Cellulose Schiff Base as a Bio-based Polymer Ligand: Extraction, Modification and Metal Adsorption Study

Cellulose was initially extracted from Safflower (Carthamus tinctorius L.) stem wastes and used for the preparation of a fully bio-based adsorbent polymer Schiff base (Sch) using oxidation reaction of the extracted compound. A safe cross-linked cellulose dialdehyde (CC-DA) was subsequently synthesized through epichlorohydrin (ECH) and sodium metaperiodate followed by Sch formation with p-phenylenediamine (p-PDA). All of the reactions carried out including cross-linking, oxidation, and Sch formation of the extracted cellulose were confirmed via Fourier-transform infrared spectroscopy (FTIR) study. The microstructure of the modified products was also investigated using scanning electron microscopy (SEM). The prepared modified cellulose was further characterized by X‐ray powder diffraction (XRD), mapping, energy‐dispersive X‐ray spectroscopy (EDX), CHNS, and thermogravimetric analysis (TGA). Furthermore, it was used in the removal of Pb(II) from wastewater. The effect of some factors such as pH, contact time, and adsorbent dosage was additionally examined in batch mode experiments. Maximum removal efficiency of Pb(II) reached 98.5% at pH 6 and the contact time of 15 min. The kinetic analyses revealed that the adsorptions of Pb(II) on the cellulose Sch adsorbent followed with a pseudo-second order model (R2 > 0.99). Moreover, the adsorption isotherms were well fitted with the Langmuir isotherm, suggesting that homogeneous monolayer surface adsorption that had occurred. The spontaneous and endothermic nature of the adsorption process was further settled by thermodynamic parameters.