An EPR study of clinoptilolite from Bigadiç in Turkey

Abstract

Natural and synthetic zeolites have wide use industry and in many other applications as food additives, as molecular sieve to trap unwanted ingredients like heavy metallic ions and groups in fluids, as shielding materials against high energy radiations etc. Clinoptilolite is a type of zeolite composed of aluminasilicate forming tetrahedrons with micro cavities among them. The size and shape of cavities, impurities and the metal ions define their usage. Electron paramagnetic resonance (EPR) spectroscopy is a technique to determine paramagnetic species in host materials, and hence in the zeolites and clay type minerals. In this study natural clinoptilolite obtained from Bigadiç district in Western Anatolia, was studied using EPR spectroscopy in natural form and after some physical and chemical treatments, namely adsorbing CO2, H2S, and SO2 gases, [Cu(H2O)6]2+ ions and after exposing to gamma rays. The clinoptilolite including non-paramagnetic manganese ions as impurities in natural form reduced to paramagnetic Mn2+ ions after CO2 and H2S adsorption, and when SO2 gas is adsorbed an unstable paramagnetic center was induced which changed with time when stored at room temperature. When Cu(H2O)6 was adsorbed Cu2+ ion complex was adsorbed in the cavity in slightly distorted octahedral structure. Gamma ray irradiation of clinoptilolite from Co-60 source produced anisotropic o23− radical ion.