Cadmium removal from aqueous solution by blended bamboo sawdust/rice-husk biochar; optimization of influencing parameters

Abstract

This study attempted to investigate the adsorptive potential of blended bamboo (Oxytenanthera abyssinica) sawdust/rice husk (BSD/RH) at a ratio of 1:1 carbonized at 400 °C for the sorption of cadmium ions from synthetic solutions in batch mode. The Box-Behnken Design in response surface methodology (RSM) was used to achieve the best removal efficiency and adsorption capacity of the biochar. With a p-value of 0.0001, the initial Cd²⁺ concentration and adsorbent dose were discovered to be the most significant parameters controlling the adsorption capacity and removal efficiency of Cd²⁺ from the solution. At a pH of 8.95, ionic strength of 0.020 mol/L KNO₃, a contact time of 15 min, an initial concentration of 200 mg/L, and an adsorbent dose of 0.5 g, the optimum Cd²⁺ removal and adsorption capacity of 99.97% and 358.65 mg/g, respectively, were obtained. The optimized conditions were later used to determine the removal efficiency and adsorption capacity of pristine biochars of rice husk and bamboo sawdust, which were found to be 79.8% and 83.7%, respectively. This finding indicates the potential for using biosorbent derived from blended feedstock materials to remove heavy metals such as cadmium.