Gordon Research Conference 2004
New London, NH, 1 – 6th August 2004
Abstracts of Attendees
Conor Braman’s Abstract
Water transport and fouling properties of crosslinked poly(ethylene glycol)
C. Braman, University of Texas at Austin
B. Freeman, University of Texas at Austin
All current ultrafiltration membranes are finely porous and are, therefore, subject to fouling by particulates, organics, and other wastewater components, resulting in a dramatic decline in the water flux (Ho 1999). Our approach to enhancing the severely limited fouling resistance of conventional ultrafiltration membranes is based on coating them with highly water permeable, nonporous, fouling resistant polymers. Crosslinked poly(ethylene glycol) (PEG) is used as the base material for the coatings because it is highly hydrophilic and has shown resistance to protein attachment (Ostuni 2001).
UV-induced radical polymerization of PEG diacrylate (PEGDA), which contains 13 PEO units, and PEG acrylate (PEGA), which contains 7 PEO units, was used to prepare crosslinked PEG films. The composition of the initial polymerization mixture used was between 20/80 and 100/0 for (PEGDA +PEGA)/water, with the focus being on those samples prepared with higher initial water concentration.
For the freestanding films, data on water flux and fouling resistant properties will be presented. Polymerization induced phase separation (PIPS) and its relevance to polymer transport properties will be discussed as well.
To characterize the properties of PEG films in crossflow experiments, a composite crosslinked PEG membrane was prepared. This composite membrane consists of a porous membrane support and ideally a thin, approximately one micron, dense coating of crosslinked PEGDA. An interfacial polymerization strategy was used to prepare a thin, uniform film at the membrane surface. This strategy is still in the development stage, and the challenges therein will be discussed. Preliminary water transport and fouling properties of these composites have been characterized and will be described. The utility of these composites is shown by comparing their performance with that of uncoated porous ultrafiltration membranes.
Emanuele Ostuni, R. G. C., R. Erik Holmlin, Shuichi Takayama, and and G. M. Whitesides (2001). “A Survey of Structure-Property Relationships of Surfaces that Resist the Adsorption of Protein.” Langmuir (17): 5605-5620.
Ho, C.-C. Z., A. L. (1999). “Effect of membrane morphology on the initial rate of protein fouling during microfiltration.” Journal of Membrane Science (155): 261-275.[/tab]
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Hao Ju’s Abstract
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Membrane Performance Modification via Mechanical Stretching
B. McCloskey, University of Texas at Austin
H. Ju, University of Texas at Austin
B. Freeman, University of Texas at Austin
D. Lloyd, University of Texas at Austin
D. Lawler, University of Texas at Austin
L. Worrel, University of Texas at Austin
J. Moorhouse, University of Texas at Austin
Y. Wu, University of Texas at Austin
One of the primary concerns in the application of microfiltration and ultrafiltration membranes is membrane fouling. There are numerous membrane properties (and foulant properties) that have an affect on fouling mechanisms and subsequently membrane performance. The literature has suggested that a membrane’s pore aspect ratio (defined as the ratio between the pore’s major and minor axis) has an affect on certain bacteria attachment to poly(ether sulfone) (PES) membranes. Therefore, by physically controlling the aspect ratio of membrane pores (i.e. through a membrane stretching process), the fouling characteristics of the membrane can be modified. The purpose of the research presented here is to look at the effect that membrane pore geometry has on membrane performance (most notably flux and rejection) when filtering solutions containing various foulants.
In this study, ~0.2 mm mean pore diameter phase inversion PES membranes were used to purify three solutions in dead-end and crossflow filtration. One can see from the data that uniaxially stretching these membranes to 150% of their original length increases pure water flux. Stretching also increases flux and reduces flux decline, but has little effect on rejection for feed solutions containing 1g/L BSA. Stretching has little effect on flux, flux decline, and rejection for feed solutions containing oil-water emulsions at 1500 ppm. After small amounts of time, stretching reduces flux and rejection for the microsphere solution, but the flux and rejection for stretched and unstretched samples converge to a single value for longer operating times.
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Bryan McCloskey’s Abstract
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Membrane Performance Modification via Mechanical Stretching
B. McCloskey, University of Texas at Austin
H. Ju, University of Texas at Austin
B. Freeman, University of Texas at Austin
D. Lloyd, University of Texas at Austin
D. Lawler, University of Texas at Austin
L. Worrel, University of Texas at Austin
J. Moorhouse, University of Texas at Austin
Y. Wu, University of Texas at Austin
One of the primary concerns in the application of microfiltration and ultrafiltration membranes is membrane fouling. There are numerous membrane properties (and foulant properties) that have an affect on fouling mechanisms and subsequently membrane performance. The literature has suggested that a membrane’s pore aspect ratio (defined as the ratio between the pore’s major and minor axis) has an affect on certain bacteria attachment to poly(ether sulfone) (PES) membranes. Therefore, by physically controlling the aspect ratio of membrane pores (i.e. through a membrane stretching process), the fouling characteristics of the membrane can be modified. The purpose of the research presented here is to look at the effect that membrane pore geometry has on membrane performance (most notably flux and rejection) when filtering solutions containing various foulants.
