COMPARISON OF ARSENIC REMOVAL FROM GROUNDWATER BY IRON OXIDE COATED SAND: MECHANISMS, KINETICS AND INFLUENCE OF ANIONS

摘要

The removal of arsenic (As), which is one of the most harmful groundwater pollutants, was studied using synthetic iron oxide-coated sand (IOCS). Batch experiments were performed to investigate the influence of pH, adsorption kinetics, adsorption isotherm, sorption mechanism and anionic effects. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) were used to characterize particle size, surface morphology and chemical composition of pristine IOCS. The adsorption capacity of As (III) and As(V) onto IOCS (10 g/L) at neutral pH were 0.064 mg As/g sand and 0.073 mg As/g sand, respectively. The arsenic species (As(III) and As(V)) were completely removed within 8 hours. The effects of competing anions indicated that H4SiO_4~0 and H2PO_4~(2-), which are ubiquitous in groundwater, are potential interferences in the As(III) and As(V) adsorption reaction. Details of arsenic adsorption and anionic interferences on arsenic molecular interactions are also discussed. Our results provide a fundamental understanding of arsenic interaction with IOCS in sub-surface environments.