Experimental and theoretical study on the degradation of Benzophenone-1 by Ferrate(VI): New insights into the oxidation mechanism

The oxidation of Benzophenone-1 (BP-1) by ferrate (Fe(VI)) was systemically investigated in this study. Neutral pH and high oxidant dose were favorable for the reaction, and the second order rate constant was 1.03 × 10 3 M −1 ·s −1 at pH = 7.0 and [Fe(VI)] 0 :[BP-1] 0 = 10:1. The removal efficiency of BP-1 was enhanced by cations (K + , Ca 2+ , Mg 2+ , Cu 2+ , and Fe 3+ ), while inhibited by high concentrations of anions (Cl - and HCO 3 - ) and low concentrations of humic acid . Moreover, intermediates were identified by LC-MS, and five dominating reaction pathways were predicted, involving single hydroxylation, dioxygen transfer, bond breaking, polymerization and carboxylation . Theoretical calculations showed the dioxygen transfer could occur by Fe(VI) attacking the C C double-bond in benzene ring of BP-1 to form a five-membered ring intermediate, which was hydrolyzed twice followed by H-abstraction to generate the dihydroxy-added product directly from the parent compound. Dissolved CO 2 or HCO 3 - might be fixed to produce carboxylated products, and Cl - led to the formation of two chlorinated products. In addition, the toxicity assessments showed the reaction reduced the environmental risk of BP-1. This work illustrates Fe(VI) could remove BP-1 in water environments efficiently, and the newly proposed dioxygen transfer mechanism herein may contribute to the development of Fe(VI) chemistry.