Metal organic framework-based photocatalyst-assisted peroxone process for formaldehyde and acetaldehyde removal from waste air stream: intermediates and mineralization

Formaldehyde (FA) and acetaldehyde (AA) are known as the two major pollutants used at industrial processes. The BiOI@NH2-MIL-125 (Ti)@Zeolite heterostructures combined with UV-assisted peroxone process were investigated for oxidative degradation of the aldehydes in a continuous waste air stream. Different characterisation methods including XRD, FTIR, FESEM, EDS, EDS elemental mapping, BET, TEM and XPS were used to characterise the photocatalyst. This study focuses on optimising the parameters selected for removal of FA and AA using the one-factor-at-a-time (OFAT) technique. Therefore, the effects of operational parameters: air flow rate, ozone feeding rate, hydrogen peroxide (H2O2) concentration, relative humidity (RH), and initial concentrations on FA and AA removal efficiency were investigated and optimised using the OFAT procedure. The results showed the complete degradation of FA and AA were achieved at optimal conditions (air flow rate: 0.2 L/min, O3 dosage: 0.3 and 0.4 mg/min for FA and AA, respectively, H2O2 concentration: 150 and 200 ppm for FA and AA, respectively, RH of 35%, and an initial pollutant concentration of 5 ppm). In addition, kinetic models revealed that the FA and AA degradation process are fitted with first-order kinetic (R2 = 0.85). Mineralisation analysis revealed that the complete degradation of FA and AA were obtained at CO2 levels of 4.3 and 3.9 ppm, respectively. Overall, it could be concluded that the suggested treatment method has the capability to efficiently eliminate the aldehydes of interest from waste gases.