Probing the Migration of Free Radicals in Solid and Liquid Media via Cr(VI) Reduction by High-Energy Electron Beam Irradiation

摘要

To probe the migration of free radicals (FRs), the reduction behaviours of hexavalent chromium (Cr(VI)) in water and ice by high-energy electron beam (HEEB) irradiation were investigated. Interestingly, the reductive efficiency (RE) of Cr(VI) in water was appreciably higher than that in ice. Thus, it was proposed that the migration ability of FRs in water is distinctly higher than that in ice, likely because the migration performance of FRs is closely related to the intermolecular distance of water molecules. Furthermore, the RE of Cr(VI) in ice decreased gradually with the distance from the irradiated area, indicating that FRs could migrate in ice and that the migration performance was closely related to the RE. Additionally, FRs (hydrated electrons (eaq−) and hydrogen radicals (·H)) generated during the irradiation process played a key role in the reduction of Cr(VI). Hydroxyl radicals (·OH) and H2O2 were the dominant negative factors for the reduction because of their oxidizing effects, but these factors could be eliminated by the removal of ·OH. This work reveals the migration performance of FRs in different media for the first time. This result may be useful for basic and applied studies in fields of environmental science related to FRs.