A method for removing micropollutants from water using a mixed chlorine system assisted by ultraviolet light

Abstract

The present invention relates to a method for removing micropollutants from water using a UV-assisted mixed chlorine system, comprising the following steps: (1) adjusting the pH of a water solution containing micropollutants to 6-9; (2) adding an oxidant mixture of chlorine dioxide and sodium hypochlorite to the solution; and (3) continuously stirring the solution and performing an oxidation reaction at an ultraviolet wavelength of 320-400 nm. Compared with the prior art, the present invention improves the photodegradation performance of micropollutants in water and effectively reduces the production of inorganic disinfection byproducts and volatile disinfection byproducts by adjusting the ratio of the oxidant.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a method for removing micropollutants in water based on an ultraviolet-assisted mixed chlorine system. Background Art

[0002] Pharmaceuticals and personal care products (PPCPs) are present in a variety of aquatic environments, including surface water, groundwater, and even drinking water. While these emerging pollutants are present at low concentrations, they are difficult to remove using conventional methods. Consequently, they can release residual pharmaceuticals into the environment, posing a threat to the ecosystem. The public health implications of environmental pollution are a growing concern.

[0003] Among them, neuroactive drugs (NPCPs) are a class of drugs that can cause poisoning or even death in aquatic organisms. These drugs are commonly used to treat psychiatric disorders such as epilepsy and depression, with carbamazepine (CBZ) being the most prominent example. However, this drug is typically used at high doses, and its recalcitrant nature makes it difficult to completely degrade in various water bodies. Studies have shown that the long-term presence of CBZ in water can cause severe oxidative damage to the brains of organisms and may also lead to growth retardation. CBZ can also be extremely harmful to human health, with studies indicating that excessive consumption of CBZ and its metabolites can damage the liver. Furthermore, with the widespread use of antibiotics, the problem of antibiotic contamination in water is becoming increasingly serious. These antibiotic residues in water not only harm aquatic organisms but also pose a potential threat to human health. Therefore, the efficient degradation of these emerging micropollutants remains a key area of ​​water treatment.

[0004] Ultraviolet advanced oxidation processes (UV-AOPs) have very low requirements for temperature and pressure and can completely oxidize micropollutants at room temperature and atmospheric pressure. They have attracted widespread attention due to their advantages in removing stubborn pollutants with high efficiency, low cost, and ease of use. This technology combines ultraviolet light with strong oxidants such as free chlorine, chlorine dioxide, hydrogen peroxide, and persulfate, and utilizes certain active species generated during the reaction to oxidize target pollutants in the water. In recent years, research has tended to combine short-wavelength ultraviolet light with strong oxidants to achieve pollutant degradation. However, short-wavelength ultraviolet light has a high energy demand and low quantum yield. In addition, the UV mercury lamps that are mostly used today have potential risks to the environment, high power consumption, non-adjustable wavelength, and require preheating. Currently, most UV-AOPs based on chlorine dioxide (ClO2) use wavelengths below 320nm, which are not as effective as NaClO. Processes using NaClO as an oxidant are usually concentrated in the UVB (wavelength 280-320nm) and UVC (wavelength 200-275nm) bands, and their photocatalytic degradation performance needs to be improved. In addition, traditional chlorine dioxide and sodium hypochlorite processes produce a large amount of inorganic disinfection by-products and volatile disinfection by-products, which can cause great harm to human health.

[0005] Therefore, the technical problem of efficiently degrading micropollutants in water has not yet been solved, and it is urgent to develop a chlorine-containing UV oxidation process that can ensure degradation performance while controlling the risk of disinfection by-products. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for removing micropollutants in water based on a UV-assisted mixed chlorine system, which can ensure degradation performance and simultaneously control the risk of disinfection by-products.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for removing micropollutants from water using a UV-assisted mixed chlorine system comprises the following steps:

[0009] (1) adjusting the pH of the aqueous solution to be treated containing micropollutants to 6-9;

[0010] (2) adding an oxidant mixture of chlorine dioxide and sodium hypochlorite to the solution;

[0011] (3) The solution is continuously stirred and an oxidation reaction is carried out under an ultraviolet wavelength of 320-400 nm.

