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Membranes for Energy and Environmental Applications

Polymer membranes are critically important in addressing urgent global needs in the 21st century for energy efficient gas separations as well as reliable, sustainable, efficient access to clean energy and clean water. In the gas separation field, polymer membranes are now well established for air separation, hydrogen purification, and, increasingly, natural gas processing. We are working on new membranes based on so-called thermally-rearranged polymers, which have among the highest combinations of gas permeability and selectivity. We are also extending the range of applications where polymer membranes are used for gas separations to applications such as olefin/paraffin separation and bioethanol purification. We have an ongoing interest in exploring fundamentals of gas transport through polymers, including studies of multicomponent transport and exploring the physics underlying long-term changes in polymer transport properties, a process called physical aging.

Polymer membranes have also emerged as a leading technology to desalinate water (e.g., reverse osmosis) and are being explored for energy generation in applications such as reverse electrodialysis and pressure retarded osmosis. Furthermore, efforts are under way to develop additional applications of membranes for water purification, such as forward osmosis and membrane-assisted capacitive deionization. In each of these applications, control of small molecule transport (gases, water and ions) across polymer membranes is critically important for optimizing performance of such membranes. One aspect of our work focuses on the fundamentals of small molecule transport in polymers obeying the solution/diffusion model. Structure/property correlations have been developed for a variety of polymers, including uncharged and charged materials. The role of free volume in governing diffusion of solutes through polymers is explored. Consistent with the so-called upper bound relations in gas separation membrane materials, the existence of a water-salt permeability/selectivity tradeoff relation is observed for polymers being considered for water purification and energy generation applications. Areas where the physics of water and ion transport are both similar to and different from those of gas transport in polymers are highlighted. Additional areas of study include development of desalination and gas separation membranes via melt processing, rather than conventional processing from organic solvents.

Across many platforms of membranes, fouling mitigation is a major challenge to be addressed to achieve the most energy-efficient, cost-effective membrane filtration processes. Previously, many surface modifications and functionalized polymers were reported to prevent fouling. However, most of these techniques and materials are practically difficult to implement in water purification membranes. We have discovered surface treatment methodologies that can be used to prepare high permeability polymeric membranes from all common water purification membrane classes. These surface-modified membranes have persistent tolerance to fouling by emulsified oil, a ubiquitous contaminant in a variety of wastewaters. These membranes were prepared by depositing bio-inspired, self-polymerized, hydrophilic polydopamine.

We are also working on new barrier materials based on oxygen scavenging technology. These materials promise to extend the range of use of polymers for many high barrier packaging applications in areas as diverse as food packaging or flexible electronic displays.

Geoff Geise wins student oral presentation award at ICOM

Congratulations to Geoff Geise who won one of four student oral presentation awards at International Congress on Membrane and Membrane Processes (ICOM) for his talk on “Positron Annihilation Lifetime Spectroscopy (PALS) Characterization of Polymeric Membrane Materials for Desalination Applications”. The award, sponsored by European Membrane Society, is selected from a group of over ninety presentations.

Daniel Miller was awarded the graduate level First Prize for North American College Student Technical Writing Competition

Daniel Miller wins North American College Student Technical Writing Competition

Congratulations to Dan Miller who was awarded the graduate level First Prize in the Society of Plastics Engineers (SPE) 2012 North American College Student Technical Writing Competition sponsored by the Polymer Modifiers and Additives (PMAD) Division. The PMAD Challenge is a technical writing competition involving the critical review of one of three selected journal articles and the development of a research proposal based upon the review of the selected paper. Submissions are reviewed and judged by a team of university professors and plastics industry technical professionals. Prizes are awarded to both undergraduate and graduate student winners of the competition who demonstrate excellence in technical writing and scientific creativity. As the First Prize winner, Dan will be invited to attend the SPE’s annual ANTEC meeting in Orlando, FL on April 2-4, 2012, where he will be recognized at the Awards Ceremony.

Success in organizing 2008 International Congress on Membranes and Membrane Processes (ICOM 2008)

2008 International Congress on Membranes and Membrane Processes (ICOM 2008)

It is a great pleasure to invite you to the 2008 International Congress on Membranes and Membrane Processes (ICOM 2008). ICOM is the world’s most profound meeting for exchange of the most important aspects in fundamental and applied membrane science and engineering.

