Biosorption performance of the lichen biomass (Diploicia canescens) for the removal of nickel from aqueous solutions

This study was focused on lichen biomass Diploicia canescens as an alternative biosorbent for the removal of nickel from aqueous solution. Experiments are carried out as a function of solution pH, biosorbent dosage, contact time, and temperature. The equilibrium data were applied to the Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherm models. The maximum Ni(II) sorption capacity of D. canescens was found to be 66.7 mg/g at pH 5, biomass concentration 4 g/L, contact time 60 min, and temperature 20°C. From the D–R isotherm model, the mean free energy was calculated as 11.2 kJ/mol, indicating that the biosorption of Ni(II) ions was taken place by chemical ion exchange. The biosorption kinetics were best described by the pseudo-second-order model. The thermodynamic parameters showed that the biosorption process was feasible, spontaneous, and exothermic. FTIR and EDAX analysis revealed that the whole biosorption process is mainly dominated by ion exchange mechanism, accompanied by a certain amount of surface complexation.