ISSN:0021-2148    

DOI:10.1002/ijch.199000021

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractScale‐up of adsorptive separations is discussed in terms of separation economics and underlying transport theory. Examination of economic data suggests that recovery of valuable solutes, such as proteins, from dilute solution is dominated by the costs of processing large masses of unwanted materials. Separation processes are classified into concentration, fractionation, and purification, and the corresponding adsorptive operations are discussed. It appears desirable to make substantial changes in both equipment configuration and operating mode upon scale‐up, and hence careful design with a firm basis in transport theory is warranted. Existing difficulties in modelling such operations, especially at the production scale, are revie

ISSN:0021-2148    

DOI:10.1002/ijch.199000022

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe recently confirmed diffusion‐limited transport model for neutral macrocyle‐mediated cation transport in membranes has been used to quantify the membrane solvent effects on the fundamental parameters in the model and their relative importance. The fundamental parameters involved are the extraction equilibrium constant, macrocycle partition coefficient, and diffusion coefficient. Experimental measurements and predictive correlation calculations have been made to quantify these fundamental parameters. Membrane stability has also been quantified by looking at solvent solubilities and solvent compatibility with various membrane types. It was found that membrane stability vs. rapid transport is the major choice to be made in choosing a membrane solvent. Retention of the macrocycle in the membrane and diffusion coefficients are greatest with short carbon chain solvents containing few chlorine atoms. On the other hand, high boiling points and low water solubility are obtained with long carbon chain solvents containing increasing numbers of chlorine atoms. Extraction equilibrium constants also decrease with increasing carbon chain lengths and increasing chlorination, but the decrease is not uniform like the changes in the other parameters. Little effect of solvent type on membrane selectivity was observed. The transport model and quantification of these fundamental parameters should allow for accurate predictions in the choice of solvent in designing stable membranes with optimal transport propert

ISSN:0021-2148    

DOI:10.1002/ijch.199000023

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe paper presents some data from an experimental investigation into the use of magnetic pretreatment, with the objective of maintaining high permeate flux and high selectivity.It was conclusively demonstrated that magnetic pretreatment inhibits and delays formation of clogging deposits on the membrane. Solid suspensoids present in the feed stock or forming in the system are removed continuously and effectively by means of a closed‐bottom hydrocyclon

ISSN:0021-2148    

DOI:10.1002/ijch.199000024

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe three principal forces that govern the interaction between dissolved proteins and solid (flat or particulate) surfaces immersed in a polar liquid are:A. Lifshitz‐van der Waals forces (LW interactions)B. Polar (hydrogen bond, or Lewis acid‐base) forces (AB interactions, which include “hydrophobic” interactions)C. Electrostatic forces (EL interactions)EL interaction energies can be determined via electrokinetic measurements. LW and AB interaction energies are derived from the LW component and the electron‐acceptor (γ⊕) and electron‐donor (γ⊖) parameters of the AB component of the surface tension, all three of which can be determined by contact angle (Θ) measurements on (a) hydrated layers of protein and (b) flat layers of particulate surface, using at least 3 polar liquids in each case. By this approach, the optimal conditions for attachment as well as for detachment of a given protein to a well‐characterized solid surface or particle can be determined quantitatively. Reversed phase liquid chromatography of immunoglobulin G (1) on phenyl Sepharose (2) shows that the elution of the protein, by an increasing concentration of ethylene glycol (EG) in the aqueous medium (3), occurs at the EG concentration where the value ofΔG132TOTchanges from

ISSN:0021-2148    

DOI:10.1002/ijch.199000025

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThin‐channel flow techniques can be used for the separation of samples ranging over 15 orders of magnitude in molecular weight, namely, macromolecules, colloids, and particles. The first part describes the group of field‐flow fractionation techniques. Flow system components are illustrated and described, as well as mode of operation and theory behind retention in the thin channel. An update of current topics under research is given, namely, normal retention mode of Brownian particles (under 1 μm in diameter) as compared to the steric retention mode of non‐Brownian particles (above 1 μm in diameter). Optimization of the separation by field programming is briefly discussed.Another group of thin‐channel techniques for small‐scale processing, the split‐flow thin (SPLITT) cells, in which fractionation is based on mass transport across the channel thickness, is presented in the second part. Principles of separation in this technology as well as possible applications are illustrated

ISSN:0021-2148    

DOI:10.1002/ijch.199000026

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractExperimental data are presented and interpreted on the foam fractionation of an extensive series of simple and complex anions from dilute (of the order 10−6−10−4molar) aqueous solutions, utilizing a quaternary ammonium surfactant with which the anions form soluble ion pairs in competition with the surfactant's counterion. Selectivity coefficients, based on a bubble‐interface, ion exchange model, are established in a single‐equilibrium‐stage, continuous‐flow, foam fractionation unit for each of a series of 13 anions and oxyanions versus the surfactant's bromide counterion. Three additional series of batch experiments with multi‐metal solutions establish the separation and concentration in the foam of the oxyanions of Re(VII), Mo(VI), Cr(VI), W(VI), and V(V); of the cyanide complex anions of Zn(II), Cd(II), Hg(II), and Au(III); and of the chloride complex anions of Zn(II), Cd(II), Hg(II), and Au(III). The metal oxyanions and metal cyanide and chloride complex anions can be separated from each other and from competing chloride, cyanide, or nitrate.Ion flotation of anionic species with a cationic surfactant involves an entirely different mechanism, in which a precipitation reaction occurs and particle flotation follows. Hexavalent chromium (primarily HCrO−4) is ion‐floated with each of a series of variable chain length quaternary ammonium surfactants, elucidating the effects of temperature, the surfactant/Cr(VI) feed ratio, mixing time, and surfactant chain length in terms of the roles of the surfactant as precipitant, dispersant, col

ISSN:0021-2148    

DOI:10.1002/ijch.199000027

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe complex formation between β‐cyclodextrin and nitrophenol isomers was studied with the aid of reversed phase liquid chromatography. The effects of temperature, pH, and methanol content on the formation constants of the nitrophenol/β‐cyclodextrin complexes were investigated. The complex formation constants were found to decrease with increasing temperatures. This decrease in formation constant was independent of the pH of the mobile phase. From the temperature dependence of the formation constants we were able to extract enthalpies and entropies of the complex formation. The values calculated in this work agree favorably with published values. Three pHs were examined: 3.57, 4.65, and 5.6. The formation constants of theorthoandmetaisomers were highest at the lowest pH and leveled off at the two higher pHs. Theparaisomer showed a minimum in the formation constant at pH 4.65. This behavior was independent of the pH of the mobile

ISSN:0021-2148    

DOI:10.1002/ijch.199000028

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractMathematical models are developed for evaluating the feasibility of in situ vapor stripping for the removal of volatile organics from contaminated soils. The models simulate both laboratory soil stripping columns and field‐scale vacuum extraction wells. Local equilibrium between the condensed and vapor phases is assumed for the volatile compounds; Henry's law or more complex isotherms may be used to describe this equilibrium. Methods for determining Henry's constants from lab data and for determining soil permeability from field data are presented. The models are used to predict the effects of well depth, Henry's constant, screened radius of well, and zone of influence radius. The use of impervious caps and passive vent wells to direct gas flow is discussed, and the effects of buried obstacles and evaporative cooling are examined. The possibility of recontamination from non‐aqueous phase liquid (NAPL) underlying the vadose zone is investigated, as is the ability of the vapor stripping technique to remove pools of NAPL floating on the water table below the vadose zone. An estimate of the maximum time required for cleanup at a site is m

ISSN:0021-2148    

DOI:10.1002/ijch.199000029

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY