Diamonds and nanodiamonds recently have become easily accessible and relatively cheap because of the development of the new technology of preparation by the detonation of oxygen-deficient explosives. Diamonds have good thermal conductivity and stability, mechanical stability at very high pressures, do not shrink and swell in the different solvents, do not undergo hydrolysis within entire pH range. Surface of diamonds can be easily modified in order to obtain required properties. These advantages make them a very perspective material for adsorption, chromatographic and extraction applications. Nevertheless, the works on research of the adsorption properties of diamond are still quite rare. Due to the complex surface chemistry the adsorption properties of diamonds need to be investigated more systematically.

This presentation will reveal our recent results on adsorption of transition metals and inorganic anions on the surface of sintered detonation nanodiamond (DND). We have studied influence of buffer chosen, pH range and ionic strength on the adsorptive properties of diamonds. Adsorption isotherms, kinetics of adsorption and distribution coefficients were studied in this work.

Various functionalities at DND surface were observed and result in both positive and negative surface charges at certain pH. Anion adsorption capacity of 50-150 µmol/g was detected over DND, which far exceeds cation exchange capacity for this material (5 µmol/g). Adsorption on the DND surface is chemical in nature and obeys Langmuir law. It was confirmed that at least 3 mechanisms can be responsible for adsorption behaviour of DND, including ion exchange, complex formation and influence of metal impurities. Distribution coefficients for anions over DND were calculated. Selectivity order for anions is different from conventional anion-exchangers and conditioned by complex surface properties and presence of metal impurities. Adsorption of cations is influenced by anionic constituents in medium, including buffer anions and counter ions.