Nitroaromatic Hydrocarbon Ozonation in Water. 2. Combined Ozonation with Hydrogen Peroxide or UV Radiation

Abstract

The combined ozonation of nitrobenzene and 2,6-dinitrotoluene with hydrogen peroxide and UV radiation has been studied. Effects of variables such as pH, hydroxyl radical scavengers, ozone feed rate, or hydrogen peroxide to ozone feed molar ratios have been investigated. Results are also compared to those obtained from UV radiation and single ozonation (Beltrán et al., 1998). Quantum yields of nitrobenzene and 2,6-dinitrotoluene at 254 nm were found to be 7.0 × 10-3 and 2.2 × 10-2 mol einstein-1, respectively. Removal rates of nitrobenzene through single or combined ozonation with hydrogen peroxide at concentration lower than 10-2 M are similar, while under the same conditions combined ozonation of 2,6-dinitrotoluene leads to higher removal rates than single ozonation. Also, the latter compound is removed faster by UV radiation alone and UV/O3 oxidation than by single ozonation. Rate constants of the reaction between the hydroxyl radical and nitrobenzene and 2,6-dinitrotoluene were found to be 2.9 × 109 and 7.5 × 108 M-1 s-1, respectively. Nitrophenols and 2,6-dinitrobenzaldehyde appear to be some of the principal intermediates formed in the treatment of nitrobenzene and 2,6-dinitrotoluene, respectively, regardless of oxidation techniques applied. Apart from economic considerations UV/O3 oxidation is the technique among those studied leading to the highest removal rates.

Catalytic Degradation of Nitrobenzene and Aniline in Presence of Ozone by Magnesia from Natural Mineral

“…Recently, considerable attention has been focused on the treatment of nitrobenzene and aniline in wastewater. Different methods have been proposed such as photo-catalytic process [4][5][6][7], wet air oxidation [1,8,9], catalytic electrochemical treatments [10][11][12] and ozonation [13][14][15][16][17][18][19].…”

Decomposition of dinitrotoluene isomers and 2,4,6-trinitrotoluene in spent acid from toluene nitration process by ozonation and photo-ozonation

“…The combination of ozonation and UV irradiation (254 nm) has been proved to be highly effective for the remediation of nitroaromatic compounds in wastewater [21,25,34,35]. According to the study by Peyton and Glaze [36], hydroxyl radicals could be generated in water by photo-ozonation (shown as follows), which should result in higher oxidation efficiency of organic compounds in comparison with that of ozone.…”

“…According to the study by Beltrán et al [24], the reaction temperature and pH value have a positive effect on the ozonation rate of 2,6-DNT, of which reaction with ozone contributes slightly to the ozonation rate. Additionally, radiation with the UV light and addition of hydrogen peroxide enhanced the ozonation rate of 2,6-DNT [25]. Currently, Liou et al [26] has investigated the oxidative degradation of 2,4-DNT and TNT, of which oxidation rates were promoted by UV irradiation.…”

PHOTOCATALYTIC DEGRADATION OF TNT FROM WATER IN UV-VIS/Fe-TiO2 SYSTEM

“…Li et al investigated the conversion of 2,4,6-TNT by Fenton's reagent, in which higher oxidation efficiency was obtained at pH 3.0 [8]. Some other publications have been focussed on the decomposition of 2,6-DNT through ozonation, H2O2/O3 or UV/O3 methods [9,10]. Beside these photo induced techniques, semiconductor photocatalysis has been proved to be effective in degradation of nitroaromatics [11].…”