[0011] , wherein the ultraviolet light source in the photochemical unit is configured to provide light including one or more ultraviolet bands with a wavelength below 260 nm.

[0013] . Further, as some preferred embodiments, the present invention also provides a cyclic treatment method for an aqueous system containing organic matter, wherein chlorine-containing compounds are present in the aqueous system, wherein the method comprises subjecting the aqueous system to be treated to one or more cyclic treatments using the system described above, each cyclic treatment comprising sequential treatment of the electrochemical unit and the photochemical unit.

[0014] .The treatment method according to

[0013] , wherein the aqueous system is wastewater containing water-soluble aromatic organic matter.

[0015] .The treatment method according to

[0013] or

[0014] , wherein the aqueous system comprises industrial wastewater or domestic wastewater. Effects of the Invention By implementing the above technical solution, the present invention can achieve the following technical effects: 1) The present invention proposes for the first time an effective means of treating organic matter in high-salinity wastewater by photoelectrochemical coupling through reductive dechlorination and enhanced free radical oxidation and decontamination. This method can effectively solve the problems of high energy consumption, low efficiency, and incomplete mineralization of organic matter in existing high-salinity wastewater treatment processes. Moreover, compared with traditional electrochemical and ultraviolet chlorine advanced oxidation technologies, the addition of the cathode dehalogenation process of the present invention is conducive to reducing the accumulation of halogenated byproducts and further reducing the toxicity of the effluent. 2) The anode and cathode in the electrochemical unit are creatively designed to be a penetrable structure. Therefore, the aqueous system can pass through the cathode and anode in sequence to complete different chemical reactions, and give the aqueous system flowing out of the electrochemical unit a specific chemical composition (chlorate and optional hydroxide). In addition, the present invention adopts a penetrable electrode, which can be operated in a high-speed cycle, and adopts a photoelectric space separation structure, which greatly solves the defects of high energy, low efficiency and severe heat generation of the reactor from three aspects. First, the reactor adopts a penetrating electrode, which can minimize the distance between the electrode plates, which is conducive to increasing mass transfer and reducing internal resistance; second, the high-speed circulation operation mode can destroy the pH micro-field on the electrode surface, reduce the voltage between the two electrodes, and enhance mass transfer; finally, the photoelectric space separation structure can avoid concentrated heat generation in the electrochemical reaction unit, which is of great significance to extending the life of the electrode. 3) Through the cycle design, after returning from the photochemical unit to the cathode of the electrochemical unit, chloride ions are recovered under the action of the cathode reaction, and can then pass through the anode again to produce hypochlorite, thereby cyclically carrying out the electrochemical-photochemical treatment. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram of the structure of a redox-coordinated electrochemical reactor Figure 2 is a morphology of the titanium foam substrate under a scanning electron microscope (SEM) in Example 1 Figure 3 is a distribution diagram of palladium clusters on the titanium foam substrate under transmission electron microscopy (TEM) in Example 1 Figure 4 shows the removal rate of benzoic acid in Example 2 Figure 5 shows the removal efficiency of various organic substances in Example 3 Description of reference numerals: 1-254nm UV lamp 2—Peristaltic pump (drive unit) 3—Penetrating reactor shell 4—Porous foam palladium titanium cathode 5—Porous foam palladium titanium anode 6—DC power supply a—Electrochemical unit b—Photochemical unit DETAILED DESCRIPTION The following is a detailed description of the present invention. The following description of the technical features is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that: In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B. In this specification, unless otherwise specified, "multiple" in "multiple", "multiple", "many" and the like means a numerical value of 2 or more. In this specification, the term "substantially" or "essentially" means that the error is less than 1%, less than 0.8%, or less than 0.6% compared to the relevant perfect standard or theoretical standard. Furthermore, when "all" or "all" is mentioned in this specification, it also means "all" or "all" in the sense of "substantially" or "essentially". In this specification, unless otherwise specified, "%" means percentage by mass. In this specification, the use of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process. In this specification, "optional" or "optionally" means that the event or situation described