Industrial separation

In aqueous solutions, trivalent lanthanides ate very stable whereas only a limited number of lanthanides exhibit a stable divalent or tetravalent state. Practically, only Ce and Eu " exist in aqueous solutions. The properties of these cations ate very different from the properties of the trivalent lanthanides. For example, Ce" " is mote acidic and cetium(IV) hydroxide precipitates at pH 1. Eu " is less acidic and eutopium(II) hydroxide does not precipitate at pH 7—8.5, whereas trivalent lanthanide hydroxides do. Some industrial separations ate based on these phenomena. 

The lanthanides form many compounds with organic ligands. Some of these compounds ate water-soluble, others oil-soluble. Water-soluble compounds have been used extensively for rare-earth separation by ion exchange (qv), for example, complexes form with citric acid, ethylenediaminetetraacetic acid (EDTA), and hydroxyethylethylenediaminetriacetic acid (HEEDTA) (see Chelating agents). The complex formation is pH-dependent. Oil-soluble compounds ate used extensively in the industrial separation of rate earths by tiquid—tiquid extraction. The preferred extractants ate catboxyhc acids, otganophosphoms acids and esters, and tetraaLkylammonium salts. 

Industrial separations are conducted in gravity or bath separators for a coarse feed, and in centrifugal separators for a fine feed (2,6,10). In gravity-type separators the feed and medium are introduced to the surface of a large quiescent pool of the medium. The float material overflows or is scraped from the pool surface. The heavy particles sink to the bottom of the separator and are removed using a pump or compressed air. The dmm separator (Fig. 13), up to 4.6 m dia and 7 m long, processes approximately 800 t/h, and treats feed of size up to 30 cm dia, operates in the gravity or the... 

ZeoHte-based materials are extremely versatile uses include detergent manufacture, ion-exchange resins (ie, water softeners), catalytic appHcations in the petroleum industry, separation processes (ie, molecular sieves), and as an adsorbent for water, carbon dioxide, mercaptans, and hydrogen sulfide. 

Solvent Extraction. The industrial separation of tantalum from niobium was carried out historicahy by the Marignac process of fractional crystallization of potassium heptafluorotantalate and potassium heptafluoroniobate (15,16) or the long-estabhshed Fansteel process (17), which involved the decomposition of the ore by a caustic fusion procedure. Processors have replaced these expensive processes by procedures based on solvent extraction. This technique was developed in the United States at Ames Laboratory and the U.S. Bureau of Mines (18). Figure 2 shows the flow sheet of an industrial instahation for the hydrometahurgical processing of tantalum—niobium raw materials. 

These tetrahedra are arranged in a number of ways to give the different zeohtes. The stmctures are unique in that they incorporate pores as part of the regular crystalline stmctures. The pores have dimensions of the order of molecular dimensions so that some molecules fit into the pores and some do not. Hence the zeohtes are molecular sieves (qv), and they are apphed in industrial separations processes to take advantage of this property. Some zeohtes and their pore dimensions are hsted in Table 2. 

Many industrial separations require a series of columns that are connected in specific ways. Some distillation programs can model such a system as a hypothetical single column with arbitrary cross-flows and connections and then carry out the distillation calculations for the modeled hypothetical column. Alternatively, such a system can be modeled as a process flow sheet using a process simulator. 

Power Supplie.s Iligh-voltage ac and dc power supplies for electrostatic separators are iisiiallv of solid-state construction and feature variable outputs ranging from 0 to 30,()()() for ac wiper transformers to 0 to 60,000 for the dc supply The maximum current requirement is approximately 1,0 to 1,5 rnA/rn of electrode length. Powder supplies for industrial separators are typically oil-insulated, but smaller diw-epoxv-insulated supplies are also available. 

The process is used mostly for industrial separations, such as the removal of yeast from beer or the recovery of emulsified cutting oils. It has been proposed as a pretreatment to RO for fouling waters, but the economics do not yet look attractive. 

Anion exchange resins are generally lower in their exchange capadty and durability than cation exchange resins and are seldom used for industrial separation. In general, ion exchange as a tool for separation is only used when other steps fail, because of its tedious operation, small capadty and high costs. 

Polyethylene industrial separators are also available from ENTER International [62], Ranking ++ very good, + good, 0 acceptable, - poor. 

Since industrial separation processes operate in the Li L2 region, it is important to determine how the Margules parameters affect the shape of the coexistence curve and the slope of the tie lines. For any liquid-liquid region to exist, at least one of the binary Margules constants must be greater than 2RT(on y positive values are considered here) this is a consequence of the... 

Industrial scales, 26 243-245 Industrial, scientific, and medical (ISM) frequency allocations, 16 510-512 Industrial screens, types of, 16 616 Industrial separations, 16 633 Industrial sheeting, LLDPE, 20 207 Industrial solvents, 23 85-124 behavior of, 23 96-109 characteristics of, 23 89-96 classification of, 23 85-87 electronic and electrical effects of, 23 96-97... 

The separation of the two sugars fructose and glucose, is currently perhaps the industrial separation of biomolecules performed on the largest scale. Since it is a typical two-component separation, the advantages of utilizing an SMB for this purpose are obvious and glucose/fructose separations by SMB are well estab-... 

Thijssen and Spicer1 1191 has given a general review of freeze concentration as an industrial separation process and Bushnell and Eagen(63) have discussed the status of freeze desalination. The potential of freeze crystallisation in the recycling and re-use of wastewater has been reviewed by Heist 120, and the kinetics of ice crystallisation in aqueous sugar solutions and fruit juice are considered by Omran and King(121). 

Although adsorption has been used as a physical-chemical process for many years, it is only over the last four decades that the process has developed to a stage where it is now a major industrial separation technique. In adsorption, molecules distribute themselves between two phases, one of which is a solid whilst the other may be a liquid or a gas. The only exception is in adsorption on to foams, a topic which is not considered in this chapter. 

HlLAIREAU, P. and Colin, H. Chromatogr. Soc. Bull. 26 (1987) 10. Gas chromatography a real industrial separation process. 

Haggin, J. 1988. New generation of membranes developed for industrial separations. Chem. Eng. News June 6 7-16. 

Zeolites in Industrial Separation and Catalysis. Edited by Santi Kulprathipanja Copyright 2010 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-32505-4... 

Adsorptive separation is a powerful technology in industrial separations. In many cases, adsorption is the only technology available to separate products from industrial process streams when other conventional separation tools fail, such as distillation, absorption, membrane, crystallization and extraction. Itis also demonstrated that zeolites are unique as an adsorbent in adsorptive separation processes. This is because zeolites are crystalline soUds that are composed of many framework structures. Zeolites also have uniform pore openings, ion exchange abiUty and a variety of chemical compositions and crystal particle sizes. With the features mentioned, the degree of zeoUte adsorption is almost infinite. It is also noted that because of the unique characteristics of zeoHtes, such as various pore openings, chemical compositions and structures, many adsorption mechanisms are in existence and are practiced commercially. 

This chapter discusses adsorption fundamentals relating to the design and operation of large-scale industrial separations using zeolite molecular sieves. 

Dehydration is by far the largest industrial separation of interest here. Removal of water was the first commercial application of molecular sieves. Dehydration and related fixed-bed adsorptive separations in the process industries account for more than half of the commercial molecular sieve business volume. 

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