Band 40, Heft 3

Although highly efficient, conventional chemical bleaching is criticized for its high cost and environmental impact. In contrast, enzyme bleaching offers a sustainable and eco-friendly alternative, especially in elemental chlorine-free (ECF) and total chlorine-free (TCF) processes. This study investigates the synergy of laccase, xylanase, and mannanase in the ECF bleaching of softwood kraft pulp, focusing on their effects on fiber morphology and bleaching performance. The results demonstrate that laccase effectively oxidizes lignin, enhancing pulp brightness, while xylanase and mannanase improve bleaching efficiency by breaking down hemicellulose. The addition of mannanase during the enzymatic treatment increased the pulp brightness by 1.58 %ISO, with almost no negative impact on physical properties. The synergistic effect of the three enzymes increased the pulp brightness by 5.37 %ISO, reaching a maximum brightness of 92.35 %ISO. Furthermore, mannanase treatment significantly reduces the consumption of chemicals, cutting laccase and violuric acid usage by 38 % or decreasing total chlorine dioxide use by 13.26 %, while maintaining the same brightness level. These findings highlight the potential of using laccase, xylanase, and mannanase for efficient and eco-friendly pulp bleaching, contributing to resource conservation and environmental benefits. This study provides valuable insights into the industrial application of enzyme-based bleaching for sustainable paper production.

Isometric straight bar refiner plates are extensively employed in low-consistency pulp refining, and a special type of these plates features different bar-groove width ratios ( a / b ) while maintaining a constant sum ( a  +  b ). Previous studies have demonstrated that the Specific Edge Load (SEL) fails to serve as a valid metric for comparing the refining intensities of pulp refining when such plates are utilized. This study systematically investigates the interrelationships among SEL, Specific Surface Load (SSL), Modified Edge Load (MEL), and related parameters, to identify refining intensities suitable for characterizing refining processes conducted by plates under constant ( a  +  b ) with variable ( a / b ),and proposing more robust metrics. Key findings reveal that neither SEL nor the net tangential force per bar crossing zone ( f t net ) effectively measures refining intensity in this configuration. Although MEL and SSL demonstrate empirical utility, their physical meaning remains limited. Instead, the net equivalent tangential or normal force per bar crossing zone, modified by the equivalent number of bar crossing zones ( N ’ BC ), emerges as a more robust metric. Futhermore, the net average shear stress ( τ τ net ), normal pressure ( p n net ), and net force per bar crossing length which are modifications of f t net or net normal force per bar crossing zone ( f n net ) in terms of bar crossing area and length, provide viable alternatives. Therefore, the net force per bar crossing zone exhibits significant potential as a universal intensity metric for characterizing a wider range of refining processes, as it can be modified based on bar crossing parameters.

Efficient mechanical dewatering in paper manufacturing is essential for reducing energy consumption and enhancing operational efficiency. Practical observations indicate that press felt and roll cover structures significantly influence dewatering performance. While previous studies have focused on micro-scale stress variations at the paper web-press felt interface, this study extends the analysis to the press felt-roll cover interface. Using a custom dynamic compression setup, we investigate how different groove patterns impact press felt dewatering. The results show that macro-scale stress variations play a crucial role, with controlled mechanical inhomogeneities enhancing felt permeability. Through multivariate regression analysis, an optimized groove pattern is identified that improves dewatering by approximately 7 % under highly dynamic pressing conditions. These findings offer valuable insights into optimizing press felt and roll cover interactions, providing a methodology to enhance nip dewatering efficiency. The study highlights the need to tailor groove patterns to specific press felts to ensure optimal water flow under saturated conditions. This research contributes to improving paper machine performance by maximizing water removal while reducing energy consumption, supporting both economic and environmental sustainability in the industry.

Paper documents hold significant cultural and historical value, with acidification being a primary factor in their degradation. To protect acidic paper, a deacidifying dispersion was developed using oleyl alcohol-modified magnesium oxide (MgO) nanoparticles in a mixture of hexamethyldisiloxane and ethanol (8:2). The results showed that ethanol can form a solvation layer on the particle surface, provided short-range solvation repulsion, and improved the dispersion stability of the particles. The modified nano MgO changed from hydrophilic to lipophilic in hexamethyldisiloxane and ethanol (8:2) for 12 h with good dispersibility. The use of these sustainable dispersions was implemented for paper deacidification, and experiments were performed to evaluate the effectiveness of this innovative approach. The results showed that the pH value of the paper surface increased to about 8 after treatment, and the pH value of the paper was retained to 7 after aging, and the tensile strength did not decrease significantly under the condition of accelerated aging. It is important to note that the deacidification process has a negligible effect on the visual appearance of the paper as well as the integrity of the ink on its surface and the paper’s hydrophobicity.

