Ion-exchange properties of microdispersed sintered detonation nanodiamond

The adsorption of transition metal cations and inorganic anions from aqueous solutions on microdispersed sintered detonation nanodiamond (MSDN) is systematically studied. The selectivity series Fe3+ > Al3+ > Cu2+ > Mn2+ > Zn2+ > Cd2+ > Co2+ > Ni2+ with maximum adsorption capacity between 2 and 5 µmol g−1 is obtained. It is found that anions may significantly contribute to the adsorption of transition metal cations, so the adsorption of CH3COO−, Cl−, B4O7 2−, ClO4 −, I−, SO4 2−, C2O4 2−, PO4 3− is also studied. For the first time, dominating adsorption of anions over cations is demonstrated for detonation nanodiamond. The maximum anion-exchange capacity of 50–150 µmol g−1 is found for MSDN. Beside of electrostatic interactions, the formation of complexes with hydroxyl groups and interaction with metal impurities contribute to the adsorption of B4O7 2− and PO4 3−, respectively. Therefore, anion exchange selectivity of MSDN is different from that observed for common anion exchange resins. In all cases, the adsorption on MSDN obeys Langmuir law. The pH effect on the adsorption of SO4 2−, PO4 3− and B4O7 2− is different from that observed for other anions due to specific interactions.