Synthesis and Physicochemical Characterization of Carboxymethylcellulose from Oil Palm Empty Fruit Bunches for Lead (II) Ion Sequestration

Abstract

Cellulose is the most abundantly available renewable polymer on earth, with an estimated annual production of one hundred billion to one trillion tonnes. Oil Palm Empty Fruit Bunches (OPEFB) were treated with alkali, acid hydrolysed and bleached in order to extract native cellulose (NC). By employing chloroacetic acid to etherify the NC, carboxymethyl cellulose was produced. The changed cellulose's chemical composition, degree of substitution, proximate analysis, structural crystallinity, and thermal analysis were all reported. Modified cellulose had lower levels of fat and ash, according to proximate analysis. The crystallinity index of the synthesised CMC was found to be reduced relative to NC. The surface disruption during carboxylmethylation was confirmed by Scanning Electron Microscopy (SEM), which showed a rough, spongy-like mass for modified cellulose and irregular rod-like morphology for native cellulose, respectively. Improved stability following chemical alteration of the NC was demonstrated by thermal analysis. A batch adsorption process complied with the monomolecular layer adsorption mechanism and the pseudo-second-order kinetic model, consistent with the experimental results of lead ion adsorption by NC and CMC. The thermodynamic quantities evaluated included the standard enthalpy (ΔH° = 3.19 Kjmol-1 for NC and 6.77 Kjmol-1 for CMC), standard entropy (ΔS° = 10.81 JK-1mol-1 for NC and 22.16 JK-1mol-1 for CMC), and standard Gibbs free energy change (ΔG°). Thermodynamic evaluation revealed that the uptake of metal ions onto NC and CMC proceeded endothermically and spontaneously.