Physicochemical characterization of lignins from rice straw by hydrogen peroxide treatment

Extraction of the dewaxed rice straw with 1% NaOH at 55°C for 2 h and following treatment without and with 0.5, 1.0, 2.0, 3.0, 4.0, and 5.0% hydrogen peroxide (H₂O₂) at 45°C for 12 h at pH 11.5 resulted in a dissolution of 68.3, 85.4, 89.4, 92.3, 92.3, 94.3, and 95.1% of the original lignin, respectively. Meanwhile, the two‐stage treatment together solubilized 67.2, 77.2, 78.7, 83.7, 85.5, 87.3, and 88.5% of the original hemicelluloses and degraded 2.5, 9.8, 11.8, 12.1, 15.6, 16.4, and 17.8% of the original cellulose under the conditions given, respectively. Analyses of these lignins revealed that alkali‐soluble lignin fractions did not suffer sever oxidation, but nearly 60% of the original lignin was dissolved out during the first stage of alkali treatment. In the second stage of alkaline peroxide treatment, the residual lignins were substantially released and enriched in oxidized carbonyl and carboxyl groups. In comparison, the isolated eight pure lignin samples were further characterized by both destructive methods such as alkaline nitrobenzene oxidation and nondestructive techniques such as ultraviolet (UV), Fourier transform infrared (FTIR), and carbon‐13 magnetic resonance spectroscopy (¹³C‐NMR) as well as gel permeation chromatography (GPC), and the results are reported. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 719–732, 2001     

Fractional Separation of Hemicelluloses and Lignin in High Yield and Purity from Mild Ball-Milled Periploca sepium

Abstract

A novel three-step procedure for separation of hemicelluloses and lignin with high yield and purity was proposed in this study, where wood is mildly milled and successively extracted to produce three hemicellulosic and lignin fractions representing the total hemicelluloses and lignin in wood. The sequential treatments of the mild ball-milled Periploca sepium with 80% aqueous dioxane containing 0.05 M HCl at 85°C for 4 h, DMSO at 85°C for 4 h, and 8% NaOH at 50°C for 3 h resulted in a total release of over 85% of the original hemicelluloses and 86% of the original lignin. In particular, approximately 36% of the original hemicelluloses and 50% of the original lignin were separated during the first mild acidolytic hydrolysis process after low intensity milling. The structure of the acidic dioxane-, DMSO-, and alkali-soluble hemicellulosic and lignin fractions were elucidated using wet chemical analysis, FT-IR, and solution-state ¹H, ¹³C, and ³¹P NMR techniques. Results showed that both the mild ball milling and the mild acidolysis under the conditions given did not affect the separated lignin macromolecular structure. On the other hand, the mild acidolytic hydrolysis condition did cause substantial hemicellulosic depolymerization exception for a significant cleavage the ether linkages between lignin and hemicelluloses. The acidic dioxane-soluble lignin fraction was structurally different from the DMSO- and alkali-soluble lignin preparations and may originate mainly from the primary wall, while the alkali-soluble lignin preparation was mainly released from the secondary wall of Periploca sepium. Furthermore, it was found that the acidic dioxane-soluble hemicelluloses mainly contained more branched and less acidic arabinoxylans, and the 8% NaOH-soluble hemicellulosic fraction H₃ was both less branched and less acidic in structure, whereas the DMSO-soluble hemicelluloses were more acidic but less branched and consisted mainly of 4-O-methylglucuronoarabinoxylan.     

