A method for degrading brominated organic pollutants in water bodies by using UV / H2O2

Abstract

The application discloses a method for degrading brominated organic pollutants in water by using UV / H2O2, and first establishes a high-level oxidation treatment method for brominated pollutants in water by combining UV and H2O2, determines the initial concentration of the brominated pollutants and the adding proportion of the oxidant H2O2 by using absorbance, Lambert-Beer law and the principle of absorbance additivity, and verifies the rationality of the concentration settings of the brominated pollutants and the oxidant in the kinetics evaluation, and further establishes a detection method for bromide ions, which, compared with the traditional ion chromatography method, does not need an additional pretreatment process, avoids the matrix interference of coexisting organic matters, and greatly saves the experimental and instrument use costs; for the identification of degradation products, the method established by the application accurately detects the evolution trend of more than twenty structural molecules in the examples along with the treatment process, and the method can be widely applied to the wastewater treatment of brominated flame retardants, brominated phenols and other bromine-containing organic matters in the environment.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control technology and analysis and detection technology, specifically involving a method for degrading brominated organic pollutants in water using UV / H2O2, as well as the determination of degradation efficiency, identification of degradation products, and evaluation of mineralization in the treatment process. Background Technology

[0002] Brominated organic pollutants (BOPs), such as polybrominated diphenyl ethers, bromobisphenol A, hexabromocyclododecane, bromophenols, bromoalkanes, and tribromoacetic acid, are widely used in the electronics, building materials, pharmaceutical, and other fine chemical industries. BOPs exhibit high environmental stability and bioaccumulation, and some have been classified as persistent organic pollutants and are subject to strict international regulations. Due to their frequent detection in environmental wastewater, BOPs may pose a threat to ecosystems and human health; therefore, rationally controlling emissions and improving wastewater treatment levels are key measures to reduce environmental risks.

[0003] 2,4,6-Tribromophenol (TBP) is the most industrially produced brominated phenol, used as a wood preservative and an intermediate in the synthesis of various pharmaceuticals. It is also used as a reactive flame retardant in adhesives and sealants such as epoxy and phenolic resins. Furthermore, TBP is an intermediate in the degradation and synthesis of other brominated flame retardants and polymers, frequently appearing in the degradation of tetrabromobisphenol A and the synthesis of poly(2,6-dibromophenyl ether). TBP has been detected in numerous chemical production wastewaters, wood preservative treatment and flame retardant production wastewaters, and even in rivers, lakes, and drinking water, making it a typical brominated phenol found in water bodies.

[0004] Because BOPs are not easily biodegradable, researchers have developed various treatment methods, including material adsorption, oxidation reactions with chlorine, permanganate, and persulfate, as well as various Fenton-like reactions and photoelectrocatalytic treatment technologies. However, these methods suffer from secondary pollution due to the addition of chemical reagents and the release of materials into the environment. Furthermore, they are costly in terms of consumables and equipment, involve complex preparation, treatment, and recycling processes, and exhibit inconsistent BOP removal and mineralization efficiencies.

[0005] Mineralization of pollutants refers to the process by which organic pollutants are completely decomposed and transformed into inorganic minerals (such as carbon dioxide, water, and inorganic salts) in the environment through various biological or chemical processes. This is an important indicator in the field of water treatment technology. The higher the degree of mineralization, the more effective the degradation of the pollutant, because it can completely decompose harmful organic pollutants, transforming them from organic forms into inorganic forms that are less harmful to the environment.

[0006] Ultraviolet-based advanced oxidation processes (UV-AOPs) are a technology that utilizes the synergistic effect of ultraviolet light and oxidants (such as hydrogen peroxide and sodium periodate) to degrade pollutants. Because it requires no additional chemicals and can easily upgrade existing treatment equipment, it has become a highly anticipated new water treatment technology that has emerged in the last 20 years. UV-AOPs can not only directly photodegrade light-absorbing organic pollutants in water, but also degrade pollutants through a chain reaction induced by ultraviolet light, which generates strong oxidizing free radicals from the oxidant. Furthermore, it can photo-initiate coexisting pollutants and solvent water to generate other high-energy molecules or free radical fragments, thereby sensitizing and degrading pollutants. This series of effects results in extremely high pollutant removal and mineralization rates.

[0007] Among these methods, the UV / H₂O₂ method readily generates hydroxyl (·OH) radicals due to the high quantum yield of hydrogen peroxide. ·OH radicals have a high oxidation potential and can non-selectively attack pollutants. Furthermore, the simple elemental composition of hydrogen peroxide minimizes the harmfulness of byproducts generated by this method. However, liquid hydrogen peroxide is prone to decomposition and explosion during transportation and storage, increasing transportation costs and usage risks. Therefore, controlling and optimizing the amount of hydrogen peroxide used is crucial. Additionally, the penetration depth of ultraviolet (200-400 nm) light sources in water is significantly affected by water turbidity; in clear water, the penetration depth may only be a few centimeters to several hundred centimeters, while in turbid water, it is negligible. Due to its high energy and easy absorption, UVC (200-280nm) is almost completely absorbed at the water surface. Therefore, investigating whether hydrogen peroxide and organic matter present on the water surface can generate other high-energy molecules or fragments after UVC irradiation, whether these high-energy fragments can break through the solvent cage and continue to degrade pollutants at greater depths, and whether they can offset the adverse effect of low light transmittance, is crucial for the efficient realization of the entire UV / H2O2 process. To directly observe whether such a mechanism exists in the system, it is necessary to determine the reaction kinetics and identify the transformation products during the UV / H2O2 degradation of pollutants. Summary of the Invention

