Microwave heating of ultramafic nickel ores and mineralogical effects

•Ultramafic nickel ores pre-treated with microwave radiation.•Ultramafic nickel ores heat well upon exposure to microwave radiation.•Serpentine gangue mineral dehydroxylated and olivine formed.•Serpentine destruction will likely benefit grinding and flotation.•Serpentine destruction will likely increase carbon storage capacity of tailings. Although mineral carbon sequestration (MCS) has several advantages over other carbon storage techniques, an economic process for MCS has not yet been developed. To reduce costs, it is suggested that MCS be combined with other processes and that waste products be used as feedstock. A process is proposed where ultramafic nickel ores are treated with microwave radiation to convert serpentine, the primary gangue mineral, to olivine. It is hypothesized the conversion of serpentine to olivine in ultramafic nickel ores may improve the mineral processing of these ores, and increase the carbon storage capacity of the flotation tailings. The microwave heating characteristics of ultramafic nickel ores, and the mineralogical changes that occur as a result of microwave treatment, are described in this paper. Ultramafic nickel ores were found to heat well in response to microwave radiation and the temperatures achieved were sufficient to convert serpentine to olivine. Microwave treatment was also found to convert pentlandite, the valuable nickel mineral, to other Fe–Ni–S minerals.