Manganese sulfide co-catalyzed Fenton and Fenton-like oxidation for degrading organic contaminants: Manganese and sulfur as dual reactive centers for sustainable FeIII/FeII cycles

Resulting from the extremely low rate constant of hydrogen peroxide (H 2 O 2 ) induced Fe III reduction, the slow kinetics of reactive oxygen species (ROS) generation in the second stage of Fenton process and high iron sludge output are the core issue for Fenton technology. In this research, manganese sulfide (MnS) was used as environmentally friendly co-catalyst to promote redox processes in Fenton and Fenton-like processes. MnS can significantly boost Fenton (Fe II /H 2 O 2 and Fe III /H 2 O 2 ) and Fenton-like (Fe III /PMS, Fe III /PDS, and Fe III /PAA) processes to degrade sulfamethoxazole (SMX), while MnS/Fe III /H 2 O 2 outperforms other peroxides involved processes. Qualitative and semi-quantitative ROS analysis reveals that hydroxyl radical is the dominating ROS in MnS/Fe III /H 2 O 2 , resulting in the oxidation of diverse organic contaminants. Based on characterizations and DFT calculations, mechanism investigation unveils that the dual reactive and low valent centers of manganese and sulfur can sustainably donate electron for reducing FeOH 2+ into Fe II with the concerted oxidation of Mn II and S 2− , while in-situ generated Fe II reacts with H 2 O 2 to produce hydroxyl radical for water decontamination. In addition, MnS manifests high co-catalytic stability during long-term operation, due to the electron-rich properties of the dual reactive centers of MnS (Mn II and S 2− ). Therefore, this study proposed a new boosted Fenton process by coupling MnS and Fe III /H 2 O 2 for controlling iron sludge output and realizing high-efficiency water decontamination.