Gel Permeation Chromatography Column Packings—Types and Uses

Abstract

Proper selection of the column packing material is an essential part of a successful gel permeation analysis. Generally the desirable properties of a packing are good chemical, thermal, and mechanical stabilities combined with good resolution and low resistance to liquid flow. Pore size distribution, particle size distribution, polar characteristics, as well as other physical parameters play a role in how well a packing will perform. This paper describes the different types of column packings which are commercially available, as well as briefly mentioning several packings used on an experimental scale. Physical characteristics of the various packings are compared. Suggested uses along with some limitations are given.     

SIMULATION AND OPTIMIZATION OF THE ELECTRO-REDUCTION PULSED COLUMN FOR THE SEPARATION OF URANIUM AND PLUTONIUM

ABSTRACT

A computational model for separation of uranium and plutonium in an electro-reduction pulsed column was developed based on the diffusion model. The model contained steady state simulation, dynamic simulation, and optimum calculation. A numerical calculation method for this model has been proposed. With this model, a calculation for an electro-reduction experiment of uranyl nitrate in a pulsed column was carried out. The calculated results were consistent with the experimental results in the literature. A comparison of the dynamic and the steady state simulations at equilibrium and an optimum calculation were also conducted. This model provides a guide for further experimental study of this process.     

CO2 Absorption Behavior with a Novel Random Packing: Super Mini Ring

Abstract

For the purpose of capturing CO₂ from flue gas the absorption of CO₂ into an aqueous solution of monoethanolamine was measured by using a column packed with a novel packing, Super Mini Ring (SMR). The SMR gave a higher absorption performance relative to pall ring packing due to a larger effective surface area and also reduced the frictional pressure gradient. The absorption mechanism was observed to be mainly gas phase controlling. It was concluded that for the treatment of flue gas the SMR packing could reduce the height of the absorption column by 20% relative to a pall ring packed column.     

EVALUATION OF PACKED COLUMNS IN SUPERCRITICAL EXTRACTION PROCESSES

The purpose of the present work is to add to the base of knowledge in the use of packed columns when used in supercritical extraction service. Experimental studies were performed on a 2·54 cm diameter supercritical fluid extraction column operated in both spray and packed column arrangements. The packing used was 6· mm Raschig rings with a surface area of 722 m²/m³. The supercritical systems studied were carbon dioxide/ethanol/water and carbon dioxide/isopropanol/water at 102 atmospheres and 35^°C and 102 atmospheres and 40^°C, respectively. In order to compare supercritical with conventional extraction, similar data were obtained in the same column with the toluene/acetone/water system at one atmosphere and 24^°C.     

复合塔板的流体力学特性(Ⅱ) 操作变量和液体物性对塔板流体力学特性的影响

在前文工作的基础上进一步研究了同时具备大孔径和高开孔率条件的复合塔板 ,研究了操作变量和流体的物理性质对该复合塔板流体力学性能的影响 .结果表明 :液体的密度增加 ,塔板压降增加 ,漏液量增加 ;黏度增加 ,塔板压降降低 ;表面张力减小 ,漏液点速度上升 ,雾沫夹带增大 ,液泛速度下降.     

Dehumidification of Air by Aqueous Lithium Chloride in a Packed Column

Abstract

A packed bed absorber-stripper system has been designed to dehumidify moist air by contact with aqueous solutions of lithium chloride. The packing material used in the study is 1.6 cm (5/8 inch) polypropylene Flexi rings, which have a surface to volume ratio of 342 m²/m³ (104 ft²/ft³). The absorber is capable of handling air face velocities from 3362.4 to 6746.4 kg/m²h and liquid flow rates from 2534.1 to 54648 kg/m²h. Solutions of 30% and 40% lithium chloride in water were employed as the dehumidifying agent. The minimum liquid flow rate calculated from the equilibrium data would be too low to wet the packing surface completely, and could not be used in the actual operating system. Therefore, liquid flow rates greater than the minimum wetting rate for the packing were used. Measured flooding conditions corresponded closely with exiting empirical correlations. Mass transfer coefficients ranged from 0.062 kmol/m³s at 40% flooding to 0.166 kmol/m³s at 80% flooding for the 40% lithium chloride solution. The height of a transfer unit calculated from the experimental data ranged from 0.340 m at a column efficiency of 71.6% to 0.617 m at a column efficiency of 50%.     

Gel Permeation Chromatography Using a Bio-Glas Substrate Having a Broad Pore Size Distribution

Abstract

Gel permeation chromatography has been performed using a porous glass of broad pore size distribution, which was subjected to hexamethyl-disilazane treatment. The elution volumes and peak widths of narrow molecular weight distribution polystyrenes using toluene as solvent have been determined. The physical characteristics of the porous glass have been studied by the methods of mercury porosimetry. nitrogen ad-sorption-desorption isotherms, and electron microscopy. The characteristics of this column packing material are compared with other packing materials in popular use.     

