CA1098719A - Solvent extraction of non-ferrous metals from iron- containing solutions - Google Patents
Solvent extraction of non-ferrous metals from iron- containing solutionsInfo
- Publication number
- CA1098719A CA1098719A CA282,192A CA282192A CA1098719A CA 1098719 A CA1098719 A CA 1098719A CA 282192 A CA282192 A CA 282192A CA 1098719 A CA1098719 A CA 1098719A
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- iron
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- organic liquid
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/0009—Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G3/00—Compounds of copper
- C01G3/003—Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G45/00—Compounds of manganese
- C01G45/01—Preparation or separation involving a liquid-liquid extraction, an adsorption or an ion-exchange
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G51/00—Compounds of cobalt
- C01G51/01—Preparation or separation involving a liquid-liquid extraction, an adsorption or an ion-exchange
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G53/00—Compounds of nickel
- C01G53/01—Preparation or separation involving a liquid-liquid extraction, an adsorption or an ion-exchange
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G9/00—Compounds of zinc
- C01G9/003—Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
- C22B3/262—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds using alcohols or phenols
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
- C22B3/32—Carboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
- C22B3/38—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds containing phosphorus
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
- C22B3/38—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds containing phosphorus
- C22B3/384—Pentavalent phosphorus oxyacids, esters thereof
- C22B3/3846—Phosphoric acid, e.g. (O)P(OH)3
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Inorganic Chemistry (AREA)
- Geochemistry & Mineralogy (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Extraction Or Liquid Replacement (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
An iron-containing solution from which a non-ferrous metal is to be recovered is contacted with an organic solution of a substituted phosphoric acid extractant to dissolve the iron as well as the non-ferrous metal. The loaded organic is stripped of the non-ferrous metal and re-used after removal of only a bleed amount of iron therefrom.
An iron-containing solution from which a non-ferrous metal is to be recovered is contacted with an organic solution of a substituted phosphoric acid extractant to dissolve the iron as well as the non-ferrous metal. The loaded organic is stripped of the non-ferrous metal and re-used after removal of only a bleed amount of iron therefrom.
Description
7.19 The present invention relates to the recovery of nickel, cobalt, m ~ anese, c~r and zinc Erom iron-containing solutions by solvent extraction with the aid of alkyl- or aryl-substituted phosphoric acids.
It is known that organic solutions of various substituted phosphoric acids, wherein one or two of the hydrogen atoms are substituted by alkyl or aryl radicals, are ~uitable for practising the solvent extraction of various non-ferrous metals from their aqueous-solutions.
It is known that during the course of such solvent extraction hydrogen ion~ are released, and the resulting lowering of the pH would, if unchecked, bring to a halt the extraction since the latter i9 pH sensitive. Various alternatives have been proposed for dealing with this, namely:
i) Adding a sufficient amount of base to the aqueous solution before carrying out the solvent extraction process. In effect, this involves carrying out the solvent extraction process on a hydroxide slurry of the non-ferrous metals.
ii) Adding the necessary amount of base to the organic phase before carrying out the solvent extraction process. In effect this involves using as extractant a salt of the phosphoric acid rather than the acid itself.
iii) Introducing the necessary base during the course of the solvent extraction. The base can be introduced directly into the extraction vessel, or alternatively a portion of the ~9~719 aqueous phase can be continuously withdrawn from the extraction vessel, neutralized, filtered if necessary, and returned to the vessel as described in U.S. Patent No. 3,479,378 (Orlandini et al).
A solvent extraction process of this type is particularly useful for incorporating in an overall hydrometallurgical process for recovering non-ferrous metale from their ores. For example, the overall process might involve acid leaching of the ore, solvent extrac-tion of the non-ferrous metals from the pregnant leach solution followed by stripping of the extracted metals from the solvent and finally electrolytic purification of the metal. Problems are encountered however when, as is almost invariably the case, the solution from which it is de~ired to extract nickel, for example, also contains some iron. The first difficulty which this raises stems from the fact that if conditions are suitable at any stage during the extraction, the iron may precipitate out of solution. When this occurs the precipitate tends to form a stable emulsion with the organic and aqueous liquid~. This emulsion, which is usually referred to in the art as "crud!', can make any further extraction impracticably 910w. The other difficulty posed by the presence of iron in the extraction vessel arises becau~e under the conditions which are suitable for the loading of the non-ferrous metal into the extractant, the iron will be loaded into the extractant at lea~t as readily as the non-ferrous metals. Once dissolved in the organic lG9~7i9 liquid, the iron is more difficult to strip than the non-ferrous metals. Thus for example, contacting the organic liquid with dilute mineral acid, as is typically done to ~trip nickel therefrom, will not effectively remove the iron. It would therefore be necessary to resort to an additional step which effectively strips the iron before recycling the organic liquid for reuse, otherwise the iron content would build up to the point where it would adversely affect the ability of the solvent to extract nickel.
For the above reasons, in much of the literature on this subject, it is tacitly assumed that the solvent extraction aqueous-organic mixture is devoid of iron.
However, while such iron-free conditions may be ensured in laboratory experiments, they are difficult to achieve in a practical commercial process for treating actual leach liquors. Thus a simple hydroxide precipita-tion ~tep performed on the aqueous ~olution, before the solvent extraction, can remove most of the iron but will generally leave traces behind. Moreover some iron may be picked up as a consequence of corrosion of the equipment by the acidic aqueous solution. Even where the amount of iron pre~ent in the aqueous solution fed to the solvent extraction stage is small enough not to cause problems initially, its accumulation in the organic phase, as described above will lead to eventual crud formation.
This problem has been recognized by some prior workers, and tt~pte to overcome it are described in U.S. Patents No. 3,193,381 (J.H.B George et al) and No. 3,666,446 (L.F. Cook et al).
