Efficient process of VOC degradation from the high airflow in conical fluidized photocatalytic reactor by mesoporous C-N doped -ZnO powder under visible light

Mesoporous carbon-nitrogen, doped ZnO powders were synthesized from the zeolite imidazolate framework (ZIF-8) by a facile thermal decomposition in the atmosphere of nitrogen and air, respectively. The prepared material was used as the photocatalyst in a conical fluidized photocatalytic reactor under visible light irradiation for degradation of acetaldehyde (as a model molecule of indoor volatile organic compounds). The synthesized samples were characterized by DRS, BET, EDAX, FTIR, XRD, TGA, and FESEM analysis. DRS analysis revealed that the absorption edge of the prepared samples from ZIF-8 was significantly shifted to the visible range. The band gap and absorption edge of the bare ZIF-8 was changed from 5.1(eV) and 243(nm), respectively, to almost 3 (eV) and 400 (nm) in the prepared C-N doped ZnO. FTIR analysis confirmed the existence of carbon and nitrogen in the surface of the prepared material. The N2 adsorption-desorption analysis revealed the IV-type isotherm confirming mesoporous structure with improved specific pore volume. The photocatalytic activity of the samples was evaluated from the airflow polluted with a trace amount of acetaldehyde, under an alkali metal halide lamp in the conical fluidized reactor, and the outlet flow was analyzed by the online GC versus the time. According to the results, all samples exhibited significant photocatalytic activity compared with the bare ZIF-8, and com-mercial ZnO powder. Almost 90% acetaldehyde removal occurred by the sample prepared by N2 thermal decomposition of ZIF-8 at 600 degrees C for 120 min, followed by air annealing at 450 degrees C for 90 min. Subsequently, the reaction rate was investigated and modeled on the base of Langmuir-Hinshelwood type equation as a function of acetaldehyde concentration and light intensity.

Automated summary

Mesoporous carbon-nitrogen doped ZnO powders were synthesized from ZIF-8 through thermal decomposition under nitrogen and air atmospheres. The prepared material exhibited significant photocatalytic activity for acetaldehyde degradation under visible light irradiation. The optical and morphological properties of the samples were characterized, and the results showed that the absorption edge of the prepared samples was shifted to the visible range. The photocatalytic activity of the samples was much higher than that of the bare ZIF-8 and commercial ZnO powder. The sample prepared by N2 thermal decomposition of ZIF-8 at 600 degrees C for 120 min, followed by air annealing at 450 degrees C for 90 min, achieved a removal rate of about 90% for acetaldehyde.