Strontium Separation with Ultrafiltration Membranes from Dilute Aqueous Solutions

Abstract

The separation of Sr²⁺ from dilute and trace solutions of low activity by means of hollow fiber Amicon ultrafiltration membranes is studied. The cation is absorbed on colloidal particles of titanium oxide formed directly in solution, and the colloidal dispersion is filtrated. The method has been studied under several different operative conditions (pH, Ti/Sr ratio, the presence of interfering ions, colloid formation time) with the aim of determining the optimum conditions to develop a separation process.     

Serum Protein Fractionation by Membrane Processes: Centrifugal Ultrafiltration,Osmosedimentation, and Multistage Ultrafiltration

Abstract

Whole sera proteins may be fractionated according to their molecular weights by using three membrane techniques: centrifugal ultrafiltration, osmosedimentation, and multistage ultrafiltration. Ultrafiltration or dialysis cells were mounted in the swinging baskets of a centrifuge in all three cases, with the membranes aligned parallel to the centrifugation radius. As a result, solute accumulated over the membrane was convectively removed from its surface, thus preventing membrane polarization and fouling. During these experiments, smaller proteins migrated across the membrane, leaving behind the larger ones. Multistage filtration experiments were performed using cells fitted with three different membranes of successively narrower pores. Four different fractions were thus obtained and analyzed by gel permeation chromatography; separation factors as high as 2000 were obtained.     

Solute Separation by Continuous Bubble Fractionation

Abstract

A continuous bubble fractionation system consisting of a vertical Plexiglas tube provided with a source of air bubbles, means of continuous liquid feed, overflow, and bottom effluent has been operated to study the performance of the system. The study primarily involves an examination of the effects of variables such as gas rate, liquid rate, solute concentration, and column size on the effectiveness of the system for separating an organic solute from a dilute aqueous solution.

The experimental results indicate that the effects of gas and liquid rate on the performance have generally followed the results expected from an equilibrium adsorption of a surfactant on the gas-liquid interface described by Gibbs' equation and material balances. An increase in gas rate increased the effectiveness of the system by providing more adsorption surface. The adverse transfer of the solute by the eddy diffusion caused by rising bubbles was found to be the factor limiting the effectiveness of the system.     

超滤和纳滤膜分离提取纳他霉素

为提高纳他霉素(natamycin)生产提取得率,减少溶剂使用,本文采用超滤、纳滤操作对工业生产的纳他霉索发酵液进行处理。实验结果表明:操作压力、操作时间及料液流速对超滤过程有很大影响。通过超滤可将蛋白质等大分子杂质去除,然后再用纳滤膜对超滤渗透液进行浓缩纯化,对纳滤工艺的操作条件如进料压力、料液pH、浓缩倍数等进行了研究。采用超滤、纳滤技术提取纳他霉素,其收率可达62.74%。     

糖-蛋白质混合体系泡沫分离过程研究

利用环流泡沫分离技术对若干糖 -蛋白质 (牛血清白蛋白 )混合模拟体系进行了分离实验 ,研究了 p H值对溶液表面张力和分离效果的影响 ,在综合考虑蛋白质泡沫夹带量、去除率、糖的损失率及分离因子的基础上 ,得到了泡沫分离的最优 p H值。研究结果表明 ,采用环流泡沫分离技术可以实现糖与蛋白质的分离 ,是生物多糖与蛋白质初级分离的一种有效方法     

Separation of Cyanide Ions by Foam Fractionation

Abstract

The technique of adsorption of cyanide ions on foam bubbles was studied as an alternative to chemical oxidation which is practiced in cyanide waste treatment. The technique of foam fractionation was previously applied to the removal of heavy metals and proved to be successful. The free cyanide ions and complex species both responded positively to the formation of a separate foam phase. The results obtained so far show that satisfactory separation of cyanide compounds is possible if certain parameters are properly selected. There are other factors which have not been investigated before, and they seem to have a major role in the performance of this operation.     

高分子分离膜的研制与应用

介绍了聚砜超滤膜、纳滤膜、聚乙烯醇膜、中空纤维富氧复合膜等的合成与研究进展,并对各种膜的应用、现状与发展进行了阐述。     

Treatment of Aqueous Ionic Surfactant Solutions by Dynamic Ultrafiltration

Abstract

This paper investigates the reduction of concentration of an ionic surfactant (sodium dodecyl benzene sulfonate) present in an aqueous solution by ultrafiltration. A dynamic filtration system consisting of a metal disk rotating near a flat circular organic membrane was used in this study. Membranes cut off tested were 10, 20, and 50 kDa. The maximum rejection rate was 92% at 10 kDa. Permeate fluxes kept increasing with transmembrane pressure until at least 1400 kPa, reaching 400 Lh^?1m^?2 at 10 kDa and 950 at 50 kDa for a rotation speed of 1000 rpm. However, raising the rotation speed above 500 rpm at 900 kPa had only a moderate effect on performance, indicating probably strong interactions between surfactant molecules and the membrane and that the permeate flux was mostly limited by pressure.     

