Chitosan as an effective low-cost sorbent of heavy metal complexes with the polyaspartic acid

Chitosan (CS) was used for the adsorption of Cu(II), Zn(II), Cd(II) and Pb(II) complexes with the 'green' chelating agent - polyaspartic acid (DS) from waste water effluents. CS samples were characterized using FT-IR spectroscopy and AFM analysis. Among different factors that influence the sorption process, the following were studied in detail: solution pH, initial concentration, phase contact time, temperature and effect of competitive ions. The most important factor affecting the effectiveness of sorption is pH and concentration. From the Langmuir adsorption model, the adsorption capacity of CS for Cu(II), Zn(II), Cd(II) and Pb(II) complexes was equal to: 85.21 mg/g, 46.82 mg/g, 89.58 mg/g and 79.05 mg/g, respectively. The results showed that the pseudo second-order model was more suitable to describe the sorption kinetics on CS. The rate constant (k(2)) decreases with the increasing metal complexes concentration, whereas the equilibrium sorption capacity (q(2)) and the initial sorption rate (h) increase. (C) 2011 Elsevier B.V. All rights reserved.