g-C3N4 quantum dot decorated MoS2/Fe3O4 as a novel recoverable catalyst for photodegradation of organic pollutant under visible light

In this research, zero-dimensional (quantum dots) of graphitic carbon nitride (g-C3N4) and Fe3O4 nanoparticles were decorated on MoS2 nanosheets to prepare MoS2/Fe3O4/g-C3N4 quantum dots. Photocatalytic activities of newly synthesized nanocatalyst were investigated by the degradation of methylene blue (MB) and methyl orange (MO) under visible LED lamp light. In these degradation reactions, the parameters effective such as dyes concentration, pH, amount of catalyst, and irradiation time were also investigated. The systematic investigations revealed that 10 mg of MoS2/Fe3O4/g-C3N4QDs catalyst was optimum to degrade 10 mg/L of MB and 40 mg of nanocatalyst to degrade 10 mg/L of MO with 60 W of LED irradiation. Nanocomposite can act as an excellent photocatalyst for degradation of MB and MO at short time intervals and also can be easily separated by an external magnet and reused several times. The kinetic data acquired for the degradation of dyes were matched to first-order rate equations, and also the apparent rate constants for the degradation of MB and MO were calculated as follows: K = 0.285 min−1 and K = 0.263 min−1, respectively. The novelty of catalyst is due to metal (Mo) and non-metal (S) in the structure of substrate (MoS2), so Fe3O4 and g-C3N4 QDs can be strongly connected to the substrate. The structure and morphology of prepared nanocomposite were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), scanning electron microscopy (SEM) energy dispersive X-ray spectroscopy (EDS), and UV–Vis spectroscopy.