Ferrous and manganese oxalate for efficient heterogenous-Fenton degradation of organic pollutants: composite active site and mechanism perception

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Composite heterogeneous catalysts of ferrous and manganese oxalate (FeC 2 O 4 /MnC 2 O 4 ) were prepared via simple chemical co-precipitation. The catalytic performance was evaluated by determining the degradation efficiency of rhodamine B (RhB). Under optimum conditions, 6-1FeMn showed the best catalytic performance, and the degradation efficiency exceeded 95 % within 2 min, which was 1.4 times more than ferrous oxalate. Under a wide pH range (1–8), 6-1FeMn showed high degradation efficiency for RhB with good recyclability and reusability. By characterizing the catalysts before and after the reaction and analyzing the degradation process, a possible mechanism was proposed: Mn 2+ and Fe 2+ synergistically catalyzed and produced a large number of hydroxyl radicals (·OH) by forming a composite active site for efficient reactivation. Mn 3+ accelerated the transfer between Fe 2+ and Fe 3+ . In addition, C 2 O 4 2− reactivated the active site in situ and enhanced the catalytic properties. This study provides new insight into the catalytic degradation of organic dyes using composite heterogeneous Fenton catalysts.