Adsorption of phosphate and cadmium on iron (oxyhydr)oxides: A comparative study on ferrihydrite, goethite, and hematite
143
Citation
69
Reference
10
Related Paper
Citation Trend
Keywords:
Ferrihydrite
Oxide minerals
Lepidocrocite
Oxide minerals
Cite
Citations (113)
Ferrihydrite
Cite
Citations (16)
Abstract 2-line ferrihydrite stored in water at ambient temperatures from 4 to 25°C and at ten different pH values between 2.5 and 12 for up to 10–12 y transformed to both goethite and hematite at all temperatures and pH values except at pH 12 where only goethite was formed. The rate and degree of transformation (20–100%) increased with increasing pH and temperature. The hematite/ (hematite+goethite) ratio varied between 0 and ~0.8, increased with increasing temperature and showed a strong maximum at pH 7–8 which increased from 0.1–0.2 at 4°C to 0.7–0.8 at 25°C. The maximum coincides with the zero point of charge of ferrihydrite where its solubility and, thus, its via-solution transformation rate to goethite are minimal. We assume, therefore, that in this pH-range the (slower) via-solution transformation to hematite can more efficiently compete with that to goethite.
Ferrihydrite
Cite
Citations (158)
The effect of clay minerals as aluminum sources on iron oxides synthesized from ferrihydrite at pH 5 and in 0.1 M KOH at 70 and 25°C was studied. Depending on type of clay mineral, temperature, and pH, aluminum released from these sources favors the formation of hematite over goethite, retards or inhibits crystallization, and enters the crystal lattice of goethite and hematite where it replaces iron. Silicate released at high pH forms Fe-O-Si bonds with the ferrihydrite and can also inhibit crystallization.
Ferrihydrite
Cite
Citations (123)
Ferrihydrite
Cite
Citations (0)
An Acrudoxic Kandiudult soil profile from Farmhill, KwaZulu-Natal Province, South Africa, was analyzed by Mössbauer spectroscopy as an example of a red soil with yellowish surface horizons, a common sequence for which iron oxide characteristics are only poorly documented. In the red lower part of the profile (62+ cm), the Fe oxide fraction consists of hematite and well-crystallized pure goethite. In the yellowish upper part (0–62 cm), the relative hematite content is lower, goethite shows a high degree of Al-for-Fe substitution, and ferrihydrite is present. Processes found to have affected the Fe oxide fraction are hematite dissolution, partial leaching, goethite precipitation with a high degree of Al incorporation, and ferrihydrite formation in conditions with a high organic matter content; the so-called DOM (dissolved organic matter) ferrihydrites.
Ferrihydrite
Cite
Citations (4)