Synthesis of mesoporous bismuth-impregnated aluminum oxide for arsenic removal: Adsorption mechanism study and application to a lab-scale column.

High mobility and toxicity of arsenic [As (III)] limit its removal from an aquatic environment and pose a threat to human health. In this work, batch adsorption experiments were conducted to investigate the adsorption capacity of bismuth-impregnated aluminum oxide (BiAl). Continuous application of As (III) removal was achieved via a lab-scale column reactor. Bismuth impregnation decreased the specific surface area of aluminum oxide and affected its pore size distribution. However, because of its abundant and well-proportioned mesoporous character, it also enhanced its adsorption capacity through the surface complexation of As (III). Batch adsorption experiments demonstrated a suitable Freundlich model and a fitted pseudo-second-kinetic model for As (III) adsorption. The main mechanism was chemisorption with both bismuth and aluminum atoms; however, physisorption also contributed to arsenic adsorption at the initial stage of the reaction. The Adams-Bohart model better described the breakthrough curves than the Thomas model. BiAl exhibited efficient As (III) adsorption over a wide pH range and could be applied to As (III) removal from wastewater. A high As (III) removal efficiency (91.6%) was obtained at an initial As (III) concentration of 5 mg L at a flow rate of 1 mL min. This study indicates the potential for the practical application of BiAl in As (III) removal.