Mechanism of Arsenate Adsorption by Basic Yttrium Carbonate in a Fixed-Bed Column

Arsenic exists ubiquitously in both groundwater and surface water and it is extremely harmful to human health. In this study, basic yttrium carbonate (BYC) was successfully synthesized using the one-step precipitation method and for the first time, we report the removal of arsenate [As(V)] from aqueous solution by BYC through fixed-bed column. Effects of various parameters, including BYC dosage, As(V) concentration, flow rate, solution pH, and coexisting anions, on adsorption efficiency were investigated. Results demonstrate that the adsorption rate and capacity of As(V) increased with decreasing BYC dosage and with an increase of As(V) concentration or flow rate. Removal of As(V) was pH dependent and optimum adsorption efficiency was achieved at pH 6. Presence of NO3-, SO42-, and CO32- had a weak influence on removal of As(V); however, PO43- significantly inhibited As(V) adsorption, suggesting that As(V) was specifically adsorbed by BYC. Under acidic and neutral conditions, ligand exchange between As(V) and hydroxyl groups or carbonate on the surface of BYC was mainly responsible for As(V) removal, while the precipitation of As(V) and Y3+ ions released from BYC partially contributed to removal of As(V). Under alkaline conditions, however, no precipitation reaction was observed. Our results reveal the underlying mechanism of As(V) removal by BYC and provide a valuable reference for practical application.