Modeling selenium (IV and VI) adsorption envelopes in selected tropical soils using the constant capacitance model.

The adsorption of selenium (Se) on soil is important because of the relevance of Se to environmental and health issues. The adsorption of Se(IV) and Se(VI) was evaluated on soil samples from São Paulo State, Brazil, as a function of varying pH, and the experimental data were fitted to the constant capacitance model. Adsorption experiments were conducted for 15 soil samples, after the addition of 20 µmol L(-1) of either Se(IV) or Se(VI), and the adjusted pH ranged between 2.