| Drugs and personal care products?PPCP?in drinking water have attracted more and more attention from domestic and foreign scholars.Trimethoprim?TMP?is one of the common drugs in water environment.Recently,the UV/free chlorine oxidation system has been considered as an emerging alternative to the UV/H2O2 process due to the generation of HO·,Cl·,Cl O·and other reactive substances in the system.But in the background conditions of water and the concentration of oxidant,and other conditions will influence on the oxidation effect,so this article has carried on the UV/free chlorine TMP degradation kinetics and influence factors of research,in order to further study the degradation effect,also studied the free chlorine effect on the degradation of TMP,and UV/free chlorine and UV/H2O2 oxidation system under different conditions were compared.The study found that for free chlorine to degrade TMP,with the change of p H,the main forms of TMP and free chlorine in the oxidation system change,so the main substances in the oxidation system under high p H conditions are TMP and Cl O-.The rate constant of Cl O-is small,which leads to a lower degradation rate.The degradation of TMP by UV/free chlorine is consistent with first-order reaction kinetics.TMP has higher degradation efficiency under acidic and neutral conditions,and at high p H?Eg p H>8?,the degradation of TMP is inhibited.In the presence of NOM?natural organic matter?,NOM has an inhibitory effect on the degradation of TMP due to its light absorption and consumption of free radicals.According to data analysis,the chlorination of NOM is negligible.The effects of HCO3-/CO32-and Cl-on the degradation of TMP are very weak.With the increase of free chlorine concentration,the degradation rate of TMP accelerated,but the degradation rate constant did not increase linearly.In addition,this study also optimizes the operating conditions and obtaining the minimum EE/O based on the heat map analysis It is 0.136 k Wh/m3,the optimal UV intensity is2.56×10-7Einstein/L-s,and the optimal free chlorine dose is 0.064m M;the relevant rate constants are collected and fitted to calculate each The contribution of several active substances in the UV/free chlorine process.It was found that Cl O·played a major role in the degradation of TMP at various p H conditions.The degradation of TMP by UV and Cl2-?is negligible.Comparing the degradation effect of UV/H2O2 and UV/free chlorine on TMP,UV/free chlorine oxidation system is superior to UV/H2O2 oxidation system in degrading TMP,which is mainly due to the higher quantum yield of HOCl,which Under the condition of the intensity and concentration of ultraviolet light,the UV/free chlorine oxidation system can generate more free radicals in the same time,so the UV/free chlorine oxidation effect is better and the cost is lower. |
PDF Full Text Request