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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, CS-coated, 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.

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]

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&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

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.

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]

Compared with traditional petroleum-based foam materials, cellulosic foam materials have significant advantages in terms of economy and environmental protection. However, the traditional cellulose-based foams have some problems such as high energy consumption in the preparation process. In this study, the recycled pulp foam (RPF) with ultra-light density (12.69 kg/m 3  ~ 13.83 kg/m 3 ) and high porosity (99.07 % ~ 99.15 %) was prepared by mechanical stirring using waste corrugated cardboard as the main raw material and further hydrophobically modified using rosin. The prepared r-RPF foam has excellent hydrophobicity with the water contact angle remaining 132.9° after 20 s. In addition, the rosin coating enhances the mechanical properties of r-RPF, and the stress of r-RPF at 50 % strain is increased by 97 %. It should be noted that after rosin treatment, the compressive strength and elasticity of r-RPF were improved. The r-RPF was stable in water and had a high oil adsorption capacity (7.8 to 28.13 g/g), which had the potential to treat current oily wastewater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

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]

The importance of recycling and utilization of recycled fiber has recently been recognized because of concerns about environmental issues and economic aspects. In spite of several advantages offered by paper recycling such as wood savings through substitution of virgin pulp and reduction in chemical usage, recycled pulp also contains plenty of fines having high relative surface area and high amount of amorphous cellulose. These fines adsorb water to a large extent and dewatering rate is lower compared to virgin pulp. Selective hydrolysis of these excess ultra-fines through eco-friendly cellulase enzymes can be utilized for enhancing the drainage rate leading to increased paper production. The present study deals with the isolation, production, biochemical characterization of alkali stable endoglucanase enzyme from Pycnoporus sanguineus NFCCI-3628 and its potential application for the improvement of pulp drainage. The enzyme produced by the fungus was stable even in neutral to alkaline pH range 7-8. In the experiments carried out, significant improvement of ~9-14% in drain ability of pulp treated with endoglucanase enzyme was achieved along with better paper properties such as tensile index & smoothness.

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 C-PAM, 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.

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]

The use of waste fibers for the reinforcement of brittle matrices is considered opportune for the sustainable management of urban solid residues. This paper examines the microstructure and mechanical properties of a composite material made of gypsum reinforced with cellulose fibers from discarded Kraft cement bag. Two different kinds of gypsum were used, natural gypsum (NG) and recycled gypsum (RG), both with an addition of 10% by mass of limestone. For the production of samples, slurry vacuum de-watering technique followed by pressing was evaluated revealing to be an efficient and innovative solution for the composites under evaluation. The composite was analyzed based on flexural strength tests, scanning electron microscopy (SEM) imaging, secondary electron (SE) detection, and pseudo-adiabatic calorimetry. The morphology of the fractured surfaces of flexural test samples revealed large gypsum crystals double the original size surrounding the fibers, but with the same overall aspect ratio. Natural fibers absorb large amounts of water, causing the water/gypsum ratio of the paste to increase. The predominance of fiber pullout, damaged or removed secondary layers and incrusted crystals are indicative of the good bonding of the fiber to the gypsum matrix and of the high mechanical resistance of composites. This material is a technically better substitute for the brittle gypsum board, and it stands out particularly for its characteristics of high impact strength and high modulus of rupture.

A set of 132 packaging materials based on paper, commonly used in the Czech Republic for food products packaging, was tested as regards the occurrence of contaminants. A number of 101 extractible substances were identified and the levels of 68 compounds, including residues from paper pulp processing (e.g. processing aids), substances originating from printing inks or adhesives (photoinitiators, plasticizers, solvents), impregnation and coating (solvents, hydrocarbons) in all the tested materials were quantified using gas and liquid chromatography coupled with tandem mass spectrometry techniques. The results indicated that phthalate plasticizers, anthraquinone, aromatic hydrocarbons and photoinitiators formed the most frequent group of xenobiotics in paper. The highest content in tested papers was determined for dibutyl phthalate (628 mg·kg-1), benzophenone (369 mg·kg-1) and diisobutyl phthalate (108 mg·kg-1). Most of the contaminants in paper packaging materials originated from materials used for modification of functional properties (water-proof or fat-proof adjustment, coating, lamination with polymer films, etc.) and/or residues from recycled pulp. [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]

Abstract: High-performance liquid chromatography (HPLC) coupled to an evaporative light scattering detector was used to quantitatively determine glucose and cellobiose in hydrolyzates from the production of cellulose nanofillers from modified lignocellulosic materials. Prevail Carbohydrate ES 5μ column proved more suitable for achieving the chromatographic separation of the model pulp hydrolyzate into its constituent sugars than the YMC-Pack Polyamine column. Linear calibration curves for the various sugars in the mixtures were developed. Glucose and cellobiose were clearly detectable in pulp hydrolyzates obtained from enzyme-mediated hydrolysis of recycled pulp, pine and hardwood dissolving pulps. Finally, the amount of glucose in the pulp hydrolyzates was generally higher than cellobiose. [Copyright &y& Elsevier]