[0012] Furthermore, in step (1), the molar concentration of the micropollutants in the aqueous solution to be treated is 5-15 mM, preferably 10 mM.

[0013] Furthermore, in step (1), the micropollutants include one or more of carbamazepine, sulfonamides, floxacins or quinolones.

[0014] Furthermore, in step (1), the reagents used for pH adjustment are 10 mM phosphate buffer, 1 M sodium hydroxide solution and 0.18 M dilute sulfuric acid solution.

[0015] Furthermore, in step (2), the molar ratio of chlorine dioxide to sodium hypochlorite is (0.25-4):1.

[0016] Furthermore, in step (2), the total concentration of the oxidant mixture in the solution is 50-90 μM.

[0017] Furthermore, in step (3), the stirring speed is 300-500 rpm, preferably 400 rpm.

[0018] Furthermore, in step (3), the oxidation reaction is carried out in a UVA-LED irradiation device in the dark.

[0019] Furthermore, the UVA-LED irradiation device includes five major parts: an outer light-proof black box, an output adjustment device, a pluggable lifting square circuit board, a heat dissipation device and a reaction area. The circuit board device can simultaneously arrange up to nine UVA-LED lamp beads, and the heat dissipation device is arranged on the back of the circuit device.

[0020] Furthermore, in step (3), the oxidation reaction is carried out at room temperature.

[0021] Furthermore, in step (3), the oxidation reaction time is 2-60 minutes. The oxidation time can be adjusted according to the actual degradation rate of the micropollutants.

[0022] The present invention also provides an application of a method for removing micropollutants in water based on an ultraviolet-assisted mixed chlorine system in the treatment of micropollutant water bodies.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention adopts an oxidant composition of chlorine dioxide and sodium hypochlorite, which significantly improves the photodegradation performance of micropollutants in water under the UVA band. At the same time, by adjusting the ratio of chlorine dioxide and sodium hypochlorite, the production of inorganic disinfection by-products and volatile disinfection by-products can be effectively reduced.

[0025] (2) By regulating the ratio of the oxidants chlorine dioxide and sodium hypochlorite, the present invention can reduce the oxidant consumption while ensuring the micropollutant degradation efficiency according to actual needs, thereby effectively improving the flexibility and operability of actual process operations.

[0026] (3) Under UVA irradiation of 320-400 nm, chlorine dioxide can produce more active species than under UVC irradiation, thereby achieving higher degradation efficiency.

[0027] (4) The UVA-LED light source selected in the present invention is not only capable of customizing wavelengths according to needs, is compact in size, environmentally friendly and mercury-free, but also can achieve adjustable pulse lighting, and is a UV light source with great development prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a graph showing the degradation performance test of carbamazepine in Examples 1-5 and Comparative Example 1.

[0029] Figure 2 The graph shows the degradation performance test of carbamazepine in Example 6 and Comparative Examples 1-5.

[0030] Figure 3 The graph is a test diagram of the degradation performance of sulfamethoxazole in Example 7 and Comparative Examples 6-9.

[0031] Figure 4 Schematic diagram of oxidant consumption in Example 3 and Comparative Examples 2-5.

[0032] Figure 5 Schematic diagram of the production of chlorate and chlorite in Examples 1-5 and Comparative Examples 4-5.

[0033] Figure 6 Schematic diagram of the production of volatile disinfection by-products in Examples 1-5 and Comparative Examples 4-5. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples were commercially available. The UVA-LED irradiation device was purchased from Shenzhen Chengzi Optoelectronics.

[0036] Example 1:

[0037] The specific steps of this embodiment are as follows:

[0038] (1) Phosphate buffer solution was added to an aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0039] (2) A ClO2 / NaClO oxidant combination was added to the solution at a final concentration of 75 μM, wherein the molar feed ratio of ClO2 to NaClO was 4:1 (i.e., [ClO2]0:[NaClO]0=4:1).

[0040] (3) Turn on the UVA-LED irradiation device, set the ultraviolet wavelength to 365 nm, and perform photocatalytic degradation reaction of the solution in the dark at room temperature. Stop the reaction after 40 minutes.

