Hematite sulfidation and its product for reductive immobilization of chromate in water
Sulfidated Hematite(SH)was synthesized using sodium sulfide as a sulfidation reagent,and its reductive immobilization performance for chromate in water was examined for the resulted material.Model fitting by Langmuir isothermal equation indicated that the material had a maximum adsorption capacity of 66.7 mg·g-1 to chromate at neutral pH,which was about 39 times that of the original hematite.The removal process of chromate by SH was well described by the pseudo-second-order kinetic model,suggesting that the process might be controlled by a chemical adsorption.TEM and XRD were utilized to characterize SH and the associated mechanism of chromate removal was analyzed in combination with the changes in XPS spectra of the material before and after adsorption.The result showed that the improved performance of SH in chromate reduction could be ascribed to the Fe-S layer formed on hematite surface.During reductive immobilization of chromate by SH,the reducing substances FeS,adsorbed Fe(Ⅱ)and S(-Ⅱ)on the surface of sulfidated hematite jointly participated in Cr(Ⅵ)reduction to Cr(Ⅲ),thereby achieving chromate stabilization.
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