Iron oxide waste to clean arsenic-contaminated water.

Abstract

Serious manifestations of arsenic toxicity in majority of human population consuming contaminated water has led to development of number of remedial methods including adsorption onto iron oxide based natural and synthetic materials. Iron oxide adsorbents generated as waste in industrial processes may be utilised for arsenic remediation. These adsorbents can be considered better in terms of least production cost as well as minimal environmental implications. Here, we studied arsenic removal from contaminated water using iron oxide wastes generated in pickling unit of a steel plant. The iron oxide obtained by steel pickling was subjected to controlled reduction in fluidised bed reactor using gaseous reductant producing magnetic iron oxide. Prior to adsorption studies, physicochemical characterisation of both the iron oxides was undertaken. This was followed by batch equilibrium and kinetics adsorption tests to investigate arsenic (V) removal properties. Several parameters such as time, pH, arsenic concentration, adsorbent dose etc were investigated using synthetic solutions. Arsenic affected ground water samples collected from West Bengal (India) were also tested using both iron oxide adsorbents. Experimental results showed more than 90% arsenic removal within 10 min, not depending on pH of water with appreciable loading (0.12-0.17 mg As/g) on both adsorbents. Presence of anions such as SO42-and PO43- adversely affected arsenic adsorption. While testing real ground water samples, initial arsenic level of 0.010–0.018 mg/L was brought down to 0.002–0.008 mg/L. Our study has established potential use of an industrial waste for the removal of arsenic (V) from water.