7i9 The approach described in the George et al patent consists of first carrying out an aqueous-organic solvent extraction under conditions such that only iron is removed from the aqueous phase; the latter is then treated with base to precipitate nickel and cobalt as hydroxide and the resulting slurry is subjected to an aqueous-organic solvent extraction to dissolve the nickel and cobalt. The step of iron removal must be practised on the whole of the aqueous stream since other-wise any traces of iron would undoubtedly cause crud problems under the alkaline conditions used for nickel-cobalt extraction.
In the Cook et al patent the method described involves extracting the iron with the non-ferrous metals and thereafter subjecting the loaded extractant to successive stripping operations. In the first stripping operation the non-ferrous metals are recovered in a con-ventional manner, while in the second stripping operation iron i~ removed by using an organic chelating agent.
It will be readily appreciated that the treat-ment of either the whole of the aqueous stream or the whole of the organic stream to remove iron therefrom contributes significantly to the overall cost of the process, and it 3 an object of the present invention to minimize such cost.
Accordingly, the present invention provides a process for recovering at least one non-ferrous metal selected from the group consisting of nickel,ooh~lt,manganese, copper and zinc from an acidic aqueous feed solution conta~ng 87:19 iron in an amount not exceeding 1 gram per liter, com-prising the steps of:
i) contacting the feed solution with an organic liquid comprising an organic-substituted phosphoric acid and an organic water-immiscible solvent therefor, while adding base to the aqueous-organic mixture to maintain its pH at a predetermined level not higher than 6.5, thereby causing the iron and desired non-ferrous metal(s) to be loaded into the organic liquid; and separating the loaded organic liquid from the depleted aqueous solution;
ii) stripping the non-ferrous metal(s) from the loaded organic liquid by contacting the loaded organic liquid with an aqueous acidic strip solution, and separating the re~ulting iron-bearing organic liquid from `the non-ferrous metal containing strip solutlon;
iii) dividing the iron-bearing organic liquid into a main stream and a bleed stream;
iv) contacting the bleed stream with an iron-stripping aqueous solution selected from mineral acid solutions capable of replacing iron by protons in the bleed stream and solutions containing citric acid,alkali metal citrate or a carbohydrate capable of forming a chelate compound with the 871~
iron, and separating the iron-containing strip solution ~rom the ~tr~pped bleed stream; and v) combining the stripped bleed stream ~ith the main ~ream of iron-bearing organic liquid, and recirculating the combined stream to perform Step (i) on a further quantity of the feed solution.
A characteristic feature of the present process is that the organic llquid which 18 recycled to the solvent extractlon stage wlll be partially loaded with iron, since iron removal is practlsed only on the bleed stream to malntaln the concentration of iron at a predetermined level in the organic phase. The economic advantage of the process stems from the fact that only a small bleed stream has to be sub~ected to the iron removal. This bleed stream can in fact constitute as little as 10~ by volume of the whole of the iron-containlng organlc liquid which is tD b~ ~eused. The precise fractlon of the organic liquid which is split off as a bleed stream will depend on the lron content of the aqueous feed as well as the level of lron to be tolerated in the organic feed. In general we prefer the bleed ætream to constltute between 10 and 25% by volume of the organlc liquid as a whole.
It should be stressed that the presence of iron in both the aqueous ~nd the organic phases in the solvent extraction vessel can only be tolerated without adverse effects on the extraction if another essential feature of the invention ls adhered to, namely, resorting to ~G~719 in situ neutralization during the solvent extraction process to ensure acidic conditions at all times. We have found that crud formation does not arise to any detectable extent at a pH lower than 6.5. However, if the pH r~e~ above this value, even temporarily, crud is formed and does not di~perse easily. Thus the process cannot be practised by adding the base needed for solvent extraction to either of the organic and aqueous feed solutions prior to introducing the ~olution into the extraction vessel. It is essential to monitor the pH
in the extraction vessel and add the necessary base, preferably sodi~m hydroxide to maintain the pH at the desired level.
The specific value of the pH to be maintained during the solvent extraction process will depend on several criteria. The first of these, which has already been mentioned, is the necessity to keep the pH below 6.5 to avoid crud formation. Secondly however too low a pH adversely affects the loadlng ef~ectiveness of the organic, and for any given organic extractant and given metal to be eYtracte~ a minimum pH can be defined to ensure adequate loading. Of course where more than one metal are present in the aqueous feed the choice of pH
will depend on whether extraction of several metals,or,as is more common, selective extraction of one of them is sought. Thus a major application of the process of the invention lies in the treatment of solutions which contain both cobalt and nickel to separate those from one another by selective extraction of the cobalt.
Yet another criterion which affects the choice 3Q of pH, within a permissible range, i9 the viscosity of ~ly719 the organic liquid. We have ~ound that on neutralizing the organic liquid, a sharp rise in its viscosity occurs upon exceeding the pH which corresponds to about 90%
conversion of the phosphoric acid to its salt form.
For example the viscosity can increase by as much as an order of magnitude in going from a pH corresponding to 90% conversion of the acid to one corresponding to 100% conversion. Since a very viscous organic phase has adverse effects on the rates of mass transfer and of phase separation, we prefer to choose a pH which corresponds to a conversion of no more than 85-90% of the phosphoric acid to its salt form. For the extractant di(2-ethylhexy pho~phoric acid this places a preferred upper limit of about 5.0 on the pH to be maintained during extraction.
