Precipitate flotation I. Removal of nickel from dilute aqueous solutions and its separation from cobalt

A new technique, called precipitate flotation of the second kind, in which no surfactant is used to float precipitates, is described. Nickel is completely removed from 1.5 × 10 −5 m‐NiCl 2 solutions in 3 minutes using a tenfold excess of nioxime. Flotation improves with increasing temperature between 21° and 40° if the pH is in the range 8–11. Increase in ionic strength has no deleterious effect, unlike conventional precipitate flotation. Nickel can be completely separated from a hundredfold excess of cobalt by complexing the latter with nitroso‐R‐salt before flotation. Iron does not float on its own but recoveries of 50% can be achieved by entrainment of ferric hydroxide in nickel nioximate.