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Effect of Phosphate on the Crystallization of Hematite, Goethite, and Lepidocrocite from Ferrihydrite
| Content Provider | Semantic Scholar |
|---|---|
| Author | Gálvez, Natividad Barrón, Vidal Torrent, José Joaquín Goberna |
| Copyright Year | 1999 |
| Abstract | We investigated the crystallization of ferrihydrite prepared by hydrolysis of Fe(NO3)3 solutions containing phosphate. Crystallization was studied at different pH (3–9), temperatures (298, 323, and 373 K), and initial P/Fe atomic ratios for periods to 730 d. Generally, crystallization was inhibited or only poorly crystallized lepidocrocite was formed at P/Fe > 2.5%. Phosphate favored the formation of hematite over goethite at all temperatures for most of the pH and P/Fe ranges investigated. This result is consistent with a model in which phosphate acts as a template for hematite formation, in analogy with other anions, such as oxalate. However, goethite was preferentially formed at alkaline pH and P/Fe > 1%, probably because high phosphate concentration resulted in a large increase in the negative charge of the ferrihydrite particles. This resulted in turn in less aggregation, a process that is known to precede dehydration to hematite. Phosphate greatly influenced the morphology of hematite and goethite. Hematite was often ellipsoidal or spindle-shaped. Twinned goethite crystals with a hematite core were formed at alkaline pH at P/Fe > 1%. Both hematite and goethite particles incorporated phosphate in an occluded form not desorbable by repeated alkali treatments. |
| Starting Page | 304 |
| Ending Page | 311 |
| Page Count | 8 |
| File Format | PDF HTM / HTML |
| DOI | 10.1346/CCMN.1999.0470306 |
| Volume Number | 47 |
| Alternate Webpage(s) | http://www.clays.org/journal/archive/volume%2047/47-3-304.pdf |
| Alternate Webpage(s) | https://doi.org/10.1346/CCMN.1999.0470306 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
