Fast adsorption of Cd2+ and Pb2+ by EGTA dianhydride (EGTAD) modified ramie fiber

In this study, the removal of Cd2+ and Pb2+ from aqueous solutions was investigated using a novel chelating material. The first part described the synthesis of ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid dianhydride (EGTAD), mercerization treatment of ramie fiber (MRF), and the MRF was then reacted with EGTAD to prepare the new material (ERF). The obtained material was characterized by weight gain, SEM, FTIR, and elemental analysis. The results of FTIR and elemental analysis confirmed that ester bond, carboxyl and amine groups were introduced onto ERF. The adsorption capacity of metals on ERF was evaluated at different contact times, pH values, initial metal concentrations, and temperatures in the second part. The adsorption equilibrium was reached within 5 min for Cd2+ and Pb2+. Adsorption isotherm could be well fitted by the Langmuir model, and the maximum adsorption capacities were 159.11 and 273.78 mg g(-1) for Cd2+ and Pb2+ at 298 K, respectively. Thermodynamic analysis showed that the adsorption process was spontaneous and endothermic. The molar ratio of adsorbed cation to grafted EGTA is close to 1.8:1, which confirmed that the adsorption was chemical process involving both surface chelation reaction and ion exchange. In addition, the absorbent was successfully regenerated using HCl and ultrasonic treatment. (C) 2014 Elsevier Inc. All rights reserved.