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Humic substances (HS) are originated from naturally decaying biomass. The main products of HS are humic acids, fulvic acids, and humins. HS are extracted from natural origins (e.g., coals, lignite, forest, and river sediments). However, the production of HS from these resources is not environmentally friendly, potentially impacting ecological systems. Earlier theories claimed that the HS might be transformed from lignin by enzymatic or aerobic oxidation. On the other hand, lignin is a by-product of pulp and paper production processes and is available commercially. However, it is still under-utilized. To address the challenges of producing environmentally friendly HS and accommodating lignin in valorized processes, the production of lignin-derived HS has attracted attention. Currently, several chemical modification pathways can be followed to convert lignin into HS-like materials, such as alkaline aerobic oxidation, alkaline oxidative digestion, and oxidative ammonolysis of lignin. This review paper discusses the fundamental aspects of lignin transformation to HS comprehensively. The applications of natural HS and lignin-derived HS in various fields, such as soil enrichment, fertilizers, wastewater treatment, water decontamination, and medicines, were comprehensively discussed. Furthermore, the current challenges associated with the production and use of HS from lignin were described. [ABSTRACT FROM AUTHOR]

[Display omitted] A majority of natural particles have deformable and rough surfaces. Past research indicated a lack of information for a numerical model to simulate the potential non-contact interaction between two deformable particles with uneven surfaces. The simulation of deformable particles is critical to better understanding the interaction of deformable particles in colloidal systems. We hypothesized that numerical models could simulate the deformation process of solid and hollow particles, and the constructed models could predict the impact of deformation on the interaction of rough-surfaced solid or hollow deformable particles. This work modeled the deformable solid and hollow particles with rough surface morphologies following a fractal geometry theory. Their non-contact interaction was simulated following the three-stages deformation model. Also, the impacts of surface tension, particle size, and surface roughness on the interaction of the particles were investigated. It was observed that the total potential energy of deformable solid and hollow particles followed a similar pattern under different conditions. The difference in the energy profile between solid and hollow particles is that the hollow particles generate a deeper primary minimum, and the energy barrier disappears, indicating that the hollow particles have better attachment affinity. The results show that the increased particle size will strengthen the deformability of deformable solid and hollow particles and their potential interaction, and particle size will be the most influential parameter in affecting the deformability of particles. When the particle size increased from 10 nm to 1000 nm, the deformation region of solid particles was enlarged from 5 nm to 90 nm. Nevertheless, increased surface tension would weaken the deformability of deformable solid and hollow particles, which would significantly reduce particle aggregation. The increase in the fractal dimension would reduce solid and hollow particles' deformability but increase the potential interaction energy. The controversial results could be found by increasing fractal roughness, which would improve the deformability of particles and reduce the interaction energy. The results of this study could be applied for foreseeing the deformation and interaction of deformable particles with potential applications in suspension systems, such as biological cell suspensions. [ABSTRACT FROM AUTHOR]

This work presents the fundamentals and applications of a new sustainable lignin-based coating formulation with superhydrophobic and flame-retardant functionalities for wood products. [Display omitted] • Fundamentals of a new sustainable lignin-based coating formulation were discussed. • The material was produced in a solvent-free environment. • The material exhibited superhydrophobic and flame-retardant functionalities. • The material could be used as a wood coating product. There is a tremendous motivation to develop eco-friendly formulas for superhydrophobic and flame-retardant coatings. Presently used coating materials, particularly fluorinated compounds and their organic solvents, are potentially toxic. Here, we demonstrate that a silsesquioxane-grafted kraft lignin (WSL) and aluminum phosphate (AP) binder, i.e., an aqueous sustainable formula, can produce a flame retardant and superhydrophobic coating that is highly resistant to water and solvents. The chemical reaction of softwood kraft lignin (SKL) and aminopropyl/methyl silsesquioxane (WAPMSS) was studied comprehensively. NMR and XPS analyses confirmed the conversion of hydroxyl groups of SKL to Si-O-C via polycondensation. The product exhibited negligible wettability and was very hydrophobic. The dip coating of stain-grade pine wood species in the best formula containing WSL and AP dispersion (1/1 wt./wt.) rendered wood with superhydrophobic (with a water contact angle of (WCA) of 158°) and flame-retardant (with a limited oxygen index (LOI) of 27.2 %) functionalities. The exposure of coated wood to different liquids and high temperatures, as well as abrasion, touching, and knife-cutting analyses, confirmed the excellent durability of the coating formulation on wood. This paper demonstrates an eco-friendly pathway to produce a sustainable wood coating formulation with superhydrophobic and flame-retardant features. [ABSTRACT FROM AUTHOR]

The simulation of rough particle surface is important to understand and control the interface behavior of particles in colloidal systems. Literature analysis suggested a lack of information for an accurate model simulating the interfacial interaction between two rough particles. It is hypothesized that the total interfacial energy developed between two rough particles would depend on the surface morphologies of particles, and it could be predicted if a mathematical model to represent the interaction of two rough particles were created accurately. In this study, mathematical models were developed to determine the interfacial energy created between two particles according to the XDLVO theory by considering the rippled particle theory and surface element integral (SEI) method. Three different scenarios of particle interactions were assumed in the simulation. The present study provides deep insights into particle interactions via considering aspect ratio, size, and surface roughness of two particles in colloidal systems. The assessment of the interfacial interaction revealed that an increase in the aspect ratio, surface roughness, and relative surface roughness of particles would weaken the total interaction energy generated between particles and promote particle aggregation. Increased interaction energy was predicted for the interaction of particles by increasing the particle size. The asperity ratio was more effective than the asperity number in controlling the interfacial energy between two particles. The results of this study could be used for foreseeing the interaction of rough particles, which has a significant application in particle coagulation or dispersion in colloidal systems. [ABSTRACT FROM AUTHOR]

In their pristine state, starch and lignin are abundant and inexpensive natural polymers frequently considered green alternatives to oil-based and synthetic polymers. Despite their availability and owing to their physicochemical properties; starch and lignin are not often utilized in their pristine forms for high-performance applications. Generally, chemical and physical modifications transform them into starch- and lignin-based materials with broadened properties and functionality. In the last decade, the combination of starch and lignin for producing reinforced materials has gained significant attention. The reinforcing of starch matrices with lignin has received primary focus because of the enhanced water sensitivity, UV protection, and mechanical and thermal resistance that lignin introduces to starch-based materials. This review paper aims to assess starch-lignin materials' production and characterization technologies, highlighting their physicochemical properties, outcomes, challenges, and opportunities. First, this paper describes the current status, sources, and chemical modifications of lignin and starch. Next, the discussion is oriented toward starch-lignin materials and their production approaches, such as blends, composites, plasticized/crosslinked films, and coupled polymers. Special attention is given to the characterization methods of starch-lignin materials, focusing on their advantages, disadvantages, and expected outcomes. Finally, the challenges, opportunities, and future perspectives in developing starch-lignin materials, such as adhesives, coatings, films, and controlled delivery systems, are discussed. [ABSTRACT FROM AUTHOR]

