Alkali Delignification Research Articles

Sugar content improvement by sonication in the pretreatment of empty fruit bunch hydrolysis

The empty palm fruit bunches (EFB) has great potential as an alternative feedstock for bioethanol production due to its high content of cellulose and hemicellulose. However, besides cellulose and hemicellulose, EFB also contains lignin, which can hinder the hydrolysis process and therefore requires delignification. This study aims to determine the effect of sonication in alkali delignification on the sugar content of hydrolysis. Ultrasonic in 37 KHz was performed at a temperature of 80 °C. Sonication process durations ranged from 30 minutes to 150 minutes using a 10 % (w/v) NaOH solvent. The hydrolysis of EFB fibers was carried out in a water bath at 80 °C using a 0.5 N sulfuric acid solvent in a ratio of 1:20 (w/v) for 2 hours. The sugar content was measured using the phenol-sulfuric acid method with UV-Visible spectrophotometry. In this study found that the ultrasonic irradiation time length gave good results at a time limit not exceeding 90 minutes due to hemicellulose characteristics . The highest sugar content was obtained at a sonication duration of 90 minutes, measuring 20.60 mg/L, which was 38.5 % higher than alkali delignification without sonication for 150 minutes. SEM analysis indicated that EFB had undergone changes in the surface morphology and structure. Qualitative FTIR analysis showed that the hydrolysis solution contained glucose and pentose, which are products of hydrolyzed cellulose and hemicellulose.

Transforming Wood into a High-Performance Engineering Material via Cellulose Nanocrystal Impregnation

Abstract The demand for wood in construction has led to shortages of strong wood types, causing a shift to costlier alternatives like concrete and nonbiodegradable materials, prompting the investigation of modifying softwoods for better engineering properties. This study investigates the optimization of a multistep impregnation process utilizing functionalized cellulose nanocrystals (f-CNCs) to enhance softwood properties. The process involves alkali delignification, ultrasonication, and vacuum pressure treatment to improve wood porosity and in turn improve CNC impregnation with uniform dispersion. Microstructural analyses through field emission scanning electron microscopy and atomic force microscopy (AFM) offer detailed insights into cell wall morphology and surface topography, whereas Fourier transform infrared spectroscopy highlights compositional shifts resulting from f-CNC impregnation. Mechanical testing demonstrates significant improvements for treated woods, particularly a 67 percent increase in modulus of elasticity for the 2 percent CNC-treated group compared with the control group; a 71 percent increase in modulus of rupture was observed for 2 percent CNC-, 3 percent NaOH-, and 2 percent acetic acid-treated group compared with the control sample. The sample delignified with 3 percent NaOH and impregnated by 2 percent f-CNC emerged as particularly effective. This research sets the stage for potential advancements in strengthening softwood using CNC, including a novel AFM method and alternative impregnation techniques like the Lowry method, inviting further exploration.

Efficient preparation of polyethylene glycol (PEG)-modified lignin from steam exploded hardwood biomass

The structures and characteristics of lignin derivatives prepared from steam exploded beech under alkali delignification and acid catalyzed polyethylene glycol (PEG) solvolysis were studied in detail. An efficient method for directly isolating PEG-modified lignin from wood was proposed to improve its thermal stability. The effects of steam explosion (SE) parameters and delignification process on lignin structure were studied by high performance anion exchange chromatograph, fourier transform infrared spectroscopy (FTIR), heteronuclear single quantum coherence (HSQC) NMR spectroscopies, ultraviolet and visible spectrophotometry, size exclusion chromatography (SEC) and thermogravimetric analysis (TGA). The results showed that SE pretreatment can greatly promote the yield of PEG-modified lignin. The PEG-modified lignin, isolated from steam exploded wood at 210 °C for 2.5 min, was ∼14% yield. The PEG moiety was located at the alpha carbon position of the β-O-4 linkage. The PEG-modified lignin exhibited improved thermal properties with a maximum weight loss temperature (Tdmax) greater than 380 ℃, and a degradation starting temperature (Tdst) in the range of 258–277 °C, met the temperature for polymer processing and contribute to improve the added value of lignin.

