Assessment of the UV/Cl2 advanced oxidation process for the degradation of the emerging contaminants amitriptyline hydrochloride, methyl salicylate and 2-phenoxyethanol in water systems

Three emerging contaminants (amitriptyline hydrochloride (AH), methyl salicylate (MS) and 2- phenoxyethanol (PE)) frequently found in wastewaters were selected to be individually degraded in ultra- pure water by the advanced oxidation process (AOP) constituted by the combination of UV radiation and chlorine. The influence of pH, initial chlorine concentration and nature of the contaminants was firstly explored. The trend for the reactivity of the selected compounds was deduced: AH > MS > PE. A later kinetic study was carried out focused on the evaluation of the first- order rate constants and the determination of the partial contribution to the global reaction of the direct photochemical pathway and the radical pathway. In a second stage, the simultaneous oxidation of mixtures of the selected contaminants in several types of water was also performed by the same combination UV/ Cl2. The efficiency of this combined system UV/ Cl2 was compared to other oxidants such as the UV/ S2O2- 8 and UV/ H2O2 AOPs, and the influence of the operating variables was discussed. Results confirmed that the UV/ Cl2 system provides higher elimination efficiencies among the AOPs tested. The presence of dissolved organic matter and bicarbonate ions in the water matrix caused a decrease in the treatment efficiency.