Pulp Consistency Research Articles

Energy absorption and resilience in quasi-static loading of foam-formed cellulose fibre materials

To avoid microplastic pollution, there is an urgent need to replace fossil-based cushioning materials in packaging with easily recyclable alternatives. Here, we investigated the potential of lightweight cellulose fibre materials as a solution for mechanical protection. The quasi-static compression was studied among a vast set of 129 different foam-formed trial points with material density ranging from 21 kg/m3 to 123 kg/m3. The trial points included two different fibre types, bleached softwood kraft pulp (BSKP) and bleached chemithermomechanical pulp (CTMP), with varied refining level, pulp consistency, foaming conditions, surfactant type, strength additives, and final material density and thickness. Besides a correlation analysis of factors affecting compression stress and resilience, the results were reflected against a new theoretical prediction of energy absorption for an ideal low-density random fibre network. The theory predicts the initially-high cushion factor to rapidly drop down to the level of 4‒5 at 40‒80% compression. A similar behaviour was seen among the actual samples, despite their various non-ideal features. At 50% compression, the average cushion factor across the whole data set was 4.84 ± 0.10, being close to the theoretical prediction of 4.61 for the ideal case. The smallest cushion factor of 3.6 was found for a CTMP sample. The recovery from compression varied slightly among the samples and appeared highest for the material density of 60‒100 kg/m3, following the predicted proportion of non-buckled fibre segments. According to the results, cellulose fibre-based cushions have a soft initial response, which is preferable for fragile items.Graphical abstract

Factor and cluster analyses of the structure of correlations between high consistency pulp properties during refining and paper strength characteristics

This article analyses high-consistency pulp refining using a disk refiner. During the experiment, the size of the gap between the rotor and stator cutters (0.5 to 1.5 mm), rotor speed (2,000 to 2,500 rpm), pulp consistency (10 to 20%), and freeness value (15 to 60 °SR) of the pulp were varied. The refining results were characterised by changes in 10 output parameters: morphological properties of cellulose fibres (average length, width, fibrillation index, water retention value, average kink angle, and coarseness) and the physical and mechanical characteristics of handsheets (breaking length, bursting strength, tearing resistance, and folding endurance). A total of 56 observations were made on the samples. Factor and cluster analysis methods were used to study the structure of correlations between the output parameters. More than 96% of the total dispersion of all output parameters was due to a change in two latent (hidden) factors: the first one was responsible for 79.6% of the dispersion and is presumably identified as the degree of external fibre fibrillation and the second one (16.6% of the dispersion) as fibre flexibility (including coarseness and average kink angle).

Physicochemical properties, Steady and Dynamic Rheological Measurements of Sour Guava (Psidium Araca) Pulp

Sour guava (Psidium araca) is a tropical fruit of the tropical region, recognized for its typical taste and nutritional composition. This work aimed to investigate how temperature affects the physicochemical and rheological characteristics of the sour guava pulp subjected to controlled scalding conditions. Physicochemical properties of fresh and scalded pulp were analyzed. Rheological analyses of steady shear rate in function of temperature (5 - 80 ºC) and viscoelastic properties were done. Scalding process did not affect the physicochemical properties (total acidity, soluble solids, pH, and maturity index) of the pulp, nevertheless, a 30% decrease in total phenolic compounds was observed. Pulps exhibit a non-Newtonian behavior type shear thinning described by using the Herschel-Bulkley model (R2 > 0.970). The influence of temperature was described by an Arrhenius-type equation on the pulp consistency index. The pulps displayed characteristics of a weak gel, where the storage modulus surpassed the loss modulus. A power function of the oscillatory frequency accurately described the storage and loss moduli, indicating elastic properties. The results showed that the sour guava pulp is suitable for use as a raw material for the development of processes for the manufacture of food products.

