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Copyright of Journal of Shaanxi University of Science & Technology is the property of Journal of Shaanxi University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Effects of cellulose nanofibers (CNF) and cationic starch (CS) were evaluated as coating components relative to the physical and mechanical properties of fluting papersheets fabricated from recycled corrugated cardboard fibers. Fabricated fluting papers were subjected to size press applications by three different coating blends. Coating suspensions were prepared at various concentrations of CNF (0.5%, 1%, 2%, 3%, and 4%) and 4 wt% CS, and the same amounts of CS/CNF. The paper sheets were fabricated using size press machine as three-time repetitive applications, followed by one-time drying section, and compared to uncoated, CScoated, and CNF-coated papers. The application of CNF suspensions increased tensile indices up to 11.7%. Moreover, CS/CNF suspensions resulted in a 67.2% increase in tensile index values. The coating of CS/CNF suspensions increased the burst index values by 163% at the CS+1%CNF concentration when compared to the control pulp. Surface application of prepared suspensions reduced the porosity of the samples under all conditions. The highest reduction in the air permeability was observed in the CS+4%CNF-coated samples as 91.5%. It can be concluded that the superficial applications of CNF on the physical and mechanical properties of recycled fluting paper was more effective in the presence of CS. [ABSTRACT FROM AUTHOR]

