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Synthesis and characterisation of layered double hydroxides and their application for water purification

Theiss, Frederick L. (2012) Synthesis and characterisation of layered double hydroxides and their application for water purification. Masters by Research thesis, Queensland University of Technology.

Abstract

Layered doubly hydroxides (LDHs) also known as hydrotalcites or anionic clays are a group of clay minerals that have shown promise for the removal of toxic anions from water through both anion exchange and a process known as the reformation effect. This project has involved the preparation and characterisation of LDH materials as well as the investigation of their ability to remove selected anions from aqueous solutions by the reformation effect.

The LDH materials were successfully prepared from magnesium, aluminium, zinc and chromium chloride salts using the co-precipitation method. Samples were characterised using powder X-ray diffraction (XRD) and thermogravimetry (TG) to confirm the presence of LDHs. Powder XRD revealed a characteristic LDH structure for all LDH samples. Thermal Analysis showed decomposition usual occurred through a three or four step process as expected for LDHs. Preliminary investigations of the removal of sulfate, nitrate and fluoride by an Mg/Al LDH were carried out, and the products were characterised using XRD and TG which showed that an LDH material similar to the original hydrotalcite was formed after reformation.

A Zn/Al LDH was investigated as a potential sorbent material for the removal of iodine and iodide from water. It was found that the LDH was a suitable adsorbent which is able to remove almost all of the iodine present in the test solutions. Again, the products were characterised by XRD, TG and evolved gas mass spectrometry (EGMS) in an attempt to better understand the iodine removal process. Powder XRD showed successful reformation of the LDH structure and TG/EGMS showed that only a small amount of iodine species were lost during thermal decomposition. Finally, the mineral stichtite a Mg/Cr LDH was successfully synthesised and investigated using XRD, TG and EGMS. Unfortunately, due to lack of time it was not possible to identify any new uses for the mineral stichtite in the current project.

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ID Code: 54620
Item Type: QUT Thesis (Masters by Research)
Supervisor: Frost, Ray
Keywords: layered double hydroxides, hydrotalcites, anionic clays, water purification, sulfate, nitrate, fluoride, iodine, iodide, stichtite, powder x-ray diffraction, thermogravametric analysis, thermogravimitry, evolved gas analysis, evolved gas mass spectrometry
Divisions: Past > Schools > Chemistry
Past > QUT Faculties & Divisions > Faculty of Science and Technology
Institution: Queensland University of Technology
Deposited On: 06 Nov 2012 10:54
Last Modified: 06 Nov 2012 10:54

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