Recycling of TEMPO-mediated oxidation medium and its effect on nanocellulose properties

The potential of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy)-mediated oxidation (TMO) to produce cellulose nanofibrils (CNFs) is hindered using costly and environmentally harmful catalysts, limiting its large-scale implementation. To promote sustainability, the TMO medium should be reused but there is a lack of knowledge on this process. The novelty of this research is the identification of the key parameters that affect the recirculation of the TMO medium, and their impact on the quality of the oxidized pulps and CNF products. Contrary to previous hypothesis, results show that the accumulation of salts is not a key parameter; instead, the pulp consistency during oxidation plays a vital role since concentrations higher than 10 g/L led to better CNF quality. Thus, reusing 75 % of the reaction medium, when high pulp consistency is used, does not alter the CNF properties. By reusing the reaction medium up to six times, the catalyst dose is dramatically reduced by >90 % for TEMPO and 80 % for NaBr, compared to the conventional process (0.1 mmol of TEMPO/g and 1 mmol of NaBr/g without medium reuse). Additionally, the high consistency oxidation enables a reduction of >80 % in the reaction time and effluent, and thus a threefold increase in CNF production.

Optimized Lytic Polysaccharide Monooxygenase Action Increases Fiber Accessibility and Fibrillation by Releasing Tension Stress in Cellulose Cotton Fibers.

Lytic polysaccharide monooxygenase (LPMO) enzymes have recently shaken up our knowledge of the enzymatic degradation of biopolymers and cellulose in particular. This unique class of metalloenzymes cleaves cellulose and other recalcitrant polysaccharides using an oxidative mechanism. Despite their potential in biomass saccharification and cellulose fibrillation, the detailed mode of action of LPMOs at the surface of cellulose fibers still remains poorly understood and highly challenging to investigate. In this study, we first determined the optimal parameters (temperature, pH, enzyme concentration, and pulp consistency) of LPMO action on the cellulose fibers by analyzing the changes in molar mass distribution of solubilized fibers using high performance size exclusion chromatography (HPSEC). Using an experimental design approach with a fungal LPMO from the AA9 family (PaLPMO9H) and cotton fibers, we revealed a maximum decrease in molar mass at 26.6 °C and pH 5.5, with 1.6% w/w enzyme loading in dilute cellulose dispersions (100 mg of cellulose at 0.5% w/v). These optimal conditions were used to further investigate the effect of PaLPMO9H on the cellulosic fiber structure. Direct visualization of the fiber surface by scanning electron microscopy (SEM) revealed that PaLPMO9H created cracks on the cellulose surface while it attacked tension regions that triggered the rearrangement of cellulose chains. Solid-state NMR indicated that PaLPMO9H increased the lateral fibril dimension and created novel accessible surfaces. This study confirms the LPMO-driven disruption of cellulose fibers and extends our knowledge of the mechanism underlying such modifications. We hypothesize that the oxidative cleavage at the surface of the fibers releases the tension stress with loosening of the fiber structure and peeling of the surface, thereby increasing the accessibility and facilitating fibrillation.

High consistency enzymatic pretreatment of eucalyptus and softwood kraft fibres for regenerated fibre products

Sustainability of regenerated cellulosic fibres could be improved by using paper grade pulp instead of dissolving pulp as a raw material in the fibre spinning process. However, the use of paper grade pulp calls for adjustment of the molar mass distribution (MMD) prior to dissolution to obtain good solubility and spinnability. The objective of this work was to adjust MMD of softwood and eucalyptus kraft pulps by enzymatic treatments at high pulp consistency. The reduction of the MMD of eucalyptus kraft pulp was found to require a nearly 30-fold higher dose of endoglucanase compared to the treatment of softwood pulp. Interestingly, when xylanase was used in combination with endoglucanase to treat eucalyptus kraft pulp, 27% of the xylan was dissolved and the required endoglucanase dose could be decreased from 0.57 to 0.06 mg/g. The endoglucanase dose could be further decreased to 0.028 mg/g when 67% of xylan was removed chemically before the enzymatic treatment. This suggests that xylan hinders endoglucanase action on eucalyptus kraft pulp. For softwood pulp, the addition of xylanase and mannanase had only a minor impact on the treatment efficiency. The different processabilities of softwood and eucalyptus kraft pulps are suggested to originate from the deviating cellulose accessibility which is affected by the fibre structures as well as their hemicellulose composition and localisation. The effect of the treatment consistency was further studied with softwood kraft pulp. Treatment at high consistency clearly enhanced the endoglucanase action whereas the effect of solid content on the hemicellulase action was modest.

