Soda Black Liquor Research Articles

Modified lignin by deep eutectic solvent as a novel coupling agent for wood-plastic composites

In this work, the influence of modified lignin by Deep Eutectic Solvent (DES) as a novel bio coupling agent on the various properties of wood flour- polypropylene composites (WPCs) was investigated. For this purpose, extracted lignin from Bagasse Soda black liquor was modified with Choline chloride–ZnCl2 deep-eutectic solvent (ChCl–ZnCl2 DES) and then different ratios of unmodified and modified lignin (0, 1, 3 and 5 wt%) were added to the wood flour/polypropylene mixture. Different properties of lignin after modification by DES along with physical and mechanical properties of the manufactured composites were measured according to the relevant standard methods. The FTIR analysis indicated that DES- modified lignin has a higher proportion of phenolic hydroxyl groups (1213 cm−1) and a lower one of methoxy groups (2854 cm−1) when compared to virgin lignin. DSC analysis also showed that the glass transition temperature (Tg) of lignin decreased from 90 °C to 80 °C by DES treatment. Based on the results obtained, the physical and mechanical properties of WPCs were continuously improved by increasing the modified lignin content from 1 to 5 wt%. The composites with DES-treated lignin presented lower water absorption and thickness swelling as well as higher flexural, tensile and impact properties compared to those prepared with unmodified lignin at the same fixed level of lignin. Moreover, based on the finding of this research, the composites with 5 wt% DES-treated lignin have relatively better physical and mechanical properties than those made from 2 wt% maleic anhydride polypropylene (MAPP) as a control sample. Modification of lignin with DES improves its uniform dispersion in the polymer matrix according to Scanning Electron Microscopy (SEM) images.

Maleated nanolignin as a new coupling agent for wood-plastic composites

In this work, the influence of maleic anhydride-treated nanolignin as a coupling agent on the various properties of wood fiber-polypropylene composites was investigated. For this purpose, extracted lignin from Bagasse Soda black liquor was modified with maleic anhydride and then different ratios of unmodified and modified nanolignin (1, 3 and 5 wt%) were added to the wood fiber-polypropylene mixture. The composites were then manufactured by injection molding after mixing mechanically to the wood flour either virgin or maleated nanolignin and polypropylene. Structural and thermal properties of nanolignin after modification by maleic anhydride along with physical and mechanical properties of the manufactured composites were determined according to standard methods. The FTIR analysis indicated nanolignin rearrangements showing that some bonds changed or formed after its modification with maleic anhydride. The glass transition temperature of the nanolignin decreased by esterification from 130°C to 100°C. The panel testing results indicated that all physical and mechanical properties of the composites were continuously improved by increasing the maleated nanolignin content from 1 to 5wt%. Thus, the composites with maleated nanolignin presented higher dimensional stability and mechanical strength compared to those prepared with unmodified nanolignin. Scanning electron microscopy (SEM) showed that treatment with maleic anhydride improves the uniform dispersion of nanolignin in the polymer matrix. The manufactured WPCs can be used as interior and exterior building materials such as decks, sidings and etc.

Mathematical Modelling of Infra-Red Evaporation Characteristics of Wheat Straw Black Liquor

Infrared (IR) evaporation characteristics of Weak Soda Black Liquor (WSBL) were determined at five different temperatures of 80, 90, 100, 110 and 120oC. The effect of constant temperature on evaporation rate and moisture content (on a dry basis) of 1.5 gm approx. WSBL tests were contemplated and required a careful time frame of IR dissipation to vanish the dampness content at a different consistent temperature. The dissipation rate expanded with expanding infrared temperature. Therefore, different numerical models, such as Page and Logarithmic, Henderson, Pabis and Lewis, were utilised to fit the experimental data properly. A Gaussian model equation was developed for evaporation rate and moisture fraction of black liquor. The probable empirical parameters, along with the relating of reduced chi-square (X2), Residual Sum of Square (RSS), and coefficients of determination (adjusted R2) from non-linear regression analysis of all the numerical model equations, were examined. In addition, the effect of evaporation temperature on the water removal rate, the effective diffusion coefficient and activation energy were also estimated. The effective diffusion coefficient ranges from 2.67 × 10–10 m2/s to 10.4 × 10–10 m2/s, and the activation energy was 39.19 kJ/mol. The statistical indicators (chi-square and determination coefficient) showed that the Decay model equation and Gaussian equation are the most suitable models for describing the evaporation process of WSBL.