Amphoteric polymers have tremendous applications in colloidal systems. Despite the enormous availability of lignin, the generation of amphoteric lignin polymer has yet to be discovered. In this work, amphoteric lignin was synthesized in an industrially attractive aqueous system via integrating the advantages of grafting quaternary ammonium groups onto lignin and polymerizing lignin with sulfonate containing monomers. The order of the reactions seemed to change the properties of the amphoteric lignin significantly, which was confirmed by 1H and 2D 1H COSY NMR analysis. In this research, the behavior of carbon chain length of the reagent containing the cationic group in inducing amphoteric lignin with superior properties was comprehensively discussed. The wettability and adhesion force analyses were performed to understand the impact of amphoteric lignin at the interface of a water/oil mixture. With the help of the contact angle and adhesion force measurements, the superior properties of the amphoteric lignin to those of only anionic or cationic modified lignin were determined. In water, the amphoteric and anionic lignin polymers strongly repelled oil droplets. In oil, both anionic and cationic lignin polymers showed poor water wettability, while the amphoteric lignin was wetted well by water. This paper discusses the fundamental mechanisms associated with the altered behavior of these lignin-based polymers at different interfaces. [ABSTRACT FROM AUTHOR]

This work primarily focusses on understanding the interaction of lignosulfonate (LS) and oxidized sulfomethylated lignin (OSL) with coal particles in a coal water slurry (CWS). LS had a charge density of −1.8 meq/g and sulfonate group content of 1.6 mmol/g, while OSL had a charge density of −1.8 meq/g and sulfonate group content of 0.6 mmol/g. LS adsorbed more on coal particles than did OSL (0.26 mg/g), and the adsorption of LS decreased with increasing the coal particle size. LS improved the wettability of coal by reducing the interfacial tension between coal particles and water. Coal particle's size significantly affected the adsorption of LS on coal surface and hence the rheological behaviour of CWS. The rheological studies confirmed that LS improved the stability of coal particles more than OSL via introducing repulsion force between the particles in the suspension. Unlabelled Image • Lignosulfonate (LS) was used as a dispersant for coal water slurries (CWS). • Performance of LS and oxidized sulfomethylated lignin (OSL) was compared. • Higher sulfonate group of LS than OSL rendered it a more effective dispersant. • Viscosity and stability of CWS were more dramatically changed by LS than OSL. • The changes were more pronounced for smaller coal particles than large ones. [ABSTRACT FROM AUTHOR]

Kraft lignin (KL) is extensively produced in industry but is mainly burned as fuel. To broaden its use, KL was grafted with dodecyl glycidyl ether to alter its thermal properties. The reaction of KL with dodecyl glycidyl ether (DGE) was analyzed using nuclear magnetic resonance (NMR), Fourier infrared spectroscopy (FT‐IR) and elemental analysis. Alternatively, KL was methylated to mask its phenolic hydroxy groups to investigate how phenolic hydroxy groups impact the grafting of the alkyl chain of DGE onto lignin (methylated Kraft lignin, MKL). The methylation facilitated the molecular weight enhancement and thermal stability reduction of Kraft lignin via grafting with DGE. The influence of grafting alkyl chains on the structural and thermal properties of KL and MKL was studied using thermogravimetric analysis and differential scanning calorimetry analysis. Our data suggest that, due to their high molecular weights and lower glass transition temperatures, the produced lignin derivatives may be promising feedstocks for composite production. [ABSTRACT FROM AUTHOR]

Microalgal cell adhesion and biofilm formation are affected by interactions between microalgae strains and membrane materials. Variations of surface properties of microalgae and membrane materials are expected to affect cell-membranes and cell-cell interactions and thus initial microalgal cell adhesion and biofilm formation rates. Hence, it should be possible to identify the dominant mechanisms controlling microalgal cell adhesion and biofilm formation. The effects of surface properties of three different microalgal strains and three different types of membrane materials on microalgal cell adhesion and biofilm formation were systematically investigated in real time by monitoring changes in the oscillation frequency and dissipation of the quartz crystal resonator (QCM-D). The results revealed that in general a higher surface free energy, more negative zeta potential, and higher surface roughness of membrane materials positively correlated with a larger quantity of microalgae cell deposition, while a more hydrophilic microalgae with a larger negative zeta potential preferred to attach to a more hydrophobic membrane material. The adhered microalgal layers exhibited viscoelastic properties. The relative importance of these mechanisms in controlling microalgae cell attachment and biofilm formation might vary, depending on the properties of specific microalgae species and hydrophobic membrane materials used. [Display omitted] • QCM-D was used to study real time microalgal cell adhesion on membrane materials. • Surface properties of cells and membrane were important in controlling cell adhesion. • Surface roughness of membrane positively correlated to the quantity of cell adhesion. • SFE of membranes positively correlated to the quantity of cell adhesion. • Zeta potential of membrane positively correlated to the quantity of cell adhesion. [ABSTRACT FROM AUTHOR]

Starch is a natural polymer with a relatively simple structure and limited solubility in water. Kraft lignin (KL) is a complex biopolymer obtained as a by-product from the delignification of wood and grasses. The present work reports developing a temperature-responsive high molecular weight macromolecule from crosslinking KL and starch (KLS). The NMR and XPS analyses quantified the changes in the aromatic and anhydroglucose units of KL and starch, observing a higher content of C-O-C bonds, which confirms the presence of glycerol ether cross-linkages between starch and KL in KLS. The rheological analysis of KLS dispersions revealed the formation of a thermo-responsive structured network. The temperature-dependent water solubility and rheological characteristics of KLS were related to the presence of hydrophilic starch chains, crosslinking degree, and physicochemical characteristics of KL. The incorporation of KL and ether crosslinks increased the thermal stability of KLS. Because of its multiple functional groups and large molecular weight (3.6–4.2 × 105 g/mol) that was arranged in an extended globular shape, KLS-5 formed a gel-like structure after a heating-cooling treatment. Overall, the results confirmed that incorporating lignin in starch would fabricate sustainable materials with potentially altered applications, such as temperature-responsive hydrogels and films. [Display omitted] [ABSTRACT FROM AUTHOR]

Lignin has been produced in large quantities in the pulp manufacturing process; however, its valorization has been challenging. The production of lignin polymers has shown pathways to produce water soluble products to be used as flocculants and dispersants. However, these lignin-based polymers may interact with each other and form large flocs that could reduce their efficiency in interacting with other colloidal particles. This study aims at evaluating the self-assembly of kraft lignin-acrylamide polymers in aqueous environments under different salt concentrations. The sedimentation studies using a vertical scan analyzer showed that a higher molecular weight lignin polymer had a higher tendency for sedimentation than a lower molecular weight one. Quartz crystal microbalance with dissipation (QCM-D) was used for studying the self-assembly behavior of lignin polymers with different molecular weights. The results suggested that lignin polymer with the higher molecular weight of 96,992 g/mol had a higher tendency to self-assemble by forming a loose floc as compared to that with a lower molecular weight. Also, salt disrupted the self-assembly of lignin polymers greatly. [ABSTRACT FROM AUTHOR]

