Four Students Received National Awards

Among 100+ Student’s Posters,
Four
UK Students Receive
Research Presentation Awards at the

2016 North American Membrane Society Annual Meeting
Bellevue, WA
May 21-25, 2016

Four UK Students Received Research Presentation Awards (PDF)

Student Poster Award Cassandra Porter, B.S. (Chemical Engineering, 2016) Transitioning to Grad School (Chemical and Materials Engineering Department)
Mentor Dibakar Bhattacharyya, Ph.D., and Yinan Wei, Ph.D., as well as Dr. DB’s Ph.D. student lab mentor Sebastian Hernandez
Award Division 2nd Place in Life Science, Biomed, and Sensors
UK Funding Source NIH-NIEHS-SRC, NSF KY EPSCOR and UK Center of Membrane Sciences
Title Functionalization of Membranes with OmpF Porins             
Abstract

Utilization of membranes in separation processes is attractive because of reduced energy costs in comparison with more typical, thermally driven methods. In addition to acting as the semipermeable barrier during reverse-osmosis (RO) separation, membranes may also act as a platform to hold other compounds. Functionalizing membranes so they are responsive to various stimuli promises even more unique applications. In this study, layer-by-layer (LbL) assembly of polycations and polyanions is utilized to immobilize porins, or cylindrical trimer beta barrel protein channels, within the pores of poly(vinylidene fluoride) (PVDF) microfiltration membranes. This poster examines methods of functionalizing the membranes with OmpF porins from Escherichia coli and characterization of the membrane during each stage of the process, including zeta potential analyses, pH responsiveness, changes in flux, and sugar rejection. Characterization of solutions containing OmpF porins is also expounded.

The major challenge was achieving an orientation of the porins parallel to the length of membrane pores so fluids may flow through their channels. The fully-functionalized membrane with OmpF porins was shown to reject 66% of D-glucose at a permeation of 3.2 LMH/bar, while the functionalized membrane lacking porins only rejected 27% at an inferior 0.59 LMH/bar, suggesting porins were properly aligned. This technique for orientating biomolecules may be applied to the immobilization of other biomolecules, such as aquaporins that have the potential to reject 100% of salts.

 

Student Poster Award Joyner Eke, Ph.D. Student (Chemical and Materials Engineering Department)
Mentor Isabel Escobar, Ph.D.
Award Divison 3rd  Place in Energy and Environment
UK Funding Source NSF KY EPSCOR and UK Center of Membrane Sciences
Title Investigation of Ultrafiltration, Nanofiltration, Biofiltration and Ozonation for the Removal of Microcystin-LR from Water
Abstract
On August 2, 2014, the greater Toledo area woke up to a Do Not Drink or Boil Water Advisory. The advisory was due to the presence of a cyanotoxin (algal toxin) produced by cyanobacteria in Lake Erie called microcystin-LR in the drinking water supply that has a WHO provisional guideline of 1 mg/L. Upon entering the City of Toledo Collins WTP crib at the Lake Erie intake, potassium permanganate is added to the water for mussel control. While potassium permanganate is needed to control mussels, it lyses cyanobacteria cells, releasing algal toxins to the water. The water is then pumped nearly three miles to the Low Service Station, where powdered activated carbon (PAC) is added to the water for taste and odor control, and the water is transported approximately six miles to the WTP (High Service Station). PAC is generally effective for removal of algal toxins through adsorption onto its surface. At High Service, alum, lime and soda ash are added to the water for coagulation-flocculation, softening, and removal of metals. The water is then sand filtered, carbonated and chlorinated before being sent to the distribution system. However, traditional physicochemical water treatment processes, such as coagulation-sedimentation-filtration, have been shown to only be partially effective for the removal of whole algal cells and not effective for the removal of algal toxins. Furthermore, chlorination is effective for oxidizing algal toxins at relatively high free chlorine concentration as long as the pH is below 8; however, for corrosion control, Toledo water is kept at a pH above 9. Therefore, the treatment process was not enough of a barrier to prevent microcystin-LR from entering the drinking water supply. By August 4, the water treatment plant increased its PAC dosage by nearly four times, and while the toxin was removed, a significant amount of PAC sludge was produced and the cost of PAC addition was unsustainable. The objective of this project is to study alternative water treatment processes, namely membrane separations, biofiltration and ozonation, for the effective removal of algal toxins.

