Methods and systems for producing calcium oxide and calcium hydroxide from aragonite

1. A method of making CaO from oolitic aragonite, the method comprising:

applying solar energy to heat a reactant mixture in a vessel, wherein the reactant mixture comprises oolitic aragonite and the reactant mixture is heated to a temperature from 500° C. to 950° C., wherein the solar energy is applied by focusing one or more mirrors in one or more heliostats.

2. The method of claim 1 , further comprising dredging the oolitic aragonite.

3. The method of claim 2 , further comprising grinding the oolitic aragonite before heating.

4. The method of claim 3 , wherein the oolitic aragonite is ground to oolitic particles between 3 μm and 10 μm in diameter.

5. The method of claim 4 , further comprising separating a first coarse portion from the oolitic aragonite.

6. The method of claim 5 , further comprising grinding the first coarse portion to produce a ground first portion and adding the ground first portion to the oolitic aragonite before heating.

7. The method of claim 6 , wherein the reactant mixture is not heated in a combustion kiln.

8. The method of claim 7 , wherein multiple heliostats are arranged in an array or a tower to reflect sunlight and provide solar energy for heating the reactant mixture.

9. The method of claim 8 , wherein the one or more mirrors in the one or more heliostats reflect sunlight to a focal vertex and the vessel is disposed at the focal vertex.

10. The method of claim 1 , further comprising admixing water with the CaO to produce Ca(OH) 2 .

11. A method for forming one or more layers of graphene from CO 2 , the method comprising:

applying solar energy to heat a reactant mixture in a vessel, wherein the reactant mixture comprises oolitic aragonite and the reactant mixture is heated to a temperature from 500° C. to 950° C. to form CaO and CO 2 , wherein the solar energy is applied by focusing one or more mirrors in one or more heliostats;

capturing the CO 2 ; and

delivering the CO 2 and at least one reducing agent to a metallic alloy substrate in a heating zone of a reactor to form the one or more layers of graphene on a surface of the metallic alloy substrate, wherein the metallic alloy substrate comprises a copper and palladium alloy (Cu—Pd alloy).

12. The method of claim 11 , wherein the Cu—Pd alloy comprises at least 80 at % Cu.

13. The method of claim 12 , wherein the reducing agent is H 2 .

14. The method of claim 13 , wherein the heating zone is at a temperature of greater than or equal to about 1000° C.

15. The method of claim 14 , further comprising annealing the metallic alloy substrate in the presence of H 2 and Ar prior to delivering the CO 2 and the reducing agent to the metallic alloy substrate.

16. A method for converting CO 2 to ethanol, the method comprising:

applying solar energy to heat a reactant mixture in a vessel, wherein the reactant mixture comprises oolitic aragonite and the reactant mixture is heated to a temperature from 500° C. to 950° C. to form CaO and CO 2 , wherein the solar energy is applied by focusing one or more mirrors in one or more heliostats;

capturing the CO 2 ;

contacting the CO 2 with an electrocatalyst, wherein the electrocatalyst comprises carbon nanospikes and copper nanoparticles disposed on the carbon nanospikes; and

applying a voltage to the electrocatalyst to produce ethanol.

17. The method of claim 16 , wherein multiple heliostats are arranged in an array or a tower to reflect sunlight and provide solar energy for heating the reactant mixture.

18. The method of claim 16 , wherein the carbon nanospikes are doped with a dopant selected from the group consisting of nitrogen, boron, phosphorous, copper, and a combination thereof.

19. The method of claim 18 , wherein the voltage is about −1.2 V.