Highlights • Hydrolysis lignin was oxidized via periodate treatment. • The mechanism of oxidation reaction was comprehensively examined. • The oxidization altered the molecular weight and carboxylate group of lignin. • Performance of oxidized lignin as a coagulant for a suspension system was evaluated. Abstract Lignin is an under-utilized biopolymer, but it can be modified to broaden its application in industry. In this work, a lignin-based coagulant was prepared by periodate oxidation of hydrolysis lignin that contained carbohydrates. The results showed that water-soluble oxidized hydrolysis lignin (OHL) with an anionic charge density of 0.9 mmol/g, carboxyl group content of 1.7 mmol/g and molecular weight of 6200 g/mol was obtained under the reaction conditions of 1/1 M ratio of sodium periodate/lignin, pH 5, 50 °C and 2 h. The mechanism of periodate oxidation of hydrolysis lignin involved the formation of quinoid intermediate, the increase in carboxylate group in final oxidized lignin, and the release of sugars from the decomposition of lignin-carbohydrate linkage. The adsorption analysis revealed that OHL adsorbed on the surface of aluminum oxide particles via charge neutralization and hydrogen bonding following Langmuir adsorption model. When 12 mg/g OHL was added to the aluminum oxide suspension, the mean chord length of particles increased from 17 μm to 39 μm, while their total counts decreased by 40%. Vertical scanning analysis was also used to evaluate the coagulation/settling performance of OHL in aluminum oxide suspensions. The settling rate of particles accelerated from 22 mL/h to 600 mL/h in the presence of OHL, increasing the transparency of suspension from 15% to 78% and the compactness of sediment from 20 g/L to 84 g/L. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cationic lignin-acrylamide was used as a flocculant for clay suspension. • Charge density of copolymers affected physicochemical properties of suspensions. • The surface and interface tensions of clay particles were investigated. • The impact of the copolymer on floc strength was evaluated. Abstract Kraft lignin valorization is achievable via making it soluble in water for treating wastewater effluents. In this paper, acrylamide (AM), (2-methacryloyloxyethyl) trimethyl ammonium chloride (DMC) and kraft lignin (KL) were polymerized in an aqueous solution to produce a water-soluble lignin-based copolymer. Two cationic KAD polymers, with the same molecular weight, but different charge densities, were used as flocculants for simulated clay suspensions. The higher charge density copolymer (KAD1) had greater adsorption on kaolin (2.58 mg/g) and bentonite particles (1.83 mg/g) at 4 mg/g (based on clay) adsorption. Furthermore, KAD's higher charge density improved its performance in changing zeta potential and turbidity of the clay suspensions. At 4 mg/g copolymer dosage in clay suspensions, the particle size of kaolin was increased from 4.7 to 22.3 and 16.2 μm, and that of bentonite was increased from 6.1 to 31.9 and 19.8 μm for KAD1 and KAD2, respectively. In addition, the interfacial tension between water and kaolin and between water and bentonite dropped from 12.3 mN/m to 5.8 mN/m and from 9.5 mN/m to 5.2 mN/m when KAD1 was used, respectively. Moreover, KAD1 produced stronger flocs and showed high regrowth affinity at different shear rates. [ABSTRACT FROM AUTHOR]

Highlights • Cationic lignin-acrylamide was used as a flocculant for clay suspension. • Molecular weight of copolymers affected physicochemical properties of suspensions. • The impact of the copolymer on floc strength was evaluated. • pH of the suspension affected the performance of cationic lignin-acrylamide. Abstract Currently, kraft lignin is burned in the recovery cycle of the kraft pulping process; despite its high potential to be extracted and converted into value-added products. In this work, kraft lignin (KL) was copolymerized with acrylamide (AM) and 2-[(methacryloyloxy) ethyl] trimethylammonium chloride (DMC) to produce cationic copolymers. Copolymers with two different molecular weights of 168,200 g/mol (KAD-1) and 103,000 g/mol (KAD-2), but with a similar charge density of 1.15 meq/g, were selected and the flocculation efficiency of the copolymers in two different clay suspensions was investigated. Suspension pH affected the adsorption of the copolymers on clay particles and the removal of the particles from the suspension. At a 8 mg/g dosage, KAD-1 adsorbed more than KAD-2 as it was larger and thus developed more bridging with clay particles. The size of particles raised from 4.7 for kaolin to 16.3 μm for kaolin/KAD-1 flocs and 15.1 μm for kaolin/KAD-2 flocs, and it increased from 6.1 for bentonite to 18.97 μm for bentonite/KAD-1 flocs and 15.35 μm for bentonite/KAD-2 flocs in the presence of 8 mg/g of copolymers, respectively. The adsorption, zeta potential and flocculation analyses confirmed that KAD-1 was a more effective flocculant than KAD-2. The evidence for the agglomeration of clay particles via bridging and electrostatic patch mechanisms was also discussed in this work. [ABSTRACT FROM AUTHOR]

In this study, oxidized and sulfomethylated lignin (OSL) with the charge density of −4.4 meq/g was used as a dispersant for coal water slurry (CWS). The impact of the OSL on CWS having different particle sizes was fundamentally investigated. The size of particles greatly influenced the adsorption of OSL on coal particles and the rheology and stability of the CWS. The maximum adsorption of OSL was found to be 0.96 mg/g on coal A having the particle size of 22 μm (coal particles with smallest size). OSL improved the wettability of coal by 5–28%. The interfacial tension between coal particle and OSL was reduced from 17 mN/m to 13 mN/m, and the zeta potential of the suspension dropped from −30 mV to −47 mV when 0.96 mg/g of OSL was adsorbed on coal A. The addition of 64 mg/L of OSL to coal A suspension (50 wt%) reduced its viscosity from 1350 to 520 mPa·s. The stability of coal particles was also improved as the destabilization index of CWS was reduced from 4 to 0.2. These results confirmed that the OSL was an effective dispersant for the coal water slurry. [ABSTRACT FROM AUTHOR]

Dispersion of kaolin in aqueous systems is important in many industries including ceramics, chemicals, pharmaceuticals and paints. In this work, kraft lignin-acrylamide (KAM) polymers were produced via polymerizing kraft lignin and acrylamide (AM) monomer with different molar masses and charge densities, and they were used for stabilizing kaolin dispersion at varied pHs. The surface tension and contact angle studies demonstrated that KAM improved the surface hydrophilicity of kaolin mineral particles. Among KAM polymers (KAM-1, KAM-2 and KAM-3), KAM-3 with the highest molar mass (M w ) of 97,000 g/mol and charge density of −2.1 meq/g had the highest adsorption of 2.16 mg/g onto kaolin mineral particles. It was also found that KAM adsorption on kaolin mineral particles was pH dependent with KAM adsorption decreasing with increasing pH from 4 to 10. Generally, increasing ionic strength enhanced the adsorption of KAM on kaolin mineral particles. Salt reduced electrostatic repulsion between the anionic KAM polymers and the negatively charged kaolin mineral particles and facilitated the adsorption. Relationship between zeta potential and relative turbidity of kaolin dispersion was developed at different levels of KAM adsorption. KAM (especially KAM-3) increased the volume fraction of kaolin mineral particles in the dispersion. It also improved the stability of kaolin dispersion, and the impact was more noticeable at pH 10. Treating the dispersion with KAM was more effective than mechanical stirring in stabilizing kaolin mineral particles. [ABSTRACT FROM AUTHOR]

