Volume 40, Issue 4

Spruce bark residues obtained after alkaline extraction of polyphenols were studied as raw material for pulping and making of pulp sheets. Kraft pulping of mixtures containing wood chips and 5 % or 20 % wt. bark residues produced unbleached pulps with higher screened yields and lower kappa number than wood pulps. During bleaching, the evolution of brightness along with kappa reduction followed a similar trend in all pulps, and bleached mixed pulps with ISO brightness >89 % could be obtained with somewhat lower intrinsic viscosity than wood pulps. The high content of calcium and other metal elements in spruce bark, which was partially reduced by the alkaline extraction, did not seem to impair the pulping and bleaching of the pulps. Sheets made from mixed pulps had rather similar optical and mechanical properties than sheets from wood pulps, and interestingly, sheets produced from mixed pulps with 20 % bark residues showed higher bulk as a function of internal bond strength, which may be exploited in packaging boards. Pulping of bark residues to produce mixed pulps would thus maximize the utilization of spruce bark streams after extracting the polyphenols, while increasing the pulp output in the mills.

Bamboo, with its long fibers, fast growth, high abundance, and short harvesting cycle, is a promising alternative to traditional wood pulp, particularly in reinforcing secondary fibers during paper recycling. In this study, different from direct addition with poor combination concerning the negative charge in recycled pulp fibers, bamboo fibers were firstly modified with 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) to get cationic bamboo fibers, the characterizations by FTIR and N contents (maximum 1.05 %) classified that the hydroxyl groups in bamboo fibers were etherified effectively with greater zeta potentials (maximum −13.2 mV) in mixed pulps. The cationic modification of bamboo fibers resulted in a significant increase in the tensile and burst index of the secondary pulp, by 49.75 % and 61.54 % with only 10 %addition, respectively, as compared to the unmodified bamboo fibers, which was contributed to the mutual attraction between positively charged modified bamboo fibers and negatively charged secondary fibers, besides the original hydrogen bonding inside fibers, which leads to the enhancements for secondary fibers strength. These findings provide valuable insights into the effective applications of bamboo fibers for reinforcing recycled paper and offer promising solutions for the sustainable development of the paper industry.

Hydrophobic paper bags are gaining popularity as a sustainable and environmentally friendly alternative to conventional packaging materials. This study focuses on the development of hydrophobic paper bags from rice straw, a major agricultural waste. The pulp was prepared by boiling the straw with sodium hydroxide, followed by grinding and molding into paper sheets. Chitosan nanoparticles (CNP) were synthesized via the ionic gelation method and applied as a coating on the rice straw paper. Beeswax was then used as a secondary coating. The resulting paper sheets were evaluated for thickness, mechanical properties, thermal stability, and hydrophobicity. The results showed that CNP and beeswax-coated papers were significantly thicker than their non-coated paper. Mechanical testing demonstrated improvements in tensile strength and elongation at break for the coated papers, with the highest values observed in CNP and beeswax-coated samples. Fourier Transform Infrared Spectroscopy confirmed the successful integration of chitosan and beeswax into the paper matrix. Scanning Electron Microscopy images revealed enhanced smoothness and binding capacity in the coated papers. Thermal analysis indicated that CNP and beeswax-coated papers exhibited superior thermal stability compared to non-coated papers. Hydrophobicity tests confirmed that the CNP and beeswax-coated papers had excellent water resistance and self-cleaning properties, while heat sensitivity tests showed that the wax coating remained stable up to 50 °C. However, neither the CNP-coated nor the CNP with beeswax-coated papers exhibited a zone of inhibition against Staphylococcus aureus and Pseudomonas aeruginosa . These findings suggest that paper coating with CNP and beeswax significantly improves its physical, mechanical properties and hydrophobic properties.

