Synthesis, Characterization, and Application of an Ecofriendly C/TiO₂ Composite to Efficiently Remove Reactive Black 5 (RB-5) Textile Dye from Aqueous Solutions

The textile industry is known for its high water consumption and production of toxic effluents, including azo dyes such as Reactive Black 5 (RB-5), which are resistant to removal. Adsorption offers a promising, cost-effective solution, particularly with value-added composites made from abundant materials. This study synthesized, characterized, and applied a C/TiO₂-based composite to remove RB-5 from water. XRD analysis only confirmed anatase as the primary support, while FTIR detected adsorbate molecules on the C/TiO₂ surface, marked by the appearance of a sulfone group band. Raman and XPS analyses indicated reduced Sp² carbon content and lower graphitization after adsorption, probably due to mechanical stress. Additionally, nitrogen physisorption analysis demonstrated that the material is mesoporous, with a surface area of 56.24 m² g^-1, and a pore diameter of 9.41 nm. The composite exhibited strong affinity for anionic species like RB-5, especially at pH values below the point of zero charge (7.47). Batch studies demonstrated Avrami kinetic adsorption at a rate of 0.3023 min^-1 (at 25 °C), while temperature effects followed the Arrhenius model, with an activation energy of +41.10 kJ mol^-1. Sips isotherm data indicated a maximum adsorption capacity of 17.48 mg g^-1 at 55 °C. Thermodynamic analysis confirmed an entropically controlled, endothermic, spontaneous process at high temperatures. These aspects confirm the potential of eco-friendly C/TiO₂ composite for effective RB-5 removal from aqueous solutions.