Effect of alpha-hydroxy acids on transformation products formation and degradation mechanisms of carbamazepine by UV/H2O2 process.

The role of dissolved organic matters (DOM) in the matrix of water on the degradation of refractory pharmaceutical has aroused broad concerns. However, The effect of alpha-hydroxy acids as vulnerable aliphatic acids in the water on the degradation of Carbamazepine (CBZ) has been lack of research. The decomposition kinetics and transformation products (TPs) of CBZ by UV/H2O2 process were studied in the existence of glycolic acid (GA) and lactic acid (LA) and the degradation pathways were proposed. Both GA and LA had significantly negative effects on the decomposition kinetics and mineralization of CBZ by UV/H 2 O 2 process. The declination of steady-state OH concentration in the presence of GA and LA justified the negative effects. GA was demonstrated to be stronger at scavenging and competing OH with CBZ, compared with LA, with the rate constant of slightly less than the common OH scavenger methanol. One-step dosing mode of H 2 O 2 was better than multi-step dosing mode for CBZ decomposition, especially in the presence of GA and LA. The identification of TP253a, TP253b, TP271a, TP271b, TP226, and TP180 in the absence and presence of GA and LA were performed by HPLC-MS/MS and two main degradation pathways were presented. Except for TP271a and TP271b, GA and LA retarded the abundance peaks of other four TPs, of which the formation kinetics rates and decay kinetics rates were negatively affected. Tailing peaks of all TPs caused by GA and LA inevitably resulted in the toxicity of the treated effluent of UV/H 2 O 2 process even when CBZ was decomposed completely. Therefore, alpha-hydroxy acids play important roles in determining the fate and transformation of refractory pharmaceuticals in AOPs treatment. Unlabelled Image • Effect of alpha-hydroxy acids, GA and LA on UV/H 2 O 2 degradation of CBZ was assessed. • Both GA and LA had significantly negative effects on the decomposition kinetics and mineralization of CBZ by UV/H 2 O 2 process. • One-step dosing of H 2 O 2 was better than multi-step dosing for CBZ decomposition, especially in the presence of GA and LA. • Six TPs in the absence and presence of GA and LA were identified by HPLC/MS/MS and two main pathways were proposed. • GA and LA negatively affected formation and decay of the TPs and led to the toxicity of the effluent after UV/H 2 O 2 process. [ABSTRACT FROM AUTHOR]