Date of Graduation

12-2015

Document Type

Thesis

Degree Name

Master of Science in Chemical Engineering (MSChE)

Degree Level

Graduate

Department

Chemical Engineering

Advisor/Mentor

Hestekin, Jamie A.

Committee Member

Wickramasinghe, S. Ranil

Second Committee Member

Beitle, Robert R. Jr.

Keywords

Applied sciences; Earth sciences; Flowback; Hydraulic fracturing; Membrane; Nanofiltration; Polysulfone

Abstract

The use of hydraulic fracturing has resulted in significant increases in the yield of oil and natural gas, as water pumped into wells at high pressure cracks the formations and releases the hydrocarbons that are locked in the rocks. This process has created large volumes of brackish water that is very difficult to process and is often disposed of into injection wells. Suspended solids and some dissolved solids are more readily removed, but the multivalent ions found in certain salts can precipitate in a well and complicate the reuse of flowback in future hydraulic fracturing operations.

Nanofiltration, a membrane separation technique, has the potential to remove these salts at a much lower cost than desalination techniques such as reverse osmosis. Secondary interactions, such as charge, can be added through functional groups to increase the rejection of the positive ions and allow for the reuse of flowback in operations where low quality water is acceptable.

To produce these membranes, polysulfone was reacted with trimethylchlorosilane and trimethylamine to produce a positively charged functional groups that would allow for selective rejection of ions. While the two-step reaction to produce these functional polymers was successful, the polymer created did not have the properties required to produce a membrane.

The positively charged polysulfone had functional groups that made it soluble in water, and membranes cast from this polymer readily swelled and deformed when exposed to most fluids, including water and air. While some characteristics of these membranes, such as pore diameter, were comparable to commercial membranes, the solubility characteristics made filtration testing impossible. However, while the final positively charged polymer was unusable, the functional precursor polymer was successfully synthesized and can be used with other methods to produce the positively charged polymers.

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