Simultaneous removal of bisphenol A and phosphate from water by peroxymonosulfate combined with calcium hydroxide

Abstract

A feasibility study was conducted for simultaneous removal of bisphenol A (BPA) and phosphate (P) using the combination of Ca(OH)2 and peroxymonosulfate (PMS). The results showed that BPA and P could be simultaneously removed in the Ca(OH)2/PMS system. The removal efficiency of BPA and P depended on the operating parameters, such as the Ca(OH)2 and PMS dosage, solution pH, co-existing anions, humic acid (HA) and water matrices. HCO3− showed an inhibitory effect on the removal of both BPA and P. The presence of Cl− enhanced the degradation efficiency of BPA but had no obvious effect on P removal. However, NO3−, SO42− and HA had no significant effect on the removal efficiencies of BPA and P. Quenching studies revealed that superoxide radical (O2−) and singlet oxygen (1O2) rather than sulfate (SO4−) nor hydroxyl (HO) were the predominant ROS responsible for BPA degradation. BPA and P showed lower removal efficiency in real waters in comparison to ultrapure water, which indicated competing side reactions of ROS and Ca2+ with the background substances of selected water samples, such as natural colloidal particles (NCPs) and HCO3−. Nevertheless, the Ca(OH)2/PMS process was still effective in the simultaneous removal of BPA and P in wastewater containing considerable NCPs. In addition, based on intermediates identified, the degradation pathways of BPA in the Ca(OH)2/PMS system were proposed. Moreover, organic contaminants (including phenol and acid orange 7) degradation and P removal were also successfully achieved in this process. Consequently, these results revealed that the Ca(OH)2/PMS system has a potential in the wastewater treatment polluted jointly by organic compounds and/or P.