Application of weibull mixture model to illustrate wheat straw black liquor pyrolysis kinetics

Wheat straw soda black liquor is by-product of agricultural based paper industry. It is a promising resource of renewable energy. It is evaluated using thermogravimetric technique at different heating rates (e.g. 5, 10, 15 and 20 °C/min) in nitrogen atmosphere. From thermogravimetric analysis (TGA) graph it is found that there are three different mass loss processes, such as moisture or water molecule separating process, volatile material burning process and alkali salts reacting and fixed carbon burning process. TGA and Differential Thermogravimetric curves slightly move towards higher temperature side with increase in the heating rate. Weibull mixture model proposed allows for fitting an overall TGA curve of soda black liquor solid pyrolysis.The TGA curves of soda black liquor solids at different heating rates (5, 10, 15 and 20 °C/min.) have been analyzed and found the corresponding adjusted R- squared value greater than 0.99 in each case, thus the calculated TGA data by Weibull mixture model are in agreement with the actual experimental TGA data. Therefore, the TGA curve of soda black liquor solids pyrolysis can be understood as combination of three parallel reactions, where each single component represents one single reaction. Ozawa and Kissinger methods are used to find out the kinetic parameters such as activation energy and pre-exponential factor for the pyrolysis of soda black liquor solids. The activation energy of soda black liquor solids is almost equal in both methods. The experimental data and data driven models can help in smooth plant operations.

Hydrogen production from supercritical water gasification of soda black liquor with various metal oxides

Supercritical water gasification is an innovative handling method of black liquor, which can also produce hydrogen-rich gases. In this study, the catalytic activity of 14 common metal oxides on SCWG of black liquor were investigated and the catalytic mechanism was studied through X-ray photoelectron spectroscopy (XPS) analysis. All the tested oxides improved the gasification efficiency and V2O5, WO3 and Co2O3 showed the highest performance. The H2 yields of 21.67 and 21.03 mol/kg were achieved with the presence of Co2O3 and ZnO respectively. The gasification efficiency increased with the increasing V2O5 amount, but the H2 fraction increased firstly and then decreased. The highest H2 fraction of 44.59% was obtained with V2O5 loading amount of 45 wt%. The increase of reaction time improved the CE, but the further prolongation had little influence. The XPS analysis of CuO and Fe2O3 showed some of them were reduced to metal (Cu) or lower-valence oxides (Cu2O, FeO). The metal oxides probably promoted black liquor decomposition by introducing reactive oxygen, and the generated metal also catalyzed the gasification. Accordingly, an oxidation reactor could be introduced to recycle the metal oxides, which may help to realize the complete gasification of black liquor or other refractory wastes at milder temperatures.

Lignin Isolation from Black Liquor for Wastewater Quality Improvement and Bio-material Recovery

Spent pulping chemicals along with liberated lignin called black liquor are a major liquid waste stream from wood digestion process. For wastewater quality improvement, lignin residue could be isolated via various techniques. According to difference in chemical pulping process (kraft and soda), variations of organic and inorganic substance were suspended in waste stream. This research aims to investigate the effects of the cooking chemical on organic waste (lignin) in black liquor. Organic waste in black liquor was isolated as soda lignin (SL) from soda black liquor (SBL) and kraft lignin (KL) from kraft black liquor (KBL) by acidic precipitation. In addition, lignin model compound (LMC) was used to establish base case measurement. The elemental analysis revealed the similarity of C, H, and O content of samples in range of 32-33%, 3-4%, and 35-38%, respectively. FTIR results showed that structures of lignin, functional group and guaiacyl to syringyl ratio were vary depended on type of chemical pulping with β-O-4 as the primary composition of the samples. Moreover, Py-GC/MS technique was applied for analyzing the degradation products in order to corroborate the result with the structure and thermal behavior analysis. The TGA results showed high stability of lignin up to around 400°C. Main degraded compounds of all samples were phenol, vanillin, catechol, and guaiacol. This finding suggested that not only lignin which caused high BOD and COD could potentially be isolated for value added product but also the discharge quality could be improved. In addition, different chemical processes effect residual lignin in black liquor and underscore the importance of lignin in black liquor as a potential material for renewable energy and chemical production.

