Photocatalytic Degradation Kinetics of Gaseous Formaldehyde Flow Using TiO2 Nanowires

A high-performance TiO2 nanowire photocatalyst was successfully prepared by a hydrothermal method to decompose gaseous formaldehyde into CO2 and H2O 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 TiO2. The experimental results show that the degradation kinetics of mobile gas-phase formaldehyde by TiO2 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.