The bleaching operation of a kraft pulping process generates a large amount of effluents with high organic loads. The affinity of biomass-based fly ash as a low-cost adsorbent for reducing lignin concentration, chemical oxygen demand (COD) and turbidity of the bleaching effluents prior to a biological treatment process was studied in this work. The results showed that the optimized conditions for obtaining the maximum removals of lignin (81.6%) and COD (67.9%) were the fly ash dosage of 6 wt% in the effluent and the treatment time of 30 min and temperature of 30 °C. The results also showed that the settling rate of the fly ash in fly ash/effluent suspension systems increased as fly ash dosage increased. Charge neutralization played a key role at a low fly ash dosage (less than 2 wt%) for removing lignocellulosic flocs smaller than 10 µm, while complexion of small flocs to larger ones (with the size of 30–500 µm) occurred at the higher fly ash dosage in the effluent. Coagulation and adsorption were the main phenomena for the removals of COD, lignin and turbidity at a higher fly ash dosage and a prolonged treatment time. [ABSTRACT FROM AUTHOR]

To generate effective dispersants for kaolin suspensions, it is important to study how the properties of dispersants affect their performance in suspensions. In this work, kraft lignin was modified via oxidation with nitric acid under varied conditions to produce oxidized lignin (OL) with different charge densities and molecular weights. The effects of anionic charge density and molecular weight of the lignin based products on the dispersion and sedimentation of kaolin particles were studied fundamentally. The adsorption of OLs on particles as well as the changes in the zeta potential, relative turbidity, hydrodynamic diameter and sedimentation of particles under static (non-stirring) and dynamic (stirring) conditions were systematically investigated. Dispersion studies suggested that both charge density and molecular weight had great impacts on the stability of kaolin particles. Sample OL8 with the charge density of −3.6 meq/g and molecular weight (Mw) of 30,243 g/mol was the most effective dispersant for kaolin suspension. The hydrophilicity of OLs were similar and thus did not affect the dispersion analysis. [ABSTRACT FROM AUTHOR]

In this work, the influence of pH and ionic strength on the flocculation performance of cationic xylan copolymer in kaolin and bentonite suspensions was systematically investigated. The cationic xylan was produced via copolymerizing xylan with 2-(methacryloyloxy ethyl) trimethylammonium chloride (METAC), and the cationic xylan copolymer (CMX) showed a maximum adsorption of 4.6 and 1.8 mg/g on kaolin and bentonite particles at the CMX dosage of 8 mg/g, pH 10, 30 °C and 1 h, respectively. The reduction in charge density of CMX from 2.66 to 2.48 meq/g was observed, with an increase in pH of CMX solution to from 2 to 10. The maximum increase in the zeta potential of kaolin (+54 mV) and bentonite (−3 mV) suspensions and the highest removal of kaolin (75%) and bentonite (96%) from the suspensions were obtained at 8 mg/g CMX and pH 7. Stability studies revealed that pH had a noticeable influence on the sedimentation of kaolin and bentonite particles. CMX increased the destabilization index of kaolin (0.4–45) and bentonite (0.2–51) suspensions by increasing the floc size of kaolin and bentonite particles to 9.5 μm and 12.7 μm, respectively. CMX removed more of bentonite than kaolin at any pH under static and dynamic conditions. The impact of inorganic salts on the removal of kaolin particles was also studied. CMX exhibited better performance than a commercial flocculant (PDADMAC) in flocculating the commercially produced effluent. [ABSTRACT FROM AUTHOR]

Tall oil is an important by-product of Kraft pulping processes. One possibility to improve the economic feasibility of Kraft pulp mills is to consider tall oil production from their wasted tall oil soaps. This review paper describes the current technology practiced to produce tall oil from the black liquor of Kraft pulping processes. Moreover, alternative processes to separate tall oil soap from black liquor, produce tall oil from the separated soap, purify tall oil, and to produce value-added products from tall oil are reviewed. The main perspectives and challenges associated with each process are comprehensively described. Currently, soap is separated from black liquor via decantation. To improve the efficiency of this separation, the application of neutral soluble colloids in dilute black liquor reported to be promising. Tall oil soap is converted to crude tall oil in the acidulation process via treating with sulfuric acid. However, the use of sulfuric acid forms calcium sulfate as a by-product of the process. The replacement of sulfuric acid with a sodium sesquisulfate solution is beneficial for decreasing the direct use of sulfuric acid in the tall oil production process. Crude tall oil can be used without purification as fuel. Its purification and subsequent reaction with methanol can lead to biodiesel production. However, this process may be complicated to implement in industry. The production of valuable lignin-based products from the tall oil production process may have benefits for the mills as these processes can be fully integrated into the Kraft pulping and tall oil production processes. [ABSTRACT FROM AUTHOR]

In this work, the performance of carboxymethylated xylan (CMX) as a dispersant for kaolin particles in an aqueous system (20 g/L) was systematically investigated. The influence of process parameters, such as pH and CMX dosage, on the kaolin dispersions was also determined. Adsorption studies revealed that CMX had a maximum adsorption of 2.48 mg/g on kaolin particles under the treatment conditions of pH 6, 15 mg/g CMX/kaolin, 30 °C and 30 min. The minimum zeta potential of − 33 mV and the highest stability for the kaolin dispersions were found under the same treatment conditions using photometric dispersion, vertical scan analysis and turbidimetry. Isotherm and kinetic studies revealed that the adsorption of CMX on kaolin particles tended to significantly impact the zeta potential and relative turbidity of the kaolin dispersion, but the zeta potential did not necessarily predict the high stability of the kaolin dispersion. CMX improved the stability of the kaolin dispersions more than unmodified xylan (UX) and mechanical stirring. [ABSTRACT FROM AUTHOR]

Acidification has been commercialized for producing kraft lignin from black liquor of kraft pulping process. This work intended to evaluate the effectiveness of acidification in extracting lignocelluloses from the spent liquor of neutral sulfite semichemical pulping (NSSC) process and from prehydrolysis liquor (PHL) of kraft-based dissolving pulp production process. The results showed that the NSSC and PHL spent liquors had some lignin-carbohydrate complexes (LCC), and that the square weighted counts of particles with a chord length of 50–150 μm in the spent liquors were significantly increased as pH dropped to 1.5. Interestingly, the acidification reduced the lignosulfonate/lignin content of NSSC and PHL by 13% or 20%, while dropped their oligosugars content by 75% and 38%, respectively. On a dry basis, the precipitates had more carbon, hydrogen and a high heating value of 18–22 MJ/kg, but less oxygen, than spent liquors. The precipitates of PHL could be used as fuel. [ABSTRACT FROM AUTHOR]

