OA19919A - Dissolution and recovery of metal from metal-bearing material. - Google Patents

Abstract

A process for the dissolution of a metallic element from a metal-bearing source material, said process including the steps of dissolving the metallic element from a metal-bearing source material with an acidified ferric chloride solution to form a pregnant digest liquor containing metal ions in solution.

Description

Field of the Invention

The présent invention relates to a process for the dissolution of a métal from a metal5 bearing source material by dissolution of the contained métal with an acidified solution of ferrie chloride. The process is applicable to broad range of metals including nickel, gold, platinum palladium, cobalt, copper, silver and rare earth metals, but in a preferred embodiment, the process relates to the dissolution and recovery of nickel, gold and platinum, and more preferably in relation to the recovery of nickel.

Whereas the process may be applied to a broad range of metals, it is convenient to discuss the process in terms of its application to nickel, gold and platinum. In its most preferred embodiment, the process relates to processing a nickel-bearing source material. A suitable nickel-bearing source material may be any nickel-bearing 15 material, including native nickel métal ore, latérite or saprolite ore, processed nickel ore such as tailings or nickel-bearing scrap métal.

A suitable gold-bearing source material may be any source of gold including a native gold source from alluvial deposits or from embedded rock or minerais, from gold 20 bearing ores, processed ore such as tailings or gold-bearing scrap métal. A suitable platinum bearing source material may be any native platinum source, or ores that hâve some platinum presence including processed ore such as tailings, or platinumbearing scrap métal.

The process may also include the further step of the recovery of the métal from the subsequently produced prégnant ferrie chloride digest liquor, for example nickel may be recovered as nickel métal, such as dried nickel powder, or a refined nickel compound precipitate, such as nickel chloride, nickel sulphate, or nickel oxide or a nickel hydroxide, or other oxyanionic or organic nickel complex, including as a 30 hydrated complex. Gold and platinum may be recovered by comparable recovery means.

Background

On a commercial scale, the bulk of nickel is hereto recovered from two types of nickel ore deposits in which the nickel occurs in the divalent cationic form. The first is latérite ore, being a mix of minerais, including nickeliferous silicate and oxide minerais, dominantly limonite and garnierite in saprolite. The other major source of nickel is from magmatic sulphide deposits, where the principal ore minerai is pentlandite. About 60% of the world’s nickel may be found in latérite deposits while

40% may be found in sulphide deposits. These occurrences are due to a very high electrochemical affinity between nickel, iron and sulphur, which results in the common formation of nickel and nickel-iron minerais as in meteorite deposits, and/or sulphide minerais as found in sulphide deposits; and the preferential substitution of nickel for the equi-atomic-sized and charged, but more soluble iron and magnésium cations, 10 which results in the rétention, and supergene enrichment of nickel in secondary clay and iron oxide minerais in saprolite and latente deposits.

The nickel is recovered from such ores using a variety of leaching processes, including high pressure and atmospheric acid leach processes for latérites, followed 15 by recovery processes and flotation processes for sulphides. Lower cost leach processes, such as heap leach processes are also being developed.

Native nickel métal ore, where large amounts of the nickel is found in its near pure metallic form, is a relatively unknown phenomenon.

Native nickel métal ore as a high purity nickel métal is usually only formed in tiny amounts in the Earth’s crust, usually in serpentinised ultra-mafic rock or in meteoric deposits with iron. The nickel métal usually occurs in very small amounts as platelets or wire forms.

In the lesser known native nickel ore deposits where the nickel is found as abundant nickel métal in pegmatite, the nickel generally occurs as metallic balls between 0.05 to 5.0 mm in diameter and may comprise more than 90% nickel, with the remainder usually iron and Silicon.

When exposed to weathering native nickel métal undergoes progressive replacement either becoming soluble and is removed in groundwater, or forms a stable secondary nickel oxide, or most notably is replaced by siliceous iron oxide where the iron is in the trivalent State.

