Microwave flow synthesis of nanostructured TiO₂

Nanostructured titanium dioxide (TiO2) is widely used in paints, cosmetics, air purifiers and solar cells. One popular method to synthesize TiO2 is by sol-gel method to crystallize the anatase phase via thermal, hydrothermal or chemical means. However, these processes often require long treatment time and proceed at high pressure and temperature. A novel continuous flow microwave crystallization of TiO2 was investigated for fast, energy efficient, low temperature process for producing photoactive TiO2 catalyst for pollution treatment. The effect of microwave operating parameters on TiO2 crystal size, crystallinity, and surface area was investigated. Microwave-crystallized samples were analyzed by X-ray diffraction (XRD), Micro-Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 physisorption. Temperature in the reaction mixture was identified as the key factor of the TiO2 crystallization followed by duration of microwave. Higher temperature resulted in better TiO2 crystallization. Modified TiO2 using zeolite doped method and template method were also presented in this study. Modified TiO2 by zeolite doped method enhanced the surface area of the particles for photocatalysis. In the modified TiO2 templating method, TiO2 rod was synthesized in order to benefit photocatalyst recovery. Microwave-crystallized TiO2 samples have adsorption ability toward diclofenac, a common endocrine disrupting chemicals (EDCs) found in water, and results in enhanced photocatalytic degradation compared to TiO2 obtained by thermal treatment. Crystallinity and adsorption ability are the critical factors for photocatalyic oxidation performance based on the studies