AU2008200404A1 - Process for the treatment of lateritic ore - Google Patents

Description

Australian Patents Act 1990 Regulation 3.2 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT William Jay Invention Title "Process for the treatment of lateritic ore" The following statement is a full description of this invention, including the best method of performing it known to me/us:- Q \OPER\PDB\2OO8Uanuary\3471905 2l doc POPER\PDBSpa'3047905 Willi, )ayomp A dm.25f0112OOS 00 O-1- 00 process for obtaining a combined nickel/iron product from lateritic ore.

PROCESS FOR THE TREATMENT OF LATERITIC ORE FIELBACKGROUND OF THE INVENTION 0 5 The present invention relates to nickeliferous lateritic ores and the leaching and recovery Currently, most nicke is produced from sulphide ore concentrates by smelting or other energy intensive process. Despite the environmental concerns due to the emission of sulphur oxides, the overall costs have been such that the bulk of the world's nickel is produced from sulphide ores.

With recovery costs rising and nickel sulphide ore reserves dwindling, increased attention is now being given to lateritic ores. These ores constitute the most likely future source of nickel and cobalt and represent some 70% of the world's known nickel resource.

Furthermore, they also contain significant quantities of iron. They are mainly found in tropical climates such as Cuba, New Caledonia, Indonesia, Guatemala and the Philippines.

Dry land or semi arid laterites also exist and occur mainly in Australia, Greece and Albania.

Whilst lateritic ores comprise most of the world's known nickel reserves, to date the use of lateritic ores has been hindered by the need to use high cost, energy intensive leaching and recovery processes. Unlike sulphide ores, smelting for nickel recovery is not applicable to lateritic ores.

The leaching and recovery processes used to date include high pressure acid oxidative leaching (PAL or HPAL), hot atmospheric leaching (AL) at about 95 0 C, matte smelting, smelting to ferronickel, and the Caron ammonia leaching process. Despite substantial P)OER1PDB\Spm*\347l90 Wil ia h Jyoapvd.-25/1O/2008 00

O

-2c' investment in these technologies none of these methods have to date proven to adequately C1 meet the industrial recovery costs required, which has limited the mining and metallurgical treatment of laterites.

In Australia, the three PAL plants commissioned to date (Cawse, Bulong and Murrin C, Murrin) have all experienced significant economic and technical difficulties. Bulong has 00 0now closed due to the problems encountered in operating the plant. Both Bulong and N Cawse reported that to be economic, a feed grade of ore to the reactor should contain about 1.7% of nickel. As most Australian nickel laterite deposits have a grade lower than this, a significant body of ore will remain unmined. Screening the ore to remove oversized lower nickel-containing minerals has resulted in upgrading several ore types to meet this feed grade but this screening does result in the loss of ore.

Seawater has also been used to pulp laterites prior to hot (>90 0 C) atmospheric leaching with sulphuric acid. In US Patent 6,261,527, the sodium ion present in the seawater is used to aid in iron precipitation as natro-jarosite. The reaction is conducted in stirred reactors for a period sufficient to dissolve the nickel, cobalt and iron from the ore. The temperature is preferably held at the boiling point of the slurry, sulphur dioxide being used to maintain the Eh preferably between 100-900 mV to avoid reduction of ferric iron. At the end of the leaching period a precipitating agent is introduced into the pulp to precipitate all of the iron. The leach liquor is then subjected to a nickel recovery operation without the need for intermediate neutralization.

The application of sulphuric acid containing an alkali metal halide, alkali metal nitrate, alkali metal nitrite, alkali metal sulphite or alkali metal thionite at about 100°C in a stirred reactor is disclosed in US Patent 6,471,743. The liquid is separated from the solids, then the dissolved iron is precipitated as its hydroxide and subsequently the nickel and cobalt are separately recovered from the partially neutralised solution.

P.%0PER\PDB\Spm\3047i90 William Jay omp v3doc-2/OI/2008 00 -3t, SA resin-in-pulp method in which the nickel and cobalt are dissolved using a mineral acid i and then, ion exchange polymers in solid form are used to directly recover the nickel and cobalt from the partially neutralized slurry is described in US Patent 6,350,420.

Hot hydrochloric acid brine leaching at about 95°C has been proposed by Harris and Magee, "Atmospheric chloride leaching: the way forward for nickel laterites", In 00 Hydrometallurgy 2003, Proceedings of the 5 th International Symposium, Vancouver, i Canada, August 24-27, 2003, Editors, C. Young, et al., pages 501-515.

Letowski and coworkers proposed the use of hydrochloric acid in heap leaching operations for the recovery of copper and cobalt from a low iron-containing laterite Fe), "Study of Hydrochloric Acid Use in Heap Leaching Operations" In Chloride Metallurgy 2002, International Conference, 32 nd Annual Hydrometalurgical Meeting Montreal, Canada, Eds.

E. Peek and G. Van Weert, Oct. 19-23, pages 593-608. In this paper, no agglomeration of the ore was considered and they experienced blocking of the heap due to the fines present in the ore forming physical barriers to the lixiviant flow. They concluded that very finesize fractions of ore or larger fractions containing components that easily disintegrate into small particles, are not suitable for heap leaching. Furthermore, they proposed that the acid concentration should be sufficiently high, or the retention time of the leaching solution in the heap should be relatively short, or the ore bed should not be very thick, to avoid hydrolytic precipitation of the extracted metals in the bed of the heap. Acid solutions containing 2-4 wt. hydrochloric acid and up to 2 M magnesium chloride were proposed.

Heap leaching has been successfully applied to the recovery of gold, copper and silver from lower grade ores in many parts of the world. In US Patent 5,571,308, heap leaching is proposed for recovering nickel from high magnesium-containing lateritic ores. The ore is subjected to leaching with mineral acid from the group consisting of hydrochloric acid, sulphuric acid and nitric acid, with hydrochloric acid being preferred. Nickel is recovered from the leach solution using an ion exchange resin selective for nickel. Pyrohydrolysis is recommended in order to recover the nickel oxide and to recycle hydrochloric acid. The P.%OPERPDB\Spci\3G47I905 Willim Jay omp v3dcc-25/OI020 00 O-4raffinate is separately pyrohydrolysed for the production of iron and magnesium oxides rC and the recovery of the hydrochloric acid. Magnesium oxide (MgO) is formed during pyrohydrolysis and is used as a neutralising agent to raise the solution pH sufficiently to enable ion exchange resins to recover the nickel and the cobalt from the leach solution.