Effect of ultrasound on the physicochemical properties of organosolv lignins from wheat straw

The extractability and physicochemical properties of the wheat straw lignins were comparatively studied by using extraction methods with 0.5M NaOH in 60% aqueous methanol with and without application of ultrasonic irradiation. The results showed that applying sonication for 5, 10, 15, 20, 25, 30, and 35 min solubilized 67.4, 68.6, 74.4, 77.3, 77.3, 77.9, and 78.5% of the original lignin, whereas the treatment with 0.5M NaOH in 60% aqueous methanol at 60°C for 2.5 h without ultrasound assistance released 61.0% of the original lignin. The lignin preparations isolated by ultrasound‐assisted extractions showed slightly lower molecular weights, associated polysaccharides, and thermal stabilities during the initial stage of decomposition. More important, there were no significant differences in the primary structural features between the lignin preparations. Ultrasound‐assisted extractions under the alkaline organosolv extractions did not affect the overall structure of the lignin from wheat straw. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2512–2522, 2002     

Fractional Separation and Structural Characterization of Chlorophyll and Lignin from Perennial Ryegrass (L. perenne) and Cocksfoot Grass (D. glomerata)

Abstract

One chlorophyll rich fraction and two lignin preparations were separated from perennial grass and cocksfoot grass by sequential three‐stage treatments with 80% ethanol containing 0.2% NaOH, 2.5% H₂O₂?0.2% EDTA containing 1.5% NaOH, and 2.5% H₂O₂?0.2% TAED containing 1.0% NaOH at 75°C for 3 h, respectively, which released 4.6 and 3.6% chlorophyll rich fraction, 2.3 and 5.8%, and 0.9 and 1.0% lignin preparations, except for releasing 8.0 and 10.4%, 79.1 and 77.0%, and 12.9 and 12.5% of the original hemicelluloses, respectively. The lignin fractions obtained from the two different grasses had very similar molecular weights and structural composition. The NMR spectra of the lignin preparations revealed the presence of p‐hydroxyphenyl, guaiacyl, and syringyl structures, and the lignin in chlorophyll rich fraction contained more guaiacyl and syringyl units than p‐hydroxyphenyl unit, whereas the reverse trend was found in the two lignin preparations. The lignin preparations are distinguished with straw and wood lignins by relatively higher contents of p‐hydroxyphenyl unit and lower amounts of condensed units (β‐5 and 5‐5′) and resinol units (β‐β). This difference in distribution of structural units indicated some structural heterogeneity between grass and straw/or wood lignin.     

Comparative study of three lignin fractions isolated from mild ball‐milled Tamarix austromogoliac and Caragana sepium

Six lignin fractions from mild ball‐milled Tamarix austromogoliac (TA) and Caragana sepium (CS) were sequentially isolated with 80% dioxane containing 0.05M HCl at 75°C for 4 h, 50% aqueous ethanol containing 1M triethylamine at 70°C for 4 h, and 8% aqueous NaOH at 45°C for 3 h. The results showed that the successive treatments made it possible to isolate lignin from wood with a high yield and purity, in which 89.4 and 90.6% of the original lignin from TA and CS were released, respectively. The lignin fractions isolated with the three‐step method were analyzed with Fourier transform infrared, ¹H‐ and ¹³C‐NMR, alkaline nitrobenzene oxidation, and gel permeation chromatography. It was found that the three lignin fractions isolated from TA were rich in syringyl units, and the molar ratio of the relatively total moles of vanillin, vanillic acid, and acetovanillin to the relatively total moles of syringaldehyde, syringic acid, and acetosyringone decreased from 1: 2.6 to 1 : 3.2 to 1: 3.6 in the lignin preparations, whereas this ratio in the corresponding lignin fractions isolated from CS was found to be 1.4 : 1, 1.1 : 1, and 1 : 1.4, respectively. More importantly, the results revealed that the sequential extractions of the mild ball‐milled TA and CS with 80% acidic dioxane, 50% alkaline ethanol, and 8% aqueous NaOH under the conditions used did not significantly cleave the β–O‐4 and α–O‐4 linkages in lignin macromolecules. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Physicochemical characterization of lignin fractions sequentially isolated from bamboo (Dendrocalamus brandisii) with hot water and alkaline ethanol solution

