Chemically Treated Rice Husk as Low-Cost Adsorbent for Metal Ions Uptake (Co2+ and Ni2+)

Rice husk is an agricultural byproduct and its final disposition has been a serious environmental problem. However, it can be conveniently applied to the sorption of undesirable species from aqueous medium. This work investigated the sorption characteristics for Co-(aq)(2+) and Ni2+ ((aq)) ions and the best conditions of the sorption processes onto in nature (IN) and modified rice husks. Chemical treatments were performed by treating rice husk with phosphoric acid (AF) and phosphoric acid/urea (AFU). The experiments were conducted in aqueous solution, pH 4.8, and under constant temperature (28 +/- 1 degrees C) and stirring. Kinetics and isotherms models were applied to the experimental data. The observed order for the maximum adsorption capacities (mmol. g(-1)) were: Co2+: 0.10 IN < 0.80 AF < 1.60 AFU, and Ni2+: 0.08 IN < 0.55 AFU < 0.75 AF.