Papers by Keyword: Radiation Chemistry

Abstract: This study demonstrates the effective dechlorination of hexachlorobenzene (HCB) in 2-propanol using γ-irradiation from a ⁶⁰Co source, showcasing the potential of radiolysis for persistent organic pollutants (POPs) remediation. Utilizing Gas Chromatography-Mass Spectrometry (GC-MS), we achieved nearly 100% degradation of HCB, quantifying and identifying the breakdown products throughout the process. The kinetic analysis revealed that HCB consumption follows pseudo-first-order kinetics, with an effective rate constant of 4 x 10⁻⁵ L mol⁻¹ s⁻¹. Our findings indicate a systematic reduction in HCB to less chlorinated benzenes (CBs), including penta-(PCB), tetra-(TeCB), and trichlorobenzene (TCB), as confirmed by the mass spectra. The full pathway of HCB degradation involves sequential dechlorination steps: starting from HCB, it is first reduced to PCB, followed by TeCB, and then TCB. Although dichlorobenzenes (DCB), monochlorobenzene (MCB), and benzene formation are theoretically predicted, they were not detected in our experiments. The detailed examination of the radiation chemical yield (G value), the degree of consumption, and the concentration change as a function of absorbed dose highlights the robust capability of γ-radiolysis in the targeted decomposition of chlorinated compounds. These results underscore γ-radiolysis as a highly efficient method for the remediation of POPs.

Abstract: Positron chemistry refers to chemical processes of high-energy positrons injected into molecular substances, the most interesting of which is the formation of positronium (Ps), the hydrogen-like bound state between a positron and an electron. Ps is formed predominantly by fast intra-track radiation chemical processes. In polymers it tends to be localized in intra/inter-molecular open space in the sparsely packed amorphous structure. Whilst short-lived singlet para-positronium (p-Ps) undergoes self-annihilation, the positron in long-lived triplet ortho-positronium (o-Ps) annihilates with one of the spin opposite electrons bound in the surrounding polymer molecules. This process is called pick-off annihilation. The pick-off annihilation lifetime reflects the polymer chain packing through the size of the volume, where Ps is localized. Positrons are used to probe the amorphous structure of various polymeric systems. In this article, basic concepts and experimental techniques of positron chemistry in polymers as well as applications to the characterization of functional polymeric materials are overviewed.