3. Adsorption of Pb(II), Cu(II), Ni(II), Zn(II), Cr(VI) and Cd(II) Ions by Microwave-Improved Grafting Technique of Cross-Linking Composite Chitosan Beads. Studies Concerning Equilibrium, Isotherm and Desorption

Due to the flexibility of chitosan, chemical improvement of chitosan has become progressively important, allowing the material to be easily changed in a way that enhances its characteristics in binding processes. Chitosan solution was cross-linked with glutaraldehyde in this study, and the cross-linked solution was used in the manufacture of the beads and then grafted with ethylene acrylic acid afterwards. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used to obtain the chemical properties of the beads. Binding of Pb(II), Cu(II), Ni(II), Zn(II), Cr(II) and Cd(II) ions from aqueous solution by grafted cross-linking chitosan beads (GXXB) was examined in relation to pH, temperature, initial concentration, contact time, agitation speed and ionic strength. The results found from binding investigation were applied in isotherm, thermodynamic and kinetic report. The model such as Langmuir, Temkin and Dubinin–kaganer–Radushkevich (DKR) was effective in explaining the isotherm data for the binding of adsorbate onto adsorbent, while the model Freundlich was not productive in explaining the experimental data. Pseudo-second-order and intraparticle model were accurate in explaining kinetic data. Thermodynamic parameters including Gibb free energy shift (G^o), enthalpy change (H^o) and entropy change (S^o) were measured and the marks reported a spontaneous and endothermic binding of Pb(II), Cu(II), Ni(II), Zn(II), Cr(II) and Cd(II) ions on GXXB. For the adsorbate examined, the regeneration of the spent GXXB was successful.