Efficient One-Pot Hydrothermal Synthesis of TiO2 Nanostructures for Reactive Black 5 Dye Removal: Experimental and Theoretical Insights

Water scarcity continues to be a major worldwide issue. Therefore, from a scientific perspective, it is crucial to develop a highly effective, affordable, environmentally friendly, and readily available metal-based adsorbent for wastewater treatment. This study focuses on synthesizing a mesoporous/nanosphere TiO2 using a free-template and eco-friendly method to effectively remove Reactive Black 5 (RB5) dye. The synthesis of TiO2 nanospheres was achieved through the use of titanium isopropoxide at 100 °C for 12 h in a one-pot hydrothermal process, successfully regulating their morphology and crystallite size. The TiO2 nanospheres were extensively characterized using multiple techniques, such as XRD, FE-SEM, zeta potential, FT-IR, HR-TEM, and BET surface area tools. Adsorption experiments revealed a notable capacity of 109 mg g−1 for RB5 dye, following pseudo-second-order kinetic behavior. The equilibrium data conformed well to the Langmuir isotherm model, indicating monolayer adsorption. Thermodynamic evaluations confirmed that the process was spontaneous, endothermic, and governed by physisorption. Calculations using density functional theory (DFT) provided additional support for the experimental findings, demonstrating strong binding interactions between the dye and the TiO2 (101) surface. The TiO2 nano-adsorbent showed excellent reusability and maintained high adsorption efficiency over multiple cycles, making it a promising candidate for wastewater treatment.