Both degradation and AOX accumulation are significantly enhanced in UV/peroxymonosulfate/4-chlorophenol/Cl⁻ system: two sides of the same coin?

Abstract

External chloride ion may lead to AOX accumulation in UV/PMS process, although 4-CP degradation was accelerated.

Selective degradation of acetaminophen from hydrolyzed urine by peroxymonosulfate alone: performances and mechanisms

“…Cl − in the degradation system of PMS undergoes a relatively complex reaction process. Combining the previous literature and our experimental data, the following three explanations can be drawn: (1) Cl − can react with PMS to generate hypochlorous acid (HClO) and Cl˙, 28 and the former can self-decompose or continue to react with PMS to generate 1 O 2 , which would accelerate the removal of ACE ( eqn (8)–(11) ); 17 (2) the reactions of Cl − with RS produced Cl˙ ( E 0 = (Cl˙/Cl − ) = 2.41 V), 7,29 in which the oxidant power was higher than for PMS (1.82 V). 30 Thus, the faster ACE degradation might be partly contributed to by the oxidation of Cl˙; (3) the ortho and para positions to the phenol moiety of ACE could be attracted by Cl˙.…”

Kinetic and mechanistic insights into the degradation of clofibric acid in saline wastewater by Co2+/PMS process: a modeling and theoretical study

“…According to previous studies, PMS can oxidize Cl − directly to generate reactive chlorine species (HClO/Cl 2 ) to degrade organic compounds. 35 However, this dual effect of Cl − was not present in H 2 O 2 -based AOPs, such as Fenton and photo-Fenton systems, 37 because Cl − cannot activate H 2 O 2 to oxidize the contaminants. Cl − + HSO 5 − → SO 4 2− + HOCl 2Cl − + HSO 5 − + H + → SO 4 2− + Cl 2 + H 2 O …”

On peroxymonosulfate-based treatment of saline wastewater: when phosphate and chloride co-exist

“…In addition, it should be much difficult to eliminate overall AOX at a higher chloride concentration due to the simultaneous occurrence of dechlorination and re-chlorination. 25 …”

“…In addition, it should be much difficult to eliminate overall AOX at a higher chloride concentration due to the simultaneous occurrence of dechlorination and rechlorination. 25 Co/PMS system, a common system to produce sulfate radicals, was compared with the PBS/PMS system on AOX formation. Fig.…”

“…22 Grebel et al 23 found that the degradation of phenol was markedly enhanced under a high concentration of chloride by PMS/Cl À process. However, our previous studies indicate that absorbable organic halides (AOX) was produced and the formation of AOX increased with chloride concentration increasing, 24,25 owing to the generation of poly-chlorinated byproducts in PMS-based oxidation system. 22,26 AOX formation and accumulation is a matter of great concern due to their potential toxicity.…”