Volume 40, Issue 1

Kraft lignin has high dispersity and low reactivity. This study aimed to obtain more homogeneous and modified chemical fractions from the application of fractionation methods using organic solvents and acid precipitation. Organic solvents used were ethyl acetate, ethanol, methanol and acetone. The pHs tested were 9, 7, 5, 3 and 1, by adding hydrochloric acid. The fractions were characterized of acid-soluble and insoluble lignin, carbohydrates, ashes, elemental analysis and by Py-GC/MS. All fractions obtained in both fractionation methods showed higher carbon contents, higher purity and lower S/G ratio than the corresponding initial materials, characteristics that are very favorable for the application in biorefinery. Acetone-soluble (sequential) and pH 1 (one-step) precipitated fractions are the most promising for carbon fiber production. Fractions soluble in ethyl acetate (one-step) and insoluble at pH 3 and 1 (sequential) appear to be the most appropriate for applications that require good oxidative properties. The fractions soluble in ethanol (one-step), methanol (one-step), acetone (one-step) and precipitated at pH 9 (one-step) and pH 5 (sequential) are the ones that allow better chemical substitution in obtaining bioproducts. Fractions soluble in ethanol (sequential) and precipitated at pHs 5 and 1 (sequential) are not of commercial interest due to their low yield.

The pulp and paper industry in Sweden annually produce millions of tons of side-stream materials as black liquor, pulp and paper mill sludge, sulfite liquor and lignosulfonate. These lignocellulosic based materials can be more utilized today in biorefinery processes with microorganisms to produce high-value products as lipids, proteins and biofuels. In this work, we used five side-stream materials as carbon source in fermentation with two oleaginous yeasts, Lipomyces starkeyi and Rhodotorula toruloides . We analyzed lipid production, fatty acid profiles, inhibitors, phenolics, free sugars and metals before and after batch fermentation in 2 L bioreactors. Steam-exploded hardwood media was used as reference as it’s known to be a good substrate for the oleaginous yeast species and after fermentation the lipid yield for R. toruloides was 17 % (w/w) and for L. starkeyi 13 % (w/w). The side-stream materials contained less than 30 % of free sugar compared to the reference media and the total lipid yield was thus less than 2.7 %, (w/w). R. toruloides utilized various sugars during fermentation and L. starkeyi mostly consumed glucose and xylose. Both yeast species also showed a possible ability to utilize various phenolics indicating their metabolic potential to convert depolymerized lignin along with wood-based sugars to lipids and proteins.

The properties of as-fired black liquor dictate kraft recovery boiler operation. If these properties could be forecasted, operations could be adjusted to optimize boiler performance. Here, we compare the performances of classic time series models and two state-of-the-art time series neural networks for forecasting as-fired liquor heating value, viscosity, and boiling point rise at a Canadian mill. Additionally, we show that, like classic time series models, autoregressive neural networks can be regarded as functions of unknown disturbances, which is useful in comparing model complexities. Our results show that classic time series models can accurately forecast as-fired liquor properties and that classic time series models perform comparably to state-of-the-art time series neural networks. We suspect this is due to the high autocorrelation of mill data that results from frequent measurements relative to long residence times. This autocorrelation is suspected to attenuate the cross-correlations between upstream disturbances and as-fired liquor properties. As a result, neural networks, which are useful for accommodating non-linear cross-correlations and dynamics, struggle to outperform classic time series models and may not always be appropriate for forecasting chemical process parameters.

The shortage of superior grade wood fibers is a prime problem faced by Indian pulp and paper industries. As a result, the pulp and paper industry find it difficult to withstand the competition in the market, which had grown extremely competitive. In order to increase the utilization of non-wood fibers resources in the production of high quality eco-friendly papers, dhaincha , a non-wood fiber resource has potential industrial application. In this research, pulp and paper were developed from Sesbania aculeata stem using kraft pulping followed by bleaching. Optimization of conditions for pulping was carried out by Response Surface Methodology. The relationship between three variables and three responses were studied using Box–Behnken experimental design. The developed pulp was evaluated for kappa number, brightness index, viscosity, FTIR and TGA. Then paper was developed by using optimized pulp and evaluated for physical properties. The statistical analysis (ANOVA) was carried out in order to establish the relationship between the concentration of NaOH, Na 2 S, treatment time and temperature with kappa number, brightness index and viscosity. The physical properties of pulp and developed handmade paper highlights the sustainable use of dhaincha plant in pulp and paper industry.

