Transformation of Bisphenol A in the Presence of Manganese Dioxide

This study investigates the abiotic transformation of bisphenol A (BPA) in the presence of manganese dioxide (MnO2) and under a spectrum of solution chemistry conditions using batch reactor systems. The results indicated that, at a fixed MnO2 concentration, the reaction rate decreased as a function of initial BPA concentration, and that at a fixed initial BPA concentration, the rate increased as a function of MnO2 concentration. It was also shown that the overall reaction rates decreased rapidly as the solution pH increased from 4.12 to 6.22, whereas a higher ionic strength of the background solution resulted in slower reaction rates. Both Zn2+ and Mn2+, present as background electrolytes, decreased the reaction rates likely because of their adsorption and then blocking of active sites on the MnO2 surfaces. Three products (2-[4- hydroxyl-phenyl]ethyl, 2-[4-hydroxyl-phenyl]-propyl, and a dimer) were identified and confirmed with deuterated BPA on gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry. It was proposed that formation of dimeric products via oxidative coupling and formation of monomeric products via hydroxylation and dealkylation of BPA were the major reaction mechanisms in the oxidation of BPA by MnO2. The study indicated that oxidative reactions with MnO2 may play an important role in the fate of BPA in soil systems.