The Mechanisms, Products, and Kinetic of Carbamazepine-Free Chlorine Reactions

Carbamazepine (CBZ) is an antiepileptic drug widely detected in drinking water supplies and wastewater effluent. It has been previously found that CBZ is recalcitrant to biological removal processes. Therefore, active CBZ will be exposed to wastewater effluent disinfection processes, which for most treatment plants in the United States involves the addition of free chlorine. However, the chlorination mechanisms of CBZ have not been fully investigated and are currently poorly understood. Our experimental studies were conducted to examine the chlorination of CBZ under controlled conditions. The kinetics, products, and reactivity of CBZ/free chlorine reactions were investigated over the pH range of 5.5-10. Results show that free chlorine reacts with CBZ and the reactivity is pH dependent. Furthermore, the results indicate that temperature affects the reactivity of CBZ with free chlorine. The temperature experiment results were fitted with the Arrhenius equation. The calculated Ea and A values are 48.8 kJ/mol and 1.41x104 s-1, respectively. Four common intermediates were detected based on both UV and mass spectral analysis proposed structures were developed based on m/z from mass spectra.