Adsorption of Cd(II) and Pb(II) by a novel EGTA-modified chitosan material: Kinetics and isotherms

• Published in: Journal of colloid and interface science Vol. 409; pp. 174 - 182
• Main Authors: Zhao, Feiping, Repo, Eveliina, Yin, Dulin, Sillanpää, Mika E.T.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.11.2013; Elsevier
• Subjects: Adsorbents; Adsorption; Adsorption isotherm; aqueous solutions; Binary system; cadmium; Cadmium - chemistry; Chelation; Chemistry; Chitosan; Chitosan - chemistry; EGTA; Egtazic Acid - chemistry; ethylene glycol tetraacetic acid; Exact sciences and technology; Fourier transform infrared spectroscopy; General and physical chemistry; Heavy metal removal; Isotherms; Kinetics; lead; Lead - chemistry; ligands; Mathematical models; Mechanism; Metal ions; Modified chitosan; Molecular Structure; Regeneration; Surface chemistry; Surface physical chemistry; Surface Properties; Thermodynamics; Regeneration; Heavy metal removal; Modified chitosan; Binary system; Adsorption isotherm; Mechanism; EGTA; Adsorption; Chitosan; Kinetics; Modified material; Heavy metal
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2013.07.062

[Display omitted] •EGTA-chitosan is an effective and recyclable adsorbent for Cd(II) and Pb(II).•The adsorption mechanism was explored by FTIR and theoretical calculations.•Adsorption kinetics complied with a pseudo-second-order model.•BiLangmuir model and its extended form described the adsorption data well.•Competition and positive synergy of chelation occurred in binary systems. 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 0.74mmol g−1 for Cd(II) and 0.50mmol 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).