Synthesis and metal ion adsorption characteristics of graphene oxide incorporated chitosan Schiff base

Abstract The work reports the development of a novel adsorbent material based on modified chitosan for removal of Cu (II) and Cr (VI) ions from aqueous solution. Heterocyclic modification of chitosan has been achieved by the reaction of chitosan with 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde resulting in a Schiff base. This was further modified by incorporation of graphene oxide at the C6 position through ester linkage. This modification results in increase in the number of binding sites like donor nitrogens, OH and COOH groups. The modified polymer was characterized using FTIR, TGA, SEM, EDS and XRD techniques. The adsorption capacity exhibited by the modified chitosan towards Cu (II) and Cr (VI) were 111.11 and 76.92 mg/g respectively which is a significant improvement compared to chitosan. The adsorption data fitted well with Langmuir isotherm model and pseudo second order kinetic model. The thermodynamic analysis of adsorption data indicated endothermic and spontaneous nature of adsorption. A high desorption of over 80% was achieved for Cu (II) in acidic solution and for Cr (VI) in basic solution indicating efficient recovery of adsorbate species.