About this Event
3700 O'Hara Street, Pittsburgh, PA 15261
Title: Enhanced liquid-liquid Separation via Surface Engineering
Abstract: Liquid-liquid separation is critical to the chemical industry in general. Application and adoption of intensified process design offers potential reduced size, increased scalability of equipment, faster separation at a lower energy cost. In this thesis, we have studied both miscible liquid-liquid extraction and immiscible liquid-liquid separation processes.
For the separation of miscible liquid-liquid mixtures, a supported ionic liquid membrane (SILM) has been demonstrated. The two-imidazolium based ILs, i.e., 1-Butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-butyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate ([BMIM][FAP]), were tested in SILMs for the benzene-heptane separation. Both ILs show successful separation within 48 hours as indicated by Nuclear Magnetic Resonance (NMR) results. Compared to the SILM with [BMIM][FAP], the SILM with [BMIM][PF6] has lower throughput and higher selectivity. The higher selectivity can be attributed to the higher hydrophilicity of [BMIM][PF6], which results in strong repulsion against heptane. The lower throughput can be attributed to the higher hydrophilicity as well since it lowers the solubility of benzene in [BMIM][PF6]. The stability of IL in SILMs has also been investigated via multiple separation cycles. The SEM, weight change of SILM and separation results indicate that the separation efficiency of [BMIM][PF6] SILM does not degrade for up to 144 hours.
For the separation of immiscible liquid-liquid mixtures, based upon a previously developed modular phase separation & extraction (MPSE) device guiding the mixture flow through a capillary force gradient ‘field’ created by surface curvature gradient, we have designed and fabricated the coatings with the desired wettability gradient to further improve the separation efficiency. Long-term reliability of Self-Assembled Monolayers (SAMs) coating, which is hydrophobic/oleophilic, on glass surfaces were studied for this purpose. Monolayer coating in contact with water for up to 100 hours undergoes hydrolysis, which can be attributed to water penetration through the coating. “Multilayer” coating has shown much better long-term reliability in contact with water, where extra layers coatings increases the coverage and stops the hydrolysis. Such “multilayer” coating is stable after 100-hour immersion in water and organic solvents, evidenced by the unchanged contact angles and coating thickness. Applying the coatings on MPSE devices increases the separation efficiency significantly.
Committee Chair:
Dr. Lei Li
Department of Chemical and Petroleum Engineering
University of Pittsburgh
Committee Members:
Dr. Sachin Velankar
Department of Chemical and Petroleum Engineering
University of Pittsburgh
Dr. Susan Fullerton
Department of Chemical and Petroleum Engineering
University of Pittsburgh
Dr. Haitao Liu
Department of Chemistry
University of Pittsburgh
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