Preparation of triethylene-tetramine grafted magnetic chitosan for adsorption of Pb(II) ion from aqueous solutions.

In this paper, a novel triethylene-tetramine grafted magnetic chitosan was synthesized. The chemical structure and the percentage content of each element of chitosan and its derivatives were characterized by elemental analysis, infrared spectroscopy, solid state (13)C NMR, X-ray diffraction analysis and thermogravimetric analysis, respectively. Their surface topography was observed by the transmission electron microscope. The results of adsorption kinetics and adsorption thermodynamics showed the adsorption mechanism could be better described by the pseudo-second-order equation (R>0.999). The adsorption isotherm was well fitted by the Langmuir equation (R>0.999), and 0<R(L)<1. The maximum adsorption capacity was 370.63 mg/g at the optimized adsorption conditions, which were pH=6, T=298 K, t=1.5h, C(0)=200 mg/L and adsorbent dose is 500 mg/L. The rate-limiting step may be the chemical adsorption rather than mass transport. The adsorbent still exhibited very good adsorption performance after the fifth regeneration cycle. The mechanism for adsorption and desorption was discussed.