Recycled Paper Pulp Research Articles

Advancing sustainable molded packaging: Integrating silica aerogel into recycled paper pulp for the fabrication of thermally and mechanically stable superhydrophobic composites

In recent years, the growing demand for sustainable packaging has significantly fueled the quest to explore novel approaches that enhance the applicability of renewable alternatives. This study leverages the unique properties of silica aerogel (SA) to address the limitations of traditional molded pulp products. By integrating SA into recycled paper pulp (RP), we aimed to improve water resistance, thermal stability, and mechanical properties. Composites were prepared with varying SA concentrations (1–10 %). Contact angle measurements showed enhanced hydrophobicity, with RP/SA3 % achieving a contact angle of 152.09°, compared to 122.39° for neat RP. The tensile index (TI) of RP/SA composites with 3 % SA increased by 21.09 % compared to neat RP, indicating better mechanical strength. Thermal conductivity significantly decreased, with RP/SA10 % reducing from 0.155 W m−1·K−1 in neat RP to 0.088 W m−1·K−1, a 43.2 % improvement in thermal insulation. Additionally, composites with 1 % and 3 % SA maintained high biodegradability, showing over 50 % degradation after six weeks in soil. These results suggest that incorporating SA into RP composites enhances their functionality without compromising biodegradability, offering a promising solution for sustainable packaging. As regulatory bodies emphasize resource management and waste reduction, the potential of these innovative and environmentally friendly packaging solutions becomes increasingly significant.

Development and Optimization of Chemical Deinking of Laser-Printed Paper

For the recycling paper process, the main problem is a high residual ink left on the paper, affecting the recycled paper's quality. Especially for laser-printed paper, ink strongly interacts with the paper fiber. A conventional chemical deinking has been used to remove laser ink with a high deinking efficiency but a low yield of recycled paper pulp. Recently, enzymatic deinking has gained attention due to its friendly environment. However, a complex procedure is required, and ink removal efficiency is lower than the conventional method. This research aims to simplify a chemical deinking process by decreasing reaction time, optimizing chemical components, and reducing experimental steps. Without pulping step, the laser-printed paper sheet was immersed in the chemical solution for a specific time, and the ink was removed by water spray. Results revealed that the chemical solution containing 1.5% sodium hydroxide, 2% sodium silicate, 1% hydrogen peroxide, and 0.3% tween-80 with a reaction time of 5 min at 60°C gave the highest paper yield of 97.3% and the lowest dirt count of 89.0 mm2/m2. The final product was still in the form of a paper sheet.

Morphological Differences between Virgin and Secondary Fibers

The properties of the fibers determine the quality of the pulp and, thus, the quality of the paper made from it. Recognition of properties, which fiber and paper pulp should be characterized by, in order to achieve required paper properties, is, therefore, a subject of research and interest of many papermaking research experts and scientists. Fibers are subject to deformation and possible weakening under the influence of chemical and mechanical factors, and therefore the quality of the fibers decreases each time they are used in production when it comes to recycled pulps. Then again, the key factor determining the quality of the primary fiber is the degree of pulp delignification. In the article, an attempt was made to define the impact of delignification of virgin pulp on morphological properties of fibers, and compare them with the properties of recycled paper pulp, in order to find correlations. The current economic and raw material situations in the wood market force one to seek new solutions to limit the use of virgin fibers, which is extremely important for the economy of the paper mill, environmental protection and raw material management.

Comparison of the sound absorption properties of acoustic absorbers made from used copy paper and corrugated board

Due to the increasing demand for eco-friendly, inexpensive sound absorbers, this study investigated composites made from recycled paper pulp and urea-formaldehyde adhesive. By varying the pulp contents, five samples from used copy paper and five samples from used corrugated board were fabricated. For the same type of porous absorber, one with a lower bulk density has a higher total porosity, resulting in a higher sound absorption coefficient (SAC) spectrum. Sound-absorbing performance of copy paper composites with bulk densities below 442.4 kg/m3 and corrugated board composites with densities of less than 474.8 kg/m3 can be alternatives to commercial polyurethane foam of the same thickness. The noise reduction coefficient (NRC), as well as the average SAC of all corrugated board composites at medium (αM) and high (αH) frequencies were greater than those of copy paper composites. However, the average SAC at low frequency (αL) was not explicitly different for copy paper and corrugated board composites. In conclusion, corrugated board composites are a better candidate as sound absorbers than copy paper composites with the same pulp content.