below may or may not occur or may occur in any of the described circumstances, and the description includes the occurrence of the event. situations in which the event occurs and situations in which the event does not occur. In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "embodiments," etc., mean that the specific elements (e.g., features, structures, properties, and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner. When the terms “include” and / or “comprising” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations. In this specification, "normal temperature" or "room temperature" refers to an indoor ambient temperature of "23±2°C". In this specification, the term "flow direction" refers to the direction of circulation of the aqueous system in the system from the electrochemical cell to the photochemical cell and (at least partially) back to the electrochemical cell. In the electrochemical cell, the flow direction is from the cathode to the anode. The present invention mainly provides a method and system for treating an aqueous system containing organic matter in a recyclable manner, wherein the aqueous system also contains chlorine-containing compounds. The present invention is mainly based on the following insights. Ultraviolet irradiation can generate free radicals, which can react with target organic matter to mineralize or inorganicize it. It has been found that further dechlorination treatment can promote the above-mentioned degree of conversion, making the treatment of the target organic matter more thorough. Based on this strategy, the present invention creatively designs an electrochemical cell with an anode and a cathode that can be penetrated by fluid, thereby allowing the aqueous system to flow from the cathode to the anode. Thus, dechlorination can be achieved at the cathode, and the chlorine element is at least partially oxidized to hypochlorite at the anode, which further flows to the photochemical cell for coupled treatment. <First Aspect> In a first aspect of the present invention, a method for treating an aqueous system containing organic matter is provided, the method comprising sequentially performing an electrochemical treatment step and a photochemical treatment step. Preferably, the above-mentioned cyclic treatment can be performed once or multiple times. Aqueous system The aqueous system of the present invention is mainly an aqueous system containing organic matter and certain inorganic salts. In some specific embodiments, the aqueous system contains organic matter and at least 3.5% by mass of total dissolved solids (TDS). In other specific embodiments, the organic matter in the aqueous system is preferably an organic matter having an aromatic structure, such as one or more aromatic groups such as phenyl groups and heterocyclic aromatic groups. Furthermore, in some preferred embodiments of the present invention, the organic matter may be an organic matter having a certain solubility, for example, a solubility of 1% by mass or greater, preferably 2% by mass or greater, in water at 80°C at normal pressure. In some preferred embodiments, the organic matter includes an aromatic fatty acid or salt thereof, typically a mixture of one or more of benzoic acid, a benzoate, phenol, bisphenol A, or derivatives thereof. Furthermore, the aqueous system of the present invention also contains a chlorine-containing compound. Preferably, the chlorine-containing compound is an inorganic salt containing chloride ions. In some preferred embodiments of the present invention, the amount of the chlorine-containing compound present in the aqueous system of the present invention is 1% by mass or more, preferably 1.5% by mass or more, and more preferably 3% by mass or more, calculated as sodium chloride (the chlorine-containing compound is converted). In addition, there is no special requirement for the COD value of the aqueous system of the present invention in principle, which is related to its source. In some specific embodiments of the present invention, the organic matter content in the aqueous system is a COD value greater than 10,000 mg / L. Furthermore, in principle, there is no particular limitation on the source of the aqueous system of the present invention. For example, it can be domestic or industrial wastewater. In some specific embodiments, it can be wastewater after domestic or production utilization, or it can be wastewater discharged during the production process of certain industrial industries, such as saponin wastewater, oil extraction wastewater, and wastewater discharged from the printing and dyeing, papermaking, pharmaceutical, chemical, dairy processing and pesticide industries. Electrochemical treatment steps The electrochemical treatment step of the present invention mainly performs electrochemical treatment on the aqueous system in the flow direction of the aqueous system. Specifically, the aqueous system flows through the cathode region and the anode region in sequence, and the present invention In order to improve the reaction efficiency of the cathode reaction and the anode reaction, the above-mentioned aqueous system passes through the cathode and the anode in