Quaternary Ammonium Functionalized Cellulose for Bromate Ion Removal: Structural Insights and Efficacy Evaluation

This study evaluates the potential of quaternary ammonium-modified cellulose as a biosorbent for bromate (BrO₃^-) removal from aqueous solutions. Elemental analysis and scanning electron microscopy (SEM) characterized the elemental composition and microstructural features of the biosorbent, whereas Fourier-transform infrared (FTIR) spectroscopy elucidated its molecular structure. Experimental results revealed that BrO₃^- removal efficiency increased with the biosorbent dose, achieving approximately 58%, 78%, and 90% removal with 0.025, 0.05, and 0.2 g of sorbent, respectively. The removal was pH-dependent, with efficiencies of 25%, 45%, and 76% at pH 2, 4, and 10, respectively, and the optimal removal was within the pH range of 6-8. Kinetic studies demonstrated rapid sorption, achieving 91% removal within 3 min. The Langmuir sorption isotherm model provided an excellent fit to the experimental data (R² = 0.9987), indicating a maximum sorption capacity of 9.40 mg/g. Thermodynamic analyses confirmed a spontaneous and endothermic sorption process (∆G° = -8.11 kJ/mol; ∆H° = +2.22 kJ/mol). Desorption studies showed ≥ 99.9% efficiency using 0.1-M H₂SO₄ and NaCl, with NaCl selected as the preferred regenerant to minimize acid consumption. The biosorbent retained over 90% removal efficiency across three regeneration cycles. These findings highlight the potential of quaternary ammonium-modified cellulose as a sustainable and efficient material for BrO₃^- removal from water systems.