Cd removal from aqueous solution using agricultural wastes

Adsorption processes are widely used by various researchers for the removal of heavy metals from wastewaters and in this type of processes, activated carbon is frequently used as an adsorbent. Despite its extensive usage in water and wastewater treatment industries, activated carbon remains as an expensive material. In recent years, the need for safe and economic methods for elimination of cadmium from contaminated water has directed research interest toward the production of other low-cost adsorbents. Therefore, there is an urgent need to find out all possible sources of agro-based inexpensive adsorbents and also for studying their feasibility for the removal of cadmium. The aim of this study was to investigate the possibility of the utilization of Phragmites australis (P. australis) and sugarcane straw in microscales as low-cost adsorbent materials for cadmium (Cd) adsorption. In this study, the effects of operation conditions including pH, contact time, adsorbent loading, and initial ion concentrations were examined. The results showed that the optimum pH was equal to 6 and 4 while the equilibrium time was 10 and 30 min for P. australis and sugarcane straw, respectively. For two adsorbents, as the adsorbent dose increased from 0.1 to 2 g, the removal percentage became 85.75% at 0.1 g for sugarcane straw and 94.75% at 0.5 g for P. australis; however, the other values remained almost constant while adsorbents dosage changed ranging from 0.1 g and 0.5 g to 2 g. With increasing initial cadmium concentration from 0.5 to 5 mg/L, the adsorption capacity of sugarcane straw and P. australis increased from 1.7 to 7.78 mg/g and 1.51 to 5.78 mg/g, respectively. The adsorption kinetics of cadmium ions on P. australis and sugarcane straw of cadmium ions fitted Freundlich isotherm. The results of the present study indicated that P. australis and sugarcane straw can be used to remove cadmium ions during water treatment process. Compared with P. australis adsorbent, sugarcane straw showed higher level of capability of cadmium adsorption.