Alkaline Black Liquor Research Articles

UV-blocking, antibacterial, corrosion resistance, antioxidant, and fruit packaging ability of lignin-rich alkaline black liquor composite film

The novel multifunctional active packaging composite film with antimicrobial, antioxidant, water-vapor and UV-barrier, and corrosion resistance properties was successfully prepared from waste biomass. In this study, waste poplar sawdust was pretreated using green liquor to extract black liquor (BL). BL was then mixed with polyvinyl alcohol (PVA) solution for synthesizing silver nanoparticles (AgNPs). PVA-BL-AgNPs film was fabricated by solution casting method, and the microstructure characterization and macroscopic performance testing of the composite film were conducted. The results revealed that PVA-BL-AgNPs film exhibited inhibitory effects against Staphylococcus aureus (inhibition zone: 33.6 mm), Pseudomonas aeruginosa (inhibition zone: 31.6 mm), and Escherichia coli (inhibition zone: 32.0 mm). It could eliminate over 99 % of 2,2-diazodi (3-ethyl-benzothiazol-6-sulfonic acid) (ABTS) free radicals and provided 100 % UV-blocking, reducing light-induced food damage. It exhibited the improvement of water-vapor barrier properties and corrosion resistance. In vitro cytotoxicity assays demonstrated that no significant impact occurred on cell proliferation, confirming the safety of the film. Packaging experiments showed that PVA-BL-AgNPs film effectively inhibited milk spoilage and prolonged the shelf-life of bread and bananas. Therefore, PVA-BL-AgNPs film might extend the shelf-life of food and offer significant opportunities in addressing the issues of low safety and environmental pollution associated with traditional packaging films.

Hydrodeoxygenation of guaiacol to bio-hydrocarbons in alkaline condition on the Ni/AC catalyst with an “acid-switch”

Due to the mass manufacturing of global papermaking black liquor, lignin remained in strong-alkaline black liquor is a promising raw material for bulk hydrocarbons production with huge carbon–neutral value. In this work, the alkaline in reactant is proved to inhibit the hydrodeoxygenation reaction of guaiacol severely due to the formation of phenates and cyclohexadienones. A hydroxyl interventional Ni/AC catalyst, on which an “acid-switch” is built with combination of hydroxyl groups and Ni nanoparticles, achieves 4-fold bio-hydrocarbons yield in alkaline condition compared to conventional Ni/AC catalyst. It is implied that hydroxy groups promote the C(sp2)-O reaction route with the aid of activated hydrogen on Ni nanoparticles, while acidic groups on catalyst reduce the size of Ni nanoparticles, thus further enhances the HDO efficiency. It is the first time we propose a reaction mechanism of HDO of guaiacol on Ni-based catalyst in alkaline condition to give insight into HDO reaction of lignin compounds in black liquor. This work gives insights into the relationship between catalyst surface properties and HDO efficiency, and provides a promising approach for green utilization of lignin in alkaline black liquor.

Sugarcane Light-Colored Lignin: A Renewable Resource for Sustainable Beauty.

Lignin has emerged as a promising eco-friendly multifunctional ingredient for cosmetic applications, due to its ability to protect against ultraviolet radiation and its antioxidant and antimicrobial properties. However, its typical dark color and low water solubility limit its application in cosmetics. This study presents a simple process for obtaining light-colored lignin (LCLig) from sugarcane bagasse (SCB) alkaline black liquor, involving an oxidation treatment with hydrogen peroxide, followed by precipitation with sulfuric acid. The physico-chemical characterization, antioxidant and emulsifying potential of LCLig, and determination of its safety and stability in an oil-in-water emulsion were performed. A high-purity lignin (81.6%) with improved water solubility was obtained, as a result of the balance between the total aromatic phenolic units and the carboxylic acids. In addition, the antioxidant and emulsifying capacities of the obtained LCLig were demonstrated. The color reduction treatment did not compromise the safety of lignin for topical cosmetic applications. The emulsion was stable in terms of organoleptic properties (color, pH, and viscosity) and antioxidant activity over 3 months at 4, 25, and 40 °C.

