Use this URL to cite or link to this record in EThOS:
Title: Synthesis and characterisation of mineral-derived and hybrid layered double hydroxides
Author: Kwok, Wing Lam Joyce
ISNI:       0000 0004 9356 5747
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2020
Availability of Full Text:
Access from EThOS:
Full text unavailable from EThOS. Please try the link below.
Access from Institution:
This thesis discusses the development of atom efficient and scalable synthesis methods for the synthesis of industrially relevant layered double hydroxides (LDHs) using a green source of magnesium derived from a waste mineral. LDHs are introduced in Chapter 1 as compositionally flexible and versatile anionic clays. The structure of LDHs confers unique and interesting properties to these inorganic compounds and as such, LDHs have found application in a wide range of applications including environmental remediation and drug delivery. Naturally occurring LDHs are low in abundance but synthetic LDHs are facile to prepare and a variety of methods are available. The growing global demand for energy and resources calls for changes in the supply chain, so there is increasing interest in technologies and methods that are more environmentally friendly. The analytical techniques and synthetic methods used are detailed in Chapter 2 ahead of the results and discussions in subsequent chapters. In Chapter 3, the mineral struvite, MgNH₄PO₄.6H₂O, is investigated as an alternative starting material for magnesium based LDHs. Struvite was acquired from wastewater treatment plants (WWTPs) and compared with a synthetic struvite. To transform this underutilised resource into commercially relevant LDHs, the effect of temperature, pH and time were investigated. The properties and morphologies of the LDHs synthesised from struvite have been characterised in detail by a number of techniques including surface area analyses and electron microscopies. Silica@LDH hybrid materials are investigated in Chapter 4. The effects of stirring speed and metal solution addition rate were systematically investigated and optimised. Strategies for core-shell synthesis using commercial silicas have also been developed to prepare high surface area silica@LDH hybrid materials that have been used as catalyst supports for ethylene polymerisation. In Chapter 5, the thermal properties of the mineral-derived and hybrid LDH materials are studied to probe their suitability for carbon dioxide (CO₂) capture. The LDHs were calcined to obtain the mixed oxide form of LDHs, layered double oxides (LDOs), and the properties of these calcined materials at different temperatures were studied. Selected LDOs were tested in CO₂ adsorption experiments and their performance has been compared to that of LDOs from commercial and conventional LDHs. Lastly, the findings of the works in this thesis are summarised in Chapter 6 and avenues for future investigations are also proposed. Supplementary information and data mentioned in the main thesis are included in the Appendices.
Supervisor: O'Hare, Dermot Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Solid state chemistry ; Chemistry ; Inorganic chemistry ; Green chemistry