共查询到18条相似文献,搜索用时 562 毫秒
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木薯羧甲基淀粉对铜离子的吸附性能 总被引:2,自引:0,他引:2
采用搅拌球磨机对木薯淀粉进行机械活化,以活化60 min的木薯淀粉为原料,干法合成羧甲基淀粉吸附剂。考察羧甲基淀粉的取代度、溶液的pH值、Cu2+的初始浓度、吸附时间、羧甲基淀粉的投加量等因素对羧甲基淀粉吸附Cu2+性能的影响。结果表明,该羧甲基淀粉对Cu2+有很好的吸附作用;用取代度为0.841的羧甲基淀粉处理含Cu2+的废水,在pH=7.0、羧甲基淀粉的投加量50.00 mg/L、吸附时间15 min时,羧甲基淀粉对废水中Cu2+的吸附率高达98.80%,处理后的水质达到国家污水综合排放标准(GB8978-1996)中一级标准要求。 相似文献
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在苯-乙醇介质中生成的羧甲基纤维素取代基分布的研究 总被引:5,自引:0,他引:5
以三组份两相液体苯 乙醇 水为介质合成羧甲基纤维素(CMC),应用1H NMR谱图分析了CMC中羧甲基在葡萄糖单元(AGU)的C2、C3及C6位上对羟基的取代分布.结果表明,取代基的分布顺序是C6>C2>C3;当取代度(DS)低于10时,C2∶C3∶C6近似于145∶1∶215;DS高于10以后,分布趋于相同,通过对CMC的X 衍射分析解释了取代基分布规律.同时研究了苯的影响,证实相同取代度下,在苯 乙醇 水中生成的CMC试样,其C6位取代基分布多于在乙醇 水中生成的试样. 相似文献
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2,4-二取代嘧啶衍生物的合成 总被引:1,自引:0,他引:1
以乙酰丙酮为原料,溴化后与硫脲缩合成噻唑环,再与DMF-DMA(N,N-二甲基甲酰胺二甲基缩醛)反应生成取代噻唑烯胺酮(6);6与取代芳香胍碳酸盐缩合得到一系列2,4-二取代嘧啶衍生物(7a~7e),其结构经1HNMR,IR和MS表征,其中7b~7e为新化合物。 相似文献
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淤浆法碱化试剂选择对PAC分子结构及其泥浆滤失性能影响 总被引:2,自引:0,他引:2
采用XRD和显微镜分析技术研究了高浴比淤浆法制备聚阴离子纤维素过程中, NaOH、KOH及其混合碱化体系对纤维素润胀度及结晶度的影响, 借助1H NMR方法分析了产物的取代度及取代基在葡萄糖环基C2、C3和C6位分布的均匀性. 通过泥浆实验研究了产品在高电解质含量中的高温滤失性能. 结果表明, 在相同摩尔浓度条件下, 棉纤维润胀度变化规律是: NaOH/KOH(摩尔比, 9∶1)>NaOH>NaOH/KOH(摩尔比, 1∶1)>NaOH/KOH(摩尔比, 1∶9)>KOH, 结晶度的顺序相反. 1H NMR测试结果表明, 含少量的K+时, 羧甲基在葡萄糖单元环内分布更均匀, 产品具有优良的耐酸、耐盐性和抗高温滤失性能; 当体系KOH成为主要碱化试剂时, 在酸碱介质中出现分层, 抗滤失性能急剧变差. 相似文献
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以羧甲基纤维素(CMC)为原料、3-氯-2-羟两基三甲基氯化铵(CHPAC)为季铵化剂,合成了一系列水溶性两性纤维素衍生物.研究了CMC季镇化反应的主要影响因素,发现不同的原料羧甲基取代度、反应用碱量、CHPAC用量及反应介质组成对CMC季铵取代度和CMC季铵化反应效率均有不同的影响,同时对原料CMC及其产物的IR、X光衍射和DSC谱图与溶液粘性行为进行了研究. 相似文献
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Hemicelluloses isolated from sugarcane bagasse were converted to carboxymethyl hemicelluloses (CMH) by carboxymethylation using sodium monochloroacetate and sodium hydroxide in ethanol/water medium. The reaction was performed under various temperatures, times, times of alkaline activation, the ways of the addition of alkali, and the amounts of sodium hydroxide and sodium monochloroacetate. The product had the maximum degree of substitution (DS) of 0.56. The structure of the resulting polymers was characterized with Fourier transform infrared (FT-IR) and 13C nuclear magnetic resonance (NMR) spectroscopies. Destructive methods such as thermal analysis and non-destructive techniques such as gel permeation chromatography (GPC) were used to characterize the carboxymethyl hemicellulose preparations. It was found that a significant degradation of the polymers occurred during carboxymethylation. The thermal stability of carboxymethyl hemicelluloses was higher than that of the native hemicelluloses. 相似文献
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Thomas Heinze Tim Liebert Ute Heinze Katrin Schwikal 《Cellulose (London, England)》2004,11(2):239-245
This paper describes the synthesis of carboxymethyl starch (CMS) ID various alcohols (methanol, ethanol, isopropyl alcohol) as slurry media and with different starch types. The products were investigated regarding their degree of substitution (DS), their reaction efficiency (RE), and their pattern of functionalization. The highest DS obtained ID a one-step procedure was 1.40 with a RE of 82%, applying isopropyl alcohol as slurry medium. Moreover, by using the synthesis concept via a reactive microstructure, CMS samples with high DS values can be achieved ID a one-step synthesis as well. A multi-step carboxymethylation ID methanol, on the other hand, leads to maximal DS values of 2.3 after 10 conversions, dependent on the amylose content of the starch. 