Tarabara Research Group
These pages complement the research summary and schematic overview given on the home page by highlighting our recent work in five areas:
- Research area 1: Membrane separation of oil-in-water
- Research area 2: Membrane materials for reactive separations
- Research area 3: Virus removal and inactivation
- Research area 4: Virus detection
- Research area 5: Plant-derived coagulants for water treatment
Navigate the tabs below to find out what we do on each of the five research topics listed above. More details can be found in our publications.
- Research area 1
- Research area 2
- Research area 3
- Research area 4
- Research area 5
MEMBRANE SEPARATION OF OIL-IN-WATER EMULSIONS
All things that share the same element tend
to seek their own kind.
Things earthy gravitate towards earth, things aqueous flow towards one another, things aerial likewise
- whence the need for the barriers which keep them forcibly apart.
Marcus Aurelius. Meditations. Book Nine (M. Staniworth's translation)
Emulsified oil is a component of wastewater generated by petroleum refineries, food processing facilities, metalworking operations, oil extraction and many other industries. Removing the oil phase is often necessary to meet environmental regulations. Membrane filtration can remove drops smaller than 10 microns (a challenging task where other high throughput technologies fail!) but membrane fouling by oil hinders a broader acceptance of this approach. Current studies in our research group focus on understanding mechanisms of membrane fouling by emulsified oil and developing methods of mitigating this problem.
The Direct Observation Through the Membrane video recorded by Emily Tummons (2016 Ph.D. graduate) during her research stay at SMTC. The video is a survey of a microfiltration membrane surface challenged by an SDS-stabilized emulsion of hexadecane in water.
We use modeling of oil-membrane interactions, oil adhesion studies, and bench-scale membrane separation tests to gain a quantitative understanding of oil drop behavior on various membrane surfaces. Our experimental methods include surface and interfacial tension measurements, light diffraction for drop size analysis, confocal microscopy, oil adhesion measurements using quartz crystal microbalance with dissipation (QCM-D), and Direct Observation Through the Membrane (DOTM) studies. The DOTM work is a collaboration with Dr. Jia Wei Chew from the Singapore Membrane Technology Center (SMTC) and is supported by the US NSF funded project "PIRE: Water and Global Commerce: Technologies to enable environmental sustainability in global markets" (grant OISE-1243433).
Charifa Hejase (PhD candidate) performs DOTM tests during her visit to Singapore Membrane Technology Center.
The research on this topic is currently carried out by Charifa Hejase (Ph.D. candidate) and Vince Marinelli (undergraduate research assistant) with earlier contributions by Dr. Emily Tummons (2016 Ph.D. graduate), Ms Seyma Kucuk (2018 MS graduate) and Dr. Ira Kolesnyk (visiting scientist from the Kyiv-Mohyla Academy, Ukraine). Recently, we started collaborating with the group of Prof. Dr.-Ing. habil. Anja Drews (Hochschule fur Technik und Wirtschaft Berlin), who is an expert on Pickering emulsions.
For more details on our research in this area see our recent publications:
- Tummons, E. N.; Chew, J.-W.; Fane, A. G.; Tarabara, V. V. Ultrafiltration of saline oil-in-water emulsions stabilized by an anionic surfactant: Effect of surfactant concentration and divalent counterions. J. Membr. Sci. 537 (2017) 384-395. DOI: 10.1016/j.memsci.2017.05.012
- Tummons, E. N.; Tarabara, V. V.; Chew, J.-W.; Fane, A. G. Behavior of oil droplets at the membrane surface during crossflow microfiltration of oil-water emulsions. J. Membr. Sci. 500 (2016) 211-224. DOI: 10.1016/j.memsci.2015.11.005
MEMBRANE MATERIALS FOR REACTIVE SEPARATIONS
In our work on reactive separations we design functional membranes by incorporating reactive nanoparticles into the membrane structure. We do this in several ways.
Figure 1: Conceptual illustration of a hierarchical nanocatalyst based on bimetallic (Pd-Au) as catalytic nanoparticles and exfoliated graphite nanoplatelets (xGnP) as catalyst support. The Pd-Au nanoparticles have core-shell morphology with Au and Pd forming the core and the shell, respectively.
