On the Calculation of Particle Electrokinetic Potential in Detonation Nanodiamond Dispersions

The applicability of various approximations of the electrophoresis theory to calculating the electrokinetic potentials in real nanodisperse systems has been estimated by the example of aqueous polydispersed thermooxidized detonation nanodiamond sols containing nanoparticle aggregates as depending on the concentration and pH of background electrolyte (NaCl) solutions. It has been found that, at low potentials |ζW| < 25 mV calculated for primary particles within the framework of the Wiersema model, allowance for particle aggregation and aggregate porosity has almost no effect on the electrokinetic potential. In the range of |ζW| = 25−50 mV, the most reliable values of the electrokinetic potentials of the aggregates can, seemingly, be obtained using the Miller equation for ion-conducting particles taking into account their real porosities, provided that the potential is constant. At |ζW| > 50 mV, knowing the real sizes of the aggregates, the Overbeek equation with the Oshima analytical expressions for the f3(κr) and f4(κr) functions can be used to calculate the electrokinetic potentials under the assumption that the aggregates are monolithic.