Extraction of hydroxycinnamic acids (ferulic and p-coumaric) from rice straw alkaline black liquor using Pluronic F-127 for potential applications in the cosmetics industry

In the present study, ferulic (FA) and p-coumaric (pCA) acids were extracted from rice straw (Oryza sativa) alkaline black liquor by an aqueous two-phase system (ATPS) based on cloud point of surfactant/copolymer Pluronic F-127 (PF-127). An acid precipitation process was studied as a primary purification step of FA and pCA and next, an extraction of these hydroxycinnamic acids (HAs) using PF-127 in different concentrations (1.1–17.3% w/w) was performed. The results showed that in PF-127 concentration of 9.4% w/w, yield extractions of 75.8% for FA and 74.3% for pCA were achieved. In addition, FA and pCA were concentrated 2.3 and 2.5-fold, respectively, compared to their original concentrations in the liquor, resulting in a PF-127 gel containing 0.12% w/w HAs. This material will be further investigated for potential applications in the cosmetics industry as an alternative for obtaining high value-added products in a rice straw-based biorefinery. Data availabilityData will be made available on request.

Green production of prebiotic xylooligosaccharides via enzymatic hydrolysis from xylan black liquor of oil palm frond

The black liquor generated from the alkaline pretreatment of lignocellulosic biomass is usually disposed of into wastewater, which could lead to environmental pollution. Alkaline black liquor (ALBL) contains a large amount of xylan with a small fraction of lignin, making it a promising raw material for the production of xylooligosaccharides (XOS). In this study, xylan was extracted from the ALBL generated upon treating the oil palm frond (OPF) with sodium hydroxide via two-stage precipitation for the separation of lignin and recovery of xylan. As a result, approximately 84.0% of xylan retrieved from the ALBL was recovered. Subsequently, enzymatic hydrolysis was optimized to recover the maximum amount of XOS from xylan. The results showed that enzymatic hydrolysis produced the highest XOS (62.5%) under optimal conditions of 50 °C, 4 U/mL xylanase, and 3% xylan loading for 48 h. The study provides insight for maximizing utilization of ALBL of OPF for future biorefinery economy.

Hydrogen Production from Enzymatic Hydrolysates of Alkali Pre-Treated Giant Reed (Arundo donax L.)

The perennial rhizomatous grass giant reed (Arundo donax L.) can be exploited to produce hydrogen by dark fermentation. This implies a high availability of simple sugars, like glucose and xylose, and, thus, a pre-treatment is necessary to remove lignin and expose the holocellulose to enzymatic attack. This study aimed at evaluating the hydrogen production from giant reed hydrolysates. Giant reed dry meal was pre-treated with diluted NaOH (1.2% weight/weight), then the solid fraction was separated from the alkaline black liquor by filtration, enzymatically hydrolyzed with a cellulase blend (Cellic CTec2), and fermented in mesophilic batch conditions with a microbial consortium derived from pig slurry. The impact on hydrogen yield of initial pH was evaluated by comparing the hydrogen production from hydrolysates with not adjusted (5.3) or adjusted initial pH (8.7) using NaOH or alkaline black liquor. The highest hydrogen yield, 2.0 mol/mol of hexoses, was obtained with alkaline initial pH 8.7, regardless of how the pH adjustment was managed. The yield was 39% higher than that obtained in reactors with initial pH 5.3. In conclusion, thermo-alkaline pre-treatment followed by enzymatic saccharification and initial pH adjustment at 8.7 with the black liquor remaining after pre-treatment is a promising strategy to produce hydrogen from giant reeds in dark fermentation.

Biobased rigid polyurethane foam using gradient acid precipitated lignin from the black liquor: Revealing the relationship between lignin structural features and polyurethane performances

Rigid polyurethane foams (RPFs) are a type of versatile polymers with a variety of applications, which can be produced by condensation polymerization of isocyanates with renewable polyols that are derived from biomass materials. This study investigates the characteristics of bio-sourced synthesized RPF using lignin fractionated from the alkaline black liquor of corn stover. GPC, FTIR, TGA, 2D-HSQC, and 31P NMR were used to characterize the isolated lignin specimens. The fractionated lignin specimens were then pre-polymerized followed by using them as the substitutes of RPFs. The characterization and properties of the RPFs substituted with the isolated lignins were analyzed. Compared with other lignin specimens, the specimen isolated in pH range of 5.5–2.0 afforded to higher compressive strength (0.39 ± 0.01 MPa), lower apparent density (41.35 ± 0.21 kg m-3), lower thermal conductivity (0.043 ± 0.0012 W m-1 K-1), and better thermal stability of the RPF product. In addition, the relationships between structural features of lignin specimens and the properties of the RPFs were investigated. Results show the content of β-O-4 bond inner lignin structure was the main factor that affected on the thermal conductivity of RPF, while a higher hydroxyl groups content in lignin would largely improve the compressive strength and leading to the reduction of the apparent density. This research helps to comprehensively understand the features of lignin on RPF’s performance, providing a new method for its functionalization which is significant in their commercialization.