This work has focused on oxygen’s role in the delignification process within the context of pulp production. We have investigated the role of oxygen in a complex set of chemical reactions taking place during this process, including both oxidative and non-oxidative reactions. This study explores the impact of pH changes during the oxygen delignification process and the characteristics of the resulting pulps. Additionally, this research examines the effect of oxygen, by comparing conventional oxygen delignification with trials using air and nitrogen. Industrial softwood kraft pulps with a kappa number of 35 were subjected to delignification for 20–120 min under alkaline conditions. The resulting pulps were assessed for kappa number, intrinsic viscosity, fiber charge, and ISO brightness. An important observation from this research is the reduction in lignin molecular weight upon exposure to oxygen and air, suggesting depolymerization reactions facilitated by oxygen species, whereas nitrogen exposure results in less pronounced changes. This finding underscores the impact of oxygen in altering lignin structure, thus informing the selectivity and effectiveness of the delignification process.

The review focuses on application of chemometric modeling in raw material characterization and quantification of parameter in various steps of pulp and papermaking processes. These models are built by supervised or unsupervised machine-learning techniques. Chemometric models are predominantly developed with data from spectroscopic instruments like, Ultraviolet spectrophotometer (UV), Near Infrared spectrophotometer (NIR), Fourier Transform Infrared Spectrometer (FTIR), Raman Spectrometer etc. These spectroscopic data are large in size which are reduced by applying different dimension reduction techniques. Moreover, these data contain instrumental noise in most of the cases, and they are de-noised or smoothed by several preprocessing techniques for developing better performing models. Among the popular calibration techniques for classification, Soft Independent Modeling for Classification Algorithm (SIMCA), Discrimination Analysis (DA) are mentionable. Multiple Linear Regression (MLR), Principal Component Regression (PCR), Partial Least Square Regression (PLSR), Artificial Neural Network (ANN), Support Vector Machine (SVM) etc., are used for quantification of different physical, morphological and chemical properties of wood, pulp and paper properties. Based on chemometric models, sensors for online measurements of different parameters in pulping and papermaking processes are being developed in recent years. Through this review, better performing multivariate analysis based chemometric modeling techniques have been identified for determining different parameters by comparing the existing ones which could be used in different processes in pulp and papermaking industries.

Brownstock washing, a critical process in cleansing kraft pulp, removes dissolved lignin residues from the pulp after it has passed through the cooking digester. It plays a significant role in kraft pulp mills by enhancing economic efficiency and environmental sustainability. Improved washing efficiency leads to better pulp quality and more effective recovery of cooking chemicals. Our study aimed to better understand the impact of different chemical compositions in washing liquors on washing performance. We tested a range of washing liquors, including neutral solutions (deionized water, 1M NaCl, 3M NaCl, 1M Na 2 SO 4 ) and alkaline solutions (tap water, washing liquor composed of 0.35M NaOH and 1M Na 2 SO 4 , and white liquor with 50 g[OH]/l and 8.77 g[HS]/l). These liquors were evaluated for their efficacy in maximizing lignin extraction. Our findings suggest that salt solutions generally reduce washing efficiency. Deionized water and white liquor proved to be the most efficient washing agents, while high-concentration salts and those with high ionic strength negatively impacted washing efficiency. This suggests that brownstock washing may not be operating at its full potential.

Industrial oxygen-delignified and fully-bleached hardwood kraft pulps were treated with chemicals to provoke carbohydrates depolymerisation: ozone, hypochlorous acid, and cellulase. The degrees of polymerisation (DP) of cellulose obtained by pulp viscosity measurement in Cuen and by size-exclusion chromatography after direct dissolution in DMAc/LiCl indicated the extent of the chemical degradation inflicted to the fibres. Molar mass distributions (MMD) described the carbohydrates depolymerisation patterns. Fibre strength was assessed by measuring the zero-span tensile index at never-dried state. Fibre strength deterioration seemed to be mainly driven by the topochemistry of the cellulose degradation (homogeneous or localised), rather than by its intensity usually measured as an average DP loss. In fact, depolymerisation by cellulase was found critically detrimental to fibres strength whereas ozone and hypochlorous acid induced little harm to the fibres despite a significant cellulose depolymerisation. According to these results, in line with several past studies, fibre strength measurements should be performed systematically as the sole pulp viscosity is an inadequate indicator. Alternatively, albeit being insufficient strength predictors on their own MMD can give valuable insight on the topochemistry of the cellulose degradation, a key aspect when monitoring fibre strength preservation during pulping and bleaching.