This study examined the production of cellulose nanocrystals from microcrystalline wood cellulose, Avicel and recycled pulp of wood pulp using sono-chemical-assisted hydrolysis. Two hydrolysis systems: deionized water and maleic acid were evaluated. In deionized water, Avicel produced cellulose nanocrystals with average diameter of 21±5nm (minimum 15nm and maximum 32nm). Cellulose nanocrystals from recycled pulp were not distinctively spherical and had an average diameter of 23±4nm (minimum 14nm and maximum 32nm). Maleic acid (50mM) sono-chemical assisted hydrolysis of Avicel at 15°C and 90% power output for 9min produced cellulose nanocrystals which were cylindrical in shape and were of dimensions, length 65±19nm and width 15nm. [Copyright &y& Elsevier]

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]

Abstract: The composition, nanostructure and distribution of extractives on fiber surfaces of a birch bleached kraft pulp (BKP) and a recycled deinked pulp (DIP) was investigated using X-ray photoelectron spectroscopy (XPS or ESCA), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM). Effects of different extraction methods on the fiber surfaces were also investigated, in addition to the analyses of extractives by gas chromatography (GC). Traces of surface extractives were observed by XPS, ToF-SIMS and AFM in the BKP after extraction using an acetone–phosphate method (AcP). This method improved the extraction yield of palmitic and stearic acids in DIP, but the removal of surface extractives was not as effective as for BKP. Contaminants, identified as siloxanes and phthalates by ToF-SIMS were observed for DIP and BKP, even after AcP extraction. Stearic acid and its calcium salts were found to form aggregates with a diameter of 100–500nm, while oleic acid formed a uniform layer. Estimations of extractive surface coverage by XPS were consistent with qualitative observations by ToF-SIMS and AFM. The combinations of different techniques strengthen the value of XPS, ToF-SIMS and AFM for fiber surface investigation. [Copyright &y& Elsevier]

Eight contaminants were used to perform a surrogate contamination test to evaluate safety of the process for producing recycled pulp for adult paper diapers. We performed a safety evaluation of the recycling process for producing recycled pulp following the European Food Safety Authority safety assessment for polyethylene terephthalate (PET) bottles using recycled PET. We also compared the first tier safety limit established on the basis of TTC (C limit) in the pulp that contained recycled pulp with residual contaminant concentrations (C res). If C limit > C res, there is no concern regarding safety of the recycling process. C limit was determined to be 0.46 mg/kg-pulp based on the human exposure threshold of 0.15 μg/person/day using the scenario in which a bedridden senior citizen uses four adult paper diapers manufactured with pulp containing 10% recycled pulp per day. C res was derived from the initial concentration in used pulp (0.17 mg/kg-pulp), and decontamination rate was obtained from the surrogate contamination test. The C res of the eight contaminants were between 0.0017 and 0.10 mg/kg-pulp, which were all below the C limit of 0.46 mg/kg-pulp. These results indicated there was no safety problem regarding this process for producing recycled pulp for adult paper diapers. • A safety evaluation of the process was performed for producing recycled pulp. • The contamination by unexpected chemicals must be considered when recycling. • A surrogate contamination test was performed using eight contaminants. • The evaluation followed the EFSA safety assessment for recycled PET. • Our results indicated there was no safety problem regarding this process. [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]

Deinking of recycled pulps is an important operation intended to provide pulps appropriate for making paper and paperboard products from recycled wastepaper. Conventionally, deinking of recycled pulp is conducted in a flotation cell equipped with an agitator. We have investigated the applicability of a new flotation cell based on a column without an agitator present to accomplish the deinking of typical wastepaper feedstocks and also a feedstock consisting of rejects from a conventional deinking cell. Experimental results on the deinking operation indicate that it is possible to achieve deinking of a mixture of photocopier and laserprinted paper in the column flotation cell. The performance of the column, as measured by the resultant pulp's brightness and ink particle size distributions, is comparable to that of a conventional laboratory cell which incorporates severe agitation regimens. Thus, it is found that the agitator can be eliminated by using the column flotation design which could yield significant electrical energy savings in addition to savings in capital costs and other operational and maintenance costs. A series of deinking experiments were also performed on a feedstock consisting of rejected waste obtained from a conventional cell in a pilot plant. We found that deinking of the rejected waste could yield significant usable fiber. This indicatesthe potential of the column flotation technique in enhancing the reuse of a waste component thus reducing the volume of deinking waste rejected into the environment. [ABSTRACT FROM AUTHOR]