the flow direction. For the aqueous system flowing through the anode, the chlorine-containing compounds, especially the chlorine element in the chlorine-containing inorganic salt, are at least partially or completely oxidized under the electrochemical action of the anode to eventually form hypochlorite. In the aqueous system flowing through the cathode, the chlorine element therein is at least partially or completely reduced to a negatively charged chlorine element, particularly chloride ions. These chlorine elements may be products of the reaction between chlorine radicals and the target organic matter in the photochemical treatment step described below, i.e., a dechlorination reaction occurs. Furthermore, the aqueous system passing through the cathode may also produce monatomic hydrogen under the action of the cathode electrochemical reaction, and the production of this monatomic hydrogen can also promote the occurrence of the above-mentioned dechlorination reaction. In principle, there is no particular limitation on the voltage and current between the cathode and the anode in the electrochemical treatment step. In some specific embodiments, a direct current may be passed between the cathode and the anode, and the current density of such a direct current may be 20 to 50 mA / cm 2 , for example 30mA / cm 2 、35mA / cm 2 , 40mA / cm 2 , 45mA / cm 2 For such a voltage, it can be 2 to 8V, for example, 3, 4, 5, 6, 7V, etc. Therefore, the aqueous system that has undergone the electrochemical treatment step contains hypochlorite and, optionally, hydroxide in the direction of flow after leaving the anode. In some specific embodiments of the present invention, the concentration of hypochlorite in the aqueous system leaving the anode, calculated as sodium hypochlorite, can be 50-500 mg / L, for example, 80 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 250 mg / L, 300 mg / L, 350 mg / L, 400 mg / L, 450 mg / L, etc. Photochemical treatment steps In the present invention, in the flow direction of the aqueous system, the aqueous system that has undergone the electrochemical treatment step is further subjected to a photochemical treatment step. The photochemical treatment step can be completed under ultraviolet light irradiation. During this process, the chlorine element and any hydroxide radicals present in the electrochemical treatment step are converted into chlorine free radicals under the action of the radiation. Hydroxyl free radicals can also be generated during this process. These free radicals can then react with organic matter in the aqueous system, thereby achieving mineralization or inorganicization of these organic matter. Furthermore, the ultraviolet light used in the photochemical treatment step is not particularly limited in principle, and light of the ultraviolet wavelength band commonly used in the art can be used. In some specific embodiments, the ultraviolet light can be one or more types of light with a wavelength of 260 nm or less. More preferably, a combination of ultraviolet light with a wavelength of 200 nm or less and ultraviolet light with a wavelength greater than 200 nm and less than 260 nm can be used. Examples of the ultraviolet light used in the present invention include the use of one or both of ultraviolet light with a wavelength of 254 nm and ultraviolet light with a wavelength of 185 nm. In the aqueous system subjected to the above-mentioned photochemical treatment, the organic matter therein undergoes mineralization or inorganicization through reaction with free radicals in the presence of ultraviolet light. In this process, at least part of the organic matter is degraded into non-aromatic organic matter or even inorganic matter through reactions such as oxidation, addition or substitution. In the aqueous system subjected to photochemical treatment in the present invention, the content of the target organic matter is significantly reduced. In some specific embodiments, the content of the target organic matter is reduced by more than 70% by mass. Preferably, the content of the target organic matter is reduced by more than 80% by mass or more than 90% by mass, or even substantially completely eliminated. Steps of loop processing In the present invention, the aqueous system treated photochemically can be at least partially or completely returned to the electrochemical treatment step, that is, partially or completely returned to the cathode and pass through the electrochemical treatment steps including cathode treatment and anode treatment in the flow direction. Furthermore, for the aqueous system returned to the cathode region, at least a portion or even all of the covalently bonded chlorine elements therein are converted into chloride ions through the electrode reaction at the cathode. Therefore, the above-mentioned treatment process of the present invention can be used to perform a cyclic treatment on the aqueous system. One cycle can include one electrochemical treatment step and one photochemical treatment step. The treatment process for the aqueous system of the present invention may include one or more of the above-mentioned cyclic treatments until the content of the target