UNSTEADY-STATE SORPTION MEASUREMENTS A TEST OF DIFFERENT METHODS TO EVALUATE THE DIFFUSIVITY FROM UNSTEADY-STATE SORPTION MEASUREMENTS

ABSTRACT

Different simple methods for evaluating the diffusivity from a sorption measurement are presented and tested when there is a surface resistance (a limited mass transfer coefficient), a non-perfect step in relative humidity or non-Fickian effects. It is concluded that the different methods have different qualities and it is impossible to give a general recommendation on which method to use. The best tactic is probably to use more than one of the methods. A knowledge of the experimental conditions will help in choosing the best method.     

涂料与涂膜物性的最新评价方法（Ⅰ）

涂料与涂膜物性检测是涂料生产和使用的重要环节。随着涂料品种及用途的不断扩大,其各种检测项目日益增多。介绍了近年来有所发展的检测项目和方法。     

坐便器用水量测试方法的比较

坐便器用水量是重要的检测指标,各国标准的测试方法有一些差异,而不同的测试方法对测试结果有一定的影响。在此比较了坐便器用水量测试的中国标准(GB 6952-2005)、美国/加拿大标准(ASME A112.19.2-2008/CSA B45.1-08)、欧盟标准(EN 997:2003/A1:2006)、澳大利亚标准(AS 1172.2-1999)四个标准。通过对相同样品的4种测试方法试验,得出了测试结果之间的差异性。结果表明,ASME/CSA方法的用水量(大冲和小冲)和GB方法基本一致,EN方法的用水量(大冲和小冲)比ASME/CSA和GB方法的小,AS方法的平均用水量最小。     

BATCH SORPTION BY LIGAND EXCHANGE: DETERMINATION OF INTRAPARTICLE DIFFUSIVITY

A mathematical model has been developed to describe batch sorption by ligand exchange. A ligand is sorbed onto an exchange sorbent from a finite bath. The sorbent particles are uniformly suspended in the fluid bath volume. The transport mechanisms are diffusion through the solid sorbent and external film diffusion. The equilibrium between the solid and fluid phase is described by a Langmuir isotherm. Two approaches are presented for representing the intraparticle mass transfer—diffusion in a pseudohomogeneous solid accompanied by sorption and diffusion through a saturated region to an unreacted shrinking core. The solid diffusion model, consisting of a partial differential equation, has been solved numerically by orthogonal collocation. The shrinking core model, a single ordinary differential equation, has been solved by conventional numerical integration. Both models successfully correlated data on diffusion of ammonia in copper-complexed carboxylic acid type ion exchange resin. The resultant sorbent diffusion coefficient is useful in designing fixed bed continuous ligand exchange columns.     

DIFFUSIVITY DETERMINATION FROM THE RESPONSE TO INJECTION INTO LAMINAR LIQUID FLOW IN A CAPILLARY

A method for the determination of diffusivities in liquids is described; the method is based on measurements of the response to injection in a laminar flow of liquid in a capillary. By injection of δ-type, the component whose diffusivity is to be measured is introduced into the inlet part of a capillary of internal diameter 1.6 mm. The response to the injection is measured at the end of the capillary by a flow-through refractometer, the output signal of which is recorded on tape at 16-s intervals. The output signal is compared with a theroetical model of the time dependence of the response, based on Taylor's analysis of the dispersion of an injected component in laminar flow. The diffusivity is calculated from one of the model parameters, which were evaluated by the method of maximum likelihood. The calibration of the instrument was performed by measuring the diffusivity of KC1 in aqueous solution. The following diffusivities at 25°C were determined: n-butanol 971 μm²/s, dioxane 1093μm²/s, caprolactame 948 μm²/s, Na₂SO₄, 1126 μm²/s, salicylaldoxime 895 μm²/s, cyclohexanone 960 μm²/s, acetone 1316μm²/s, oxine 820.5 μm²/s, all in water; caprolactame in trichlorethylene 1958μm²/s, caprolactame in 10% aqueous (NH₄4)₂,SO₄ solution 1148 μm²/s, salicylaldoxime in chloroform 1878 μm²/S.     

