盐种类和浓度对蛋白质疏水性吸附过程有效孔扩散系数的影响

研究了牛血清白蛋白在配基密度不同的两种疏水性吸附剂Phenyl Sepharose FF low sub和Phenyl Sepharose FF high sub上的吸附平衡和孔内传质动力学,重点考察了盐种类和浓度的影响.结果表明,Na2SO4溶液中盐浓度的增加导致蛋白质吸附容量的增大和解离常数的降低比(NH4)2SO4溶液更显著.利用孔扩散模型得到的有效扩散系数随盐浓度及配基密度的增大而提高,表明表面扩散作用对孔内传质的贡献随吸附容量提高而增大.     

纸张干燥中湿分扩散系数的估算

纸张干燥过程涉及到多孔介质的热质传递,如何确定质量扩散系数是所建立的多孔物料湿分扩散模型能否进行数值计算的关键。按Liukov公式将湿分扩散系数视为含湿质量分数的非线性函数,在恒温下进行纸张干燥实验,通过比较湿分蒸发质量的测量值与理论计算值,采用多变量寻优的方法对多孔介质一维情况下的湿分扩散系数进行估算,得到了实验条件下的纸张湿分扩散系数的计算公式。并进一步确定了纸张中的湿分扩散系数与含湿质量分数和温度之间的函数关系式。     

第二液相的加入对气液传质系数的影响

以搅拌罐中的水吸收CO2为研究体系,分别采用异戊醇、苯和正己烷为第2液相,通过实验考察了第2液相的加入对气液传质的影响.实验结果表明:第2液相的加入对气液体积传质系数KLa有很大的影响,且不同的第2液相的影响程度也不同.在一定的操作条件下,KLa均随搅拌速度和第2液相体积分数的增加呈先增大后减小的趋势,随表观气速(在一...     

Concentration-dependent molecular diffusion coefficient of gaseous ethane in liquid toluene

We report new experimental data on concentration-dependent molecular diffusion coefficient of ethane in toluene at temperatures ranging from 21 to 125°C and pressures up to 4.14 MPa. An analytical model has also been developed for estimation of the diffusion coefficient utilizing the experimental data of the interface velocity as a result of swelling and the rate of gas dissolution in the liquid phase. It is shown that the diffusion coefficient of ethane in toluene is dependent on the initial mass fraction of the gaseous component in the liquid. In addition, the effect of concentration dependency of the molecular diffusion coefficient on diffusive mass flux is quantified. The results reveal that the assumption of a constant diffusion coefficient introduces ~10–60% error in calculation of diffusional mass transfer flux. The developed methodology finds application in estimation of the concentration-dependent molecular diffusion coefficient of gases in liquids.     

Film‐surface diffusion during the adsorption of acid dyes onto activated carbon

A mass transport model has been developed and applied to the adsorption of three acid dyes onto activated carbon in three single component systems. The mass transfer model is based on two rate controlling mass transfer steps, namely external film mass transfer and homogeneous solid‐phase surface diffusion (HSD). Almost all previous film‐HSD models have been based on numerical solutions to the diffusion equation using orthogonal collocation or Crank–Nicolson finite difference solutions. However, in the present model a semi‐analytical solution to the solid surface diffusion equation is presented, yielding a sophisticated solution of the differential equations. The solutions provide a good correlation between the experimental concentration–time decay curves by incorporating the Langmuir equilibrium isotherm to describe the solid phase surface dye concentrations. However, the surface diffusivities show a dependence on the carbon particle surface coverage and these diffusivities have been correlated using a Darken relationship. Copyright © 2004 Society of Chemical Industry     

液相化学氧化表面处理的研究进展

分别以无机型、有机型以及化学氧化聚合型3种化学氧化处理液分类介绍了液相化学氧化处理在材料表面处理方面的应用,并对液相化学氧化处理在处理表面隋性有机材料和含碳材料方面的研究进展进行了综述。     

