Development of novel nanocomposite membranes for hybrid forward osmosis processes

清洁的水是一种稀缺资源，因为地球上只有2.5%的水适合人类直接消费。同时，不断增长的世界人口、工业化、农业和污染极大地增加了对水的需求。这导致了水危机，这是21世纪的重大挑战之一。膜工艺，特别是反渗透（RO），是目前海水和微咸水淡化中使用的主要分离技术。反渗透是一种压力驱动的过程，在高于进料和渗透物之间渗透压差的压力下泵送给水，允许纯水渗透，同时排除盐。反渗透膜海水淡化是目前解决水危机的最佳方案。然而，它仍然是一项昂贵的技术，许多第三世界国家负担不起。在正向渗透（FO）中，是渗透压的差异（进料处于环境压力下）驱动水从进料（可能是废水）渗透到更浓缩的提取溶液中。如果抽提液是海水，FO过程会稀释海水，使后续的RO能耗更低，更不容易出现污垢和结垢问题。FO不能是一个独立的脱盐过程。然而，将反渗透与FO结合成混合工艺可以显著降低膜脱盐的纯水成本。不幸的是，尽管有大量的商用反渗透膜，但目前可用的FO膜不足以用于这种混合过程。拟议的研究计划解决了这一挑战。本提案的核心是一种新型薄膜纳米复合材料（TFN） FO膜的方法，同时优化了用于混合工艺的RO膜。我们还将介绍一种新的基于动态FO测试的膜表征方法来评估渗透膜的结构参数。这种新方法代表了这一研究领域的根本转变。TFN膜将利用纯的和功能化的纤维素纳米晶体，即安全的纳米颗粒，这在加拿大是丰富的。咸淡水的脱盐对油砂工业至关重要。在加拿大，FO-RO混合工艺的另一个关键应用是从废水中去除重金属，这对我们的采矿、铜冶炼厂和纺织工业至关重要。最后，通过该项目培训的学生将获得独特的技能组合，在科学和工程交叉领域的强大基础，以及动手实践经验。他们将成为该领域的领导者，使加拿大对膜分离技术的贡献得到认可和相关。

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.