Isolation and characterization of cellulose nanofibrils from agro-biomass of Jackfruit (Artocarpus heterophyllus) rind, using a soft and benign acid hydrolysis

Cellulose nanofibrils (CNFs) were exfoliated from the rind of jackfruit (Artocarpus heterophyllus) through pretreatments like dewaxing, moderate alkali delignification and bleaching with alkaline hydrogen peroxide. CNFs were extracted via organic-inorganic mixture acid hydrolysis using acetic acid-HCl mixture (6:1) under mild hydrothermal conditions followed by homogenization. Transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), thermo-gravimetric analysis (TGA/DTA), dynamic light scattering (DLS), zeta potential, energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) spectroscopy were used to define the materials that were produced in each stage of the extraction process. The CNFs have an average diameter of about 28 nm, crystallinity index of 87.36 % and crystalline size ca. 3.38 nm. The fibers exhibited a maximum degradation temperature of 328.5 °C and mean zeta potential value −24.1 mV signifying high degrees of stability. The elemental analysis confirms the excellent purity of CNFs with 48.02 % carbon and 51.98 % oxygen, pointing to the success of the isolation method. These fibers can be used in the synthesis of biodegradable organic/inorganic nanocomposites, especially for catalytic applications.

A Solar-Driven Oil-Water Separator with Fluorescence Sensing Performance.

Presently, the separation of oil and water through functional membranes inevitably entails either inefficient gravity-driven processes or energy-intensive vacuum pressure mechanisms. This study introduces an innovative photothermal evaporator that uses solar energy to drive oil-water separation while concurrently facilitating the detection of Fe3+ in wastewater. First, by alkali delignification, small holes were formed on the side wall of the large size tubular channel in the direction of wood growth. Subsequently, superhydrophilic SiO2 nanoparticles were in situ assembled onto the sidewalls of the tubular channels. Finally, carbon quantum dots were deposited by spin-coating on the surface of the evaporator, paralleling the growth direction of the wood. During the photothermal evaporation process, the tubular channels with small holes in the side wall parallel the bulk water, which not only ensures the effective water supply to the photothermal surface but also reduces the heat loss caused by water reflux on the photothermal surface. The superhydrophilic SiO2 nanoparticles confer both hydrophilic and oleophobic properties to the evaporator, preventing the accumulation of minute oil droplets within the device and achieving sustained and stable oil-water separation over extended periods. These carbon quantum dots exhibit capabilities for both photothermal conversion and fluorescence transmission. This photothermal evaporator achieves an evaporation rate as high as 2.3 kg m-2 h-1 in the oil-water separation process, and it has the ability to detect Fe3+ concentrations in wastewater as low as 10-9 M.

The Viscoelastic and Hygroscopicity Behavior of Delignified and Densified Poplar Wood

The combination of alkaline delignification and densification was applied to improve wood mechanical strength. Poplar wood samples were subjected to alkali delignification with varying degrees of lignin and hemicellulose removal followed by hot pressing. Dynamic mechanical performances and dynamic sorption behavior of the untreated and densified wood were then evaluated. Results showed that appropriate removal of lignin can improve the stiffness of densified wood and reduce moisture sorption and the numbers of sorption sites. Fourier transform infrared (FTIR) microscopy along with X-ray diffraction (XRD) were used to explain the viscoelastic and hygroscopicity of delignified and densified wood. Hemicelluloses and lignin were selectively dissolved during alkali treatment. Wood crystallinity was increased after alkali treatment at a moderate concentration of 2%, beneficial to improving the dimensional stability and mechanical performance of delignified and densified wood. The crosslinking of cellulose chains through hydrogen bonding, the decreased content of free hydroxyl groups, and the increased crystallinity in the cell wall contributed to higher storage modulus and lower hydrophilicity. The results support mild delignification and densification as a feasible way towards extending the service life of wood products used as structural materials.

