| Abstract: |
The effects of changes in ionic strength on the adsorption behavior of selenite (SeO32−) and selenate (SeO42−) on goethite and hydrous ferric oxide have been modeled using a generalized version of the triple-layer surface complexation model. Selenite adsorption, which is relatively unaffected by changes in ionic strength, is best modeled assuming that selenite forms an inner-sphere (surface coordination) complex; selenate adsorption, which is markedly reduced by increasing ionic strength, is best modeled assuming that selenate forms an outer-sphere (ion-pair) surface complex. The modeling results suggest that it is possible to distinguish between inner-sphere and outer-sphere anion surface complexes by studying the effects of ionic strength on anion partitioning. |
