RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

We have investigated the adsorption of CrO₄²⁻ onto goethite as a function of pH, background electrolyte and adsorbate loading. Experimental data were interpreted with a three-plane model (TPM) that accounts for spatial charge distribution of inner-sphere surface complexes. In accordance with EXAF spectroscopic data [S. Fendorf, M.J. Eick, P. Grossl, D.L. Sparks, Environ. Sci. Technol. 31 (1997) 315] >FeO^0.2CrO₃^−1.3 and (>FeO)^0.4₂CrO₂^−0.6 surface species were selected for TPM calculations. TPM simulations replicate CrO₄²⁻ adsorption data well when CrO₄²⁻ coverage was <2×10⁻⁷ mol m⁻².