Background and Objectives: The use of recycled pulp in papermaking reduces the quality of the resultant papers. Hence, employing enzyme pre-treatment in isolation or in combination with sequential pulp bleaching methods can prove to be effective approaches for enhancing the quality of the end product derived from recycled pulp. This study was undertaken to examine the impact of cellulase and laccase enzyme pre-treatment sequences on the bleachability of the resultant pulp with hydrogen peroxide, as well as to assess the quality of the final pulp following the bleaching process. Materials and Methods: At first, the mixture of waste newspaper and magazine papers were deinked using enzyme pre-treatment (combined sequence of cellulase and laccase) as well as conventional chemical method. Enzymatic pre-treatment was done as experimental treatments C1L1 (cellulase usage: 0.1% and duration time: 10 minutes; laccase usage: 20u and duration time: 120 minutes), C1L2 (cellulase usage: 0.1% and duration time: 10 minutes; laccase usage: 40u and duration time: 120 minutes), C2L1 (cellulase usage: 0.1% and duration time: 20 minutes; laccase usage: 20u and duration time: 120 minutes) and C2L2 (cellulase usage: 0.1% and duration time: 20 minutes; laccase usage: 40u and duration time: 120 minutes) under specific process conditions. Additionally, control pulp samples (without the addition of chemicals or enzymes) and chemically deinked pulp samples were prepared. The bleaching of the deinked pulp was then conducted using a hydrogen peroxide bleaching system, which consisted of 2% hydrogen peroxide, 2% sodium hydroxide, 2% sodium silicate, 0.2% DTPA chelating agent, and 0.1% magnesium sulfate. The bleaching process took place in separate plastic bags, under specific process conditions of 10% consistency, a temperature of 70 °C, and a duration of 2 hours in a water bath. Finally, the optical and strength characteristics of the bleached pulp were assessed. Results: The findings revealed that incorporating enzyme pre-treatment during the deinking process enhances the overall efficiency of hydrogen peroxide bleaching. Consequently, the resulting papers exhibited superior optical and strength characteristics after bleaching, as compared to pulp that underwent conventional chemical-based deinking. Specifically, the application of C2L2 and C2L1 enzymatic pre-treatments, followed by bleaching with hydrogen peroxide, resulted in brightness improvements of 11.12% (equivalent to approximately 5 units) and 9.5% (equivalent to approximately 4 units), respectively. In these pretreatments, the whiteness of the paper increased by 31.92% and 24.54% (an increase of about 9 and 6 units), respectively. Also, the yellowness of the paper decreased by 40.19% and 44.25%, respectively, and the opacity of the paper reduced by 37.74% and 23.97%, respectively. Also, in experimental runs of C2L1 and C2L2, the paper tensile index increased 29.17% and 35.64%, respectively (40.64 Nm/g and 38.7 Nm/g, respectively), breaking length enhanced by 64.42% and 99%, respectively (5.92 km and 4.89 km), and the paper burst index also increased by 70.85% and 92.37% (3.81 mN.m² /g and 4.29 kPa.m² /g), respectively. The tear indices of the paper in these experiments were found to average approximately 6.82 mN.m 2 /g and 6.62 mN.m ² /g, which are slightly lower compared to the chemically deinked pulp after bleaching. However, in the pretreatment utilizing the combined sequence C2L1, the tear index of the paper was nearly equivalent to that of the chemically deinked pulp. Conclusion: The findings demonstrate that the combined sequences of cellulase and laccase resulted in a substantial enhancement in the bleachability of pulp with hydrogen peroxide, surpassing that of chemically deinked pulp. Moreover, these enzymatic pre-treatment sequences led to the production of papers with superior optical and strength properties. Notably, the most favorable optical and strength characteristics were observed in the C2L2 and C1L2 enzymatic pre-treatment sequences following hydrogen peroxide bleaching. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of size press coating on two types of recycled papers using different types of nanofibrillated cellulose (NFC) and cationic starch (CS) on physical and mechanical properties. Wheat straw was used as a cellulose source, and NFC was obtained through oxidative and enzymatic pretreatments. Recycled fluting and coreboard papers were coated with cationic starch/NFC blends at various concentrations of NFC (0.5%, 1%, 2%, 3%, and 4%) using a three-time repetitive size press application, followed by one-time drying section, and compared to uncoated papers. The application of a coating suspension containing 4% periodate-oxidized NFC on both paper surfaces resulted in a significant improvement in the tensile index, burst index, and internal bond strength of the papersheets, with increases of up to 60.6%, 96.3%, and 119.9%, respectively. Furthermore, significant decreases in air permeability were also observed with reductions of 75% and 81.6% for coreboard and fluting papers, respectively. Compared to other pretreatment methods, periodate oxidation resulted in higher viscosity values in NFC samples. Therefore, the application of periodate-oxidized NFC with a size press resulted in a significant improvement in the mechanical and barrier properties of papers made from recycled pulps. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The influence of nanofibrillated cellulose (NFC) was investigated as a reinforcing agent to improve strength properties of papersheets fabricated from recycled pulp fibers of mixtures of old newspapers, old magazines, and old corrugated cardboards. To determine the effects of the NFC on the mechanical and physical properties of the recycled pulp papers, cellulose nanofibrils (NFC) were isolated from wheat straw, pretreated chemically and enzymatically (NFC-OX), and then added to the bulk suspensions of papermaking pulp slurries at various percentages. The electrokinetic and drainage properties of the pulps and the mechanical and physical properties of the papersheets were analyzed and compared. As expected, the addition of NFC/NFC-OX significantly increased the strength properties of papers. Papers containing 4% of NFC-OX (periodate pretreated) presented higher increases in tensile index (43%) and burst index (59.3%) than other papers. However, a high addition of NFC/NFC-OX increased the water retention, which is undesirable for papermaking. Hence, with optimum selection of NFC/NFC-OX and process conditions, higher mechanical properties could be acquired without increasing drainage rate. Compared to the other pretreated NFC/NFC-OX types, sodium-periodate-oxidized NFC-OX samples significantly increased the mechanical properties of the papers fabricated from the recycled pulps. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Industrially produced bleached recycled pulp (R) comprising essentially hardwood fibres was subjected to enzymatic treatment with endo-xylanase from Thermomyces lanuginosus with or without ultra-high hydrostatic pressure (UHP) pre-treatment at 300-600 MPa for 10 min. The kinetics and the extent of enzymatic hydrolysis after UHP pre-treatment under different conditions have been evaluated by released reducing sugars and the analysis of neutral sugars in pulps, respectively. The changes in surface chemical composition of pulps were assessed by UV-vis diffuse reflectance spectroscopy. UHP-pre-treated R under optimal conditions (400 MPa), with or without posterior enzymatic treatment, was used for the production of handsheets and evaluation of its mechanical properties. It was suggested that enzymatic modification improves significantly the papermaking properties of recycled pulp. These improvements were related with selective removal of xylan bound to impurities and to aggregated cellulose fibrils on the fibre surface, thus favouring the ensuing swelling and inter-fibre bonding in paper. UHP pre-treatment and posterior enzymatic treatment revealed a synergetic effect on the mechanical properties of recycled pulp. This fact was assigned to enhanced accessibility of fibres towards xylanase and by forced hydration and favourable rearrangement of cellulosic fibrils in fibres after UHP pre-treatment. The increase of basic strength properties after UHP-promoted xylanase treatment was up to 30 % being the most pronounced for the tensile strength and the burst resistance. [ABSTRACT FROM AUTHOR]

