Petroleum waste-derived activated carbon/TiO₂ nanocomposites synthesized via sol–gel method for photodegradation of pollutants

This work reports on the preparation and photocatalytic evaluation of TiO₂/activated carbon (TiO₂/AC) nanocomposite derived from petroleum coke waste, offering a sustainable route for converting oil and gas byproducts into high-value functional materials. The composite was produced using the sol–gel method and systematically characterized using SEM-EDX, BET, XPS, XRD, TEM, FTIR, and UV–Vis diffuse reflectance spectroscopy. The results confirmed the successful formation of mixed-phase TiO₂, mainly composed of anatase with minor rutile contributions and an average crystallite size of ∼6.78 nm, a reduced band gap of 2.97 eV, and BET surface area of 70.02 m²/g. These structural and optical properties enhanced dye adsorption capacity, light absorption, and charge separation. Photocatalytic performance was assessed against methylene blue (MB), congo red (CR), and rhodamine B (RhB) dyes under UV irradiation. The TiO₂/AC composite exhibited outstanding activity, achieving near complete degradation of MB (10 ppm) within 35 min, ∼90% removal of CR (15 ppm) within 95 min, and ∼27% degradation of RhB (20 ppm). Kinetic studies revealed that the degradation followed a pseudo-second-order model (R² = 0.993, k₂ = 2.667 g·mg⁻¹·min⁻¹), emphasizing the significance of surface adsorption together with the availability of active sites in the catalytic process. Petroleum-waste-derived TiO₂/AC nanocomposites demonstrate excellent photocatalytic efficiency, showing potential for wastewater remediation while simultaneously mitigating the environmental burden of oil and gas industry byproducts.