[0008] The purpose of this invention is to provide a method for degrading brominated organic pollutants (BOPs) in water using UV / H2O2, as well as the determination of degradation efficiency, identification of degradation products, and evaluation of mineralization in the treatment process. Several key steps are involved in the construction of this method: first, determining the initial concentration of BOPs and the addition ratio of H2O2 to visually demonstrate the improvement in pollutant degradation efficiency and mineralization compared to UV photolysis of BOPs alone; second, controlling the wavelength and intensity of the light source irradiation; third, establishing a method for identifying conversion products; and fourth, evaluating the efficiency of the method.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] In a first aspect, the present invention provides a method for degrading brominated organic pollutants in water using UV / H2O2, comprising the following steps:

[0011] (1) Determination of the initial concentration of the brominated organic pollutant solution: The lower limit of the initial concentration range is determined based on the solubility of the brominated organic pollutant in water and the light absorbance at the wavelength of the light source. The upper limit of the concentration range is determined based on the requirement of "dilute solution" according to the Lambert-Beer law. The initial concentration of the brominated organic pollutant solution should be set so that its absorbance at the wavelength of the light source is in the range of 0.1 to 0.8. The substrate absorbance in the range of 0.1 to 0.8 can ensure that the photochemical reaction occurs effectively and ensure the linear light absorption characteristics of the reaction substrate without introducing additional complex correction factors in subsequent reaction kinetics and other experimental measurements. If it is lower than 0.1, organic solvents or surfactants can be added to aid dissolution.

[0012] (2) Determination of H2O2 addition ratio: The oxidant addition ratio is set according to the principle of "absorbance additivity" in multi-component system. Combined with the initial concentration of substrate solution in step (1), the initial molar concentration ratio of H2O2 oxidant to brominated organic pollutant is 10-200:1.

[0013] (3) Selection of light source and distance between reaction tube and lamp tube and construction of reaction device: Select a low-pressure mercury lamp with a main emission wavelength of 254nm as the ultraviolet light source, and a quartz glass tube as the reaction tube. The reaction tube is placed parallel to the lamp tube at a distance of 3-5cm.

[0014] (4) After preparing the brominated organic pollutant solution according to the initial concentration requirements in step (1), add it to the reaction tube and add H2O2 to the concentration of H2O2 set in step (2). Then, irradiate the reaction tube with an ultraviolet light source to degrade the brominated organic pollutants in the solution.

[0015] Based on the above technical solution, the brominated organic pollutants mentioned in step (1) further include polybrominated diphenyl ethers, bromobisphenol A, bromobenzene series, bromoalkanes, and bromocarboxylic acids.

[0016] Based on the above technical solution, further, the brominated organic pollutant mentioned in step (1) includes 2,4,6-tribromophenol.

[0017] Based on the above technical solution, further, the initial concentration of 2,4,6-tribromophenol in step (1) is 80-120 μM.

[0018] Based on the above technical solution, further, the concentration of H2O2 in step (2) is 5-15 mM.

[0019] Based on the above technical solution, further, the light irradiance received by the outer surface of the reaction tube near the ultraviolet light source in step (3) is 200-300 mW / cm². 2 .

[0020] Based on the above technical solution, further, the temperature of the solution in the reaction tube in step (4) is controlled at 20-25℃.

[0021] Secondly, this invention provides a method for kinetic evaluation during the above-mentioned UV / H2O2 degradation of brominated organic pollutants in water. The method uses high-performance liquid chromatography (HPLC) to determine the signal peaks of brominated organic pollutants in the reaction solution system. The chromatograph is equipped with a C18 column, the column temperature is stabilized at 20–35°C, the sample injection volume is 10–40 μl, and a gradient elution program is used to separate the sample. The mobile phase is an aqueous solution containing 0.1% formic acid (V / V) and acetonitrile, and the flow rate is 1.0 ml / min. The gradient elution program is set as follows: the initial mobile phase is 10% acetonitrile (V / V), held for 2 min, and then... Acetonitrile was linearly increased to 100% at a rate of 3.0% / min within 30 min, maintained for 10 min, and then restored to 10% within 1.2 min and maintained for 7.8 min. The signal peak of brominated organic pollutants was detected using a single-electrode array detector at a wavelength of 220 nm, 254 nm, or 290 nm. By comparing the pollutant reaction kinetics with the control group "direct photolysis of brominated organic pollutants", the rationality of the H2O2 addition ratio setting in step (2) of technical scheme 1 (a method for degrading brominated organic pollutants in water using UV / H2O2) was further evaluated.

[0022] Thirdly, this invention provides a method for detecting conversion products during the UV / H2O2 degradation of brominated organic pollutants in water. The method involves solid-phase extraction enrichment of the reaction system solution for UV / H2O2 degradation of brominated organic pollutants in water using pentachlorophenol as both an extraction internal standard and an instrument injection internal standard. The conversion products are then qualitatively identified using liquid chromatography-mass spectrometry (LC-MS) and quantitatively determined using high-performance liquid chromatography (HPLC). The method includes the following steps:

[0023] 1) Add internal standard for extraction: After removing the reaction tube containing the reaction system solution, add 1 ml of a 100 μg / ml pentachlorophenol-acetonitrile solution to the tube and mix well;

[0024] 2) Solid-phase extraction solvent replacement and sample concentration: The water in the solution from step 1) was replaced with acetonitrile using an HLB column (500 mg, 6 ml / 30 pcs) to enrich the analytes;

[0025] 3) Detection and qualitative analysis of transformation products using liquid chromatography-mass spectrometry: The test solution obtained in step 2) was tested using a high performance liquid chromatography-tandem triple quadrupole mass spectrometer. The most significant signals in the spectrum were qualitatively analyzed by retention time, mass number and isotope ion abundance ratio.

