Enhanced removal of organic contaminants in water by the combination of peroxymonosulfate and carbonate

Abstract

In this study, a favorable CO32−/PMS system for efficient degradation of organic contaminants (acid orange 7 (AO7), acetaminophen, para-aminobenzoic acid, phenol, methylene orange, methylene blue) in water was firstly reported. Under optimal conditions, the decolorization ration of AO7 was 100% within 40 min. Data fitting showed that the AO7 decolorization could be described by the pseudo-first-order kinetics, and the rates constant values ranging from 0.0006 to 0.2297 min−1 depending on the operating parameters (initial PMS, CO32−, AO7 concentrations). Radical scavenging studies revealed that superoxide anion radical (O2−) and singlet oxygen (1O2) rather than sulfate (SO4−) nor hydroxyl (HO) were the dominant oxidants might be responsible for AO7 degradation. The presence of NO3−, HPO42− and low concentration of Cl−, NO2−, HCO3−, H2PO4−, HA had no significantly effect on the decolorization of AO7. Adding a higher Cl− concentration displayed favorable effects on the removal efficiencies of AO7, but adding a higher NO2−, HCO3−, H2PO4− and HA concentration apparently inhibited this process. The decolorization of AO7 was lower in wastewater in comparison to other natural waters and ultrapure water, which was probably due to the presence of higher concentration of colloids in wastewater. Nevertheless, up to 94.8%, 97.0% and 85.1% of AO7 were degraded from the filtrate, permeate, and retentate phases of wastewater within 60 min, respectively. Consequently, CO32−/PMS would be promising for removal methodology for AO7 in wastewater containing considerable colloids. Finally, three intermediates were identified and degradation pathways of AO7 were proposed.