CA1329005C - Method for precipitation of chromium and/or vanadium from waste sulphuric acid from the titanium dioxide production - Google Patents
Method for precipitation of chromium and/or vanadium from waste sulphuric acid from the titanium dioxide productionInfo
- Publication number
- CA1329005C CA1329005C CA000565304A CA565304A CA1329005C CA 1329005 C CA1329005 C CA 1329005C CA 000565304 A CA000565304 A CA 000565304A CA 565304 A CA565304 A CA 565304A CA 1329005 C CA1329005 C CA 1329005C
- Authority
- CA
- Canada
- Prior art keywords
- sulphuric acid
- aging
- chromium
- aluminum
- waste
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/90—Separation; Purification
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/90—Separation; Purification
- C01B17/901—Recovery from spent acids containing metallic ions, e.g. hydrolysis acids, pickling acids
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Waste sulphuric acid resulting from the titanium dioxide production is concentrated by evaporation followed by an aging process during which the metals, except chromium and vanadium, are precipitated. In order to sufficiently precipitate chromium and vanadium in a reasonably short time, the evaporated waste sul-phuric acid is mixed with aluminum having an active surface, which may be achieved by comminution e.g. cutting or pulverization not more than 4 hours before adding it to the waste sulphuric acid.
Waste sulphuric acid resulting from the titanium dioxide production is concentrated by evaporation followed by an aging process during which the metals, except chromium and vanadium, are precipitated. In order to sufficiently precipitate chromium and vanadium in a reasonably short time, the evaporated waste sul-phuric acid is mixed with aluminum having an active surface, which may be achieved by comminution e.g. cutting or pulverization not more than 4 hours before adding it to the waste sulphuric acid.
Description
The invention concerns a method for precipitating chromium and/or vanadium from evaporated waste sulphuric acid from the titanium dioxide production by aging after evaporation.
In titanium dioxide production waste sulphuric acid is generated having a concentration between 18 and 28 % containing metal impurities such as iron, aluminum, magnesium, titanium, chromium, vanadium, manganese, etc., of concentrations up to some % by weight.
In various publications, for example, DE-A-28 07 308, DE-A-28 07 360 and DE-A-28 07 304, it is described that such waste sulphuric acid can be conditioned for recycling by evaporating water from the dilute acid to a concentration of e.g. 65 to 70 %
~ollowed by an aging process during which the metal impurities are precipitated and separated. The aging process allows to precipit-ate the metal impurities within hours or days to such a degree that the conditioned sulphuric acid is fit for reuse.
It soon became clear that especially chromium and vana-dium precipitate only very slowly, e.g. at an initial chromium concentration of between 300 and 400 ppm, the final concentration after one weekls aging is still more than 200 ppm. Due to the strong colorific effect, sulphuric acid with such chromium and vanadium amounts can only be used to a limited extent in e.g. the pigment or dyestuff industry, especially for the production of titanium dioxide. A reduction of the chromium concentration to values below 200 ppm, if possible to below 100 ppm, would be desirable.
It is also described in DE-A-26 18 121 and DE-A-27 29 756 that during evaporation the removal of chromium from waste sul-phuric acid resulting from titanium dioxide production can be improved by adding metal sulphates especially ferric (II)-sulphate.
When using this method, however, the chromium precipitation is often insufficient~
In DE-A-24 46 117 and United States Patent3,575,853, it ; is described that chromium complex compounds and chromates result-ing from industrial waste water, e.g. from the galvanic industry such as metal chroming can be separated or floculated by contact with aluminum plates or particles. The application of this method for the purifica~ion of waste sulphuric acid resulting from titanium dioxide production, where chromium is found in a different form, has not shown the expected results.
It is further described, for example, in Swiss Patent Publication 409,800, DE-A 678 034 and Unexamined Japanese Patent Publication 79/65 194 that a number of heavy metals such as copper, ;~ iron, mercury or lead can be precipitated from waste waters con-; taining sulphuric acid by the influence of aluminum. However, also with this method is~ the chromium s~parati`o~ insufficient to allow reuse of the sulphuric acid for the titanium dioxide production.
