Tevfik ÜNALDI - Academia.edu (original) (raw)

Papers by Tevfik ÜNALDI

InTech eBooks, Nov 7, 2012

Adsorption Science & Technology, Jul 1, 2009

Physicochemical characterization of the natural solid-phase Gördes clinoptilolite and of the Na +... more Physicochemical characterization of the natural solid-phase Gördes clinoptilolite and of the Na +-, K +-, Ca 2+-and Mg 2+-modified forms of the mineral (as obtained through ion-exchange) by batch methods, X-ray diffractometry (XRD), X-ray fluorescence (XRF), infrared spectroscopy (IR) and scanning electron microscopy (SEM) is described. It was found that the Na +-and Ca 2+-forms exhibit high ion-exchange rates relative to the Mg 2+-and K +-forms. In addition, the high rate of ion selectivity towards Na + and K + ions, together with lower rates for Mg 2+ and Ca 2+ ions, indicate that the rate of ion selectivity is negatively correlated with the ionic potential of the ions. Such ion-exchange and ion selectivity result in a decrease in pore size and an increase in the surface area of the modified clinoptilolite relative to the natural form; this may possibly be related to the entrance of the ions into the mineral structure. It was concluded that clinoptilolite modified with exchangeable ions from aqueous solutions at two different normalities exhibits features which differ from those of natural clinoptilolite. Thus, modification of clinoptilolite by different cationic forms from aqueous solutions at different normalities might prove suitable for applications in other fields of study.

Anadolu Üniversitesi Bilim ve Teknoloji Dergisi - A : Uygulamalı Bilimler ve Mühendislik, 2009

Journal of Materials Science: Materials in Electronics, 2019

Borotellurite glasses doped with low ratio of V2O5 have successfully been synthesized according t... more Borotellurite glasses doped with low ratio of V2O5 have successfully been synthesized according to the xV2O5 − 25B2O3 − (75 − x)TeO2 (x = 0, 0.25, 0.50, 0.75, 1, 2 mol%) composition. Structural characteristics of the synthesized glasses have been determined. Synthesized glasses had amorphous structures and the probable compounds in the glass has been estimated with comparison of theoretical data. Glass transition, crystallization, melting temperatures and thermal stabilities were determined. Thermal stability changed within the region of 54–98 °C with increasing ratio of V2O5. Structural units of tellurium, boron and vanadium were determined according to FTIR and Raman data. Optical properties are among the properties that V2O5 alter most prominently. Significant shifts were observed in the transmittance spectrum. Optical gap decreased to 1.85 eV from 3.19 eV and Urbach energies increased from 0.141 to 0.130 eV with increasing V2O5. Densities, molar volumes, molar refractions, electronic polarizability and metallization criterion of the synthesized samples were also given and interpreted.

Journal of Molecular Structure, 2013

Abstract Physicochemical characterisation of natural K-clinoptilolite and heavy-metal (Ag + , Cd ... more Abstract Physicochemical characterisation of natural K-clinoptilolite and heavy-metal (Ag + , Cd 2+ , Cr 3+ and Co 3+ ) forms was accomplished through ion exchange by batch, X-ray diffractometric (XRD), X-ray fluorescence (XRF), infrared-spectral (FT-IR), differential thermal analysis–thermal gravimetric (DTA–TG) and scanning-electron microscopic (SEM) methods. Increasing the normality in the cases of heavy-metal forms resulted in decrease in crystallinity and increases in unit-cell volume, rate of ion exchange, and percentage of ion selectivity. In this study, the order of ion-selectivity percentages (rather than ion selectivity) of heavy-metal forms was determined to be Ag + > Cd 2+ > Cr 3+ > Co 3+ . This finding is consistent with the results of worldwide research on the order of ion selectivity in modified clinoptilolite.