共查询到20条相似文献，搜索用时 171 毫秒
1.
为了将废弃的香蕉茎秆制备纤维的工艺运用到纺织领域,采用化学法脱胶工艺提取香蕉茎秆纤维。研究预酸,预氧及碱液煮炼工艺条件对香蕉茎秆纤维脱胶率和残余木质素率的影响,确定较佳的脱胶工艺。采用傅立叶红外光谱(fourier transformed infrared spectroscopy,FTIR)、X射线衍射(X-ray diffraction,XRD)和扫描电镜(scanning electron microscopy,SEM)分析较佳工艺制备的香蕉茎秆纤维的理化特性;并对其力学性能进行测试与分析。结果表明:预酸采用H2SO4质量浓度2 g/L,浴比1∶20,水浴温度55℃,时间2 h;预氧处理工艺采用H2O2质量浓度7 g/L;助剂Na2Si O3质量分数3%,多聚磷酸钠质量分数2%;温度95℃,p H值11,浴比1∶20,时间1.5 h,升温时间35~40 min;碱液煮炼Na OH溶液质量浓度9 g/L,常压0.1 MPa煮沸,温度100℃,时间3 h,浴比1∶20;酸洗用H2SO4体积分数0.1%,温度28℃,时间5 min。在此条件下,香蕉茎秆纤维的脱胶率为68%,残余木质素率为8.21%。FTIR结果表明对比香蕉茎秆粗纤维,化学法较佳工艺制备的香蕉茎秆纤维去除了大部分的半纤维素和木质素,相对结晶度为60%;断裂截面的SEM图表明化学法制备的香蕉茎秆纤维呈现脆性-塑形复合型断裂形式,直径范围在0.068 mm左右。力学性能测试结果表明较佳工艺制备的香蕉茎秆纤维拉伸强度,杨氏模量和断裂伸长率分别是353.09 MPa,18.34 GPa和1.70%。结果表明化学法较佳工艺制备的香蕉茎秆纤维在纺织工业具有一定的应用前景。 相似文献
2.
为了探索用草酸预处理竹材制备溶解浆,该文用不同用量的草酸对竹材进行预水解,测定预水解过程竹材木质素含量的变化,用场发射扫描电镜(field emission scanning electron microscope,FE-SEM)观察水解后假木质素在竹纤维表面的分布状况,用核磁共振技术(cross polarisation/magic angle spinning carbon-13 nuclear magnetic resonance,CP/MAS 13C-NMR)分析木质素的结构变化。研究结果表明,在竹片草酸预水解过程中,竹片预水解得率将随着预水解时间的延长而下降,并且,草酸用量越大,得率下降越多。基于水解后竹材基质的木质素含量会随着预水解时间的延长而逐渐升高,并且,草酸用量越大,木质素含量升高越多;而基于竹材原料的木质素含量则随着预水解时间的延长先下降再增加,并且,草酸用量越大,增加的速率也越大。竹材木质素由于芳基醚键(β-O-4)断裂,酚型木质素含量提高。纤维素和半纤维素降解产物在预水解过程形成的假木质素类物质会以微球的形式附着在竹片表面。该研究可为探索竹材快速高选择性去除半纤维素的预水解方法提供参考。 相似文献
3.
木质素的来源、催化剂和溶剂对木质素整体转化和产物分布起着至关重要的作用。该文主要综述了国内外有关木质素优先解聚的最近研究进展,分析比较了酸催化剂、碱催化剂、贵金属催化剂以及非贵金属催化剂的优势与不足,指出金属负载型催化剂能有效促进木质素苯丙烷单元间C-C键或C-O键的断裂转化为芳烃化合物,并对木质素脱出率和单体产率进行了评述与分析。对比分析了不同种类的溶剂对木质素的脱出率、碳水化合物的脱出率以及浆液的宏观结构造成的影响,发现醇类溶剂不仅可以断开木质素和半纤维素之间的酯键,而且可以保护纤维素和半纤维素不受破坏,从而达到生物质高值化利用的效果。最后对当前生物质解聚所面临的挑战以及未来研究趋势进行了总结与展望,指出通过催化剂和溶剂结合可以有效地解聚出木质素单体,因此催化剂开发和溶剂的选择将是该领域未来研究重点。 相似文献
4.