Nine lignin fractions from bamboo (Dendrocalamus brandisii) were sequentially isolated with hot water at 80, 100, and 120°C for 3 h and 60% aqueous ethanol containing 0.25, 0.5, 1.0, 2.0, 3.0, and 5.0% NaOH at 80°C for 3 h. Molecular weight and purity analysis revealed that the lignin fractions isolated by hot water (L₁, L₂, and L₃) had lower weight-average molecular weights (between 1350 and 1490 g mol⁻¹) and contained much higher amounts of associated hemicelluloses (between 9.26 and 22.29%), while the lignin fractions isolated by alkaline aqueous ethanol (L₄, L₅, L₆, L₇, L₈, and L₉) had higher weight-average molecular weights (between 2830 and 3170 g mol⁻¹) and contained lower amounts of associated hemicelluloses (between 0.63 and 1.66%). Spectroscopy (UV, FTIR, ¹³C-NMR, and HSQC) analysis showed that the bamboo (Dendrocalamus brandisii) lignin was typical grass lignin, consisting of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units. The major interunit linkages presented in the alkaline aqueous ethanol extractable bamboo lignin were β-O-4′ aryl ether linkages (about 74.3%), followed by β-β′ resinol-type linkages and β-1′ spirodienone-type linkages (both for 7.8%), together with small amounts of β-5′ phenylcoumaran (6.8%) and p-hydroxycinnamyl alcohols end groups (3.1%). In addition, a small percentage (1.0%) of the lignin side-chain was found to be acetylated at the γ-carbon, predominantly over syringyl units. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of steaming pressure on steam explosion pretreatment of Lespedeza stalks (Lespedeza cyrtobotrya). II. Characteristics of degraded lignin

Lignin fractions obtained by steam explosion pretreatment and subsequent alkaline ethanol solution post‐treatment from Lespedeza cyrtobotrya stalks were studied in terms of chemical characteristics, to reflect the influence of elevating steam pressure from 15 to 25 kg/m². Because of the remarkable selectivity with respect to lignin, the post‐treatment with 60% ethanol solution containing 1% NaOH yielded 8.3, 13.0, 16.0, 16.4, and 17.8% lignin fractions from the samples steam‐exploded at 15, 17.5, 20, 22.5, and 25 kg/m² for 4 min, respectively, comparing to 7.7% lignin removal from the raw material. Steam explosion pretreatment, not only obviously cleaved the linkage between carbohydrates and lignin resulting in the significantly decrease of the associated hemicelluloses in lignin fractions, but also broke the β‐O‐4 bond between lignins to some degrees. In particular, slightly more guaiacyl moieties than syringyl units were affected. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Extraction and Characterization of Hemicelluloses and Cellulose from Oil Palm Trunk and Empty Fruit Bunch Fibres

Abstract

The cell walls of oil palm trunk fibre and empty fruit bunch (EFB) fibre were initially extracted with 5% NaOH at boiling for 2 h, which removed 17.3% and 15.2% hemicelluloses, respectively. Further extraction of the delignified palm trunk and EFB fibre was conducted with 10% NaOH at 20°C for 16 h and 24% KOH-2% H₃BO₃ at 20°C for 2 h. This resulted in the release of 11.9%, 13.5%, 12.7% and 14.9% residual hemicelluloses, respectively. The cellulose content, isolated by 24% KOH-2% H₃BO₃ from the two fibre samples, was found to be 41.3-41.7%, most of which was relatively free of associated lignin and hemicelluloses. The hemicelluloses, extracted with 5% NaOH from the lignified palm trunk fibre and EFB fibre, contained relatively high amounts of xylose, and minor arabinose and rhamnose than the hemicelluloses, extracted with 10% NaOH and 24% KOH-2% H₃BO₃ from the delignified fibres. While the hemicelluloses, extracted with 10% NaOH and 24% KOH-2% H₃BO₃ from the delignified palm trunk and EFB fibre, contained slightly more galactose, glucose, and mannose than the hemicelluloses, extracted with 5% NaOH from the lignified fibres. Further studies implied that the hemicelluloses, extracted with 5% NaOH from the lignified fibres, were more linear and acidic and had a large molecular size (weight-average, 17,400-22,900), together with comparatively high associated lignins (12.0-15.7%). Which were found to be linked to hemicelluloses mainly via syringyl unit. On the other hand, the hemicelluloses, extracted with 10% NaOH and 24% KOH-2% H₃BO₃ from the delignified fibres, were more branched but less acidic and had a comparatively small molecular size (weight-average, 6,600-10,800), together with trace amounts of associated lignin (0.3-1.1%). The hemicelluloses in the cell walls of palm EFB had a higher degree of polymerizaton than the hemicelluloses in the cell walls of palm trunk fibre as indicated by the molecular-average weights, ranging from 7,200 to 22,900, and from 6,600 to 17,400, respectively.     

