Degradation of Bisphonel AF (BPAF) by zero-valent iron activated persulfate: Kinetics, mechanisms, theoretical calculations, and effect of co-existing chloride.

The removal of Bisphonel AF (BPAF) by zero-valent iron activated persulfate (Fe/PS) system was systematically evaluated in this work. 30.0 μM BPAF was removed by 94.4% in 60 min of treatment under optimal conditions of pH = 3.0 and [PS] = [Fe] = 3.0 mM. Cl significantly accelerated the removal of BPAF, resulting from accelerated Fe release and reactive chlorine species (RCS) formation. Liquid chromatography-time-of-flight-mass spectrometry identified thirteen degradation products, and bond breaking, coupling reactions, hydroxylation and sulfate addition were considered as the major transformation pathways. When Cl was present, six new chlorinated byproducts were also generated. Based on density functional theory (DFT) calculations, the occurrence of radical addition reactions was verified and the preferential reaction channels were determined. Significantly BPAF degradation products were less toxic, according to toxicity assessment by the ECOSAR program. Moreover, a high removal efficiency of BPAF (>90%) was also obtained in the three actual water matrixes. The present work demonstrates the feasibility of Fe/PS system for treating BPAF, which could also provide new insights into the influence of coexisting Cl on the environmental fate of organic pollutants in sulfate radicals based advanced oxidation processes.