Environmental Engineering and Science Program, Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221, USA.
Department of Chemical Engineering, Escola Politécnica, University of São Paulo, tr. 3, São Paulo 380, Brazil.
Water Res. 2022 Jul 1;219:118457. doi: 10.1016/j.watres.2022.118457. Epub 2022 Apr 20.
Reported herein is an investigation of the impact of water quality parameters on the formation of carbonate radical anion (CO) and hydroxyl radical (HO) in UV/sodium percarbonate (UV/SPC) system versus in UV/hydrogen peroxide (UV/HO) system for bisphenol A (BPA) degradation in water. Pathways of CO oxidation of BPA were proposed in this study based on the evolution of direct transformation products of BPA. Observed in this study, the degradation of BPA in the UV/SPC system was slower than that in the UV/HO system in the secondary effluents collected from a local wastewater treatment plant due to the significant impact of coexisting constituents in the matrices on the former system. Single water quality parameter (e.g., solution pH, common anion, or natural organic matter) affected radical formations and BPA degradation in the UV/SPC system in a way similar to that in the UV/HO system. Namely, the rise of solution pH decreased the steady state concentration of HO resulting in a decrease in the observed pseudo first-order rate constant of BPA (k). Chloride anion and sulfate anion played a negligible role over the examined concentrations; nitrate anion slightly suppressed the reaction at the concentration of 20 mM; bicarbonate anion decreased the steady state concentrations of both CO and HO exerting significant inhibition on BPA degradation. Different extents of HO scavenging were observed for different types of natural organic matter in the order of fulvic acid > mixed NOM > humic acid. However, the impact was generally less pronounced on BPA degradation in the UV/SPC system than that in the UV/HO system due to the existence of CO. The results of this study provide new insights into the mechanism of CO based oxidation and new scientific information regarding the impact of water quality parameters on BPA degradation in the sytems of UV/SPC and UV/HO from the aspect of reactive radical formation, which have reference value for UV/SPC application in wastewater treatment.
本文研究了水质参数对水中双酚 A（BPA）在 UV/过碳酸钠（UV/SPC）和 UV/过氧化氢（UV/HO）体系中降解时生成碳酸根自由基（CO）和羟基自由基（HO）的影响。基于 BPA 的直接转化产物的演变，提出了 CO 氧化 BPA 的途径。本研究中，由于当地污水处理厂二级出水中共存成分对前者体系的显著影响，SPC 体系中 BPA 的降解速度比 HO 体系慢。单个水质参数（如溶液 pH 值、常见阴离子或天然有机物）对 SPC 体系中自由基的形成和 BPA 的降解的影响与 HO 体系相似。即溶液 pH 值的升高降低了 HO 的稳态浓度，导致观察到的 BPA （k）的伪一级速率常数降低。氯离子和硫酸根离子在考察的浓度范围内作用可以忽略不计；硝酸盐阴离子在 20 mM 的浓度下略有抑制作用；碳酸氢根离子降低了 CO 和 HO 的稳态浓度，对 BPA 的降解有显著抑制作用。不同类型的天然有机物对 HO 的清除程度不同，顺序为富里酸>混合 NOM>腐殖酸。然而，由于 CO 的存在，SPC 体系中 BPA 降解受其影响的程度通常小于 HO 体系。本研究结果为 CO 基氧化机制提供了新的见解，并从反应性自由基形成的角度提供了水质参数对 UV/SPC 和 UV/HO 体系中 BPA 降解影响的新科学信息，对 UV/SPC 在污水处理中的应用具有参考价值。