Producing Direct Food Packaging Using Deinked Office Paper Grades—Deinkability and Food Contact Suitability Evaluation

Paper recycling is the most eco-efficient waste management option, since the use of recycled fibers reduces the need for virgin wood fiber and lowers energy consumption, and hence has a positive effect on the environment. The use of recycled paper is by far the highest in the packaging industry. In food packaging production, recycled paper is often favored over paper and board made from virgin fibers. However, due to the possible hazardous chemicals that can be found in recycled paper, there is a dilemma of how to overcome food safety issues while making food packaging more circular. The objective of the study was to determine if deinked office paper grades could be used as an alternative fiber source in the production of food packaging white top linerboards. For that purpose, three different types of digitally printed papers were submitted to a chemical deinking flotation in laboratory conditions, and the handsheets formed after each recycling trial were tested on the suitability for direct food contact. Evaluation of deinkability for each group of recycled prints was performed, as well. Deinkability was evaluated by calculating the flotation yield, pulp’s brightness and whiteness increase, ink elimination factor, determination of residual ink area, as well as ash content elimination. Food safety evaluation was performed by determining the content of heavy metals (Cd, Pb, Hg, and Cr VI), primary aromatic amines, diisopropylnaphthalenes (DIPN), phthalates, and polychlorinated biphenyls (PCB) from aqueous or organic solvent extracts of recycled paper pulp. The fastness of the fluorescent whitening agents was determined, as well. Of all evaluated deinking flotation efficiency parameters, only flotation yield and ash reduction by flotation were positively assessed. High content of residual ink particles detected after the flotation stage indicates that the flotation was not a successful method for the elimination of disintegrated ink particles, which was also confirmed by deficient results of ink elimination measurements and whiteness increase. Flotation proved to be the least efficient in the recycling of inkjet prints, where the lowest ink elimination, whiteness, and brightness values were achieved. As far as food safety assessment of deinked pulp is concerned, all tested deinked handsheets were found suitable to be used in direct contact with foods.

Hardened wood as a renewable alternative to steel and plastic

Hardened wood as a renewable alternative to steel and plastic

Utilizing a novel fungal enzymatic cocktail as an eco-friendly alternative for cellulose pulp biobleaching

Enzyme cocktails can alter the lignin and hemicellulose content in wood cell walls, improving the bleaching process during pulp production and offsetting the need for toxic chemicals. In this study, brown pulp was biobleached with a mixture of crude fungal extracts rich in xylanase and laccase, respectively produced from Aspergillus tamarii Kita and Trametes versicolor on waste materials. The optimal conditions for biobleaching were a mixture of xylanase and laccase crude extracts (1 to 2 v/v), at a temperature of 36 °C and a pH of 5.5. The treated brown cellulose pulp showed a reduction in the Kappa number by 1.83 points, representing an efficiency of 20.3%. In addition, the brightness increased by 4.65 points in comparison to the control. Hence, studies involving the application of the standardized cocktail during the hydrolysis of lignocellulosic residues, e.g., barley residue and sugarcane bagasse, led to the formation of 85 g/L and 25 g/L of reducing sugars, respectively. Moreover, the standardized cocktail caused greater deinking of the recycled paper pulp.

Evaluating effects of activated sludge and nanochitosan on physical and strength properties of recycled pulp

The present research aims to shed light on the effect of activated sludge (from a paper mill) and nanochitosan on the physical and strength properties of recycled pulp. Firstly, activated sludge was treated with 3% acetic acid for 30 min and then placed in a beaker for 90 min at 100 °C. Then, the ingredients were mixed and refined with recycled newsprint pulp in different proportions (0, 5, 10, and 15%). Finally, 2% nanochitosan was optionally added. Test specimens were prepared according to TAPPI standards with a basis weight of 120 g/m2, and their physical (water absorption) and strength (tear strength, tensile strength, burst strength, and ring crush test) properties were measured and compared. The results showed that with the increase of untreated activated sludge in recycled paper pulp, the indicators of tear resistance, ring crush test, and burst strength decreased and water absorption increased. Strength properties increased and water adsorption decreased when adding activated sludge treated with 3% acetic acid. Through the addition of nanochitosan to activated sludge treated with acetic acid, a significant increase in strength properties and a decrease in water absorption were observed.

