Study of Adsorbent Derived from Exhausted Olive Pomace for the Removal of Pb 2+ and Zn 2+ from Aqueous Solutions

Batch experiments were performed to evaluate the effects of contact time, solution pH, and temperature on both lead and zinc adsorption onto exhausted olive pomace ash (EOPA) from aqueous solution. Equilibrium data were analyzed using Langmuir and Freundlich isotherm models to calculate isotherm constants. Kinetic studies showed that an equilibrium time of 2 h was required for the adsorption of Pb(II) and Zn(II) onto EOPA. Equilibrium adsorption is affected by the initial pH (pH0) of the solution. pH0 = 6.0 was found to be optimum for individual removal of Cd(II) and Ni(II) ions by EOPA. Adsorption tests of EOPA in synthetic wastewater revealed that the adsorption data of this material for lead and zinc ions were better fit to the Langmuir isotherm based on correlation coefficients. Monolayer sorption capacities of EOPA were 8.76 and 7.75 mg g−1 for lead and zinc ions, respectively. Effect of temperature was investigated by determining isotherms at 10, 23, and 40°C. The enthalpy change (ΔH°), the free energy change (ΔG°), and the change in entropy (ΔS°) were calculated. They showed that adsorption of Pb2+ and Zn2+on EOPA is an endothermic process. Results of this study suggest that EOPA may be a promising adsorbent for environmental remediation.