Photodegradation of aqueous tetracycline using CuS@TiO₂ composite under solar-simulated light: Complete mineralization, catalyst efficiency, and reusability.

While CuS/TiO₂ has been previously synthesized and employed in a limited number of photodegradation studies, the current study investigated its effectiveness for TC degradation under UV-visible light irradiation. CuS is known to be a nontoxic, environmentally friendly material; hence, it has great potential as an alternative to CdS and CdSe, which are used conventionally as sensitizers. In this work, the CuS/TiO₂ photocatalysts achieved a maximum 95 % removal of TC at an initial concentration of 20 ppm, confirming the good utilization of active sites. Even though the efficiency decreased for higher TC concentrations due to the saturation of the active sites, the values of the quantum yield showed that photon utilization was still effective. Consequently, the photocatalyst showed an optimum yield at 0.20 g, and its further addition increased the efficiency rather insignificantly. In addition to the near-complete mineralization of TC by the CuS/TiO₂ composite with few byproducts, its reusability was excellent because it showed almost consistent performance in successive cycles. These results further confirm the continuous relevance and potential of CuS/TiO₂ as a practical, sustainable solution for organic pollutant degradation, reinforcing its value in environmental remediation applications.