Straw Black Liquor Research Articles

Exploring the utilities of rice straw black liquor (Part X): biomass-derived copper (lignin/silica/fatty acids) complex as a natural antioxidant for EPDM composites (Part V)

Exploring the utilities of rice straw black liquor (Part X): biomass-derived copper (lignin/silica/fatty acids) complex as a natural antioxidant for EPDM composites (Part V)

Lignin Nanoparticles Produced from Wheat Straw Black Liquor Using γ-Valerolactone.

The valorization of the black liquor produced during the chemical pulping of wheat straw is the key to the sustainable use of this abundant agricultural waste. However, the silica problem has hampered the recovery process. Herein, nanoprecipitation technology was used to produce lignin nanoparticles (LNPs) from wheat straw black liquor using γ-valerolactone (GVL) as a solvent and water as an anti-solvent. The results showed that a uniform, well-dispersed, and stable LNP was produced. The particle size and Zeta potential of 161 nm and -24 mV of the LNP suspension were obtained at a GVL concentration of 87%. The chemical structure and bonding of the lignin were adequately preserved after nanoprecipitation based on two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D-HSQC NMR) spectroscopy, Fourier transform infrared (FTIR) analysis, and thermal stability was improved based on thermogravimetric analysis. In addition, the abundant phenolic hydroxyl groups of LNP quantified by 31P-NMR analysis are beneficial for chemical cross-linking and modification. This work not only achieved the valorization of wheat straw black liquor but also opened up a new avenue for advanced nanomaterials.

Technological and Economic Optimization of Wheat Straw Black Liquor Decolorization by Activated Carbon

Wheat straws are a globally abundant agro-waste that may play a critical role in the global transition from single-use plastics to green materials as an inexpensive and renewable raw material. Vast amounts of wastewater are produced during the technological process of wheat straw-cellulose/hemicellulose conversion. In this context, this work focuses on wastewater decolorization via activated carbon adsorption. A set of carefully planned experiments enabled the identification of a model that described the relationship between the system’s outputs and parameters. While process optimization is frequently connected with identifying process parameters that improve efficiency, this work employed a multi-objective optimization approach from both a technological and economic aspect. Nondominated sorting genetic algorithm versions II and III—NSGA-II and NSGA-III algorithms—were applied. As objectives, maximum efficiency and minimum cost per experiment were followed in different scenarios using pseudoweights and trade-off metrics. When optimizing only the efficiency, the results indicated a 95.54% decolorization yield, costing 0.1228 Euro/experiment, and when considering both the efficiency and cost, different solutions were obtained. The lowest cost was 0.0619, with a 74.42% decolorization. These findings indicate that incorporating an economic perspective into the optimization procedure can improve cost estimation and facilitate managerial decision-making.

Development and comparison of membrane separation schemes for byproduct recovery from Egyptian rice straw black liquor

BackgroundRecovery of valuable ingredients from black liquor could lead to an environmentally and economically sound bioethanol production technology. In this work, two schemes comprising hybrid membrane systems incorporating ultrafiltration (UF) and nanofiltration (NF) are developed for the recovery of lignin, silica rich and cellulose/hemicellulose hydrolysates byproducts from alkaline pretreated rice straw.MethodsThe first scheme (I) comprises UF, NF and thermal vapor compression (TVC), while, the second scheme (II) includes UF, 2 stages of NF and 2 TVC units. Further treatments are suggested to produce solid byproducts with an economic value. Furthermore, material balance of the two schemes based on 1000 m3/d of black liquor and the main design features and comparative direct cost indicators of the main adopted units were deduced using WT Cost II© software.ResultsResults revealed that about (80–90%) yield of recovered byproducts from both schemes with equivalent amounts of 9.5, 5.5 and 18.5 ton/d of lignin, silica rich and cellulose/hemicellulose hydrolysates dry products, respectively. Moreover, reusable water recovery approaches 26% and 70% for schemes (I) and (II), respectively.ConclusionsFurther, the wastewater generated from scheme (II) is 2.9 times folds scheme (I) which improves the environmental impact of the former. Preliminary cost indicators revealed that both schemes have almost the same total direct capital cost.

Effect of pH, temperature, and solids content on rheological properties of wheat straw black liquor

Effect of pH, temperature, and solids content on rheological properties of wheat straw black liquor

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

There was a typo in Table 6 in the initial online publication.