The substituted phosphoric acid used in prac-tising the invention may be any of the various organo-phosphoric acids which are known in the art to be capable of extracting metals such as nickel and cobalt from aqueous solut1ons. The best known of these is probably di(2-ethylhexy1)phosphoric acid (D-2-EHPA). Other suitable - acids include di-octyl phosphoric acid, octylphenyl phosphoric acid, di(l-methylheptyl)phosphoric acid, dodecyl phosphoric acid among others. They can be represented by the general formula HRR'P04, where each of R and R' may an alkyl, aryl or alkaryl radical.
The solvent, by which term we mean the diluent which constitutes a part of the organic phase in the process of the invention, may be any organic liquid which is immiscible with the aqueous phase and in which the extractant is at least partially soluble. The concentration of the extract in the solvent is chosen in accordance with the amount of metal to be extracted from the aqueous phase.
Preferably the solvent used is one in which the solubility of the extract ant is 20~ or more. Typical solvents comprise aliphatic or aromatic hydrocarbons, such as kerosene, as well as alcohols such as isodecanol, and phenols such as paranonyl phenol, or mixtures of such compounds. Where the solvent consists of a mixture of organic liquids, one of the component liquids is often termed a modifying agent, one of its functions being to avoid splitting of the organic into two phases. In general we prefer to employ as solvents diluents which do not require the presence of a modifier to avoid such organic phase splitting. Particularly suitable diluents include the commercial solvents available under the trade names Escaid 100* (from Imperial Oil Ltd) as well as Kermac 470B** (from Kerr McGee Corp).
The contacting of the aqueous and organic phases may need to be accomplished in more than one extraction stage. In such a case it may be necessary, depending on the initial pH of the aqueous feed, to control the pH by adding alkali to only some of the stages. The addition of the alkali can be conveniently effected automatically with the aid of a pH meter-titrator connected to pH
electrodes directly immersed in the phase mixture.
After separation from the spent aqueous solution, the organic is treated to recover nickel, cobalt or man-ganese from it. Where as is common two of these metals _ _ _ _ _ _ _ * Escaid 100 - an organic liquid sold by Imperial Oil Ltd. under the trade name ESCAID 100.
** Kermac 470B - an organic liquid sold by Kerr McGee Corp. under the trade name KERMAC 47OB.
are present in the loaded organic, it will be desirable to remove one of these non-ferrous metals by a scrub-bing operation to leave an organic liquid containing essentially only iron and the other non-ferrous metal.
The latter is then stripped from the organic liquid to leave essentially only iron in the organic. In this way an aqueous scrub liquor and an aqueous strip liquor are obtained from which the respective non-ferrous metals can be recovered separately, for example by electrowinning.
The scrubbing and stripping operations to remove the non-ferrous metals can be performed with aqueous solutions of the same, or of different, composition.
Iypic lly a 1 N sulfuric acid solution will be used for this task. When the first metal to be removed from the organic is only present therein in small amounts, it will be convenient to recycle the aqueous ~crub liquor to the main extraction operation where it is combined with further aqueous feed to build-up the concentration o~ the non-ferrous metal in question therein. Using such an approach the recycled non-ferrous metal i~ recovered from the raffinate, i.e. the aqueous solution from ~hich the iron and other non-ferrous metal have been organically extracted.
The stripping of the iron from the bleed stream can be effected by using a more concentrated mineral acid solution than that used to strip the non-ferrous metal. For example a hydrochloric acid solution of 4-6N ~trength can be used to strip the iron providing the organic solution does not contain a modifier. The 1~9~19 substantially iron-free bleed stream is then separated from the ferric chloride-containing aqueous phase, and the former is ready for reuse in combination with the main stream of organic which may contain up to several grams per liter of iron.
An alternative method of stripping iron from the bleed stream entails using as a stripping liquor an aqueous solution of a complexing agent such as an alkali metal citrate. In such a case the stripping liquor can itself be regenerated for reuse by treating it with alkali and separating the ferric precipitate. Other iron-stripping reagents which can be used include saccharides and various polihydric alcohols, such as mannitol, al~
of which are capable of forming chelate complexes with the iron.
In theory iron could be stripped from an organic liquid such as the bleed stream by direct addition of a strong base. However this would necessarily bring about ferric hydroxide precipitation in the presence of the organic liquid, so that the subsequent phase separation needed to provide a crud-free bleed stream which can be recycled would be very difficult to achieve. Accordingly the direct addition of base to the bleed stream to strip iron therefrom i9 not used in the process of the invention.
Instead it is a feature of the proce~s of the invention that during the met~l loading operation as well as the various metal stripping operations, neither the organic stream as a whole nor any portion thereof i8 at any time subjected to alkaline pH conditions that could lead to crud-formation.
1~91~719 Some examples will now be described ~o illustrate the invention.
The process of the invention was used to separate nickel and cobalt from one another and from iron. The aqueous feed solution was a sulfate solution which contained 6.5 g~l of cobalt, 11.7 g/l of nickel and 0.088 g/l of iron. The organic liquid used was a 30%
by volume solution of D-2-EHPA in the above-mentioned commercial solvent Escaid 100.
A continuous extraction was carried out by causing the aqueous and organic phases tthe volume ratio of which was 3 to 1, aqueous to organic) to flow, counter-currently to one another, through five mixer-settlers.
The temperature of the phase mixture was maintained at 60C during the extraction, and in response to signals from pH electrodes immersed in the last mixer (viewed from the direction of aqueous flow) alkali was automati-cally fed to that mixer. The alkali, which was a 36-50%
by weight solution of sodium hydroxide in water,was used to maintaln the pH at between 4.8 and 4.9.
The loaded organic mixture obtained from the above extraction was subjected to a scrubbing operation to remove the small amount of nickel which had been loaded under the chosen conditions. This was accomplished in a three stage operation with a 1 M sulfuric acid solution, using a 1 to 10 aqueous to organic phase ratio.
