Lignin Precipitation Research Articles

Solubility effect of deep eutectic solvent and ethanol concentration on corncob lignin extraction

This research investigates the solubility effect of deep eutectic solvent (DES) mass ratio and ethanol–water solution concentration on corncob lignin extraction. The objective is to propose a solubility matching technique based on like-dissolves-like theory to optimize lignin extraction conditions. The choline chloride (ChCl):lactic acid (LA) mass ratio that maximized lignin extraction was determined by varying DES mass ratio between 1:2 and 1:5, and ethanol–water solution (5–95 % (v/v)) was added to precipitate lignin. By using the solubility matching technique, the maximum lignin extraction was achieved at 1:4 ChCl:LA mass ratio, and 70 % (v/v) ethanol–water concentration yielded the highest lignin precipitation. Lignin is highly soluble where the solubility (δ-values) of lignin, DES, and precipitant are similar. Unlike conventional trial-and-error methods, the solubility matching technique relies on δ-values calculated by the Hildebrand and Scott equation. The proposed technique can also be applied to optimize the extraction conditions of other biomass materials.

Valorization of Kraft Lignins from Different Poplar Genotypes as Vegetable Oil Structuring Agents via Electrospinning for Biolubricant Applications.

This work explores the use of Kraft lignins sourced from different poplar genotypes (Populus alba L. "PO-10-10-20" and Populus × canadensis "Ballotino") isolated by selective acid precipitation (at pHs 5 and 2.5) to produce electrospun nanostructures that can be further employed for structuring vegetable oils. This approach offers a new avenue for converting these waste materials into high-value-added ingredients of eco-friendly structured lubricants. Electrospinning of poplar Kraft lignin (PKL)/cellulose acetate (CA) solutions yielded homogeneous beaded nanofiber mats that were able to generate stable dispersions when they were blended with different vegetable oils (castor, soybean, and high-oleic sunflower oils). Electrospun PKL/CA nanofiber mats with larger average fiber diameters were achieved using the lignins isolated at pH 5. Dispersions of PKL/CA nanofibers in vegetable oils presented gel-like viscoelastic characteristics and shear-thinning flow behavior, which slightly differ depending on the nanofiber morphological properties and can be tuned by selecting the poplar lignin genotype and precipitation pH. The rheological properties and tribological performance of PKL/CA nanofibers suitably dispersed in vegetable oils were found to be comparable to those obtained for conventional lubricating greases. Additionally, lignin nanofibers confer suitable oxidative stability to the ultimate formulations to different extents depending on the vegetable oil used.

Assessment of deep eutectic solvents (DES) to fractionate Paulownia wood within a biorefinery scheme: Cellulosic bioethanol production and lignin isolation

Five deep eutectic solvents (DES) were evaluated to disrupt Paulownia wood structure to produce bioethanol and lignin. The DES formulated with choline chloride:lactic acid provided the most promising result. Temperature (110–130 °C), residence time (30–120 min), molar ratio (1:2–1:9), and liquid-to-solid ratio (8–15 mL/g) were optimized for cellulose recuperation (93% retained in the solid phase) and lignin removal (94% delignification yield). The spent solid was used for bioethanol production, achieving up to 43.6 g ethanol/L (89.7% ethanol yield). Lignin (84% of purity) was isolated from the black liquor and thoroughly characterized by FTIR, 1H NMR, TGA-DTG and SEM, while the liquor after lignin precipitation was chemically characterized for monomers/oligomers, total phenolic content, antioxidant activity and phytochemical profile (highlighting the presence of 25.06, 10.21 and 2.51 mg of syringaldehyde, vanillin and 3,4-dihydroxibenzoic acid per g of initial biomass). Overall, this study show that DES pre-treatment is a promising strategy for simultaneous lignin extraction and cellulose digestibility enhancement.

