Liquid extractions, characteristics

Nonselective membranes can assist enantioselective processes, providing essential nonchiral separation characteristics and thus making a chiral separation based on enantioselectivity outside the membrane technically and economically feasible. For this purpose several configurations can be applied (i) liquid-liquid extraction based on hollow-fiber membrane fractionation (ii) liquid- membrane fractionation and (iii) micellar-enhanced ultrafiltration (MEUF). 

Chapter 3 concerns the dynamic characteristics of stagewise types of equipment, based on the concept of the well-stirred tank. In this, the various types of stirred-tank chemical reactor operation are considered, together with allowance for heat effects, non-ideal flow, control and safety. Also included is the modelling of stagewise mass transfer applications, based on liquid-liquid extraction, gas absorption and distillation. 

Fig. 4. a Schematic of porous membrane-based separation of immiscible liquids with different wetting characteristics, b Liquid-liquid extraction device (Kralj et al. 2007)... 

Important applications of liquid-liquid extraction include the separation of aromatics from kerosene-based fuel oils to improve their burning qualities and the separation of aromatics from paraffin and naphthenic compounds to improve the temperature-viscosity characteristics of lubricating oils. It may also be used to obtain, for example, relatively... 

With the widening use of the liquid-liquid extraction for the separation of complex mixtures into their components, it has been necessary to develop fluids with highly selective characteristics. The metallurgical, nuclear, biotechnolgy and food industries are now major users of the technique, and many of the recent developments have originated in those fields. Some of the characteristics and properties of two classes of fluids of increasing importance-supercritical fluids and aqueous two-phase systems are described in this section. 

Row, S. B., Koffolt, J. H., and Withrow, J. R. Trans. Am. Inst. Chem. Eng. 37 (1941) 559. Characteristics and performance of a nine-inch liquid-liquid extraction column. 

Wan, J. B., Yang, F. Q., Li, S. P., Wang, Y. T., and Cui, X. M. (2006b). Chemical characteristics for different parts of Panax notoginseng using pressurized liquid extraction and HPLC-ELSD. /. Pharm. Biomed. Anal. 41, 1596-1601. 

Transport properties play an important role in chemical reactions, electrochemistry, and liquid-liquid extraction. This concerns mainly the viscosity of ILs and fheir solutions wifh molecular solvenfs. Viscosity of ILs, typically at the level of 10-500 cP af room femperafure, is much higher than that characteristic of wafer ( /(HjO) = 0.89 cP af 298.15 K) and aqueous solutions. The high dynamic viscosity (viscosity coefficient) of ILs causes difficulties... 

Otos could be computed. All the Hixson and Smith data plot well in this fashion, and the straightness of the lines indicate the utility of the time-of-a-transfer-unit concept. Hixson, Drew, and Knox (H3) showed that a characteristic agitation number may be defined as the product of 0tOE and a velocity term for the agitated system. If then the mass transfer coefficient varies as the first power of the chosen velocity term, the agitation number would be constant for a given ratio of interfacial surface to total number of moles of extract phase. In liquid extraction, speed of agitation influences both terms of the quantity Ke[Pg.307]

Liquid-liquid extraction has also been employed as a cleanup step, with separations being made between an acid or alkaline aqueous phase and an organic solvent (48). This procedure takes advantages of differences in the physical and chemical characteristics between the carbamate and the substrate. Another commonly used procedure is based on the generally high solubility of carbamates in polar solvents and their low solubility in saturated hydrocarbons. Table 5 summarizes the use of the various cleanup procedures in the determination of carbamate pesticides. 

To ascertain if the cognac is coloured with artificial organic colouring matters, the alcohol is evaporated off, ammonia solution added and the liquid extracted with amyl alcohol evaporation of the amyl alcohol gives the colouring matters, which may be detected by their characteristic reactions and by dyeing tests with wool in acid or alkaline solution (see also Wine, and Colouring Matters). 

The development of the program for the production of transplutonium elements, americium 241, americium 243 and curium 244 in France required a major effort from the technological and chemical standpoints. Pre-existing hot cells were reconditioned and others were specially built for these production operations. From the chemical standpoint, the development of extractive chromatography on the preparative scale has allowed the definition of simple processes whose performance characteristics in our operating conditions have proved to be better than those obtained by liquid-liquid extraction. This type of process, initially developed for the treatment of Pu/Al targets, is ideal for the treatment of industrial wastes for their decontamination and for the production of americium 241. 

Oleoresin Capsicum Obtained by the solvent extraction of dried pods of Capsicum frutescens L. or Capsicum annum L. (Fam. Solanaceae) as a clear red to dark red, somewhat viscous liquid of characteristic odor, flavor, and bite. It may be decolorized through good manufacturing practices. It is partly soluble in alcohol (with oily separation and/or sediment) and is soluble in most fixed oils. The bite is usually standardized according to the label declaration. 

Aromatic and Nonaromatic Hydrocarbon Separation. Aromatics are partially removed from kerosines and jet fuels to improve smoke point and burning characteristics. This removal is commonly accomplished by hydroprocessing, but can also be achieved by liquid —liquid extraction with solvents, such as furfural, or by adsorptive separation. Table 7 shows the results of a simulated moving-bed pilot-plant test using silica gel adsorbent and feedstock components mainly in the C1Q—1C15 range. The extent of extraction does not vary greatly for each of the various species of aromatics present. Silica gel tends to extract all aromatics from nonaromatics (89). 

Deviations from Raoult s law in solution behavior have been attributed to many characteristics such as molecular size and shape, but the strongest deviations appear to be due to hydrogen bonding and electron donor-acceptor interactions. Robbins [Chem. Eng. Prog., 76 (10), 58 (1980)] presented a table of these interactions. Table 15-4, that provides a qualitative guide to solvent selection for liquid-liquid extraction, extractive distillation, azeotropic distillation, or even solvent crystallization. The activity coefficient in the liquid phase is common to all these separation processes. 

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