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1.
Na型斜发沸石上Na+-Cu2+离子交换过程动力学   总被引:4,自引:0,他引:4  
用静态离子交换法研究了Na型斜发沸石上2Na=Cu^2+离子交换动力学,分别测定了液膜扩散常数R,粒内扩散系数D和滞留时间Td,实验发现,离子交换起始为液膜扩散控制,随后在交换的大部分时间内为粒内扩散控制,并就温度、浓度对离子交换过程速率,Cu^2+平衡交换数量以及滞留时间的影响进行了讨论。  相似文献   

2.
气液固三相反应过程固体溶解增强因子   总被引:3,自引:0,他引:3  
基于双膜理论,考虑了气液液膜内、固液液膜内传质过程,推导出一个较确切的描述液固相界面随反应进行发生变化时伴有气体吸收与固体溶解并在液膜内发生瞬间反应的模型,给出一个描述三相反应过程的固体溶解增强因子的表达式。用本模型计算的固体溶解增强因子能很好地描述实验数据。  相似文献   

3.
本文研究了强酸性阳离子交换树脂上Zn^2+-Na^+交换过程的动力学。讨论了交换方向、温度和粒径对交换速率的影响。测出不同控制机理,不同交换方向时的传质参数和25℃-53℃范围内的扩散活化能。发现在低浓度ZnCl2溶液与Na^+型树脂交换时,用液相分析是液膜扩散控制过程,但用电子探针固相分析却表明树脂内有明显的浓度梯度。说明仅用液相浓度变化与模型方程拟合的方法来判断速率控制机理具有一定的局限性。  相似文献   

4.
质子交换膜燃料电池零下冷启动研究   总被引:2,自引:0,他引:2  
张剑波  王诚 《化学通报》2017,80(6):507-516
在零下启动过程中,质子交换膜燃料电池阴极中氧气还原反应生成的水会在催化剂层内部结冰,因而阻碍氧气传输,覆盖催化剂层反应活性位点,降低电化学活性面积,影响燃料电池发电性能,甚至会导致零下启动失败;同时,结冰/融化循环还会破坏膜电极结构,影响燃料电池寿命。因此,质子交换膜燃料电池零下启动技术的研究对促进燃料电池汽车的推广应用有重要意义。本文针对质子交换膜燃料电池的零下启动过程,从实验研究、机理解释、模型分析及策略开发等角度对文献内容进行了梳理,并对涉及质子交换膜燃料电池零下启动过程的专利技术进行了总结。  相似文献   

5.
本文研究了亚铁氰化钾钛在模拟酸性高放废液中交换Cs 的行为。通过改变温度、粒度、振荡频率、料液不同的稀释倍数等因素对Cs 交换速度的影响,测定了交换过程中交换体中组分随所交换的Cs 的变化,得出亚铁氰化钾钦对Cs 的交换主要是粒扩散和膜扩散混合控制,是交换体中的K 与溶液中的Cs 进行了交换。  相似文献   

6.
研究了甲醛-苯氧乙酸树脂对重金属离子铅、镉、汞的交换性能,并考察了温度、pH值、浓度等因素对交换性能的影响。结果表明,树脂对3种重金属离子的等温交换过程均符合Langmuir交换等温式,交换受液膜扩散控制;其交换容量可分别达1.85mmol/g、1.73mmol/g、1.13mmol/g。  相似文献   

7.
Sol-gel法在燃料电池用质子交换膜制备中的应用   总被引:1,自引:0,他引:1  
主要综述了溶胶-凝胶(sol-gel)法在制备质子交换膜中的应用。将Sol-gel法应用到质子交换膜的制备中,提供了一种制膜和优化膜的行之有效的途径。本文着重从利用sol-gel法制备有机/无机杂化型、磷酸/二氧化硅型以及全氟磺酸膜的改进型质子交换膜等方面加以介绍。  相似文献   

8.
在零下启动过程中,质子交换膜燃料电池阴极氧气还原反应生成的水会在催化剂层内部结冰,因而阻碍氧气传输,覆盖催化剂层反应活性位点,降低电化学活性面积,影响燃料电池发电性能,甚至会导致零下启动失败;同时,结冰/融化循环还会破坏膜电极结构,影响燃料电池寿命。因此,质子交换膜燃料电池零下启动技术的研究对促进燃料电池汽车的推广应用有重要意义。本文针对质子交换膜燃料电池的零下启动过程,从实验研究、机理解释、模型分析及策略开发等角度对文献进行了综述分析,并对涉及质子交换膜燃料电池零下启动过程的专利技术进行了总结。  相似文献   

9.
用溶出伏安法测定蛋白胨细胞生长液中易变形态铜   总被引:1,自引:0,他引:1  
采用阳极阶梯溶出伏安法 ,测定了蛋白胨细胞生长液中的易变形态铜 ,并获得了总铜量中易变形态的摩尔分数以及易变形态的表观稳定常数。通过使用交换介质法 ,较好消除了由于蛋白胨细胞生长液中各种氨基酸或其它组分吸附在汞膜表面而引起的干扰  相似文献   

10.
由于液/液界面可以看作是模拟生物膜或人造膜的简单模型,研究在此其上的电子转移过程对理解生物体复杂的生理变化过程具有重要意义。薄层伏安法因其简单、易操作等优点成为研究液/液界面电子转移过程的有力手段,因此对该方法的定量分析理论研究显得尤为重要。本文综述了薄层伏安法液/液界面电子转移速率理论近年来的研究进展,并对其可能的影响因素进行了分析。  相似文献   

