首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 78 毫秒
1.
本研究对产自云南省西双版纳1.5年生的山黄麻(Trema orientalis)进行制浆造纸基础评价。结果表明,山黄麻的木质部纤维平均长度接近1.2 mm,综纤维素和酸不溶木素的含量分别为78%和21%。采用硫酸盐法制浆,在最高蒸煮温度160℃、NaOH用量21%、升温时间90 min、保温时间90 min的条件下,细浆得率为52.7%,再经氧脱木素-二氧化氯-过氧化氢加氧气强化的碱抽提(ODEop)短程漂白后,其纸浆得率99.6%,白度85.0%,漂白浆的抗张指数为79.0 N·m/g、耐破指数为5.15 kPa·m2/g、撕裂指数为5.81 mN·m2/g。  相似文献   

2.
在正交实验的基础上,结合抄纸实验,运用坐标综合评定法确定了相思木硫酸盐法制浆的最佳蒸煮条件。实验结果表明,在用碱量15%(以Na2O计)、硫化度30%、液比1∶4、蒸煮最高温度165℃、升温时间60 min、保温时间120 min的条件下进行硫酸盐法蒸煮,所得纸浆得率52.25%,卡伯值17.9,黏度987.3 mL/g,裂断长9.32 km,抗张指数93.6 N·m/g,撕裂指数10.0 mN·m2/g,耐破指数5.34 kPa·m2/g。  相似文献   

3.
本研究探讨了杨木CTMP碱性过氧化氢漂白中,MgO取代NaOH比例和漂白时间对杨木CTMP中碳水化合物和木质素含量及纸浆性能的影响。结果表明,在漂白初期,杨木CTMP中的碳水化合物和木质素溶出较快,漂白后期溶出的速率较缓慢。随MgO取代NaOH比例的增加,杨木CTMP的漂白得率显著提高,漂白浆中的碳水化合物和木质素含量明显增加。与对照样(以NaOH为碱源)相比,漂白时间90 min,MgO取代NaOH比例为75%时,漂白浆中的综纤维素和木质素含量分别达67.60%和23.09%;浆张的松厚度从2.09 cm3/g上升到2.21 cm3/g,增加了5.74%;白度略微下降;浆张的抗张指数和撕裂指数分别下降了14.16%和14.32%,达40.6 N·m/g和3.47 mN·m2/g。  相似文献   

4.
纤维素纳米晶体提高箱纸板强度性能的研究   总被引:1,自引:0,他引:1       下载免费PDF全文
本研究以废纸浆为原料,采用硫酸水解法制备纤维素纳米晶体(CNC),并将其用于箱纸板的增强。结果表明,所制备的CNC呈典型的棒状结构,其直径和长度范围分别为11~23 nm和115~240 nm,长径比为5∶1~22∶1,Zeta电位为-56.37 mV,CNC聚集态呈纤维素I型结构,结晶度为71.1%,热稳定性较废纸浆略有降低;在CNC用量为3%的一元增强实验中,箱纸板的抗张指数、撕裂指数、耐破指数、环压指数和耐折度分别为30.5 N·m/g、6.22 mN·m2/g、1.55 kPa·m2/g、9.18 N·m/g和3次;将2%阳离子淀粉(CS)和阳离子聚丙烯酰胺(CPAM)分别与3%CNC复合形成二元增强体系时,箱纸板的抗张指数、撕裂指数、耐破指数、环压指数和耐折度较CNC一元增强时分别提高了30.5%、4.1%、12.7%、11.6%、33.3%和21.9%、3.5%、12.3%、10.6%、33.3%。  相似文献   

5.
废旧箱纸板(OCC)造纸废水回用过程中面临着微细胶黏物沉积和因Ca2+浓度过高引起的厌氧颗粒污泥钙化两大难题。本研究对比评估了电絮凝法、物理法、化学法、生物酶法对模拟OCC造纸废水的处理效果;结果表明,电絮凝法能够更好去除OCC造纸废水中的微细胶黏物和Ca2+。在此基础上研究了电絮凝处理的最佳条件:铝为阳极材料,电流密度、电极间距和反应时间的最佳处理条件分别为115 A/m2、5 cm和60 min。在最佳条件下,经电絮凝处理后得到的絮凝体中,Al3+和Ca2+的相对含量高于对照组,表明电絮凝法能有效去除OCC造纸废水中的微细胶黏物、COD和Ca2+,且该方法绿色无污染,符合可持续发展的要求。  相似文献   

