Removal of Emerging Contaminants by Fenton and UV-Driven Advanced Oxidation Processes

The removal efficiencies of four different parabens (methylparaben (MP), ethylparaben (EP), propylparaben (PP), and butylparaben (BP)) using Fenton reagent, UV irradiation, UV/H2O2, and UV/H2O2/Fe2+ were evaluated to assess the level of paraben degradation achieved using different advanced oxidation processes (AOPs). UV irradiation by itself provided paraben conversions between 27 and 38 % after a reaction time of 180 min. The UV/H2O2 system increased the paraben conversion to values between 62 and 92 %, and the Fenton process was revealed as inefficient in paraben degradation within the experimental conditions used. Photo-Fenton presented similar removal rates to the UV/H2O2 process. Among the four parabens studied, butylparaben was the most easily removed, and it was possible to attain degradations higher than 90 %. In the UV/H2O2 and photo-Fenton processes, the overall kinetic constant could be split into two main components: direct oxidation by UV radiation (photolysis) and oxidation by free radicals (mainly HO center dot) generated from the photodecomposition of H2O2. This work reveals that UV-driven oxidation processes can be widely used to remove parabens from contaminated aqueous solutions.