- Title
- Synthesis of mesoporous silica particles using an asymmetric precursor: application to heavy metal removal
- Creator
- Hosseini, Layla
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Porous materials have a significant role in a number of different aspects of technology and science because many biological and industrial processes can occur in the confined geometry of their pores. Amongst these type of materials, the porous silica nanoparticles, in which silica is the main building block, are of considerable interest as silica itself is chemically inert, thermally stable, harmless and inexpensive. Altering the conditions of the synthesis results in changes in the product’s properties, and therefore its potential applications. The silanes used in a SBA-15 synthesis employing a Pluronic P123 template have so far been structurally symmetrical. The most used sources of silica for the synthesis of SBA-15, tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS) and tetrapropyl orthosilicate (TPOS), consist of four identical groups. The use of asymmetric trimethoxy(methyl)silane (MTMS) as the only source of silica used in the synthesis of SBA-15 has never previously been investigated. In this research, an innovative porous silica was synthesised with MTMS as a novel silica source in order to investigate the feasibility of using an asymmetric silica source with Pluronic P123 as a template. Apart from being asymmetric, MTMS is less hazardous than TMOS and its reaction rate is higher than TEOS (Hosseini et al., 2019). The novel Pluronic P123-MTMS particles, which were referred to as MS-Asym (mesoporous silica - asymmetric) particles, were synthesised using the same triblock copolymer, EO20PO70EO20 (P123), and within the same acidic media as those used for the SBA-15 synthesis (Zhao et al., 1998a). However, MTMS was used as a new silica source in this process. The MS-Asym is believed to be a novel silica which has been synthesised for the first time. The structures of the MS-Asym samples were analysed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 physisorption and X-ray diffraction (XRD) analysis, as well as Attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR). The analysis characterised the shapes, sizes, textures, compositions and chemistry of the samples. The next stage of the study consisted of the development of amorphous MS-Asym materials by investigating the effects of silica on the template molar ratio, with seven samples being investigated. In the first sample, in which the concentration of the MTMS was less than that of the SBA-15, no product was obtained. However, different types of products were obtained when the MTMS/Pluronic molar ratio was increased, from 59.1 to 591. It was evident from the experimental results that the MS-Asym-1 was a gel-like product which was grindable after the calcination step. However, the MS-Asym-2 and MS-Asym-3 samples, which were quite similar in nature, consisted of porous silica nanoparticles. The last four samples, namely MS-Asym-4, MS-Asym-6, MS-Asym-8 and MS-Asym-10, were shaped completely differently to the previous samples and were a granular type of product. The next phase of the current research included studying the applications of porous silica in removing copper from aqueous solutions. The adsorption capabilities of the silica particles were effective only when the functional groups were anchored to the silica skeletons. To optimise the impregnation characteristics of the silica particles, three different molecular weights of polyethylenimine (PEI), which contains amine groups, were employed to modify the surfaces of the silicas. The gradual structural disordering of a functionalised silica due to a PEI binding was fully addressed for the first time, to the researcher’s knowledge. The weight percentage of each molecular weight of PEI was also altered to reach a deeper understanding of the effects that PEI-modification has on the structures of porous silicas. This investigation was conducted by using multiple techniques, including energy-dispersive X-ray spectroscopy (EDX), SEM, TEM, XRD, and N2 adsorption and ATR-FTIR analyses. The proposed optimised percentage and molecular weight of the PEI were then used to investigate the potential application of the PEI-modified silica in removing copper ions from aqueous solutions. The adsorption behaviour of the as-synthesised silica particles with respect to Cu2+ was studied by employing a batch-binding method. The applicability of both the amino-functionalised ordered and the amorphous silica for the removal of copper ions from aqueous solutions was then studied and compared using binding efficiency studies.
- Subject
- SBA-15; MTMS; mesoporous silica; Pluronic P123; MS-Asym; amino-functionalised silica; copper removal; water treatment; pollutant removal
- Identifier
- http://hdl.handle.net/1959.13/1419587
- Identifier
- uon:37472
- Rights
- Copyright 2020 Layla Hosseini
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
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| View Details Download | ATTACHMENT02 | Abstract | 765 KB | Adobe Acrobat PDF | View Details Download |