Transformação de serpentinito em hidróxido de magnésio para aplicações tecnológicas com menor pegada de carbono

Abstract

Magnesium oxides and hydroxides have several technological applications and are important raw materials for several industrial sectors. Currently, these compounds are obtained mainly by thermal decomposition of magnesite (MgCO3), which requires high energy consumption and releases large amounts of CO2, one of the main greenhouse gases (GHGs). In this picture, an advantageous alternative is the use of serpentinite rock, which is a highly available source of non-carbonated magnesium in the world. Thus, in this work, two acidic routes were developed to obtain magnesium hydroxide from serpentinite (aqueous and thermal routes). In the aqueous route, sulfuric and hydrochloric acids were tested as leaching agents, while in the thermal route, ammonium sulfate was used. Both routes were divided into 3 main stages, characterized by the production of solids 1, 2 and 3. The influence of the parameters of temperature, reaction time and amount of leaching agent was studied considering as reference the efficiency in the extraction of magnesium from serpentinite. In the aqueous route, experiments were carried out at 3 scales – 80 mL, 1 L and 5 L, reaching a maximum magnesium extraction efficiency of 79%, with a magnesium recovery as Mg(OH)2 of 82%. Analyses by XRF showed the production of Mg(OH)2 with purities between 94-97% of MgO. In the thermal route, the efficiency in the extraction of magnesium from serpentinite was 86% and the recovery of magnesium as Mg(OH)2 was 39% with a purity of 84% of MgO, analyzed by SEM/EDS. The use of serpentinite to obtain magnesium hydroxide proved to be promising, since, from routes with low energy demand that presented satisfactory magnesium extraction efficiencies, it was possible to obtain Mg(OH)2 of high purity.