Date of Graduation

12-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Chemical Engineering

Advisor/Mentor

Ranil Wickramasinghe

Committee Member

David Ford

Second Committee Member

Ed Clauson

Third Committee Member

Wen Zhang

Fourth Committee Member

Xianghong Qian

Keywords

Aromatic separation, Ionic liquids, Membrane separation

Abstract

Ionic liquids represent an emerging attractive material in membrane technology. The central theme of this doctoral dissertation is to develope novel membranes using ionic liquids. Two different approaches were used to prepare ionic liquid membranes including the immobilization of ionic liquid within the membrane pores or the use of pressure assembly method to deposit a selective ionic liquid layer on the top membrane surface.

In chapter 2, imidazolium ionic liquids with three different alkyl halides were successfully synthesized and used to prepare supported ionic liquid membranes (SILMs). SILMs preraper were tested for aqueous and nonaqueous applications. For nonaqueous applications, the trend of separation was found to be divinylbenzene>styrene>toluene, which was attributed to the extended conjugation of π electron cloud. For nonaqueous system, preferential separation of different dyes was achieved.

In chapter 3, SILMs have been tested for the fractionation of organic compounds. Fractionation of a feed stream consisting of benzene, naphthalene, and phenanthrene in tetradecane and cis- and trans-stilbene in hexane were investigated. Differences in the π electron cloud density of the aromatic solutes influence their interactions with the imidazolium cation which can affect the rates of transport. In the case of the three aromatic solutes the degree of conjugation and molecular weight increase in the order of benzene, naphthalene, and phenanthrene. However, for cis-and trans-stilbene, the mass transfer coefficient was larger for all three ionic liquids. Aqueous SILM was used as the liquid membrane phase to fractionate two nucleobases: thymine and cytosine in water. The mass transfer coefficient for thymine was 5.5 times greater than cytosine indicating the possibility of exploiting multimodal interactions fractionate compounds.

Chapter 4 constitutes the preparation of novel polyionic liquid augmented membranes that were fabricated using pressure assisted self-assembly and employed for π- electron cloud mediated separation of aromatics from their aliphatic homologs. The prepared membranes can be employed for the fractionation of aromatics such as benzene, toluene, p-xylene, nitrobenzene. Further, these augmented membranes were demonstrated to have preferential separation of one stereoisomer over others.

Finally, chapter 5 includes conclusions drawn out of this research and future directions and recommendations.

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