A magnetic NiFe2O4 / TiO2-SiO2 composite photocatalyst: Sol-gel synthesis and its application in UV-driven phenol removal from aqueous solution

Advanced oxidation processes (AOPs), particularly photocatalysis, have proven to be highly effective process for phenol degradation. In this study, a novel TiO 2 -based photocatalyst was developed for phenol degradation from aqueous solution under UV light (365 nm). The catalyst was synthesized via the sol-gel method, and the composite contained 5 wt% of NiFe 2 O 4 and 95 wt% of TiO 2 -SiO 2 . Characterization techniques including XRD, FESEM with EDX, FTIR, UV-Vis spectroscopy, and VSM were performed to reveal crystallinity, surface morphology, surface chemistry, bandgap and magnetic properties. XRD peaks confirmed the successful integration of spinel NiFe 2 O 4 (a ≈ 8.35 Å) into the anatase TiO 2 -SiO 2 phase (a ≈ 3.79 Å, c ≈ 9.51 Å) with an average crystallite size of 5.55 nm. FESEM revealed a rough, spherical and partially agglomerated morphology, while FTIR verified composite formation through characteristic Ti-O-Si, Ti-O-Ti, Ni-O, and Fe-O vibrational bands. Under the catalyst comparison condition (pH 7), the NiFe 2 O 4 /TiO 2 -SiO 2 nanocomposite achieved 97.6% phenol removal, which was further increased to complete removal (100%) after optimization of solution pH to 5. It also showed a narrow band gap of 2.40 eV, whereas TiO 2 showed 3.2 eV, displaying a redshift. Furthermore, VSM analysis revealed a saturation magnetization of 1.48 emu/g, indicating that the composite retains a measurable magnetic response. Under the optimized laboratory conditions (0.5 g/L catalyst dose, pH 5, and 10 ppm initial phenol concentration), complete phenol removal was achieved under UV irradiation within 240 min. Kinetic study revealed that phenol degradation follows a pseudo first order kinetic model as the best fit. These findings demonstrate the potential of NiFe 2 O 4 /TiO 2 -SiO 2 as a magnetic photocatalytic material for phenol removal under the investigated laboratory conditions. Further studies on catalyst reusability, real wastewater performance, mineralization, and environmental impact assessment are required to evaluate practical applicability.