为提升杨木的酶解发酵效率，该研究探究了酸-碱两段组合预处理对半纤维素、木质素的降解、纤维素保留以及后续发酵的影响；通过扫描电镜（scanning electron microscopy，SEM）、X射线衍射（X-ray diffraction，XRD）和傅里叶变换红外光谱（fourier transform infrared spectroscopy，FT-IR）对杨木进行表征分析，探究预处理对杨木表面形貌、组成成分和热稳定性的影响。对杨木进行两段HAc-NaOH组合预处理，第一段是采用1% HAc作为酸性催化剂在不同预处理温度（160～200 ℃）下进行预处理，第二段预处理则是以第一段预处理后样品为底物进行不同NaOH质量分数（0.3%～1.2%）的碱预处理。结果表明酸-碱两段预处理的效果优于仅一段酸预处理，在200 ℃ HAc组合0.8% NaOH的两段预处理下获得的乙醇浓度为18.72 g/L，结合SEM、XRD和FT-IR分析发现预处理中半纤维素和木质素的脱除显著提升预处理杨木中纤维素含量，木质纤维致密结构被破坏，提高了酶对纤维素的可及性，也有助于提高后续乙醇发酵浓度。最后通过对葡聚糖、木聚糖、酸不溶性木素含量、木聚糖、酸不溶性木素去除率以及结构特性对乙醇得率的相关性进行分析，表明预处理样品中具有较低半纤维素/木质素含量和较高纤维素结晶度的预处理样品具有更强的发酵潜力。 相似文献
5.
NaOH预处理提高甘蔗叶产甲烷性能及其机理分析 总被引：2，自引：0，他引：2
为提高甘蔗叶厌氧消化的产甲烷性能,采用NaOH对粉碎后的甘蔗叶进行了预处理,得到了不同NaOH浓度、不同预处理时间条件下甘蔗叶厌氧消化的甲烷产率,并研究比较了预处理前后甘蔗叶微观物理形态、化学分子结构和化学组分的变化。结果表明:与未预处理甘蔗叶相比,NaOH预处理甘蔗叶的累计产甲烷量提高了22.02%～89.94%,厌氧消化时间T80缩短了2～4 d,其中6%NaOH-5d预处理甘蔗叶的产甲烷性能最好;NaOH破坏了甘蔗叶表面蜡质层和细胞壁结构,促进了甘蔗叶表面二氧化硅、木质素等分解,打破了对纤维素的束缚;预处理后甘蔗叶的木质纤维素结构发生明显变化,其中木质素的羟基、甲氧基和羰基等部分官能团发生不同程度断裂,紧致的大分子结构发生分解,纤维素的结晶度降低,部分氢键遭到破坏,半纤维素发生了分子间和分子内的降解;预处理甘蔗叶的木质纤维素含量均有不同程度的降低,可被微生物分解利用的有机物质增多,其中6%NaOH-5d预处理甘蔗叶厌氧消化的木质素、纤维素、半纤维素降解率分别提高了9.27%、25.14%和21.52%。因此NaOH预处理是一种提高甘蔗叶厌氧消化产甲烷性能的有效方法。 相似文献
6.
