Volume 38, Issue 2

The uses of kraft lignin (KL), obtained from the black liquor (BL) in the pulping process, allow the production of activated carbon (AC), a product with high added value in the pulp mill. The AC can be used in three different sectors in a cellulose pulp mill: sectorial treatment of the cellulosic pulp bleaching filtrates; wastewater treatment; and in the treatment of water received by the mill. Thus, this article considers the steps in the production of AC, their types, and the advantages and challenges of its use in the kraft cellulose pulp mill as well as in other industries.

The biomass deconstructed by kraft process and the lignin dissolved in the black liquor are burned to generate energy in a pulp mill. This study used the black liquor from coffee parchment cooking, a residue from the coffee industry, to isolate kraft technical lignin. The parchment was subjected to the kraft pulping process to obtain pulps of kappa number 60 and 25, and the resulting black liquors were used for lignin extraction. Chemical characterization, elemental analysis and heating value of liquors and lignins were performed, as well as FTIR and Py-CG-MS analysis of lignins. The cooking provided liquors with similar characteristics, with lignin content of 31.67 and 32.63% for kappa 60 and 25 liquors, respectively. The extractions resulted in high purity lignin (92.35% for K#60 lignin and 93.96% for K#25 lignin). The higher heating values were 23.8 and 25.4 MJ/kg for K#25 and K#60 lignins, respectively. FTIR analysis showed characteristic peaks of lignin. Through Py-GC-MS, it was possible to observe the slight predominance of guaiacyl-type lignin, which can be an advantage depending on the application. It is possible to extract lignin from the black liquor obtained from the coffee parchment pulping to generate products with high-added value.

Pulping of rice straw was studied using mild nitric acid in mild conditions. Spent nitric acid was chosen as soil nutrient rather than followed by the liquor recovery. The rice straw was treated with 11.03% nitric acid at 90 °C for 3 h, yielded 53.09% pulp. Nitric acid treated rice straw pulp had high residual lignin and minerals. However, further treatment with 7% potassium hydroxide reduced the residual lignin and produced pulp with kappa number 20.36. The papermaking properties of the nitric acid followed by KOH treated pulp showed better quality than the nitric acid pulp. The spent nitric acid liquor was reused repeatedly, pulp yield decreased and residual lignin content increased in each step of spent nitric acid reusing. The spent nitric acid liquor and potassium hydroxide liquor-mixed together to get a neutral effluent liquor which was rich with potassium, nitrogen and biomass. The nutritional capacity of the effluent liquor was assessed by incubation with control soil. The labile form of organic carbon, nitrogen, potassium phosphorous and iron increased in the incubated soil.

The present work was based on analysis of the flow regime of fibre suspensions, that corresponds to furnishes and process conditions typically established for tissue paper manufacturing, i.e. , under the common range of stock consistencies at the machine headbox and most usual furnish compositions. The flocculation potential of fibre suspensions used for toilet papers, facial tissues, paper towels and table napkins were evaluated on the principles of analytical concepts for fibre agglomeration propensity. The results show crowding numbers from 5.0 to 69.0, depending on the type of fibre or fibre blending ratios. The findings regarding agglomeration factors indicate that flow regimes are mainly in semi-concentrated and around gel state zones but reached the concentrated flow regime, in extreme conditions of fibre morphology and stock consistency. The influence of hardwood and softwood mixture ratios on the fibre suspension features is shown and discussed for common formulations of tissue base paper. The effect of fibre length and coarseness on the flocculation potential and the impacts of fibre suspension flow regimes on the structural properties of tissue paper, such as the formation uniformity are discussed, demonstrating the reasons for the preferred use of high hardwood content in furnish balance for tissue paper manufacturing.

For coated paperboard with large deformations, there is limited knowledge on the mechanisms that lead to coating damage and on the key properties that affect damage. Large deformations produce complex non-linear mechanical responses which often result in significant internal damage. The objective of this work was to establish methods to directly measure local deformation at a fold using a stereo digital image correlation (DIC) technique and a folding device designed in-house. This allowed monitoring of deformation from both cross-section and surface views, from which curvature and strain could be analyzed. This approach allowed observation and quantification of the initiation and propagation of damage. Testing showed that elastic estimation of deformation is valid only at very small curvatures but is still qualitatively useful. It was found that CD fold line shows a lower strain than MD fold line at a given curvature, but it ultimately reaches a higher level of surface strain. Additionally, localized maximum surface strain was shown to correlate better with surface damage at fold than the average surface strain. Furthermore, the introduced discontinuity index can provide a useful tool to compare surface damage at fold even for paperboard samples with different thicknesses.

