Separation methods centrifugation

A number of special processes have been developed for difficult separations, such as the separation of the stable isotopes of uranium and those of other elements (see Nuclear reactors Uraniumand uranium compounds). Two of these processes, gaseous diffusion and gas centrifugation, are used by several nations on a multibillion doUar scale to separate partially the uranium isotopes and to produce a much more valuable fuel for nuclear power reactors. Because separation in these special processes depends upon the different rates of diffusion of the components, the processes are often referred to collectively as diffusion separation methods. There is also a thermal diffusion process used on a modest scale for the separation of heflum-group gases (qv) and on a laboratory scale for the separation of various other materials. Thermal diffusion is not discussed herein. 

Reversible Processes. Distillation is an example of a theoretically reversible separation process. In fractional distillation, heat is introduced at the bottom stiUpot to produce the column upflow in the form of vapor which is then condensed and turned back down as Hquid reflux or column downflow. This system is fed at some intermediate point, and product and waste are withdrawn at the ends. Except for losses through the column wall, etc, the heat energy spent at the bottom vaporizer can be recovered at the top condenser, but at a lower temperature. Ideally, the energy input of such a process is dependent only on the properties of feed, product, and waste. Among the diffusion separation methods discussed herein, the centrifuge process (pressure diffusion) constitutes a theoretically reversible separation process. 

The DPE reduction is used as a test reaction to characterize the materials and optimize the preparation conditions of the catalyst. Since hydroaluminations can also be used for the synthesis of carboxylic acids, deuterated products, or vinyl halides via quenching with CO2, D2O or Br2 [44], the method is also a valuable organic synthesis tool. However, as compared with molecular catalysts like Cp2TiCl2 that are known to catalyze hydroaluminations [44], the titanium nitride materials described here are solid catalysts and can be separated by centrifugation. Moreover, they can be reused several times, which is an advantage as compared to molecular catalysts. 

The physical separation methods find wide application in this industry because of the nature of the wastes. Centrifugation may be feasible in some applications, but it is not suitable for abrasive or very fine particles (less than 5 pm). 

Although, many other methods (e.g. electrostatic separation, heating, centrifugation, etc.) may be used to separate the oil and water phases, chemical demulsification is the most inexpensive and widely used technique to resolve crude oil emulsions. The demulsifiers are oil-soluble water-dispersible non-ionic polymeric... 

Significant effort has been devoted to the development of separation methods for the post-BDS stage. Simple approach employing two phase separation methods like filtration or use of centrifugal forces have been studied as well as newer approaches including modification of biocatalyst to facilitate separation have been studied. Information has been obtained from patents as well as publications in open literature. 

Physical separation methods can be based on equilibrium considerations, but the majority are not. Ordinary filtration is an example of a non-equilibrium, physical method and so is ordinary centrifugation— e.g.—the separation of a precipitate from the suspending liquid using an artificial gravity field. There are separation methods, which are called filtration which are not such as gel filtration. Ultracentrifugation in a salt gradient is a physical equilibrium method. 

Other separation methods mentioned by Fisk and Remeika (1989) include centrifuging off low-melting fluxes, evaporation of a high-vapour pressure metal, cutting crystals from the melt, etc. In the conclusion of their review, Fisk and Remeika... 

Stibnite nanorods Regular stibnite (Sb2S3) nanorods (20-40 nm diameter, 220-350 nm length) have been synthesized by a sonochemical method under ambient air from an ethanolic solution containing SbCl3 and thioacetamide. In about 2 hours the solution self-heated up to about 60°C. The reaction product was separated by centrifuging and washing, in sequence, with absolute ethanol, water, acetone. 

Collection of blood samples (10 ml) was effected over 12 h following dosing. Plasma was separated by centrifugation and stored at -20°C until analysed, ibuprofen concentration was determined by HPLC using the method described in ref. 14. 

Fat absorption and binding properties are determined by mixing food ingredients with fats and oils, and after a separation step (centrifugation) the amount of oil absorbed is measured. The test is similar to water uptake, that is, the method includes steps of subdivision, agitation, separation, and measurement. 

Adsorption Studies Appropriate amounts of cleaned latex and surfactants were mixed, equilibrated for 24 hours and the excess surfactant in serum analyzed after separation by centrifugation. Igepal CO-630 and Alipal surfactants were analyzed by colorimetric titration with cetyltrimethylammonium chloride in the presence of methylene blue and a chloroform layer similar to the method of Epton (9). Some non-ionic surfactants and solubil-... 

Separation Method. Trial experiments with small portions of the coked catalyst in progressively more dense mixtures of carbon tetrachloride (d - 1.594 g/cc) and 1,1,2,2- tetrabromoethane (d - 2.967 g/cc) showed that the lightest catalyst fractions exhibited a density of about 2.3 g/cc. A solvent mixture with d - 2.33 g/cc was prepared from a mixture of 46.4 ml of carbon tetrachloride and 53.6 ml of tetrabromoethane. A 20 g portion of coked catalyst was placed in a 120 ml quantity of this solvent mixture in a 250 ml Teflon centrifuge bottle. The mixture was thoroughly agitated for several minutes and then placed in a centrifuge at 3,600 rpm for 30 minutes. Upon removal from the centrifuge, the mixture was allowed to stand for several hours in order to obtain well-defined float and sink fractions. 

That portion of solids and aqueous solution in an emulsion that separates out on standing or is separated by centrifuging in a standardized test method. Basic sediment may contain emulsified oil as well. Also referred to as BS W, BSW , Bottom Settlings and Water, and Bottom Solids and Water. 

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