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41.
A novel freeze-drying protocol has been explored to render fast and cost-effective freeze drying of hyperamylase producing Bacillus subtilis MTCC2396 employing a tungsten halogen lamp radiator (THLR) as a heat source. Response surface methodology assessed the maximum reduction in moisture content (96.07%) and minimum reduction in α-amylase (EC 3.2.1.1) activity (1.02%) in 4 h drying time at 42.5°C radiation temperature. α-amylase activity (0.046 U) and final moisture content (3.93%) of the optimally freeze-dried bacterial strain appeared satisfactory. The freeze-drying time using THLR (4 h) is remarkably lower compared to that under a conventional conductive plate heater (CPH) (10 h) at otherwise identical conditions. The higher effective moisture diffusivity of 0.0052 to 0.0078 m 2/s under THLR compared to 0.00084 to 0.0015 m 2/s under CPH (corresponding to 20–50°C) advocated the superiority of the THLR heating protocol. The higher efficacy of THLR was also evidenced through lower activation energy (8.42 kJ/mol) of moisture diffusion compared to that (12.051 kJ/mol) of CPH. The optimally freeze-dried bacteria demonstrated the same growth rate in addition to exhibiting excellent retention of bioremedial (Hg2+ removal) activity to that of the control. 相似文献
42.
In this work, uniform core-shell structure of polypyrrole wrapped on tungsten oxide nanorods (PPy@W18O49 core-shell nanorods) were synthesized via a two-step process for gas-sensing applications. The core-nanorods of W18O49 were first grown by solvothermal method with tungsten hexachloride (WCl6) as precursor. The PPy-shell layer was then formed uniformly on the solvothermally synthesized W18O49 nanorods by in-situ chemical polymerization of pyrrole monomer (Py), with sodium dodecyl benzene sulfonic acid (DBSA) as dopant and ammonium persulfate (APS) as oxidant. High dispersion of Py achieving in ethanol is proved to be crucial to form the uniform PPy-shell layer, and the layer thickness of PPy-shell is highly controlled by adjusting the Py concentration in polymeric solution. The morphology and structure of the nanocomposite were characterized systematically; it shows that the composite exhibits perfect core-shell structure of one-dimensional (1D) nanorods with average diameter of around 70–90 nm. The NH3-sensing properties of the sensors based on the PPy@W18O49 core-shell nanorods were investigated at operating temperature of 15–130 °C over NH3 concentration ranging from 1 to 200 ppm. The response magnitude of the PPy@W18O49 sensor can be affected seriously by temperature fluctuation, even in room temperature range (15–30 °C), and meanwhile, a temperature-dependent p-n response characteristic reversal is observed for the heteronanorods sensor. At much low room temperature of 15 °C, the present PPy@W18O49 nanorods show quick and sensitive response to NH3 gas mainly due to the ultrathin, uniform PPy shell and the special heterojunction effect between p-type PPy and n-type W18O49. The underlying gas-sensing mechanism is analyzed. 相似文献
43.
Serge Hiligsmann Laurent BeckersJulien Masset Christopher HamiltonPhilippe Thonart 《International Journal of Hydrogen Energy》2014
A horizontal tubular fixed bed bioreactor (HFBR) and an anaerobic biodisc-like reactor (AnBDR) were designed to both fix Clostridium biomass and enable rapid transfer of the hydrogen produced to gas phase in order to decrease the strong effect of H2 partial pressure and H2 supersaturation on the performances of Clostridium strains. The highest H2 production rate (703 mL H2/L h) and yield (302 mL/g glucose consumed i.e. 2.4 mol/mol) with the pure culture were recorded in the AnBDR with 300 mL culture medium (total volume 2.3 L) at pH 5.2 and a glucose loading rate of 2.87 g/L h. These results are about 2.3 and 1.3-fold higher than those achieved in the same bioreactor with 500 mL liquid medium and with the same glucose consumption rate. Therefore, our experimentations and a short review of the literature reported in this paper emphasize the relevance of performing bioreactors with high L/G transfer. 相似文献
44.