organic matter therein reaches a set or required standard. Water system treatment methods The present invention further provides a method for treating a water system, wherein the water system can be transformed into the above-mentioned aqueous system of the present invention after undergoing any physical or chemical process. Regarding the water system treatment method of the present invention, in addition to the above-mentioned In addition to the method for treating an aqueous system containing organic matter, other arbitrary water treatment steps may optionally be included, such as filtration, incineration, evaporation, ion exchange, adsorption, membrane separation, etc. <Second Aspect> A second aspect of the present invention relates to a treatment system for the aforementioned aqueous system, which can significantly reduce or completely eliminate target organic matter in the aqueous system. In particular, the treatment system of the present invention can be used to perform the treatment method described in the first aspect. Specifically, the system of the present invention includes an electrochemical cell, a photochemical cell, a driving unit, and a connecting unit, wherein the connecting unit connects the electrochemical cell, the photochemical cell, and the driving unit. electrochemical cell The electrochemical unit of the present invention is used to perform an electrochemical treatment step on an aqueous system, preferably, the electrochemical treatment step described in the first aspect. For the electrochemical cell of the present invention, it is necessary to comprise a power source, an inlet, an outlet, an anode and a cathode. For the power supply, preferably, it can be a direct current power supply. In some specific embodiments, such a power supply is configured to provide 20-50 mA / cm 2 current density. The inlet and outlet can be configured as two ports in the external container of the electrochemical unit for the aqueous system to enter and flow out. There is no particular limitation on the specific configuration of the inlet and outlet, which is related to the shape of the container. The cathode and anode of the present invention may be disposed within the container, and preferably, the cathode and anode are configured such that the aqueous system flows entirely through the cathode and then through the anode. Therefore, in the present invention, the cathode and anode are configured to have a penetrating structure such that the aqueous system can flow through the cathode and anode. In principle, there are no particular limitations on the cathode and anode having a through-structure. For example, the through-structure may have a multi-layered structure, a comb-like structure, a porous honeycomb structure, a mesh structure, a sponge structure, or a foam structure extending along the flow direction. In some specific embodiments of the present invention, the through-structure is a sponge structure or a foam structure. Furthermore, there is no particular limitation in principle on the overall external shape of the cathode and anode, and they may be, for example, flat, columnar, or cubical in shape. In principle, there are no special requirements for the material of the cathode as long as it can achieve the reduction of covalently bound organic chlorine. In some preferred embodiments of the present invention, the cathode can have metal palladium as the electrode material. In some typical schemes, a metal palladium layer can be formed on the surface of the conductive substrate to obtain the cathode of the present invention. Preferably, the conductive substrate is cleaned, activated, and other treatments before forming the metal palladium layer. Optionally, an oxygen-free calcination treatment can be performed after the metal palladium layer is formed. In some specific embodiments of the present invention, such a metal palladium layer can be formed by sputtering deposition. In addition, there are no special restrictions on the conductive substrate layer. From the perspectives of conductivity, durability, and chemical resistance, it can usually be metal titanium. The cathode preparation method of the present invention can be obtained by the following steps in some preferred embodiments of the present invention: Step 1: Using a porous titanium foam electrode as a substrate, the porous titanium foam electrode is first cleaned with deionized water and acetone ultrasonically to remove surface stains, chemically polished in a mixed solution of V hydrofluoric acid: V nitric acid: V water = 1:3:6, and dried in an oven for later use. Step 2: Use magnetron sputtering to load metal palladium onto the surface of porous titanium foam and sputter a palladium nanolayer of a certain thickness. Step 3: calcining at 250° C. for 1 hour in an atmosphere of argon-hydrogen mixed gas with a hydrogen content of 10%. Step 4: Calcination at 450°C for 2 hours in a nitrogen atmosphere. In principle, there are no special requirements for the material of the anode as long as it can achieve the oxidation of chlorine atoms to positively valenced chlorine elements. In some preferred embodiments of the present invention, the anode may