Isolation and Fractionation of the Tobacco Stalk Lignin for Customized Value-Added Utilization

Research Status of Lignin-Based Polyurethane and Its Application in Flexible Electronics

Polyurethanes (PU) have drawn great attention due to their excellent mechanical properties and self-healing and recyclable abilities. Lignin is a natural and renewable raw material in nature, composed of a large number of hydroxyl groups, and has a great potential to replace petroleum polyols in PU synthesis. This review summarizes the recent advances in modification methods such as the liquefaction, alkylation, and demethylation of lignin, and a systematic analysis of how to improve the reactivity and monomer substitution of lignin during polyurethane synthesis for the green manufacturing of high-performance polyurethanes was conducted. Polyurethane can be used in the form of films, foams, and elastomers instead of conventional materials as a dielectric or substrate material to improve the reliability and durability of flexible sensors; this review summarizes the green synthesis of polyurethanes and their applications in flexible electronics, which are expected to provide inspiration for the wearable electronics sector.

Current status and future prospects of pretreatment for tobacco stalk lignocellulose

With the growing demand for sustainable development, tobacco stalks, as a resource-rich and low-cost renewable resource, hold the potential for producing high-value chemicals and materials within a circular economy. Due to the complex and unique structure of tobacco stalk biomass, traditional methods are ineffective in its utilization, making the pretreatment of tobacco stalk lignocellulose a crucial step in obtaining high-value products. This paper reviews recent advancements in various pretreatment technologies for tobacco stalk lignocellulosic biomass, including hydrothermal, steam explosion, acid, alkaline, organic solvent, ionic liquid, and deep eutectic solvent pretreatment. It emphasizes the impact and efficiency of these pretreatment methods on the conversion of tobacco stalk biomass and discusses the advantages and disadvantages of each technique. Finally, the paper forecasts future research directions in the pretreatment of tobacco stalk lignocellulose, providing new insights and methods for enhancing its efficient utilization.

Composition of Lignocellulose Hydrolysate in Different Biorefinery Strategies: Nutrients and Inhibitors

The hydrolysis and biotransformation of lignocellulose, i.e., biorefinery, can provide human beings with biofuels, bio-based chemicals, and materials, and is an important technology to solve the fossil energy crisis and promote global sustainable development. Biorefinery involves steps such as pretreatment, saccharification, and fermentation, and researchers have developed a variety of biorefinery strategies to optimize the process and reduce process costs in recent years. Lignocellulosic hydrolysates are platforms that connect the saccharification process and downstream fermentation. The hydrolysate composition is closely related to biomass raw materials, the pretreatment process, and the choice of biorefining strategies, and provides not only nutrients but also possible inhibitors for downstream fermentation. In this review, we summarized the effects of each stage of lignocellulosic biorefinery on nutrients and possible inhibitors, analyzed the huge differences in nutrient retention and inhibitor generation among various biorefinery strategies, and emphasized that all steps in lignocellulose biorefinery need to be considered comprehensively to achieve maximum nutrient retention and optimal control of inhibitors at low cost, to provide a reference for the development of biomass energy and chemicals.

Comparative investigation of the structural characteristics of tobacco stalk lignin during the DES and alkaline deconstruction toward sustainable materials

Lignin polymer as a natural aromatic macromolecule presents significant prospects in producing functional and sustainable materials, and achieving a comprehensive characterization will facilitate their target valorization. In the present study, deep eutectic solvent (DES) and alkaline delignification were adopted to deconstruct tobacco stalk before and after hydrothermal pretreatment, obtaining diverse lignin fractions with fascinating characteristics. DES lignin exhibited a higher yield and homogenous molecular structure than MWL. A severe cleavage of the inter-unit linkages in lignin was also observed. This result mostly originated from the efficient delignification of the DES deconstruction system adopted. Moreover, all the recovered lignin fractions exhibited good micro-nanoparticle size that can enhance the valorization of lignin in nanomaterial production, in which the hydrothermal-assisted DES deconstruction promoted the formation of the smaller lignin nanoparticle size. Next, all the recovered lignin presented an excellent UV absorption and structure-related absorption performance or thermal properties. Overall, this work provides an important foundation for further exploiting DES/alkaline delignification lignin that can be applied as an ideal feedstock for producing sustainable functional or micro/nanomaterials.

Customized Utilization Strategies of Industrial Lignin to Produce Adsorbents and Flocculants Based on Fractionation and Adequate Structural Interpretation

Lignin, a by-product of pulping and biorefinery, has great potential to replace petrochemical resources for wastewater purification. However, the defects of lignin, such as severe heterogeneity, inferior reactivity and poor solubility, characterize the production process of lignin-based products by high energy consumption and serious pollution. In this study, several lignin fractions with relatively homogeneous structure were first obtained by organic solvent fractionation, and their structures were fully deciphered by various characterization techniques. Subsequently, each lignin component was custom-valued for wastewater purification based on their structural characteristics. Benefiting from the high reactivity and reaction accessibility, the lignin fraction (lignin-1) refined by dissolving in ethanol and n-butanol could been used as a raw material to produce cationic lignin-based flocculant (LBF) in a copolymerization system using green, cheap and recyclable ethanol as solvent. The lignin fraction (lignin-2) extracted by methanol and dioxane showed low reactivity and high carbon content, which was used to produce lignin-based activated carbon (LAC) with phosphoric acid as activator. Moreover, the influences of synthetic factors on the purification capacity were discussed, and the LBF and LAC produced under the optimal conditions showed distinguished purification effect on kaolin suspension and heavy metal wastewater, respectively. Furthermore, the corresponding purification mechanism and external factors were also elaborated. It is believed that this cleaner production strategy is helpful for the valorization of lignin in wastewater resources.