CA1195511A - Separation of cobalt from nickel - Google Patents
Separation of cobalt from nickelInfo
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- CA1195511A CA1195511A CA000412960A CA412960A CA1195511A CA 1195511 A CA1195511 A CA 1195511A CA 000412960 A CA000412960 A CA 000412960A CA 412960 A CA412960 A CA 412960A CA 1195511 A CA1195511 A CA 1195511A
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Abstract
ABSTRACT
Directed to a process for separating the nickel and cobalt contents of an alkaline mixed nickel-cobalt compound, such as a carbonate, wherein acid is added to dissolve a portion of the compound, and treating the resulting liquor with gaseous chlorine while maintaining the pH of the liquor between 2.5 and 4 to provide a nickel solution low in cobalt and a cobalt precipitate low in nickel with high efficiency in reagent consumption, particularly chlorine.
Directed to a process for separating the nickel and cobalt contents of an alkaline mixed nickel-cobalt compound, such as a carbonate, wherein acid is added to dissolve a portion of the compound, and treating the resulting liquor with gaseous chlorine while maintaining the pH of the liquor between 2.5 and 4 to provide a nickel solution low in cobalt and a cobalt precipitate low in nickel with high efficiency in reagent consumption, particularly chlorine.
Description
of Cobalt from Nickel The present invention re:Lates to the separation of nickel from cobalt present in an alkaline mixed nickel-cobalt compound~
During the course of some processes for extracting nickel and cobalt from their ores, for example after an ammoniacal leach of a reduced nickel calcine, an alkaline mixed nlckel-cobalt compound is obtained. This compound is usually treated to separate the cobalt content from the nickel content by dissolving it in hydrochloric or sulphuric acid and sparging the resulting solution with gaseous chlorine in the presence of an alkali, for example sodiurn carbonate. Cobalt is selectively oxidised from cobaltous ions (Co+ ) to cobaltic ions (Co ), which precipitate as the insoluble cobaltic hydroxide. Thus a cobalt-rich and nickel deficient precipita-te and a nickel-rich and cobalt-deficient solution are obtalned.
Such a process, however, is expensive since it not only uses expensive reagents hut also uses them in considerable quantities.
It has been proposed in British Patent Specification No. 1,565,752 to selectively dissolve nickel present in the form of an oxygen~containing compound that is admixed with similar compounds of cobalt and iron by forming a suspension of the compounds in water or an aqueous solution of, for example, sodium chloride, treating the suspension with gaseous chlorine while ensuring that the pH of the liquor is always in excess of 1 so as to dissolve -the nickel and retain the other elements in an essentially insoluble state and finally separating the liquor, which is rich in nickel, from the solid residue, which is rich in the other elements. However, such a process uses a large amount of chlorine to selectively dissolve the nickel and this is not only wasteful of chlorine, . ~
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but also increases the redox potential to such an extent -that nickel can be oxidised to its trivalent s-tate which precipitates wlth the cobalt.
It is an object of the present invention to provide a simple process that will separate cobalt from nickel present in an alkaline mixed nlckel-cobalt compound using srnaller amounts of reagen-ts than have hitherto been usedO As used herein~ the term "alkaline mixed nickel-cobalt compound" is intended to mean a mixture of compounds of nickel and cobalt that dissolve in, and at least partly neutralise, strong acids, for example hydrochloric and sulphuric acids.
Examples of such compounds are hydroxides, oxides, carbonates and basic carbonates of nickel and cobalt.
According to the present invention, there is provided a process of separating cobalt from nickel present in an alkaline mixed nickel-cobalt compound which comprises dissolving a portion of the compound in acid~ treating the resulting liquor with gaseous chlorine while adding one or more further portions of the compound to~ether with as much acid or alkali as is needed to maintain the pH of liquor within the range of
During the course of some processes for extracting nickel and cobalt from their ores, for example after an ammoniacal leach of a reduced nickel calcine, an alkaline mixed nlckel-cobalt compound is obtained. This compound is usually treated to separate the cobalt content from the nickel content by dissolving it in hydrochloric or sulphuric acid and sparging the resulting solution with gaseous chlorine in the presence of an alkali, for example sodiurn carbonate. Cobalt is selectively oxidised from cobaltous ions (Co+ ) to cobaltic ions (Co ), which precipitate as the insoluble cobaltic hydroxide. Thus a cobalt-rich and nickel deficient precipita-te and a nickel-rich and cobalt-deficient solution are obtalned.
Such a process, however, is expensive since it not only uses expensive reagents hut also uses them in considerable quantities.
