ZnO Nanoparticles Coprecipitation with Aluminum and Copper Ions for Efficient Photocatalytic Degradation of Commercial Glyphosate

Abstract

Most agricultural activities involve herbicides, especially glyphosate, which is one of the most common herbicides. Glyphosate has toxic effects and causes contamination of water and soil. To reduce contamination, photocatalytic degradation is used because it can be activated by sunlight and applied anywhere. Herein, ZnO, ZnO:Al, and ZnO:Cu were synthesized, characterized, and applied as photocatalytic materials to investigate the degradation potential of commercial glyphosate. The photocatalytic materials were synthesized under heating and stirring at ambient pressure. ZnO:Cu exhibits spherical, polygon, and hexagon shapes similar to ZnO but with smaller grain sizes, while ZnO:Al exhibited irregular morphology. All synthesized samples feature hexagonal wurtzite polycrystalline structures. The smaller crystal size of ZnO:Al and ZnO:Cu compared to that of ZnO was attributed to the metal ionic substitution, which causes structural defects. Al and Cu coprecipitations have a significant effect on the reduction of the lattice constants in correspondence with lower crystal and grain sizes. The detection of functional groups explored chemical defects in all samples. Both structural and chemical defects turned diamagnetic nature to be a weak ferromagnetic behavior. However, there were similar absorbance peaks in the UV region. The synergy of structural and chemical defects results in an improvement in the photocatalytic activity as they act as interaction centers. Pseudo-first-order kinetic analysis demonstrates that ZnO:Cu is the best photocatalytic material because it exhibited the maximum degradation rate constant (1.84 × 10−3) min−1 compared to ZnO:Al (1.72 × 10−3 min−1) and ZnO (1.52 × 10−3 min−1). The ZnO:Al degradation rate constant was also higher than that of ZnO. Therefore, ZnO synthesized with Al or Cu coprecipitation can be considered as an efficient photocatalytic material for commercial glyphosate degradation.