Synthesis and Characterization of Lignin-Incorporated Carboxymethyl Cellulose (CMC) Films from Oil Palm Lignocellulosic Waste

Abstract

An environmentally friendly, biobased film was prepared from cellulose and lignin extracted from oil palm dried long fiber (DLF). DLF crude cellulose was first extracted from this lignocellulosic biomass by an alkaline pretreatment process at an elevated temperature (5.75 wt% NaOH, 200 °C, and 1 h), before it was carboxymethylated to obtain carboxymethyl cellulose (CMC). CMC is highly soluble in water, whereas lignin was precipitated out of the filtrate of the alkaline pretreatment process by adding acid to pH 2 (50 wt% H2SO4). The lignin/CMC films were synthesized at varying lignin concentrations of 0.25%, 0.5%, and 1% (w/v) in ethanolic solution with 0.25% (v/v) of glycerol; a neat CMC film was also prepared as a control. These lignin/CMC films were evaluated and compared for their morphological, physical, chemical, and thermal characteristics. The films displayed a brownish physical appearance, which was attributed to the natural color of lignin. The successful incorporation of lignin in the films was confirmed with the characteristic spectral bands of lignin in the mid-IR range (4000–400 cm−1). When measured with UV-vis spectrometer, the lignin/CMC films showed more enhanced UV blocking properties than the neat CMC film. The CMC films incorporated with lignin also showed slightly improved hydrophobicity and thermal stability. However, due to the low compatibility of lignin with CMC, the distribution of the lignin/CMC film was observed to be inhomogeneous in SEM images. Nonetheless, the addition of lignin to CMC in synthesizing biobased films is promising, potentially providing better properties that can be useful as biodegradable material.