This study explores paired electrolysis, leveraging the oxygen reduction reaction (ORR) and industry-relevant lignosulfonate oxidation to enhance sustainable electrochemical processes. The anode reaction is driven by the direct oxidation of lignosulfonate, an abundant biopolymer derived from sulfite pulping, on bare graphite electrodes, eliminating the need for costly catalysts. This process occurs in a membrane electrolyzer, where the cathode catalyst dictates ORR selectivity: a carbon paper cathode modified by the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) favors hydrogen peroxide formation via a 2-electron pathway, while a platinum-modified carbon paper cathode facilitates full oxygen reduction to water via a 4-electron pathway. When applying a cell voltage of 0.7 V (a geometrical current density of 0.04 mA cm^–2), the air-saturated catholyte had an 8-fold decrease in dissolved oxygen, which corresponded to 68% faradaic efficiency and an electrical energy consumption of 0.0233 W hour l^–1. Removing the low molecular weight lignosulfonate (<3.5 kDa) via dialysis minimizes membrane crossover but also reduces oxygen consumption rates. The oxidation process preserves the lignosulfonate backbone while enriching its quinone content, offering a novel, energy-efficient approach to biomass valorization. By integrating lignosulfonate oxidation with ORR, this work presents a cost-effective and sustainable alternative to conventional anodic processes, with potential applications in green hydrogen peroxide production and biobased electrochemical systems.

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.

Brownstock washing, a critical process in cleansing kraft pulp, removes dissolved lignin residues from the pulp after it has passed through the cooking digester. It plays a significant role in kraft pulp mills by enhancing economic efficiency and environmental sustainability. Improved washing efficiency leads to better pulp quality and more effective recovery of cooking chemicals. Our study aimed to better understand the impact of different chemical compositions in washing liquors on washing performance. We tested a range of washing liquors, including neutral solutions (deionized water, 1M NaCl, 3M NaCl, 1M Na2SO4) and alkaline solutions (tap water, washing liquor composed of 0.35M NaOH and 1M Na2SO4, and white liquor with 50 g[OH]/l and 8.77 g[HS]/l). These liquors were evaluated for their efficacy in maximizing lignin extraction. Our findings suggest that salt solutions generally reduce washing efficiency. Deionized water and white liquor proved to be the most efficient washing agents, while high-concentration salts and those with high ionic strength negatively impacted washing efficiency. This suggests that brownstock washing may not be operating at its full potential.

Lignin nanoparticles (LNPs) are gaining increasing interest for applications in various fields, where the particle homogeneity, morphology, and surface properties are critical for performance. In this study, lignin obtained via kraft process from spruce and eucalyptus was employed as precursor for the fabrication of lignin nanoparticles with tunable physicochemical properties. Linear ester groups with varying chain lengths were introduced to systematically investigate the effects of the hydrophobic moiety distribution on lignin nanoparticle formation via solvent-shifting self-assembly. Results demonstrated that esterification-induced structural changes altered the balance of key noncovalent interactions (hydrogen bonding, π–π stacking, and hydrophobic interactions), which collectively governed the self-assembly process, with longer ester chains promoting compact particles with hydrophobic surfaces. By directly linking molecular-level modification of lignin to alterations in the inter- and intramolecular interactions driving the self-assembly of nanoparticles, this study provides a mechanistic framework for the rational design of lignin nanoparticles through controlled chemical modification, thereby expanding their application flexibility.

The growing demand for sustainable packaging, stricter regulations on non-biodegradable plastic waste, and increasing consumer awareness of environmental pollution are driving the development of water-soluble packaging materials. This study investigates the potential of lignin nanoparticles (LNPs) derived from spruce kraft lignin (SKL) and eucalyptus kraft lignin (EKL), as functional additives in polyvinyl alcohol (PVA)-based films to achieve an optimal balance between high transparency and effective UV protection. To improve LNP dispersion within the PVA matrix, hydrophobic domains were introduced into lignin via acetylation, as confirmed by ³¹P NMR spectroscopy. The morphology of the nanoparticles was analyzed using transmission electron microscopy (TEM). The resulting PVA–LNP nanocomposite films exhibited excellent transparency and outstanding UV-shielding capabilities. UV–Vis spectroscopy confirmed the UV-blocking performance of the films, revealing that EKL-derived nanoparticles (EKL-C1) enhanced UV absorption more than eightfold compared to neat PVA, while SKL-derived nanoparticles (SKL-C1) achieved a 6.5-fold increase. This superior performance can be attributed to the higher syringyl (S) unit content and abundant methoxy groups in EKL-C1, which can improve UV absorption efficiency. Atomic force microscopy (AFM) further demonstrated smoother surface morphologies for EKL-C1-containing films, indicating improved nanoparticle dispersion and reduced aggregation. Mechanical testing before and after UV exposure confirmed the suitability of the films for packaging applications. These findings highlight the potential of lignin-based nanocomposite films as eco-friendly packaging and coating materials, offering a unique combination of high transparency and robust UV protection while, providing valuable insights into the structure–property relationships of lignin nanoparticles in biodegradable polymer films.