have a metal ruthenium oxide as the electrode material. In some typical schemes, a metal ruthenium oxide layer can be formed on the surface of a conductive substrate to obtain the anode of the present invention. Preferably, the conductive substrate is cleaned, activated, and other treatments before forming the metal ruthenium oxide layer. In some specific embodiments of the present invention, such a metal ruthenium oxide layer can be formed by a treatment method of solution-coprecipitation-deposition-calcination of a water-soluble ruthenium salt. In addition, there are no special restrictions on the conductive substrate layer. From the perspectives of conductivity, durability, and chemical resistance, it can usually be metal titanium. The method for preparing the anode of the present invention can be obtained by the following steps in some preferred embodiments of the present invention: Step 1: Using a porous titanium foam electrode as a substrate, the porous titanium foam electrode was first cleaned with deionized water and acetone ultrasonically to remove surface stains, then chemically polished in a mixed solution of V hydrofluoric acid: V nitric acid: V water = 1:3:6, and dried in an oven for later use; Step 2: Prepare the coating solution: Use hydrated ruthenium chloride, calculate the amount of RuCl3·xH2O to be used, add RuCl3·xH2O to the isopropanol solution, and then add various solutions in different proportions as needed to prepare the solution, and ultrasonically dissolve it for 20 minutes. Step 3: The polished porous titanium foam is then immersed in the prepared precursor solution, dried, and calcined in a muffle furnace at 400° C. for 5 minutes, and repeated 10 times. Step 4: Finally anneal in a muffle furnace at 450 °C for 2 hours. Furthermore, with regard to the arrangement of the cathode and anode of the present invention, in some preferred embodiments of the present invention, the cathode and anode can be arranged opposite to each other in a parallel manner. In principle, there is no particular restriction on the distance between the two. In some specific embodiments, from the perspective of resistance control, it can be 1 to 20 mm, for example, 3 mm, 5 mm, 7 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, etc. In the present invention, by arranging the above-mentioned electrodes in the flow direction of the aqueous system, the aqueous system can be sequentially subjected to cathode electrochemical reaction treatment and anode electrochemical reaction treatment in a flowing manner. Moreover, since the aqueous system is flowing, unnecessary resistance caused by concentration polarization on the electrode surface can be reduced, thereby improving the treatment efficiency of the electrochemical unit of the present invention. The aqueous system passing through the electrochemical cell contains hypochlorite after leaving the anode in the cell in the flow direction. In some specific embodiments of the present invention, the concentration of hypochlorite in the aqueous system leaving the anode can be 50-500 mg / L, for example, 80 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 250 mg / L, 300 mg / L, 350 mg / L, 400 mg / L, 450 mg / L, etc., calculated as sodium hypochlorite. Photochemical Unit The photochemical unit of the present invention is mainly used for treating aqueous systems, especially those that have discharged the above The aqueous system of the electrochemical cell is further irradiated with ultraviolet light, as a result of which chlorine radicals and optionally hydroxyl radicals are generated in the aqueous system. In some specific embodiments, the photochemical unit of the present invention may include a container, an inlet, an outlet, and an ultraviolet light source. The container is used to contain the flowing aqueous system and provide a place for ultraviolet light irradiation, and serves as an inlet and an outlet for introducing and discharging the aqueous system. For the ultraviolet light source of the present invention, in principle, there is no particular limitation, and a light source of ultraviolet band commonly used in the art can be used. In some specific embodiments, the ultraviolet light source can emit one or more lights with a wavelength of less than 260nm. More preferably, a combination of an ultraviolet light source having an emission wavelength of less than 200nm and an ultraviolet light source having an emission wavelength greater than 200nm and less than 260nm can be provided. Typically, for the ultraviolet light source of the present invention, a combination of two ultraviolet light sources having an emission wavelength of 254nm and a wavelength of 185nm can be enumerated. Furthermore, in the aqueous system passing through the photochemical unit, the target organic compound undergoes a chemical reaction with free radicals, thereby being converted. Consequently, the target organic compound content in the aqueous system passing through the unit is significantly reduced. In some specific embodiments, the target organic compound content is reduced by more than 70% by mass, preferably by more than 80% or more than 90% by mass, or even substantially