Bleached Pulp Research Articles

Influence of different curing regimes and accelerated carbonation on the physical, mechanical, and aging performances of fiber cement

The curing process in fiber cement is essential to improving the characteristics of the fiber-matrix interface, physic-mechanical performance, and durability. This work studied the effect of different curing regimes and accelerated carbonation on fiber cement to optimize these materials' production stages and physic-mechanical performance. The fiber cement flat sheets were produced with 10% bleached eucalyptus pulp by slurry-dewatering method to reproduce the commercial Hatschek process. Carbonated and non-carbonated samples were assessed at different regimes and curing ages to provide a comparative parameter. Thermal curing at 60 °C (7 days) and wet curing (28 days) was carried out after carbonation as supplementary curing. The accelerated carbonation was performed in a climatic chamber at 60 °C, 90% RH, and 20% CO2 concentration. Accelerated aging trials were also conducted for durability evaluation. X-ray diffraction, TGA, and scanning electron microscopy analyses determined the mineralogical composition, chemical components, and fiber cement microstructure. Mechanical results presented an average increase of 33% in resistance of carbonated samples compared to non-carbonated fiber cement. Additional curing increased the materials' hydration potential and demonstrated an 11% increase in calcium carbonate amounts. However, there was no statistically significant difference in fiber cement’ physic-mechanical performance with additional curing. The carbonated samples without supplementary curing presented a fiber-matrix interface like that observed in other curing regimes, even after being subjected to a shorter curing time (3 days) and accelerated aging cycles. The accelerated carbonation process enables the materials’ production at reduced ages, achieving physic-mechanical performance and durability like materials produced at more advanced ages with conventional curing regimes.

Cellulose nanofibrils derived from pulp as a high performance separator for lithium‐ion batteries

AbstractCellulose nanofibrils (CNFs) from hardwood bleached kraft pulp (HwBKP) are produced via enzymatic, chemical, and mechanical treatment. A nanoporous structured CNF‐based separator is produced, and the electrochemical performance, morphology, and thermal stability analyses are performed in comparison to the commercial polyethylene separator. The results obtained show that the electrolyte‐philic CNF separator has capacity retention of 88.6% over 200 cycles and very good ionic conductivity and wettability results due to its high hydrophilic nature. At 140°C, the CNF separator was resilient to heat and remained intact. The CNF separator reflects high thermal resistance and good electrolyte uptake properties that are among the mandatory requirements of a separator hence, a promising contender for use in lithium‐ion batteries.

Role of intrinsic and extrinsic xylan in softwood kraft pulp fiber networks

Xylan is primarily found in the secondary cell wall of plants providing strength and integrity. To take advantage of the reinforcing effect of xylan in papermaking, it is crucial to understand its role in pulp fibers, as it undergoes substantial changes during pulping. However, the contributions of xylan that is added afterwards (extrinsic) and xylan present after pulping (intrinsic) remain largely unexplored. Here, we partially degraded xylan from refined bleached softwood kraft pulp (BSKP) and adsorbed xylan onto BSKP. Enzymatic degradation of 1 % xylan resulted in an open hand sheet structure, while adsorption of 3 % xylan created a denser fiber network. The mechanical properties improved with adsorbed xylan, but decreased more significantly after enzymatic treatment. We propose that the enhancement in mechanical properties by adsorbed extrinsic xylan is due to increased fiber-fiber bonds and sheet density, while the deterioration in mechanical properties of the enzyme treated pulp is caused by the opposite effect. These findings suggest that xylan is decisive for fiber network strength. However, intrinsic xylan is more critical, and the same properties cannot be achieved by readsorbing xylan onto the fibers. Therefore, pulping parameters should be selected to preserve intrinsic xylan within the fibers to maintain paper strength.

