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The uncontrolled production of waste is a daily phenomenon that is experienced by most global communities, and the situation worsens due to the lack of effective waste management procedures. Solid waste such as sawdust is primarily produced by the forestry industry and although it is utilized by certain countries as briquettes to make fire or as an absorbent to clean fluid spillage as well as a component of ceilings, most of the sawdust along the Lagos Lagoon in Nigeria is left unattended as waste, contributing to environmental pollution. Cellulose, composed of glucose units is a structural component of sawdust and when saccharified the resulting glucose can be fermented into renewable substances such as bio-ethanol. The cellulose degradation process can be performed with a cellulase enzyme such as available in the fungus Aspergillus niger and during the current investigation, this enzyme system was used to bio-convert the cellulose component of sawdust from ten different trees along the Lagoon into glucose. To increase the cellulase action all sawdust materials were delignified before cellulase action with the main aim of determining the optimum pH value for maximum degradation of the various sawdust materials. The pH-related saccharification profile of each type of sawdust was constructed as well as the relative percentage of saccharification and it was concluded that all the materials were optimum degraded at acidic pH-values which varied between pH 5.0 and pH 6.0 that are like optimum pH-values reported for the other types of cellulose materials.

This work reports the isolation of cellulose from giant reed through an ecofriendly multistep procedure including alkali treatment and totally chlorine free delignification, followed by acid hydrolysis to prepare microcrystalline cellulose using different acidic solutions (HCl, HNO 3 , H 2 SO 4 , HCl/HNO 3 (2:1, v/v), and HCl/H 2 SO 4 (2:1, v/v)). Several characterizations were performed in order to investigate the properties of each sample. FTIR results affirmed that the successive alkali treatment, totally chlorine free bleaching, and acid hydrolysis remove efficiently hemicellulose, lignin, and amorphous regions from the giant reed, and showed that the characteristic peaks of the prepared giant reed microcrystalline celluloses (GRMCC-HCl, GRMCC-HNO 3 , GRMCC-H 2 SO 4 , GRMCC-HCl/HNO 3 , and GRMCC-HCl/H 2 SO 4 ) were similar to those of the commercial one. XRD measurements exhibited that microcrystalline cellulose produced from giant reed belong to cellulose I allomorph, with crystallinity index ranging from 73 to 80%. SEM micrographs revealed non-uniform micro sized rod-like shape morphology of GRMCC samples. The thermal analysis results displayed that the thermal decomposition of the obtained GRMCCs shifted to higher temperatures compared to the respective giant reed cellulose. This work opened a new pathway to prepare cellulose and microcrystalline cellulose from an abundant natural source using an ecofriendly process, and it could be expected to have applications in several areas. Graphic abstract

Rice husk (RH) is a by-product of the rice milling process and is regarded as agricultural waste if not utilized properly. RHs are recognized to contain significant nutritional benefits, including cellulose, hemicellulose, lignin, hydrated silica, organic carbons, and potassium. One of the most often used cellulose derivatives in the food and pharmaceutical business is microcrystalline cellulose (MCC). MCC's isolation process consists of four stages, which are delignification, bleaching, hydrolysis, and drying. These steps are linked to various crucial reactions, including cellulose yield (%wt/wt), MCC yield (%wt/wt), and crystallinity index (%CrI). This review aims to identify the ideal parameters for the delignification, bleaching, hydrolysis, and drying processes involved in the extraction of MCC from RH. The effects of these parameters on the yield of cellulose, MCC, and CrI are also discussed. The result shows that alkaline pulping is usually utilized to treat 100% of the delignification process. MCC yield is negatively correlated with the number of delignification processes, with one step being the ideal amount. The cost-effective reagent for the bleaching process is NaClO, which also reduces CrI compared to samples that have not been bleached. For hydrolysis, HNO3 is utilized to provide higher yields of MCC. There is no association between the drying process and the three dependent variables, which is at odds with the current theory. Further investigation is required to ascertain the impact of the drying process's time, temperature, and technique in addition to the previously listed factors.

Lignin is a natural polymer, one that has an abundant and renewable resource in biomass. Due to a tendency towards the use of biochemicals, the efficient utilization of lignin has gained wide attention. The delignification of lignocellulosic biomass makes its fractions (cellulose, hemicellulose, and lignin) susceptible to easier transformation to many different commodities like energy, chemicals, and materials that could be produced using the biorefinery concept. This review gives an overview of the field of lignin separation from lignocellulosic biomass and changes that occur in the biomass during this process, as well as taking a detailed look at the influence of parameters that lead the process of dissolution. According to recent studies, a number of ionic liquids (ILs) have shown a level of potential for industrial scale production in terms of the pretreatment of biomass. ILs are perspective green solvents for pretreatment of lignocellulosic biomass. These properties in ILs enable one to disrupt the complex structure of lignocellulose. In addition, the physicochemical properties of aprotic and protic ionic liquids (PILs) are summarized, with those properties making them suitable solvents for lignocellulose pretreatment which, especially, target lignin. The aim of the paper is to focus on the separation of lignin from lignocellulosic biomass, by keeping all components susceptible for biorefinery processes. The discussion includes interaction mechanisms between lignocellulosic biomass subcomponents and ILs to increase the lignin yield. According to our research, certain PILs have potential for the cost reduction of LC biomass pretreatment on the feasible separation of lignin.