超滤膜分离研究

简要介绍了超滤技术的原理、应用、超滤膜的改性和污染问题。     

Separation of Tea Saponin by Two-Stage Continuous Foam Fractionation

A technology of two-stage continuous foam fractionation for tea saponin recovery was studied for increasing both the enrichment ratio and the recovery percentage. In the first stage, the effect of air flow rate, the initial pH, the feed flow rate, and the feed position were studied at a temperature of 60°C. The results showed that when the conditions of the first stage were at a temperature of 60°C, air flow rate 150 mL/min, pH 5.3, feed flow rate 1.92 mL/min, and feed position at the interface between the liquid phase and the foam phase, the enrichment ratio, and the recovery percentage of tea saponin were 4.02 and 56.4%, respectively, and the effluent solution was added to the second stage as the initial solution. When the conditions of the second stage were at a temperature of 30°C and an air flow rate of 300 mL/min, the recovery percentage of tea saponin reached 47.6%, and the foamate was added to the first stage as feed solution. The total recovery percentage of tea saponin reached 86.3% by the two-stage continuous foam fractionation.     

泡沫分离法分离桔梗皂苷的工艺研究

采用间歇式泡沫分离法对桔梗提取液中的桔梗皂苷予以分离工艺条件研究;实验以富集比、回收率以及带液率为指标衡量分离效果,在单因素试验基础上,通过正交试验法,获得桔梗皂苷的最佳分离条件。结果表明分离桔梗皂苷的最佳工艺条件为:进料浓度0.014 mg/m L,气体流速700 m L/min,温度30℃,表面活性剂用量(0.505 mg/m L)30 m L,回收率为77.58%,富集比为2.50,带液率为21.67%。因此泡沫分离桔梗皂苷是一种简单、有效、可行的分离方法。     

超滤系统存在的问题及改进

介绍了高压法三聚氰胺装置中超滤系统的工艺特点,对其在应用中所存在的有关问题进行了分析与总结并介绍了相应的处理措施,有利的保证了超滤系统的稳定运行。     

Enantiomeric Separation of Tryptophan by Ultrafiltration Using the BSA Solution System

Abstract

The optical resolution of racemic tryptophan was performed by ultrafiltration using the BSA solution system. The pH of the feed solution had a strong influence on the complexation constants between BSA and tryptophan, especially for L-tryptophan. The complexation constant for L-tryptophan reached a maximum value at pH 9 (K _L = 110,000), varying by 2 orders of magnitude in the range from pH 6 (K _L = 1000) to pH 11 (K _L = 21,000). Smaller variations of the complexation constant of D-tryptophan were observed. Based on these data, the recovery and the purity of the permeate were optimized by a proper control of the physicochemical parameters of the feed solution (essentially pH and initial concentrations). In one stage, 91% purity with a 89% recovery of D-tryptophan has been easily obtained with a high permeation rate (6.3 × 10^?4 mol·m^?2s^?1 at 1.5 bar).     

Removal of Dyes from Aqueous Solutions by Low Pressure Batch Ultrafiltration

Abstract

The use of a low pressure batch ultrafiltration method to separate dyes from aqueous solutions was investigated at 22°C. Several factors affecting the membrane performance, such as the hydraulic permeability and the rejection coefficient, were examined, including initial dye concentration, the operating pressure, as well as especially the membrane material and the ionic nature of dye molecules.     

Separation of Whey Proteins using Cascaded Ultrafiltration

Whey protein isolate, containing α-Lactalbumin and β-Lactoglobulin, was separated by using a continuous three-stage ultrafiltration cascade system. Single-stage experiments were optimized to enable good and stable cascade operation. Three different cascade configurations, a non-constrained ideal system (Configuration A), and adapted version (Configuration B), and a countercurrent cascade (Configuration C) were experimentally tested and compared. The countercurrent cascade system showed the traditional trade-off between yield and purity. Both the adapted cascade system and the non-constrained ideal cascade gave better performance in terms of recovery and purity and show potential for application, albeit for different purposes.     

