SURFACE FREE-ENERGY COMPONENTS AND FLOTABILITY OF BARITE PRECOVERED WITH SODIUM DODECYL-SULFATE

Surface free energy components, apolar gamma(s)(LW) and polar electron donor gamma(s)- and electron acceptor gamma(s)+, have been determined for barite surface precovered with 0.4 and 1.0 statistical monolayers of sodium dodecyl sulfate (DD)SO4Na). The components were compared with those for the bare surface. The component gamma(s)+ was found meaningless. The adsorbed collector drastically decreased the hydrogen-bonding interaction appearing in the component gamma(s)-. Simultaneously, the apolar dispersion component, gamma(s)(LW), increased at 0.4 (DD)SO4Na monolayer precoverage (probably as a result of the surface dehydration), and then, at 1-monolayer precoverage, it decreased to the value characteristic for a long-chain hydrocarbon (28 mJ/m2). These results are consistent with the flotation results as straight-line dependence was found between free energy DELTA-G and flotability changes. The negative DELTA-G attending the process of mineral/water replacement by mineral/gas is the thermodynamic condition to be fulfilled before efficient flotation occurs. The obtained results support the importance of this approach to the concept of surface free energy components.