In order to solve the problem of bacterial resistance, increase the antibacterial performance and delay the aging of paper, the berberine modified trimethoprim carboxymethyl cellulose was prepared using trimethoprimethylate carboxymethyl cellulose as raw material and trimethoprimethylate lactate (TMP) as antibacterial modifier by Schiff Base reaction. At the same time, berberine (BBR) was used as graft monomer to prepare a multifunctional protective solution integrating strengthening, antibacterial and good biocompatibility. The optimal process conditions were determined by single factor experiment and response surface method. The structure and properties of the product were characterized by FT-IR, XRD, TG and SEM and the antibacterial properties were evaluated by AGAR disk diffusion method. The results showed that when the mass ratio of dialdehyde carboxymethyl cellulose and modified berberine was 7:15, reaction temperature was 40 °C, and pH was 6.0, the optimum synthetic conditions was obtained. And the minimum inhibitory concentration of the product against Staphylococcus aureus and Escherichia coli were 0.2 mg/mL, minimum diameter of antibacterial zone of 6.7 mm and 7.1 mm, respectively, with good antibacterial effect. This paper lays a foundation for further research on the safe and effective antiquities antibacterial agent, and provides a reference for its further development in paper protection.

In this work, we aimed to analyze suspensions of cationic starch by adding 5 wt%, 7 wt%, and 10 wt% of bentonite as a bilayer coating on kraftliner paper (85 g/m 2 ). The controls were doubly-wet-and-dry and uncoated kraftliner paper. In a coating machine, the formulations were applied until reaching a grammage of 15 g/m 2 and then dried at 103 ± 2 °C. The test was carried out about pH, solids content, and viscosity of the suspensions. The physical characteristics of the coated papers were evaluated, as well as their ability to block water, water vapor, and oil/grease. We also analyzed with scanning electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy. The packaging, having a water contact angle of up to 78° and 189 g/m² for Cobb, showed a low resistance to water, which is further responsible for decreased mechanical resistance. Nevertheless, the coating did not change the permeability to water vapor, however, bentonite promoted a decrease in wettability and Cobb value of the paper. The addition of 7 wt% bentonite to the cationic starch matrix promoted high oil resistance with 12 for kit-oil, while 10 wt% bentonite promoted greater pencil hardness, with a value of 8H. Bentonite strength and cationic starch showed good interaction, increasing oil resistance.

A never-dried (ND) fines-free softwood bleached kraft pulp was converted to air-dried and thermally dried handsheets, which were then disintegrated or sonicated in water under various conditions. These disintegrated or sonicated pulps were converted to handsheets and used to obtain fundamental data on paper recycling. The water-vapor-adsorption isotherms of the pulp and sheet samples after super-critical-point drying showed clear differences between the water volumes adsorbed by the ND pulp, once-dried pulp, and dried sheets at the same relative humidities above 50%. These differences are caused by hornification of the pulp and sheet samples during drying and recycling. Air and thermal drying of wet webs decreased the adsorbed-water-vapor volume by 7%–9% and 14%–18%, respectively, relative to that adsorbed by the original ND pulp. We hypothesize that the decrease in water-vapor-adsorption volume from that of the original ND pulp at relative humidities >50% reflects the degree of irreversible formation of hydroxyl groups in the originally hydrophilic hemicelluloses and crystalline cellulose microfibril surfaces in the pulp and sheet samples during drying and paper recycling. The water-vapor-adsorption isotherms of pulp and sheet samples can be used to quantify the degree of hornification or the amount of irreversible hydrogen bonds formed during paper recycling.

Waste paper, the use of which is increasing day by day as a raw material, has a heterogeneous structure as it contains non-fiber material from different sources. It is desired to have a homogeneous product when recycled. Within the scope of this study, the SEM images of the raw materials determined according to EN 643 standard and the products made with the recycling of these raw materials were examined, ash content, fines content and ash on sieve were stated and the results obtained by determining filler content (removed) and fiber fines (removed) were discussed. While the samples with the highest ash content were H3 and U3, the lowest samples were H6 and U9. It was determined that the samples with the highest fines content were H2 and U1, while the lowest samples were H4 and U2. While the samples with the highest ash on sieve were H3 and U3, the samples with the least were determined as H2 and U9. The filler content was highest in H1 and U3 samples, while the lowest was in H6 and U9 samples. The samples with the most fiber fines were found as H2 and U9, and the least as H1 and U3 samples.

Paper has been used in the field of hygiene for centuries. Tissue papers have low grammage, creped or non-creped surface, and consisting of one or more layers from virgin papers. Toilet paper, which has an important area of use, comes at the beginning of the tissue papers divided into various product groups. Its use has increased even more with the effect of the coronavirus pandemic. Increasing use of toilet paper causes clogging in sewers as solid waste. Because an important and large part of the sewage is composed of cellulosic structures. Therefore, the disintegration of toilet paper is an important issue. The main properties of toilet paper are characterized by grammage, thickness, polymerization degree, softness and wet tensile strength. This study, it was aimed to determine the relationship between the degree of polymerization, thickness, grammage, softness and wet tension strength of toilet papers, which accumulate in the sewer pipes and cause clogging, and their disintegration in tap water and pure water at environment of different pH levels. A great level and positive linear relationship was found between grammage and in disintegration pH9. It was determined a low level and positive relationship with wet tensile strength in disintegration tap water.

