Retention aids Subject

Guar gum [9000-30-0] derived from the seed of a legume (11,16), is used as a flocculant in the filtration of mineral pulps leached with acid or cyanide for the recovery of uranium and gold (16). It is also used as a retention aid, usually in a chemically modified form (14,17). Starch and guar gum are subject to biological degradation in solution, so they are usually sold as dry powders that are dissolved immediately before use. Starch requires heating in most cases to be fully dissolved. 

Retention aids are necessary to coagulate and flocculate the pulp and to avoid losses due to fibers, fillers and additives passing through the mesh of the forming screen. ->Cationic starches are the only RR-based polymers used to retain mineral fillers and cellulose-reactive sizes. The market is dominated by polyacrylamide, which is applied as W/O emulsion. The aqueous polymer solution is dispersed in kerosene, the substitution of which by RR-based oils (e. g., rape seed oil) is subject of intensive investigations. 

Retention distance (or time) is normally used to aid the identification of a component of a mixture, provided that a known sample of the component has been subjected to separation under identical conditions. Because of the variations that can occur in the retention time due to technical factors, e.g. fluctuations in flow rate, condition of the column, the relative retention or selectivity factor (a) is sometimes used. This expresses the test retention time as a ratio of the retention time of another component or reference compound when both are injected as a mixture ... 

The theory of solute retention, as controlled by molecular interactions between the solutes aid the phase system is, in fact, not germane to the subject of this book. Nevertheless, as distribution and distribution coefficients together with retention volumes and capacity ratios will be discussed or used In the subsequent theoretical development of column theory, the basic principles of molecular interaction will be given. 

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