Bleached Hardwood Pulp Research Articles

Upgrading paper-grade bleached hardwood pulp towards dissolving pulp using γ-valerolactone

γ-Valerolactone (GVL) is a promising biomass-based platform compound that can be used for the removal of hemicellulose in pulp. In this study, a paper-grade pulp was treated using GVL to generate dissolving pulp for viscose production. The GVL concentration, treatment temperature, and reaction time had significant effect on the hemicellulose dissolution. The dissolving pulp with α-cellulose content of 92.3% and hemicellulose content of 5.45% was achieved with 60% GVL at 120 °C for 2 h. The Fock reactivity and intrinsic viscosity of the obtained dissolving pulp were 54.6% and 595 mL/g, which is comparable with the commercial product. In addition, GVL spent liquor was also recycled and reused to upgrade paper-grade pulp. By using purified recycled GVL to treat original pulp, the Fock reactivity of pulp was improved, and the cellulose content of as-prepared upgraded pulp increased to 92.1%, which was close to the cellulose content of dissolving pulp obtained from fresh GVL solution, while the intrinsic viscosity decreased significantly to 598 mL/g. Therefore, the efficient reuse of GVL not only ensured the high quality of dissolving pulp, but it also saved production costs and reduced environmental pollution.

Efficient fractionation of pure hemicellulose with high DP from bleached hardwood pulp using LiBr·3H2O and co-production of dissolving pulp

Hemicellulose was efficiently fractionated from BHKP using LBTH with the coproduction of high-quality dissolving pulp. The obtained hemicellulose was pure glucuronoarabinoxylan with high DP (>200) and unique crystalline and nano structure.

Microfibrillated cellulose (MFC) barrier coating for extending banana shelf life

This study evaluated, for the first time, the feasibility of using 100% microfibrillated cellulose (MFC) for a barrier coating to preserve the shelf life of bananas. MFC was produced from a commercial bleached kraft hardwood pulp through mechanical milling. Barrier coating was accomplished by dipping bananas into aqueous MFC suspensions. Performance of the barrier coating on the banana peel surface was evaluated from visual observations, weight loss, firmness, and dissolved soluble sugars content of the bananas. The results indicated that coating the banana peel surface with MFC delayed the browning and softening of the banana and the conversion of banana carbohydrates into soluble sugars. Furthermore, the extent of mechanical fibrillation in producing MFC affected MFC suspension wettability of banana peel surface, as well as the effectiveness of banana preservation. Casting-made MFC films were used to understand various factors of MFC barrier coating performance. The extent of MFC fibrillation was found to be more effective than increasing the amount of coating in reducing water vapor permeation for better fruit protection.

Thermal-degradation characteristics of mechanically nanofibrillated bleached pulps from hardwood and softwood

Nanofibrillated cellulose (NFC) consists of ultrafine cellulose structures in which the fibrils can have widths in the range from about 5 to 100 nm. NFC has been studied and developed in the paper industry, using bleached pulp from wood as the raw material. One of the issues in the application of NFC is their heat resistance to thermal degradation. The production process of NFC results in a decrease in their pyrolysis temperature during the nanofibrillation of bleached pulp; however, the details behind the reason and mechanisms are still unclear. In this study, NFC was prepared from bleached hardwood and softwood pulp by mechanical nanofibrillation using a grinder, and the pyrolysis behavior was investigated. For both bleached pulps, a decrease in the pyrolysis temperature was observed after nanofibrillation. The results suggest that the decrease in the pyrolysis temperature from nanofibrillation is not due to damage of the crystalline cellulose by nano fibrillation, but the damage of the hemicellulose components in the surface of the cellulose microfibrils or the interface between the crystalline cellulose and hemicellulose. If the hemicellulose on the surface of crystalline cellulose could be removed from the NFC, then the decrease in the pyrolysis temperature could be suppressed.

Efficacy of Biodegradable Chitosan Polymer for Simultaneous Improvement in Ash and Strength Properties of Paper

ABSTRACT Strength properties of paper are of great significance in terms of its mechanical performance and are attributed to cellulosic fibers. When filler is used in papermaking, the cost and strength properties get reduced but optical properties are improved. So far, modification of fillers using chitosan (CH) is not explored in such a way that all aspects of wet-end of papermaking get covered. The novelty lies in showing the effect of CH as filler modifier at various doses on different fillers and the wet-end application of modified fillers at different doses along with other additives used in papermaking. The impact of addition of modified fillers on end paper properties is also analyzed. Here, CH was applied to modify fillers characteristics so that the ash in paper can be increased without compromising the strength properties. Three different doses (0.25%, 0.50% and 1.00%) of CH were added to the fillers. The addition of modified fillers to bleached mixed hardwood (BMHW) pulp increased the filler retention in paper while the reduction in strength properties was found to be less and in some properties even an increase was observed. The particle size distributions of fillers were found to be affected after modification of fillers.

