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Synthesis and Integration of Nanoparticles in Thin Film Nanocomposite Membranes for Water Treatment
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- Author / Creator
- Almansoori, Zayed
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The most widely used method for desalination, the process of removing salts and minerals from saltwater for human consumption and irrigation, is membrane technology. There are various types of membrane technologies, but the use of thin film nanocomposite (TFN) polyamide (PA) membranes for nanofiltration (NF) and reverse osmosis (RO) are central to seawater and wastewater treatment. TFN membranes incorporate nanoparticles (NPs) into their PA layer which are able to increase the membranes contaminant rejection, mechanical strength, and water flux, resulting in a more efficient separation process that produces water with higher quality. This thesis focuses on the synthesis and integration of conductive indium tin oxide (ITO) NPs into membranes with the goal of demonstrating improved thermal stability and hydrophilicity. The NPs are dispersed in the organic solution during synthesis of the TFN membrane, however the tendency of NPs to form large aggregates has been a major limitation to their successful integration. The challenge of aggregation extends to widespread applications of NPs, where utilizing monodisperse and stable suspension of NPs is essential. The aggregation of NPs becomes more challenging when there is less affinity between the dispersed phase (NPs) and the continuous phase (solvent), such as, dispersion of hydrophilic metal oxide NPs into a nonpolar (organic) solvent. The objective of the first part of this study is to systematically investigate the synergistic effects of eight dispersion parameters on the size an d stability of indium tin oxide (ITO) NPs in heptane. The matrix of experimentation was designed using an L18 Taguchi method. The analysis of variance (ANOVA) of the experimental results revealed that the most significant factors on the size and stability of NPs were the mass of ITO NPs and the volume of the dispersing agent. Taguchi signal-to-noise (SN) ratio analysis was used to determine the optimal factor levels for the preparation of well-dispersed and stable NP suspensions. Confirmation tests were carried out at the suggested levels of the ANOVA predictive model, and highly stable ITO NPs in heptane with the size distribution of 43.0–68.3 nm were obtained. The results of the parametric study can be used for a broad range of applications where effective stabilization of metal oxide NPs in organic solvents is desired. The ITO NP suspension is utilized in the second part of the work to synthesize ITO TFN membranes. The presence of ITO NPs at a weight percentage of 0.02% were shown to nearly double the water flux of the control membrane during the treatment of salt water, from 25.3 LMH to 41.5 LMH, while maintaining a 98% rejection of salt. Contact angle measurements showed an increase in the concentration of ITO NPs in the PA layer successfully increased the hydrophilicity of the membrane. The incorporation of ITO NPs was shown to increase the zeta potential of the PA layer across a wide range of pH measurements. Thermogravimetric analysis demonstrated that the ITO TFN membrane demonstrated greater thermal stability, with a thermal degradation temperature of 472°C compared to a temperature of 455°C, than the control membrane. Finally, field emission scanning electron microscopy, transmission electron microscopy, and an energy-dispersive X-ray spectroscopy acquisition system were used to show well integration of the ITO NPs in the PA layer without the formation of defects.
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- Subjects / Keywords
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- Graduation date
- Spring 2018
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.