Oleate Adsorption at an Apatite Surface Studied by Ex-Situ FTIR Internal Reflection Spectroscopy
✍ Scribed by Yongqiang Lu; Jaroslaw Drelich; Jan D. Miller
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 248 KB
- Volume
- 202
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
and even some foods contain phosphate and/or phosphate Oleate adsorption at an apatite surface was investigated by exderivatives. However, the major use of phosphate is as a situ Fourier transform infrared internal reflection spectroscopy fertilizer, providing one of the three major nutrients required (FTIR/IRS). Adsorption isotherms have been determined using to sustain plant growth (1-6).
an apatite internal reflection element (IRE) and it has been found
Phosphates are produced from phosphate rock, containing that pH has a significant influence on oleate adsorption by apatite.
apatite (in the case of igneous deposits) and francolite (in the At pH 8.0 and 20ЊC, oleate adsorption density increases monotonicase of sedimentary deposits) together with other impurity cally as equilibrium oleate concentration increases from 5 1 10 06 gangue minerals. An ever-increasing global demand for food to 1 1 10 03 M. These results are in contrast to the results at pH has resulted in an increase in fertilizer use and therefore in 9.5 and 20ЊC in which case the adsorption density is limited to that corresponding to approximately monolayer coverage. Oleate an increase in consumption of phosphate rock. Generally the adsorption by apatite was compared to oleate adsorption by fluophosphate rock has to be processed prior to use in order to rite and calcite and the different adsorption behavior at these three obtain phosphate-enriched raw materials. Each year about mineral surfaces is attributed to the differences in the densities of 15-20 million tons of phosphate production is accomplished surface calcium sites and to the differences in the solubilities of by froth flotation (7,8). In this process fatty acids are the these minerals.
most commonly used surfactants (collectors). Such surfac-
The spectral results at pH 8.0 and 20ЊC, suggest that the domitants adsorb selectively at phosphate mineral surfaces and nant adsorbed species at the apatite surface is oleic acid as indicreate a hydrophobic state. In the flotation process these cated by the appearance of a strong IR absorbance peak at about hydrophobic mineral particles attach to air bubbles and are 1710 cm 01 for the whole oleate concentration range investigated carried to the froth phase while the hydrophilic gangue minfrom 5 1 10 06 to 1 1 10 03 M. On the other hand at pH 9.5, 20ЊC, eral particles such as quartz particles remain in the pulp. In and low surface coverage, it appears that oleate is chemisorbed as indicated by a peak at 1554 cm 01 and an increased adsoption this way the desired separation is realized.