[0026] The liquid chromatography conditions are as follows:

[0027] Column: C18 (150mm × 2.1mm × 5μm); Column temperature: 20–35℃;

[0028] Mobile phase A: Water; Mobile phase B: Methanol; Mobile phase C: Acetonitrile;

[0029] The gradient elution conditions were as follows: 0-17 min, 20-70% C, 80-30% B; 17-26 min, 0-30% A, 30-0% B, with the C phase maintained at 70%; 26-31 min, 30% A, 70% C; 31-31.2 min, 30-0% A, 0-80% B, 70-20% C; 31.2-37 min, 80% B, 20% C.

[0030] Flow rate: 0.2 ml / min; Injection volume: 10 μL;

[0031] The mass spectrometry interface conditions are as follows:

[0032] Ionization mode: Electrospray negative ion mode;

[0033] Detection mode: Multiple reaction monitoring mode; Quality scan type: Full scan;

[0034] Quality scan range: 90,000-800,000 m / z;

[0035] Electrospray capillary voltage: 3000V; Ion transport capillary temperature: 300℃;

[0036] Sheath gas: nitrogen, pressure 20 psi; Auxiliary gas: nitrogen, pressure 50 psi.

[0037] 4) Quantitative determination of conversion products using high performance liquid chromatography: The concentrated sample obtained in step 2) is subjected to liquid chromatography under the conditions described in technical scheme 2 (the method for kinetic evaluation during the degradation of brominated organic pollutants in water using UV / H2O2 as described above), and the content of degradation products and the recovery rate of the sample processing process are calculated using the internal standard method.

[0038] Based on the above technical solution, further, the specific process of step 2) is as follows: activate the column with 2 column volumes of methanol, then add 6-12 ml of deionized water at a rate of 1-2 ml / min to rinse and equilibrate the column, load the sample at a flow rate of 1-2 ml / min, extract, dry the column under vacuum for 20-30 min, and elute the analyte from the adsorbent into a 15 ml glass tube with 6-10 ml of methanol at a flow rate of 1 ml / min. After drying the solvent under a mild nitrogen flow below 40°C, redissolve the sample with 1 ml of acetonitrile.

[0039] Fourthly, the present invention provides a method for detecting "bromine ions" in the process of the above-mentioned UV / H2O2 degradation of brominated organic pollutants in water, wherein "bromine ions" are detected by liquid chromatography-mass spectrometry and mineralization is evaluated.

[0040] i) Establish an instrumental method for separating and detecting bromide and iodide ions in a reaction system solution using liquid chromatography-mass spectrometry (LC-MS).

[0041] The liquid chromatography conditions are as follows:

[0042] Column: C18 (150nm x 2.1mm x 5μm); Column temperature: 20–35℃;

[0043] Mobile phase: 70% acetonitrile and 30% water; isocratic elution;

[0044] Flow rate: 0.2 ml / min; Injection volume: 10 μl;

[0045] The mass spectrometry interface conditions are:

[0046] Ionization mode: Electrospray negative ionization source;

[0047] Select ion mode (SIM), and select two ion scanning channels (79.000 and 129.900 m / z) to monitor bromide and iodide ions; the voltage of the tube lens is set to 70V.

[0048] ii) Prepare bromide ion standard samples and construct a standard curve for bromide ion corrected for iodine internal standard: Prepare a series of bromide ion standard samples of different concentrations, and add the same volume and concentration of iodine ions as internal standards to each sample. Construct a standard curve with the peak area of ​​bromide ions relative to iodine ions at each concentration as the ordinate and the bromide ion content as the abscissa. The linear regression fitting formula for the curve is as follows:

[0049]

[0050] In the formula: Area(I) - 0 — Peak area of ​​iodine ions at a fixed concentration in the sample;

[0051] Area(Br- ) c —Peak areas of bromide ions at different concentrations in the sample;

[0052] (Br - ) c —The concentration of bromide ions in the sample;

[0053] M and B are the slope and intercept of the fitted line, respectively;

[0054] iii) Add an internal standard of iodine ions with the same concentration as that used in step ii) to the reaction system solution for the degradation of brominated organic pollutants by UV / H2O2. After filtering the mixed sample through an aqueous filter membrane, inject it into a liquid chromatography-mass spectrometry (LC-MS) instrument and quantitatively determine the bromide ion content in the sample according to formula (I).

[0055] Compared with the prior art, the present invention has at least the following beneficial effects:

[0056] (1) Based on absorbance, Beer-Lambert law, and the principle of "absorbance additivity", this invention can quickly determine the initial concentration of BOPs and the reasonable addition ratio of H2O2. Kinetic analysis shows that direct photolysis and photo-initiated H2O2-generated ·OH radicals both contribute significantly to the degradation reaction; mineralization evaluation shows that the high-energy fragments generated after the reaction substrate absorbs light on the surface of the reaction tube can break through the "solvent cage" and trigger secondary photochemical reactions through solvent transfer, ultimately leading to a decrease in the mineralization of deep solutions, thus breaking the traditional understanding that "UVC light sources can only repair surface water".

