Structural study on PVA assisted self-assembled 3D hierarchical iron (hydr)oxides

Abstract

Polymers with hydroxyl groups may have great influence on the formation process of metal oxides due to complexation. To better study the interaction mechanism between polyhydric polymer and iron (hydr)oxide, herein, without using surfactants or toxic matters, 3D hierarchical iron (hydr)oxide with different nanostructures were obtained with the assistance of polyvinyl alcohol (PVA). The influences of PVA concentration, temperature, and reaction time on the product structure were investigated. Then, the formation mechanisms are discussed. Under different PVA concentrations and temperature, varies products were obtained, such as α-FeOOH, α-Fe₂O₃, and their mixtures. On increasing the PVA concentrations, the material morphology changes from flower-like nanostructures to urchin-like microspheres and finally into nanoplates. Furthermore, an increase in reaction temperature would lead to the formation of microspheres with a smoother surface. The urchin-like α-FeOOH obtained at a moderate PVA condition has the best adsorption performance for Congo red with a maximum adsorption capacity of 287.35 mg g⁻¹, which was a great improvement when compared to that of the sample obtained from pure water (173.01 mg g⁻¹). The results reflect the potential advantages of the polymer applied for the structural improvement of nanomaterials.