Electron-Beam Treatment of Aromatic Hydrocarbons That Can Be Air-Stripped from Contaminated Groundwater. 1. Model Studies in Aqueous Solution

Abstract

As a model for the electron-beam degradation of volatile aromatics (benzene, toluene, ethylbenzene, xylenes, BTEX) in groundwater strip gas, to be reported in Part 2, the gamma-radiolysis of benzene has been studied in aqueous solutions. Addition of *OH to the aromatic ring gives rise to hydroxycyclohexadienyl radicals which either dimerize or disproportionate. The various dimers undergo acid-catalyzed water elimination yielding biphenyl. Phenol is formed upon disproportionation directly, but also via dihydroxycyclohexadiene which subsequently undergoes acid-catalyzed water elimination. Co-radiolysis of benzene with nitrite generates *NO2 in addition to the hydroxycyclohexadienyl radical. These not only interact with one another (product: nitrobenzene via nitro-hydroxycyclohexadienes) but the *NO2 radical is also capable of abstracting cyclohexadienylic hydrogens. This reaction leads to the formation of 2- and 4-nitrophenol and to further nitrated products that were not identified. These are suggested to be formed in an analogous reaction of *NO2 with the hydroxycylohexadienyl dimers. The effect of O2 on these reactions and the relevance for the gas-phase radiolysis of BTEX is discussed.

Experimental and theoretical studies on aqueous-phase reactivity of hydroxyl radicals with multiple carboxylated and hydroxylated benzene compounds

“…This product in the N 2 O-saturated solution of this experiment is expected to be a higher molecular weight species resulting from the dimerization or disproportionation of hydroxylcyclohexadienyl radicals as was postulated by the product study for benzene compound. 48 Simic et al (1973) 49 investigated the reaction of HO with benzoate at pH of 9.2 and obtained a peak maximum at 330 nm with a corresponding molar absorptivity of 3800 M À1 cm À1 , consistent with our experimental findings.…”

The Green Method in Water Management: Electron Beam Treatment

“…Radiolytic processes, especially those associated with the formation of excited molecules, dissociative capture of radicals, and oxidation, can lead to the formation of cleavage products of C–C bonds as well as bonds between a carbon and a heteroatom. Under anaerobic conditions, radiolysis eliminates gaseous fragmentation products such as H 2 , CO 2 , CH 4 , N 2 , etc. ,− Under aerobic conditions, organic pollutants can undergo sequential cleavages, leading to their complete conversion to CO 2 and H 2 O or, in the presence of heteroatoms, to oxides of the corresponding elements (SI, section S1). Such a process is called mineralization.…”

Degradation of Nitrobenzene by Pulsed High Voltage Discharge in Water

“…The energy efficiency estimation of such processes as electric radiation, radiation and pulsed discharge in water often uses the G value. The G value is defined as the number of substrate molecules converted per 100 eV of energy [19]. Here we used a easily understood and calculated value G defined as milli mole number of substrate converted per kWh of electricity energy.…”