聚丙烯填料的生物亲和亲水磁化改性对其润湿及挂膜性能的影响

引　言生物填料是生物膜水处理技术的核心之一 ,目前生物填料种类繁多 ,按常用的安装方式分为固定式 (主要有蜂窝状和波纹板状硬性填料 )、悬挂式(包括软性填料、半软性填料、组合填料和弹性填料 )和分散式 (散堆式和悬浮式填料 )等几种类型 .生物填料主要以聚丙烯、聚乙烯、聚氯乙烯或聚酯等高分子材料为原材料而制成 .在实际应用中 ,人们发现以这些材质制成的填料 ,其亲水性能(材料表面吸附水分的能力 )和生物亲和性 (生物相容性与生物活性 )较差 ,导致生物填料表面润湿、传质性能和微生物附着生长特性欠佳 ,在微生物挂膜启动速度、挂膜量…     

热扩散塔分离甲烷和氢的实验研究

引言用甲烷直接合成C_2以上的碳氢化合物非常困难,例如,由甲烷脱氢合成乙烯,按热力学计算在1000K下甲烷的平衡转化率只有4.8％,所以至今甲烷仍主要用作燃料．为了充分利用这一化工基础原料,作者利用热扩散塔进行了甲烷的催化脱氢反应,使反应与分离同时进行,大幅度提高了甲烷的转化率．为考察热扩散的分离效果,本文用甲烷脱氢反应的主要成分甲烷和氢混合物为原料,在热扩散塔中分别进行了空塔和填料塔的热扩散分离实验,考察了一些操作参数对分离效果的影响,以期对反应操作条件提供必要的参考．l原理所谓热扩散现象,就是在温度场…     

Scale-up of Hollow Fiber Extractors

Abstract

The performance of a commercial-scale hollow fiber extraction system was investigated by the Separations Research Program (SRP) at the University of Texas at Austin. In this work, hexanol was extracted from water into octanol using a large-scale extraction/distillation system. In the membrane extractor studies, the octanol-rich phase was fed on the tube-side while in the packed column studies, the octanol-rich phase was chosen as the dispersed phase. This chemical system was selected because of its high solute distribution coefficient. As a result, the required solvent to feed ratio was low which creates hydraulic problems for conventional dispersive extractors such as the packed column. Under identical operating conditions, the mass transfer performance of the hollow fiber extractor compared favorably with that of a commercial-scale type 2 structured packing. A height equivalent to a theoretical stage (HETS) of 1.5 meters was obtained with the membrane extractor as compared to 15 meters for the type 2 structured packing. A staged hollow fiber extraction mass transfer model for scale-up was developed and found to agree with data obtained in this work and with data obtained earlier using the n-butanol/succinic acid/water system.     

塑料花心球填料流体力学及传质性能研究

在φ600填料塔中。用空气-氨-水系统分别对φ30、φ40花心球形填料进行流体力学及传质特性实验研究。结果表明此种填料由于各向同性,对液体有良好的分散作用,其性能与同尺寸环矩鞍相当。     

Ligand-Exchange Chromatography of Some Amino Acids on Co(II)-Loaded CMDAE-Sporopollenin Resin

Abstract

Sporopollenin obtained from Lycopodium clavatum has been modified as an ligand-exchange material. In this study, the possibility of using sporopollenin as a ligand exchanger in the chromatographic separation of amino acids is examined. Since sporopollenin has important advantages (it is stable to chemicals and has a constant mesh size), it can be used as a column packing material. By first treating sporopollenin with 1,2-diaminoethane and then with bromoacetic acid, carboxylated diaminoethylsporopollenin (CMDAE-sporopollenin) was obtained. This new resin was loaded with Co(II) transition element and used as a ligand-exchange material in the separation of amino acids. Using the ligand-exchange technique on Co(II)-loaded carboxylated diaminoethylsporopollenin is a suitable chromatographic method for the separation of most common amino acids.     

NATURAL ZEOLITES IN AIR DRYING

ABSTRACT

The local clinoptilolite from Bigadis region in Turkiye, was used for air drying in packed column. The effective diffusion coefficient of water in natural zeolite was found as 5×10^?10 m² s^?1 from isothermal uptake measurements. Effects of packing height and airvelocity on breakthrough curves were studied.     

ION EXCHANGE CHROMATOGRAPHIC SEPARATION AND MS ANALYSIS OF ISOTOPES OF BORON

ABSTRACT

Using electrochemical techniques sch as pH-metry and conductimetry, the choice of a suitable complexrng reagent was made amongst ethylene glycol, propylene glycol, dextrose and mannitol for cost-effective separation of isotopes of boron by ion 'exchange chromatography. Quantitative relationships between pH and concentration; pK_a and concentration of each of these complexing reagents were determined by least square polynomial curve fitting and an attempt was made to determine the formation constants of mannitol - borate complexes. The results of experiments carried out for selection and regeneration of a resin; separation factor determinations using batch as well as column techniques, and monitoring of band movements using these electrochemical techniques are discussed.     

