Chitosan/Gelatin Blend Membranes for Pervaporation Dehydration of 1,4-Dioxane

Abstract

This paper deals with the development of compatible blend membranes of chitosan (CS) and gelatin (GL) by solution casting and crosslinking with glutaraldehyde. The membranes were tested in pervaporation (PV) dehydration of 1,4-dioxane. Membrane characterizations by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, and a universal testing machine were done to understand their physicochemical properties and for their suitability under PV conditions. The blend membranes were more water selective compared to pristine chitosan membrane at 30°C. Flux increased with increasing wt.% of water of the feed and also by increasing the gelatin content of the blend, but selectivity decreased. Sorption experiments gave information on the interaction between feed mixture and membrane polymers. Membranes of this study could extract nearly 97 wt.% of water from the feed mixture. Arrhenius activation parameters and diffusion coefficients estimated from a temperature dependence of PV results could explain the PV results satisfactorily.     

Methodology for advanced measurement accuracy of the overall volumetric oxygen transfer coefficient with application to hydrocarbon–aqueous dispersions

Accurate quantification of the overall volumetric oxygen transfer coefficient (K_La) is essential for the success of aerobic bioprocesses. In hydrocarbon‐based bioprocesses where K_La is depressed at higher viscosities, this is particularly critical. In this study an accessible methodology for K_La determination has been developed and validated for alkane‐based systems under a wide range of process conditions. Critical to measurement accuracy in around 90% of the K_La values was the incorporation of the response lag. Neglect of the response lag resulted in errors greater than 5% above K_La = 0.3K_p to K_La = 0.6K_p (where K_p is the inverse response lag or probe constant), at least 1.5‐fold to 3‐fold lower than the analogous K_La in water. Further, K_p varied significantly with both alkane concentration and chain length. A sensitivity analysis confirmed ? 25% to 90% error in K_La with 30% over‐ and under‐estimation of K_p respectively. When incorporating K_p values specific to the process conditions, accurate K_La values were confirmed in 0 to 20% (v/v) C_10–13 and C_14–20 aqueous dispersions over 600 to 1200 rpm agitation. Copyright © 2012 Society of Chemical Industry     

Swelling and Diffusion Properties of Poly(acrylamide-co-maleic acid) Hydrogels: A Study with Different Crosslinking Agents

Crosslinked hydrogels comprising acrylamide (AAm) and maleic acid (MA) were synthesized by free radical polymerization in presence of a crosslinker using ammonium persulfate (APS) and N,N,N¹,N¹-tetramethylethylenediamine (TMEDA) as initiator and activator, respectively. The crosslinked hydrogel formation was confirmed by IR analysis. The swelling/de-swelling characteristics were studied in detail for crosslinked poly(acrylamide-co-maleic acid) [poly(AAM-co-MA)] hydrogels containing different amounts of maleic acid. Four different crosslinkers such as 1,2-ethyleneglycol dimethacrylate (EGDMA), 1,4-butanediol diacrylate (BDDA), 1,6-hexanediol diacrylate (HDDA), and diallyl phthalate (DP) were utilized to study their influence on the swelling behavior of the hydrogels. The effect of reaction parameters such as the concentration of crosslinker and initiator on swelling capacity of the crosslinked poly(AAm-co-MA) hydrogels was also investigated. Further, the influence of various salts, simulated biological fluids, and pH solutions on the swelling pattern of hydrogels was studied extensively. Phase separation morphology of crosslinked hydrogels was also studied by differential scanning calorimetry. The morphology of crosslinked hydrogels were revealed using scanning electron microscopy (SEM).     

UST条干仪测试的影响因素及控制

分析 U ST条干仪测试原理 ,阐述长丝 UST条干仪测试误差、差错的产生及消除方法 ;操作环境对测试的影响及控制 ;正确选用测试条件的方法 ,以及稳定、正确操作的必要性。     

多组元溶液分相条件的探讨

本文通过改型的UNIQUAC方程 ,利用NEWTON RAPHSON法计算了二元、三元及四元液液平衡数据。从中发现 ,当具有部分互溶性质组分的活度系数发生突变时 ,则该体系就会出现分层现象。为此 ,本文认为具有部分互溶组分活度系数的突变可做为多组元溶液分相的判据。     

