Deposition and assembly of magnesium hydroxide nanostructures on zeolite 4A surfaces

dc.contributor.advisor Teja, Amyn S.
dc.contributor.author Koh, Pei Yoong en_US
dc.contributor.committeeMember Deng, Yulin
dc.contributor.committeeMember Koros, William
dc.contributor.committeeMember Nair, Sankar
dc.contributor.committeeMember Tannenbaum, Rina
dc.contributor.department Chemical Engineering en_US
dc.date.accessioned 2011-03-04T20:18:18Z
dc.date.available 2011-03-04T20:18:18Z
dc.date.issued 2010-11-15 en_US
dc.description.abstract A deposition - precipitation method was developed to produce magnesium hydroxide / zeolite 4A (Mg(OH)₂ - Z4A) nanocomposites at mild conditions and the effect of processing variables such as precursor concentration, type of base added, and synthesis time on the composition, size, and morphology of the nanocomposite were studied. It was determined that the precursor concentration, basicity, and synthesis time had a significant effect on the composition, size, and morphology of the deposited magnesium hydroxide (Mg(OH)₂) nanostructures. The properties of the Mg(OH)₂ - Z4A such as surface area, pore volume and composition were characterized. Mg(OH)₂ - Z4A samples and bare zeolite 4A were dispersed in Ultem® polymer to form a mixed matrix membrane. The thermal and mechanical properties of the resulting films were investigated. It was found that the addition of rigid bare zeolites into the polymer decreased the mechanical properties of the polymer composite. However, some of these adverse effects were mitigated in the polymer composite loaded with Mg(OH)₂ - Z4A samples. Isotherms for the adsorption of Mg(OH)₂ petals on zeolite 4A were measured in order to determine the optimum conditions for the formation of magnesium hydroxide / zeolite 4A nanocomposites at ambient conditions. The loading of the Mg(OH)₂ can be determined from the adsorption isotherms and it was also found that the adsorption of Mg(OH)₂ on zeolite A occurs via 3 mechanisms: ion exchange, surface adsorption of Mg²⁺ ions, and surface precipitation of Mg(OH)₂. Without the addition of ammonium hydroxide, the predominant processes are ion exchange and surface adsorption of Mg²⁺ ions. In the presence of ammonium hydroxide, Mg(OH)₂ crystals are precipitated on the surface of zeolite 4A at moderate Mg²⁺ ions concentration and the loading of Mg(OH)₂ was found to increase with increasing Mg²⁺ ions concentration. A detailed examination of the interactions between Mg(OH)₂ and functional groups on the zeolite surface was conducted. Solid-state 29Si, 27Al, and 1H NMR spectra were coupled with FTIR measurements, pH and adsorption studies, and thermogravimetric analyses to determine the interactions of Mg(OH)₂ with surface functional groups and to characterize structural changes in the resulting zeolite after Mg(OH)₂ deposition. It was discovered that acid - base interactions between the weakly basic Mg(OH)₂ and the acidic bridging hydroxyl protons on zeolite surface represent the dominant mechanism for the growth of Mg(OH)₂ nanostructures on the zeolite surface. en_US
dc.description.degree Ph.D. en_US
dc.identifier.uri http://hdl.handle.net/1853/37159
dc.publisher Georgia Institute of Technology en_US
dc.subject Adsorption isotherms en_US
dc.subject Solid-state NMR en_US
dc.subject Nanocomposite en_US
dc.subject Deposition-precipitation en_US
dc.subject Zeolite en_US
dc.subject Magnesium hydroxide en_US
dc.subject.lcsh Zeolites
dc.subject.lcsh Nanocomposites (Materials)
dc.subject.lcsh Nanostructures
dc.subject.lcsh Metallic oxides
dc.title Deposition and assembly of magnesium hydroxide nanostructures on zeolite 4A surfaces en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Teja, Amyn S.
local.contributor.corporatename School of Chemical and Biomolecular Engineering
local.contributor.corporatename College of Engineering
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