Valorization of old corrugated container to dissolving pulp

As an alternative raw material for various cellulose derivatives, the current research studied the processing of old corrugated container (OCC) in the subsequent stages of homogenization (soda cooking) and purification (bleaching with hypochlorite). The properties were characterized in four different categories including chemical composition or purity, accessibility, reactivity, and structural features. Alkali delignification and a bleaching sequence of HEHEHEA were selected for homogenization and purification of pulp followed by characterization of the pulp properties. The dissolving pulp exhibited the following properties: yield, 78%; cellulose, hemicellulose, and lignin content, 90.5%, 7.76%, and 0.3%, respectively; alpha cellulose, 70%. Pulp reactivity measured with two experiments showed Fock reactivity value of 85.67% as well as iodine sorption value (ISV) of 94.95 g/g; accessibility represented by two tests of water retention (WRV) and alkali retention capacity (ARC) with 6.87 for the first and 6.1% for the latter, degree of polymerization (DP), 913.4; crystallinity index, 76.95%; and brightness, 72.87%. FTIR spectroscopy and Brunauer-Emmet-Teller (BET) isotherms were utilized to examine the modifications of OCC to dissolving pulp. The results indicated that the dissolving pulp produced from OCC as a raw material is suitable for DP applications of cellulose derivatives.

Oil palm empty fruit bunch (OPEFB) (Elaeis guineensis Jacq.) cellulose conversion into levulinic acid using hierarchical Mn/ZSM-5 heterogeneous catalyst

Oil palm empty fruit bunch (OPEFB) is one of the potential biomasses containing cellulose that can be used as a source for renewable energy. However, the cellulose is tightly connected with lignin in lignocellulose system, which needs to be separated, so called delignification, before being used. To investigate the effect of delignification on conversion reaction, the pretreated cellulose was treated with different delignification processes, i.e. alkali delignification using 10 % NaOH (w/v) and oxidative delignification using 2 % NaOCl (v/v). Furthermore, cellulose conversion from OPEFB into levulinic acid was performed using hierarchical Mn/ZSM-5 (Mn/Hi_ZSM-5) heterogeneous catalyst with various reaction times and concentration of H3PO4. The cellulose conversion into levulinic acid in the absence of catalyst was also conducted to study the effect of catalyst. High Performance Liquid Chromatography (HPLC) analysis showed the highest cellulose conversion into levulinic acid was achieved using cellulose from alkali delignification (28.08 % yield) in optimum reaction condition of 40 % H3PO4 (v/v), 30 % H2O2 (v/v), and 0.1 g of Mn/Hi_ZSM-5 at 100 °C for 10 h. Mn/Hi_ZSM-5 revealed good selectivity for levulinic acid with the absence of 5-HMF as an intermediate compound in conversion reaction.

Alkali delignification and Bacillus sp. BMP01 hydrolysis of rice straw for enhancing biofuel yields

BackgroundLignocellulose biomass such as agricultural residues is increasingly important for biofuel production. Using agricultural residues like rice straw for biofuel production has dual purposes of utilizing the huge waste generated. The abundant availability and high polysaccharide contents are the main reason for biofuel production. However, the use is limited due to the reluctant nature of lignin in the biomass. Therefore, sodium hydroxide was used for solubilizing lignin and preserving the polysaccharides.ResultsAbout 71.29% of lignin (maximum amount of lignin) was removed after 7% sodium hydroxide (NaOH) pretreatment followed by 3% pretreatment (about 67.13%). Also, maximum cellulose (about 71.33%) was preserved after 7% NaOH pretreatment. Results of reducing sugars obtained by spectrophotometric analysis (3,5-dinitrosalycilic acid method) of pretreated rice straw show about 88.27% conversion (753 mg/g) after the 13th day of hydrolysis by bacteria isolated from a termite. FE-SEM, XRD, FTIR, and TGA analyses show a significant amount of lignin was removed which helps in releasing cellulose tangled in lignin.ConclusionRice straw pretreatment at 7% NaOH and hydrolysis by Bacillus sp. BMP01 achieved the release of a high yield of fermentable sugars that increased the yield of bioethanol. This study demonstrates the potential of alkali pretreatment coupled with microbial hydrolysis for efficient bioethanol production from agricultural residues like rice straw.

