New insights into stoichiometric efficiency and synergistic mechanism of persulfate activation by zero-valent bimetal (Iron/Copper) for organic pollutant degradation

Extensive studies have been devoting to investigating the catalytic efficiency of zero-valent iron (Fe-0)-based bimetals with persulfate (PS), while little is known in the stoichiometric efficiency, underlying mechanisms and reaction center of zero-valent bimetallic catalysts in activating PS. Herein, nanoscale zero-valent Fe/Cu catalysts in decomposing 2,4-dichlorophenol (DCP) have been investigated. The results show that the increase of Cu ratio from 0 to 0.75 significantly enhances the DCP degradation with a rate constant of 0.025 min(-1) for Fe-0 to 0.097 min(-1) for Fe/Cu(0.75) at pH similar to 3.3, indicating Cu is likely the predominate reaction centers over Fe. The PS decomposition is reduced with the increase of Cu ratios, suggesting the stoichiometric efficiency of Fe/Cu in activating PS is notably enhanced from 0.024 for Fe-0 to 0.11 for Fe/Cu(0.75). Analyses indicate Cu atoms are likely the predominant reaction site for DCP decomposition, and Fe atoms synergistically enhance the activity of Cu as indicated by DFT calculations. Both SO4 center dot- and (OH)-O-center dot radicals are responsible for reactions, and the contribution of SO4 center dot- is decreased at higher pH conditions. The findings of this work provide insight into the stoichiometric efficiency and the reaction center of Fe/Cu catalysts to activate PS for pollutant removals.

Automated summary

Extensive studies have been conducted on the catalytic efficiency of zero-valent iron-based bimetals with persulfate, but little is known about the stoichiometric efficiency, underlying mechanisms, and reaction centers of these catalysts. This study investigated nanoscale zero-valent Fe/Cu catalysts in decomposing 2,4-dichlorophenol, revealing that Cu is likely the predominant reaction center over Fe. The findings shed light on the stoichiometric efficiency and reaction centers of Fe/Cu catalysts in activating PS for pollutant removal.