Synthesis and photocatalytic activity of porous ZnO stabilized by TiO2 and Fe3O4 nanoparticles: investigation of pesticide degradation reaction in water treatment

The present research studies the photocatalytic degradation of a pesticide using TiO2 and Fe3O4 nanoparticles supported on ZnO mesoporous (mZnO) substrate. Chlorpyrifos is an organophosphate pesticide with a C9H11Cl3NO3PS chemical formula. It is broadly utilized in agricultural fields to control product pests. The chlorpyrifos toxicity is acute and still dangerous to any aquatic organisms. The mZnO/TiO2-Fe3O4 material was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and N2 adsorption and desorption (Brunauer-Emmett-Teller; BET). In order to optimize three important operating parameters, i.e., chlorpyrifos concentration, mZnO/TiO2-Fe3O4 nanocomposite amount, and pH, for photocatalytic degradation of chlorpyrifos, response surface methodology (RSM) was applied. The central composite design (CCD) including 20 experiments was used to conduct experiments. The highest photodegradation performance of about 94.8% was obtained for a chlorpyrifos concentration of 8 ppm, a pH of 10, and an amount of mZnO/TiO2-Fe3O4 nanocomposite of 60 mg. The degradation of chlorpyrifos using mZnO/TiO2-Fe3O4 presented good performance (more than 94%). The photocatalytic reaction followed pseudo-first-order kinetics with a rate constant of 0.058 min−1 for chlorpyrifos degradation. The results propose that mZnO/TiO2-Fe3O4 nanocomposite is a suitable alternative for the degradation of chlorpyrifos in aqueous solution. The improved photocatalytic efficiency could be attributed to the effective separation of electron-hole pairs via a Z-scheme mechanism.