Heterogeneous separations froth flotation

Materials mined from a mineral deposit usually consist of a heterogeneous mixture of solid phases that are generally crystalline and contain various minerals. Crushing and grinding operations are used to liberate the mineral species from one another and to reduce the size of the solids to a range suitable for subsequent processing. Of the various separation techniques, those of froth flotation and agglomeration exploit the chemical and physical properties of the surfaces of minerals, which can be controlled by various chemical interactions with species in an aqueous phase. 

None of the effects brought about by these metal sulphides could therefore be taken at face value. However, lead and other sulphides do act as genuine heterogeneous catalysts in the important process of froth flotation by which these minerals are separated from sand and other "gangue materials [120— 122],... 

Flotation is the term used to describe a process in which the species being separated from the bulk liquid media are insoluble particulates. Froth flotation is another one of the two foam separation processes. It also involves the production of foam in a heterogeneous aqueous system, and has a great deal of potential for the water and wastewater treatment. Froth flotation can be subdivided into at least seven categories (42,43,84), including precipitate flotation, ion flotation, molecular flotation, microflotafion, adsorption flotation, ore flotation, macroflotation, and adsorbing colloid flotation. They are described separately below. 

The separation of desired particles from a heterogeneous mixture of particles dispersed in a liquid is called flotation, not floatation. A gas is bubbled through the mixture and collects selectively on the desired particles, thereby lowering their density and floating them to the top where they can be skimmed away. This is known as gas assisted flotation, froth flotation. 

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