Oil/water mixtures are produced in upstream and downstream operations during the extraction and refining of crude oil. Separating oily water is essential in industries for product specification and to avoid corrosion in pipelines. Besides, removing oily products from water is imperative before it can be discharged into the environment. Several techniques are in practice to deal with industrial oil/water mixtures, such as in situ burning, bioremediation, and solidifiers that change the physical shape of oil via chemical interaction. Physical separation of oil/water mixtures is in industrial practice; however, the existing technologies to do so often require either dissipation of large amounts of energy (such as in cyclones and hydrocyclones) or significant residence times or inventories of fluids (such as in decanters). Recently, materials with selective wettability have gained attention for application in the separation of oil/water mixtures, and surfactant stabilized emulsions. For example, a superhydrophobic material is selectively wettable towards oil whilst having a poor affinity for the aqueous phase. Therefore a superhydrophobic porous material can efficiently adsorb the oil while rejecting the water from an oil/water mixture, thus physically separating the two components. The ease of separation, low cost, and low energy requirements and potential for scale-up are some of the advantages of these materials over existing oil/water separation practices. This work studied the nanoscale engineering of various materials to separate biphasic mixtures and broader application in environmental remediation and energy. The first chapter of this thesis provides a background of the project and a state of the art literature review of various nanomaterials for oil/water separation. Research work on renewable nanocomposite adsorbent for emulsion separation has been presented in the second chapter. Nanocomposites were prepared by coating sawdust particles with a thin layer of alumina nanoparticles and a nanoscale siloxane coating to make them superhydrophobic. The synthesis conditions were extensively studied, and nanocomposites were thoroughly characterized to establish a structure-property relationship. Optimised samples were used for the separation of surfactant stabilized oil/water emulsions. Findings from the 2nd chapter inspired the research work on magnetic adsorbent for the separation of emulsions (3rd chapter). High surface area silica-based magnetic nanocomposites were synthesised for fast separation of stable emulsions. Both sawdust and magnetic nanocomposites were used for batch scale separation of emulsions. The findings from those works and guidance from industrial partners lead to macroscopic superhydrophobic materials for continuous separation. Chapter 4 presents a new spray based method for the fabrication of nanofibrous superhydrophobic membranes. Very small (13 nm) hydrophobic alumina nanoparticles were mixed with thermoplastic polyurethane and spray-coated on a water interface to acquire porous membranes. The membrane's pore size and surface properties were adjusted, and optimized samples were used to separate oil/water mixtures and emulsions.
Engineering Surface for Next Generation Fluid Separation
Zulfiqar, U. (Author). 31 Dec 2021
Student thesis: Phd