New insights into the Ferrate-Sulfite system for the degradation of polycyclic aromatic Hydrocarbons: A dual role for sulfite

The presence of polycyclic aromatic hydrocarbons (PAHs) in water is a significant environmental concern due to their potential health risks. While sulfite activation of ferrate (Fe(VI)) has shown promise in enhancing the degradation of antibiotics and pesticides in water systems, its applicability to the degradation of PAHs remains largely unexplored. Here, we investigated the efficiency and mechanisms of PAH degradation via sulfite-activated ferrate. The ferrate-sulfite system significantly accelerated PAH degradation, achieving a 1.53 to 3.13-fold rate increase compared to ferrate-only treatment. Key active species involved in PAHs degradation were Fe(V), Fe(IV), and SO4●−. Sulfite accelerated the degradation of PAHs by undergoing a swift reaction with Fe(VI), leading to the formation of Fe(V) and SO4●−. Sulfite accelerated the degradation of PAHs by undergoing a swift reaction with Fe(VI) resulting in the production of Fe(V) and SO4●−. Through the reduction of ferrate species by sulfite, Fe(III) were produced and accelerated the decomposition of residual Fe(VI) into Fe(IV). Sulfite accelerates the degradation of PAHs by ferrate through these two processes. It promotes Fe(V) and Fe(IV) production from ferrate in a different way. Importantly, the toxicity of PAHs degradation intermediates is significantly reduced. Overall, these findings indicate that the ferrate-sulfite combination has significant potential to address environmental and health concerns associated with PAHs in water sources.