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ABSTRACT

 

Full Name:[Talal Farhan Ahmed Qahtan]
Thesis Title:[Physics of Textured Surfaces with Selective Wettability and Photocatalytic Activity for Multifunctional Applications]
Major Field:[Physics]
Date of Degree:[December, 2017]

Combination of oil-water separation and water-soluble organic pollutants removal in a single unit operation is highly desirable for oily wastewater remediation (i.e. separation of water-insoluble oils and degradation of water-soluble pollutants).  In this study, we fabricated textured surfaces with selective wettability and photocatalytic activity (i.e. multifunctional textured surfaces) for oily wastewater treatment in a single unit operation.

For developing of specific materials which act as superhydrophobic (water contact angle > 150o and sliding angle < 10 o) and  superoleophilic (oil contact angle ~ 0o), a facile synthesis method for highly stable carbon nanoparticle (CNP) dispersion through the incomplete combustion of paraffin candle flame is also presented. The synthesized CNP dispersion is the mixture of graphitic and amorphous carbon nanoparticles size in 20-50 nm range and manifested the mesoporosity with an average pore size of 7 nm and a BET surface area of 366 m2g-1. As an application of this material, the carbon nanoparticle dispersion was spray coated (spray-based coating) on a glass surface to fabricate water jet resistance superhydrophobic surfaces.

Also, we developed a universal, scalable, solvent-free, one-step methodology based on thermal annealing of stainless steel meshes to create appropriate surface texture and simultaneously modify its surface energy (i.e, chemical composition, Fe2O3 and/or Fe2O3-based composites). These annealed stainless steel meshes are mechanically robust and exhibit under-water selective wettability of water over oil for gravity-driven oil-water separation and visible light responsive photocatalytic activity for water-soluble organic pollutants degradation under visible light irradiation. We believe that our approach will enable the fabrication of robust multifunction membranes for large-scale applications in oily wastewater treatment.

Furthermore, for the first time, a simple and facile spray coating method was successfully used to fabricated a novel Janus membrane that possess superhydrophilic-superoleophboic surface on the feed side and photocatalytic surface on the permeate side. We developed a mathematical model that describe the photocatalytic degradation of organics upon UV illumination and showed that our model match very well with the experimental result. Our Janus membrane exhibits high separation efficiency of free/emulsified oil-water mixtures and high in-situ photo-degradation efficiency of organic pollutants in the water-rich permeate upon UV light illumination. We believe that our Janus membrane has a great potential for large-scale treatment of oily wastewater.

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