Ultrafiltration of Albumin-Ethanol Solutions on Mineral Membranes

Abstract

This paper investigates the ultrafiltration of albumin-ethanol solutions on ZrO₂ mineral membranes for the preparation of human albumin from plasma. The classical process consists of a preconcentration phase of a 20% ethanol-albumin 7.5 g/L solution to raise albumin concentration to 80 g/L, then a diafiltration to reduce ethanol concentration to less than 0.3 g/L, and a final concentration to adjust albumin concentration to its final value of 210 g/L. The potential advantages of mineral membranes relative to the polysulfone membranes presently used are a longer membrane life and higher permeate fluxes in the presence of ethanol. In addition, they lend themselves to the use of back flushing or pulsatile flows for reducing membrane fouling. Using 2.7 mm i.d. Carbosep membranes with a 10 kd cut-off and velocities of 7 m/s, permeate fluxes of 40 L/hμm² at 4[ddot]C were obtained with 50 g/L albumin, 20% ethanol solutions representative of the preconcentration phase, while 45 to 50 L/hμm² were obtained at albumin concentrations of 100 g/L without ethanol at 8[ddot]C, representative of the final concentration phase. These fluxes compare favorably with fluxes obtained previously in our laboratory with polysulfone membranes which were respectively of 22 and 40 L/hμm² for the same solutions. This study confirms the expectation of a smaller reduction in the presence of ethanol of the permeate flux for the mineral membranes while albumin concentration in the permeate remained generally under 0.4 g/L irrespective of retentate concentration. The superposition of pressure and flow pulsations on the filter inlet by a piston-in-cylinder system decreases concentration polarization and increases permeate flux by 50 to 60% as compared with steady flows under the same conditions.     

A Numerical Study of the Apparent Selectivity in the Fractionation of Two Macromolecules by Ultrafiltration

The fractionation of two macromolecules by ultrafiltration in a parallel plate cell was studied by computational fluid dynamics (CFD). The in-house code developed takes on account of the pressure drop, the variation of the permeate velocity along the cell, the concentration polarization over the membrane, and the variation of the transport properties and of the osmotic pressure with the concentration of the solutes. A convective-diffusive model, to simulate the solute transmission, was also adopted. The real and apparent selectivity, local and mean, were determined, in order to study the effect of transmembrane pressure, Reynolds number, inlet solute concentrations, specific area of the membrane pores, and membrane resistance. The code was applied to study the separation of Bovine Serum Albumin (BSA) and Dextran-T10 macromolecules. The mean apparent selectivity increases with increasing transmembrane pressures until it reaches a maximum after which it decreases. The mean apparent selectivity increases with increasing Reynolds number consequence of a polarization decrease. Moreover, the selectivity increases with a decrease of the pore size and, also, with an increase of the membrane resistance. For low inlet concentrations of the solutes, the variation of the physical properties with the concentration does not produce any appreciable effect on the apparent selectivity.     

超滤-醇沉法从发酵液中提取1,3-丙二醇

介绍了超滤-醇沉法从发酵液中提取1,3-丙二醇的工艺. 首先通过超滤,菌体、蛋白质与核酸的去除率分别为99%, 89.4%和69%,然后减压蒸馏浓缩发酵液,最后醇沉浓缩发酵液,使核酸、多糖、蛋白质等生物大分子沉淀析出,乙醇加入量与浓缩发酵液的最佳体积比为2:1. 粗产品中总蛋白和核酸与发酵液相比分别减少了97.4%和89.7%,溶液电导率下降了95.8%. 考察了浓缩发酵液的含水量、pH值对醇沉效果的影响及醇沉对发酵液中蛋白质、核酸、盐类的去除效果. 实验发现,浓缩液含水量越低,醇沉效果越好,浓缩发酵液含水量为1%时,杂质去除率达90%以上. 浓缩发酵液pH值的变化对醇沉杂质的影响较大,强碱和强酸条件下可沉淀出大量杂质.     

Ultrafiltration Behavior of Organic Mixtures Simulating Sweetwater Solutions

In the present study, attempts were made to examine the filtration behavior of organic mixtures (oleic acid-triglycerides) compared to single organic solute (triglycerides) contained in synthetic glycerol-water solutions (known as sweetwater). Furthermore, the rejections of individual solutes were studied. The TG-FA mixtures permeated preferentially when compared with single TG which is mainly due to the solubility as well as diffusivity of small fatty acid in the TG-FA mixtures. Furthermore, PVDF membrane provided higher fluxes and experienced less fouling than PES membrane for both cases. In case of the PVDF membrane the rejection of fatty acid was 6.20% while oil rejection in glycerol-water plus TG and TG-FA mixtures was 82.42% and 84.67%, respectively. However, the PES membrane underwent higher fatty acid rejection (20.93%) as well as oil rejection in single TG (94.70%) and TG-FA mixtures (91.08%). It is noteworthy that the nature of the membrane, membrane MWCO, and the feed characteristics had a significant effect on the fouling potential and filtration performance.