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.

Synthesis and Characterization of Lignin Grafting Modification-based Aliphatic Superplasticizer

Lignin as the main component of black liquor is generally employed to modify aliphatic superplasticizer (AFS). However, the modification effect is hard to evaluate correctly due to the uncertain molecular structure of lignin and the disturbance from the complexity of black liquor compositions. In this paper, the purified lignin via acid precipitation from straw black liquor is used to modify AFS. The modified AFS named as LAFS for short presents lower molecular mass than AFS. It is assumed that it is due to the single active site of guaiacol segments in lignin by which lignin graft modifies AFS in virtue of methylolation reaction. In order to verify this assumption, guaiacol and dihydro eugenol as the typical segments of lignin macromolecule were selected, respectively, as the simplified model compounds of lignin to modify AFS, and corresponding products are abbreviated in GAFS and DAFS. Both GAFS and DAFS show the lower molecular mass than unmodified AFS. FTIR and TG-DTG analyses prove that lignin is successfully grafted onto AFS. The graft modification of lignin results in a decrease in electrostatic epulsion, but an enhanced steric hindrance. Therefore, although the replacement rate of lignin in LAFS was about 23.3%, the dispersion performance was only slightly affected.

Development of rice straw black liquor based porous carbon-poly(aniline-co-methoxy aniline) as supporting for electrochemical performances of alcohol oxidations

The present work had attempted to develop rice straw black liquor based porous carbon-poly (aniline-co-methoxy aniline) composite added catalysts for alcohol oxidation. In this aspect, nanoparticles of platinum-iridium and platinum were deposited on poly(aniline-co-methoxy aniline)-rice straw black liquor based porous carbon (Poly(Ani-co-MAni)-RSBLPC) composite. The electrochemical test has been carried out using Pt-Ir/Poly(Ani-co-MAni)-RSBLPC and Pt/Poly(Ani-co-MAni)-RSBLPC electrocatalysts in an alkaline solution of methanol, ethylene glycol, and glycerol. For comparison, the electrochemical performance test is also done using Pt/Poly(Ani-co-MAni) and Pt/RSBLPC catalysts in basic solution of methanol. From electrochemical studies, it was noticed that platinum nanoparticles decorated Poly(Ani-co-MAni)-RSBLPC reveals a significant enhancement towards the oxidation of methanol in comparison with Pt/Poly(Ani-co-MAni) and Pt/RSBLPC catalysts, which will be expected from the synergic effect of rice straw black liquor based porous carbon and conductive polymer material. Furthermore, the bimetallic Pt-Ir/Poly(Ani-co-MAni)-RSBLPC catalyst showed enhanced catalytic activity in comparison with monometallic Pt/Poly(Ani-co-MAni)-RSBLPC catalyst. The above results suggested that Poly(Ani-co-MAni)-RSBLPC composite is a potent support and could be used as a potent low cost support for catalyst deposition towards fuel cell industries that include the applications of sensor and super capacitor.

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...

Removal of silicon from green liquor with low-temperature precausticizing

Nonwood materials contain a high percentage of silicon, which causes numerous problems in the chemical recovery section. Researchers previously proposed the method of silicon removal by two-stage causticizing at temperatures of 90ºC to 95ºC, finding that the desilication rate was about 72.9% and the causticizing efficiency was 22.7% when 30% of the causticizing quicklime (calcium oxide; CaO) was added. The present paper deals with the desilication of green liquor recovered from wheat straw black liquor by a low-temperature precausticization method. The results showed that about 89.3% silicon removal and 10.3% causticizing efficiency were achieved under the following precausticizing conditions: added lime amount of 20%, temperature of 20ºC, and reaction time of 60 min. While precausticizing at 90ºC with the same lime amount, only about 63.5% silicon removal and 13.0% causticizing efficiency were gained. Therefore, precausticizing with low temperature was beneficial for silicon removal and retention of carbonate (CO3 2-).