泵型叶轮表面曝气机的性能评价新方法

本文提出了一种更新的污水传氧系数KLaW的现场测定方法,并应用于重庆某污水处理厂曝气设备的能效研究中。该方法稳妥可行可靠,易于实现。     

基于三点弯曲实验的混凝土抗拉软化关系的求解方法

确立了分别基于开裂强度准则和断裂韧性准则的由三点弯曲实验确定混凝土材料抗拉软化关系的方法.该方法应用扩展的黏聚裂纹模型,通过使模拟的荷载一裂纹口张开位移(stress-crack width relationship,Load-CMOD,P-CMOD)曲线与三点弯曲实验获得的P-CMOD曲线吻合来确定相应的混凝土抗拉软化关系参数.求解中的所有参数均由三点弯曲实验结果确定,其优点是只需用简单的位移控制试验机完成弯曲实验,与单轴拉伸实验相比,实验成功率更高、更容易实现.     

不同试验方法对GFRP筋粘结强度的影响研究

基于拉拔和粱式试验，探讨了这两种试验方法对GFRP筋与不同种类混凝土(包括混凝土C30、掺纤维与不掺纤维的混凝土C50等)之间粘结强度的影响。研究表明，梁式试验的GFRP筋粘结强度稍低于拉拔试验的结果；混凝土强度等级以及是否掺加聚丙烯纤维对GFRP筋的粘结强度影响较小。     

减少人造板甲醛释放量的方法

介绍了人造板释放甲醛的来源以及甲醛对人体的危害 ,同时介绍了减少人造板甲醛释放量的有效措施     

MEASUREMENTS OF EFFECTIVE DIFFUSIVITY IN LARGE-PORE PERMEABLE PELLETS WITH VARIOUS GEOMETRIES USING THE CHROMATOGRAPHIC METHOD

Mathematical models for solid cylinder and hollow cylinder pellets, where intraparticle convection was considered, have been established and solutions in the Laplace domain have been obtained. Consequently, the equivalence between the hollow cylinder and the slab characteristic dimensions was presented for the first-order-reaction/diffusion/convection problem. A modified chromatographic method has been developed to measure the intraparticle diffusivity in solid cylinder pellets. The axial dispersion of the column packed with the hollow cylinder pellets was measured and a correlation for the Peclet number versus Reynolds number has been obtained. Intraparticle convection has been measured with large pore sphere pellets which present a “foam structure” by using the conventional chromatographic method. Intraparticle Peclet numbers and the permeability of this pellet were determined.     

抗菌高分子材料抗菌性检验方法的研究

介绍抗菌高分子材料抗菌性的定性与定量检验方法。这些方法可对抗菌高子材料进行评价。     

生物降解塑料试验评价方法的进展

简介了活性污泥、土壤分解和特定酶、微生物分解等三类生物降解塑料的试验评价方法,以及日、美有关试验评价工作的进展,特别是美国ASTM的有关标准制订工作概况.另外,本文也简单综述了聚乙烯、乙烯基聚合物、聚酯、聚醚、聚氨酯、聚酰胺等聚合物的生物降解性及其影响因素及机理.     

成型方法对用辊棒废料制备的瓷球性能的影响

分别采用等静压成型与手搓成型工艺制造氧化铝瓷球；研究表明不同的成型方法不仅对瓷球的烧成及物理性能有影响，且对其磨损规律有着很大的影响；等静压成型瓷球的烧结温度较手搓成型瓷球要低，硬度及密度比手搓成型瓷球要高；手搓成型瓷球的磨损率随时间增加而增加，等静压成型瓷球的磨损率随时间增加而相应减小。     

