Insight into the Ferrate(Vi)/Ozone Process: Multiple Oxidation Systems Constructed by Mutual Activation of Ferrate(Vi) and Ozone Promote the Elimination of Electron-Deficient Pollutants

Abstract

The utilization of ferrate(VI) (Fe(VI)) is constrained by its limited efficacy in removing electron-deficient pollutants. This study provided insights into the enhanced removal of such pollutants by employing a blend of ozone (O3) and Fe(VI). The removal of electron-deficient pollutants by individual Fe(VI) (50μM) or O3 (25μM) ranged from 5% to 50% at pH 8.0. The synergistic Fe(VI)/O3 process enhanced the removal to a range of 60%-95%. The Fe(VI)/O3 process exhibited an increase in total organic carbon removal by 40-90%, while the rate constant showed a significant increase ranging from 3 to 14 times. Multiple enhanced oxidation systems were constructed by intermediates derived from the Fe(VI) and O3. The self-decomposition of Fe(VI) released H2O2, which coupled with O3 to form ·OH. Revealed through XPS analysis, the Fe(III) flocs derived from Fe(VI) decomposition contained structures of Fe2O3 and FeOOH. The combined flocs/O3 processes facilitated the production of both ·OH and Fe(IV)/Fe(V). Product analysis and Fukui function calculation demonstrated that, many hydroxylated initial products were exclusively found in the Fe(VI)/O3 process. ·OH initially transforms electron-deficient pollutants into electron-rich products, rendering them more susceptible to electrophilic attack by Fe(IV)/Fe(V). The employment of the Fe(VI)/O3 method demonstrates a concurrent increased production of ·OH and Fe(IV)/Fe(V), presenting a potential resolution for tackling the issue related to stubborn electron-deficient pollutants.

Keywords: ferrate(VI), Ozone, electron-deficient micropollutants, reactive iron species, reactive oxygen species