Influence of sodium carbonate addition on weight loss of bagasse alkaline black liquor during pyrolysis

To understand the effects and the mechanism of sodium carbonate (Na2CO3) addition on the bagasse alkaline black liquor (BABL) pyrolysis, the reaction variables such as temperature, heating rate, and amount of Na2CO3 addition into BABL-solids were investigated under N2 atmosphere from 50 °C to 1000 °C by thermogravimetic analysis (TGA). Scanning electron microscopy (SEM) and the Coats–Redfern method (CRM) were employed for surface microscopic morphology observations and kinetic analysis, respectively. The results showed that Na2CO3 plays an inhibiting and promoting role during devolatilization (200 °C to 650 °C) and the reduction stages (650 °C to 1000 °C), respectively. Adding Na2CO3 into BABL-solids tends to increase the thickness of the salt layer covering the BABL-solids surface, which increases the activation energy and reduces the weight loss ratio of BABL-solids pyrolysis within 200 °C to 650 °C. Adding Na2CO3 into the BABL-solids tends to increase the number of alkaline compounds or the active site of the reduction reaction, which reduces the activation energy and increases the weight loss ratio of BABL-solids pyrolysis within 650 °C to 1000 °C. The role of Na2CO3 as an additive could be well understood by studying the influence mechanism of Na2CO3 on BABL-solids pyrolysis.

Effect of Alkaline Black Liquor Recycling on Alkali Combined with Ozone Pretreatment of Corn Stalk.

In the early stage, the best conditions for alkali-bound ozone pretreatment were studied. But after treatment, the alkaline black liquor was directly discarded due to the large amount of organic matter, resulting in environmental pollution and waste of resources. In this paper, the alkaline black liquor was recycled under the optimal pretreatment conditions. The results showed that the number of alkaline black liquor cycles had little effect on hemicellulose content, and had a great influence on cellulose content and lignin content. Through structural characterization of corn stover, it was found that the pretreatment caused structural changes of lignin in straw. However, when the alkaline black liquor was recycled for the fourth time, the ether bond in the side chain of lignin and the covalent bond between the components were not sufficiently destroyed, and the damage to the phenolic hydroxyl group was also weakened. It was indicated that when the alkaline black liquor was recycled for the fourth time, the destruction effect of the alkaline black liquor on the straw was significantly inhibited. Therefore, the optimal circulation time of alkaline black liquor was three times, and the cellulolytic conversion rate was 81.53%.

Enhancement of high xylan recovery from black liquor of alkaline pretreated oil palm frond and its physicochemical properties

The xylan recovered from alkaline black liquor (ABL) of oil palm frond (OPF) has the potential to be converted into value-added products that hold promise, especially for the pharmaceutical industry. This research highlights the maximum xylan relative recovery extracted from ABL by varying the extraction parameters such as the concentration of sodium hydroxide (NaOH) (2 to 10%) (w/v), reaction temperature (60 to 140 °C), and extraction time (30 to 150 min), followed by a 2-stage precipitation method. 6 M of hydrochloric acid (HCl) was used in the first stage to separate the lignin sub-fraction (LF) from the ABL, and 95% ethanol was used in the second stage to obtain xylan sub-fraction (XF). The optimal condition of 6% NaOH (w/v), 100 °C, and 60 min was able to recover 84% of xylan, with low contamination of lignin (7.7%) and glucan (0.3%) in XF, while higher contamination of lignin (19.3%) and glucan (10.9%) with lower amount of xylan (8.8%) were found in LF. The amount of lignin and glucan in LF through the first precipitation was higher than in XF from the second precipitation, leaving remaining fraction of XF mainly composed of xylan. In sum, the developed process reduced the alkali consumption while retaining a high xylan recovery under mild process conditions.

Co-gasification of Alkaline Black Liquor and Coal in Supercritical Water at High Temperatures (600–750 °C)

The catalytic activity of the alkali compounds in alkaline black liquor can be used in supercritical water gasification (SCWG) of coal to lower the reaction temperature and improve the hydrogen production, and the black liquor can be handled simultaneously. In the present study, the gasification features of coal/black liquor blends at high temperatures (600–750 °C) were studied through thermodynamic analysis and experimental study. A synergetic effect was found during co-gasification of coal and black liquor, where both the gasification efficiency and hydrogen production was improved by efficiently using the alkali catalyst in black liquor. The highest improvement of the gasification was found at the blending ratio of about 50:50. Both the thermodynamic analysis and experiments indicated that higher temperature favors the hydrogen production. The gasification efficiency was improved with temperature and the maximum carbon conversion of 79.46% was achieved at 750 °C. The dilution of the black liquor/coal b...