The efficiency of mechanical pulping has long been of interest due to the large energy consumed by the process. Previous estimates of theoretical efficiency have accounted for less than 20 % of the energy employed. In this study, we make new estimates based on fracture mechanics and abrasion as the mechanisms of new surface creation. We postulate that fracture mechanics comminutes wood into fibres and creates pores in fibre walls. This consumes around 100 kWh/t. Abrasion peels surface material from fibres in the form of morphologically different fines particles. Based on abrasion theory, we estimate this specific energy to be around 1,330 kWh/t. Together, fracture mechanics and abrasion, account for about 70 % of the specific energy (2,000 kWh/t) to produce TMP for printing paper grades. We postulate that the remaining energy is consumed as hysteresis losses from viscoelastic strains not linked to creation of new surface. The largest single source of energy consumption, abrasion, alone accounts for about 66 % of the energy of the process. Finally, we discuss how energy may be reduced by refining intensity and other means.

Alternative crop fibers have shown great potential for paper applications, especially packaging. We demonstrate Australian wheat straw processing using a Regmed MD-3000 disc refiner to produce mechanical pulp fibers and assessment by making 60, 120 and 300 g/m 2 handsheets. Wheat fibers and spotted gum fibers were then enzymatically sized (hydrophobized) by esterification to reduce the surface spread of water by 51 % and 36 %, respectively. Coffee pods (300 g/m 2 equivalent) were manufactured using a thermoformer to demonstrate the versatility of mechanical wheat straw pulp fibers as a sustainable resource for food packaging application.

A new compression refining technology has been tested in various conditions with a model Eucalyptus bleached kraft pulp. Its performances were also compared with those obtained with traditional LC refining of the same pulp. Compression refining of the Eucalyptus pulp led to a much better °SR/strength compromise than conventional LC refining. High strength properties can also be achieved by compression refining, in a similar range, or depending on the conditions, even better than LC refining. The higher the strength requested, the largest the advantages of this technology: for a given resistance, up to 40°SR difference with LC refined pulp can be obtained. The lower °SR is due to less cellulosic fines release which also results in papers combining a high strength and a high permeability which cannot be obtained with traditional LC refining. Indeed, with LC refining, a high strength is generally associated to a low permeability. The upscaling of this technology seems possible since large production devices are already on the market for other applications than paper/pulp. With this new pulp behaviour, papermakers will have to learn to think differently as paper strength and °SR can now be decorrelated.

This study investigated the properties of paper coated with nanocelluloses and nanocellulose-enhanced recycled paper derived from diverse waste paper sources. The grammages and thicknesses of both coated and recycled paper increased proportionally with the number of coating layers and the concentration of added cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC). While the tensile index and modulus of elasticity of coated paper decreased post-coating, these properties of recycled paper improved with higher CNF concentrations, with minimal changes observed with CNC. The burst strength of coated paper increased with additional coating layers, regardless of whether CNF or CNC was used. The tear index of coated paper surpassed that of the base paper, while the burst strength of recycled paper with CNF exceeded that of CNC. Recycled paper with added nanocellulose exhibited higher tear index values than control paper, with CNF addition notably enhancing tear index compared to CNC. The types of nanocellulose significantly influenced the optical and barrier properties of both coated and recycled paper. In conclusion, this study suggests that leveraging CNF and CNC can enhance the quality of low-grade and recycled paper, potentially opening new avenues for their applications.

The pulping ability and quality of paper high relay on the wood properties. However, the relationship between them are profound. Based on the extracting digital information from the anatomical, chemical, and physical properties of poplar wood, predictive models were developed for paper properties (tensile index, burst index and tear index) and pulping properties (Kappa number and pulp yield) using six algorithms, namely PLSR, ENR, RF, XGBoost, LightGBM, and CatBoost. The prediction results revealed that among the six algorithms, PLSR, ENR, and RF exhibited results of most prediction greater than 0.79. Notably, XGBoost, LightGBM, and CatBoost algorithms demonstrated superior predictive performance, with results greater than 0.9, except for the tear index. Furthermore, SHAP analysis suggested that the cellulose content is the primary factors to modulate pulping ability and the morphological features of cell wall shows apparent effects on mechanical properties of paper. It hopes the result will benefit to provide information to evaluate the value of poplar wood from different resources and then deliver instructions to genetic breeding program and forest management of poplar plantation.