It has been proposed in British Patent Specification No. 1,565,752 to selectively dissolve nickel present in the form of an oxygen~containing compound that is admixed with similar compounds of cobalt and iron by forming a suspension of the compounds in water or an aqueous solution of, for example, sodium chloride, treating the suspension with gaseous chlorine while ensuring that the pH of the liquor is always in excess of 1 so as to dissolve -the nickel and retain the other elements in an essentially insoluble state and finally separating the liquor, which is rich in nickel, from the solid residue, which is rich in the other elements. However, such a process uses a large amount of chlorine to selectively dissolve the nickel and this is not only wasteful of chlorine, . ~
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but also increases the redox potential to such an extent -that nickel can be oxidised to its trivalent s-tate which precipitates wlth the cobalt.
It is an object of the present invention to provide a simple process that will separate cobalt from nickel present in an alkaline mixed nlckel-cobalt compound using srnaller amounts of reagen-ts than have hitherto been usedO As used herein~ the term "alkaline mixed nickel-cobalt compound" is intended to mean a mixture of compounds of nickel and cobalt that dissolve in, and at least partly neutralise, strong acids, for example hydrochloric and sulphuric acids.
Examples of such compounds are hydroxides, oxides, carbonates and basic carbonates of nickel and cobalt.
According to the present invention, there is provided a process of separating cobalt from nickel present in an alkaline mixed nickel-cobalt compound which comprises dissolving a portion of the compound in acid~ treating the resulting liquor with gaseous chlorine while adding one or more further portions of the compound to~ether with as much acid or alkali as is needed to maintain the pH of liquor within the range of
2.5 to 4Ø
Although we do not wish to be constrained by any particular theory we believe that the reactions taking place when, for example, a mixture of nickel and cobalt (II) hydroxides are dissolved in hydro-chloric acid are;
(a) Ni(OH)2 (solid) + 2HCl (soln~ -~ NiC12 (soln) -~ 2 H20 (b) Co(OH)2(solid) + 2HCl (soln) ~ CoC12 (soln) + 2 H20 When chlorine gas is added, we believe that the cobalt is oxi.dised according -to the equation;
(c) 2CoC12 ~soln~ ~ C12 (g) ~ 6 H~O ~ 2ColOH)3 (solid) 6HCl (soln) ~hen the further portions of nickel and cobalt hydroxide feedstock are added, the nickel hydroxide dissolves according to equation (a) above and part of the cobalt hydroxide may well dissolve according to reaction (b3, b~t we belie~e that -the following reaction also occurs:
(d) 2Co(OH)2 (solid) + C12 (g) + 2 H20 -~2Co(OH)3 (solid) ~ 2HCl (soln) In the above-mentioned reaction schemes, (g) indicates that the reagent is in a gaseous state, (solid) that it is in a solid state and (soln) that lt is dissolved.
It can be seen from the above equations that if the molar ratio of Ni:Co equals 0.5, the amount of acid generated by cobalt oxidation matches the amount cons~ned by dissolution of the nickel. If the ratio is in excess of 0.5, acid must be added to the reaction mixture, preferably in a slurry wi.th a further portion of the mixed nickel-cobalt compound,to maintain the acid balance of the reaction mixture and the pH within the range 2.5 to 4Ø However, the amount of acid added should be sufficient to dissolve the amount of nickel in excess of the ratio only. Likewise, when the ratio is ~5 less than 0.5, alkali must be added, but the amount of alkali added should be sufficient to neutral.ise the acid generated by the oxidation of the cobalt content that is in excess of twice the nickel content of the compound. This is to be contrasted with the usual process for treating this type of compound described earlier in this specifi.cation .in which the whole of the . compound is dissolved in acid and chlorine is fed into the resultincl solution in the presence of sodium carbonateO ~lhis process consumes two moles of hydro chloric acid for each mole of nlckel and cobalt ~s~
~ 4 present in the compound and in excess of one and a half moles of sodium carbonate for each ~ole of cobalt precipitated. Thus it can be seen that the present invention represents a real saving in the amount of acid and alkali utilised.
The chlorine efficiency of the process of the present invention is good and it 1s possible to use an amount of chlorine that is only slightly in excess of that needed to oxidise the cobalt present in the nicke~cobalt compound. The molar ratio of chlorine (calculated on a molecular as opposed to an atomic basis) fed into the reaction mixture to cobalt contained in the compound is preferably less than 1:1 since we have found that adding more chlorine has little effect on the degree of nickel-cobalt separation or on the reaction rate..This is to be contrasted with the amount of chlorine consumed in the process described ln British Patent Specification No. 1,565,752 in which the molar ratio of chlorine utilized to cobalt precipitated is typically about 75 1.