[0041] Example 2:

[0042] The specific steps of this embodiment are as follows:

[0043] (1) Phosphate buffer solution was added to an aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0044] (2) A ClO2 / NaClO oxidant combination was added to the solution at a final concentration of 75 μM, wherein the molar feed ratio of ClO2 to NaClO was 3:1 (i.e., [ClO2]0:[NaClO]0=3:1).

[0045] (3) Turn on the UVA-LED irradiation device, set the ultraviolet wavelength to 365 nm, and perform photocatalytic degradation reaction of the solution in the dark at room temperature. Stop the reaction after 40 minutes.

[0046] Example 3:

[0047] The specific steps of this embodiment are as follows:

[0048] (1) Phosphate buffer solution was added to an aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0049] (2) A ClO2 / NaClO oxidant combination was added to the solution at a final concentration of 75 μM, wherein the molar feed ratio of ClO2 to NaClO was 1:1 (i.e., [ClO2]0:[NaClO]0=1:1).

[0050] (3) Turn on the UVA-LED irradiation device, set the ultraviolet wavelength to 365 nm, and perform photocatalytic degradation reaction of the solution in the dark at room temperature. Stop the reaction after 40 minutes.

[0051] Example 4:

[0052] The specific steps of this embodiment are as follows:

[0053] (1) Phosphate buffer solution was added to an aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0054] (2) A ClO2 / NaClO oxidant combination was added to the solution at a final concentration of 75 μM, wherein the molar feed ratio of ClO2 to NaClO was 1:3 (i.e., [ClO2]0:[NaClO]0=1:3).

[0055] (3) Turn on the UVA-LED irradiation device, set the ultraviolet wavelength to 365 nm, and perform photocatalytic degradation reaction of the solution in the dark at room temperature. Stop the reaction after 40 minutes.

[0056] Example 5:

[0057] The specific steps of this embodiment are as follows:

[0058] (1) Phosphate buffer solution was added to an aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0059] (2) A ClO2 / NaClO oxidant combination was added to the solution at a final concentration of 75 μM, wherein the molar feed ratio of ClO2 to NaClO was 1:4 (i.e., [ClO2]0:[NaClO]0=1:4).

[0060] (3) Turn on the UVA-LED irradiation device, set the ultraviolet wavelength to 365 nm, and perform photocatalytic degradation reaction of the solution in the dark at room temperature. Stop the reaction after 40 minutes.

[0061] Example 6:

[0062] The specific steps of this embodiment are as follows:

[0063] (1) Phosphate buffer solution was added to an aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 9.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0064] (2) A ClO2 / NaClO oxidant combination was added to the solution at a final concentration of 75 μM, wherein the molar feed ratio of ClO2 to NaClO was 1:4 (i.e., [ClO2]0:[NaClO]0=1:4).

[0065] (3) Turn on the UVA-LED irradiation device, set the ultraviolet wavelength to 365 nm, and perform photocatalytic degradation reaction of the solution in the dark at room temperature. Stop the reaction after 40 minutes.

[0066] Example 7:

[0067] The specific steps of this embodiment are as follows:

[0068] (1) Phosphate buffer solution was added to an aqueous solution containing sulfamethoxazole to a final concentration of 10 mM sulfamethoxazole, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0069] (2) A ClO2 / NaClO oxidant combination was added to the solution at a final concentration of 75 μM, wherein the molar feed ratio of ClO2 to NaClO was 1:1 (i.e., [ClO2]0:[NaClO]0=1:1).

[0070] (3) Turn on the UVA-LED irradiation device, set the ultraviolet wavelength to 365 nm, and perform photocatalytic degradation reaction of the solution in the dark at room temperature. Stop the reaction after 40 minutes.

[0071] Comparative Example 1:

[0072] The specific steps of this comparative example are as follows:

[0073] (1) Phosphate buffer solution was added to an aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0074] (2) Turn on the UVA-LED irradiation device and set the ultraviolet wavelength to 365 nm. The solution is reacted in the dark at room temperature and the reaction is stopped after 40 minutes.

[0075] Comparative Example 2:

[0076] The specific steps of this comparative example are as follows:

[0077] (1) Phosphate buffer solution was added to the aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 7.0 using 1 M sodium hydroxide solution and 0.18 M dilute sulfuric acid solution. The flask containing the solution was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0078] (2) Add ClO2 to a final concentration of 75 μM to the solution, carry out the reaction at room temperature in the dark, and stop the reaction after 40 minutes.