Intermixed nickel and iron metal oxides were not considered.

00

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SA heap leach process was described in US Patent 6,312,500 for the recovery of nickel and C, cobalt from lateritic ores that have a tangible clay content (greater than 10% by weight).

The ore is pre-treated by ore selection, size reduction and pelletisation. The formation into pellets is done by the use of a lixiviant containing 20-100 kg of concentrated sulphuric acid per tonne of ore (to neutralise the ore) as an agglomeration aid. Subsequently the pellets are formed into heaps and leached with 300 to 700 kg of sulphuric acid per tonne of dry ore, and in one example the leaching solution was a mixture of sulphuric acid and seawater (containing 27 g/1 NaCI). Production of mixed metal oxides was not considered.

In all of the methods disclosed or reported upon to date, a requirement is the separate recovery of iron for disposal into tailings dams and the recovery of nickel, cobalt or other valuable metals as separate metals or metal complexes.

It is desirable to be able to produce a combined nickel/iron product. Such a product is economically and environmentally advantageous as it allows for a simple and cost effective recovery of iron contained in the laterite rather than its precipitation as a jarosite or alunite and its subsequent disposal in a tailings dam.

The application of ion exchange resins for the production of ferro nickel or nickel matte by a combined hydrometallurgical and pyrometallurgical process is disclosed in WO 2006/029443. In this process the iron and nickel are selectively co-extracted on to an ion exchange resin and then stripped from the resin using sulphuric acid. This strip solution is then neutralised using magnesium hydroxide to precipitate the mixed metals as their hydroxides and the precipitate is then reduced and smelted to form ferro nickel or nickel matte. However, the disadvantages of this process include the requirement for P:N0PER\PDB\Sp.i\3O47190 Wifi, Jy cop 0,doc-251011200S 00 O magnesium oxide or magnesium carbonate to neutralise the sulphuric acid, the loss of r sulphuric acid via neutralisation, and the production of the metal hydroxides which on drying produce a dusty product not highly suited as a feedstock for the electric arc furnace.

There remains a need therefore, for alternative processes for producing a combined Snickel/iron product. Advantageously, one or more of these may overcome, alleviate or 00 reduce one or more of the disadvantages associated with prior art processes.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 depicts a schematic representation of various embodiments of the invention, including agglomeration, leaching, ion exchange recovery, pyrohydrolysis and hydrochloric acid regeneration and recycling steps.

SUMMARY OF THE INVENTION The invention provides a process for producing a combined nickel and iron product and is particularly applicable to the treatment of a liquor obtained by leaching of lateritic ore.

The process involves selectively extracting, or sorbing, the nickel and iron dissolved in the liquor onto an ion exchange medium and stripping the metal ions from the ion exchange medium using a hydrochloride solution. The hydrochloride solution is then directly subjected to pyrohydrolysis, advantageously without a neutralisation step, to recover the mixed nickel and iron product as their mixed metal oxides or as a combined mixed metal oxide and metal depending upon the pyrohydrolysis temperature.

Thus, in a first aspect, the present invention provides a process for producing a combined nickel and iron product comprising the steps of: contacting a liquor solution containing nickel and iron, obtained by acid leaching of lateritic ore, with an ion exchange medium at a pH such that the nickel and iron are selectively recovered by the medium; (ii) stripping the loaded medium with hydrochloric acid solution; and P: 0PEMPDBSp=A'347l905 Willi=a lay )onp v3doc25Ol2OO 00 -6tq (iii) recovering the nickel and iron from the chloride solution by pyrohydrolysis.

In certain embodiments of the invention the process is preceded by the step of acid leaching of lateric ore. The laterite ore may be heap, slurry, vat or dump leached with a lixiviant containing a mineral acid to produce a liquor containing at least nickel, iron and Scobalt. In one embodiment, the laterite ore is heap leached. Optionally the lixiviant 00oO contains an alkali metal chloride and/or alkaline earth chloride. In further embodiments, N the lixiviant is a sulphuric acid solution which contains an alkali earth chloride and/or an alkali metal chloride. In yet further embodiments, the alkali earth chloride is calcium or magnesium chloride and the alkali metal chloride is sodium chloride.

In certain embodiments of the leaching step the concentration of the alkali metal chloride and/or alkaline earth chloride is at least 100 g/l, such as more than 150 g/l, for example around 200 g/l.

In advantageous embodiments the average temperature within the heap, slurry, vat or dump is less than 90'C, for example, no greater than 80'C, such as no greater than 60 0

C.

Advantageously, the lixiviant and/or heap, slurry, vat or dump is heated by solar means.

The heap, slurry, vat or dump may include a coarse substrate selected from crushed glass, coarse ore particles, silicates and silicates containing nickel or other valuable metals, iron or other suitable metal sulphides, scats generated in milling nickel-containing ores, crushed aggregate, gravel, lava rock and molded polyethylene balls.

The leaching process may include a step of agglomerating the laterite ore. In some embodiments thereof, the agglomeration step includes the addition of an agglomeration aid to the laterite ore. The agglomeration aid may be sodium silicate or a polymeric organic binder. In some embodiments an agglomeration solution containing a polymeric organic binder is added to the laterite ore.

P.%0PERTDB\Spai%300710 Willim JAycmop v3 dxc25/OIM2008 00 -7- The process may also include the use of wetting and/or surface active aids. One or more wetting or surface active agents may be included within an agglomeration solution applied to the laterite ore before the leaching process.

In certain embodiments, part or all of the alkali metal chloride or alkaline earth chloride is N, included as part of the agglomeration solution.

00 Bacterial oxidation may be used to generate sulphuric acid and heat within the heap, slurry, vat or dump if sulphide ores or sulphur form part of the ore placed on the heap. In advantageous embodiments, the heap, slurry, vat or dump is aerated.

In certain embodiments of the invention, the liquor obtained is recycled through the heap.

The pH of a portion of the liquor solution leaving the heap may be raised by the addition of a hydroxyl- or carbonate-containing material, or by recycling the liquor through a part of a heap where minerals exist which are capable of reacting with lixiviant to raise its pH.

The iron and nickel may be recovered from the liquor solution by using ion exchange monomeric or polymeric materials in solid or liquid form. The iron and nickel are stripped (recovered) from the ion exchange medium as their chlorides.

In certain embodiments, the iron and the nickel chlorides recovered from the ion exchange process are pyrohydrolysed to recover the mixed iron and nickel oxides, and the hydrochloric acid so generated is recycled.

