US4353741A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Silver coated particles and a process for preparing them
Assignee: Arch Chemicals Inc
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Filing: 1980-03-27
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Granted: 1982-10-12
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Expires: 2000-03-27
Abstract
Abstract Silver coated particles having high concentrations of metallic silver are produced which are useful in forming alloys with metals such as mercury. The process comprises admixing carrier particles with an aqueous solution of a silver salt to form a slurry. A hydrazine compound is added to the slurry to precipitate metallic silver on the carrier particles in a medium which becomes increasingly acidic. Silver coated particles having a metallic silver content up to 90 percent by weight of the coated particle can be produced in a single impregnation under conditions which prevent the formation of explosive by-products such as silver nitride. The silver coated particles are particularly suitable for the recovery of metals such as mercury from fluids.
Inventors
- 👤 Italo A. Capuano
- 👤 Lawrence P. Carr
- 👤 Patricia A. Turley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 03:18
CPC Classifications
C; C22; C22B; C22B11/00; C22B11/04; C22B11/10; C22B3/00; C22B3/20; C22B3/22; C22B3/24; C22B43/00; C23; C23C; C23C18/00; C23C18/16; C23C18/31; C23C18/42; C23C18/44; Y; Y02; Y02P; Y02P10/00; Y02P10/20
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
122 words
A process for producing silver coated particles which comprises: (a) admixing active carbon carrier particles with an aqueous solution of a silver salt to form a slurry consisting of said active carbon carrier particles in said aqueous solution of the silver salt; (b) adding a reducing agent consisting of a hydrogen compound to said slurry to deposit metallic silver on said active carbon carrier particles and therby form a reaction mixture of the resulting silver coated active carbon carrier particles in an acid medium having an increasing acidity as said silver is deposited, at the conclusion of said silver deposition, said reaction mixture having a pH of less than about 4; and (c) recovering said silver coated particles from said reaction mixture.
Claim 2
Dependent Claim
122 words
A process for producing silver coated particles which comprises: (a) admixing active carbon carrier particles with an aqueous solution of a silver salt to form a slurry consisting of said active carbon carrier particles in said aqueous solution of the silver salt; (b) adding a reducing agent consisting of a hydrogen compound to said slurry to deposit metallic silver on said active carbon carrier particles and therby form a reaction mixture of the resulting silver coated active carbon carrier particles in an acid medium having an increasing acidity as said silver is deposited, at the conclusion of said silver deposition, said reaction mixture having a pH of less than about 4; and (c) recovering said silver coated particles from said reaction mixture.
Claim 3
Dependent Claim
28 words
The process of claim 1 in which said hydrazine compound is selected from the group consisting of anhydrous hydrazine, aqueous solutions of hydrazine, hydrazine salts, and alkyl hydrazines.
Claim 4
Dependent Claim
26 words
The process of claim 2 in which said reaction mixture is maintained at a temperature in the range at from about 0° to about 55° C.
Claim 5
Dependent Claim
30 words
The process of claim 3 in which said silver coated particles have a metallic silver content of from about 2 to about 90 percent by weight of the coated particles.
Claim 6
Dependent Claim
26 words
The process of claim 4 in which said silver salt is selected from the group consisting of silver nitrate, silver fluoride, silver metaborate, and silver silicofluoride.
Claim 7
Dependent Claim
25 words
The process of claim 5 in which said carrier is an active carbon material selected from the group consisting of coconut carbon, wood and charcoals.
Claim 8
Dependent Claim
29 words
the process of claim 6 in which said silver coated particles have a silver content of from about 25 to about 80 percent by weight of the coated particles.
Claim 9
Dependent Claim
16 words
The process of claim 7 in which said hydrazine compound is an aqueous solution of hydrazine.
Claim 10
Dependent Claim
13 words
The process of claim 8 in which said silver salt is silver nitrate.
Claim 11
Dependent Claim
13 words
The process of claim 9 in which said carrier particles are coconut carbon.
Claim 12
Dependent Claim
28 words
the process of claim 10 in which sad silver coated particles have silver content of from about 30 to about 70 percent by weight of the coated particles.
Claim 13
Dependent Claim
166 words
A process for producing silver coated particles having a high content of metallic silver which comprises: (a) mixing particles of porous active carbon with an aqueous solution of silver nitrate to form a slurry consisting of said particles of porous active carbon in an aqueous solution of silver nitrate; (b) adding a reducing agent consisting of a hydrazine compound to said slurry to deposit metallic silver on the surface and in the pores of said porous active carbon particles and thereby to form an acid reaction mixture of the resulting silver coated carrier particles and nitric acid, said reaction mixture having an increasing concentration of nitric acid as said silver is deposited, at the conclusion of said silver deposition, said reaction mixture having a pH of less than about 4, said silver coated particles having a metallic silver content in the range of from about 30 to about 70 percent by weight of the coated particle; and (c) recovering said coated particles from said reaction mixture.
