Approaches to modelling uranium(VI) adsorption on natural mineral assemblages

Component additivity (CA) and generalised composite (GC) approaches to deri ving a suitable surface complexation model for description of U(VI) adsorpt ion to natural mineral assemblages are pursued in this paper with good succ ess. A single, ferrihydrite-like component is found to reasonably describe uranyl uptake to a number of kaolinitic iron-rich natural substrates at pH > 4 in the CA approach with previously published information on nature of s urface complexes, acid-base properties of surface sites and electrostatic e ffects used in the model. The GC approach, in which little pre-knowledge ab out generic surface sites is assumed, gives even better fits and would appe ar to be a method of particular strength for application in areas such as p erformance assessment provided the model is developed in a careful, stepwis e manner with simplicity and goodness of fit as the major criteria for acce ptance.