Characteristics of hemicelluloses obtained from sweet sorghum based on successive extractions

Hemicelluloses were successively extracted from sweet sorghum by hot water, dioxane, DMSO, and different concentrations of NaOH between 0.5% and 6.0%. The yields of the seven fractions together accounted for 88.6% of the original hemicelluloses. The obtained hemicellulosic subfractions were comprehensively investigated by both destructive methods such as alkaline nitrobenzene oxidation and acid hydrolysis and nondestructive techniques such as gel permeation chromatography, Fourier‐transform infrared, ¹³C‐nuclear magnetic resonance, and 2D‐heteronuclear singular quantum correlation. Sugar composition studies showed that the water‐soluble polysaccharides consisted mainly of glucose, while xylose, arabinose, and glucuronic acid were the major sugars in other hemicellulosic fractions. It was found that the hemicelluloses from sweet sorghum were l‐ arabino‐(4‐O‐methyl‐d‐ glucurono)‐xylans. Comparison with the hemicellulosic fractions dissolved by the alkali treatment, the hemicellulosic fraction extracted by DMSO had lower molecular weight. In addition, it was also found that the hemicelluloses prepared by dioxane and DMSO were more branched since that they had higher nonxylose/xylose ratios than those extracted by the alkali treatment, which were more linear and contained higher amounts xylose. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42790.     

Fractionation of Lignocellulosic Materials for the Biorefinery: Separation and Characterization of Lignin from Calamagrostis angustifolia Kom

Dewaxed Calamagrostis angustifolia Kom was pretreated with hot water at 60 and 90°C for 3 h, and then the residue obtained was successively treated with 70% ethanol, and 70% ethanol containing 0.2%, 1.0%, 2.0%, 4.0%, and 8.0% NaOH at 80°C for 3 h. The dissolved components were subjected to further separation to get eight lignin fractions, which were characterized by gel permeation chromatography, Fourier transform infrared, and sugar analysis. All the lignin fractions had small weight-average molecular weights between 810 and 2580 g/mol. Two typical lignins, L₃ (prepared with 70% ethanol) and L₅ (prepared with 70% ethanol containing 1.0% NaOH), were further analyzed using ¹H, ¹³C NMR and HSQC spectroscopy. Signals from guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H) units observed in aromatic/olefinic region of HSQC spectra indicated that the lignin from Calamagrostis angustifolia Kom could be classified as “GSH” lignin. In aliphatic-oxygenated region, β-O-4′ together with small amounts of β-5′, β-β′, and p-hydroxycinnamyl alcohol end group were the main interunit linkages observed. Aqueous ethanol, which could avoid the cleavage of ether bonds in lignin at neutral condition, was more effective than water on lignin extraction.     

Structural characterization of residual lignins isolated with cyanamide-activated hydrogen peroxide from various organosolvs pretreated wheat straw

The posttreatment of various organosolvs pretreated wheat straw with cyanamide-activated hydrogen peroxide was studied. About 44–80% of the total residual lignin and 38–85% of the total residual hemicelluloses were released or degraded during the posttreatment with 1.8% H₂O₂–0.18% cyanamide at 50°C under pH 10.0 for 4 h from different aqueous organic acids or alcohols pretreated straw. The seven degraded residual lignin preparations were subjected to a comprehensive physicochemical and structural characterization by UV, FTIR, and ¹H and ¹³NMR spectroscopy, and GPC. The nitrobenzene oxidation method was also applied to the in situ lignins. It was found that the seven residual lignin preparations contained large amounts of noncondensed syringyl and guaiacyl units, together with fewer noncondensed p-hydroxyphenyl units, esterified p-coumaric acid, and mainly etherified ferulic acid. All of the lignin fractions are free of associated polysaccharides and had molecular-average weights ranging between 2980 and 3820 g mol⁻¹. Analysis of these low molecular weight degradation products revealed an oxidation of residual lignin had occurred. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Comparative study of cellulose isolated by totally chlorine‐free method from wood and cereal straw