[0057] (2) The pretreatment process for identification of transformation products in this invention is simple. The established and optimized chromatographic and mass spectrometric parameters enable the liquid chromatography-mass spectrometry and high performance liquid chromatography in this invention to quantitatively identify a variety of transformation products. At the same time, the established liquid chromatography separation method enables mass spectrometry to identify a variety of isomers, which is very helpful for determining the reaction site and reaction pathway.

[0058] (3) The bromide ion detection method established in this invention does not require additional pretreatment and avoids matrix interference from coexisting organic matter, thus greatly saving experimental and instrument usage costs. Attached Figure Description

[0059] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.

[0060] Figure 1 The images show the UV-Vis absorption spectra of 100 μM TBP aqueous solution, 10 mM H2O2- aqueous solution, and 100 μM TBP + 10 mM H2O2 aqueous solution.

[0061] Figure 2 This is the emission spectrum of the low-pressure mercury lamp used in this invention.

[0062] Figure 3 This is a light irradiance diagram measured on the outer surface of the reaction tube, 5.0 cm away from the lamp tube, near the lamp tube in Example 1.

[0063] Figure 4 This is a schematic diagram of a simplified apparatus for a photochemical reaction.

[0064] Figure 5 This is a kinetic diagram of the degradation of TBP in aqueous solution under two reaction conditions: UV and UV / H2O2.

[0065] Figure 6 This is the total ion chromatogram of the sample to be tested in Example 1 when the reaction time was 1 min, obtained by HPLC analysis.

[0066] Figure 7 This is the total ion chromatogram and the mass spectrum of the typical structure of the sample to be tested when the reaction time was 1 min in Example 1, analyzed by HPLC-MS.

[0067] Figure 8 This is a graph showing the evolution of the yield of the clustered conversion products detected under UV / H2O2 conditions in Example 1 as a function of reaction time. The right vertical axis represents the degradation rate of TBP.

[0068] Figure 9 This is a bubble diagram of the dimer detected under UV / H2O2 conditions in Example 1, with reaction times ranging from 15 seconds to 4 minutes.

[0069] Figure 10 This is a graph showing the evolution of bromide ion content under UV / H2O2 conditions as a function of reaction time in Example 1.

[0070] Figure 11 This is a graph showing the evolution of TOC (mineralization) of the system under UV / H2O2 conditions with treatment time in Example 1.

[0071] Figure 12 This is a diagram showing the intermediate products and degradation pathway of TBP under UV / H2O2 conditions in Example 1. Detailed Implementation

[0072] The experimental details of the technical solutions in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings, tables, and specific examples. This embodiment is described based on the technical solutions of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all protected by the present invention.

[0073] Example 1:

[0074] In this embodiment, TBP was selected as the brominated organic pollutant. The method for degrading brominated organic pollutants in water using UV / H2O2 was established, including the following steps:

[0075] (1) Prepare chemical reagents: 2,4,6-tribromophenol (99.8% analytical standard), 30% hydrogen peroxide (wt%), Milli-Q water, acetonitrile (chromatographic grade), methanol (chromatographic grade).

[0076] (2) Determination of initial concentration of BOPs: The lower limit of the initial concentration range of BOPs was determined by measuring the light absorbance of BOPs in the aqueous solution (too low absorbance will not trigger photolysis reaction). The upper limit of the initial concentration range of BOPs was determined according to Beer-Lambert law (changes in the association form of solute molecules in concentrated solutions and changes in the refractive index of concentrated solutions will cause light shielding effect). The initial concentration of BOPs in this invention should make the absorbance of the solution at 254 nm in the range of 0.1 to 0.8. The saturated solubility of TBP in water is 70 mg / L (25℃). The initial concentration of the prepared TBP aqueous solution was 100 μM (33 mg / L), and its absorbance at 254 nm was 0.21.

[0077] (3) Control of H2O2 addition in TBP aqueous solution: To visually demonstrate the difference in BOPs removal efficiency between the UV / H2O2 method and the control group (UV direct photolysis), the H2O2 addition ratio was set based on the principle of "absorbance additivity" in multi-component systems. "Absorbance additivity" means that when multiple absorbent substances are present in a solution, the total absorbance of the solution equals the sum of the absorbances of each substance. If the two substrates conform to this principle, it indicates that their absorption behavior at that wavelength does not interfere with each other, and no complexation or other chemical reactions occur, ensuring that they absorb light independently and undergo photolysis at the start of the reaction. Based on the initial BOPs concentration in step 2), and after repeated experimental measurements, the final H2O2 concentration in a 100 μM TBP aqueous solution was determined to be 10 mM. (See also...) Figure 1 The sum of the absorbance of the individual substrates at 254 nm is equal to the absorbance of the two components in the system when they are present simultaneously.

[0078] (4) Selection of reaction tube: Quartz glass is made of high-purity silicon dioxide, with excellent optical properties and high transmittance in the ultraviolet to visible light range, which can allow light to pass through and irradiate the reactants, thus maximizing the photochemical reaction. A commercially available cylindrical quartz glass tube with an outer diameter of 1.5 cm and a total volume of 60 ml was selected as the reaction tube.

