Aqueous zinc-ion batteries have gained significant interest, offering several distinct advantages over conventional lithium-ion batteries owing to their compelling low cost, enhanced battery safety, and excellent environmental friendliness. Nevertheless, the unfortunate growth of zinc dendrites during cycling leads to poor electrochemical performance of zinc batteries, primarily attributed to the diminished wet mechanical properties and limited electrolyte uptake of existing commercial separators. Herein, a bio-based separator was developed from sustainable resources using natural polymers derived from wood pulp to replace fossil-based polyolefin separators. The inherent hydrophilicity and swelling ability of cellulose fibers provide separators with superior electrolyte wettability and uptake. Notably, the structural reinforcement provided by lignin, especially after hot pressing, enhances the separator's wet mechanical integrity and performance during battery cycling. These improvements contribute to the separator's more stable electrochemical performance and improved ion transport properties. Separators composed of lignin-rich microfibrillated cellulose fibers showed superior dimensional stability under heat compared to Celgard, ensuring higher thermal safety and enhanced performance of aqueous zinc-ion batteries. Our results reveal the great potential of lignin-rich cellulose-based separators for future zincion batteries.

The study presents cellulose-based membranes derived from lignin-rich (unbleached high-kappa number softwood and hardwood) and lignin-free (fully bleached softwood) kraft pulps for the removal of cationic dyes from both simulated and real aqueous environmental systems. Characterization techniques revealed that the lignin-enriched cellulose-based membranes exhibited enhanced wet mechanical properties and a broader range of functional groups. The functional diversity inherent in lignin-containing membranes resulted in superior adsorption capacity for dyes such as Methylene Blue and Crystal Violet, compared to lignin-free counterparts. Detailed adsorption performance metrics—including kinetics, equilibrium studies, and the effects of pH and ionic strength—were thoroughly investigated. The adsorption capacity was 99–102 μmol g−1 for hardwood-derived membranes and 79–85 μmol g−1 for softwood-derived membranes at 25 °C. The process followed the pseudo-first-order kinetic model, likely due to the membranes' low porosity and energy homogeneity, which facilitated rapid adsorption. Electrostatic interactions played a pivotal role in dye attraction, while pH and ionic strength studies emphasized the importance of hydrogen bonding between cationic dyes and lignocellulose-based membranes. This research highlights the significance of utilizing cellulose-based membranes with enhanced lignin content in water purification, demonstrating their effective adsorption capabilities in both controlled and real-world environments. The approbation tests of these membranes showcased their substantial potential for practical water purification applications, contributing to the development of sustainable and efficient water treatment solutions.

Biobased alternatives to synthetic perfluorinated proton exchange membranes (PEMs) are needed to advance sustainable energy systems. This study evaluates lignin-containing microfibrillated cellulose (LMFC) as a material for PEMs. We produced LMFC from unbleached softwood and hardwood kraft pulps containing 11% and 14% klason lignin, respectively. Compared to lignin-free microfibrillated cellulose (MFC) membrane, LMFC membranes showed enhanced mechanical properties and proton conductivity due to its retained lignin content. The presence of carboxyl groups in LMFC led to doubled proton conductivity versus MFC under varied temperatures and high humidity conditions. While conventional PEMs show significant conductivity loss above 80 °C due to dehydration, both MFC and LMFC membranes demonstrated increasing proton conductivity at temperatures up to 120 °C under high humidity conditions. LMFC membranes exhibited tensile strength above 220 MPa with Young’s modulus exceeding 12 GPa. Gas transport tests revealed high selectivity for H₂/N₂ and H₂/O₂ pairs in LMFC and MFC membranes (α(H₂/N₂) ≈ 210), essential for preventing fuel loss in practical PEM applications. The achieved property ranges convincingly demonstrate LMFC’s potential as a sustainable alternative to conventional PEM materials.