In this study, carboxymethylated beechwood xylan was produced under alkali conditions using sodium chloroacetate. Taguchi orthogonal design was used to explore the influence of the process parameters, i.e. NaOH concentration, time, temperature, the molar ratio of sodium chloroacetate to xylan and the concentration of the reaction medium on the charge density and degree of substitution (DS) of xylan. Carboxymethylated xylan (CMX) with the maximum charge density of 1.62 meq/g and DS of 0.21 was produced under the optimal conditions of 0.75 M NaOH concentration, 1.0 mol/mol sodium chloroacetate (SCA)/xylan ratio, 2 h reaction time, 70 °C and 15 g/L xylan concentration. The carboxylate group of the product was 1.48 mmol/g. The attachment of the carboxymethylated group to xylan was confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance ( 1 H NMR) spectroscopy. The molecular weight of xylan increased and its thermal stability was improved via carboxymethylation. The dispersion performance of the carboxymethylated xylan in clay suspensions was determined by photometric dispersion analyzer (PDA). CMX showed better performance than sodium carbonate-polyacrylic acid (Na 2 CO 3 -PAA) in dispersing the clay suspension. The unmodified xylan did not show any dispersion performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Interfacial energy between ellipsoidal particles with rough surfaces was simulated. • Impacts of surface morphology and geometrical shape were considered in the model. • Surface morphology significantly affected the interaction energy between particles. • Prolate particles provided greater interfacial energy than spherical particles did. • Amplifying the aspect ratio diminished interaction energy between oblate particles. Currently, information on the interaction of ellipsoidal particles with rough topography is limited. In this work, a mathematical model was developed based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory and surface element integral (SEI) to simulate the total interaction energy created between ellipsoidal particles with rough surfaces, which were constructed by the modified two-variable Weierstrass-Mandelbrot (WM) function. The simulated results revealed that an increase in the fractal roughness and relative fractal roughness of particle surface would increase the surface roughness of particles and weaken the total interaction energy between ellipsoidal particles. Compared with spherical shape particles, the ellipsoidal particles provided greater interaction energy because an ellipsoidal shape would generate a greater interaction area than a spherical shape between particles. Amplifying the aspect ratio diminished the interaction energy between particles but enlarging particles would strengthen the interaction energy. In addition, the orientation angle of ellipsoidal particles would affect their interaction. [ABSTRACT FROM AUTHOR]

The spent liquor, SL, of neutral sulphite semi chemical pulping process contains lignosulfonate and hemicelluloses, but it is currently treated in the wastewater treatment of the process. This treatment decomposes the lignosulfonate. However, lignosulfonate can be extracted for a better use, but the extraction process is not an easy task. The main objective of this work was to extract lignosulfonate from SL via treating the SL with surfactant. The results showed that the acidification of SL to pH 1.8 caused 6% lignosulfonate, 53% hemicelluloses, and 7% COD removals from SL. Acidification followed by dodecyltrimethylammonium chloride, DTAC, treatment of SL at the optimal conditions of 22 °C, 1.8 pH and 10 mg/g of DTAC/SL yielded 40% lignosulfonate, 78% hemicelluloses, and 25% COD removals. Model solutions were prepared via dissolving commercial lignosulfonate and xylan in solutions or purifying SL via membrane dialysis in order to investigate the impact of SL components, i.e. hemicelluloses and residual cooking chemicals, on the isolation of lignosulfonate from SL. The model analyses confirmed that the presence of impurities, i.e. residual cooking salts, significantly affected the isolation of lignosulfonate from the SL, but the presence of hemicellulose had a minor effect in extracting lignosulfonate from SL via DTAC treatment. In addition, the elemental analysis confirmed that DTAC and lignosulfonate had a ratio of 0.584 mol/mol in precipitates. [ABSTRACT FROM AUTHOR]

Respiratory diseases debilitate more than 250 million people around the world. Among available inhalation devices, the soft mist inhaler (SMI) is the most efficient at delivering drugs to ease respiratory disease symptoms. In this study, we analyzed the SMI performance in terms of the aerosol's velocity profiles, flow pattern, size distribution, and deposition by employing computational fluid dynamics (CFD) simulations. We modeled two different simplified mouth geometries, idealized mouth (IM), and standard mouth (SM). Three different locations (x = 0, x = 5, and x = 10 mm) for the SMI nozzle orifice were chosen along the mouth cavity centerlines, followed by two different SMI nozzle angles (10 deg and 20 deg) for IM geometry. A flowrate of 30 L/min was applied. The simulation results were evaluated against experimental data. It was found that the SMI could be simulated successfully with a level of error of less than 10%. The inhalation flowrate significantly impacted the aerosol's velocity profile and deposition efficiency on both the IM and SM walls. The lowest particle deposition on the mouth wall occurred when a fixed flowrate (30 L/min) was applied inside both geometries, and the SMI nozzle position moved forward to x = 10 mm from the IM and SM inlets. An increase in the SMI nozzle angle increased particle deposition and decreased the deposition fraction for particles with a diameter above 5 μm inside the IM. [ABSTRACT FROM AUTHOR]

A mathematical model was created based on surface element integral (SEI) and XDLVO theory for assessing the interfacial interaction between rough spherical surfaces with random topographies, which were generated following a modified two-variable Weierstrass-Mandelbrot (WM) function. The surface construction and interfacial interaction equations used in this study facilitated the generation of randomly rough spherical surfaces, which assisted in improving the prediction accuracy of particle interactions for natural colloidal particles. This modeling study presented discussions on the interaction of rough surfaces having different asperity heights, asperity positions, random landscape, and roughness in colloidal systems. We observed that the asperity number and ratio were primary parameters for influencing the interfacial interaction between spherical surfaces. The arrangement and randomness in the position of asperities on the surface had negligible effects on the interfacial interaction. The elevated asperity height, as a result of increased fractal roughness or relative fractal roughness on spherical surfaces, could hamper the interfacial energy between surfaces. However, increasing the fractal dimension and relative fractal dimension generated smoother surfaces and thus elevated the interfacial energy developed between surfaces. The most impactful parameter of surface morphologies in altering interfacial energy was fractal dimension as it could control the asperity height and asperity number simultaneously. The largest primary maximum was predicted (216 kT) when the fractal dimension was 2.43, which represented the strongest stability of particles in a suspension. [Display omitted] • Surfaces with altered topographies were generated via surface element integral and XDLVO theory. • Asperity number and ratio were main parameters affecting the interaction between surfaces. • Arrangement and randomness in the position of asperities had minimal effect on the interaction. • Fractal roughness and relative fractal roughness hampered interfacial energy between surfaces. • Fractal dimension and relative fractal dimension elevated interfacial energy between surfaces. [ABSTRACT FROM AUTHOR]

In this work, the adsorption of lignocelluloses from spent liquor (SL) of neutral sulfite semi chemical (NSSC) pulping process on bentonite was investigated. It was observed that 0.26 g/g of lignin and 0.27 g/g of hemicelluloses from SL were adsorbed on bentonite under the conditions of 50 °C, 100 rpm and 40 g/g SL/bentonite after 3 h of treatment. The adsorptions of lignin and hemicellulose were increased to 1.8 g/g and 0.45 g/g, respectively, via adding 15 mg/g of polydiallyldimethylammonium chloride (PDADMAC) in the system of SL/bentonite. The turbidity and COD removals were improved from 69% to 93% and from 25% to 38% by adding PDADMAC to the SL/bentonite system, respectively. The increase in the heating value of bentonite (from 0 to 15.4 MJ/kg) confirmed the adsorption of lignocelluloses. The modified bentonite can be used as filler in corrugated medium paper production or as fuel. [ABSTRACT FROM AUTHOR]

