Visible Light Induced Photocatalytic Degradation of Malachite Green by Solid State Synthesized MgFeO3–MgFe2MxO4 + δ (M = None, Mn4+, Ni2+, Zn2+, Eu3+, Dy3+, Yb3+) Nanocomposites

Abstract

MgFe2O4 composite samples were synthesized by one-step solid state reactions between MgCl2 and FeCl3 at 600, 800 and 900 °C. The doped materials were synthesized using Ni(NO3)2, MnO2, Yb2O3, Zn(NO3)2 and Eu2O3dopant raw materials at 800 °C for 12 h. The obtained materials were characterized by powder X-ray diffraction technique. Rietveld analysis data showed that the obtained MgFe2O4 materials were crystallized in the cubic crystal system with the space group Fd-3m and lattice parameters a = b = c = 8.38 A. The morphologies of the synthesized materials were studied by field emission scanning electron microscope. The optical properties of the obtained materials showed that the materials had absorption in ultraviolet–visible light region. Direct optical band gap energies data of the obtained materials indicated that there are two band structure ranges. A strong band structure was in the range of 2.7 to 2.8 eV. The weak band structure was in the range of 1.8 to 2.0 eV. The photocatalytic performance of MgFe2O4 was also investigated for the degradation of Malachite Green (MG) in aqueous solution under direct visible light irradiation (Light power and colour: 40 W and white, respectively). The optimum conditions were obtained by design expert software for S3. It was found that the optimum conditions were 0.09 mL of H2O2, 28 mg of catalyst, and 40 min reaction time. The initial volume and concentration of MG solution were 60 mL and 70 ppm, respectively. It was found that MgFe2O4 had excellent efficiency under the optimized conditions at the presence of direct visible light irradiation. The degradation yield in the optimized conditions was 100%. According to the Langmuir–Hinshelwood (L–H) kinetic model, the kinetic degradation of MG followed a pseudo-first order kinetic model. The apparent rate constant (kapp) and correlation coefficient (R2) values were 0.1367 min−1 and 0.9225, respectively.