Ionic liquid- modified lignin as a bio- coupling agent for natural fiber- recycled polypropylene composites

In this study, the influence of ionic liquid-treated lignin as a bio coupling agent on the various properties of bagasse fiber-recycled polypropylene composites was investigated. For this purpose, extracted lignin from Bagasse Soda black liquor was modified with 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid and then different ratios of unmodified and modified lignin (0, 1, 3 and 5 wt%) were added to the bagasse fiber/recycled polypropylene mixture. The composites were then manufactured by injection molding after mixing mechanically of the bagasse fiber, virgin or modified lignin and recycled polypropylene. Structural and thermal properties of lignin after modification by ionic liquid along with physical (water absorption and thickness swelling) and mechanical (flexural modulus, flexural strength, tensile strength and impact strength) properties of the manufactured composites were measured according to ASTM standard methods. The FTIR analysis indicated lignin rearrangements showing that some bonds changed or formed after its modification with IL. The DSC analysis showed that the glass transition temperature (Tg) of lignin decreased from 92 °C to 80 °C by increasing the weight ratio of ionic liquid to lignin from 20 to 30 wt%. The panel testing results indicated that all physical and mechanical properties of the composites were continuously improved by increasing the lignin content from 1 to 5 wt%. Thus, the composites with IL-treated lignin presented higher dimensional stability and mechanical strength compared to those prepared with unmodified lignin. Scanning electron microscopy (SEM) showed that treatment with ionic liquid improves the uniform dispersion of lignin in the polymer matrix.

Direct lignin depolymerization process from sulfur-free black liquors

Agricultural residues (olive tree pruning and almond shell) were subjected to different delignification treatments (organosolv and soda) and the obtained liquors were treated in a high-pressure reactor at 300 °C for 80 min to depolymerize the dissolved lignin. In this way, the step of precipitating lignin from the liquor was avoided. The phenolic oil obtained after liquors treatment was around 20% of the organic matter contained in previous liquors in all cases. However, phenolic monomeric compounds varied in function of the liquor source. Soda black liquors produced higher quantity of catechols, phenol and cresols whereas using organosolv black liquors, more guaiacol and syringol were obtained, highlighting the higher potential enabled by base catalyst for demethoxylation, demethylation and dealkylation reactions. Furthermore, the NaOH present in soda black liquors prevented undesirable repolymerization reactions by inhibiting the char formation and noticeably dropping the molecular weight of residual lignin. However, organosolv liquors presented a significant higher yield of phenolic monomers, about three times higher than the one obtained in the soda process. Residual lignin, which was not only unconverted lignin, was proved to be different from the initial lignin, pointing out the totally conversion of the initial lignin samples.

Novel chromatographic process for the recovery and purification of hydroxy acids from alkaline spent pulping liquors

In this study, an efficient sequential chromatographic process for recovering hydroxy acids (HAs) from soda and kraft black liquors (BLs) has been developed. Lignin and pulping chemicals are also recovered and can be recycled back to the pulping process. A weak cation exchange resin in Na+ form separates lignin from BL. Up to 95% lignin yield was obtained, with over 50% yield for HAs as Na salts. A cellulose-based resin is used to separate HAs from NaOH. Complete separation, and thus 100% yield for HAs and NaOH, was achieved. The HAs in soda BL are liberated by ion exchange. In case of kraft BL, the solution is acidified with H2SO4 and subjected to ion exchange and ion exclusion chromatography to recover the remaining pulping chemicals. It was found that fouling, which limits the efficiency of membrane-based processing of BLs, is avoided with the appropriate choice of chromatographic separation materials.

