报告题目：Multi-Functional Membranes for Advanced Separations

　　报 告 人：Ranil Wickramasinghe教授

　　工作单位：Ralph E. Martin Department of Chemical Engineering, University of Arkansas, USA

　　报告时间： 2014年11月25日（星期二）上午9:30-10:30

　　报告地点：行政办公楼201培训教室

　　报告摘要：

　　Inspired by nature, there is great interest in developing multi-functional membranes that conduct more than one function simultaneously. Here two categories of advanced multi-functional membranes will be discussed: stimuli responsive membranes that change their physical properties in response to changes in environmental conditions; catalytic membranes that both catalyze a reaction and separate the product in one step.

　　Often, in membrane based separation processes the properties of the membrane surface that contact the feed stream can have a significant effect on membrane performance. For example, membrane surface properties have been shown to affect the rate of fouling during processes such as microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Modifying just the membrane surface has the potential to retain the properties of the bulk membrane material but modify the interactions between components of the feed and the membrane surface. Here we have developed responsive membranes by surface modification. As an example of stimuli responsive membranes two examples; magnetic field responsive and ionic strength responsive membranes will be discussed

　　Magnetically responsive nanobrushes have been grafted from the barrier surface of commercially available nanofiltation membranes. In an oscillating magnetic field, movement of the magnetically responsive nanobrushes leads to suppression of concentration polarization resulting in higher permeate fluxes and better rejection during filtration. In addition we have grafted magnetically responsive nanorbrushes to the pore surface of track etched microfiltration membranes. Movement of the nanobrushes can lead to changes in pore size and hence change the rejection properties of the membrane. These novel magnetically responsive membranes could lead to a new class of fouling resistant membranes for separation applications.

　　In the second example of stimuli-responsive membranes, we have developed responsive membrane for hydrophobic interaction chromatography. Poly N-vinylcaprolactam (PVCL) chains were grown from the surface of regenerated cellulose membranes using atom transfer radical polymerization (ATRP). PVCL is a thermo-responsive polymer with a lower critical solution temperature (LCST) that depends on the concentration of salt ions present in solution. The LCST decreases below room temperature in buffer containing 1.8 M (NH₃)₂SO₄ where the polymer adopts a more hydrophobic/collapsed conformation. At low ionic strength, the LCST remains above room temperature. Ligands that respond to solution ionic strength show promise for high performance hydrophobic interaction chromatography.

　　Finally as an example of catalytic membranes, ceramic membranes have been functionalized by growing poly(styrene sulfonic acid) (PSSA) chains as well as polymeric ionic liquid (PIL) chains from the surface of ceramic membranes. Our results indicate the feasibility of hydrolyzing cellulose and hemicellulose and simultaneously removing hydrolyzed sugars. Further by removing the monomeric sugars as they are produced, production of sugar degradation products is minimized. Thus hydrolysate conditioning is significantly simplified and could potentially be eliminated.

　　报告人简介：

　　Prof Wickramasinghe obtained his Bachelor’s and Master’s degrees from the University of Melbourne, Australia in Chemical Engineering. He obtained his PhD from the University of Minnesota, also in Chemical Engineering. He worked for 5 years in the biotechnology/biomedical industry in the Boston area before joining the Department of Chemical Engineering at Colorado State University. He joined the Department of Chemical Engineering at the University of Arkansas in 2011 where he holds the Ross E Martin Chair in Emerging Technologies. Prof Wickramasinghe has published over 120 peer reviewed journal articles, several book chapters and is co-editor of a book on responsive membrane and materials. He is active in AIChE and was the Meeting Program Chair of the 2013 Annual Meeting in San Francisco. He has also served on the Board of Directors of the North American Membrane Society.

　　Prof Wickramasinghe’s research interests are in membrane science and technology. His research focuses on synthetic membrane-based separation processes for purification of pharmaceuticals and biopharmaceuticals, treatment and reuse of water and for the production of biofuels. Typical unit operations include: microfiltration, ultrafiltration, virus filtration, nanofiltration, membrane extraction etc. A current research focus is surface modification of membranes in order to impart unique surface properties. His group is actively developing responsive membranes. These membranes change their physical properties in response to changed environmental conditions. A second research focus is the development of catalytic membranes for biomass hydrolysis by grafting catalytic groups to the membrane surface.