Investigations on some zeolitic volcanic tuffs from Cluj County (Romania), used for zinc ions removal from aqueous solution

Abstract

Representative samples of zeolitic tuffs from M a cica s , Aluni s , and Apahida occurrences (Cluj County, Romania) were investigated using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and wet chemical analyses. The studied tuff samples are represented mainly by vitric and vitric crystal varieties. The mineral assemblage suggests a rhyodacitic volcanic tuff. Diagenetic alteration led to the formation of zeolites, mainly clinoptilolite. Zn 2+ removal was performed on some bulk samples: Alunis (labelled A1), Apahida (Ap), and Macicas (M2) grain size of 0.2-0.4 mm. Each sample was chemically modified with HCl 1M (Z-H form) and NaCl + NaOH 1M pH = 10 (Z-Na form). The ionic exchange experiments were performed in a batch reactor (immobile phases) and in a fixed bed column. Ionic exchange efficiencies for the samples considered are presented for static and dynamic regimes. Removal efficiencies higher than 53.97% and exchanged Zn 2+ quantities higher than 1.05 mg/g were obtained. Therefore, the zeolitic tuffs under investigation are considered to be active in the ionic exchange process and can be used in wastewaters treatment to remove Zn 2+ ions. The results for all the samples considered in batch and fixed bed