Energy saving potential of interstage screen fractionation for production of board grade BCTMP

Over the last few decades, the continuing decline in mechanical pulp-based grades has led pulp producers to modify operations and implement measures to reduce production costs in order to stay competitive. In spite of a considerable effort to reduce energy consumption, the latter is still a major portion of production costs in the process of making bleached chemithermomechanical pulp (BCTMP). In this study, we evaluated the impact of interstage screening fractionation (ISSF) and secondary refining strategy for producing BCTMP with the objective of reducing refining energy consumption while maintaining or improving bulk and strength properties. In the first step and to establish a baseline for a mill’s existing configuration, the collected primary refined pulp and reject streams from the ISSF were refined in a high consistency (HC) refiner to target freeness levels. The accepts and refined rejects streams were recombined, and their properties were compared to those of the refined primary pulp. The results showed that, at a given freeness of 400 mL and compared to the control case (without fractionation), the ISSF using an 0.070 in. basket followed by rejects refining could lead to about 25% energy saving in the second stage HC refining. Handsheet properties showed that utilization of ISSF could produce BCTMP with higher bulk and similar average fiber length and tear index. However, a slight reduction in tensile strength was observed. In the second set of trials, the primary refined pulp and the rejects from the ISSF using the 0.070 in. basket were refined by a low-consistency (LC) refiner. The results showed that, at the same freeness of 400 mL and compared to refined primary pulp, the ISSF saved about 26% in net LC refining energy. At a specific edge load (SEL) of 0.4 J/m, the produced pulp had similar bulk and strength properties compared to those of the control sample. A higher SEL of 0.6 J/m in LC refining could further decrease net refining energy consumption; however, it also led to reduction in fiber length, bulk, and strength properties.

Isolation of Nanocellulose by Enzymatic Hydrolysis of Bleached Musa textilis (Abaca) Pulp

Nanocellulose is commonly isolated from cellulosic materials by chemical methods using strong acids. In this study, the enzymatic method was explored to isolate nanocellulose from commercial bleached S 2 grade abaca pulp. It was first disintegrated for 10 min and was subjected to enzyme hydrolysis while incubated with Bacillus sp. cellulase for 72 h at 50 °C and 120 revolutions/min. A clear liquid material was obtained after enzymatic hydrolysis after a series of centrifugation and ultrasonication. Results showed that the isolated nanocellulose had an average particle size of 375.9 nm ± 2.9 with a polydisperse index of 0.404 ± 0.059. Transmission electron and atomic force images showed that nanocellulose was longitudinal in size and highly aggregated and agglomerated. Through FTIR analysis, crystallinity indexes (i.e. lateral order index, total crystallinity index, and hydrogen bond intensity) of bleached abaca pulp and the isolated nanocellulose were compared. Results showed that the enzymatic hydrolysis of bleached abaca pulp resulted in higher cellulose crystallinity. Overall, nanocellulose can be isolated using biological methods using Bacillus sp. cellulase. These results could be used as a baseline to isolate smaller particle sizes, highly monodisperse, and stable nanocellulose that could be further applied in packaging, papermaking, cosmetics, medicine, and numerous other applications.

Microstructural Origin of Selective Water Oxidation to Hydrogen Peroxide at Low Overpotentials: A Study on Mn-Alloyed TiO2

