Investigation of Se(IV) sorption on Na-kaolinite: batch experiments and modeling

Se(IV) sorption on purified Na-kaolinite was investigated under ambient temperature as functions of contact time, pH, ionic strength and Se(IV) concentration using batch techniques. The rate of sorption is relatively rapid and sorption kinetics of Se(IV) can be successfully described by the pseudo-second-order model. The amount of Se(IV) sorbed was moderately dependent on the solution pH but insensitive to ionic strengths. The sorption/desorption isotherms of Se(IV) show that the sorption process is reversible. A double layer model was set up and used to quantitatively interpret the experimental data. Three surface complexes (a parts per thousand Al)(2)SeO3, a parts per thousand AlSeO3 (-) and a parts per thousand AlOHSeO3 (2-) were proposed which satisfactorily fit our data.