The energy efficiency of papermaking critically depends on how much of the web moisture can be removed by wet pressing before the dryer section. Here, we explored an operation where the pressing was conducted over an extended period (70–540 ms) at an elevated temperature (approaching 100 °C). We found a large increase in the solids content for the tissue and board grades studied. The maximum measured solids content was 83 ± 2 % for tissue and 62 ± 2 % for linerboard, with approximately 5 % pt. (tissue) or 1.5 % pt. (linerboard) attributable to moisture evaporation after the pressure pulse based on our drying model. Both solids content levels were notably higher than those achieved with conventional pressure pulses. The results open up intriguing new directions for technological development towards a wet pressing concept that mimics the current metal-belt pilot lines but operates at higher web moisture levels. The high solids content achieved with extended wet pressing significantly reduces the amount of evaporated water. Thus, an ineffective Yankee + hood drying system with high temperature and energy loss would be no longer needed in tissue production. This would enable up to 90 % drying energy savings and a corresponding CO 2 emission reduction compared to existing pressing and drying technologies.

Wood has traditionally been the primary raw material for papermaking, but its use contributes to deforestation. Vegetable waste offers a sustainable alternative for the paper industry. This study explores the potential of cabbage waste combined with wastepaper in varying compositions (20–100 wt% at 20 wt% intervals) for paper production. The prepared tissue papers were evaluated for grammage, thickness, tensile strength, burst strength, moisture content, and FTIR analysis. Results showed that increasing cabbage leaf content led to a decrease in grammage and thickness indicating reduced fibre density and increased porosity. The optimum tensile strength (3.33 Nm/g) and burst strength (6 kPa m 2 /g) were observed at 60 wt% cabbage leaves, suggesting enhanced fibre bonding and structural integrity at this composition. Beyond this threshold, mechanical properties declined due to weaker fibre interactions. Moisture content increased up to 60 wt% (7.4 %), then decreased at higher cabbage leaf proportions, balancing water retention and porosity. FTIR analysis revealed the presence of cellulose fibers and polysaccharide functional groups in the prepared tissue paper. The obtained results showed that 60 wt% cabbage leaf mixtures provide an optimal combination of strength, flexibility, and moisture control, making them suitable for tissue paper applications.

Pulp and paper industry, though vital, strains forest resources, highlighting the importance of alternative materials and waste paper recycling. This study explores how beating degree and microwave expansion affect Simao pine fibers and recycled paper. Beating damages fiber cell walls, enhancing water-related and fibrillation abilities, increasing fine fiber content and water retention, and boosting paper tensile strength (from 11.5 kN/m at 13°SR to 48.45 kN/m at 62°SR), but over-beating weakens fibers. More recycling cycles reduce mechanical strength (except tear index). Microwave expansion improves fiber water retention and fine fiber content; 13°SR un-beaten fibers see 49.34 % more fiber-fiber bonds. Recycled paper with microwave-expanded fibers has stronger bonds. For example, 24°SR microwave-expanded paper after three cycles has 39.83 % higher tensile strength than conventional paper, and secondary expansion makes 13°SR paper after three cycles 51.82 % stronger. The study, by reducing hornification via microwave puffing and improving fiber water retention, provides theoretical and technical support for better waste paper recycling efficiency.

With the progression of society, aquatic pollution has intensified, prompting a search for greener materials for wastewater treatment. Here, we present a mycelium-based paper developed via alkaline deacetylation of fungal mycelial fibers to chitosan, followed by vacuum filtration, and reinforcement with long plant fibers to enhance mechanical performance. The resulting mycelium–paper composite exhibits a highly dense structure, with very low air permeability (0.42 mL/min), tensile strength of approximately 14 MPa, and tear resistance up to 1,384 mN. In filtration tests, a single pass of 30 mg/L Cu 2+ solution yielded a removal efficiency of 98 %, corresponding to an adsorption capacity of 8.75 mg/g; for methylene blue dye, the adsorption capacity was 7.42 mg/g. Compared to conventional cellulose-based powder adsorbents, which often suffer from material loss and require post-treatment, the mycelial paper can be formed directly into membrane-like filters, simplifying handling. Furthermore, this mycelial membrane displayed strong adsorption across various heavy metal ions and dyes, underscoring its significant potential for sustainable water purification.

