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氢气在炭狭缝微孔内吸附的预测 总被引:1,自引:0,他引:1
通过边界的平均场近似,推导二平板狭缝孔格子理论Ono-Kondo吸附等温方程.利用格子气模型特性和微观物理学理论,计算氢分子在石墨平面的最大吸附容量.比较由氢分子在石墨平面二典型聚集状态标定的Ono-Kondo方程,并用预测精度较高的方程计算了与文献相同条件下的吸附等温线.在比较了计算结果、试验结果和GCMC分子模拟结果后,对Ono-Kondo吸附等温方程的特点、理论基础作了分析,指出了方程的适用范围. 相似文献
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疏水性二氧化硅气凝胶吸附水中微量苯酚和甲醛的研究 总被引:2,自引:0,他引:2
气凝胶是一种新型纳米多孔非晶材料,其密度低、比表面积大、孔隙率高,可以作为吸附剂.本文研究了稻壳灰为硅源制成的合甲基的疏水性二氧化硅气凝胶对水中微量苯酚和甲醛的吸附性能.结果表明,疏水性气凝胶对水中微量苯酚和甲醛具有一定的吸附能力,实验中对苯酚的吸附容量是1.93mg/g,要大于对甲醛的吸附容量0.92mg/g;增大气凝胶的疏水化程度可以增加其对水中微量苯酚和甲醛的平衡吸附容量;苯酚的吸附平衡等温曲线符合Langmuir和Freundlich方程,甲醛的吸附平衡等温曲线符合Freundlich方程. 相似文献
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巯基树脂对重金属离子的吸附性能 总被引:16,自引:1,他引:16
研究了自合成的巯基树脂对重金属离子Pb^2 、Cu^2 、Cd^2 .Ni^2 、Co^2 的吸附容量、吸附动力学、等温吸附过程等静态吸附性能,同时研究了影响吸附的因素和吸附机理.结果表明,该树脂对软酸型重金属离子吸附容量高.pH=5.0-5.7,低温有利于吸附,树脂对各重金属离子等温吸附在实验浓度范围内均符合Langmuir和Freundnch方程.吸附机理研究表明,巯基与重金属离子发生了离子交换和配位反应,化学吸附起支配作用。 相似文献
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多壁碳纳米管对微量苯二氮卓类药物的吸附性能研究 总被引:2,自引:0,他引:2
研究了静态吸附条件下多壁碳纳米管(MWCNTs)对地西泮、艾司唑仑、阿普唑仑和三唑仑 4种苯二氮卓类药物的吸附性能,10 min内能达到吸附平衡.MWCNTs对药物的吸附容量随药物浓度的增加而增加,最小初始浓度时MWCNTs对4种药物的静态吸附容量分别为7.95、7.88、7.99和7.73 mg/g,吸附容量较大.295、303和313 K温度下的吸附实验表明,吸附容量随温度的升高而减小,降低温度有利于药物的吸附.对不同温度下的吸附等温线采用Freundlich和Langmuir方程进行拟合,结果显示Langmuir方程具有更好的拟合效果.在动态吸附条件下穿透体积的测定显示MWCNTs对药物也具有大的吸附容量且萃取回收率高达90%以上. 相似文献
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采用共沉淀法成功制备了Mg/Fe类水滑石(Mg/Fe-hlc),并研究了其对废水中磷酸根的吸附性能及吸附机理。研究结果表明:制备的Mg/Fe-hlc具有典型的类水滑石结构和较大的比表面积(156.7 m~2·g~(-1));Mg/Fe-hlc对磷酸根的吸附动力学过程符合准二级动力学模型;Langmuir和Tempkin方程都可以很好地拟合Mg/Fe-hlc对磷酸根的等温吸附数据,Langmuir方程拟合得到的最大吸附量可达47.38 mg·g~(-1);共存阴离子NO_3~-、Cl~-和SO_4~(2-)对磷吸附性能的影响很小;通过分析吸附磷酸根前后的Mg/Fe-hlc的结构和织构性质以及表面官能团变化,并结合溶液pH对磷酸根吸附影响实验结果,发现静电相互作用、配体交换和阴离子交换是Mg/Fe-htl吸附磷酸根的三种主要机制。 相似文献
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用改良尿素法制备了镁铁水滑石(MgFe-LDH),对其在小球藻油脂合成生物柴油反应中的催化性能进行了研究。利用XRD、FT-IR、SEM及FT-IR拟合、去卷积分析等技术对所制备的MgFe-LDH进行了表征,考察了pH值、Mg/Fe摩尔比、反应温度和时间对其结构和性能的影响。结果表明,Mg/Fe摩尔比为3或4、pH值为9.5,在110 ℃条件下反应10 h,所制备的MgFe-LDH(Mg3Fe或Mg4Fe)结晶度最高,粒径均匀,结构规整。与Mg/Fe摩尔比为2的MgFe-LDH(Mg2Fe)相比,Mg3Fe或Mg4Fe在完全分解焙烧时,其层板结构保持稳定,具有较高的晶体结晶度、较多的催化活性位和较高的催化活性。以Mg3Fe金属氧化物为催化剂,在醇/油摩尔比为6时反应1.5 h,生物柴油产率可达87%;该催化剂循环使用3次,仍具一定催化活性。 相似文献
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Preparation of poly (methyl methacrylate)/LDH nanocomposite by exfoliation-adsorption process 总被引:2,自引:0,他引:2
Exfoliated nanocomposite based on Mg, Al layered double hydroxide (Mg,Al-LDH) and poly(methyl methacrylate) (PMMA) has been prepared by exfoliation/adsorption process with acetone as co-solvent. The product was characterized by X-ray diffraction (XRD), thermal analysis and High Resolution Transmission Electronic Microscope (HREM). The results suggest that the brucite-like sheets of LDH disperse individually in the polymer matrix, and the thermal stability of the nanocomposite increases highly. 相似文献
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Dodecyl sulfate-hydrotalcite nanocomposites for trapping chlorinated organic pollutants in water 总被引:7,自引:0,他引:7
A series of hybrid organic-inorganic nanocomposite materials was synthesized by three different procedures using sodium dodecyl sulfate (DDS) and magnesium-aluminum layered double hydroxide (Mg/Al LDH with a Mg/Al molar ratio of 2 to 5). Both the pH of the exchange medium (6.5 to 10) and the Mg/Al molar ratio of the LDH affected the basal spacing, the content of DDS retained and the orientation of the DDS chains within the interlamellar space. For LDH with higher charge density (Mg/Al=2 and 3), DDS molecules likely formed a perpendicular monolayer within the LDH interlayer and the solution pH had little effect on the basal spacing, with a mean and standard deviation of 25.5+/-0.4 A. However, for LDH with lower charge density (Mg/Al=4 and 5), DDS molecules more likely formed an interpenetrating bilayer, and the basal spacing significantly increased with increasing pH, with a mean and standard deviation of 32.7+/-5.2 A. Sorption of trichloroethylene and tetrachloroethylene