Effects of silica on chemical recovery in the direct causticization of wheat straw black liquor

Straw black liquor is relatively difficult to recover using the Tomlinson process because of the presence of silica in inorganic components. Gasification with direct causticization might serve as a promising alternative; however, the interaction between silica and direct causticization agents needs to be evaluated. In this work, desilication was achieved using a laboratory-scale membrane electrolysis cell adopted from the chlor-alkali industry. Then raw and desilicated straw black liquors were carried out through direct causticization with titanium dioxide (TiO2) and recycled sodium tri-titanate (Na2O·3TiO2) at 850°C using a tube furnace. The results show that these two agents exhibit different silica transfer mechanisms. When using TiO2, approximately 80% of the silica is retained in the solid residue after hydrolysis because of chemical interactions. Almost all of the silica transfers to the hydrolysis-derived white liquor when using Na2O·3TiO2. This means that the process of treating straw black liquor by direct causticization might need additional lime causticization to improve the efficiency of sodium recovery. This observation also indicates that silica will not consume the direct causticization agent Na2O·3TiO2 after the initial step using TiO2. The sodium hydroxide (NaOH) yield was 60% when using raw black liquor as the feed to the Na2O·3TiO2 recycling tests and 80% when using desilicated straw black liquor. Considering the NaOH recovered in the electrolysis cell, the total NaOH yields exceed 85% of total titratable alkali. No detectable deterioration of the direct causticization agents was found within the limited number of recycles tested. A greater number of cycles need to be tested at a larger scale to evaluate the feasibility of applying a direct causticization process to straw black liquor.

Hydrochar preparation from black liquor by CO2 assisted hydrothermal treatment: Optimization of its performance for Pb2+ removal

Hydrochar was produced from hydrothermal treatment of corn straw black liquor. Response surface methodology (RSM) and the central composite design (CCD) were employed for determination of optimal char with maximum Pb2+ removal capacity. The operational parameters such as hydrothermal temperature (°C), duration (min) and solid liquid ratio (LSR) were chosen as independent variables in CCD. The statistical analysis indicates that the effects of hydrothermal temperature, duration, LSR and combined effect of hydrothermal temperature and duration are all significant for the Pb2+ removal capacity. The optimal condition for achieving the maximum Pb2+ adsorption capacity is obtained as the following: hydrothermal temperature (205 °C), duration (28min), LSR (12) with Pb2+ removal capacity reaching 47mg/g. The BET specific surface area of char prepared at optimal conditions could reach 85m2/g.

Effects of Catalysts and pH on Lignin in Partial Wet Oxidation of Wood and Straw Black Liquors

Partial wet oxidation (PWO) of kraft black liquor (KBL) and wheat straw black liquor (WSBL) was carried out at 170–230 °C. PWO was conducted under oxygen gas only or in the presence of iron catalysts or hydrogen peroxide as an additional oxidant. Unlike the catalysts, increasing temperature enhanced the PWO process in general. Lignin concentration decreased 57–64% and weight-average molar mass of lignin from 2.7–3.3 kDa of original black liquors to 1.5–1.8 kDa after PWO at 210–230 °C. Unlike in KBL, presence of hemicellulose in WSBL was responsible for increasing total acid concentration from 16 g/L to 30 g/L in PWO at 230 °C. A two-stage process comprising lignin precipitation before subsequent PWO decreased chemical oxygen demand of the liquid fraction by 38–41%. Lignin was fractionated into a solid fraction and a water-soluble fraction which showed 21–26% lower polydispersity compared to lignin in the original black liquors.

Effects of titanium dioxide as direct causticization agent on the pyrolysis and steam gasification characteristics of straw black liquor solid

Black liquor gasification process with direct causticization using titanium dioxide (TiO2) is considered a promising technology for black liquor recovery in the future. In this study, laboratory-scale pyrolysis and steam gasification experiments with direct causticization using TiO2 for straw black liquor solid were performed in a thermogravimetric analyzer and a tube furnace, respectively. Effects of TiO2 on the pyrolysis and steam gasification characteristics are discussed on the basis of product analysis. The results show that after adding TiO2 at temperature higher than 550°C, the direct causticization reactions happened, while the thermogravimetric behavior of the black liquor solid along with releasing pattern of carbon dioxide and carbon monoxide was changed. In the presence of TiO2, swelling and agglomeration were prevented during the pyrolysis process. Meanwhile, sodium emission was significantly decreased and the steam gasification rate of the black liquor char at 850°C was substantially improved. The melting process during gasification was suppressed with direct causticization. Moreover, the yield of hydrogen was kept constant while the yields of carbon dioxide and carbon monoxide were increased during the steam gasification process with direct causticization.

