Facile, low-energy routes for the production of hydrated calcium and magnesium salts from alkaline industrial wastes
Divalent ions are extracted from solids by leaching to form a divalent ion-containing solution. The divalent ion-containing solution is subjected to concentration to form a concentrated divalent ion-containing solution. Precipitation of a divalent ion hydroxide salt is induced from the concentrated divalent ion-containing solution. In other cases, the concentrated divalent ion-containing solution is exposed to carbon dioxide to induce precipitation of a divalent ion carbonate salt.
1 . A method comprising:
extracting divalent ions from solids by leaching to form a divalent ion-containing solution;
subjecting the divalent ion-containing solution to concentration to form a concentrated divalent ion-containing solution; and
inducing precipitation of a divalent ion hydroxide salt from the concentrated divalent ion-containing solution;
wherein subjecting the divalent ion-containing solution to concentration comprises using reverse osmosis or nanofiltration to separate divalent ions from monovalent ions.
2 . The method of claim 1 , wherein subjecting the divalent ion-containing solution to concentration is performed using a nanofiltration membrane.
3 . The method of claim 1 , wherein subjecting the divalent ion-containing solution to concentration is performed using a reverse osmosis membrane.
4 . The method of claim 1 , wherein inducing precipitation of a divalent ion hydroxide salt from the concentrated divalent ion-containing solution comprises contacting the concentrated divalent ion-containing solution with carbon dioxide.
5 . The method of claim 1 , wherein the solids include at least one of (a) slags or (b) fly ashes.
6 . The method of claim 1 , wherein extracting the divalent ions from the solids includes exposing the solids to a leaching solution.
7 . The method of claim 6 , wherein the leaching solution includes a leaching agent.
8 . The method of claim 6 , wherein the leaching solution includes an acid.
9 . The method of claim 1 , wherein extracting the divalent ions from the solids includes pulverizing the solids, and exposing the pulverized solids to a leaching solution.
10 . The method of claim 1 , wherein subjecting the divalent ion-containing solution to concentration further comprises subjecting the divalent ion-containing solution to capacitive concentration.
11 . The method of claim 10 , wherein subjecting the divalent ion-containing solution to capacitive concentration includes disposing the divalent ion-containing solution between a pair of electrodes, and applying an electrical input to the electrodes.
12 . The method of claim 10 , wherein subjecting the divalent ion-containing solution to capacitive concentration includes passing the divalent ion-containing solution through a series of n connected capacitive concentration cells, wherein n is 1 or greater.
13 . The method of claim 1 , wherein inducing the precipitation of the divalent ion hydroxide salt includes heating the concentrated divalent ion-containing solution to a temperature at or below 100° C.
14 . The method of claim 1 , wherein the divalent ions include calcium ions, and inducing the precipitation of the divalent ion hydroxide salt includes inducing precipitation of portlandite.
15 . The method of claim 1 , wherein the divalent ions include magnesium ions, and inducing the precipitation of the divalent ion hydroxide salt includes inducing precipitation of brucite.