Application of organic waste for adsorption of Zn(II) and Cd(II) ions

Abstract

Biosorption of Zn(II) and Cd(II) ions from aqueous solutions onto organic waste – orange peel, hazelnut shell, and walnut shell was studied using batch adsorption experiments. In the biosorption studies, equilibrium metal ion concentration was determined. Experimental data obtained were analysed in terms of Freundlich, Langmuir, Temkin, Dubinin–Radushkevich, Redlich–Peterson, Sips, Toth, and Khan isotherms. The results of the study showed that orange peel, hazelnut shell, and walnut shell can be adequately used as low-cost alternatives for the removal of Zn(II) and Cd(II) ions from aqueous solutions with maximum sorption capacities of 15.51 and 19.8 mg/g, 11.55 and 16.65 mg/g, and 26.60 and 21.10 mg/g, respectively. The highest removal efficiency of Zn(II) and Cd(II) ions was obtained for hazelnut shells. The process was fast and about 90% of metal ions were removed by all the studied biosorbents. The sorption process was possibly chemisorption occurring on a heterogeneous surface.