Highly purified cellulose preparations were obtained by pretreatment of dewaxed barley straw, oil palm frond fiber, poplar wood, maize stems, wheat straw, rice straw, and rye straw with 2.0% H₂O₂ at 45°C and pH 11.6 for 16 h, and sequential purification with 80% acetic acid–70% nitric acid (10/1, v/v) at 120°C for 15 min. The purified cellulose obtained was relatively free of bound hemicelluloses (2.3–3.2%) and lignin (0.4–0.6%) and had a yield of 35.5% from barley straw, 39.6% from oil palm frond fiber, 40.8% from poplar wood, 36.0% from maize stems, 34.1% from wheat straw, 23.4% from rice straw, and 35.8% from rye straw. The weight‐average molecular weights of the purified cellulose ranged from 39,030 to 48,380 g/mol. The thermal stability of the purified cellulose was higher than that of the corresponding crude cellulose. In comparison, the isolated crude and purified cellulose samples were also studied by Fourier transform IR and cross‐polarization/magic‐angle spinning ¹³C‐NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 322–335, 2005     

Selective hydrolysis of lignocelluloses from corn stalk in an ionic liquid

In this work, a selective two‐stage hydrolysis of lignocelluloses from corn stalk was developed through pH adjustment in 1‐n‐butyl‐3‐methylimidazolium chloride ([C₄mim]Cl). In the first stage, the lignin–hemicelluloses matrix of corn stalk was disrupted and hydrolyzed in the ionic liquid at pH 4.5 and 90°C to obtain xylose with 23.1% yield. In the second stage, cellulose‐rich materials in solid residues were further hydrolyzed in the ionic liquid at pH 2–3 and 90°C to produce glucose with 26.9% yield, and pure lignin was also obtained. Structures of the hydrolysates were identified by ¹³C NMR and IR spectrum analysis, and the ionic liquid was recycled throughout the process. It is expected that the information provided here would be useful for the development of new methods to selectively produce monosaccharides from catalytic hydrolysis processes of biomass. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of several factors on peracetic acid pretreatment of sugarcane bagasse for enzymatic hydrolysis

BACKGROUND: Lignocellulose should undergo pretreatment to enhance its enzymatic digestibility before being saccharified. Peracetic acid (PAA) is a strong oxidant that can remove lignin under mild conditions. The sulfuric acid in the PAA solution also can cause degradation of hemicelluloses. The objective of the present work is to investigate the effect of several factors on peracetic acid pretreatment of sugarcane bagasse. RESULTS: It was found that PAA charge, liquid/solid (l/s) ratio, temperature, time, interactions between PAA charge and l/s ratio, temperature and time, all had a very significant effect on the enzymatic conversion ratio of cellulose. The relative optimum condition was obtained as follows: PAA charge 50%, l/s ratio 6:1, temperature 80 °C and time 2 h. More than 80% of the cellulose in bagasse treated under the above conditions was converted to glucose by cellulase of 20 FPU g^?1 cellulose. Compared with H₂SO₄ and NaOH pretreatments under the same mild conditions, PAA pretreatment was the most effective for enhancement of enzymatic digestibility. CONCLUSION: PAA pretreatment could greatly enhance the enzymatic digestibility of sugarcane bagasse by removing hemicelluloses and lignin, but removal of lignin was more helpful. This study can serve as a step to further optimization of PAA pretreatment and understanding the mechanism of enhancement of enzymatic digestibility. Copyright © 2007 Society of Chemical Industry     

