UV/PS And UV/SO₃^2- Processes For The Degradation Of Typical Emerging Pollutants In Water

Artificial sweeteners（Ass）and perfluorinated compounds（PFCs）,typical emerging contaminants,are frequently detected in the water environment,and even the presence of PFCs has been detected in human serum.Since Ass and PFCs are highly stable and persistent and cannot be effectively removed by conventional water treatment methods,the accumulation of Ass and PFCs in the aqueous environment over time will not only have a negative impact on humans but also pose a great threat to the safety of the water environment,so such environmental problems cannot be ignored.As an advanced oxidation/reduction process with UV irradiation as the activation method,it can degrade emerging pollutants by generating strong oxidizing radicals or strong reducing hydrated electrons through UV excitation,and has become a key research direction in the removal of trace pollutants.In this study,we will investigate the degradation effect of typical emerging pollutants under UV advanced oxidation/reduction process,analyze the reaction mechanism and evaluate the ecological risk during the reaction process,in order to provide theoretical basis and technical support for the removal of wastewater or environmental water containing typical emerging pollutants.In this study,the advanced oxidation processes of UV/peroxynitrite（UV/PS）,UV/chlorine,and advanced reduction processes of UV/sulfite(UV/SO₃^2-)were used to investigate the removal and degradation characteristics of typical artificial sweeteners and perfluorinated compounds among emerging pollutants,respectively.To evaluate the removal effect of UV/PS advanced oxidation process on sucralose（SUC）,a typical artificial sweetener among emerging pollutants,compare the reaction conditions,explore the optimal degradation conditions,and investigate the effects of UV light intensity,initial PS concentration,initial p H of solution and anion type and concentration on the reaction.Evaluate the advanced oxidation processes such as UV/Persulfate,UV/Chlorine and UV/SO₃^2-advanced reduction processes to study the degradation of perfluorooctanoic acid（PFOA）and perfluorooctane sulfonic acid（PFOS）,typical pollutants in emerging pollutants PFCs,and compare the process conditions to explore the best reaction process.The structural analysis and mass spectrometry of the three typical emerging pollutants were combined to identify the degradation intermediates,explore the reaction pathways and predict the toxicity changes during the reaction process.The results showed that in the reaction process of UV/PS degradation of SUC,comparing single UV and single PS,the degradation rate of SUC under UV/PS process was as high as 98.6%,the reaction rate constant of SUC degradation increased with the increase of light intensity and PS dosage,neutral conditions were more favorable to SUC degradation,background ions NO₃^-and HCO₃^-had a certain inhibitory effect on UV/PS degradation of SUC,while Cl^-and SO₄^2-promote the degradation process.From the structural features and spectral analysis of SUC molecules,it is clear that C11 and O6 on SUC molecules may be the most easily attacked positions.Based on the high-resolution mass spectrometry HRMS and GC-MS,16 SUC intermediates were resolved,and the degradation process mainly involved hydroxylation,oxidation and ether cleavage reactions.The results of photobacterial toxicity experiments and ECOSAR predictions indicated that the UV/PS degradation of SUC produced intermediates with higher toxicity than the parent material.In the reaction process of PFOA and PFOS degradation by UV/SO₃^2-advanced reduction process,the degradation rate of PFOA was up to 99.6%and the degradation rate of PFOS was up to 94%under UV/SO₃^2-process conditions compared with UV/PS and UV/chlorine advanced oxidation processes.From the structural characteristics and spectral analysis of PFOA and PFOS molecules,it can be seen that the positions of F11,F12 and F13 in PFOA molecule and The S26-O29 molecular bond in PFOS molecule is easily attacked by hydrated electrons.Based on the high-resolution mass spectrometry HRMS and GC-MS,nine PFOA intermediates and eight PFOS intermediates were resolved,and the degradation process was mainly achieved by defluorination and dehydrogenation of the-CH₂ group.the ECOSAR prediction showed that the UV/SO₃^2-degradation of PFOS produced intermediates with higher toxicity than the parent substance.Therefore,it is necessary to further investigate the ecological risk of the advanced oxidation/advanced reduction process based on the UV activation method to reduce the environmental risk to safeguard the water environment.