Species size 13, Table colloidal

To verify whether or not colloid species were present in solution, phase separation was thoroughly examined with different ultrafilters. Tables HI and IV show results from various ultrafiltrations for the Am(III) and Pu(VI) solutions, respectively. The solution at solubility equilibrium was first filtered with the Millex-22 (0.22 u) filter and further passed through different ultrafilters of nearly the same pore size ( 2nm). Table ID demonstrates that the americium concentration in filtrates... 

In water studies it is standard practice to filter the sample soon after collection, usually through a 0.45p,m membrane disc (made of cellulose acetate, cellulose nitrate or polycarbonate). This process arbitrarily divides the sample components into soluble and insoluble fractions, but as shown in Table 2.3, the average size of different chemical species varies widely, and some differentiation between species can be obtained through using filter media of different pore sizes. For example, fully dissolved compounds can be separated from finer colloidal forms by using gel filtration and dialysis, and sub-division of the total content into fractions based on particle or molecular size (see Section 2.3) has been used for speciation of elements in waters. 

In this method, the preformed metal is adsorbed as individual particles onto a carrier, both suspended in a solvent (Table I) (67, 68). The size and structure of the colloids are not influenced by the support (69), but the liquid medium may contain species that are by-products of the preparation and that may complicate the situation unless removed by dialysis. In various attempts to use this method the metal particle size, which depends on the metal and the preparation conditions, is usually larger than that obtained by the preceding methods. 

Definition and Classification of Foams. Colloidal species of any kind (bubbles, particles, or droplets), as they are visually defined, have at least one dimension between 1 and 1000 nm. Foams are a special kind of colloidal dispersion one in which a gas is dispersed in a continuous liquid phase. The dispersed phase is sometimes referred to as the internal (disperse) phase, and the continuous phase as the external phase. In practical occurrences of foams, the bubble sizes usually exceed the size limit given, as may the thin liquid-film thicknesses. Table II lists some simple examples of petroleum industry foam types. Solid foams, dispersions of gas in a solid, will not in general be covered in this chapter. A glossary of frequently encountered foam terms in the science and engineering of petroleum industry foams is given at the end of this volume. 

What all of these have in common is their ability to remove or separate species on the basis of size. UF can remove fine particles and colloids RO can remove all ionic species from water nanofiltration, being an intermediate process, actually distinguishes between ions of different size. It is the ability to manufacture materials not only with very fine pores but also with closely controlled pore size and narrow pore size distribution that has made all these processes commercially feasible. Table 7.24 shows the spectrum of applications. Nanofiltration is the newest application in the chlor-alkali field. We can expect the number of membrane-based installations to continue to grow. 

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