In the last decade diamonds and nanodiamond have gained a strong interest as a promising  adsorbent for the use in liquid chromatography and solid phase extraction  [1]. Diamond has significant advantages,  regarding of excellent mechanical, chemical and thermal stability over conventional adsorbents. Nevertheless, there is still a lack of information about adsorption properties of diamond, and especially of detonation nanodiamond (DND), due to its complex surface chemistry. Various functional groups including hydroxyls, carbonyls and carboxyls are presented on DND surface, which results in both positive and negative surface charges of DND depending on pH. The current  investigation is about adsorption of transition metal cations and inorganic anions on sintered DND.

The effects of pH, ionic strength and the type of pH buffers on the adsorptive properties of diamonds are investigated. The adsorption isotherms, kinetics plots of adsorption and distribution coefficients are obtained for transition metal cations: Ni²⁺, Co²⁺, Cd²⁺, Zn²⁺, Mn²⁺, Cu²⁺, Al³⁺, Fe³⁺, and anions: CH₃COO^-, Cl^-, B₄O₇^2-, ClO₄^-, I^-, SO₄^2-, PO₄^3-, C₂O₄^2-. It is shown that the adsorption of cations and anions on the DND obeys Langmuir law. Maximum adsorption capacity of anions is between 50 and 150 µmol/g for DND, which far exceeds adsorption capacity for cations on this material (5 µmol/g). It is confirmed that there are several mechanisms responsible for adsorption  of ions on DND, including ion exchange, complex formation and other specific interactions. The calculated values of distribution coefficients for anions on DND  ranged between 10 and 870 ml/g. Selectivity order for anions is found to be CH₃COO^-<Cl^-<B₄O₇^2-<ClO₄^-<I^-< SO₄^2-<C₂O₄^2-, which is different from the order known for traditional anion-exchangers. The evidences for the influence of metal impurities on the adsorption of anions such as sulphate and oxalate are obtained. In turn, the adsorption of cations is influenced by anionic constituents in medium, such as buffer anions and other counter ions.