Kinetic and mechanistic investigations of progesterone reaction with ozone.

The removal of progesterone by ozone in aqueous solution was studied in this work. The absolute rate constant was evaluated and first by-products were identified. The reaction was studied in the 2.0-8.0 pH range and was found to be a second-order reaction, first-order relative to each compound concentration. The rate constant, determined by kinetic experiments in presence of an OH radical scavenger (tert-butanol), was independent of pH. The value was evaluated to be equal to 480+/-30 M(-1)s(-1) by two kinetic methods. Mass spectrometry analyses were performed to investigate primary degradation products generated by the reaction of ozone with progesterone. Two by-products were evidenced. According to these results, a degradation pathway of progesterone reacting with ozone was proposed.