Modification of the surface chemistry of microdispersed sintered detonation nanodiamonds and its effect on the adsorption properties

Microdispersed sintered detonation nanodiamonds (MSDN) with different surface chemistry were characterized using X-ray diffraction method, energy dispersive spectroscopy (EDS) and adsorption of ionogenic and nonionogenic compounds in static and dynamic (with HPLC instrumental design) conditions. It was shown that for MSDN, conditioned with 3 × 10⁻³ M H₃PO₄, adsorption of substances with basic properties increases by 13.5–22.0, while washing of MSDN with 1.3 × 10⁻⁵ М ammonium hydroxide decreases adsorption of bases as a result of modification of ionic state of functional groups at the surface. It is found that concentration of H₃PO₄ solution significantly effects on adsorption of ionogenic organic substances. The effect of organic solvent is investigated by obtaining of isotherms of excessive adsorption of pyridine on MSDN from solutions in water and acetonitrile under static conditions. It is found that the equilibration of MSDN with acid solution activates its surface for adsorption of pyridine that may be due to desorption of substances blocking acidic adsorption centers. It was shown that usage of buffers containing additives of ammonium, potassium and sodium electrolytes results in decrease of adsorption of basic molecules, which is explained by competitive adsorption of cations on dissociated carboxyl functional groups on the surface of MSDN.