It is attempted in the pr~sent invention to devise a method which allows a better chromium and/or vanadium separation from evaporated sulphuric acid resulting from the titanium dioxide production within a shorter time and achieving a lower concentra-tion so that the purified sulphuric acid can be reused for the , 1 32 q 0 0~ 22511 150 titanium dioxide production.
According to the invention, metallic aluminum having an active sur~ace is added to the waste sulphuric acid after evapora-tion but before the aging process. The formation of the active surface may be achieved by comminution, especially cutting or pulverization of aluminum at a predetermined period of time before adding to the waste sulphuric acid.
To maintain an active surface, the comminution should preferably be done not more than 4 hours before adding it to the waste sulphuric acid when it is stored under normal conditions.
The chromium separation can additionally be improved by adding seed crystals taken from the solids separated from the sulphuric acid, preferably in an amount of 1.5 to 2.5% by weight.
It is assumed that the favorable effect of adding aluminum having active surface is based on the very negative redox potential of the aluminum resulting in a redo~ reaction, when chromium is present in the titanium dioxide waste sulphuric acid in a specific form. The higher valence chromium ions, e.g. 6-3-valence ions are thus probably reduced to lower valued e.g. 3-valued chromium ions or to metallic chromium. In this way the solubility of some salts of the 3-valued chromium especially sul-phate and calcium chromite is much lower as compared to the corres-ponding salts in the 6-valence chromium so that in this special waste acid the reduction by means of active chromium results in a faster and quantitatively higher precipitation of chromium salts than with conventional methods. A similar effect is achieved for .~ ~
.
, .
1 3290~5 the precipitation ofvanadium in a waste sulphuric acid of said origin.
The evaporated sulphuric acid is usually in a slurry form and has a sulphuric acid concentration of about 60-70% by weight.
Usually, the necessary amount of aluminum to be added is at least 0.2, preferably about 0.3 % by weight based on the eva-porated sulphuric acid, depending on the initial material. A
higher temperature results in a further increase of the chromium separation. The aging is performed preferably at 40 to 70C.
Although a remarkably increased chromium separation is achieved at 40VC, much more favorable results are obtained at temperatures of up to 60C. Under these conditions and at an initial material with a chromi~m content of over 300 ppm a reduction of the chromium concentration in the concentrate to below 200 ppm within 24 hours and to below 100 ppm within two to four days is achieved whereas the reduction to 200 ppm without the addition of aluminum re~uired one week, and a reduction to 100 ppm was not achieved at all~
The basic material, a 22% sulphuric acid from an ilmenit/
slag disintegration was heated up to the relevant boiling point up to max. 150C and evaporated to a sulphuric acid salt slurry with a free H2SO4 content of 63.9 ~ and the following metal impurities in the filtrate:
.
~ _ 4 _ ~: Fe 0.40 %
Al 0.45 %
Mg 0.48 %
Cr 320 ppm V 300 ppm ', Mn 300 ppm Ti 0.11 %
;: A part of this test acid was aged without additives at 55C during one week (test 1). Another part of the test acid was mixed with seed crystals (2 % by weight) taken from the precipitat-: ed, aged substance of an earlier test and then aged at 55C resp.
; 40C (tests 2 and 3). A further part of the test acid was mixed with 0.3 % by weight aluminum chips which had been cut less than one hour before adding them to the acid (test 4).
.' The reduction of ahromium content as to time was observea ~ in all ~our samples, and the following results were achieved: -.'~ Co~parison examples .,~
', Aging Sample 1 Sample 2 Sam~le 3 Sample 4 time -/-/55C -/2%/40C -/2%/55C 0.3%/2%/55C
'Hours ppm Cr ppm Cr ppm Cr ppm Cr 19 27~ 290 270 230 , 63 265 275 220 130 The test results show that with an addition of 0.3%
. active aluminum the chromium content can be reduced to the in ,' many cases admissible limit value of 200 ppm within 2a houxs.
., _ 5 _ :~ .
1 3290n5 After less than 4 days aging the chromium content is almost reduced to the value required if the acid is reused, i.e. below 100 ppm. The comparison examples show that a reduction of the chromium content to below 200 ppm can only be achieved by adding seed crystals in the amount of 2% by weight and aging at a tem-perature of 55C during four days. In the comparison example without additives, this value was not achieved even after one week of aging.
