Chitosan-based nano-sorbents: synthesis, surface modification, characterisation and application in Cd (II), Co (II), Cu (II) and Pb (II) ions removal from wastewater

Abstract

In contemplation of treating hazardous industrial wastewater, sodium tripolyphosphate (TPP) and vanillin (V)-modified chitosan-based magnetic nano-sorbents (TPP-CMN and V-CMN) were prepared, and the physical and surface properties of both nano-sorbents were characterised. The results of FE-SEM and XRD showed an average size of between 6.50 and 17.61 nm for Fe3O4 magnetic nanoparticles. The Physical Property Measurement System (PPMS) was carried out, and the saturation magnetisations for chitosan, Fe3O4 nanoparticles, TPP-CMN, and V-CMN were 0.153, 67.844, 7.211, and 7.772 emu.g−1, respectively. By using multi-point analysis, the BET surface areas of the synthesised TPP-CMN and V-CMN nano-sorbents were found to be 8.75 and 6.96 m2/g, respectively. The synthesised TPP-CMN and V-CMN were investigated as effective nano-sorbents to uptake Cd (II), Co (II), Cu (II), and Pb (II) ions, and the results were investigated by AAS. The adsorption process of heavy metals was investigated by the batch equilibrium technique, and the sorption capacity values of Cd (II), Co (II), Cu (II), and Pb (II) ions by TPP-CMN were 91.75, 93.00, 87.25, and 99.96 mg/g. By V-CMN, the values were 92.5, 94.00, 88.75, and 99.89 mg/g, respectively. The equilibrium times for adsorption were found to be 15 minutes for TPP-CMN and 30 minutes for V-CMN nano-sorbents. The adsorption isotherms, kinetics, and thermodynamics were studied to understand the adsorption mechanism. Furthermore, the adsorption of two synthetic dyes and two real wastewater samples was studied and obtained significant results. These nano-sorbents’ simple synthesis, high sorption capability, excellent stability, and recyclability may provide highly efficient and cost-effective nano-sorbents for wastewater treatment.