Electron Paramagnetic Resonance of Natural and Γ-Irradiated Alunite and Kaolin Mineral Powders

Abstract

Natural alunite and kaolin minerals obtained from West Anatolia were investigated by electron paramagnetic resonance (EPR) in natural and γ-irradiated states at room temperature and at 113K. The paramagnetic centres at ambient temperature in natural alunite were attributed to the ĊH<inf>2</inf>OH, ĊO<inf>3</inf>-, ṠO<inf>2</inf> -, ĊO<inf>2</inf>- and [AlO<inf>4</inf>]0 radicals. In natural kaolin, the paramagnetic centres were attributed to the ĊO<inf>3</inf>-, ṠO<inf>2</inf>-, ĊO <inf>2</inf>- and [AlO<inf>4</inf>]0 radicals. The γ-irradiation does not produce any detectable effects on these radicals. At 113 K, the lines for ĊH<inf>2</inf>OH could not be observed well, probably due to the anisotropic behaviour of the hyperfine interaction of the methylene protons, but the lines for [AlO<inf>4</inf>]0 centres were found to be perfectly observable at above 20 mW microwave power in both alunite and kaolin powders before and after γ-irradiation. The EPR parameters of the observed paramagnetic centres were reported.