Synergistic degradation of polycyclic aromatic hydrocarbons using ferrate (VI) and periodate: Efficiency and mechanisms

Polycyclic aromatic hydrocarbons (PAHs) in water pose significant environmental and health risks, necessitating the development of rapid and effective remediation strategies. Here, we present a novel approach that combines ferrate(VI) (Fe(VI)) and periodate (PI) for the efficient degradation of PAHs, alongside an in-depth exploration of the underlying mechanisms. The PI/Fe(VI) system achieved a 57.62 % increase in phenanthrene (PHE) removal at pH 8.0 and a 4.98-fold enhancement in degradation kinetics compared to Fe(VI) alone. Mechanistic investigations, including electron paramagnetic resonance, quenching experiments, and the use of PMSO as a probe, identified Fe(IV) and Fe(V) intermediates as the primary active species. Complementary studies with ABTS and As(III) transformations revealed that PI does not directly activate Fe(VI) but forms complexes with high-valent iron, enhancing Fe(IV)/Fe(V) utilization while suppressing their self-decomposition. PI also facilitated electron transfer from PAHs to high-valent iron species. Experimental and theoretical analyses demonstrated that PI elongates the Fe-O bond, increasing the oxidative capacity of high-valent iron. Importantly, PI is transformed into non-toxic iodate (IO3-), eliminating concerns of iodinated byproduct formation. The PI/Fe(VI) system significantly reduced toxicity in PHE contaminated water, lowering the bioluminescence inhibition rate from 33.20 % to 10.26 %. Collectively, these findings elucidate the pivotal role of PI in enhancing PAH degradation by Fe(VI), underscore the potential of the PI/Fe(VI) system for water remediation, and offer valuable insights into advanced oxidation processes for environmental applications.