ZA200301671B

ZA200301671B - Selective recovery of metal values from a spent catalyst composition.

Info

Publication number: ZA200301671B
Application number: ZA200301671A
Authority: ZA
Inventors: De Wet Ewald Watermeyer; Matjie Ratale Henry; Mdleleni Masikana Millan
Original assignee: Sasol Tech Pty Ltd
Priority date: 2000-08-29
Filing date: 2003-02-28
Publication date: 2004-03-11

Description

‘ .

SELECTIVE RECOVERY OF METAL VALUES FROM A SPENT

CATALYST COMPOSITION

* Field of the Invention . 5

This invention relates to the selective recovery of metal values from a spent catalyst composition. In particular this invention relates to a process for the selective recovery of aluminium, Cobalt and Platinum and/or compounds thereof, from a spent catalyst composition. :

Background to the Invention

The specific spent catalyst composition of the current invention is obtained from Fischer Tropsch synthesis reactions for the production of predominantly paraffinic hydrocarbons.

The catalyst is an impregnated Fischer Tropsch Catalyst comprising an alumina carrier and active component selected from the group consisting of cobalt and/or iron and mixtures thereof. The catalyst may also comprise of a group VIII noble metal as promoter.

The Fischer-Tropsch process is used to produce hydrocarbons from carbon monoxide and hydrogen. In the Fischer-Tropsch process, a cobalt catalyst may be used to activate the catalytic reaction. This catalyst may be prepared with a cobalt nitrate and tetra amine platinum nitrate that are used as cobalt and platinum precursors respectively. Aluminium oxide may be used as a support. Continual processing causes a drop in the activity of the catalyst mainly due to sulphur, which is originally present in the mixture of gases, which may , accumulate on the surface of the catalyst to form either cobalt sulphide or : 30 platinum sulphide during the process. Coke formation may also be experienced " during the process and subsequently the catalyst reaches a stage of deactivation and becomes a spent catalyst.

The spent catalyst typically contains organic material, cobalt oxide, platinum and aluminium oxide. As a result of the organic content in the catalyst coupled with the fact that both cobalt and platinum are considered to * be environmentally toxic, dumping is not a viable option. If the adequate . 5 disposal of this spent catalyst, which is oily and sticky, is considered, the chemical fixation method should be recommended. In this method, which is very expensive, the pollutants like heavy and base metals can react with cement or pozzolanic materials to form water insoluble compounds. This encapsulation of heavy and base metals on the spent catalyst is efficacious only if the heavy metals are not absolutely leached out in the soil by water. To avoid the disposal of the spent catalyst or encapsulated deactivated catalyst in the landfills, the recovery of these high value metals is important.

The inventor is aware that the above catalyst composition contains valuable metal values which, if recovered, could lead to a substantial profit and also to eliminate the existing environmental problems. At present the catalyst composition is disposed of without substantial recovery thereof.

Summary of the Invention

To produce environmentally friendly products from the spent catalyst, a method of recovering high value metal compounds from the spent cobalt based catalyst which is environmentally safe, has been developed.

In this selective recovery process initially either the mixture of spent catalyst and sodium carbonate or the spent catalyst containing organic material is calcined at different temperatures in the presence of air to oxidise the organic material. Following the calcination of this spent catalyst, metal : oxides such as cobalt oxide (CoO and C0304), cobalt aluminate (Co2AIO,) and sodium aluminate (NazAl,O4) are formed. A solution of caustic soda ’ (sodium hydroxide) is used to selectively and efficiently dissolve aluminium oxide at a relatively high temperatures (ranging from 110 to 220 Degrees

Celsius) and pressures (ranging from 5 to 20 bars) with substantially no dissolution of cobalt and platinum from the spent catalyst. The pH of the mixture is around 13. ) Alternativley, water leaching may be used to solubilise sodium “ 5 aluminate formed during the calcination step. This sodium aluminate solution which is formed during the leaching step may be used in the precipitation step of the aluminium hydroxide. The cobalt and platinum, which are theoretically insoluble in a solution of sodium hydroxide under afore-given conditions, remain in the leached residue after the base leaching. This leached residue containing mainly platinum and cobalt are dissolved in a solution of nitric acid to form cobalt nitrate while the platinum remains in the acid-residue after the acid leaching step.