Introduction: Hydrogen Peroxide, H2O2, is a versatile chemical with applications ranging from industrial to household use such as pulp bleaching, wastewater treatment, and sterilization. In addition to these established uses, H2O2 is emerging as a green energy carrier which can release 96 kJ mol−1 of energy via exothermic chemical decomposition with only water and oxygen as by-products. Currently, more than 95% of H2O2 produced globally originates from anthraquinone autoxidation. This process requires precious metal catalysts and expensive liquid-liquid extraction processes that are only feasible for large-scale chemical plants.Electrochemical and photochemical syntheses are promising alternatives for distributed H2O2 production. H2O2 can be produced by 2e- processes both via oxidatively, via water oxidation reaction (WOR) or reductively via oxygen reduction reaction (ORR). These approaches take advantage of abundant energy sources, i.e., renewable electrical or solar energy, and enables the storage of intermittent energy as the free energy of chemical bonds for distributed energy storage. Charge Transfer: H2O2 can be (photo-)electrochemically synthesized via a two-electron (2e−) water oxidation pathway, as shown in equation 1.2H2O → H2O2 + 2H+ + 2e−, E = +1.77 VRHE (1)However, existing catalysts often exhibit low faradaic efficiency (FE) due to the competitive four-electron (4e−) pathway of O2 evolution reaction (OER) equation 2.2H2O → O2 + 4H+ + 4e−, E = +1.23 VRHE (2)The thermodynamic driving force for OER is always at least +0.54 V greater than that of the 2e− H2O2 pathway which can allow the undesired O2 evolution pathway to overcome any kinetic barriers and dominate. In addition, the produced H2O2 can be over-oxidized to O2 at an excess potential of at least +1.09 V equation 3.H2O2 → O2 + 2H+ + 2e−, E = +0.68 VRHE (3)Thus, the partial oxidation of water to hydrogen peroxide presents a model system of a common challenge in catalysis where the desired product is kinetically feasible but thermodynamically unfavorable.In this work, we utilize X-ray Photoelectron Spectroscopy to quantify the presence of Mn(III) defect states within the TiO2 band gap which are energetically aligned to peroxide generating reactive intermediates.During operation, the energy levels of CB and VB of TiO2 are fixed, or “pinned”, at −0.05 and 3.29 VRHE, respectively, yet the empty states of the Mn defect states can precisely align with the energetics of H2O2 producing intermediates. Under a higher applied potential, i.e., +2.3 VRHE, there would exist a moderate overpotential for the 2e− water oxidation, but such a potential also enables the other pathways including 1e− water oxidation to produce radicals, leading to an overall reduction in H2O2 production rates due to the reduced selectivity. Thus, this strategy of defect state tuning is best suited to low overpotentials, <100mV, catalysis. Conclusion: This study presents a new strategy of introducing charge-transport defect states and demonstrates the design of H2O2-producing surfaces that oxidize water to H2O2 with high selectivity at very low overpotentials. Given the growing literature related to H2O2 selective catalysis, this approach is expandable to a range of host oxides that prevent H2O2 disproportionation to favor 2e− H2O2 electrochemistry.Faradaic efficiency of >90% at < 150 mV overpotentials was achieved for H2O2 production, accumulating 2.97 mM H2O2 after 8 hours. Nanoscale mixing of Mn2O3 and TiO2 resulted in a partially filled, highly conductive Mn3+ intermediate band (IB) within the TiO2 mid-gap to transport charge across the (Ti,Mn)Ox coating. This IB energetically matched that of H2O2-producing surface intermediates, turning a wide bandgap oxide into a selective electrocatalyst capable of operating in the dark. Figure 1

Assessing the Genotoxicity of Cellulose Nanomaterials in a Co-Culture of Human Lung Epithelial Cells and Monocyte-Derived Macrophages.

Cellulose micro/nanomaterials (CMNMs) are innovative materials with a wide spectrum of industrial and biomedical applications. Although cellulose has been recognized as a safe material, the unique properties of its nanosized forms have raised concerns about their safety for human health. Genotoxicity is an endpoint that must be assessed to ensure that no carcinogenic risks are associated with exposure to nanomaterials. In this study, we evaluated the genotoxicity of two types of cellulose micro/nanofibrils (CMF and CNF) and one sample of cellulose nanocrystals (CNC), obtained from industrial bleached Eucalyptus globulus kraft pulp. For that, we exposed co-cultures of human alveolar epithelial A549 cells and THP-1 monocyte-derived macrophages to a concentration range of each CMNM and used the micronucleus (MN) and comet assays. Our results showed that only the lowest concentrations of the CMF sample were able to induce DNA strand breaks (FPG-comet assay). However, none of the three CMNMs produced significant chromosomal alterations (MN assay). These findings, together with results from previous in vitro studies using monocultures of A549 cells, indicate that the tested CNF and CNC are not genotoxic under the conditions tested, while the CMF display a low genotoxic potential.

