Characterization of MgO calcined from Mg(OH)2 produced from reject brine

Reactive magnesia (MgO) has received attention as a cement binder due to the lower calcination temperatures used during its production and its ability to absorb and store CO2 permanently. While a majority of the MgO is produced from the calcination of magnesium carbonate, an alternative route involves its extraction from reject brine, a concentrated by-product obtained from treating brackish water or seawater in desalination plants. Brine is preferred for the recovery of MgO due to its local global abundance and its high Mg²⁺ content. The proposed process involves the synthesis of Mg(OH)2 from waste brine collected from a desalination plant via the addition of different amounts of aqueous ammonia (NH3H2O). The results include the determination of an optimum amount of NH3H2Ofor a high reaction rate, leading to the synthesis of a high amount of pure Mg(OH)2. The obtained Mg(OH)2 was then calcined to produce MgO at different temperatures (500-700°C) and durations (2-48 hours). The morphologies of the synthesized Mg(OH)2 plates and MgO particles produced under a range of conditions were investigated in detail, indicating the feasibility of MgO production from waste brine and highlighting the factors influencing the properties of the final product.