Recently, pulp mold material has emerged as an eco-friendly substitute for plastic due to its natural and recyclable properties. To investigate hybrid effect on pulp mold materials, wood, sugarcane and hybrid pulp (wood: sugarcane=1:1) were used to make boxes. The results of mechanical tests revealed that tensile index, stiffness, bursting index, and static compressive ultimate load of hybrid pulp mold materials are better than those of wood or sugarcane pulp mold materials. It was speculated that the failure mode observed in wood and sugarcane pulp mold boxes was delamination caused by interfacial instability. The eigenvalues, loads, and stresses corresponding to each buckling mode were obtained via buckling simulation analysis. To verify the hybrid mechanism, scanning electron microscope was exploited to distinguish the morphological differences of different fibers. Ultimately, a novel hybrid reinforcement mechanism in pulp mold material was proposed that hybrid effect reinforced the stability of the interface, which impacted the mechanical properties of hybrid pulp mold materials. This study advances the exploration of hybrid effect of interfaces, and the mechanism of interfacial instability and reinforcement can be implied to other pulp mold products.

In order to protect the paper, increase the mechanic performance and delay the aging of paper, CMC- β -CD was synthesized by carboxymethyl cellulose as substrate, epichlorohydrin (ECH) as crosslinking agent, sodium hydroxide (NaOH) as catalyst and solvent, and water as medium, β -Cyclodextrin as grafter, through single factor experiment and response surface method, suitable conditions for the synthesis of CMC- β -CD was obtained; The structure of the synthesized CMC- β -CD was characterized by infrared spectroscopy and SEM and the mechanic properties were evaluated. The results showed that when the mass ratio of CMC- β -CD was 7:15, reaction temperature was 40 °C, and pH was 6.0, the optimum synthetic conditions was obtained. And good anti-age properties was also obtained by thermal aging tests. This paper provides some theoretical guidance for the protection of paper cultural relics.

Natural inks have emerged as eco-friendly alternatives to synthetic inks in the paper printing industry due to their biodegradability, non-toxicity, and sustainability. Derived from renewable sources such as plants, algae, minerals, and fungi, these inks reduce environmental pollution and dependence on petroleum-based materials. This review highlights recent advancements in natural ink extraction, formulation, and application, emphasizing improvements in physical and chemical properties. Studies show natural indicator inks using Lycium ruthenicum anthocyanins achieve a sensitivity of 2178.57 μA mM −1  cm −2 with a rapid response time of 18 s. Cobalt blue pigments derived from dolomite and kaolin tailings demonstrate high color performance (L* = 37.63, a* = 10.68, b* = −54.87) and 94.96 % light absorption efficiency. Packaging papers containing triticale straw fibers reduced color variation (ΔE*) by 20 % after aging and rubbing tests. Plasma treatment and nano-chitosan coatings have improved color depth by up to 214 % and washing durability after 45 cycles. Despite these advancements, challenges remain in enhancing color fastness, water resistance, and scalability. This review outlines future research directions focused on advanced extraction, formulation optimization, and life cycle assessments to promote the industrial application of sustainable natural inks.