New System for Efficient Removal of Lignin with a High Proportion of Chlorine Dioxide

Chlorine dioxide is used extensively as the bleaching agent in the clean pulp bleaching process. To further improve the efficiency of chlorine dioxide delignification, this study discusses the effect of a new system of a high proportion of chlorine dioxide on lignin removal. When the mass ratio of chlorine dioxide to lignin was 4 in this system, 50% of lignin was removed in a short time. To optimize the new bleaching system, the effects of temperature and pulp consistency on the new system were studied. The ratio of lignin removed was 50% when the reaction time was 30 min, temperature was 25 °C, and the pulp consistency was 5%. Compared with traditional chlorine dioxide bleaching, high proportion of chlorine dioxide bleaching can shorten the reaction time by 50%, reduce the reaction temperature to 25 °C, and greatly reduce energy consumption and adsorbable organic halogen (AOX) production by 45%. The new system provides a novel idea for clean bleaching of pulp.

The quality of potato tubers and yield by using fertilizer systems

Potatoes belong to the most important food crop, are a useful food product and a valuable raw material for food products. The quality of potato tubers depends on the fertilizer’s application and the doses of the active substance. The study about the influence of fertilizer systems (organic, organic-mineral, mineral) on the productivity and quality of potato tubers is relevant. The effect on the quality of potatoes when using fertilizer systems depends on the soil and climatic conditions of the natural cultivation zone, biological characteristics of the variety and other factors. Starch is an indicator of the quality of potato tubers. The starch content in potato tubers increases with the use of mineral fertilizers. The starch content in tubers of early-ripening potato varieties increases their marketability. During heat treatment, the size of starch grains affects the consistency of potato pulp.

Accessibility Improvement of Bleached Kraft Pulp by Alkali Treatment

Super absorbent polymer (SAP) is used in various fields as a super absorbent material that can absorb a large amount of moisture relative to its weight, but it is not biodegradable and causes environmental pollution. Accordingly, the necessity of cellulose-based substitutes, a natural resource material, is being emphasized. Alkaline solvent based cold caustic extraction (CCE) is one of the fibers swelling treatment methods, which improves the accessibility of OH groups by destroying the structure of the cellulose crystal region and breaking the cellulose chain. The swelling of the fibers affects the reactivity between the pulp and chemicals. In this study, the alkali dosage was adjusted to 5%, 10% and 15% during CCE treatment, and the experiment was conducted by adjusting the pulp consistency to 1%, 5% and 10%. The treatment temperature was adjusted to room temperature and 60℃. The yield of the treated pulp under each condition, alpha-cellulose and sugar composition were analyzed to determine the pulp purity and chemical composition according to the CCE treatment conditions. For the structural characterization of the pulp, XRD, FE-SEM and specific surface area measurements were performed to confirm the swelling of the cellulose through alkali treatment and the characteristics of the pulp according to the increase in voids.

Spectral analysis and kinetic studies of enzymatic delignification of kraft wood pulp by xylanase

The traditional bleaching methods used chlorine as bleaching agent which produced large amount of chlorinated organic compounds including dioxins which are persistent environmental pollutants. The alternate methods using peroxides and enzymes were developed to achieve total chlorine free bleaching. The xylanase enzyme was used as bleaching agent in this study. The delignification study was performed to evaluate the optimum conditions required for obtaining minimum kappa number of the pulp to remove maximum lignin from the wood fibres. The interactions of various factors such as pulp consistency, enzyme dosage and temperature were studied. The best conditions for enzymatic bleaching obtained were 10% consistency, 50 IU of enzyme dosage and 52oC in the range studied. The predicative mathematical models were developed for enzymatic bleaching. The activation energy for xylanase delignification of paper pulp was 13.989kJ/mol. The significant functional groups in bleached pulp samples were analysed using Fourier transform infrared spectroscopy and the surface morphology of pulp fibres was studied using Scanning electron microscopy images.