理化预处理麦秸改善其聚丙烯复合材料抗霉菌腐蚀力学性能 总被引：3，自引：2，他引：1
为探讨麦秸秆不同处理方法对其制备的聚丙烯（polypropylene,PP）复合材料耐霉菌腐蚀性能影响,采用NaOH、HAc、水热、微波4种方法对麦秸秆纤维进行表面预处理,并对未处理和4种处理麦秸秆制备的复合材料进行霉菌加速腐蚀试验,测试了5种复合材料腐蚀前后的力学性能、颜色变化和吸水性,用傅立叶红外光谱分析其官能团的变化,观察并分析复合材料表面霉菌生长情况及表面微观结构。结果表明：霉菌能腐蚀麦秸秆纤维中的纤维素、半纤维素和木质素,使复合材料表面产生裂纹和孔洞,预处理可改善麦秸秆纤维和PP基体间的界面结合,有效地阻止霉菌腐蚀复合材料中麦秸秆的纤维素、半纤维素和木质素,其中5%NaOH预处理效果最佳,其弯曲强度、拉伸和冲击强度分别比未处理的提高了1.68%、3.67%和75.28%,吸水率和色差值降低12.99%和55.25%,经预处理麦秸秆制备复合材料腐蚀后表面裂纹和较大孔洞减少。该研究结果可为提高木塑复合材料防霉效力提供试验数据和理论参考,有利于延长木塑复合材料使用寿命。 相似文献
7.
常压温和条件下丙酸预处理小麦秸秆的工艺优化 总被引：1，自引：1，他引：0
为了提高小麦秸秆木质纤维素的能源化利用效率,该文研究了常压温和条件下丙酸预处理小麦秸秆的工艺优化。该方法的最佳工艺条件为：料液比1∶16、粒度40目、丙酸质量浓度900 g/L、催化剂质量浓度3 g/L、温度70℃,处理时间150 min。在此条件下,小麦秸秆的纤维素保留率为92.6%,半纤维素和木质素的脱除率分别为98.3%和70.5%。丙酸预处理后小麦秸秆的酶解得率90.3%。研究表明,在常压温和条件下,丙酸法预处理小麦秸秆,可有效地将其分离为纤维素、半纤维素、木质素3大组分。 相似文献
8.
互花米草中温厌氧发酵木质纤维结构的变化 总被引：4，自引：1，他引：4
采用扫描电子显微镜（SEM）、傅立叶变换红外光谱（FTIR）和X射线衍射（XRD）对互花米草中温（35℃）厌氧发酵前后木质纤维结构的变化进行了对比分析。结果表明,互花米草茎秆的生物降解主要发生在维管束组织部位,而薄壁细胞是一种生物难降解组织;发酵60 d后互花米草木质素的相对含量升高,木质素官能团所对应的FTIR光谱的特征峰的峰强与其纤维素和半纤维素所对应的特征峰的峰强的比值是发酵前的2倍以上;厌氧发酵使互花米草的结晶度有所降低,由发酵前的0.510降到了0.479。总之,木质素对纤维素和半纤维素的包裹作用,以及纤维素的结晶结构是影响互花米草厌氧生物转化的主要因素。 相似文献
9.
膨化预处理玉米秸秆提高还原糖酶解产率的效果 总被引：6，自引：3，他引：3
为了提高玉米秸秆的可发酵还原糖转化率,采用膨化技术对玉米秸秆木质纤维素进行预处理。扫描电镜观察,玉米秸秆的纤维束受到破坏,木质素包裹作用减弱,纤维素酶的空间作用面积提高。红外光谱分析表明有部分半纤维素和少量木质素水解;X射线衍射测定纤维素结晶度降低了12.68%。通过进一步纤维素酶解试验,与未处理的相比膨化处理后原料酶解时间可缩短16 h,未经膨化处理原料还原糖的酶解产率为13.48%,膨化处理后原料还原糖的酶解产率可达24.91%。结果表明,膨化预处理技术可明显提高玉米秸秆木质纤维素的能源化利用效率。该 相似文献
10.
