The influence of small molecules on the precipitation of silica

Belton, DJ, 2005. The influence of small molecules on the precipitation of silica. PhD, Nottingham Trent University.

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Abstract

A study has been conducted into the mechanisms of interactions between silicic acid solutions and silica surfaces with a range of amino acids, homopeptides, diamines and short polyamines. The dissociation mechanism of the monosilicic acid precursor, (a 1,2-diolato benzene complex), was investigated and the dissociation confirmed to be rapid and stoichiometrically controllable at the desired pH. Investigations by mass spectrometry and monitoring the development profile of silicomolybdic acid from condensing monosilicic acid solutions did not indicate the presence of any kinetically interfering species and statistical analysis of the isolated kinetic domains showed good experimental control of the model system. Activation energies for the early condensation stages were determined and the process was shown to be controlled by the ease of anion formation of silicate species and the solubility limit for amorphous silica estimated by extrapolation of the kinetic data.

The addition of amino acids to the model system showed most pronounced effects when basic side chain functionalities were present and amine species were shown to influence the condensation and aggregation rates in line with the relative proportions of hydrophobic domains to amine functionality, chain length and electrostatic effects, allowing the formation of unusual non-porous material at circumneutral pH when partially protonated polyamine species were introduced. The mechanistic change in the condensation process was found to be a function of the number of repeat ethyleneamine units in the polyamine and the consequent amine charge density, and entrainment of the polyamine in the highly condensed silica resulted in microporous channels after removal.

Item Type:	Thesis
Creators:	Belton, D.J.
Date:	2005
ISBN:	9781369324419
Identifiers:	Number Type PQ10290192 Other
Divisions:	Schools > School of Science and Technology
Record created by:	Linda Sullivan
Date Added:	12 Nov 2020 11:49
Last Modified:	12 Oct 2023 09:22
URI:	https://irep.ntu.ac.uk/id/eprint/41634

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