Because of the hereto relatively low abundance of native nickel métal in commercial nickel deposits, very few if any commercial operations hâve endeavoured to recover native nickel métal from such deposits.

Gold is commonly found as a native métal which may be alloyed with other metals such as silver and/or copper. As it usually exists as a native métal, native gold can occur as sizeable nuggets, but usually as fine grains or flakes in alluvial deposits or as grains or microscopie particles embedded in rock minerais. It can also exist in a solid solution where gold atoms are occluded in the crystal structure, often in sulphide minerais. More rarely, gold can form solid Chemical compounds such as gold tellurides. Gold may be recovered from such native métal deposits by gravitational concentration through panning and other techniques, but on more commercial scales, is recovered most often with the use of a cyanide solution in order to leach gold from crushed ores. Gold may also be recovered through flotation techniques particularly where the gold is associated with sulphide minerais such as pyrite.

Platinum is a scarce element but may be found in some gold, chromium, nickel and copper ores. Native deposits of platinum may also be found, for example, in alluvial sands and rivers. Platinum naturally occurs in a number of isotopic forms but primarily exists as a compound in either the +2 or +4 oxidation state.

There also exists an abundance of recoverable métal including nickel, gold, platinum, copper, silver and palladium amongst other metals in tailing sites from the processing of metals ores. Whereas some processes hâve been developed to recover metals from tailings such as through recycling processes, such recovery processes are often uneconomic due to high toxicity levels and/or high levels of contaminants such as in the case of recovery of nickel, high concentrations of iron in the tailings.

Recoverable métal also exists in scrap metals. Attempts to recover valuable métal from scrap métal items has taken many forms over a long period of time, some of which hâve proven successful, others presented with difficulties either through being uneconomic or, not being environmentally sound due to the use of corrosive acids.

It is a desired feature of the process of the présent invention to develop a process where metals such as nickel, gold, platinum, copper, silver and palladium may be recovered from a metal-bearing source material in a manner that reduces environmental impact

It is a further desired feature of the présent invention to provide a process where metals may be recovered economically from tailings or metal-bearing scrap material that includes a recoverable métal value.

It is a further desired feature of the présent invention to provide a process for the recovery of metals in a manner to provide greater économie value in the recovery of the métal.

It is a further desired feature of the présent invention to provide a process for the 15 économie recovery of metals, such a nickel from a native métal source.

A reference herein to a patent document or any other matter identified as prior art, is not to be taken as an admission that the document or other matter was known or that the information it contains was part of the common general knowledge as at the 20 priority date of any of the claims.

Throughout the description and the claims of this spécification the word “comprise” and variations of the word, such as “comprising” and “comprises” is not intended to exclude other additives, components, integers or steps.

Summary of the Invention

The présent invention relates to a process for the dissolution of a metallic element from a source material by dissolution ofthe metallic element with the use of an acidified solution of ferrie chloride. The source material could be any source of metallic element.

It is convenient to discuss the process in relation to the dissolution of nickel, but it is to be appreciated that the process is applicable to the processing of other metals, for example gold, platinum, copper, silver or palladium.

In a particularly preferred embodiment of the invention, the process relates to the dissolution of nickel from a nickel-bearing source material by dissolution of the nickel with the use of an acidified solution of ferrie chloride. The nickel bearing source material is most preferably a nickel bearing ore material. The process may be applied to the recovering of nickel from a native nickel-metal ore, a latérite ore particularly a saprolite ore, or processed ores such as tailings and scrap métal.

In a further preferred embodiment, the présent invention also relates to the dissolution 10 of gold from a gold metal-bearing source material by dissolution of the gold métal with use of an acidified solution of ferrie chloride. The gold bearing source material could be any source of gold métal, but is preferably a gold-bearing native métal, a goldbearing rock material or processed ore such as tailings, or scrap métal.

In a further preferred embodiment, the présent invention further relates to a process for the dissolution of a platinum-bearing source material by dissolution of the platinum métal with the use of an acidified solution of ferrie chloride. The platinum-bearing source material again could be any source of platinum métal including ores, processed ores such as tailings or scrap métal.