The above discussion is a simplification, and in practice the compound will contain metallic elements other than nickel and cobalt, *or example soluble hydroxides or carbonates of copper, zinc, sodium, potassium, calcium and magnesium/ which metallic elements repor-t with the nickel in the final solution, and also compounds of readily oxidisable metals e.g. iron and manganese, which will report with the cobalt in the precipitate. The acid balance of the process must be adjusted to compensate for these extraneous elements.
In order to take full advantage of the process of the present invention, it is preferred that the molar Ni:Co ratio in the compound is in the range of 2:1 to 1:4.
The process may be opera-ted in batches or continuously, although continuous operation is preferxed because it makes more efficient use oE available apparatus.
Preferably, the process of the present invention is so operated tha-t the pH of the liquor while chlorine is being added is in the range of 2.6 to
Although we do not wish to be constrained by any particular theory we believe that the reactions taking place when, for example, a mixture of nickel and cobalt (II) hydroxides are dissolved in hydro-chloric acid are;
(a) Ni(OH)2 (solid) + 2HCl (soln~ -~ NiC12 (soln) -~ 2 H20 (b) Co(OH)2(solid) + 2HCl (soln) ~ CoC12 (soln) + 2 H20 When chlorine gas is added, we believe that the cobalt is oxi.dised according -to the equation;
(c) 2CoC12 ~soln~ ~ C12 (g) ~ 6 H~O ~ 2ColOH)3 (solid) 6HCl (soln) ~hen the further portions of nickel and cobalt hydroxide feedstock are added, the nickel hydroxide dissolves according to equation (a) above and part of the cobalt hydroxide may well dissolve according to reaction (b3, b~t we belie~e that -the following reaction also occurs:
(d) 2Co(OH)2 (solid) + C12 (g) + 2 H20 -~2Co(OH)3 (solid) ~ 2HCl (soln) In the above-mentioned reaction schemes, (g) indicates that the reagent is in a gaseous state, (solid) that it is in a solid state and (soln) that lt is dissolved.
It can be seen from the above equations that if the molar ratio of Ni:Co equals 0.5, the amount of acid generated by cobalt oxidation matches the amount cons~ned by dissolution of the nickel. If the ratio is in excess of 0.5, acid must be added to the reaction mixture, preferably in a slurry wi.th a further portion of the mixed nickel-cobalt compound,to maintain the acid balance of the reaction mixture and the pH within the range 2.5 to 4Ø However, the amount of acid added should be sufficient to dissolve the amount of nickel in excess of the ratio only. Likewise, when the ratio is ~5 less than 0.5, alkali must be added, but the amount of alkali added should be sufficient to neutral.ise the acid generated by the oxidation of the cobalt content that is in excess of twice the nickel content of the compound. This is to be contrasted with the usual process for treating this type of compound described earlier in this specifi.cation .in which the whole of the . compound is dissolved in acid and chlorine is fed into the resultincl solution in the presence of sodium carbonateO ~lhis process consumes two moles of hydro chloric acid for each mole of nlckel and cobalt ~s~
~ 4 present in the compound and in excess of one and a half moles of sodium carbonate for each ~ole of cobalt precipitated. Thus it can be seen that the present invention represents a real saving in the amount of acid and alkali utilised.
The chlorine efficiency of the process of the present invention is good and it 1s possible to use an amount of chlorine that is only slightly in excess of that needed to oxidise the cobalt present in the nicke~cobalt compound. The molar ratio of chlorine (calculated on a molecular as opposed to an atomic basis) fed into the reaction mixture to cobalt contained in the compound is preferably less than 1:1 since we have found that adding more chlorine has little effect on the degree of nickel-cobalt separation or on the reaction rate..This is to be contrasted with the amount of chlorine consumed in the process described ln British Patent Specification No. 1,565,752 in which the molar ratio of chlorine utilized to cobalt precipitated is typically about 75 1.
The above discussion is a simplification, and in practice the compound will contain metallic elements other than nickel and cobalt, *or example soluble hydroxides or carbonates of copper, zinc, sodium, potassium, calcium and magnesium/ which metallic elements repor-t with the nickel in the final solution, and also compounds of readily oxidisable metals e.g. iron and manganese, which will report with the cobalt in the precipitate. The acid balance of the process must be adjusted to compensate for these extraneous elements.
In order to take full advantage of the process of the present invention, it is preferred that the molar Ni:Co ratio in the compound is in the range of 2:1 to 1:4.
The process may be opera-ted in batches or continuously, although continuous operation is preferxed because it makes more efficient use oE available apparatus.
