Radiation-Induced Catalysis on Oxide Surfaces: Degradation of Hexachlorobenzene on γ-Irradiated Alumina Nanoparticles

There is a need to understand fundamentally the radiolytic processes occurring on metal oxide surfaces, processes which may determine the fate of pollutants in high level nuclear storage tanks and may also be used to remediate contaminated materials, such as soils. Radiation-induced, surface chemical processes on alumina (Al 2 O 3 ) were studied to determine if the phenomena of charge separation and subsequent charge-transfer resulted in the catalytic degradation of an adsorbed compound, hexachlorobenzene (HCB). Radiolytic transformation of HCB adsorbed to alumina and potassium bromide (KBr) was monitored by a suite of analytical methods including diffuse reflectance, UV, and Fourier transform infrared spectroscopy (FTIR), as well as GC-ECD and GC-MS. γ irradiation of solid samples was conducted over a dose range of 0−83 kGy. On alumina in the presence of air, HCB was reductively dechlorinated to penta- and tetrachlorobenzene. No HCB reaction was observed on KBr, which served as a noncatalytic support to check the extent of direct radiolytic reaction. HCB conversion to dechlorinated products decreased as a function of increasing surface coverage on alumina, indicating the critical, catalytic role played by the support material. A reaction scheme is proposed.