Fabrication and Characterization of N-TiO2/C/ATP Composite with Enhanced Visible-Light Photocatalytic Performance for the Degradation of Polyacrylamide in Wastewater

A novel N-TiO2/C/attapulgite (N-TiO2/C/ATP) composite photocatalyst was prepared by sol-gel method using ATP supported o-phenanthroline modified TiO2. The as-prepared samples were characterized by X-ray diffraction (XRD), fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) and N-2 adsorption-desorption measurements. The activity of these photocatalysts was tested by degrading polyacrylamide (PAM) under visible light irradiation while N-TiO2/C/ATP shows significant photocatalytic enhancement compared to pure TiO2. The optimal ratio of N-TiO2/C/ATP photocatalyst is n (TiO2): n (o-phenanthroline)=20 : 1 and the m (N-TiO2/C): m (ATP)=1 : 1. When the initial concentration of PAM is 300 mg/L and the catalyst dosage is 1.5 g/L, the removal rate of chemical oxygen demand (COD) reaches 86.3 % at pH 2 under 2 h of visible light. The enhanced performance can be attributed to the C element in o-phenanthroline is modified on the TiO2 surface as a surface sensitizer and the N element may enter anatase TiO2 lattice and replace to form O-Ti-N bond. Meanwhile, some TiO2 particles were permeated into the layer of ATP, which made the composite photocatalyst more stable and the N-TiO2/C/ATP composite exhibits good stability after three times recycling. In addition, the possible photocatalytic mechanism is proposed at the end.