Adsorption of Zinc and Copper Ions by the Solid Waste of the Olive Oil Industry

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Abstract
The adsorption capacity of dried olive oil husks (SWOOI) for zinc ions (Zn2+) and copper ions (Cu2+) was studied. It was verified that the Freundlich and Langmuir isotherms describe the adsorption of Cu2+ and Zn2+ ions reasonably well. Up to 90% of Zn2+ ions and 80% of Cu2+ ions were adsorbed from aqueous solutions when the initial adsorbent and metal concentrations were 30 mg/ml and 20 ppm, respectively. An increase in the SWOOI concentration resulted in greater metal removal from the aqueous solution, and an increase in Zn2+ ion or Cu2+ ion concentration at constant SWOOI concentration increased the metal loading per unit weight of the adsorbent. An increase in the initial pH of the metal solutions enhanced the SWOOI adsorption process. The uptake of Zn2+ ions was also enhanced by decreasing the SWOOI particle size. The presence of a high concentration of soft ions (Na+) strongly suppressed the uptake of Zn2+ ions by SWOOI.