Cobalt may also be separated and recovered from the liquor solution. In one embodiment, this can be effected by using ion exchange monomeric or polymeric materials in solid or liquid form. The cobalt may be recovered together with the nickel and iron or may be separately recovered from the raffinate liquor solution which has been stripped of nickel and iron). In another embodiment, the cobalt may be recovered by precipitation from the raffinate as its hydroxide, carbonate or sulphide.

P \0PER\PDB\Spm3047I905 Willian Jay cmp v3doc-25/O1/2008 00 O -8c The order of recovery of the valuable metals from the leach solution leaving the heap (the liquor) may be varied depending upon the metal ion extractant method employed and the preference of those skilled in the art and as discussed below.

C In another aspect, the invention provides a mixed iron oxide/nickel oxide product.

00 N DETAILED DESCRIPTION OF THE INVENTION The process of the present invention may advantageously provide a much lower cost nickel leaching and iron recovery method and may provide a more economic and environmentally acceptable metal oxide recovery process by the combination of the nickel and iron as oxides and optionally, the cobalt as its oxide, hydroxide, sulphide or carbonate complex for further processing. Alternatively, a combined nickel, iron and cobalt product can be produced in the form of their mixed metal oxides. The production of the iron in a saleable form removes both the requirement for, and the cost of, disposal of the iron in a stable form in a tailings dam.

In this invention, the term "laterite" or "lateritic" is used to describe all nickel-containing ore types including nickeliferous ochre, nickel oxide, laterite, saprolite, limonite or nontronite, regardless of their actual mineralogy.

Simplistically, the term "limonite" is used to describe ores containing in excess of iron and less than 6% of magnesium and "saprolite" to describe ores containing less than about 25% of iron and generally greater than 10% of magnesium, although these percentages are given as a guide only and vary widely from one ore body to another. The limonitic fraction is generally located close to, or at the surface, with the saprolite ore occurring at lower levels and often separated from the limonite by a transition zone. These zones can vary widely in thickness.

P:AOPER\POHMSpm\3047905 Willii.4 )4yc v3d-25/IOI12O8 00 -9- The term "alkali metal chloride" is used to refer to chlorides of group I elements (the alkali N metals), which include lithium, sodium and potassium. In certain embodiments, the alkali metal chloride is sodium chloride.

The term "alkaline earth chloride" is used to refer to chlorides of group II elements, which Sincludes beryllium, magnesium and calcium. In certain embodiments the alkaline earth 00 chloride is magnesium or calcium chloride.

Whilst the invention will be described below with reference to heap leaching, it will be understood that slurry, vat or dump leaching methods may also be used.

In the heap leaching process, the ore is directly removed from the deposit and placed in heaps or piles on an impermeable pad or liner. Prior to emplacement on the pad, the ore may be agglomerated, for example, in combination with an inert substrate, to improve the percolation of the lixiviant (leaching solution) through the heap. The heap may vary considerably in its height. The lixiviant is introduced on to the upper surface of the heap and allowed to percolate downward through it until it reaches a drain section located in the base of the heap. The leach solution may then be recycled through the heap or it may be transported to a recovery circuit where the valuable metals are recovered. The solution, after recovery of the desired metals, may then be adjusted in reagent strength and recycled to the heap.

The heap leaching process can be conventionally modified. For example, after the desired metals have been dissolved and recovered, an additional heap, or "lift" may be placed upon the existing heap and the leaching process continued. If oxygenation of the heap is desired, or additional drainage is required, these may be placed at the time that the further lift in heap height is being constructed. Alternatively, the solid residue from the heap may be reused.

Aside from containing nickel and iron, laterite ores often contain up to about 15% of magnesium together with other acid soluble minerals (such as manganese, aluminium, PV'OPER\PDM\SpOdi30471905 Willi= Jay cop d3doc-2VOMlOOS 00 ,cobalt, chrome, etc.). Thus, depending upon the acid selected as the lixiviant, manganese, C cobalt, chromium, aluminium, magnesium and other soluble metals can also dissolve with the nickel and the iron. Therefore, when using heap leaching, significant quantities of the heap material may dissolve with acid leaching. It is envisaged that at least 15% of the heap will dissolve and in some instances, significantly more than 50% of the total minerals CI present in the heap may dissolve. Such dissolution can lead to collapse within the heap 00 resulting in loss of heap integrity and therefore the loss of percolation and loss of the I valuable metals. A particular advantage of incorporating the inert substrate into the heap construction is for the purpose of establishing and maintaining heap integrity and percolation as discussed below.

Furthermore, laterite ores are often fine in particle size and therefore when broken, produce a high concentrations of fines. In a heap leach operation, fines generation can lead to blockage of the heap and prevent, or significantly reduce percolation. To improve percolation, sulphuric acid may be used as an agglomeration aid to form pellets.

However, not all laterites contain minerals capable of reacting with sulphuric acid to form an insoluble binding agent. Such laterites may instead require the use of polymeric-based agglomerating techniques.

To overcome these deficiencies, an inorganic binder such as sodium silicate or, more preferably, a polymeric organic binder such as described in US Patents 4,875,935, 4,898,611, 4,960, 461, 5,077,021, 5,077,022, 5,100,631, 5,186,915, 5,211,920, 5,823,937 and 5,834,294, all of which are specifically incorporated herein by reference, may be added to the ore in a sufficient quantity during the agglomeration step to provide integrity to the cured agglomerate. Thus, a binder may be added to aid in forming stable agglomerates which when stacked onto a heap will remain stable allowing the lixiviant to percolate through the heap. Agglomeration is conducted prior to the ore being placed on the heap.

P. OPER\PDBWSW\O471I905 Willi= Jy coip v3dix-251OlflOOS 00 -11- Suitable polymeric agglomeration aids include copolymer emulsions such as Nalco® 9760 N EXTRACT-ORE, or other acid stable polymer emulsions or solutions.

In order to ensure acid is available throughout the heap, strong acid solutions are added to the ore during agglomeration with the polymeric binder. Wetting or surface active agents N and part or all of the alkali metal chloride or alkaline earth chloride may also be included 00oO in the formulation of the agglomeration solution. Suitable wetting or surface active agents N are described in US Patent 6,099,615, and are incorporated herein by reference. A typical wetting aid would include Dearcodox® a mixture of surfactants manufactured by BetzDearborn.

