Sequential alkaline-organosolv pretreatment of coconut mesocarp biomass: a sustainable strategy for enhanced carboxymethylcellulose production

Abstract

Lignocellulosic biomass is a valuable, renewable resource with great potential for various industrial uses. Among these, coconut fiber stands out as a promising agro-industrial residue for enhancing the bioeconomy due to its abundance. In this context, aiming to enhance the value of coconut byproducts, this study suggests of a more efficient method for extracting extractives, hemicellulose, and lignin from coconut mesocarp, thereby obtaining a cellulosic fraction appropriate for producing carboxymethylcellulose (CMC). The developed methodology employs a sequential pretreatment process that integrates alkaline extraction (NaOH 0.50 mol/L, 55 °C, 2 h) and organosolv (ethanol:water 1:1, alkaline catalyst, 2 h, 185 °C) techniques. Chemical and structural characterization analyses of both treated and untreated biomass reveal that sequential pretreatment is critical for the effective extraction of lignocellulosic fractions. A significant reduction in residual lignin content is seen, dropping from 43.31 to 11.41 in the treated sample, while cellulose content rises to 47%, resulting in a 22% yield of CMC. Changes in the chemical structure are confirmed by FTIR analysis, which reveals more distinct cellulose peaks in the sequentially treated samples. TGA and SEM analyses also support the removal of lignin and hemicellulose. This study introduces a novel method for producing CMC from lignocellulosic biomass through a sequential pretreatment that effectively removes non-cellulosic components from coconut fiber. Beyond increasing CMC production, this proposed process encourages the creation of innovative products and uses derived from lignocellulosic biomass. This initiative not only enhances sustainability but also optimizes the use of renewable resources, driving significant progress in the biorefinery sector.

Graphical Abstract