Kenaf bast nanocrystalline cellulose: Analysis of morphological, chemical, crystalline, and thermal

Cellulose nanocrystals (CNC) were prepared from delignified kenaf bast fiber by using alkaline pulping, based on soda anthraquinone, hydrogen peroxide bleaching, and acid hydrolysis treatment with H2SO4. The size and morphology of the fibers were characterized by scanning electron microscopy (SEM), and the isolated fiber from unbleached and bleached pulp had a diameter between 9 to 30 µm. Fourier transform infrared (FTIR) spectroscopy exhibited that the content of lignin decreased in the pulping process, and the lignin was almost completely removed during hydrogen peroxide bleaching. Moreover, fibers were characterized for crystallinity using X-ray diffraction (XRD). The fiber crystallinity gradually increased at each stage of the process (raw kenaf bast, unbleached pulp, bleached pulp, and acid hydrolysis). The fiber was characterized by atomic force microscopy (AFM), which showed that the isolated pulp nanofibers had diameters of approximately 30 nm.

Improved bleached eucalyptus kraft pulp-based tissue papers incorporating wet-strength resins

Abstract Common tissue paper manufacturing trends aim at partial or total replacement of softwood pulp with hardwood pulp for its production, such as bleached eucalyptus kraft pulp (BEKP), in order to optimize the process and the final product properties such as softness. However, the use of a single type of hardwood fiber results in lower strengths of both wet and dry webs. To maintain necessary strength and desired properties, the incorporation of several additives is often required. In this context, low molecular weight polyethylene glycol (PEG) and different wet strength resins, such as polyamideamine-epichlorohydrin (PAE) and glyoxalated polyacrylamide (GPAM) resins, were combined to achieve an innovated product with improved properties. In particular, wet and dry tensile strength was significantly improved when combining PEG and wet strength resins, especially observed in tissue papers prepared with PAE resin, high-charge cationic agent and bulk applied aqueous PEG solution. Noteworthy that water absorption capacity and softness of tissue paper were not critically affected by PEG incorporation, regardless of application method used (in bulk or by spray).

Структурно-морфологические свойства вторичного волокна из влагопрочного сырья при мягком размоле. Часть 2. Характеристика волокнистой мелочи

The process of recycled pulp refining is usually associated with a significant change in the morphological characteristics of the secondary fiber and the formation of additional amounts of fines. It is well known that fines have a great impact on the pulp properties, the papermaking process and the quality of the resulting paper. At the same time, the effect of fines both on the paper properties and on the papermaking process depends on the morphological characteristics of the fines. The aim of the study was to evaluate the changes in the morphological characteristics of the fines during gentle low-consistency refining of the recycled pulp. The recycled pulp was obtained from commercial wet-strength tissue paper, consisting of 100 % bleached softwood kraft pulp (BSKP) made from pine (Pinus sylvestris L.). The repulping of wet-strength paper was performed at 60 °C in three ways, namely, repulping with sodium hydroxide (indicated as RP (NaOH)), repulping with sodium hydroxide and sodium persulfate (RP (NaOH + Na2S2O8)), and finally repulping with sodium hydroxide and potassium monopersulfate (RP (NaOH + KHSO5)). Using an optical fiber analyzer, L&amp;W Fiber Tester, it was found that accelerated persulfate and monopersulfate repulping of the wet-strength paper led to an increase in fines content after pulp refining by 0.20…0.28 % on length and by 0.9…1.5 % on number of particles. In addition, some fines were not detected due to the limited resolution of the measuring device. The morphological characteristics of the recycled pulps showed that the studied fines were relatively straight particles (Sl = 93.5...94.0 %) with low length polydispersity ((Ll/Ln) = 1.08...1.09). Fines had a mean slenderness ratio (L/W)l and (L/W)w of about 7, which in some length classes reached 8...9. Taking into account the experimental data on fines length (Ll = 132…134 µm) and fiber width (Wl = 29.7…30.0 µm), as well as SEM images of recycled paper, we can conclude that these particles can form fines-assisted bridges between several close deposited fibers in the fiber network, thus strengthening the paper web. For citation: Penkin A.A., Kazakov Y.V. Changes in the Morphological Characteristics of Secondary Fiber Obtained from Wet-Strength Paper During Gentle Refining of the Recycled Pulp. Part 2. Fines Characteristics. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 4, pp. 169–179. (In Russ.). https://doi.org/10.37482/0536-1036-2023-4-169-179

