Recent Advances in the Synthesis of Metal Oxide Nanofibers and Their Environmental Remediation Applications

Recently, wastewater treatment by photocatalytic oxidation processes with metal oxide nanomaterials and nanocomposites such as zinc oxide, titanium dioxide, zirconium dioxide, etc. using ultraviolet (UV) and visible light or even solar energy has added massive research importance. This waste removal technique using nanostructured photocatalysts is well known because of its effectiveness in disintegrating and mineralizing the unsafe organic pollutants such as organic pesticides, organohalogens, PAHs (Polycyclic Aromatic Hydrocarbons), surfactants, microorganisms, and other coloring agents in addition to the prospect of utilizing the solar and UV spectrum. The photocatalysts degrade the pollutants using light energy, which creates energetic electron in the metal oxide and thus generates hydroxyl radical, an oxidative mediator that can oxidize completely the organic pollutant in the wastewater. Altering the morphologies of metal oxide photocatalysts in nanoscale can further improve their photodegradation efficiency. Nanoscale features of the photocatalysts promote enhance light absorption and improved photon harvest property by refining the process of charge carrier generation and recombination at the semiconductor surfaces and in that way boost hydroxyl radicals. The literature covering semiconductor nanomaterials and nanocomposite-assisted photocatalysis—and, among those, metal oxide nanofibers—suggest that this is an attractive route for environmental remediation due to their capability of reaching complete mineralization of organic contaminants under mild reaction conditions such as room temperature and ambient atmospheric pressure with greater degradation performance. The main aim of this review is to highlight the most recent published work in the field of metal oxide nanofibrous photocatalyst-mediated degradation of organic pollutants and unsafe microorganisms present in wastewater. Finally, the recycling and reuse of photocatalysts for viable wastewater purification has also been conferred here and the latest examples given.