This acid residue may be dissolved in the aqua regia (a solution of nitric acid and hydrochloric acid) to form chloroplatinic acid.

Subsequently, purification methods such as solvent extraction and selective precipitation may be used to selectively remove impurities or the desired metal ions from the leach liquors of the basic residue and acidic residue. The purified leach liquors may be reserved for the crystallisation method. In this method, chemically pure crystalline cobalt nitrate or diammonium hexachloroplatinate are formed.

The platinum salts are important in the purification of platinum metal and sponge while the cobalt nitrate is commercially used in the production of high purity cobalt, in the electronics and chemical industries.

Thus, according to a first aspect of the invention, there is provided a ¢ process for the selective recovery of aluminium, cobalt and platinum, and compounds thereof, from a catalyst composition including aluminium, cobalt ’ and platinum, said process including the steps of: - treating the catalyst composition to selectively get ions of substantially only one of the aluminium, cobalt and platinum into solution;

k | ! - recovering, in separate process steps, the thus treated aluminium, cobalt, or platinum in salt or metal form; and - repeating the treating and recovering steps for each of the ) aluminium, cobalt and platinum. « 3

The treating steps may include process steps such as leaching, washing, dissolving, stripping, and the like.

The recovery steps may include filtration, precipitation, separation, flocculation, and the like.

Thus, according to a second aspect of the invention, there is provided a process for the selective recovery of aluminium, cobalt and platinum, and compounds thereof, from a catalyst composition including aluminium, cobalt and platinum, said process including the steps of: oxidising substantially all organic material present with the catalyst composition; - leaching the aluminium and/or compounds thereof from the oxidised catalyst composition with a strong or weak base to form an aluminium containing product and a filtrate; - filtering of alkali insoluble residue from the filtrate; - washing of the alkali insoluble residue with water to remove the residual alkali aluminate solution; - precipitating of silica from alkali aluminate with slaked lime or quicklime; - filtering of insoluble silicate from alkali aluminate; - crystalising aluminium trinydrate from the alkali aluminate e solution; - filtering aluminium trihydrate crystals from the alkali ) aluminate solution : - recycling of the alkali solution to the leaching step;

- dissolving the cobalt and compounds thereof present in the water washed-insoluble residue composition with an inorganic acid; ’ - separating a substantial portion of the cobalt rich solution

N 5 from a solid component present after the dissolving step; - precipitating substantially all non-cobalt and/or non-cobalt compound impurities from the cobalt rich solution; - crystallizing the cobalt and/or cobalt compounds out of the cobalt rich solution to form impure cobalt nitrate salt; 10 or - as an alternative to the crystallizing step, selectively loading substantially all cobalt ions from the impure cobalt rich solution into an organic phase by solvent extraction; - subsequently stripping the cobalt-containing organic 15 phase with a solution of nitric acid to form a pure cobalt nitrate salt; - dissolving the platinum and compounds thereof, as well as non-cobalt and/or non-cobalt compound impurities from the cobalt rich solution out of the water washed solid 20 component to obtain a platinum rich solution; and - recovering platinum and/or platinum salts from the platinum rich solution.

After the aluminium leaching step and prior the alkali insoluble residue 25 filtration step a flocculation step may be included to remove ultra fine solids which inhibit efficient filtration.

Also, after the cobalt dissolution step and prior to the separation of a ‘ substantial portion of the cobalt rich solution a flocculation step may be 30 included to remove ultra fine solids which may inhibit efficient separation.

