The formation of Fe oxides is influenced by pedogenic factors including ionic environments However, the surface chemistry of Fe oxides formed under different ionic conditions remains obscure Tins study reveals the impact of the structural chemistry of the Fe oxides formed under the influence of low-molecular-weight organic acids and inorganic ligands on their surface chemistry. The selected ligands at optimal ligand/Fe(II) molar ratios (MRs) promoted the crystallization of the Fe oxides formed and decreased their specific surface area through fundamental structural changes. At relatively high ligand/Fe(II) MRS, the ligands inhibited the crystallization of the Fe oxides formed, resulting in the development of micropores, the increase in their surface roughness and irregularity as revealed by atomic force microscopy, as well as the increase in their specific surface area. The net negative surface charge of the Fe oxides consistently increased as the ligand/Fe(II) MR increased. The ligands altering the surfaceproperties of the Fe oxides generally followed the order of the stability constants of the Fe-ligand complexes: silicic acid > citrate > tartrate > oxalate > sulfate > carbonate. The kinetics and mechanisms of adsorption/desorption of P and Ph on the Fe oxides formed at various citrate/Fe(II) MRs were investigated by conventional batch method, pressure-jump relaxation spectrometry and differential Fourier transform infrared spectroscopy. The apparent rate constants, intrinsic rate and equilibrium constants, activation energies, pre-exponential factor values of P and Ph adsorption by the Fe oxides formed and the coordination of P and Ph on the Fe oxide surfaces greatly varied with the amount of the citrate ligands coprecipitated with Fe and their surface properties. The mechanistic rate laws of P and Pb adsorption by the Fe oxides formed at the citrate/Fe(II) MRs of 0 and 0.001 were different. The P adsorption occurred in two sequential reactions whereas the Pb adsorption included two parallel reactions. The role of organic and inorganic ligands in influencing the surface properties of Fe oxides through their effect on crystallization is profound. The subsequent impact on the dynamics of nutrients and pollutants in terrestrial and aquatic environments merits close attention.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-10212004-002233 |
| Date | 01 January 1999 |
| Creators | Liu, Chen |
| Contributors | Huang, Pan Ming, de Jong, Eeltje |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-10212004-002233 |
| 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, dissertation, 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 University of Saskatchewan 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. |
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