Sustainable and efficient extraction of lignin from wood meal using a deep eutectic system and adsorption of neutral red dye with the extraction residue

Abstract

In this study, the efficient extraction of lignin from wood meal using a deep eutectic system (DESys) was explored, and the obtained lignin was characterized. The impact of various factors, such as the type of DESys components, extraction time, temperature, water content, and solid-liquid ratio, on the lignin extraction process was systematically investigated. The results indicated that a DESys with a carboxylic acid as the HBD provided the highest lignin extraction efficiency. The obtained lignin was characterized in terms of its molecular weight distribution, elemental composition, functional groups, crystalline structure, and thermal stability. The results showed that the lignin obtained by DESys-based extraction had similar properties to lignin extracted using traditional method. Additionally, the study examined the utilization of the residue left after lignin extraction for the adsorption of cationic pollutants, such as the cationic dye neutral red (NR). The residue was found to contain carboxyl groups, which enabled it to adsorb NR efficiently. The kinetic and thermodynamic models suggested that the adsorption was a chemisorption process. Furthermore, the residue showed selective adsorption for cationic dye over anionic dye. This selectivity was attributed to interactions between the residue's functional groups and the cationic dye molecule. Overall, this study provided a sustainable and comprehensive approach to lignin extraction from lignocellulosic biomass using DESys. It also demonstrated the potential of using the residue from the extraction process for the removal of cationic pollutants from wastewater, showcasing a multi-faceted approach to the valorization of lignocellulosic materials.