An efficient chitosan-based adsorption material containing phosphoric acid and amidoxime groups for the enrichment of Cu(II) and Ni(II) from water

Abstract A novel modified chitosan (CS) material, CS-g-AOPAM, was prepared by the amidoximation of the crosslinking compound of CS and a terpolymer of acrylamide, acrylonitrile and 3-dimethylaminoallyl phosphonic acid, which was applied to adsorb Cu(II) and Ni(II). The material CS-g-AOPAM was characterized by SEM, FTIR, XPS and TG, indicating porous structure and excellent thermal stability. In order to investigate the effects of coexisting ions, pH, initial concentration, adsorption time, and temperature on adsorption capacity of CS-g-AOPAM, batch adsorption experiments were carried out to obtain the corresponding adsorption behavior. According to the linear fitting of Langmuir model, the results proved that CS-g-AOPAM had excellent adsorption performance, exhibiting the maximum adsorption capacities of 215.5 mg·g−1 and 213.4 mg·g−1 for Cu(II) and Ni(II), respectively, which was higher than that of most similar CS adsorbents. The adsorption isotherms were in good agreement with Langmuir model, indicating a monolayer adsorption. Moreover, various adsorption kinetic and thermodynamic models were employed for analyzing adsorption behavior of CS-g-AOPAM, suggesting that the adsorption was a chemisorption as well as spontaneous endothermic process. Further, based on the analysis of FTIR and XPS, the adsorption sites and potential bonding modes of Cu(II) and Ni(II) were proposed. Overall, CS-g-AOPAM is a pretty promising novel adsorption material for the removal of heavy metal ions from wastewater.