Characterization of Lignin Precipitated From The Soda Black Liquor of Oil Palm Empty Fruit Bunch Fibers by Various Mineral Acids

Soda lignin from oil palm empty fruit bunch was directly isolated by various mineral acids i.e. sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid at three levels of concentration (20% v/v, 60%v/v and concentrated). A comparison study was performed through physicochemical properties and structural features using FT-IR, UV, 13C-NMR and nitrobenzene oxidation. The FT-IR results showed that there is no significant difference between the main structures of the lignin isolated by various acids. However, low concentration of phosphoric acid is preferable because of its highest yield. The S: V: H ratio of 7-15:6-11:1 as evaluated by the nitrobenzene oxidation procedure suggests that soda lignin can be classified as belonging to either the cereal straw on grass type. The UV results indicate that phosphoric acid consistently gave the highest absorbance value among the four acids tested in this study regardless of its concentration level. The C13-FTNMR spectra, suggest that the lignin structure is independent of the type of acid used for precipitation.

The effect of alkali on the product distribution from black liquor conversion under supercritical water

ABSTRACTLignin in chemical pulping waste, or black liquor (BL), can be converted into various products via supercritical water gasification (SCWG). However, the inherited alkaline contents from the pulping chemicals may affect the product yields and properties. In this research, the influence of the residual alkali on the product distribution via SCWG of soda BL and kraft BL was evaluated. The SCWG was performed in a batch quartz reactor for 10 min at various temperatures (673, 773 and 873 K) and pressures (250, 300 and 400 bar). The highest hydrogen (H2) production occurred at 873 K for the soda BL. The water–gas shift reaction with sodium ions played an important part in the H2 production, while only small amounts of methane and carbon monoxide were detected. Hydrocarbons, carboxylic acids and esters were the dominant substrates in the liquid products, which denoted the potential of this method for bond cleaving of the lignin macromolecule. As a result, BL, which typically contains alkali salt, was an appropriate feedstock for the SCWG reaction to produce renewable fuel. This method not only has a positive influence on the generation of value added products from highly corrosive waste but also helps avoid some technical problems commonly encountered with direct firing in a recovery boiler.

Vanillin Formation by Electrooxidation of Lignin on Stainless Steel Anode: Kinetics and By-Products

Galvanostatic electrooxidation runs on stainless steel (SS-304) anode were carried out on soda lignins from wheat straw and bagasse obtained from acidification of respective soda black liquors. Vanillin concentration, produced during electrooxidation, is found to increase, attain a maximum, and then decline. Pseudo-first-order specific reaction rate constants for lignin degradation in electrooxidation over SS-304 anode were found to be 0.0308 and 0.0368 h−1, respectively, for the two lignin samples. Degradation of vanillin during electrooxidation was found to be of second order with respect to vanillin concentration with specific reaction rate constant being 0.0009 L/(mg h). A kinetic model was proposed based on series-parallel multiple reaction scheme using a fourth-order Runge–Kutta iteration to fit the time-dependent vanillin concentration during electrooxidation. It was proposed that a vanillin precursor was formed from the parent lignin macromolecule with a pseudo-first-order specific reaction rate constant of 0.03 h−1 for wheat straw soda lignin and 0.036 h−1 for bagasse soda lignin. The vanillin precursor subsequently converted to vanillin with a pseudo-first-order specific reaction rate constant of 0.044 h−1. In addition to vanillin, 4-hydroxy-3,5-dimethoxyphenyl ethanone, and 1,2-benzenedicarboxylic acid were detected as major by-products. Interestingly, some aliphatic and aromatic hydrocarbons were also formed.

