Improved performance of immobilized TiO2 under visible light for the commercial surfactant degradation: Role of carbon doped TiO2 and anatase/rutile ratio

Nanoparticles of TiO2 with different ratios of anatase (A)/rutile (R) phases were successfully synthesized via solgel method. Carbon-doped TiO2 (CDT) was supported on the surfaces of granular activated carbon (GAC) for photocatalytic degradation and mineralization of the commercial nonylphenol (NP) surfactant under visible light irradiation. The physicochemical characteristics of the synthesized composites (TiO2, CDT, and CDT/GAC) were determined in detail by X-ray diffraction, scanning electron microscopy, elemental mapping, Brunauer-Emmett-Teller, UV-Vis absorption and PL spectra. The results indicated that the band gap decreased from 3.17 eV to 2.72 eV after C doping, and to 2.66 eV by changing the calcination temperature from 475 degrees C to 600 degrees C; the visible light absorption also increased. This study demonstrates that the CDT/GAC photocatalyst with an A (53.06)/R (46.94) ratio exhibited high degradation efficiency. COD and TOC removal of 99% and 89%, respectively, and 80% NP decrease within 60 min. The NP degradation increases with increasing temperature and light intensity. The Langmuir-Hinshelwood kinetic model fitted with the experimental data. In addition, it is reported that the synthesized photocatalyst became stable and highly active, even after five cycles. The results also showed that the values of the carbon oxidation state (COS) and the average oxidation state (AOS) were highly increased after the decomposition of NP by the Xenon/CDT (A/R)/GAC process over 3.37 and 3.87, respectively.