Interfacially Active Magnetic Nanoparticles for Efficient Oil/Water Separation from Oil-in-Water or Water-in-Oil Emulsions

• Author / Creator

  He, Xiao

• The emulsions, either oil-in-water (O/W) or water-in-oil (W/O) emulsions, are inevitably formed during the industrial production processes and the daily household activities. The O/W emulsions such as crude oil-in-water emulsions or oily wastewaters generated from the industrial fields, oil spills or domestic sewages can contaminate valuable freshwater resources, harm human health, and destruct the marine ecological systems. The W/O emulsions such as water-in-crude oil emulsions from the extraction of bitumen or crude oil could cause damages to the downstream processing equipment or poison the catalyst during the refinery process due to the presence of harmful salts in the emulsified water phase. Therefore, the oil/water separation of such emulsions prior to their discharge or downstream processing is essential if not required. However, natural emulsion stabilizers such as asphaltenes in the crude oil, oil impurities in the cooking oil or detergent contained in the wastewaters could significantly enhance the stability of those undesirable emulsions, causing difficulties in desired oil/water separation. There are significant drawbacks to the current oil/water separation strategies. Researchers are therefore motivated to find more effective methods for the efficient oil/water separation. In this thesis, a series of magnetically responsive and interfacially active nanoparticles (nanoparticles with uniform or asymmetric surface wettability) were designed and applied to the efficient oil/water separation. With their desirable interfacial activities, such nanoparticles could effectively deposit onto the oil-water interface, tagging the target oil or water droplets. With the introduction of an external magnetic field, the nanoparticle-tagged droplets could be attracted and transported to the desired locations, achieving effective oil/water separation. Characterization using FE-SEM, TEM, zeta potential measurements, thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR) confirmed the successful synthesis of the nanoparticles with uniform and asymmetric surface properties. The results from interfacial property measurements of interfacial tension, interfacial pressure-area (π-A) isotherm, crumpling ratio and coalescence time confirmed the effective deposition (anchoring) of such nanoparticles at the oil-water interface and demonstrated the satisfying interfacial activities of the synthesized nanoparticles. Based on the results of interfacial property measurements, the synthesized Janus nanoparticles exhibited superior interfacial activities including further lowering of the oil-water interfacial tension, prevention of the emulsified droplets from coalescence, and quicker and firmer deposition onto the target oil-water interface, making the oil-water interface more rigid as compared with the nanoparticles of uniform surface wettability. The synthesized nanoparticles could achieve effective oil/water separation from either O/W or W/O emulsions with the Janus nanoparticles of superior interfacial activities exhibiting higher oil/water separation efficiency. Furthermore, the synthesized nanoparticles of uniform or asymmetric surface wettability could be recycled and reused by retaining high oil/water separation efficiency without complex regeneration. With their satisfying interfacial activities, high oil/water separation efficiency and exceptional recyclability, such magnetically responsive and interfacially active nanoparticles have promising applications to efficient oil/water separation of water-in-crude oil emulsions from crude oil-related extraction processes, or oil-in-water emulsions as encountered in oil spills in the marine system and oily wastewaters from industrial production processes and daily household activities.

• Subjects / Keywords

  • Magnetic Janus nanoparticle
  • oil/water separation
  • asymmetric surface wettability
  • Pickering emulsion

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-n22c-rq53

• 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.