Theoretical evidence of enhanced interaction between H2O and O3 leads to improved performance of catalytic ozonation with copper doping α-FeOOH

Abstract

The catalytic performance of copper doped α-FeOOH in ozonation process for wastewater treatment was explored through both experimental method and DFT calculations. The results revealed that when Cu was doped to α-FeOOH, part of the Fe atoms in crystal lattice were replaced by Cu atoms. As the Cu mole content increased from 3% to 10%, the doped compounds was gradually transformed into oxides of Fe2O3 and CuO. 5%Cu-α-FeOOH/ozone achieved the highest naproxen removal of 79.6% in water, which was more effective than ozone alone or α-FeOOH/ozone system. The main active species in the catalytic ozonation system were found to be hydroxyl radicals, the accumulative hydroxyl radical amount could reach 14.2 μmol in 15 min in 5%Cu-α-FeOOH catalyzed ozonation. According to the characterization of catalysts and the detection of active species, it could be conjectured that during copper doping a certain amount of oxygen vacancy were formed in the condensed hydroxyl oxides, resulting in the increase of surface oxygen species. Based on density functional theory (DFT) calculation, the enhanced performance with Cu doping in α-FeOOH might be attributed to the decrease in adsorption energy of H2O & O3 as well as the increase in formation energy of free radicals.