The scrub liquor was recycled to the extraction stage to be combined with further aqueous feed solution to be treated.
In this way all of the nickel in the initial feed would 1(~9~719 report ultimately in the final raffinate,i.e. the aqueous stream exiting from the five-stage extraction operation.
The scrubbed organic liquid was then fed to a cobalt stripping operation where it was once again contacted, by countercurrent flow through three-mixer settlers, with a 1 M sulfuric-acid solution. The phase ratio in thi~ case was chosen to be 1 to 3, aqueous to organic.
The organic liquid, which was now loaded es6en-tially only with iron, was split into two streams. The major of the two was recycled to the extraction operation, while the minor stream which constituted only about 15%
by ~olume of the stripped organic was first stripped of iron as follows. The organic bleed stream was contacted with a 0.5 M solution of sodium citrate using equal volumes of aqueous and organic phases. The fully stripped organlc was then recycled to the extraction ves~el to be combined with the recycled iron-containing main stream of organic.
The ironrbearing citrate solution was treated with a 50% by weight sodium hydroxide solutlon to raise its pH to 10.5, thereby precipitating the iron contained therein as ferric hydroxide. After filtration of the precipitate, the citrate solution could be re-used for iron stripping without pH adjustment since upon contact with the iron-containing bleed stream its pH fell naturally to about 5Ø
Analysis of the various aqueous and organic streams showed that:
a) In the extraction operation all of the iron and cobalt had been loaded into the organic.
Thus the aqueous raffinabeobtained from the extraction contained less than 0.0003 g/l iron, and had a nickel to cobalt ratio of 166.
b) The loaded organic obtained from the extraction operation contained nickel in an amount corresponding to about 2% of the total amount of nickel in the original aqueous feed.
~) ~he scrubbing operation removed all the nickel, but none of the iron from the organic liquid.
d) The cobalt stripping operation also removed no iron from the organic liquid. The aqueous cobalt strip liquor contained 58 g/l of cobalt and had a cobalt to nickel ratio of 10,280. It could therefore be used to yield an electrowon cobalt product of very high purity.
e) The effect of iron-stripping from the bleed stream was to control the iron content of the organic fed to the extraction operation at about 1.5 g/l.
Thus the process was carried out with aqueous and organic feeds, both of which contained substantial amounts of iron. These iron contents did not result in any crud formation in the circuit, nor did they adversely affect its performance.
~o inve~tigate the effect of even more sub~tan-tial iron contents in the organic feed solution, a series 109~719 of tests were carried out in which an iron-free aqueous phase containing 8 g/l of cobalt and 20 g/l of nickel was contacted with various organic feeds all of which were similar to that used in Example 1 except that they contained between 1 and 12 g/l of ferric ions. In each case the extraction was carried out at 50C, with equal volumes of aqueous and organic phases, and caustic soda was used to maintain a pH of 5.0 + 0.05. It was found that for the high iron contents no precipitation was observed and in all cases there was no change in the iron concentration of the organic as a result of the extraction.
The effectiveness of iron stripping w~th citrate solution is shown by the results of this test.
An organic phase containing 1.3 g/l of iron was contacted with an equal volume of 0.5 M citric acid solution at 65C. A caustic soda solution was added to raise the pH gradually to 5.0 and the liquids analyzed at various intervals. The results are shown in the Table below.
TABLE
. ~ g/l o~ ' iron in Organic Aqueous .
1.5 1.32<0.001
It is known that organic solutions of various substituted phosphoric acids, wherein one or two of the hydrogen atoms are substituted by alkyl or aryl radicals, are ~uitable for practising the solvent extraction of various non-ferrous metals from their aqueous-solutions.
It is known that during the course of such solvent extraction hydrogen ion~ are released, and the resulting lowering of the pH would, if unchecked, bring to a halt the extraction since the latter i9 pH sensitive. Various alternatives have been proposed for dealing with this, namely:
i) Adding a sufficient amount of base to the aqueous solution before carrying out the solvent extraction process. In effect, this involves carrying out the solvent extraction process on a hydroxide slurry of the non-ferrous metals.
ii) Adding the necessary amount of base to the organic phase before carrying out the solvent extraction process. In effect this involves using as extractant a salt of the phosphoric acid rather than the acid itself.
iii) Introducing the necessary base during the course of the solvent extraction. The base can be introduced directly into the extraction vessel, or alternatively a portion of the ~9~719 aqueous phase can be continuously withdrawn from the extraction vessel, neutralized, filtered if necessary, and returned to the vessel as described in U.S. Patent No. 3,479,378 (Orlandini et al).
A solvent extraction process of this type is particularly useful for incorporating in an overall hydrometallurgical process for recovering non-ferrous metale from their ores. For example, the overall process might involve acid leaching of the ore, solvent extrac-tion of the non-ferrous metals from the pregnant leach solution followed by stripping of the extracted metals from the solvent and finally electrolytic purification of the metal. Problems are encountered however when, as is almost invariably the case, the solution from which it is de~ired to extract nickel, for example, also contains some iron. The first difficulty which this raises stems from the fact that if conditions are suitable at any stage during the extraction, the iron may precipitate out of solution. When this occurs the precipitate tends to form a stable emulsion with the organic and aqueous liquid~. This emulsion, which is usually referred to in the art as "crud!', can make any further extraction impracticably 910w. The other difficulty posed by the presence of iron in the extraction vessel arises becau~e under the conditions which are suitable for the loading of the non-ferrous metal into the extractant, the iron will be loaded into the extractant at lea~t as readily as the non-ferrous metals. Once dissolved in the organic lG9~7i9 liquid, the iron is more difficult to strip than the non-ferrous metals. Thus for example, contacting the organic liquid with dilute mineral acid, as is typically done to ~trip nickel therefrom, will not effectively remove the iron. It would therefore be necessary to resort to an additional step which effectively strips the iron before recycling the organic liquid for reuse, otherwise the iron content would build up to the point where it would adversely affect the ability of the solvent to extract nickel.