1H NMR spectroscopic investigations show a reactivity ID the order O-2 > O-6 O-3 for the samples prepared ID alcoholic slurry media. ID contrast, the CMS synthesized via reactive microstructure reveals a preferred substitution ID position 6 and a non-statistic distribution of the carboxymethyl groups along the chain. A significant amount of 2,3,4,6-tetra--functionalization, caused by the branched structure of starch, was found. 相似文献
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S. N. K. Chaudhari K. C. Gounden G. Srinivasan Vadiraj S. Ekkundi 《Journal of polymer science. Part A, Polymer chemistry》1987,25(1):337-342
Results of NMR studies on intact sodium carboxy methyl cellulose (SCMC) are presented. Similar studies in the literature are all on partially depolymerized SCMC. The degree of substitution and the relative distribution of substituents at OH-2, OH-3, and OH-6 of anhydro D -glucose residue in intact SCMC were determined by high resolution 13C-NMR spectroscopy (125 MHz). It is observed that the degree of substitution at OH-6 is almost equal to that at OH-3. In two SCMC samples, which are widely different in molecular weight and degree of substitution (ds), the relative reactivity order of the hydroxyl groups was found to be OH-2 > OH-6 ? OH-3. The NMR assignments were based on calculated shifts of carbons of anhydroglucose moiety in an oligosaccharide due to substitution. 相似文献
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Carbamoylation of cellulose esters (CE) and investigation of the mixed derivatives obtained with NMR spectroscopy represents a useful analytical tool for the determination of the degree of substitution (DS) and analysis of the distribution of substituents on the level of the anhydroglucose unit (AGU). Especially the carbethoxymethylcarbamoylation and the ethylcarbamoylation of CE combined with 1H NMR spectroscopy are efficient and inexpensive ways to gain information on the over-all DS and partial DS values in position 2, 3, and 6 of the AGU. Complete subsequent phenylcarbamoylation can be achieved even for CE with bulky substituents, e.g., adamantanecarboxylic acid esters. In addition to NMR experiments the carbamoylated CE were studied by HPLC after complete chain degradation. Carbethoxymethylcarbamoylation has turned out to be the most useful tool for this path. Chromatograms comparable to carboxymethylated cellulose (CMC) were obtained, which can be exploited to calculate the mole fractions of the basic building units (un-, mono-, di- and tri-substituted glucoses) of the polymer. Comparison with statistic calculations gave a first hint on the distribution of substituents along the polymer chain. For a commercial cellulose diacetate a statistic pattern of substitution was determined. 相似文献
