Potential of rice husks for antimony removal

The adsorption behavior of rice husks for antimony ions from aqueous soluti ons has been investigated as function of appropriate electrolyte, equilibra tion time, hydrogen ions, amount of adsorbent, concentration of adsorbate, effect of diverse ions and temperature. The best conditions in which this m aterial can be used as adsorbent have been explored. The radiotracer techni que 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 solutio ns (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 t hat the adsorption decreases with the increase in the concentrations of all the acids. The adsorption data follow the Freundlich isotherm over the ran ge of 1.92 x 10(-5) to 2.05 x 10(-4) mol L-1 antimony concentration. The ch aracteristic 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 o f antimony increases with the rise in temperature (299-323 K). Thermodynami c quantities i.e., Delta G(0), Delta S-0 and Delta H-0 have also been calcu lated for the system. The sorption process was found to be endothermic. (C) 2000 Elsevier Science Ltd. All rights reserved.