Abstracts Engineering

The adsorption of sodium oleate on metal hydroxides.

by John G. Paterson

The aqueous adsorption of sodium oleate on copper and iron precipitates, commonly termed cupric and ferric hydroxide, was investigated over a pH range of 8.5 to 12.5. The adsorption isotherms can be described by a Freundlich type equation, r = kCon where n ranged from 1.19 to 3.92 at low oleate concentrations and 0.28 to 0.65 at high concentrations. Adsorption decreases with increasing pH, and iron does not adsorb above pH Il.5. At low oleate concentrations adsorption is chemisorption and the adsorbed species have been interpreted as, cupric hydroxy mono-oleate and ferric hydroxy di-oleate. At high concentrations sodium oleate physically adsorbs in reverse orientation to form a hydrophilic surface. Maximum flotation recovery is obtained at oleate concentrations below that required for the completion of the chemisorbed layer. Adsorption of the second layer seriously depresses flotation.