Turning low-cost recycled paper into high-value binder-free all-cellulose panel products

In this work, the feasibility of producing low-cost, recyclable and biodegradable binderless all-cellulose fibreboards was demonstrated through the successful manufacturing of self-binding composites based on recycled paper and kraft fibres. These all-cellulose composites were made by a simple and environmentally friendly solvent-free mechanical fibrillation method using water as a processing aid. Kraft fibres and recycled paper pulp were mixed in a 30/70 w/w ratio and refined simultaneously in a Valley beater for different periods of time. The mechanical properties of the composites, consisting of a ‘matrix’ of recycled paper reinforced with kraft fibres, were highly dependent on the level of fibrillation of the kraft fibres. Optimal levels of fibrillation resulted in a good balance of self-binding properties and reinforcing efficiency. The hot-pressed all-cellulose panels exhibited a flexural strength of 75 MPa and a modulus of 5·9 GPa, which are impressive values compared with those of conventional fibreboard materials. In addition, these panels showed better water resistance than some existing wood panel products. These binder-free all-cellulose composites have potential as cost-effective sustainable alternatives to existing panel board products, as they are entirely made from renewable and recycled materials, which at the end of life can potentially be recycled or composted, making them perfectly fit for a circular economy.

Alternative Filler Recovery from Paper Waste Stream

The study is a first investigation of the feasibility to preserve recycled fillers (e.g. calcium carbonate, kaolin) from deinking paper sludge for newspaper production using an alternative approach respect to the actual methods. Deinking paper sludge was incinerated at 575 °C. The thermal stability of the incinerated sludge (ash) was evaluated by infrared analysis. Subsequently, the resulting ash was bleached by sodium dithionite. The particle size of the ashes was analysed by laser diffraction. The effect of recycled fillers on recycled paper pulp, after blending, was evaluated by the analysis of the physical and optical properties of the obtained paper sheets. Analysis showed the conservation of the calcium carbonate and other fillers’ molecular structure, both after incineration of the sludge and after bleaching. The dithionite treatment of the ashes resulted in ISO brightness levels of more than 70. The brightness was stable over one month. Paper sheets made by blending the bleached ashes with recycled paper showed an improvement of brightness and opacity but a decrease in terms of porosity and breaking length compared to paper sheets made without any filler. The proposed method still requires further studies to evaluate the economical application but offers an opportunity for the recycling of inorganic materials and valorisation of the sludge.

Mechanical characterization of blends containing recycled paper pulp and other lignocellulosic materials to develop hydromulches for weed control

Spreading of hydromulch as a crop management technique might show important advantages over plastic films for weed control, because it can be applied anywhere in a field, even in orchard and vineyard rows. In the present work, 24 blends were prepared by mixing paper pulp, from recovered paper and cardboard coming from paper mills, with different additives: (a) wheat straw, rice hulls, and substrate used for mushroom cultivation on the one hand as fillers, and (b) rice bran, white glue, sodium silicate, and powered gypsum on the other hand as agglomerating agents. The blends were tested with a texture analyser to evaluate their mechanical properties, testing the puncture resistance (24 blends) and the tensile strength (15 blends). Scanning electron photomicrographs of some blends were obtained in order to explore the relationship between their components and the mechanical properties. The results indicate that a blend prepared with paper pulp, wheat straw sieved at 2.5 mm and gypsum attained the highest stress resistance and tensile strength. An environmentally controlled experiment was performed on this and another hydromulch in which rice husk substituted wheat straw to evaluate their efficiency for reducing weed seedling emergence, using propagules of four common summer weeds. Compared with the control treatment performed, the hydromulches reduced seedling emergence from 64.6% to 95.9%. In general, the percentage of dead seedlings underneath was greater than that which passed through the barrier, making the hydromulches promising tools for preventing seedling emergence and for managing the weed seed bank in field conditions.

Functional Expression of a Thermostable Endoglucanase from Thermoascus aurantiacus RCKK in Pichia pastoris X-33 and Its Characterization.

Thermostable cellulases offer several advantages like higher rates of substrate hydrolysis, lowered risk of contamination, and increased flexibility with respect to process design. In the present study, a thermostable native endoglucanase nEG (EC 3.2.1.4) was purified and characterized from T. aurantiacus RCKK. Further, it was cloned in P. pastoris X-33 and processed for over expression. Expression of recombinant endoglucanase (rEG) of molecular size ~ 33kDa was confirmed by SDS-PAGE and western blotting followed by in gel activity determination by zymogram analysis. Similar to nEG, the purified rEG was characterized to harbor high thermostability while retaining 50% of its initial activity even after 6- and 10-h incubation at 80 and 70°C, respectively, and exhibited considerable stability in pH range 3.0-7.0. CD spectroscopy revealed more than 20% β-sheets in protein structure consistently when incubated upto 85°C as a speculated reason for protein high thermostability. Interestingly, both nEG and rEG were found tolerant up to 10% of the presence of 1-ethyl-3-methylimidazolium acetate [C2mim][OAc]. Values of the catalytic constants Km and Vmax for rEG were recorded as 2.5mg/ml and 303.4µmol/mg/min, respectively. Thermostability, pH stability, and resistance to the presence of ionic liquid signify the potential applicability of present enzyme in cellulose hydrolysis and enzymatic deinking of recycled paper pulp.

