Ozone-Assisted photocatalytic degradation of benzene using nano-zinc oxide impregnated granular activated carbon (ZnO-GAC) in a continuous fluidized bed reactor

Benzene is one of the volatile organic compounds, exposure to which causes different complications including coughs, headache, dizziness, and even cancer. Therefore, methods are required to remove benzene from polluted air. In this study, for the first time, benzene degradation was examined using photocatalytic ozonation process in the presence of nano-zinc oxide impregnated granular activated carbon (ZnO-GAC) in a continuous fluidized bed reactor. The experiments were performed with the aim of investigating the effect of factors including the ratio of superficial gas velocity to the minimum fluidization velocity (UgUfm), initial benzene concentration, relative humidity, catalyst dosage, bed temperature, ozone dosage, and intensity of UV lamp in removing benzene from the air. The results of this study indicated that the minimum fluidization velocity (U-mf) was obtained as 0.47 L/min, while benzene removal efficiency reached its maximum at UgUfm= 2.5. Addition of ozone to the ZnO-UV/GAC process enhanced the process efficiency considerably. With elevation of benzene concentration from 50 to 300 ppm, removal efficiency by UV/ZnO-GAC process declined from 84.14 to 45.12%, while with O-3/ZnO-GAC/UV, it decreased from 93.8 to 68.78%. The range of the optimal humidity for benzene removal in both processes was obtained as 30-35%. With elevation of ZnO-GAC dosage from 0 to 10 mg, benzene removal efficiency increased from 42.07 to 70.24 and from 60.9 to 89.57% using UV/ZnO-GAC and O-3/ZnO-GAC/UV processes, respectively. Furthermore, the efficiency of O-3/ZnO-GAC was directly related to bed temperature, while UV/ZnO-GAC and UV/O-3/ZnO-GAC processes were inversely related. Eventually, the removal efficiency of the processes had a direct relation with the ozone dosage and UV intensity. (c) 2018 American Institute of Chemical Engineers Environ Prog, 38:e13082, 2019