Surfactant Recovery in Adsorbing Colloid Flotation

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Abstract
The displacement of surfactants from floc–water interfaces by salts is examined by statistical mechanical methods. The effect of added salts on the adsorption isotherm is exhibited, and it is found that surfactant condensed films can readily be displaced. This may markedly improve the economics of adsorbing colloid flotation by facilitating surfactant recovery. Preliminary experimental results supporting the theory are presented; Na2CO3 is used to displace sodium lauryl sulfate from Fe(OH)3. The viscous drag forces on floc particles attached to rising bubbles are calculated for bubbles having diameters in the range 0 to 1 mm. At the upper end of this range these forces appear to be large enough to reduce the efficiency of foam flotation.