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 a source of metal oxides from a first industrial process;
b) charging the aqueous solution with carbon dioxide from a source of carbon dioxide from the same or a second industrial process, wherein the source of carbon dioxide further comprises SO x , NO x , mercury, or any combination thereof; and
c) subjecting the aqueous solution to precipitation conditions under atmospheric pressure to produce at least one carbonate-containing precipitation material, wherein the precipitation material comprises calcium carbonate, optionally in combination with magnesium carbonate, wherein the calcium carbonate comprises a precipitation material selected from the group consisting of aragonite, vaterite, and mixtures thereof.
2. The method of claim 1 , wherein the source of metal oxides and the source of carbon dioxide are from the same industrial process.
3. The method of claim 1 , wherein contacting the aqueous solution with the source of metal oxides occurs prior to charging the aqueous solution with the source of carbon dioxide.
4. The method of claim 3 , wherein the source of carbon dioxide is flue gas from a coal-fired power plant or kiln exhaust from a cement plant.
5. The method of claim 4 , wherein the source of metal oxides is fly ash from a coal-fired power plant or cement kiln dust from a cement plant.
6. The method of claim 3 , wherein the source of metal oxides provides divalent cations for producing the precipitation material, and wherein the divalent cations comprise Ca + , optionally in combination with Mg 2+ .
7. The method of claim 3 , wherein the source of metal oxides provides proton-removing agents for producing the precipitation material upon hydration of CaO, optionally in combination with MgO, in the aqueous solution.
8. The method of claim 7 , wherein the source of metal oxides further provides silica, alumina, ferric oxide, or a combination thereof.
9. The method of claim 7 , wherein electrochemical methods effecting proton removal also provide for producing precipitation material.
10. The method of claim 3 , further comprising processing the precipitation material to form a building material selected from the group consisting of hydraulic cement, pozzolanic cement, and an aggregate.
11. The method of claim 1 , wherein the precipitation material further comprises calcite.