Because of the large quantity of minerals being dissolved in the heap as described above, it can be advantageous to bind the laterite to an inert substrate as this can enhance percolation by maintaining heap integrity. Suitable substrates include those proposed in US Patents 6,083,730, 6,107,065, 6,159,726 and 6,063,158, and include crushed glass, coarse ore particles, screened silicate minerals produced from the screening upgrade of lateritic ores, scats from the milling of laterite ores, crushed aggregate, gravel or lava rock crushed iron or other suitable metal sulphide ores; molded polyethylene balls all of which are specifically included by reference may be considered in this invention. If required, once the heap is depleted of the desired metals, the substrate may be reused. This will reduce the total quantity of inert material required for the overall heap operation.

For example, the substrate selected should have a relatively large surface area so that the laterite can be bound to it and retained in place without the heap collapsing. Furthermore, the surface area produced within the heap acts, or creates, a large number of small reactors enabling the lixiviant process to be improved by creating more pathways for the lixiviant to penetrate through the heap. The total reactive surface area within the heap can be enhanced by decreasing the particle size of the substrates and by using substrates that have a rough, non-uniform surface morphology. Substrates varying in size from about 600 [tm to about 2.5 cm in nominal size are preferred, but this concept is not limited to this size P %OPER\PDBRSp\3-o47l905 Williani Jay cop vdc.25OI.'200 00 -12- -n range. Smaller sized substrate particles will help to limit airflow through the heap helping ttn I to maintain reaction temperature within the heap.

Equipment for conducting the agglomeration process is well known to those in the industry. Agglomeration is generally performed in rotating drums placed at a slightly "I inclined angle to the horizontal into which is added the substrate and the laterite. The 00 reagent mixture, generally consisting of the polymer binder, wetting agents, acid and on C occasions water or other additives is uniformly added into the drum, generally by spraying.

The agglomerates are then transported to the heap for placement. In some instances, the agglomerated ore may be held on a temporary pad prior to ultimate placement on the heap.

In certain embodiments, the lixiviant preferably includes chloride ions provided by strong brine solutions prepared from sodium chloride, magnesium chloride, calcium chloride, or mixtures thereof, or other available alkali or alkaline earth metal salts. Alternatively, such solutions may be obtained in parts of Australia by use of the hypersaline groundwaters.

Such solutions, when acidified, may successfully and more rapidly leach nickel and iron from laterite ore.

It is advantageous to use high concentrations of these brines as this can significantly enhance the kinetics of the leach reaction. The concentration of the salt may be in the order of at least 100 g/l, such as more than 150 g/l, for example, around 200 g/l.

The magnesium content of the ore may be used to supplement the alkaline earth salts present in the lixiviant. The magnesium salts in the laterite ore, when dissolved by hydrochloric acid will form soluble magnesium chloride to aid in the dissolution of the iron, nickel and cobalt. In this manner, when hydrochloric acid becomes part or all of the lixiviant, the magnesium becomes part of the lixiviant, rather than being a waste product.

After the selective recovery of iron and nickel, the magnesium chloride can be returned to the leach step, or it can be pyrohydrolysed to form magnesium oxide and then used as a possible neutralising (pH adjustment) agent.

P.WER\PDB1Sp=30471905 WiIli=, Iy cmp v3doc251112008 00 -13c, The magnesium oxide which may be generated in the nickel and iron recovery step, and N which has been used as a partial neutralising agent, can be used as a source of the magnesium chloride reagent by the neutralisation reaction with hydrochloric acid.

It is preferred to use mineral acids as the acidifying reagent in the lixiviant, with hydrochloric acid and sulphuric acid being particularly preferred. Mixtures of 00 hydrochloric and sulphuric acid or other mineral acids may also be used as the acidifying N reagent.

Generally, hydrochloric acid will dissolve nickel and iron more rapidly than sulphuric acid at the same molarity and same temperature and its use, in combination with a salt of an alkali metal or of an alkaline earth such as sodium chloride or magnesium chloride, can rapidly bring the desired metals into solution. Notwithstanding this, its transportation can be an issue at remote mining locations. Furthermore, on or near site production of the acid requires a supply of energy, and the costs could be prohibitive at remote sites.

Hydrochloric acid has a lower boiling point than sulphuric acid and can be lost from the heap at higher temperatures.

Therefore, in certain embodiments of the invention it may be advantageous to use sulphuric acid, for example at a concentration varying from 0.2M to 5M. At 40 0 C it is preferred to use a 1M sulphuric acid as this concentration has proved to be highly efficacious. In some embodiments, the concentration of the acid in the heap is maintained above 0.2M unless the heap is being flushed of residual metal ions, or the heap is being used to partially neutralise the acid solution to aid in metal ion recovery.

The sulphuric acid used in the lixiviant in this heap leach process may be produced at the mine site by the combustion of sulphur. This is an exothermic reaction, providing energy for other mine energy requirements.

Certain strains of bacteria can also be used to consume sulphur or sulphur-containing minerals to generate sulphuric acid. This can be conducted within the heap being leached, PPER DBOPM Spa47I905 Willi= Iy cmp 3doc.25/01200 00 O 14or in specially constructed heaps of sulphur or sulphide minerals, such as pentlandite, to CN generate acid for supply to the heap undergoing active leaching, or in specific reactor vessels. Useful strains of bacteria include Thiobacillus ferrooxidans, Thiobacillus thiooxidans, Thiobacillus organoparus, Thiobacillus acidophilus, Leptospirillum ferrooxidans, Sulfolobus acidocaldarius, Sulfolobus solfataricus and the like. If bacterial CN oxidation is conducted then oxygen (generally air) is introduced into the heap to act as an 00 Soxidant.

The leaching step can be conducted at ambient temperature although increasing the temperature of the heap to above that of the prevailing diurnal temperature will increase the rate of dissolution of the nickel and iron from ore.

A significant increase in the dissolution kinetics can be obtained by increasing temperature within the heap. Raising the temperature within the heap from about 20 0 C to about 40 0

C

will approximately double the reaction rate, regardless of the acid under consideration. In some embodiments, the upper heap temperature may be considered to be 50 0 C, but is not limited to this temperature and the lixiviant may be at a higher temperature than the heap.

It is expected that the external surfaces of the heap will be less than the core temperature of the heap.

To achieve an increase in temperature, solar heating methods are preferred. For example, the solution being pumped to the heap may be pumped through coils of polyethylene or other suitable pipe, preferably black in colour. During daylight hours this will significantly elevate the temperature of the lixiviant.

Another method would be to pump the lixiviant through solar panels so designed to achieve a similar outcome.

