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

Abstract

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.

Effect of chloride ions on persulfate/UV-C advanced oxidation of an alcohol ethoxylate (Brij 30)

“…The concentration of Brij 30 was measured using a modified version 38 of The Spectrometric Iodine/Iodide (I–I) method defined by Baleux and Champetier 39 . The colorimetric method was used to measure persulfate in solution, as described in more detail elsewhere 1 . Total organic carbon (TOC) measurements were performed to determine the level of mineralization reached during photocatalytic oxidation.…”

“…Our previous study 1 extensively discussed the effect of initial PS concentration, initial pH, and model target concentration on Brij 30 removal by PS/UV-C oxidation. The results showed that Brij 30 was rapidly oxidized within 30 min and there was a significant improvement in mineralization with increasing initial PS concentrations up to 3.0 mM at initial pH values of 3.0 and 6.0.…”

“…Alcohol ethoxylates (AEs) with a general formula of CH 3 (CH 2 ) n (OCH 2 CH 2 ) y OH (n: 11–15, 17 and y: 0–18) are one of the most important classes of nonionic surfactants. They are widely used in industrial and commercial formulations as detergents, emulsion stabilizers, paints, dispersing agents, pesticides, petroleum recovery chemicals, foaming agents and wetting enhancers 1 – 4 . The widespread use of these chemicals has led to a growing concern about their impact on the environment.…”

“…Morrall et al reported that the concentration of AEs could vary in a wide range from 35.4 to 2717 μg/L in different stages of municipal wastewater treatment plants in the USA 5 , 9 . While AEs are considered as biodegradable surfactants, in particular, their metabolites such as polyethylene glycol and carboxylated AE chains 10 , 11 have the potential to act as endocrine disrupting agents in aquatic organisms, wildlife and even humans 1 , 12 . Therefore, the degree of treatment of AEs is a key parameter for accurately assessing the potential risk to the environment posed by their release 8 , 9 , 13 – 15 .…”

“…Therefore, the degree of treatment of AEs is a key parameter for accurately assessing the potential risk to the environment posed by their release 8 , 9 , 13 – 15 . Until now, advanced oxidation processes (AOPs) based on either HO ·− 4 , 16 or SO 4 ·− 1 , 2 , 4 radical production have been successfully applied for the treatment of AEs. Published data demonstrated that AEs could be effectively removed from aqueous solutions when some operating parameters such as initial pH, the applied oxidant dose and reaction time were selected properly.…”