Target Contaminants-Facilitated Mn(II)/Periodate Activation via Self-Sacrificial Coordination: Enhanced Self-Driven Degradation Process

Current understanding of the coordinating role of organic contaminants in metal-activated periodate (PI) processes remains limited. This study demonstrates that contaminants, e.g., tetracycline (TTC) acts as a self-sacrificial ligand coordinating with Mn(II), thereby activating PI for its own degradation. Experimental and theoretical analyses reveal that TTC–Mn(II) complexation creates a unique microenvironment that markedly enhances the electron density at the Mn(II) center. Density functional theory calculations revealed that TTC coordination lowers the Mn(II) to Mn(III) oxidation barrier and enhances electron delocalization within the Mn–TTC complex, supporting its role as a self-sacrificial ligand that accelerates PI activation via a SET pathway. This contrasts with the fundamental mechanism of the oxygen atom transfer pathway with exogenous ligands (such as ethylenediaminetetraacetic acid) observed in the traditional Mn(II)/PI system. This electron transfer process simultaneously generates iodate radicals (IO3•) and oxidizes Mn(II) to transient Mn(III), which rapidly disproportionates into colloidal MnO2 (cMnO2). Critically, the in situ-formed cMnO2 played a catalytic role in activation, further promoting the degradation process. The mechanism exhibits ligand-dependent specificity, selectively degrading strongly complexing pollutants (e.g., TTC) while showing minimal reactivity toward noncomplexing contaminants. This “self-activation” paradigm, leveraging the pollutant’s molecular architecture as an intrinsic catalytic component, presents a novel strategy for precision oxidation in wastewater treatment with minimized external chemical inputs.