A new paper filler, comprising microcapsules with a urea-formaldehyde resin shell and a porous calcium silicate core (UF@CS-MC), was prepared by in situ polymerization. UF@CS-MC, which has good retention in the paper matrix and enhances both whiteness and opacity, provides a low-cost alternative to titanium dioxide, which is traditionally used as a filler for Bible paper. Conditions for the preparation of UF@CS-MC, including core to coating ratio, emulsification time, emulsifier concentration, stirring rate, pH and polymerization time, were investigated and optimized. The UF@CS-MC filler was characterized using a variety of analytical techniques, including optical microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy and laser Raman spectroscopy. Incorporation of UF@CS-MC into Bible paper produced a notable improvement in both whiteness (10.75 %) and opacity (13.97 %). Compared with titanium dioxide, UF@CS-MC as Bible paper filler achieved a 20 % improvement in filler retention and a 49.4 % reduction in cost.

In packaging, the structural integrity of paperboard under complex stresses is essential. This study examines the delamination behavior of paperboard under normal and shear loading modes, which are the base for developing mixed-mode models. Four commercial paperboard grades, sourced from fibers across three geographical regions, are investigated using Double Cantilever Beam (DCB) and Split Double Cantilever Beam (SDCB) tests, which are used to calibrate a cohesive zone model from the literature. This model introduces a shape parameter that governs the cohesive traction-separation relationship, consistent across both normal and shear modes. Experimental findings support this approach, demonstrating that, while the shape parameter remains mode-independent, its numerical value varies uniquely for each paperboard quality.

Micro-CT analysis of experimentally creased and folded multilayer cardboards reveals insights into how the material deformation due to the creasing and folding process of cardboard impact the material concerning delaminations and position of broke particles. Delaminations were found in various locations and varied in size from just under a tenth of a millimeter to up to four times the thickness of the cardboard. The particles varied in size, ranging from a few micrometers to slightly larger than the cardboard thickness. Characteristic dimensions for the creased and folded cardboard were measured for selected cross sections. The differences in characteristic dimensions for the cross sections among the samples were typically a few hundredths of a millimeter. There are differences between cross-sections that are a few hundredths of a millimeter apart.

Acidification is an important factor in the damage of paper documents. At present, it is recognized that deacidification is an effective means to solve the problem. In this work, aiming at the problems of the traditional single deacidification agent, such as uncontrollable alkali strength, insufficient alkaline reserve, uneven deacidification effect, and high local alkalinity, MgO/CaCO 3 nanocomposites were prepared as a new paper deacidification agent. The composites combined the immediate and efficient deacidification of MgO and the long-term mild deacidification of CaCO 3 . The morphologies and structures of MgO/CaCO 3 nanocomposites were characterized by TEM and XRD. When applied to the deacidification of paper documents, the MgO/CaCO 3 nanocomposites showed excellent deacidification performances and high alkaline reserve. The alkali strength of the MgO/CaCO 3 nanocomposites can be controlled by adjusting the ratio of MgO to CaCO 3 so that the pH value and alkaline reserve of the paper after deacidification are within a reasonable range.

This study investigates the effects of plasma treatment, alkaline treatment, and their sequential application on eucalyptus cellulose fibers and laboratory-made paper sheets. Handsheet samples were prepared from eucalyptus cellulose under four different conditions: untreated (control), plasma-treated, alkaline-treated, and plasma-treated followed by alkaline treatment. The untreated eucalyptus cellulose handsheets served as the control group. Plasma treatment was performed in air under a vacuum of 89.2 kPa using a 100 kHz radio frequency at a flow rate of 0.6 L/min. The samples were exposed to 200 W of radio frequency power for 2 min on both sides. Alkaline treatment was applied at concentrations of 1 and 3 wt%. In the sequential treatment, the alkaline solution was applied at the same concentrations following plasma modification on both sides under the same conditions. An increase in plasma intensity and treatment duration resulted in a decrease in dry tensile strength. Overall, the use of modified fibers had a significant impact on the water absorption properties of the handsheets. This study highlights the potential of sequential fiber modification to enhance paper properties and supports the development of more sustainable paper-based products.

The use of active packaging is increasing to reduce and prevent the risks of bacterial and viral infections. Recently, studies on this subject have attracted much attention. Especially how Ag nanoparticles enable the easy destruction of many microorganisms. This feature increases the use of silver nanoparticles in active packaging. Moreover, silica nanoparticles can be used in coatings to give different properties to the paper surface. This study aims to use it in active packaging by creating a paper surface coating. In the study, coatings were prepared using silver and silica nanoparticles. The coatings were applied on base paper. The antibacterial activity of coated papers against Staphylococcus aureus ( S.aureus ) and Escherichia coli ( E.coli ) was measured by the agar diffusion method. Water absorbency tests (surface contact angle, liquid absorption behavior and surface energy) were measured and analyzed using pendant drop analysis with FTA200 device. Magenta ink was printed on the coated papers with the IGT-C1 test printer, and the CIE L*a*b* color values of the base paper surface, coatings and prints were measured and printability analysis was performed according to ΔE color differences. Simultaneously, the brightness of coated papers (75°) and prints (60°) were measured with BYK Gardner micro glossmeter. As a result, it was determined that especially AgNP’s and AgNP’s + Silica NP’s coated papers showed antibacterial properties and the printing parameters were close to standard values.