The process of the invention may also be extended to other metals such as copper palladium, silver or rare earth metals.

The ferrie chloride digest liquor can be a product in itself or evaporated to yield a 25 concentrate as a commercial product.

In a further embodiment, the présent invention relates to the recovery of a purified métal product from the prégnant ferrie chloride digest liquor. The métal is recovered from the prégnant ferrie chloride digest liquor with a reducing agent, for example 30 hydrogen gas or an organic acid, but may be recovered by other techniques, such as electrowinning, ion exchange, solvent extraction, sulphidation, multi-stage neutralisation or pyrohydrolysis. For example, the recovered métal may take the form of nickel métal, such as a dried nickel powder or a refined nickel compound precipitate, such as nickel chloride or nickel sulphate, or a nickel oxide or a nickel hydroxide, or other oxyanionic or organic nickel complex, including as a hydrated complex. Other metals may be recovered in a comparable form.

Detailed Description of the Invention

The présent invention résides in a process for the dissolution of a metallic element from a metal-bearing source material or dissolution of métal from a metal-bearing source material by dissolution of the metallic element with the use of an acidified ferrie chloride solution. The metal-bearing material may be any métal source containing recoverable métal. The présent invention is particularly applicable to the recovery of 10 nickel, gold, copper, palladium, silver and platinum from the metal-bearing source material containing one or more of those metallic éléments. The présent invention is particularly applicable to the recovery of nickel-bearing material by dissolution of the nickel métal with the use of an acidified ferrie chloride solution and it is convenient to discuss the recovery of nickel in more detail herein. It should however be kept in mind 15 that the process is applicable to a broad range of metals including gold, platinum, copper, silver and palladium.

The nickel-bearing source material may be any nickel métal source containing recoverable nickel métal including nickel bearing ores, such as latentes, and in 20 particular saprolites, native nickel ores, and also modified geological materials containing nickel métal, such as that found in pre-processed tailings; or nongeological materials containing nickel métal, such as waste.

The invention is particularly applicable to the dissolution of nickel from any nickel25 bearing ore including pegmatite, latérite, sulphide or serpentinised ultra-mafic rock ores, and native nickel ores.

In a preferred embodiment, the process involves the dissolution of nickel métal from the nickel-bearing source with the use of an acidified ferrie chloride solution leading to 30 the dissolution of nickel ions in an acidified ferrie chloride digest liquor. The invention further includes a process for the recovery of a purified nickel product following the recovery of nickel from the acidified ferrie chloride digest liquor.

The process is a relatively cost-effective process that makes it applicable to the 35 processing of low-grade ores and other nickel-bearing material. Whereas the process may hâve broad applications and may cater for a variety of feed material, it is convenient to describe the process herein with reference to processing native nickel métal found in native nickel métal ore.

The nickel found in a native nickel métal ore deposit generally exists as a relatively pure metallic nickel resource. A native nickel métal ore deposit may also include weathered ore where the native nickel métal is found part altered to a nickel-iron oxide. A native nickel métal deposit is a deposit including native nickel métal ore where the ore includes naturally formed metallic nickel or as a secondary nickel oxide.

The native nickel métal ore may comprise any form where the nickel exists as relatively pure metallic nickel. The particulate size or physical form of the metallic nickel is not limiting, and it may, for example include metallic nickel balls, where the balls may typically be 0.05 to 5.0 mm in diameter. Altematively, the metallic nickel may occur as platelets or wire form, as may be found in serpentinised ore and other ore types. The nickel content may vary quite considerably between various native nickel métal ores, from low-grade nickel content with small amounts of contained nickel métal to high-grade ores with nickel as 95% nickel métal and above in some deposits.

The native nickel métal ore is susceptible to weathering and the nickel may exist as a secondary oxide, notably where the nickel is replaced with siliceous iron oxide where the iron is in the trivalent state.

Reference to the term “native nickel métal ore” used herein is a reference to an ore 25 that comprises a naturally formed metallic nickel or a secondary nickel oxide, and is inclusive of both high-grade and low-grade ores.

