STUDIES ON REMOVAL OF ARSENIC FROM GROUNDWATER BY BIOSORPTION METHOD

Abstract

Various types of arsenic related diseases have been reported in recent years around the world due to the continuous consumption of arsenic contaminated water for drinking purpose. Arsenic remediation of aqueous streams is of great concern due to its highly toxic, carcinogenic and persistent nature. Various conventional treatment techniques are available for arsenic removal from groundwater. Amongst the available techniques activated carbon adsorption process seems to be most popular for the removal of arsenic from groundwater due to its low initial cost and sludge free environment. But the application of this technique in arsenic removal is also prohibitive due to its high operational cost. Under the above backdrop, the present study has been undertaken to develop suitable biosorbent for removal of arsenic from groundwater. In the continuing search to achieve the desired objectives, Chitosan Flakes, Iron Coated Chitosan Flakes, Calcium Coated Chitosan Flakes, Zinc Coated Chitosan Flakes and Copper Coated Chitosan Flakes were evaluated as new adsorbents for the removal of arsenic from aqueous solutions. Among them Zinc Coated Chitosan Flakes and Iron Coated Chitosan Flakes removed arsenic effectively. So Further batch experiments were performed to study the adsorption of arsenic ions on Zinc Coated Chitosan Flakes and Iron Coated Chitosan Flakes adsorbents. Characterization of all the adsorbents was carried out using various techniques such as Surface area analyser, FTIR, TGA, XRD, FE-SEM and EDAX. Effects of process parameters like adsorbent concentration, contact time, pH, and temperature on the removal of arsenic from groundwater have been investigated using Zinc Coated Chitosan Flakes and Iron Coated Chitosan Flakes adsorbents to determine the optimum process conditions for maximum removal of arsenic. Effects of initial arsenic concentration on the removal of arsenic have also been investigated. Optimum adsorbent concentrations for both Zinc Coated Chitosan Flakes and Iron Coated Chitosan Flakes for the removal of arsenic at agitation period of 4 hr and temperature of 25 °C are found to be 10 g/L. To facilitate mathematical modeling adsorption kinetic models, adsorption isotherms and thermodynamic study have been developed. Adsorption of arsenic ion on both Zinc Coated Chitosan Flakes and Iron Coated Chitosan Flakes has been found to follow pseudo second order kinetic model and intraparticle diffusion model. Amongst the conventional isotherms Freundlich isotherm gave better prediction of specific uptakes for arsenic ions at equilibrium for both the above stated adsorbents. Study of thermodynamic parameters revealed the endothermic, spontaneous and feasible nature of adsorption process.