Amidoxime-functionalized polyacrylamide-modified chitosan containing imidazoline groups for effective removal of Cu2+ and Ni2+

Herein, an amidoxime-functionalized chitosan (CTS) AM/AO/AEBI-CTS containing imidazoline groups was facilely prepared through amidoximation of cyano groups in cross-linked CTS obtained by crosslinking of imidazoline-functionalized polyacrylamide and CTS. AM/AO/AEBI-CTS exhibited porous structure, good water wettability, and higher selectivity for Cu2+ than Ni2+. The adsorption process correlated well with Sips isotherm and pseudo-second-order kinetics models. The adsorption capacities for Cu2+ and Ni2+ onto AM/AO/AEBI-CTS were 190.7 and 128.9 mg/g, respectively. The adsorption thermodynamics demonstrated that the adsorption of Cu2+ and Ni2+ ions onto AM/AO/AEBI-CTS was a spontaneous endothermic process. The FTIR and XPS analyses revealed that nitrogen and oxygen atoms were involved in the chelation with metal ions. The presence of Na+, K+ and Ca2+ had weakly impact on the adsorption efficiency of AM/AO/AEBI-CTS. Furthermore, the adsorption efficiency of AM/AO/AEBI-CTS remained above 90 % after five adsorption-desorption successive cycles. Overall, this CTS material has a good application prospects for wastewater treatment.

Automated summary

In this study, AM/AO/AEBI-CTS with high selectivity for Cu2+ was successfully prepared. The adsorption process followed Sips isotherm and pseudo-second-order kinetics models, and the adsorption efficiency remained high even after multiple cycles.