[0079] Comparative Example 3:

[0080] The specific steps of this comparative example are as follows:

[0081] (1) Phosphate buffer solution was added to the aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 7.0 using 1 M sodium hydroxide solution and 0.18 M dilute sulfuric acid solution. The flask containing the solution was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0082] (2) Add NaClO to a final concentration of 75 μM to the solution, and carry out the reaction at room temperature in the dark. Stop the reaction after 40 minutes.

[0083] Comparative Example 4:

[0084] The specific steps of this comparative example are as follows:

[0085] (1) Phosphate buffer solution was added to an aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0086] (2) Add ClO2 oxidant to the solution at a final concentration of 75 μM.

[0087] (3) Turn on the UVA-LED irradiation device, set the ultraviolet wavelength to 365 nm, and perform photocatalytic degradation reaction of the solution in the dark at room temperature. Stop the reaction after 40 minutes.

[0088] Comparative Example 5:

[0089] The specific steps of this comparative example are as follows:

[0090] (1) Phosphate buffer solution was added to an aqueous solution containing carbamazepine to a final carbamazepine concentration of 10 mM, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0091] (2) Add NaClO oxidant to the solution at a final concentration of 75 μM.

[0092] (3) Turn on the UVA-LED irradiation device, set the ultraviolet wavelength to 365 nm, and perform photocatalytic degradation reaction of the solution in the dark at room temperature. Stop the reaction after 40 minutes.

[0093] Comparative Example 6:

[0094] The specific steps of this comparative example are as follows:

[0095] (1) Phosphate buffer solution was added to an aqueous solution containing sulfamethoxazole to a final concentration of 10 mM sulfamethoxazole, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0096] (2) Turn on the UVA-LED irradiation device and set the ultraviolet wavelength to 365 nm. The solution is reacted in the dark at room temperature and the reaction is stopped after 15 minutes.

[0097] Comparative Example 7:

[0098] (1) Phosphate buffer solution was added to the aqueous solution containing sulfamethoxazole to a final concentration of 10 mM sulfamethoxazole, and the pH was adjusted to 7.0 using 1 M sodium hydroxide solution and 0.18 M dilute sulfuric acid solution. The flask containing the solution was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0099] (2) Add ClO2 to a final concentration of 75 μM to the solution, carry out the reaction at room temperature in the dark, and stop the reaction after 15 minutes.

[0100] Comparative Example 8:

[0101] The specific steps of this comparative example are as follows:

[0102] (1) Phosphate buffer solution was added to the aqueous solution containing sulfamethoxazole to a final concentration of 10 mM sulfamethoxazole, and the pH was adjusted to 7.0 using 1 M sodium hydroxide solution and 0.18 M dilute sulfuric acid solution. The flask containing the solution was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0103] (2) Add NaClO to a final concentration of 75 μM to the solution, and carry out the reaction at room temperature in the dark. Stop the reaction after 15 minutes.

[0104] Comparative Example 9:

[0105] The specific steps of this comparative example are as follows:

[0106] (1) Phosphate buffer solution was added to an aqueous solution containing sulfamethoxazole to a final concentration of 10 mM sulfamethoxazole, and the pH was adjusted to 7.0 using a 1 M sodium hydroxide solution and a 0.18 M dilute sulfuric acid solution. The pH-adjusted solution to be treated was placed in a culture dish and placed in a UVA-LED irradiation device; the UVA-LED irradiation device was placed on a magnetic stirrer and stirred at a constant speed of 400 rpm.

[0107] (2) Add NaClO oxidant to the solution at a final concentration of 75 μM.

[0108] (3) Turn on the UVA-LED irradiation device, set the ultraviolet wavelength to 365 nm, and perform photocatalytic degradation reaction of the solution in the dark at room temperature. Stop the reaction after 15 minutes.

[0109] The present invention performs the following tests on Examples 1-6 and Comparative Examples 1-9:

[0110] (1) Photodegradation performance test:

[0111] Detection instrument: The concentrations of micropollutants (carbamazepine and sulfamethoxazole) in this study were detected using an Agilent HPLC1260 Ultra Performance Liquid Chromatography (UPLC) equipped with a UV detector and a Waters, USA MSC18 chromatographic column (250.00 mm × 2.10 mm, 3.50 μm).