The flocculation for an alkali slurry may be carried out with the aid of flocculating agents, such as modified anionic polyacrylamides. The flocculation may be carried out at a pH of about 12. The flocculation may y assist the sedimentation rate and filterability of suspended ultra fine solid particles from the slurry

The flocculation for an acidic slurry may be carried out with the aid of . 5 flocculating agents such as cationic a flocculant. The flocculation may carried : out at a low pH about 1.5. The flocculation may assist the sedimentation rate and filterability of suspended ultra fine solid particles from the slurry.

The catalyst composition may be in the form of waxy lumps of spent catalyst composition from a hydrocarbon processing reactor.

The oxidising step may be performed by heating the catalyst composition and contacting it with oxygen.

Typically, for performing the oxidising step, the catalyst composition is heated to a temperature of between 600°C and 1400°C, generally between 700°C and 1000°C. In specific embodiments of the invention the catalyst composition was heated to 700°C, 800°C, 900°C and 1000°C.

Where the catalyst composition is Co/Pt/Al,03/SiO,, then the oxidised spent catalyst composition typically contains about from 0.0125 g Pt per 100 g

Al,03 to 0.175 g Pt per 100 g AlO3 and from 5 g Co per 100 g Al203 to 70 g

Co per 100 g AlxOs.

The leaching of the aluminium and/or the aluminium compounds, such as Al,O3 from the oxidised spent catalyst composition may be carried out with a solution of sodium hydroxide of about 20% to 50% w/w NaOH, typically 25%. This selectively and efficiently dissolves aluminium oxide at a relatively ’ high temperature ranging from 110°C to 250°C, typically 200°C, and at a high pressure ranging from 5 to 20 bar, typically 15 bar, with substantially no dissolution of cobalt and platinum from the spent catalyst composition. The leachate may be in the form of slurry.

The flocculation of the slurry prior to filtration may be carried out using approximately 2 % w/w of flocculant prepared using a solution of sodium . hydroxide of about 2 % w/w NaOH, whereafter the flocculant solution is conditioned at ambient temperature for one hour to form homogeneous © 5 solution, whereafter it is diluted with a solution of sodium hydroxide of 2 % w/w NaOH to produce a final solution containing about 0.25 % w/w of the flocculant.

Approximately 3000 to 6000 g/t of the final solution heated to 90 degrees Celsius may be added to the slurry and mixed thoroughly until flocs form. These flocs may be separated from the mixture by filtration and eventually washed with water to remove aluminium-containing filtrate absorbed during the filtration.

Alternatively, water leaching could also be used to selectively solubilize sodium aluminate formed during the oxidising of the spent catalyst in the presence of either sodium carbonate or sodium chloride. The water leaching may be carried out at any temperature and pressure, and 50°C at atmospheric pressure has been found to be satisfactory. A solution of sodium aluminate from the water leaching step may be reserved for the precipitation of aluminium hydroxide while the water- washed base insoluble residue may be used in the strong or weak inorganic acid cobalt dissolving step.

The leached residue recovered from the aluminium leaching step typically contains 51% w/w cobalt, 0.124% w/w platinum and 4.9% w/w aluminium.

Cobalt and platinum are currently considered to be environmentally toxic and thus dumping of this leached residue is not a viable option. Also, ‘ both cobalt and platinum are high value products. “ 30

Cobalt recovery is initiated by dissolving the cobalt and compounds thereof present in the water- washed leached residue of the oxidised catalyst composition with a strong acid such as nitric acid. The water washed-leached residue may be contacted with a solution of nitric acid of about 55 % wiv

HNQ; at a temperature of between 80°C and 200°C and at a pressure of between 1 -bar and 20 bar, in order to selectively dissolve cobalt. Typically this cobalt dissolution step is carried out at 100° and 1 atmospheric pressure. . 5 The impure cobalt nitrate may be used in the chemical, ceramics

Industries and the production of high purity cobalt for use in the electronics and related industries. The washed nitric acid insoluble residue, which is mainly composed of platinum compounds and impurities, may be used in the step of producing platinum compound.

