The by-products produced during chlorination of pharmaceutically active compounds (PhACs) have created widespread public concern. Chlorination of a typical PhAC, naproxen (NAP), was studied. NAP chlorination parameters, intermediates identification, chlorination mechanism, and risk assessment during chlorination process have also been discussed. The results showed that NAP chlorination could fit well with the fist-order kinetics. The rate of removal and rate constants of NAP chlorination decreased with increasing initial NAP concentration and ammonium dosage, while these values increased with increasing initial free chlorine concentration. Acidic condition of the solution could significantly promote NAP chlorination. Five intermediates were identified by HPLC-MS/MS, and the mechanism of NAP chlorination was also put forward. Vibrio fischeri toxicity analysis and ESCOAR prediction indicated that higher toxicity intermediates were produced during NAP chlorination, which pose a potential threat to drinking water safety.
Keywords: chlorination; degradation mechanism; intermediate product; naproxen (NAP); risk assessment.