Synthesis and photocatalytic activity of ferrites under visible light: A review
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This review presents the use of ferrites in photocatalytic conversion of visible solar energy to generate e -/h +, which in turn produce reactive oxygen species through redox processes, for the degradation of the contaminants. Spinel ferrites have a relatively narrow band gap (2.0 eV) making them capable of such processes. Synthesis approaches of ferrites include thermal methods, sol-gel and citrate methods, co-precipitation, and solid-state reactions. Different techniques to characterize ferrites are X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning-electron microscopy (SEM), and transmission electron microscopy (TEM). Ferrites have been applied as photocatalysts alone, in composites with other photocatalysts, as well as with other oxidants such as H 2O 2. Ferrites are effective in each case, however when used as composite photocatalysts their degradation efficiency are enhanced. Combination of ferrites with H 2O 2 either under light irradiation or dark conditions, a Fenton-type system is created, which produces hydroxyl radicals to enhance the degradation processes. Examples are presented for applications of ferrites for the degradation and/or adsorption of a number of different contaminants for environmental purification including inorganics, bacteria, and large organic molecules such as dyes. 2011 Elsevier B.V. All rights reserved.
