Oxidative removal of bisphenol A by permanganate: Kinetics, pathways and influences of co-existing chemicals

Batch experiments were carried out to investigate the decomposition of bisphenol A (BPA) by permanganate. Permanganate (100 μM) was very effective for BPA degradation and over 99% BPA (5 μM) was eliminated in 15 min at pH 7.0. A parabola-like shaped pH-rate profile for BPA oxidation by aqueous permanganate was found over the pH range of 4.0-11.0. The rate constants of permanganate reaction with BPA were strongly dependent on temperature and the activation energy was determined to be 67.8 kJ mol^-1. Eleven degradation intermediates were observed by LC-MS/MS and the pathways of BPA degradation by permanganate were proposed. The intermediates generated in the processes of BPA oxidation by permanganate, ferrate, ozone, chlorine or hydroxyl radical indicated that benzoic ring was the reaction site at the early stage of BPA oxidation by various oxidants. The presence of humic acid (HA), HCO3-, Fe²⁺ and Fe³⁺ at their environmentally relevant concentrations enhanced BPA removal following the order: HA > HCO3- > Fe²⁺> Fe³⁺. BPA degradation in tap water, river water, and synthetic water at pH 7.0 was faster than that in deionized water, indicating that permanganate was selective for BPA oxidation. These results suggested that permanganate oxidation is an effective method for the purification of waters containing phenolic EDCs.