Search Results (108)

Phosphorylated cellulose nanocrystals (P-CNCs) are a superior alternative to conventional sulfuric acid-derived CNCs because of their enhanced thermal and colloidal stability. However, further research is needed to understand the factors influencing their synthesis and properties for advanced material applications. In this study, P-CNCs were synthesized from bleached hardwood kraft pulp (BEKP) using a controlled hydrolysis method involving pretreatment with H₃PO₄ followed by reaction with metaphosphoric acid (HPO₃) and urea. To optimize the process, a full factorial design was employed to evaluate the effects of reaction time (60–90 min) and HPO₃ concentration (3–4 M). The P-CNCs were characterized using physicochemical, morphological, and thermal analyses. Surface charge densities ranged from 757 to 1993 mmol/kg, with exceptional colloidal stability, as evidenced by zeta potentials ranging from −30.17 to −67.40 mV. Statistical analysis showed that reaction time had a significant main effect on surface charge (p-value = 0.0022) and zeta potential (p-value = 0.0448), while a significant interaction between reaction time and HPO₃ concentration was observed when analyzing the surface charge (p-value = 0.0097), suggesting a combined effect of these factors on the surface modification of CNC. Crystallinity indices ranged from 63.6% to 71.3%, and the thermal stability exceeded that of the raw material. These findings contribute to a better understanding of the surface modification and stability of P-CNCs and support efforts to sustainably produce functional CNCs for advanced composite applications. Full article

The urgent need to decarbonize the construction sector has prompted research into sustainable alternatives to conventional concrete. This study compares two industrially produced pulps with contrasting lignin contents: a bleached kraft cellulose pulp with near-zero lignin used in paper production and a thermo-mechanical lignocellulose pulp with high lignin content used in MDF production. Fiber-reinforced composites were produced by partially replacing mineral aggregates with fibers at dosages from 0.1% to 3% by mass and air-curing to simulate practical curing conditions. The specimens were evaluated for density, water absorption, and compressive strength, with compressive strength measured at 7, 28, and 60 days. Results showed a reduction in density for both fiber types, along with increased water absorption and decreased compressive strength at higher fiber contents. Cellulose composites achieved a more favorable mechanical performance than lignocellulose composites but showed markedly higher water absorption, raising concerns about long-term durability. By testing two pulps that differ primarily in lignin content across multiple replacement ratios, the study provides a systematic comparison of their effects on composite properties. The comparison explicitly contrasts the lignin contents of the two industrial pulps—bleached kraft (~0.1%) versus thermo-mechanical (27.4%)—to isolate lignin-driven effects on hydration and property development. A practical air-curing protocol was adopted, leveraging fiber-bound/process water, thereby reflecting use cases where external water curing is constrained. Full article

Phosphorylated cellulose is proposed as a bio-resin for the removal of heavy metals, as a substitute for synthetic polymer-based materials. Phosphorylation is carried out using kraft pulp fibers as the cellulose source, with phosphate esters and urea as reactants to prevent significant fiber degradation. Herein, phosphorylated fibers, with three types of counterions (sodium, ammonium, or hydrogen), are used in adsorption trials involving four individual metals: nickel, copper, cadmium, and lead. The Langmuir isotherm model is applied to determine the maximum adsorption capacities at four different temperatures (10, 20, 30, and 50 °C), enabling the calculation of the Gibbs free energy (ΔG), entropy (ΔS), and enthalpy (ΔH) of adsorption. The results show that the adsorption capacity of phosphorylated fibers is equal or even higher than that of commercially available resins (1.7–2.9 vs. 2.4–2.6 mmol/g). However, the nature of the phosphate counterion plays an important role in the adsorption capacity, with the alkaline form showing a superior ion exchange capacity than the hybrid form and acid form (2.7–2.9 vs. 2.3–2.7 vs. 1.7–2.5 mmol/g). The thermodynamic analysis indicates the spontaneous (ΔG = (-)16–(-)30 kJ/mol) and endothermic nature of the adsorption process with positive changes in enthalpy (0.45–15.47 kJ/mol) and entropy (0.07–0.14 kJ/mol·K). These results confirm the high potential of phosphorylated lignocellulosic fibers for ion exchange applications, such as the removal of heavy metals from process or wastewaters. Full article

The traditional papermaking process uses petroleum-based additives, which raise environmental concerns. As a result, these concerns have attracted the scientific community to explore green additives by introducing environmentally friendly cellulose modifications as additives to the papermaking process. A promising way to process pulp is the application of deep eutectic solvent-like mixtures, which expand new possibilities for delignification processes. This article aims to characterize the physical properties of pulps modified with deep eutectic solvent-like mixtures and to compare these properties to untreated softwood kraft pulp and pulp obtained after oxygen delignification (commercially available pulp; obtained from Mondi Štětí a.s.). The physical properties (mechanical and optical) of the original pulp and delignified pulps were evaluated based on the degree of beating (Schopper–Riegler degree), zeta potential, water retention value, tensile strength, modulus of elasticity, and whiteness. Technology employing deep eutectic solvent-like mixtures shows great promise for sustainable pulp production; however, its full-scale adoption will require further research focused on process optimization, solvent recovery, and economic cost reduction. Full article

