Extraction of Various Magnesium Species from Slovenian Dolomites Using Chemical and Hydrometallurgical Approaches

Although one of the most abundant elements, magnesium is classified as a critical raw material by the EU. Demand for Mg and its compounds is increasing because of their widespread applications and emerging potential uses in various industries. Most primary Mg metal production occurs outside the EU and is dominated by thermal reduction and molten salt electrolysis, both energy-intensive processes. Furthermore, converting dolomite, CaMg(CO3)2, one of the main Mg sources, into usable feed material requires high temperatures. In our study, the production of Mg(OH)2 was achieved through a two-step process involving selective leaching of Slovenian dolomite with H2SO4 and selective precipitation with hydroxide. The product contained 95% of the initial Mg and only 1% of Ca, resulting in a 97-fold enrichment in favour of Mg expressed as the Ca:Mg molar ratio. This process also supplied a CaSO4 by-product, a potential source of Ca. Modifying the precipitation step with the use of chelating agents EDTA, EGTA, and DTPA did not significantly affect the Mg yield, but reduced Ca traces, thereby increasing the molar ratio to over 200. As an alternative pathway, calcination and silicothermic reduction of the dolomite demonstrated its suitability for the production of crystalline metallic Mg.