The process of the présent invention aims to provide a process for the dissolution of nickel from a nickel-bearing source material. Preferably, the process relates to the 30 dissolution of nickel métal from a nickel-bearing ore including latérite and sulphide ores, but most preferably, the process relates to the dissolution of nickel from native nickel métal deposits bearing native nickel métal ore and modified geological materials containing nickel métal, such as that found in tailings, pre-processed tailings; or non-geological materials containing nickel métal, such as waste.

The process of the présent invention may however be applicable to a broad range of metals, and in particular naturally occurring metals such as nickel, gold, copper, palladium, silver and platinum. In one embodiment, the invention résides in a process for the dissolution of métal from a metal-bearing source material, said process 5 includes the step of dissolving the métal from the metal-bearing source material with an acidified ferrie chloride solution to form a prégnant digest liquor containing métal ions in solution.

The process is particularly applicable to the recovery of nickel, gold, copper, 10 palladium, silver and platinum but in a preferred embodiment, the process relates to the dissolution of nickel from a nickel bearing source material including native nickel métal ore, saprolite ore, or tailings and non-geological materials containing nickel, such as waste.

In a further embodiment, the invention résides in a process for the dissolution of métal from a metal-bearing source material, including métal bearing ores and modified geological materials containing nickel, gold, copper, palladium, silver and platinum métal, such as that found in tailings, pre-processed tailings; or non-geological materials containing such métal, such as waste. For example, the process has been 20 found to be useful for the sélective recovery of gold from an ore that includes more than one métal, for example a platinum oxide ore bearing both gold and platinum.

Where a métal ore is processed, or a source material is such that the metallic element is not predominantly exposed to the surface, it is preferred that the process includes a 25 step of grinding the métal bearing source material first, so that the metallic éléments are exposed to the acidified ferrie chloride solution.

The Applicants hâve found that nickel métal dissolution may occur if the nickelbearing source material is subjected to a nickel métal digestion process with acidified 30 ferrie chloride solution. Accordingly, in a preferred aspect of the présent invention there is provided a process for the dissolution of nickel from a nickel-bearing source material, said process including the step of dissolving the nickel métal from the ground nickel-metal-bearing source material with an acidified ferrie chloride solution to form a prégnant digest liquor containing nickel ions in solution.

Preferably, the nickel-bearing source material is a nickel bearing ore. Most preferably, the nickel bearing source material is a native nickel métal ore or a latérite ore, preferably saprolite. The nickel-bearing source material may also be nongeological materials containing nickel such as processed nickel such as tailings or scrap métal.

Where a nickel ore is processed, or the nickel source material is such that the nickel element is not predominantly exposed to the surface, it is preferred that the process includes a step of grinding the nickel-bearing source material first, so that the nickel éléments are exposed to the acidified ferrie chloride solution.

If the process includes a step of grinding the material and in particular an ore, it is preferred to crush the ore to a particle size of less than 2.54cm, more preferably to a particle size of between 100 microns and 2cm. Energy costs and métal recovery balance may be determining factors in any crushing process. If the metal-bearing source material is for example tailings or scrap métal, crushing may not be necessary, but a grinding process may take place if it is deemed désirable to increase the surface area ofthe métal exposed to the acidified ferrie chloride solution.

The ferrie chloride is preferably an acidified solution wherein the dissolution takes place by providing a solution of a minerai acid together with ferrie chloride. The minerai acid may be any suitable minerai acid, for example hydrochloric acid, sulfuric acid, boric acid or nitric acid, but most preferably hydrochloric acid. Hydrochloric acid is preferred as it is believed to assist nickel solubility as a divalent cation, making the nickel readily recoverable. An acid, such as hydrochloric acid provides a positive hydrogen ion, creating the acid solution. Having an acid solution allows the divalent nickel ion to go into and stay in solution during the dissolution phase.