Preferably, the process of the present invention is so operated tha-t the pH of the liquor while chlorine is being added is in the range of 2.6 to
3.3, more preferably 2.B to 3.1. The temperature of operation may be in the range of 30 to 80C but at optirnum pH values temperature appears to have little influence on the degree of nickel-cobalt separation and accordingly the process is preferably operated within the lower half of the above range i.e. 30 to 60C, to save energy. However, at a pH below the minimum~ we have found that the degree of nickel-cobalt separation increases with increasing temperature and accordingly the temperature is preferably in the upper half of the above range when operating outside the optimum pH rangeO
Several examples of the process of the present invention will now be given.
Example-l A nickel~cobalt carbonate cake containing, in percentage by weight, Ni 19.4, Co 12.7, Cu 0.77, Fe 0.17 was dissolved in 5 litres of feed solution containing, in grams per litre: Ni 53, Cl 42l-H2S0~
39, until the resulting solution had a pH of 3. This required 359 grams of cake. Chlorine gas was then introduced into the solution through a fritted glass inlet tube at a rate of ~g of chlorine per litre of solution per hour. The pH of the solution was maintained in the range of 2.9 to 3.0 b~ adding feed cake. When the cobalt content of the solution had dropped to below 0.5 g/l, whlch took 330 minutes~ the chlorine intro-duction was discontinued and the leach solution was separated from the residue by flltxation. The ~esidue was then washed ~lth demineralised watex. The results of the process are shown in Tahle l-A.
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~ 8 --It can be seen from Table 1-~ that, within experimental accuracy, 97% o the iron, 98% of the cobalt, and 7% of the nickel originally present in the cake reported to the final leach residue ~nd that the leach liquor contalnedthe remaining 93~ of the nickel and about half the copper content originally present in the cake. The amount of chlorine ad~ed was 110 g, of which 95 g was converted to chloride ions~ which means that -the chlorine efficiency, i.e. the amount of chlorine dissolved divided by the amount of cobalt precipitated, was 0.78 g/g or 0.65 on a molar hasis.
The nickel separatlon, l.e. the ratio of the weigh-t of - nickel in solu-tion to the weight of oxidlsable metals (cobalt, lead and iron) in solution was 200 (g/g). The cobalt separation i.e. the ratio of the weight of oxidisable elements (cobalt~ lead and iron) in the leach residue to the weight of nickel in the residue was 10.4 (g/g) .
Table ~-B sho~s the amount of cake and chlorine added a-t various stages of the process and the varying composition of the reaction liquor as the process progressed. It can be seen from the Table that the cobalt that was leached when the first portion of cake was dissolved in the feed solution was gradually oxidised and precipitated throughout the chlorination treatment. It can also be seen that the actual consumption of gaseous chlorine was about 1 gram for each gram of cobalt precipitated, which is to be compared with a theoretical consumption of 0.6 grams per gram of cobalt and the chlorine efficiency ~i.e. the weight of chlorine that is reduced to chloride ions divided by the weight of cobalt precipitated) of 0.78.
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Example 2 This Example demonstrates the effect of pH
on the separa-tion of cobalt from nickel in the treatment of a feed nickel-cobalt carbonate cake with a feed acidic nickel sulphate solution and chlorine gasO The feed cake contained (in weigh-t percent) Co 18.4, Ni 27.4, Cu 1.12, Fe 0.28, Na 1054, Ca 1.48, S04 1080~ The feed solution contained (in grams per l.itre)~ Ni 40, H2504 50~ NaCl 660 Ten tests were carried out batchwise in the following sequence: (1) partially neutralising the feed solution with sufficient feed cake to achieve a pH of 3 at the temperature at which the test is to be conducted, (2) treating the neutralised solution with chlorine gas while maintaining the pH
of the reaction liquor with the desired range by adding a slurry of cake and partially neutralised solution, (3) separating the cobalt-rich precipitate from the nickel~rich final solution by filtration, and (4) washing the precipitate with water. The process conditions and the results of the tests are shown in Table 2.
For the sake of simplicity, in the results given in Table 2~ and also in Tables 3, :~ and 5 ollowing7 the "final solution" includes both the filtrate from step (3) abo~e and the washing water from step ~4), the"cobalt precipitate"refers to the precipitate when washed and dried,and under the heading "Ni-Co Separation Efficiency", "% Ni Liquor" refers to the weight percentage of nickel initially present in the feed cake that was leached out during the course of the process and "% Co Ca]ce?' refexs to the weight percentage of cobalt initially present in the feed cake that was precipi~ted durlng the processD
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- l2 -I-t can be seen from Table 2 that in the temperature range of 30 to 80C~ the percentage of nlckel leached decreases~ and -the percentage o~ cobalt precipitated increases, with increasing pH. Optimum separati.on of nickel from cobalt is achieved in the pH
range 2.~ to 3.1 t which seems to be the optimum throughout the.temperature range. We believe that at a pH of less than 2.8, the cobalt precipitation is incomplete and at a pH in excess of 3.1,nickel dissolution is incomplete.