eliminated. Regarding the above-mentioned target organic matter conversion result, at least a portion of the target organic matter is converted into non-aromatic organic chlorides or even inorganic chlorides. Furthermore, the aqueous system flowing out of the outlet of the photochemical cell can be at least partially returned to the electrochemical cell and circulated into the electrochemical cell again from the inlet of the electrochemical cell. Thus, the electrochemical unit and the photochemical unit of the present invention can be connected in series to form a cyclic treatment of the aqueous system. Drive unit and connection unit The driving unit of the present invention is mainly used to provide flow force of the aqueous system in the flow direction. There is no particular limitation on the specific configuration of the drive unit of the present invention. A pump device commonly used in the art, such as a peristaltic pump, etc. is used. Further, in some preferred embodiments of the present invention, at least one pump / peristaltic pump can be provided between the outlet of the electrochemical unit and the inlet of the photochemical unit to provide the above-mentioned flow force. Furthermore, the connection unit of the present invention is used to provide connectivity between the above units. Such a unit can be a connecting pipe or pipeline. Furthermore, if necessary, a switch, valve, or diverter device can be provided. Other units Other auxiliary units may be used for the above-mentioned system of the present invention, and in principle there is no particular limitation. These auxiliary units may include one or more of a flow control unit, a material detection unit, a system pressure and control unit, a temperature control unit, and the like. Typical examples in Figure 1 Figure 1 provides a specific exemplary illustration of the aforementioned system of the present invention. Box a shows the electrochemical unit, and box b shows the photochemical unit. Arrows indicate flow direction, and 2 is a peristaltic pump providing power for the aqueous system. As shown in Figure 1, the aqueous system flows through cathode 4 and anode 5, and a DC voltage is applied between the cathode and anode via a DC power supply. The cathode 4 is a porous palladium-titanium foam cathode, and the anode 5 is a porous ruthenium-titanium foam anode. Both cathode 4 and anode 5 are disposed within a housing 3. The aqueous system treated by the electrochemical unit further enters the photochemical unit and is treated under the irradiation of the 254 nm ultraviolet lamp 1. Finally, the aqueous system flowing out of the photochemical unit is all guided back to the electrochemical unit (cathode). Example The embodiments of the present invention are described in detail below with reference to the examples. Where specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products. Example 1 (Preparation of porous titanium ruthenium foam anode and porous palladium titanium foam cathode, and construction of a penetrating electrochemical reactor) The porous titanium ruthenium electrode (anode) is prepared by the following method: Step 1: Using a porous titanium foam electrode as a substrate, the porous titanium foam electrode was first cleaned with deionized water and acetone ultrasonically to remove surface stains, then chemically polished in a mixed solution of V hydrofluoric acid: V nitric acid: V water = 1:3:6, and dried in an oven for later use; Step 2: Prepare the coating solution: Using hydrated ruthenium chloride, calculate the amount of RuCl3·xH2O to be used. Add RuCl3·xH2O to the isopropanol solution. Subsequently, add various solutions in varying proportions as needed. The resulting ruthenium chloride solution should be 0.1 mol / L. Ultrasonicate and dissolve for 20 minutes. Step 3: Then immerse the polished porous titanium foam in the prepared precursor liquid. After keeping it in the precursor liquid for 1 minute, take it out and dry it in an oven for 10 minutes. After drying, calcine it in a muffle furnace at 400°C for 5 minutes. The heating rate is set to 5°C per minute. Repeat this process 10 times. Step 4: Annealing in a muffle furnace at 450°C for 2 hours to complete the preparation. The porous palladium titanium foam electrode (cathode) is prepared by the following method: Step 1: Using a porous titanium foam electrode as a substrate, the porous titanium foam electrode is first cleaned with deionized water and acetone ultrasonically to remove surface stains, chemically polished in a mixed solution of V hydrofluoric acid: V nitric acid: V water = 1:3:6, and dried in an oven for later use. Step 2: Use magnetron sputtering to load metal palladium onto the surface of porous titanium foam with a sputtering thickness of 30 nm. Step 3: calcining at 250° C. for 1 hour in an atmosphere of argon-hydrogen mixed gas with a hydrogen content of 10%, with a heating rate set at 5° C. per minute. Step 4: calcining at 450°C for 2 hours in a nitrogen atmosphere, with the heating rate set at 5°C per minute. The electrochemical reaction zone is equipped with a porous titanium ruthenium foam anode and a porous palladium titanium foam cathode. The