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CO2-Responsive O/W Microemulsions Designed for Treating Oil-Contaminated Drill Cuttings
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- Author / Creator
- Chen, Xiangyu
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The oil-based drilling fluids are mainly used to explore hydrocarbon resources. During the drilling operation, a significant amount of oil-contaminated drill cuttings, which are crushed rocks, sands and clays mixed with the drilling fluids, are transported to the surface. In order to reduce the residual oil content in the drill cuttings for safe disposal, energy and time-consuming methods such as thermal desorption and land farming have been used to treat the oil-contaminated waste. However, a large amount of energy is used in the high-temperature treatment process and transportation from the drilling platforms to the treatment stations.
In the treatment of the oil-contaminated drill cuttings, it is difficult to reduce the residual oil content (retention of oil on cuttings, ROC) to less than 1 wt% as required by governmental regulations. The objective of this thesis is to investigate and develop an innovative treatment process using CO2-responsive O/W microemulsions with the prominent capability of solubilizing oil for the purpose of washing the oil-contaminated drill cuttings and reducing the residue oil level for safe disposal.
In the theoretical part of the thesis, a novel CO2-responsive O/W microemulsion of rapid switching responses was designed based on a CO2-responsive superamphiphile which had a linear structure and assembled via electrostatic interactions between cationic Jeffamine D-230 and anionic oleic acid at a mole ratio of 1:1. The thermodynamically stable heptane-in-water microemulsions were spontaneously formed by adding the switchable superamphiphile and 1-butanol as a co-surfactant. After treating this stable microemulsion with CO2 for 20 seconds, the superamphiphile dissociated into interfacial inactive building blocks, which led to complete phase separation of the microemulsion. Removing the CO2 from the system by N2 sparging at 60 ºC for 10 minutes switched the phase-separated system back to a transparent microemulsion as a result of the in-situ formation of the superamphiphile. The O/W microemulsion designed using this novel superamphiphile featured not only unique thermodynamical stability of nano-sized droplets, but also a rapid response to CO2 to achieve a complete phase separation, and re-microemulsification as desired with N2 purging. This CO2-responsive O/W microemulsion can be potentially utilized for the drill cuttings treatment, and many other applications such as soil remediation, enhanced oil recovery and nanomaterial synthesis.
The second half of the thesis mainly focused on the application using such microemulsions. Based on the CO2-responsive microemulsions, a rapid oil-contaminated drill cuttings treatment process was developed at the ambient temperatures with low energy consumption, which could significantly reduce the ROC from ~15 wt% to below the 1 wt % discharge limit for safe disposal. The treatment process exhibited a fast and deep extraction of residue oil due to the ultra-low interfacial tension and the strong capability of solubilizing oil of the O/W microemulsions. Purging the microemulsions with CO2 for seconds caused the dissociation of the superamphiphile, leading to a complete phase separation and a concentration of the extracted residue oil at the top. The formed aqueous phase between the oil phase and the clean sediments efficiently prevented the further recontamination of the clean solids.
Compared with other treatment methods from the previous studies, this innovative treatment process using CO2-responsive microemulsions is easy to operate at the ambient temperatures without any expensive equipment or extreme working conditions, making this microemulsion treatment a promising candidate for commercialization. The results in this thesis can contribute to the feasibility research of using microemulsions to extract the residual oil from the oil-contaminated drill cuttings, and the technical foundation for the scale-up study in the fields to significantly reduce the treatment cost and the associated carbon emission.
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- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.