Mechanistic analysis of carbamazepine degradation in hybrid advanced oxidation process of hydrodynamic cavitation/UV/persulfate in the presence of ZnO/ZnFe2O4

The present study has addressed carbamazepine (CBZ) degradation by hybrid advanced oxidation system of hydrodynamic cavitation (HC) assisted UV/persulfate with composite ZnO/ZnFe2O4 particles. This hybrid system is comprised of several parallel pathways for generation of both center dot OH and SO4 center dot- radicals. 98.13 +/- 1.03% CBZ degradation was obtained at optimum operational conditions: inlet pressure = 9 atm, pH = 4, initial concentration of CBZ = 15 mg/L, UV power = 18 W, Na2S2O8 = 500 mg/L, ZnO/ZnFe2O4 = 500 mg/L. HC alone resulted in 7.70% degradation of CBZ, while the binary HC + Na2S2O8 system resulted in markedly high degradation of 65.73%. Composite ZnO/ZnFe2O4 particles had dual characteristics, viz. photocatalytic activity and a source of Fe2+/Fe3+ ions released through surface leaching. Relative contributions of (OH)-O-center dot and SO4 center dot- radicals to CBZ degradation were identified through permutation-combination of different oxidation systems. Thermodynamic and kinetic behaviors of reactions of CBZ with (OH)-O-center dot and SO4 center dot- radicals were analyzed using density functional theory (DFT) at B3LYP/6-31 g(d) level. Single electron transfer (SET) between CBZ and SO4 center dot- was the primary (and thermodynamically favorable) reaction pathway in initiation of degradation. Degradation intermediates revealed ionization of CBZ through SET before hydroxylation and oxidation - which was corroboration of DFT simulations.

Automated summary

The study investigated the degradation of carbamazepine (CBZ) using a hybrid advanced oxidation system of hydrodynamic cavitation (HC) assisted UV/persulfate with composite ZnO/ZnFe2O4 particles. The system achieved 98.13% degradation of CBZ under optimal conditions. Analysis using density functional theory (DFT) revealed that single electron transfer (SET) between CBZ and SO4·- was the primary reaction pathway for degradation initiation.