As the comparison examples l to 3 show, chromium separa-tion at 55C is slightly higher than at 40C. A mere temperature increase however is not sufficient even at aging periods of one week to reduce the chromium content to below lO0 ppm.
As has been proved by further tests, an increased aluminum addition resulted in a faster chromium separation. How-ever, the addition of aluminum chips made the day before showed a result which was not substantially better than in example 3.
Similar observations were made as regards to the reduc-tion of the concentration of other, scarcely precipitatable impurities, especially vanadium. It is recommended to use well-aged seed crystals for better reduction of the concentration.
In titanium dioxide production waste sulphuric acid is generated having a concentration between 18 and 28 % containing metal impurities such as iron, aluminum, magnesium, titanium, chromium, vanadium, manganese, etc., of concentrations up to some % by weight.
In various publications, for example, DE-A-28 07 308, DE-A-28 07 360 and DE-A-28 07 304, it is described that such waste sulphuric acid can be conditioned for recycling by evaporating water from the dilute acid to a concentration of e.g. 65 to 70 %
~ollowed by an aging process during which the metal impurities are precipitated and separated. The aging process allows to precipit-ate the metal impurities within hours or days to such a degree that the conditioned sulphuric acid is fit for reuse.
It soon became clear that especially chromium and vana-dium precipitate only very slowly, e.g. at an initial chromium concentration of between 300 and 400 ppm, the final concentration after one weekls aging is still more than 200 ppm. Due to the strong colorific effect, sulphuric acid with such chromium and vanadium amounts can only be used to a limited extent in e.g. the pigment or dyestuff industry, especially for the production of titanium dioxide. A reduction of the chromium concentration to values below 200 ppm, if possible to below 100 ppm, would be desirable.
It is also described in DE-A-26 18 121 and DE-A-27 29 756 that during evaporation the removal of chromium from waste sul-phuric acid resulting from titanium dioxide production can be improved by adding metal sulphates especially ferric (II)-sulphate.
When using this method, however, the chromium precipitation is often insufficient~
In DE-A-24 46 117 and United States Patent3,575,853, it ; is described that chromium complex compounds and chromates result-ing from industrial waste water, e.g. from the galvanic industry such as metal chroming can be separated or floculated by contact with aluminum plates or particles. The application of this method for the purifica~ion of waste sulphuric acid resulting from titanium dioxide production, where chromium is found in a different form, has not shown the expected results.
It is further described, for example, in Swiss Patent Publication 409,800, DE-A 678 034 and Unexamined Japanese Patent Publication 79/65 194 that a number of heavy metals such as copper, ;~ iron, mercury or lead can be precipitated from waste waters con-; taining sulphuric acid by the influence of aluminum. However, also with this method is~ the chromium s~parati`o~ insufficient to allow reuse of the sulphuric acid for the titanium dioxide production.
It is attempted in the pr~sent invention to devise a method which allows a better chromium and/or vanadium separation from evaporated sulphuric acid resulting from the titanium dioxide production within a shorter time and achieving a lower concentra-tion so that the purified sulphuric acid can be reused for the , 1 32 q 0 0~ 22511 150 titanium dioxide production.
According to the invention, metallic aluminum having an active sur~ace is added to the waste sulphuric acid after evapora-tion but before the aging process. The formation of the active surface may be achieved by comminution, especially cutting or pulverization of aluminum at a predetermined period of time before adding to the waste sulphuric acid.
To maintain an active surface, the comminution should preferably be done not more than 4 hours before adding it to the waste sulphuric acid when it is stored under normal conditions.
The chromium separation can additionally be improved by adding seed crystals taken from the solids separated from the sulphuric acid, preferably in an amount of 1.5 to 2.5% by weight.
It is assumed that the favorable effect of adding aluminum having active surface is based on the very negative redox potential of the aluminum resulting in a redo~ reaction, when chromium is present in the titanium dioxide waste sulphuric acid in a specific form. The higher valence chromium ions, e.g. 6-3-valence ions are thus probably reduced to lower valued e.g. 3-valued chromium ions or to metallic chromium. In this way the solubility of some salts of the 3-valued chromium especially sul-phate and calcium chromite is much lower as compared to the corres-ponding salts in the 6-valence chromium so that in this special waste acid the reduction by means of active chromium results in a faster and quantitatively higher precipitation of chromium salts than with conventional methods. A similar effect is achieved for .~ ~
.