有机-无机溶剂连续抽提巨龙竹木质素及其结构表征

为了分析巨龙竹木质素的结构特征,采用有机-无机溶剂连续抽提的方式将木质素和半纤维素进行分离,脱蜡竹粉依次用80%二氧六环、80%二氧六环-0.5% NaOH、2% NaOH、5% NaOH和8% NaOH连续抽提后,得5个木质素样品L₁~L₅,计算了木质素得率,并对抽提所得的木质素样品进行了红外光谱(FT-IR)、紫外光谱(UV)、核磁共振碳谱(¹³C NMR)和二维核磁共振(2D HSQC)分析。结果表明:在二氧六环和不同浓度碱性水溶液的连续抽提下,最终从巨龙竹原料中分离得到70.6%的原本木质素,其中木质素样品L₂的纯度最高,表明该方法是一种较为有效的竹材木质素组分分离方法。木质素的苯环骨架结构在分离过程中没有被破坏,但碱浓度的增加导致木质素中部分酯键发生断裂。巨龙竹木质素大分子主要由愈创木基单元(G)、紫丁香基单元(S)、对羟基苯基单元(H)组成,木质素大分子基本单元之间的联接键主要是β-O-4'醚键,除此之外还有β-β'、β-5'和β-1'联接。     

Structural and physicochemical characterization of hemicelluloses isolated by alkaline peroxide from barley straw

Seven hemicellulosic preparations were obtained from barley straw by extraction with 1.5% H₂O₂ at pH 12.0 for 14 h at 45 °C with extractant to straw ratios of 10:1, 13:1, 15:1, 18:1, 20:1, 25:1 and 30:1. The respective yields of dissolved hemicelluloses were 28.4 wt%, 28.8 wt%, 29.7 wt%, 30.1 wt%, 30.6 wt%, 30.8 wt% and 30.8 wt% or dry barley straw, corresponding to release of 78.7%, 79.8%, 82.3%, 83.4%, 84.8%, 85.3% and 85.3% of the original hemicelluloses. The polymers were mainly composed of xylose, arabinose, glucose, galactose and 4-O-methyl-D -glucuronic acid (59.3–62.6%, 19.7–22.0%, 8.8–12.5%, 5.6–6.9% and 5.8–6.7%, respectively) and had weight-average molecular weights of between 38 470 and 41 050 g mol⁻¹.¹³ CNMR spectroscopy confirmed the results obtained by chemical methods, and showed that the hemicellulosic fraction was mostly by L -arabino-(4-O-methyl-D -glucurono)-D -xylan. More importantly, it was found that lignin provides some protection for the hemicelluloses in barley straw against attack by hydrogen peroxide. © 2002 Society of Chemical Industry     

The mechanism and technology parameters optimization of alkali‐H2O2 one‐bath cooking and bleaching of hemp

Hemp is cooked and bleached in alkali‐H₂O₂ one‐bath. The analysis of physical and chemical properties related to acid, alkali, and hydrogen peroxide about various types of components in hemp such as hemicelluloses and pectin, and lignin components makes it ascertained. In this one‐bath process, alkali and H₂O₂ have cooperative effects to remove most proportions of the noncellulosic components efficiently. The additive MgSO₄ and a stabilizer of H₂O₂ as auxiliary agents are introduced to protect cellulose from degradation and, meanwhile, they improve the efficiency of H₂O₂. The universal rotatable composite experiment design is employed to get the highly precise equation, in which the variables of NaOH and H₂O₂ concentrations, and the processing time are considered to be the main technological parameters of this alkali‐H₂O₂ one‐bath process. The residual gum content and residual lignin content of hemp fiber are the evaluation indexes. Based on regression equations, the figures are plotted to analyze the influences of parameters on the evaluation indexes; the optimization multicriteria mathematical model is simultaneously established to obtain the optimum parameters. Finally, an experiment is carried out to further test the acceptance of the calculated optimum values. It is shown that, for the hemp taken from Anhui Province of China, this alkali‐H₂O₂ one‐bath process can substantially remove gum and lignin from raw hemp. NaOH 10.5 g/L, H₂O₂ 9.8 g/L, and the processing time of 127 min with 0.1% MgSO₄ + 2.7 g/L stabilizer of H₂O₂ at 100°C are recommended to be the optimum parameters; then, a compromise is achieved among the lowest lignin content, the residual gum content, and the best strength and whiteness of hemp fiber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2279–2285, 2005     

