Adsorption of Nickel(II) Ions by Natural Zeolites Type

Abstract

The adsorption of nickel (II) ions by natural zeolites of the Sokirnitskoe (Transcar-pathia, Ukraine) and Kholinskoye (Eastern Transbaikalia, Russia) deposits has been studied. According to X-ray phase analysis data, the zeolite-containing sample of the Sokirnitskoe deposit contains at least 75 wt. % clinoptilolite and impurity rock - quartz SiO2. The sample of the Kholinskoye deposit consists of heulandite (not less than 75 wt. %), as well as an impurity rock - potassium spar KAlSi3O8. The assessment of the ad-sorption capacity of zeolites with respect to nickel (II) ions was carried out on the basis of the analysis of adsorption isotherms. The pH of the medium of the studied aqueous solutions was 5.5–5.8. The value of ad-sorption of nickel (II) ions by heulandite is twice that for clinoptilolite and amounts to 0.104 mmol/L. The adsorption of nickel (II) ions was investigated using the Langmuir, Freundlich and Dubinin-Radushkevich models. On the basis of the Dubinin-Radushkevich adsorption model, the values of the free energy of adsorption are determined. That indicates the physical nature of the interaction of the adsorptive and the adsorbent, in the case of the zeolite of the Sokirnitskoe deposit. It is shown that the adsorption of nickel (II) ions by the zeolite of the Kholinskoye deposit proceeds according to the ion-exchange mechanism. This explains the higher adsorption values of nickel (II) ions by this sample.