Bi2O3 immobilized 3D structured clay filters for solar photocatalytic treatment of wastewater from batch to scaleup reactors

3D structured clay filters were synthesized using the 3D printed molds. The Bi2O3 photocatalyst was immobilized on the surface of the clay filter using sol-gel dip, soak and calcination at 450 °C. The X-Ray Diffraction analysis of the immobilized filter showed the growth of tetragonal β-Bi2O3 on the clay. The diffused reflectance UV–Vis spectroscopy confirmed the presence of β-Bi2O3 on the clay with a broad optical absorption in the visible range and an estimated bandgap of 2.38 eV. The morphology of the Bi2O3 filter showed uniform layered films on the irregular grains of calcined clay with a crackly appearance. The photocatalytic properties of the Bi2O3 filter were evaluated for the degradation of the anionic indigo carmine (IC) dye and Bisphenol-A (BPA) under visible light and natural sunlight. Bi2O3 coated filter was more effective under natural sunlight because of the high intensity of solar irradiation. Total organic carbon analysis revealed up to 30% and 70% mineralization of the IC and BPA moieties, respectively. A recirculating semi-batch reactor with the upscaled configuration of the Bi2O3 filter was designed to degrade a large volume of both individual and mixed IC and BPA solutions. The overall results revealed a high potential of the Bi2O3 clay filter for the treatment of organic pollutants.