An overview on non-wood fiber characteristics for paper production: Sustainable management approach

The amount of paper and paperboard a country uses are a reliable barometer of its development. Having access to them is essential to our daily life. The Indian paper industry faces a number of challenges, one of which is a scarcity of high-quality raw materials. Agricultural waste products have become essential alternative sources of supply as a result of an increase in the need for fibrous raw materials, a global lack of trees, and a growing awareness of sustainability. When compared to the manufacturing of pulp and paper from wood sources, the use of non-wood sources (including bagasse, maize stalks, cotton stalks and rice straws) offers a number of advantages. These benefits include superior quality of the bleached pulp and excellent sources for specialty papers. Paper manufacture is more ecologically friendly and sustainable when non-wood fibers are processed since non-wood pulping technologies use less energy than wood-based pulping processes. Furthermore, the financial advantages include cost savings, market differentiation, enhanced sustainability, and access to government subsidies. By investing in non-wood fibers to satisfy rising customer demand for environmentally friendly goods, paper manufacturers may position themselves for long-term prosperity and environmental responsibility. The non-wood fibers are cellular and have a complex cell wall structure. A thorough understanding of their properties is essential for effective use. Therefore, the objective of the present review is to explore the wide variation between critical characteristics (morphological, chemical, and mechanical) and the most appropriate pulping and bleaching processes for commonly used agricultural residues (Rice straw, Bagasse, Wheat straw and Bamboo) in the Indian pulp and paper industry for the production of paper, board, and packaging.

On the Roles of Cellulose Nanocrystals in Fiber Cement: Implications for Rheology, Hydration Kinetics, and Mechanical Properties.

Fiber cement reinforced with pulp fibers is one of the key drivers for the decarbonization of nonstructural building materials, where the inclusion of sustainable pulp fibers at high proportions (i.e., > 8 wt %) renders poor workability of fiber-cement slurry with a concomitant loss in mechanical strength. Petrochemical-derived superplasticizers, i.e., polycarboxylates (PCEs), are predominantly used in fiber cement (including cement mortars) because they dramatically improve (content <0.5 wt %) the slurry rheology but reduce the rate of hydration and weaken the strength of the cured composite. Thus, it is crucial to explore renewable and bio-based superplasticizers devoid of any negative traits (if possible) of the conventional PCEs. In this study, we examined wood-derived cellulose nanocrystals (CNCs) as a multifunctional additive in fiber cement (bleached pulp fiber content: 8 wt %). In fiber cement, variation of the content (0.02-4 wt %) of CNCs resulted in improvement in the shear thinning behavior of the fiber-cement slurry and thereafter increased the hydration kinetics at high CNC contents (2-4 wt %). Notably, the flexural strength of the composite also exhibited improvement upon the addition of CNCs; the maximum strength was observed at 4 wt % of CNCs. Overall, the beneficial roles of CNCs afforded >10 wt % (in-total) bio-based content in fiber cement without compromising the mechanical strength and curing time (compared to PCEs); hence, the findings of this study could unravel new avenues in interface engineering of cement composites leveraging the multifunctional features of biomaterials, thus enhancing sustainability.