6.
以聚乳酸(PLA)为基体、乙酰化改性纤维素纳米纤丝(m-CNF)为增强材料制得复合涂料,将其涂覆于A4纸表面制得PLA/m-CNF阻隔纸,探讨了复合涂料中m-CNF添加量对纸张阻隔性能、疏水性能、强度性能等的影响。结果表明,与原纸相比,当m-CNF添加量为3%时,PLA/m-CNF3%阻隔纸的抗张指数、耐破指数、疏水性能分别提高了30.6%、40.1%、24.8%,透气度降低了36.6%。原纸水蒸气透过量为1815 g/(m2·d),PLA/CNF阻隔纸的氧气和水蒸气阻隔性能相较原纸显著提升;其中,PLA/CNF3%阻隔纸的水蒸气透过量为443 g/(m2·d)、氧气透过量为45 cm3/(m2·d·(0.1 MPa));PLA/m-CNF3%阻隔纸的水蒸气透过量为385 g/(m2·d)、氧气透过量为35 cm3/(m2·d·(0.1 MPa)),与PLA/CNF3%阻隔纸相比,分别下降了13.1%和22.2%;表明PLA/m-CNF阻隔纸具有优异的保鲜效果。  相似文献   

7.
本研究以马来酸-丙烯酸共聚物(MA-AA)为主体稳定剂,与螯合型助剂复合,制备了新型过氧化氢(H2O2)稳定剂,通过测定新型H2O2稳定剂对金属离子的螯合值、H2O2分解率及进行化机浆H2O2漂白实验,研究新型H2O2稳定剂对H2O2漂白的稳定性能,并与进口稳定剂进行比较。结果表明,新型H2O2稳定剂对Fe3+、Mg2+、Mn2+、Ca2+的螯合能力分别达262.3、105.2、141.4、160.3 mg/g;在模拟国内4个地区水质中不同金属离子含量条件下,新型H2O2稳定剂能够有效抑制H2O2分解,具有与进口产品相当的稳定能力。在纸浆漂白工艺条件下,新型H2O2稳定剂在低用量时,对桉木化机浆、杨木化机浆、蔗渣化机浆和芦苇化机浆的漂白均有良好的稳定效果。  相似文献   

8.
以麦草高得率浆为原料,戊二醛和聚乙烯亚胺为改性试剂,通过造纸工艺制得低成本、高湿强、具有优异吸附性能和油水分离性能的多功能纸基材料。改性纸基材料表面引入了大量氨基,含量可达3.33 mmol/g;其内部纤维间形成了共价键交联网络结构,湿抗张指数达到干抗张指数的29%。吸附实验研究表明,该纸基材料对吸附质的吸附动力学和热力学分别较好地拟合了准二级方程和Langmuir模型,其对刚果红和Pb2+的实际吸附容量分别为89.26和190.1 mg/g;理论最大吸附容量分别为91.04和232.4 mg/g。聚乙烯亚胺改性纸基材料对大豆油和正己烷的水下油接触角分别为152.5°和151.7°,具有水下超疏油性;此外,其对水包油乳液(平均粒径50 μm)的分离效率达到99.4%,膜通量达到12560 L/(m2·h)。  相似文献   

9.
以杨木化机浆为原料,以柠檬酸(多元酸)为改性剂,基于造纸工艺技术,制备了低成本、易回收、高重金属离子吸附容量和高效油水分离的木质纤维纸基吸附-分离材料。柠檬酸改性可同时提高木质纤维之间的交联程度和羧基含量,进而提高纸基吸附-分离材料的湿强度和增加重金属离子吸附位点。研究结果显示,纸基吸附-分离材料的湿抗张指数可达其干抗张指数的40%~50%,羧基含量最高可达0.66 mmol/g。随柠檬酸浓度提高,纸基吸附-分离材料对重金属离子的吸附容量显著提高,其吸附动力学和热力学均很好地拟合了准二级方程和Langmuir模型(相关系数R2≥0.998),对Cu2+和Pb2+的理论最大吸附容量分别达到44.29和132.1 mg/g。此外,高羧基含量使纸基吸附-分离材料亲水性显著增强,并赋予其优良的油水分离性能,最大水下油接触角可达155°以上,油水分离效率可达99.8%以上。该多功能纸基吸附-分离材料克服了传统吸附剂和油水分离材料的缺点,可同时进行高效的重金属离子吸附去除和油水分离,并且具备了大规模生产的潜力,在工业废水处理领域具有重要的应用前景。  相似文献   