For the above reasons, in much of the literature on this subject, it is tacitly assumed that the solvent extraction aqueous-organic mixture is devoid of iron.
However, while such iron-free conditions may be ensured in laboratory experiments, they are difficult to achieve in a practical commercial process for treating actual leach liquors. Thus a simple hydroxide precipita-tion ~tep performed on the aqueous ~olution, before the solvent extraction, can remove most of the iron but will generally leave traces behind. Moreover some iron may be picked up as a consequence of corrosion of the equipment by the acidic aqueous solution. Even where the amount of iron pre~ent in the aqueous solution fed to the solvent extraction stage is small enough not to cause problems initially, its accumulation in the organic phase, as described above will lead to eventual crud formation.
This problem has been recognized by some prior workers, and tt~pte to overcome it are described in U.S. Patents No. 3,193,381 (J.H.B George et al) and No. 3,666,446 (L.F. Cook et al).
7i9 The approach described in the George et al patent consists of first carrying out an aqueous-organic solvent extraction under conditions such that only iron is removed from the aqueous phase; the latter is then treated with base to precipitate nickel and cobalt as hydroxide and the resulting slurry is subjected to an aqueous-organic solvent extraction to dissolve the nickel and cobalt. The step of iron removal must be practised on the whole of the aqueous stream since other-wise any traces of iron would undoubtedly cause crud problems under the alkaline conditions used for nickel-cobalt extraction.
In the Cook et al patent the method described involves extracting the iron with the non-ferrous metals and thereafter subjecting the loaded extractant to successive stripping operations. In the first stripping operation the non-ferrous metals are recovered in a con-ventional manner, while in the second stripping operation iron i~ removed by using an organic chelating agent.
It will be readily appreciated that the treat-ment of either the whole of the aqueous stream or the whole of the organic stream to remove iron therefrom contributes significantly to the overall cost of the process, and it 3 an object of the present invention to minimize such cost.
Accordingly, the present invention provides a process for recovering at least one non-ferrous metal selected from the group consisting of nickel,ooh~lt,manganese, copper and zinc from an acidic aqueous feed solution conta~ng 87:19 iron in an amount not exceeding 1 gram per liter, com-prising the steps of:
i) contacting the feed solution with an organic liquid comprising an organic-substituted phosphoric acid and an organic water-immiscible solvent therefor, while adding base to the aqueous-organic mixture to maintain its pH at a predetermined level not higher than 6.5, thereby causing the iron and desired non-ferrous metal(s) to be loaded into the organic liquid; and separating the loaded organic liquid from the depleted aqueous solution;
ii) stripping the non-ferrous metal(s) from the loaded organic liquid by contacting the loaded organic liquid with an aqueous acidic strip solution, and separating the re~ulting iron-bearing organic liquid from `the non-ferrous metal containing strip solutlon;
iii) dividing the iron-bearing organic liquid into a main stream and a bleed stream;
iv) contacting the bleed stream with an iron-stripping aqueous solution selected from mineral acid solutions capable of replacing iron by protons in the bleed stream and solutions containing citric acid,alkali metal citrate or a carbohydrate capable of forming a chelate compound with the 871~
iron, and separating the iron-containing strip solution ~rom the ~tr~pped bleed stream; and v) combining the stripped bleed stream ~ith the main ~ream of iron-bearing organic liquid, and recirculating the combined stream to perform Step (i) on a further quantity of the feed solution.
A characteristic feature of the present process is that the organic llquid which 18 recycled to the solvent extractlon stage wlll be partially loaded with iron, since iron removal is practlsed only on the bleed stream to malntaln the concentration of iron at a predetermined level in the organic phase. The economic advantage of the process stems from the fact that only a small bleed stream has to be sub~ected to the iron removal. This bleed stream can in fact constitute as little as 10~ by volume of the whole of the iron-containlng organlc liquid which is tD b~ ~eused. The precise fractlon of the organic liquid which is split off as a bleed stream will depend on the lron content of the aqueous feed as well as the level of lron to be tolerated in the organic feed. In general we prefer the bleed ætream to constltute between 10 and 25% by volume of the organlc liquid as a whole.
It should be stressed that the presence of iron in both the aqueous ~nd the organic phases in the solvent extraction vessel can only be tolerated without adverse effects on the extraction if another essential feature of the invention ls adhered to, namely, resorting to ~G~719 in situ neutralization during the solvent extraction process to ensure acidic conditions at all times. We have found that crud formation does not arise to any detectable extent at a pH lower than 6.5. However, if the pH r~e~ above this value, even temporarily, crud is formed and does not di~perse easily. Thus the process cannot be practised by adding the base needed for solvent extraction to either of the organic and aqueous feed solutions prior to introducing the ~olution into the extraction vessel. It is essential to monitor the pH
in the extraction vessel and add the necessary base, preferably sodi~m hydroxide to maintain the pH at the desired level.
The specific value of the pH to be maintained during the solvent extraction process will depend on several criteria. The first of these, which has already been mentioned, is the necessity to keep the pH below 6.5 to avoid crud formation. Secondly however too low a pH adversely affects the loadlng ef~ectiveness of the organic, and for any given organic extractant and given metal to be eYtracte~ a minimum pH can be defined to ensure adequate loading. Of course where more than one metal are present in the aqueous feed the choice of pH
will depend on whether extraction of several metals,or,as is more common, selective extraction of one of them is sought. Thus a major application of the process of the invention lies in the treatment of solutions which contain both cobalt and nickel to separate those from one another by selective extraction of the cobalt.
