Sustainable calcium hydroxide production for green cement
A method of making a composition of matter comprising calcium hydroxide. The method includes the steps of contacting a calcium-containing molecule with an aqueous solution of a water-soluble salt having ammonium cation and a counter-anion, under conditions effective to yield a compound containing calcium and the counter-anion; and reacting the compound comprising calcium and the counter-anion with ammonia and water under conditions to yield calcium hydroxide.
1. A method of making a composition of matter comprising calcium hydroxide, the method comprising:
(a) contacting a feedstock comprising a material selected from the group consisting of crystalline, amorphous, or hydrated phases of calcium silicate, calcium aluminate, calcium aluminosilicate, and combinations thereof with an aqueous solution comprising a water-soluble salt comprising ammonium cation and a counter-anion, for a time, and at a temperature, pH, and pressure effective to yield a compound comprising calcium and the counter-anion; and
(b) reacting at least a portion of the compound comprising calcium and the counter-anion with ammonia and water for a time, and at a temperature, pH, and pressure effective to yield calcium hydroxide.
2. The method of claim 1 , wherein the water-soluble salt comprising ammonium cation and a counter-anion is selected from the group consisting of ammonium halide, ammonium acetate, ammonium phosphate, ammonium oxalate, and ammonium lactate.
3. The method of claim 1 , wherein the water-soluble salt comprising ammonium cation and a counter-anion is ammonium chloride or ammonium acetate.
4. The method of claim 1 , wherein step (b) yields calcium hydroxide and ammonium halide and further comprising:
(c) recycling at least a portion of the ammonium halide formed in step (b) and using it as the water-soluble salt comprising ammonium cation and a counter-anion.