Effect of hemicellulose content on the solution properties of cellulose carbamates in NaOH/ZnO aqueous system

Hemicellulose removal from bleached bamboo pulp is key to produce qualified dissolving pulps. In this work, alkali/urea aqueous solution was firstly applied to remove hemicellulose in bleached bamboo pulp (BP). The effect of urea usage, time and temperature on the hemicellulose content of BP was studied. The reduction of hemicellulose content from 15.9 to 5.7 % was achieved in 6 wt% NaOH/1 wt% urea aqueous solution at 40 °C for 30 min. Cellulose carbamates (CCs) were obtained from the esterification of BP with urea. The dissolution behavior of CCs in NaOH/ZnO aqueous solutions with different degree of polymerization (DP), hemicellulose and nitrogen contents were studied by using optical microscope and rheology. The highest solubility was up to 97.7 % when the hemicellulose was 5.7 % and Mη was 6.5 × 104 (g/mol). With the decrease of hemicellulose content from 15.9 % to 8.60 % and 5.70 %, the gel temperature increased from 59.0, 69.0 to 73.4 °C. The apparent gelation time increased from 5640 to 12,120 s with the hemicellulose content increased from 8.60 % to 15.9 %. CC solution with 5.70 % hemicellulose always keeps a liquid-state (G" > G') until the test time reached 17,000 s. The results showed that the removal of hemicellulose, the decrease of DP and the increase of esterification endowed CC with higher solubility and solution stability.

Utilization of Recycled Egg Carton Pulp for Nitrocellulose as an Accelerant in Briquette Production.

Nitrocellulose (NC) is a conservative material that is used in a variety of applications, such as coating agents, biodegradable plastics, and propellant main charge. Nitrocellulose raw materials are easily obtained from lignocellulose sources, most notably cotton and wood pulp. The egg carton, a recycled paper waste designed for packaging and transporting eggs, is used in this study to make nitrocellulose in pulp form. The effects of different nitration durations (40, 50, and 60 min) from egg carton pulp bleached with various KOH concentrations (0.6 M, 1.0 M, and 1.5 M) on NC properties were evaluated. The accelerant properties of the NC of nitration time in 50 min were studied in a rice husk charcoal briquette. Rice husk charcoal briquettes are made in various ratios with nitrocellulose as an accelerant (97:3, 96:4, and 95:5). The NC was characterized using Fourier transform infrared (IR) spectroscopy and thermogravimetric (TG) analysis. 1.0 M of bleached egg carton pulp has the highest cellulose content (86.94%) with the presence of crystalline structure of cellulose at peak 1430 cm-1 after the bleaching process. Meanwhile, different nitration times revealed that 50 min had the highest nitrogen content (7.97%) with a 1.23 degree of substitution (DS) value. Based on its TG analysis, NC 50 has met the requirements for use as an accelerant for briquettes, with an onset temperature of 91.60 °C and a weight loss of 62.60%. Infrared at peak 1640 cm-1 confirmed the presence of NO2 groups in nitrocellulose successfully formed by nitration. After the addition of nitrocellulose, the calorific value of the briquette increased from 13.54% to 15.47%. Fixed carbon and volatile matter showed the same pattern. The combustion of nitrocellulose-briquette has also been demonstrated by Td10% of degradation, which degraded between 310 and 345 °C.

Oxidation of fully bleached paper-grade kraft pulps with H2O2 activated by Cu(Phen) and the effect of the final pH

Hydrogen peroxide is an environmentally friendly bleaching chemical that is widely used in alkaline media in the pulp and paper industry. In this study, unconventional reaction conditions of the conventional bleaching P-stage were performed to evaluate its effect on cellulose. The objective was to “tailor” the cellulose degradation according to different applications, such as dissolving pulps. Different operating conditions were studied: pH variation (alkaline or acidic medium), as well as the addition of Cu(II) or the Cu(II)-phenanthroline complex. The hypotheses considered were (1) Using H2O2 in unconventional conditions will favor hemicelluloses removal after depolymerization and will lead to the desired cellulose degradation, and (2) H2O2 oxidation carried out under unconventional conditions will favor the dissolving ability of cellulose.

