Synergistic green degradation of organic dyes using a BiSI catalyst: Adsorption, sonocatalysis, and photocatalysis

Water contamination due to the uncontrollable release of organic dyes into water bodies poses a serious threat to human health and ecosystems biodiversity. To address the harmful impact caused by these compounds, the development of suitable removal techniques and materials is critical. In this regard, bismuth sulfide iodide (BiSI) emerges as a promising semiconductor for wastewater treatment due to its adsorptive, sonocatalytic, and photocatalytic properties. In this study, BiSI was successfully synthesized via a wet chemistry route at moderate temperatures (120 °C) and employed as catalyst on the degradation of Rhodamine B (RhB). The main purpose addressed in this work was to achieve a synergistic effect between sono- and photocatalysis to improve the performance of the catalyst for the fast and effective removal of organic compounds. The synthesized BiSI was thoroughly characterized including its morphology, structure, surface, and optical properties. The removal capacity of RhB onto BiSI was examined under different operating conditions. BiSI catalyst demonstrated a remarkable efficiency of 95.0 % and a maximum removal capacity (Qmax) of 16.5 mg/g in just 3 min by using single sonocatalysis and photocatalysis. Besides, applying the combined sonophotocatalytic approach, the performance of the BiSI catalyst was significantly enhanced (Qmax of 28.7 mg/g), when simultaneously subjected to ultrasonic waves and ultraviolet (UV) irradiation. In addition, a possible degradation mechanism was proposed. In short, the results achieved in this study effectively demonstrated the synergistic effect when combining sono- and photocatalysis in a single method, and also the suitability of the developed BiSI catalyst for the rapid and effective degradation of RhB, employing a sustainable approach that relies on ultrasound energy and light irradiation.