Efficient activation of ferrate by Ru(III): Insights into the major reactive species and the multiple roles of Ru(III)

Ferrate (Fe(VI)) has aroused great research interest in recent years due to its environmental benignancy and lower potential in disinfection by-product generation. However, the inevitable self-decomposition and lower reactivity under alkaline conditions severely restrict the utilization and decontamination efficiency of Fe(VI). Here, we discovered that Ru(III), a representative transition metal, could effectively activate Fe(VI) to degrade organic micropollutants, and its performance on Fe(VI) activation exceeded that of previously reported metal activators. The high-valent metal species (i.e., Fe(IV)/Fe(V) and high-valent Ru species) made a major contribution to SMX removal by Fe(VI)-Ru(III). Density functional theory calculations indicated the function of Ru(III) as a two-electron reductant, leading to the production of Ru(V) and Fe(IV) as the predominant active species. The characterization analyses proved that Ru species was deposited on ferric (hydr)oxides as Ru(III), indicating the possibility of Ru(III) as an electron shuttle with the rapid valence circulation between Ru(V) and Ru(III). This study not only develops an efficient way to activate Fe(VI) but also offers a thorough understanding of Fe(VI) activation induced by transition metals.

Automated summary

In recent years, Ferrate (Fe(VI)) has attracted great research interest due to its eco-friendliness and lower potential in disinfection by-product generation. However, the self-decomposition and lower reactivity of Fe(VI) under alkaline conditions have limited its utilization and decontamination efficiency. This study discovered that the transition metal Ru(III) could effectively activate Fe(VI) to degrade organic micropollutants, surpassing previously reported metal activators. The high-valent metal species and Ru(III) acted as major contributors to SMX removal by Fe(VI)-Ru(III), and theoretical calculations revealed the role of Ru(III) as a two-electron reductant.