Поверхностная обработка картона суспензиями наноцеллюлозы растительного и бактериального происхождения

This study investigates powdered cellulose materials, particularly nanocellulose derived from plant and bacterial sources. The nanocellulose was generated by hydrolyzing bleached sulphate softwood and hardwood pulp samples with strong acids. The original materials are present in the product lines of leading Russian pulp and paper companies. The bacterial cellulose was produced under laboratory conditions from Medusomyces gisevii. The dimensional parameters of the nanocellulose samples were evaluated using electron microscopy, and the degree of polymerization was measured by determining the viscosity of the cellulose solutions in cadoxene. The bleached softwood pulp had a nanocellulose particle length of 80–200 nm, a particle diameter of 80–100 nm, and a degree of polymerization of 60. The bleached hardwood pulp had a particle length of 80–150 nm, a particle diameter of 70–100 nm, and a degree of polymerization of 50. The bacterial nanocellulose had a particle length of 120–250 nm, a particle diameter of 70–120 nm, and a degree of polymerization of 110. Suspensions of various concentrations (from 1 to 10 %) were prepared from nanocellulose samples, which were subsequently used as reinforcing additives in cardboard samples. The additive was applied to the surface in one or two layers. Additives of nanocellulose preparations reduced the breaking length (from 9.6 to 40.4 %) along with an increase in cardboard density (from 6.3 to 23.8 %), tensile rigidity (from 14.0 to 25.0 %) and bursting strength (up to 31.9 %). The best results were obtained by applying a nanocellulose suspension of bleached softwood pulp to the board surface in two layers: a 9.6 % decrease in breaking length was observed with an increase in density of 23.8 %, tensile rigidity of 25.0 %, and bursting resistance of 31.9 % relative to the control sample. Therefore, the study showed the possibility of using nanocellulose suspensions derived from plants and bacterial sources by acid hydrolysis for the surface treatment of cardboard. For citation: Toptunov Е.А., Sevastyanova Yu.V., Vashukova K.S. Surface Treatment of Cardboard with Plant and Bacterial Derived Nanocellulose Suspensions. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 3, pp. 162–172. (In Russ.). https://doi.org/10.37482/0536-1036-2023-3-162-172

Gamma-valerolactone biorefinery: Catalyzed birch fractionation and valorization of pulping streams with solvent recovery

In this study, we propose a full gamma-valerolactone (GVL) organosolv biorefinery concept including the utilization of all pulping streams, solvent recovery, and preliminary material and energy balances. GVL is a renewable and non-toxic solvent that fractionates woody biomass. The silver birch chips were pulped (45–65 wt% GVL, 150 °C, 2 h) under a series of acid-catalyzed conditions (5–12 kg H2SO4/t), and the fully bleached pulp was spun into fibers by the IONCELL® process and knitted into the fabric. The dissolved lignin was precipitated by water from spent liquor (1:1) and processed into polyhydroxyurethane. Most of the dissolved hemicelluloses were in the form of xylose, therefore, the crystallization efficiency of xylose from spent liquor in the presence of residual GVL was studied. The GVL recovery rate in the lab column was 66%, however by increasing the number of equilibrium stages, 99% recovery could be achieved.

Preparation of micro-fibrillated cellulose fibers by a simple two-step refining process for paper- based flexible electronic devices