THE SORPTION OF COBALT FROM AQUEOUS SOLUTIONS BY POTASSIUM NICKEL HEXACYANOFERRATE COMPLEX

ABSTRACT

The inorganic complex, potassium nickel hexacyanoferrate, KNiFC, was used for the separation of cobalt from diluted nitric acid aqueous solutions using the batch technique. The effect of hydrogen ion concentration on the distribution coefficient of cobalt has been studied in the pH range 2–5.5. The effect of particle size and temperature on the sorption isotherm and rate of uptake of cobalt were investigated. The increase of temperature was found to enhance the sorption equilibrium and rate of uptake. The diffusivity of cobalt ions into different particle sizes of KNiFC was calculated. The effect of the presence of cesium ions on the rate of uptake of cobalt is presented.     

预测水化水泥浆体离子扩散性能的一种新方法

为了预测水泥基复合材料的离子扩散性能并进而将其用于耐久性研究与寿命预测模型中,基于Einstein-Smoluchowski公式,提出了一个将宏观离子扩散行为和微观粒子Brown运动相关联的方法。为了验证这个方法的可靠性,首先用计算机模拟的方法生成一个水化水泥浆体的微观结构(HYMOSTRUC3D),然后用自回避随机行走算法预测这个微观结构的离子有效扩散系数。在这个过程中,应用统计分析的方法确定了水泥浆体微观结构的代表性体积单元的大小,此后在这个代表性体积单元的基础上,通过与文献数据比较,验证了用该方法预测水泥浆体宏观氯离子扩散行为的合理性,最后应用该方法预测了水泥浆体氯离子有效扩散系数随水胶比和养护龄期变化的关系。     

混凝土中氯离子迁移特征的表征

混凝土中氯离子的迁移是个非常复杂的过程.一般将测量和计算硬化水泥浆体和混凝土中氯离子的迁移的方法分为非稳态和稳态两大类.对混凝土中氯离子迁移的测试方法进行了评述,并分析了其优点和缺点.北欧标准NTBuild492是目前非稳态条件下快速测试氯离子扩散性最好的方法,但实际的氯离子浓度分布与其计算公式用的模型的模拟仍存在一定的差异.北欧标准NT Build 355是目前稳态条件下快速测试氯离子扩散性最好的方法,但理论基础过于简化.尽管ASTM C1202或AASHTO T277在世界上被广泛应用,但实际上它是一个测量混凝土电导的方法,它可用于混凝土的质量控制,如其结果没有与混凝土的氯离子渗透性试验结果建立相关性时,不能直接用于评价混凝土的氯离子渗透性.     

用不同粘土矿物合成Sialon粉末的研究

本文以高岭土、蒙脱石、叶腊石为原料,将粘土矿物与碳混合,加入适量的添加剂,在Ｎ２气氛１４００°Ｃ下,经４ｈ碳热还原氮化合成Ｓｉａｌｏｎ,产物经ＸＲＤ、ＸＰＳ、ＥＰＭＡ等分析,结果表明：用不同粘土矿物合成Ｓｉａｌｏｎ,矿物的Ａｌ／Ｓｉ比与碳的含量直接影响最终的合成产物,但主晶相仍为Ｚ＝３的β′－Ｓｉａｌｏｎ。     

热塑性复合材料制件热残余应力产生原因及测试方法分析

纤维增强热塑性复合材料以其优异的综合性能被广泛用于大型民用飞机结构,但在复合材料成型过程中基体材料需要经历较高的工艺温度和降温速率;增强纤维和聚合物基体之间因热膨胀系数不匹配、铺层间各向异性和温度的梯度分布等因素将导致在基体中形成热残余应力,这将对所得热塑性复合材料构件的力学性能产生影响,需要在复合材料结构的设计和分析中加以考虑。为有效控制和降低复合材料制件中热残余应力,需要对其产生来源及发展机理进行分析。对热塑性复合材料中热残余应力的形成原因从三个不同层次进行讨论,并分析热塑性复合材料在成型过程中残余应力水平的控制方法,最后对热残余应力的测试方法进行研究,评价了各测试方法的优缺点。