In order to recover commercially viable cobalt, the process includes the separating of a substantial portion of the impure cobalt nitrate, i.e. the cobalt rich solution, from the strong acid insoluble residue, i.e. the solid component present after the dissolving step. This separation may include a precipitation step during which impurities such as Aluminium and Iron are precipitated out of the cobalt rich solution.

The separation may be aided by flocculating ultra fine solids using a suitable flocculant, such as ZN9O2V Zetafloc produced by Zetachem Company.

The flocculant may be used as 0.1 % w/w solution.

The still impure cobalt rich solution is then purified by selectivley removing substantially all only cobalt ions from the cobalt rich solution by solvent extraction. The impurities may remain in the aqueous phase after the solvent extraction step.

The cobalt rich solution from the precipitation step typically contains

Co, Pt, Al, Fe, NOs and NH," ions. To selectively separate Co ions from this ’ solution, a suitable type of an acidic extractant like di- (2-ethylhexyl)

A 30 phosphoric acid (DEHPA) and tributylphosphate (TBP) as a modifier in illuminating paraffin for extracting Co ions from the cobalt rich solution may be used. Usually this solvent extractant is used as an ammonium salt which assists in keeping the pH of the mixture relatively constant after contacting the acidic cobalt rich solution with the organic extractant phase.

The aqueous phase recovered from the solvent extraction may be used in the precipitation of Fe and Al ions step, while the loaded organic phase (containing mainly Co ions) is reserved for a stripping step. . 5 :

In this step, the Co loaded organic phase is contacted with a solution of the stripping agent, such as a solution of nitric acid, to remove the extracted species i.e. Co ions.

The purified. cobalt rich solution is finally crystallised to form a red- brown crystalline cobalt nitrate salt, Co(NOs)26H,0 or Co(NO3z)24H20 depending on the retention time when heating the crystals at 55°C.

This salt is currently used in the production of high purity cobalt and also electronics and chemical industries.

The crystallisation liquor containing free water and nitric acid may be utilised in the crystallisation step of cobalt nitrate or in the dissolution step of cobalt from the washed insoluble basic residue.

Platinum is recovered from the nitric acid insoluble solid component from the cobalt dissolution step by dissolving the platinum and compounds thereof, as well as non-cobalt and /or non-cobalt compound impurities from the cobalt rich solution out of the solid component to obtain a platinum rich solution. The dissolving of platinum may be achieved by a mixture of HCI and

HNO; or by using H202 and HC! or HCI and C2

The dissolved platinum may be precipitated out of the platinum rich ' solution by using NaOH and/or NH4Cl to form platinum salts complex which

N 30 can be recovered by a liquid: solid separation process such as filtration.

The recovered aluminium, cobalt and platinum, and/or compounds or salts thereof may be further processed.

Specific Description and Examples

The invention will now be described with reference to the following examples, which are not intended to limit the scope of the invention. . 5 1. Oxidising Of The Spent Catalyst Composition — Oxidising Step

The spent catalyst composition from a Fischer-Tropsch reaction for the industrial synthesis of certain hydrocarbons from carbon monoxide and hydrogen typically contains about 60 to 75 % of the organic content.

This spent catalyst is initially heated to a temperature ranging from 700 to 1000°C at atmospheric pressure for 2 to 6 hr in the presence of air to oxidise the organic material. A high temperature furnace (maximum temperature of the furnace is 1400°C was used for the heating.

In another run, the spent catalyst composition was oxidised in the presence of either sodium carbonate or sodium chloride to prevent the formation of the spinels such as cobalt aluminate (Co2Al04) and cobalt (Il) dicobalt (Ill) oxide (Co304) during the oxidising step. The aluminium oxide or cobalt oxide that is present in the spinels may possibly dissolve with difficulty in a solution of sodium hydroxide or mineral acid solution. During the oxidising step, sodium oxide from either sodium carbonate or sodium chioride could possibly react with water-insoluble aluminium oxide to form water-soluble compounds such as sodium aluminate or silicate.

