[EPR spectroscopy studies on surface reactivity of quartz]

With the technique of Electron Paramagnetic Resonance Spectroscopy (EPR), we studied the surface reactivity of quartz on adsorbing Cu(II) ions from aqueous solution over the pH range from 2 to 11. The surface sorption mass of Cu(II), gamma Cu, is as a function of pH. The Cu(II) surface coverage for powered quartz samples changes from 0 to 10.23%. The EPR spectra can be demonstrated with the coexistence of several binding forms of Cu(II) ions on the surface, that is, (SO)2Cu at pH = 4.7, SOCu2+ at pH = 6.5, SOCu (OH)(4)3- at pH = 7, and SOH...Cu(OH)2(s) at pH = 10. Therefore, the sorption tendency that the Cu(II) ions are either adsorbed at isolate sites or form multinuclear complexes versus three-dimensional precipitates onto the surface of quartz is strongly dependent on the natures of quartz surface and aqueous solution medium.