When 2:00 PM - 4:00 PM Aug 22, 2014
Where NCRC, Bldg. 10, Room ACR2-001
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Smart methodologies for effective separation of liquid mixtures


Gibum Kwon
Thesis Defense

Anish Tuteja, advisor

 

There is a critical need for new energy-efficient solutions for separating liquid mixtures. Among the variety of current separation technologies, membrane-based operations are attractive because they are relatively energy-efficient, and are applicable to a wide range of industrial effluents. However, traditional membrane-based technologies have disadvantages of fouling or poor separation efficiency. This research explores the systematic design of membranes, as well as, the development of smart separation methodologies to separate a wide variety of both immiscible or miscible liquid mixtures.

 

The first part of my thesis describes membranes that can separate oil-water mixtures, solely under gravity. Guided by design parameters, we have developed novel membranes with hygro-responsive surfaces, which are both superhydrophilic and superoleophobic. These membranes are oleophobic both in air and when submerged under water. Utilizing these membranes, we have developed capillary force-based separation (CFS) methodology that can separate a range of different oil-water mixtures, with > 99% efficiency. We have also engineered an apparatus that uses two CFS-based operations in parallel, to achieve continuous, solely gravity-driven separation of oil-water emulsions, with a separation efficiency > 99.9%.

 

In the second part, we have demonstrated that controlled silanization of cellulose-based filter papers can create a robust and homogeneous, hygro-responsive, coating on the filter surface. This hygro-responsive coating can be applied to filter having pore sizes as small as 10 nm. The developed membranes were found to have unique “self-cleaning” ability as water can displace oil from the membrane surface. This allows the membranes to be extremely fouling resistant. We have also demonstrated that our membranes can separate surfactant-stabilized oil-in-water emulsions with the oil droplets diameter as small as 10 nm.

 

The third part of my thesis investigates the separation methodology where the separation is triggered on-demand. In the CFS methodology utilizing hygro- responsive membranes described in previous parts, the separation takes place instantaneously as soon as water contacts the membrane. By contrast, we have also developed a new separation methodology where the separation can be triggered by applying an electric field. For an effective on-demand separation of oil-water mixtures, both water and oil must be retained above the membrane before the application of the electric field. Such membranes have been fabricated based on the understanding of the roles of surface texture along with surface chemistry. We have also successfully estimated required voltage to trigger the separation using a breakthrough pressure model that incorporates the Maxwell stress and the hydrostatic pressure. Finally, we have engineered a continuous oil-water emulsion separation apparatus that removes > 99% of the emulsified drops.

 

In the final part of this thesis, a new methodology to separate miscible components from a liquid mixture is discussed. In order to separate miscible components or azeotropes, we have developed a new energy-efficient methodology that combines liquid-liquid extraction using surfactant-stabilized emulsions, and solely gravity-driven separation of these emulsions into a single unit operation. We have demonstrated that our methodology is applicable to a wide range of separations, including separation of miscible dye, alcohols and sulfur compounds from oils as well as separation of alcohol-hydrocarbon azeotrope.