This study investigates lignin nanoparticles (LNPs) from spruce and Eucalyptus kraft lignins as sustainable additives for sunscreen formulations. The lignins and their nanoparticles were characterized using spectroscopic, chromatographic, and microscopic techniques and incorporated into oil-in-water sunscreen emulsions, where they were evaluated for UV-blocking efficiency, stability, and rheological properties. Results demonstrated that LNPs significantly enhanced UV protection, with spruce kraft lignin nanoparticles providing superior broad-spectrum coverage (280–400 nm) and an SPF of 12.94, compared to Eucalyptus lignin nanoparticles, which primarily absorbed in the UVB range (280–320 nm) and reached an SPF of 7.00. Additionally, LNPs improved emulsion stability through Pickering stabilization and enhanced rheological properties, making them promising eco-friendly and multifunctional sunscreen additives.

The role of sodium sulfate was considered relative to pulp washing liquors and its impact on the reattachment of lignin to pulp fibers during the brownstock washing process. The dissolution of lignin during washing and its potential redeposition onto the pulp fibers is influenced by various factors. Three distinct types of pulp-unbleached, bleached, and cotton linters-were used to explore these effects. The washing experiments were conducted using industrial wash liquor and were repeated further with the addition of sodium sulfate. The resulting products of the washing process, including the liquor discharge and the washed pulp, were thoroughly evaluated. Analytical techniques, such as UV measurements of lignin content in the liquor discharge and characterization of the pulp, were employed to assess the outcomes. The findings reveal that the addition of sodium sulfate to the washing liquor resulted in an increase in its conductivity and ionic strength. Moreover, it was observed that lignin reattachment to pulp fibers was noticeably greater when washing was performed with sodium sulfate addition. Among the pulps studied, unbleached kraft pulp exhibited the highest degree of lignin reattachment, followed by bleached kraft pulp, with cotton linters showing the least.

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.

This work has focused on oxygen's role in the delignification process within the context of pulp production. We have investigated the role of oxygen in a complex set of chemical reactions taking place during this process, including both oxidative and non-oxidative reactions. This study explores the impact of pH changes during the oxygen delignification process and the characteristics of the resulting pulps. Additionally, this research examines the effect of oxygen, by comparing conventional oxygen delignification with trials using air and nitrogen. Industrial softwood kraft pulps with a kappa number of 35 were subjected to delignification for 20-120 min under alkaline conditions. The resulting pulps were assessed for kappa number, intrinsic viscosity, fiber charge, and ISO brightness. An important observation from this research is the reduction in lignin molecular weight upon exposure to oxygen and air, suggesting depolymerization reactions facilitated by oxygen species, whereas nitrogen exposure results in less pronounced changes. This finding underscores the impact of oxygen in altering lignin structure, thus informing the selectivity and effectiveness of the delignification process.

Lignin, a bio-originated polymer, is being explored as an alternative to nonrenewable fossil resources. It is obtained from biomass during pulping and is mostly burned for energy. In most kraft pulp lines, residual lignin in the pulp is oxidized and solubilized during an oxygen delignification step. This study proposes an isolation method for lignin solubilized during oxygen delignification, which we refer to as "oxlignin", and explores its structural characteristics and properties. The study found acid precipitation to be an effective method for partially isolating oxlignin from the oxygen delignification step. Various analytical methods were employed, including UV-vis absorption analysis, 31P NMR spectroscopy, FT-IR spectroscopy, SEC, and TGA. In addition, the solubility of the lignin was studied in four different solvents and compared to the commercial kraft lignins. The study found that oxlignin is a promising substitute for lignosulfonates in certain applications due to its hydrophilicity and high solubility in water, methanol, and ethanol. Compared to kraft lignins, oxlignin has a lower phenolic group content but higher carboxylic acid content.