Preparation of calcined hydrotalcite/TiO2-Ag composite and enhanced photocatalytic properties

A series of calcined hydrotalcite/TiO2-Ag (HTC/TiO2-Ag) composites with different silver (Ag) contents were successfully prepared and investigated as a catalyst for the photodegradation of phenol using UV-vis light (λ>300 nm). The Ag nanoparticles were deposited on the surface of TiO2 (TiO2-Ag) through photodeposition method. The TiO2-Ag nanoparticles were supported on hydrotalcite (HT) by the co-precipitation method at variable pH (HT/TiO2-Ag), and then calcined at 500 °C to obtain the HTC/TiO2-Ag composites. The composites were characterized by inductively coupled plasma mass spectrometry (ICP-MS), N2 adsorption/desorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance spectra (DRS). Results show that there is an optimum silver ratio to obtain the highest photocatalytic performance in the HTC/TiO2-Ag photocatalyst which is 2 wt%, and is assigned as HTC/TiO2-Ag(2). The association of silver nanoparticles on TiO2 enhanced photocatalytic activity of the bare semiconductor composite. Only 56% of phenol was photodegraded when photodegradation was performed with HTC/TiO2, whereas ~100% was photodegraded using HTC/TiO2-Ag(2). The data gathered from the photocatalytic degradation of phenol were successfully fitted to Langmuir-Hinshelwood model, and can be described by pseudo-first order kinetics. The results showed the HTC/TiO2-Ag(2) as efficient photocatalyst, low cost, separable from solution by sedimentation, and reusable. The superior performance of HTC/TiO2-Ag(2) composite photocatalyst may be attributed to the synergic catalytic effect between silver and TiO2, dispersion of TiO2-Ag(2) nanoparticles supported on calcined hydrotalcite, and the calcined hydrotalcite like photocatalyst.