Comparison of the usage of fines and PCC pigment in handsheets

PurposeThis paper aims to investigate the influences of fines and precipitated calcium carbonate (PCC) pigment and their contents on the fundamental properties of handsheets and also evaluate these results in terms of mechanical and chemical data.Design/methodology/approachA design research approach has been based on the production of various laboratory handmade papers. Any of the paper additives were not added to the paper web to compare the results of the effects of fines and PCC pigment in a literal way. For this purpose, the target grammages of handsheets and the production variables such as pulp consistency, temperature and other variables of formation, pressing and drying processes were kept constant and studied meticulously.FindingsThis study is confirmed that with the addition of fines to the pulp of the control handsheets, an increase of up to 125% has been observed in the tensile index values, while a decrease of up to 30% has been observed with the addition of PCC pigment as filler. The tensile results have been changed depending on the pulp content and hence chemical bonds formed in the paper web. These mechanical changes have been explained by correlating with the data of FT-IR spectrums. Especially, the variations have been seen at 950–1150 cm−1, which referring to C-OH and C-O-C stretching vibrations.Originality/valueThe originality of this work is based on understanding and comparing the effects of fines and the effect of PCC pigment as a paper filler on the structural and chemical characteristics of laboratory-made handsheets.

A review of process and wastewater reuse in the recycled paper industry

Water plays several essential roles in paper manufacturing. It serves as a suspending medium and a swelling agent for the fibres, dispersing and forming them into a uniform sheet during the initial stage of the papermaking process. It also serves as the solvent for a variety of chemicals and additives to adjust product quality. Water reclamation has always been a momentous task in the pulp and paper (P&P) industry. The main driving forces for the adoption of process water and wastewater treatment technologies are environmental regulations, costs of wastewater discharge and the high cost of freshwater. Recent developments have made it possible to not only reduce water consumption and environmental impacts, but also to recover treated water and valuable compounds such as fibres, making water recycling technologies cost-efficient. Thus, the economic viability of these technologies has played an important role in their application. The technologies applied, the level of reduction in water consumption and the extent of water recycling are different for each mill, since the quality of whitewater and wastewater varies depending on the raw materials and products. The maintenance of the balance between partial equilibria of process variables such as water flowrates, pulp consistency, physiochemical, thermal and microbiological properties through water management is important for maintaining efficient water use and lowering the need for consumption of additional fresh water.

USING OF LACCASE IN PAPERMAKING PROCESS FROM OLD CORRUGATED CONTAINER (OCC) PULP

Old Corrugated Container (OCC) is one of the most potential raw material for paper and paperboard manufacture but it has some disadvantage of a continued decrease in the quality of the fiber during the recycling process. It’s caused by decreasing of carboxyl groups when the fibers undergo drying, resulting in decreased ability for swelling, thereby reducing the ability of the bond between the fiber and the fiber strength. Modification of waste paper using laccase enzyme may increase the fiber content of the carboxyl group of waste paper, therefore will increase paper strength. Experiments carried out with the addition of laccase in various dosage paper stock originating from OCC by 5% pulp consistency. 80 g/m Laboratory sheets, was made from stock, then analyzed by tensile index, burst index, wet tensile index, the content of carboxyl groups and SEM analysis. The experimental results showed addition of 50 U/g laccase at OCC giving optimum value for physical properties. Keywords : OCC, laccase, Physical properties, Carboxyl groups, SEM. DOI: 10.7176/CMR/13-3-04 Publication date: November 30 th 2021

Effect of pulp consistency during refining on physical and mechanical characteristics of handsheets

At the moment, the pulp and paper industry produces a wide variety of types of paper and board, which can serve as an alternative to plastic packaging products. The main requirement for paper packaging is high strength properties, which include: breaking length, resistance to breaking, bursting and tearing. The required strength properties can be ensured at the stage of refining the semi-finished product from which the paper product will be made by changing the consistency of the pulp. Since the influence of the consistency of the pulp during refining on the strength characteristics of the finished product has not been fully studied, it was of interest to find out how the strength properties of castings change when refining the pulp with a change in concentration.