The expanding field of lignin-containing nanocellulose offers a sustainable alternative to fossil-based substances in applications such as packaging, coatings, and composites. This has underscored the importance to explore the impact of raw materials due to the complexities of lignin structures and different raw fiber characteristics, which plays a significant role in determining the properties of the resultant lignin-rich cellulose materials. This study presents a detailed investigation and comparison on the production and structure-property relationships of lignin-containing microfibrillated cellulose (LMFC) fibers prepared from unbleached softwood and hardwood kraft pulps. The microfibrillation process was analyzed for both softwood and hardwood pulps, comparing the results across various stages of fibrillation. Distinguishing features of lignin structures in softwood and hardwood pulps were identified through Py-GC/MS analysis. Additionally, Digital Image Correlation was employed to investigate the varying failure patterns in LMFC films derived from different wood species. Softwood-derived LMFC films demonstrate less strain-concentrated regions and strain variation, attributed to the formation of more physical crosslinking joints by the elongated fibers. Consequently, softwood-origin LMFC films displayed superior load-sharing and enhanced tensile strength (287 MPa) compared to those derived from hardwood. Additionally, the denser lignin structures in unbleached softwood pulp further boosted the stiffness of resultant softwood-derived films. Upon recycling, LMFC films exhibited superior recovery of mechanical properties following drying, suggesting their significant potential for widespread commercial use.

The primary objective of this investigation is to evaluate how the incorporation of lignin and high-viscosity modifiers impacts the performance of asphalt binders. Lignin-modified asphalt binder (LBA) and lignin-high viscosity modifier composite-modified asphalt binder (LHA) were created by blending 5 % and 15 % lignin, respectively. To understand the physicochemical interactions, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were employed to analyze functional groups, thermal properties, and phase changes. Additionally, the linear rheological behavior and nonlinear rheological behavior were evaluated through frequency sweep and multiple stress creep recovery tests. The findings suggest that lignin blends physically with the asphalt binder and high-viscosity modifier without a chemical reaction. Although the onset pyrolysis temperature of lignin is significantly lower than that of asphalt binders, due to its relatively low content, the thermal decomposition of lignin-modified asphalt binders is primarily controlled by the asphalt binder itself and still exceeds the construction temperature. However, lignin incorporation increases the asphalt binder's glass transition temperature, potentially affecting low-temperature performance. Lignin significantly enhances the modulus in the high-frequency region of both unmodified and high-viscosity modified asphalt binder. However, it has a negative effect on the modulus in the low-frequency region of high-viscosity modified asphalt binder. Furthermore, nonlinear creep recovery test results demonstrate that lignin positively contributes to the deformation resistance of unmodified asphalt binder in a content-dependent manner, whereas it reduces the elastic behavior and deformation resistance of high-viscosity modified asphalt binder. In addition, low levels of lignin increase the stress sensitivity of binders, while high levels of lignin decrease it. Despite these effects, the performance of lignin and high-viscosity additive composite-modified asphalt binder remains superior to that of unmodified asphalt binder. These findings offer valuable insights into the combined use of lignin and polymers in asphalt binder modification.

Lignocellulosic biomass, particularly wood-derived cellulose, offers an abundant and renewable resource for producing advanced bio-based materials. This thesis explores the development and application of lignin-rich microfibrillated cellulose (LMFC) films produced from high-kappa number kraft pulp, highlighting their potential as sustainable alternatives to petrochemical-based materials. The research focuses on understanding the influence of residual lignin and raw fiber characteristics on the properties of LMFC films. The effects of drying conditions on the physicochemical and mechanical properties of these films were also investigated.

The study demonstrates that residual lignin enhances the thermal stability and hydrophobicity of the films while also improving their mechanical properties under optimized processing conditions. Furthermore, hardwood and softwood pulps exhibit distinct fibrillation behaviors, with softwood-derived LMFC films showing superior tensile strength due to the formation of more fiber joints within the fiber networks. The exceptional mechanical performance of LMFC films, comparable to chemically modified cellulose nanofibers, demonstrates their potential for industrial applications. These lignin-rich films show promise in high-value fields such as battery, organic dye adsorption, and proton exchange application. Notably, LMFC films are ideal candidates as separators in aqueous zinc-ion batteries, where their enhanced wet tensile strength, superior electrolyte uptake, and good ionic conductivity enable stable cycling performance. Additionally, the films' enhanced affinity for cationic organic dyes positions them as effective and eco-friendly adsorbents for water treatment. The findings of this thesis contribute to the sustainable development of bio-based cellulose materials by optimizing lignocellulosic resources for a wide range of applications. 

