Date of this Version
Abdullah Al Balushi, Fabrication of Polyvinylidene Fluoride Hollow Fiber Membranes for Membrane Distillation, M.S. thesis, University of Nebraska-Lincoln, 2019
Desalination technologies can help humanity tap into the most abundant source of water on earth, seawater; however, desalination is an energy-demanding process. Most of the desalination plants worldwide use conventional energy resources; therefore, desalination leaves a large carbon footprint. Solar energy is an available source of energy that can be harvested and integrated into desalination systems.
Membrane distillation (MD) is an emerging purification technology that many offers many advantages over traditional desalination systems. For starters, it can utilize low-grade thermal energy to drive the separation, therefore, it can be suitably integrated into the solar-thermal energy scheme. Additionally, MD can be used to desalinate challenging water streams with minimal pretreatment, which makes it a suitable candidate for off-grid desalination in rural regions.
Herein, the lack of proper membranes and designed modules, membrane wetting and fouling, and the thermodynamic inefficiency in this system were identified as the bottleneck of the MD process, and novel solutions to tackle challenges were investigated. Polyvinylidene fluoride (PVDF) membranes suitable for MD were fabricated using nonsolvent induced phase separation (NIPS). The membranes were fully characterized to gain insight into the characteristics of MD membranes. By adjusting the parameters controlling NIPS, membrane characteristics such as porosity, thickness, geometry, surface topography, and gas permeability were controlled. The desalination performance of the membranes, as well as their fouling and wetting propensity, were evaluated and studied. Some post-processing methods were employed on the membranes to hinder their fouling and wetting tendencies in MD operation. The membranes that were fabricated in this study displayed robust performance in challenging water streams.