Synthesis and characterization of ZnO-TiO2 nanocomposites and their application as photocatalysts

Md Ahsan Habib,Iqbal M I Ismail,Newaz Mohammed Bahadur,Abu Jafar Mahmood,Md Tusan Shahadat

doi:10.1186/2228-5326-3-5

Abstract

Nanocomposite ZnO-TiO2 powders of varying ZnO/TiO2 molar ratios have been prepared from their salt/compound by heating at 600°C and 900°C and characterized using scanning electron microscope and X-ray diffraction techniques. The nanosized powders can decolorize/degrade brilliant golden yellow (BGY), an azo dye extensively used in textile industries, in water under solar irradiation. The effects of various parameters such as photocatalyst loading, molar ratio of ZnO/TiO2, pH of the solution, initial dye concentration, and irradiation time on the photodecolorization have been investigated. ZnO-TiO2 nanocomposite (6 g/L) in the molar ratio of 1:1 or 3:1, prepared at 900°C, can efficiently decolorize about 98% of 20 mg/L BGY at pH of about 7 by 2-h illumination in sunlight. The initial dye decolorization follows pseudo-first-order kinetics. Finally, trial experiments were done using real textile wastewater to find out the effectiveness of the photocatalysts to a more complex system.

Highlights

Effluents containing dyes often create severe environmental pollutions because of their direct disposal into the nearby water bodies [1]
The nanocomposites were characterized by scanning electron microscope (SEM)/X-ray diffraction (XRD) technique, and the as-prepared nanocomposites were used as photocatalysts to decolorize the brilliant golden yellow (BGY), an azo dye which is extensively used in textile/ dyeing industries, under solar irradiation
ZnO/TiO2 photocatalysts Figure 2a, b shows the SEM images of ZnO/TiO2 nanocomposites prepared by the thermal method at 600°C and 900°C, respectively

Summary

Background

Effluents containing dyes often create severe environmental pollutions because of their direct disposal into the nearby water bodies [1]. The photocatalytic degradation of various kinds of organic and inorganic pollutants using semiconductors as photocatalysts has been widely studied [4,5,6,7]. Among these semiconductors, TiO2 has been extensively investigated as the most promising photocatalyst due to its high photocatalytic activity, non-toxicity, high photochemical stability, and low-cost. The coupling of different semiconductor oxides seems useful in order to absorb a wide range of solar radiation (both UV and visible regions) and to achieve a more efficient electron–hole pair separation, and a higher photocatalytic activity will be attained [9]. The nanocomposites were characterized by scanning electron microscope (SEM)/X-ray diffraction (XRD) technique, and the as-prepared nanocomposites were used as photocatalysts to decolorize the brilliant golden yellow (BGY), an azo dye which is extensively used in textile/ dyeing industries, under solar irradiation

Methods

Results and discussion

Conclusions