Effective removing of methylene blue from aqueous solution by tannins immobilized on cellulose microfibers

Tannin-supported on cellulose (TM) microfibers were successfully prepared to remove cationic dye in aqueous solution. SEM and mechanical tests were employed to characterize their structures and properties. Methylene blue (MB) as a cationic organic dye was applied to estimate the adsorption ability of TM microfibers. The network structure of TM microfibers, and electrostatic attractions between tannins and MB molecules attribute to the good adsorption. TM fibers have higher adsorption capacity at higher pH. The Q_max of TM fibers is 31.7 mg/g at 333 K. Thermodynamic analysis demonstrated that the adsorption process was spontaneous and favorable. Adsorption-desorption experiments demonstrated that TM microfibers possessed excellent stability and reusable ability. The pseudo-second-order and Langmuir isotherm model could better describe the adsorption behaviors of TM microfibers. The adsorption-desorption experiments of TM microfibers were recycled 5 times with no obvious decrease of adsorption capacity. Tannins supported on TM serve as binding sites to combine MB through electrostatic attractions, making for the excellent adsorption effect of TM microfibers. This work provides a novel method to fabricate tannin-supported materials for sewage treatment.