Optimization of lignin precipitation from black liquor using organic acids and its valorization by preparing lignin nanoparticles

This work focuses on the precipitation of lignin from kraft black liquor (BL) along with its valorization into lignin nanoparticles (LNP). Two organic acids namely, acetic acid, and lactic acid were used for the precipitation of lignin as an alternative to sulfuric acid. An optimization study was carried out to determine the effect of three key variables, namely acid type, temperature, and pH, on the isolation yield and purity of lignin. The study showed that all factors primarily influenced the lignin yield, while the purity of precipitated lignin varied only around 1 % between minimum to maximum purity. Further, the acid precipitation method was selected for the preparation of LNP. The study aimed to observe the effect of pH, lignin concentration, and surfactant concentration over the properties of the prepared nanoparticles. The results showed that a smaller nanoparticle size and maximization of phenolic content was achieved with a lignin concentration of 35 mg/mL, a surfactant concentration of 10 % (w/w lignin), and a pH of 5. Additionally, the antibacterial activity of LNPs against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa bacteria was evaluated. The results showed only minor activity against Staphylococcus aureus. Overall, the study demonstrates the potential method for precipitation and valorization of lignin through the production of LNP with desirable properties.

A tailored deep eutectic solvent for high-yield conversion of poplar residues to bio-based building blocks at mild conditions

The generation of condensed compounds in a deep eutectic solvent (DES) pretreatment has become a paramount factor that inhibits the further conversion of pretreated cellulose-rich substrate. This study proposed a novel three-constituent DES system for the value-added utilization of poplar residues by efficiently suppressing hemicellulose derived condensation reactions. The results showed that adding ethanol into the DES system could effectively deconstruct the recalcitrant structure of poplar residues, simultaneously hindering the condensed composition formation. Under optimum ethanol addition (30%), the maximum xylan and lignin removal of 87.94% and 90.99% could be achieved, with more than 90.47% of glucan being preserved. With this, the glucan enzymatic hydrolysis efficiency was remarkably improved to 100% under the pretreatment conditions of 100 °C for 60 min, which was 84.69 times higher than the regular DES-pretreated poplar residues (1.17%). The working mechanism of relieving condensation reactions was characterized by Py-GC–MS, NMR, SEM, FTIR, and others. The results demonstrated that the addition of ethanol could regulate the degradation/conversion pathway of hemicellulose and lignin precipitation, thus inhibit the formation of condensed compounds during the pretreatment.

Intensification of evaporative precipitation of lignin in a spinning disc evaporator

A continuous process for the evaporative precipitation of lignin derived from Organosolv black liquor was successfully developed and implemented in a spinning disc evaporator (SDE). A maximum of 95 % of the lignin was recovered at a disc speed of 1200 rpm, black liquor feed flow rate of 1 ml s−1 on a smooth disc surface heated to 100 ⁰C. These optimal flow rate and disc speed values corresponded to conditions which maximised residence time to <1 s in 4 disc passes without compromising on the rate of evaporative heat transfer. The lignin precipitate did not have any detectable impurities present after being washed and dried. The particle size for the lignin precipitate was in the region of 3 – 9 µm with minor agglomeration occurring, providing good filterability. A scaled up version of the process was modelled for benchmarking purposes and it was found that the SDE had a better theoretical performance than a falling film evaporator (FFE) system developed for the same process, with the energy consumption reduced by 23% and a higher lignin recovery rate per volume of black liquid processed once adjusted for processing time (38.1 g L−1 h−1 for the SDE vs. 3.23 g L−1 h−1 for the FFE).

Highly selective extraction of lignin and hemicellulose with retained original structure from sugarcane bagasse via low-temperature soaking and acidic precipitation

Low-temperature soaking can be used to extract the majority of the hemicellulose and lignin from bagasse without substantially changing its structure.The effects of temperature, alkali concentration, and treatment duration on the extraction of hemicellulose and lignin from bagasse via low-temperature alkaline soaking were investigated. Acid precipitation provided a solution by separating lignin from black liquor and enabled the categorization of the lignin into different groups based on the reduced pH of the solution. The precipitation of hemicellulose and lignin from black liquor under different pH conditions was investigated. The optimal pretreatment conditions for bagasse were determined to be an alkali concentration of 75 g L–1 at 35 °C for 8 d, achieving a pentose selectivity of 0.97. The main organic components of lignin and carbohydrates precipitated in different pH environments. The highest xylose content in the precipitate was obtained at pH 13.65 (above 85%), whereas the lignin content was above 90% at pH 2. The results of fourier transform infrared (FTIR) spectroscopy and two-dimensional nuclear magnetic resonance (2D NMR) analyses showed that the structure of the water-soluble substances and precipitates slightly changed during alkali pretreatment, which allowed for increased accessibility in subsequent biorefineries, such as in catalytic hydrogenolysis.