10.
以尿素为N源对TiO2进行掺杂改性制备N掺杂TiO2光催化剂(N-TiO2),将N-TiO2与纤维素溶液混合,然后经静电纺丝制备光催化复合纤维,最后将光催化复合纤维与纸浆纤维配抄,制备光催化纸,用于降解甲醛。结果表明,所制备光催化剂N-TiO2颗粒小、分散均匀,易与纤维素溶液纺丝成光催化复合纤维;所抄造光催化纸对甲醛的降解率达53.8%,抗张指数大于41.9 N·m/g,耐破指数大于2.03 kPa·m2/g,具有良好的强度性能。  相似文献   

11.
Plant biotechnology--genetic engineering to enhance plant salt tolerance   总被引:4,自引:0,他引:4  
Plants not only provide food to humans and animals, but also provide a large number of non-food products of industrial and chemical importance. Moreover, they have the ability to purify the air, soil and water on the earth. Various trials to genetically improve the potential of plants are actively in progress. Salt-tolerance would be an especially important ability to bestow upon plants for agricultural and industrial purposes, because high salinity conditions are ubiquitous on earth and represent major barriers to growth. Enhancement of resistance against both hyper-osmotic stress and Na+ toxity is necessary for successful molecular breeding of salt tolerant plants. Introduction of genes for osmolyte bio-synthesis is useful to increase hyperosmotic tolerance of plant cells. It is introduced in this review that genetically engineered ectoine synthesis results in increased hyperosmotic tolerance of tobacco cells. High concentrations of Na+ reduce cellular activity by interfering with vital Na+-sensitive enzymes and by affecting K+ transport. Understanding the regulation of K+ and Na+ homeostasis is thus indispensable for enhancement of plant Na+ tolerance. My research group is investigating the Na+ efflux activity of the yeast Na+-ATPase (Ena1) when installed in the plasma membrane of plant cells, and the rice K+-Na+ co-transporters (HKT) that contribute to the regulation of K+ and Na+ uptake in root cells.  相似文献   

12.
以宁夏贺兰山东麓产区2012年和2013年瓶储陈酿的13个红葡萄酒样品为材料,采用紫外可见分光光度法和国际照明委员会推荐的CIE L*a*b*均匀色空间参数,来量化葡萄酒的颜色指数,初步研究均匀色空间下红葡萄酒颜色的量化分级。数据量化结果表明:在标准光源D65下,所测试的红葡萄酒色相分为3级,紫红、胭脂红、宝石红;彩度分为5级,灰、淡、中、浓、鲜艳;明度分为5级,中等、稍亮、较亮、亮、明亮。建立CIE L*a*b*下的模型:Ry CX(1-5)LX(1-5)、Rz CX(1-5)LX(1-5)、Rb CX(1-5)LX(1-5),试验表明13种酒样分布在Ry C5+L2+、Ry C4+L3+、Rz C4+L2+、Rz C3+L3+、Rz C3+L4+、Rz C2+L4+、Rb C2+L4+、Rb C+L5+以上8级。  相似文献   

13.
Within the EU-project “Pure Juice” established stable isotope methods (δ2H, δ13C, δ15N) have been applied and improved in order to determine and verify the geographical origin of orange juices. In addition, new approaches employing analyses of δ34S and 87Sr/86Sr have been developed and tested. Approximately 150 authentic orange juice samples from several regions in North- and South-America, Africa and Europe have been analysed. A discrimination of orange producing regions, based on the results which ultimately depend on geographical, climatic and lithological differences was successfully performed. Furthermore, we demonstrate that blending of single strength juice by adding concentrate can be revealed by comparing 87Sr/86Sr of soluble and insoluble components of the juices. We conclude that regional assignment of orange juice samples is most successful when single parameters are combined in a “multi-element approach”.  相似文献   

