Biosorption of lead(II) ions onto waste biomass of Phaseolus vulgaris L.: estimation of the equilibrium, kinetic and thermodynamic parameters

Biosorption of lead(II) ions onto Phaseolus vulgaris L. waste was investigated with the variation in the parameters of pH, contact time, biosorbent and lead(II) concentrations and temperatures. The nature of the possible biosorbent and metal ion interactions was examined by the FTIR technique. The lead(II) biosorption equilibrium was attained within 20 min. Biosorption of lead(II) ions onto P. vulgaris L. waste followed by the Langmuir and Dubinin–Radushkevich isotherm models. Maximum biosorption capacity (qmax) of biosorbent for lead(II) ions was 2.064×10−4 mol g−1 or 42.77 mg g−1 at 20°C. Thermodynamic parameters such as the changes of free energy, enthalpy and entropy were also evaluated for the biosorption of lead(II) ions onto P. vulgaris L. waste. It was indicated that the biosorption of lead(II) ions onto P. vulgaris L. waste is a spontaneous endothermic process.