E ample_ This Example illustrated the efect of temperature on the separation efficiency. The feed cake used in this Example had the same composition as that used in Example 2 and the procedure used was the same as that described in Example 2. Eight tests were carried out and the conditions used and the results are given in Table 3.
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- ~4 -It can be seen ~rom Table 3 that in the pH
range 2.8 to 3~1, -the temperature has llttle effect on the nickel-cobalt separation efficiency. In the pH range 2.4 to 2.6, however, the percentage of nickel leached decreases and the percentage of cobalt precipitated increases with increased temperature.
Thus, when opexating within a pH range of 2.8 to 3.1, it is preferable to use a low temperature, e.g. 30C
50C, to save energy.
Example 4 This Example illustrates the effect of reaction time on the nickel-cobalt separation efficiencyO Experimental procedures and the composition of the feed cake are the same as those described in Example 2. The particular conditions prevailing in the six tests that make up this Example and the results are shown in Table 4.
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It can be seen from Table ~ that the percentaye of nickel leached dec~eases and the percentage of cobalt increases with increasing reacti,on timeO
~lowever, by comparing tests 21 and 2~ with tests 19, 20, 23 and 24, it can be seen that the effect of increased time is less rnarked when operating in the optimum pH range of 2.8 to 3.1 than in the lower range of 2.4 to 2.6. The reaction time used in practice should be sufficiently long to maximise cobalt recovery in the precipitate.
Exa'mple 5 This Example illustrates the effect of -the rate oE gaseous chlorine feed on the nickel-cobalt separation efficiency in the treatment of a nickel~
cobalt carbonate cake with an acidic cobalt sulphate solution and chlorine gas. The experimental procedure used and the composition of the cake were the same as those set out in connection with Example 2~ In al,l the tests, at least one grarn of chlorine per gram of cobalt to be precipitated was added, which is at least 66% in excess of the stoichiometric requirement. The particular conditions used and the results obtained are shown in Table 5.
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- .~8 -The xesults clearly show that when operatlng within the optimum pH range of 2.8 to 3.1 increased ra-tes of chlorine addition have little effec-t on -the separation efficiency. It is therefore preferred to add chlorine at a low rate e.g~ 2 to 5 g per litre per hour to maximise the use of chlorine. Since nearly all the cobalt originally present in the cake ls precipi-tated, it appears that excess chlorine gas escapes from the reaction mixture and is wasted~
Example 6 In this Example, the process of the presen-t invention is carried out on a continuous basis as opposed to the ba-tch of processes described in previous ExamplesO The vessel used had a capacity o~
one litre and included a fritted glass inlet tube through which gaseous chlorine could be fed and a stirrer that was rotated at 1,000 revolutions per minute throughout the process~ An acid feed solution containing, in grams per litre~ Ni 40, H2S04 50 and NaCl 66 was fed to the vessel together with chlorine and a nickel-cobalt carbonate cake, which was added in the form of a slurry containing S00 gran~s per litre of the cake in feed solution. The feed rate of the solution was 0035 litres per hour (including that added in the slurry)~ the feed rate of the chlorine was 10 grams per hour and the feed rate of the cake was 55 grams per hour, which was sufficient to keep the pH in the reaction vessel in the range 2.8 to-3.1.
The reaction vessel was maintained at 60C and the process was operated continuously for 11 hours and the average residence time in -the vessel was 150 minutes.
The results of the process are shown in Table 6. The chlorine consumption was 1.47 grams per gram of precipitated cobal-t (20 45 times the stoichiometric 3S requlrement) whlch was high but could be reduced as indicated in Example 5~ It can be seen that about ~ ~9 e r~
90% oE t}~e nickel o~i~inall~ pxesent in the c~ke reported to -the solution and about 90~ of the cobalt repor-ted to -the precipi,tate~
.. . ..
T~BLE 6 5 STREAM ~LOW AN~LySES DISI'RIBUTIONS*
RATE ('g/l~or(wt%~ ~
Ni Co Ni Co ....... .. .......
~EED SOLUTION Oo 351/h 40 0 129 10 Ni--Co CARBONATE
CAKE 55 g/h 190 7 13.6 100 100 .. .... .... ... ....