Erratum to: Stabilization of mineral oil hydrocarbons in recycled paper pulp by organo-functionalized mesoporous silicas and evaluation of migration to food

Erratum to: Stabilization of mineral oil hydrocarbons in recycled paper pulp by organo-functionalized mesoporous silicas and evaluation of migration to food

Stabilization of mineral oil hydrocarbons in recycled paper pulp by organo-functionalized mesoporous silicas and evaluation of migration to food

The occurrence of mineral oil hydrocarbons (MOH) in cellulose-based packaging is mainly due to the offset printing process where MOH are used as a ink pigments’ solvent. The MOH migration from paper/paperboard to food is matter of concern for EFSA, members state authorities, consumers, and food industry. In this study, the feasibility to stabilize MOH by adding a sorbent into recycled paper obtained through a common washing process was investigated and the migration to wheat flour/Tenax® assessed. Among several white/pale yellow porous materials, organo-modified powder silica MCM-41-Si(CH3)3 showed the best combination between affinity for MOH (184% dw) and stability to thermal regeneration. A freshly issued newspaper with >3000 mg MOH kg−1 was used to produce recycled paper at a laboratory-scale plant. MCM-41-Si(CH3)3 was added at the pulping step (1% dw) and the sorbent-enriched pulp handled according to a washing paper production process with no effect on the paper optical brightness. The MOH content of the wheat flour in contact with the sorbent-enriched paper under accelerated migration conditions (15 days at 40 °C) resulted 20% of that contacted with control paper (4.3 ± 1.1 and 20.4 ± 5.5 mg kg−1, respectively), despite its contamination was 24% higher than the control. On the contrary, Tenax® contamination resulted 56.0 ± 10.0 and 47 ± 14.0 mg kg−1 when exposed to sorbent-enriched and control paper, respectively.

A flexible electrode based on recycled paper pulp and reduced graphene oxide composite

In this work, a facile and scalable method to produce cellulose based flexible electrodes is introduced. Composite paper electrodes from recycled paper pulp and graphene oxide (GO) were fabricated by solvent casting at room temperature. Electrical conductivity and surface chemistry of the nanocomposite samples were tuned by chemical reduction of GO. Contact angle measurements showed a change in water droplet angle from 0° to 89° depending on the GO content and degree of reduction. Electrical measurements depicted high electrical conductivity with an ideal Ohmic behavior for the composite paper electrodes. Sheet resistance of the sample containing 4 wt% of reduced GO (rGO) was 1.649 × 103 Ω/□ which is 5 orders of magnitude higher than paper pulp. The obtained sheet resistance for the sample with 16 wt% rGO was remarkably high for cellulose based conductive electrode compared with previously reported data. Moreover, the sample containing only 0.5 wt% of rGO showed 40% higher modulus than the neat recycled paper in tension. The resultant nanocomposite can be introduced as a highly conductive and low cost flexible electrode.

Optimization of Polymer-Amended Fly Ash and Paper Pulp Millings Mixture for Alternative Landfill Liner

