Abstract
Climate change and its resulting consequences, such as changes in the natural system contributing to glacier melting, sea-level rise and evaporation, are among the challenges facing humanity. Consequently, this has resulted in increased seawater intrusion and exacerbated freshwater depletion. Population growth, on the other hand, is also putting stress on the freshwater system. Although controlling climate change and seawater desalination have proven to be a huge problem, the lack of cost-effective water purification technology has intensified the issue and has raised the need to find other ways to provide clean and safe water. While often an expensive process because of energy consumption, desalination is a promising way to address the increasing freshwater scarcity in many parts of the world. The energywater nexus is intricately related; reducing the energy consumption of water purification processes will directly impact the overall cost of the system. Reverse osmosis (RO) is the most widely used process in the current commercial desalination system; however, it still suffers from significant limitations such as high energy consumption, low flux, low salt rejection and inferior fouling resistance; therefore, a change in RO membrane technology is necessary for desalination to live up to the water challenges of the 21st century. Advances in nanotechnology have led to the development of new materials such as MoS2 that promises energy reduction in desalination and water purification. In this thesis, computational simulations were used to explore the use of nanoporous MoS2 membrane for water desalination. This was studied in relation to water desalination using MoS2 as a function of the pore size, applied pressure, temperature effects and porosity. The ion rejection order follows the trend trilayer > bilayer > monolayer for all threemembrane layers examined, and the permeability was obtained as (~ 21.68 to 38.10) L. m-2 .h-1. bar-1. For a monolayer MoS2, the water flux was greater than that for the bilayer and trilayer MoS2. The results show that operating temperatures greatly influence the desalination performance of nanoporous MoS2 membranes. Also, we studied the mechanical robustness of MoS2 as a membrane for water desalination. Findings from the molecular dynamics (MD) simulation studies on the mechanical properties and failure mechanism of monolayer and bilayer MoS2 were highlighted...
Ph.D. (Mechanical Engineering Science)