Accurate and direct quantification of native brucite in serpentine ores—New methodology and implications for CO2 sequestration by mining residues

An original method was developed to accurately quantify brucite content in mining residues whereby the thermal decomposition of pure brucite, olivine, serpentine and mining residues was comprehensively studied. The simultaneous dehydroxylation of brucite and various serpentine minerals was investigated using a combination of isothermal and nonisothermal thermogravimetric analyses with mass spectrometry. The dehydroxylation rate of brucite was highly influenced by its particle size distribution. However, the technique proposed here revealed similar particle size distributions of native brucite irrespective of the analyzed mining residue samples. This suggests the technique could also be extended to coarse mining residue particle samples containing invariant brucite size distributions. Native brucite dehydroxylation was shown to start at lower temperatures than serpentines. The weight loss due to dehydroxylation registered for brucite-doped olivine and residues revealed a quasi-linear correlation with brucite content (R2 = 1) and provided a reliable and straightforward approach for the quantification of free brucite in single minerals as well as in mining residues. The accuracy was higher than most of the current techniques used for brucite quantification. The uncertainties were as low as ∼0.05 wt% for mining residues and ∼0.02 wt% for single minerals rendering this method a promising tool for native brucite quantification.