Photocatalytic Degradation of Tetracycline Hydrochloride Using TiO2/CdS on Nickel Foam Under Visible Light and RSM–BBD Optimization

Abstract

This study investigates the photocatalytic degradation of tetracycline hydrochloride (TCH) using a TiO2/CdS composite nanocatalyst synthesized on flexible nickel foam via a dipping–pull method. By comparing the photocatalytic degradation of TCH by TiO2/CdS with different precursor ratios, it was found that TiO2/CdS-1.43% exhibited better photocatalytic degradation performance. The X-ray diffraction (XRD) pattern of the TiO2/CdS composite retains the characteristic peaks of both TiO2 and CdS, indicating the successful formation of the composite. According to the analysis of ultraviolet–visible spectroscopy (UV–Vis), the absorption edge of TiO2/CdS is approximately 530 nm. The transmission electron microscopy (TEM) images show Cd and S evenly, densely distributed in TiO2/CdS, further validating its successful synthesis. X-ray photoelectron spectroscopy (XPS) analysis reveals that Cd and Ti elements exist in the forms of Cd2+ and Ti4+, respectively. TiO2/CdS loading uniformity on the nickel foam was assessed using super-depth microscopy. The removal efficiency of 10 L of 20 mg/L TCH solution achieved 53.89%, respectively, under response surface methodology—Box–Behnken design (RSM–BBD) optimal conditions (28 g catalyst, 325 rpm, pH = 9.04 within 150 min). Furthermore, five successive cycling experiments demonstrated strong stability, with a catalyst loss of only 4.44%. Finally, free radical scavenging experiments revealed that ·O2− radicals are the primary active species. This study highlights the potential of TiO2/CdS composites supported on nickel foam for efficient photocatalytic degradation of antibiotic pollutants in water.