Hydration of TiO<sub>2</sub> Facets Regulates As(III) Adsorption: DFT and DRIFTS Study
Shao‐Yu Lu, Yan Li, Wen Zhong, Chuanyong Jing
Abstract
Hydration of TiO2 facets controls the reactions occurring at the mineral–water interfaces. However, the underlying mechanism of the facet-dependent hydration and the effect of hydration on contaminant adsorption are still ambiguous. Herein, arsenite [As(III)] adsorption on hydrated {001}, {100}, {101}, and {201} TiO2 was explored by integrating multiple characterizations and density functional theory (DFT) calculations. Our macroscopic adsorption results show an As(III) adsorption density order of {201} > {100} > {101} > {001}, though As(III) on each facet formed a bidentate binuclear structure, as evidenced by the extended X-ray absorption fine structure analysis. The in situ diffuse reflectance infrared Fourier transform spectroscopy analysis identified distinctive surface hydroxyls on four-faceted TiO2 upon water adsorption. The hydrated surface regulated the subsequent As(III) adsorption, giving an As(III) adsorption energy order of {201} (−0.95 eV) < {100} (−0.38 eV) < {101} (−0.005 eV) < {001} (0.04 eV) according to DFT calculations. The As(III) adsorption energy on hydrated facets was linearly correlated with the macroscopical As(III) adsorption density (R2 = 0.99, p < 0.05), revealing that the impregnable water binding highly suppressed the exchange of As(III) molecules with adsorbed water. Our study provided a novel insight into the facet-dependent interfacial adsorption.