The oxidised spent catalyst composition sample produced in this step is digested with either water or a weak solution of sodium hydroxide (approximately 10 to 25 % wiw NaOH) at a relatively high temperature ranging ) 30 from 90 to 230°C and at high pressure ranging from 1 to 20 bars.

The main objective of the oxidising step is to burn out almost all of the organic material present in the spent catalyst composition prior to the leaching step as this organic material can decompose the lixiviant reagents during the leaching step. a. Experimental Procedure . 5

Approximately 1000 g of the waxy lumps of the spent catalyst composition was placed in a stainless steel dish. A gas burner was used to ignite the waxy lumps in the presence of air. A self —supporting combustion of the waxy lumps of the spent catalyst composition under natural convection was carried out for two hours and no more combustion takes place. To oxidise all of the organic material remaining in the oxidised spent catalyst composition, a sample of a free flowing powder was oxidised at different temperatures ranging from 600 to 1000°C for six hours in the presence of air.

A second sample of free flowing powder and sodium carbonate or sodium chloride were mixed together using solid to solid ratio of 1:1(a sample of flowing powder: either sodium carbonate or sodium chloride) and finally, reoxidised under the above conditions. Subsequently, a sample of free flowing powder produced after a self-supporting combustion and a sample after oxidising the spent catalyst at various temperatures were submitted for the organic carbon analysis. b. Results and discussion

Visual observation showed that no significant catalyst dust loss was experienced during the oxidising. After the oxidising step, a free flowing powder with a small amount of residual carbon was produced. Following the oxidising of the spent catalyst at 1000°C in the absence of both sodium ’ carbonate and sodium chloride the colour of the oxidised spent catalyst composition turned to blue. This may possibly be attributed to the formation of cobalt aluminate at a high temperature. While after oxidising the spent catalyst composition at a temperature ranging from 700 to 1000°C in the presence of sodium carbonate or sodium chloride, the colour of the oxidised spent catalyst composition turned black. This may mean that sodium aluminate was formed.

The loss on ignition (L.O.l) analysis of a free flowing powder formed during self-supporting combustion was determined to be 2.7 %. This implies that the organic material was still contained in the free flowing powder after . 5 the self-supporting combustion. After reoxidising the free flowing powder for a period of six hours, the L.O.I of the final oxidised spent catalyst was determined to be <0.1. This implies that all of the residual carbon was effectively removed after the second oxidising step.

It can be concluded that all of the organic material present in the waxy lumps of the spent catalyst composition was successfully oxidised after the oxidising step. Spinels such as cobalt aluminate and cobalt(ll) dicobalt (lil) oxide were formed at high temperatures ranging from 900 to 1000°C during the heating of the spent catalyst in the absence of either sodium carbonate or sodium chloride. 2. Leaching Of The Oxidised Spent Catalyst Composition — Base

Leaching Step

The oxidised spent catalyst from the waxy lumps of the spent catalyst composition typically contains about 60 to 65 % Al,Os, 18.7 to 19.6 % w/w Co and 0.046 to 0.05 % w/w Pt. A solution of sodium hydroxide of about 20 to 50% w/w NaOH was used to selectively and efficiently dissolve aluminium oxide at relatively high temperatures ranging from 110 to 170°C and at high pressures ranging from 5 to 20 bars with substantially no dissolution of cobalt and platinum from the spent catalyst.

In a separate run, water leaching was used to selectively solubilize sodium aluminate formed during the calcination of the spent catalyst in the

X 30 presence of either sodium carbonate or sodium chloride.

A solution of sodium aluminate from the leaching step was reserved for the precipitation of aluminium hydroxide while the water- washed base insoluble residue was used in the nitric acid leaching step.