Yet another criterion which affects the choice 3Q of pH, within a permissible range, i9 the viscosity of ~ly719 the organic liquid. We have ~ound that on neutralizing the organic liquid, a sharp rise in its viscosity occurs upon exceeding the pH which corresponds to about 90%
conversion of the phosphoric acid to its salt form.
For example the viscosity can increase by as much as an order of magnitude in going from a pH corresponding to 90% conversion of the acid to one corresponding to 100% conversion. Since a very viscous organic phase has adverse effects on the rates of mass transfer and of phase separation, we prefer to choose a pH which corresponds to a conversion of no more than 85-90% of the phosphoric acid to its salt form. For the extractant di(2-ethylhexy pho~phoric acid this places a preferred upper limit of about 5.0 on the pH to be maintained during extraction.
The substituted phosphoric acid used in prac-tising the invention may be any of the various organo-phosphoric acids which are known in the art to be capable of extracting metals such as nickel and cobalt from aqueous solut1ons. The best known of these is probably di(2-ethylhexy1)phosphoric acid (D-2-EHPA). Other suitable - acids include di-octyl phosphoric acid, octylphenyl phosphoric acid, di(l-methylheptyl)phosphoric acid, dodecyl phosphoric acid among others. They can be represented by the general formula HRR'P04, where each of R and R' may an alkyl, aryl or alkaryl radical.
The solvent, by which term we mean the diluent which constitutes a part of the organic phase in the process of the invention, may be any organic liquid which is immiscible with the aqueous phase and in which the extractant is at least partially soluble. The concentration of the extract in the solvent is chosen in accordance with the amount of metal to be extracted from the aqueous phase.
Preferably the solvent used is one in which the solubility of the extract ant is 20~ or more. Typical solvents comprise aliphatic or aromatic hydrocarbons, such as kerosene, as well as alcohols such as isodecanol, and phenols such as paranonyl phenol, or mixtures of such compounds. Where the solvent consists of a mixture of organic liquids, one of the component liquids is often termed a modifying agent, one of its functions being to avoid splitting of the organic into two phases. In general we prefer to employ as solvents diluents which do not require the presence of a modifier to avoid such organic phase splitting. Particularly suitable diluents include the commercial solvents available under the trade names Escaid 100* (from Imperial Oil Ltd) as well as Kermac 470B** (from Kerr McGee Corp).
The contacting of the aqueous and organic phases may need to be accomplished in more than one extraction stage. In such a case it may be necessary, depending on the initial pH of the aqueous feed, to control the pH by adding alkali to only some of the stages. The addition of the alkali can be conveniently effected automatically with the aid of a pH meter-titrator connected to pH
electrodes directly immersed in the phase mixture.
After separation from the spent aqueous solution, the organic is treated to recover nickel, cobalt or man-ganese from it. Where as is common two of these metals _ _ _ _ _ _ _ * Escaid 100 - an organic liquid sold by Imperial Oil Ltd. under the trade name ESCAID 100.
** Kermac 470B - an organic liquid sold by Kerr McGee Corp. under the trade name KERMAC 47OB.
are present in the loaded organic, it will be desirable to remove one of these non-ferrous metals by a scrub-bing operation to leave an organic liquid containing essentially only iron and the other non-ferrous metal.
The latter is then stripped from the organic liquid to leave essentially only iron in the organic. In this way an aqueous scrub liquor and an aqueous strip liquor are obtained from which the respective non-ferrous metals can be recovered separately, for example by electrowinning.
The scrubbing and stripping operations to remove the non-ferrous metals can be performed with aqueous solutions of the same, or of different, composition.
Iypic lly a 1 N sulfuric acid solution will be used for this task. When the first metal to be removed from the organic is only present therein in small amounts, it will be convenient to recycle the aqueous ~crub liquor to the main extraction operation where it is combined with further aqueous feed to build-up the concentration o~ the non-ferrous metal in question therein. Using such an approach the recycled non-ferrous metal i~ recovered from the raffinate, i.e. the aqueous solution from ~hich the iron and other non-ferrous metal have been organically extracted.
The stripping of the iron from the bleed stream can be effected by using a more concentrated mineral acid solution than that used to strip the non-ferrous metal. For example a hydrochloric acid solution of 4-6N ~trength can be used to strip the iron providing the organic solution does not contain a modifier. The 1~9~19 substantially iron-free bleed stream is then separated from the ferric chloride-containing aqueous phase, and the former is ready for reuse in combination with the main stream of organic which may contain up to several grams per liter of iron.
An alternative method of stripping iron from the bleed stream entails using as a stripping liquor an aqueous solution of a complexing agent such as an alkali metal citrate. In such a case the stripping liquor can itself be regenerated for reuse by treating it with alkali and separating the ferric precipitate. Other iron-stripping reagents which can be used include saccharides and various polihydric alcohols, such as mannitol, al~
of which are capable of forming chelate complexes with the iron.
In theory iron could be stripped from an organic liquid such as the bleed stream by direct addition of a strong base. However this would necessarily bring about ferric hydroxide precipitation in the presence of the organic liquid, so that the subsequent phase separation needed to provide a crud-free bleed stream which can be recycled would be very difficult to achieve. Accordingly the direct addition of base to the bleed stream to strip iron therefrom i9 not used in the process of the invention.
Instead it is a feature of the proce~s of the invention that during the met~l loading operation as well as the various metal stripping operations, neither the organic stream as a whole nor any portion thereof i8 at any time subjected to alkaline pH conditions that could lead to crud-formation.
1~91~719 Some examples will now be described ~o illustrate the invention.
