Photocatalytic Degradation Kinetics of Gaseous Formaldehyde Flow Using TiO 2 Nanowires

Abstract

A high-performance TiO 2 nanowire photocatalyst was successfully prepared by a hydrothermal method to decompose gaseous formaldehyde into CO 2 and H 2 O in a homemade tube reactor without secondary pollution under ultraviolet irradiation. The photocatalytic oxidization kinetics fits well with the traditional Langmuir-Hinshelwood-Hougen-Watson model. Multiple parameters, including the formaldehyde concentration, flow rate, and light intensity, were monitored online and proved to be key factors affecting the rate of the photocatalytic reactions. The crystallinity of the photocatalyst and its surface reactive site density determined the adsorption equilibrium constant (K HCHO ) of formaldehyde on TiO 2 . The experimental results show that the degradation kinetics of mobile gas-phase formaldehyde by TiO 2 nanowires did not strictly conform to the first-order reaction kinetics, and its photocatalytic degradation rate increases with an increase in ultraviolet light-emitting diode irradiation intensity. It takes only 8.6 min to completely degradate formaldehyde at a flow rate of 50 mL/min with 50 mg of 700TiO 2 , and the reaction performance remains unchanged during the 1200 min duration of the decomposing process.