Short-Fiber Chromatography Columns: Potential for Process-Scale Bioseparations

Abstract

Chromatographic supports with short-fiber geometry have been evaluated for process-scale applications. Using a prototype silica-based ion-exchange fiber and bovine serum albumin as the model biomolecule, a comparison of the throughput characteristics of fiber columns with those of conventional columns (spherical packing) has been made. The comparison accounts for the influences of pressure drop, adsorption thermodynamics, and mass transfer. It has been shown that retention characteristics, mass dispersion, and intraparticle mass-transfer resistance are critical in determining which column has a higher throughput. In general, if the capacity factor of the desired product is high, it is predicted that the fiber column will give higher throughputs, except for separations that involve closely eluting impurities. Based on these results, guidelines detailing desired properties of short-fiber chromatographic supports are provided.     

THE BULK AND SURFACE STRUCTURE OF γ-ALUMINA

This paper presents the real-time application of the learning control theory to the control of a chemical pilot plant: a pulsed liquid-liquid extraction column.

The behaviour of an agitated liquid-liquid extraction column can be related to random mechanisms such as the phenomena of droplets breakage and coalescence. Previous studies on hydrodynamic and mass transfer aspects showed that a pulsed liquid-liquid extraction column had an optimal behaviour for operating conditions close to flooding. These results led to choose the following strategy to control the column in its optimal behaviour zone:

- the measure of the conductivity of the liquid medium below the distributor which gives a good information about flooding, is the controlled variable

-the pulse frequency is the control action.

The learning control algorithm is based on a multilevel system of automata which operates in a random environment. By means of an evaluation unit of the performances of the column which generates either penalty (inaction) or reward on the basis of heuristic rules, the automaton chooses a value of the pulse frequency. This approach is essentially connected to artificial intelligence in so far as human knowledge on the plant is included in these rules.

This algorithm has been implemented on a microcomputer for control purposes. The experimental results presented show the good performances of the approach.     

Effects of Porosity and Surface Area of Octadecyl-Derivatized Silica on Fractionations of Oligomers of 800 MW Polystyrene

Abstract

Increasing the pore size of silica used to produce a C₁₈-derivatized column packing decreased the exclusion of the larger oligomers of an 800 MW sample of monodisperse polystyrene. More important was the decrease in surface area which degraded the fractionation of oligomers, which was based upon adsorption. Larger sample volumes and higher concentrations also degraded that fractionation, as expected.     

PREDICTION OF BREAKTHROUGH CURVE OF METAL ION ON EXTRACTION CHROMATOGRAPHIC COLUMN

ABSTRACT

A mathematical model to predict the breakthrough curve of metal ion on an extraction chromatographic column was proposed. This model, which is the extension of that proposed in the previous paper (12), consists of the mass transfer equation of metal ion into a polymer gel impregnated with an extractant and the mass balance equation of chromatographic column. SDB (styrene-divinylbenzene copolymer) gels impregnated with CMP (dihexyl-N,N'-diethylcarbamoylmethylphosphonate), CMPO (octyl(phenyl)N,N'-diisobutylcarbamoylmethylphosphine oxide) and the equimolar mixture of CMP and CMPO were prepared. The column experiments for the extraction of Ce(III) from an aqueous solution containing nitrate ion were carried out. The predicted breakthrough curves of Ce(III) for the gels impregnated with CMP and the mixture of CMP and CMPO were in good agreement with the experimental ones. That for the gel impregnated with CMPO, however, overestimated the experimental data. This is due to adhesion among gel particles which is caused by the deliquescence of CMPO and not attributable to the mathematical model. These results suggest that the proposed model is applicable to the prediction of breakthrough curve and available as a design tool of extraction chromatographic column.     

Boron Isotope Fractionation in Liquid Chromatography with Boron-Specific Resins as Column Packing Material

Abstract

Boron-specific resins with n-methyl glucamine as the functional group were used as column packing material of liquid chromatography for boron isotope separation. The shapes of chromatograms in reverse breakthrough experiments were heavily dependent on the pH of the eluents, and there existed a pH value at which a chromatogram of the displacement type was realized nearly ideally. The value of the single-stage separation factor for the boron isotopes varied between 1.010 and 1.022, depending on the temperature and the form of the resins. The existence of the three-coordinate boron species in addition to the four-coordinate species in the resin phase is suggested.     

EXTRACTION OF COPPER BY LIX65N IN A VESSEL AND A MULTI-STAGE COLUMN UNDER STIRRED CONDITIONS

ABSTRACT

The extraction experiments of copper from aqueous solutions of copper sulfate by LIX65N-kerosene solutions were carried out at 25^°C in liquid-liquid dispersions. Both reaction rates of the forward and backward extractions were obtained in a stirred vessel, being combined with the equilibrium data. For a multistage column in continuous operation, the holdup data of the dispersed organic phase were correlated with the stirring speed, flow rates and LIX65N concentration. It was found that the extracted fraction of copper in the multi-stage column can be predicted from a stage-to-stage calculation using the extraction kinetics and the holdup obtained in the present work.