Efficient Removal of Uranium From Aqueous Solutions Using Nanocomposite Composed of Activated Graphitic Carbon Nitride Integrated With Tamarind Shell-Structured TiO₂

Abstract

A novel composite material, Ac-gC₃N₄@TSS-TiO₂, was successfully synthesized by integrating acid-treated graphitic carbon nitride (Ac-gC₃N₄) with tamarind shell-structured TiO₂ (TSS-TiO₂), prepared via thermolysis followed by solvothermal synthesis. Comprehensive characterization techniques, including FT-IR, XRD, TGA, BET, FESEM, and XPS, confirmed the successful formation and structural features of the composite. The adsorption performance of Ac-gC₃N₄@TSS-TiO₂ for uranium(VI) removal from aqueous solutions was systematically investigated using batch experiments. The composite exhibited rapid adsorption kinetics and reached equilibrium within 60 min for an initial U(VI) concentration of 25 mg/L at pH 6.0. The adsorption performance of Ac-gC₃N₄@TSS-TiO₂ demonstrates a superior adsorption capacity of 370.3 mg g-1, as described by the Langmuir isotherm model, compared to previously reported similar nanomaterials and nanocomposite adsorbents. The enhanced performance was attributed to the synergistic interactions between the U(VI) species and the surface functional groups (amine, carboxyl, and hydroxyl) of Ac-gC₃N₄@TSS-TiO₂. Thermodynamic studies revealed that uranium adsorption on Ac-gC₃N₄@TSS-TiO₂ increased with increasing temperature. The composite demonstrated a higher affinity in the presence of competing electrolytes and various metal ions, exhibited excellent regeneration using dilute nitric acid, and maintained its adsorption efficiency over multiple cycles. These results establish Ac-gC₃N₄@TSS-TiO₂ as a sustainable and high-performance adsorbent for U(VI) remediation in real-world water treatment applications.