Background and purpose: Among the numerous chemicals utilized in agriculture, 2,4-Dichlorophenoxyacetic acid (2,4-D) is widely used to control weeds. This herbicide is considered as a carcinogen and high toxic pollutant which is very difficult to remove due to its biological and chemical stability. This study aimed at photocatalytic degradation of 2,4-D using indium oxide nanoparticles in the presence of ultraviolet light.

Materials and methods: This study was carried out in bench scale and batch system. The effect of operating parameters such as pH (2-11), contact time (5-240 min), catalyst dose (0.1-2 g/l) and initial concentration of herbicide (5-40 m/l) on the efficiency of the process were studied. The experimental data were fitted to a pseudo-first-order kinetic model.

Results: Increasing the pH and initial concentration of herbicide led to reduced efficiency while increasing the contact time and catalyst dose increased the efficiency. The best result (70% efficiency) was achieved at pH 3, 1 g/l catalyst dose, 120 min contact time, and 5 mg/l initial concentration. The process data well followed the pseudo-first-order kinetic model (R² = 0.915).

Conclusion: The results demonstrated that the photocatalytic process using indium oxide nanoparticles in the presence of ultraviolet light have a relatively good efficiency in removing 2,4-D.