Forward osmosis of water across ionic membranes for desalination

Abstract

Although 70% of the earth is covered by water, only 3% is available for consumption in daily human life or for industrial use. With the sharp rise in population over recent decades, the growing demand for fresh water has led to water scarcity and water stress. As a result, a total of 2.7 billion people suffer from water scarcity for at least one month per year[1]. The lack of pure water has threatened the development of many countries and motivates us to seek novel approaches to obtain pure water via the desalination of seawater. These can be mainly divided into two categories, one using membranes, and the other using evaporation. Here, we focus on a membrane-based method to purify seawater, i.e. forward osmosis. ☐ The objective of this thesis is to test the effectiveness of an ionic liquid to draw water from a saltwater solution across an ionic membrane by forward osmosis. Due to the high cost of ionic liquid, most of the experiments were conducted with Potassium Acetate solution which is thought to have similar physical properties to ionic liquid. Forward osmosis experiments were conducted using a baseline Nafion115 membrane as well as proprietary membranes supplied by Xergy Inc. Water transport was measured at varying temperatures and concentrations of Potassium Acetate solution. These measurements were then used to create a simple model for the design of a shell-and-tube mass exchange apparatus.