Simulation of stable and metastable sea-type carbonate systems for optimization of MgCO3·3H2O precipitation from waste sea brines

• Thermodynamic modeling of stable and metastable sea-type four component carbonate systems
• Thermodynamic simulation of alkaline precipitation of metastable MgCO3·3H2O from waste sea brines
• Design of the purified MgCO3·3H2O precipitation from waste sea brines

The thermodynamic simulation of the systems Na+, Mg2 +/Cl−, CO32 −//H2O and Na+, Mg2 +/SO42 −, CO32 −//H2O using the Pitzer method at 25 °C revealed that both stable and metastable crystallizations take place in these systems. MgCO3·3H2O is always a metastable phase. Thermodynamic modeling of Mg2 + removal as a part of desalination of hyper-saline sea-salt waste brines, which can be described by these systems, pointed to the co-precipitation of various salts. Ensuing from the obtained data and considering the crystal chemistry and kinetic crystallization of the co-crystallizing salts we designed the precipitation of MgCO3·3H2O from sea-salt brines avoiding its further transformation to metastable 4MgCO3·Мg(ОН)2·4H2O and stable MgCO3. Our experimental studies confirmed the designed method and optimized the conditions for precipitation of high-purity MgCO3·3H2O with good filtration characteristics.

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