Processing an ultramafic ore using fiber disintegration by acid attack

Ultramafic ores are a potential major resource of nickel. For the Thompson area deposits of northern Manitoba, Canada, a processing challenge is the serpentine polymorph chrysotile, the dominant gangue mineral. Due to its fibrous nature chrysotile causes physical entanglement and increased pulp viscosity which reduces selectivity in flotation. The proposed approach involves disintegration of the fibers by a combination of chemical (H2SO4) and mechanical (grinding) treatment adapting technology explored for CO2 sequestration. The use of H2SO4 also led to collectorless flotation traced to elemental sulphur formation, and release of magnesium increased solution ionic strength sufficient to eliminate the need for frother. Significant improvement in Ni grade-recovery with higher rejection of MgO-bearing gangue was achieved compared to untreated ore. Structural changes in the fibers were followed using spectroscopic techniques. A mechanism of fiber disintegration is suggested.

Figure optionsDownload as PowerPoint slideHighlights
► A processing route has been designed for serpentine rich ultramafic Ni-ore.
► Process based on fiber disintegration by combined chemical/mechanical treatment.
► Low pH slurry after the treatment effects collectorless flotation.
► Significant improvement in Ni-metallurgy and MgO rejection was achieved.
► A mechanism of fiber disintegration is proposed.