A brief study on the Eriochrome Black T photodegradation kinetic by CdS/BiVO4 coupled catalyst

The coupled CdS/BiVO4 coupled catalyst was prepared via mechanical mixing of the as-synthesized CdS and BiVO4 NPs. Samples were investigated by scanning electron microscope (SEM), X-ray diffraction diffractometer (XRD), UV–Vis diffuse reflectance spectroscope (DRS), and Furrier transformation infrared spectrophotometer (FT-IR). The average crystallite sizes for CdS, BiVO4, and CdS/BiVO4 were obtained about 5.8, 34.9, and 37.3 nm By the Scherrer formula), and about 1.7, 23.1, and 12.5 nm (by the Williamson-Hall formula), respectively. The absorption edges of 622, 529, and 571 nm corresponding to bandgap energies of 1.99, 2.24, and 2.17 eV were respectively obtained for CdS, BiVO4, and CdS/BiVO4. A boosted photocatalytic activity of the coupled system was observed in the photodegradation of EBT (Eriochrome Black T). When moles of the BiVO4 component were 3–4 times greater than CdS, the highest activity was achieved. The rate constant of 0.032 min−1 and 0.007 min−1 were respectively obtained by the absorbencies recoded for the photodegraded EBT solutions and chemical oxygen demand (COD) data obtained in the photodegraded solutions. These values correspond to t1/2-values of 21.7 min and 99 min for the degradation and mineralization of EBT molecules during the photodegradation process. Here, a cheap and straightforward mechanical method was used to prepare the binary visible-light active CdS/BiVO4 photocatalyst with satisfying charge carriers’ transfer and good photocatalytic activity.