Mechanism analysis of selenium (VI) immobilization using alkaline-earth metal oxides and ferrous salt.
The immobilization of selenate (SeO42-) using metal oxides (CaO and MgO) and ferrous salt as the immobilization reagents were examined by the leaching test and solid-phase analysis via XRD, XAFS, TGA, and XPS. The results indicated that nearly all of SeO42- was reduced to SeO32- in the CaO-based reaction within 7 days. Then, the generated SeO32- was mainly sorbed onto the iron-based minerals (Fe2O3 and FeOOH) through the formation of both bidentate mononuclear edge-sharing (1E) and monodentate mononuclear corner-sharing (1V) inner-sphere surface complexes, suggested by PHREEQC simulation and EXAFS analysis. Differently, less amount of SeO42- (approximately 45.50%) was reduced to SeO32- for the MgO-based reaction. However, if the curing time increases to a longer time (more than 7 days), the further reduction could occur because there are still Fe(II) species in the matrix. As for the associations of Se in the solid residue, most of the selenium (SeO32- and SeO42-) was preferentially distributed onto the Mg(OH)2 through outer-sphere adsorption. Definitely, this research can provide a deep understanding of the immobilization of selenium using alkaline-earth metal oxide related materials and ferrous substances.
['Tian|Quanzhi|Q|', 'Guo|Binglin|B|', 'Chuaicham|Chitiphon|C|', 'Sasaki|Keiko|K|']
D000327:Adsorption D017610:Calcium Compounds D004785:Environmental Pollutants D005296:Ferrous Compounds D008277:Magnesium Oxide D008962:Models, Theoretical D010087:Oxides D064586:Selenic Acid D018508:Water Purification
Immobilization Ferrous salt Selenate CaO and MgO