Adsorption behavior of arsenic onto protonated titanate nanotubes prepared via hydrothermal method

Abstract

A mesoporous material, titanate nanotubes (TNs) with different surface areas (197–312 m 2 g −1) and pore size diameters (2–6 nm) was synthesized by alkaline hydrothermal method. Their adsorption abilities to arsenic, the notoriously poisonous inorganic contaminant in groundwater were evaluated. Batch experiments showed that the adsorption of arsenate [As (V)] was more favored in acid solution, while the uptake of arsenite [As (III)] was preferred in alkaline solution. The maximum uptake of As (V) and As (III) calculated by Langmuir equation was 208 mg g −1 (pH 3.0) and 60 mg g −1 (pH 7.0) respectively achieved on TN (180-1) adsorbent (312 m 2 g −1, internal diameter, 5 nm), which was 33 and 10 times greater than those of nanosized titania particles (40–50 nm, 15 mg g −1). Silicate anions, phosphate and sulfate had little effect on arsenic adsorption onto TNs. In several real water samples, TNs still showed high uptake efficiency to arsenic at pH 7.0. More than 80% of As (III) and 95% of As (V) adsorbed on TNs could be desorbed with 1.0 M NaOH solution within 1 h. Comparison study indicated that all the tubular titanate materials exhibited great adsorption capacity to arsenic regardless their surface areas. Since the equipment required for TNs synthesis is simple and cheap, and alkali solutions are reusable, TNs can be regarded as an efficient, low-cost adsorbent for the removal of arsenic.