CARBOXYMETHYL CELLULOSE SYNTHESIS FROM TREATED OIL PALM EMPTY FRUIT BUNCH USING IONIC LIQUID AND HYDROGEN PEROXIDE

The synthesis of carboxymethyl cellulose (CMC) generally uses isolated crude cellulose with alkaline or acid pretreatment followed by bleaching with sodium chlorite. In this study, the simple [BMIM][Cl] ionic liquid was used as a solvent in the pretreatment process before conduct the bleaching process with hydrogen peroxide (H2O2) to isolate cellulose from empty fruit bunch (EFB) for further synthesis of CMC. The isolated crude EFB cellulose obtained was converted to CMC by adding 30 wt.% NaOH and various concentrations of sodium monochloroacetic acid (SMCA) at 55 °C for 3 h. The effects of SMCA concentration on the degree of substitution (DS) and CMC yield were investigated. The physicochemical properties of the CMC products were characterized using proton nuclear magnetic resonance, scanning electron microscope-energy dispersive spectrometry, X-ray diffraction, and thermogravimetric analysis. Based on the results, CMC was demonstrated to be synthesized using ionic liquid pretreatment with H2O2 bleaching. Carboxymethyl cellulose synthesized in this study showed a high DS of 0.82. The CMC synthesized from EFB cellulose through ionic liquid pretreatment presented good chemical and physical properties as that reported in other studies.

The Dual Effect of Ionic Liquid Pretreatment on the Eucalyptus Kraft Pulp during Oxygen Delignification Process

Oxygen delignification presents high efficiency but causes damage to cellulose, therefore leading to an undesired loss in pulp strength. The effect of ionic liquid pretreatment of [BMIM][HSO4] and [TEA][HSO4] on oxygen delignification of the eucalyptus kraft pulp was investigated at 10% IL loading and 10% pulp consistency, after which composition analysis, pulp and fiber characterizations, and the mechanism of lignin degradation were carried out. A possible dual effect of enhancing delignification and protecting fibers from oxidation damage occurred simultaneously. The proposed [TEA][HSO4] pretreatment facilitated lignin removal in oxygen delignification and provided fibers with improved DP, fiber length and width, and curl index, resulting in the enhanced physical strength of pulp. Particularly, its folding endurance improved by 110%. An unusual brightness reduction was identified, followed by detailed characterization on the pulps and extracted lignin with FTIR, UV, XPS, and HSQC. It was proposed that [TEA][HSO4] catalyzed the cleavage of β-O-4 bonds in lignin during the oxygen delignification, with the formation of Hibbert’s ketones and quinonoid compounds. The decomposed lignin dissolved and migrated to the fiber surface, where they facilitated the access of the oxidation agent and protected the fiber framework from oxidation damage. Therefore, it was concluded that ionic liquid pretreatment has a dual effect on oxygen delignification.