Radiolytic Decomposition Of Sulfamethoxazole,Ciprofloxacin Hydrochloride,and Dexamethasone Using ? Irradiation In Aqueous Solution

The factors of degradation of Sulfamethoxazole(SMZ),Ciprofloxacin Hydrochloride(CIP),Dexamethasone(DEX),the impact of combined pollution on the degradation of SMZ,CIP and DEX were researched under ? irradiation in this study.In addition,the changes of COD and TOC o the degradation of CIP and SMZ,and the effect of DEX degradation products on the algae were studied.Geometry structures of SMZ,CIP,DEX and those losing electrons were optimized respectively using Gaussian 09 software at density functional theory(DFT)in the level of B3LYP/6-3 1G(d).Use the charge distribution and bond length to deduce the reaction mechanism of SMZ,CIP,DEX and LC-MS is conducted to confirm the result.Conclusions are as follow:(1)Low initial concentration and acidic condition were favorable for SMZ removal under y irradiation.By contrast,radiolytic decomposition of SMZ was inhibited with the addition of anions and organic additives,such as NO3-,NO2-,humic acid,methanol,2-propano and tert-butanoll;H2O2 promoted the degradation of SMZ and the effect of promotion reduced with the concentration increasing;Cr6+ and I-was separately mixed with SMZ to produce compound pollutants:Cr6+ promoted the degradation of SMZ while I-inhibited the degradation of SMZ;TOC and COD of SMZ decrease in different degree.(2)Low initial concentration and highly acidic condition were favorable for CIP removal under y irradiation;radiolytic decomposition of CIP was inhibited with the addition of CO32-,NO3-,NO2-,humic acid,methanol,2-propano and tert-butanoll.HCO3-has almost no effect on the degradation of CIP;The effect of H2O2 to the degradation of CIP is influenced by its concentration;As a strong carcinogen,BrO3-and Cr6+ was separately mixed with CIP to produce compound pollutants and the degradation efficiencies of the two pollutants were markedly improved compared to that of the single pollutant during y irradiation;TOC and COD of CIP decrease in different degrees.(3)Low initial concentration and alkaline condition were favorable for DEX removal during ?irradiation.H2O2 promoted the degradation of DEX and the effect of promotion increased with the concentration increasing;Cr6+ was especially mixed with SMZ to produce compound pollutants and the degradation efficiencies of the two pollutants were markedly improved compared to that of the single pollutant during ? irradiation.(4)The results of quantum chemical calculations and LC-MS analysis demonstrate that the SMZ,CIP and DEX degradation pathways are mainly attributed to the oxidation process of hydroxyl radicals OH· and the direct decomposition of their molecules.