Core-shell structured Fe0/Mn0@Fe/Mn oxides bimetallic nanocomposites as novel heterogeneous electro-Fenton catalysts for methylene blue removal

Zero-valent iron (Fe0) is a promising catalyst for the heterogeneous electro-Fenton (EF) process. However, for practical application of Fe0, there are some problems such as the Fe2+/Fe3+ cycle is not fast enough, the leaching stability is poor, and F0 is easy to be oxidized. Herein, to overcome the defects, core–shell structured Fe0/Mn0@Fe/Mn oxides bimetallic nanocomposites (C-nZVIM) were developed, which were used as novel heterogeneous EF catalysts for treating MB-containing wastewater to explore their catalytic effect and mechanism. Results indicated that the suitable Mn/Fe mass ratio for the preparation of C-nZVIM was 3:1. C-nZVIM had a core–shell structure with an Fe0/Mn0 core surrounded by an Fe/Mn oxides shell. C-nZVIM could be applied to the heterogeneous EF process over a wide range of initial pH (2.5–8) with high MB removal efficiencies (96.75 %–81.97 %). Mn doped in C-nZVIM promoted the Fe2+/Fe3+ cycle and enhanced •OH generation. Considerable MB mineralization (62.3 % at 150 min and 71.2 % at 300 min) was gained due to •OH. The application of C-nZVIM in the heterogeneous EF process for MB removal achieved a low total leaching of Fe and Mn and desirable catalytic effect. This work offered a novel efficient and stable catalyst for the heterogeneous EF process and provided accurate guidance for its application.