Identification of Nickel Uranyl Phosphate Deposits on Citrobacter sp. Cells by Electron Microscopy with Electron Probe X-ray Microanalysis and by Proton-Induced X-ray Emission Analysis
1998 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 32, no 6, 760-765 p.Article in journal (Refereed) Published
Immobilized cells of a Citrobacter sp. can remove heavy metals from wastewaters by deposition ofmetals with enzymatically liberated phosphate. Nickel is not removed effectively by this technique, but Ni2+ can be intercalated into cell-bound, crystalline HUO2PO4 previously deposited enzymatically. This technique for efficient removal of Ni from solution has been generically termed microbially enhanced chemisorption of heavy metals(MECHM). The nickel uranyl phosphate deposits bound to Citrobactersp. cells immobilized in polyacrylamide gel (FAG) were analyzed using scanning transmission electronmicroscopy with electron probe X-ray microanalysis (EPXMA) and proton-induced X-ray emissionanalysis(PIXE). Both methods gave the molar ratios of nickel, uranium, and phosphorus in the depositsas close to 1:2:2 in all analyzed parts of the sample. EPXMA proved that the deposits were localized onthe surface of cells inside FAG particles as well as those immobilized on the edge. Small deposits ofnickel uranyl phosphate were also found in FAG between the cells, indicating the possible involvementof extracellular polymeric substances (EPS) in the creation of intercellular deposits. These findings confirm the mechanism of MECHM and show that this mechanism operates throughout the immobilized cell matrix. The use of two independent methods of solid-state analysis in a common sample provides validation of both techniques for the spatial and quantitative analysis of biomass-bound elements.
Place, publisher, year, edition, pages
1998. Vol. 32, no 6, 760-765 p.
IdentifiersURN: urn:nbn:se:uu:diva-35284DOI: 10.1021/es9705553ISI: 000072571800006OAI: oai:DiVA.org:uu-35284DiVA: diva2:63184