Affecting factors and kinetics of formaldehyde degradation by photocatalytic oxidation process

The effects of humidity, initial formaldehyde concentration, ozone amount and temperature on photocatalytical degradation of formaldehyde in gas-solid phase were investigated. The experimental results indicated that the best relative humidity was 30%, and the lower initial formaldehyde concentration, the higher its degradation. However, the degrading load of formaldehyde on the unit catalyst was increased at first and then decreased as increasing initial formaldehyde concentration. The decomposing efficiency of formaldehyde is direct proportion of temperature. Furthermore, addition of ozone can considerably increase decomposing of formaldehyde, and combination of ozonation with photocatalytic oxidation on formaldehyde showed a synergism. The kinetics of formaldehyde degradation reaction can be described by Langmuir-Hinshelwood model, that is, the degradation rate of formaldehyde can be expressed by first-order kinetics model.