Heterogeneous Catalytic Degradation of [Fe(CN)₆]^4– over CuO–MgO Catalysts: Remarkable Efficiency at Low Temperature

The degradation of ferrous cyanide complexes ([Fe(CN)6]4–) in industrial wastewater remains a crucial environmental challenge. A heterogeneous catalytic approach is proposed for the effective degradation of [Fe(CN)6]4–, in which a CuO–MgO solid solution catalyst was synthesized using (Mg,Cu)2(CO3)(OH)2 as a precursor. The effects of Cu/Mg ratio and calcination temperature on the structure and catalytic properties of CuO–MgO were investigated. The results show that Mg2+ enters the lattice of CuO to form a solid solution. The solid solution is characterized by a large specific surface area, uniformly distributed mesopores and low crystallinity. The conversion of [Fe(CN)6]4– reached 97.90% at 100 °C for 1 h over CuO–MgO, which was 5.46 times higher than that in the absence of the catalyst. The outstanding performance was attributed to the MgO-induced electronic polarization of CuO, which promotes the electron transfer from CN– to Cu2+, thus weakening the Fe–CN bond. In addition, the activity of 88.75% was maintained after four cycles of CuO–MgO.