White ledger is white-grade recycled pulp that replaces the bleached kraft pulp (BKP) that typically forms the top ply of duplex boards. However, sheets made from white ledger are inferior in strength compared with those made from virgin pulp. Therefore, it is necessary to select a proper additive in order to overcome the disadvantages of using white ledger. In this study, the physical properties of white ledger used at a mill that produced duplex boards were analyzed. The effect of cationic polyacrylamides (C-PAMs) with different charge densities and molecular weights on first-pass retention and paper strengths was simultaneously measured. White ledger contains fiber fines and filler fines, which reduced the strength of paper made from white ledger compared with paper made with BKP. This indicates that the improvement of first-pass retention and paper strength is important when the amount of white ledger increases in the top ply of a duplex board. The charge density of CPAM, which acts as a retention aid, is more important than its molecular weight in terms of improving the first-pass retention and paper strength of white ledger. The charge density of C-PAM must be high enough to catch anionic fine particles. [ABSTRACT FROM AUTHOR]

The utilization of waste paper is very important for saving wood resources and reducing waste generation. Various techniques for preparing cellulose nanofibers, which is a material recently proposed for potential applications in the paper industry, have been investigated. In the present study, fine fibers were prepared using recycled pulp and a nanoengineering aqueous counter collision treatment, and sheets composed of these fine fibers were prepared by filtration under reduced pressure conditions. Measurement of specific surface area and optical microscopic observation of fine fibers showed the recycled pulp was not readily miniaturized by the treatment compared with virgin pulp. The tensile strength of sheets produced from recycled pulp by 5 times of the treatment was higher than of those prepared from recycled pulp by 60 times and from virgin pulp regardless of the number of the treatment. Furthermore, the density of the sheet produced from recycled pulp by 5 times was lower than other sheets. [ABSTRACT FROM AUTHOR]

Fibre fines and fibrils within recycled cellulosic pulp have high amorphous cellulose content. These fines, having a high surface area, restrict the free drainage of water and retain bound water within the pressed sheet but contribute little to the hydrogen bonding potential of the fibre slurry. The advantage of higher freeness, achieved by selective hydrolysis of excess fines through enzymes, can be used for enhancement of the drainage rate, leading to increased paper production. In this study, monocomponent cellulase treatment of recycled pulp for drainage improvement as a result of selective and controlled hydrolysis is investigated. The effectiveness of specific types of enzyme activity, endoglucanase or cellobiohydrolase, is studied. The increased solubilization of amorphous cellulose mediated by endoglucanase treatments improved pulp drainability by 11-25 %, along with providing better paper properties such as tensile index and smoothness. [ABSTRACT FROM AUTHOR]

The article presents a study regarding the production of a multi-fiber modifying enzyme from Mamillisphaeria sp. BCC8893. It mentions that the Mamillisphaeria sp. BCC8893 was optimized in submerged fermentation using a response-surface methodology. Result reveals the characteristics of the complex multi-fiber modifying enzyme utilized in refining and suggests its potential for local on-site enzyme production for the development an environmentally refining process in the pulp industry.

Separation of vessel elements and fibers was carried out for Eucalyptus kraft and recycled pulp as raw materials. A new separation method is presented. The surface morphology, surface chemical characteristics and chemistry of individual vessel elements were studied using field emission scanning electron microscopy (FE-SEM), microbeam X-ray photo-electron spectroscopy (μ-XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). By FE-SEM it could be seen that vessel elements in recycled pulp were almost intact or only partly broken via the pits. They were also detected on the surface of newsprint paper. The chemical composition of vessel element surfaces was similar to that of fibers. The surface coverage by lignin in vessels showed scattered results by μ-XPS. However, normalized lignin peak intensities of ToF-SIMS indicated that vessels had lower surface lignin counts than fibers. Vessel elements in recycled pulp were rich in phthalates and other hydrocarbons originating probably from printing ink and paper chemicals. Fillers, sizes, and other paper chemicals were not completely removed from the recycled vessel surfaces during the de-inking. [ABSTRACT FROM AUTHOR]

