Detection Of Halogenated Bisphenol A In Water And Study Of Its Photocatalytic Degradation Mechanism By CuO/Ce₂O₃

Halogenated bisphenol A due to its excellent flame-retardant properties,is widely used as a flame retardant or additive in electronic products,home furnishings,and plastics.It possesses the toxic characteristics of persistent organic pollutants and endocrine disruptors,and is detectable in various environmental media and organisms.Improper handling could pose a threat to the ecological environment and human health.Thus,establishing efficient detection and removal methods for understanding the pollution level of brominated bisphenol A,environmental remediation,and human health is of great significance.Photocatalytic technology,due to its simplicity,lack of secondary pollution,and high efficiency,has been widely used for pollutant removal.The key is to develop efficient photocatalysts.Cerium oxide,because of its rich oxygen vacancies,ability to utilize visible light,low cost,good stability,and simple synthesis method,has attracted widespread attention.Therefore,this paper establishes a fast and accurate analysis detection method,providing technical support for subsequent removal.Highly efficient photocatalytic materials were prepared for the removal of brominated bisphenol A under visible light,and its degradation mechanism and reaction pathway were deeply investigated.The main research contents are as follows:（1）To understand the distribution characteristics of tetrabromobisphenol A（TBBPA）in water,a gas chromatography-mass spectrometry（GC-MS）method was established to measure TBBPA in the water of Xiong’an New Area.The best extraction conditions were determined by orthogonal experiments:the best derivatization time and temperature were 70℃and 30 min,respectively,the amount of derivatizing reagent（N,O-bis（trimethylsilyl）trifluoroacetamide）was 40μL,hexane-dichloromethane（1:1,v:v）was used as the extraction solvent,and the best extraction efficiency was obtained when the salt addition amount was 6 g/L.The reliability of the method was verified by the spiking recovery experiment of water samples from Baiyang Lake.The results of water sample analysis from Baiyang Lake and Fuhe River showed that the TBBPA concentration in the samples ranged from 18.5 to 82.6 ng/L,which is at a medium level compared to the data published in other regions of the country.This paper provides a reference for studying the distribution characteristics of TBBPA in the waters of the Xiong’an New Area.（2）A series of CuO/Ce₂O₃ nanocomposites with different proportions were synthesized using the co-precipitation method.The composition,surface structure,and optical properties of the prepared materials were characterized using X-ray diffraction（XRD）,Fourier-transform infrared spectroscopy（FTIR）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,UV-visible diffuse reflectance spectroscopy（UV-Vis）,Brunauer-Emmett-Teller surface area（BET）,transient photocurrent response spectra,and electrochemical impedance spectroscopy（EIS）.The optical properties of the materials were also analyzed in conjunction with density functional theory（DFT）calculations.Results indicated that the 1:20 CuO/Ce₂O₃ composite exhibited a relatively uniform and dense porous structure with a large specific surface area,a clear heterojunction structure,and favorable light absorption effects,resulting in effective removal of tetrabromobisphenol A（TBBPA）.The cycling experiments and ionic leaching experiments proved that 1:20 CuO/Ce₂O₃ has good stability and recyclability,does not cause secondary pollution and has a potential application in the removal of organic pollutants in water.（3）The photocatalytic degradation mechanism of TBBPA in the 1:20 CuO/Ce₂O₃ system under visible light was comprehensively investigated by combining quantum chemical theory calculations.The 1:20 CuO/Ce₂O₃ was effective in removing TBBPA with a removal efficiency of 80.46%within 120 minutes,and the degradation process followed pseudo-second-order kinetics.The effects of p H,humic acid（HA）,common anions(NO₃^-,SO₄^2-,Cl^-),and heavy metal ions(Pb²⁺,Cr⁶⁺/Cr³⁺,Cd²⁺)in water on the degradation process of TBBPA were analyzed to provide reference for practical application.The results showed that the removal effect is better when the p H of the solution is less than or equal to 7,and the removal of TBBPA is inhibited as the p H increases.NO₃^-and Pb²⁺has no significant effect on the removal of TBBPA,Cd²⁺and Cr³⁺have a slight inhibitory effect,and HA,SO₄^2-,Cl^-,Cr⁶⁺has a more significant inhibitory effect.Free radical scavenging experiments and electron spin resonance（ESR）experiments show that h⁺,·OH and·O₂^-were the active substances in the photocatalytic degradation process of TBBPA.Based on this,the photocatalytic mechanism of TBBPA in the1:20 CuO/Ce₂O₃ system was proposed.Combining gas chromatography-mass spectrometry（GC-MS）and high-performance liquid chromatography-mass spectrometry（HPLC-MS）detection results,degradation pathways of TBBPA were proposed,mainly involving debromination,β-cleavage,and ring-opening,with the final degradation products being small organic acids and small molecular alcohols.In addition,by calculating molecular orbital occupancy,electrostatic potential（ESP）,and Fukui indices,reactive sites in the TBBPA molecular structure were predicted,with the bromine atoms and hydroxyl groups being the most active.The microscopic reaction mechanism of TBBPA degradation was explored at the molecular level using DFT calculations,which revealed that the C-C bond cleavage reaction involving free radicals was more likely to occur.Toxicity assessment of the degradation products showed that most of them were less toxic than TBBPA.（4）Current research on the removal and mechanism of tetrachlorobisphenol A（TCBPA）is relatively scarce.In this study,the photocatalytic degradation mechanism of TCBPA under visible light in a 1:20 CuO/Ce₂O₃ system was investigated.The removal efficiency of TCBPA reached 79.3%within 120 minutes and the degradation process followed quasi-secondary kinetics.The results of the investigation of the influencing factors show that the removal efficiency is better when the p H of the solution was less than or equal to 7,and the inhibitory effect on TCBPA removal increases with increasing p H.The presence of anions NO₃^-and Pb²⁺ions in the solution had no significant effect on the removal of TCBPA;SO₄^2-,Cl^-,Cd²⁺,and Cr³⁺ions had a slight inhibitory effect on the removal efficiency of TCBPA;HCO₃^-and Cr⁶⁺inhibited the removal of TCBPA.Combined with GC-MS detection results,degradation pathways for TCBPA were proposed,mainly including dechlorination,β-cleavage,and ring-opening processes.In addition,reactive site calculations show that chlorine atoms and hydroxyl groups are most susceptible to free radical attack.DFT calculations were used to explore the reaction mechanism of the TCBPA degradation process,where the C-C bond cleavage reaction requires the least energy and occurs most readily.The toxicity of the degradation products was all reduced compared to TCBPA,and some were even non-toxic and harmless,indicating that the removal of TCBPA by the CuO/Ce₂O₃ catalyst can reduce environmental pollution and provide a valuable reference for water pollution treatment and remediation.