Cellulose micro/nano-materials are potential substrates for energy storage/ electronics applications. However, developing efficient/cost-effective technologies that can obtain these micro/nano-materials suited for flexible electronics continue to be a challenge. In this study, we report a simple process for extracting micro-fibrillated cellulose fibers from conventional bleached kraft pulp that are particularly applicable to flexible electronics applications. The process is made of two step refining: 1) refining in a Valley beater, and 2) further fibrillation in a ball mill. The Valley beater is to induce fibrillation of pulp fibers as a result of compression and shearing forces. Subsequently, the partially fibrillated cellulose fibers are further subjected to ball milling to obtain micro-fibrillated cellulose fibers (MFCs). These MFCs have a much higher specific surface area than the conventional pulp fibers due to fibrillation and reduction in fiber size, which leads to favorable properties to the as- prepared MFCs network, including high transparence, and high tensile strength. The MFCs paper exhibits excellent transparency of 82% at 550 nm (a significant increase of about 56% for the control), with exceptionally high tensile strength (35.16 MPa). Thanks to the high surface area of these MFCs, silver nanowires (AgNWs) can be well distributed into the MFCs network so that conductive paper with high conductivity was prepared. The MFCs/AgNWs composite paper was then assembled into the paper-based triboelectric nanogenerator (P-TENG) device, which shows excellent performance. The MFCs/AgNWs composite paper- based P-TENG system can also serve as self-powered sensors for monitoring human motions. This work provides a method for the production of micro- fibrillated cellulose fibers that can be applied for the production of flexible electronic devices.

Characterizing lignin-containing microfibrillated cellulose based on water interactions, fibril properties, and imaging

Morphological characterization of microfibrillated cellulose (MFC) is critically important to process control in production and product specification for trade and product development yet is extremely difficult. This study evaluated several indirect methods for relative comparison of the morphology of lignin-free and lignin-containing ((L)MFCs). The (L)MFCs studied were produced using a commercial grinder through different passes from a dry lap bleached kraft eucalyptus pulp, a virgin mixed (maple and birch) unbleached kraft hardwood pulp, and two virgin-unbleached kraft softwood (loblolly pine) pulps with one bleachable grade (low lignin content) and one liner grade (high lignin content). The (L)MFCs were indirectly characterized using techniques based on water interactions, i.e., water retention value (WRV) and fibril suspension stability, as well as fibril properties, i.e., cellulose crystallinity and fine content. Optical microscopy and scanning electron microscopy were also applied to directly visualize the (L)MFCs to provide some objective measure of the morphology of the (L)MFCs. The results indicate that most measures such as WRV, cellulose crystallinity, fine content cannot be used to compare (L)MFCs from different pulp fibers. Measures based on water interactions such as (L)MFC WRV and suspension stability appeared can provide some degree of indirect assessment. This study provided the utilities and limits of these indirect methods for relative comparison of the morphologies of (L)MFCs.

Innovative system based on natural polyelectrolyte complex and cellulose micro/nanofibers to improve drainability and properties of recycled paper

In this work, the efficiency of a polyelectrolyte complex (PEC) to retain different cellulose micro/nanofibers (CMNFs) during paper formation and to improve the physical properties of recycled unbleached fiber paper was analyzed. CMNFs were obtained from a commercial bleached eucalyptus pulp (BEP) using a PFI refiner followed by a chemical treatment with oxalic acid at two different concentrations. Finally, the pulp was fibrillated using a high-pressure homogenizer at three different intensities. The PEC was formed by addition of the xylan (Xyl) solution on chitosan (CH) solution with a Xyl/CH mass ratio of 80/20. The required dosages of PEC solution to neutralize the charges of different nanocellulose fractions were determined by ζ-potential measurements, and the CMNF retentions on recycled unbleached fibers were evaluated in a Britt Dynamic Drainage Jar. The results showed that the maximum retention was obtained when the neutral PEC-CMNF system was added to pulp. Besides, a significant decrease on °SR was observed when PEC and PEC-CMNF systems were added to the untreated pulp, limiting the negative effects of nanocellulose addition on pulp drainability. The incorporation of PEC-CMNF systems to the handsheets increased the tensile index (up to 28%), Mullen index (up to 40%) and internal bonding (up to 255%). Finally, the compressive strength of the handsheets, namely SCT and CMT, increased up to 30 and 70%, respectively. These simultaneous improvement on drainability and mechanical properties makes the proposed PEC-CMNF system a promising solution for the production of packaging paper.