Reductive Remediation of Cr(VI)-Contaminated Soils in the Presence of Zero-Valent Metals and Bimetals

The time-dependent efficiency of zero-valent metals (ZVMs) including Al۰ and Zn۰ and their bimetals (Fe/Al and Fe/Zn, ۰.۱ g shell metal/g core metal) to reduce Cr(VI) in three contaminated soils (calcareous, non-calcareous near neutral and slightly acidic) was studied. The Cr(VI)-contaminated soils (۱۰۰ and ۵۰۰ mg/kg) were amended with the reductants (۰, ۵, and ۱۰ g/kg) and the concentration of exchangeable Cr(VI) was determined after ۰.۵, ۴, ۲۴, ۴۸ and ۱۶۸ hours. It was found that the average reducing capacity of the bimetallic particles (۱۱.۴ mg Cr/g) was much higher than the ZVMs (۳.۳ mg Cr/g). The ZVMs showed rapid passivation within only a few minutes, while the bimetallic particles preserved their reactivity even up to one hour. In addition, the efficiency of ZVMs in the slightly acid soil was much higher than in two other soils. There was a good performance of Fe/Al in the calcareous soil with a higher hazard potential than the two other soils. The Cr(VI) reduction capacity of the bimetallic particles in non-calcareous near-neutral soil was two times more than in calcareous soil. The pseudo-first-order Cr(VI) reduction rate constant for the bimetals (۰.۲۴۸ h-۱) was on average higher than those of the ZVMs (۰.۰۷۴ h-۱).

کلیدواژه ها:

Bimetallic particles ، Cr(VI) reduction ، Cr(VI)-contaminated soil ، Zero-valent metal