Metastable zone width and nucleation threshold of aluminium hydroxyfluoride hydrate

Ntuk, Ubong and Steel, Karen (2016) Metastable zone width and nucleation threshold of aluminium hydroxyfluoride hydrate. Crystal Research and Technology, 51 4: 265-275. doi:10.1002/crat.201500294

Author Ntuk, Ubong
Steel, Karen
Title Metastable zone width and nucleation threshold of aluminium hydroxyfluoride hydrate
Journal name Crystal Research and Technology   Check publisher's open access policy
ISSN 1521-4079
Publication date 2016-04-01
Year available 2016
Sub-type Article (original research)
DOI 10.1002/crat.201500294
Open Access Status Not Open Access
Volume 51
Issue 4
Start page 265
End page 275
Total pages 11
Place of publication Weinheim, Germany
Publisher Wiley
Language eng
Formatted abstract
This paper considers the metastable zone width (MSZW) of aluminium hydroxyfluoride hydrate (AHF, AlF2OH.H2O) crystallizing solution, with a view to identifying suitable conditions for crystal growth. Speciation calculations combined with experimental validations have been used to estimate the degree of saturation at varying pHs leading to the identification of the metastable zone width (MSZW). From the results obtained, the solutions are saturated at pH 3.0 ± 0.3 and remain metastable until the nucleation threshold is reached at pH 5.0 ± 0.3. A narrowing of the MSZW at elevated temperatures has been observed and is attributed to the decrease in AHF solubility with increasing temperatures. This phenomenon was applied to obtain a tripling of the crystal particles in 30 minutes. The pH profile of the crystallizing solution is similar to that of acid/base titration curves and is found to be a quick and accurate method of estimating the MSZW. Using similar terminologies, the equivalent point corresponds to solution saturation while the mid-point corresponds to the nucleation threshold. These results are applicable in the recovery of fluoride values of spent pot lining.
Keyword Spent potlining
Aluminium hydroxyfluoride
Ionic speciation
Metastable zone width
Nucleation threshold
Crystal growth
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
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