The growing demand for sustainable packaging solutions is driving the development of new paper-based forming processes. Among these, 3D forming of paper has shown particular promise (Groche, P. and Huttel, D. (2015). Paperboard forming - specifics compared to sheet metal forming. BioRes 11). However, limited formability remains a key challenge, restricting potential applications. Since moisture content significantly affects both bending stiffness and stretchability (Franke, W.; Stein, P.; Dörsam, S.; Groche, P. (2018): Formability of paperboard during deep-drawing with local steam application. In: Proceedings of the 21ST international esaform conference on material forming . ESAFORM 2018, Palermo, Italy, 2018: Author(s) (AIP Conference Proceedings), S. 100008), targeted moistening is critical. For high-speed packaging lines with cycle times of 1–3 s, rapid and controlled moistening is required. Previous studies have shown that methods like water baths or sponge applications can improve forming results especially when combined with pressure to ensure even moisture distribution (Stotz, H., Vogt, L., Kasparian, T., Klauser, M., Rauschnabel, J., and Hauptmann, M. (2022). TAPPICon 2022 - advanced development in 3D forming methods for paper packaging . Charlotte, North Carolina, USA, 30 April-4 May 2022. Curran Associates, Inc., Red Hook, NY). However, practical, process-integrated solutions have been lacking. This study investigates a newly developed moistening unit using a porous aluminum interface for one-sided application (Bischoff, B.; Stotz, H.; Klauser, M. (2023). Verfahren und vorrichtung zur herstellung eines verpackungselementes . Angemeldet durch Syntegon Technology GmbH am 05.05.2023. Anmeldenr: 23171862.8. Veröffentlichungsnr.: EP 4 292 805 A1). Experiments with bleached board demonstrated that higher water pressure and longer contact times significantly increased moisture content. Moisture levels of up to 26 % were achieved in just 1–3 s. As a result, formability improved noticeably: the maximum strain increased from 13 % to 19 %, enabling deeper geometries and steeper wall angles – a clear advancement for sustainable packaging design.

As a key raw material in fluting paper production, NSSC pulp from hardwoods is crucial in sustainable packaging applications. Hence, efforts are underway to increase the quality of this pulp. This study aims to enhance the physical and mechanical properties of papers produced from Populus deltoides NSSC pulp by reinforcing them with cellulose nanofibrils (CNFs) derived from rice straw. The NSSC pulping of poplar wood was optimized, and then CNFs were added at 5, 10, and 15 % to refined NSSC pulp. Papers (127 g/m 2 ) were fabricated, and the impact of CNF reinforcement on the physical and mechanical properties of papers was evaluated. Results demonstrated that the addition of CNFs significantly improved tensile, burst, and tear indices, bending stiffness, and ring crush test (RCT) by 32.46 %, 19.85 %, 18.22 %, 78.76 % and 65.71 %, respectively. Furthermore, the addition of CNF increased density (30.88 %) and simultaneously reduced thickness (20 %) and bulk (23.23 %). Cobb test showed that water absorption decreased by 35.48 %, indicating better water resistance, while drainage time increased by 87.30 %, reflecting changes in fiber network structure. CNFs facilitate extensive hydrogen bonding, yielding a denser and more robust fiber network. This study highlights CNFs’ potential as an additive for reinforcing NSSC papers and improving packaging performance.

This study evaluated the use of three Sequencing Batch Moving Bed Biofilm Reactors (SBMBBR) with Mutag biochip 30™ (MB) carriers for treating regenerated papermaking wastewater. The reactors operated at filling ratios of 15 % (MB15), 30 % (MB30), and 45 % (MB45). Biomass stabilized after 30 days, reaching 2.26 g/L, 4.01 g/L, and 5.58 g/L, respectively. The process parameters of the reactors were optimized using Response Surface Methodology (RSM). Under conditions of a C/N ratio of 21:1, an aeration rate (AR) of 2.65 L/min, a hydraulic retention time (HRT) of 9 h, and a 45 % filling ratio, the chemical oxygen demand (COD) removal efficiency of the wastewater achieved the highest value of 68.28 ± 2.03 %, with the average effluent COD reduced to approximately 170 mg/L while ammonia nitrogen and total nitrogen were below 10 mg/L and 15 mg/L, meeting the discharge standards for recycled paper mill wastewater in China. Kinetic analysis using an improved Stover-Kincannon model showed good fitting (R 2 > 0.93) and the highest degradation rate (U max ) of 2.6413 g/Lday in the MB45 reactor. These results support SBMBBR’s potential for treating papermaking wastewater and addressing challenges in other industrial wastewater treatments.