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A multi-technique study of the effect of aqueous aluminium speciation on hydrolytic gelation of aluminium (oxy)hydroxide

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Title: A multi-technique study of the effect of aqueous aluminium speciation on hydrolytic gelation of aluminium (oxy)hydroxide
Authors: Fournier, A.C.1, Shafran, K.L., Perry, C.C. carole.perry@ntu.ac.uk
Source: Journal of Colloid & Interface Science. Apr2009, Vol. 332 Issue 1, p122-129. 8p.
Subjects: Aluminum, Metal ions, Chemical speciation, Gelation, Aluminum hydroxide, Buffer solutions, Hydrolysis
Abstract: Abstract: The sol–gel transformation of aqueous solutions of aluminium ions into aluminium (oxy)hydroxides induced by the addition of a ‘soft base’—‘Tris-buffer’ () has been investigated using monotonous single-batch titrations and a combination of four complimentary techniques for monitoring pH, conductivity, viscosity and ultrasound parameters (velocity and attenuation). The multi-probe monitoring of the formation of aluminium (oxy)hydroxides enabled important stages of the sol–gel transformation process including: the structural conversion of aluminium Keggin-like polynuclear clusters into nanoparticles of aluminium (oxy)hydroxide; the aggregation of primary nuclei of aluminium (oxy)hydroxide into larger particles, and the ‘arrested growth’ of the aggregates with the formation of the three-dimensional gel network to be followed. The effect of aluminium ion molecular speciation on the sol–gel transformation stages is discussed. The data presented show that ultrasonic spectrometry, although a novel tool for sol–gel studies, is beneficial for the non-invasive monitoring of the latter stages of aluminium (oxy)hydroxide formation and its eventual breakdown in the presence of excess base. [Copyright &y& Elsevier]
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Database: Engineering Source
Description
Abstract:Abstract: The sol–gel transformation of aqueous solutions of aluminium ions into aluminium (oxy)hydroxides induced by the addition of a ‘soft base’—‘Tris-buffer’ () has been investigated using monotonous single-batch titrations and a combination of four complimentary techniques for monitoring pH, conductivity, viscosity and ultrasound parameters (velocity and attenuation). The multi-probe monitoring of the formation of aluminium (oxy)hydroxides enabled important stages of the sol–gel transformation process including: the structural conversion of aluminium Keggin-like polynuclear clusters into nanoparticles of aluminium (oxy)hydroxide; the aggregation of primary nuclei of aluminium (oxy)hydroxide into larger particles, and the ‘arrested growth’ of the aggregates with the formation of the three-dimensional gel network to be followed. The effect of aluminium ion molecular speciation on the sol–gel transformation stages is discussed. The data presented show that ultrasonic spectrometry, although a novel tool for sol–gel studies, is beneficial for the non-invasive monitoring of the latter stages of aluminium (oxy)hydroxide formation and its eventual breakdown in the presence of excess base. [Copyright &y& Elsevier]
ISSN:00219797
DOI:10.1016/j.jcis.2008.12.042