, .
1 3290~5 the precipitation ofvanadium in a waste sulphuric acid of said origin.
The evaporated sulphuric acid is usually in a slurry form and has a sulphuric acid concentration of about 60-70% by weight.
Usually, the necessary amount of aluminum to be added is at least 0.2, preferably about 0.3 % by weight based on the eva-porated sulphuric acid, depending on the initial material. A
higher temperature results in a further increase of the chromium separation. The aging is performed preferably at 40 to 70C.
Although a remarkably increased chromium separation is achieved at 40VC, much more favorable results are obtained at temperatures of up to 60C. Under these conditions and at an initial material with a chromi~m content of over 300 ppm a reduction of the chromium concentration in the concentrate to below 200 ppm within 24 hours and to below 100 ppm within two to four days is achieved whereas the reduction to 200 ppm without the addition of aluminum re~uired one week, and a reduction to 100 ppm was not achieved at all~
The basic material, a 22% sulphuric acid from an ilmenit/
slag disintegration was heated up to the relevant boiling point up to max. 150C and evaporated to a sulphuric acid salt slurry with a free H2SO4 content of 63.9 ~ and the following metal impurities in the filtrate:
.
~ _ 4 _ ~: Fe 0.40 %
Al 0.45 %
Mg 0.48 %
Cr 320 ppm V 300 ppm ', Mn 300 ppm Ti 0.11 %
;: A part of this test acid was aged without additives at 55C during one week (test 1). Another part of the test acid was mixed with seed crystals (2 % by weight) taken from the precipitat-: ed, aged substance of an earlier test and then aged at 55C resp.
; 40C (tests 2 and 3). A further part of the test acid was mixed with 0.3 % by weight aluminum chips which had been cut less than one hour before adding them to the acid (test 4).
.' The reduction of ahromium content as to time was observea ~ in all ~our samples, and the following results were achieved: -.'~ Co~parison examples .,~
', Aging Sample 1 Sample 2 Sam~le 3 Sample 4 time -/-/55C -/2%/40C -/2%/55C 0.3%/2%/55C
'Hours ppm Cr ppm Cr ppm Cr ppm Cr 19 27~ 290 270 230 , 63 265 275 220 130 The test results show that with an addition of 0.3%
. active aluminum the chromium content can be reduced to the in ,' many cases admissible limit value of 200 ppm within 2a houxs.
., _ 5 _ :~ .
1 3290n5 After less than 4 days aging the chromium content is almost reduced to the value required if the acid is reused, i.e. below 100 ppm. The comparison examples show that a reduction of the chromium content to below 200 ppm can only be achieved by adding seed crystals in the amount of 2% by weight and aging at a tem-perature of 55C during four days. In the comparison example without additives, this value was not achieved even after one week of aging.
As the comparison examples l to 3 show, chromium separa-tion at 55C is slightly higher than at 40C. A mere temperature increase however is not sufficient even at aging periods of one week to reduce the chromium content to below lO0 ppm.
As has been proved by further tests, an increased aluminum addition resulted in a faster chromium separation. How-ever, the addition of aluminum chips made the day before showed a result which was not substantially better than in example 3.
Similar observations were made as regards to the reduc-tion of the concentration of other, scarcely precipitatable impurities, especially vanadium. It is recommended to use well-aged seed crystals for better reduction of the concentration.
Claims (12)
1. A method for the precipitation of chromium, vanadium or a mixture thereof from waste sulphuric acid resulting from a titanium dioxide production, which method comprises:
(a) concentrating the waste sulphuric acid which contains the said metal by evaporation of water, (b) mixing with the concentrated sulphuric acid, metallic aluminum which has an active surface, and (c) aging the sulphuric acid after mixing with aluminum.
(a) concentrating the waste sulphuric acid which contains the said metal by evaporation of water, (b) mixing with the concentrated sulphuric acid, metallic aluminum which has an active surface, and (c) aging the sulphuric acid after mixing with aluminum.
2. A method according to claim 1, wherein the aluminum hav-ing an active surface has been cut or pulverized not more than four hours before mixing with the concentrated sulphuric acid.
