US3939249A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Purification of talc
Assignee: BASF Catalysts LLC
•
Filing: 1974-11-07
•
Granted: 1976-02-17
•
Expires: 1994-11-07
Abstract
Abstract An arsenic sulfide mineral impurity, such as gersdoffite, is removed from talc by an oxidative leach treatment at a pH below 2.
Inventors
- 👤 Fred R. Huege
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 13:04
CPC Classifications
C; C01; C01B; C01B33/00; C01B33/20; C01B33/22
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
83 words
A method for removing an arsenic sulfide impurity from talc which comprises acidifying an aqueous pulp of said impure talc to a pH below 2 with an acid selected from the group consisting of sulfuric and hydrochloric, adding to said pulp an oxidizing agent having an oxidation potential with a greater negative value than -1.0 volts, maintaining the pH of said pulp below 2 until said impurity is dissolved therein, separating the talc from said pulp and washing the resulting purified talc product.
Claim 2
Independent Claim
83 words
A method for removing an arsenic sulfide impurity from talc which comprises acidifying an aqueous pulp of said impure talc to a pH below 2 with an acid selected from the group consisting of sulfuric and hydrochloric, adding to said pulp an oxidizing agent having an oxidation potential with a greater negative value than -1.0 volts, maintaining the pH of said pulp below 2 until said impurity is dissolved therein, separating the talc from said pulp and washing the resulting purified talc product.
Claim 3
Dependent Claim
35 words
The method of claim 1 wherein the oxidant is selected from the group consisting of ozone, hydrogen peroxide, chlorine, hypochlorite salts, perchlorate salts and persulfate salts and sulfuric acid is used to acidify the pulp.
Claim 4
Dependent Claim
11 words
The method of claim 1 wherein the oxidant is hydrogen peroxide.
Claim 5
Dependent Claim
14 words
The method of claim 1 wherein the arsenic sulfide impurity is a complex arsenic-nickel-sulfide.
Claim 6
Dependent Claim
13 words
The method of claim 1 wherein said talc is in platy crystalline form.
Claim 7
Dependent Claim
38 words
The method of claim 1 wherein the pulp containing the oxidant is maintained at a pH below 2 for a time sufficient to reduce the acid soluble arsenic content to a value of about 2 p.p.m. or less.
Claim 8
Dependent Claim
28 words
The method of claim 1 wherein the impure talc contains carbonate minerals and after said oxidizing agent is incorporated, additional acid is added to maintain pH below 2.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-02-16 | 1979-08-18 | 1980-02-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-02-16 | 1983-08-18 | 1984-02-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-02-16 | 1987-08-18 | 1988-02-17 | $7700.00 | Window Closed / Lapsed |