Structure and thermal stability of polysaccharide fractions extracted from the ultrasonic irradiated and cold alkali pretreated bamboo

Polysaccharide fractions were extracted from partially delignified bamboo (Neosinocalamus affinis) culms pretreated with ultrasonic irradiation for varied times and cold sodium hydroxide/urea solution, and their structure and thermal stability were comparatively characterized. In this case, ball‐milled bamboo culms were treated with ultrasonic irradiation for varied times (0, 5, 15, and 25 min), dissolved with 7% sodium hydroxide/12% urea solution at −12°C, and then extracted with ethanol and dioxane to obtain partially delignified solid fractions. Subsequently, the solid fractions were subjected to be extracted with dimethyl sulfoxide followed by precipitation in ethanol and yielded the polysaccharide fractions. Sugar analysis indicated that the total sugar content increased from 60.63% in the polysaccharide fraction prepared without ultrasonic irradiation to 81.26% in the polysaccharide fraction prepared with an ultrasonic irradiation time of 25 min. Glucose (∼ 50–55%) was the major sugar component, and xylose (∼ 41–44%) was the second major sugar in polysaccharide fractions in all cases. Spectroscopy (FTIR, ¹H‐NMR, ¹³C‐NMR, and HSQC) analysis suggested that the polysaccharide fractions were mainly composed of (1→4)‐linked α‐D ‐glucan from amylose and (1→4)‐linked β‐D ‐xylan attached with minor amounts of branched sugars from hemicelluloses. In addition, thermal analysis showed that the main degradation stage of the polysaccharide fractions occurred between 210 and 320°C. Compared to the polysaccharide fraction prepared without ultrasonic irradiation, the polysaccharide fraction prepared with ultrasonic irradiation had a slightly lower thermal stability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chemical Modification of Methanol-Insoluble Kraft Lignin Using Oxypropylation Under Mild Conditions for the Preparation of Bio-Polyester

Methanol-insoluble high-molecular weight (M_w = 26,610 g mol^?1) soft wood kraft lignin was oxypropylated under the mild condition of 40°C and 1 atm for 12 h in the presence of NaOH catalyst for the production of bio-polyester. Fourier transform infrared spectra showed that polyether chains were extended due to the oxypropylation reaction. The M_w and M_n of the oxypropylated lignin were 46,330 and 17,110 g mol^?1, respectively. The high-molecular weight oxypropylated lignin was reacted with sebacic acid or polybutadiene (dicarboxy terminated) for bio-polyester synthesis. While the decomposition temperatures of the oxypropylated lignin were 217°C and 367°C, those of the bio-polyesters prepared with sebacic acid and polybutadiene (dicarboxy terminated) were 380°C and 453°C, respectively, indicating that the bio-polyesters possessed enhanced thermal properties. The oxypropylation of methanol-insoluble high-molecular weight lignin under mild conditions is one of the promising approaches for preparing bio-plastics with an enhanced thermal property.     

Purification of Polonium-210 Using Pyrochemical Extraction

Abstract

An efficient extraction process that does not utilize halides or organic solvents has been developed for the recovery and purification of 210_po. Polonium-210, produced in bismuth metal by neutron irradiation, is extracted from molten bismuth metal into molten NaOH in an unique 3-compartment contactor under an inert atmosphere. At a temperature of 450±25°C, and at a NaOH/Bi weight ratio of 0.044, five successive 60-minute extractions remove >96% of the 210_po.

Following phase separation and freezing, additional purification steps include dissolution of the solidified NaOH in HN03, recovery of ²¹⁰po from this solution by MnO₂ carrier precipitation, dissolution of the precipitate by H₂O₂ in HNO₃, and, finally, electrodeposition of ²¹⁰po onto platinum gauze.