1. Direct calcination method
In this method, magnesium salt or magnesite is directly calcined at high temperature to obtain magnesium oxide. Calcining basic magnesium carbonate pentahydrate (4MgCO3·Mg(OH)2·5H2O) and magnesium hydroxide for 3h at 450°C gave magnesium oxide products with average sizes of 9nm and 4.8nm, respectively.
Its reaction mechanism is:
The direct calcination method has a simple process, does not require high equipment, and is easy to industrialize. However, this method is not easy to control the morphology of MgO.
2. Ammonium immersion method
The method is to react the product obtained after calcining dolomite with ammonium salt solution, after filtering, react the filtrate with ammonia water to obtain Mg(OH)2, and calcinate Mg(OH)2 to obtain magnesium oxide. Huang et al. used calcined dolomite as the source of magnesium, ammonium sulfate as the leaching agent, and the molar ratio of (NH4)2SO4 to MgO was 1.8:1, the volume of distilled ammonia was 350mL, and the amount of calcined dolomite was 20g. The leaching rate reached 96.81%. And calcining the obtained Mg(OH)2 at 500–1000°C to prepare magnesium oxide with a particle size of 12.4–42.2nm.
Its reaction mechanism is:
The ammonium leaching method will generate ammonia gas during the experiment, which can be used as a precipitant for the subsequent magnesium precipitation step after being recovered with water, which can form a closed-loop process and be recycled, and the purity of the obtained magnesium oxide is also high. However, the ammonium salt leaching agent is more expensive and has a long process flow.
3. Acid leaching method…
https://meixi-mgo.com/preparation-of-magnesium-oxide-by-ore-method/
0 Comments