Floating Bi–N–TiO₂ photocatalysts were synthesized using a novel sol–gel method grafted on expanded graphite C/C composites with high adsorption capacity and photocatalytic activity. The Bi–N–TiO₂/EGC were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), the N₂ adsorption/desorption method (BET), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and X-ray photoelectron spectroscopy (XPS). The SEM and XRD results revealed that all the composites had with mesoporous structures; the crystalline phases were mainly influenced by calcination temperature and anatase transformed into rutile at 800 °C. The N₂ adsorption/desorption method (BET) indicated that the specific surface area and pore size could be changed through adjusting the calcination temperature and Bi dosage. All Bi modified N–TiO₂ composites exhibited higher photocatalytic activity for degradation of diesel (≥53.7%) than N–TiO₂ under visible light irradiation. The composite Bi_1.0–N–TiO₂/EGC calcined at 550 °C with evenly distributed TiO₂ exhibited the highest activity (83.8%), which was attributed to the high surface area, red shift of absorptive light to visible light as well as improved efficient charge separation. The results of influence experiments, under different conditions of pH, salinity, emulsifier and humic acid, also evidenced that Bi–N–TiO₂/EGC composites are stable catalysts for the in situ remediation of diesel contaminated water.

N–F codoped TiO₂/straw charcoal composites (NF–TiO₂/SC) were synthesized using a simple, bioframe-assisted sol–gel method and confirmed by XRD, SEM, EDX, TEM, N₂ adsorption–desorption, Raman, FT-IR, XPS, and UV-vis DRS measurements.