It is believed that ferrie ions, provided by the ferrie chloride solution, assist in oxidising the nickel métal to form the divalent nickel cation by an électron transfer mechanism between the nickel métal and the adsorbed trivalent ferrie ion from solution. The hydrogen ion of the acid promûtes the formation and solubility of the positively charged nickel ion product of the reaction by allowing the divalent nickel cation to go into and stay in solution. Gold and platinum will also be solubilized and stay in solution when subjected to the acidified ferrie chloride solution.

Hydrochloric acid is preferred as it also provides a chloride anion. This means that 5 there is no additional contamination of the ferrie chloride solution, as the ferrie chloride also provides a chloride anion. Whereas other acids may provide the acidic solution and be suitable for the process, it may be less désirable if a NOs anion or a SO4²' anion was introduced with nitric acid or sulphuric acid respectively, as this may introduce unnecessary contaminâtes with the additional anion species.

This process has been found to be particularly advantageous as the prégnant digest liquor is substantially free of sulphur or other contaminants, which allows for recovery of a relatively pure métal product.

It is most preferred that the acidified ferrie chloride solution is a relatively dilute acidified solution wherein the ratio between the acid and the ferrie chloride may vary from 1:1 to 1:10, preferably in a ratio of 1:1 to 1:6, while most preferably around 1:1 to 1:4. A ratio of around 1:4 is found to be preferred, but may be adjusted so as to hâve trivalent iron in stoichiometric excess of the nickel. The acid is there to facilitate 20 dissolution and not get in the way by forming undesirable secondary précipitâtes.

Preferably, hydrochloric acid is added in a sufficient amount to maintain an acid pH. The amount of acid will vary depending on the composition of the ore feed. Preferably, the pH is maintained at a level of from 2 to 7. Sufficient ferrie chloride will be added to dissolve the contained nickel métal.

Preferably, the concentration of the hydrochloric acid for the digest solutions falls within the dilute range of from 0.01 M to 2M, preferably 0.02M to 1.0M, but more preferably 0.1 M to 0.2M. Sufficient ferrie chloride should be added to dissolve the contained nickel métal in the ore feed, and this will vary depending upon the ore 30 grade. Preferably, the ore grade is maintained at a reasonably constant level by mixing ore grade types. The ferrie chloride is preferably maintained in stoichiometric excess ofthe contained nickel métal. The concentration of the ferrie chloride may, for example fall within the range of from 0.01 M to 2.0M, preferably between 0.05M to 1 .OM, but more preferably between 0.08M and 0.4M. It has been noted that a higher 35 concentration of the ferrie chloride may slow down the dissolution. The concentration of acid and ferrie chloride is preferably as low as possible but still at a level that is effective and efficient.

The hydrochloric acid concentration can be delivered by adding the hydrochloric acid 5 to the aqueous solution or by adding sufficient ferrie chloride to produce hydrochloric acid by hydrolysis.

The process may be conducted at atmospheric température and pressure. It may be possible to achieve faster reaction times under elevated température and/or pressure.

The Applicants hâve found that the rate of dissolution is increased with higher température and higher concentration of hydrochloric acid. Température and hydrochloric acid concentration should be maximised, or optimised within the constraints of cost, safety and environmental hazard. Preferably the température should be between 25°C and the atmospheric boiling point of aqueous solution.

It is preferred that agitation takes place during the dissolution process. Agitation could take place in any standard agitation equipment. Preferably the solution is agitated for a period of 1 to 10 hours. Contact time is preferably between 1 to 10 days for good results.

²⁰

In a further embodiment of the invention, the process includes the additional step of recovering a purified métal product from the prégnant acidified ferrie chloride digest liquor. In one embodiment, the process includes the step of adding a reducing agent to the prégnant leach solution so as to precipitate the métal to be recovered such as 25 nickel, gold, platinum, palladium, silver or copper.

In a preferred embodiment, for example a nickel, gold, platinum, palladium, silver or copper recovery process, hydrogen gas is used as a reductant to precipitate the métal in metallic form. The métal may then be recovered and dried to a powder form.