Most petroleum-based polymers are non-biodegradable, leading to serious environmental concerns. Paper has become an important substitute for plastic. The hygroscopicity of paper in a humid environment causes its physical and mechanical strength to decrease. The development of superhydrophobic paper offers an effective solution that significantly improves water resistance and wettability, while also imbuing self-cleaning and stain resistance. In this study, the superhydrophobic oil coating was prepared with tetraethyl orthosilicate (TEOS) and octadecyl trichlorosilane (OTS) as organic components and nano titanium dioxide particles as inorganic components by hydrolysis condensation under alkaline conditions. The microstructure and chemical composition of the coating were analyzed by SEM and other techniques. In addition, we also studied the influence of TiO 2 quantity and other factors on the wettability of the paper interface, and determined the optimal preparation process to achieve the super hydrophobic oil repellent coating. The results show that when the addition amount of nano-titanium dioxide is 0.16 %, the reaction time is 6 h, the volume ratio of organosilane TEOS to OTS is 1:2 and the addition amount of TEOS is 6 mL (that is, when the total addition amount of organosilane is 23 %), the water contact angle on the surface of the layer is 159°±1.5°, the rolling angle is 3.5°±0.5°, the glycerol contact angle is 155°, and the ethylene glycol contact angle is 142°, indicating that this coating has excellent superhydrophobic and highly oleophobic properties. In addition, the coating has low adhesion to water, good self-cleaning ability and corrosion resistance.

In the dry-forming process, paper pulp is formed without adding water, making it more resource-effective than traditional papermaking. It is a relatively new technology, patented only in recent years, and very few material investigations exist in the literature; hence, little is known of the constitutive behaviour. The stress state during forming is highly complex, including multiaxial loading, extreme densification, friction, large strains, and fibre-joint formation. This paper studies dry-formed materials at different compression levels, from the sparse mat to the highly densified network. Three primary loading modes are investigated: in-plane tension, out-of-plane shear and out-of-plane compression. The results indicate that the tensile modulus and strength scale quadratically and cubically to the density, respectively, while the shear properties start developing after the density passes a threshold value. The compressive properties proved difficult to quantify, mainly because of the discrepancy between the density before and after the compressive test. The dry-formed material was compared to wet-formed paper materials in the literature. This showed that the in-plane (tensile) properties and the out-of-plane shear strength are visibly lower while the shear stiffness is similar, compared to wet-formed materials. Nonetheless, the findings set a starting point for numerical simulations of the dry-forming process.

Lactic acid impregnated ground film paper was prepared using the method of lactic acid impregnation of raw paper. The physical properties, chemical composition, crystallinity, thermal stability, surface morphology of the paper, barrier properties, and light transmittance of the lactic acid paper were investigated using FT-IR, XRD, TGA, SEM, water vapor blocking, oxygen blocking, mechanical properties testing, and optical property testing. Results showed that at room temperature (20 °C), when lactic acid concentration was 100 %, reaction time was 48 h, and 100 °C high temperature drying prepared lactic acid paper, it exhibited superior performance: dry strength of 2.83 IkN/m, wet strength of 0.36 kN/m, Cobb value of 4.50 g/m 2 , tear of 359.42 mN, water vapor barrier of 693.46 g m −2 24 h −1 , and oxygen barrier of 933.43 cm 3 m −2 24 h −1 . Degradation rate reached 22.94 % after two weeks of soil landfill.

