Flocculation agglomeration

Examples of the kinds of fine solids that have been separated from suspension in the form of floes or spherical agglomerates include phosphate ore particles from water, calcium phosphate from phosphoric acid, soot from various aqueous process streams, coal particles from coal-washing slurry, and iron ore from aqueous tailings [324-326], 

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Emulsion flotation is analogous to carrier flotation. Here, small-sized particles become attached to the surfaces of oil droplets (the carrier droplets). The carrier droplets attach to the air bubbles and the combined aggregates of small desired particles, carrier droplets, and air bubbles float to form the froth. An example is the emulsion flotation of submicrometre-sized diamond particles with isooctane. Emulsion flotation has also been applied to the flotation of minerals that are not readily wetted by water, such as graphite, sulfur, molybdenite, and coal [623]. Some oils used in emulsion flotation include mixed cresols (cresylic acid), pine oil, aliphatic alcohols, kerosene, fuel oil, and gas oil [623], A related use of a second, immiscible liquid to aid in particle separation is in agglomeration flocculation (see Section 5.6.4). 

Some colloidal systems such as polymer solutions and surfactant solutions containing micelles are thermodynamically stable and form spontaneously. These types of colloids are called lyophilic colloids. However, most systems encountered contain lyophobic colloids (particles insoluble in the solvent). In the preparation of such lyophobic colloidal dispersions, the presence of a stabilizing substance is essential. Because van der Waals forces usually tend to lead to agglomeration (flocculation) of the particles, stability of such colloids requires that the particles repel one another, either by carrying a net electrostatic charge or by being coated with an adsorbed layer of large molecules compatible with the solvent. 

Size and size distribution Shape Agglomeration, flocculation state Charge Density Liquid/solid ratio Viscosity Density pH Expression mechanism Pressure Temperature Operating time Filter medium Pretreatments... 

In particle size measurements, one of the most inqKatant problems is the obtaining of a representative sample. It is the most difficult problem, and one that is often overlooked or undoestimated, especially for latexes. This problem increases in magnitude as the sample source increases in size, such that it is easier to obtain a representative sample from a 1-litre container than it is to obtain one from a 200-litre drum and, in turn, it is even more difficult to obtain a representative sample from a rail tank car. The reasons for this are obvious when one takes into consideration such factors as agglomeration, flocculation, settling, contamination and so forth. It is sufficient simply to call attention to this problem while collecting a sample for measurement as well as raising this question before measurements are made. 

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