Carbonation of metal silicates for long-term CO2 sequestration

A process of carbonating a metal silicate comprising the steps of:

• a) reacting a metal silicate with a first caustic alkali-metal hydroxide in a first reactor to produce a metal hydroxide comprising metal from the metal silicate;
• b) reacting a second caustic alkali-metal hydroxide with a source of carbon dioxide in a second reactor that is separate from the first reactor to produce a metal carbonate comprising metal from the second caustic alkali-metal hydroxide;
• c) reacting the metal hydroxide produced from said step a) with the metal carbonate produced from said step b) to form at least a reconstituted caustic material;
• and
• d) introducing the reconstituted caustic material that is produced in step c) as at least one of the first caustic alkali-metal hydroxide in said step a) and the second caustic alkali-metal hydroxide in said step b).