Claims

F309ZA Amendment AMENDED SHEET Claims

1. A process for the selective recovery of aluminium, cobalt and platinum, and compounds thereof, from a catalyst composition including aluminium, cobalt and platinum, said process including the steps of: - oxidising substantially all organic material present with the catalyst composition; : - leaching the aluminium and/or compounds thereof from the oxidised catalyst composition with a strong or weak base to form an aluminium containing product and a filtrate; - filtering of alkali insoluble residue from the filtrate; - washing of the alkali insoluble residue with water to remove the residual alkali aluminate solution; - precipitating of silica from alkali aluminate with slaked lime or quicklime; - filtering of insoluble silicate from alkali aluminate; - crystalising aluminium trihydrate from the alkali aluminate solution; - filtering aluminium trihydrate crystals from the alkali + aluminate solution - recycling of the alkali solution to the leaching step; - dissolving the cobalt and compounds thereof present in the water washed-insoluble residue composition with an inorganic acid; - separating a substantial portion of the cobalt rich solution from a solid component present after the dissolving step; - precipitating substantially all non-cobalt and/or non-cobalt compound impurities from the cobalt rich solution; - crystallizing the cobalt and/or cobalt compounds out of the cobalt rich solution to form impure cobalt nitrate salt; or

’ F309ZA Amendment AMENDED SHEET - as an alternative to the crystallizing step, selectively : loading substantially all cobalt ions from the impure cobalt rich solution into an organic phase by solvent extraction; - subsequently stripping the cobalt-containing organic phase with a solution of nitric acid to form a pure cobalt nitrate salt; - dissolving the platinum and compounds thereof and non- cobalt and /or non-cobalt compound impurities from the cobalt rich solution out of the water washed solid component to obtain a platinum rich solution; and - recovering platinum and/or platinum salts from the platinum rich solution.

2. A process as claimed in claim 1, wherein after the aluminium leaching step and prior the alkali insoluble residue filtration step, a flocculation step is included to remove ultra fine solids which inhibit efficient filtration.

3. A process as claimed in claim 1 or claim 2, wherein after the cobalt dissolution step and prior to the separation of a substantial portion of the cobalt rich solution, a flocculation step is included to remove ultra fine solids which may inhibit efficient separation.

4. A process as claimed in claim 2, wherein the flocculation is carried out with the aid of flocculating agents selected from a group including modified anionic polyacrylamides.

5. A process as claimed in claim 2 or claim 4, wherein the flocculation is carried out at a pH of about 12.

6. A process as claimed in any one of claims 1 to 5, wherein for the oxidising step, the catalyst composition is heated to a temperature of between 600°C and 1400°C, generally between 700°C and 1000°C.

POZA Amendment AMENDED SHEET

7. A process as claimed in any one of claims 1 to 6, wherein where the catalyst composition is Co/Pt/Al,03/SiO, then the oxidised spent catalyst composition contains about 0.0125 g Pt per 100 g Al,O3 to 0.175 g Pt per 100 dg Al2O3 and from 5 g Co per 100 g Al,O3 to 70 g Co per 100 g Al,O3.

8. A process as claimed in any one of claims 1 to 7, wherein the leaching of the aluminium and/or the aluminium compounds from the oxidised spent catalyst composition is carried out with a solution of sodium hydroxide of about 20% to 50% w/w NaOH, generally 25%, at a temperature ranging from 110°C to 250°C, typically 200°C, and at a high pressure ranging from 5 to 20 bar, typically 15 bar, with substantially no dissolution of cobalt and platinum from the spent catalyst composition.

9. A process as claimed in claim 8, wherein the leachate is in the form of a slurry.

10. A process as claimed in any one of claims 3 to 9, wherein the flocculation of the slurry prior to filtration is carried out using a flocculant solution prepared from approximately 2 % w/w of flocculant which in turn is prepared using a solution of sodium hydroxide of about 2 % w/w NaOH, whereafter the flocculant solution is conditioned at ambient temperature for one hour to form homogeneous solution, whereafter it is diluted with a solution of sodium hydroxide of 2 % w/w NaOH to produce a final solution containing about 0.25 % w/w of the flocculant.

11. A process as claimed in any one of the preceding claims, wherein water leaching is used to selectively solubilize sodium aluminate formed during the oxidising of the spent catalyst in the presence of either sodium carbonate or sodium chloride.