Lignin Depolymerization Process Intensification by Direct Treatment of Delignification Black Liquor

In this study, lignin obtained from almond shell by soda delignification treatment was directly depolymerized to produce phenolic monomers without the need of isolating it after its extraction. Thus, the black liquor from the delignification treatment, where lignin is dissolved, was treated in a high pressure reactor at 300 °C for 80 minutes to depolymerize the dissolved lignin. In this way, the step of precipitating lignin from the liquor was suppressed intensifying the whole process of lignin valorization. On the other hand, in order to have a reference, lignin from black liquor was isolated using selective precipitation methods and was submitted to a depolymerization process with the same conditions applied to the black liquor, employing in this case sodium hydroxide dissolution (4 wt.%) in a solid:liquid ratio of 1:20. After both depolymerization treatments, three main products were obtained: oil, residual lignin and char. These products were quantified and analytically characterized by Gas chromatography/Mass spectroscopy (GC/MS) and gel permeation chromatography (GPC). The direct treatment of soda black liquor to depolymerize the lignin dissolved in there, gave better results regarding oil and char yields than depolymerizing the isolated solid lignin.

High-Efficiency Gasification of Wheat Straw Black Liquor in Supercritical Water at High Temperatures for Hydrogen Production

Supercritical water gasification (SCWG) is an innovative handling method for black liquor, which can eliminate its pollution and produce hydrogen simultaneously. In this study, we investigated SCWG of wheat straw soda black liquor with higher temperature and longer reaction time for efficient gasification in a batch reactor. The influence of temperature (600–750 °C), reaction time (10–50 min), and black liquor concentration (2.5–9.5 wt %) were studied. Higher temperature, longer reaction time, and lower concentration promoted hydrogen production and carbon conversion. For black liquor with an initial concentration of 9.5 wt %, maximum carbon conversion of 94.10% was achieved at 750 °C. Higher carbon conversion (98.17%) was obtained when black liquor was diluted to 2.5 wt %. From thermodynamic analysis and experimental results in literature, we compared low- and high-temperature SCWG of black liquor and found that high-temperature SCWG has better opportunities. On the basis of gasification results, potenti...

Biorefinery Process Combining Specel® Process and Selective Lignin Precipitation using Mineral Acids

Soda black liquors from the Specel® process, which used wheat straw as the raw material, were subjected to an acid precipitation process to recover the lignin. Lignin was isolated by acid precipitation using three different inorganics acids (H3PO4, H2SO4, and HCl) at three concentration levels, and at pH values of 2 and 4. Even though the highest lignin yield was achieved using phosphoric acid, the most economical inorganic acid was sulphuric acid. Physico-chemical characterizations of the precipitated lignin samples were performed using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) (for thermal properties), Fourier transform infrared spectroscopy (FT-IR), and heteronuclear single quantum correlation spectroscopy (HSQC) (for chemical structures). No significant differences were found in the thermal properties and chemical structures of the isolated lignins, except for the lignin obtained with phosphoric acid to lower the black liquor from pH 10.72 to pH 2. Apart from the lignin fraction collected, the soda pulp obtained by the Specel® process using wheat straw could represent a good alternative for packaging industries.

Combustion kinetics for soda black liquor-bagasse pith

ABSTRACTIn order to discover the incineration characteristics bagasse pith and low-quality soda black liquor solids were studied in thermogravimetric analyzer under dry air from ambient temperature to 800°C, to obtain thermogravimetric analysis (TGA) and derivative thermogravimetric (DTG) analysis curves. The experimental results show that the combustion process is not a summing up calculation, but has clearly synergistic effects. Bagasse pith generally affects the devolatization of volatile materials in the combustion. It is inhibited in the beginning and accelerated in the middle and afterward periods. Due to the increment of bagasse-pith’s proportion in the mixture, it is found that temperature difference of the volatile materials’ devolatization rise, volatile materials evolve out quickly, and both the rate and speed of mass loss enhance. Kinetic analysis indicates that parameters E and A of Arrhenius equation during the volatile matter degradation are found to be exponentially fitted well in the combustion process.