[0112] Test Method: Before starting the degradation experiment, prepare the required substrate stock solutions, including carbamazepine solution and sulfamethoxazole solution. Before the experiment, dilute the stock solution to the target concentration (5 μM) and add phosphate buffer solution to a concentration of 10 mM. Adjust the pH to the desired value by adding NaOH and dilute H2SO4 solution.

[0113] At the beginning of the experiment, 50mL of reaction solution was placed in a culture dish and a small magnet was placed in the container. In the degradation experiment, the reaction container was placed on a magnetic stirrer and stirred at the same speed. In Examples 1-7, an oxidant (ClO2, NaClO) with a total oxidant concentration of 75uM was added according to the oxidant molar feed ratio according to the experimental requirements; in Comparative Examples 2-3, an oxidant (ClO2 or NaClO) of 75μM was added according to the experimental requirements. For experiments requiring photocatalysis, the UV-LED device was turned on synchronously for ultraviolet irradiation, and the reaction started timing. The reaction stopped after the experimental required time, wherein the experimental time of Examples 1-6 and Comparative Examples 1-5 was 40min, and the experimental time of Example 7 and Comparative Examples 6-9 was 15min. Take out 1mL of water sample and inject it into the liquid phase vial, and add a quencher (Na2S2O3) to quench the remaining oxidant, shake well and wait for high performance liquid chromatography detection. In the figure, ln(C / C0) is the vertical axis and time (min) is the horizontal axis:.

[0114] (2) Oxidant consumption test:

[0115] Testing Instruments: The oxidant sodium hypochlorite was measured using the DPD spectrophotometric method, and a portable residual chlorine analyzer was used for concentration analysis. The concentration of the oxidant chlorine dioxide was determined using the DMSO masking method. Measurements were performed at room temperature not exceeding 20°C and in the absence of direct sunlight.

[0116] Test Method: Before the degradation experiment begins, prepare the desired carbamazepine substrate solution. Before the experiment, dilute the stock solution to the target concentration (5 μmol / L) and add phosphate buffer solution to a concentration of 10 mM. Adjust the pH to the desired value by adding NaOH and dilute H2SO4 solution.

[0117] At the beginning of the experiment, 50mL of reaction solution was placed in a culture dish and a small magnet was placed in the container. In the degradation experiment, the reaction container was placed on a magnetic stirrer and stirred at the same speed. In Example 3, an oxidant (ClO2, NaClO) with a total oxidant concentration of 75μmol / L was added according to the oxidant molar feed ratio according to the experimental requirements; in Comparative Examples 2-5, 75μmol / L of oxidant (ClO2 or NaClO) was added according to the experimental requirements. For experiments requiring photocatalysis, the UV-LED device was turned on simultaneously for ultraviolet irradiation, and the reaction started timing. The reaction stopped after the experimental time required, and the experimental time was 40min. In the figure, the oxidant concentration (μmol / L) is the vertical coordinate and the time (min) is the horizontal coordinate.

[0118] (3) Inorganic disinfection by-product test:

[0119] Detection instrument: The concentrations of inorganic disinfection by-products chlorate and chlorite were determined using a Dionex ICS-5000 ion chromatograph (AS11-HC anion analysis column, 250 mm × 4.0 mm).

[0120] Test Method: Before the degradation experiment begins, prepare the desired carbamazepine substrate solution. Before the experiment, dilute the stock solution to the target concentration (5 μM) and add phosphate buffer solution to a concentration of 10 mM. Adjust the pH to the desired value by adding NaOH and dilute H₂SO₄ solutions.

[0121] At the beginning of the experiment, 50mL of reaction solution was placed in a culture dish and a small magnet was placed in the container. In the degradation experiment, the reaction container was placed on a magnetic stirrer and stirred at the same speed. In Examples 1-5, an oxidant (ClO2, NaClO) with a total oxidant concentration of 75μM was added according to the oxidant molar feed ratio according to the experimental requirements; in Comparative Examples 4-5, 75μM of oxidant (ClO2 or NaClO) was added according to the experimental requirements. At this time, the UV-LED device was synchronously turned on for ultraviolet irradiation, and the reaction started timing. The reaction stopped after the experimental time required, and the experimental time was 40min. In the figure, the concentration (μmol / L) is the vertical coordinate and the oxidant molar feed ratio is the horizontal coordinate.

