Zinc oxide-mediated photocatalytic decolorization of Ponceau S in aqueous suspension by visible light

Muhammad Muslim, Md Ahsan Habib, Abu Jafar Mahmood, Tajmeri Selima Akhter Islam, Iqbal Mohmmad Ibrahim Ismail
2012 International Nano Letters  
ZnO, comprising nanosize particles (approximately 40 nm) has been prepared by heating (300°C) ZnCO 3 , which was obtained as precipitate by mixing ZnSO 4 and (NH 4 ) 2 CO 3 solutions. The prepared ZnO was characterized by X-ray diffraction, scanning electron microscopy (SEM), laser-induced breakdown spectroscopy, and adsorption studies. It has been used to catalyze the decolorization of Ponceau S (PS), a model diazo dye, in an aqueous suspension under visible light (I ≈ 1.8 × 10 −4 W cm −2 ).
more » ... 10 −4 W cm −2 ). This ZnO was found to be more efficient as a photocatalyst compared to pristine ZnO. ZnO samples with higher temperatures (500°C and 700°C) show less catalytic activity. SEM images show that the particle size of ZnO increases with the increase in calcined temperature of ZnO through agglomeration, resulting in a decrease in surface area. Photodecolorization of PS is affected by its and ZnO concentrations, but unaffected by the initial pH of the solutions in the range of 4 to 7. Illumination for a sufficiently long time completely mineralizes the dye, but no Zn 2+ can be detected in the clear solution. Photodegradation kinetics in the ZnO suspension obeys the Langmuir-Hinshelwood equation, and some activation of the ZnO surface by light is indicated.
doi:10.1186/2228-5326-2-30 fatcat:5q5dfba3pzfz5pgz537rea3dke