3. A method according to claim 1, wherein the amount of the aluminum added is at least 0.2% by weight.
4. A method according to claim 1, 2 or 3, wherein the amount of aluminum added is about 0.3% by weight.
5. A method according to claim 1, 2 or 3, wherein the aging is performed at a temperature in the range of 40°C to 70°C.
6. A method according to claim 1, 2 or 3, wherein the aging is performed at a temperature about 55°C.
7. A method according to claim 1, 2 or 3, wherein, before the aging, the waste sulphuric acid is mixed with seed crystals taken from a material separated from the acid after the aging.
8. A method according to claim 1, 2 or 3, wherein, before the aging the waste sulphuric acid is mixed with seed crystals in the range of 1.5 to 2.5% by weight taken from a material separated from the acid after the aging.
9. A method according to claim 1, 2 or 3, wherein the aging time is not more than four days.
10. A method for the preparation of chromium, vanadium or a mixture thereof from waste sulphuric acid resulting from a titan-ium dioxide production, the said waste sulphuric acid having a sulphuric acid concentration of about 18 to 28% by weight and con-taining chromium, vanadium or both in the range of between 300 and 400 ppm and other impurity metals including iron, aluminum, magnesium, titanium and manganese, which process comprises:
(a) concentrating the waste sulphuric acid by evaporation of water, thereby obtaining a concentrated waste sulphuric acid having a sulphuric concentration of about 60 to 70%, (b) mixing with the concentrated sulphuric acid, metallic aluminum having an active surface in an amount of at least 0.2% by weight based on the concentrated sulphuric acid, (o) aging the aluminum-mixed sulphuric acid at a temperature of 40 to 70°C for about 24 hours to seven days, thereby precipit-ating chromium, vanadium or a mixture thereof together with the other impurity metals, and (d) separating the precipitated metals from the concentrated-aged sulphuric acid.
(a) concentrating the waste sulphuric acid by evaporation of water, thereby obtaining a concentrated waste sulphuric acid having a sulphuric concentration of about 60 to 70%, (b) mixing with the concentrated sulphuric acid, metallic aluminum having an active surface in an amount of at least 0.2% by weight based on the concentrated sulphuric acid, (o) aging the aluminum-mixed sulphuric acid at a temperature of 40 to 70°C for about 24 hours to seven days, thereby precipit-ating chromium, vanadium or a mixture thereof together with the other impurity metals, and (d) separating the precipitated metals from the concentrated-aged sulphuric acid.
11. A method according to claim 10, wherein the aluminum having an active surface has been cut or pulverized not more than four hours before mixing with the concentrated sulphuric acid.
12. A method according to claim 11, wherein the aging is performed with seed crystals previously separated in step (d) in an amount of 1.5 to 2.5% by weight.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH1649/87A CH669184A5 (en) | 1987-04-30 | 1987-04-30 | METHOD FOR SEPARATING IMPURITIES, ESPECIALLY CHROME, FROM WASTE SULFURIC ACID. |
| CH01649/87-3 | 1987-04-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1329005C true CA1329005C (en) | 1994-05-03 |
Family
ID=4215394
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000565304A Expired - Fee Related CA1329005C (en) | 1987-04-30 | 1988-04-28 | Method for precipitation of chromium and/or vanadium from waste sulphuric acid from the titanium dioxide production |
Country Status (12)
| Country | Link |
|---|---|
| EP (1) | EP0313592B1 (en) |
| JP (1) | JPH01503230A (en) |
| KR (1) | KR940006033B1 (en) |
| AU (1) | AU596001B2 (en) |
| CA (1) | CA1329005C (en) |
| CH (1) | CH669184A5 (en) |
| DE (2) | DE3730950A1 (en) |
