Evaluation of sorption behavior of selenide onto montmorillonite

Sugiura, Yuki  ; Tomura, Tsutomu*; Doi, Reisuke  ; Ishidera, Takamitsu ; Tachi, Yukio  

We carried out batch sorption and XAFS experiments in various solution conditions identifying the aqueous species to evaluate the sorption behavior of Se(-II) onto montmorillonite. The values were independent of ionic strength. The values were nearly constant between pH 8-11, while the value decreased around pH 12. The aqueous species of Se(-II) were stable in 7d, and hydroselenide (HSe) was the dominant species at pH 8; whereas, polyselenide (Se, Se) increased with the increase of pH. These behavior implies that Se(-II) sorption onto the edge site of montmorillonite by complexation is not a dominant sorption mechanism. The XANES spectra indicate that Se in the collected solid phase exists as Se(0). These results suggest that the values were independence of ionic strength and pH due to the oxidation and precipitation of Se by contacting montmorillonite in this work.