Lignin, one of the most abundant biopolymers on Earth, holds significant promise as a feedstock for applications such as resins, biofuels, foams, and carbon fibres. However, despite extensive research, lignin remains largely underutilised, with its primary use limited to combustion for energy. While lignin’s structural features are well documented, there is a lack of consistent data on its key physical properties such as density. This study addresses that gap by providing experimentally determined values for skeletal and bulk densities of lignins obtained through different extraction methods, including Kraft; soda pulping; and particularly the ionoSolv process, using ionic liquids such as N,N-dimethyl butyl ammonium hydrogen sulphate ([DMBA][HSO₄]). The results reveal correlations between lignin chemical structure and density in ionoSolv-extracted lignins from Eucalyptus Red Grandis, suggesting opportunities to tune the extraction parameters for targeted material properties. The skeletal density of the lignin samples ranged from 1.3370 to 1.4598 g/cm³, while the bulk density varied more widely—from 0.0944 to 0.5302 g/cm³—reflecting significant differences in particle packing and porosity depending on the biomass source and extraction method. These findings contribute valuable data for process design and scale-up, advancing the commercial viability of lignin-based products. Full article

Alkaline treatment is well suited for extracting high-molecular-weight hemicelluloses, specifically hardwoods xylans, which, due to their polymer structure and chemical characteristics, enable the production of films with desirable mechanical, barrier, and optical properties for packaging applications. Despite its relevance, the optimization of antisolvent addition has received little attention in the literature. This study explores the use of eucalyptus industrial residue as feedstock, utilizing a statistical design to determine the optimal extraction conditions for hemicelluloses while minimizing the lignin content in the recovered liquor. The process uses alkali loads that are compatible with those in conventional Kraft pulp mills. Optimal extraction conditions involve a temperature of 105 °C, 16.7% NaOH charge, and 45 min at maximum temperature. The resulting liquor was subjected to ethanol precipitation under varying pH conditions (initial pH, 9, 7, 5, and 2) and different ethanol-to-liquor ratios (1:1 to 4:1). The acidification was performed using hydrochloric, sulfuric, and acetic acids. Ethanol served as the main antisolvent, while isopropyl alcohol and dioxane were tested for comparison. Results show that 2.3 ± 0.2% of xylans (based on oven-dry biomass) could be extracted, minimizing lignin content in the liquor. This value corresponds to the extraction of 15.6% of the xylans present in the raw material. The highest xylan precipitation yield (78%) was obtained at pH 7, using hydrochloric acid for pH adjustment and an ethanol-to-liquor ratio of 1:1. These findings provide valuable insight into optimizing hemicellulose recovery through antisolvent precipitation, contributing to more efficient biomass valorization strategies within lignocellulosic biorefineries. Full article

This study analyzes the effect of artificial aging on the mechanical deformational and optical properties of various paper samples, which allows us to evaluate their durability and suitability for long-term storage. The methods of accelerated aging, measuring the breaking length, specific resistance, elongation, and fracture strength, were used, and the optical characteristics were estimated by the R₄₅₇ and CIE whiteness indices, as well as opacity. Mechanical measurements (breaking length, specific resistance, elongation, and fracture strength) revealed that bleaching reduces residual lignin and strengthens interfiber bonds, boosting pine pulp strength by up to 8%. Optical properties initially improve slightly, then increase sharply after the second bleaching cycle and stabilize, while opacity decreases, providing greater light transmittance. After accelerated aging, the following deterioration is observed: for bleached samples, R₄₅₇ whiteness changes; and for unbleached samples, CIE whiteness and opacity increase. After aging, aspen pulps and kraft papers retained over 90% of their initial strength and whiteness, whereas untreated and office papers lost up to 20–25%. These findings identify that aspen-based and kraft papers demonstrate better mechanical deformational and optical properties, which makes it possible to predict the operational characteristics of paper depending on the processing and aging methods used. Full article