This study collected sludge samples from the kraft pulp mills of a Brazilian industry and physicochemically characterized them to investigate their biovalorization. The objective was to identify opportunities to produce value-added products, promoting the circular economy and environmentally appropriate destinations. The types of processes and raw materials influence sludge characteristics. The primary sludge was composed mainly of fibers and water, has a slightly alkaline pH, Carbon:Nitrogen (C:N) ratio is high attributed to fibers, and contains calcium, magnesium, phosphorus, and organic carbon. The biological sludge was rich in proteins, bacterial cells, and minerals. The analyses revealed functional groups such as hydroxyls and aliphatic methylene, high concentrations of carbon and oxygen, a fibrous and crystalline structure of cellulose in the primary sludge, and dense microparticles in the biological sludge. Thermogravimetry found a mass loss of 11 % and final combustion at 742 °C for the biological sludge. The primary sludge showed a mass loss of 38 % with peaks at 329 and 784 °C, which suggests that the primary sludge could be used as fuel. Potential routes for the use of the primary and biological sludge included its use as agricultural fertilizer, thermal processing, biochar, and production of activated carbon, despite the low calorific values.

In this work, a strategy of in situ 3D hierarchical porous HKUST-1/cellulose/chitosan (CSGA/HKUST-1) composite aerogels were synthesized using ethylene glycol diglycidyl ether (EGDE) as a cross-linking agent. The effect of EGDE on CSGA/HKUST-1 and the adsorption of tetracycline (TC) was investigated: the composite aerogel (CSGA) was produced by the ring-opening reaction of the epoxy group of EGDE in alkaline solution. The chemical structure of CSGA/HKUST-1 composite aerogel was characterized by FT-IR, XRD and XPS.49.33 % mass loading of CSGA1/HKUST-1 was achieved and N 2 adsorption and desorption experiment showed the BET specific surface area reached 694.514 m 2  g −1 . SEM observed the CSGA/HKUST-1 composite aerogel pores were filled with a large number of octahedral HKUST-1 crystal particles. CSGA/HKUST-1 composite aerogel has excellent tetracycline adsorption capacity (285.7 mg g −1 ), and the removal efficiency remained at 92.7 % after five cycles of adsorption–desorption. The pseudo-second-order kinetic model and Langmuir model adsorption mechanism was successfully concluded. This study can provide ideas for in situ synthesis of MOFs on 3D composite aerogel to prepare adsorption materials, improve the mass loading rate of MOFs and prevent MOFs from falling off, etc., and enrich the application of MOFs materials in the treatment of antibiotic pollutants.

Pulp mill effluents contain organic compounds derived from wood processing that resist conventional biological treatment. Studies suggest that powdered activated carbon (PAC) can enhance the quality of these effluents. Two types of PAC, chemically activated (PAC1) and physically activated (PAC2), were characterized and applied in dosages of 1, 2, and 3 g/L to reduce chemical oxigen demand (COD) and color in kraft pulp mill effluent. In Phase 1, physicochemical tests identified the optimal PAC type, dosage, and maximum cycles for effective COD and color reduction. In Phase 2, biological aerobic sequencing batch reactors (SBR) were tested with the optimal PAC from Phase 1. Results indicated PAC1 could be reused for COD reduction for up to 8 cycles and PAC2 for up to 6 cycles. For color reduction, PAC1 was effective for up to 4 cycles, while PAC2 failed to reduce color. The type of activation used by PAC1 proved to be more effective in reducing both COD and color than PAC2. Adding PAC1 (3 g/L) to the SBR increased COD removal from 70.5 % to 75.5 % and color removal from 26.6 % to 43.8 %, also improving sludge settling.

This study investigates the potential of using waste newspaper (WN) as an adsorbent for removing methylene blue (MB) dye from water, emphasizing the environmental benefits of repurposing waste materials. Activated carbon (AC) was synthesized from WN using sodium phosphate (NaH 2 PO 4 ) as the activating agent, which is known for producing high mesopore content and requiring relatively low activation temperatures. The activated carbon’s physicochemical properties were thoroughly characterized using techniques such as FTIR, SEM, and surface area analysis based on the Brunner-Emmett-Teller (BET) theory. The specific surface area of AC was 917 m 2 /g. Continuous adsorption experiments were conducted to evaluate the efficiency of the synthesized activated carbon in a dynamic flow system. Various operating conditions, including initial dye concentration, influent flow rate, and bed height, were explored to optimize the adsorption process. This study applied the Yoon-Nelson, Thomas, Adams-Bohart and modified Logistic models to analyze the breakthrough curves and predict adsorption capacities. Results demonstrated that the AC exhibited high adsorption capacity (14.7 mg/g), particularly at lower flow rates and higher bed heights. This work offers valuable insights into sustainable wastewater treatment methods, showcasing the effectiveness of using low-cost, waste-derived activated carbon for dye removal in industrial applications.