In 2012 the City of Flagstaff partnered with researchers at the Dept. of Civil and Environmental Engineering at Northern Arizona University to successfully develop a mix design utilizing sludge derived from the manufacturing of recycled paper pulp sludge (PPS) and fly ash as a component of a landfill cap. This research has been extended to explore the addition of polymers to the mix of waste materials in order to optimize a design that would be suitable as a component for an EPA Subtitle D-approvable landfill liner. Cinder Lake Landfill (CLL) serves several communities in Northern Arizona and is managed by the City of Flagstaff. CLL does not have a reliable source of clay needed to construct a required landfill liner, which is necessary for the upcoming 108-acre landfill expansion. However, CLL receives approximately 80 tons of recycled PPS daily from the local tissue manufacturing plant. PPS is currently used as daily cover and was tested for use as part of a landfill cap, as noted above. Incorporating polymers in alternative materials such as PPS and fly ash has the potential to meet performance criteria and be approved by state and federal regulators, and has the potential to save the City millions of dollars over conventional composite liners of geomembrane and clay. Different mixtures of PPS, fly ash and three different polymers are currently being subjected to testing for the following: Water Content, Specific Gravity, Porosity, Organic Content, Atterberg Limits (plasticity), Proctor Compaction, Consolidation, California Bearing Ratio, Shear Strength, Gas Permeability, and Liquid Permeability. The optimal mixture of PPS and fly ash will be blended with a range of polymer concentrations. The goal is to find an optimal mix of PPS, fly ash, and polymer to achieve regulatory standards related to permeability, along with other desirable properties such as strength and flexibility. The optimum mixture(s) will then be subjected to field trials, scheduled to begin in 2016, in which test cells will be created at CLL. The liner will be constructed with the optimized mixture(s), and the cells will be operated as landfills for 1-2 years. Results from lab and field testing will be submitted to federal and state regulators for consideration as an alternative liner approach.

Prediction of acoustic performance of banana fiber-reinforced recycled paper pulp composites

This paper presents an investigation conducted on the development of banana fiber-reinforced paper pulp biocomposites. The investigations focus on parameters, such as fiber length, fiber volume fraction, and composite thickness, those affect the properties of the biocomposites. Regression models, using Box and Behnken experimental design, have been developed to predict acoustic performance of the biocomposite along with the analysis of these parameters. The correlation coefficient between observed and predicted values was found to be 0.95. The maximum Noise Reduction Coefficient is observed (through experimental) in the bulk density of 154 kg/m3 at frequency ranges between 250 Hz and 4000 Hz with the average value of 0.55.

Websites of Note

Websites of Note

Production of xylanases by mangrove fungi from the Philippines and their application in enzymatic pretreatment of recycled paper pulps

Mangrove fungi are vastly unexplored for enzymes with industrial application. This study aimed to assess the biocatalytic activity of mangrove fungal xylanases on recycled paper pulp. Forty-four mangrove fungal (MF) isolates were initially screened for xylanolytic activity in minimal medium with corn cob xylan as the sole carbon source. Eight MF were further cultivated under submerged fermentation for the production of crude xylanases. These crude enzymes were then characterized and tested for the pretreatment of recycled paper pulps. Results showed that 93 % of the tested MF isolates exhibited xylanolytic activity in solid medium. In submerged fermentation, salinity improved the growth of the fungal isolates but did not influence xylanase production. The crude xylanases were mostly optimally active at 50 °C and pH 7. Changes in pH had a greater effect on xylanase stability than temperature. More than half of the activity was lost at pH 9 for majority of the crude enzymes. However, two thermophilic xylanases from Fusarium sp. KAWIT-A and Aureobasidium sp. 2LIPA-M and one alkaliphilic xylanase from Phomopsis sp. MACA-J were also produced. All crude enzymes exhibited cellulase activities ranging from 4 to 21 U/ml. Enzymatic pretreatment of recycled paper pulps with 5 % consistency produced 70-650 mg of reducing sugars per gram of pulp at 50 °C after 60 min. The release of high amounts of reducing sugars showed the potential of mangrove fungal crude xylanases in the local paper and pulp industry. The diverse properties shown by the tested crude enzymes also indicate its potential applications to other enzyme-requiring industries.

Production of Multi-Fiber Modifying Enzyme fromMamillisphaeriasp. for Refining of Recycled Paper Pulp

Enzymatic modification of pulp is receiving increasing interest for energy reduction at the refining step of the paper-making process. In this study, the production of a multi-fiber modifying enzyme from Mamillisphaeria sp. BCC8893 was optimized in submerged fermentation using a response-surface methodology. Maximal production was obtained in a complex medium comprising wheat bran, soybean, and rice bran supplemented with yeast extract at pH 6.0 and a harvest time of 7 d, resulting in 9.2 IU/mL of carboxymethyl cellulase (CMCase), 14.9 IU/mL of filter paper activity (FPase), and 242.7 IU/mL of xylanase. Treatment of old corrugated container pulp at 0.2-0.3 IU of CMCase/g of pulp led to reductions in refining energy of 8.5-14.8%. The major physical properties were retained, including tensile and compression strength. Proteomic analysis showed that the enzyme was a complex composite of endo-glucanases, cellobiohydrolases, beta-1,4-xylanases, and beta-glucanases belonging to various glycosyl hydrolase families, suggestive of cooperative enzyme action in fiber modification, providing the basis for refining efficiency.