Response surface optimization of acid pretreatment of cassava stem for bioethanol production

AbstractAgricultural waste, cassava stem was found to contain about 25 and 40% of hemicellulose and cellulose, respectively. Bioethanol is produced from cassava stem by dilute acid pretreatment followed by alkali delignification, cellulase digestion, and fermentation by Fusarium oxysporum. Dilute acid pretreatment was optimized by response surface methodology based Box–Behnken design. The optimum xylose concentration obtained by the experiment was 11.24 g/L and the model was sulfuric acid concentration of 2.02% (v/v), solid to liquid ratio of 0.05 g/ml and 79 min. After alkali delignification and cellulase hydrolysis of pretreated cassava stem, the glucose content was 18.1 g/L and the bioethanol concentration obtained through co‐fermentation of xylose and glucose by F. oxysporum was 13.62 g/L. The optimum values indicated that 91.1% yield was achieved with cassava stem using dilute sulfuric acid pretreatment. Hence, the dilute acid pretreatment of cassava stem was found to be the promising method for bioethanol production.

Multiproduct biorefinery from vine shoots: Bio-ethanol and lignin production

Vine shoots were hydrothermally processed and the effect of the different assayed severities on the subsequent enzymatic saccharification of the remaining solids was evaluated. The solid obtained at a severity of 4.47 showed the highest yield on glucose (74.01%) and therefore, it was used as the substrate for the obtaining of bio-ethanol through a SSF process. Under the evaluated conditions (LSR 10 g/g, 20 FPU/g and 10 IU/FPU) 13.3 g/L of bio-ethanol were produced (corresponding to 67.4% of ethanol conversion). Moreover, lignin has been extracted by an alkali delignification treatment from the vine shoots unprocessing and from the solids resulting from the stages of the proposed biorefinery scheme, which were the autohydrolysed vine shoots and the bio-ethanol residue. The isolated lignins were characterized by HPLC, total phenolic content, FTIR, HPSEC, Py-GC/MS and TGA and it was observed that the successive stages of processing to which the vine shoots were submitted provoked chemical and structural changes in the extracted lignins. The knowledge of the structural modifications that the lignin present in the vine shoots during the autohydrolysis and the SSF process could help determining at which stage of the bio-ethanol production would be suitable to recover the lignin for value-added applications.

Delignification Alternatives of Spent Solid from Autohydrolysis of Vine Shoots

Vine shoots are residues obtained from an important agricultural activity as the viticulture. Although these residues have not received much attention yet, in the recent years the employment of these residues under a biorefinery approach has increased, being possible the obtaining of products of added value as polyphenols or lactic acid for instance. Davila et al. (2016) carried out the hydrothermal treatment in a non-isothermal regimen in a range of temperatures between 180-215 °C with a liquid/solid ratio of 8 Kg/Kg vine shoots, in order to obtain oligosaccharides which can be used as food ingredients due to their prebiotic effect. In this previous study it was observed that the optimum temperature of the treatment to obtain the maximum oligosaccharides with the minimum formation of degradation products was 201 °C. In this work, organosolv, acetosolv and alkali delignifications of the spent solid enriched in lignin and glucan were studied. The alkali delignification, using 8 w/w % of NaOH at 124°C for 105 min, was more promising than the other two treatments, being possible to remove 61% of the lignin present in the autohydrolized vine shoots. The lignin isolated in this process presented the highest content of Klason lignin (86%) and a high molecular weight (11401 g/mol) compared with the lignins isolated by applying the other delignification conditions.

Evaluation of tablet disintegrant properties of microcrystalline cellulose obtained from cassava fermentation waste