为探究乌拉草纤维的热解性能及其在热解过程中挥发性有机物释放情况,基于傅里叶红外光谱仪及同步热分析质谱联用系统对乌拉草纤维及汉麻纤维的主要化学成分进行分析,探究其热分解过程,采用Coats-Redfern法进行热动力学计算,并对其热分解过程中挥发性有机物释放进行检测。研究结果发现,乌拉草纤维与汉麻纤维主要成分相似,以纤维素、半纤维素、木质素为主。其热分解过程可依次分为水分挥发失重、半纤维素热解、纤维素及木质素热解3个主要阶段,并可用半纤维素热解、纤维素热解、木质素热解3个独立的一级反应描述,纤维素与木质素热解阶段反应活化能较高,热解过程与汉麻纤维热分解过程相似。在乌拉草纤维热解过程中,除H2O、CO2气体释放以外,同时释放少量甲醛等挥发性有机物。研究结果为乌拉草纤维实际应用中阻燃及环保问题的考虑提供参考。 相似文献
11.
为研究光照对香菇菌丝后熟转色过程中活性氧代谢的影响,通过设置自然光照条件与黑暗条件下香菇菌丝后熟转色对比试验,分析其活性氧含量、丙二醛(MDA)含量、还原型烟酰胺腺嘌呤二核苷酸磷酸(NADPH)氧化酶活性、抗氧化酶活性及自噬的差异。结果表明,自然光照条件下香菇菌丝正常后熟转色,黑暗条件下香菇菌丝不转色。自然光照条件下香菇菌丝活性氧含量、MDA含量、NADPH氧化酶活性、过氧化氢酶(CAT)活性、过氧化物酶(POD)活性均显著高于黑暗条件,超氧化物歧化酶(SOD)活性变化则与之相反。同时,香菇菌丝细胞自噬的透射电镜分析及实时荧光定量PCR(qRT-PCR)对自噬基因Atg8的表达水平分析结果表明,在自然光照条件下香菇菌丝细胞的自噬特征明显。本研究结果为优化香菇栽培的环境条件提供了一定的理论依据,也为后续对光照环境下香菇体内氧化平衡的作用机理研究提供了有效参考。 相似文献
12.
13.
《CATENA》2005,59(1):69-78
The wetting capacity of Hapludands and Palehumults under grassland and forest in southern Chile was assessed by measuring contact angles of solid, water and air interfaces. Microaggregates obtained from natural aggregates of two sizes (4–6.3 and 10–12 mm) were spread onto microscope slides and drops of saturated aqueous KCl solution were placed on the surface of the aggregates. The wetting angles of the drops were measured with a microscope with a horizontal viewing direction and an ocular containing a goniometer. The wetting capacity was determined on layers peeled progressively from the walls of aggregates toward their centres, and the organic matter content of the different aggregate layers was determined. The water stability of the aggregates was measured by dry and wet sieving. Hapludands always showed greater hydrophobicity than Palehumults. The wetting resistance of the soil matrix samples was less than that of the single layers of aggregates. The wetting resistance of aggregates generally increased from the exterior to their centre. The increase was strongest in the topsoil under grassland. Smaller aggregates under both grassland and forest showed a greater hydrophobicity than larger ones. Organic matter content increased towards the aggregate interiors, especially in the fine aggregates. Aggregates with greater water repellence were more stable to dry and wet sieving, especially under forest. Therefore, intensive management decreases wetting resistance and makes the soil less stable. 相似文献
14.
