Qom University of Medical Sciences Journal

Background and Objectives: Formaldehyde is one of the toxic volatile organic compounds which is necessary to be removed from polluted air. Photocatalysis is one of existing technologies used for the removal of this compound. This study was performed aimed at determination of the effect of the combination of zinc oxide (ZnO) nanoparticles and bone char (BC) on the photocatalytic removal of formaldehyde gas.   Methods: In this experimental study, characteristics of the catalysts produced by specific surface area were determinated using BET method and scanning electron micrograph (SEM). The degradation of formaldehyde gas was studied using UV/BC, UV/ ZnO, and UV/ZnO-BC processes, under the continuous flow mode condition. The effects of initial concentration, relative humidity, and residence time on degradation of formaldehyde gas were investigated.   Results: The results of the BET surface area measurements and SEM images showed agglomeration of ZnO nanoparticle on the pores of the BC surface structure. The SEM imaging from ZnO-BC catalyst showed that the BC particles pores filled with ZnO nanoparticles formed a homogenous surface. Also, the combination of BC with ZnO nanoparticles had a synergetic effect on the photocatalytic degradation of formaldehyde. In UV/ZnO-BC process in the initial concentration range between 2.5-25mg/m 3 , the degradation efficiency of formaldehyde was between 40% and 73% and the optimum relative humidity was 35%. This effect seems to be due to the strong adsorption of the formaldehyde molecule on BC that results in higher diffusion to the ZnO catalytic surface and that increase in the rate of photocatalysis.   Conclusion: Increase in the formaldehyde degradation by the ZnO-BC composite can be attributed to the synergetic effect of adsorption and subsequent photocatalytic decomposition.