[0079] (5) Selection of light source and distance between reaction tube and lamp tube, and construction of simple device: Based on the first law of photochemical reaction and the measurement of the light absorption characteristics of the reaction substrates BOPs and H2O2, two commercially available ultraviolet light sources were first selected: low-pressure mercury lamps with main emission wavelengths of 185nm and 254nm, respectively. Considering that after the solar light passes through the ozone layer and atmosphere, there is 1% UVC (200-280nm) and no light waves below 200nm remaining, in order to facilitate the comparison between the advanced oxidation method of this invention and the series of reactions triggered by UV light irradiation on the water surface when H2O2 and BOPs are present in the natural water environment, a low-pressure mercury lamp with an output power of 8W was finally selected (the emission spectrum of the light source is shown in the figure). Figure 2 ).

[0080] The reaction tube was placed parallel to the lamp tube on a magnetic stirrer for the photodegradation experiment of TBP. The light irradiance received by the outer surface of the reaction tube near the lamp source was measured to be 267 mW / cm². 2 (See Figure 3 The final simplified device model for photochemical experiments is shown in the diagram. Figure 4 .

[0081] (6) Comparative determination of the degradation kinetics of selected concentrations of TBP under UV and UV / H2O2 conditions: 100 μM TBP aqueous solution and 100 μM TBP-10 mM H2O2 aqueous solution were prepared and subjected to light irradiation experiments. At the set time points, 1 ml of sample was taken from the reaction tube, passed through a 0.45 μm water film, and the concentration of tribromophenol in the sample at different reaction times was determined using a high-performance liquid chromatograph equipped with a C18 (250 mm × 4.6 mm × 5 μm) column. The contribution of ·OH radicals generated by H2O2 photolysis to the advanced oxidation process was determined by plotting kinetic curves. The column temperature was stabilized at 30 °C, the sample injection volume was 30 μl, and a gradient elution program was used to separate the reaction mixture in the sample. The mobile phase was an aqueous solution containing 0.1% formic acid (V / V) and acetonitrile, and the flow rate was 1.0 ml / min. The gradient elution program was set as follows: the initial mobile phase was 10% acetonitrile, held for 2 min, then the acetonitrile was linearly increased to 100% at a rate of 3.0% / min over 30 min, held for 10 min, and then restored to 10% over 0.2 min and held for 7.8 min. A diode array detector was selected, and the detection wavelength was set to 290 nm to measure the signal peak of tribromophenol. Qualitative analysis was performed with a retention time of 24.5 min, and the absolute concentration of tribromophenol was corrected using the external standard method. The obtained kinetic curves are shown in [Figure number missing]. Figure 5 The degradation of TBP in both systems follows pseudo-first-order kinetics (ln(C0 / C)). t )=kt), according to the formula (Where k1 represents the slope of the fitted kinetic curve under UV conditions, and k2 represents the slope of the fitted kinetic curve under UV / H2O2 conditions), the calculation shows that the contribution rate of ·OH free radicals generated by H2O2 photolysis to TBP degradation in the UV / H2O2 degradation system of the present invention is 51.3%, which is consistent with... Figure 1 The distribution of absorbance of the two reaction substrates at 254 nm is consistent, which proves the rationality of the reaction substrate concentration setting.

[0082] (7) Identification of organic conversion products during the degradation of TBP aqueous solution by UV / H2O2: After solid-phase extraction and enrichment of the reaction system solution using pentachlorophenol as an internal standard, the products were qualitatively identified by liquid chromatography-mass spectrometry (HPLC-MS). HPLC-MS is a complex instrument, and its state is affected by a variety of factors, such as poor column efficiency, incomplete separation of components in the sample, mass ionization and the "mass discrimination effect" in mass analysis, and unstable mass spectrometry signals. These factors can all affect the accuracy of quantification. Therefore, a more stable high-performance liquid chromatograph (HPLC) was selected to quantify the products using the internal standard method.

[0083] Prepare 500 ml of 100 μM TBP-10 mM H2O2 aqueous solution and dispense it into 10 reaction tubes. Perform photolysis experiments at the set time points. Then, add 1 ml of 100 μg / ml pentachlorophenol-acetonitrile solution to each reaction tube and perform solid-phase extraction using an HLB column (500 mg, 6 ml / 30 pcs). The specific procedure is as follows: activate the column with 10 ml of methanol, then add 10 ml of deionized water at a rate of 1-2 ml / min to rinse and equilibrate the column. Load the sample at a flow rate of 1 ml / min. After extraction, dry the column under vacuum for 30 min. Elute the analyte from the adsorbent to a 15 ml glass tube with 10 ml of methanol at a flow rate of 1 ml / min. Dry the solvent under a mild nitrogen flow below 40°C and redissolve with 1 ml of acetonitrile. Finally, after filtering these 1 ml samples through a 0.45 μm organic filter membrane, the analytes in the samples were identified using HPLC-MS and HPLC (pentachlorophenol in the samples was used as an internal standard for instrument injection). The conditions for HPLC-MS and mass spectrometry are listed in Table 1. The detection wavelength for the analytes was 290 nm. Based on the HPLC analysis results, the spiked recoveries of pentachlorophenol in each sample were calculated to be higher than 70%, which fully demonstrates the reliability of the sample processing procedure and analytical method. According to the instrument identification results, a total of 27 transformation products were detected within the sampling time. The time point at which the transformation products concentrated was 1 min. The total ion chromatograms (HPLC and HPLC-MS) and mass spectra of typical structures of the test samples in the system are shown in [Table 1]. Figure 6 and Figure 7The identified products from these time points were clustered and plotted, as shown in the figure. Figure 8 and Figure 9 .

