Photocatalytic oxidation of low mass concentration formaldehyde with glass beads coated with nano-TiO_2

A packed-bed photocatalytic reactor filled with glass beads coated with nano-TiO2 was designed for decomposition of low mass concentration formaldehyde.The conversion and reaction rate of formaldehyde at different inlet formaldehyde mass concentration,reaction temperature and relative humidity were investigated.The results indicate that 61.3% of the formaldehyde is decomposed with 0.095 g photocatalyst for inlet formaldehyde mass concentration of 20 mg/m3.The conversion of formaldehyde initially decreases and then increases with the increase of inlet formaldehyde mass concentration.The reaction rate increases with the increase of inlet formaldehyde mass concentration,which basically conforms to Langmuir-Hinsherwood Model.The reaction rate of formaldehyde decreases with the rise of temperature.The influence of temperature on the formaldehyde reaction rate was relatively weak at lower formaldehyde mass concentration.The formaldehyde reaction rate initially decreases and then levels off with increasing relative humidity.The formaldehyde reaction rate is quite similar when the relative humidity is above 30%.Carbon dioxide is the main product of the reaction.The formaldehyde in reaction can be completely converted into carbon dioxide when the temperature is higher than 115 ℃.