Analysis of the behavior of almond shells biomass in the biosorption of lead(II) and nickel(II) cations in aqueous solution

Biosorption of lead and nickel onto almond shells from aqueous solution at various temperatures have been investigated kinetically and thermodynamically. The biomass was characterized by SEM and EDX analysis which additionally authenticated the sorption phenomenon. Thermodynamic parameters clearly demonstrated that all the biomass-metal interactions are favourable and exothermic in nature. The experimental data obtained from batch studies revealed that the biosorption kinetics on the biomass may be well described by the pseudo second-order kinetic model. The C-e/q(e) values correlated linearly with the equilibrium metal cation concentration in the solution (C-e) according to the Langmuir model, allowing us to determine the biosorption capacity of the biosorbent. About 89.28 and 75.76 mg g(-1) of Pb(II) and Ni(II) cations, respectively, have been found. The Dubinin-Radushkevich approach is also discussed and showed that the mean free energy (E) obtained for both metal cations suggests a chemical ion-exchange mechanism.