Photocatalytic degradation of organic dyes by titanium dioxide in an air-lift reactor

Abstract

The photocatalytic degradation of crocein orange G and methylene blue in aqueous solution over TiO[subscript2] in three different photoreactors namely, airlift reactor, bubble column reactor, and stirred tank reactor were investigated. Titanium dioxide was synthesized via a sol-gel method and titanium isopropoxide is employed as a precursor. Characterization of the catalyst revealed that TiO[subscript2] primarily consists of anatase phase with a very small amount of brookite phase. The crystallite size of anatase TiO[subscript2] was approximately 5 nm and the specific surface area of TiO[subscript2] was 170 m[superscript2] g[superscript-1]. The parameters studied included diameter of draft tube aeration rate, pH of dye solution, initial concentration of dye and types of photoreactors. Diameter of draft tube had no significant effect on the performance of the photoreactor system The performance of the system was better when aeration rate was higher, pH of the solution is suitable to the type of dyes and the initial concentration of dye was lower. Among the three photoreactors studied, an airlift reactor performed the best due to high dissolved oxygen concentration and good mixing and good circulation in the reactor. Furthermore the Langmuir-Hinshelwood kinetic model was able to describe the reaction kinetics fairly well.