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

The Impact of Fibre Oxidation on the Preparation of Cellulose Nanocrystals (CNC)

This study aimed to evaluate the effect of fibre oxidation on the extent of substituted sulfate on cellulose nanocrystals (CNC). In this investigation, fully bleached softwood (SW) and hardwood (HW) pulps from an Alberta pulp mill were oxidized under low (4%), medium (10%), and the higher-end of medium (14%) oxygen consistencies. The oxidized pulp samples were hydrolyzed with concentrated sulfuric acid under conventional procedures to produce CNC. The CNC materials were then characterized by different qualitative and quantitative techniques to evaluate the effect of oxidations on the number of substituted sulfates and the overall sulfate charge of isolated CNC to develop novel high-value applications. The experimental data show that fibre oxidation helped improve the overall CNC yield, with lower half-ester sulfate contents compared to the controls. The half-ester sulfate contents and the viscosity for SW CNC were found to be higher than their HW CNC counterparts. However, the thermal stability of CNC was found to be better for HW than SW pulps. The emerging data help to prepare and engineer CNC tailored to specific applications.

A novel approach in increasing carboxymethylation reaction of cellulose

Carboxymethyl cellulose (CMC) with a high degree of substitution (DS) was prepared from hardwood bleached pulp by a novel method. In this method, pulp was refined in PFI mill and/or enzymatically treated prior to carboxymethylation. The DS value of CMC increased from 0.5 to 2.4. The yield and molecular weight of CMC increased with increasing DS value. The correlation coefficient between DS and molecular weight was 0.9992. Spectroscopic, thermogravimetric, x-ray diffraction and scanning electron microscopic (SEM) and titrimetric analyses were performed to confirm the degree of substitution and surface modification of the cellulose. Micrograph and SEM image confirm surface modification of cellulose in prior treatment. A comparison of the FTIR spectra of the prepared CMC and standard CMC shows the presence of bands corresponding to ˗O˗, CH2˗ and ˗COO in the CMC, while these bands do not appear for cellulose. The crystallinity of untreated pulp was slightly decreased, while the crystallinity of the prepared CMCs was diminished.

EFFECT OF CHITOSAN ADDITION DURING PAPER-MAKING ON AGEING STABILITY OF DOCUMENT PAPER

The aim of the present work has been to study the influence of chitosan addition into the composition of paper intended for documents on its ageing stability, with a view of enhancing the resistance of paper strength and optical properties over time. The chitosan solution was added during the formation of the paper sheets in various amounts: 0.2%, 1% and 2% o.d.f. Paper samples of different fibrous compositions were prepared from bleached sulphate softwood pulp (BSWP) and bleached sulphate hardwood pulp (BHWP) in the following ratios: 50% BSWP:50% BHWP, 80% BSWP:20% BHWP, 100% BSWP and 100% BHWP. Then, paper samples were subjected to accelerated thermal ageing for 24 hours at 105 °C. It was found that the use of chitosan as additive in the composition of bleached cellulose paper samples led to improved strength and hygroscopic properties. The study showed that chitosan could be used in the production of kraft document papers comprising aluminium sulphate, as the presence of aluminium sulphate had no negative effect on the action of the biopolymer. Regarding the complex evaluation of the properties of the obtained papers, it could be summarized that, for the studied fibrous compositions, the optimum amount of the additive was 1% chitosan for a fibrous composition of 50% bleached softwood pulp and 50% bleached hardwood cellulose. Therefore, preparing document paper with the addition of chitosan is a convenient procedure to enhance a number of paper properties, even after the ageing process.

The paper-forming properties of hemp fire peroxide cellulose in combination with wood sulphate cellulose

Hemp fire (Cannabis sativa) was delignified with the reaction mix “acetic acid - hydrogen peroxide - sulfuric acid catalyst - water” under sulfuric acid concentration of 0.45%, liquid module of 6, and temperature of 85 ° C. The cellulose was ground to 34 … 36°SHR and mixed in different ratios in compliance with the simplex-centroid experimental design with bleached sulfate softwood and hardwood pulp. The influence of the mixed composition formulations on the main strength properties of paper castings has been studied. It has been concluded that technical cellulose obtained from hemp fire applying this method, can be used for paper products manufacturing in combination with sulphate cellulose from coniferous and deciduous wood.