We believe that Hawaii is a perfect location for this event because it captures the cultures from the East and the West. ICOM 2008 will be a very special meeting in membrane science history.

With best wishes,

Ingo Pinnau, Chair, ICOM 2008
Benny Freeman & Yoram Cohen, Co-Chairs, ICOM 2008

Dr. Ho Bum Park, a Post-doc, publishes a Science paper

New Membrane Strips Carbon Dioxide from Natural Gas Faster and Better

A modified plastic material greatly improves the ability to separate global warming-linked carbon dioxide from natural gas as the gas is prepared for use, according to engineers at The University of Texas at Austin who have analyzed the new plastic’s performance.

Like a sponge that only soaks up certain chemicals, the new plastic permits carbon dioxide or other small molecules to go through hour-glass shaped pores within it, while impeding natural gas (methane) movement through these same pores. The thermally rearranged (TR) plastic works four times better than conventional membranes at separating out carbon dioxide through pores.

Dr. Ho Bum Park, a postdoctoral student in the laboratory of Professor Benny Freeman, also found that TR plastic membranes act quicker. They permit carbon dioxide to move through them a few hundred times faster than conventional membranes do – even as they prohibit natural gas and most other substances from traveling through their pores for separation purposes.

“If this material was used instead of conventional cellulose acetate membranes, processing plants would require 500 times less space to process natural gas for use because of the membranes’ more efficient separation capabilities, and would lose less natural gas in their waste products,” said Freeman, noting that, pound for pound, natural gas has a worse global warming impact on the atmosphere than carbon dioxide.

When developed for commercial use, the plastic could also be used to isolate natural gas from decomposing garbage, the focus of several experimental projects nationally. The TR plastic described in tomorrow’s issue of Science could also help recapture carbon dioxide being pumped into oil reservoirs in West Texas and elsewhere, where it serves as a tool for removing residual oil.

Freeman is a co-author on the Science article about the research. He holds the Kenneth A. Kobe Professorship and Paul D. and Betty Robertson Meek & American Petrofina Foundation Centennial Professorship of Chemical Engineering. Elizabeth Van Wagner, a graduate student in chemical engineering, also is a co-author in Austin.

Park, lead author of the article, initially engineered the membrane while at Hanyang University in Korea. As a research assistant in the lab of Professor Young Moo Lee, Park investigated whether plastics made of rings of carbon and certain other elements could work well at separating carbon dioxide out of gas wastes produced by power plants. Separating the greenhouse gas from other gases at power plants must occur at high temperatures, which usually destroy plastic membranes.

Lee and Park not only found that the TR plastic could handle temperatures above 600 degrees Fahrenheit, but that the heat transformed the material into the better performing membrane described in Science. That membrane breaks a performance barrier thought to affect all plastic membranes.

“I didn’t expect that the TR plastic would work better than any other plastic membranes because thermally stable plastics usually have very low gas transport rates through them,” Park said. “Everyone had thought the performance barrier for plastic membranes could not be surpassed.”

Park joined Freeman’s laboratory in Austin because of the professor’s expertise in evaluating membranes. Park then verified that the TR plastic separated carbon dioxide and natural gas well. Natural gas that is transported in pipelines can only contain 2 percent carbon dioxide, yet often comes out of the ground with higher levels of the gas, requiring this separation step.

“This membrane has enormous potential to transform natural gas processing plants,” Freeman said, “including offshore platforms, which are especially crunched for space.”

To better understand how the plastic works, Dr. Anita Hill and her group at Australia’s national science agency analyzed the material using positron annihilation lifetime spectroscopy. The method used at the Commonwealth Scientific and Industrial Research Organization suggested the hour-glass shape of the pores within the plastic, which are much more consistent in size than in most plastics.

The pores appear and disappear depending on how often the chains of chemicals that make up the plastic move.

“The plastic chains move, and as they do, they open up gaps that allow certain gas molecules to wiggle through the plastic,” Freeman said.

Freeman and Park intend to learn more about how these mobile pores behave as they develop the TR plastic for commercial purposes.

Park said, “These membranes also show the ability to transport ions since they are doped with acid molecules, and therefore could be developed as fuel cell membranes. However, a lot of research still needs to be done to understand gas and ion transport through these membranes.”

(Author: Barbra Rodriguez, Engineering School)