Photocatalytic removal of 2,4-Dichlorophenoxyacetic acid from aqueous solution using tungsten oxide doped zinc oxide nanoparticles immobilised on glass beads

Abstract

ABSTRACT Groundwater is the only source of high quality water for human consumption in most parts of the world; however, it can be easily contaminated by domestic, industrial, and agricultural wastes such as fertilisers and pesticides. The main objective of the present research was to study the photocatalytic removal of 2,4-Dichlorophenoxyacetic acid pesticide (2,4-D) from aqueous media. This was a laboratory scale study in which the zinc oxide nanoparticles were doped with 0.5, 1, and 2 molar percent of tungsten oxide. The nanoparticles synthesised were characterised using powder XRD, SEM, FTIR, and UV-Vis Spectroscopy analyses. During the photodegradation of 2,4-D, the operational parameters studied were pH, nanoparticles dosage, initial pesticide concentration, light intensity, contact time, and the mineralisation trend of organic matter. It was found that the doped nanoparticles had a smaller band gap energy, which confirms the effect of doping. The percentage of the dopant can affect the pesticide removal efficiency. The optimal pH value obtained was 7. In addition, the process efficiency, increased from 27% to 78% with increasing UV light intensity from 172 to 505 W/m2 respectively. Moreover, it was found that, with increasing light intensity, contact time and nanoparticle concentration all caused the pesticide removal efficiency to be increased too. In addition, the increase of the pesticide concentration would cause a reduction in the process removal efficiency. This study indicated that the photocatalytic process using tungsten doped zinc oxide nanoparticles can remove the 2,4-D pesticide by around 80% from the aquatic environment.