Photocatalytic degradation of organic pollutants under solar irradiation using single-walled carbon nanotube/titanium dioxide nanocomposites

Abstract

A nanocomposite of titanium dioxide nanoparticles (TiO<inf>2</inf> NPs: P25) modified with single-walled carbon nanotubes (SWCNTs) was synthesized using a simple mixing method, with varying TiO<inf>2</inf> NP mass ratios (5–20 wt%). The nanocomposites were characterized using field emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and UV–Vis diffuse reflectance spectroscopy (DRS). Photocatalytic degradation performance was evaluated using methylene blue as a model organic pollutant under solar light irradiation. FE-SEM images confirmed the effective dispersion of TiO<inf>2</inf> NPs within SWCNT bundles, while FTIR analysis verified the incorporation of both TiO<inf>2</inf> NPs and SWCNTs. Adding SWCNTs extended TiO<inf>2</inf>'s light absorption from the ultraviolet to the visible range, enhancing photocatalytic degradation under solar light compared to TiO<inf>2</inf>. Tauc plot analysis revealed TiO<inf>2</inf>NPs have an indirect energy band gap of 3.24 eV, while the SWCNTs/TiO<inf>2</inf> nanocomposites with a 1:5 mass ratio showed a direct energy band gap of 1.22 eV. The SWCNTs/TiO<inf>2</inf> nanocomposite (1:5) exhibited the highest specific surface area. Photocatalytic experiments with this ratio achieved up to 99 % removal of methylene blue within 60 min of sunlight exposure. Furthermore, SWCNTs can accelerate the formation of TiO<inf>2</inf> NPs sludge within 2 h. The SWCNTs-supported TiO<inf>2</inf> sludge is reusable in catalytic applications, helping to minimize waste disposal concerns.