Green synthesis of a dendritic Fe₃O₄ @Fe^o composite modified with polar C-groups for Fenton-like oxidation of phenol

In this work, a hierarchical dendritic Fe₃O₄@Fe⁰ composite modified with polar C-groups was obtained by electrodeposition and post-solvothermal methods. SEM, EDS, TEM, XRD, Zeta analysis and ESR were employed to study the structure and composition of catalyst, and the catalytic capability was evaluated by phenol degradation experiments. With the increase of water ratio in thermal solution, the composition of prepared catalyst changes into Fe₃O₄/Fe₂O₃ from Fe/Fe₃O₄, and the dendritic structure turns into particle-like structure. The phenol degradation experiments indicate the catalyst prepared in pure-ethanol solution possesses the optimal catalytic capability, which has a Fe@Fe₃O₄ core-shell structure with some polar C-groups on Fe₃O₄ outer layer. Under the condition of 0.18 g/L of catalyst dosage, 6 mmol/L H₂O₂ and pH = 4.0, the composite catalyst prepared in pure ethanol could remove 98% phenol for 5 min, greatly higher than dendritic bare Fe^o under the same condition. The enhancement of degradation efficiency by Fenton-like reaction might be ascribed to polar groups that facilitate the adsorption of H₂O₂, phenol and hydroxyl radicals and promote the transformation of Fe^III to Fe^II on the catalyst surface. This work provides a new insight into the design and application of high-efficient Fe⁰-based Fenton-like composite catalysts for wastewater purification.