Degradation of bisphenol A by ozonation: rate constants, influence of inorganic anions, and by-products

The second-order rate constants for the reaction between bisphenol A (BPA) and ozonewere evaluated over the pH range of 2-12. The rate constants showed minimum values (×104 M-1s-1)under acidic condition (pH < 4) and were of maximum values (×109 M-1s-1) under basic condition(pH >10). From pH 4 to 7, the second-order rate constants were found to increase by a magnitudeof almost 102 and this was due to the increase in anionic BPA species in the solution. The rateconstants increased almost twofold when pH increased from 9.6 to 10.2. The presence of commoninorganic anions at levels commonly found in the environment did not affect the rate of degradationof BPA.The degradation by-products from the ozonation of BPA were identified as 4-(prop-1-en-2-yl)phenol, hydroquinone, 4-hydroxyacetophenone, 2-(2-(4-hydroxyphenyl)propan-2-yl)succinaldehyde,2-(1-(4-hydroxyphenyl)vinyl)pent-2-enal, 3-formyl-4-(4-hydroxyphenyl)-4-methylpent-2-enoic acid, monohydroxy-BPA and dihydroxy-BPA. In conclusion, ozonation was found to be aneffective method for the removal of BPA even in the presence of common inorganic anions atenvironmental concentrations. However, incomplete treatment of BPA might produce a variety ofdegradation by-products.