Hydrometallurgical processing and sustainable valorization of brucitic dolomites for high-purity magnesium oxide production

This study evaluates CO₂-assisted magnesium recovery from Budureasa brucitic dolomites using historical laboratory records and three additional one-hour repeatability tests. The proposed route avoids direct hydrochloric-acid leaching of the calcium-rich feed: magnesium is extracted in a mechanical flotation cell, precipitated, and the recovered filter cake may subsequently be dissolved in HCl to produce MgCl₂ feedstock. Historical tests used thermal activation at 650 °C. The additional tests were conducted at 21 °C, with a feed grade of 22.76 wt.% MgO equivalent, a recorded dilution of 1:10, a CO₂ flow of 5 dm3/min, a nominal cell capacity of 3 dm3 and 800 min-1 yielded extractions of 60.7%, 62.1% and 61.3% (mean 61.37%, sample standard deviation 0.70 percentage points, n = 3). These results support repeatability under a single condition. Calcination at 850 °C was used for analytical mass stabilization, not as a required downstream production step; the reported 99.06 wt.% MgO equivalent does not establish periclase phase purity. The historical 4.5 Mg/h product projection is distinguished from a recalculated theoretical maximum of 4.160 Mg/h at 72% Mg extraction and an assumed 99% MgO-equivalent product grade, before downstream losses. The proposed direct HCl conversion, environmental advantages, and overall experimental Mg balance remain unverified.