: ::::: : : : : :
. . . ~
FINAL LIQUO~ 0~ 351/h 66 ~.0 214 9.4 COB~LT
15 PRECIPITATE 21. 3 g/h 5 . l 32 lO 91 .. .. ....
, , . , . . . . . . -. .
* by weight based on the amount of the metal present in the feed cake.
Example 7 This Example shows the effect of the presence of meta7s other than nickel and cobalt in the process of the present invention. A feed solution having a composition set out in Table 7 and in addition containing 30 grams pex litre of HCl was contacted with 25 a portion o~ a feed cake made by mixing nickel-cobalt carbonate and nickel~cobalt hydroxide. 5 grams per litre per hour of chlorine gas was introduced into the resulting solution together with sufficien-t additional cake ~ixture (slurried with t~e feed solution) 30 to maintain the pH in the range 2.8 to 3.1. The process was continued for t~o hours b~ which time 193 g of the cake h~d been used. The ~esults a~e $hown in Table 7 which sho~$ that coppe~ iron ~nd lead xepoxt to the pxecipit~te with the cob~lt. Al-though not 35 shown in the Table, the sodiu~ and calciu~ reported - ~o -in the solution with 78~ of the nickel. The chlor,ine consump-tion per ~r~ precipi-t~ted co~lt was 0.34 grams.
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Several examples of the process of the present invention will now be given.
Example-l A nickel~cobalt carbonate cake containing, in percentage by weight, Ni 19.4, Co 12.7, Cu 0.77, Fe 0.17 was dissolved in 5 litres of feed solution containing, in grams per litre: Ni 53, Cl 42l-H2S0~
39, until the resulting solution had a pH of 3. This required 359 grams of cake. Chlorine gas was then introduced into the solution through a fritted glass inlet tube at a rate of ~g of chlorine per litre of solution per hour. The pH of the solution was maintained in the range of 2.9 to 3.0 b~ adding feed cake. When the cobalt content of the solution had dropped to below 0.5 g/l, whlch took 330 minutes~ the chlorine intro-duction was discontinued and the leach solution was separated from the residue by flltxation. The ~esidue was then washed ~lth demineralised watex. The results of the process are shown in Tahle l-A.
~5 3~
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~ 8 --It can be seen from Table 1-~ that, within experimental accuracy, 97% o the iron, 98% of the cobalt, and 7% of the nickel originally present in the cake reported to the final leach residue ~nd that the leach liquor contalnedthe remaining 93~ of the nickel and about half the copper content originally present in the cake. The amount of chlorine ad~ed was 110 g, of which 95 g was converted to chloride ions~ which means that -the chlorine efficiency, i.e. the amount of chlorine dissolved divided by the amount of cobalt precipitated, was 0.78 g/g or 0.65 on a molar hasis.
The nickel separatlon, l.e. the ratio of the weigh-t of - nickel in solu-tion to the weight of oxidlsable metals (cobalt, lead and iron) in solution was 200 (g/g). The cobalt separation i.e. the ratio of the weight of oxidisable elements (cobalt~ lead and iron) in the leach residue to the weight of nickel in the residue was 10.4 (g/g) .
Table ~-B sho~s the amount of cake and chlorine added a-t various stages of the process and the varying composition of the reaction liquor as the process progressed. It can be seen from the Table that the cobalt that was leached when the first portion of cake was dissolved in the feed solution was gradually oxidised and precipitated throughout the chlorination treatment. It can also be seen that the actual consumption of gaseous chlorine was about 1 gram for each gram of cobalt precipitated, which is to be compared with a theoretical consumption of 0.6 grams per gram of cobalt and the chlorine efficiency ~i.e. the weight of chlorine that is reduced to chloride ions divided by the weight of cobalt precipitated) of 0.78.
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Example 2 This Example demonstrates the effect of pH
on the separa-tion of cobalt from nickel in the treatment of a feed nickel-cobalt carbonate cake with a feed acidic nickel sulphate solution and chlorine gasO The feed cake contained (in weigh-t percent) Co 18.4, Ni 27.4, Cu 1.12, Fe 0.28, Na 1054, Ca 1.48, S04 1080~ The feed solution contained (in grams per l.itre)~ Ni 40, H2504 50~ NaCl 660 Ten tests were carried out batchwise in the following sequence: (1) partially neutralising the feed solution with sufficient feed cake to achieve a pH of 3 at the temperature at which the test is to be conducted, (2) treating the neutralised solution with chlorine gas while maintaining the pH
of the reaction liquor with the desired range by adding a slurry of cake and partially neutralised solution, (3) separating the cobalt-rich precipitate from the nickel~rich final solution by filtration, and (4) washing the precipitate with water. The process conditions and the results of the tests are shown in Table 2.
