An efficient Ag₂SO₄-deposited ZnO in photocatalytic removal of indigo carmine and phenol under outdoor light irradiation

Abstract

Silver sulfate (Ag₂SO₄) was successfully deposited on ZnO via a simple impregnation method. The as-synthesized sample was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, fourier transform infrared spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activities of pure ZnO and 10 wt% Ag₂SO₄/ZnO were evaluated for the removal of indigo carmine and phenol under outdoor light irradiation. The results showed that the photocatalytic activity of Ag₂SO₄/ZnO was higher than those of pure ZnO and commercial TiO₂ for both pollutants removal. Identification of intermediate products and radical scavengers test were also carried out. The effects of process variables such as initial pollutants concentration and solution pH toward the photocatalytic degradation efficiency were also investigated. The optimum initial pollutants concentration was found to be 10 mg/L for both pollutants. The photo removal of indigo carmine was favorable at pH 7 while in the case of phenol, maximum degradation rate was observed at pH 5. The excellent photocatalytic property of Ag₂SO₄-deposited ZnO suggested its potential usage for practical applications in wastewater remediation.

Keywords:

• Photocatalysis
• Silver sulfate
• Zinc oxide
• Indigo carmine
• Phenol

Acknowledgement

This research was supported by Research Universiti Grant (No. 814176) and International Research Collaboration Fund (No. 910404) from Universiti Sains Malaysia and MyBrain 15 scholarship through Malaysia Government.