Optimization of ethanol-extracted lignin from palm fiber by response surface methodology and preparation of activated carbon fiber for dehumidification

Abstract

Lignin is a renewable bioresource that can be used for a variety of value-added applications. However, the effective separation of lignin from lignocellulosic biomass remains an ongoing challenge. In this study, lignin was extracted from waste palm fiber and successfully converted into a dehumidifying material. The following four process parameters of lignin extraction from palm fiber were optimized systematically and comprehensively using the response surface methodology: reaction time, extraction temperature, ethanol concentration and solid/liquid ratio. The results revealed that under the optimum processing conditions (111 min of extraction at 174 °C using 73% ethanol at 1/16 g/mL solid/liquid ratio), the extraction yield of lignin was 56.2%. The recovery of ethanol solvent was as high as 91.8%. Further, the lignin could be directly used without purification to produce lignin-based activated carbon fibers (LACFs) with specific surface area and total pore volume of 1375 m2/g and 0.881 cm3/g, respectively. Compared with the commercial pitch-based activated carbon fiber, the LACF has a higher specific area and superior pore structure parameters. This work provides a feasible route for extracting lignin from natural palm fiber and demonstrates its use in the preparation of activated carbon fiber with a remarkable performance as a solid dehumidification agent. Graphical Abstract

Extraction and characterisation of kudzu root residue lignin based on deep eutectic solvents

“…Therefore, five factors including the type of DES, molar ratio of DES, solid–liquid ratio, reaction temperature, and reaction time have been selected for optimisation, in accordance with the literature. In this study, we changed the HBA (FA, AA, PA, LA, and LaA) of the DES, the molar ratio of the DES (1/2, 1/3, 1/4, 1/5, and 1/6), the solid–liquid ratio (1/10, 1/20, 1/30, 1/40, and 1/50 g/mL), the reaction temperature (110°C, 130°C, 150°C, 170°C, and 190°C), and the reaction time (1, 2, 3, 4, 5, and 6 h) to compare the extraction ratio, while maintaining the other conditions constant 12 …”

“…To determine the influencing factors of lignin yield and properties, many researchers have successively investigated different extraction methods and extraction conditions. 12 However, due to the diversity of lignin in different plants, we cannot determine whether the conditions for extracting lignin from other plants are suitable for extracting lignin from kudzu root residue. Thus, four typical influencing factors were selected as the optimisation objects in this study to conduct the experiments sequentially.…”

“…11 It is worth noting that different natural sources and extraction methods lead to various lignins with different structures and physicochemical properties. 12 Nevertheless, there are still many problems in these methods including grave environmental pollution, complicated procedures, and high cost. 13 Deep eutectic solvents (DESs) are non-toxic, biodegradable, simple to synthesise, and inexpensive solvent systems, formed by a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA).…”

“…For example, a number of researchers have extracted lignin with kraft pulping, acid hydrolysis, alkaline pretreatment, organic solvent methods, and ionic liquids from biomass materials such as pine straw, wheat straw, alfalfa, and flaxfiber 11 . It is worth noting that different natural sources and extraction methods lead to various lignins with different structures and physicochemical properties 12 . Nevertheless, there are still many problems in these methods including grave environmental pollution, complicated procedures, and high cost 13 …”