Approaches to obtain nanocellulose have been extensively suggested, and among the most competitive methodologies includes mechanical defibrillation, which results in a nanocellulose gel suspension that can be used in a variety of applications. However, standard procedures results in inhomogeneous fibre sizes due to its physical approach. Pre-treatments have been suggested, such as enzymes, but their cost is a disadvantage. In this work, we suggest the use of cryoslash for bleach kraft pulp using a simple methodology of embedding the dry kraft pulp in distilled water following by freezing at −80 °C, which was slashed using a common blender and submitted to an ultra-fine friction grinder. Samples were studied at various grinding steps 5, 15, 30, 60 and 120. Overall, the energy difference required to defibrillate with cryoslash was ∼3.26 kWh/kg at 30 steps and ∼6 at 120 steps, which was similar to enzymatic pre-treatment with nanofibrils significantly smaller. Cryoslash presented a unique C–H in plane structure from nanocellulose, related to a decrease in average size of fibrils, while crystallinity and thermal properties of nanocellulose remained stable at 60 steps, but mechanical properties increased until 120 steps along with the transmittance values related to the energy consumption curve.

In this study, the effect of different concentrations of calcium hydroxide (Ca(OH) 2 ) was evaluated as a pre-treatment for accelerated carbonation and its influence on the fibrillation of cellulosic pulps to obtain nanofibrils, and its application as a coating agent for papers. Eucalyptus (EUC) and Pine (PIN) unbleached cellulosic fibers were submitted to pre-treatment with Ca(OH) 2 at concentrations of 5 and 10% and subjected to accelerated carbonation, being subsequently mechanically fibrillated to produce cellulose nanofibrils (CNF). Pretreatment with calcium hydroxide followed by accelerated carbonation provided a 35% reduction in energy consumption. Cellulosic pulps EUC and PIN pretreated with calcium hydroxide showed higher fibrillation efficiency. There was a reduction in the cobb test values for papers coated with CNF in PIN. The WVP was lower for papers coated with CNF of EUC and control PIN. The CNF coating of EUC and PIN provided an oil barrier for the kit 11 solution. The CNF coating improved the dispersion of PVA and PVOH. The papers coated in this work have the potential to be used as packaging for fatty and oily foods or as a spreading agent for other industrial coatings.

In this experiment, we explored how to control the penetration of palmitoyl chloride in the gas grafting of PVOH-coated paper. When calcium carbonate was pre-coated, the gas grafting reaction of the PVOH-coated paper tended to be inhibited. It is believed that palmitoyl chloride is additionally consumed by moisture generated when calcium carbonate neutralizes hydrochloric acid gas, a by-product of the graft reaction, thereby inhibiting the graft reaction and reducing the hydrophobization efficiency by generating unreacted residual free fatty acids. Unlike calcium carbonate, the clay coating layer blocks the penetration of vaporized palmitoyl chloride and improves the gas grafting density of PVOH without moisture generation. The PVOH coating layer, where vaporized palmitoyl chloride penetrates, is thinly processed to avoid unnecessary graft reactions in the thickness direction, and the propagation of palmitoyl chloride in the gas phase is blocked by the clay-coating layer. In previous studies, an excess of 1400 mg/m 2 of palmitoyl chloride was required to secure strong hydrophobicity of less than 10 g/m 2 of Cobb hot water absorption. However, by pre-coating the clay, only 650 mg/m 2 of palmitoyl chloride, which was about a 53% reduction compared to previous studies, was sufficient to perform a strong hydrophobic treatment.

This study developed an efficient and green method for isolating and purifying lignin from black liquor (BL) using deep eutectic solvents (DESs). After the short and mild process (700 W microwave-assisted, 100 °C, DES: BL 1:5 (v: v), 30 min) using optimized DES (lactic acid (LA): choline chloride (ChCl) 10:1, molar ratio), the yield and purity of lignin obtained from 100 mL BL was 1.58 g and 88.12%, respectively, which was more efficient than the results of 1.18 g and 78.54% of the conventional process. Furthermore, more than 95% of initial results were obtained after three cycles. The composition and structure of DESs and conventionally purified lignin were slightly different. The solvent costs for both processes were also evaluated, showing that the DES process has great potential to replace traditional bulky and environmentally unfriendly procedures for lignin isolation and purification and to help develop new strategies for the potential added value of lignin.

In order to solve the conflict between precipitated calcium carbonate (PCC) filling and alkyl ketene dimer (AKD) sizing for paper, this study explored two new flocculation methods: AKD and PCC were flocculated separately in the process ((A)(P)F), while the two pre-flocs from AKD and PCC were blended in the process ((AP)F). The result showed that increasing the dosage of the flocculant cationic starch (CS) resulted in a significant growth in the median size of PCC flocs and reduction in the specific surface area, turbidity, the negative charge of Zeta potential, as well as the adsorption capacity of PCC to AKD. Consequently the sizing degree and filler retention rate of the handsheets rose markedly. With 125 mg g −1 of CS, compared with the conventional process, the filler retention rate for (A)(P)F grew up to 86.16%; the Cobb 60 values for both (AP)F and (A)(P)F declined, and the contact angle (CA) increased to 120.65° and 127.65° respectively. At the same time, the filler bondability factor (FBF) were increased due to the intensified bonding force between fibers, and resultantly the comparable mechanical properties of papersheets with a high level of filler retention was obtained from (AP)F and (A)(P)F flocculation processes.