The pre-hydrolysis liquor (PHL) of the kraft-based dissolving pulp production process is currently sent to the recovery boiler and incinerated. However, PHL contains about 5-8% lignocelluloses that can be utilized in the production of value-added chemicals. In this study, a process for producing xylitol from hemicelluloses in PHL is developed. This process involves several acidification, neutralization, adsorption (along with reactivation) and evaporation stages. The mass balance indicates that 533kg/h xylitol (with 99% purity), 187kg/h lignin, 806kg/h basic ferric acetate, and 1600 kg/h gypsum can be produced from 41,670 kg/h PHL. The energy balance shows that the evaporators are the largest consumers of energy, while the reactivation kiln, acidification, neutralization, and precipitation processes generate some heat. Overall, 41% conversion of xylose to xylitol is achieved. [ABSTRACT FROM AUTHOR]

• Hydroxypropyl sulfonated kraft lignin was compared with lignosulfonate as a dispersant. • The adsorption of the biopolymers on the aluminum oxide surface was studied. • The dispersion, sedimentation, and particle size of the system were studied. • The results confirmed that both biopolymers behaved very similarly in the suspension. • Hydroxypropyl lignin can replace lignosulfonate due to its attractive production process. In this work, the adsorption and dispersion characteristics of hydroxypropyl sulfonated lignin (HSL) were assessed and compared with those of lignosulfonate (LS). HSL was synthesized in an environmentally friendly manner by reacting kraft lignin (KL) with 3-chloro-2-hydroxypropansulfonic acid (CHPS) under alkaline conditions. This reaction produced HSL with a charge density (-2.48 mmol/g) and molecular weight (42,000 g/mol) that were similar to those of LS. The adsorption behavior of HSL and LS on the aluminum oxide surface was fundamentally analyzed using a quartz crystal microbalance with dissipation monitoring (QCM-D). HSL and LS formed films of similar thickness, though the HSL films exhibited looser and more viscous structures. The dynamic and static dispersion behaviors of HSL and LS in an aluminum oxide suspension were investigated via ζ potential, particle size, and sedimentation analyses. HSL and LS decreased the suspended particle size and improved suspension stability via electrostatic repulsion similarly. The similar properties, adsorption behavior, and stabilizing performances of HSL and LS indicate that HSL may be an effective substitute for commercial LS dispersants. Furthermore, its environmentally friendly synthesis and use of widely available KL as a starting material make HSL production a commercially attractive option. [ABSTRACT FROM AUTHOR]

Cationic kraft lignin (CKL) polymers with different degrees of grafting (35.2–125.5 mol%) were synthesized via polymerizing kraft lignin (KL) and [2-(acryloyloxy)ethyl]trimethylammonium chloride (ATAC) or [2 (methacryloyloxy)ethyl]trimethylammonium methyl sulfate (METAM) to investigate the impact of the chain extension of the polymers on the physicochemical behavior of CKL in an aqueous solution. It was observed that, at the same grafting ratio, the structural difference of CKLs influenced their hydrophilicity, in which the contact angle of KL-METAM and KL-ATAC solution (1 g/L) reached 9.4° and 11.8° on a glass slide, respectively, at the maximum degree of grafting of ~125 mol%. KL-METAM had a more three-dimensional and flexible structure than KL-ATAC in solution, which promoted its self-assembly (with the aggregate diameter of 235–532 nm) and sedimentation (with the TSI value of 16.8). The rheological studies confirmed the more elasticity of KL-METAM than KL-ATAC with the elastic modulus of 9.3 and 8 Pa at the highest frequency. Quartz crystal microbalance (QCM) adsorption studies illustrated that KL-METAM adsorbed more greatly and generated a bulkier and more viscoelastic adlayer than KL-ATAC did on a rigid surface, below saturation (ΔD/Δf slope of 0.13–0.45) and at equilibrium (ΔD/Δf slope of 0.02–0.17). For the deposited adlayer, the alterations in the slope of dissipation/frequency (ΔD/Δf) between the early and late stages of adsorption were claimed to be related to the conformational changes of CKLs upon adsorption. The findings of this study showed that the architecture of cationic monomers could affect the structure of CKLs so significantly that the lignin polymers would have different chain conformations and flexibility in solution, varied rheological properties, and adsorption performance on a solid surface. The significance of the monomer architecture on the properties and performance of CKLs was more observable at a higher grafting ratio. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In this work, we aimed at adsorbing the oligo-sugars of prehydrolysis liquor on precipitated calcium carbonate (PCC) to produce modified PCC. The results showed that the adsorptions of oligo-sugars, lignin and furfural were greater on porous PCC (PCC2) than on nano-sized PCC (PCC1) due to the larger surface area of PCC2. The adsorption reached its maximum in 5h on PCC1, but it gradually increased on PCC2 due to the diffusion of oligo-sugars and lignin into the pores of PCC2. Also, the experimental isotherm and kinetic results were well fitted into Langmuir and pseudo-second order models, respectively. The adsorption was greater at a lower temperature (i.e. 40°C) and pH (i.e. 7). Alternatively, cationic poly acrylamide (CPAM) was added to the PHL/PCC system, which led to more promising results (than that to PHL/PCC system) with the maximum lignocelluloses adsorption of 0.36g/g on PCC2, among which 0.22g/g was oligo-sugars. [Copyright &y& Elsevier]

Abstract: The main objective of this work was to study the adsorption behavior of various components dissolved in the pre-hydrolysis of kraft process on activated carbon. In this work, model prehydrolysis liquor (PHL) solutions (MPHL)s were prepared via mixing various commercially available monosugars, xylan, lignin and furfural; and their adsorption performance on activated carbon (AC) was investigated. In singular (one component) MPHL/AC systems, furfural had the maximum and xylose had the minimum adsorption, and the adsorption of monosugars was basically similar on AC. Also, polydiallyldimethylammonium chloride (PDADMAC) was added (0.5g/l) to singular xylan or lignin MPHL/AC system, which increased the lignin and xylan adsorptions to 350 and 190mg/g on AC, respectively. [Copyright &y& Elsevier]

Abstract: In this work, the adsorption of lignocelluloses of pre-hydrolysis liquor (PHL) on precipitated calcium carbonate (PCC) was studied in the presence of poly diallyldimethylammonium chloride (PDADMAC) or cationic polyacrylamide (CPAM). The results revealed that adding PCC to PHL and subsequently adding cationic polymers to PHL/PCC systems was more effective than adding cationic polymers to PHL and then adding PCC to the cationic polymer/PHL systems. At the same dosage applied, PDADMAC resulted in a higher adsorption of lignocelluloses on PCC than CPAM did due to its higher charge density. The adsorption of lignocelluloses on PCC reached its maximum in 3h, and a high temperature reduced the adsorption level as the adsorption was an exothermic process. The maximum adsorptions of 530mg/g oligo-sugars, 203mg/g lignin and 58mg/g furfural on PCC were achieved via adding 0.8mg/g PDADMAC2 (i.e. higher MW PDADMAC) to PCC/PHL system. [Copyright &y& Elsevier]

