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

Abstract

ABSTRACT. Representative samples of zeolitic tuffs from Măcicaş, Aluniş, 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: Aluniş (labelled A1), Apahida (Ap), and Măcicaş (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 experiments are presented by means of cation exchange capacity (CEC) and removal efficiency.

Low-Cost Carbon Paste Cu(II)-Exchanged Zeolite Amperometric Sensor for Hydrogen Peroxide Detection

“…The zeolitic tuff sample was collected from a natural outcrop in Macicas (Cluj County, Romania). To prepare the electrode material, the zeolitic tuff sample was ground to 0.2-0.4 mm (based on a previous test which showed that this fraction is the best for retaining metal ions in fixed-bed column experiments) via grinding and size separation, then washed with distilled water and dried at 105 • C. This physical treatment was followed by an alkaline treatment (NaCl 1 M), as described in a previous work [49].…”

“…The value of the L.O.I indicates that secondary and hydrated materials (zeolite and clay minerals) are present in high amounts. The tuff samples collected from the studied area are remarkably homogeneous in their mineralogical and chemical composition [49,50].…”

“…Based on a semi-quantitative estimation, the zeolite-clinoptilolite-represented 70-80% of the crystallized fraction of the tuff. Quartz, plagioclase, biotite and montmorillonite were identified as accompanying minerals [2,49,50].…”