Surfactant-Free Solvothermal Synthesis of 3D Flowerlike Iron Alkoxide (Fe-EG) Micro/Nanostructures: Structure, Formation Mechanism, and Fenton Oxidation of Azo Dyes

A three-dimensional (3D) flowerlike iron alkoxide (Fe-EG) micro/nanostructure has been fabricated for the first time via a facile surfactant-free solvothermal method using CH₃COONa·3H₂O as the alkali source and systematically characterized. The green-colored 3D flowerlike Fe-EG micro/nanostructure is a polymeric ferrous glycolate with the chemical formula [Fe₂(OCH₂CH₂O)₂(HOCH₂CH₂OH)₂]_n. Upon quasi-in situ monitoring of the morphology and composition of the samples collected at various reaction times, a coordination/ligand substitution/reduction/polymerization mechanism for Fe-EG is tentatively proposed. The Fe-EG micro/nanostructure exhibited ∼99.7% Acid Orange 7 (AO7) degradation efficiency in 40 min with H₂O₂ as the oxidant at pH₀ = 6.0. It is believed that the high dispersion of a large amount of Fe³⁺ on the surface of in situ-formed 3D flowerlike amorphous FeOOH with a large surface area and rich porous structure by the moderate interfacial hydrolysis process of Fe-EG benefits the adsorption of dye molecules and the formation of hydroxyl radicals.