Results
After correcting for existing carbonates, the authors estimated that 0.59% of the calcium and none of the magnesium were released from silicates. Total measured magnesium release was 0.03 mg. Three of four disk samples gained inorganic carbon over 16 days.
How it was tested
A roughly 500 mg fresh-tailings sample underwent 60 hours of flow-through dissolution at 22°C, using water equilibrated with 10% CO₂. Separate moist tailings disks were exposed to 10% CO₂ at about 22°C and over 90% relative humidity.
Assumptions and limits
The silicate-release calculation subtracts estimated contributions from existing calcite and hydromagnesite. Global storage estimates assume other tailings share Stillwater’s composition; the authors call these rough estimates.
Further work proposed
The authors propose improved calcium and magnesium extraction and carbonation, and characterisation of other tailings. They warn that more intensive reaction conditions must be assessed against the emissions they create.
Original sources
Caleb M. Woodall; Xueya Lu; Gregory Dipple; Jennifer Wilcox (2021). Carbon Mineralization with North American PGM Mine Tailings—Characterization and Reactivity Analysis.