Unleashing the power of sunlight: Bi2O3/Sb2S3 photocatalysis for sustainable wastewater remediation of Tetracycline and Rhodamine-B

The use of heterojunction photocatalysts for pollutant decomposition has garnered significant interest in mitigating water contamination and environmental pollution. Our present study focuses on synthesizing Bi2O3/Sb2S3 heterojunction photocatalyst having variable mole ratios by employing a hydrothermal technique. Loading Sb2S3 onto Bi2O3 enables broad-spectrum solar light absorption, efficient segregation of charges, and enhanced surface area, which are excellent traits for photocatalysis. Both Bi2O3 and Sb2S3 showed nano-rod type morphology, while Sb2S3 was present as smaller nano-rods and Bi2O3 as larger ones. The photocatalytic performance of this heterojunction photocatalyst was examined using Rhodamine-B (RhB) and Tetracycline (TC) under solar light illumination for 120 min. Remarkable decomposition efficiency was achieved, with a 98.2% degradation rate observed for RhB having a rate constant of 0.03149 min−1. Similar experiments were conducted using other light sources as well, such as visible light and UV light. However, only 83% and 69% RhB degradation rates were attained with visible and UV light, respectively, indicating that natural sunlight is the superior light source for our catalyst. A 91.5% degradation rate was achieved for TC with the rate constant of 0.01749 min−1, in the presence of sunlight for 120 min. A small amount (0.3 g/L) of 1:3 Bi2O3/Sb2S3 (13BOSBS) photocatalyst was enough to bring such a good result. The photocatalytic activity of our catalyst, that is, 98.2% RhB degradation, is much higher than that of commercially available TiO2–P25 powder, as the latter only achieved 52% RhB degradation. The pH at which the surface of Bi2O3/Sb2S3 has a zero charge (pHpzc) was determined to be 5.37 and the maximum decomposition of RhB was achieved at pH 7. Reusability tests verified the remarkable stability of this catalyst, with about 74.4% of RhB degradation still present after seven consecutive cycles. Scavenger experiments highlighted the crucial role of •OH radicals in the photodecomposition mechanism, as the incorporation of DMSO significantly influenced the photocatalytic efficiency of the 13BOSBS composite, leading to a notable decrease to 37.5% in RhB degradation. For the RhB dye, the 13BOSBS catalyst demonstrated remarkable 90.2% and 85% reductions in COD and TOC, respectively. The commercially available TC powder substantially reduced 84% in COD and 80% in TOC, whereas there was a 78% reduction in COD and 73% in TOC for TC tablets. The degradation of the contaminants was followed by the formation of simpler intermediates, which were discovered using the GC-MS approach. Owing to its excellent attributes and simple synthesis method, the fabricated heterojunction offers a promising solution to prevent the persistent buildup of harmful toxic pollutants in industrial wastewater systems.