This study was aimed at exploring the application of microcrystalline cellulose from cassava fermentation waste as a disintegrant in the formulation of paracetamol tablets for immediate release. Alkali delignification of the dried cassava fermentation fibres, followed by bleaching and acid depolymerisation was employed in the extraction of α-cellulose and conversion to microcrystalline cellulose (MCC). The MCC obtained was evaluated for some of its physicochemical properties. Thereafter, a comparative evaluation of paracetamol granules and tablets formulated using the MCC and Avicel ® PH 101 as disintegrants was undertaken. Drug-excipient interaction was also investigated using fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Results showed a 48% yield of α-cellulose from the waste material. The MCC powder was off-white in colour, insoluble in water and gritty in texture. It showed negative reaction to the presence of starch, sugar and lignin but positive to cellulose. It exhibited a moisture content and swelling capacity of 2.1 and 63.3%, respectively. The paracetamol granules formulated showed good flowability with angles of repose ≤ 31 °, Hausner’s ratios of 1.07 - 1.18 and Carr’s indices of 6.58 - 16.00%. The formulated tablets showed good hardness (> 7 kp) and friability values (≤ 0.7%). Two batches of tablets containing 7.5 or 10% (w/w) of the MCC and three batches of tablets containing Avicel® (5, 7.5 and 10% (w/w) disintegrated within 15 min. The tablets containing 5 - 10% (w/w) of the MCC or Avicel® passed the dissolution test for tablets which specifies that at least 70% of the drug should be in solution after 30 min. FTIR and DSC analyses revealed no interaction between the excipients and paracetamol. MCC from cassava fermentation waste may serve as an alternative substance to explore as a pharmaceutical excipient in solid dosage form even though its tableting parameters are not as good as those of Avicel® PH 101. Keywords: cassava, microcrystalline cellulose, disintegrant, paracetamol granules, tablets

Enzymatic hydrolysis of cellulose from oat husks at different substrate concentrations

Pulps prepared from oat husks via a method combining prehydrolysis, alkali delignification, and nitric acid treatment were demonstrated to possess high fermentability upon hydrolysis using multienzyme preparations, such as BrewZyme BGX and CelloLux-A. A dependence of the increment of the yield of reducing substances on the initial substrate concentration ranging from 15 to 120 g/dm3 was studied. The final yield of reducers at 72 h was shown to decline from 88 to 65% with an increase in the initial concentration of the substrate.

3D imaging of sugarcane bagasse using X-ray microtomography

X-ray microtomography (XMT) provides new possibilities for microstructural characterization of lignocellulosic materials. The present article explores XMT application to characterize raw and treated sugarcane bagasse. Tridimensional images are presented, showing sugarcane anatomical features as well as particle damages due to sugarcane crushing. One major advantage of XMT is its non-invasiveness, making this technique unique for unambiguous characterization of intraparticle morphology. Finally, bagasse morphological changes due to dilute acid treatment and alkali delignification are discussed based on tridimensional images.

Starch‐based biocomposite films reinforced with cellulose nanocrystals from garlic stalks

The study was conducted to reinforce starch‐based biocomposite films using cellulose nanocrystals (CNCs) from garlic stalks. An average yield of 4.6% by mass based from air‐dried garlic stalks was obtained through alkali delignification, acid hydrolysis and sonication. The isolated CNCs are spherical and have an average diameter of 35 nm and crystallinity of 62%. Fourier transform infrared spectra correspond to the structure of cellulose, but some absorption bands corresponding to hemicelluloses were also noticed. Starch‐based biocomposite films with varying amount of the isolated CNCs as reinforcing filler were prepared by solution casting and evaporation method. Scanning electron micrographs of the films showed homogeneous dispersion of CNC in the starch matrix. Improvement in tensile strength and modulus was at maximum when the starch to CNC ratio is 100:5. The thermal stability of the films, on the other hand, decreased with the addition of CNC. Finally, CNC‐reinforced films had lower moisture uptake than nonreinforced films. POLYM. COMPOS. 34:1325–1332, 2013. © 2013 Society of Plastics Engineers

Description of kraft cooking and oxygen–alkali delignification of bamboo by pulp and dissolving material analysis

The oxygen delignification of two bamboo ( Bambusa procera) kraft pulps with kappa numbers of 13.6 and 20.0 were studied under typical conditions. Based on detailed analysis data on both the kraft and oxygen-delignified pulps and the corresponding spent liquors (black liquors and oxygen stage effluents), three yield and four selectivity estimation methods, utilizing component material balances, were tested resulting in the value ranges 96.2–97.9% and 43.5–60.4%, respectively, for oxygen delignification process studied. The traditional selectivity using the viscosity and kappa number relation was 66.9–68.4%. The studied bamboo kraft pulps behaved typically as birch kraft pulps during oxygen delignification, resulting, for example, in similar carbohydrate-derived degradation products.

