7. Use of Diethylenetriamine Grafted onto Glyoxal Cross-Linked Chitosan Beads for Efficient Batch System Adsorption

This study examined the removal of synthesized wastewater ions Cu(II), Pb(II), Cd(II), Zn(II), Ni(II) and Cr(VI) using modified chitosan material. Chitosan beads (CS) were produced and interlinked with glyoxal solution. Cross-linking was observed to intensify the mechanical intensity and chemical firmness of the beads in acid mixture and also to intensify the crystallinity of the beads in the process, which is a drawback, as the beads tend to have decreased rate of removal of adsorbate. The cross-linked chitosan beads (DCS) were grafted with diethylenetriamine to reduce this drawback. Before tests of adsorption, the beads were characterized. The amine concentration of the grafted cross-linked beads (GDCS) was observed to be almost equal to the binding capability (q_max); this suggests that the chitosan amine group is the most reactive group. The q_max was found to be 6.3 mmol/g with a grafting degree of 44.2%. However, with the Swan model, where the experimental and simulated data were in near agreement, the kinetics of the adsorption process was represented relatively well. The effective diffusion coefficients (D_eff) found by applying the model to the data from the experimental were observed to be in the range of 2.25 × 10⁻¹⁰ and 2.50 × 10⁻¹⁰ for adsorption to GDCS by Cu(II), Pb(II), Cd(II), Zn(II), Ni(II) and Cr(VI).