Flocculation Sweep

Swaits reactions Sweat glands Sweep flocculation Sweet basil Sweet basil oil Sweet chocolate Sweet crude oil Sweeteners... 

A fourth mechanism is called sweep flocculation. It is used primarily in very low soflds systems such as raw water clarification. Addition of an inorganic salt produces a metal hydroxide precipitate which entrains fine particles of other suspended soflds as it settles. A variation of this mechanism is sometimes employed for suspensions that do not respond to polymeric flocculants. A soHd material such as clay is deUberately added to the suspension and then flocculated with a high molecular weight polymer. The original suspended matter is entrained in the clay floes formed by the bridging mechanism and is removed with the clay. 

A fourth mechanism is called sweep flocculation. It is used primarily in very low solids systems such as raw water clarification. Addition of an inorganic salt produces a metal hydroxide precipitate which entrains fine panicles of other suspended solids as it settles. 

Sweep Flocculation A mechansim of aggregation or flocculation in which particles are enmeshed by a coagulant matrix. The particles are aggregated not due to charge neutralization but rather to enmeshment. Example the rapid precipitation of a metal hydroxide from supersaturated solution where the settling fluffy hydroxide particles trap and enmesh other suspended particles. See reference 23. 

IgM, an immunoglobulin in milk, forms a complex with lipoproteins. This complex, known as cryoglobulin, precipitates onto the fat globules and causes flocculation. The process is known as cold agglutination. As fat globules cluster, the speed of rising increases and sweeps up the smaller globules with them. The cream layer forms very rapidly, within 20 to 30 min, in cold milk. 

Steady-state shear stress-shear rate measurements are by far the most commonly used method in many industrial laboratories. Basically, the dispersion is stored at various temperatures and the yield value and plastic viscosity r are measured at various intervals of time. Any flocculation in the formulation should be accompanied by an increase in tr and r. One rapid technique for studying the effect of temperature changes on the flocculation of a formulation is to perform temperature sweep experiments, running the samples from perhaps 5 to 50 °C. Any trend in the variation of tr and r with temperature can quickly provide an indication of the temperature range at which a dispersion will remain stable, since during that temperature range cr and r will remain constant. 

An alternative rheological technique for assessing flocculation involves oscillatory measurements which, as noted above, can include two sets of experiments, namely strain and oscillatory sweep measurements. 

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