Fe(III) reduction in Hanford sediments and its application to chromium immobilization
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2015
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ndltd-OhioLink-oai-etd.ohiolink.edu-miami14384426372021-08-03T06:32:33Z Fe(III) reduction in Hanford sediments and its application to chromium immobilization Bishop, Michael Edward Environmental Geology Biogeochemistry Geochemistry Geotechnology Inorganic Chemistry Rehabilitation Soil Sciences XANES EXAFS bioreduction chromium Iron Hanford sediments sediments Mossbauer chlorite Geobacter sulfurreducens kinetics montmorillonite nontronite reduction oxidation redox This dissertation investigates the iron reduction-oxidation (redox) cycle andmicrobe-mineral interactions in clay minerals associated with sediments samples from theoxic-anoxic interface of a sediment core located in the 300 area of the Hanford site,Washington State, USA, in the summer of 2008. The applicability of the products of thisredox reaction towards environmental problems such as heavy metal (Cr6+ Tc(VII) orU(VI)) contaminants is largely unexplored. This dissertation, therefore, seeks todevelop a fundamental understanding of how redox cycled sediment samples canreduce/immobilize aqueous hexavalent chromium (Cr6+). These results are important forour understanding of how various clay minerals associated with sediment samples may beutilized to reductively immobilize heavy metal contaminants in the environment.The first subproject involves research on iron biogeochemistry in different clayminerals [nontronite (NAu-2), montmorillonite (SWy-2) and chlorite (CCa-2)] and sizefractionated sediments [0.5- 2.0 µM (Hanford-C), 0.02-0.5 µM (Hanford-F)]. NAu-2and SWy-2 were most effective in reducing Cr6+. Characterization of the Cr-clayreaction product utilizing scanning electron microscopy (SEM) with a focused ion beam(FIB) and transmission electron microscope (TEM) with electron energy lossspectroscopy (EELS) revealed that reduced chromium possibly formed as a subnanometerCr2O3 as micro-aggregates in association with residual clay minerals.The second subproject focused on Fe redox cycling in size fractionatedsediments. The rate and extent are determined as a result of structural Fe concentrationand physiochemical properties of the clay minerals in association with sediment. Therate and extent of bioreduction decreased with increased cycle numbers with somevariations. X-ray diffraction (XRD) and SEM revealed that biogenic quartz andclinoptilolite formed as secondary minerals as a result of dissolution-precipitation.The third subproject focused on utilizing the products of redox cycled sedimentstowards Cr6+ reduction. The reduction kinetics were well-described by a second orderrate equation with respect to Cr6+ and Fe(II) concentrations. Characterization of theCr-reacted products utilizing TEM and EELS revealed: an expansion in the latticefringe (1.0 to 1.32 nm), suggesting Cr resided in the inter-layers of clay minerals inassociation with the sediment sample, supporting the EXAFS data; reduction of Cr6+ toCr(III), supporting the XANES data; and oxidation of Fe(II) to Fe(III), supporting theM¿ssbauer data. 2015-08-03 English text Miami University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=miami1438442637 http://rave.ohiolink.edu/etdc/view?acc_num=miami1438442637 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
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NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Environmental Geology Biogeochemistry Geochemistry Geotechnology Inorganic Chemistry Rehabilitation Soil Sciences XANES EXAFS bioreduction chromium Iron Hanford sediments sediments Mossbauer chlorite Geobacter sulfurreducens kinetics montmorillonite nontronite reduction oxidation redox |
| spellingShingle |
Environmental Geology Biogeochemistry Geochemistry Geotechnology Inorganic Chemistry Rehabilitation Soil Sciences XANES EXAFS bioreduction chromium Iron Hanford sediments sediments Mossbauer chlorite Geobacter sulfurreducens kinetics montmorillonite nontronite reduction oxidation redox Bishop, Michael Edward Fe(III) reduction in Hanford sediments and its application to chromium immobilization |
| author |
Bishop, Michael Edward |
| author_facet |
Bishop, Michael Edward |
| author_sort |
Bishop, Michael Edward |
| title |
Fe(III) reduction in Hanford sediments and its application to chromium immobilization |
| title_short |
Fe(III) reduction in Hanford sediments and its application to chromium immobilization |
| title_full |
Fe(III) reduction in Hanford sediments and its application to chromium immobilization |
| title_fullStr |
Fe(III) reduction in Hanford sediments and its application to chromium immobilization |
| title_full_unstemmed |
Fe(III) reduction in Hanford sediments and its application to chromium immobilization |
| title_sort |
fe(iii) reduction in hanford sediments and its application to chromium immobilization |
| publisher |
Miami University / OhioLINK |
| publishDate |
2015 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=miami1438442637 |
| work_keys_str_mv |
AT bishopmichaeledward feiiireductioninhanfordsedimentsanditsapplicationtochromiumimmobilization |
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