Electrochemical system, apparatus and method to generate metal hydroxide in the presence of metal silicates
An apparatus and method are provided for the electrochemical production of hydrogen, oxygen and metal hydroxide wherein the metal is derived from a metal silicate. The process involves the electrolysis of a metal salt solution where hydrogen and a metal hydroxide are produced at the cathode, and oxygen, or chlorine, and an acid are produced at the anode. The acid is reacted with a metal silicate producing a soluble metal salt and water that is used in turn to make solid or dissolved metal hydroxide. The net CO 2 and acid gas emissions of the invention and its products may therefore be significantly reduced or turned negative.
1. A method of generating magnesium hydroxide, the method comprising:
(a) in an electrolytic container having an anode, a cathode, an electrolyte solution containing a monovalent metal salt dissolved in water, generating an acidic solution at the anode, and a metal hydroxide solution at the cathode, a metal in said metal hydroxide solution containing monovalent metal ions derived from the monovalent metal salt;
(b) in another container:
(b1) supplying the acidic solution removed at the anode;
(b2) supplying a metal silicate mass comprising 38% of magnesium oxide;
(b3) setting a mass ratio of the removed acidic solution and the metal silicate mass within a range from 2:1 to 6:1;
(b4) irrigating said metal silicate mass with the removed acidic solution at an irrigation rate from 0.08 to 0.4 liters per minute per square meter of the metal silicate mass to generate water and a metal salt solution comprising magnesium salt;
(c) in yet another container:
(c1) supplying the metal salt solution containing the magnesium salt of the step (b4);
(c2) supplying the metal hydroxide solution of the step (a) containing monovalent metal ions; and
(c3) reacting the metal salt solution with the metal hydroxide solution to produce a reaction mixture containing the electrolyte solution and the magnesium hydroxide; and
(d) separating the magnesium hydroxide from the electrolyte solution of the step (c3).
2. The method of claim 1 , further comprising purifying the metal salt solution after the step (b4).
3. The method of claim 1 , wherein the magnesium hydroxide in the step (d) is a solid magnesium hydroxide.
4. The method of claim 1 , further comprising using the magnesium hydroxide for removing an acid gas from air or a gas volume.
5. The method of claim 4 , wherein the acid gas is carbon dioxide.
6. The method of claim 1 , further comprising purifying the electrolyte solution of the step (d).
7. The method of claim 1 , wherein said metal is Na.
8. The method of claim 1 , wherein, said metal is K.
9. The method of claim 1 , further comprising supplying said water generated in the step (c3) back to the electrolytic container, thereby regenerating water in the electrolyte solution of the electrolytic container.
10. The method of claim 1 , further comprising supplying the electrolyte solution of the step (d) back to the electrolytic container, thereby regenerating the electrolyte solution.
11. The method of claim 1 , wherein the step (a) further comprises removing the acidic solution at the anode and adding de-ionized water at the anode at such rate that a concentration of the removed acidic solution is >7 wt %, corresponding to pH<3.
12. The method of claim 1 , wherein the step (a) further comprises removing a portion of the metal hydroxide solution at the cathode, wherein a removal rate is such that at least 10 wt %, corresponding to pH>12, of the metal hydroxide solution is removed.
13. The method of claim 1 , wherein the step (b3) comprises setting a mass ratio of the removed acidic solution and the metal silicate mass within a range from 3:1 to 5:1.
14. The method of claim 1 , wherein the step (b4) comprises irrigating at the irrigation rate from 0.12 to 0.28 liters per minute per square meter of the metal silicate mass.
15. The method of claim 1 , wherein the acidic solution is sulfuric acid solution, and the magnesium salt is magnesium sulfate.
16. The method of claim 13 , wherein a molar ratio of the sulfuric acid supplied in the step (b1) versus the magnesium sulfate formed in the step (b4) ranges from 0.35 to 0.95, and preferably from 0.45 to 0.65.
17. The method of claim 1 , further comprising dissolving the magnesium hydroxide and adding the dissolved magnesium hydroxide to a water body in a concentration that effects a water body pH of <9.
18. A method of generating magnesium hydroxide, comprising:
(a) in an electrolytic container having an anode, a cathode, an electrolyte solution containing magnesium salt solution, generating an acidic solution at the anode, and magnesium hydroxide solution at the cathode;
(b) in another container:
(b1) supplying the acidic solution removed at the anode;
(b2) supplying a metal silicate mass comprising 38% of magnesium oxide;
(b3) setting a mass ratio of the removed acidic solution and the metal silicate mass within a range from 2:1 to 6:1;
(b4) irrigating said metal silicate mass with the acidic solution removed at the anode at an irrigation rate from 0.08 to 0.4 liters per minute per square meter of the metal silicate mass, and from 0.12 to 0.28 liters per minute per square meter of the metal silicate mass, to generate water and magnesium salt solution; and
(c) supplying the magnesium salt solution to the electrolytic container as the electrolyte.
19. The method of claim 18 , wherein the acidic solution is sulfuric acid solution of concentration >7 wt %, corresponding to pH<3, and the magnesium salt is magnesium sulfate.
20. The method of claim 19 , wherein the step (a) further comprises removing a portion of the metal hydroxide solution at the cathode, wherein a removal rate is such that at least 10 wt %, corresponding to pH>12, of the metal hydroxide solution is removed.