Density Functional Theory Investigation into the Effects of Dissolved Organic Matter on H2O2 Activation over α-Fe2O3 (001) Surfaces

The heterogeneous Fenton process is one of the efficient methods for wastewater treatment, and the effects of dissolved organic matter (DOM) when treating actual wastewaters are anticipated. However, the impact of DOM on H2O2 activation is not clearly understood yet. In this work, the α-Fe2O3 (001) surfaces are chosen as the model materials and the effects of the major functional groups in DOM on H2O2 activation are systematically investigated using density functional theory simulations. First, the adsorption and activation of H2O2 on the surfaces are simulated, confirming the superior catalytic properties of the Fe sites on the α-Fe2O3 (001) surface with an oxygen vacancy. Then, the adsorption configurations with various DOM functional group representations are obtained. Phenol, carboxyl, amide, and quinone groups adsorb more strongly on the surfaces than H2O2, while the hydroxyl and aldehyde groups show weaker adsorption. Finally, the coadsorption of the DOM molecules and H2O2 is simulated and the influences on the activation barrier of H2O2 are studied. For the pristine surface, the intermolecular interactions can promote or inhibit the H2O2 cleavage with some DOM molecules. However, for the surface with an oxygen vacancy, due to the competition for adsorption sites, some DOM functional groups are found to substitute the H2O2 at the most reactive Fe site, thus inhibiting its activation. The direct interactions between the DOM molecules and H2O2 do not significantly affect H2O2 activation. This work reveals the various effects of DOM on H2O2 activation and contributes to the application of the heterogeneous Fenton technology.