Also, if sulphuric acid is included in the lixiviant, then addition of sulphur or other sulphur-containing material to the heap, preferably during the agglomeration step and, with the addition of a suitable sulphur oxidizing bacteria to the heap will, in the presence of P.WPERPDBMSpmd\3O471905 WiUim, Iay omp 3dmo-25IOIlO 00 t, Soxygen, generate sulphuric acid and at the same time, raise the core temperature of the C heap.

During the leaching process the dissolution of nickel and iron will be accompanied by the dissolution of cobalt, magnesium, manganese, aluminium and other acid soluble minerals.

STo minimize acid usage, it is desirable that as much of the acid can be recovered as is 00 economically possible. This can be performed by hydrolysis. Hydrolysis reactions are Snormally conducted at elevated temperature, generally above 100C. A review of some these hydrolysis reactions is given by J.H. Kyle in "Jarosite/alunite in nickel laterite leaching Friend or foe?" ALTA 2003 Nickel/Cobalt Conference, Perth Australia. It is advantageous to include an acid recovery step, such as hydrolysis or pyrohydrolysis, in any overall process.

The nickel and iron can be selectively separated and recovered together from the liquor solution by sorption onto an appropriate ion exchange medium using known procedures.

The ion exchange medium may be in solid or liquid form. Depending upon the sorption medium selected, the pH of the liquor may need to be adjusted to above 1 and normally less than 6. In one embodiment of the invention the pH of the liquor may be raised by contact over a section of the heap, or a second heap, containing agents which will raise the pH. Typically, the liquor may be adjusted to a pH in the range of 1-4, such as a pH of about 1-2, 2-3 or 3-4.

The pH may be adjusted to a level where the iron and nickel, and optionally cobalt, are selectively extracted, or sorbed, onto the ion exchange medium. Alternatively a first pH level may be selected such that first iron and nickel are selectively sorbed, and a second level whereby the cobalt is selectively sorbed. The cobalt may be sorbed onto a same or different exchange medium as the iron and nickel.

Liquid extractants (also known as solvent extractants or liquid ion exchange reagents) dissolved in kerosene are the most widely adopted method for the separation and recovery of nickel and cobalt from aqueous solutions and may be used with the process of the P OPER\PD3)Spa3D471905 Willi= Jay cmp v3dom.201100S 00 -16a present invention. Suitable liquid extractants include Versatic 10, a product manufactured C- by Shell Chemicals, and Cyanex 272, which is manufactured by Cytec, or D2EPHA. The extraction steps should also include a partial or complete neutralization of the leach solution (and which must be clarified prior to the solvent extraction step). The extraction and stripping of the organic extractant is normally conducted by pH adjustment. These C steps are conducted in conventional mixer-settlers or pulse columns or similar equipment 0well known to those versed in the industry.

The separation and recovery process can also be conducted by using an ion exchange medium in solid form (an ion exchange resin). This has the advantage of eliminating the need for the use of kerosene, which has been the cause of many fires. The ion exchange resins which may be used include polyethyleneimine-based, iminodiacetic acid-based, bipicolylamine-based or ion exchange resins in which solvent extractants have been imbibed, or other suitably formulated polymers. Suitable ion exchange resins have been disclosed in PCT/AU00/01383, PCT/AU02/00325 and PCT/AU02/01298, the contents of which are included herein by reference. Examples of suitable iminodiacetic acid ion exchange resin types include Purolite® S930, Indion® SIR, Amberlite® IRC 748 and LanXess Lewatit® Monoplus TP 207. Examples of suitable bipicolylamine resins include Dowex M4195 and TPE 247, an ion exchange resin manufactured in Russia.

Alternatively, ion exchange resins based upon a silica substrate onto which polyethyleneimine has been reacted, and if required, functionalised using 4-methyl pyridine could also be considered. Alternatively, strong or weak acid ion exchange resins could also be considered.

If sulfuric acid is used as the primary lixiviant, the iron and the nickel can be directly recovered from this liquor using an iminodiacetic resin at a solution pH of about 2.0 to After sorption of the metal ions by the ion exchange resin, the resin is then stripped of its metal ion content. The metal ion(s) are stripped from the ion exchange resin by hydrochloric acid and optionally in the presence of chloride ions using known methods.

For example, the metal ions could be removed by using a strip solution lower in pH than P1OPERkPDB1Spdi304790 Willi= Jay compv3 d-25/O/2DO 00

O

-17c' the acid solution emanating from the heap and then recovered. In some embodiments of N the invention, the pH of the strip solution may be about 1. In other embodiments it may be desirable for the pH to be such that the iron is only partially stripped. Equipment for conducting metal ion recovery using ion exchange resins is well known to those versed in the industry.

0 0 Liquid polymeric forms of ion exchange resins, particularly based upon polyethyleneimine 0 C as described in PCT/AU00/01383, PCT/AU02/00325 and PCT/AU02/01298 (the contents of which are incorporated herein) can also be considered. In this case, after mixing the aqueous solution containing the nickel and iron metal ions with the specifically formulated polymer, the solution is pumped through a membrane cell. The polymer containing the desired metal ions reports to the retentate, the residual aqueous solution to the permeate.

The metals are then recovered from the retentate and the polymer is recycled. The permeate can then be recycled to the heap.

With hydrochloric acid as the stripping solution for the recovery of the metals from the solid or liquid ion exchange step, the metals are recovered as their chlorides. The metal chlorides may then be subjected to pyrohydrolysis to convert the nickel and iron to their oxides or metal, depending upon temperature at which pyrohydrolysis step is conducted.

A mixed metal oxide so produced can form the feedstock for an electric arc furnace to produce a ferro-nickel product or nickel matte.

Pyrohydrolysis is a method by which a metal chloride in the presence of water vapour can be thermally decomposed to its oxide. This process is well known and well established in the steel pickling industry. The equipment design, fuel source, temperature and/or oxidising/reducing conditions (oxygen availability) of the pyrohydrolysis step can influence the composition of the nickel/iron product. The reaction is generally conducted at temperatures between about 600 0 C or about 700°C to about 900'C (in any event less than about 950°C, at which nickel chloride sublimes), and advantageously from about 800°C. Depending upon the oxygen availability, various oxides of iron are formed, namely, Fe 2 0 3 >Fe30 4 >FeO. Nickel will form either its oxide, or under reducing P: PER\PDB\SpoA3O71905 William Jay comp v3.d-25/lZOOS 00 -18t, -n conditions, as the metal. The reaction may be conducted in either fluid bed reactor or in tn' N spray roasters. Fluid bed reactors have the advantage that a dense, granular, dust free product is formed. Both types of equipment are well established in industry and may be employed. In one embodiment, the fuel is natural gas, as this assists in avoiding reducing conditions (although some Ni may nevertheless form). The resulting mixed iron oxide/nickel oxide product may therefore contain NiO (and possibly some Ni) and at least 00 one iron oxide selected from FezO 3 Fe30 4 and FeO.

