Treatment of emerging pathogens and micropollutants with potassium ferrate(VI)

Potassium ferrate (K₂FeO₄, Fe(VI)), a powerful and environmentally friendly oxidizing agent, is attracting growing attention as an emerging water treatment chemical. This study reports on recent work examining the effectiveness of Fe(VI) for oxidation of pharmaceutically active compounds (PhACs) and inactivation of viral pathogens (surrogate pathogen: coliphage MS2) during water treatment. Twelve PhACs from representative compound classes were screened to assess potential reactivity with Fe(VI) on timescales of interest to water utilities. Eight of the 12 PhACs surveyed, including the antiepileptic drug carbamazepine and phenolic endocrine disruptor compounds (EDCs), were found to have moderate to high reactivity with Fe(VI). Results also show that Fe(VI) is an effective disinfectant for MS2 phage. The CT value for 99% inactivation of MS2 is ∼2 mg-min L^-1 as Fe at pH 7 and 25 °C. Both rates of PhAC oxidation and virus inactivation are highly dependent upon solution pH, increasing with decreasing pH as Fe(VI) speciation shifts towards more reactive protonated species (HFeO₄^- and H₂FeO ₄). Kinetic models that consider changing speciation of both Fe(VI) and the reacting PhAC or virus, illustrated for the case of carbamazepine, were developed to account for pH-dependent reactivity trends.