Systems and methods for alkaline earth production
Hydrometallurgical systems, methods, and compositions are described in which amine-based lixiviants are utilized in substoichiometric amounts to recover alkaline earths from raw or waste materials. The lixiviant can be regenerated and recycled for use in subsequent iterations of the process or returned to a reactor in a continuous process. Extraction of the alkaline earth from the raw material and precipitation of the extracted alkaline earth is performed in the same reactor and essentially simultaneously.
1. A method for the recovery of an alkaline earth from a particulate raw material comprising;
providing the particulate raw material in the form of a mud or slurry in a reactor, wherein the particulate raw material comprises an alkaline earth;
in the same reactor, exposing the raw material to a
source of carbon dioxide at ambient temperature and pressure, thereby generating a first reaction mixture;
during contact with the source of carbon dioxide, monitoring pH of the first reaction mixture;
discontinuing contact with the source of carbon dioxide when pH of the first reaction mixture becomes less than 8;
monitoring pH of the first reaction mixture following discontinuation of contact with the source of carbon dioxide;
re-establishing contact with the source of carbon dioxide at ambient temperature and pressure when pH of the first reaction mixture exceeds 8 to generate a second reaction mixture comprising an alkaline earth precipitate, and an extracted raw material; and
separating the alkaline earth precipitate from the extracted raw material,
wherein the method is performed in the absence of an added lixiviant.
2. The method of claim 1 , wherein the alkaline earth precipitate and the extracted raw material are separated on the basis of particle diameter.
3. The method of claim 1 , wherein the alkaline earth precipitate and the extracted raw material are separated on the basis of at least one of particle characteristics selected from the group consisting of particle density, particle shape, and effective particle hydrodynamic radius.
4. The method of claim 1 , wherein the separation is performed using a centrifugal separator.
5. The method of claim 1 , wherein the separation is performed using a filter.
6. The method of claim 1 , wherein the separation is performed within a portion of the reactor that is configured as a settling tank.
7. The method of claim 1 , wherein the raw material is introduced into the reactor in an essentially continuous manner.
8. The method of claim 1 , wherein the precipitant is introduced into the reactor in an essentially continuous manner.
9. The method of claim 1 , wherein separating is performed in an essentially continuous manner.
10. The method of claim 1 , wherein the extracted raw material is subjected to further processing.
11. The method of claim 1 , wherein the alkaline earth is calcium.
12. The method of claim 1 , wherein the raw material is selected from the group consisting of steel slag, lime, dolime, acetylene waste, and municipal ash waste.
13. The method of claim 1 , wherein at least 50% of alkaline earth content of the raw material is recovered as the alkaline earth precipitate.