14.
张效伟 《食品与机械》2021,37(11):55-60
目的:研究石墨烯量子点的电化学发光性能。方法:制备发光强度高、性能稳定的氮硫掺杂石墨烯量子点(NS-GQDs),并构建关—开型电化学发光(ECL)传感器以实现对Fe3+和F-的连续检测。结果:在0.1~460.0 μmol/L范围内,Fe3+浓度与ECL猝灭值呈良好的线性关系,检出限为0.028 μmol/L;在1~5 600 μmol/L范围内,F-浓度与ECL恢复值呈良好的线性关系,检出限为0.62 μmol/L。结论:NS-GQDs ECL信号的猝灭和恢复具有较好的可逆性,可应用于饮用水中Fe3+和F-的连续检测。  相似文献   

15.
This study aimed to compare the transfer of 2 manmade radionuclides, radiocesium (137Cs) and radiostrontium (90Sr), from cow milk to whey and cheese in 3 different types of French cheese production with rennet coagulation. Most of the 137Cs was present in the aqueous phase and became concentrated in the whey. For 137Cs transfer to whey, the processing factor (Pf; i.e., the ratio of the activity concentrations) ranged between 0.86 and 1.30 (n = 12). The food processing retention factor (Fr), calculated using the processing efficiency, ranged between 0.85 and 1.19 (n = 9). No statistical difference of Pf and Fr to whey is identified for 137Cs and the cheese products. The Pf calculated for 90Sr transfer to cheese ranged between 3.95 and 12.16, with significant differences depending on the type of cheese. In addition, a linear correlation is observed between 90Sr Pf to cheese and the Ca level in the cheese (r2 = 0.57). Thus, the Pf is enhanced in hard cheeses that are enriched in calcium. This is confirmed by nearly constant Fr values, ranging between 0.66 and 0.83.  相似文献   

16.
The combination of gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) and gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-P-IRMS) is applied to the authenticity assessment of cinnamaldehyde from various sources. For that reason, cinnamon oils were self-prepared by steam distillation from three different varieties of cinnamon bark on the market, C. ceylanicum (ceylon), C. cassia (cassia) and C. burmanii (cassia vera). Furthermore, the so-called wood cinnamon was investigated, which is produced from the outer bark of older branches of cinnamon of minor quality. Self-prepared oils were analysed from commercial cinnamon powder. In addition several commercial samples of cinnamon oil and cinnamaldehyde, some of them declared to be natural, were investigated. 2V-SMOW and 13CV-PDB values of cinnamaldehyde were determined and characteristic authenticity ranges were deduced, allowing the differentiation between synthetic and natural samples. By correlation of both the 2V-SMOW and 13CV-PDB values, characteristic authenticity ranges were defined for ceylon, cassia and wood cinnamon. The 2V-SMOW and 13CV-PDB values of cassia vera samples are in the range of cassia. By comparing the 2V-SMOW values of different self-prepared samples (ground bark, distillate) of cinnamon determined by TC/EA-IRMS with the corresponding GC-IRMS values, online GC-IRMS methods are proved to be essential in the authentication of complex natural products.  相似文献   

17.
Oxidative stress and upregulation of gastric H+, K+-ATPase enzyme activity have been known to cause ulcer pathogenicity for which safer drugs are yet to be identified. Aqueous extracts of seven commonly consumed vegetable sources were screened for inhibition of H+, K+-ATPase and antioxidant activities. Results indicated that Z. officinale (Ginger) followed by M. arvensis (Pudina) are potent gastroprotective sources with inhibition of H+, K+-ATPase of IC50 of 18.3 ± 0.7 and 25.2 ± 0.9 μg gallic acid equivalents/ml respectively, which is almost equivalent or better than the known inhibition of H+, K+-ATPase—Omeprazole (IC50 ?27 μg/ml). Further, all these vegetable extracts showed multi-potent antioxidant activity, such as free radical scavenging, reducing power ability, and inhibition of lipid peroxidation, which are required to inhibit complex steps of ulcerations. On the basis of the absolute amounts and potency of inhibition of H+, K+-ATPase as well as antioxidant activity of individual phenolic acids, the relative percentage contribution of phenolic acids from different vegetable extracts to both inhibition of H+, K+-ATPase and antioxidant activity was calculated and data revealed that gentisic and protocatechuic acid contributes significantly to both inhibition of H+, K+-ATPase and antioxidant activity.  相似文献   

