Designing and Developing Surface-Engineered Fouling-resistant Ultrafiltration (UF) Pre-treatment Membranes for Water Desalination

Ultrafiltration (UF) processes have widespread applications in a number of scientific and engineering fields including seawater/brackish water purification, wastewater treatment, water reuse and reclamation, food, dairy, paper, chemical and biomedical industry. Polymeric UF membranes are invariably used in almost all of these applications. Of paramount interest is the use of polymeric UF membranes as pre-treatment in reverse osmosis (RO) desalination plants. Pre-treatment of the seawater by UF process is an important and integral step in the RO desalination process. A major challenge that limits the efficiency of the UF pre-treatment step is membrane fouling by proteins and other biomolecules present in the feed stream. The current state-of-the-art polymeric UF membranes, developed to date, are much prone to this type of fouling, which results not only in the flux decline reducing the efficiency of the pre-treatment process but also increases the energy demand for optimally running ultrafiltration process. To counteract this problem, membranes need to be frequently cleaned, often with aggressive chemicals which account for various problems including degradation of membranes integrity, shortening of their life, and the most seriously, cause environmental problems. Thus, huge sums of money and resources can be saved if the fouling resistance of the UF membranes can be enhanced. Seawater desalination is a multi-billion dollar industry in the Kingdom of Saudi Arabia. With the largest hybrid-desalination (producing 728million liters/day) plant at Al-Khair, Saudi Arabia is also producing the largest quantities (9,170,391 m3/day) of commissioned desalted water worldwide. Among various technologies developed to separate water from salt, use of membrane technology has been on the forefront. In this research, we propose to design and develop organic fouling resistant UF membranes with enhanced characteristics and performance compared to the existing commercial UF membranes. Surface modification of commercially available UF membranes will be performed to fabricate the fouling-resistant UF membranes via Spin-Assisted Layer-by-Layer (SA-LbL) assembly. Ultra-thin (~30-100 nm) films of advanced polymer/copolymer materials (e.g. polyelectrolytes and/or zwitterions) known for their antifouling properties will be deposited onto the surface of UF membranes. These materials have surface-enriched moieties that discourage the irreversible adhesion of foulants. Furthermore, the nano-thick film deposited onto the surface of UF membranes is expected to minimally affect the performance of membranes. These unique characteristics together with functionalities from polymer materials provide UF membranes with many outstanding properties as separation membranes. The surface-modified UF membranes will be characterized, evaluated and optimized for the best combination of coating thickness, chemistry and morphology to yield membranes with the most efficient, environment-friendly and economical seawater pre-treatment characteristics.