Membrane Drying of Ionic Liquid

<p>Room temperature ionic liquids (RTILs or, simply, ILs) are liquid salts at temperatures near or slightly above room temperature. ILs consist entirely of bulky, asymmetric organic cations and a variety of anions and, as a consequence, ILs have non-measureable vapor pressure. Due to their unique physical properties, RTILs can be used and recycled as environmentally benign solvents without loss due to evaporation. Envisioned applications range from carbon dioxide capture to battery electrolyte replacement to cellulose dissolution and processing.</p><p>Nanostructural organization of aqueous ILs and its change with water concentration are of interest in many recent studies. Water molecules can form hydrogen bond with anions in ILs. At low water concentrations water molecules form complexes mostly with anions rather than with other water molecules and begin to form clusters at high water concentrations. </p><p>Diffusion is the macroscopic result of random thermal motion on a microscopic scale which is useful to understand the movement of a single molecule while viscosity is a collective transport property for the entire system. Viscosity can increase dramatically as water concentration decreases and is accompanied by large decreases in water diffusivity and equilibrium water vapor pressure. Additionally, solvation properties can change dramatically and necessitate careful control of water concentration. Experimental measurements of [C2mim][OAc] cation and anion self-diffusivity, water self-diffusivity, and water vapor pressure are investigated. The role of temperature and water concentration on the physical-chemical characteristics is studied.</p><p>Pervaporation is a membrane separation process which has been developed for the recovery of dilute solutes from aqueous or organic bulk solvents. The removal of water from aqueous RTIL solutions using pervaporation is reported here. The driving force for separation is the difference in partial pressure of the components on the two sides of the membrane. Pervaporation may prove more versatile than solvent extraction techniques. Additionally, membrane processes may have dramatically lower energy requirements than distillation if one can identify an appropriate membrane and process for the separation problem.</p><p>A number of membranes of varying composition and molecular weight cut-off are evaluated for pervaporation with a dry gas sweep. The dependence of overall water transport rates on temperature, liquid flow and gas flow is evaluated. The mass transfer resistance of each flow channel and the membrane are determined from the results. The effects of membrane properties and the temperature dependence of water vapor pressure on performance are reported.</p>

Name thesis:degree_name

Doctor of Philosophy in Engineering

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Chemical Engineering

Grantor dc:publisher

University of Toledo

Year dc:date

2012

Author dc:creator

• Du, Xi

Contributors dc:contributor

• Lipscomb, Glenn

• Chemical Engineering
• Sustainability
• membrane
• reverse osmosis
• pervaporation
• ionic liquid
• dehydration
• energy cost

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353077367

OAI identifier oai:identifier

oai:etd.ohiolink.edu:toledo1353077367