Degradation And Transformation Mechanisms Of Bezafibrate And Phenacetin During UV/chlorine Process

Recent years,pharmaceutically active compounds(PhACs)have been frequently detected all over the world in aquatic environment which has received great attention.Traditional wastewater treatment processes cannot effectively remove PhACs which make PhACs widely exist in potable water,threaten public health and ecological environment.As the last barrier of wastewater reaching into aquatic environment,disinfection acts a significant role in removing PhACs.UV/chlorine,as a novel disinfection method,has become a study focus by aboard scholar.However,there are few researches on degradation and transformation mechanisms of PhACs during UV/chlorine process,and therefore to study the degradation mechanisms of the PhACs during UV/chlorine process is essential for its application prospects.This study chose Bezafibrate(BZF),a typical antilipemic drug,and Phenacetin(PNT),an antipyretic-analgesic drug,as the objective pharmaceuticals to investigate their degradation kinetics and pathways during UV/Chlorine process.The results showed that the degradation rate constant of objective pharmaceuticals during UV/chlorine process is higher than that in UV alone,chlorine alone,UV/H2O2 and UV/S2O82-.The degradation of BZF and PNT followed the pseudo-first-order kinetics model,and the degradation rate constants(kobs)of them increased linearly with the increase of chlorine dosage.Taking BZF as an example,the changes of different radical concentration in different chlorine dosage were simulated by Matlab.The results showed that the linearly increase of kobs could be attributed to the BZF reacting with CIO·and the rate constant is 5.0×108 M-1s-1.Meanwhile,the degradation condition of different pharmaceuticals were summarized and found that pharmaceuticals whose kobs increased linearly contained acylamino,which indicated that CIO·could react with pharmaceuticals with acylamino.The kobs of BZF and PNT decreased with the increase of pharmaceutical and humic acid concentration,and enhanced with the increase of chloridion concentration while carbonate concentratuin has no influence.With the increase of pH,the kobs of BZF decreased while the pH of PNT first decreased and then increased.Using nitrobenzene as the HO·probe,it could be concluded that the contribution of HO·in degrading pharmaceuticals is lower in basic solutions.The degradation mechanism of two pharmaceuticals was similar,and initial degradation products were arisen from hydroxylation,chlorine substitution and further oxidized to generate hydroxylation,acylamino cleavage,methoxy group cleavage and ring opening products.