[0084] (8) Detection and quantification of bromide ions during the UV / H2O2 degradation of TBP aqueous solution: This invention does not follow the current national standard (HJ 84-2016) method for determining inorganic anions in water quality using ion chromatography to identify bromide ions. The reason is that the content of organic matter and bromide ions in the reaction system is similar, and the amount of organic matter containing ionizable groups varies at different reaction times. These organic substances exist as anions in the alkaline eluent, which severely interferes with the affinity of bromide ions for the exchange resin when loaded onto the anion exchange column, causing matrix effects, inconsistent sample spots, affecting bromide ion exchange behavior, peak time, and even leading to false negative results. Determining bromide ions according to the national standard method requires a cumbersome pretreatment process to remove organic matter, which may result in partial loss of bromide ions. Therefore, this invention selects HPLC-MS, which combines chromatographic separation and strong ion detection capabilities. The bromide ions generated in the reaction system can be directly detected simply by passing the sample through an aqueous membrane and adding an iodine ion internal standard. The specific steps are as follows:

[0085] 1) Establish an instrumental method for separating and detecting bromide and iodide ions in the reaction system solution using HPLC-MS:

[0086] The chromatographic conditions are as follows:

[0087] Column: C18 (150mm × 2.1mm × 5μm); Column temperature: 20–35℃;

[0088] Mobile phase: 70% acetonitrile and 30% water; isocratic elution;

[0089] Flow rate: 0.2 ml / min; Injection volume: 10 μl;

[0090] The mass spectrometry interface conditions are:

[0091] Ionization mode: Electrospray negative ionization source;

[0092] Select ion mode (SIM), and select two ion scanning channels (79.000 and 129.900 m / z) to monitor bromide and iodide ions; the voltage of the tube lens is set to 70V.

[0093] 2) Prepare bromide ion standard samples and construct a standard curve for bromide ion corrected for iodine internal standard: Prepare a series of bromide ion standard samples of different concentrations, and add the same volume and concentration of iodine ions as internal standards to each sample. Construct a standard curve with the peak area of ​​bromide ion relative to iodine ion at each concentration as the ordinate and the bromide ion content as the abscissa. The linear regression fitting formula for the curve is as follows:

[0094]

[0095] In the formula: Area(I) - 0 — Peak area of ​​iodine ions at a fixed concentration in the sample;

[0096] Area(Br - ) c —Peak areas of bromide ions at different concentrations in the sample;

[0097] (Br - ) c —The concentration of bromide ions in the sample;

[0098] M and B are the slope and intercept of the fitted line, respectively;

[0099] 3) Add an internal standard of iodine ions with the same concentration as when preparing the standard curve in step 2) to the UV / H2O2 reaction system solution. After filtering the mixed sample through an aqueous filter membrane, inject it into HPLC-MS and quantitatively determine the bromide ion content in the sample according to formula (I).

[0100] First, bromide ion standard solutions of 0, 5, 10, 20, and 40 mg / L were prepared. Iodide ion internal standards were added to these standard samples to ensure an iodide ion concentration of 10 mg / L. After passing through an aqueous membrane, the samples were injected to obtain a bromide ion standard curve corrected for the iodine internal standard (R² > 0.995). Then, the UV / H₂O₂ degradation reaction of TBP was carried out. At a specific reaction time, approximately 1 ml of the test solution was removed, and 900 μl of this solution was taken and mixed with 100 μl of 100 mg / L iodide ion standard solution. The mixed test solution was then passed through an aqueous membrane and injected into HPLC-MS. The established instrumental analytical method for bromide ion determination was used to separate bromine and iodine, as well as other organic compounds in the system. Both ions elute within 5 min. Finally, the bromide ion content in the sample was quantitatively determined according to the bromide ion standard curve. The Br content after complete debromination of TBP was used as the standard, and the evolution curve of the debromination rate over time was calculated and plotted. Figure 10 It can be seen that the method described in this invention enables a 33 mg / L TBP solution to be completely debrominated within 1 hour. However, the debromination and the removal of TBP are not synchronized because the former involves the stepwise debromination of intermediate conversion products, which is related not only to the degradation efficiency of TBP but also to the mineralization of the system.

[0101] (9) Determination of TOC (mineralization) during the UV / H2O2 degradation of TBP aqueous solution: The TOC of the system at different reaction times was determined using a TOC-L CPH (SHIMADZU, 638-91112-43) analyzer. The results are shown in […]. Figure 11The change in debromination rate over time demonstrates that the advanced oxidative degradation method for TBP described in this invention can effectively mineralize pollutants and achieve the purpose of water purification.

