Equilibriums and kinetics studies for adsorption of Ni(II) ion on chitosan and its triethylenetetramine derivative

The adsorption of Ni(II) ions from aqueous solution by chitosan (CTS) and its triethylenetetramine derivative beads (CCTS) was investigated in a batch adsorption system. Chitosan beads were crosslinked with epichlorohydrin and then grafted with triethylenetetramine to obtain sorbents that are insoluble in aqueous acidic solution and improve adsorption capacity, respectively. Elemental analysis, scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy were used to analyze the structure and characteristics of chitosan and its derivative. It showed that the derivative of chitosan possessed good stability in acidic solution and achieved optimal adsorption capacity at pH higher than 4.5 and the max adsorption capacity of chitosan and chitosan derivate were 58.09 and 91.44 mg/L, respectively. Their adsorption processes could be best described by the pseudo second-order model, which suggested that the rate-limiting step may be the chemical adsorption rather than the mass transport. The experimental data of adsorption of Ni2+ by chitosan derivate was fitted well by the Langmuir isotherm model with a high correlation coefficient (R-2 > 0.99), showing that monolayer adsorption took place on the surface of chitosan derivate absorbents, while the adsorption isotherm was well fitted by Freundlich for chitosan. Furthermore, the chitosan derivate exhibited good adsorption performance after regeneration for 5 cycles. At last, FTIR and XPS analysis showed that both the nitrogen and oxygen functional groups were involved in the adsorption of Ni2+. (C) 2016 Elsevier B.V. All rights reserved.