The raffinate solution remaining after nickel and iron extraction from the liquor solution) may be further treated to recover cobalt. Since low concentrations of cobalt, may be present, the raffinate may advantageously be recycled through the leaching process several times, and thus build up an increased concentration of cobalt. Once a sufficient concentration of cobalt is reached in the liquor, the cobalt may be recovered by either ion exchange or solvent extraction methods as previously described. The cobalt could then be recovered by precipitation as either a hydroxide, carbonate or sulphide. Thus, the cobalt can be recovered from solution by neutralisation via the addition of magnesium oxide or a suitable hydroxyl-containing reagent such as sodium hydroxide or as a carbonate such as magnesium carbonate or as the sulphide by the addition of sodium hydrogen sulphide (NaSH). Other suitable reagents may be employed as known to those skilled in the art.

Alternatively, the cobalt can be recovered by the use of ion exchange polymeric materials in solid or liquid form and if required, either together with or separately from the nickel and iron as their chlorides as previously described and recovered as its oxide by pyrohydrolysis.

The invention also provides a process for providing a mixed nickel and cobalt oxide product which advantageously allows for regeneration of hydrochloride. Hydrochloric acid may be used to strip the nickel and cobalt from a nickel and cobalt loaded medium and the nickel and cobalt can be recovered as their oxides (some metallic Ni may also be present) from the hydrochloric acid by pyrohydrolysis. The hydrochloric acid can be regenerated and reused in either the leaching process or to strip a loaded medium.

PAOPERPDBSpi3o47195 Willi.. J.y 03 doc-251OIrIM 00 O -19- If other valuable metals, such as chromium, are present in the ore and are dissolved in the r, acidic leach solution then they may be selectively recovered from the solution. For example, chromium (VI) may be recovered by using resins with a quaternary ammonium functionality.

N Other methods for separating and recovering other valuable metals from the leach solution 00 are known and may be incorporated in process of the invention.

Figure 1 depicts generalised processes according to the invention. Lateritic ore, acid, substrate, binder and wetting agent are first agglomerated. The agglomerated ore is then heap leached using acid lixiviant. Some or all of the resulting liquor may be recycled through the heap with an appropriate pH adjustment as required. The resulting pregant liquor is then adjusted to the appropriate pH as required for the desired metal ion recovery and subjected to an appropriate ion exchange medium for recovery of the nickel and iron and, optionally cobalt. The raffinate resulting from recovery of the nickel and iron can either be recycled back through the heap or subjected to an ion exchange medium for the further recovery of cobalt. The nickel and iron are stripped from the ion exchange medium using HCI and recovered as their chlorides. Pyrohydrolysis of the nickel and iron chlorides affords the metal oxides as a mixed iron oxide and nickel oxide product. The hydrochloric acid regenerated from the pyrohydrolysis process can be recycled to strip the ion exchange medium. Similarly, the cobalt is stripped from the ion exchange medium using HCI. The resulting raffinate can be recycled back through the heap. The recovered cobalt chloride may be subjected to pyrohydrolysis to afford the cobalt oxide, and the HCI generated may be recycled to strip the ion exchange medium or back through the leach heap.

Alternatively, the strip solution containing the cobalt chloride can be treated with a precipitant to afford the cobalt as its hydroxide, carbonate or sulphide.

Certain embodiments of the invention include one or more of the additives or process steps selected from to the mineral acid lixiviant is 0.2M to 5M sulphuric acid or hydrochloric acid or a mixture of these acids; P:IOPER\PDBSp.'\30471905 Willim Jay omp v3doc.25/012O00 00 c, the heap, slurry, vat or dump includes an inert substrate selected from crushed C glass, coarse ore particles, silicate type minerals, crushed aggregate, gravel, lava rock iron or other selected mineral sulphide ores and molded polyethylene balls; an agglomeration aid, preferably sodium silicate or a polymeric organic binder, Ni, is added to the laterite ore 00 the agglomeration aid contains all or part of the alkali metal chloride or alkaline C' earth chloride; a wetting and/or surface active aid is applied to the laterite ore before the leaching process; bacterial oxidation is used to generate sulphuric acid and heat within the heap, slurry, vat or dump; the heap, slurry, vat or dump is aerated; the leach liquor is recycled through the heap; slurry, vat or dump nickel and iron are separated and recovered together from the liquor by using ion exchange monomeric or polymeric materials in solid or liquid form and then stripped from the ion exchange medium as their chlorides and pyrohydrolysed; the iron and nickel are recovered from the pyrohydrolysis step as mixed metal oxides and the hydrochloric acid is regenerated; agglomeration can be used to increase the particle size of the metal oxide product; the cobalt is recovered from the raffinate resulting from step as a hydroxide, carbonate or sulphide, or is recovered from the raffinate by an ion exchange resin at an appropriate pH.