Nanofibrillated Cellulose Extracted by Enzymatic Hydrolysis Followed by Mechanical Fibrillation

ABSTRACT In a comparison with certain one-step processes, enzymatic hydrolysis followed by mechanical defibrillation may avoid the use of nonrenewable resources, mitigate the generation of toxic effluents, and reduce the energy consumption related to a single mechanical process. In the present study, bleached and unbleached hardwood pulps were employed as raw materials for producing nanofibrillated cellulose (CNF) using a two-step process, in which a cellulase enzyme was inoculated to act as a pretreatment for a subsequent grinding process. The obtained CNF reached high crystallinity indexes (above 70%) and high thermal stability (degradation onset temperatures around 200°C). Increases in enzyme concentration yielded decreases in diameter and increases in both thermal stability and crystallinity index. These findings indicated that the enzymatic hydrolysis used as a pretreatment to a further grinding process can allow the production of valuable CNF-based products.

Micro-nanofibrillated cellulose preparation from bleached softwood pulp using chemo-refining approach and its evaluation as strength enhancer for paper properties

An industry compatible chemo-refining approach was tested for preparation of micro-nanofibrillated cellulose (MNFC) from bleached softwood pulp using sodium meta-periodate and sodium chlorite as oxidizers followed by refining in Valley beater. SEM and FTIR analyses confirmed micro-nano scale fibrillation and chemical functional group modification in laboratory prepared MNFC, respectively. The water retention value, carboxyl content and viscosity of MNFC were found comparable with imported NFC as reference (R-NFC). To evaluate MNFC as strength enhancer for paper properties, 5% MNFC addition to bleached mixed hardwood pulp showed 6% reduction in bulk with 36%, 24% and 97% increment in breaking length, burst index and double fold of the handsheets, respectively without affecting tear index and optical properties than the control. Surface properties were also improved. Pulp drainability (37°SR) after MNFC addition was found suitable for papermaking. These laboratory results confirmed the potential of MNFC as a suitable strength additive for paper quality improvement.

Production of a fine fraction using micro-perforated screens

Abstract The objective for this work was to investigate the possibility to use a pressure screen equipped with a micro-perforated screen basket to produce a fine fraction from bleached chemical pulp. Trials were performed with unrefined bleached chemical hardwood pulp, and with unrefined and refined bleached chemical softwood pulp. The effect of feed concentration, feed flow, and volumetric fine fraction flow was evaluated. The difference between the fine fraction (i. e. the particles passing the screen) and the feed was analysed by studying the fibre morphology. The results showed that high feed concentration was positive for both the fine fraction concentration and the separation efficiency. A higher fine fraction concentration was also obtained when using hardwood pulp, which was explained by the shorter fibre length. Refining of the pulp prior to the fractionation proved beneficial, as a larger share of the refined pulp passed the screen, resulting in a twice as high concentration of the fine fraction when compared to unrefined pulp.

Preparation of nanocellulose acetate from bleached hardwood pulp and its application for seawater desalination

AbstractNanocellulose acetate was prepared from commercial bleached Kraft hardwood cellulose by a two‐stage process. Firstly, the pulp was purified with sodium hydroxide solution followed by an acetylation process to form cellulose triacetate. Secondly, nanocellulose acetate was produced by treating the cellulose acetate obtained from the previous step with dilute sulfuric acid in presence of hydrogen peroxide at 120 °C. The synthesized products were applied to seawater desalination. Obtained results indicates that nanocellulose acetate is a promising material for seawater treatment since it shows better behavior and efficiency in this process than cellulose acetate.

Biocatalysis of Industrial Kraft Pulps: Similarities and Differences between Hardwood and Softwood Pulps in Hydrolysis by Enzyme Complex of Penicillium verruculosum

Kraft pulp enzymatic hydrolysis is a promising method of woody biomass bioconversion. The influence of composition and structure of kraft fibers on their hydrolysis efficiency was evaluated while using four substrates, unbleached hardwood pulp (UHP), unbleached softwood pulp (USP), bleached hardwood pulp (BHP), and bleached softwood pulp (BSP). Hydrolysis was carried out with Penicillium verruculosum enzyme complex at a dosage of 10 filter paper units (FPU)/g pulp. The changes in fiber morphology and structure were visualized while using optical and electron microscopy. Fiber cutting and swelling and quick xylan destruction were the main processes at the beginning of hydrolysis. The negative effect of lignin content was more pronounced for USP. Drying decreased the sugar yield of dissolved hydrolysis products for all kraft pulps. Fiber morphology, different xylan and mannan content, and hemicelluloses localization in kraft fibers deeply affected the hydrolyzability of bleached pulps. The introduction of additional xylobiase, mannanase, and cellobiohydrolase activities to enzyme mixture will further improve the hydrolysis of bleached pulps. A high efficiency of never-dried bleached pulp bioconversion was shown. At 10% substrate concentration, hydrolysates with more than 50 g/L sugar concentration were obtained. The bioconversion of never-dried BHP and BSP could be integrated into working kraft pulp mills.

