Ultrasound-assisted reverse co-precipitation synthesis of biphasic Zn, Ni, or Co spinel ferrite/hematite nanocomposite for the photocatalytic degradation of nitrobenzene

Abstract

An optimized Iron spinel ferrite (Fe3O4) synthesis for the highest catalytic activity by the ultrasonic-assisted reverse co-precipitation (US-RP) method was tested, substituting the divalent cation (Me2+) source from Fe2+ for Zn2+, Ni2+ or Co2+. The respective ZnFe2O4, NiFe2O4 or CoFe2O4 spinel ferrite nanoparticles were successfully synthesized in this work. The use of this US-RP method employing the ion source MeCl2 (Me2+ = Zn2+, Ni2+ or Co2+) yields a magnetic biphasic monocrystalline composite MeFe2O4/α-Fe2O3 nanomaterial with potential photocatalytic properties. The amount of ferrite in the biphasic composite differed for each ion source, being 25.6%, 34.2%, and 38.2% for the CoFe2O4 < NiFe2O4 < ZnFe2O4, respectively. With an inverse trend in the magnetic properties, CoFe2O4 > NiFe2O4 > ZnFe2O4, with a magnetic saturation (Ms) of 42.5, 28.4, and 2.7 emu g−1. These magnetic properties were attributed to the differences in the degree of inversion (δ) calculated from Raman spectroscopy and Rietveld refinements. As for the photocatalytic potential for nitrobenzene (NB) degradation, the half-life calculated under the tested conditions was in the range of 72 – 113 min, following a reaction mechanism that yields H2O, CO2 and 4-nitrophenol (4-NPh) as an intermediate product (< 5.65%). Showing an optimal efficiency at a pH = 2 when using the sample containing CoFe2O4.