Synthesis and characterization of binary bismuth tungstate-graphitic carbon nitride (BWO/g-C3N4) heterojunction nanocomposites for efficient photodegradation of ibuprofen in aqueous media

Bismuth tungstate-graphitic carbon nitride (BWO/g-C3N4) heterojunction composites were synthesized by wet-impregnation of bulk g-C3N4 nanosheet with octahedron-shaped BWO, characterized and investigated for their photocatalytic capacity in the oxidative degradation of ibuprofen, under visible light irradiation. The characterization of the synthesized composites was done using X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy equipped with EDS, photoluminescence spectroscopy, N2 adsorption-desorption analysis, and thermogravimetric analysis. The synthesized heterojunction composites of different masses of BWO/g-C3N4 showed superior photocatalytic performance for the degradation of ibuprofen, compared to pure BWO and g-C3N4 nanoparticles. The photodegradation efficiency of the 7 wt% BWO/g-C3N4 composite for the degradation of ibuprofen was 94.80 %, which is about 5 and 6 folds higher than those of pure BWO nanoparticles and g-C3N4 nanosheets, respectively. The enhancement in the photocatalytic performance of the BWO/g-C3N4 heterojunction composites may be due to the energy-lowering effect resulting from reduced bandgap of 2.43 eV, which is caused by the coupling of BWO and g-C3N4. The improved composite surface area of 46.15 m2/g facilitates effective charge separation of the photogenerated electron-hole pairs in the composites. Active species trapping experiments showed that the •OH and h+ reactive species were the main radicals involved in the catalytic degradation process ibuprofen. A 67.20 % degradation efficiency was achieved when the composite was tested for practical application in the degradation of ibuprofen in wastewater samples.