Construction of flower-like MnO ₂ decorated by SrCuFe ₂O ₄ as a magnetic nanocomposite for the photocatalytic degradation of methylene blue under visible light

A novel magnetizable nanocomposite (NC) photocatalyst SrCuFe ₂O ₄@MnO ₂-f, consisting of SrCuFe ₂O ₄ loaded onto flower-like manganese oxide, was synthesized using a simple template-free method. A hydrothermal route using KMnO ₄ was employed to produce and control the shape of the MnO ₂-f nanoparticles, while the SrCuFe ₂O ₄ nanoparticles (NPs) were created by a sol–gel method from the nitrates of strontium, copper and iron. The physicochemical properties of the synthesized nanomaterials were characterized by FTIR, FE-SEM with EDAX, XRD, VSM, TGA/DTA, BET, and TEM techniques. The effects of experimental variables on the visible light-induced photocatalytic activity of SrCuFe ₂O ₄@MnO ₂-f for methylene blue (MB) dye degradation were studied. The results showed that the photocatalyst achieved superior photocatalytic performance i.e. 98.3 % MB photolysis within 56 min using 3 mg catalyst dose per 50 mL of 10 ppm MB concentration at pH 10, compared to 58.5 % and 49.51 % for MnO ₂-f and SrCuFe ₂O ₄, individually. The degradation kinetics fitted a pseudo-first order kinetics model with a rate constant of 0.06246 min ⁻¹. The enhanced photocatalytic efficiency, was assigned to better light absorption, more effective separation of electron-hole pairs and faster transfer of charge carriers within the SrCuFe ₂O ₄/MnO ₂-f structure. Moreover, the as-prepared photocatalyst achieved 89.7 % MB degradation efficiency after 4 times recyclability, making it potentially valuable for large scale polluted water purification systems.