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%.

Hydrogen production from supercritical water gasification of alkaline wheat straw pulping black liquor in continuous flow system

Supercritical water gasification of alkaline black liquor was investigated in a continuous flow system. The experiments were carried out at 400–600 °C, 25 MPa, with residence times ranging from 4.94 to 13.71 s. The results showed that the increase of temperature and residence time and the decrease of feeding concentration enhanced the gasification. The gaseous product contained high level of hydrogen (40.26–61.02%). Maximum COD removal efficiency (88.69%) was obtained at 600 °C. The alkalis in black liquor were found to be precipitated in the reactor during the gasification, which decreased the pH of the effluent to the neutral region (6.4–8.0). The precipitated alkalis were dissolved in the water when the fluid temperature in the reactor was cooled to about 360 °C which increased the pH of the effluent to 11.0. A simplified kinetic study for COD removal efficiency was done by the pseudo-first order reaction assumption. The apparent activated energy was 74.38 kJ/mol and the apparent pre-exponential factor was 10 4.05 s −1.

Bacterial decolorization of black liquor in axenic and mixed condition and characterization of metabolites

The pulping byproducts (black liquor) cause serious environmental problem due to its high pollution load. In order to search the degradability of black liquor, the potential bacterial strains Citrobacter freundii (FJ581026) and Citrobacter sp. (FJ581023) were applied in axenic and mixed condition. Results revealed that the mixed bacterial culture are more effective than axenic condition and can reduce 82% COD, 79% AOX, 79% color and 60% lignin after 144 h of incubation period. Additionally, the optimum activity of lignin degrading enzyme was noted at 96 h and characterized as manganese peroxidase (MnP) by SDS–PAGE analysis. Further, the HPLC analysis of control and bacterial degraded sample has shown the reduction as well as shifting of peaks compared to control indicating the degradation as well as transformation of compounds of black liquor. The comparative GC-MS analysis of control and degraded black liquor revealed that along with lignin fragment some chlorophenolic compounds 2,4,6-trichlorophenol, 2,3,4,5-tetrachlorophenol and pentachlorophenol were detected in black liquor degraded by axenic culture whereas these chlorophenolic compounds were completely absent in black liquor degraded by mixed bacterial culture. These chlorophenol inhibit the oxidative degradation which seems a major reason behind the low degradability of axenic degradation compared to mixed culture. The innovation of this aerobic treatment of alkaline black liquor opens additional possibilities for the better treatment of black liquor along with its metabolic product.

Metabolic versatility of halotolerant and alkaliphilic strains of Halomonas isolated from alkaline black liquor

Wheat straw black liquor is a notorious pulp mill wastewater with very high pH and pollution load. Two halotolerant and alkaliphilic bacteria, designated as Halomonas sp. 19-A and Y2, were isolated from wheat straw black liquor and shown to be able to use guaiacol, vanillin, dibenzo-p-dioxin, biphenyl and fluorene, as sole carbon and carbazole as sole carbon and nitrogen source at pH 9.5 and in the presence of 10% NaCl. The two strains produced carboxymethylcellulase (CMCase), xylanase, lipase, amylase, and pullulanase. High activities of CMCase, xylanase, and amylase were observed at pH 5.0–11.0 and NaCl concentrations of 0–15%. The metabolic versatility of these Halomonas strains even under extreme pH and salinity conditions makes them promising agents for bioremediation and industrial processes.

A novel microbial habitat of alkaline black liquor with very high pollution load: Microbial diversity and the key members in application potentials

A microbial community which developed naturally in alkaline black liquor was investigated by culture-based and culture-independent techniques. The community was effective in lowering pH, color, and chemical oxygen demand (COD) of black liquor, and the community activities varied in different seasons. Both 16S ribosomal DNA (rDNA) clone library and polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) analyses suggested that the seasonal bacterial communities had obvious differences in diversities and compositions. Clostridium species were suggested to be the key agents in black liquor treatment. Moreover, the isolates of the genera Halomonas and Bacillus were shown to be effective in treating very heavily polluted black liquor. The strains of Halomonas, Clostridium and especially Bacillus, might be the key producers of xylanase and CMCase in the community. The worldwide problem of black liquor treatment and renewable resource utilization would benefit from these microorganisms in application potentials.

