Process for producing a nanoscale zero-valent metal
This invention describes a process for producing a nanoscale zero-valent metal, including reduction of a metal ion solution with a dithionite compound, wherein the reduction is carried out under alkaline conditions under substantially an inert atmosphere. A nanoscale zero-valent metal obtainable by this process, and having a new crystalline form, is also described. The nanoscale zero-valent metal produced by the process of the invention is preferably iron, and is advantageously used for the remediation of contaminated water.
1. A process for producing a nanoscale zero-valent metal, said process including reduction of a metal ion solution with a reductant salt, wherein said reduction is carried out under alkaline conditions and under a substantially non-oxygen-containing atmosphere.
2. The process of claim 1 , wherein said metal ion is selected from the group consisting of: iron, nickel, zinc, tin, copper, silver, gold, lead, cadmium, mercury, cobalt, molybdenum, chromium, platinum, palladium and phosphorus.
3. The process of claim 1 , wherein said metal ion solution is a ferrous (Fe II) solution.
4. The process of claim 3 , wherein said ferrous solution is an aqueous solution.
5. The process of claim 3 , wherein said ferrous solution is an aqueous solution of FeSO4, FeCl2, FeBr2, FeI2, Fe(NO3)2, FeCO3, Fe3(PO4)2 or a mixture of any thereof.
6. The process of claim 1 , wherein said reductant salt is a metal salt of dithionite.
7. The process of claim 1 , wherein said dithionite salt is a compound selected from Na2S2O4, Li2S2O4, K2S2O4, MgS2O4, CaS2O4 or mixtures thereof.
8. The process of claim 1 , wherein said metal ion solution has a pH in the range of about pH 9 to about pH 11.
9. The process of claim 1 , wherein said alkaline conditions are provided by including a hydroxide compound in said metal ion solution.
10. The process of claim 9 , wherein said hydroxide compound is selected from LiOH, NaOH, KOH, Mg(OH)2, Ca(OH)2 or a mixture of any thereof.
11. A nanoscale zero-valent metal obtainable by a process according to claim 1 .
12. The nanoscale zero-valent metal according to claim 11 , which is nanoscale zero-valent iron (ZVI).
13. A zero-valent metal including nanoscale particles of crystalline platelets, each said crystalline platelet including said zero-valent metal.
14. The zero-valent metal of claim 13 , wherein said crystalline platelets include metal particles imbedded in a sulfite hydrate crystal matrix.
15. The zero-valent metal according to claim 13 , which is iron.
16. The zero-valent metal according to claim 11 , which is coated with a layer of palladium or platinum.
17. A process for treating a material contaminated with an organic contaminant, said process including the step of contacting the material with a zero-valent metal according to claim 11 .
18. The process of claim 17 , wherein said organic contaminant is a halogenated organic compound (HOC), a nitroaromatic compound, or a mixture thereof.
19. The process of claim 17 , wherein said zero-valent metal is in the form of a colloidal suspension.
20. The process of claim 17 , wherein said contaminated material is contaminated water.