Enhanced performance of hierarchical heterostructures CuS@ZnS-Ag-doped core-shell quantum dots towards photocatalytic degradation of pesticide contaminants in aqueous solution

In recent years, the pollution of the water by pesticides has become a significant global concern due to the harmful effects these compounds have on human health and the environment. Therefore, removal of pollutants or making them ineffective is necessary for life. In this study, removal of agricultural pesticides such as Deltamethrin, Flumethrin and Phoxim was performed through photodegradation process using CuS@ZnS-Ag quantum dots as photocatalyst. The synthesised CuS@ZnS-Ag heterojunction nanocomposite has suitable charge separation and low electron-hole recombination rate with good optical properties. The synthesised photocatalyst was characterised by various techniques such as X-ray diffraction, Fourier transform infrared spectrometry, UV-Visible spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The effects of pH, temperature, photocatalyst dose and agitation rate on the degradation were investigated. The optimised conditions were obtained as follows: pH 7 (+/- 0.5), temperature 30 (+/- 2) degrees C, photocatalyst dose for Flumethrin 30 mg/L, Deltamethrin 10 mg/L and Phoxim 15 mg/mL and agitation rate 500 rpm. Results showed that under optimal conditions, the CuS@ZnS-Ag as photocatalyst can degrade 96% of the pollutants using light-emitting diode lamp. Kinetic studies indicated the pseudo-second-order model.