FUNDAMENTAL-ASPECTS OF SOLUBLE SALT FLOTATION

The sign of the surface charge for alkali halides in their saturated brines has been established from nonequilibrium electrokinetic measurements. These surface charge results for alkali halides are generally as expected from simplified lattice ion hydration theory. Based on this electrokinetic information, it has been demonstrated that the flotation of alkali halide salts is due to the adsorption of oppositely charged collector colloids by heterocoagulation. For example, the classic flotation separation of KCl from NaCl with alkyl amines is thus explained. Now, the surface charge/collector colloid adsorption hypothesis has been extended to succesfully explain the flotation behavior of certain alkali oxyanions including nitrates and sulfates as well as double salts including schoenite (K2SO4.MgSO4.6H(2)O) and kainite (KCl.MgSO4.3H(2)O). As was done previously for the alkali halides, the sign of the surface charge for these alkali oxyanion salts was established from nonequilibrium electrokinetic measurements by laser-doppler electrophoresis. These results together with the results from flotation/bubble attachment experiments indicate that the surface charge/collector colloid adsorption hypothesis accounts for the flotation response of many different soluble salt minerals when alkyl amines and carboxylates are used as collectors.