Facile chemo-refining approach for production of micro-nanofibrillated cellulose from bleached mixed hardwood pulp to improve paper quality

Micro-nanofibrillated cellulose was prepared using bleached mixed hardwood pulp by a low energy consuming chemo-refining approach having potential to be implemented easily in paper industry. Bleached mixed hardwood pulp was pretreated with sodium meta-periodate and sodium chlorite and micro-nanofibrillated by using refining in Valley beater. Scanning electron microscopy images of prepared micro-nanofibrillated cellulose showed 87 % fibre distribution in nano range, 4.47 ± 0.5 g/g water retention value and 2.13 ± 0.1 meq/100 g carboxyl content. Carboxylation effect of given chemical pretreatment was further confirmed by FTIR analysis. Paper handsheets, having bleached mixed hardwood pulp and prepared micro-nano-fibrillated cellulose, resulted in about 5% lower bulk with 27 %, 32 % and 87 % higher breaking length, burst factor and double fold, respectively than control (without nano-fibrillated cellulose). Prepared micro-nanofibrillated cellulose addition didn’t show negative effect on pulp drainability (33 °SR). This work showed that micro-nanofibrillated cellulose might also be prepared using conventional routes of paper industry to improve paper properties.

In Situ Synthesis of Silver Nanoparticles on Cellulose Fibers Using D-Glucuronic Acid and Its Antibacterial Application.

The development of ecofriendly procedures to avoid the use of toxic chemicals for the synthesis of stable silver nanoparticles (AgNPs) is highly desired. In the present study, we reported an eco-friendly and green technique for in situ fabrication of AgNPs on bleached hardwood pulp fibers (bhpFibers) using D-glucuronic acid as the only reducing agent. Different amounts of D-glucuronic acid were introduced and its effect on the size and distribution of AgNPs on the bhpFibers was discussed. The morphology and structures of bhpFibers@AgNPs were proved by electron microscope-dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). Then, a series of bhpFibers@AgNPs with different AgNPs loadings were also prepared by adjusting the concentration of the AgNO3 solution. After a papermaking process via vacuum filtration, the prepared papers displayed an outstanding antibacterial performance against Escherichia coli (gram -negative) and Staphylococcus aureus (gram-positive). It is foreseeable that the bhpFibers@AgNPs have a promising application in the field of biomedical.

Chirality and bound water in the hierarchical cellulose structure

The origins of the unique properties of natural fibres have remained largely unresolved because of the complex interrelations between structural hierarchy, chirality and bound water. In this paper, analysis of the melting endotherms for bleached hardwood pulps indicates that the amount of non-freezing bound water (0.21 g/g) is roughly half of the amount of freezing bound water (0.42 g/g). We link this result to the two smallest constitutive units, microfibrils and their bundles, using molecular dynamics simulations at both hierarchical levels. The molecular water layers found in the simulations correspond quite accurately to the measured amount of non-freezing and freezing bound water. Disorder that results from the microfibril twist and amphiphilicity prevents co-crystallisation, leaving routes for water molecules to diffuse inside the microfibril bundle. Moreover, the simulations predict correctly the magnitude of the right-handed twist at different hierarchical levels. Significant changes in hydroxymethyl group conformations are seen during twisting that compare well with existing experimental data. Our findings go beyond earlier modelling studies in predicting the twist and structure of the microfibril bundle.Graphic abstract

Photoluminescent Composites of Lanthanide-Based Nanocrystal-Functionalized Cellulose Fibers for Anticounterfeiting Applications

Photoluminescent materials have been applied worldwide in anticounterfeiting and security fields due to their unique performance of better security, easy identification, and difficulty of duplication. Herein, a facile, green, and low-cost strategy to fabricate biomass-based composites composed of lanthanide rare earth ions-doped nanocrystals and cellulose fibers for anticounterfeiting application was presented. The photoluminescent materials were prepared via in situ chemical deposition of rare earth ions onto bleached hardwood pulp cellulose fibers (bhpFibers) surface using polyvinylpyrrolidone (PVP) as coupling agent, forming bhpFibers-PVP@LaF3:Eu3+ composites. The bhpFibers-PVP@LaF3:Eu3+ composites showed excellent luminescence, and their fluorescence intensity can be simply controlled by varying the addition of the right amount of lanthanum (La3+) and europium (Eu3+) ions in aqueous medium. Furthermore, the composites have been used as blocks to form photoluminescence paper via a suction filtration pr...

Comparable Characterization of Nanocellulose Extracted from Bleached Softwood and Hardwood Pulps

Comparable Characterization of Nanocellulose Extracted from Bleached Softwood and Hardwood Pulps