Mechanistic investigations of Se(VI) treatment in anoxic groundwater using granular iron and organic carbon: An EXAFS study

作者：Gibson Blair D^*; Blowes David W; Lindsay Matthew B J; Ptacek Carol J

来源：Journal of Hazardous Materials, 2012, 241: 92-100.

DOI：10.1016/j.jhazmat.2012.09.015

• Se(VI) reduction
• Anoxic groundwater
• Micro XRF mapping
• Micro XANES/EXAFS

The removal of aqueous Se(VI) from a simulated groundwater by granular iron (GI), organic carbon (OC), and a mixture of these reactive materials (GI-OC) was evaluated in laboratory batch experiments. The experiments were performed under anoxic conditions to simulate subsurface treatment. A total reaction time of 120h (5 d) was chosen to investigate the rapid changes in speciation occurring over reaction times that are reasonable for permeable reactive barrier (PRB) systems. After 120 h, concentrations of Se decreased by %26gt;90% in the Cl system, 15% in the OC system and 35% in the GI-OC mixture. Analysis of the materials after contact with Se using synchrotron-radiation based X-ray absorption spectroscopy (XAS) indicated the presence of Se(IV) and Se(0) on the margins of Cl grains after 6h with evidence of Se-O and Se-Se bonding, whereas Se(VI) was not observed. After 72 h, Se(0) was the only form of Se present in the GI experiments. In the OC batches, the XAS analysis indicated binding consistent with sorption of aqueous Se(VI) onto the OC with only minor reduction to Se(IV) and Se(0) after 120h. Selenium XAS spectra collected for the GI-OC mixture were consistent with spectra for Se(IV) and Se(0) on both the margins of GI grains and OC particles, suggesting that the presence of dissolved Fe may have mediated the reduction of sorbed Se(VI). The results suggest that the application of granular Fe is effective at inducing aqueous Se removal in anoxic conditions through reductive precipitation processes.

• 出版日期2012-11-30