Adsorption characteristics of chitosan modified by chelating agents of a new generation

Removal of Cu(II), Zn(II), Cd(II) and Pb(II) complexes with IDS (iminodisuccinic acid) and EDDS (ethylenediaminedisuccinic acid) from the synthetic aqueous solutions through adsorption on chitosan (CS) under batch equilibrium experimental conditions at different phase contact time (1–120 min), pH values (1–12), temperatures (20–50 °C) has been investigated. The effect of CS modification by preparing the bead cross-linked by glutaraldehyde and epichlorhydrin was also tested. The appropriate model of adsorption was proposed for better understanding of the mechanism of adsorption on CS. For this aim the Langmiur, Freundlich, Temkin and Dubinin–Radushkevich (D–R) adsorption models were used. The parameters in the adopted adsorption isotherm models were discussed in detail. The study of equilibrium isotherm shows that the best model for analysis of experimental data is the Langmuir model, which is in agreement with high values of correlation coefficients (R2). The results also showed that with the increasing pH and temperature, the adsorption ability of CS decreases. The maximum conditions for adsorption of Cu(II) in the presence of IDS were determined as CS dose 0.2 g, pH = 2–3, t 1 h and T 20 °C. The thermodynamic constants of adsorption such as ΔH° and ΔS° were also calculated. The negative value of the Gibbs free energy ΔG° demonstrates the spontaneous nature of the studied ions adsorption on CS in the presence of IDS. The obtained results showed that the pseudo second-order model was more suitable to describe the sorption kinetics on CS.

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► Chitosan modified by IDS and EDDS was used in removal of heavy metals from solutions.
► The different factors affecting the metal ions loading in CS.
► The pH, contact time and system composition were studied.