ARSENIC REMOVAL FROM WATERS BY ZERO VALENT IRON: INFLUENCE OF PHYSICOCHEMICAL PARAMETERS

摘要

Contamination of water recourses by arsenic is a well-known environmental problem that can pose severe human health implications.The occurrence of arsenic in groundwater is due to natural processes such as weathering of arsenic minerals as well as to anthropogenic activities including mining, industrial waste discharges and application of certain herbicides and pesticides. The most common forms of arsenic occurred in groundwater are As(V) (arsenate) and As(lll) (arsenite); arsenite is more toxic and more mobile than arsenate. High arsenic concentrations in groundwater have been found in several countries. According to European legislation, the arsenic concentration in drinking water should be below the limit of 10ng/L (98/83/EC). Relatively high concentrations of arsenic, exceeding the proposed limit, have been determined in many areas in Greece. Several technologies have been proposed for the removal of arsenic from drinking waters such as coagulation, precipitation, ion exchange, reverse osmosis, nanofiltration and adsorption. Several studies report that zero valent iron can be used for treatment of drinking water with elevated concentrations of arsenic as well as a permeable reactive barrier for remediation of polluted groundwater. This paper examines the use of zero valent iron for removal of arsenate As (V) and arsenite As(lll) from drinking water. Batch experiments were carried out to investigate the removal kinetics of arsenate and arsenite in the presence of low and high concentrations of various ions (chloride, carbonate, nitrate, phosphate, sulphate and borate), manganese and organic matter. Column tests were carried out to investigate the removal of arsenate, arsenite and 1:1 mixture of both species from spiked tap water under dynamic conditions. Arsenate, arsenite, ferrous and total iron, pH and Eh were measured in column effluents. Column tests were also applied in natural waters with elevated arsenic concentrations.