Study on the mechanism of high effective mineralization of Rhodamine B in three dimensional electrochemical system with γ-Fe2O3@CNTs particle electrodes

•The existence of γ-Fe2O3@CNTs can significantly increase the mass transfer efficiency.•A lot of hydroxyl radicals are generated on the surface of γ-Fe2O3@CNTs.•After 5 cycles, the mineralization efficiency of RhB remains at 92.55%.•The mineralization efficiency of RhB in γ-Fe2O3@CNTs/Mn@FNE-3DER system is more than 99.16% within 7 min.