A quadripartite Cu2O-CdS-BiVO4-WO3 visible-light driven photocatalyst contained three cascade Z-scheme systems: Focus on conditions’ optimization, scavenging agents and the mechanism pathway towards sulfasalazine

The explosive pollution of water suppliers via the discharge of various industrial and pharmaceutical effluents prompted researchers to construct novel adsorbents and photocatalysts, especially their visible-light driven photocatalysts. A novel coupled Cu2O-CdS-BiVO4-WO3 quadripartite nanoscale catalyst was prepared and characterized by XRD, SEM-DX, x-ray mapping, and DRS techniques. Its pHpzc was also determined to be about 9. The Eg-values obtained were 1.95, 1.96, 2.16, 2.38, and 2.19 for Cu2O, BiVO4, CdS, WO3, and quadripartite catalysts, respectively. The photodegradation experiments were designed via RSM. The significance of the suggested model was confirmed by a greater model F-value of 26.19 than F0.05,14,15=2.55. The optimal run in the photodegradation of sulfasalazine (SFSZ) included the CSFSZ: 7 mg/L, pH 6.25, 30 min irradiation time, 0.45 g/L of the catalyst dose, by a catalyst with a Cu2O-CdS-BiVO4-WO3 mole ratio 3:1:1:1 under visible light illumination. The effects of the scavenging agents were also studied, and the results confirmed the critical role of superoxide in SFSZ photodegradation and the hydroxyl radicals. The photodegradation pathway obeyed the direct Z-scheme mechanism, which involved three successive binary Z-scheme components involving WO3-BiVO4, BiVO4-CdS, and CdS-Cu2O, which accumulates the photoinduced electrons in the CB-Cu2O and the holes in the VB-WO3, the more powerful reducing and oxidizing centers, respectively. Research Highlights • A novel quadripartite Cu2O/CdS/BiVO4/WO3 containing three cascade Z-scheme systems. • All components used are visible light active photocatalyst. • A red shift in Eg of the quadripartite catalyst concerning WO3. • Satisfy photocatalytic applicability of the quadripartite catalyst in various water samples.