Comparative study of Hg(ii) biosorption performance of xanthated and charred sugarcane bagasse from aqueous solutions

The main target of this study was to evaluate the efficiency of charred xanthated sugarcane bagasse (CXSB) and charred sugarcane bagasse (CSB) in the removal of Hg(ii) ions from aqueous media. Batch experiments were performed to study the experimental parameters such as effects of pH, concentration, contact time and temperature. The adsorption velocity of Hg(ii) onto CSB and CXSB was fast and reached equilibrium within 60 minutes. Isotherm and kinetic studies showed that Hg(ii) uptake using both the biosorbents followed Langmuir isotherm and pseudo second order kinetics. The maximum adsorption capacity of Hg(ii) at optimum pH 4.5 onto CSB and CXSB was found to be 125 mg g^-1 and 333.34 mg g^-1, respectively. A negative value of ΔG° and positive ΔS° value (0.24 kJ mol^-1 for CSB and 0.18 kJ mol^-1 for CXSB) for both the biosorbents confirm the spontaneous nature of Hg(ii) adsorption. A positive value of ΔH° (52.06 kJ mol^-1 for CSB and 30.82 kJ mol^-1 for CXSB) suggests the endothermic nature of biosorption. The investigated results shows that CXSB compared to CSB can be used as a low cost and environmentally benign bio-adsorbent for the removal of Hg(ii) ions from aqueous solutions.