Application of diethylenetriamine grafted on glyoxal cross-linked chitosan composite for the effective removal of metal ions in batch system

This investigation studied the removal of Cu2+, Pb2+, Cd2+, Zn2+, Ni2+ and Cr6+ ions from synthesised wastewater using modified chitosan macromolecules. On this note, chitosan beads (CS) were prepared and cross-linked with glyoxal solution. It was found that cross-linking increased the beads mechanical strength and chemical stability in acid solution and also increased the crystallinity of the beads in the process, which is a shortcoming, as the beads tend to have reduced adsorption capacity. To reduce this shortcoming, the cross-linked chitosan beads (DCS) were grafted with diethylenetriamine. The beads were characterised prior to adsorption studies. The amine concentration of the grafted cross-linked beads (GDCS) was observed to be nearly the same as the adsorption capacity (qmax); this concludes that the amine group of chitosan are the main reactive group. Also, the qmax was found to be 6.3 mmol/g with a 44.2% degree of grafting. The kinetics of the adsorption process was described reasonably well with the Swan model, where the experimental and simulated data were in close agreement. The effective diffusion coefficients (Deff) obtained by fitting the model to experimental data were found to be between 2.25·10−10 to 2.50·10−10 for Cu2+, Pb2+, Cd2+, Zn2+, Ni2+ and Cr6+ adsorption unto GDCS.