《Canadian Metallurgical Quarterly》2013,52(4):358-363
AbstractA coprecipitation–adsorption method based on a novel Mo sulphidation process is proposed for deep removal of molybdenum from tungstate solutions. First, a new sulphur source, P2S5, is used to provide HS? for the Mo sulphidation process. The MoO42? can be thoroughly converted into MoS42? while tungsten still exists as WO42?. Next, in the sodium tungstate solution, 99·4% of MoS42? is removed with precipitated ‘nascent’ CuS under 6 h reaction at 30°C when the molar ratio Cu/Mo is 3. Similarly, in a commercial (NH4)2WO4 solution, by controlling the molar ratio Cu/Mo at 6, 98·4% of MoS42? is removed after 1 h at 30°C. Subsequently, phosphorus introduced during Mo sulphidation is removed using the magnesium ammonium phosphate method allowing the ammonium paratungstate to reach the GB 10116-88 APT-0 standard.On propose une méthode de co-précipitation et adsorption basée sur un nouveau procédé de sulfuration du Mo pour l’enlèvement en profondeur du molybdène de solutions de tungstate. Premièrement, on utilise une nouvelle source de soufre, P2S5, pour obtenir le HS? pour le procédé de sulfuration du Mo. Le MoO42? est entièrement converti en MoS42? alors que le tungstène existe encore sous la forme de WO42?. Ensuite, 99·4% du MoS42? est enlevé de la solution de tungstate de sodium avec le CuS ‘naissant’ précipité, en moins de 6 heures de réaction à 30°C lorsque le rapport molaire de Cu/Mo est de 3. De façon similaire, 98·4% du MoS42? est enlevé d’une solution commerciale de (NH4)2WO4, après une heure à 30°C, en contrôlant à une valeur de 6 le rapport molaire de Cu/Mo. Subséquemment, le phosphore introduit lors de la sulfuration du Mo est enlevé en utilisant la méthode du phosphate ammoniaco-magnésien, permettant ainsi au paratungstate d’ammonium d’atteindre la norme GB de 10116-88 APT-0. 相似文献
45.
Zhe Guo Qihua Zhu Shan Wu Changzheng Hu Laijun Liu Liang Fang 《Ceramics International》2018,44(7):7700-7708
Unfilled tungsten bronze ceramics with the nominal formula Ba4PrFe0.5Nb9.5O30 were synthesized via the standard solid-state sintering route, and the effects of oxygen vacancies on the dielectric and electrical properties were investigated in addition to the structure. Room-temperature X-ray diffraction showed that the N2-annealed sample had the largest cell volume. Low-temperature spectrum showed that N2 annealing rendered the dielectric constant and dielectric loss more frequency dispersive, whereas O2 annealing inhibited the frequency dispersion. The dc conductivity of all the samples originated from the electrons produced in the second ionization of oxygen vacancies and was most likely controlled by a mixed conduction mechanism of the electron and oxygen-vacancy ions. The N2-annealed sample has the highest dc conductivity owing to its high concentration of oxygen vacancies. The broadening of the Raman lines and the decrease of Raman intensity for the N2-annealed sample originated from a significant structural disorder. X-ray photoelectron spectra demonstrated that the increased oxygen vacancies caused by the change of valences of Fe and Pr ions contributed to the structural disorder. 相似文献
46.
47.
苗承鹏 《中国材料科技与设备》2011,(4):74-76,79
本文主要通过介绍金属轧制宽展构成及影响宽展的因素,利用典型宽展计算基本方法和参数,对纯镍盘圆半连续孔型轧制过程中椭圆一圆孔型系的宽展实际生产情况进行分析,并对轧制孔型设计优化。 相似文献
48.
广东棉土窝钨矿深部探矿方向探讨 总被引:1,自引:0,他引:1
棉土窝钨矿是一个开采了50多年的老矿山,保有储量仅5年左右,属资源危机矿山。笔者从成矿规律、以往探矿经验等方面分析,认为该矿西南部的深部有寻找隐伏矿脉的潜力。 相似文献
49.
50.