Precipitate flotation: A preliminary study of the underlying mechanism

Precipitate flotation has been investigated in a continuous steady‐state unit using magnesium hydroxide suspensions (con centration range 2‐28 × 10 −4 g‐mole/l) and sodium dodecylbenzene sulphonate as surfactant (concentration range 1.5. 10 × 10 −5 g‐mole/l) at a pH of 11.75. Experimental results indicate essentially instantaneous equilibrium of the surfactant at the bubble‐liquid interface, and a substantial adsorption of surfactant on the metal hydroxide particles. The latter adsorption affects particle removal. Electron microscopy and photography have been employed to determine the sizes of the particles and bubbles respectively. A model is proposed based on collisions between the particles and the bubbles. It allows for the coverage of surfactant on the particles and the available area for particles to adsorb on the bubbles. Tests of the model with data from continuous operation show an average deviation from experiment of under 10%.