Establishing a chromium/periodate advanced oxidation process for trace organic contaminants removal: The positive...

Advanced oxidation processes (AOPs) are among the most effective methods for industrial wastewater treatment, but their applications to remove trace organic contaminants (TrOCs) are hampered by a lack of "selectivity". Here, an AOP was established using Cr(III) to activate periodate (PI) (Cr(III)/PI system) realizing rapid TrOCs removal, in which 2 μM tetracycline hydrochloride was completely degraded within 8 min (with 29 μM Cr(III) and 30 μM PI, pH 8). Mechanism analysis revealed the positive effect of Cr(III) complexation on enhancing both the efficiency and selectivity of TrOCs removal. The complexation between Cr(III) and PI triggered the Cr(III)/PI system, promoting water-exchange and inner-sphere redox reactions for efficient PI activating to IO₃^-, which generated mainly ¹O₂ along with the stepwise oxidation of Cr(III). The complexation between Cr(III) and degradation targets also facilitated the selective degradation. These Cr(III) complexations were primarily attributed to H-bonds and van der Waals forces. Toxicity evaluation demonstrated the persistent redox cycle between Cr(IV/V) and Cr(III) over an extended period, avoiding the accumulation of Cr(VI). The generation of highly toxic by-products was also excluded during the PI reduction and the TrOCs degradation. Finally, the Cr(III)/PI system exhibited anti-interference capabilities, including the evaluation in actual secondary effluent of industrial wastewater. Considering the probability of Cr coexisting with organic contaminants, this research provided a simple and rapid approach for the in-depth treatment of Cr-containing wastewater.