RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

A synthetic δMnO₂ was characterized with respect to intrinsic equilibrium constants and surface charge density as a function of pH. Site binding-surface complexation theory was used to model adsorption of Cu, Pb, and Zn onto the δMnO₂ surface. The model response was tested with respect to changes in solution ionic strength, total trace metal concentration, δMnO₂ in suspension, substrate surface area, and the presence of competitive trace metals. Results indicate that both freshly precipitated and aged δMnO₂ act as heterogeneous surfaces with a spectrum of binding site energies. The distribution of site energies was examined by determination of apparent equilibrium binding constants. Highest energy sites were saturated once less than 0.1% of all surface sites had been occupied. Adsorption experiments were performed for solutions which simulate conditions in the channel of a mountainous stream. The natural system is actively precipitating δMnO₂ in a watershed containing base metal sulfide deposits.