脂肪酸在甲基丙烯酸异丁酯凝胶中扩散系数的估测

采用分散质分子染色、跟踪手段,对游离脂肪酸分子在甲基丙烯酸异丁酯高分子凝胶体系中有效扩散系数进行测定和估算,实验测得有效扩散系数为10-11 m2/s数量级范围,处于估测范围之内。同时对比了分散质分子在纯液相中的自由扩散系数,并分析了凝胶体系中脂肪酸分子的扩散机制。结果表明:利用染色、跟踪定量法对大分子分散介质在凝胶体系中扩散行为的研究和有效扩散系数的估测具有可行性。     

用改进的基团贡献法计算二元体系液相分子扩散系数

一种改进的用基团贡献原理计算二元体系液相分子扩散系数的方法,可用于大部分非理想液相体系。用150多个体系的1000多个实验点对此方法进行了验证,结果表明对于理想体系和无限稀释溶液的分子扩散系数,计算值与实验值平均相对误差不超过5%,对于大部分的非理想体系其平均相对误差小于10%。与原有的经验、半经验关联式相比,改进的方法具有更大的适用范围,能更准确地预测液相分子扩散系数。     

Analysis of intraparticle diffusion on adsorption of crystal violet on bentonite

Abstract

In the present work, kinetics of crystal violet (CV) adsorption on bentonite was studied by pore volume and surface diffusion model (PVSDM), surface diffusion model (SDM), and pore volume diffusion model (PVDM). The adsorption decay curves were obtained in batch system using different adsorbent dosages. The PVDM model did not interpreted the kinetic adsorption since the calculated value of D_p equal to 5.64?×?10^?7 cm² s^?1 predicted a slower adsorption than that obtained by the experimental data. The PVSDM results indicates that the intraparticle diffusion is predominantly due to surface diffusion (93%) and the pore volume diffusion can be negligible. Once the surface diffusion was the limiting step, the estimation with one (D_s) and two (D_sq and α) parameters were tested in the SDM model. The statistical analysis revealed that the one-parameter SDM model was most appropriate to predict the CV adsorption on bentonite. The optimal values of Ds ranged from 6.19?×?10^?10 to 6.49?×?10^?10 cm² s^?1, and decrease with the adsorbent dosage.     

Measurement of intraparticle diffusion in reversed phase liquid chromatography

The intraparticle diffusion coefficient was measured using a method based on the fitting of a set of experimental chromatographic profiles to the lumped pore diffusion model. For this purpose, both the analytical solution of the model in the Laplace domain and a numerical method were used. There was an excellent agreement between the results given by the two methods. These results are compared to those obtained by moment analysis of the same set of chromatographic profiles and by the determination of the intraparticle diffusion coefficient from the second central moment of these bands. Nearly identical results were obtained with these two independent methods. The values of the intraparticle diffusion coefficient, D_e, for rubrene in pure methanol was found to be by the modeling method and by the moment analysis method. These values increase with increasing water concentration, to 1.10×10⁻⁶ and , respectively, in a methanol/water solution and to 1.63×10⁻⁶ and , respectively, in a solution.These results confirm the validity and the consistency of the lumped pore model and the moment analysis theory. They show that both approaches describe correctly the mass transfer kinetics in the particles of packing material during the chromatographic process. Systematic determinations of the intraparticle diffusion coefficient can now be undertaken and the influence of various experimental parameters on this important property of packing materials can be investigated.     

基于MPHC活度系数模型关联烃－水体系液－液平衡

基于普遍化范德华配分函数理论，应用由局部组成概念导出的方阱流体配位数模型导出了链状分子混合物的配位数模型，并由此建立了一个新的活度系数模型；将其应用于高度非理想体系汽－液平衡活度系数的关联，结果与Ｗｉｌｓｏｎ方程相当，但方程参数随温度变化较小；其于Ｎｅｗｔｏｎ－Ｒａｐｈｓｏｎ－Ｇａｕｓｓ液－液平衡算法，应用新模型对烃－水体系的液－液平衡进行了关联计算，结果优于ＮＲＴＬ方程     

基于MPHC活度系数模型关联烃－水体系液－液平衡

基于普遍化范德华配分函数理论，应用由局部组成概念导出的方阱流体配位数模型导出了链状分子混合物的配位数模型，并由此建立了一个新的活度系数模型；将其应用于高度非理想体系汽－液平衡活度系数的关联，结果与Ｗｉｌｓｏｎ方程相当，但方程参数随温度变化较小；其于Ｎｅｗｔｏｎ－Ｒａｐｈｓｏｎ－Ｇａｕｓｓ液－液平衡算法，应用新模型对烃－水体系的液－液平衡进行了关联计算，结果优于ＮＲＴＬ方程     

