Controllable synthesis of Mn.sub.3O.sub.4 nanoparticles through in situ reduction reaction via PVA hydrogel template for Fenton-like degradation

A facile strategy for preparing Mn.sub.3O.sub.4 nanoparticles by a soft template method in water was reported. The poly(vinyl alcohol) (PVA) hydrogel, which was used both as template and reducing agent, underwent an in situ reduction reaction with KMnO.sub.4, so that the precursor nanoparticles could be uniformly dispersed in the hydrogel. The size and chemical structure of prepared Mn.sub.3O.sub.4 nanoparticles was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), while the N.sub.2 adsorption/desorption isotherm was carried out to determine its surface area. The prepared Mn.sub.3O.sub.4 nanoparticles with different sizes had good ability for Fenton-like degradation of methylene blue (MB). Their degradation ability was enhanced with the decrease in particle size. The Mn.sub.3O.sub.4 nanoparticles with minimum size of 8 nm showed the 99.0% degradation efficiency for MB (40 mg/L, 40 mL) with 6 wt% H.sub.2O.sub.2 as oxidant in 60 min, which reached the state-of-the-art activity for Mn.sub.3O.sub.4 nanomaterials.