Biomassa från lignocellulosa, särskilt cellulosa från trä, utgör en rikligt förekommande och förnybar resurs för produktion av avancerade biobaserade material. Denna avhandling undersöker utvecklingen och tillämpningen av ligninrik mikrofibrillerad cellulosa (LMFC)-filmer, framställda av hög-kappa sulfatmassa, och belyser dess potential som hållbart alternativ till petrokemiskt baserade material. Forskningen fokuserar på att förstå hur restlignin och råfiberkarakteristika påverkar egenskaperna hos LMFC-filmer. Effekterna av torkningsförhållanden på de fysikalisk-kemiska och mekaniska egenskaperna hos dessa filmer undersöktes också.

Studien visar att restlignin ökar den termiska stabiliteten och hydrofobiciteten hos filmerna samt förbättrar deras mekaniska egenskaper under optimerade bearbetningsförhållanden. Vidare uppvisar lövträ- och barrträmassor olika fibrilleringsbeteenden, där LMFC-filmer framställda från barrträ visar överlägsen draghållfasthet på grund av bildningen av fler fiberförbindelser inom fibernätverket. Den exceptionella mekaniska prestandan hos LMFC-filmer, jämförbar med kemiskt modifierade cellulosananofibrer, visar deras potential för industriella tillämpningar. Dessa ligninrika filmer har lovande användningsområden inom högvärdesfält som batterier, organisk färgadsorption och protonutbytande tillämpningar. Särskilt LMFC-filmer är idealiska kandidater som separatorer i vattenbaserade zink-jonbatterier, där deras förbättrade våtstryka, överlägsna elektrolytupptag och goda jonledningsförmåga möjliggör stabil cyklingsprestanda. Dessutom ger filmernas ökade affinitet för katjoniska organiska färgämnen dem till effektiva och miljövänliga adsorbenter för vattenrening. Resultaten i denna avhandling bidrar till hållbar utveckling av biobaserade cellulosamaterial genom optimering av lignocellulosaresurser för ett brett spektrum av tillämpningar.

Recent progress in nanocellulose production favors lignin-rich raw fibers due to their cost effectiveness, higher yield of unbleached pulp, and added benefits from residual lignin, positioning them as ideal substitutes for fossil-based materials in composites and packaging. Nonetheless, their application has been impeded due to their inferior mechanical properties. This study introduces a simplified method to enhance the strength of lignin-containing microfibrillated cellulose (LMFC) films using water as a plasticizer during drying. Both LMFC from unbleached pulps and lignin-free microfibrillated cellulose (MFC) from fully bleached industrial kraft pulp were prepared through an environmentally friendly and scalable method. Given the charged carboxylic groups from hemicellulose and residual lignin, the LMFC gel demonstrated greater colloidal stability compared to MFC. Moreover, lignin-rich films displayed heightened hydrophobicity and exceptional thermal stability (T-max > 345 degrees C). A significant improvement in tensile strength and Young's modulus of LMFC films was achieved with an elevated drying temperature from 40 degrees C to above 90 degrees C, increasing tensile strength from 248 to 283 MPa and Young's modulus by 84%. These improvements are attributed to the thermoplastic nature of lignin and the plasticizing effect of water at elevated temperatures. The longer fibers in microfibrillated films also improved the resistance to cracking in a folded state. The study highlights that enhancement of the properties of lignin-rich films can occur during the film making step itself, hinting at a sustainable, innovative method for creating robust and scalable materials for flexible devices, biocomposites, and packaging.

The morphology control of lignin through particle size reduction to nanoscale seems to be a suitable conversion technology to overcome the intrinsic limitations of its native form to develop a wide range of biomaterials with high performance. Colloidal lignin particles (CLPs) in the range of 150-200 nm were synthesised from hardwood and softwood kraft lignins by the solvent shifting method. The initial molecular features of kraft lignins were evaluated in terms of purity, molecular weight distribution, and chemical functionalities. The impact of the lignin source and structure on the morphology, size distribution, and surface chemistry of CLPs was evaluated by particle size analyser, SEM, TEM and H-1 NMR. The results evidenced the influence of the botanical origin on the morphology and surface chemistry of particles. Furthermore, the antioxidant properties and cytotoxicity of lignins and corresponding CLPs, towards lung fibroblast cells were compared. CLPs from hardwood kraft lignins exhibited higher antioxidant power against DPPH free radical and a higher cytotoxic effect (IC30 = 67-70 mu g/mL) against lung fibroblast when compared to CLPs from softwood kraft lignin (IC30 = similar to 91 mu g/mL). However, the cytotoxicity of these biomaterials was dose-dependent, suggesting their potential application as active ingredients in cosmetic and pharmaceutic products at low concentrations.