Oxidizing Capacity of Periodate Activated with Iron-Based Bimetallic Nanoparticles

Nanosized zerovalent iron (nFe0) loaded with a secondary metal such as Ni or Cu on its surface was demonstrated to effectively activate periodate (IO4–) and degrade selected organic compounds at neutral pH. The degradation was accompanied by a stoichiometric conversion of IO4– to iodate (IO3–). nFe0 without bimetallic loading led to similar IO4– reduction but no organic degradation, suggesting the production of reactive iodine intermediate only when IO4– is activated by bimetallic nFe0 (e.g., nFe0–Ni and nFe0–Cu). The organic degradation kinetics in the nFe0–Ni(or Cu)/IO4– system was substrate dependent: 4-chlorophenol, phenol, and bisphenol A were effectively degraded, whereas little or no degradation was observed with benzoic acid, carbamazepine, and 2,4,6-trichlorophenol. The substrate specificity, further confirmed by little kinetic inhibition with background organic matter, implies the selective nature of oxidant in the nFe0–Ni(or Cu)/IO4– system. The comparison with the photoactivated IO4– system, in which iodyl radical (IO3•) is a predominant oxidant in the presence of methanol, suggests IO3• also as primary oxidant in the nFe0–Ni(or Cu)/IO4– system.