by DDS-LDH varied with synthesis conditions, LDH type and DDS configuration in the interlayer. DDS-Mg(3)Al-LDH had the highest affinity for both trichloroethylene and tetrachloroethylene in water, either comparable to or as much as four times higher than other clay-derived sorbents, followed by DDS-Mg(4)Al-LDH and DDS-Mg(5)Al-LDH. DDS-Mg(2)Al-LDH had the lowest sorption affinity although the highest amount of DDS. The pH of the exchange solution also affected the amount of DDS retained by the LDH as well as the sorption efficiency. Mg(3)Al-LDH has a charge equivalent area of 32.2 A(2)/charge, which allows the formation of optimal DDS configuration within its interlayer, thus resulting in the highest affinity for the chlorinated compounds. The DDS-Mg/Al-LDHs can be easily synthesized either ex situ or in situ at low temperature, indicating the feasibility of practical applications. The results obtained by controlling the synthesis procedure suggest that different arrangements of DDS molecules in the LDH interlayers can be obtained and optimized for the sorption of specific sorbates. 相似文献
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Palmer SJ Grand LM Frost RL 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(1):156-160
Raman spectroscopy has been used to characterise nine hydrotalcites prepared from aluminate and magnesium solutions (magnesium chloride and seawater). The aluminate hydrotalcites are proposed to have the following formula Mg(6)Al(2)(OH)(16)(CO(3)(2-))·xH(2)O, Mg(6)Al(2)(OH)(16)(CO(3)(2-),SO(4)(2-))·xH(2)O, and Mg(6)Al(2)(OH)(16)(SO(4)(2-))·xH(2)O. The synthesis of these hydrotalcites using seawater results in the intercalation of sulfate anions into the hydrotalcite interlayer. The spectra have been used to assess the molecular assembly of the cations and anions in the hydrotalcite structures. The spectra have been conveniently subdivided into spectral features based upon the carbonate anion, the hydroxyl units and water units. This investigation has shown the ideal conditions to form hydrotalcite from aluminate solutions is at pH 14 using a magnesium chloride solution at a volumetric ratio of 1:1. Changes in synthesis conditions resulted in the formation of impurity products aragonite, thenardite, and gypsum. 相似文献
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H. Zazoua A. Saadi K. Bachari D. Halliche C. Rabia 《Research on Chemical Intermediates》2014,40(3):931-946
Layered double hydroxides or hydrotalcite-like compounds with different kinds of metal ions (Mg–Al, Mg–Fe and Mg–Cr) in the brucite-like sheets were prepared by a co-precipitation method with Mg/M3+ molar ratio of ~2. The hydrotalcites were characterized by chemical analysis, X-ray diffraction, Fourier transform infrared spectroscopy, temperature programmed reduction, SEM microscopy, and specific surface area measurements. The activity is evaluated for benzaldehyde reaction. The selectivity to benzyl alcohol is always 90 % even though benzaldehyde conversion depends on the nature of the metal active phase and reaction conditions. 相似文献
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Five hydrotalcites with Mg/Al molar ratio range of 3-15 were prepared. The structure and basicity of Mg-Al mixed oxides (Mg(Al)O) transformed from hydrotalcites were investigated by TPD, XPS, XRD, FT-IR and NMR techniques. The results of elemental analysis and XPS indicate that Al is enriched in the surface regions of Mg(Al)0, and its amount increases with the Mg/Al molar ratio and the calcination temperature. 27Al-MAS-NMR results show that Al exists in two chemical environments: tetrahedral aluminium (Al(t)) and octahedral aluminium (Al(o)) in Mg(Al)O. The amount of Al(t) increases with the Mg/Al molar ratio and the calcination temperature. It is assumed that Al(t) may be mainly from the surface Al. Temperature-programmed desorption (TPD) of CO2 shows that the number of basic sites of Mg(Al)O samples increases with the Mg/Al molar ratio, and the maximum number of basic sites is obtained for hydrotalcite calcined at 773 K. Infrared spectra of adsorbed CO2 and B(OCH3)3 reveal that there are two kinds of 相似文献
