Green synthesis of cellulose nanocomposites from Pentaclethra macrophylla Benth pod as efficient adsorbent for the removal of lead ion in aqueous solution

Abstract

Progressive industrialization and increasing world population have led to severe water pollution. In this study, Penthaclethra macrophylla benth pod was suggested as possible inexpensive adsorbent for the synthesis of cellulose nanocrystals, and the removal of lead at low concentrations. FTIR peaks observed at 3204 and 3414 cm− 1 represented the stretching and bending vibrations of O-H, while the peak at 664.2 cm− 1 represented the β-glycosidic linkage of the cellulose. XRD peaks at 2θ = 12.4o, 20.3o and 26.4o represented the typical cellulose-I structure. Surface morphology revealed a stacked flake-like structure, while transmission electron micrographs indicated clusters of spherical-shaped nanoparticles, with particle sizes between 1 and 10 nm. EDX spectra showed the presence of carbon, oxygen, and other trace elements. Maximum adsorption percentage was noted for CNC-GO-PLA-MWCNT (99.73), CNC-GO (99.77), and CNC (99.75), at the pH of 8. Isotherm plots revealed that the adsorption behaviour of Pb(II) ion was best described by the Freundlich model (R2 > 0.99). Kinetics study showed that the PSO model (R2 > 0.99) has a better fit for all nanocomposites. Thermodynamic investigation showed negative values for all ΔG° across samples and temperatures. Adsorption is exothermic for all composites, except for CNC-GO-PLA-MWCNT. Positive values of ΔS° indicated increased disorder.