For the sake of simplicity, in the results given in Table 2~ and also in Tables 3, :~ and 5 ollowing7 the "final solution" includes both the filtrate from step (3) abo~e and the washing water from step ~4), the"cobalt precipitate"refers to the precipitate when washed and dried,and under the heading "Ni-Co Separation Efficiency", "% Ni Liquor" refers to the weight percentage of nickel initially present in the feed cake that was leached out during the course of the process and "% Co Ca]ce?' refexs to the weight percentage of cobalt initially present in the feed cake that was precipi~ted durlng the processD
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- l2 -I-t can be seen from Table 2 that in the temperature range of 30 to 80C~ the percentage of nlckel leached decreases~ and -the percentage o~ cobalt precipitated increases, with increasing pH. Optimum separati.on of nickel from cobalt is achieved in the pH
range 2.~ to 3.1 t which seems to be the optimum throughout the.temperature range. We believe that at a pH of less than 2.8, the cobalt precipitation is incomplete and at a pH in excess of 3.1,nickel dissolution is incomplete.
E ample_ This Example illustrated the efect of temperature on the separation efficiency. The feed cake used in this Example had the same composition as that used in Example 2 and the procedure used was the same as that described in Example 2. Eight tests were carried out and the conditions used and the results are given in Table 3.
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- ~4 -It can be seen ~rom Table 3 that in the pH
range 2.8 to 3~1, -the temperature has llttle effect on the nickel-cobalt separation efficiency. In the pH range 2.4 to 2.6, however, the percentage of nickel leached decreases and the percentage of cobalt precipitated increases with increased temperature.
Thus, when opexating within a pH range of 2.8 to 3.1, it is preferable to use a low temperature, e.g. 30C
50C, to save energy.
Example 4 This Example illustrates the effect of reaction time on the nickel-cobalt separation efficiencyO Experimental procedures and the composition of the feed cake are the same as those described in Example 2. The particular conditions prevailing in the six tests that make up this Example and the results are shown in Table 4.
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It can be seen from Table ~ that the percentaye of nickel leached dec~eases and the percentage of cobalt increases with increasing reacti,on timeO
~lowever, by comparing tests 21 and 2~ with tests 19, 20, 23 and 24, it can be seen that the effect of increased time is less rnarked when operating in the optimum pH range of 2.8 to 3.1 than in the lower range of 2.4 to 2.6. The reaction time used in practice should be sufficiently long to maximise cobalt recovery in the precipitate.
Exa'mple 5 This Example illustrates the effect of -the rate oE gaseous chlorine feed on the nickel-cobalt separation efficiency in the treatment of a nickel~
cobalt carbonate cake with an acidic cobalt sulphate solution and chlorine gas. The experimental procedure used and the composition of the cake were the same as those set out in connection with Example 2~ In al,l the tests, at least one grarn of chlorine per gram of cobalt to be precipitated was added, which is at least 66% in excess of the stoichiometric requirement. The particular conditions used and the results obtained are shown in Table 5.
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- .~8 -The xesults clearly show that when operatlng within the optimum pH range of 2.8 to 3.1 increased ra-tes of chlorine addition have little effec-t on -the separation efficiency. It is therefore preferred to add chlorine at a low rate e.g~ 2 to 5 g per litre per hour to maximise the use of chlorine. Since nearly all the cobalt originally present in the cake ls precipi-tated, it appears that excess chlorine gas escapes from the reaction mixture and is wasted~
Example 6 In this Example, the process of the presen-t invention is carried out on a continuous basis as opposed to the ba-tch of processes described in previous ExamplesO The vessel used had a capacity o~
one litre and included a fritted glass inlet tube through which gaseous chlorine could be fed and a stirrer that was rotated at 1,000 revolutions per minute throughout the process~ An acid feed solution containing, in grams per litre~ Ni 40, H2S04 50 and NaCl 66 was fed to the vessel together with chlorine and a nickel-cobalt carbonate cake, which was added in the form of a slurry containing S00 gran~s per litre of the cake in feed solution. The feed rate of the solution was 0035 litres per hour (including that added in the slurry)~ the feed rate of the chlorine was 10 grams per hour and the feed rate of the cake was 55 grams per hour, which was sufficient to keep the pH in the reaction vessel in the range 2.8 to-3.1.
The reaction vessel was maintained at 60C and the process was operated continuously for 11 hours and the average residence time in -the vessel was 150 minutes.