Efficient and accurate fractionation of eucalyptus using glycolic acid-catalyzed hydrothermal treatment and alkali treatment comprehensive technology

The effective utilization of lignocellulosic biomass is the key to evaluating the profitability of the process, and precise fractionation is a prerequisite for effective utilization. In this study, a high yield of fermentable sugars and lignin rich in phenolic hydroxyl groups were successfully obtained from eucalyptus using glycolic acid-catalyzed hydrothermal and alkaline treatment. The results showed that 88.20% of xylan and 85.07% of lignin were separated, and 62.68% of lignin was extracted from the hydrolysate. The extracted lignin has a complete structure and is rich in guaiacyl and syringyl units, which is conducive to the subsequent high-value utilization of lignin. 85% of glucan was recovered, and the glucose conversion yield was 84.24% after enzymatic hydrolysis. The hydrolysate can be concentrated, impurity removed, and purified to produce biofuels or chemicals after the precipitation of lignin. In summary, the two-step process based on glycolic acid has great potential in converting eucalyptus into biomass energy and chemicals, and this process is a promising precision fractionation strategy.

Comprehensive insights into hydrothermal pretreatment of rice straw from physicochemical structure, organic matter transformation and hydrolysate reuse

Anaerobic digestion is an effective means of biomass utilization from solid waste, but the complex structure and low biodegradability of lignocellulose severely limit the anaerobic degradation conversion efficiency. In this study, hydrothermal pretreatment combined with chemicals was conducted to investigate physicochemical structure, chemical composition and changes, and enzymatic hydrolysis performance of rice straw under various combination hydrothermal pretreatment. The transformation mechanism of main components during alkaline-thermal pretreatment and the potential reuse of hydrolysate were further explored. Results showed that the total sugar concentration after hydrothermal pretreatment was 1.49 times higher than that after dissolution pretreatment. Hydrothermal-KOH pretreatment could destroy the waxy and siliceous layer on the straw surface. The roughness increased from 0.525 to 1.170 nm, and the average pore size 6.20 to 8.99 nm. Alkaline-thermal pretreatment could facilitate lignin dissolution and retained more cellulose and hemicellulose in the solid phase, and sugar concentration after pretreatment could reach 40.82 g/L. Porosity was affected by the dissolution of chemicals, and the pore structure also affected subsequent enzymatic hydrolysis. Dissolution of cellulose and hemicellulose resulted in a reduction in particle size and the formation of micropores, while re-aggregation and precipitation of lignin after dissolution led to the pore collapse and an increase in pore size. Furthermore, the hydrolysates contained nutrients, humic acids, plant hormones, and micronutrients, which had the potential to be developed into foliar fertilizers and reused. The results of this study will provide new insights and technical support for high-value utilization of straw.

Structural elucidation and targeted valorization of untractable lignin from pre-hydrolysis liquor of xylose production via a simple and robust separation approach

Effective separation of lignin macromolecules from the xylose pre-hydrolysates (XPH) during the xylose production, thus optimizing the separation and purification process of xylose, is of great significance for reducing the production costs, achieving the high value-added utilization of lignin and increasing the industrial revenue. In this study, a simple and robust method (pH adjustment) for the separation of lignin from XPH was proposed and systematically compared with the conventional acid-promoted lignin precipitation method. The results showed that the lignin removal ratio (up to 60.34 %) of this simple method was higher than that of the conventional method, and the proposed method eliminated the necessity of heating and specialized equipment, which greatly reduced the separation cost. Meanwhile, this simple method does not destroy the components in XPH (especially xylose), ensuring the yield of the target product. On the other hand, the obtained lignin was nano-scale with less condensed structures, which also possessed small molecular weights with narrow distribution, excellent antioxidant activity (8–14 times higher than commercial antioxidants) and UV protection properties. In conclusion, the proposed simple separation method could effectively separate lignin from XPH at low cost, and the obtained lignin had potential commercial applications, which would further enhance the overall profitability of industrial production.

