Deng, Wei (2019-08). Development of Advanced Photocatalysis and Membranes for Wastewater Treatment. Doctoral Dissertation. Thesis uri icon

abstract

  • Inadequate access to clean water is a pressing problem across the world, which calls out enormous research efforts to develop efficient and economic solutions to the safe reuse of wastewater. In this dissertation, heterogeneous photocatalysis, superwetting membranes, and photocatalytic superwetting membranes have been studied for the removing organic pollutants, separating immiscible oil/water mixtures, and treating of oil/water emulsions, respectively. Specifically, four research works are included. (1) A sulfite-promoted photodegradation process was developed. It was found that the degradation rate of methyl orange (MO) could be greatly enhanced by sulfite and scavenging study suggested that sulfite radicals generated by the reactions of sulfite with holes or hydroxyl radicals were the reactive species. The developed approach was demonstrated as a general approach as it was successfully applied to various pollutants and photocatalysts. (2) To evaluate the adsorption-photocatalysis synergy, mesoporous TiOv2 (amorphous)-BiOBr microspheres were facilely synthesized as the model photocatalysts. Homogeneously distributed TiOv2 in BiOBr microplates tailored the crystallite size of BiOBr, and consequently surface area (22 to 155 m^2 /g) and adsorption capacity (16 to 54 mg/g of MO) of the composites. Developed kinetic modeling that combined adsorption with photocatalysis aided elucidating the synergy and quantitatively evaluating the composites. Though high adsorption promoted MO photodegradation, we found adverse effects on photocatalysis that could be caused by high levels of MO adsorption as revealed by cycling tests. (3) Uniform and smooth TiOv2 films were conformally coated on stainless steel mesh (SSM) via a biomineralization approach that is environmentally benign, facile, and scalable. The TiOv2-coating made the meshes superhydrophilic and underwater superoleophobic. The coated meshes could separate immiscible oil/water mixtures solely driven by gravity with high flux (~3x10^4 Lm^-2 h ^-1 ), high separation efficiency (~ 99.999%), and excellent anti-fouling capability. The meshes also had great chemical, mechanical and thermal durability. (4) Photocatalytic and superhydrophilic PVDF-BiOBr composite membranes were fabricated by a facile and scalable phase-inversion method. The composite membranes showed photocatalysis-enhanced anti-fouling capability for treating oil/water emulsions. In summary, rational engineering of the photocatalytic reactions, photocatalysts, and membrane surface wettability were studied and could help advance the development of photocatalysis and membrane technology in wastewater treatment.
  • Inadequate access to clean water is a pressing problem across the world, which calls out enormous research efforts to develop efficient and economic solutions to the safe reuse of wastewater. In this dissertation, heterogeneous photocatalysis, superwetting membranes, and photocatalytic superwetting membranes have been studied for the removing organic pollutants, separating immiscible oil/water mixtures, and treating of oil/water emulsions, respectively. Specifically, four research works are included. (1) A sulfite-promoted photodegradation process was developed. It was found that the degradation rate of methyl orange (MO) could be greatly enhanced by sulfite and scavenging study suggested that sulfite radicals generated by the reactions of sulfite with holes or hydroxyl radicals were the reactive species. The developed approach was demonstrated as a general approach as it was successfully applied to various pollutants and photocatalysts. (2) To evaluate the adsorption-photocatalysis synergy, mesoporous TiOv2 (amorphous)-BiOBr microspheres were facilely synthesized as the model photocatalysts. Homogeneously distributed TiOv2 in BiOBr microplates tailored the crystallite size of BiOBr, and consequently surface area (22 to 155 m^2 /g) and adsorption capacity (16 to 54 mg/g of MO) of the composites. Developed kinetic modeling that combined adsorption with photocatalysis aided elucidating the synergy and quantitatively evaluating the composites. Though high adsorption promoted MO photodegradation, we found adverse effects on photocatalysis that could be caused by high levels of MO adsorption as revealed by cycling tests. (3) Uniform and smooth TiOv2 films were conformally coated on stainless steel mesh (SSM) via a biomineralization approach that is environmentally benign, facile, and scalable.
    The TiOv2-coating made the meshes superhydrophilic and underwater superoleophobic. The coated meshes could separate immiscible oil/water mixtures solely driven by gravity with high flux (~3x10^4 Lm^-2 h ^-1 ), high separation efficiency (~ 99.999%), and excellent anti-fouling capability. The meshes also had great chemical, mechanical and thermal durability. (4) Photocatalytic and superhydrophilic PVDF-BiOBr composite membranes were fabricated by a facile and scalable phase-inversion method. The composite membranes showed photocatalysis-enhanced anti-fouling capability for treating oil/water emulsions. In summary, rational engineering of the photocatalytic reactions, photocatalysts, and membrane surface wettability were studied and could help advance the development of photocatalysis and membrane technology in wastewater treatment.

publication date

  • August 2019