Kinetic Modeling of the Biosorption of Lead(II) from Aqueous Solutions by Solid Waste Resulting from the Olive Oil Production

Abstract

Solid waste from olive oil production, the two-phase olive mill solid (OMS), was investigated for the removal of Pb(II) from aqueous solutions. This work focuses mainly on the kinetics of biosorption. The sorption kinetics was experimentally measured using stirred-batch systems under different initial concentrations and at varying solution temperatures. The pseudo-nth order kinetic model, pseudofirst-order kinetic model, pseudosecond-order kinetic model, and the Elovich equation were used to represent the kinetic data. The pseudosecond-order equation fitted the dynamic data very well under all the operating conditions. A contact time of approximately 60 min was required to reach the equilibrium. The results obtained for the effect of initial concentration on lead uptake by OMS showed that the equilibrium sorption capacity and the initial sorption rate increase as the initial metal concentration increases, while the kinetic constant of the process decreases. The effect of temperature on kinetic parameter values is less significant than the effect of lead concentration although a decrease on kinetic constant and initial sorption rate is produced as temperature rises, mainly at lower lead concentrations. Finally, the apparent activation energy of sorption was determined as −18.62 kJ·mol–1 for an initial lead concentration of 10 mg·L–1. The negative value of activation energy showed that the Pb(II) adsorption process by OMS may involve a nonactivated chemical adsorption or a physical adsorption.