Adsorption of zinc and copper ions by the solid waste of the olive oil industry

The adsorption capacity of dried olive oil husks (SWOOI) for zinc ions (Zn) and copper ions (Cu2+) was studied. It was verified that the Freundlich an d Langmuir isotherms describe the adsorption of Cu2+ and Zn2+ ions reasonab ly well. Up to 90% of Zn2+ ions and 80% of Cu2+ ions were adsorbed from aqu eous solutions when the initial adsorbent and metal concentrations were 30 mg/ml and 20 ppm, respectively. An increase in the SWOOI concentration resu lted in greater metal removal from the aqueous solution, and an increase in Zn2+ ion or Cu2+ ion concentration at constant SWOOI concentration increas ed the metal loading per unit weight of the adsorbent. An increase in the i nitial pH of the metal solutions enhanced the SWOOI adsorption process. The uptake of Zn2+ ions was also enhanced by decreasing the SWOOI particle siz e. The presence of a high concentration of soft ions (Na+) strongly suppres sed the uptake of Zn2+ ions by SWOOI.