Reaction Kinetics and Efficiencies for the Hydroxyl and Sulfate Radical Based Oxidation of Artificial Sweeteners in Water

Abstract

Over the past several decades, the increased use of artificial sweeteners as dietary supplements has resulted in rising concentrations of these contaminants being detected in influent waters entering treatment facilities. As conventional treatments may not quantitatively remove these sweeteners, radical-based advanced oxidation and reduction (AO/RP) treatments could be a viable alternative. In this study, we have established the reaction kinetics for both hydroxyl ((•)OH) and sulfate (SO(4)(•-)) radical reaction with five common artificial sweeteners, as well as their associated reaction efficiencies. Rate constants for acesulfame K, aspartame, rebaudioside A, saccharin, and sucralose were <2 × 10(7), (2.28 ± 0.02) × 10(9), (2.1 ± 0.1) × 10(8), <2 × 10(7), and (1.7 ± 0.1) × 10(8) M(-1) s(-1) for the sulfate radical, and (3.80 ± 0.27) × 10(9), (6.06 ± 0.05) × 10(9), (9.97 ± 0.12) × 10(9), (1.85 ± 0.01) × 10(9), and (1.50 ± 0.01) × 10(9) M(-1) s(-1) for the hydroxyl radical, respectively. These latter values have to be combined with their corresponding reaction efficiencies of 67.9 ± 0.9, 52.2 ± 0.7, 43.0 ± 2.5, 52.7 ± 2.9, and 98.3 ± 3.5% to give effective rate constants for the hydroxyl radical reaction that can be used in the modeling of the AOP based removal of these contaminants.

Photocatalytic degradation of saccharin under UV‐LED and blacklight irradiation

“…According to the results, the photocatalytic transformation of SAC under both irradiation sources, starts by the hydroxylation of the molecule giving rise to the formation of three isomers (TP4, TP5, TP6). The hydroxylation mechanism proposed in the present study is consistent with a previous work that reported relatively high reactivity of hydroxyl radicals towards the studied sweetener and proposed that the oxidation mechanism involves the addition of hydroxyl radicals in the aromatic ring, resulting in hydroxylated products …”

“…The hydroxylation mechanism proposed in the present study is consistent with a previous work that reported relatively high reactivity of hydroxyl radicals towards the studied sweetener and proposed that the oxidation mechanism involves the addition of hydroxyl radicals in the aromatic ring, resulting in hydroxylated products. 37 Hydroxylation of phenyl ring as well as N atom can be considered. Sequential hydroxylation of the above-mentioned TPs results to di-and tri-hydroxy derivatives (TP7 and TP1).…”

Effects of bromide on the degradation of organic contaminants with UV and Fe2+ activated persulfate

“…The rate constant of t-BuOH with hydroxyl radical (k HO•/t-BuOH = 6.0 x 10 8 M -¹ s -¹ [17]) is around three-order higher than with sulfate radical (k SO4• -/ t-BuOH = 8.4 x 10 5 M -¹ s -¹ [44]). Thus, the addition of an excessive amount of t-BuOH allowed a strong suppression of the reaction of target compounds with hydroxyl radical [45][46][47]. Though the presence of the competitors and t-BuOH influenced the steady-state radical concentrations, without the radical concentration values, the second order rate constant of BZ4 with the radical species could still be calculated according to equation (1) without knowledge of the radical concentrations [48] which is in fact an integrated equation for eq (8)- (11) in Gonzalez-Olmos, 2011 [49]:…”

Effectiveness of Engineered and Natural Wastewater Treatment Processes for the Removal of Trace Organics in Water Reuse

“…j As reported by Hyunwoong (2010). k As reported by Toth et al (2012). l As reported by Dodd et al (2009).…”