Simultaneous posthydrolysis and liquid–liquid extraction: a SIMPLLE process to detoxify eucalyptus prehydrolysis liquor

AbstractThe prehydrolysis liquor from the prehydrolysis Kraft process is rich in sugars and could thus serve as a sustainable feedstock for the production of various chemicals. However, its industrial utilization is impeded by the presence of fermentation inhibitors and extensive lignin precipitation, the latter receiving only little attention in the literature.In order to provide a feedstock suitable for biotechnological or chemical conversion, the prehydrolysis liquor from eucalyptus wood must be detoxified whilst preventing the precipitation of lignin. To increase the yield of monomeric sugars, acid posthydrolysis should be investigated.Various solvents and solvent mixtures were screened for the high temperature liquid–liquid extraction of isothermally separated prehydrolysis liquor. Their capability to prevent lignin precipitation and to extract fermentation inhibitors was assessed using mass balances and size-exclusion chromatography. Based on the solvent screening, a process for simultaneous posthydrolysis and liquid–liquid extraction of eucalyptus prehydrolysis liquor was proposed and investigated using statistic experimental design.Liquid–liquid extraction using aliphatic alcohols effectively prevents lignin precipitation, and the addition of 25% (w/w) tri-n-octylamine was found to increase the overall inhibitor extraction efficiency. The conditions for the simultaneous posthydrolysis were investigated using a Box-Behnken experimental design, allowing for a maximum monomeric sugar yield of 83.0% at a sugar purity of 91.6%.The simultaneous posthydrolysis and liquid-liquid extraction (SIMPLLE) process thus avoids industrial-level problems associated with lignin precipitation. It provides a carbohydrate-rich stream with low levels of fermentation inhibitors, enabling further conversion to value added products.

Use of Photo isomers to enhance the removal of lignin from woody biomass hydrolysate: UV irradiated photo isomerization of 4,4-diethoxy-azobenzene enhances precipitation of organosolv lignin from extraction solvents

Conversion of lignocellulose to bioproducts and biofuels is often initiated with a hydrolytic pretreatment process that helps to depolymerize the native polymers in biomass and produce a cellulose rich pulp stream. Extracting dissolved components (lignin) from this hydrolysate is an important step to derive value from the biomass components other than cellulose. In this investigation we propose a novel method to enable precipitation of desired solutes using photo-isomers in the extraction solvent. This photo-switchable solvent enables dissolution or precipitation of desired components using alternating UV or visible light to modify the solubility of the compounds of interest. It was found that among different combinations of three solvents and three photo-isomers, the combination of acetone with 4,4′-diethoxy azobenzene solution was most efficient at precipitating dissolved Organosolv lignin in response to UV light exposure. To our knowledge this is the first demonstration of this approach to separating lignin from organic solvents. This method is significant because it minimizes the high energy demands of traditional lignin extraction methods that involve distillation or large amounts of dilution using antisolvents.

Consequential life cycle assessment of kraft lignin recovery with chemical recycling

The recovery of kraft lignin from black liquor allows an increasing of the pulp production of a kraft mill (marginal tonnage) and at the same time provide a valuable material that can be used as energy or chemical feedstock. However, because lignin precipitation is an energy- and material-consuming process, the environmental consequences from a life cycle perspective are under discourse. The aim of this study is to investigate, through the application of consequential life cycle assessment, the potential environmental benefits of kraft lignin recovery and its subsequent use as an energy or chemical feedstock. A newly developed chemical recovery strategy was assessed. The results revealed how the use of lignin as energy feedstock is not environmentally advantageous compared to producing energy directly from the pulp mill's recovery boiler. However, the best results were observed when lignin was used as a chemical feedstock in four applications to replace bitumen, carbon black, phenol, and bisphenol-A.

Bioprocess development for levulinic acid production using sugarcane biomass

Developing technologies for converting lignocellulosic biomass to products such as energy, fuels, and value-added chemicals is an important step in making biorefineries a feasible alternative to the current oil-based productive system. In this study, the conversion of lignocellulosic biomass composed of a mixture of bagasse and sugarcane straw into a cellulose pulp and a sulfonated carbonaceous solid catalyst synthesized from lignin fraction were investigated, as well as the use of this solid acid catalyst to convert cellulose to levulinic acid, an important chemical platform. To overcome this challenge, firstly, the fractionation of lignocellulosic biomass was optimized. Then, tests were carried out to find the best condition for isolation of the soluble lignin from black liquor produced in the optimal condition of delignification. The lignin precipitate was subjected to carbonization tests followed by functionalization tests with concentrated sulfuric acid to synthesize the catalyst. This catalyst was then used to convert cellulose into levulinic acid (LA). The experimental design for cellulose recovery and lignin removal showed that under relatively mild reaction conditions of 110 °C, 117 min, and a solid/NaOH (4.4% w/v) ratio of 1:20, more than 91% of the lignin was dissolved into the black liquor, recovering a solid with a cellulose content higher than 78%. Lignin was fully recovered in the form of precipitate by simply reducing the pH of the black liquor to 3 (under this condition 11 g of precipitate were recovered per liter of liquor). Having the recovered lignin, it was then possible to synthesize a solid carbonaceous catalyst with a total acid site density of 1.48 mmol/g which was able to convert up to 17.11% of the cellulose and obtain yields of up to 38.55% of levulinic acid when a catalyst/cellulose ratio of only 8:10 (w/w) was used. Overall, the future of LA production using carbonaceous acid catalysts looks promising. As research in this area continues, there is the potential to further improve the production process and make it more cost-effective and sustainable. This could lead to wider adoption of this technology and increased use of levulinic acid in various industrial applications, including as a platform chemical to produce a range of chemicals and materials.