氯乙烯悬浮聚合计算机在线实时检测及智能化

以实现氯乙烯悬浮聚合过程智能化为目的,在计算机集散控制的基础上,组建在线实时检测流程,建立检测和计算模型,开发数据采集处理、模型计算、结果显示界面等软件,建成计算机在线实时聚合转化率、聚合速率、传热系数检测系统。经对约200釜聚合过程的在线实时检测,最大误差在2％以内。该系统的开发应用对于优化引发剂体系和操作条件,缩短聚合时间、提高聚合釜生产强度有着重要的作用。     

Effect of electro-chemical properties of sodium salts of various anions on their diffusional parameters in symmetrical cellulose acetate membranes

A relation was obtained between electro-chemical properties of sodium salts (NaCl, NaBr, and Na₂SO₄), and the thermodynamic property of permeability in symmetrical cellulose acetate membranes, the distribution coefficient K and the kinetic property, the overall diffusion coefficients D. K and D were obtained by the method we proposed using measured unsteady- and steady-state dialysis data. The K values increase with the increase of water content and are in the range of 10⁻² for sodium halides and 10⁻³ for Na₂SO₄. D is found to increase with the increase of the solute concentration, and the extrapolated values of D to zero concentration D⁽⁰⁾ are obtained as 0.015–0.03 μm²/s and increase with the increase of water content in the membrane. D can be divided into the concentration independent diffusion coefficients in the dense part of the membrane D_d and in the porous D_p, applying a two-part (perfect or dense and imperfect or porous) model of the membrane. Contrary to D_d, D_p increases with the increase of W_w and can be correlated as D_p,c = _d exp (γ × W_w). It is shown that the averaged D_d, _D increases with the increase of the quantity of the ionic mobility u of the solutes at infinite dilution divided by valence, and that the parameter γ increases with the increase of the ionic mobility u. The value of K increases slightly with the increase of water content and decreases with the increase of the Flory—Huggins parameter χ. The Flory—Huggins parameter χ is calculated from the measured values of distribution coefficients and data obtained from the literature. And it was found that the gradient of linear decrease of χ (λ_cation) depends on equivalent ionic conductivity of anion of salt, λ_an.     

A SHORT-CUT METHOD FOR DETERMINING CONCENTRATION DEPENDENT DIFFUSIVITY IN LIQUID FOODS AND POLYMER SOLUTIONS FROM REGULAR REGIME DRYING CURVES

A simple method for determining concentration (water or solvent content) dependent diffusivity in liquid foods and polymer solutions from the regular regime drying curve was developed on the basis of the power-law diffusion model. The method was first tested to the drying data generated from numerical solutions of the diffusion equation with various types of concentration dependent diffusivities. The present method was found to be very simple yet accurate compared with the previous methods. Then, the drying rates of various sugar solutions experimentally obtained were analyzed on the basis of the present method to determine the moisture content dependent diffusivities.     

Oil viscosity measurement by ultrasonic reflectance

Pulses of shear-mode ultrasound (center frequency 10 MHz) are reflected from the surface of a series of vegetable and synthetic high-viscosity calibration oils at a range of temperatures (5–50°C). For all samples and temperatures there is a single negative correlation between the magnitude of the echo from the interface between the delay-line and the sample and the viscosity of the sample. Similar experiments with longitudinal ultrasonic waves show the amount of sound reflected decreased with increasing viscosity, but there is no single correlation for all samples.     

不同异氰酸酯型聚氨酯弹性体的制备与力学性能研究

采用不同结构的异氰酸酯和多元醇制备了一系列聚氨酯弹性体,主要考察了异氰酸酯种类对聚氨酯弹性体力学性能的影响.研究表明,由1,5-萘二异氰酸酯制得的弹性体拉伸强度和撕裂强度较高,分别为38.75MPa和109.77 kN/m,而由对苯二异氰酸酯制得的弹性体具有最大的扯断伸长率(557.84％).此外还研究了多元醇种类和扩链系数α对弹性体力学性能的影响,研究表明,选用聚ε-己内酯二醇制得的弹性体具有较好的性能,且拉伸强度和撕裂强度均随扩链系数的增大先增大后减小,而扯断伸长率一直增大.