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91.
Saša Zeljković Dijana Jelić Hiraku Maruyama Juan C. Nino 《Ceramics International》2019,45(8):10063-10071
The reaction mechanism and kinetics of CeO2 synthesis using a solvent-deficient method are investigated by simultaneous thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The decomposition process of the cerium(III) nitrate hexahydrate and ammonium bicarbonate precursor mixture with four observed stages is monitored using TGA/DSC measurements in a nonisothermal regime with heating rates of 5, 10, 15 and 20?°C min?1. The proposed mechanism indicates a complex synthesis with several parallel reactions, some of which occur at room temperature. A detailed kinetic analysis is performed using isoconversional (expanded Friedman, modified Coats-Redfern and Kissinger) and model fitting (Nth order and nucleation and growth models) methods. The first three stages are best described by the Nth order model with activation energy values of 21, 53 and 90?kJ?mol?1. The last stage, during which ammonium nitrate decomposition occurs, is best fit by the nucleation and growth model and has an activation energy of 129?kJ?mol?1. The proposed mechanism, supported by the kinetic analysis in our study, indicates that CeO2 has already formed before the reaction reaches 200?°C. The average crystallite size of CeO2 synthesized at 300?°C, which was calculated from the XRD measurements and observed in the SEM and TEM data, is between 10 and 20?nm. 相似文献
92.
The recovery and separation of metals from aqueous solutions is one of the research hotspots in hydrometallurgy, environment protection, analytical chemistry, etc. Much attention has been paid to solvent‐impregnated resins (SIRs) since these were firstly proposed for the extraction of metals. SIRs are characterized by high efficiency and selectivity, convenient preparation, and easy operation because they combine the unique advantages of solvent extraction and ion exchange. The preparation and features of SIRs are summarized and their applications in the extraction of various metals from solutions are reviewed. In addition, the equilibrium, thermodynamics, and sorption kinetics of the metals onto SIRs are elucidated in detail. 相似文献
93.
《溶剂提取与离子交换》2013,31(5):751-762
Abstract The extraction of Tb(III), Dy(III), Ho(III), Er(III), Tm(III), and Yb(III) with 5,7‐dibromo‐8‐hydroxyquinoline (Hdbq or HA) in chloroform from aqueous perchlorate solutions was investigated. The formation of the LnA3 species (where Ln = Tb, Dy, Ho, Er, Tm, and Yb) in the organic phase was supported by the data. The parameters of the extraction processes were determined, and the separation factors between two adjacent lanthanides(III) were calculated. 相似文献
94.
Zoubida Lachachi Samih Bendjeda Kheira Meddah Houari Hamani Haddou Boumediene 《Chemical Engineering Communications》2016,203(4):566-574
Water dissociation and proton leakage using the anionic exchange membrane (AMH) are studied by means of current/voltage characteristics and confirmed by simulation of transport number using Hittorf's method. The acids used are HCl, HNO3, and H2SO4 and the salts are NaCl, ZnCl2, and NaNO3. Concentration polarization of such membrane is accompanied by a change in the electrolyte concentration/solution interface due hydrolysis reactions. The results show that when the concentration of the electrolyte increases, the limiting current density increases linearly and the transmembrane resistance decreases systematically. The thickness of the diffusion layer is always higher in presence of acid than salt, making in evidence the proton leakage through the membrane. Besides, when the membrane is selectively permeable to chloride anion in the case of ZnCl2, the thickness of the double layer is rather bigger and far exceeds that of the membrane. The voltamperometry method seems reliable and offers some advantages over that of Hittorf because it shows the effects of some parameters on the value of limiting current: concentration, counter-ion types (Cl?, NO3? SO42?), and the gradient of concentration in the anode and cathode compartments. It can, therefore, allow to optimize the value of the current which should be used in electrodialysis in any form and without a great consumption of energy. Moreover, the simulation carried out for transport number of proton, shows its sensitivity toward the variation in concentration in the receiving compartment. In effect, a small decrease in concentration implies an enormous decrease in its value. 相似文献
95.
Ling Yun Wang 《分离科学与技术》2016,51(5):759-766
Hafnium can be selectively extracted over zirconium from strong sulfuric acid solutions by D2EHPA or PC 88A. Solvent extraction experiments have been performed to identify the reaction of Hf from strong sulfuric acid solutions (1 to 7 M) by these two extractants. Hafnium extraction was gradually decreased and then increased again with the increase of sulfuric acid concentration. By applying a slope method, the extracted Hf species was proposed to be HfA4·(HA)2 by D2EHPA and Hf(HSO4)2A2·(HA)2 by PC 88A, respectively. This difference in the nature of the extracted species was verified by FT-IR spectra. 相似文献
96.
聚醋热熔胶在其溶剂一沉淀剂混合液中加热“溶胀”后。再利用搅拌破碎而冷却成粉的方法。通过计算得到聚酯胶的溶解度参数(δ=21.8),参照比值选择溶剂和沉淀剂,并确定混合液的配比。文中还时制粉工艺和混合原料制粉的性能进行了研究。 相似文献
97.
Bipan Bansal Xiao Dong Chen Md. Monwar Hossain 《Chemical Engineering and Processing: Process Intensification》2005,44(12):1327-1336
A mathematical transport model is developed for the extraction of lithium from dilute synthetic solution, simulating geothermal water, using a supported liquid membrane (SLM) of LIX54 (major component is -acetyl-m-dodecylacetophenone) and TOPO (tri-n-octylphosphine oxide) in kerosene. The model is based on fundamental mass transfer and kinetics mechanisms that account for all possible transport resistances. The model is solved numerically and is used to investigate the effect of various extraction conditions and membrane support characteristics. Reasonable agreement is found between the predicted and the experimental results reported in literature. 相似文献
98.
99.
硅橡胶—金属高温硫化粘接的研究 总被引:6,自引:0,他引:6
以VTPS(乙烯基三叔丁基过氧硅烷)作为硅橡胶与金属高温硫化粘接的增粘剂,可将硅橡胶与金属的高温硫化粘接剪切强度从低于0.4MPa提高到5.0MPa以上。用溶液浸蚀分析证明:硅橡胶与金属粘接界面的相互作用力包括色散作用和化学键作用。 相似文献
100.