Precipitate flotation. III. Parameters of precipitate flotation of the first kind

Precipitates of strontium carbonate (10 −3 mole litre −1 ) were floated using dodecylpyridinium chloride, hexadecylpyridinium bromide, hexadecyltrimethylammonium chloride and a dialkyldimethylammonium chloride. Flotations were performed at a gas flow‐rate of 7 litre hour −1 for 3 minutes or 2 litre hour −1 for 20 minutes. Complete recoveries were possible by both methods, provided optimum concentrations of collector were used. If too little collector was present, redispersion of precipitate occurred because the foam formed was insufficient to support it. With too much collector, the precipitate was excluded from the bubbles and also became coated by a double layer of collector which gave a hydrophilic surface. Increase of temperature and of time allowed for precipitation, improved recoveries because of increased particle size. Flotations were not complete below 10 −3 m unless the strontium carbonate was co‐precipitated in calcium carbonate, when 10 −8 m could be recovered. Increased ionic strength reduced recoveries because it caused precipitation to be slower, attachment of collector to the precipitate to be less secure, flotation of the collector to be more rapid and foam drainage, and hence redispersion, to increase.