Comparisons of structural iron reduction in smectites by bacteria and dithionite: II. A variable-temperature Mössbauer spectroscopic study of Garfield nontronite

• DOI: 10.1351/pac-con-08-11-16
• Publication Date: 2009-07-24T14:29:32Z
• Authors: Fabiana R. Ribeiro; José D. Fabris; Joel E. Kostka; Peter Komadel; Joseph W. Stucki
• Keywords: Nontronite; Sodium dithionite; Dithionite

The reduction of structural Fe in smectite may be mediated either abiotically by reaction with chemical reducing agents or biotically various bacterial species. effects abiotic on clay surface chemistry are much better known than the biotic reduction, and differences between them still need investigation. purpose present study was to compare dithionite (abiotic) bacteria (biotic) nontronite structure as observed variable-temperature Mössbauer spectroscopy. Biotic accomplished incubating Na-saturated Garfield (sample API 33a) Shewanella oneidensis strain MR-1 (Fe II /total achieved ~17 %). Partial ~23 %) using pH-buffered sodium dithionite. also reduced ~96 %. Parallel samples were reoxidized bubbling O 2 gas through suspensions at room temperature prior analysis 77 4 K. At K, treatments all gave spectra composed doublets for III nontronite. largely restored that unaltered sample, except sample 96 spectrum % highly complex clearly reflected magnetic order sample. When partially reduced, exhibited order, but features completely different depending whether abiotically. appeared contain distinctly separate domains within structure, whereas partial produced a representative –Fe pairs dominant domain type. K fully virtually same reoxidation consisting magnetically ordered sextet minor contribution from doublet, indicating significant alterations compared