The results of the process are shown in Table 6. The chlorine consumption was 1.47 grams per gram of precipitated cobal-t (20 45 times the stoichiometric 3S requlrement) whlch was high but could be reduced as indicated in Example 5~ It can be seen that about ~ ~9 e r~
90% oE t}~e nickel o~i~inall~ pxesent in the c~ke reported to -the solution and about 90~ of the cobalt repor-ted to -the precipi,tate~
.. . ..
T~BLE 6 5 STREAM ~LOW AN~LySES DISI'RIBUTIONS*
RATE ('g/l~or(wt%~ ~
Ni Co Ni Co ....... .. .......
~EED SOLUTION Oo 351/h 40 0 129 10 Ni--Co CARBONATE
CAKE 55 g/h 190 7 13.6 100 100 .. .... .... ... ....
: ::::: : : : : :
. . . ~
FINAL LIQUO~ 0~ 351/h 66 ~.0 214 9.4 COB~LT
15 PRECIPITATE 21. 3 g/h 5 . l 32 lO 91 .. .. ....
, , . , . . . . . . -. .
* by weight based on the amount of the metal present in the feed cake.
Example 7 This Example shows the effect of the presence of meta7s other than nickel and cobalt in the process of the present invention. A feed solution having a composition set out in Table 7 and in addition containing 30 grams pex litre of HCl was contacted with 25 a portion o~ a feed cake made by mixing nickel-cobalt carbonate and nickel~cobalt hydroxide. 5 grams per litre per hour of chlorine gas was introduced into the resulting solution together with sufficien-t additional cake ~ixture (slurried with t~e feed solution) 30 to maintain the pH in the range 2.8 to 3.1. The process was continued for t~o hours b~ which time 193 g of the cake h~d been used. The ~esults a~e $hown in Table 7 which sho~$ that coppe~ iron ~nd lead xepoxt to the pxecipit~te with the cob~lt. Al-though not 35 shown in the Table, the sodiu~ and calciu~ reported - ~o -in the solution with 78~ of the nickel. The chlor,ine consump-tion per ~r~ precipi-t~ted co~lt was 0.34 grams.
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Claims (6)
1. A process of separating cobalt from nickel present in an alkaline mixed nickel-cobalt compound, which process comprises dissolving a portion of the compound in acid, treating the resulting liquor with gaseous chlorine while adding one or more further portions of the compound together with as much acid or alkali as is needed to maintain the pH of the liquor within the range of 2.5 to 4Ø
2. A process as claimed in claim 1, wherein the amount of acid or alkali added is sufficient to maintain the pH of the liquor within the range 2.6 to 3.3.
3. A process as claimed in claim 2, wherein the amount of acid or alkali added is sufficient to maintain the pH of the liquor within the range 2.8 to 3.1.
4. A process as claimed in claim 2 or claim 3, which is operated at a temperature in the range of from 30 to 80°C.
5. A process as claimed in claim 1, wherein the molar wherein the molar ratio of the chlorine fed into the liquor to the cobalt contained in the compound utilized is less than 1:1.
6. A process as claimed in claim 1, wherein the nickel to cobalt ration in the compound is in the range of from 2:1 to 1:4.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8130832 | 1981-10-13 | ||
| GB8130832 | 1981-10-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1195511A true CA1195511A (en) | 1985-10-22 |
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ID=10525127
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000412960A Expired CA1195511A (en) | 1981-10-13 | 1982-10-06 | Separation of cobalt from nickel |
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| CA (1) | CA1195511A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012100293A1 (en) | 2011-01-25 | 2012-08-02 | The University Of Queensland | Improved method of ore processing |
| US10662503B2 (en) | 2011-01-25 | 2020-05-26 | The University Of Queensland | Method of ore processing using mixture including acidic leach solution and oxidizing agent |
-
1982
- 1982-10-06 CA CA000412960A patent/CA1195511A/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012100293A1 (en) | 2011-01-25 | 2012-08-02 | The University Of Queensland | Improved method of ore processing |
| EP2668303A4 (en) * | 2011-01-25 | 2016-06-22 | Univ Queensland | Improved method of ore processing |
| US9447480B2 (en) | 2011-01-25 | 2016-09-20 | The University Of Queensland | Method of ore processing |
| AU2012211033B2 (en) * | 2011-01-25 | 2016-10-20 | The University Of Queensland | Improved method of ore processing |
| KR101861885B1 (en) | 2011-01-25 | 2018-05-28 | 더 유니버서티 어브 퀸슬랜드 | Improved method of ore processing |
| US10662503B2 (en) | 2011-01-25 | 2020-05-26 | The University Of Queensland | Method of ore processing using mixture including acidic leach solution and oxidizing agent |
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