With growing use of synthetic adjuvants in modern agriculture, their impacts on the environment are being questioned. In a search for an environmentally safe phyto-adjuvant, we have investigated natural glycosidic saponin for delivery of agromaterials through plant cuticle membranes. Four saponin preparations from Quillaja saponaria bark (QE), obtained from Sigma-Aldrich, and Balanites aegyptiaca fruit mesocarp (ME), kernel (KE), and root (RE), isolated and characterized in our laboratory, were used for testing the delivery of [14C]-2,4-dichlorophenoxyacetic acid (2,4-D) across isolated intact astomatous adaxial Citrus grandis leaf cuticle membranes (CMs). The results showed that both Q. saponaria and B. aegyptiaca saponin preparations enhanced delivery of 2,4-D through CMs. Among the saponin preparations, ME exhibited a significantly higher level of delivery of 2,4-D with a concentration effect (2% being the highest). Transmission electron microscope (TEM) and dynamic light scattering (DLS) characterization of these saponin preparations in aqueous solution clearly demonstrated the formation of nanoscale vesicles. Various possibilities for a natural amphiphatic phyto-saponin as a delivery adjuvant through CMs are discussed. 相似文献
15.
In the space of just a few years, nanotechnology has become a topical subject not only in academia, but also in the daily lives of people. In order to investigate the properties of natural nanoparticles (NNPs) and to obtain a better understanding of their environmental behaviour and impacts from a new perspective, transmission electron microscope (TEM), zeta potential analysis and time‐resolved dynamic light scattering (DLS) analysis were used to examine the main properties and aggregation kinetics of NNPs extracted from Chinese soils added to various concentrations of the electrolytes NaCl, CaCl2 and LaCl3. The NNPs that were less than 100 nm remained stable for 100 days. The classic Derjaguin‐Landau‐Verwey‐Overbeek (DLVO) model partially revealed the aggregation behaviour of NNPs, in which ionic strength, composition and size may play important roles. The influence of hematite and natural organic matter (NOM) was demonstrated by aggregation kinetics and critical coagulation concentrations (CCC). The size of NNPs could also change the maximum total potential energy of interactions in the systems (VT(h)). These factors make the aggregation of NNPs in electrolytes different from that of soil colloids and influence the environmental behaviour of NNPs. 相似文献
16.
~(60)Coγ辐照对稻草纤维组织及酶解效果的影响 总被引：4，自引：2，他引：2
用60Coγ射线处理干稻草秸秆及粗纤维,评价辐照对稻草纤维组织降解作用以及提高稻草秸秆纤维酶降解效果。采用DNS法和硫酸-苯酚法分别测定稻草辐照样品热水浸提液中水溶性还原糖和总糖的含量,通过高效气相色谱分析稻草秸秆各辐照处理提取液中还原糖各组分的变化,并用电子显微镜扫描观测辐照对稻草秸秆纤维组织结构的影响。结果表明,用1000~1500kGy的剂量处理稻草秸秆,能有效破坏稻草的纤维组织结构,特别是稻草表面硅晶结构和纤维结构,且随辐照剂量加大破坏程度增强,辐照稻草热水浸提液水溶性还原糖和总糖含量显著增加。辐照与酶复合处理后稻草秸秆纤维的转化率提高到88.7%,辐照稻草秸秆酶降解后的水溶性还原糖含量达到214.4mg/g,总糖含量达758.5mg/g,极显著地提高甘露糖、半乳糖、葡萄糖、阿拉伯糖、木糖含量,其中葡萄糖含量提高最大,占单糖总量的62.64%,其次是甘露糖。辐照对稻草秸秆木质素降解无明显影响。 相似文献
17.
《Communications in Soil Science and Plant Analysis》2012,43(9):1061-1072
Calcium (Ca) is an essential plant nutrient and is important in determining quality of fruits in storage. The analytical method presently known to determine Ca concentration in vegetables measures total Ca, and there is a need to develop methods that can determine the distribution of Ca within vegetable tissues. The objective of this study was to determine the ability of fluorescent probes to visualize Ca location and distribution in vegetable tissues. We examined three protocols using fluorescent dyes developed to detect Ca. The first tested Fura 2 acetoximetil (AM) probe in fresh cuts from grapes at different combinations of temperatures and incubation times. The second protocol was developed with the aim of lowering the natural autofluorescense. In the third protocol, the Fura 2 probe was used in tissues previously fixed in formalin, acetic acid, and alcohol solution (FAA). Tissues were observed under an epifluorescence microscope and, to compare and complement the observations, under a scanning electron microscope (SEM). No sign of fluorescence was observed in fixed and fresh tissue using the Fura 2 AM. In fresh cuts, there was autofluorescent interference, provoked mainly by chlorophyll, but also from the vascular system and tannins. The Fura 2 probe was introduced to vegetable tissues by utilizing a pH of 4.5, and a more intense signal was observed in tissues with greater Ca concentration. This signal was also associated with Ca crystals, which might have had some degree of hydrolysis at low pH. Under a SEM microscope, Ca oxalate crystals were clearly observed in those tissues. Our results show that Fura 2 probe can be used to detect Ca and its distribution in vegetable tissues. 相似文献
18.