As an important commodity wood material, poplar has porous structure, which is worthy of being investigated. Especially, the lignin concentration is closely related to the formation and change of pores. Although a few studies reported the relation between the pore volume and the lignin removal of the ground wood (Stone and Scallan in J Polym Sci C Polym Symp 11(1):13–25, 1965), no information of the distribution of pore sizes versus the whole delignification process steps was reported. This study initially explored the effect of delignification level on the pore size distribution and pore structure in poplar cell walls using nitrogen absorption measurement. It was found that delignification increased the N2 adsorption amount and specific surface area of poplar. It also caused a large number of mesopores in the cell wall, mainly in the 2–10 nm pore size range, and decreased the average pore size. The whole delignification process can be roughly divided into three major phases, namely, the initial phase, the transitional phase and the stable phase, in which, the change process was not completely uniform. During the delignification, the size of poplar cell wall pores continued reducing, and finally a large number of uniform pores of about 2.1 nm was formed.

The paper is a review on the extraction processes of cellulosic fibers from flax and hemp. The two lignocellulosic crops have a long history of use by humans for extraction of the bast fibers among other purposes. The utility of bast fibers declined over time with industrial advances and changes to the economy, but of late, with an increase of focus on environmental impact and sustainability, there is a renewed interest in these resources. The use of biomass-based resource requires an appreciation of plant anatomy and the agronomical variables in their cultivation and harvesting. This review provides an overview of these aspects as well as of the processes of retting for initial weakening of the plant structure in preparation for fiber extraction, degumming to isolate fiber bundles, and delignification.

Chlorite delignification is popular in preparation of advanced functional biomaterials or pulping processes. To get more knowledge about the effects of chlorite delignification on wood, the dynamic mechanical performance and dynamic sorption behavior of Populus euramericana Cv. delignified at three levels were investigated. Results showed that partial delignification whitened wood but did not break the intact integrity. Some mesopores generated, and even cell separation appeared when too severe delignification was applied, indicating the binding functionality of lignin. Delignification increased the overall crystallinity while did not destroy the crystalline structure of cellulose. The crystallinity increase compensated for the stiffness loss for delignification and helped to restrict the molecular mobility at glass transition temperature indicated by dynamic mechanical analyses. Delignified wood presented stronger dynamic vapor sorption, which was further confirmed by increased hydrated moisture and dissolved moisture analyzed by Hailwood-Horrobin theory. The increasing concentration of sorption sites and accommodation for water molecules could account for this sorption increase after delignification. Delignified wood exhibited lower sorption hysteresis primarily for the synergies of acceleration of matrix relaxation and facilitation of molecular chain slippage of hemicelluloses and amorphous cellulose caused by delignification. This study connected wood hierarchical structures with dynamic mechanical and sorption properties for better understanding the behavior of delignified wood and underlying mechanisms. The results can provide basis for wood (or other lignocellulosic biomaterial) modification and advanced biomaterial functionalization based on delignification.Graphic abstract

The efficient removal of lignin is crucial for process optimization, as it enhances the exposure of polar groups in wood and provides interfacial binding sites for subsequent material modifications. In this study, an environmentally friendly peracetic acid/ hydrogen peroxide system was employed to delignify fast-growing wood. The results indicated mass loss rates of 30.7% for poplar and 31.3% for Chinese fir, with corresponding decreases in relative lignin content by 95.3% and 87.2%, respectively. Additionally, the specific surface area increased by 6.4% in poplar and 30.9% in Chinese fir. The relative crystallinity was enhanced by 31.2% in poplar and 15.7% in Chinese fir, and the O/C ratio increased by 29.6% and 19.7%, respectively. Microsocopic morphological analysis revealed noticeably thinner and slightly collapsed cell walls in the treated samples. The disappearance of lignin-specific peaks at 1507 cm −1 , 1460 cm −1 , and 1264 cm −1 confirmed the effective removal of lignin. Additionally, delignification resulted in a lower pyrolysis temperature, increased surface brightness, and reduced color variation. Due to the differences in internal structures and chemical compositions between poplar and Chinese fir, the effects of lignin removal varied, leading to significant changes in their physicochemical properties. These findings provide a theoretical foundational for lignin removal from wood and support future efforts in wood functionalization.

This work describes the effect of the hot chlorine dioxide delignification (D HT ) on the properties of bagasse fiber and the formation of AOX. The bagasse pulp was subjected to both D HT and normal temperature chlorine dioxide delignification (D 0 ), and the AOX contents in the effluent were determined respectively. The GC–MS results showed that the main components of the D 0 stage wastewater were chlorinated hydrocarbons and chlorinated diphenyls. In contrast, those AOXs in the D HT stage wastewater were very few. The GC–MS, ATR-FTIR, and XPS results showed the D HT process is more effective in the removal of the residual phenolic lignin and the hemicellulose-linked HexA compared with D 0 . Furthermore, in comparison, the AOX content could be reduced by 50% with D HT . The fully bleached pulp obtained via D HT E p D process has a higher brightness than that obtained by D 0 E p D, which provides a reliable theoretical basis for industrial application.