Construction of three-dimensional reduced graphene oxide wrapped nZVI doped with AlO as the ternary Fenton-like catalyst: Optimization, characterization and catalytic mechanism.

The rational design and synthesis of novel nanocomposites as effective heterogeneous catalysts is meaningful for the advances in Fenton-like technology. Herein, multiple variants of three-dimensional reduced graphene oxide wrapped nZVI doped with AlO (3D-RGO@nZVI/AlO) were prepared by three different self-assembly methods. The composites were characterized by field emission scanning electron microscopy, nitrogen adsorption/desorption isotherms, Raman spectrum analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. A series of experiments on chloramphenicol degradation at different pH values were employed to evaluate the catalytic properties of the prepared catalysts. With the systematical investigation of their morphologies, chemical components and catalytic performance, the optimal 3D-RGO@nZVI/AlO catalyst was synthesized, which was favorable for inducing the Fenton-like reaction by activation of dissolved oxygen (DO) within a wide pH range. The anchored nZVI particles were the main active sites for catalytic oxidation, and doped Al played a major role in buffering the pH of CAP solution. Electron spin resonance spectroscopy revealed the existence of the superoxide radicals (·O) and singlet oxygen (O), which provides a new insight into the reaction mechanism of reactive oxygen species in the Fenton-like system. This work is an essential effort to explore the promoting effect of synthesis methods on the catalytic behavior of catalysts, and to further study the Fenton-like reaction triggered by DO activation.