Biological approach in deinking of waste paper using bacterial cellulase as an effective enzyme catalyst

Paper has become the basic elixir in everyone's activities and usage of paper has increased day by day, the waste generated by paper is also enormous. The primary source of paper is wood (tree) yet, waste paper is environmentally good and biodegradable; however, it is the primary source of deforestation. Current research aims to find an alternate way to recycle paper in the biological approach. Hence in our work, twelve cellulose-producing bacteria were isolated, out of which one bacterial strain proved to be the best. Cellulase enzyme was extracted and purified, and used for enzymatic de-inking of photocopy papers. The optimal conditions for cellulase synthesis were at 60 °C, glucose as the only carbon source, and potassium nitrate as the nitrogen source. The enzyme demonstrated excellent de-inking at a lower pulp consistency of 3% with a 20% enzyme dose. The cellulose and hemicellulose levels decreased, which can be attributed to fiber breaking. Further, the changes in the functional groups identified by Fourier-transform infrared spectroscopy analysis and the changes in the surface morphology of the pulp fibers were obtained using scanning electron microscope analysis.

Study of bleaching of old newsprint recycled paper: reproduction of newspaper material

With the utilization of used newspaper into the paper making industry, bleaching has been an area of concern to obtain a balance between desired brightness and the amount of treatment it requires. Motivation of this study was to optimize bleaching of recycled newsprint fibers in terms of five variables namely hydrogen peroxide charge, amount of sodium hydroxide employed, pulp consistency, bleaching temperature, and bleaching time. Experimental work was conducted in the laboratory to simulate bleaching plant and it was found that higher peroxide charge is better for improvement in brightness, but it is uneconomical to increase peroxide charge indefinitely. The amount of hydrogen peroxide is added so that the residual peroxide at the end of the reaction is not less than 10% of the initially added peroxide. Sodium hydroxide provides alkalinity which is very important for making the fibers flexible and softening of ink particles but it also contributes to pulp yellowing if residual hydrogen peroxide contents are lesser than the minimum required value. So, for 16 kg t−1 of hydrogen peroxide, 6 kg t−1 of sodium hydroxide prevented the brightness reversion in this study. Higher pulp consistency is better but unavailability of very high consistency pulp mixer in the industry is a limiting factor for higher than 30% pulp consistency. Temperature and time are quite interrelated and, with the given bleaching conditions, a temperature of 95 °C with 10 min residence time was found to be optimum for this study. It was also observed that multiple pre-washings increase brightness and save bleaching chemicals.

Eco-friendly bleaching of sugarcane bagasse with crude xylanase and pectinase enzymes to reduce the bleaching effluent toxicity.

Bio-bleaching effect on bagasse pulp using xylano-pectinolytic enzymes produced by a bacterial species was studied in order to evaluate the potential of these enzymes in paper industry. In this study, action of enzymes was maximum with xylanase/pectinase dose 7/1.75 IU/g, pulp consistency 1:12.5 g/L, pH 8.5, temperature 50° C and 180 min of treatment time. Under the optimized bio-bleaching conditions, removal of reducing sugars (6.15±0.05 mg/L), brightness (16.08%), whiteness (25.54%) and release of chromophores (hydrophobic and phenolic compounds and lignin impurities) were maximum, along with decrease in kappa number (26.28%), and yellowness (27.88%) values were obtained. Improvement in the various physical properties like breaking length (10.28%), burst index (29.55%), tear index (5.02%), double fold (14.89%), Gurley porosity (15%) and viscosity (8.6%), along with the reduction of chlorine dioxide dose by 27%, was also observed. There is also reduction in COD and BOD values of bio-bleached effluents by 27.62% and 20.52%, respectively. This is the first report on bio-bleaching of bagasse pulp using xylano-pectinolytic enzymes.