In this study, ~0.2 mm mean pore diameter phase inversion PES membranes were used to purify three solutions in dead-end and crossflow filtration. One can see from the data that uniaxially stretching these membranes to 150% of their original length increases pure water flux. Stretching also increases flux and reduces flux decline, but has little effect on rejection for feed solutions containing 1g/L BSA. Stretching has little effect on flux, flux decline, and rejection for feed solutions containing oil-water emulsions at 1500 ppm. After small amounts of time, stretching reduces flux and rejection for the microsphere solution, but the flux and rejection for stretched and unstretched samples converge to a single value for longer operating times.
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Rajeev Prabhakar’s Abstract
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Not Available
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Alyson Sagle’s Abstract
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Characterization of Commercial Reverse Osmosis Membranes
A. Sagle, University of Texas at Austin
B. Freeman, University of Texas at Austin
Reverse osmosis (RO) membranes have been used for several decades to purify water. Most commercial RO membranes today are thin film composites of crosslinked polyamides on a polysulfone support. The membranes used in this work, GE Osmonics AG and AK RO membranes, are thin film composites of this nature. Work was done to characterize the performance of these materials. As a starting point, water flux measurements in dead-end cells were done with phosphate buffered water of pH 7.4. Fouling by oil was also investigated in dead-end cells by measuring the flux and rejection from an oil/water emulsion. It was found that the surfactant used to create the emulsion was also contributing to membrane fouling. Further oil/water fouling studies will be conducted with a different surfactant. Protein fouling and rejection was also tested in both dead-end and crossflow configurations. The RO membranes showed excellent rejection of protein with a nominal decrease in flux in a crossflow configuration.
In addition to fouling studies, chemical stability of the membranes was also tested. Polyamide membranes have shown that exposure to even small levels of chlorine greatly reduces their performance. Chlorine is often used in water treatment processes as a disinfectant or for membrane cleaning. Studies were done to examine the chemistry behind the degradation and the effects of the amount of chlorine exposure on the membrane performance. FTIR analysis showed that the polyamide underwent ring chlorination as the literature suggests. This basic work characterizing commercial membranes lays a foundation for future research into the modification of membranes to reduce fouling. Possibilities being considered for modification include grafting molecular branches onto the membrane surface. A second method could be applying a hydrophilic thin coating to the surface. This can be done via several methods (i.e. hydrogen abstraction, interfacial reactions, or redox reactions). A wide range of materials are available for use in modifying membrane surfaces, however factors such as mechanical strength, hydrophilicity, and functionality all must be considered.
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Yuan-Hsuan Wu’s Abstract
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Membrane Performance Modification via Mechanical Stretching
B. McCloskey, University of Texas at Austin
H. Ju, University of Texas at Austin
B. Freeman, University of Texas at Austin
D. Lloyd, University of Texas at Austin
D. Lawler, University of Texas at Austin
L. Worrel, University of Texas at Austin
J. Moorhouse, University of Texas at Austin
Y. Wu, University of Texas at Austin
One of the primary concerns in the application of microfiltration and ultrafiltration membranes is membrane fouling. There are numerous membrane properties (and foulant properties) that have an affect on fouling mechanisms and subsequently membrane performance. The literature has suggested that a membrane’s pore aspect ratio (defined as the ratio between the pore’s major and minor axis) has an affect on certain bacteria attachment to poly(ether sulfone) (PES) membranes. Therefore, by physically controlling the aspect ratio of membrane pores (i.e. through a membrane stretching process), the fouling characteristics of the membrane can be modified. The purpose of the research presented here is to look at the effect that membrane pore geometry has on membrane performance (most notably flux and rejection) when filtering solutions containing various foulants.
In this study, ~0.2 mm mean pore diameter phase inversion PES membranes were used to purify three solutions in dead-end and crossflow filtration. One can see from the data that uniaxially stretching these membranes to 150% of their original length increases pure water flux. Stretching also increases flux and reduces flux decline, but has little effect on rejection for feed solutions containing 1g/L BSA. Stretching has little effect on flux, flux decline, and rejection for feed solutions containing oil-water emulsions at 1500 ppm. After small amounts of time, stretching reduces flux and rejection for the microsphere solution, but the flux and rejection for stretched and unstretched samples converge to a single value for longer operating times.
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