Lignin, a complex aromatic biopolymer abundant as waste in biorefineries and the pulp and paper industry, holds significant potential for valorization. This study presents the oxidative depolymerization of Lignoboost lignin (LB) using H₂O₂ under mild, solvent- and catalyst-free, inherently acidic conditions at 50–70 °C. The process aimed to produce functionalized low-molecular-weight oligomers, retaining aromaticity, and aliphatic dicarboxylic acids, rather than complete monomerization. The depolymerized LB was rich in aromatic dimers-trimers (68.6 wt.%) with high functionalization (2.75 mmol/g OHphen, 3.58 mmol/g OHcarb, 19.5 wt.% of H in -CH=CH-), and aliphatic dicarboxylic acids (53.4 wt.% of monomers). Acidic conditions provided higher depolymerization and functionalization than alkaline, alongside simplified product recovery. The process was also successfully applied to Kraft lignin, demonstrating versatility and robustness even with higher polymeric content feedstocks. The optimized conditions were scaled up (×25), improving efficiency and yielding Mw 464 g/mol and Đ 1.3. As proof of concept, the scaled-up product underwent radical crosslinking, resulting in a new biopolymer with higher thermal stability than LB (54.2 wt.% residual mass at 600 °C versus 36.1 wt.%). This green, scalable process enhances lignin valorization by producing functionalized low-molecular-weight lignin oligomers and dicarboxylic acids that can be used independently or together to form crosslinked networks. Full article

The kraft pulp process generates liquors with different physicochemical characteristics at each treatment stage. These liquors can accidentally spill into the biological treatment, hindering it and harming ecosystems where the effluents are discharged. Due to the lack of studies on the effects these liquors can have on the aerobic biomass of activated sludges and ecosystems, this investigation aims to assess the toxicity of each liquor spill to the aerobic biomass of an activated sludge, using Selenastrum capricornutum as a bioindicator of water quality. This evaluation used a laboratory-scale activated sludge, which was fed with an effluent with pH 6.62–6.67 and chemical organic demand (COD) of 611–638.5 mg/L. The liquors used had the following parameters: pH = 13 and COD = 1911 mg/L (white); pH = 13 and COD = 141,350 mg/L (black); pH = 13 and 2755 mg/L (green); and pH = 7.5 and COD = 358 mg/L (condensate). White liquor produced the greatest toxicity (EC₂₀ of 17.8 mgCOD/L) and lowest oxygen uptake rate (8.42 mgO₂/L·h with 287.7 mgCOD/L) in the aerobic biomass compared to the other liquors. White liquor presented the greatest inhibition of Selenastrum capricornutum, with 81.7% (48 h) and 98.0% (96 h). Meanwhile, black liquor presented an inhibition of 94.7% (48 h), but a 13% increase in microalga growth at 96 h of culture. The information from this study makes it possible to calculate how much liquor can be fed to an activated sludge system, keeping it optimized to eliminate liquor discharges generated within the kraft mill’s processing units. Full article

Using fatty acids has generated significant interest in the building sector for improving energy storage in the form of latent heat. In this work, using vacuum impregnation, we analyzed the properties of a capric acid and myristic acid eutectic (83-17%) as a bio-based phase change material in Pinus radiata. The delignification of Pinus radiata samples facilitated the impregnation process, which was carried out using the Kraft pulping method. Morphological, chemical, mechanical, thermal, and acoustic impedance analyses were performed. The results revealed that impregnating PCM in Pinus radiata samples increases the thermal inertia of the impregnated samples, which is comparable to that of delignified samples. Additionally, the analyses showed no significant difference between natural and delignified samples after treatment with PCM. Full article

Lignin, a significant industrial byproduct from paper manufacturing processes, exhibits ultraviolet (UV) radiation absorption properties. Cellulose nanofibers (CNFs) demonstrate universal ligand characteristics and represent an innovative approach for converting industrial waste into value-added products. Given their potential applications in cosmetic formulations, their efficacy and safety parameters, such as their photoprotection mechanisms and phototoxicity, need to be investigated. Therefore, two kraft lignin fractions, LE and R1, along with a kraft-bleached pulp CNF, were evaluated for their phototoxicity and photoprotection mechanisms, both using the HaCaT cell line (immortalized human keratinocytes) as the in vitro model. Phototoxicity assessment involved exposing cells to UVA radiation (4 J/cm²), with the subsequent comparison of cell viability between irradiated and non-irradiated samples. ROS quantification was performed using a 2′,7′-dichlorofluorescein diacetate (DCF-DA) probe, with fluorescence intensity measurements, and was then used to evaluate the photoprotection effect. The results demonstrated that both LE and R1 exhibited concentration-dependent increases in phototoxicity, whereas CNF showed no phototoxic effects under the conditions tested. For photoprotection, LE, R1, and CNF reduced UV-induced ROS production, a result which could be associated with antioxidant properties in the case of the lignin fractions. These findings suggest that both lignin fractions and CNF hold promise for use in renewable and sustainable cosmetic formulations. Full article

