Chair:

Dr. Lei Li, Chemical and Petroleum Engineering Department, University of Pittsburgh

Committee:

Dr. Susan Fullerton, Chemical and Petroleum Engineering Department, University of Pittsburgh

Dr. Sachin Velankar, Chemical and Petroleum Engineering Department, University of Pittsburgh

Dr. Haitao Liu, Chemistry Department, University of Pittsburgh

 Title: Graphene Wetting Transparency and Oil-water Separation using 3D-printed Devices”

Abstract: This proposal is based on the following two projects.

1. The wetting transparency of graphene provides tremendous opportunities for designing multi-functional devices in which the wettability of an atomic-thick film can be tuned by selecting an appropriate supporting substrate. Nevertheless, the underlying mechanism of the graphene wetting transparency is still under debate. Understanding the mechanisms of wetting transparency of graphene on liquid substrates and demonstrating the real-time control of surface wettability would be crucial to fundamental understanding and many applications. To overcome the challenge of studying graphene wetting transparency on a liquid substrate experimentally, we developed an experimental method, using contact angle measurements based on Neumann’s triangle model, to characterize the wetting transparency of single-layer graphene (SLG) on the liquid substrate. We systematically changed the liquid below SLG by gradually adding ethanol into the water below the SLG.  The contact angles before and after ethanol addition suggest the partially wetting transparency of SLG. Moreover, our results also demonstrate the “real-time” control of the contact angles of graphene by changing the liquid under SLG.

2. Wastewater treatment is critical to the chemical industry. Application and adoption of intensified process design and 3D-printed devices offer the prospect of revolutionizing the oil-water separation. A 3D-printed device that takes the advantage of potentially reduced size, increased scalability, and process intensification through faster extraction and phase separation at a lower energy cost is highly amenable to modular chemical manufacturing. We developed two types of devices for different oil-water separation applications. Firstly, a 3D-printed membrane device capable of separating multicomponent and multiphase liquid mixture (water/benzene/heptane) by combining supported ionic liquid membranes (SILM) and a hydrogel-coated hydrophilic/oleophobic membrane. To improve separation throughput, the 3D-printed device structure was optimized to increase the total surface area of SILM. Secondly, a novel 3D-printed device for oil-water phase separation by guiding the mixture flow through a capillary force gradient ‘field’ created via a slope design feature in between two glass slides. Surface coatings with modified hydrophilicity/oleophobicity were applied to glass slides to enhance oil-water separation efficiency through the channel. Our work demonstrated the potential of these devices for oil-water treatment applications.