Adsorption studies on the removal of lead ions by magnetic cellulose nanocrystals as an eco-friendly nanoadsorbent derived from maize waste

Abstract

ABSTRACT This study describes the synthesis and characterisation of magnetic cellulose nanocrystal (MCNC) nanocomposite derived from maize stalk as an adsorbent for the adsorptive removal of Pb(II) from wastewater. The FT-IR analysis revealed the presence of C=O, COOH, CH, OH and Fe3O4 stretching frequencies, while the P-XRD diffractograms confirmed the monoclinic type 1 cellulose with 1β lattice and magnetite cubic spinel phases. The needle, rod and spherical or irregular and irregular shapes were observed for CNC, magnetite and the MCNC, respectively, as shown in the TEM images. The P-XRD confirmed particle sizes of 31, 14 and 21 nm for CNC, magnetite and MCNC, respectively. For the morphology, SEM indicated a smooth fibroid surface of CNC, while the magnetite showed rod-like and spherical structures indicating the presence of iron and oxygen. The UV-Vis spectra displayed the presence of both CNC and magnetite. Furthermore, the thermal stability studies indicated that MCNC was stable after 600°C. The BET displayed the surface area, pore size and pore volume of the MCNC as 56 m2/g, 98Å and 0,1465 cm3/g.Å, respectively. The optimum conditions of the adsorption process were investigated by using multivariate optimisation tools, and the optimal conditions were 60 mg, 5 min, 10 ppm, pH 6 and 60°C. The maximum removal of 97% was obtained for Pb(II) with acceptable precision (≤3%) and adsorption capacity 47 mg/g. The MCNC demonstrated reusability for four consecutive cycles with the highest removal of 96%. However, for real wastewater samples, a removal of 53% was achieved. These results showed that the adsorption best fitted Langmuir isotherms and Pseudo first order with the endothermic and spontaneous thermodynamic reaction. The Temkin isotherm revealed the endothermic nature of the interaction between the adsorbent surface and Pb(II) ions, while the Frenkel–Halsey–Hill isotherm confirmed the non-multilayer interaction of the adsorbent and Pb(II) ions.