[0122] (4) Volatile disinfection by-products test:

[0123] Detection instrument: Volatile disinfection by-products were measured using a GC2010 gas phase GC-ECD (Shimadzu Corporation, Japan), equipped with an HP capillary column (30.00 m × 0.25 mm, 0.25 μm, J&W, USA) and an automatic sampler (AOC-20i, Shimadzu, Japan), and high-purity nitrogen (purity ≥99.99%) was used as the carrier gas.

[0124] Test Method: Before starting the degradation experiment, prepare the required substrate stock solutions, including carbamazepine solution and sulfamethoxazole solution. Before the experiment, dilute the stock solution to the target concentration (5 μM) and add phosphate buffer solution to a concentration of 10 mM. Adjust the pH to the desired value by adding NaOH and dilute H2SO4 solution.

[0125] At the beginning of the experiment, 50 mL of reaction solution was placed in a culture dish and a small magnet was placed in the container. In the degradation experiment, the reaction container was placed on a magnetic stirrer and stirred at the same speed. In Examples 1-5, an oxidant (ClO2, NaClO) with a total oxidant concentration of 75 μM was added according to the oxidant molar feed ratio according to the experimental requirements; in Comparative Examples 4-5, 75 μM of oxidant (ClO2 or NaClO) was added according to the experimental requirements. At this time, the UV-LED device was turned on synchronously for ultraviolet irradiation, and the reaction started timing. The reaction stopped after the experimental time required, and the experimental time was 40 minutes.

[0126] The disinfection byproducts measured in the experiment are: trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), dichloroacetaldehyde (DCAL), trichloroacetaldehyde (TCAL), dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN), bromochloroacetonitrile (BCAN), and trichloropicrin (TCNM).

[0127] The experiment evaluates the cytotoxicity risk of water bodies by detecting the theoretical toxicity of disinfection by-products. The method requires the use of LC 50 The value is determined when Chinese hamster ovary (CHO) cells reach 50% mortality after 72 hours of exposure to a specific disinfection byproduct concentration. The cytotoxicity index (CTI) is calculated as shown below, where [DBP] is the disinfection byproduct concentration.

[0128]

[0129] LC of different disinfection by-products 50 The values ​​are shown in Table 1.

[0130] Table 1 LC values ​​corresponding to different disinfection by-products 50 value

[0131]

[0132] like Figure 1-2 As shown in Figure 1, when only UV irradiation is used (i.e., Comparative Example 1), carbamazepine cannot be degraded. When only oxidant is added (i.e., Comparative Examples 2-3) without UV assistance, carbamazepine still cannot be degraded. 365 The degradation effect of carbamazepine by the single oxidant process with UV light and ClO2 (Comparative Example 4) is significantly higher than that by UV light alone and oxidant alone without light. 365 / NaClO (Comparative Example 5) is better than UVA 365 / ClO2 process (ie comparative example 4). 365 / ClO2 and UVA 365 The rate constants of the / NaClO process were 2.11×10 -4 s -1 , 3.55×10 -4 s -1 , while UVA 365 The rate constant of the / ClO2 / NaClO process is 4.17×10 -4 s -1 , so compared with the two single oxidant processes with additional UV irradiation, UVA 365 The degradation efficiency of carbamazepine was significantly improved by the / ClO2 / NaClO process, which was the best process among the six processes for degrading carbamazepine.

[0133] like Figure 3 As shown, when UVA alone 365 Under the conditions of irradiation (ie, comparative example 6), almost no degradation reaction occurs, and the micropollutant sulfamethoxazole cannot be effectively degraded. When only a single oxidant is added (ie, comparative examples 7-8) and there is no light condition, the degradation of sulfamethoxazole cannot be achieved. When using UVA 365 The degradation effect of sulfamethoxazole by the single oxidant process with UV light and NaClO (Comparative Example 9) is significantly higher than that by UV light alone and single oxidant without light. UVA365 / ClO2 / NaClO >k UVA / NaClO >k ClO2 >k NaClO >k UVA Compared with the single oxidant process with additional ultraviolet light, UVA 365 The degradation efficiency of sulfamethoxazole in the / ClO2 / NaClO process was significantly improved, and the degradation could be completed within 2 minutes, making it the best process for degrading sulfamethoxazole.