This paper provides an insightful analysis of research trends, publication venues, and future perspectives in the realm of Natural Coatings for Paper-based Food Packaging. Through bibliometric and keyword analyses, alongside co-authorship network visualization, it illuminates the evolving landscape of this interdisciplinary field. Findings reveal a notable surge in interest and collaboration, with a focus on sustainable materials, functionality enhancement, and barrier properties. Key themes include structural design, biopolymers, essential oils, and water resistance. Top journals such as the International Journal of Biological Macromolecules, Coatings, and Polymers serve as prominent platforms for disseminating research in this domain. Looking ahead, future research should explore innovative approaches like composite materials and essential oil applications. Understanding the synergistic effects of cellulose and essential oils, optimizing coating parameters for oxygen barrier performance, and enhancing water resistance are crucial avenues for advancing sustainable packaging solutions. Collaboration across disciplines and international borders will be vital in addressing the multifaceted challenges facing the food packaging industry. By leveraging interdisciplinary expertise and sustainable materials, researchers can drive progress towards safer, more efficient, and environmentally friendly food packaging solutions, benefiting both consumers and the planet.

This study optimizes spray-coating parameters for cellulose nanocrystals extracted from young coconut husks onto paper substrates using response surface methodology. CNCs were produced through acid hydrolysis and mechanical grinding, yielding nanocrystals with an average size of 116 nm and a crystallinity index increase from 28.89 % to 86.13 %. XRD and FTIR analyses confirmed high purity, while UV-vis revealed significant optical absorption in the UV range. Spray-coating parameters, including CNC concentration, volume, heating temperature, and heating duration, were optimized using a central composite design. The 2FI model revealed that CNC concentration and heating duration significantly affected film thickness, where higher CNC levels and longer heating durations produced thicker coatings. However, excessive CNC content led to agglomeration, compromising film quality. The quadratic model highlighted a significant relationship between coating parameters and tensile strength. Heat treatment notably enhanced mechanical properties, with optimal tensile strength reaching 26.15 ± 0.61 MPa-15 % higher than uncoated paper-under conditions of 4 % w/v CNC concentration, 1.5 ml volume, 75 °C heating temperature, and 35 min heating duration. This research highlights the potential of CNCs from young coconut husks as a sustainable reinforcement material, promoting agricultural waste valorization and enhancing paper properties.

The pulp and paper industry is focused on developing sustainable and energy-efficient production methods due to rising energy costs and environmental concerns. This study evaluates the Fenton reaction for modifying Neutral Sulphite Semi-Chemical (NSSC) pulp, applying varying dosages of Fenton chemicals followed by refining in a Jokro mill. Results indicate that the Fenton reaction reduced energy consumption during refining by up to 36 %, while maintaining similar pulp freeness. Under optimized conditions, tensile strength was enhanced by up to 10 % compared to untreated pulp at the same energy input. However, high chemical dosages caused significant fiber damage, leading to shorter fiber lengths and up to a 20 % reduction in burst index at a given pulp freeness. Low dosages achieved energy savings of up to 10 % without significantly compromising paper strength. Cationic starch was also applied to treated NSSC pulp to investigate if increased fiber charge or carboxylic groups would enhance its effect, but no significant benefit was observed. Instead, oxidative treatment led to a 25 % reduction in zero-span index at high dosages, indicating fiber weakening. Under specific economic conditions, such as high energy costs and low chemical prices, this approach could provide advantages in industrial applications.

The production of pulp and paper (P&P) is a significant industrial sector that heavily relies on fresh water, generating effluents with flow rates, which in the new plants reach around 3,000 m 3 /h. Traditionally, P&P effluents are treated through biological processes such as activated sludge and aerated lagoons, effectively removing biochemical oxygen demand (BOD) and colour, complying with environmental standards. However, increasing water scarcity driven by climate change necessitates reassessing production rates to conserve water quality and volume while maintaining compliance. This study explores enhancements in effluent treatment by integrating an advanced oxidation step after conventional biological treatment. Specifically, the study evaluates and compares the efficiency of: (i) the conventional Fenton reaction with soluble iron salts, (ii) conventional coagulation, and (iii) a Fenton process using zero-valent iron (ZVI) from commercial steel wool, operating at near-neutral pH (5.5–7.5). Batch experiments were performed using jar tests with industrial effluent samples from a bleached Kraft pulp mill. The analyses included dissolved organic carbon (DOC), BOD, chemical oxygen demand (COD), lignin (measured at 280 nm absorbance), and true colour, with characterizations of steel wool via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) before and after treatment. Results indicated that the ZVI-steel wool/H 2 O 2 Fenton process achieved superior removal rates of lignin and recalcitrant compounds, with average removals of 57.1 % COD, 67.2 % BOD, 90.5 % colour, and 83.4 % lignin compounds. Notably, treatment at pH 7.5 exhibited efficiencies comparable to pH 5.5, allowing lower chemical costs by eliminating the need for acid and alkali for pH adjustments before and after the Fenton step. These findings suggest the ZVI-steel wool/H 2 O 2 process as a viable polishing step for treating effluents from P&P plants, contributing to better sustainability by reducing the need for additional chemicals for pH adjustment, and increasing the quality of effluents for discharge and reuse.