Removal of arsenic from realgar-containing water by Spirogyra: Implications for in situ remediation of arsenic in the mine area

Abstract

Realgar (As4S4) is an arsenic sulfide mineral, occurring widely in metamorphic-hydrothermal deposits, reductive soil and wetland sediments. The dissolution of realgar releases arsenic, which is toxic to the environment, so the process that causes this problem deserves attention. Native Spirogyra sp. was collected and cultured from a realgar mine area and used to create varying concentrations of algae to investigate the dissolution of realgar using a photosynthesis microcosm. Separately the dynamic adsorption and uptake processes of arsenic (III) and arsenic (V) were investigated. The dissolution rate equation of realgar under Spirogyra sp. is R = 10−6.36[DO]1.84[H+]−0.60. The diurnal growth of Spirogyra sp. increases arsenic release by as much as three times than the control group and significantly changes aqueous arsenic species by varying the dissolved oxygen and pH. The amounts of arsenic (III) and arsenic (V) removed from living Spirogyra sp. were 14605 μg⋅g−1⋅h−1 and 6511 μg⋅g−1⋅h−1. Increasing amounts of –COOH, CO and carbonyl groups from the live Spirogyra sp. also promoted the dissolution of realgar. The results suggest that filament Spirogyra sp. would be an effective method for in situ acceleration of arsenic sulfide dissolution and remediation of arsenic pollution in environments such as paddy soil.