Xylanase Production by Mixed Culture Using Crude Hemicellulose from Rice Straw Black Liquor and Peat Moss as an Inert Support

Black liquor (BL) is a by-product of rice straw pulping process. It is a low costs raw material for production value-adding proteins and enzymes, which has been paid more and more attention to reduce its environmental pollution. Mixed cultures of micelial fungi, Trichoderma reesei Northern Regional Research Laboratory (NRRL)11236, Trichoderma reesei NRRL 6165 and Aspergillus niger strains NRC 5A, NRC 7A, and NRC 9A were evaluated for their ability to produce xylanase using crude hemicellulose (CHC) prepared from BL and peat moss as an inert support under solid state fermentation (SSF). The most potent strains, A. niger NRC 9A (818.26 U/g CHC) and T. reesei NRRL 6165 (100.9±57.14 U/g CHC), were used in a mixed culture to enhance xylanase production by co-culturing under SSF. In the mixed culture, xylanase production (1070.52±12.57 U/g CHC) was nearly1.3 and 10.6-fold increases over the activities attained in their monocultures, A. niger NRC 9A and T. reesei NRRL 6165, respectively. Optimization of the culture parameters of the mixed culture SSF process, concentration of ammonium sulfateand corn steep liquor, CHC/peat moss ratio, inoculum size and ratios of the two strains, initial pH value, initial moisture content and incubation time, exhibited a significant increase (2414.98± 84.02 U/g CHC) in xylanase production than before optimization.

Proper use of rice straw black liquor: lignin/silica derivatives as efficient green antioxidants for SBR rubber

Purpose – The purpose of this paper is to study the efficiency of lignin/silica and calcium lignate/calcium silicate as natural antioxidants in styrene-butadiene rubber (SBR) vulcanizates. Design/methodology/approach – It has been found that thermal aging data of the aged sample revealed that SBR vulcanizate undergoes crosslink reactions that lead to embrittlement and ultimately failure. Incorporation of lignin/silica or calcium lignate/calcium silicate, however, resulted in significant improvement of the degradation profile of the vulcanizates at 90±1°C. Loss of tensile strength and flexibility during aging of the SBR compounds with 8 phr lignin/silica or calcium lignate/calcium silicate was mild relative to unfilled polymer, indicating a restricted degradation due to the presence of the investigated compounds. The results obtained revealed that the investigated compounds are good antioxidant, and the evaluation was confirmed by physico-mechanical properties of the vulcanizates, FT-IR spectroscopy, transmission (TEM) and scanning (SEM) electron microscope. Findings – It was noticed that SBR vulcanizates having 8 phr of lignin/silica or calcium lignate/calcium silicate exhibited the best mechanical properties in comparison with other concentrations (1, 2, 4, 6 and 10 phr). Also, results revealed that the lignin/silica derivatives are efficient antioxidants in SBR vulcanizates compared to vulcanizates containing conventional antioxidants used in rubber industry, namely polymerized 2,2,4-trimethyl-1, 2-dihydroquinoline (TMQ), and N-isopropyl-N'-phenyl-P-phenylenediamine (IPPD). Research limitations/implications – All these results indicated that lignin/silica and calcium lignate/calcium silicate in SBR had good heat resistance and aging resistance, calcium lignate/calcium silicate has an application limitation as not all vulcanizates need to use CaCO3/calcium salts. Practical implications – Lignin is usually seen as a waste product of pulp and paper industry and is often used as fuel for the energy balance of the pulping process. It is simple isolation along with silica from rice straw and using it as an antioxidant added further practical utility for this waste. Originality/value – The importance of lignin/silica derivatives is arisen from their biodegradability and their ease availability from rice straw black liquor.

β-Glucosidase production by mixed culture using crude hemicellulose from rice straw black liquor and peat moss as an inert support

