Ion-exchange properties of high pressure high temperature synthetic diamond

The adsorption and chromatographic properties of microparticulated diamond (1–2 μm and 4–6 μm fractions) from high pressure and high temperature synthesis (HPHT diamond) are investigated, with a focus on their cation-exchange capacity. Several adsorbents were prepared, either by wet oxidation of the surface of HPHT with H2O2/H2SO4or HNO3/H2SO4 mixtures, or by oxidation in air at 700 °C, or following a four-step reduction using LiAlH4 and n-butyllithium. The zeta-potential profiles as a function of pH and ion-exchange capacities were measured for the prepared adsorbents as well as isotherms of adsorption. The ion-exchange selectivity of oxidised HPHT diamond was studied towards alkali, alkaline-earth and transition metal cations.