In one embodiment of the invention there is provided a process for extracting nickel and iron together from laterite ore, the process including:providing laterite ore; admixing an inert substrate with the laterite ore; P:PER\PDBHSpA3DO471905 WiIiUm Jay comp 3do-23OVflOO 00 O -21providing an agglomerating solution containing polymeric organic binder(s), C wetting and/or surface active agent(s), acid, alkali metal chloride and/or alkaline earth chloride and optionally, a source of sulphur together with a suitable strain of bacteria; agglomerating the laterite ore with the agglomerating solution; C placing the agglomerated ore on to an impervious pad or barrier; 00 0(f) providing a lixiviant comprising mineral acid, preferably together with a Ci solution of alkali metal chloride and/or alkaline earth chloride; heating the lixiviant to a temperature less than applying the heated lixiviant to the agglomerated, inert substrate containing laterite ore so that it percolates through the ore; repeatedly collecting the lixiviant that has percolated through the ore, adjusting the solution pH if required and applying the collected lixiviant to the agglomerated, inert substrate containing laterite ore so that it percolates through the ore; separating a least a portion of the collected lixiviant, adjusting the solution pH, to extract the metals therefrom; recovering the nickel and iron using a solid or liquid ion exchange resin or polymer and stripping the nickel and the iron from the ion exchange medium as their chlorides; adjusting the pH of the raffinate (stripped solution after metal ion removal) by acid adjustment and return the solution to the heap; recovering the nickel and iron as their oxides by pyrohydrolysis of the metal ion containing strip solution produced in step and returning the regenerated chloride stripping solution to the ion exchange stripping circuit; if required, agglomerating the mixed iron and nickel oxides to eliminate or substantially reduce dust content; and optionally, once the concentration of cobalt reaches a sufficient concentration in the raffinate from step recovering the cobalt as its hydroxide, sulphide or carbonate or by the use of ion exchange polymeric materials in solid or liquid form and if required, recovering the cobalt as its oxide by pyrohydrolysis; or PAOPER\PDB\SpmA3047905 William Jay comp v3.doc-25/OI/2OO 00 -22separating at least a portion of the collected lixiviant as described in step (i) Ci above, adjusting the solution pH and extracting all of the iron, nickel and cobalt therefrom by precipitation or using an ion exchange resin or polymer in solid or liquid form recovering the iron, nickel and cobalt as described in steps to 00 Throughout this specification and the claims which follow, unless the context requires Ci otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

The invention will now be further described with reference to the following examples which are intended to illustrate certain embodiments and are not intended to limit the generality hereinbefore described.

P'OPER\PDBWSpmi\347190 Willi Jay cop v3dom-25/012OO8 -23-

EXAMPLES

Example 1 A limonitic ore obtained from Western Australia was agglomerated with 20 kg/t sulphuric acid containing 250 g/t Extract Ore 9560 (manufactured by Nalco) and then placed in a 3 metre high by 100 mm diameter column. 0.28 M sulphuric acid 165 g/l NaCI was then allowed to flow downwards through the column. After 70 days leaching at 20 0 C, the following results were obtained: Ni Co Fe Mg Ore (dry wt 0.96 0.07 37.41 0.26 extraction 11 33 8 The final sulphuric acid consumption was calculated to be 203 kg/tonne of ore.

Example 2 A limonitic ore obtained from Western Australia was agglomerated with 20 kg/t sulphuric acid containing 250 g/t Extract Ore 9560 (manufactured by Nalco) and then placed in a 3 metre high by 100 mm diameter column. 1 M sulphuric acid was then allowed to flow downwards through the column. After 56 days leaching at 40 0 C, the following results were obtained: Ni Co Fe Mg Ore (dry wt 0.96 0.07 37.41 0.26 extraction 90 83 85 102 The final sulphuric acid consumption was calculated to be 1141 kg/tonne of ore.

P\0PER\PDBSp-\347i905 Williai Jay c~op v3doc.2101/200 -24- Example 3 A limonitic ore obtained from Western Australia was agglomerated with 20 kg/t sulphuric acid containing 250 g/t Extract Ore 9560 (manufactured by Nalco) and then placed in a 3 metre high by 100 mm diameter column. 1 M sulphuric acid containing 200 g/l chloride (as magnesium chloride) was then allowed to flow downwards through the column. After 56 days leaching at 40 0 C, the following results were obtained: Ni Co Fe Mg Ore (dry wt 0.96 0.07 37.41 0.26 extraction 90 105 86 100 The final sulphuric acid consumption was calculated to be 1148 kg/tonne of ore.

Example 4 A saprolitic ore obtained from Western Australia was agglomerated with 20 kg/t sulphuric acid containing 250 g/t Extract Ore 9560 (manufactured by Nalco) and then placed in a 3 metre high by 100 mm diameter column. 0.28 M sulphuric acid containing 165 g/1 sodium chloride was then allowed to flow downwards through the column. After 70 days leaching at 20 0 C, the following results were obtained: Ni Co Fe Mg Ore (dry wt 0.98 0.03 15.1 3.67 extraction 37 64 17 The final sulphuric acid consumption was calculated to be 365 kg/tonne of ore.

P.PER\PD8BSpw3047190 Willim Ilay mp doc.2502003 Example A saprolitic ore obtained from Western Australia was agglomerated with 20 kg/t sulphuric acid containing 250 g/t Extract Ore 9560 (manufactured by Nalco) and then placed in a 3 metre high by 100 mm diameter column. 0.28 M sulphuric acid containing 165 g/l sodium chloride was then allowed to flow downwards through the column. After 28 days the sodium chloride concentration was raised to 330 g/l. After 70 days of total leaching at the following results were obtained: Ni Co Fe Mg Ore (dry wt 0.98 0.03 15.1 3.67 extraction 74 95 57 103 The final sulphuric acid consumption was calculated to be 588 kg/tonne of ore.

Example 6 A solution containing Fem 26.5 mg/l, Ni 223 mg/l, and Co 3.2 mg/1 was adjusted to a range of pHs and contacted for 24 hours with 300 mL/L of Purolite S930, an ion exchange resin manufactured by Purolite Corporation, UK and containing iminodiacetic acid functional groups. The following metal ion extractions were achieved.

Equilibrium Metal Extraction, pH Fe Ni Co 1.4 57.2 18.9 15.0 1.7 70.4 13.9 11.4 67.3 13.9 12.1 These results indicated that iron was strongly adsorbed to approximately 25 g/l and that the equilibrium pH had only a minor effect on the adsorption of nickel.

P. OPERPDB\SpaiU47905 Willi=,,Jay comp v3.doc-201008 -26- Example 7 A solution containing Fe 26.5 mg/l, Ni 223 mg/1, and Co 3.2 mg/l was adjusted to a range of pHs and contacted for 24 hours with 300 mL/1 of Purolite S940, an ion exchange resin manufactured by Purolite Corporation, UK and containing aminophosphonic acid functional groups. The following metal ion extractions were achieved.

Equilibrium Metal Extraction, pH Fe Ni Co 1.4 27.5 13.3 9.9 1.7 26.9 10.7 9.4 46.4 13.1 9.4 As shown, the metal extraction of iron increased from 10 g/l at pH 1.4 to approximately 17 g/l at pH 2. Nickel adsorption was consistent at approximately 5 g/l.