Eucalyptus black liquor properties in a lignin extraction process: density, dry solids, viscosity, inorganic, and organic content

Extracting lignin from black liquor is becoming more common, although only a few research papers discuss the impact of the process on the liquor’s primary properties. This work aims to determine the changes in black liquor properties as it undergoes a lignin extraction process using carbon dioxide (CO2). A diluted eucalyptus black liquor sample (DBL) was acidified with CO2 to a final pH of 8.5. After filtration, the kraft lignin was removed, and the filtrated lignin lean black liquor (LLBL) was collected. Five acidified black liquors (ABL) samples were collected during acidification at pH 10.5; 10.0; 9.5; 9.0; and 8.5. The samples were analyzed regarding lignin content in solution, sodium carbonate (Na2CO3), sodium sulfate (Na2SO4), density, dry solids content, and viscosity. While Na2SO4 remained almost constant, Na2CO3 presented an enormous increase in its concentration when comparing DBL with LLBL. As pH decreased, the lignin content in the solution was also reduced due to lignin precipitation. The results showed similar behavior for dry solids, density, and viscosity of the supernatant, but an increase in density was observed around pH 9.00. In light of this, the density of LLBL turns out to be closer to the one in the initial DBL. The significant increase in carbonate content could explain this behavior during acidification with CO2 once the inorganic content significantly influences the property. The viscosity was determined from 10 s−1 to 2000 s−1. We observed a Newtonian behavior for all samples. The increase in carbonate content in the sample is crucial information to the recovery cycle, especially for calculating the mass and energy balance when targeting the use of the LLBL.

Characterisation of lignins isolated from Bamboo organosolv and kraft black liquor

Bamboo biomass was pulped using organosolv methods: Acetic acid and formic acid; hydrogen peroxide and formic acid; ethanol and water and kraft process with varying concentrations of the cooking chemicals. The properties of the isolated lignin were influenced by the black liquor pH as well as the pulping method. Highest pH (12,8) was recorded for kraft at 70:30 liquor concentration while lowest pH of 2,5 was recorded for both Aceticformic (70:30) and Ethanol/water (70:30 and 60:40). There were obvious differences in the characteristic colours, shapes and sizes of the lignin samples. Bamboo kraft lignin samples formed large pieces much easier than that of Organosolv. Aceticformic (70:30) had the best filteration properties (FC) while Ethanol/water had the poorest. Generally, kraft recorded the highest lignin yield while all the organosolv processes recorded reduced yield. Highest yield (119,25 g/L) was gotten from kraft (50:50) while Peroxyformic (60:40) had the lowest yield of 8,20 g/L. The results showed that higher liquor pH favours total dissolved solid as well as lignin precipitation. As the pH increases, total dissolved solid, yield, Klason and low molecular weight (LMW) lignin content increases while FC decreases. The Klason and LMW lignin content increased with incresing lignin yield.