In this study, a modified synthetic method for labeling a lignin dimer (guaiacylglycerol-β-guaiacyl ether-[α-¹³C]) was developed. The chemical structure of the target compound was analyzed using ¹H-NMR, ¹³C-NMR, and other analytical techniques. Then, the ¹³C-labeled phenolic lignin model compound was subjected to kraft pulping in the presence of xylose. Finally, the resulting reaction products were fractionated using acid precipitation and ethyl acetate extraction, and each fraction was analyzed by carbon-13 nuclear magnetic resonance (¹³C-NMR) and two-dimensional heteronuclear multiple quantum coherence (HMQC) spectroscopy. This aimed to investigate the occurrence of lignin–carbohydrate complexes (LCCs) during the conventional kraft pulping process. Employing ethanol as the reaction medium facilitated the bromination of 4-acetylguaiacol-[α-¹³C], resulting in a homogeneous reaction and significantly improving the yield of the brominated product to over 90%. Additionally, kraft pulping of the phenolic lignin model compound in the presence of xylose led to the occurrence of minor quantities of benzyl ether-type lignin–carbohydrate complex (LCC) structures, which were predominantly detected in the ethyl acetate extractive. Full article

By reflecting on the history and environmental impact of conventional biorefining, such as kraft pulping, we aim to explore important questions about how natural polymers can be more sustainably sourced to develop bio-products and reduce reliance on plastics. Since the Industrial Revolution, chemical pulping processes have enabled the mass production of cellulosic products from woody biomass. Kraft pulping, which dominates within modern pulp and paper mills, has significantly contributed to environmental pollution and carbon emissions due to sulfurous byproducts and its high water and energy consumption. While chemical pulping technologies have advanced over time, with improvements aimed at enhancing sustainability and economic feasibility, conventional biorefineries still face challenges related to biomass conversion efficiency and environmental impact. For example, efforts to fully utilize wood resources, such as isolating lignin from black liquor, have made limited progress. This perspective provides a thoughtful examination of the growth of chemical pulping, particularly the kraft process, in the production of consumer goods and its environmental consequences. It also presents key insights into the bottlenecks in developing truly sustainable biomass conversion technologies and explores potential alternatives to traditional chemical pulping. Full article

Cellulose nanocrystals (CNC) receive great attention for their physical and optical properties, high surface area, high tensile strength, rigidity (Young’s modulus up to 140 GPa), and ease of surface modification. However, controlling the properties of CNC is still challenging, given the wide variety of pulp sources and the complexity of finding suitable processing conditions. In the present study, acid hydrolysis efficiently isolated CNC from wood Acacia mearnsii brown kraft pulp (AMKP). Initially, the AMKP was delignified by the treatment with acidified sodium chlorite. The Acacia mearnsii kraft pulp obtained was then subjected to acid hydrolysis with sulfuric acid at concentrations of 50 to 58% 45 °C for 60 min. The hydrolysate was sonicated in an ultrasonic processor for 30 min. The chemical composition was determined by Fourier transform infrared spectroscopy (FTIR), crystallinity by X-ray diffraction (XRD), zeta potential by Zetasizer ZS equipment, thermal stability by thermogravimetric analysis (TGA), and morphology by transmission electron microscopy (TEM) to verify the effect of acid concentration on the yield and properties of CNC. The optimization of the isolation process demonstrated that the maximum yield of 41.95% can be obtained when AMWP was hydrolyzed with sulfuric acid at a concentration of 54%. It was possible to isolate CNC with a crystallinity index between 71.66% and 81.76%, with the onset of thermal degradation at 240 °C; zeta potential of −47.87 to 57.23 mV; and rod-like morphology, with lengths and widths between 181.70 nm and 260.24 nm and 10.36 nm and 11.06 nm, respectively. Sulfuric acid concentration significantly affected the yield of acid hydrolysis, allowing the isolation of CNC with variable dimensions, high thermal stability, high crystallinity index, and great colloidal stability in aqueous medium. Full article

China is the country with the most abundant bamboo resources in the world. Using bamboo as a raw material for pulping and papermaking can save a lot of wood and protect forests. Bamboo pulping enterprises mostly adopt sulfate processes to produce a large amount of black liquor (BL), which contains monosaccharides, polysaccharides, oligosaccharides, pectin, lignin, etc. The utilization of the high-value organic matter is of great economic and environmental significance. In this study, blue-green carbon dots (C-dots) were prepared from bamboo (Lingnania chungii) kraft pulp BL using a hydrothermal method. The changes in carbohydrate content in BL in relation to hydrothermal temperature and hydrothermal time were discussed in detail. Then, a series of characterizations of BL-C-dots, prepared under one of the hydrothermal conditions (180 °C, 6 h), were performed and the BL-C-dots showed an excitation-dependent photoluminescence (PL) spectrum and a quantum yield (QY) of 2.9% in an aqueous solution. Finally, the as-prepared BL-C-dots were successfully used as fluorescent materials to develop an anti-counterfeiting code. The fluorescent code exhibited a clear outline, an excitation-tunable color, good stability, and high security, showing great anti-counterfeiting potential and realizing the high-value utilization of BL. Full article