Recent research indicates that siderophores, a class of biogenic ligands with known exceptional affinity for Fe(III), can also strongly complex Co(III), an element essential to normal metabolic function of microbes and animals. This study was conducted to examine the siderophore-promoted dissolution rates and mechanisms of Co from model synthetic Co-bearing minerals to elucidate the role of siderophores in biogeochemical processes of Co. Dissolution of heterogenite (CoOOH) and four Co-goethites (Co-FeOOH) with different levels of Co substitution were investigated in the presence of a trihydroxamate siderophore, desferrioxamine B (DFOB), using batch and flow-through experiments, respectively. By measuring the complex and total metal concentrations in dissolution products, dissolution rates via multiple pathways were measured as a function of pH. Results showed that DFOB promoted dissolution of Co from Co-bearing minerals via pH-dependent mechanisms. For heterogenite, ligand-promoted dissolution was the dominant pathway at neutral to alkaline pH, while reductive dissolution became dominant for pH < 6. Cobalt substitution in Co-goethite resulted in increased total dissolution rates of both Co and Fe, but ligand-promoted and reductive Co dissolution pathways were difficult to examine due to the slow dissolution rates. The fast dissolution rate of heterogenite, coupled with the high affinity of Co(III) for DFOB, suggests that siderophore-promoted dissolution of Co(III) oxides is a biogeochemically favorable process. Although the association of Co with Fe oxide mineral may limit the Co dissolution rate, siderophore-promoted Co dissolution may still be an effective enough way to increase Co bioavailability. The results also suggest the possibility of radionuclide 60Co by siderophores from recalcitrant Fe oxide phases, which may be important to the fate and transport of 60Co in contaminated environments.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-05062009-120031 |
| Date | 13 July 2009 |
| Creators | Bi, Yuqiang |
| Contributors | Owen Duckworth, Dean Hesterberg, Detlef Knappe |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-05062009-120031/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dis sertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.0025 seconds