ADVANCING THE FUNDAMENTAL UNDERSTANDING OF ACTIVE LAYER FORMATION FOR DEVELOPING HIGH-PERFORMANCE NANOFILTRATION MEMBRANE

Abstract

Growing water scarcity is one of the leading challenges of our time, impacting over one-third of the world’s population. While several measures have been taken to improve water-usage efficiency among the industrial and domestic water consumption, these methods can only improve the usage of existing water resources instead of increasing them. The only approach to increasing the available water supply is through desalination and water purification. Pressure-driven membrane separation represents a highly-efficient approach to achieving molecular level separation because it requires only one-tenth energy to process an equivalent amount of liquid as compared to other industrial separation processes, e.g., evaporation and distillation, due to the latent heat of vaporization. Nanofiltration (NF) has received increasing interest in recent years due to its strong potential in addressing many of the environmental problems under growing stringent regulations and higher requirements for water quality in a variety of applications, e.g., desalination of brackish groundwater, water softening, and wastewater reuse. Increasing demands for more energy-efficient and more precise separations in the applications including desalination, chemical synthesis, and gas separation have stimulated the vigorous research interests in designing the next generation separation membranes. Herein, the overarching goal of this dissertation is to advance the fundamental understandings of the active layer formation mechanism of two most commonly used NF membranes, i.e., Thin-Film-Composite polyamide NF membranes and polyelectrolyte multilayer NF membranes in order to design and fabricate the next-generation nanofiltration membranes with multi-fold enhancement of perm-selectivity.