Polysulfide intercalated layered double hydroxides for metal capture applications
Polysulfide intercalated layered double hydroxides and methods for their use in vapor and liquid-phase metal capture applications are provided. The layered double hydroxides comprise a plurality of positively charged host layers of mixed metal hydroxides separated by interlayer spaces. Polysulfide anions are intercalated in the interlayer spaces.
1. A polysulfide intercalated layered double hydroxide comprising:
a layered double hydroxide comprising a plurality of positively charged host layers comprising mixed metal hydroxides, wherein the host layers are separated by interlayer spaces; and
polysulfide anions intercalated in the interlayer spaces.
2. The layered double hydroxide of claim 1 , wherein the layered double hydroxide is a magnesium-aluminum layered double hydroxide.
3. The layered double hydroxide of claim 2 , wherein the polysulfide anions have the formula [S x ] 2− , where x=2, 4 or 5.
4. The layered double hydroxide of claim 1 , wherein the polysulfide anions have the formula [S x ] 2− , where x=2, 4 or 5.
5. A method of removing metal from a sample comprising the metal, the method comprising:
exposing the polysulfide intercalated layered double hydroxide of claim 1 to the sample, wherein the metal reacts with the polysulfide anions to form compounds comprising metal-sulfur bonds in the interlayer spaces; and
removing the polysulfide intercalated layered double hydroxide and the compounds from the sample.
6. The method of claim 5 , wherein the sample comprises vaporized Hg which reacts with the polysulfide anions to form HgS.
7. The method of claim 6 , wherein the polysulfide intercalated layered double hydroxide has a Hg capture capacity of at least about 5×10 5 μg/g, as measured by inductively coupled plasma.
8. The method of claim 5 , wherein the sample comprises metal ions which react with the polysulfide anions to form MS x compounds, where x is an integer in the range from 1 to 8.
9. The method of claim 8 , wherein at least 40% by weight of the metal ions are removed from the sample.
10. The method of claim 8 , wherein at least 70% by weight of the metal ions are removed from the sample.
11. The method of claim 8 , wherein the metal ions are Hg 2+ ions, Ag + ions, Cu 2+ ions or a combination thereof.
12. The method of claim 8 , wherein the metal ions are Hg 2+ ions and the polysulfide intercalated layered double hydroxide has a metal ion absorptive capacity of at least 6×10 5 μg/g.
13. The method of claim 5 , wherein the sample comprises uranium-containing ions which react with the polysulfide anions to form compounds having U-S bonds.
14. The method of claim 13 , wherein the uranium-containing ions are uranyl cations.
15. The method of claim 13 , wherein the sample comprises sea water.
16. The method of claim 13 , wherein the sample comprises waste water.
17. The method of claim 16 , wherein the waste water is from a nuclear power plant.
18. A method of making a polysulfide intercalated layered double hydroxide from a layered double hydroxide comprising: a plurality of positively charged host layers comprising mixed metal hydroxides, wherein the host layers are separated by interlayer spaces; and charge-balancing anions within the interlayer spaces, wherein the charge-balancing anions are anion-exchangeable with polysulfide anions, the method comprising: exposing the layered double hydroxide to a solution comprising polysulfide anions, wherein the polysulfide anions undergo anion exchange with the charge-balancing anions in the interlayer spaces.
19. The method of claim 18 , wherein the charge-balancing anions are NO 3 − anions.
20. The layered double hydroxide of claim 1 , further comprising NO 3 − anions intercalated in the interlayer spaces.
21. The method of claim 5 , wherein the layered double hydroxide further comprises NO 3 − anions intercalated in the interlayer spaces.