Methods and systems for utilizing waste sources of metal oxides
Methods are provided for producing a composition comprising carbonates, wherein the methods comprise utilizing waste sources of metal oxides. An aqueous solution of divalent cations, some or all of which are derived from a waste source of metal oxides, may be contacted with CO2 and subjected to precipitation conditions to provide compositions comprising carbonates. In some embodiments, a combustion ash is the waste source of metal oxides for the aqueous solution containing divalent cations. In some embodiments, a combustion ash is used to provide a source of proton-removing agents, divalent cations, silica, metal oxides, or other desired constituents or a combination thereof.
1. A method comprising:
a) contacting an aqueous solution with metal oxide comprising CaO wherein the metal oxide provides proton-removing agent upon hydration of the CaO in the aqueous solution, wherein the metal oxide is slag, and wherein the aqueous solution further comprises a supplemental proton removing agent comprising ammonia;
b) charging the aqueous solution with carbon dioxide from an industrial process; and
c) subjecting the aqueous solution to precipitation conditions favoring precipitation of precipitation material comprising aragonite, vaterite, or mixture thereof.
2. The method of claim 1 , wherein the metal oxide and the carbon dioxide are from the same industrial process.
3. The method of claim 1 , wherein contacting the aqueous solution with the metal oxide occurs prior to charging the aqueous solution with the carbon dioxide.
4. The method of claim 1 , wherein the carbon dioxide further comprises SO x , NO x , mercury, or any combinations thereof.
5. The method of claim 1 , wherein the carbon dioxide is flue gas from a coal fired power plant or flue gas from cement plant.
6. The method of claim 1 , wherein the slag is blast furnace slag, electric arc slag, steel slag, copper slag, nickel slag, phosphorus slag, or combinations thereof.
7. The method of claim 1 , wherein the slag is steel slag.
8. The method of claim 1 , wherein the metal oxide provides divalent cations comprising calcium ions, magnesium ions, or combinations thereof, for producing the precipitation material.
9. The method of claim 1 , wherein the metal oxide further provides silica, alumina, ferric oxide, or a combination thereof.
10. The method of claim 1 , wherein the aqueous solution comprises brine, seawater, or freshwater.
11. The method of claim 1 , wherein the precipitation material further comprises MgCO 3 .
12. The method of claim 1 , wherein the precipitation material further comprises bicarbonate.
13. The method of claim 1 , further comprising processing the precipitation material to form a building material selected from the group consisting of hydraulic cement, pozzolanic cement, and aggregate.
14. The method of claim 1 , wherein the precipitation conditions are selected from the group consisting of temperature, pH, additive, ion ratio, rate of precipitation, mixing rate, form of agitation, presence of seed crystal, catalyst, membrane, or substrate, and combinations thereof.
15. The method of claim 1 , further comprising separating the precipitation material from the supernatant.
16. The method of claim 1 , further comprising drying the precipitation material.