P-nitrophenol (PNP) as an industrial waste effluent is present in many industries, including the dye and textile industries and tanneries, and is the cause of severe human and environmental health risks. In the present study, a facile, effective, and innovative sonochemical procedure was developed at low frequency (20 kHz) and room temperature for the synthesis of graphite (G)/C, N co-doped TiO2 nanocomposite. Herein, tetra n-butyl orthotitanate as the titanium precursor, graphite as the C, and NH4Cl as the N sources were applied in the synthesis of the nano-photocatalyst. The effect of the molar ratio of N/TiO2 was studied in the synthesis of G/C, N co-doped TiO2 nanocomposite. Various techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM), High-resolution microscopy (HRTEM), X-ray Photoelectron Spectroscopy (XPS), photoluminescence (PL), Brunauer–Emmett–Teller (BET), Elemental and Mapping analyses (EDS) and UV/Vis diffuse reflectance (UV/vis DRS) were used to characterize the nanocomposite. The results also showed that ultrasound decreased the particle size and improved the size distribution. DRS results showed a narrower band-gap and a red shift of light absorption edge for G/C, N codoped TiO2 nanocomposite compared to TiO2. The data obtained from XPS established the presence of C, N, Ti, and O elements in the nanocomposite. In addition, the efficiency of the photo-catalytic performance of the nanocomposite was assessed using the pollutant PNP. The fabricated nanocomposite presented photo-catalytic activity much more than TiO2 in PNP degradation with an efficiency of 100 % within 70 min under the illumination of 400 W Xe light. The extraordinary activity of nanocomposite concerning TiO2 was mostly attributed to its high crystallinity, strong visible light absorption, and the impressive separation of photo-induced charge carriers. The radicals in the charge of destruction process were checked via the scavenging tests. The results confirmed that ◦O2???? radical had a basic role in the process of photo-catalytic and an acceptable mechanism was proposed for the photo-catalytic degradation.

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