Correction: A Constructed Alkaline Consortium and Its Dynamics in Treating Alkaline Black Liquor with Very High Pollution Load

Correction: A Constructed Alkaline Consortium and Its Dynamics in Treating Alkaline Black Liquor with Very High Pollution Load

A Constructed Alkaline Consortium and Its Dynamics in Treating Alkaline Black Liquor with Very High Pollution Load

BackgroundPaper pulp wastewater resulting from alkaline extraction of wheat straw, known as black liquor, is very difficult to be treated and causes serious environmental problems due to its high pH value and chemical oxygen demand (COD) pollution load. Lignin, semicellulose and cellulose are the main contributors to the high COD values in black liquor. Very few microorganisms can survive in such harsh environments of the alkaline wheat straw black liquor. A naturally developed microbial community was found accidentally in a black liquor storing pool in a paper pulp mill of China. The community was effective in pH decreasing, color and COD removing from the high alkaline and high COD black liquor.FindingsThirty-eight strains of bacteria were isolated from the black liquor storing pool, and were grouped as eleven operational taxonomy units (OTUs) using random amplified polymorphic DNA-PCR profiles (RAPD). Eleven representative strains of each OTU, which were identified as genera of Halomonas and Bacillus, were used to construct a consortium to treat black liquor with a high pH value of 11.0 and very high COD pollution load of 142,600 mg l−1. After treatment by the constructed consortium, about 35.4% of color and 39,000 mg l−1 (27.3%) CODcr were removed and the pH decreased to 7.8. 16S rRNA gene polymerase chain reaction denaturant gradient gel electrophoresis (PCR-DGGE) and gas chromatography/mass spectrometry (GC/MS) analysis suggested a two-stage treatment mechanism to elucidate the interspecies collaboration: Halomonas isolates were important in the first stage to produce organic acids that contributed to the pH decline, while Bacillus isolates were involved in the degradation of lignin derivatives in the second stage under lower pH conditions.Conclusions/SignificanceTolerance to the high alkaline environment and good controllability of the simple consortium suggested that the constructed consortium has good potential for black liquor treatment. Facilitating the treatment process by the constructed consortium would provide a promising opportunity to reduce the pollution, as well as to save forest resources and add value to a waste product.

Kinetics of CO2 Gasification of Alkaline Black Liquor from Wheat Straw. 2. Evolution of CO2 Reactivity with the Solid Conversion and Influence of Temperature on the Gasification Rate

Results obtained in recent studies have shown that black liquor (BL) gasification can be considered as an attractive recovery system. However, limited information has been published on the gasification kinetics of alkaline BL char (ABLC). Part 1 of this work (Gea, G.; Sanchez, J. L.; Murillo, M. B.; Arauzo, J. Ind. Eng. Chem. Res. 2004, 43, 3233) studied the CO 2 gasification of ABLC, specifically the influence of [CO] and [CO 2 ] on the gasification rate at different temperatures. The present work is focused on the variation of this reaction rate with solid conversion during the gasification process. The results obtained show that the gasification rate increases with the solid conversion up to a maximum value and then decreases. The effect of various factors such as pyrolysis operating conditions on this variation has also been analyzed. Furthermore, the dependence of the ABLC gasification rate on the temperature has been evaluated, and the apparent average activation energy over the range 170-234 kJ/mol has been determined for the temperature range 750-850 °C.

Isolation and structural characterization of polysaccharides dissolved in Eucalyptus globulus kraft black liquors

Polysaccharides dissolved in black liquors from Eucalyptus globulus kraft pulping were isolated by acid precipitation, analysed for monosaccharide composition and structurally characterized by methylation analysis and NMR spectroscopy. The precipitated oligo- and polysaccharides, representing 20% of the dissolved and/or degraded wood polysaccharides are essentially composed of xylan and amylopectin. The xylan dissolved in the alkaline black liquor showed a M w of about 17–19 kDa as revealed by GPC analysis. The major part of the 4- O-methylglucuronic residues in the xylan from black liquor were degraded to hexenuronic (4-deoxy-β- l- threo-hex-4-enopyranosyluronic acid) units, which was not found to be so pronounced in the case for xylan in the corresponding kraft pulps. The overall structural and molecular weight features of both black liquor and pulp xylans during the kraft pulping are discussed.