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The conformations of the major coat protein of a filamentous bacteriophage can be described by nuclear magnetic resonance spectroscopy of the protein and the virus. The NMR experiments involve detection of the 13C and 1H nuclei of the coat protein. Both the 13C and 1H nuclear magnetic resonance (NMR) spectra show that regions of the polypeptide chain have substantially more motion than a typical globular protein. The fd coat protein was purified by gel chromatography of the SDA solubilized virus. Natural abundance 13C NMR spectra at 38 MHz resolve all of the nonprotonated aromatic carbons from the three phenylalanines, two tyrosines, and one tryptophan of the coat protein. The alpha carbons of the coat protein show at least two different classes of relaxation behavior, indicative of substantial variation in the motion of the backbone carbons in contrast to the rigidity of the alpha carbons of globular proteins. The 1H spectrum at 360 MHz shows all of the aromatic carbons and many of the amide protons. Titration of a 1H spectra gives the pKas for the tyrosines. 相似文献
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This paper describes the first coupling of a commercial capillary HPLC system with a diode array spectrophotometric detector and a custom-built nuclear magnetic resonance (NMR) flow microprobe. The eluent from a 3-microm diameter C18 HPLC column is linked to a 500 MHz 1H-NMR microcoil probe with an observe volume of 1.1 microl. The separation and structurally-rich detection of a mixture of terpenoids under both isocratic and gradient solvent elution conditions is presented. The lowest limits of detection yet reported for capillary HPLC on-line measurement (i.e., 37 ng for alpha-pinene) are achieved with this system. The complementary nature of diode array and NMR detection allows stopped-flow data collection from analytes which would otherwise go unnoticed in continuous-flow NMR. Moreover, stopped-flow NMR data is presented for the detection of a trace (sub-nmol) impurity in the sample mixture. Since NMR signals degrade and shift during solvent gradients, flow injection analysis studies are conducted with injected solvent plugs differing in mobile phase composition. The NMR signal degradation accompanying these injections is largely due to the variance in chemical shift with the solvent composition rather than to changes in magnetic susceptibility of the solvent. Characterization of such effects enables the development of improved NMR probes for the coupling of capillary HPLC and NMR. 相似文献
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Abid Nazir Gill Areeba Iftikhar Ayoub Rashid Muhammad Amin Rana Rashad Mahmood Khan Hafiz M. Rafique Seemal Jelani Ahmad Adnan 《Journal of the Iranian Chemical Society》2018,15(9):1939-1945
The present study reports the green synthesis of starch–maleate (SM) at ambient temperature in solvent-free system using Rhizopus arrhizus lipase as a biocatalyst and maleic acid (MA) as an esterification agent. The synthetic scheme was found to be efficient, economical, and ecofriendly. The newly synthesized SM samples were characterized using Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopic techniques. The degree of substitution (DS) was found in the range of 0.53–0.62. Moreover, DS was found to be temperature and time-dependent. X-ray diffraction (XRD) exhibited that maleation did not change the crystalline nature of native starch. Scanning electron microscopy (SEM) revealed that size of SM granules was in the range of 4–18 µm. The activation energy (Ea) of SM formation was calculated to be 42.94 kcal mol?1 which clearly indicated the effective and rapid interaction of functional groups. Hence, the solvent-free solid-state synthetic methodology proved to be excellent for the synthesis of novel biomaterials with appreciable high DS for drug delivery and sorption of heavy metal ions from water. 相似文献