Self-Competitive Adsorption Behavior of Arsenic on the TiO2 Surface

TiO2 is a commonly used material to removearsenic fromdrinking water by adsorption as well as photocatalytic oxidation (PCO).In the present paper, arsenic adsorption and PCO at different pH environmentsare studied on the (1 1 0) facet of rutile TiO2 (r-TiO2). A self-competitive adsorption (SCA) behavior of arsenicis observed; i.e., arsenic species compete to adsorb on the surface.Related DFT calculations are carried out to simulate adsorption. SCAbehavior is the key to connecting calculation results with experimentalresults. Furthermore, PCO of arsenite is performed at different pHvalues. Of note, PCO is related to adsorption; namely, the adsorptionprocess determines the whole PCO reaction speed. Therefore, SCA isalso helpful for the PCO reaction. The SCA behavior is useful notonly for arsenic on r-TiO2 but also for arsenic on anataseTiO(2) (a-TiO2). It may be helpful to furtherstudy arsenic adsorption and PCO on other materials such as Fe2O3 and MnO2. The SCA behavior extendsour understanding of arsenic and provides new insights into arsenicremoval and its cycle in nature.