Solvent-free syntheses of silver products produced thereby
Described herein are methods of making metallic or elemental silver in the solid state. These methods generally include a step of forming an at least substantially solvent-free solid state reaction mixture that includes a silver-containing compound and an organic acid, followed by heating the reaction mixture at a temperature and for a time effective to form metallic silver from a cationic silver species of the silver-containing compound. Also described herein are metallic or elemental silver produced by these methods.
1. A method for making metallic silver, the method comprising:
contacting a silver-containing compound with an organic acid to form an at least substantially solvent-free solid state reaction mixture, wherein the concentration of the organic acid is equimolar to or in a stoichiometric excess of the concentration of the cationic silver species in the silver-containing compound, the contacting is performed in a presence of an alkali metal-containing compound; and
heating the at least substantially solvent-free solid state reaction mixture to a temperature less than the melting temperature of the organic acid for a time effective to produce a reaction product comprising metallic silver from the cationic silver species of the silver-containing compound.
2. The method of claim 1 , wherein the silver-containing compound comprises silver nitrate, silver nitrite, silver oxide, silver sulfate, silver phosphate, a silver halide, or a mixture thereof.
3. The method of claim 1 , wherein the organic acid comprises lactic acid, citric acid, oxalic acid, ascorbic acid, fumaric acid, maleic acid, or a mixture thereof.
4. The method of claim 1 , wherein the alkali metal-containing compound comprises a sodium-containing compound, a potassium-containing compound or a mixture thereof.
5. The method of claim 4 , wherein the sodium-containing compound is sodium nitrate, and the potassium containing compound is potassium nitrate.
6. The method of claim 4 , wherein an anionic species of the alkali metal-containing compound is the same as an anionic species of the silver-containing compound.
7. The method of claim 1 , wherein the temperature of the heating is at least about 50 degrees Celsius.
8. The method of claim 1 , wherein the temperature of the heating is about 100 degrees Celsius to about 150 degrees Celsius.
9. The method of claim 1 , wherein the time of the heating is about 10 minutes to about 24 hours.
10. The method of claim 1 , wherein the time of the heating is about 15 minutes to about 5 hours.
11. The method of claim 1 , further comprising recovering the metallic silver from the reaction product.
12. The method of claim 11 , wherein the recovering comprises:
disposing the reaction product in a solvent; and
separating the metallic silver from the solvent.
13. The method of claim 11 , further comprising cooling the reaction product before recovering the metallic silver from the reaction product.
14. The method of claim 1 , wherein the metallic silver is produced in a fractional yield of greater than 90 percent.
15. A method for making metallic silver, the method comprising:
contacting a silver-containing compound with an organic acid in the presence of a catalytically effective amount of a catalyst comprising an alkali metal-containing compound to form an at least substantially solvent-free solid state reaction mixture, wherein the concentration of the organic acid is equimolar to or in a stoichiometric excess of the concentration of the cationic silver species in the silver-containing compound;
heating the at least substantially solvent-free solid state reaction mixture to a temperature less than the melting temperature of the organic acid for about 10 minutes to about 24 hours to produce a reaction product comprising metallic silver from the cationic silver species of the silver-containing compound;
cooling the reaction product;
disposing the cooled reaction product in a solvent, wherein the metallic silver is dispersed in the solvent; and
separating the metallic silver from the solvent.
16. The method of claim 15 , wherein the silver-containing compound is silver nitrate, the organic acid is ascorbic acid, and the alkali metal-containing compound is sodium nitrate.