Rheological Properties and Statistical Analysis of Wheat Straw Soda Black Liquor

The rheograms of wheat straw soda black liquor in a shear rate range of 10–103 s−1 were investigated by a Physica MCR 100 rheometer. The rheological properties of wheat straw soda black liquor with different solids content were deliberated in 60–100°C temperature range. All samples exhibit shear-thinning properties with the flow behavior index (n) between 0.715 and 0.865. The Arrhenius model was used to explain the influence of temperature on apparent viscosity of soda black liquor. The Arrhenius parameters, ηo and Ea are functions of solids content and expressed by the Ostwald-de-Waele model. The empirical model obtained from the study could well depict the combined effect of solid content and temperature within the range of study. It was concluded from the results that temperature along with the solids content had significant effect on the rheological properties of soda black liquor.

Fragmentation of Lignin from Organosolv Black Liquor by White Rot Fungi

The mycelial growth ability of 13 white rot fungi were separately evaluated in kraft, organosolv, and soda black liquor agar-plates. The fungus able to best grow and decolorize black liquor agar-plates was grown in organosolv black liquor to investigate whether it reduced organosolv lignin molar mass. The fungus Bjerkandera adusta showed fair mycelial growth and decolorization ability in 10% black liquor-agar plates. To obtain low-molecular weight (MW) lignin, B. adusta was cultivated in 150-mL Erlenmeyer flasks containing 10% black liquor and maintained in a shaking culture for 15 days. Lignin was recovered from each Erlenmeyer flask by acid precipitation and was analysed by size exclusion chromatography (SEC) and Fourier transform infrared (FTIR) spectroscopy. The lowest MW of lignin from black liquor was observed on the 11th and 12th days, at 1461 and 1790 kDa, respectively, with the polydispersity close to 1.0, indicating that the molecules were similar in size. Fourier transform infrared spectra bands showed modification of the lignin structure during 9 days, with new bands appearing after five days of lignin biodegradation.

Purification process for recovering hydroxy acids from soda black liquor

Black liquor, a side product of chemical pulping, contains hydroxy acids that have many potential applications, e.g., as polymer precursors. Currently there are no feasible separation processes available for recovery of hydroxy acids from such solutions. Neutralization is usually though to be a necessary pre-treatment, but it adds into chemical consumption and may impede the integration of the recovery process to a pulp mill. In this work, an experimental investigation of a new process concept for the recovery and purification of hydroxy acids from soda black liquor without neutralization is presented. The process consists of ultrafiltration, size-exclusion chromatography, ion-exchange, adsorption, and evaporation. Mixtures of hydroxy acids in high purity were produced from black liquor of soda pulping using the process. A reduction of 99% in lignin content of the organic acid fraction was achieved. In the chromatographic separation step, the recovery of sodium hydroxide was almost 100%. The average purities of hydroxy acids isolated from softwood and hardwood black liquors were 81% and 63% on mass basis, respectively.

Properties Change of Black Liquor in Process of Biological Purification Lignin

Removing the carbohydrate of black liquor through biological treatment to converted it into alcohol, as to improve the purity of lignin. Through the study we found that the content of lignin and carbohydrate decreased in the biological purification process. The content of lignin in alkaline black liquor decreases 12.9% after fermentation. And in alkaline sodium sulfite black liquor it decreases 6.4%. Compared with black liquor, the content of total sugar in soda black liquor decreased 77.1%. And in alkaline sodium sulfite it decreases 77.8%. The lignin purity of two kinds of black liquor will improve after the biological treatment. Lignin of alkaline black liquor by biological treatment and organic matter of black liquor ratio increase 28.74%, which increases 29.35% in alkaline sodium sulfite black liquor. The viscosity and CODcr of two kinds of black liquor will reduce after the biological treatment. The relative viscosity of alkaline black liquor after enzymolysis reduces to 1.178, while the relative viscosity of alkaline sodium sulfite black liquor reduces to1.164. The CODcr of alkali black liquor after biological treatment decreases 15.65%; and the CODcr of alkaline sodium sulfite liquor reduces 10.59%.