title: Adsorption of Cd(II) and Pb(II) by a novel EGTA-modified chitosan material: kinetics and isotherms.
abstract: In this study, a novel adsorbent was synthesized by functionalizing chitosan with ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) ligands. The adsorption capability of EGTA-modified chitosan was investigated by the removal of Cd(II) and Pb(II) from aqueous solutions. The adsorption and regeneration studies were performed by batch techniques. The effects of pH, contact time, and initial metal concentration were studied. Metal uptake by EGTA-chitosan was 0.74 mmol g(-1) for Cd(II) and 0.50 mmol g(-1) for Pb(II). The adsorption mechanism, that the adsorbent formed octahedral chelate structures with bivalent metal ions, was proposed tentatively based on the experimental results of FTIR and the theoretically calculated data of point charges. The kinetics of Cd(II) and Pb(II) on EGTA-chitosan complied with the pseudo-second-order model and the adsorption rate was also influenced by intra-particle diffusion. BiLangmuir isotherm model was well fitted to the experimental data of one-component adsorption suggesting the surface heterogeneity of the novel adsorbent. The extended form of the BiLangmuir model was tested for the modeling of two-component adsorption equilibrium of Cd(II) and Pb(II) on EGTA-chitosan. In the two-component solution, both competitive adsorption and positive synergy of chelation between metal ions occurred and the novel adsorbent showed higher affinity toward Cd(II).
authors: Laboratory of Green Chemistry, Department of Chemistry, Faculty of Technology, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli, Finland; Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education), National & Local Joint Engineering Laboratory for New Petro-chemical Materials and Fine Utilization of Resources, Hunan Normal University, 410081 Changsha, PR China. Electronic address: feiping.zhao@lut.fi.
authors: Feiping
authors: F
authors: Zhao
authors: Eveliina
authors: E
authors: Repo
authors: Dulin
authors: D
authors: Yin
authors: Mika E T
authors: ME
authors: Sillanpää
mesh_terms: D000327:Adsorption; D002104:Cadmium / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry*; D004533:Egtazic Acid / Q000737:chemistry*; D007700:Kinetics; D007854:Lead / Q000737:chemistry*; D015394:Molecular Structure; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D002104:Cadmium; D007854:Lead; D004533:Egtazic Acid; D048271:Chitosan
keywords: Adsorption isotherm; Binary system; EGTA; Heavy metal removal; Mechanism; Modified chitosan; Regeneration