two electrodes are located between the fluid inlet and outlet and connected to a power source via a conductive titanium wiring sheet. A 254nm UV lamp is inserted into the UV irradiation zone for UV irradiation. After assembling the above-mentioned penetrating photoelectrochemical reactor device, organic wastewater containing benzoic acid as the target pollutant is injected into the UV lamp container. The entire reactor is driven by a peristaltic pump. The solution flows from the UV irradiation zone, through the cathode, through the anode, and finally back to the UV irradiation zone, finally returning to the UV irradiation zone, thus completing the cycle. Example 2 The reactor in Example 1 is used to efficiently remove benzoic acid in a high-salt system, and the implementation steps are as follows: Step 1: Set the initial experimental solution to 170 mL, containing 50 ppm benzoic acid and 0.5 mol NaCl. Step 2: Set the DC power supply to a constant current of 140mA. Step 3: Take 0 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, and 40 min as sampling points. Continue UV irradiation during the experiment and take out 1 mL of solution from the UV lamp container as the test solution; Step 4: Filter the test solution through a 0.22 μm water filter membrane and place it into a liquid chromatography vial for testing; Step 5: Analyze the benzoic acid degradation concentration of the prepared sample by high performance liquid chromatography, with the UV detector wavelength set to 228 nm; Step 6: After each experiment, rinse the permeable electrochemical reactor and electrodes with deionized water several times. Each group of experiments was repeated three times. As shown in Figure 4, benzoic acid was removed within 20 minutes, proving that the photoelectrochemical reactor for reductive dechlorination enhanced radical oxidation removal can produce OH and Cl radicals stably through chlorine production at the anode and UV irradiation, and enhance free radical oxidation removal in coordination with reductive dechlorination at the cathode, thereby improving the mineralization efficiency of organic matter in high-salt wastewater. Example 3 The reactor in Example 1 is used to efficiently remove different organic matter in a high-salt system. The implementation steps are as follows: Step 1: Set the initial experimental solution to 170 mL, the concentrations of organic matter phenol, p-nitrophenol, and bisphenol A to 100 ppm, and the NaCl content to 0.5 mol; Step 2: Set the DC power supply to a constant current of 140mA. Step 3: Take 0min, 10min, 20min, 30min, 40min, 50min, and 60min as sampling point, UV irradiation was continued during the experiment, and 1 mL of solution was taken out from the UV lamp container as the test solution; Step 4: Filter the test solution through a 0.22 μm water filter membrane and place it into a liquid chromatography vial for testing; Step 5: Analyze the benzoic acid degradation concentration of the prepared sample by high performance liquid chromatography, with the UV detector wavelength set to 228 nm; Step 6: After each experiment, rinse the permeable electrochemical reactor and electrodes with deionized water several times. Each group of experiments was repeated three times. As shown in Figure 5, all organic matter can be removed within 40 minutes, which further proves that the photoelectrochemical reactor with reductive dechlorination and enhanced radical oxidation removal can produce OH and Cl radicals stably through chlorine production at the anode and coordinated with ultraviolet irradiation, and enhance the free radical oxidation removal by synergistically reducing dechlorination at the cathode, thereby improving the mineralization efficiency of organic matter in high-salt wastewater. It should be noted that, although the technical solutions of the present invention are described with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto. While various embodiments of the present invention have been described above, the above descriptions are intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for treating an aqueous system containing organic matter, characterized in that: A chlorine-containing compound is present in the aqueous system, and the method comprises: electrochemical treatment steps and photochemical treatment steps, in, In the electrochemical treatment step, the aqueous system flows from the cathode toward the anode. In the flow direction, the aqueous system passes through the cathode and the anode, and the aqueous system flowing out of the anode generates hypochlorite through the anode electrochemical reaction. In the photochemical treatment step, the aqueous system flowing out of the anode is irradiated with ultraviolet light to generate chlorine free radicals in the aqueous system, and the free radicals react chemically with the organic matter. Furthermore, the aqueous system that has completed the photochemical treatment step is at least partially returned to the cathode in the electrochemical treatment step. At least part of the aqueous system is subjected to one or more cycles comprising an electrochemical treatment step and a photochemical treatment step.