The process of the invention was used to separate nickel and cobalt from one another and from iron. The aqueous feed solution was a sulfate solution which contained 6.5 g~l of cobalt, 11.7 g/l of nickel and 0.088 g/l of iron. The organic liquid used was a 30%
by volume solution of D-2-EHPA in the above-mentioned commercial solvent Escaid 100.
A continuous extraction was carried out by causing the aqueous and organic phases tthe volume ratio of which was 3 to 1, aqueous to organic) to flow, counter-currently to one another, through five mixer-settlers.
The temperature of the phase mixture was maintained at 60C during the extraction, and in response to signals from pH electrodes immersed in the last mixer (viewed from the direction of aqueous flow) alkali was automati-cally fed to that mixer. The alkali, which was a 36-50%
by weight solution of sodium hydroxide in water,was used to maintaln the pH at between 4.8 and 4.9.
The loaded organic mixture obtained from the above extraction was subjected to a scrubbing operation to remove the small amount of nickel which had been loaded under the chosen conditions. This was accomplished in a three stage operation with a 1 M sulfuric acid solution, using a 1 to 10 aqueous to organic phase ratio.
The scrub liquor was recycled to the extraction stage to be combined with further aqueous feed solution to be treated.
In this way all of the nickel in the initial feed would 1(~9~719 report ultimately in the final raffinate,i.e. the aqueous stream exiting from the five-stage extraction operation.
The scrubbed organic liquid was then fed to a cobalt stripping operation where it was once again contacted, by countercurrent flow through three-mixer settlers, with a 1 M sulfuric-acid solution. The phase ratio in thi~ case was chosen to be 1 to 3, aqueous to organic.
The organic liquid, which was now loaded es6en-tially only with iron, was split into two streams. The major of the two was recycled to the extraction operation, while the minor stream which constituted only about 15%
by ~olume of the stripped organic was first stripped of iron as follows. The organic bleed stream was contacted with a 0.5 M solution of sodium citrate using equal volumes of aqueous and organic phases. The fully stripped organlc was then recycled to the extraction ves~el to be combined with the recycled iron-containing main stream of organic.
The ironrbearing citrate solution was treated with a 50% by weight sodium hydroxide solutlon to raise its pH to 10.5, thereby precipitating the iron contained therein as ferric hydroxide. After filtration of the precipitate, the citrate solution could be re-used for iron stripping without pH adjustment since upon contact with the iron-containing bleed stream its pH fell naturally to about 5Ø
Analysis of the various aqueous and organic streams showed that:
a) In the extraction operation all of the iron and cobalt had been loaded into the organic.
Thus the aqueous raffinabeobtained from the extraction contained less than 0.0003 g/l iron, and had a nickel to cobalt ratio of 166.
b) The loaded organic obtained from the extraction operation contained nickel in an amount corresponding to about 2% of the total amount of nickel in the original aqueous feed.
~) ~he scrubbing operation removed all the nickel, but none of the iron from the organic liquid.
d) The cobalt stripping operation also removed no iron from the organic liquid. The aqueous cobalt strip liquor contained 58 g/l of cobalt and had a cobalt to nickel ratio of 10,280. It could therefore be used to yield an electrowon cobalt product of very high purity.
e) The effect of iron-stripping from the bleed stream was to control the iron content of the organic fed to the extraction operation at about 1.5 g/l.
Thus the process was carried out with aqueous and organic feeds, both of which contained substantial amounts of iron. These iron contents did not result in any crud formation in the circuit, nor did they adversely affect its performance.
~o inve~tigate the effect of even more sub~tan-tial iron contents in the organic feed solution, a series 109~719 of tests were carried out in which an iron-free aqueous phase containing 8 g/l of cobalt and 20 g/l of nickel was contacted with various organic feeds all of which were similar to that used in Example 1 except that they contained between 1 and 12 g/l of ferric ions. In each case the extraction was carried out at 50C, with equal volumes of aqueous and organic phases, and caustic soda was used to maintain a pH of 5.0 + 0.05. It was found that for the high iron contents no precipitation was observed and in all cases there was no change in the iron concentration of the organic as a result of the extraction.
The effectiveness of iron stripping w~th citrate solution is shown by the results of this test.
An organic phase containing 1.3 g/l of iron was contacted with an equal volume of 0.5 M citric acid solution at 65C. A caustic soda solution was added to raise the pH gradually to 5.0 and the liquids analyzed at various intervals. The results are shown in the Table below.
TABLE
. ~ g/l o~ ' iron in Organic Aqueous .
1.5 1.32<0.001
2.1 1.28<0.001 2.6 1.26<0.001
3.0 1.32<0.001 3.5 1.060.007
4.0 0.960.007 4.5 0.121.16
5.0 0.083 1.27 . l 1~9~9 Thus it will be seen that at a pH of 5.0 or above, such a citrate solution will extract ~ubstantially all the iron present in the organic bleed stream.
While the present invention has been described with reference to preferred embodiments thereof, it will be understood that various modifications may be made to such embodiments without departing from the scope of the invention, which is defined by the appended claims.
While the present invention has been described with reference to preferred embodiments thereof, it will be understood that various modifications may be made to such embodiments without departing from the scope of the invention, which is defined by the appended claims.
