Leaching behavior of arsenite and arsenate from the contaminated sediment by the effect of phosphate ion under anaerobic conditions

Abstract

This article presents the effect of phosphate ion on the potential leaching of arsenic from the contaminated sediment under anaerobic conditions near neutral pH for 120 h. Arsenic content in the selected sediments was 450 mg/kg. In the leaching experiment, 50 g of sediment sample was added into 400 mL of five different concentrated 0 (no phosphate), 3, 10, 15, and 20 mg/L phosphate solutions, and leachates were analyzed by distinguishing As(III) and As(V) with the sequential hydride generation flow injection analyzer (SHGFIA). The results indicate that arsenic concentration in the leachates was increased for As(V) up to 72 h, and subsequently As(V) concentration was decreased in the suspension. The leached amount of As(V) concentration in the aqueous phase was increased with increasing the phosphate concentration in the suspensions, and statistically significant correlation (R2 = 0.9959) was found. Conversely, As(III) concentration in the leachates was almost constant up to 24 h then As(III) concentration was decreased in the suspension. The phosphate ion was potentially leached arsenic, especially As(V) as phosphate (PO43−) ion has more charge density than arsenate (AsO43−) resulting more As(V) was leached from the contaminated sediment with increasing the phosphate concentration in the suspensions.