18.
A survey on long-lived artificial radionuclides 137Cs and 90Sr in vegetables produced in Finland was carried out in 2009–2010. The mean 137Cs concentrations of all the outdoor vegetables were well below 0.5 Bq kg?1, ranging from <0.01 to 8.15 Bq kg–1 (fresh weight). The highest 137Cs contents were found in potato and root vegetables. The uneven distribution of the 137Cs deposition after the Chernobyl accident in 1986 was still seen in the 137Cs contents of outdoor vegetables. The 137Cs contents of greenhouse vegetables varied from <0.01 to 9.3 Bq kg?1, and the highest concentrations were found in organic lettuce grown in peat pots. The concentrations of 90Sr in the vegetables varied from 0.0087 to 0.17 Bq kg?1 fresh weight. The mean effective dose resulting from 137Cs and 90Sr in vegetables in 2009–2010 was <0.3 µSv a?1 and poses no health risk to the consumers.  相似文献   

19.
Fractional passage rates are required to predict nutrient absorption in ruminants but data on nutrient-specific passage kinetics are largely lacking. With the use of the stable isotope ratio (δ) as an internal marker, we assessed passage kinetics of fiber and fiber-bound nitrogen (N) of intrinsically labeled grass silage from fecal and omasal excretion patterns of δ13C and δ15N. In a 6 × 6 Latin square, lactating dairy cows received grass silages [455 g/kg of total diet dry matter (DM) ] in a 2 × 3 factorial arrangement from ryegrass swards fertilized at low (45 kg of N/ha) or high (90 kg of N/ha) levels of N and harvested at 3 maturity stages. Feed intake (16.7 ± 0.48 kg of DM/d; mean ± standard error of the mean) and milk yield (26.7 ± 0.92 kg/d) increased at the high level of N fertilization and at decreasing maturity. Nutrient digestibility decreased with increasing plant maturity, particularly at the high level of N fertilization, essentially reflecting dietary treatment effects on the nutritional composition of the grass silage. Fractional rumen passage rates (K1) were highest and total mean retention time in the gastrointestinal tract (TMRT) was lowest when based on the external marker chromium mordanted fiber (Cr-NDF; 0.047/h and 38.0 h, respectively). Fecal δ13C in the acid detergent fiber fraction (13CADF) provided the lowest K1 (0.023/h) and the highest TMRT (61.1 h) and highest peak concentration time (PCT; 24.3 h) among markers. In comparison, fecal fiber-bound N (15NADF) had a considerably higher K1 (0.032/h) and lower TMRT (46.4 h) than 13CADF. Total N (measured with 15NDM) had a comparable K1 (0.034/h) to that of 15NADF but provided the highest fractional passage rates from the proximal colon-cecum (K2; 0.37/h) and lowest PCT (17.4 h) among markers. A literature review indicated unclear effects of grass silage maturity on K1 and unknown effects of N fertilization on K1. Our study indicated no effect of advancing maturity on fecal K1 and a trend for K1 to increase with the high level of N fertilization. Parameter K2 increased, whereas PCT and TMRT generally decreased with the high level of N fertilization. Omasal digesta sampling largely confirmed results based on fecal sampling. Results indicate that the use of δ13C and δ15N can describe fiber-specific passage kinetics of forage.  相似文献   

20.
N. Kadi  J. Crouzet 《Food chemistry》2006,98(2):260-268
Enzymatic synthesis of two phenyl xylopyranosyl glucopyranosides, through transfer reaction by Trichoderma longibrachiatum endoxylanase, was achieved in the presence of n-hexane used as solvent, phenyl glucoside (10 mM) as acceptor and xylan (2 g/l) as donor. Kinetic study showed that only one compound, identified by 1H and 13C NMR and heteronuclear 2D (1H–13C) chemical shift correlation as phenyl primeveroside (phenyl 6-O-β-xylopyranosyl-1-β-d-glucopyranoside), was synthesized when the reaction time was beyond 1 h. Benzyl and hexyl primeverosides were obtained under the same conditions. When several phenyl glucoside concentrations, from 5 to 50 mM, were used with 2 g/l of xylan, a phenyl primeveroside isomer, identified as phenyl 4-O-β-xylopyranosyl-β-d-glucopyranoside, accumulated in the medium whereas the production of phenyl primeveroside decreased. Only phenyl primeveroside was produced when several xylan concentrations from 2 to 10 g/l were used with 10 mM of phenyl glucoside and its concentration in the reaction mixture increased with the increase of xylan concentration.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号