Potential of rice husks for antimony removal

The adsorption behavior of rice husks for antimony ions from aqueous solutions has been investigated as function of appropriate electrolyte, equilibration time, hydrogen ions, amount of adsorbent, concentration of adsorbate, effect of diverse ions and temperature. The best conditions in which this material can be used as adsorbent have been explored. The radiotracer technique was employed to determine the distribution of antimony (Sb-122) using a batch method. Maximum adsorption was observed at 0.01 mol L-1 acid solutions (HNO3, HCl, H2SO4 and HClO4) using 1.0 g of adsorbent for 1.92 x 10(-5) mol L-1 antimony concentration in 10 min equilibration time. Studies show that the adsorption decreases with the increase in the concentrations of all the acids. The adsorption data follow the Freundlich isotherm over the range of 1.92 x 10(-5) to 2.05 x 10(-4) mol L-1 antimony concentration. The characteristic Freundlich constants i.e., 1/n = 0.82 +/- 0.05 and K = 4.61 +/- 0.07 m mol g(-1) have been computed for the sorption system. The uptake of antimony increases with the rise in temperature (299-323 K). Thermodynamic quantities i.e., Delta G(0), Delta S-0 and Delta H-0 have also been calculated for the system. The sorption process was found to be endothermic. (C) 2000 Elsevier Science Ltd. All rights reserved.