 

Student Poster Award Michael Detisch, Ph.D. Student (Chemical and Materials Engineering Department)
Mentor Dibakar Bhattacharyya, Ph.D. and John Balk, Ph.D.
Award Division 2nd Place in Materials, Modeling and Novel Applications
UK Funding Source NIH-NIEHS-SRC and by NSF KY EPSCOR and UK Center of Membrane Sciences
Title Nanoporous Metallic Films as Components of Composite Membranes
Abstract

Magnetron sputtering is a physical vapor deposition method that allows the deposition of thin films of different materials on a variety of substrate materials.  Sputtering allows fine control of the film thickness and composition through co-sputtering from multiple target materials.  As part of this study thin films have been sputtered on top of microfiltration polysulfone membrane substrates.  The resulting composite membranes have remained permeable under testing with deionized water.  The base Nanostone PS35 membrane showed permeability of 1941 LMH at 1.7 bar, while the membrane-film composite had a permeability of 163 LMH at 1.7 bar.

Thin films of metallic alloys deposited in this way can be made nanoporous through a process called dealloying.  The process involves the removal of the less noble component of an alloy by an etchant creating an open nanoporous structure.  The pores created by this method commonly vary from a few nanometers to a few hundred nanometers. 

This research focuses on using magnetron sputtering to deposit precursor metallic alloy films from 100 to 250nm thick on top of porous membrane substrates.  These dense precursor films are then dealloyed to produce pore/ligament structures of approximately 10nm characteristic size.  In these studies iron and palladium were chosen as a precursor alloy.  A portion of the iron is etched away with sulfuric acid to generate a nanoporous structure.  Fe/Pd nanoparticles have been used with success to dechlorinate various chlorinated organic compounds (COCs) for wastewater treatment purposes.  Nanoporous Fe/Pd shows promise to be similarly reactive with COCs due to its high surface area and curved structure.  Taken together this means the composite membrane produced by fabricating a high surface area, porous Fe/Pd film on top of a microfiltration or nanofiltration membrane substrate shows promise both as a catalyst and as a platform for separations.

 

Student Poster Award Hongyi Wan (Derek), Ph.D. Student (Chemical and Materials Engineering Department)
Mentor Dibakar Bhattacharyya, Ph.D. and Lindell Ormsbee, Ph.D.
Award Division 2nd Place in Energy and Environment
UK Funding Source NIH-NIEHS-SRC and UK Center of Membrane Sciences
Title Iron Nanoparticle Functionalized Membrane for PCB Degradation from Water
Abstract

The development of functionalized membranes with catalytic metal nanoparticles provides an effective method of environmental remediation and wastewater treatment. Polyvinylidene fluoride (PVDF) is an excellent polymer for both chemical and mechanic resistance as well as thermal stability. By immobilizing zero-valent iron (ZVI) or bimetallic nanoparticles (NPs), functionalized PVDF membranes can be used in chlorinated organic treatment. Polyacrylic acid (PAA) was polymerized inside PVDF membrane pores to maximize iron adsorption. Adsorbed iron was reduced to form NPs in-situ in order to prevent metal ion loss, NPs aggregation and iron precipitation. Furthermore, tunable membrane pore size could be achieved by changing the environmental pH because of ionization of PAA.

This study includes three major aspects: 1. Reactivity toward model toxic chlorinated organic compounds--polychlorinated biphenyl (PCBs) in both batch and convective flow study; 2. NPs characterization of its average sizes, composition, extent of oxidation and distribution inside membrane pores; 3. Simulating pH responsive behavior and PCB reaction within the membrane.

PCBs are not biodegradable and tend to cycle between air, water and soil, which might accumulation in living organisms. PCBs dechlorination can be achieved by Fe/Pd reductive pathway. The hydrogen, generated from reaction between ZVI and water, gets activated by Pd for hydrodechlorination. In batch study, 95% of PCB 126 ([Co]=15 µM) was consumed and 67% was converted to biphenyl in 5 hours. In convective flow study, 96% of PCB 126 was consumed at 26s residence time. However, the final product biphenyl still showed toxicity. In order to degrade biphenyl, the further oxidative pathway was combined to break down the aromatic ring and eventually form organic acid. Both iron oxide with H2O2 method (Fenton Reaction) and persulfate method significantly reduced toxicity of the products of PCB degradation.

Fe/Pd NPs size distribution was analyzed by SEM and TEM (TEM samples were prepared by Focus Ion Beam) and the average size of NPs was 19.4±3.2nm. Iron core and discontinuous palladium shell was tested by STEM-EELS line scan and elemental mapping and extent of oxidation was studied by XRD. Furthermore, membrane permeability change from 32.2LMH/bar to 1.1LMH/bar when environmental pH change from 2 to 6.5. The pH-responsive behavior was simulated and fitted with experimental data, which is a part of PCBs reactivity model.

This research is supported by the NIEHS-SRP grant P42ES007380, and by the NSF KY EPSCOR program. Full scale PVDF membranes were provided by Nanostone/Sepro (USA).