Magnesium Extraction by Solid-State Reaction of Brazilian Serpentinite with Ammonium Sulfate

Magnesium oxides and hydroxides have several technological applications and are important raw materials for industrial sectors. Currently, these compounds are obtained mainly by thermal decomposition of magnesite (MgCO 3 ), which consumes high energy and releases large amounts of carbon dioxide (CO 2 ). An advantageous alternative is the use of serpentinite, a highly available source of non-carbonated magnesium. In this work, a thermal route using ammonium sulfate (AS) was investigated to obtain magnesium hydroxide (Mg(OH) 2 ) from Brazilian serpentinite. Under the selected operating conditions, the magnesium extraction efficiency was approximately 63% based on inductively coupled plasma optical emission spectrometry analysis of the liquid phase. Higher values estimated by scanning electron microscopy with energy-dispersive spectroscopy of the solid residue highlight the tendency of this technique to overestimate extraction when applied to powder samples. The recovery of magnesium extracted as Mg(OH) 2 was approximately 79%, resulting in an overall yield of approximately 50% of rock Mg as Mg(OH) 2 . Although obtained from single experiments, these results suggest that the proposed thermal route deserves further investigation as a potential approach for magnesium hydroxide production from serpentinite, an abundant non-carbonated magnesium resource.