The nickel recovery process from the prégnant acidified ferrie chloride digest liquor may also include other techniques, such as ion exchange, solvent extraction, electrowinning, or multi-stage neutralisation, to produce a nickel chloride, nickel oxide or a nickel hydroxide, or other oxyanionic or organic nickel complex, including as a 35 hydrated complex. Alternatively, it could include pyrohydrolysis to produce a nickel oxide or sulphidation to produce nickel sulphate. The means of recovery may vary depending upon the final use of the nickel product, for example a nickel hydroxide product could be produced for battery material or a nickel sulphate material produced for electric coating and nickel cathodes.

Gold, platinum, copper, silver and palladium or other rare earth metals may also be recovered from a prégnant acidified ferrie chloride digest liquor by similar known recovery processes. For example, gold may be recovered with use of sorbents. Absorption on carbon being the most common. Gold may also be recovered by ion exchange processes, précipitation, for example the Merrill-Crowe process using zinc dust or electroplating. Platinum group éléments may be recovered with the use of sorbents, for example absorption onto activateb carbon, magnetite, novel biomass sorbents or synthetic sorbents; ion exchange processes; précipitation or electroplating.

It is generally preferreb however that the métal, anb in particular nickel is recovereb with the use of rebucing agents inclubing hybrogen gas or an organic acib such as oxalic acib. Hybrogen gas is the preferreb rebucing agent. Whereas any rebucing agent is likely to achieve results, hybrogen gas is preferreb as it is most likely to be compatible with the bigest solution chemistry. This is because the process of hybrogen rebuction of the bivalent nickel ion back to nickel métal probuces a hybrogen ion, which may provibe the acib requireb for the bigestion process. Hybrogen gas may not however be suitable in ail environments, so alternative embobiments anb/or rebuctants are still contemplateb.

After recovery of the nickel, the nickel bepleteb acibifieb ferrie chloribe bigest liquor may then be recycleb back to treat further nickel-bearing feeb such that the cycle is continuous. The recycleb solution shoulb be relatively free of contaminants, particularly if hybrochloric acib is useb anb/or if hybrogen gas is useb as the rebucing agent. It is believeb that if hybrochloric acib has been useb to acibify the ferrie chloribe solution, there is less likely to be contamination of the bigest liquor leabing to a greater ability to recycle the bigest liquor for further use.

If acibs other than hybrochloric acib or rebuctants other than hybrogen are useb, an abbitional step to remove any contaminants may be introbuceb buring the re-cycle process. Adjustment of the solution chemistry may also be required depending on the nickel-bearing material used, and in particular the native nickel métal ore feed composition, for example as in the case that the ore feed is inherently strongly acidor alkaline-producing, or contains sulphide minerais. Top-up acid or ferrie chloride solution may be added so as to maintain the efficacy of the process.

The effectiveness of the nickel recovery process will be monitored by comparison of the nickel content in the unprocessed ore feed, the prégnant digest liquor and the spent ore tailings, and adjustments to the pH of the solution and the content of ferrie 10 chloride or acid, may be made during the process to maximise the dissolution of the nickel métal from the ore.

The following Examples are illustrative of the invention described herein. They are not intended to be limiting upon the scope or ambit of the invention described.

Example 1

A pilot test was trialled with one gram of native nickel métal ore, which came in the form of metallic balls. The balls of 2 to 3 mm in diameter contained approximately 93 wt.% nickel as found from électron microscopy (SEM EDAX analysis) on similar balls.

The nickel balls were subjected to digestion in an acidified solution of ferrie chloride at a ratio of 1:4 0.1 M HCL and 0.1 M FeCh. The solution was magnetically stirred for a total period of about 5 hours in the first 24 hours. The initial solution of ferrie chloride was yellow but after 24 hours the solution had definite green tinge indicative of nickel métal dissolution. The digestion experiment was kept going for several days with no 25 significant change in colour.

