Synthesis of nano-titanium dioxide by sol-gel method for photocatalysis application

Abstract

The purpose of this research was to develop nano-titanium dioxide (TiO₂) for photocatalytic application. The TiO₂ was synthesized by a sol-gel method from tetrabutyl orthotitanate solution in the presence of hydrochloric or nitric acid. Synthesis parameters such as concentration, water content, aging time, as well as the type and amount of hydrolysis catalyst were manipulated to optimum value in order to obtain desired phase structure and properties of the TiO₂ photocatalyst. It was found that higher concentration of Ti precursor led to faster sol formation and greater yield of the TiO₂ particles. Increasing water content and prolong aging time resulted to rapid anatase-to-rutile phase transformation and caused the crystal growth. Hydrochloric catalyst was found to promote the formation of rutile phase while nitric catalyst promoted the formation of the anatase phase. The as-synthesized TiO₂ powders were calcined at 300 - 700°C for 4-10 h to induce the crystallization as well as to burn out any residual organic matters. The TiO₂ sol was then coated on AI₂O₃ beads and glass tubes to reduce the amount of the TiO₂ catalyst and for easy recovery. The resulting photocatalyst had good efficiency for Cibracron Red dye removal. The photocatalytic efficiency was found to relate with phase composition, crystallite size, as well as specific surface area. Incorporation of vanadium into the TiO₂ retarded anatase-to-rutile phase transformation but did not improve photocatalytic efficiency.