TiO2/SiO2/g-C3N4 flower-like spheres with g-C3N4 sheets for enhanced visible-light driven photodegradation of industrial pollutions via an adsorption-photocatalysis synergy

Abstract Wastewaters containing toxic pollutants such as dye, pharmaceuticals and other chemicals have adverse effect on human and aquatic life. The pharmaceuticals cannot be efficiently removed by conventional wastewater treatment processes. The use of the proper photocatalyst for the removal of pharmaceuticals in aquatic systems is getting extensive attention. In this research, TiO2/SiO2/g-C3N4 nanostructured photocatalysts in the form of powder (NP) and thin film (TF) with different concentrations of graphite-carbon nitride (g-C3N4) sheets were prepared by simple hydrothermal and dip-coating methods, respectively. The morphology, composition, structure, and optical properties of the samples were systematically investigated using proper characterization technics. Based on the obtained results, it was indicated that modification of Titanium dioxide (TiO2) with Silicon dioxide (SiO2) effectively preserves the active anatase phase of TiO2, increases the specific surface area of the TiO2 sample and improves the ability of visible light absorption due to the formation of imperfection in the crystal structure. The results of photocatalytic experiments indicated that adding g-C3N4 enhances photodegradation of methylene blue (MB) and tetracycline (TC) due to increase in effective surface area, charge carrier separation, and increased light absorption in the visible region. Highest efficiency was achieved for the sample with 0.03 g of g-C3N4 in the precursor solution. TiO2/SiO2/g-C3N4 NP compared to its TF counterpart possesses higher visible photodegradation with an efficiency of ~96% for a solution of 20 mg/l MB with corresponding adsorption of 88% in darkness within 60 min. In addition, TF photocatalysts showed good reusability and feasible separation from the refined solution. Efficient removal of TC by a reactor with a design to be applicable for both synthesized TF and NP photocatalysts was achieved under visible light illumination. This work may propose an effective approach to remove antibiotics in wastewater.