Electron Spin Resonance and Nuclear Magnetic Relaxation Dispersion Studies of Commercial Clay Minerals and Zeolites

Abstract

Nuclear magnetic relaxation dispersion measurements on water protons and EPR spectra are reported for a series of clays and zeolite samples. The paramagnetic components of the samples make strong contributions to the proton spin-lattice relaxation rates at low magnetic field strengths, although the shape of the magnetic relaxation dispersion profile is not accurately fitted by standard relaxation models. For the iron-rich clay minerals, the water-proton spin-lattice relaxation rate is approximately a linear function of the log of the magnetic field strength. The zeolite relaxation profiles are different and may be approximately modeled with a function of the form rate = Av-B , where B ranges from 0.16 to 0.43. The EPR spectra of the clays and zeolites demonstrate significant contributions from iron(III) and manganese(II). The manganese(II) spectra are complicated by zero-field interactions that in some cases add a number of additional transitions to the spectra.