12. A process as claimed in claim 11, wherein the water leaching is carried out at 50°C at atmospheric pressure.

oF F309ZA Amendment ' AMENDED SHEET

13. A process as claimed in claim 11 or claim 12, wherein a solution of sodium aluminate from the water leaching step is reserved for the precipitation of aluminium hydroxide.

14. A process as claimed in any one of claims 11 to 13, wherein the water- washed base insoluble residue is used in the strong or weak inorganic acid cobalt dissolving step.

15. A process as claimed in any one claims 1 to 14, wherein the leached residue recovered from the aluminium leaching step contains 51% w/w cobalt, 0.124% w/w platinum and 4.9% w/w aluminium.

16. A process as claimed in any one of the preceding claims, wherein cobalt recovery is initiated by dissolving the cobalt and compounds thereof present in the water- washed leached residue of the oxidised catalyst composition with a strong acid.

17. A process as claimed in claim 16, wherein the water washed- leached residue is contacted with a solution of nitric acid of about 55 % wiv HNO; at a temperature of between 80°C and 200°C and at a pressure of between 1 bar and 20 bar, in order to selectively dissolve cobalt.

18. A process as claimed in claim 17, wherein the cobalt dissolution step is carried out at 100° and 1 atmospheric pressure.

19. A process as claimed in claim 18, wherein including the separating of a substantial portion of the impure cobalt nitrate as the cobalt rich solution, from the strong acid insoluble residue in the form of the solid component present after the dissolving step.

20. A process as claimed in claim 19, wherein the separation includes a precipitation step during which impurities are precipitated out of the cobalt rich solution.

21. A process as claimed in claim 19 or claim 20, wherein the separation is aided by flocculating using a suitable flocculant used as 0.1 % w/w solution.

22. A process as claimed in any one of claims 16 to 21, wherein the cobalt rich solution is purified by selectivley removing substantially only cobalt ions from the cobalt rich solution by solvent extraction so that the cobalt rich solution from the precipitation step typically contains Co, Pt, Al, Fe, NO3™ and NH," ions.

23. A process as claimed in claim 22, wherein a suitable type of an acidic extractant is used.

24. A process as claimed in claim 23, wherein the acidic extractant is di- (2-ethylhexyl) phosphoric acid (DEHPA) and tributylphosphate (TBP) as a modifier in illuminating paraffin for extracting Co ions from the cobalt rich solution.

25. A process as claimed in claim 23 or claim 24, wherein the solvent extractant is used as an ammonium salt which assists in keeping the pH of the mixture relatively constant after contacting the acidic cobalt rich solution with the organic extractant phase.

26. A process as claimed in any one of claims 22 to 25, wherein the aqueous phase recovered from the solvent extraction is used in the precipitation of Fe and Al ions step, while the loaded organic phase containing mainly Co ions is reserved for a stripping step.

27. A process as claimed in claim 26, wherein the Co loaded organic phase is contacted with a solution of the stripping agent to remove the extracted species.

28. A process as claimed in any one claims 1 to 27, wherein the purified cobalt rich solution is crystallised to form a red-brown crystalline

’ F309ZA Amendment AMENDED SHEET cobalt nitrate salt, Co(NO3),6H,0 or Co(NO3),4H20 depending on the retention time when heating the crystals at 55°C.

29. A process as claimed in any one of claims 1 to 28, wherein platinum is recovered from the nitric acid insoluble solid component from the cobalt dissolution step by dissolving the platinum and compounds thereof and non-cobalt and /or non-cobalt compound impurities from the cobalt rich solution out of the solid component to obtain a platinum rich solution.

30. A process as claimed in claim 29, wherein the dissolved platinum is precipitated out of the platinum rich solution by to form platinum salts complex which can be recovered by a liquid: solid separation process.

31. A process as claimed in claim 1, substantially as hereinbefore described and illustrated.

32. A new process substantially as hereinbefore described.