Oxidation of the emerging contaminants amitriptyline hydrochloride, methyl salicylate and 2‐phenoxyethanol by persulfate activated by UV irradiation

BACKGROUNDDespite the small concentration of emerging contaminants (ECs) in water systems, in recent years numerous works have reported potential toxicological risks associated with their presence in the environment, and recommending their elimination by different procedures, such as chemical oxidation processes. RESULTSThe elimination of three selected ECs, amitriptyline hydrochloride, methyl salicylate and 2-phenoxyethanol in aqueous solutions by photochemically activated persulfate has been investigated. The main operating conditions, such as persulfate dose, temperature, pH and buffer used, were varied and efficiencies of elimination and apparent pseudo-first-order rate constants of the oxidation reactions were determined for comparison purposes. The role of reactive oxygen species generated in the system, such as SO4- and HO, in the overall oxidation of the ECs was determined by using suitable scavenger compounds. Moreover, thermally activated persulfate was around 15-50 times less reactive than the UV/persulfate system. Finally, second-order rate constants for the reaction between sulfate radical and each EC were determined by competition kinetics, and the values obtained were (4.80.6)x10(9)M(-1)s(-1) for amitriptyline hydrochloride, (9.2 +/- 0.9)x10(8)M(-1)s(-1) for methyl salicylate, and (1.38 +/- 0.02)x10(9)M(-1)s(-1) for 2-phenoxyethanol. CONCLUSION Both radical species SO4- and HO play important roles in the oxidation of the ECs investigated when using the UV/persulfate system, with the contribution of sulfate radicals predominating for those compounds with low reactivity towards HO radicals. (c) 2015 Society of Chemical Industry