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91.
E. Tomaszewicz 《Thermochimica Acta》2006,447(1):69-74
Reactivity in the solid state between CoWO4 and some rare-earth metal tungstates RE2WO6 (RE = Sm, Eu, Gd) was investigated by the XRD method. Two families of new isostructural cobalt and rare-earth metal tungstates, Co2RE2W3O14 and CoRE4W3O16, were synthesized. The Co2RE2W3O14 phases are formed by heating in air the CoWO4 and RE2WO6 compounds mixed at the molar ratio 2:1, while the CoRE4W3O16 phases are synthesized at the molar ratio of CoWO4/RE2WO6 equals to 1:2. The Co2RE2W3O14 phases as well as the CoRE4W3O16 compounds crystallize in the orthorhombic system. The Co2RE2W3O14 and CoRE4W3O16 compound melt above 1150 °C. A melting manner of the Co2RE2W3O14 and CoRE4W3O16 compounds was determined in an inert atmosphere. The formation of CoWO4−x phase was observed during heating in an inert atmosphere. 相似文献
92.
With frontal analysis(FA),the dependence of adsorption isotherms of insulin on the composition of mobile phase in reversed phase liquid chromatography (RPLC) has been investigated,This is also a good example to employ the stoichiometric displacement theory (SDT) for ivestigating solute adsorption in physical chemistry.Six kinds of mobile phase in RPLC were employed to study the effects on the elution curves and adsorption isotherms of insulin.the key points of this paper are:(1) the stability of insulin due to delay time after preparing,the organic solvent concentration,the kind and the concentration of ion-pairing agent in mobile phase were found to affect both elution curve and adsorption isotherm very seriously.(2)To obtain a valid and comparable result,the composition of the mobile phase employed in FA must be as same as possible to that in usual RPLC of either analytical scale or preparative purpose.(3)Langmuir Equation and the SDT were employed to imitate these obtained adsorption isotherms.The expression for solute adsorption from solution of the SDT was found to have a better elucidation to the insulin adsorption from mobile phase in RPLC. 相似文献
93.
建立了酱油中1,3-二氯-2-丙醇、2,3-二氯-1-丙醇、3-氯-1,2-丙二醇和2-氯-1,3-丙二醇的分散固相萃取-气相色谱-高分辨质谱快速筛查检测方法。样品采用乙酸乙酯提取,提取液浓缩后经N-丙基乙二胺净化,气相色谱-高分辨质谱测定,内标法定量。结果表明,该方法对于酱油中4种氯丙醇的定量限为0.5~10 μg/kg。在3个浓度水平下的加标回收率为78%~103%;相对标准偏差均不大于8.8%。该方法快速、简便、准确、灵敏,可作为酱油中4种氯丙醇的有效检测方法。 相似文献
94.
Crespi M. S. Silva A. R. Ribeiro C. A. Oliveira S. C. Santiago-Silva M. R. 《Journal of Thermal Analysis and Calorimetry》2003,72(3):1049-1056
The thermal behavior and non-isothermal kinetics of thermal decomposition of three different kinds of composting of the USR
like: stack with drilled PVC tubes (ST), revolved stack (SR) and stack with material of structure (SM), from the usine of
composing of Araraquara city, Săo Paulo state, Brazil, within a period of 132 days of composting were studied. Results from
TG, DTG and DSC curves obtained on inert atmosphere indicated that the cellulosic fraction present, despite the slow degradation
during the composting process, is thermally less stable than other substances originated from that process. Due to that behavior,
the cellulosic fraction decomposition could be kinetically evaluated through non-isothermal methods of analysis. The values
obtained were: average activation energy, Ea=248, 257 and 259 kJ mol-1 and pre- exponential factor, logA=21.4, 22.5, 22.7 min-1, to the ST, SR and SM, respectively. From Ea and logA values and DSC curves, Málek procedure could be applied, suggesting that the SB (Šesták-Berggren) kinetic model is the appropriated
one to the first thermal decomposition step.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
95.
