Abstract
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 ({{rm{e}}}_{{rm{aq}}}^{-}) 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.
Highlights
The precipitation occurred because a large amount of Cr(VI) ions were reduced to insoluble Cr(III) by high-energy electron beam (HEEB), which was proved by the following X-ray photoelectron spectrometer (XPS) and Fourier transform infrared (FTIR) analyses
The reduction performance of HEEB for Cr(VI) was attributed to reductive radicals such as e−aq (e− + nH2O = e−aq) and ·H (H2O = ·H + ·OH) generated from water radiolysis during the irradiation process. This result demonstrated that HEEB had a significant reduction capacity on Cr(VI) in aqueous solution and that this method is convenient and clean compared with traditional methods based on reducing agents such as nano zero-valent iron and amorphous FeS221,22
These results indicate that HEEB irradiation could effectively transform soluble CrO72− into insoluble Cr(OH)[3], which could be removed from the solution
Summary
The migration behaviours of FRs are still unclear, creating an important gap limiting basic and applied studies of FRs in chemistry[15]. The RE of Cr(VI) could be used as a key indicator for investigating the migration behaviour of FRs under HEEB irradiation. The migration behaviours of FRs in water and ice were investigated under HEEB irradiation using the RE of Cr(VI) as an indicator. That the amount of FRs in ice decreased substantially with distance from the irradiated target. These findings have great value in promoting studies of FR-induced reactions in chemistry[15], the bystander effect in radiation biology[20], and other phenomena. This work is of great significance in promoting environmental studies on FRs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
