removal of toluene from air with photocatalytic oxidation by go/zno composites

Abstract: one of the most important issues facing human being is the availability of clean air. volatile organic compounds (vocs) are hydrocarbons that in usual temperature and pressure, their normal vapor pressure is more than 10.3 kpa, and they easily evaporate. the release of these compounds into the air causes respiratory problems. toluene is one of the most common volatile organic compounds and is used in the military industry to make tri nitro toluene and in the chemical industry is used as a solvent in the manufacture of paints, paint polishes, nail polishes, printing materials, pharmaceuticals and tobacco. due to the extensive use of toluene in various industries and to prevent damages to workers' health (possibility of carcinogenesis), appropriate methods must be used to remove or reduce toluene vapors in the air. the photocatalytic oxidation process has attracted a lot of attention, due to high efficiency and effective in removing pollutants. during the photocatalytic oxidation process, with light radiation and in the presence of semiconductor catalysts, pollutants decompose into carbon dioxide and water. in this research, graphene oxide (go) with different percentages was loaded on zinc oxide and the resulting composites (go/zno) were investigated in the photocatalytic removal of toluene from air under visible light radiation. the results showed that go/zno composites had high photocatalytic activity and finally, go (40%)/zno composite as an optimal photocatalyst degraded 76% of toluene under visible light radiation. diffuse reflectance spectroscopy analysis showed that go (40%)/zno composite has high absorption in visible light and photoluminescence analysis also showed that due to go loading, recombination of photoelectrons and holes is greatly reduced. the go acts as an electron acceptor and transmitter and causes better separation of charge carriers and consequently, photocatalytic performance is enhanced.