2. The method according to claim 1, characterized in that The aqueous system produces monatomic hydrogen via a cathode electrochemical reaction; The aqueous system flowing out of the anode is irradiated with ultraviolet light so that hydroxyl radicals are generated in the aqueous system, and the free radicals also produce a photochemical reaction with the organic matter.

3. The method according to claim 1 or 2, characterized in that The anode includes ruthenium oxide; the cathode includes metal palladium; and during the electrochemical treatment step, direct current is passed between the anode and the cathode.

4. The method according to any one of claims 1 to 3, characterized in that In the photochemical treatment step, the light in the ultraviolet band includes one or more types of light with a wavelength of less than 260 nm.

5. The method according to any one of claims 1 to 4, characterized in that At least part of the chlorine elements in the aqueous system after the photochemical treatment step forms non-aromatic organic matter in the form of covalent bonds.

6. The method according to any one of claims 1 to 5, characterized in that After completing the photochemical treatment step, the aqueous system is returned to the cathode in the electrochemical treatment step, and under the action of the cathode, the chlorine element is at least partially converted into chloride ions.

7. A treatment system for an aqueous system containing organic matter, characterized in that: There is a chlorine-containing compound in the aqueous system, The system includes an electrochemical cell, a photochemical cell, a driving unit, and a connecting unit, wherein the connecting unit connects the electrochemical cell, the photochemical cell, and the driving unit. The driving unit provides the flow force of the aqueous system in the treatment system. The electrochemical unit includes a power source, an inlet, an outlet, an anode, and a cathode. The anode and the cathode are arranged between the inlet and the outlet and have a fluid-penetrating structure. The aqueous system flows from the cathode toward the anode. In the flow direction, the aqueous system passes through the cathode and the anode. The photochemical cell comprises an inlet, an outlet and an ultraviolet light source, and the ultraviolet light source irradiates the aqueous system flowing out of the anode of the electrochemical cell with ultraviolet radiation. Furthermore, the outlet of the photochemical cell is in communication with the inlet of the electrochemical cell, so that at least a portion of the aqueous system flowing out of the photochemical cell is returned to the electrochemical cell.

8. The system according to claim 7, characterized in that The electrochemical cell is configured such that the aqueous system flowing out of the electrochemical cell outlet includes hypochlorite.

9. The system according to claim 8, characterized in that At least part of the hypochlorite originates from an electrochemical reaction at the anode of the electrochemical cell.

10. The system according to any one of claims 7 to 9, characterized in that: In the electrochemical unit, the anode comprises metal ruthenium oxide; the cathode comprises metal palladium; and the power supply is a direct current power supply.

11. The system according to any one of claims 7 to 10, characterized in that: The photochemical unit is configured to generate chlorine radicals, and optionally also hydroxyl radicals, in an aqueous system irradiated by the ultraviolet light source.

12. The system according to any one of claims 7 to 11, characterized in that: The ultraviolet light source in the photochemical unit is configured to provide light including one or more ultraviolet bands with a wavelength below 260 nm.

13. A method for circulating treatment of an aqueous system containing organic matter, characterized in that: Chlorine-containing compounds are present in the aqueous system, and the method comprises subjecting the aqueous system to be treated to one or more cycles of treatment using the system according to any one of claims 7 to 12, wherein each cycle comprises sequential treatment of the electrochemical unit and treatment of the photochemical unit.

14. The processing method according to claim 13, characterized in that: The aqueous system is wastewater containing water-soluble aromatic organic matter.

15. The processing method according to claim 13 or 14, characterized in that The aqueous system includes industrial wastewater or domestic wastewater.

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