Abstract

The paper deals with the study of nuts of European walnut (Juglans regia) arising as waste from the agricultural production for the removal of heavy metals from aqueous solutions. The suitability of the given biosorbent was verified through the determination of its adsorption capacity (equilibrium) and rate (kinetics) of adsorption of the studied metal (lead). The shells of the European walnut were first activated by 0.1 M of HCl and 0.1 M of NaOH, while the activation by sodium hydroxide was more effective than activation by HCl. In order to identify the most suitable method of activation for the given biosorbent, biosorption of European walnut shells activated by NaOH at concentrations of 0.01, 0.1, 1 and 2 mol/L was further studied, and the time of activation was 5, 15, 30 and 45 min. The output analyses imply that the most effective chemical treatment of the biosorbent is the activation of European walnut shells by means of NaOH at concentration of 1 mol/L for 30 min. However, also activation by sodium hydroxide at concentration of 1 mol/L for 15 min is suitable, which is very important with regard to the economy in time.

Key words: Biosorption, heavy metals, adsorption capacity, biosorption kinetics, isotherms, walnut shell, biosorbent.