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21.
22.
以环烷氧锡化合物引发L-丙交酯开环聚合制备高分子量聚L-乳酸。考察了单体引发剂配比、聚合温度和聚合时间等聚合条件对聚合产物特性黏度的影响。用1H-NMR、13C-NMR分析聚合产物微观结构表明,环烷氧锡引发L-丙交酯开环聚合是基于酰氧键断裂开环聚合的“配位-插入”机理。DSC、TGA、XRD等测试结果表明,所得聚L-乳酸具有较高的结晶度和立构规整度。 相似文献
23.
《Journal of Nuclear Science and Technology》2013,50(8):735-743
Solvent extraction is the major unit operation employed in spent nuclear fuel reprocessing. The operation yields three streams; fission product waste, uranium product and plutonium product. Ion exchange is primarily used in reprocessing as a tail-end method to concentrate and isolate the plutonium product stream. This review will describe the details of plutonium recovery and purification by both cation- and anion-exchange processing. A brief overview of miscellaneous uses of ion-exchange employed in reprocessing will also be given. 相似文献
24.
The main purpose of this work was the modification of NaX nanozeolite using copper oxide nanoparticles and various monovalent cations such as K~+, Cs~+, and Ag~+in order to make the negatively charged zeolite surface accessible for anionic forms of uranium which are the most dominant species of uranium in the contaminated radioactive waters at natural p H. Various methods such as the X-ray fluorescence(XRF), X-ray powder diffraction(XRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FT-IR), and atomic absorption spectroscopy(AAS) were used to characterize the final synthesized absorbents. Batch technique was used to study the adsorption behavior of uranium ions from polluted drinking water by Na X nanozeolite and its modified forms. In order to better understand the performance of them, the results were compared with those that were obtained for synthesizing bulk NaX zeolite and Na-form of clinoptilolite natural zeolite. Preliminary results indicated that uranium sorption increased as the loading level of CuO nanoparticles on NaX nanozeolite increased from 2.1 wt% to 11.2 wt%. In addition,from the obtained data, an increase in uranium removal efficiency resulted as charge/ionic radius ratio of exchanged cation decreased. Also, the effect of contact time, solid–liquid ratio, initial concentration and temperature on the adsorption process was studied. It is worth mentioning that, in this study, the sorption of uranium was performed under natural conditions of pH and the presence of competing cations and anions which are available in drinking waters. 相似文献
25.
本文归纳、总结、介绍了钛醇盐的一些重要物理性质和化学性质.并摘要讨论了它们的用途和合成方法。 相似文献
26.
M. Di Serio P. Iengo G. Vairo E. Santacesaria 《Journal of surfactants and detergents》1998,1(1):83-91
Zirconium dodecanoxide sulfate is a very active catalyst in promoting fatty alcohol narrow-range ethoxylation. The catalytic activity is initially very high but rapidly decreases after the addition of one mole of ethylene oxide per mole of substrate. This peculiar behavior makes it possible to obtain narrow-range ethoxylated products containing not more than two or three ethylene oxide units. Because the catalyst shows a very feeble Brönsted acidity, it must be concluded that its activity originates from the Lewis acidity. This acidity is strongly enhanced from the introduction of the sulfate group in the catalyst molecule, because of the strong electron-withdrawing effect of this group. A kinetic model was developed for explaining experimental results. 相似文献
27.
The formation of lead niobates in the PbO-rich region is studied using powders prepared by the simultaneous hydrolysis of lead and niobium alkoxides. Cubic 3PbO·2Nb2P O5 solid solutions crystallize at low temperatures from amorphous materials having concentrations of 58 to 75 mol% PbO. The lattice parameter a increases linearly from 1.0544 to 1.0708 nm with increasing PbO. At higher temperatures the solid solutions made with 66.67 and 71.43 mol% PbO transform into 2PbO·Nb2 O5 (monoclinic) and 5PbO·2Nb2 Os (monoclinic), respectively. Monoclinic 5PbO·2Nb2 O5 transforms into a new modification at = 3850° to = 3900°C. It has a rhombohedral unit cell with a = 0.7461 nm and c = 4.8092 nm ( a = 1.6599 nm, a = 25.97°). In the presence of excess lead, monoclinic 5PbO·2Nb2 O5 transforms into tetragonal 3PbO·Nb2 O5 . 相似文献
28.
Influence of Some Hofmeister Anions on the Krafft Temperature and Micelle Formation of Cetylpyridinium Bromide in Aqueous Solution
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Md. Nazrul Islam Khokan Chandra Sarker Komol Kanta Sharker 《Journal of surfactants and detergents》2015,18(1):9-16
In this work, the effect of some Hofmeister anions on the Krafft temperature (TK) and micelle formation of cetylpyridinium bromide (CPB) have been studied. The results show that more chaotropic anions increase, while the less chaotropic ones lower the TK of the surfactant. More chaotropic I? and SCN? form contact ion pairs with the cetylpyridinium ion and reduce the electrostatic repulsion between the CPB molecules. As a result, these ions show salting‐out behavior, with a consequent increase in the TK. In contrast, less chaotropic Cl? and NO3? increase the activity of free water molecules and enhance hydration of CPB molecules, showing a decrease in the TK. A rather unusual behavior was observed in the case of SO42? and F?. These strong kosmotropes shift from their usual position in the Hofmeister series and behave like moderate chaotropes, lowering the TK of the surfactant. Because of the high charge density and the strong tendency for hydration these ions preferentially remain in the bulk. Rather than forming contact ion pairs, these ions stay away from the CPB molecules, decreasing the TK of the surfactant. In term of decreasing the TK, the ions follow the order NO3? > SO42? > Cl? > F? > Br? > SCN? > I?. The critical micelle concentration (CMC) of the surfactant decreases significantly in the presence of these ions due to the screening of the micelle surface charge by the excess counterions. The decreasing trend of the CMC in the presence of the salts follows the order SCN? > I? > SO42? > NO3? > Br? > Cl? > F?. 相似文献
29.
论述了一种负离子面膜的研制过程。在面膜的制作过程中通过适当的途径加进负离子添加剂,从而使负离子在皮肤表面发挥还原性作用,使已经氧化的皮肤还原,恢复健康状态。通过多次实验,所得产品负离子释放量超过了700个/cm3,具有释放负离子稳定持久、发射远红外线、杀菌、消毒、保健等功效,达到了健康要求。 相似文献
30.
文章研究了用离子色谱法直接测定降水中阴离子的色谱条件、线性范围。实验研究表明,Fˉ、Clˉ、NO3ˉ、SO42ˉ方法的最小检出限分别为:0.006、0.012、0.020、0.037 mg/L;相对标准偏差均在10%以下,加标回收率为95.9%~102.4%。用离子色谱法直接测定大气降水中的阴离子,操作简单、快捷,具有可靠的准确度和良好的精密度,且灵敏度高,实验结果令人满意。 相似文献