Adsorption studies on nano-zirconia in water and a water-1,2-propanediol mixture

Abstract

The adsorption of an electrosteric (polyacrylic acid, PAA), an electrostatic (triammonium citrate, TAC) and a steric dispersant (2-(2-(2 methoxy ethoxy) ethoxy)acetic acid, TODA) onto nanozirconia particles in deionized (d.i.) water and in a 75 wt% water-25 wt% 1,2-propanediol mixture was investigated. The amount of dispersant in d.i. water yielding the lowest apparent viscosity was measured via rheology. For PAA this was determined to be 6 wt%, for TAC 2 wt% (which corresponds to ≈ 0.43 mg/m2) and for TODA also 2 wt% (corresponding to ≈ 0.34 mg/m2). In the water-propanediol mixture the minimum viscosity was measured and the adsorbed amount was determined by adsorption isotherms using the depletion method. For TAC this was ≈ 0.076 mg/m2, which is five times less than the value in pure water. Furthermore, zeta-potential measurements were performed to confirm the dispersion mechanism. Zirconia particles in water showed the same zeta-potential as in waterpropanediol, although in water-propanediol less TAC molecules were adsorbed on the surface. For TODA the adsorbed amount was calculated to be ≈ 0.4 mg/m2, which fits well to the value determined in water. Propanediol seems not to influence the adsorption in that case.