[0134] like Figure 4 As shown, within 40 minutes, the oxidant consumption during carbamazepine oxidation using ClO2 or NaClO alone was 8.32% and 15.35% of the initial dose, respectively. With the assistance of UVA-LED, ClO2 consumed 50.59% of the initial dose, while the NaClO process consumed 86.42% of the NaClO dose. The UVA-LED / ClO2 / NaClO process of Example 3 consumed 73.67% of the oxidant. This demonstrates that the present invention can reduce NaClO consumption while maintaining high carbamazepine degradation efficiency.

[0135] like Figure 5As shown in the figure, the UVA-LED / ClO2 / NaClO process can effectively reduce the amount of chlorate generated compared to using ClO2 alone. When the concentration of NaClO in the reaction solution increases, the amount of chlorate generated can be reduced. When the molar ratio of ClO2 to NaClO is 1:4, the amount of chlorate generated is reduced by 74.27%.

[0136] like Figure 6 As shown in the figure, the risk of volatile disinfection by-products can be effectively controlled by adjusting the concentration ratio of the oxidant. The CTI index of comparative example 5 is 6.027×10 -3 The CTI indexes of Examples 1 to 5 were 1.1544×10 -3 , 1.3073×10 -3 , 1.969×10 -3 , 2.579×10 -3 and 2.580×10 -3 This result shows that the UVA-LED / ClO2 / NaClO process can effectively reduce the amount of volatile disinfection byproducts produced compared to the UVA-LED / NaClO process (i.e., Comparative Example 5), and that as the NaClO ratio decreases in several examples, the risk of volatile disinfection byproducts decreases accordingly. In summary, the present invention can reduce the production of inorganic disinfection byproducts and volatile disinfection byproducts by adjusting the ratio of ClO2 and NaClO according to actual needs.

[0137] The present invention adopts an oxidant composition of chlorine dioxide and sodium hypochlorite, which significantly improves the photodegradation performance of micropollutants in water under the UVA band. At the same time, by adjusting the ratio of chlorine dioxide and sodium hypochlorite, the generation of inorganic disinfection by-products and volatile disinfection by-products can be effectively reduced.

[0138] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for removing micropollutants from water using a UV-assisted mixed chlorine system, characterized in that: The following steps are involved: (1) Adjusting the pH of the aqueous solution to be treated containing micropollutants to 6-9; (2) adding an oxidant mixture of chlorine dioxide and sodium hypochlorite to the solution; (3) The solution is continuously stirred and the oxidation reaction is carried out under ultraviolet wavelength of 320-400 nm; In step (1), the micropollutants include one or more of carbamazepine, sulfonamides, floxacins, or quinolones; In step (2), the molar ratio of chlorine dioxide to sodium hypochlorite is (0.25~4):

1.

2. The method for removing micropollutants from water using a UV-assisted mixed chlorine system according to claim 1, wherein: In step (1), the molar concentration of the micropollutants in the aqueous solution to be treated is 5-15 mM.

3. The method for removing micropollutants from water using a UV-assisted mixed chlorine system according to claim 1, wherein: In step (2), the total concentration of the oxidant mixture in the solution is 50-90 μM.

4. The method for removing micropollutants from water using a UV-assisted mixed chlorine system according to claim 1, wherein: In step (3), the stirring speed is 300-500 rpm.

5. The method for removing micropollutants from water using a UV-assisted mixed chlorine system according to claim 1, wherein: In step (3), the oxidation reaction is carried out in a UVA-LED irradiation device in the dark.

6. The method for removing micropollutants from water using a UV-assisted mixed chlorine system according to claim 1, wherein: In step (3), the oxidation reaction is carried out at room temperature.

7. The method for removing micropollutants from water using a UV-assisted mixed chlorine system according to claim 1, wherein: In step (3), the oxidation reaction time is 2-60 min.

8. Use of the method for removing micropollutants in water using a UV-assisted mixed chlorine system according to any one of claims 1 to 7 in the treatment of micropollutant water.

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