Paper mills processing recycled paper suffer from biofouling causing problems both in the mill and final product. The total bacterial community composition and identification of specific taxa in the process water and biofilms at the stock preparation and paper machine areas in a mill with recycled paper pulp was described by using a DNA-based approach. Process water in a similar mill was also analyzed to investigate if general trends can be found between mills and over time. Bacterial community profiles, analyzed by terminal-restriction fragment length polymorphism (T-RFLP), in process water showed that the dominant peaks in the profiles were similar between the two mills, although the overall composition was unique for each mill. When comparing process water and biofilm at different locations within one of the mills, we observed a separation according to location and sample type, with the biofilm from the paper machine being most different. 16S rRNA gene clone libraries were generated and 404 clones were screened by RFLP analysis. Grouping of RFLP patterns confirmed that the biofilm from the paper machine was most different. A total of 99 clones representing all RFLP patterns were analyzed, resulting in sequences recovered from nine bacterial phyla, including two candidate phyla. Bacteroidetes represented 45% and Actinobacteria 23% of all the clones. Sequences with similarity to organisms implicated in biofouling, like Chryseobacterium spp. and Brevundimonas spp., were recovered from all samples even though the mill had no process problems during sampling, suggesting that they are part of the natural paper mill community. Moreover, many sequences showed little homology to as yet uncultivated bacteria implying that paper mills are interesting for isolation of new organisms, as well as for bioprospecting. [ABSTRACT FROM AUTHOR]

Porapak has been studied as a solid-food simulant in experiments on paper and board packaging. Three samples of paper with different recycled pulp content and surface treatment, and of different grammage and thickness, were used for the studies. Kinetic behaviour from 25 °C to 100 °C and different contact times ranging from 5 min at 100 °C to 10 days at 25 °C were studied using Porapak or, occasionally, Tenax or milk powder. Similar results were obtained with Porapak and Tenax but those from Porapak were more stable with temperature. Porapak behaves as good solid-food simulant even at high temperature. [ABSTRACT FROM AUTHOR]

The mechanical, physical, and chemical properties of recycled pulps were evaluated after a series of treatments designed to improve and/or modify the pulp characteristics. Tensile strength, bursting strength, and apparent density of the pulps decreased with recycling. However, the tear strength, in most cases, increased after the first recycle and then decreased after the second recycle. Carboxyl content and WRV of pulps also decreased with recycling. Chemical treatments did not increase the bonding ability of recycled pulps and, in most cases, decreased the physical properties of the pulps. Altering the physical state of the cellulose microstructure through additional swelling did not appear to be a significant factor for strength restoration. It may be that the hemicelluloses plan a greater role in recycling than originally thought. [ABSTRACT FROM AUTHOR]

Surface properties of bleached kraft pulps were evaluated before and after recycling, and after a series of chemical treatments designed to improve and/or modify the pulp characteristics. The surface free energy characteristics of the pulps were determined using the Wilhelmy technique, and ESCA and ATR-FTIR methods were used to evaluate the chemical composition of the surfaces of the pulp fibers. In general rather small changes were noted at the fiber surfaces with recycling and chemical treatment. Recycling tended to increase the acid component and decrease the base component of the surface free energy of the pulps. This could result from exposure of carboxyl groups from hemicelluloses and/or from oxidized layers from the bleaching process. ESCA analyses also indicated increased carboxyl concentration at the surfaces of the recycled fibers. Although treatment with aqueous bases and organic solvents tended to increase the hydroxyl content on the surface of recycled pulps, the chemical treatments were not beneficial to pulp quality. AFM and SEM of fiber and fine surfaces of kraft pulps revealed that the fines fraction was altered to a much greater extent with recycling. Although recycled fibers appeared to have improved wettability, these small changes in the surface characteristics do not appear to play the dominant role in the characteristics of recycled pulps. Recycling did not change the crystallinity of whole pulps, but it increased the crystallinity of the fines fraction. The increase in the crystallinity of the fines fraction and the reduction in the water retention value (WRV) and the bulk carboxyl content (xylan) of the recycled pulps, as noted in Part I of this paper, appear to play the predominant role in determining the characteristics of recycled pulps. It appears that the loss of the hemicelluloses in the bulk of the fiber with recycling is much more important for internal fibrillation than the apparent small increase of hemicelluloses at the surface of recycled fibers. [ABSTRACT FROM AUTHOR]