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

A nanocomposite of titanium dioxide nanoparticles (TiO 2 NPs: P25) modified with single-walled carbon nanotubes (SWCNTs) was synthesized using a simple mixing method, with varying TiO 2 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 2 NPs within SWCNT bundles, while FTIR analysis verified the incorporation of both TiO 2 NPs and SWCNTs. Adding SWCNTs extended TiO 2 's light absorption from the ultraviolet to the visible range, enhancing photocatalytic degradation under solar light compared to TiO 2 . Tauc plot analysis revealed TiO 2 NPs have an indirect energy band gap of 3.24 eV, while the SWCNTs/TiO 2 nanocomposites with a 1:5 mass ratio showed a direct energy band gap of 1.22 eV. The SWCNTs/TiO 2 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 2 NPs sludge within 2 h. The SWCNTs-supported TiO 2 sludge is reusable in catalytic applications, helping to minimize waste disposal concerns. • SWCNT/TiO 2 nanocomposites were synthesized via a simple, low-cost mixing method without chemical functionalization. • SWCNTs in TiO 2 nanoparticles boost visible-light absorption and photocatalytic performance by narrowing the band gap. • The 1:5 SWCNT:TiO 2 ratio exhibited the highest specific surface area (95.24 m 2 /g) and 99 % degradation of methylene blue within 60 min under solar irradiation. • Photocatalytic degradation followed pseudo-first-order kinetics, with a rate constant of 0.05573 min −1 for the optimal nanocomposite. • SWCNTs promoted sludge formation, enabling easy separation and reuse of the catalyst, addressing a key challenge in wastewater treatment applications.