Claims (6)
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A process for recovering at least one non-ferrous metal selected from the group consisting of nickel, cobalt,manganese, copper and zinc from an acidic aqueous feed solution containing iron in an amount not exceed-ing 1 gram per liter comprising the steps of:
i) contacting the feed solution with an organic liquid comprising an organic-substituted phosphoric acid and an organic water immis-cible solvent therefor, while adding base to the aqueous-organic mixture to maintain its pH at a predetermined level not higher than 6.5, thereby causing the iron and desired non-ferrous metal(s) to be loaded into the organic liquid; and separating the loaded organic liquid from the depleted aqueous solution;
ii) stripping the non-ferrous metal(s) from the loaded organic liquid by contacting the loaded organic liquid with an aqueous acidic strip solution, and separating the resulting iron-bearing organic liquid from the non-ferrous metal containing strip solution;
iii) dividing the iron-bearing organic liquid into a main stream and a bleed stream;
iv) contacting the bleed stream with an iron-stripping aqueous solution selected from mineral acid solutions capable of replacing iron by protons in the bleed stream and solutions containing citric acid, alkali metal citrate or a carbohydrate capable of forming a chelate compound with the iron, and separating the iron-containing strip solution from the stripped bleed stream; and v) combining the stripped bleed stream with the main stream of iron-bearing organic liquid, and recirculating the combined stream to per-form Step (i) on a further quantity of the feed solution.
i) contacting the feed solution with an organic liquid comprising an organic-substituted phosphoric acid and an organic water immis-cible solvent therefor, while adding base to the aqueous-organic mixture to maintain its pH at a predetermined level not higher than 6.5, thereby causing the iron and desired non-ferrous metal(s) to be loaded into the organic liquid; and separating the loaded organic liquid from the depleted aqueous solution;
ii) stripping the non-ferrous metal(s) from the loaded organic liquid by contacting the loaded organic liquid with an aqueous acidic strip solution, and separating the resulting iron-bearing organic liquid from the non-ferrous metal containing strip solution;
iii) dividing the iron-bearing organic liquid into a main stream and a bleed stream;
iv) contacting the bleed stream with an iron-stripping aqueous solution selected from mineral acid solutions capable of replacing iron by protons in the bleed stream and solutions containing citric acid, alkali metal citrate or a carbohydrate capable of forming a chelate compound with the iron, and separating the iron-containing strip solution from the stripped bleed stream; and v) combining the stripped bleed stream with the main stream of iron-bearing organic liquid, and recirculating the combined stream to per-form Step (i) on a further quantity of the feed solution.
2. A process as claimed in claim 1 wherein the bleed stream constitutes between 10 and 25% by volume of the iron-bearing organic liquid.
3. A process as claimed in claim 1 wherein the substituted phosphoric acid is di(2-ethylhexyl) phosphoric acid.
4. A process as claimed in claim 3 wherein the aqueous feed solution contains iron, nickel and cobalt.
5. A process as claimed in claim 4 wherein the predetermined pH level is between 4.8 and 5.0, whereby the loaded organic of Step (i) contains most of the cobalt and only a minor part of the nickel present in the aqueous feed solution.
6. A process as claimed in claim 5 wherein the stripping of Step (ii) comprises a first operation in which nickel is stripped from the loaded organic and a second operation in which cobalt is stripped from the nickel depleted loaded organic.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA282,192A CA1098719A (en) | 1977-07-06 | 1977-07-06 | Solvent extraction of non-ferrous metals from iron- containing solutions |
| FR7819871A FR2396573A1 (en) | 1977-07-06 | 1978-07-04 | SOLVENT EXTRACTION OF NON-FERROUS METALS FROM AN ACIDIC AQUEOUS SOLUTION CONTAINING IRON |
| NO782342A NO782342L (en) | 1977-07-06 | 1978-07-05 | PROCEDURE FOR EXTRACTING NON-IRON METALS FROM AN IRONOUS SOLUTION |
| AU37770/78A AU3777078A (en) | 1977-07-06 | 1978-07-05 | Solvent extraction of non-ferrous metals |
| FI782181A FI782181A7 (en) | 1977-07-06 | 1978-07-06 | SOLVENSEXTRAKTION AV ICKE-JAERNMETALLER FRAON JAERNINNEHAOLLANDE LOESNINGAR |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA282,192A CA1098719A (en) | 1977-07-06 | 1977-07-06 | Solvent extraction of non-ferrous metals from iron- containing solutions |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1098719A true CA1098719A (en) | 1981-04-07 |
Family
ID=4109080
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA282,192A Expired CA1098719A (en) | 1977-07-06 | 1977-07-06 | Solvent extraction of non-ferrous metals from iron- containing solutions |
Country Status (5)
| Country | Link |
|---|---|
| AU (1) | AU3777078A (en) |
| CA (1) | CA1098719A (en) |
| FI (1) | FI782181A7 (en) |
| FR (1) | FR2396573A1 (en) |
| NO (1) | NO782342L (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4246240A (en) * | 1978-07-24 | 1981-01-20 | Nippon Mining Co., Ltd. | Process for separating cobalt and nickel from a solution containing cobalt and nickel |
| LU81600A1 (en) * | 1979-08-13 | 1981-03-24 | Metallurgie Hoboken | METHOD FOR TREATING AN ORGANIC PHASE CONTAINING IRON CHLORIDE, MOLYBDENE CHLORIDE AND HCl |
| DE3705721A1 (en) * | 1987-02-23 | 1988-09-01 | Henkel Kgaa | USE OF CITRONIC ACID PARTIAL ESTERS AND THEIR MIXTURES FOR IRON EXTRACTION |
-
1977
- 1977-07-06 CA CA282,192A patent/CA1098719A/en not_active Expired
-
1978
- 1978-07-04 FR FR7819871A patent/FR2396573A1/en not_active Withdrawn
- 1978-07-05 NO NO782342A patent/NO782342L/en unknown
- 1978-07-05 AU AU37770/78A patent/AU3777078A/en active Pending
- 1978-07-06 FI FI782181A patent/FI782181A7/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| FI782181A7 (en) | 1979-01-07 |
| NO782342L (en) | 1979-01-09 |
| AU3777078A (en) | 1980-01-10 |
| FR2396573A1 (en) | 1979-02-02 |
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