Sedimentation equipment principles

Various techniques and equipment are available for the measurement of particle size, shape, and volume. These include for microscopy, sieve analysis, sedimentation methods, photon correlation spectroscopy, and the Coulter counter or other electrical sensing devices. The specific surface area of original drug powders can also be assessed using gas adsorption or gas permeability techniques. It should be noted that most particle size measurements are not truly direct. Because the type of equipment used yields different equivalent spherical diameter, which are based on totally different principles, the particle size obtained from one method may or may not be compared with those obtained from other methods. 

Alternatively, plain sedimentation basins with mechanical equipment for continuous collection of the fresh sludge may be used. The fresh sludge, so collected, is discharged into separate sludge digestion tanks which operate on the principle of the lower story of the Imhoff tank except that by means of higher and better temperature control the digestion cycle is much more rapid and efficient than for the Imhoff tank. 

Fairly wide use has been made of preparative gel electrophoresis in protein chemistry, and in principle there is no reason why the same procedures should not be adopted for use with nucleic acids which have the advantage that much may be accomplished with very small quantities of purified material. Thus, it is relatively easy in many situations to introduce radioactive label at very high levels and specific activity, and the use of for this purpose offers a degree of sensitivity that cannot be matched in work on proteins. The extinction coefficients of nucleic acids are also very high in the ultraviolet, so that with say 20 pg in 1 ml or less it is possible to measure optical properties, thermal melting profiles, sedimentation coefficients, and even molecular weights by sedimentation equilibrium in an instrument equipped with scanner optics. Consequently, the sacrifice of resolution that, by a malign law of nature, always accompanies any attempt to scale up an analytical fractionation method is often at least partly avoided. 

Industrial separators nearly all provide for the continuous removal of settled solids. The separation may be partial or very nearly complete. A settler that removes virtually all the particles from a liquid is known as a clarifier, whereas a device that separates the solids into two fractions is called a classifier. The same principles of sedimentation apply to both kinds of equipment. 

The detection of munitions on the seabed or buried in the sediment is performed with detection equipment of similar principles as the land-based methods, but, of course, in a specialised waterproof version. In addition, there are a number of technologies available which are specific to underwater work. Some of these will be highlighted in the second part of the presentation. 

Disk centrifuges Disk centrifuges operate on the principle of differential sedimentation and are used for two-phase (liquid-solid or liquid-liquid) and three-phase (liquid-liquid-solid) separations. Disk centrifuges are essentially a rotating bowl equipped with an internal set of conical settling plates which... 

Although comprehensive descriptions of equipment selection are given in this chapter the specifics of data analysis and equipment simulation are presented elsewhere. Chapter 4 provides practical methodologies, theories and principles that underpin the analysis of filtration, jar sedimentation and expression tests. Chapters 6 and 7 respectively present extensive descriptions of batch and continuous filter simulations, however, an introduction to simulation is described here. 

A second general method of separation is by selective dissolution and precipitation. In principle, this method is capable of purifying bonded, blended, and filled plastics. Dissolntion of the polymer releases the impurities, which can be removed by filtration, adsorption, or flotation/sedimentation [58,59]. This is capable of yielding a polymer of high parity. The major drawback of a solvent system is the increased expense dne to the complexity of equipment and the higher energy requirements. 

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