The adsorption of lead species on goethite

Adsorption of lead ionic species at the goethite aqueous interface, as well as the electrokinetic properties of the system, were measured as a functio n of pH. The interpretation was based on the Surface Complexation Model ass uming that association of lead species with negatively charged surface site s takes place. The electrostatic potential affecting the state of the surfa ce species was obtained from the electrokinetic potential by Gouy-Chapman t heory introducing the electrokinetic slipping plane as an adjustable parame ter. It was found that singly charged lead species (PbOH+) are bound to neg atively charged surface sites with the equilibrium adsorption constant log K-a = 14 +/- 0.2. The capacitance of the Hehmholtz layer was found to be C- 1 = 0.4 +/- 0.1 F m(-2). These findings were confirmed by employing the sta ndard triple layer model (TLM). (C) 2000 Elsevier Science B.V. All rights r eserved.