RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

The surface chemistry of δMnO₂ in major ion seawater is defined by determining the stoichiometry of the reactions which describe the association of the surface hydroxyl groups with Na, Mg, Ca, and K ions, the intrinsic equilibrium constants which define these reactions, and the speciation of the surface at pH 8. The results indicate:

1. that the surface forms monodentate compfexes with Na and K ions and bidentate complexes with Mg and Ca ions;
2. that pK₂^INT = 4.2, p*K_Na^INT = 3.0 ± 0.3, p*K_K^INT = 2.0 ± 0.2, p*K_>Mg^INT = 3.9 ± 0.1, and p*K_>Ca^INT = 3.3, and
3. ion exchange processes other than with H are important and as a result 84.8% of the surface sites of δMnO₂ in major ion seawater at pH 8 are complexed by H, 8.4% by Mg, 4.6% by Ca, 1.6% by Na, and 0.6% by K. Chloride and sulphate do not adsorb on δMnO₂ in the pH range of natural waters.