Physicochemical mechanisms and ion flotation possibilities using columns for Cr6+ recovery from sulphuric solutions

In addition to problems inherent to flotation of precipitate or element of negligible mass, ion flotation of Cr6+ is particularly difficult as the same chemical plays both the role of precipitating, dispersing and frothing agent, A major consequence of this situation involves nearly impossible precipitate adsorption on bubbles and carrying away of particularly stable and loaded froths with the liquid, Flotation columns are tools well adapted to the collection of precipitate because of the weak energy dissipated during flotation. Besides, several modes of association of bubble generator/column have been tested and it has thus been possible to develop a new mode of precipitation-flotation called 'Precipitation on bubbles', With this new mode, the rate of Cr6+ removed by column flotation is about 81% for a collector/Cr ratio of 1.2 and with between 1 and 4% liquid lost in the froth. A re-treatment of the exhausted solution allows to obtain a total Cr recovery of 91.6%. (C) 1997 Elsevier Science B.V.