Photocatalytic degradation of caffeine by ZnO-ZnAl2O4 nanoparticles derived from LDH structure

In this research, ZnO-ZnAl2O4 mixed phases were prepared by calcination of Zn-Al-CO3 layered double hydroxides (LDH) precursors. Firstly, a series of Zn-Al-CO3 LDH were synthesized at different Zn/Al molar ratios (r = 1, 3 and 5) and then calcined at different temperatures (300, 400, 500, 600, 800 and 1000 °C) for 6 h. The materials were characterized by XRD, FTIR, TGA/DTA, ICP-AES and TEM. The photocatalytic activity of the samples was evaluated for the degradation of caffeine as a model pharmaceutical pollutant in aqueous solution under UV irradiation. The effect of the Zn/Al molar ratio, calcination temperature and initial pH of aqueous solution was investigated. The experimental results show that the sample obtained from the molar ratio of 3 and calcined at 500 °C with a large capacity of adsorption obtained by reconstruction process was photocatalytically much higher than standard Degussa P-25 titanium dioxide.