Industrial from solution

Synthetic Fiber and Plastics Industries. In the synthetic fibers and plastics industries, the substrate itself serves as the solvent, and the whitener is not appHed from solutions as in textiles. Table 6 Hsts the types of FWAs used in the synthetic fibers and plastic industries. In the case of synthetic fibers, such as polyamide and polyester produced by the melt-spinning process, FWAs can be added at the start or during the course of polymerization or polycondensation. However, FWAs can also be powdered onto the polymer chips prior to spinning. The above types of appHcation place severe thermal and chemical demands on FWAs. They must not interfere with the polymerization reaction and must remain stable under spinning conditions. 

MIBK is a highly effective separating agent for metals from solutions of their salts and is used in the mining industries to extract plutonium from uranium, niobium from tantalum, and zirconium from hafnium (112,113). MIBK is also used in the production of specialty surfactants for inks (qv), paints, and pesticide formulations, examples of which are 2,4,7,9-tetramethyl-5-decyn-4,7-diol and its ethoxylated adduct. Other appHcations include as a solvent for adhesives and wax/oil separation (114), in leather (qv) finishing, textile coating, and as a denaturant for ethanol formulations. 

The chlorides, bromides, nitrates, bromates, and perchlorate salts ate soluble in water and, when the aqueous solutions evaporate, precipitate as hydrated crystalline salts. The acetates, iodates, and iodides ate somewhat less soluble. The sulfates ate sparingly soluble and ate unique in that they have a negative solubitity trend with increasing temperature. The oxides, sulfides, fluorides, carbonates, oxalates, and phosphates ate insoluble in water. The oxalate, which is important in the recovery of lanthanides from solutions, can be calcined directly to the oxide. This procedure is used both in analytical and industrial apptications. 

Lithium Hydroxide. Lithium hydroxide monohydrate [1310-66-3], Li0H-H2 0, is prepared industrially from the reaction of lithium carbonate and calcium hydroxide in aqueous slurries. The calcium carbonate is subsequently separated to yield a lithium hydroxide solution from which lithium hydroxide monohydrate can be crystallized. Lithium hydroxide is the least soluble alkaH hydroxide, and solubiHty varies Htfle with temperature. 

Alkali Meta.IPhospha.tes, A significant proportion of the phosphoric acid consumed in the manufacture of industrial, food, and pharmaceutical phosphates in the United States is used for the production of sodium salts. Alkali metal orthophosphates generally exhibit congment solubility and are therefore usually manufactured by either crystallisation from solution or drying of the entire reaction mass. Alkaline-earth and other phosphate salts of polyvalent cations typically exhibit incongment solubility and are prepared either by precipitation from solution having a metal oxide/P20 ratio considerably lower than that of the product, or by drying a solution or slurry with the proper metal oxide/P20 ratio. 

Because the aminophenols are oxidized easily, they tend to remove oxygen from solutions. Hence, if they are released from industrial waste waters into streams and rivers, they will deplete the capacity of these environments to sustain aquatic life. Concern has also been raised that chlorination of drinking water may enhance the toxicity of aminophenols present as pollutants (138) chlorinated aminophenols are known to be more toxic (139). 

The first equation is an example of hydrolysis and is commonly referred to as chemical precipitation. The separation is effective because of the differences in solubiUty products of the copper(II) and iron(III) hydroxides. The second equation is known as reductive precipitation and is an example of an electrochemical reaction. The use of more electropositive metals to effect reductive precipitation is known as cementation. Precipitation is used to separate impurities from a metal in solution such as iron from copper (eq. 1), or it can be used to remove the primary metal, copper, from solution (eq. 2). Precipitation is commonly practiced for the separation of small quantities of metals from large volumes of water, such as from industrial waste processes. 

CiystaUization may be carried out from a vapor, from a melt, or from a solution. Most of the industrial applications of the operation involve crystalhzation from solutions. Nevertheless, crystal sohdifica-tion of metals is basically a crystalhzation process, and much theoiy has been developed in relation to metal ciystallization. This topic is so specialized, however, that it is outside the scope of this subsection, which is hmited to ciystaUization from solution. 

The kind of single crystals discussed above are all made starting from solution. In industrial practice, bulk polymeric products are generally made from the melt, and... 

Nyvlr, J-, Industrial Crystalltsation from Solutions. Butterworths, London 1971. 

Cisternas, L.A. and Rudd, D.F., 1993. Process designs for fractional crystallization from solution. Industrial and Engineering Chemistry Research, 32, 1993. 

Hostomsky, J. and Jones, A.G., 1993a. Modelling and analysis of agglomeration during precipitation from solution. In Industrial Crystallization 93. Ed. Z. Rojkowski, University of Warsaw, 1993, pp. 2037-2041. 

Nyvlt J., 1970. Industrial crystallisation from solution. London Butterworth Group. 

Li and Hsiao [143] provide a useful approach to the environmental problem of removing (by stripping) volatile organics from solution in a contaminated water stream by using fresh air as the stripping medium. It should be noted that a number of industrial firms perform this stripping with steam. The mass balance on the VOC component around the column (trayed or packed) as shown in Figure 8-55 uses the symbols of Reference 143. 

They may also be required in industrial applications where they become part of venting systems on fermenters, centrifuges, autoclaves and freeze-dryers. Certain types of filter (membrane filters) also have an important role in sterility testing, where they can be employed to trap and concentrate contaminating organisms from solutions under... 

Homogeneous nucleatlon might apply to precipitation processes where homogeneous nucleation must occur spontaneous before any precipitation process can occur. Since precipitation of compounds from solution is a common industrial process, we include it here. 

Nyvit, J., 1971, Industrial Crystallization from Solutions , Butterworths, London. 

From NIST in the USA similar air filters spiked from solutions are also available for a number of elements. Although the element content of these filters is less representative for actual exposure levels in industrial settings, these samples are also of primary interest in the documentation of measurement uncertainties see also Table 6.2. 

On an industrial scale, evaporation and crystallisation are the main processes used for the recovery of dissolved solids from solutions. 

Solvent extraction, also called liquid-liquid extraction, can be used to separate a substance from a solution by extraction into another solvent. It can be used ether to recover a valuable substance from the original solution, or to purify the original solvent by removing an unwanted component. Examples of solvent extraction are the extraction of uranium and plutonium salts from solution in nitric acid, in the nuclear industry and the purification of water. 

The host lattices are frequently prepared from ZnS, Zn xCdxS2, alkaline earth carbonates, MHP04 (M = Ca, Sr, or Ba), and MNH4P04 H20 (M = Cd or Mn).8 The general (industrial method) of preparation involves precipitation of the phosphor itself, or an intermediate, from solutions of pure cationic and anionic precursors. The purity of all materials used is vital, and impurities must not be present at levels great than 1.0 ppm. Impurities, which are detrimental to phosphor quality and are usually referred to as killers , 4 may include M2+ (M = Fe, Co, Ni, Cu, Pd, and Pt), M3+ (M = Ti, V, Cr, Fe, Ru, Zr, Nb, Mo, Rh, Hf, Ta, and W), and M4+ (M = Os, Ir, and Re). Such cations are usually removed by precipitation or sequestration by selective chelation on solutions before processing.8... 

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