Study of collection samples of table watermel with unconventional pulp color

Relevance. The study of the collection is one of the main sources of replenishing the source material for the breeding process. The presence of the necessary genetic traits can speed up the breeding process. Therefore, at the Bykovskaya melon breeding experimental station, the genetic diversity of melon plants is assessed and promising samples are selected for use in breeding.Materials and methods. The object of research was samples of table watermelon with an unconventional color of the pulp. The aim of the work is to study and isolate the source material of watermelon for use in the breeding process to create new varieties and hybrids of melon crops. In the course of the study, 12 varieties of table watermelon were identified from 33 varieties of the collection nursery, which are sources of economically valuable traits. The selection was carried out according to the yield, the rate of entry into fruiting, taste, color of the pulp.Results. In the course of the research, the obtained samples of table watermelon with an unconventional color of the pulp were evaluated according to a set of economic characteristics in comparison with the standards: Zenith and Sinchevsky. The analysis of the tested samples made it possible to identify 12 samples by economically valuable traits: 3 samples by early maturity and taste: White sugar lump, White wonder, Golden revenge F1; 7 samples with a high dry matter content, in terms of yield and large fruit: Moon and stars yellowflesh, Sweet Siberian, Orangeglo, Daisy, Clay county yellow meat, Mountain sweet yellow, Tendergold; 2 samples for color and pulp consistency: Early moon beane Bakerlneek, Tenderweet orange. The selected samples meet the modern requirements of the industrial melon growing industry, resistant to stress factors of the environment, good taste and consumer properties.Findings. The obtained experimental data will be used to create a genetic collection of watermelon according to the traits that determine the economic value of the gene pool for further use in the breeding process.

The Dual Effect of Ionic Liquid Pretreatment on the Eucalyptus Kraft Pulp during Oxygen Delignification Process.

Oxygen delignification presents high efficiency but causes damage to cellulose, therefore leading to an undesired loss in pulp strength. The effect of ionic liquid pretreatment of [BMIM][HSO4] and [TEA][HSO4] on oxygen delignification of the eucalyptus kraft pulp was investigated at 10% IL loading and 10% pulp consistency, after which composition analysis, pulp and fiber characterizations, and the mechanism of lignin degradation were carried out. A possible dual effect of enhancing delignification and protecting fibers from oxidation damage occurred simultaneously. The proposed [TEA][HSO4] pretreatment facilitated lignin removal in oxygen delignification and provided fibers with improved DP, fiber length and width, and curl index, resulting in the enhanced physical strength of pulp. Particularly, its folding endurance improved by 110%. An unusual brightness reduction was identified, followed by detailed characterization on the pulps and extracted lignin with FTIR, UV, XPS, and HSQC. It was proposed that [TEA][HSO4] catalyzed the cleavage of β-O-4 bonds in lignin during the oxygen delignification, with the formation of Hibbert’s ketones and quinonoid compounds. The decomposed lignin dissolved and migrated to the fiber surface, where they facilitated the access of the oxidation agent and protected the fiber framework from oxidation damage. Therefore, it was concluded that ionic liquid pretreatment has a dual effect on oxygen delignification.

Potential of crude xylano-pectinolytic enzymes in bleaching of rice straw pulp for improving paper quality and reducing toxic effluent load generation.

The objective of this study was to check the potential of crude xylano-pectinolytic enzymes in bleaching of rice straw pulp, in order to reduce the toxic waste load for managing the environmental pollution. The xylano-pectinolytic enzymatic bleaching step for delignification was found to be most effective at pulp consistency 1:10 g/ml, xylanase:pectinase dose of 9:4 IU/ml, pH 8.5 and treatment time 180 min at temperature of 55 °C, and resulted in lowering of kappa number of the rice straw pulp by 15.29%. In subsequent bleaching stages, this enzymatic pre-bleaching treatment also resulted in 30% reduction of active chlorine dioxide dose without any loss of optical properties. Significant improvement in various physical properties of the enzymes treated pulp, tear index (15.43%), breaking length (11.11%), double fold number (25.92%), burst index (9.88%) and viscosity (13.63%), and Gurley porosity (39.86%) was also noticed. This approach resulted in reduction of BOD and COD values by 21.07% and 26.57%, respectively. This is the first study on the use of crude xylano-pectinolytic enzymes for bio-bleaching of rice straw pulp.