Degradation Of Sulfamethoxazole By UV/Persulfate In Different Water Samples:Influential Factors,Transformation Products And Toxicity

Recently,antibiotic pollution problem in marine aquaculture water has attracted wide attention,and the effective degradation of residual antibiotics in water has become one of the international research focuses.Sulfamethoxazole is a typical antibiotic,which is frequently used in marine aquaculture water and has a high residual concentration in water.UV/persulfate?UV/PS?is an advanced oxidation processe based on sulfate radical(SO₄^·-),which can degrade SMX in freshwater efficiently without causing the formation of other halogenated disinfection by-products.Few studies were focused on the kinetics and mechanism of degradation of sulfamethoxazole?SMX?in marine aquaculture water.In this work,SMX was treated with the UV/PS in different water samples.The molecule of SMX was calculated by Guassian09 program and investigated with the density functional theory?DFT?to deduce the characteristic of structure and its charge distribution.Bioaccumulation factor?BCF?,absorbable organic halogen?AOX?and growth inhibition of Chlorella vulgaris were used to evaluate the biotoxicity.The results show that:?1?SMX could be effectively degraded by UV/PS in three water samples.Chloride ions?Cl^-?and bicarbonate?HCO₃^-?had inhibitory effect on the degradation of SMX.Bromide ions?Br^-?had a slight effect on SMX degradation.Sulfate ions(SO₄^2-)showed a negligible impact in thesystem.The reaction rate of SMX and the ionization of SMX were affected by the initial p H in UV/PS system,the formation of SO₄^·-in the system is inhibited under alkaline conditions.The degradation of SMX by UV/PS was an organic mineralization process,the removal rate of TOC reached 70.7%after 8 h reaction.?2?The active sites of SMX were calculated to be the N1 and C7atoms of the isoxazole ring,as well as the C9,C13 and N3 atoms of the benzene ring.Seven organic transformation products were identified by LC/MS/MS.Bromate?Br O₃^-?and chloromethane were not detected from the reaction system of UV/PS with SMX in three water samples.In marine aquaculture and seawater,SMX could inhibited the formation of Br O₃^-and ClO₃^-in UV/PS system.?3?Log Kow and log BCF values proved that the products of SMX degraded by UV/NaClO were more biotoxic and easier to accumulate in organisms than those by UV/PS.Preliminary analysis of toxicity by absorbable organic halogen?AOX?analysis and growth inhibition of Chlorella vulgaris proved that UV/PS is relatively safer than UV/NaClO disinfection.