Abstract: Hemicelluloses present in the pre-hydrolysis liquor (PHL) of the kraft-based dissolving pulp production process can potentially be converted into value-added products such as ethanol and xylitol. However, the lignin present in the PHL is an inhibitor of fermentation processes, and thus should be isolated from the PHL prior to fermentation. In this study, a new process was proposed for isolating the lignin of PHL by overliming and surfactant treatment. The fundamentals associated with the interactions of lignin, surfactants and calcium hydroxide were discussed. In the experimental part of this work, three different cationic surfactants were applied to industrially produced PHL, and the most effective one, dodecyltrimethyl ammonium chloride (DTAC), was selected for further analysis. The optimum dosage of 0.3% DTAC/PHL was identified via turbidity and particle size analyses. Additionally, overliming via CaO treatment resulted in removing 36.1% lignin and 23% hemicelluloses. Overliming followed by the DTAC treatment was more effective than the DTAC treatment followed by overliming in removing lignin. In the former, the maximum removals of 43.6% lignin and 27% hemicelluloses were obtained. The formation of lignocelluloses/surfactant complexes was confirmed by means of a Fourier transform infrared spectroscopy (FTIR) and thermo gravimetric analyzer (TGA). [Copyright &y& Elsevier]

Abstract: A process for removing inhibitors from pre-hydrolysis liquor (PHL) of a kraft-based dissolving pulp production process by adsorption and flocculation, and the characteristics of this process were studied. In this process, industrially produced PHL was treated with unmodified and oxidized activated carbon as an absorbent and polydiallyldimethylammonium chloride (PDADMAC) as a flocculant. The overall removal of lignin and furfural in the developed process was 83.3% and 100%, respectively, while that of hemicelluloses was 32.7%. These results confirmed that the developed process can remove inhibitors from PHL prior to producing value-added products, e.g. ethanol and xylitol via fermentation. [Copyright &y& Elsevier]

Abstract: Dissolved lignocelluloses from the pre-hydrolysis liquor (PHL) of kraft-based dissolving pulp production process were recovered by adsorption to lime mud produced in the causticizing plant of the kraft process. The adsorption of lignocelluloses was a fast process, and could be completed within one hour. The addition of polydiallyldimethylammonium chloride (PDADMAC) significantly increased the amounts of adsorbed lignin and hemicelluloses, which more than doubled at the PDADMAC dosage of 0.1% (based on the weight of PHL). The measured heating values of the adsorbed lignocelluloses indicate that adsorption of lignocelluloses to lime mud may result in the energy saving of the lime kiln. The process proposed in this study could also be adapted to decrease inhibitor concentrations (lignin and acetic acid) if the dissolved hemicelluloses in the PHL were used to produce value-added products, e.g., ethanol, xylitol, based on the fermentation process. [Copyright &y& Elsevier]

Abstract: In this work, the flocculation concept was employed to recover the dissolved lignocellulosic materials of industrially produced pre-hydrolysis liquor (PHL) using two different molecular weights of chitosan. The analysis revealed the maximum turbidity of 1000NTU or 1900NTU via adding 2.2mg/g low molecular weight (LMW) or 1.7mg/g high molecular weight (HMW) chitosan to the PHL, respectively. Also, the maximum furfural removal of 55% or 50% was obtained by adding 0.7mg/g or 0.5mg/g LMW or HMW chitosan to the PHL, respectively. The maximum recovery of oligomeric sugars was 20% or 25% by adding 1.5 or 0.5mg/g LMW or HMW chitosan, while that of lignin was 40% or 35% by applying 2.2mg/g or 1.7mg/g LMW or HMW chitosan to the PHL, respectively. The removal of monomeric sugars and acetic acid was rather limited. The particle size and nitrogen analyses were also hired to characterize the properties of the formed complexes. [Copyright &y& Elsevier]

Abstract: Hemicelluloses in industrially produced pre-hydrolysis liquor (PHL) were precipitated with ethanol. These PHL-derived hemicelluloses (PHL-EH) and a commercial, pure birch wood xylan sample (powder form) (BWX) were bleached using chlorine dioxide (D0 and D1) and hydrogen peroxide (Ep) in the D0EpD1 sequence, and the chemical compositions, molecular weights and charge densities of the treated samples were assessed. When applied to high-yield pulp (HYP) at 50mg/g, 26 and 20mg/g of the bleached PHL-EH and BWX, respectively, were adsorbed without significantly affecting paper properties. These results suggest that semi-bleached hemicelluloses could be used to increase the basis weight of paper products. Furthermore, an integrated process was proposed that converts the kraft-based dissolving pulp production process into a biorefinery unit with dissolving pulp, bleached hemicelluloses and lignin as main products. [Copyright &y& Elsevier]

Abstract: The cationization of polymers has been regarded as an effective method to improve their performance for various applications. In this work, the cationization of poly vinyl alcohol (PVA) was investigated under different conditions, i.e., various glycidyl-trimethylammonium chloride (GTMAC) to PVA ratios, reaction temperatures, times, PVA and NaOH concentrations and solvent compositions. The results showed that the overall efficiency of the cationic modification was rather low, which was due to the hydrolysis of both GTMAC and cationic-modified PVA (CPVA) under the strong alkaline conditions employed. The results also showed that the optimum GTMAC/PVA ratio depended on the solvent composition. The cationization was confirmed by means of 1H NMR and FTIR analyses. The maximum efficiency in water was obtained under the conditions of 95°C, 1h, 0.5 (mol) GTMAC/PVA ratio, and 5% (mol) NaOH concentration, while that in the ethanol/DMSO mixture (1.25v/v) was obtained under the conditions of 70°C, 1h, 0.5 (mol) GTMAC/PVA ratio, and 5% (mol) NaOH concentration. Additionally, the interaction of CPVAs with a silicon wafer (as a substrate) was determined by employing an atomic force microscope (AFM) in water and air. [Copyright &y& Elsevier]

Abstract: The presence of lignin impairs the utilization of the hemicelluloses dissolved in the pre-hydrolysis liquor (PHL) of the kraft-based dissolving pulp production process. In this paper, a novel process was developed by combining the acidification and poly ethylene oxide (PEO) flocculation concepts to improve the lignin removal. The results showed that the lignin removal was improved by the addition of PEO to the acidified PHL, particularly at a low pH of 1.5. The main mechanisms involved are the lignin/PEO complex formation and the bridging of the formed complexes. This hypothesis was supported by the turbidity, FTIR and particle size measurements. Interestingly, the hemicelluloses removal from the acidification/PEO flocculation was marginal, which would be beneficial for the down-stream ethanol production from the PHL. Additionally, a process flow diagram was proposed that incorporates this new concept into the existing configuration of kraft-based dissolving pulp production process. [Copyright &y& Elsevier]