[0102] (10) Mechanism Analysis: Based on the analysis of the identified degradation products, a TBP degradation pathway diagram was drawn, see [link to diagram]. Figure 12 The molecules highlighted in red are the two products with the highest yields detected in the early and mid-stages of the degradation process. In general, the mechanism of TBP degradation using the advanced oxidation method described in this invention can be categorized as follows: ·OH substitution of Br (path ①, the main reaction pathway); self-coupling reaction of TBP (path ②) and coupling reaction between TBP and its main product, dibromodihydroxybenzene (path ③); the dimer generated by the coupling reaction being replaced by ·OH (path ④), the electrophilic addition reaction between ·OH and the dimer (path ⑤), and the C-Br bond cleavage reaction initiated by the dimer itself under light (path ⑥); electrophilic addition reaction between TBP and ·OH (path ⑦); ring-opening cleavage of TBP, oxidizing it to tribromoacetic acid (path ⑧); alkylation of TBP (path ⑨), and finally, the TBP and its intermediate degradation products in the system are mineralized into smaller molecules containing bromic acid, carbon dioxide, water, and bromide ions. Analysis of the mechanism revealed that the degradation of TBP by this advanced oxidation method leads to a continuous decrease in mineralization. However, in the early stages of the reaction, small amounts of different types of dimers are generated (hydroxylated polybrominated diphenyl ethers, hydroxylated brominated dioxins, hydroxybromobiphenyls, etc.). This indicates that under UV photolysis and H₂O₂ oxidation, the system contains not only ·OH radicals but also significant coupling reactions between intermediates such as phenyl radicals or phenoxy radicals. The presence of these intermediates and the C-Br bond breaking phenomenon of the dimer in pathway ⑥ demonstrate the contribution of direct UV photolysis to this advanced oxidation process. Simultaneously, the presence of tribromoacetic acid and alkoxylated dibromophenol in the early and middle stages of the reaction indicates that the reaction is subjected to intense photooxidation or -OH radical oxidation, generating numerous alkyl fragments. These neutral single-electron alkyl fragments can further undergo radical reactions with TBP or dihydroxydibromophenyl. A summary of the degradation pathway revealed that regardless of the complexity of the reaction mechanisms within the system, the ·OH radical is the dominant reactive species, excluding ultraviolet light (pathway ① and the hydroxylation of dimers and the formation of small molecule acids). This suggests that its formation is not solely due to the photolysis of H₂O₂ (as opposed to...). Figure 5 The contribution of H2O2 to the formation of ·OH was found to be 51%, which may also originate from the excited-state sensitized solvent water generated after the main organic products in the system are excited by light. Finally, the analysis of degradation products and degradation pathways shows that the advanced oxidation method described in this invention is not only effective for the removal of TBP itself, but also for organic pollutants with similar structures such as dibromodiphenol, alkylated bromophenol, and hydroxylated polybrominated biphenyls. This advanced oxidation method can be applied to the remediation and treatment of wastewater containing these pollutants.

[0103] Table 1. Chromatographic and mass spectrometric parameters for HPLC-MS determination of degradation products

[0104]

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for degrading brominated organic pollutants in water using UV / H2O2, characterized in that, Includes the following steps: (1) Determination of the initial concentration of the brominated organic pollutant solution: The lower limit of the initial concentration range is determined based on the solubility of the brominated organic pollutant in water and its light absorbance at the wavelength of the light source. The upper limit of the concentration range is determined based on the requirement of Lambert-Beer's law for "dilute solutions". The initial concentration of the brominated organic pollutant solution should be set so that its absorbance at the wavelength of the light source is in the range of 0.1-0.

8. (2) Determination of H2O2 addition ratio: The oxidant addition ratio is set according to the principle of "absorbance additivity" in multi-component system. Combined with the initial concentration of substrate solution in step (1), the initial molar concentration ratio of H2O2 oxidant to brominated organic pollutant is 10-200:

1. (3) Selection of light source and distance between reaction tube and lamp tube and construction of reaction device: Select a low-pressure mercury lamp with a main emission wavelength of 254nm as the ultraviolet light source, and a quartz glass tube as the reaction tube. The reaction tube is placed parallel to the lamp tube at a distance of 3-5cm. (4) After preparing the brominated organic pollutant solution according to the initial concentration requirements in step (1), add it to the reaction tube and add H2O2 to the concentration of H2O2 set in step (2). Then, irradiate the reaction tube with an ultraviolet light source to degrade the brominated organic pollutants in the solution.

2. The method according to claim 1, characterized in that, The brominated organic pollutants mentioned in step (1) include polybrominated diphenyl ethers, bromobisphenol A, bromobenzene compounds, bromoalkanes, and bromocarboxylic acids.

3. The method according to claim 1, characterized in that, The brominated organic pollutants mentioned in step (1) include 2,4,6-tribromophenol; the initial concentration of 2,4,6-tribromophenol is 80-120 μM.

4. The method according to claim 1, characterized in that, The concentration of H2O2 in step (2) is 5–15 mM; the light irradiance received by the outer surface of the reaction tube near the ultraviolet light source in step (3) is 200–300 mW / cm². 2 .

5. The method according to claim 1, characterized in that, The temperature of the solution in the reaction tube in step (4) is controlled at 20-25℃.

6. The method for kinetic evaluation during the UV / H2O2 degradation of brominated organic pollutants in water as described in any one of claims 1-5, characterized in that, The signal peaks of brominated organic pollutants in the reaction solution system were determined using high-performance liquid chromatography (HPLC). The chromatograph was equipped with a C18 column, and the column temperature was stabilized at 20–35 °C. The sample injection volume was 10–40 μL. A gradient elution program was used to separate the sample. The mobile phase was an aqueous solution containing 0.1% formic acid (V / V) and acetonitrile, and the flow rate was 1.0 mL / min. The gradient elution program was set as follows: the initial mobile phase was 10% acetonitrile (V / V), held for 2 min, then the acetonitrile was linearly increased to 100% at a rate of 3.0% / min over 30 min, held for 10 min, and then restored to 10% over 0.2 min and held for 7.8 min. The signal peaks of brominated organic pollutants were detected using a diode array detector at wavelengths of 220 nm, 254 nm, or 290 nm.

