Benzenecarboxylate surface complexation at the goethite (alpha-FeOOH)/water interface - III. The influence of particle surface area and the significance of modeling parameters

A surface complexation model describing the adsorption of three benzenecarb oxylates (phthalate, trimellitate, and pyromellitate) on goethite (alpha-Fe OOH) was calibrated on data using goethite particles of 37 and 43 m(2)/g su rface area. The models predict potentiometric titration and batch adsorptio n data with the multisite complexation model coupled with the three-plane m odel to account for surface electrostatics. The modeling parameters were fo und to be similar to those calibrated on benzenecarboxylate adsorption data on goethite particles of 90 m(2)/g (Boily et al. Geochim. Cosmochim. Acta, in press). The significance of the benzenecarboxylate-dependent values of the modeling parameters is also discussed. The values of the capacitances o f the inner- and outer-Helmholtz planes were shown to be important modeling parameters to model the benzenecarboxylate-dependent slopes of the adsorpt ion edges. It was shown that the larger the charge of the ligand, the large r the capacitance of the outer-Helmholtz plane. (C) 2000 Academic Press.