Regenerable Composites for Removal of Organic Dye in Aqueous Media and Water in Heavy Oil and the Associated Interaction Mechanism

• Author / Creator

  Zhang, Jiawen

• Water plays an indispensable role in all aspects of life, including farming, domestic and industrial uses. In industries, water has been extensively applied in mining, production and surface treatment, producing a large quantity of contaminated water that threatens human health, endangers environment and undermines sustainable development. Besides, in some cases, after the application of water, the remnant of water in products (e.g., heavy oil) can result in difficulties in refining and transport. Thus, technique development is immediately necessary to eliminate the contaminants in aqueous effluents and to remove water from products. Herein, in this dissertation, regenerable composites are designed, synthesized and employed for sustainable dye elimination from water and water removal from heavy oil, and the associated interaction mechanism has also been investigated. Dyes, as a kind of most common pollutants existing in wastewater, can endanger the health of living creatures. The adsorbents nowadays for dye removal usually suffer from low adsorption capacity, sludge production and low regenerability. Herein, in this work, a poly (acrylic acid) (PAA) functionalized magnetic Fe3O4 nanoparticle-graphene oxide nanocomposite (PAA/MGO), with high adsorption capacity and rapid adsorption rate for dye (using methylene blue as a model compound), was synthesized by a facile method. It was found that PAA/MGO composite (291 mg/g) possessed elevated maximum adsorption capacity (pH ~7) compared with MGO (70 mg/g), and with the aid of magnetic separation, PAA/MGO composite showed remarkable regenerability for 5 times of usage. The adsorption mechanism was also surveyed by Langmuir and Freundlich isotherm models fitting and studying adsorption capacity difference at different pH (pH ~3-11). Graphene oxide (GO), as a 2-dimentional nanomaterial, has been widely applied in dye removal via adsorption due to its affinity to dyes, high surface area and rich functional groups available for further modification. However, the fundamental understanding of the effect of specific functional groups of GO on the interaction between GO and dyes is still unclear. Herein, single-molecular force spectroscopy (SMFS) and Density Functional Theory (DFT) calculations were applied to study the interaction between a single dye molecule and GO, which suggested that the carboxylic groups could interact with cationic dye by electrostatic interaction under ionized condition, whereas the epoxy groups on the basal plane of GO could enhance the π-π interaction between aromatic parts of GO and cationic dye under both ionized and unionized conditions of carboxylic groups on GO. The configuration of dye on GO was also investigated and discussed. This fundamental study can shed light to GO nanocomposites designing and enhance their performance in discoloration of wastewater. Global demand for crude oil has constantly increased, which leads to a rising production of heavy oil. However, the water residue in heavy oil can be stabilized by asphaltenes, the heaviest components in heavy oil, and results in many problems in oil production and refining, which include corrosion and low petroleum recovery. Asphaltenes tend to aggregate, precipitate and lead to foulings on appliances and adsorbents, which can also undermine oil production and the process to remove water from heavy oil. In this work, inspired by the long-range attraction property of zwitterionic polyelectrolytes to water in oil, zwitterionic polyelectrolyte poly (3-[dimethyl(2-methacryloyloxyethyl) ammonium] propanesulfonate) (PMAPS) grafted polydopamine (PDA) coated silicon wafer substrates and sponges were fabricated, manifesting great underwater self-cleaning ability, anti- oil property and regenerability. After being soaked in model heavy oil (asphaltene toluene solution) under dry state, the PMAPS-PDA coating on silicon wafer substrates still showed underwater superoleophobicity after being cleaned by acidic, neutral and alkaline water, showing promises to minimize the fouling concerns in the handling and transport of heavy oil. The PMAPS-PDA modified sponges could remove more than 90% of water from model heavy oil for ten cycles, showing promises for water removal from heavy oil. Single-charged polyelectrolytes cationic poly (2-(methacryloyloxy)ethyl trimethylammonium chloride) (PMTAC) and anionic poly (3-sulfopropyl acrylate potassium) (PSPAK) were used to fabricate coatings using the same method as PMAPS, and their performance in fouling cleaning-up and water removal from model heavy oil was not comparable to PMAPS, demonstrating the superiority of zwitterionic polyelectrolytes in anti-fouling and water removal applications in heavy oil industries.

• Subjects / Keywords

  • Regenerable
  • Graphene oxide
  • Adsorption
  • Interaction mechanism
  • Dye
  • Water removal

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3Z02ZQ5Q

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.