7. The method for detecting conversion products during the UV / H₂O₂ degradation of brominated organic pollutants in water as described in any one of claims 1-5, characterized in that, Using pentachlorophenol as both extraction and instrument injection internal standards, the solution of the UV / H₂O₂ degradation reaction system for brominated organic pollutants in water was enriched by solid-phase extraction. The transformation products were then qualitatively identified by liquid chromatography-mass spectrometry (LC-MS) and quantitatively determined by high-performance liquid chromatography (HPLC). The process included the following steps: 1) Add internal standard for extraction: After removing the reaction tube containing the reaction system solution, add 1 ml of a 100 μg / ml pentachlorophenol-acetonitrile solution to the tube and mix well; 2) Solid-phase extraction solvent replacement and sample concentration: The water in the solution from step 1) was replaced with acetonitrile using an HLB column (500 mg, 6 ml / 30 pcs) to enrich the analytes; 3) Detection and qualitative analysis of transformation products using liquid chromatography-mass spectrometry: The test solution obtained in step 2) was tested using a high performance liquid chromatography-tandem triple quadrupole mass spectrometer. The most significant signals in the spectrum were qualitatively analyzed by retention time, mass number and isotope ion abundance ratio. The liquid chromatography conditions are as follows: Column: C18 (150mmΔ2.1mm×5μm); Column temperature: 20~35℃; Mobile phase A: Water; Mobile phase B: Methanol; Mobile phase C: Acetonitrile; The gradient elution conditions were as follows: 0-17 min, 20-70% C, 80-30% B; 17-26 min, 0-30% A, 30-0% B, with the C phase maintained at 70%; 26-31 min, 30% A, 70% C; 31-31.2 min, 30-0% A, 0-80% B, 70-20% C; 31.2-37 min, 80% B, 20% C. Flow rate: 0.2 ml / min; Injection volume: 10 μl; The mass spectrometry interface conditions are as follows: Ionization mode: Electrospray negative ion mode; Detection mode: Multiple reaction monitoring mode; Quality scan type: Full scan; Quality scan range: 90,000-800,000 m / z; Electrospray capillary voltage: 3000V; Ion transport capillary temperature: 300℃; Sheath gas: nitrogen, pressure 20 psi; Auxiliary gas: nitrogen, pressure 50 psi. 4) Quantitative determination of conversion products by high performance liquid chromatography: The concentrated sample obtained in step 2) is subjected to the liquid chromatography conditions described in claim 6, and the content of degradation products and the recovery rate of the sample processing are calculated using the internal standard method.

8. The detection method according to claim 7, characterized in that, Step 2) is as follows: Activate the column with 2 column volumes of methanol, then add 6-12 ml of deionized water at a rate of 1-2 ml / min to rinse and equilibrate the column. Load the sample at a flow rate of 1-2 ml / min. After extraction, dry the column under vacuum for 20-30 min. Elute the analyte from the adsorbent into a 15 ml glass tube with 6-10 ml of methanol at a flow rate of 1 ml / min. After drying the solvent under a mild nitrogen flow below 40°C, redissolve the sample with 1 ml of acetonitrile.

9. The method for detecting "bromine ions" during the UV / H2O2 degradation of brominated organic pollutants in water as described in any one of claims 1-5, characterized in that, The bromide ion was detected by liquid chromatography-mass spectrometry, and its mineralization was evaluated. i) Establish an instrumental method for separating and detecting bromide and iodide ions in a reaction system solution using liquid chromatography-mass spectrometry (LC-MS). The liquid chromatography conditions are as follows: Column: C18 (150mm × 2.1mm × 5μm); Column temperature: 20–35℃; Mobile phase: 70% acetonitrile and 30% water; isocratic elution; Flow rate: 0.2 ml / min; Injection volume: 10 μl; The mass spectrometry interface conditions are: Ionization mode: Electrospray negative ionization source; Select ion mode (SIM), and select two ion scanning channels (79.000 and 129.900 m / z) to monitor bromide and iodide ions; the voltage of the tube lens is set to 70V. ii) Prepare bromide ion standard samples and construct a standard curve for bromide ion corrected for iodine internal standard: Prepare a series of bromide ion standard samples of different concentrations, and add the same volume and concentration of iodine ions as internal standards to each sample. Construct a standard curve with the peak area of ​​bromide ions relative to iodine ions at each concentration as the ordinate and the bromide ion content as the abscissa. The linear regression fitting formula for the curve is as follows: In the formula: Area(I) - 0 — Peak area of ​​iodine ions at a fixed concentration in the sample; Area(Br - ) c —Peak areas of bromide ions at different concentrations in the sample; (Br - ) c —The concentration of bromide ions in the sample; M and B are the slope and intercept of the fitted line, respectively; iii) Add an internal standard of iodine ions with the same concentration as that used in step ii) to the reaction system solution for the degradation of brominated organic pollutants by UV / H2O2. After filtering the mixed sample through an aqueous filter membrane, inject it into a liquid chromatography-mass spectrometry (LC-MS) instrument and quantitatively determine the bromide ion content in the sample according to formula (I).

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