Tannin-immobilized cellulose microspheres as effective adsorbents for removing cationic dye (Methylene Blue) from aqueous solution

BACKGROUND: Tannin-immobilized cellulose (T/C) microspheres were fabricated by a facile homogeneous reaction in a water/oil (W/O) emulsion for the removal of cationic dye from aqueous solution. The microspheres were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Zeta potentials test. Setting methylene blue (MB) as a cationic dye model, the adsorption isotherms, kinetics and effect factors of MB adsorption were investigated to evaluate the effectiveness for dye removal. RESULTS: The microspheres exhibited porous structure. Cellulose contributed to provide a support for the porous structure, and immobilized tannins acted as adsorbent sites which combined with MB by electrostatic attraction, resulting in the attractive adsorption ability of T/C microspheres. Microspheres exhibited rapid adsorption rate even when the initial MB concentration was 1500 mg L-1. The pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to fit adsorption data in the kinetic studies. Results indicated that the adsorption kinetic was more accurately described by the pseudo-second-order model. It has been demonstrated that the better agreement was with the Langmuir isotherm with correlation coefficient > 0.9996. Regeneration experiments showed that T/C microspheres can be reused at least three times without obvious loss of their original adsorption capacity. CONCLUSION: The results revealed that the T/C microspheres can be considered as a stable and effective adsorbent for cationic dye removal from industrial effluents. Tannin immobilization and material forming were simultaneously implemented by a facile homogeneous reaction in W/O emulsion, providing a new pathway to fabricate tannin-immobilized materials for water treatment. (C) 2016 Society of Chemical Industry