Background and objectives Rice straw black liquor (RSBL) has no commercial significance and causes environmental pollution because of its poor disposal, although it holds promise as a cheap substrate for the production of β-glucosidase. The objective of the present work was to improve and optimize the cultural conditions of mixed cultures of Trichoderma reesei NRRL 6165 and Aspergillus niger NRC 9A under solid-state fermentation (SSF) for the production of β-glucosidase using crude hemicellulose (CHC) prepared from RSBL and peat moss as an inert support. Materials and methods Mixed cultures of the mycelial fungi T. reesei NRRL 11236 and T. reesei NRRL 6165 and A. niger strains (NRC 5A, NRC 7A, and NRC 9A) were evaluated for their ability to produce β-glucosidase using CHC prepared from RSBL and peat moss as an inert support under SSF. Optimization of initial pH (4-8), supplementation with different concentrations of corn steep liquor and ammonium sulfate, the initial moisture content (63.6-87.4% v/w), inoculum size and ratio of microorganisms, CHC/peat moss ratio, and incubation time (0-14 day) were studied. The extracted enzyme was assayed using p-nitrophenyl-β-d-glucopyranoside as a substrate. Data analysis was performed by one-way analysis of variance using computer software Minitab 16. Results and conclusion Mixed cultures of the mycelial fungi T. reesei NRRL 11236 and T. reesei NRRL 6165 and A. niger strains (NRC 5A, NRC 7A, and NRC 9A) were evaluated for their ability to produce β-glucosidase using CHC prepared from RSBL and peat moss as an inert support under SSF. The most potent coculture composed of A. niger NRC 9A (192.39 ± 7.37 U/g CHC) and T. reesei NRRL 6165 (12.56 ± 0.42 U/g CHC) was used in a mixed culture to enhance β-glucosidase production by coculturing under SSF. In mixed culture, β-glucosidase of the coculture (265.32 ± 0.25 U/g CHC) was nearly 1.3-fold and 10.6-fold than that of monocultures of A. niger NRC 9A and T. reesei NRRL 6165, respectively. Optimization of the environmental and culture parameters, different solid supports, concentration of nitrogen sources (ammonium sulfate and corn steep liquor), initial pH value, CHC/peat moss ratio, inoculum size and ratios of the two strains, moisture content, and incubation time exhibited a significant increase (466 ± 5.42 U/g CHC) in β-glucosidase production compared with before optimization. The study demonstrated that a substrate that does not find any commercial significance and causes environmental pollution because of its poor disposal holds promise as a cheap substrate for the production of β-glucosidase.

Preparation of Lignin-Based Superplasticizer by Graft Sulfonation and Investigation of the Dispersive Performance and Mechanism in a Cementitious System

A practical graft sulfonation process was developed to synthesize a lignin-based superplasticizer using acid-precipitated lignin from wheat straw black liquor as raw material. The graft-sulfonated lignin, prepared in optimal reaction conditions, was named GSL. The properties of GSL in a cementitious system were investigated. The adsorption isotherms of GSL fractions separated by ultrafiltration and the thickness of their absorbed films on cement particles were measured to reveal the dispersion mechanism. Also, it was found that the molecular weight of graft-sulfonated lignin increased with the dosage of acetone and formaldehyde, but having too high a molecular weight reduced its dispersive performance. High sulfonic group content in graft-sulfonated lignin severely inhibited the increase of molecular weight, resulting in a decrease of dispersive performance. GSL has stronger compressive strength enhancement in concrete and lower hydration heat temperature than the commercial naphthalene-sulfonated formald...

Fractionated Wheat Straw Lignin and Its Application as Antioxidant

Three kinds of wheat straw black liquor were extracted by alkaline solution at 25 °C, 100 °C, and 165 °C, and were precipitated by the stepwise addition of acid to pH 10.5, 9.0, and 2.0, respectively. The corresponding three lignin fractions were isolated. The characteristics of these lignin fractions were investigated, and their impacts on anti-oxidant properties were evaluated. The pH 10.5 fractions with low lignin content, low phenolic hydroxyl content, and high lignin molecular weight showed very poor radical scavenging ability. The pH 9.0 and 2.0 fractions with high phenolic hydroxyl contents exhibited excellent radical scavenging ability. The major portion of the degraded lignin was precipitated in the pH 2.0 fraction, resulting in a lower molecular weight and higher phenolic hydroxyl content as compared to the pH 10.5 and pH 9.0 fractions. The high extraction temperature degraded more lignin and generated more phenolic hydroxyl groups. Therefore, the lignin fractions extracted at 165 °C exhibited the best radical trapping potential as compared to the lignin extracted at 100 °C and 25 °C. The coefficients of DPPH• removal for the lignin fractions were ordered in sequence by phenolic hydroxyl content, methoxyl content, molecular weight, E+T content, and NO yield of lignin. The lignin fraction extracted at higher temperature and precipitated at lower pH had the best radical scavenging ability.