US3981965A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Suppression of water pollution caused by solid wastes containing chromium compounds
Assignee: Honeywell International Inc
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Filing: 1975-06-17
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Granted: 1976-09-21
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Expires: 1995-06-17
Abstract
Abstract A method of treating solid waste material containing minor amounts of water soluble chromium compounds with a reductant, particularly sulfide ions, to convert the soluble chromium to an insoluble state, and produce a solid waste from which substantially no chromium can be leached by water, as by exposure to rain.
Inventors
- 👤 Alan B. Gancy
- 👤 Christian A. Wamser
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 01:56
CPC Classifications
C; C02; C02F; C02F1/00; C02F1/70; C01; C01G; C01G37/00; C02F2101/00; C02F2101/10; C02F2101/20; C02F2101/22; Y; Y10; Y10S; Y10S210/00; Y10S210/902; Y10S210/911; Y10S210/912; Y10S210/913
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
80 words
A method fpr continuously insolubilizing essentially all water-solubilized hexavalent chromium compounds leached from a chrome ore residue obtained by production of chromium chemicals for chromite ore by roasting the ore under alkaline oxidizing conditions to form water-soluble hexavalent chromium compounds, which comprises adding to said residue a sulfur-containing reductant, thereby continuously effecting reduction of said water-solubilized hexavalent chromium compounds in the presence of an aqueous medium under conditions sufficient to reduce said water-solubilized hexavalent chromium compounds to their insoluble form.
Claim 2
Independent Claim
80 words
A method fpr continuously insolubilizing essentially all water-solubilized hexavalent chromium compounds leached from a chrome ore residue obtained by production of chromium chemicals for chromite ore by roasting the ore under alkaline oxidizing conditions to form water-soluble hexavalent chromium compounds, which comprises adding to said residue a sulfur-containing reductant, thereby continuously effecting reduction of said water-solubilized hexavalent chromium compounds in the presence of an aqueous medium under conditions sufficient to reduce said water-solubilized hexavalent chromium compounds to their insoluble form.
Claim 3
Dependent Claim
35 words
The method of claim 1 wherein at least part of the aqueous medium is separated from the residue and recycled for use in the reduction of water-solubilized hexavalent chromium compounds in said chrome ore residue.
Claim 4
Dependent Claim
27 words
The method of claim 1 wherein the reduction is an organic sulfur-containing compound, selected from the group consisting of thiourea, thioglycolic acid, sodium xanthate, thioacetamide and bis(dimethylthiocarbamoyl)disulfide.
Claim 5
Dependent Claim
11 words
The method of claim 1 wherein the reductant is calcium sulfide.
Claim 6
Dependent Claim
11 words
The method of claim 1 wherein the reductant is sodium hydrosulfide.
Claim 7
Dependent Claim
26 words
The method of claim 1 in which the reductant is produced by reaction of a calcium compound contained in said or residue with an added sulfide.
Claim 8
Dependent Claim
63 words
The method of claim 1 wherein the reductant is selected from the group consisting of alkali metal and alkaline earth metal sulfides, and the sulfide ions are present in an amount of at least equivalent to about one-third of the amount of sulfide ions stoichiometrically required to reduce the total water-soluble hexavalent chromium compounds in the chrome ore residue to the trivalent state.
Claim 9
Dependent Claim
43 words
The method of claim 1 wherein the reductant is selected from the group consisting of alkali metal and alkaline earth metal hydrosulfides and wherein polysulfide formation is suppressed by the addition of a minor amount of sodium sulfite to the chrome ore residue.
Claim 10
Dependent Claim
40 words
The process of claim 4 wherein the amount of calcium sulfide added is equivalent to from about 1 to 3 moles of calcium sulfide per 2 moles of hexavalent chromium, calculated as CrO 4 , in said chrome ore residue.
Claim 11
Dependent Claim
40 words
The process of claim 5 wherein the amount of sodium hydrosulfide added is equivalent to from about 1 to 3 moles of sodium hydrosulfide per 2 moles of hexavalent chromium, calculated as CrO 4 , in said chrome ore residue.
Claim 12
Dependent Claim
26 words
The method of claim 1 wherein the sulfur-containing reductant is selected from the group consisting of alkali metal and alkaline earth metal hydrosulfides and mixtures thereof.
Claim 13
Dependent Claim
23 words
The method of claim 1 wherein the sulfur-containing reductant is selected from the group consisting of alkali metal and alkaline earth metal sulfides.
Claim 14
Dependent Claim
23 words
The method of claim 1 wherein the sulfur-containing reductant is selected from the group consisting of alkali metal and alkaline earth metal dithionites.
Claim 15
Dependent Claim
35 words
The method of claim 1 wherein the chrome ore residue contains water-soluble hexavalent chromium compounds in an amount of from about 0.5 to 5 percent chromium, based on the weight of the chrome ore residue.
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) | 1979-09-21 | 1980-03-22 | 1980-09-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-09-21 | 1984-03-22 | 1984-09-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-09-21 | 1988-03-22 | 1988-09-21 | $7700.00 | Window Closed / Lapsed |