Removal of manganese (Mn²⁺) from water samples using a biocomposite sorbent

Herein, tannic acid-tethered cellulose was developed as an efficient and selective sorbent for Mn²⁺ removal from aqueous solutions. The modified cellulose was characterized through scanning electron microscopy, infrared spectroscopy, and elemental analyses. Sorption performance was evaluated using various parameters, including pH, initial Mn²⁺ concentration, contact time, and the presence of interfering ions. Results indicated that Mn²⁺ removal was highly pH-dependent, with removal efficiency increasing from 8% at pH 2 to99% at pH 9, achieving a remarkable 99% removal rate within only 30 min, highlighting the rapidity of the cellulose sorption kinetics. The results of isotherm studies confirmed that the sorption conformed to the Langmuir model with a monolayer sorption mechanism. Using a sorbent dose of 0.05 g, 99% of Mn²⁺ could be effectively eliminated from water, achieving a maximum sorption capacity of 32.2 mg/g dry-sorbent. The modified cellulose could be effectively regenerated using 0.5-M HCl or 0.1-M H₂SO₄, with no considerable deterioration in sorption performance after three sorption-regeneration cycles. The presence of Na⁺ and K⁺ had minimal impact on Mn²⁺ removal, whereas the presence of Ca²⁺ and Mg²⁺ at low concentrations facilitated moderate-level Mn²⁺ removal.