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^-). nFe ⁰ 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)/IO ₄^- 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.