Sulfate radical-based oxidation of an alcohol ethoxylate (Brij30^®) by the PS/UV-C process

In this study, sulfate radical-based oxidation of an alcohol ethoxylate (AE) was explored by the persulfate (PS)/UV-C process. Poly(oxyethylene)(4)laurylether, commercially known as Brij30^®, was used as a model AE. PS/UV-C oxidation of aqueous Brij30^® (8-20 mg/L) was performed at initial PS concentrations varying between 0.50 and 6.50 mM and at initial pH values of 3.0 and 6.0. Results indicated that an increase in both initial PS and Brij30^® concentrations did not have a significant effect on Brij30^® removal efficiency and that Brij30^® abatements of more than 90% could be achieved after 60 min of treatment time. Total organic carbon (TOC) removals were significantly improved with increasing initial PS concentrations for both initial pH values. On the other hand, an increase in initial Brij30^® concentration had a negative effect on mineralization. By employing the competitive kinetic method, the second-order reaction rate coefficient of Brij30^® with the sulfate radical (SO₄ ^•-) was determined as 1.62 × 10⁹ ± 3.5 × 10⁷ M^-1s^-1. The second-order reaction rate constant of TOC, originating from Brij30^® and reaction intermediates, was found to be 9.09 × 10⁵ ± 2.91 × 10⁵ M^-1s^-1 and 1.13 × 10⁶ ± 0.46 × 10⁶ M^-1s^-1 for pH values of 6.0 and 3.0, respectively. Toxicity of PS/UV-C treated aqueous Brij30^® solutions towards Vibrio fischeri was also investigated to determine the possible toxic behavior of oxidation products.