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层板剥离水滑石的制备及影响因素 总被引:1,自引:0,他引:1
采用阴离子表面活性剂N-月桂酰基谷氨酸(LG)为插层分子,研究了烷烃-LG-水(O/W)微乳液中烷烃量的变化对插层水滑石层间距的影响,同时研究了烷烃分子大小和水滑石层板阳离子不同对水滑石剥离难易程度的影响。实验表明,随着微乳液中烷烃含量的增加,制备得到了由插层到层板剥离的水滑石,并且烷烃的链长越长,水滑石的剥离越容易实现。层板化学组成对剥离难易程度也有影响,难易程度依次是Mg/Al-LDH,Zn/Al-LDH和Ni/Al-LDH。 相似文献
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《Journal of Energy Chemistry》2014,23(1):91-96
A series of Cu-Mg-Al hydrotalcites derived oxides with a (Cu+Mg)/Al mole ratio of 3 and varied Cu/Mg mole ratio (from 0.07 to 0.30) were prepared by co-precipitation and calcination methods, then they were introduced to the hydrogenation of furfural in aqueous-phase. Effects of Cu/Mg mole ratio, reaction temperature, initial hydrogen pressure, reaction time and catalyst amount on the conversion rate of furfural as well as the selectivity toward desired product cyclopentanol were systematically investigated. The conversion of furfural over calcined hydrotalcite catalyst with a Cu/Mg mole ratio of 0.2 was up to 98.5% when the reaction was carried out under 140 °C and the initial hydrogen pressure of 4 MPa for 10 h, while the selectivity toward cyclopentanol was up to 94.8%. The catalysts were characterized by XRD and SEM. XRD diffraction of all the samples showed characteristic pattern of hydrotalcite with varied peak intensity as a result of different Cu content. The catalytic activity was improved gradually with the increase of Cu component in the hydrotalcite. 相似文献
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Hydrotalcite-like compounds (HTlcs) can be used as the catalysts as it is since they contain various transition metal cations
as the catalytically active species well dispersed on the basic support materials. Moreover, increasing numbers of the applications
of HTlcs after the heat treatment have been found since the oxides with very small crystal size, stable to thermal treatments,
are obtained after the calcination. The oxides possess interesting properties such as high surface area, basic properties
and further form small and thermally stable metal crystallites by reduction. Moreover, the calcined oxides show a unique property,
i.e., “memory effect,” which allows the reconstitution of the original hydrotalcite structure. We have developed the catalytic
applications of hydrotalcites as it is and moreover the mixed oxides derived from hydrotalcites for various catalytic reactions,
i.e., oxidation, dehydrogenation and reforming of hydrocarbons, and even for the reforming of methanol and the CO shift reaction.
Aerobic oxidation of alcohols, Baeyer−Villiger oxidation of ketones and O3 oxidation of oxalic acid have been successfully carried out with the Mg−Al hydrotalcites containing Ni, Fe and Cu, respectively,
as the catalysts in liquid phase. In the O3 oxidation of oxalic acid, the catalytic activity was enhanced by the “memory effect,” i.e., Mg(Cu)–Al hydrotaclite was reconstituted
on the surface of Mg(Cu,Al)O periclase particles and oxalic acid was incorporated as anions in the hydrotalcite layer, resulting
in an enhanced oxidation of oxalic acid. As the catalysts in the vapor phase reactions, Mg/Fe/Al mixed oxides prepared from
Mg–Al(Fe) hydrotalcites and effectively catalyzed the dehydrogenation of ethylbenzene. Supported Ni metal catalysts have been
prepared from Mg(Ni)–Al hydrotalcites and successfully used in the steam reforming and the oxidative reforming of methane
and propane. Moreover, the Ni catalysts have been improved by combining a trace amount of noble metals by adopting the “memory
effect” and used in the production of hydrogen for the PEFC under the daily startup and shutdown operation. Also starting
from aurichalcite or hydrotalcite precursor as the precursor, Cu/Zn/Al catalysts with high Cu metal surface area have been
prepared and successfully applied in the steam reforming of methanol and dimethyl ether, and moreover in the CO shift reaction. 相似文献