Ultrasound-enhanced zero-valent copper activation of persulfate for the degradation of bisphenol AF

Ultrasound (US) was introduced into a persulfate (PS)/zero-valent copper (ZVC) system for the degradation of bisphenol AF (BPAF). In this system, ZVC worked as a catalyst to activate PS. Compared with the PS/ZVC process, the degradation rate of BPAF in the PS/ZVC/US system raised significantly from 59.8% to 97.0% due to a synergistic interaction between sonolysis and a heterogeneous reaction. When ultrasound was 120 W at 20 kHz and initial BPAF concentration was 20 μmol/L, the BPAF could be completely removed after a 60-min reaction with 0.5 g/L ZVC, 1 mM PS. According to kinetics research, the decomposition of BPAF in a PS/ZVC/US system could be separated into two stages with a demarcation point after about 20 min of reaction via pseudo-first-order rate constants (kobs). A Quantitative analytical modeling for the study of main radicals was established, and the result indicated SO4∙- was the predominant radical in acidic conditions and both ·OH and SO4∙- were the predominant radicals in relative basic conditions. Moreover, the effects of initial persulfate dosage, initial BPAF concentration, and coexisting inorganic anions on BPAF degradation were evaluated. A high-accuracy mass spectrometer was used to study the oxidation process and potential activities were deduced. Finally, the possible reaction mechanisms in the PS/ZVC/US system is proposed that the surface heterogeneous catalysis was the key step to activate PS. This work will promote the understanding of the utilization of ZVC in advanced oxidation and also the key role of Cu+ in activating PS.