Transient liquid phase diffusion process for porous mullite ceramics with excellent mechanical properties

Porous mullite ceramics were fabricated by the transient liquid phase diffusion process, using quartz and fly-ash floating bead (FABA) particles and corundum fines as starting materials. The effects of sintering temperatures on the evolution of phase composition and microstructure, linear shrinkage, porosity and compressive strength of ceramics were investigated. It is found that a large amount of quartz and FABA particles can be transformed into SiO₂-rich liquid phase during the sintering process, and the liquid phase is transient in the Al₂O₃-SiO₂ system, which can accelerate the mullitization rate and promote the growth of mullite grains. A large number of closed pores in the mullite ceramics are formed due to the transient liquid phase diffusion at elevated temperatures. The porous mullite ceramics with high closed porosity (about 30%) and excellent compressive strength (maximum 105?MPa) have been obtained after fried at 1700?°C.     

在加热阶段滚塑模具内表面传热系数的两种研究方法

提出了获得电加热滚塑模具内表面传热系数的两种研究方法,这两种方法适用于模内粉料开始熔融前的加热阶段。第一种方法是首先在4种情形下测量该滚塑模具的外表面温度和模内温度,然后根据能量守恒原理建立一个传热模型,并通过该模型将这些实测的温度值转换为在这4种情形下模具的内表面传热系数。第二种方法是将实际的滚塑模具等效地简化为一个二维圆筒,将模内空气当成主相流体,粉料当成第二相流体,通过FLUENT软件的多相流模块中的Mixture模型进行仿真计算以得到模具内表面的传热系数。结果表明,这两种方法所得的结果在其中的3种情形下都吻合得很好。随着模内粉料的体积百分比的增加,模具的内表面传热系数先是快速增大,然后增大的速率变慢,在达到最大值61.2 W/（m²·K）后开始减小。当粉料的体积百分比不在58 %~74 %的范围内,由第二种方法仿真所得的模具内表面传热系数的相对误差不超过10 %。     

离子液体［BMIM］Br的水溶液VLE与扩散系数的分子模拟

在Linux操作系统下采用Towhee软件和NPT-Gibbs系综Monte-Carlo方法（GEMC）,模拟了不同温度、不同压力下二元体系［BMIM］Br+H₂O的汽液相平衡性质。提出了一种修正介电常数的方法来计算长程力,所得结果与非极化模型、极化模型及实验结果进行了比较。结果表明：相比于极化模型和非极化模型,修正介电常数的计算结果更接近实验值。此外,采用DL_POLY软件和分子动力学模拟的方法对［BMIM］Br水溶液的扩散系数进行了计算。结果表明：随着溶液中水含量的增多,ILs阴阳离子以及水分子的扩散系数得到了明显的改善。     

Effective diffusion coefficient of chloride in porous concrete

A simplified diffusion model is given in the present paper to represent the chloride diffusion in porous concrete. The model with appropriate effective diffusion coefficient is shown to represent equally well as the more complex diffusion/reaction model proposed by Pereira and Hegedus.⁴ However the present model has the main advantages of being amenable to an analytic solution and ease of model parameter estimation.     

Estimation of an effective water diffusion coefficient during infrared-convective drying of a polymer solution

This article deals with the drying of an aqueous solution of polyvinyl alcohol mixed with a plasticizer. A heating combining forced convection and short-infrared radiation was investigated. A one-dimensional model taking into account the shrinkage of the product was developed to get the temperature and moisture content evolutions during the drying. The water diffusion coefficient was estimated by an inverse method. A sensitivity analysis and numerical tests showed the relevance of using an objective function taking both mass and temperature measurements into account for the estimation procedure. This estimation was performed on several convective and infrared-convective experimental drying kinetics. The model predictions fit well mass and temperature experimental data. © 2009 American Institute of Chemical Engineers AIChE J, 2009