Title page for ETD etd-11302009-183749


Document Type Master's Dissertation
Author Moyo, Lumbidzani
Email s27499619@tuks.co.za
URN etd-11302009-183749
Document Title A critical assessment of the methods for intercalating anionic surfactants in layered double hydroxides
Degree MSc
Department Chemistry
Supervisor
Advisor Name Title
Prof W W Focke Supervisor
Keywords
  • infrared spectroscopy
  • reconstruction
  • calcinations
  • anionic surfactant
  • intercalation
  • layered double hydroxide
  • X-ray diffraction analysis
  • thermogravimetry
Date 2009-09-02
Availability unrestricted
Abstract
The intercalation of surfactant anions, namely sodium dodecyl sulphate, sodium benzene sulphonate and lauric acid, into commercial layered double hydroxides (LDH-CO3) with approximate composition [Mg0.654AI0.346 (OH)2](CO3)0.173.0.5H2O] was explored. LDH-CO3 is commercially available in bulk form owing to its large scale applications as a PVC stabiliser and acid scavenger in polyolefins. It is therefore of interest to investigate intercalation methods using LDH-CO3 as starting material. The intercalation method used was compared with the pre existing procedures, for instance the co-precipitation, ion exchange and regeneration methods. Due to the tenacity with which the carbonate ion is held in LDH-CO3, direct ion exchange is an intricate matter. Hence, in the regeneration method the carbonate ion is removed by thermal treatment and the LDH-surfactant is obtained by reaction of the LDH and surfactant in an aqueous medium. Nevertheless, the resulting products are impure and poorly crystallised, and only partial intercalation is achieved. The underlying principle of the current method is protonation of the carbonate anion to a monovalent anion that is easily exchanged with surfactant anions.

Improved results were obtained when water-soluble organic acids were used, the most suitable being lower aliphatic carboxylic acids, e.g. acetic, butyric and hexanoic acid. In contrast, higher linear aliphatic carboxylic acids are preferentially intercalated to the anionic surfactants. In both cases the carboxylic acids are assumed to assist intercalation by facilitating the elimination of the carbonate ions present in the anionic clay galleries. X-ray diffraction analysis, thermal analysis and infrared spectroscopy confirmed the monolayer intercalation of LDH-dodecyl sulphate and LDH-dodecylbenzene sulphonate. In contrast, LDH-laurate featured a bilayer structure.

2009, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Moyo, L 2009, A critical assessment of the methods for intercalating anionic surfactants in layered double hydroxides, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-11302009-183749/ >

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