Singlet oxygen is also involved in the formation of hypoiodous acid during the transformation of phenolic pollutants by peracetic acid in the presence of iodide

Peracetic acid (PAA) has been used as a disinfectant/oxidant in wastewater treatment. However, considering that the presence of iodide (I-) would induce the iodinated products in wastewater, the effect of I- on the transformation of phenolic pollutants by PAA was investigated. Herein, the presence of I- enhanced the transformation of phenolic pollutants (bisphenol S (BPS), bisphenol A (BPA), and p-hydroxybenzoic acid (p-HBA)) by PAA. Furthermore, hypoiodous acid (HOI) was reactive species in the PAA/I- system based on radical quenching experiments and electron spin resonance. In this system, PAA, together with 1O2 that was produced in PAA oxidized I- into HOI. Increasing PAA and I- dose promoted the transformation of phenolic pollutants but the promoting effect was less significant at higher dosage. The increase in H2O2 dose retarded the transformation of phenolic pollutants because of HOI being quenched by H2O2. In a wide range of pH (pH 4.0-10.0), the transformation of BPS, BPA, and p-HBA was pH-dependent and most effective at pH 7.0. The presence of chloride and bromide accelerated the transformation of phenolic pollutants by PAA/I- due to the formation of HOCl and HOBr. Furthermore, HOI substitution was the primary reaction pathway in the transformation of BPS, BPA, and p-HBA by PAA/I-. Finally, the transformation products of phenolic pollutants during the PAA/I- posed higher cytotoxicity compared to the parent pollutants. Overall, our findings improved the understanding of the chemical behavior of PAA in the presence of I- and suggested that the generation of iodinated products raised concerns for water safety.

Automated summary

This study found that the presence of iodide (I-) can enhance the transformation of phenolic pollutants by peracetic acid (PAA) in wastewater treatment. Hypoiodous acid (HOI) was identified as the reactive species in the PAA/I- system. Increasing the doses of PAA and I- promoted the transformation of phenolic pollutants, but the effect was less significant at higher doses. Additionally, the presence of H2O2 hindered the transformation process, while chloride and bromide accelerated it. The transformation products of PAA/I- showed higher cytotoxicity than the parent pollutants.