Methods for producing silver-amended carbon materials
Silver-amended carbon materials containing silver nanoparticles are prepared by a process involving an initial reduction of a porous carbon material, followed by contacting the reduced porous carbon material with an aqueous solution of a silver salt. Such silver-amended carbon materials may contain a relatively high loading of silver nanoparticles on both the outside surface and within the interior of the porous carbon material and are useful for disinfecting and/or otherwise purifying fluids such as microbe-containing fluids.
1. A method of preparing a silver-amended carbon material, comprising a step of:
contacting a reduced porous carbon material with an aqueous solution containing the silver ion (Ag(I) or Ag + ), whereby the reduced porous carbon material acts as a reducing agent with respect to the silver ion and reduces the silver ion to form elemental silver (Ag(0)), which deposits in the form of nanoparticles both on and within the exterior of the reduced porous carbon material,
wherein the reduced porous carbon material is prepared by contacting a starting porous carbon material having an electron storage capacity with a pre-determined amount of a reducing agent in an aqueous solution to obtain the reduced porous carbon material, wherein the reducing agent is capable of donating electrons to the starting porous carbon material, and
wherein an amount of silver ion is used which is selected based on the electron storage capacity of the starting porous carbon material.
2. The method of claim 1 , wherein the electron storage capacity of the starting porous carbon material is at least 0.5 mmol/g.
3. The method of claim 1 , wherein the starting porous carbon material is selected from the group consisting of biochars, activated carbons, pyrolyzed hydrochars, soot, graphite, graphene oxides, fullerenes, char, charcoal, carbon black, and carbon nanotubes.
4. The method of claim 1 , wherein the contacting of the reduced porous carbon material with the aqueous solution containing the silver ion is carried out at a pH of from 3 to 8.
5. The method of claim 1 , wherein the reducing agent is selected from the group consisting of dithionites, thiosulfates, (poly)sulfides, cysteine, glutathione, titanium (III) compounds and complexes, iron (II) compounds and complexes, borohydrides, aluminum hydrides, hydrazine, and hydroxylamine.
6. The method of claim 1 , wherein the aqueous solution containing silver ion comprises a salt selected from the group consisting of silver nitrate, silver sulfate, silver perchlorate, silver acetate, silver nitrite, silver bicarbonate and combinations thereof.
7. The method of claim 1 , wherein the contacting of the starting porous carbon material with the pre-determined amount of a reducing agent is carried out under oxygen-free or oxygen-limited conditions.
8. The method of claim 1 , wherein the predetermined amount of reducing agent used is an amount which is at least 5% by mole of the electron storage capacity of the starting porous carbon material.
9. The method of claim 1 , wherein the predetermined amount of reducing agent is an amount which is in excess by mole of the electron storage capacity of the starting porous carbon material.
10. The method of claim 1 , wherein the reduced porous carbon material is fully reduced, as determined by the electron storage capacity.
11. The method of claim 1 , wherein the reduced porous carbon material has been collected, optionally rinsed with water and dried, prior to being contacted with the aqueous solution of the silver ion.
12. The method of claim 1 , wherein the aqueous solution containing the silver ion is added incrementally to an aqueous suspension of the reduced porous carbon material.
13. The method of claim 12 , wherein the aqueous solution containing the silver ion is added at a rate effective to maintain an Ag+ concentration in the aqueous suspension of at least 0.1 mM.
14. The method of claim 1 , wherein the silver-amended carbon material is comprised of at least 5% by weight silver based on the total weight of the silver-amended carbon material.
15. The method of claim 1 , wherein the silver nanoparticles have an average size of 1 to 100 nm as determined by Scanning Electron Microscopy (SEM) analysis.
16. The method of claim 1 , wherein at least 50% of the silver in the silver-amended carbon material is in the form of elemental silver.
17. The method of claim 1 , wherein the silver-amended carbon material is in a form selected from the group consisting of powder, granules, fibers, blocks and nanotubes.
18. The method of claim 1 , wherein the starting porous carbon material has a BET surface area of at least 10 m 2 /g.
19. The method of claim 1 , wherein the starting porous carbon material has an internal porosity of at least 5%.
20. A silver-amended carbon material produced by the method of claim 1 .
21. A method of purifying and disinfecting a fluid containing microorganism(s) comprising contacting the fluid with a silver-amended carbon material produced by the method of claim 1 .
22. The method of claim 21 , wherein the fluid additionally comprises one or more contaminants selected from the group consisting of organic compounds and metal ions.