(Source: Environ. Sci. Nano. 3 (2016) 453-461, graphical abstract)
One approach employs exfoliated graphite nanoplatelets, xGnPs for short, as a support material for reactive nanoparticles. We think of xGnPs as "carrier mats" that immobilize and "deliver" nanoparticle-based reactive sites into the membrane matrix to ensure that the smaller, reactive nanoparticles are not shed by the membrane into the permeate flow. The resulting nanomaterials have a hierarchical structure (Figure 1) where the xGnP and different components of nanoparticles (which can be bimetallic, for example) correspond to different levels of the hierarchy. By populating different levels of this hierarchy to different extents we can manipulate membrane structure and reactivity independently. Based on this concept, we designed membranes with embedded hierarchical Pd-based nanocatalysts (xGnP-supported Pd and Pd-Au nanoparticles) for reductive dehalogenation of trichloroethylene (TCE) in batch and membrane reactors. With Pd-Au/xGnP-filled membranes, we achieved 96% removal of TCE at the specific permeate flux of 47.4 L/(m2.h). The reactive flux is 80 times higher than what the reactive flux measured in control experiments with commercial Pd/Al2O3 catalyst. To our knowledge, this was the first demonstration of high throughput TCE dechlorination in a membrane reactor. In collaboration with our colleagues from Istanbul Technical University, we also implemented this approach with hollow fiber membranes.
Figure 2: Schematic illustration of a cross-section of an asymmetric ceramic membrane with the permeate side coated by catalytic nanoparticles and exposed to UV light for flow-through photocatalysis.
(Source: J. Membr. Sci. 514 (2016) 340-349, graphical abstract)
Another approach entails modifying membrane surface (and surface only) with reactive nanoparticles. Figure 2 illustrates how an outside surface of a tubular membrane can be decorated by photocatalyst to make a photocatalytic membrane for flow-through reactive separations. The challenge is to create a conformant mono- or submonolayer coating of nanoparticles (photocatalyst!) on a microporous support (membrane) without plugging the micropores. In collaboration with Dr. Andre Ayral and Dr. Stephanie Roualdes from the European Institute of Membranes, we developed such coatings using two methods: layer-by-layer self-assembly and plasma-enhanced chemical vapor deposition. See Research Area 3 for the description of how permeate-side photocatalysis can be employed to inactivate viruses in a high throughput membrane reactor.
This work has been supported by the NSF funded project "PIRE: Water and Global Commerce: Technologies to enable environmental sustainability in global markets" (grant OISE-1243433).
VIRUS REMOVAL AND INACTIVATION
"... Yet I have found that the sap of leaves attacked by the mosaic disease
retains its infectious qualities even after filtration ..."
Ivanovski, D., Uber die Mosaikkrankheit der Tabakspflanze, St. Petersb. Acad. Imp. Sci. Bul. 35 (1892) 67-70.
The smallest of all known microorganisms, viruses are difficult to detect and remove. For this reason and because of their low infectivity doses and high survivability, pathogenic viruses can pose a formidable challenge as a public health threat. Work in our laboratory focuses on the development of low footprint water treatment and water reuse technologies that synergistically combine membrane separation with UV disinfection to remove and inactive viruses.
As an example, we designed a photocatalytic membrane reactor with permeate-side photocatalysis (Figure 1). The membrane in this reactor serves as photocatalyst support and removes poisons and scavengers upstream from photocatalysis. The efficient use of UV photons results in higher virus removals to allow for larger pore size membranes and higher permeate fluxes. To our knowledge, the paper was the first report on the use of photocatalytic membranes for virus removal and inactivation. We have tested this technology in experiments with lake water seeded with human adenovirus 40 (HAdV40) and showed ~3 log removal of infective HAdV40 at the specific permeate flux of ~3300 L/(m2.h.bar).
Figure 1: Conceptual illustration of the hybrid membrane filtration-UV disinfection process.