天然花青素提取物与壳聚糖明胶复合膜的制备和表征 总被引：2，自引：1，他引：2
为了开发天然的抗氧化活性包装材料,以紫甘蓝、黑米、玫瑰、蓝莓为原料制备天然花青素提取物与壳聚糖明胶的复合膜,比较分析了不同天然花青素提取物对复合膜的物理、机械、抗氧化活性及形貌结构的影响。结果表明：天然花青素提取物的加入,增加了膜的厚度,显著（P<0.05）影响膜的含水率、水溶性及外观形貌。壳聚糖明胶复合膜的水蒸汽透过率（water vapor permeability,WVP）为10.69×10-11 g/(m·s·Pa)。玫瑰花青素提取物的加入使得WVP值降低,而其他花青素提取物的加入使得WVP值增大。玫瑰复合膜的拉伸强度最大,达到27.03 MPa,断裂伸长率最小,黑米花青素提取物可增加复合膜的延展性,断裂伸长率最大为57.67%。傅里叶红外光谱表明天然花青素提取物的羟基基团与壳聚糖的氨基基团产生相互作用。扫描电镜结果表明花青素提取物影响微观结构,而且生物相容性较好。加入天然花青素提取物后,复合膜抗氧化活性均显著（P<0.05）提高,且玫瑰复合膜有着较高的抗氧化活性,1,1-二苯基-2-苦基肼（DPPH）自由基清除能力达到95.47%。结果表明：玫瑰花青素提取物更有利于开发阻湿性能好,水溶性低,抗拉伸和抗氧化活性高的包装材料,具有良好的应用前景。 相似文献
19.
Summary The protein A-gold technique with subsequent silver amplification was used to visualize specific bacteria in plant roots by light microscopy. Polyclonal antibodies against diazotrophic rods were labelled with staphylococcal protein A-gold on semithin sections of resin-embedded samples. The visibility of colloidal-gold-labelled structures was enhanced by additional silver amplification. Results showed that embedding the bacteria in resin LR White soft grade preserved bacterial structure and avoided loss of antigenicity. Application of this method avoided problems with autofluorescence of plant material and eliminated and the requirement for a fluorescence microscope, and gave a specific staining of the bacteria, which remained well fixed. Diazotrophic rods occurring in high numbers inside the roots of Kallar grass plants at a natural site in Pakistan were able to colonize the aerenchyma of Kallar grass roots grown in gnotobiotic culture. 相似文献
20.
To elucidate the mechanism of podzolization in its first stages we studied the fate of the water-soluble organic matter (WSOM) in incipient podzols in sandy soils by comparing the composition of the WSOM from L, F and H horizons with that in the bulk of the Bh horizons and fibres of three profiles. The WSOM appeared to consist significantly of ligno-cellulose and proteins, but these biopolymers were hardly present in the Bh horizons. The material of the fibres, however, greatly resembled the WSOM composition, thereby suggesting that in these soils most of the WSOM is transported through the B horizon and accumulates hardly changed in thin bands where the water stops moving. This implies that in the early steps of podzolization, accumulation of organic matter in the B horizon is not likely to be caused by water-soluble material. 相似文献