Developing an efficient nanocatalyst system for enhanced photocatalytic degradation of toxic aqueous contaminants

Heterogeneous photocatalysis is an emerging treatment option for degrading phenolic contaminants. This dissertation focused on using Titanium dioxide (TiO2) nanomaterials as a potential heterogeneous photocatalyst. The various factors affecting the TiO2 nanoparticle catalyzed photo-degradation process were discussed and the photocatalysis of phenol using TiO2 nanoparticles was evaluated. A statistical model was developed to consolidate the factors based on the Box-Benkhen statistical design (BBD) technique. The degradation rate constant was considered as the model response, and expressed as a function of the independent variables for the photocatalysis. The independent variables considered for developing the BBD based model were as follows: TiO 2 nanoparticle size and concentration, dissolved oxygen (DO) concentration, and substrate concentration. The model-predicted phenol photocatalytic rates were in agreement with the experimental rates for all four variables under consideration. The model developed for phenol degradation was later used to predict the photocatalytic degradation rate of p-cresol, a substituted phenol. Except at high DO concentration and low p-cresol concentration, the model-predicted rates were in close agreement with the experimental degradation rate for p-cresol. A comparison of quantum yield and activation energy for phenol and p-cresol revealed that the latter degraded faster than the former. The practical limitations associated with the use of TiO2 nanoparticle slurry in photocatalytic process, and the challenges in immobilizing TiO2nanoparticles onto a solid catalyst support were discussed. A study on fabrication of immobilized TiO2 nanofiber using sol-gel electrospinning was presented in the later chapters of this dissertation. The characterization procedures followed to fabricate the immobilized TiO 2 nanofiber catalyst was presented. Literature suggested that stability of the immobilized nanofiber catalyst was an issue. A surface treated catalyst support material was used to improve the stability of the immobilized nanofiber catalyst. The optimum process variable settings of sol-gel electrospinning for minimum nanofiber diameter were identified using the BBD procedure. The diameter of the TiO2 nanofiber generated from the BBD optimization was significantly lower than that reported in the literature. Other than the electrospinning variables, the calcination condition and catalyst loading on the support affected the specific surface area (SSA) of the immobilized catalyst. The immobilized TiO2 nanofiber catalyst fabricated by sol-gel electrospinning under optimum process conditions had high SSA and improved catalytic property. A comparison of phenol photocatalytic rates of TiO2 nanoparticle slurries against the immobilized TiO2 nanofiber demonstrated that the latter had higher (approximately twice) catalytic activity than that of the former at comparable SSA