Development of novel nanocomposite membranes for hybrid forward osmosis processes

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Clean water is a scarce resource because only 2.5% of all the water present on Earth is suitable for direct human consumption. Simultaneously, the growing world population, industrialization, agriculture, and pollution have dramatically increased water demand. This has led to a water crisis, one of the grand challenges of the 21st century. Membrane processes, in particular reverse osmosis (RO), are now the primary separation technology used in seawater and brackish water desalination. RO is a pressure-driven process in which the feedwater is pumped at a pressure higher than the osmotic pressure difference between the feed and permeate, allowing pure water to permeate while salts are rejected. Water desalination by RO membranes is currently the best solution to tackle the water crisis. However, it is still an expensive technology, which is not affordable by many third world countries. In forward osmosis (FO), it is the difference in osmotic pressure (feed is at ambient pressure) that drives water permeation from feed (could be wastewater) to a more concentrated draw solution. If the draw solution is seawater, the FO process will dilute it, making subsequent RO less energy-intensive and less prone to fouling and scaling problems. FO cannot be a stand-alone desalination process. However, combining RO with FO into a hybrid process could significantly reduce pure water cost by membrane desalination. Unfortunately, despite the abundance of commercial RO membranes, currently available FO membranes are not adequate for such a hybrid process. The proposed research program addresses this challenge. This proposal's heart is the approach to a novel thin-film nanocomposite (TFN) FO membrane, optimized while simultaneously optimizing the RO membrane for the hybrid process. We will also introduce a new membrane characterization method based on dynamic FO tests to evaluate the osmotic membrane's structural parameter. The new method represents the fundamental shift in this research field. TFN membranes will utilize pure and functionalized cellulose nanocrystals, i.e., safe nanoparticles, which and abundant in Canada. Desalination of brackish water is vital for the oil sand industry. Another critical application of hybrid FO-RO processes in the Canadian context is removing heavy metals from wastewaters, vital for our mining, copper smelter and textile industries. Finally, students trained through this program will gain a unique combination of skills, strong fundamentals at the intersection of science and engineering, with hands-on practical experience. They will become leaders in the field, making Canada contributions to membrane separation technology recognizable and relevant.