| ES (1) | ES2007220A6 (en) |
| FI (1) | FI86626C (en) |
| SU (1) | SU1736332A3 (en) |
| WO (1) | WO1988008405A1 (en) |
| ZA (1) | ZA883040B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106186064A (en) * | 2016-07-26 | 2016-12-07 | 大连博融新材料股份有限公司 | A kind of method that degree of depth produces high-purity ammonium metavanadate except chromium |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101812593B (en) * | 2010-04-22 | 2011-06-22 | 攀钢集团钢铁钒钛股份有限公司 | Method for depositing vanadium wastewater by utilizing vanadium-extraction tailings and acid ammonium salt |
| RU2651019C2 (en) * | 2016-09-19 | 2018-04-18 | Федеральное государственное автономное образовательное учреждение высшего образования "Уральский федеральный университет имени первого Президента России Б.Н. Ельцина" | Method for processing liquid wastes of titanium dioxide production |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE578034C (en) * | 1931-06-28 | 1933-06-08 | Dr Paul Weinstock | Purification of sulfuric acid containing metallic impurities |
| DE591056C (en) * | 1932-08-23 | 1934-01-16 | Paul Weinstock Dr | Process for purifying sulfuric acid |
| DE1119835B (en) * | 1958-04-02 | 1961-12-21 | Willy Carl Ferdinand Buesching | Process and device for the continuous processing of sulphate-containing dilute waste sulfuric acids by means of evaporation |
| NL258598A (en) * | 1959-12-03 | |||
| LU39457A1 (en) * | 1960-08-24 | 1961-01-25 | ||
| US3575853A (en) * | 1968-12-24 | 1971-04-20 | Lab Betz Inc | Waste water treatment |
| DE2446117B2 (en) * | 1974-09-27 | 1979-04-26 | Freie Und Hansestadt Hamburg Behoerde Fuer Wirtschaft Und Verkehr, 2000 Hamburg | Device for the separation of complex-bound transition metals from industrial wastewater |
| DE2729756A1 (en) * | 1977-07-01 | 1979-01-11 | Kronos Titan Gmbh | CONCN. AND PURIFICN. OF SULPHURIC ACID FROM TITANIUM DI:OXIDE MFR. - by boiling in presence of ferrous sulphate to remove chromium |
-
1987
- 1987-04-30 CH CH1649/87A patent/CH669184A5/en not_active IP Right Cessation
- 1987-09-15 DE DE19873730950 patent/DE3730950A1/en not_active Ceased
-
1988
- 1988-04-26 KR KR1019880701653A patent/KR940006033B1/en not_active IP Right Cessation
- 1988-04-26 EP EP88903163A patent/EP0313592B1/en not_active Expired - Lifetime
- 1988-04-26 WO PCT/CH1988/000081 patent/WO1988008405A1/en active IP Right Grant
- 1988-04-26 JP JP63503297A patent/JPH01503230A/en active Granted
- 1988-04-26 DE DE8888903163T patent/DE3861843D1/en not_active Expired - Fee Related
- 1988-04-26 AU AU15977/88A patent/AU596001B2/en not_active Ceased
- 1988-04-28 ZA ZA883040A patent/ZA883040B/en unknown
- 1988-04-28 CA CA000565304A patent/CA1329005C/en not_active Expired - Fee Related
- 1988-04-29 ES ES8801332A patent/ES2007220A6/en not_active Expired
- 1988-12-07 FI FI885674A patent/FI86626C/en not_active IP Right Cessation
- 1988-12-28 SU SU884613175A patent/SU1736332A3/en active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106186064A (en) * | 2016-07-26 | 2016-12-07 | 大连博融新材料股份有限公司 | A kind of method that degree of depth produces high-purity ammonium metavanadate except chromium |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3861843D1 (en) | 1991-04-04 |
| JPH01503230A (en) | 1989-11-02 |
| FI86626B (en) | 1992-06-15 |
| WO1988008405A1 (en) | 1988-11-03 |
| KR890700539A (en) | 1989-04-25 |
| CH669184A5 (en) | 1989-02-28 |
| FI86626C (en) | 1992-09-25 |
| FI885674A (en) | 1988-12-07 |
| AU1597788A (en) | 1988-12-02 |
| KR940006033B1 (en) | 1994-07-02 |
| SU1736332A3 (en) | 1992-05-23 |
| FI885674A0 (en) | 1988-12-07 |
| JPH0512286B2 (en) | 1993-02-17 |
| EP0313592B1 (en) | 1991-02-27 |
| EP0313592A1 (en) | 1989-05-03 |
| ZA883040B (en) | 1989-01-25 |
| ES2007220A6 (en) | 1989-06-01 |
| DE3730950A1 (en) | 1988-11-10 |
| AU596001B2 (en) | 1990-04-12 |
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