Study on the Adsorption of Pb, Zn, Cu, Ni, and Cd by Modified Ligand in a Single Component Aqueous Solution: Equilibrium, Kinetic, Thermodynamic, and Desorption Studies

In this investigation, an amino functionalized adsorbent was developed by grafting 4-aminobenzoic
acid onto the backbone of cross-linked chitosan beads. The 3 sets of beads including chitosan (CX),
glutaraldehyde cross-linked chitosan (CCX), and 4-aminobenzoic acid grafted cross-linked chitosan
(FGCX) were characterized by FTIR, XRD, SEM, and TGA. The water content and amine
concentration of FGCX were determined. The effect of adsorption parameters was studied and the
optimum was used for further studies. Equilibrium data was obtained from the adsorption experiment
carried out at different initial concentration; the data were applied in isotherm, thermodynamics, and
kinetic studies. The Langmuir and Dubinin-Kaganer-Radushkevich (DKR) models were successful in
describing the isotherm data for the considered metal ions while the Freundlich and Temkin model fit
some of the considered metal ions. Pseudo-second-order and intraparticle model described the
kinetic data quite well. Thermodynamic parameters such as Gibb’s free energy change (Δ ° ),
enthalpy change (Δ°), and entropy change (Δ°) were calculated and the results showed that the
adsorption of Pb, Cu, Ni, Zn, and Cd ions onto FGCX is spontaneous and endothermic in nature.
Regeneration of the spent adsorbent was efficient for the considered metal ions.