Plant tannin modified chitosan microfibers for efficient adsorptive removal of Pb2+ at low concentration

Bayberry tannin (BT), a typical plant tannin, was grafted onto chitosan microfibers (CF) through the Mannich reaction to synthesize biosorbent (BT-CF) that was effective for adsorptive removal of Pb 2+ from aqueous solutions. The adsorption capacity of Pb 2+ on the BT-CF was pH-dependent, which increased from 4.5 mg/g to 21.7 mg/g along with increasing solution pH from 2.5−5.5. The adsorption capacity increased with the increase of temperature from 303 K to 323 K, and thermodynamic calculations indicated that the adsorption of Pb 2+ on the BT-CF was an endothermic process. The adsorption isotherms were well described by the Langmuir isotherm model with correlating constant (R 2 ) higher than 0.980. The adsorption kinetics were well described by the pseudo-second-order rate model. The Pb 2+ adsorbed on the BT-CF was desorbed using diluted acid solution. Column adsorption experimental results confirmed that the BT-CF was applicable for continues adsorptive removal of Pb 2+ at the low concentration of 2.0 mg/L.