11.
XDA-1树脂对茶多酚的吸附及吸附柱放大研究   总被引:5,自引:0,他引:5  
研究了XDA-1树脂对茶多酚的吸附及吸附柱放大规律。建立了XDA-1树脂柱吸附茶多酚过程的传质模型,并根据该模型分别计算了不同操作条件下相应的物质总传质系数及传质区长度.结果表明,在实验操作的流速范围内,过程属于外扩散控制.按照操作线速度相等的原则进行固定床设备的放大,传质区长度的放大误差在10%左右,实验所得传质区长度的结果可作为吸附柱设计的基础.  相似文献   

12.
研究搅拌槽中732阳离子交换树脂吸附L-酪氨酸的交换平衡和动力学特性,考查了搅拌速度、温度、料液初始pH值、树脂粒径和料液初浓度对离子交换过程的影响.在研究的温度和浓度范围内,该离子交换等温线符合Henry等温式.搅拌速度为350rpm时,可以将外传质阻力忽略.料液初始pH值介于2.5~5.5 时,对交换量影响不大,而料液中Na 的存在会降低树脂的交换量.在忽略外传质阻力的条件下,采用不同粒径计算方法对动力学曲线影响很小.用间歇搅拌槽吸附动力学模型拟合出无外传质阻力条件下、不同初始浓度条件下离子交换的表面扩散系数Ds.结果表明,随着初始浓度的增大,Ds的数量级始终在10-8左右.  相似文献   

13.
The stability of emulsions is studied using, as a model of two interacting drops, an aqueous film of a surfactant immersed in an oil phase. It is shown that the mass transfer of a solute across the film changes its life-time. This change depends on several parameters as the nature and concentration of the solute. the direction of mass transfer, the time elapsed after the formation of the film. The destabilizing effect, of the transfer is found to be much less pronounced when the solute is in the continuous water phase. The instability is ascribed to the Marangoni effect and/or to liquid flow from the film drawn by diffusion of the solute.  相似文献   

14.
Hydrogen mass transfer through a composite membrane represented by a film of palladium (or its alloys) applied onto a porous substrate has been studied. The hydrogen flux through the composite membrane has been shown to be governed by the ratio between the diffusion permeabilities of the film and the porous substrate, the mechanism of the transfer through the film, and the external pressure. It has been found that the intensity of hydrogen transfer through the composite membrane may depend on the transfer direction. The transfer is most asymmetric when the diffusion permeabilities of both layers are close and the hydrogen transfer in the film is limited by diffusion. At the same time, the transfer asymmetry effect does not arise when the hydrogen transfer in the film is limited by adsorption processes on its surface.  相似文献   

15.
The diffusion and mass transfer, reaction, integration and growth processes of the metalions on the activated carbon fibers (ACFs) are discussed. Based on the diffusion film theory, thediiffusion and the integration model are developed to describe the deposition processes of metal ionsfrom the solution to ACFs in the fiuidized beds. The model of heat transfer of this process isestablished to expound the important role-played in deposition processes by the influence of thereaction heat released at ACFs surface and the non-uniform temperature distribution caused byhydrodynamics.  相似文献   

16.
The sorption of three metal ions, namely, copper, cadmium, and zinc, onto bone char has been studied in terms of equilibrium and rate studies. Equilibrium studies have been analyzed using the Langmuir isotherm equation and the maximum sorption capacities for the metals were 0.477, 0.709, and 0.505 mmolg(-1) bone char for cadmium, copper, and zinc ions, respectively. The kinetic experimental data were used to analyze the effect of external film boundary layer and intraparticle mass transfer resistance on the sorption process and its significance. Four methods of determining the external film transport coefficient were developed and tested; three utilized experimental data to obtain the coefficient and the fourth method was completely empirical. The three experimentally based models give very similar results and consequently similar values of the deviation error values, whereas the error values for the empirical correlation were greater than these three values. The results also demonstrated that the methods for determining the film coefficient could be integrated into more complex diffusion-transport models such as film-intraparticle diffusion processes.  相似文献   

17.
18.
1. INTRODUCTION Study on the deposition of metal ions on ACFs indicated that such a process consists of several consecutive steps [1]: (1) transfer of the solvated ions (metal ions) from the bulk solution to the proximity of the ACFs surface; (2) absorpt…  相似文献   

19.
A derivation is presented of a ternary diffusion model to describe the mass transfer processes associated with the quench bath period of the phase inversion process for membrane formation. The complete governing equations, initial conditions, and boundary conditions in the casting film and coagulation bath are presented. Equations for ternary chemical potentials and diffusion coefficients are consistently based on constant specific volume formulations. The model is applied to the analysis of mass transfer paths and their effects on membrane structure formation. Precipitation times are determined for given sets of conditions by superposing calculated mass transfer paths on the ternary phase diagram and observing when the miscibility gap is crossed. Comparisons are made with an earlier reported study on the membrane-forming system: water-acetone-cellulose acetate (CA). Agreement between predicted and measured precipitation times is found to be excellent. The polymer film composition profile at the moment of precipitation is shown to be a useful indicator of both skin and sublayer structures, allowing distinctions to be made between conditions leading to spongelike and fingerlike morphologies. The influence of model parameters on the mass transfer paths and associated polymer profiles is also discussed.  相似文献   

20.
乙烯-丙烯气相共聚动力学研究   总被引:1,自引:0,他引:1  
应用自行设计的烯烃气相聚合半连续反应装置 ,对乙烯 丙烯气相共聚动力学进行了研究 .并结合传质研究结果 ,求得了乙 丙共聚反应速率常数、竞聚率及其与温度的关系  相似文献   

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