Understanding the anions effect on the selectivity and surface complexation kinetics of arsenic to iron-based adsorbent

Abstract

Arsenate is highly toxic and carcinogenic, which can lead to serious health problems on exposure beyond the safe level in drinking water (0.01 mg/L). Several promising adsorbents have been developed to inhibit the mobility of arsenic. Herein, we quantified the effects of common anions including chloride, sulfate, and phosphate on arsenate selectivity and surface complexation using binary separation factor and phenomenological kinetic model. Specifically, the interfering effect of the anions on the adsorbent’s selectivity for arsenate removal is in the order of chloride > sulfate >> phosphate. The results obtained from the kinetic analysis showed that chloride and sulfate have a negligible effect on the kinetics of arsenate surface complexation. Whereas, phosphate co-existence greatly inhibits the kinetics of arsenate surface complexation by competitive adsorption. Besides, the higher contribution of inner-sphere complexation to the total adsorption of arsenate in a free system is similar to that of the co-existing medium. The findings from this research are essential in creating the practical application of promising materials for arsenic sequestration.