Claim 14
Dependent Claim
166 words
A process for producing silver coated particles having a high content of metallic silver which comprises: (a) mixing particles of porous active carbon with an aqueous solution of silver nitrate to form a slurry consisting of said particles of porous active carbon in an aqueous solution of silver nitrate; (b) adding a reducing agent consisting of a hydrazine compound to said slurry to deposit metallic silver on the surface and in the pores of said porous active carbon particles and thereby to form an acid reaction mixture of the resulting silver coated carrier particles and nitric acid, said reaction mixture having an increasing concentration of nitric acid as said silver is deposited, at the conclusion of said silver deposition, said reaction mixture having a pH of less than about 4, said silver coated particles having a metallic silver content in the range of from about 30 to about 70 percent by weight of the coated particle; and (c) recovering said coated particles from said reaction mixture.
Claim 15
Dependent Claim
26 words
The process of claim 12 in which the temperature of said reaction mixture is maintained in the range of from about 0° to about 55° C.
Claim 16
Dependent Claim
16 words
The process of claim 13 in which said hydrazine compound is an aqueous solution of hydrazine.
Claim 17
Dependent Claim
13 words
The process of claim 14 in which said active carbon is coconut carbon.
Claim 18
Dependent Claim
27 words
The process of claim 1 or 2 in which, at the conclusion of said silver deposition, an excess of hydrazine is employed to neutralize said reaction mixture.
Claim 19
Dependent Claim
157 words
A process for producing silver coated particles which comprises: (a) admixing carrier particles with an aqueous solution of an ionic silver salt to form a slurry consisting of said carrier particles in said aqueous solution of an ionic silver salt; (b) adding a reducing agent consisting of a hydrazine compound to said slurry to reduce said ionic silver to metallic silver while forming an acidic reaction mixture which increases the acidity of said slurry, said rate of addition of said hydrazine compound being controlled to maintain the reaction mixture within the desired temperature range; (c) depositing said metallic silver on said carrier particles; (d) continuing said hydrazine addition until the slurry is substantially depleted of silver ions and said slurry is highly acidic, the pH of said slurry being less than about 4; (e) adding a neutralizing agent to said slurry to form a neutralized slurry; and (f) recovering said silver coated particles from said neutralized slurry.
Claim 20
Dependent Claim
157 words
A process for producing silver coated particles which comprises: (a) admixing carrier particles with an aqueous solution of an ionic silver salt to form a slurry consisting of said carrier particles in said aqueous solution of an ionic silver salt; (b) adding a reducing agent consisting of a hydrazine compound to said slurry to reduce said ionic silver to metallic silver while forming an acidic reaction mixture which increases the acidity of said slurry, said rate of addition of said hydrazine compound being controlled to maintain the reaction mixture within the desired temperature range; (c) depositing said metallic silver on said carrier particles; (d) continuing said hydrazine addition until the slurry is substantially depleted of silver ions and said slurry is highly acidic, the pH of said slurry being less than about 4; (e) adding a neutralizing agent to said slurry to form a neutralized slurry; and (f) recovering said silver coated particles from said neutralized slurry.
Claim 21
Dependent Claim
33 words
The process of claim 17 in which following step (f), said neutralized liquor is treated with an oxidizing agent selected from the group consisting of alkali metal hypochlorites and alkaline earth metal hypochlorites.
Claim 22
Dependent Claim
72 words
A process for the recovery of metallic mercury from a mercury-containing liquid having a pH of about 5 or higher which comprises: (a) producing silver particles by the process of claim 7, (b) contacting said mercury-containing liquid with said silver coated particles to dissolve said mercury in said silver coated particles to form a silver amalgam, (c) recovering a purified liquid containing less than about 200 parts per billion of metallic mercury.
Claim 23
Dependent Claim
37 words
The process of claim 19 in which said mercury-containing liquid is selected from the group consisting of solutions of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal alkoxides, alkaline earth metal alkoxides, and alkali metal hydrosulfites.
Claim 24
Dependent Claim
13 words
The process of claim 2 in which said mercury-containing liquid is sodium methylate.
Claim 25
Dependent Claim
42 words
In a process for the oxidation of alkylene hydrocarbons in the presence of a silver catalyst to produce alkylene oxides, the improvement which comprises producing silver particles by the process of claim 12 and employing said silver particles as said silver catalyst.
Claim 26
Dependent Claim
28 words
The process of claim 11 or 12 in which the temperature of said reaction mixture is maintained in the range of from about 0° to about 25° C.
Claim 27
Dependent Claim
29 words
The process of claim 11 or 12 in which said temperature of said reaction mixture is maintained in the range of from about 25° C. to about 35° C.
References Cited (Backward Citations)
US4130506A
Cited
US4126582A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-10-11 | 1986-04-12 | 1986-10-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-10-11 | 1990-04-12 | 1990-10-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-10-11 | 1994-04-12 | 1994-10-12 | $7700.00 | Window Closed / Lapsed |