Abstract: In this paper, we proposed a new modification for an ethanol-based pulping process, which would consist of the pre-hydrolysis (pre-extraction) of wood chips for removing hemicelluloses; the ethanol extraction of pre-hydrolyzed wood chips for removing lignin; and the post purification of cellulose, leading to the production of pure cellulose. We also experimentally evaluated the separation of hemicelluloses from the pre-hydrolysis liquor (PHL) obtained from a pulp mill. To remove lignin from the PHL, it was acidified to a pH of 2, which resulted in 47% lignin precipitation. The lignin separation from the acidified PHL was further improved via adding polyethylene oxide and poly aluminum chloride or adding ethyl acetate. To recover the hemicelluloses from the acidified PHL, ethanol was added to the acidified PHL with a volumetric ratio of 4 to 1. The isolated lignin and hemicelluloses were characterized by a Fourier transform infrared spectroscopy (FTIR) and a gas permeation chromatography (GPC). [ABSTRACT FROM AUTHOR]

High-yield pulp (HYP) is gaining increasing interest in wood-free papers, because it can improve the bulk, formation, and opacity of papers. However, one of the challenges for the papermakers is the strength of papers when a large amount of HYP is replaced with hardwood kraft pulp. In this work, we explored the potential of using cationic-modified polyvinyl alcohol (C-PVA) in increasing the strength properties of HYP. Also, C-PVA was applied to the paper-sheets made of softwood/hardwood bleached kraft pulps (SBKP/HBKP) and HYP under various conditions, and the corresponding paper properties were evaluated. It was observed that C-PVA increased the strength properties of these paper-sheets, and the results obtained from using C-PVA were only slightly less effective than those obtained from using cationic starch (C-starch). Furthermore, the addition of C-PVA to HYP, and subsequently mixing with the blend of SBKP/HBKP (option no. 1) improved the tensile and burst indices, light scattering coefficient and apparent density of paper-sheets more significantly than did the addition of C-PVA directly to the mixed furnish of SBKP/HBKP/HYP (option no. 2). Additionally, atomic force microscope (AFM) analysis showed that the attraction force, developed between the AFM-tip and the fiber surface, was changed by the C-PVA modification. The tensile and burst indices of paper-sheets were improved by adding 10 mg g-1 C-PVA and substituting 30% of HYP for HBKP, whereas the tear index, apparent density, PPS-roughness, and brightness decreased. [ABSTRACT FROM AUTHOR]

Abstract: Non-wood is one of the most important raw materials for pulp and paper production in several countries due to its abundance and cost-effectiveness. However, the pulping and papermaking characteristics of canola straw have rarely been investigated. The objective of this work was to determine the potential application of canola straw in the chemimechanical pulping (CMP) process. At first, the chemical composition and characteristics of canola straw were assessed and compared with those of other non-woods. Then, the CMP pulping of canola straw was conducted using different dosages of sodium sulfite and sodium hydroxide. The results showed that, by applying a mild chemical pretreatment, i.e., 4–12% (wt.) NaOH and 8–12% (wt.) Na2SO3, in the CMP pulping of canola straw, the pulp brightness reached almost 40%ISO, and the strength properties were comparable to those of bagasse CMP and of wheat straw CMP. The impact of post-refining on the properties of canola straw CMP was also discussed in this work. [Copyright &y& Elsevier]

Abstract: Previously, the application of modified chitosan (MCN) and carboxymethyl cellulose (CMC) in a dual polymer system showed promising results in increasing the strength of fiber networks. This work evaluates the influence of CMC molecular weight (MW) and of CMC/MCN ratio on the characteristics of formed CMC/MCN complexes in polymer solutions and on the properties of cellulosic fiber networks. The results showed that the application of MCN and the high MW CMC (HCMC) (1:1 charge ratio) enhanced the tensile, burst, and tear indices, but reduced the light scattering coefficient of the fiber network more significantly than that of MCN and the low MW CMC (LCMC). Increasing the ratio of HCMC/MCN marginally affected the tensile index, the burst index, and the light scattering coefficient of the fiber network, even though the ratio significantly affected the characteristics of the CMC/MCN complexes in polymer solutions. The tear index and brightness were improved by increasing the HCMC/MCN ratio. These results were explained based on the retention of HCMC/MCN complexes and the layer-by-layer assembly of HCMC and MCN on the fiber surface. [Copyright &y& Elsevier]

Abstract: The characteristics of dry strength additives affect their efficiency in improving fiber bonding. In this work, the influence the charge density and molecular weight, MW, of cationic poly (vinyl alcohol), CPVAs, in improving the strength of papers was investigated at equilibrium level of CPVA adsorption. In the case of CPVAs with the charge density of 0.75meq/g, the small CPVAs (hy <8nm) did not alter the paper properties, though they adsorbed more than the large CPVAs. The large CPVAs (hy >8nm) improved the paper properties to some extent, but the hydrodynamic size of CPVAs did not affect their efficiency in improving the paper properties. Also, the low-charged (0.4meq/g) high molecular weight (MW) CPVA improved the paper properties more than the high-charged high MW ones, even though the total charges introduced to fibers were less by applying low-charged CPVA than by applying high-charged ones. Similar trends were obtained by adsorbing various CPVAs on refined fibers. However, the properties of papers made from unmodified refined fibers were generally superior to those of papers made from CPVA-modified refined fibers, probably due to the coverage of fibrils on the fiber surface. [Copyright &y& Elsevier]

Abstract: In this work, the diffusion of cationic poly (vinyl alcohol) (CPVA) with well-defined structures into the pores of bleached kraft fibers was investigated at equilibrium level of adsorption by means of adsorption, solute exclusion technique (SET), and nuclear magnetic resonance (NMR) relaxation method. The results showed that the interaction between CPVA and dextran polymers was weak, which allowed us to use the SET method to investigate the variation in the pore size of fibers upon diffusing CPVAs. Both adsorption and SET methods confirmed the diffusion of CPVA polymers into the fiber pores. However, the NMR technique was unable to reflect the pore size changes. The main reason for such results was probably the error that occurred in removing water between fibers via applying the water retention value (WRV) test prior to the NMR analysis. In fact, not all of the water on the fiber surface, especially on the surface of CPVA-modified fibers, could be removed by the WRV, introducing some error in the NMR analysis. [Copyright &y& Elsevier]

Abstract: Poly (vinyl alcohol) (PVA) has been widely used in papermaking and coating processes. However, its application as a strength agent is confined due to its poor affinity to adsorb on fibers. To address this problem, PVA with different molecular weights were rendered cationic via introducing quaternary ammonium groups along PVA chains. The work presented in this paper focused on the adsorption behavior of the cationic-modified PVA (C-PVA) on cellulose fibers (sulfite pulps). The results, obtained from polyelectrolyte titration, indicated that the adsorption of C-PVA with low charge densities was enhanced, regardless of polymer molecular weight (MW). However, the C-PVA with high MW had markedly lower maximum coverage than the C-PVA with low MW. Adsorption of low MW polymers achieved saturation at a relatively shorter period than high MW polymers. The influence of pH, ionic strength (or electrolyte concentration) and temperature on the adsorption of C-PVA on fibers were also investigated. Apart from the study on the adsorption using colloidal titration, the degree of substitution of cationic groups on PVA was quantified using 1H NMR. [Copyright &y& Elsevier]