Biosorption of Pb(II), Ni(II) and Cd(II) ions from aqueous phase by Ceaser weed (Urena Lobata) bark, a low cost biosorbent.

Abstract

In this study, an effective biosorbent was developed from Urena Lobata for removing Pb2+, Ni2+, and Cd2+ from its aqueous solution. Different experiments were conducted in a batch system to determine the effects of the system variable such as biosorbent dosage, initial metal concentration range of 10 to 50 mg/L, and temperature. The uptake capacity and distribution coefficients (Kd) were determined for the adsorption system as a function of sorbate concentration. The equilibrium adsorption data were analysed by the Langmuir, Freundlich, Tempkin, and Dubinin Radushkevich (DKR) isotherm models but Dubinin–Radushkevich best interprets the experimental data. The maximum adsorption capacity of Ni(II), Pb(II), and Cd(II) are 0.00 mg/g,333.33 mg/g and -52.63 mg/g respectively. Different thermodynamic parameters, like Gibbs free energy (∆G), enthalpy (∆H), and entropy (∆S) of the adsorption process have also been evaluated. The negative value of G indicates the feasibility of the process. The positive value of H: 21026.11, 6927.23, and 6815.82 J/mol for Ni(II), Cd(II) and Pb(II) ions respectively confirms the endothermic nature of adsorption. Moreover, the positive value of S: 87.55, 59.65, and 6.90 J/mol for Ni(II), Cd(II), and Pb(II) ions respectively observed for the adsorption of metal ion molecules suggested the increased randomness at the solid-solution interface during the adsorption process. According to the equilibrium studies, the selectivity sequence is given as Pb2+ > Ni2+ > Cd2+. These results show that Urena Lobata holds great potential to remove cationic heavy metal species from industrial wastewater.