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.