Adsorption of H⁺, OH^- and background electrolyte ions on alumina - Point of zero charge, Triple Layer Model (TLM) parameters and thermodynamic parameters

The surface charge σ₀ on aqueous suspensions of alumina was measured as a function of pH in various NaNO₃ concentrations and at different temperatures. The values of the point of zero charge (p.z.c.), pK_1(int), pK_2(int), pK_Na+(int) and pK_NO3-(int) for alumina suspended in NaNO₃ solutions were obtained in the temperature range 17-45°C from potentiometric titration data. The values of ΔS⁰and ΔH⁰ of the dissociation equilibria and complexation equilibria were calculated from these equilibrium constants. Standard Gibbs energies, enthalpies and entropies for proton adsorption on alumina were also obtained. The surface charge σ₀ on aqueous suspensions of alumina was measured as a function of pH and concentration of Ca(NO₃)₂ or Na₂SO₄ solution.