Professor John Ralston - Summit Speaker Series - September 7, 2016

Professor John Ralston 

                             

Emeritus Laureate Professor University of South Australia

September 7, 2016 2:00 pm

8-207 Donadeo Innovation Centre for Engineering

Selective Alteration of Surface Chemistry in the Flotation Separation of MgO Minerals from a Metal Sulphide Ore”

The selective rejection of MgO type minerals is of critical importance to the production of high grade metal concentrates from ores in Canada, Australia and elsewhere. High levels of MgO in the concentrate cause downstream processing problems as well as increased smelting costs. The gangue mineral pyrrhotite, among others, is also a serious problem.Through electron microscopy  examinations we show that serpentine slime coatings on pentlandite [NiFeS ] surfaces depress its flotation. Electrokinetic measurements show that the surfaces of pentlandite and serpentine are oppositely charged at the normal separation pH values. Atomic Force Microscopy determinations shown that there are strong attractive forces between the particles; these may be reduced or reversed by polymer adsorption. The use of high MW organic polymers, together with judicous control of grinding conditions and liberation, in conjunction with cycloning, yields effective dispersion of serpentine gangue particles from the surface of pentlandite. By substituting P containing groups into the structure of the high MW polymers , the distribution of polymers in the concentrate and tails can be determined, as well as the relative distribution of polymer on  pentlandite, pyrrhotite and Mgo-rich mineral surfaces. We show that the choice of polymer structure can have a remarkable influence on the removal of pentlandite, as well as  the  adsorption of xanthate, with  very substantial improvements in the grade-recovery curves.We extend these ideas to several other metal sulphide minerals and their accompanying gangue minerals, showing that the approach is quite generic.