Development of g-C3N4/TiO2/Fe3O4@SiO2 heterojunction via sol-gel route: A magnetically recyclable direct contact Z-scheme nanophotocatalyst for enhanced photocatalytic removal of ibuprofen from real sewage effluent under visible light

The inefficiency of conventional treatment technologies for the removal of ibuprofen has shifted the attention of water researchers towards TiO2-based photocatalysis due to its various advantages. However, the disadvantages limit practical applicability: (a) ability to exploit UV light (2-3% of the solar spectrum) only, (b) high recombination rates of photogenerated e(-) and h(+), and (c) difficulty in separation after use. To overcome these challenges, a highly photoactive magnetically recyclable direct contact Z-scheme g-C3N4/TiO2/Fe3O4@SiO2 (gCTFS) heterojunction nanophotocatalyst was synthesized via a sol-gel route, using only a small amount of ultrathin g-C3N4 nanosheets (0.00021:1 wt ratio of ultrathin g-C3N4 nanosheets to the TiO2 precursor). The synthesized nanophotocatalyst was characterized by X-ray diffraction, vibrating sample magnetometer, UV-vis diffuse reflectance spectrophotometer, fluorescence spectrophotometer, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, and Zeta potential. The nanophotocatalyst was able to remove 97% of ibuprofen after 15 min of similar to 330Wm(-2) integrated irradiance of visible light. The superparamagnetic behavior of the nanophotocatalyst with saturation magnetization of 8 emu g(-1) enabled its successful magnetic recovery from the solution after use for further application. Furthermore, reusability studies of the nanophotocatalyst over three cycles, ibuprofen removal studies at various pH (3, 5, 7, 9, and 11) and in the presence of various anions (Cl-, NO3-, PO43-, and SO42-), and mineralization capability for ibuprofen removal under visible light irradiation were also investigated. Overall, the recyclable direct contact Z-scheme gCTFS nanophotocatalyst was also found to be applicable under ibuprofen-spiked real sewage effluent thereby proving its practical applicability for environmental applications.