Ozone and UV/O
3 were employed to mineralize dinitrotoluene (DNT) isomers and 2,4,6-trinitrotoluene (TNT) in spent acid from toluene nitration process. The
oxidative degradation tests were carried out to elucidate the influence of various operating variables on the performance of mineralization of total organic compounds (TOC) in spent acid, including reaction temperature, intensity of UV (254 nm) irradiation, dosage of
ozone and concentration of sulfuric acid. It is remarkable that the nearly complete mineralization of organic compounds can be achieved
by ozonation combined with UV irradiation. Nevertheless, the hydroxyl radicals (
OH) would not be generated
by either
ozone decomposition or photolysis of
ozone under the experimental condition of this study. According to the spectra identified
by gas chromatograph/mass spectrometer (GC/MS) and further confirmed
by gas chromatograph/flame ionization detector (GC/FID), the multiple oxidation pathways of DNT isomers are given, which include
o-,
m-,
p-mononitrotoluene (MNT) and 1,3-dinitrobenzene, respectively. In addition,
oxidative degradation of 2,4,6-TNT leads to a 1,3,5-trinitrobenzene intermediate.