An EPR study of clinoptilolite from Bigadiç in Turkey

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 o₂^3- radical ion.