Bioconversion and biotransformation of coir pith for economic production of Pleurotus florida: chemical and biochemical changes in coir pith during the mushroom growth and fructification

Coir pith represents ∼50% of the waste from the coir industries and was tested for its potential in serving as a growth substrate for the production of species of oyster mushroom, Pleurotus florida. Due to its high lignin (∼48%) content and amorphous powdery nature, coir pith supported poor mushroom mycelial growth and yields were considerably low (∼25% bioconversion efficiency). Pre-treating coir pith with hot water did not prove economical to produce the mushroom yields. Acid swelling and alkali delignification of coir pith though served to change the structure of coir pith; the mushroom yields were not improved. Amendment of coir pith with rice (Oryza sativa) straw and horse gram (Dolichos biflorus) plant residue tended to greatly modify the physical characteristics of the inoculated mushroom bed. Such a supplementation of coir pith growth substrate resulted in production of mushroom yields with 110–125% bioconversion efficiency. Implications of supplementing coir pith with rice straw/horse gram plant residue in terms of holocellulose:lignin ratio are discussed. Sensorially, the mushrooms so produced did not differ from that on rice straw, the economic growth substrate recommended for production of the mushroom yields on commercial scale. Changes in cellulose, hemicellulose and lignin contents of coir pith amended with rice straw were studied. Cellulase, hemicellulase and protease enzyme activities in the amended coir pith substrate showed a continuous increase from inoculation till the end of fructification, whereas laccase activity decreased during fructification, in consonance with decreased lignin degradation during fructification.

Kinetics of polysaccharide degradation during ethanol–alkali delignification of giant reed—Part 1. Cellulose and xylan

The degradation kinetics of the principal polysaccharides (cellulose and xylan) of the agro-fibre crop Arundo donax L. (giant reed) during ethanol–alkali delignification is reported. Based on the properties of a multi-component reaction system, the degradation kinetics of both polysaccharides was accurately described in terms of two simultaneous irreversible first-order reactions corresponding to removal of two kinetically homogeneous fractions. The moderate cellulose losses during pulping (about 4.5%) result mainly from the removal of the more reactive cellulose fraction, that accounted for 4% of initial cellulose. The bulk of the cellulose (96%) degrades slowly with three orders lower rate with pulping progress. The apparent activation energy of cellulose fractions degradation was estimated as 105.2 and 106.5 kJ mol −1, respectively. Substantial loss of xylan during pulping (about 55%, as a homoxylan) is caused by fast removal of the first very reactive fraction, covering about 48% of total xylan. The degradation rate of the second xylan fraction is only one order higher of the bulk cellulose degradation. The activation energy of xylan fractions degradation was found as 74.4 and 140.9 kJ mol −1, respectively.

Kinetics of organosolv delignification of fibre crop Arundo donax L

Kinetics of ethanol–alkali delignification of fibre crop Arundo donax L. (giant reed) has been studied. The improved approach for determination of the reaction rate constants by accurate quantification of lignin fractions with different reactivity during standard procedure of graphical differentiation was applied. Following to a simplified model, the delignification process was considered as a complex of n-parallel irreversible first-order reactions with similar final product and analysed as a multi-component reaction system. Three kinetically distinguishable lignin fractions of A. donax were revealed and quantified in proportion of approximately 61, 23 and 16% (as initial, bulk and residual lignin, respectively) and their effective degradation rate constants were determined for different pulping conditions. The proportion of lignin fractions was different from that reported for wood, but close to another crop—wheat straw, where the initial lignin fraction was also found as a major fraction (about 90%). The values of apparent activation energy were estimated respectively as 64, 89 and 96 kJ mol −1, and were generally within the range of those reported for wood kraft and organosolv pulping. The simulation of ethanol–alkali delignification using found kinetic parameters showed the high reproducibility of experimental data on lignin removal, providing thereby the adequate test on validation of the suggested kinetic approach. The data reproducibility was substantially higher in comparison with conventional consecutive kinetic model (sum of square residuals (SQR) 0.0036 versus 0.0856).