偏钛酸型锂离子交换剂固相合成反应动力学 总被引:1,自引:1,他引:1
偏钛酸型锂离子交换剂固相合成反应动力学钟辉*郭灵虹(成都理工学院应用化学系成都610059)(四川联合大学分析测试中心成都)关键词偏钛酸锂,离子交换剂,合成,固相反应动力学1997-08-25收稿,1997-12-10修回四川省应用基础研究基金资助项... 相似文献
96.
97.
A novel sensitive and simple method for rapid and selective extraction, preconcentration and determination of iron (as its
bathophenanthroline complex) and copper (as its neocuproine complex) using octadecyl silica cartridges and dual wavelength
spectrophotometry is presented. The dual wavelength method (533 nm for the iron-bathophenanthroline and 454 nm for the copper-neocuproine
as the analytical wavelength) is used to eliminate spectral interferences. Extraction efficiency and the influence of flow
rates of sample solution and eluent, pH, amount of neocuproine, bathophenanthroline and hydroxylamine hydrochloride, type
and least amount of eluent for elution of iron and copper complexes from cartridge, break-through volume and limit of detection
are evaluated. The effects of various cationic and anionic interferences on percent recovery of iron and copper are also studied.
Extraction efficiencies >95% are obtained by elution of cartridges with minimal amount of organic solvent. Iron and copper
were determined in the range of 3–100 ng mL−1. The limits of detection are 0.98 and 1.13 ng mL−1 for iron and copper, respectively. The proposed method is applied successfully to the determination of both analytes in river,
tap and well water samples.
Author for correspondence. E-mail: yyamini@modares.ac.ir
Received September 18, 2002; accepted December 12, 2002
Published online May 5, 2003 相似文献
98.
S. N. Shkerin D. I. Bronin S. A. Kovyazina V. P. Gorelov A. V. Kuz'min Z. S. Martem'yanova S. M. Beresnev 《Journal of Structural Chemistry》2003,44(2):216-221
Electric conductivity, Raman spectra, and thermal expansion of La0.88Sr0.12Ga0.82Mg0.18O2.85 solid solution (LSGM1218) based on lanthanum gallate were studied at various temperatures, and Xray phase analysis was performed at room temperature. Dilatometric measurements showed that secondorder phase transitions occur at 775±10$ and 880± 20 K. The transition around 880 K is confirmed by Raman spectra and by a change in the conductivity activation energy in this temperature range. This transition is associated with a symmetry change in the oxygen sublattice. 相似文献
99.
采用穆斯堡尔谱及X光衍射法研究了共沉淀法制备的不同Fe/Mn比催化剂在焙烧、合成气还原及FT反应后体系相结构的变化。结果表明:锰助剂的加入使催化本相由铁磁性逐渐转化为超顺磁性,相应使催化剂还原逐渐难,Mn助剂促进了FT合成反应进行。反应性能与Fe/Mn尖晶石(Fe1-yMny)3O4组成含量及式中y大小密切相关,与MnCo3及MnO的存在也有一定关系。富铁催化剂中Mn主要起电子助剂作用,而富锰催化 相似文献
100.
采用柠檬酸溶胶鄄凝胶法制备CeO2基固溶体催化剂(Ce0.7Zr0.3O2-δ、Ce0.7Pr0.3O2-δ和Ce0.7Gd0.3O2-δ), 并考察了固溶体和三种常用载体(TiO2、SiO2和Al2O3)及其负载KNO3后的催化碳黑燃烧活性. 结果表明, CeO2基固溶体催化剂具有很高的催化燃烧活性, 其活性接近TiO2、SiO2和Al2O3负载30%KNO3催化剂的活性. 因为纳米CeO2基固溶体的形成, 提高了催化剂的抗烧结能力, 使氧更活泼, 从而提高氧化还原性能, 有利于碳颗粒燃烧. 由于CeO2基固溶体本身的高活性, 因此KNO3的添加不能明显提高CeO2基固溶体催化剂(尤其是Ce0.7Zr0.3O2-δ和Ce0.7Pr0.3O2-δ)的催化燃烧活性, 但KNO3能显著提高TiO2, SiO2和Al2O3的催化燃烧活性. 相似文献