Example 8 The PLS solution used in Example 6 (containing Fe" 26.5 mg/1, Ni 223 mg/1, and Co 3.2 mg/1) was adjusted to pH 2.9 by passing the leach solution through an additional column containing agglomerated but unleached lateritic ore. 100 ml of this PLS solution was then contacted with 3 ml of Purolite S930, an ion exchange resin containing iminodiacetic acid functional groups and manufactured by Purolite Corporation, UK. The following metal extractions were achieved: Resin Type Metal Extraction, Fe Ni Co S930 66 35.9 0

I

P.%OPER\PDBMSca3O47IM5 Willin Jay comp 0doc25O0/20 00 O -27- Example 9

(N

The PLS solution used in Example 6 (containing Fe 26.5 mg/l, Ni 223 mg/I, and Co 3.2 mg/1) was adjusted to pH 2.9 by passing the leach solution through an additional column containing unleached lateritic ore. 100 ml of the mixed metal solution was then contacted CN with 3 ml of Purolite S940, an ion exchange resin containing aminophosphonic acid 00 Sfunctional groups and manufactured by Purolite Corporation, UK. The following metal CN extractions were achieved: Resin Type Metal Extraction, Fe Ni Co S940 88.7 15.7 6.3 Example The PLS solution used in Example 8 was pumped through a column containing 30 ml volume of Purolite S930 ion exchange resin in a top-down manner at a flowrate of approximately 4 bed volumes per hour. The discharge liquor was collected into separate 100ml fractions and analysed. After 7 bed volumes of solution were passed through the column a maximum metal loading onto the resin was obtained. A maximum loading of g/1 of iron and 2 g/l nickel were obtained.

Example 11 Litres of the PLS solution used in Example 8 was passed through a column containing 200 ml of Purolite S930 ion exchange resin. This was equivalent to 175 bed volumes of liquor. The results of an assay on both the feed and barren solution were as follows: P:\OPER\PDB\'Spi\O471903 Williai Jay cop ,doc23/012008 oo

OO

O

t-s

O

N 0

O

O

N

O

O

0 -28- Solution Assay, mg/L Fe Ni Co PLS 26.5 223 3.2 Raffinate (Barren) 0.2 194 3.4 A 5 mL portion of the raffinate was neutralised using sodium hydroxide. The test confirmed that both Ni and Co remained stable in solution at up to pH 7.

The pH of the raffinate from this Example was raised to 4.5 and 5.0.

adjusted solution and then contacted with 3 ml volume of Purolite S resin to give the following extractions.

100 ml of this pH 930 ion exchange pH Extraction, Ni Co 98.8 18.1 99.2 100 Example 12 A 10 ml volume of the loaded Purolite S930 ion exchange resin from Example 10 was placed in a column and eluted at the rate of approximately 5 bed volumes of either 0.25 M sulphuric acid or 0.5 M hydrochloric acid. Within 6 bed volumes of eluate passing through the column, both sulphuric acid and hydrochloric acid stripped 100% of the iron and nickel from the resin.

Example 13 A 10 ml volume of the loaded Purolite S930 ion exchange resin from Example 11 was placed in a 30 ml elution column and contacted at approximately 5 bed volumes per hour with either 0.25 M sulphuric acid or 0.5 M hydrochloric acid. After 7 bed volumes had of the elution solution had passed through the column, sulphuric acid had eluted

I

PVOER\PDRWSpmi\47190 WiUi Jayy cop 0 da-2IOOV2001 00 O -29- -n approximately 90% of the nickel and 70% of the cobalt. Hydrochloric acid eluted CN approximately 99% of the nickel and 100% of the cobalt.

Example 14 0C The hydrochloric acid eluate from Example 12 was neutralised with magnesium oxide at 00 0pH 9 to 14 to precipitate the iron and nickel as a mixed iron/nickel hydroxide product. The rc dried product was able to be smelted in a furnace at approximately 1575 0 C to make ferronickel.

Example The hydrochloric acid eluate from Example 12 was heated to approximately 900 0 C to pyrohydrolyse the solution giving a mixed iron and nickel oxide product. The hydrochloric acid which was evolved was cooled and contacted with water to regenerate hydrochloric acid.

Example 16 The hydrochloric acid eluate from Example 13 was neutralised with magnesium oxide at pH 9 to 14 to precipitate the nickel and cobalt as a mixed nickel/cobalt hydroxide product.

The dried product was able to be shipped to a specialist refiner for further refining.

Example 17 The hydrochloric acid eluate from Example 13 was heated to approximately 900 0 C to pyrohydrolyse the solution giving a mixed nickel and cobalt oxide product. The hydrochloric acid which was evolved was cooled and contacted with water to regenerate hydrochloric acid.

Claims (11)

1. A process for producing a combined nickel and iron product comprising the steps of: contacting a liquor solution containing nickel and iron, obtained by acid leaching of lateritic ore, with an ion exchange medium at a pH such that the nickel 00 0and iron are selectively recovered onto the medium; C (ii) stripping the loaded medium with hydrochloric acid solution; and (iii) recovering the nickel and iron from the hydrochloric acid solution by pyrohydrolysis.

2. The process according to claim 1 preceded by the step of obtaining the liquor solution by heap leaching lateritic ore with a lixiviant containing a mineral acid, and optionally an alkali earth metal chloride and/or alkaline earth chloride.

3. The process of claim 2, wherein the average temperature of the heap is less than 0 C.

4. The process according to claim 1, 2 or 3 whereby iron and nickel are recovered from the pyrohydrolysis step as mixed metal oxide and the hydrochloric acid is regenerated.

The process according to claim 4 wherein the mixed iron and nickel oxide product also contains metallic nickel.

6. A process according to claim 4 where the hydrochloric acid regenerated is recycled to a heap leaching step or to strip the ion exchange medium.

7. The process according to any one of claims 1 to 6 wherein the liquor solution also contains cobalt. P: OPER\PDB\Spmi\347I1905 Willi= Jay comp v3.doc23/OI/2D 00 O -31-

8. The process according to claim 7 comprising the additional step of contacting the CN liquor solution obtained by acid leaching or a raffinate resulting from step with an ion exchange medium at a pH such that the cobalt is also selectively absorbed onto the ion exchange medium, stripping said medium with hydrochloric acid and recovering the cobalt as its oxide by pyrohydrolysis or by or precipitating the cobalt as its hydroxide, sulphide or carbonate. 00 C

9. A process according to claim 7 comprising the additional step of precipitating the cobalt in the raffinate resulting from step as its hydroxide, sulphide or carbonate.

A mixed iron oxide/nickel oxide product comprising NiO and at least one iron oxide selected from Fe20 3 Fe 3 04 and FeO.

11. A product according to claim 10 further comprising metallic Ni.