Exhaustive radiolysis of 11 mM aqueous benzene solutions: effect of added oxygen

The gamma radiolysis of aqueous benzene solutions was studied under various conditions (oxygenated, aerated and anoxic) to ascertain the role that oxygen plays in the destruction of benzene. For the oxygenated and aerated systems, phenol and biphenyl were the major quantified products. For the anoxic system, phenol was the sole quantified product. Benzene was initially consumed with approximately the same yield in each of the three systems; G(-benzene) was 0.49 mumol J(-1). Initial yields of phenol, G(phenol), were found to be 0.12, 0.060 and 0.030 mumol J(-1) for the oxygenated, aerated and anoxic systems, respectively. Biphenyl was initially formed with G = 0.028 and 0.019 mumol J(-1) in the oxygenated and aerated systems, respectively. The percent conversion of benzene to CO2 after an absorbed dose of 2500 kGy was 55.1%, 30.5% and 12.5%, respectively, for the oxygenated, aerated and anoxic systems. The last traces of benzene disappeared by a dose of ca. 60 kGy in all three systems. A mechanism was proposed for each system that depended upon the presence or absence of O-2. The total solution toxicity for each system was calculated by summing the individual toxicities of benzene and each quantified product. For the oxygenated and aerated systems, the total solution toxicity was found to go through a maximum at a dose of 22 kGy and then decrease to a value below that of the original solution. The total solution toxicity of the anoxic system was found to decrease from the onset of irradiation. (C) 2003 Elsevier Ltd. All rights reserved.