Degradation Mechanisms Of NAP And Effects Of Water Matrices On Free Radicals Conversion In UV/Peracetic Acid Process

In recent years,pharmaceutical active compounds(PhACs)have been frequently detected all over the world in aquatic environment which has received great attention.The UV/peracetic acid(UV/PAA)process as a novel advanced oxidation process has been reported to produce carbon-centered radicals(R-C·)for Naproxen(NAP)degradation,which is a representative of naphthyl structure substances.Real water matrices,such as carbonate and bicarbonate ions(CO32-/HCO3-),humic acid(HA),and chloride ion(Cl-),may react with these reactive radicals and change their contributions to NAP degradation.However,there is few research on R-C·during UV/PAA process,and it is essential to study the contributions of reactive radicals,degradation kinetics and influencing factors of NAP during UV/PAA process.The results showed that R-C·contributed 60.8%and·OH contributed 39.2%to NAP degradation in UV/PAA pure water process by a competition method.The degradation rate constants(kobs)of NAP increased linearly with the increase of PAA dosage.kobs will decrease as the initial concentration of the NAP and pH increases.CO32-/HCO3-(0-20 mM)showed minimal effect on NAP degradation in the UV/PAA process.This results suggested that CO32-/HCO3-could react with·OH yielding CO3·-with low reactivity to NAP,and CO3·-could further react with PAA to produce R-C·.This speculation was confirmed by the increased contribution of R-C· to NAP degradation with the increase of CO32-/HCO3-concentration through the competition method.HA(0-5 mg/L)had a higher scavenging capacity for R-C·than ·OH because HA with naphthyl structure was likely to be attacked by R-C·Cl-(0-200 mM)had little effect on NAP degradation in the UV/PAA and UV/H2O2 processes,while exerted an observable inhibition on NAP degradation in the UV/PAA process with TBA.This finding suggested that Cl-could react with R-C·to produce Cl·,which could be further converted into HOCl·-,and then excess·OH was formed.With the increase of Cl-concentration,the contribution of R-C·and·OH to NAP degradation is almost unchanged.