High Temperature Lignin Separation for Improved Yields in Ethanol Organosolv Pre-Treatment

The full utilization of renewable raw materials is necessary for a sustainable economy. Lignin is an abundant biopolymer, but is currently mainly used for energy production. Ethanol organosolv pre-treatment produces high-quality lignin, but still faces substantial economic challenges. Lignin solubility increases with temperature, and previous studies have shown that it reprecipitates during cooling after the pre-treatment. Thus, a possibility for the optimization of lignin production with this process can be the separation of extract and residual biomass at high temperatures. In this work, lignin was extracted from wheat straw at 180 °C, and the extract was separated from the remaining solids at several temperatures after the pre-treatment. The results show that 10.1 g/kg of lignin and 2.2 g/kg of carbohydrates are dissolved at the pre-treatment temperature of 180 °C, which is reduced to 8.6 g/kg of lignin and 1.2 g/kg of carbohydrates after cooling. The precipitation of lignin separated from the extracts at 180 °C showed that a higher lignin concentration at high temperatures results in a 46% improvement in the yield of solid lignin, while there was no significant impact on the lignin purity.

Development of the lignin extraction method from para rubber wood sawdust with choline chloride-lactic acid deep eutectic solvent

This work investigated the extraction of lignin from para rubber wood sawdust by deep eutectic solvent extraction (DES) using choline chloride-lactic acid (ChCl-LA). The DES extraction was operated using ChCl/LA with molar ratio of 1:10, and the lignin was extracted with good yields. To determine the optimal conditions for lignin extraction by this technique, various factors were studied, including extraction temperature (90-150 °C), extraction time (6-24 h), the amount of water required for lignin precipitation (150-300 mL), and precipitation time (24-48 h). The optimized conditions were achieved at 150 °C, 24 h, 300 mL of DI water and 48 h of precipitation time, and the highest extracted lignin content was 17.54%. Moreover, excessive water in the extracted solution can be recovered with evaporation, and it was discovered that similar extracted lignin content could be obtained (16.85%) by only using 150 mL of DI water during lignin precipitation but extending the precipitation time to 48 h. This study provides a simple, inexpensive, and environmentally friendly lignin extraction technique.

Integrated process for the co-production of bioethanol, furfural, and lignin nanoparticles from birch wood via acid hydrotropic fractionation

This study proposes an efficient biorefining strategy for co-producing of bioethanol, furfural, and lignin nanoparticles (LNPs) from birch wood based on acid hydrotropic fractionation. Birch was fractionated into glucan-rich washed water-insoluble solids (WIS) fraction and xylose-rich spent liquor (SL) fraction with a low p-toluenesulfonic acid (p-TsOH) concentration of 15% (w/v). The obtained WIS was utilized to produce 75.5 g/L ethanol (76.3% ethanol yield based on initial sugars in the enzymatic hydrolysate) through separate hydrolysis and fermentation. Meanwhile, the xylose-rich SL was concentrated and catalyzed by dehydration to produce furfural with tetrahydrofuran (THF) as a co-solvent. The furfural concentration of 27.3 g/L (78.2% theoretical yield) was achieved from the 3-fold concentrated SL (without lignin precipitation) with a 3:1 THF-SL ratio at 160 °C for 7 min. The enzymatic hydrolysis solid residue of WIS was further fractionated by p-TsOH to prepare LNPs with an average particle size of 37.4 nm. The mass balance showed that 6.5 t oven-dry birch wood produced 1.0 t ethanol, 0.61 t furfural and 0.63 t LNPs.

The effects of pH on the precipitation of rice straw lignin from An Giang, Vietnam

This research aimed to extract lignin from rice straw and reveal the pH value of diluted acid at which the most effective yield of lignin was precipitated. In this study, rice straw obtained from local fields in the An Giang province of Vietnam and sodium hydroxide 2 M was employed to extract lignin from rice straw. Hydrochloric acid was used to adjust the sample pH values to be in the range of 1.5-3.5. Fourier-transform infrared spectroscopy (FTIR) analysis was used to characterize the functional groups of the lignin materials. Thermogravimetric analysis (TGA) analysis was employed to supply information on the thermal decomposition of the lignin samples. Herein, the results showed that lignin precipitated at different pH values affected its thermal properties. At 700oC, the yield of the remaining lignin components were 56% at pH 2.0, but the weight loss of lignin samples precipitated at pH 3.5 dropped to 85% because many non-lignin substances existed in the samples. The yield of the crude lignin samples obtained were 16.51, 17.66, 15.27, 14.33 and 13.26% for pH of 1.5, 2.0, 2.5, 3.0 and 3.5 respectively. The crystallite regions played an important role in the lignin structures. The spectrum peaks at pH 1.5, 2.0 and 2.5 were broader than the peaks at pH 3.0 and 3.5. The results demonstrated the highest percentage of lignin precipitate was collected at pH 2.0.