Title : Synthesis of magnetic cellulose nanocrystals derived from maize waste for the adsorptive removal of lead (Pb) from wastewater samples
Abstract:
Over the past few years, heavy metal ions (HMIs) pollution has become a crucial matter by threatening human health and the ecological system, owing to their toxic nature. It has been reported by various researchers that Pb (II) has the potential to transform the water quality into polluted and non-drinkable water. Thus, this study describes the synthesis and characterization of magnetic cellulose nanocrystal (MCNC) nanocomposite derived from maize stalk as an adsorbent for the adsorptive removal of Pb (II) from wastewater. The synthesised MCNC using a co-precipitation method was confirmed and characterised using FTIR, XRD, TEM, SEM/EDX, UV-Vis, TGA, and BET. FTIR analysis revealed the presence of C=O, COOH, CH, OH and Fe3O4 stretching frequencies. The XRD diffractograms confirmed the monoclinic type 1 cellulose with 1β lattice and magnetite cubic spinel phases. TEM analysis confirmed the needle shape, rods and spherical or irregular shape and both rods, needle and irregular shapes for CNC, magnetite and the MCNC, respectively. The SAED confirmed the same crystallographic planes as the P-XRD and the particle sizes obtained for all the three materials were 31 nm, 14 nm 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 56m2/g, 98Å and 0,1465 cm3/g.Å, respectively. For the removal of Pb (II), the multivariate optimization tools were used. An average maximum adsorptive removal percentage of 97% for Pb (II) with acceptable precision (≤ 3%) and an adsorption capacity was obtained at 47 mg/g. The MCNC could still be reused for 4 consecutive cycles with the highest removal of 96%. Moreover, against real wastewater samples a removal of 53 % was achieved. These results showed that the reaction followed Freundlich adsorption isotherms and Pseudo first order reaction with the exothermic and spontaneous thermodynamic reaction.
Keywords: Cellulose nanocrystals, adsorption, adsorption capacity, kinetics and thermodynamics, adsorption removal of lead, wastewater remediation