(Source: Separ. Purif. Technol. 149 (2015) 245-254, graphical abstract)
Dr. Bin Guo (2016 Ph.D. graduate) and Dr. Samuel Snow (now a faculty member at LSU) have been key contributors to this project. We also collaborate with Dr. Irene Xagoraraki who is an environmental virologist.
Current research focuses on the effect of membrane fouling on downstream photocatalysis and on novel target-specific catalysts. Our goal is to translate the technology know-how and fundamental understanding of membrane-UV hybrid process into water reuse applications including membrane bioreactors.
"One has in practical life to act upon probabilities, and ... act with vigor without complete certainty."
Bertrand Russell, 1960
Globally, waterborne diseases kill millions of people per year, and many of the disease outbreaks result from undetected microbial agents, particularly viruses. Concentration and recovery of these pathogens from water samples to volumes amenable to rapid assays (a few mL) is a critical first step in virus quantification (Figure 1). The variability and complexity of viruses and water composition lead to highly variable virus recoveries that are often unacceptably low. These problems frequently prohibit definitive association of waterborne viruses with specific disease outbreaks. The problem and specific challenges are discussed in our recent review paper.
Figure 1: Virus preconcentration and recovery from water remains the most significant challenge in virus detection.
Research in our laboratory focuses on the development of a sample processing technology that ensures fast and predictably high recovery of viruses from water.
We have proposed and demonstrated a conceptually novel method of virus recovery from water based on membranes coated with anti-adhesive "skins" of nanoscale thickness. These polyelectrolyte multilayer coatings require less than an hour to deposit and increase pre-elution recovery of bacteriophages from DI water and an MBR wastewater treatment plant effluent. In a followup project, we designed virus eluents to disrupt virus-membrane interactions and maximize virus recovery. We applied this approach to concentrate and recover human adenovirus serotype 40 (HAdV 40) from a number of water matrices. The results showed high HAdV 40 post-elution recoveries from ultrapure water (99%), tap water (~91%), and high carbon content surface water (~84%) - a major improvement over the status quo (very low adenovirus recoveries have been reported to date for other methods.)
Our group's engagement with this topic begun with the Ph.D. project of Elodie Pasco (2012 Ph.D. graduate) and was continued in the Ph.D. work of Hang Shi (2017 Ph.D. graduate). Currently, Xunhao Wang builds on our earlier results as he studies virus adhesion to fomites and personal care products.
We also develop novel methods of virus detection on surfaces of different chemistries and morphologies. These studies combine experimental measurements that employ quartz crystal microbalance with numerical modeling of virus-surface interactions.
PLANT-DERIVED COAGULANTS FOR WATER TREATMENT
And I should raise in the east
A glass of water
Where any-angled light
Would congregate endlessly
Coagulation is one of the main unit processes used in water treatment worldwide. Commonly used coagulants such as Al2(SO4)3 and FeCl3 are not affordable or otherwise unavailable in many settings. Coagulants derived from local vegetation can be a cost-effective alternative to inorganic salts. In a striking example, seeds of Moringa oleifera have been shown to yield an effective coagulant. This is significant because Moringa oleifera is broadly cultivated in tropical and subtropical areas spanning large swaths of the developing world where water treatment infrastructure is lacking.
We use chemical analyses, measurements of physicochemical properties that govern colloidal stability, and standard jar testing to evaluate the coagulation efficiency of Moringa oleifera with respect to model and natural waters. Our goal is to understand mechanisms of coagulation by Moringa oleifera and, ultimately, design practical guidelines for a cost-effective and safe application of this coagulant. We also explore other natural materials as sources of cationic species that can be used for coagulation.
The project is in its early stages with the first manuscript still in the making. Early contributors to the project were Brendan Wrobel and Daniel Thomas (both - undergraduate research assistants), Noah Burns (high school research intern) and Remi Gonety (Honors College research scholar). Akshay Murali (Ph.D. student and ESPP Fellow) works on the project now.
We thank Phipps & Bird for making PB-900 programmable jar tester available to us through the company's academic support program.