The balls were then removed from the solution, sectioned in a block mount, and examined by SEM EDAX analysis. They were found to contain less than 0.75 wt.% nickel in a porous network of residual silica oxide. It was concluded that the nickel 30 métal had been dissolved and removed. It shows that the low strength acidified ferrie chloride dissolution process appears to be highly effective.

Example 2

A comparable trial was conducted using a 1:4 ratio of 0.2M HCl and 0.5M FeCh and similar results were found. It was found that the reaction did not appear to proceed any faster with the higher potency digest solution.

Example 3

Digest solutions of ferrie chloride and hydrochloric acid were tested on samples of fresh native nickel métal balls containing minor iron and silica and their alteration product in various stages of iron oxide replacement, a saprolite ore of nickel latérite, and a gold-bearing platinum oxide ore to test the application of the digest method to metal-bearing ores; and applied to marine grade 316 stainless steel washers to test the digest method to remediate métal from waste material. The dissolution of nickel was measured by ICP-AES for test solutions. The dissolution of gold and platinum was measured by ICP-MS for the platinum oxide ore. Tests were also conducted for the recovery of copper and palladium from scrap metals containing those metals.

It was found that the rate of dissolution of each of these metals increased with higher température (70°C) and higher concentration of hydrochloric acid (0.1 M) as shown in Table 1. Table 1 demonstrates the recovery of metals from solution following dissolution ofthe éléments from platinum oxide ore after 6 hours. The solution was proved to be effective for dissolving gold selectively from platinum in the conditions tested.

Table 1 - Dissolution extent of various éléments from a platinum oxide ore after 6 hours.

	Solution recoveries (%)
	Au	Cu	Ni	Pd	Pt
FeCI3 (0.4 M) HCl (0.1 M) 50°C 6 hours	59.3	6.5	3.8	2.5	0.2
FeCI3 (0.08 M) HCl (0.02 M) 50°C 6 hours	66.5	7.6	6.9	5.3	1.0
FeCI3 (0.4 M) HCl (0.1 M) 70°C 6 hours	100	13.8	11.9	14.8	10.5
FeCI3 (0.08 M) HCl (0.02 M) 70°C 6 hours	0	6.3	3.6	8.2	0.0

Figure 1 and 2 show that the rate of dissolution of metallic nickel from fresh and iron oxide altered balls in ferrie chloride solution is increased by a higher concentration of hydrochloric acid. Figure 1 and 2 also show that the rate of stirring does not seem to affect the rate of dissolution between a stirring speed of 300 and 500 rpm.

Figure 3 shows that the dissolution of nickel from a 316 stainless steel washer is greatly increased by higher température.

Figure 4 shows that a higher température will increase the dissolution rate of nickel from a saprolite ore.

Figure 5 shows that a higher concentration of hydrochloric acid will increase the rate of dissolution of nickel from a saprolite ore. Where ferrie chloride (0.4m) is added without hydrochloric acid, it is suggested that the ferrie chloride is causing hydrolysis and producing hydrocholoric acid.

Figures 6 to 9 illustrate the effectiveness of the digestion process using SEM imagery. Each of figures 6 to 9 illustrâtes nickel depleted honeycomb texture of native nickel balls of a native nickel ore after digestion. The honeycomb texture is illustrative of the nickel depleted siliceous framework of leached nickel balls in the digest residue.

Claims:

Claims (22)

1. Claims:

   1. A process for the dissolution of a metallic element from a metal-bearing source material, said process including the steps of dissolving the metallic element from a metal-bearing source material with an acidified ferrie chloride solution to form a prégnant digest liquor containing métal ions in solution.
2. 2. A process according to claim 1 wherein the metal-bearing source material is a metal-bearing ore, or processed métal ore such as tailings or scrap métal.
3. 3. A process according to claim 1 or 2 where the metallic element is nickel, gold, copper, palladium, silver, platinum or rare earth métal.
4. 4. A process according to anyone of claims 1 to 3 wherein the process includes a step of grinding the metal-bearing source material where the source material is an ore, or a material where the metallic element is not predominantly exposed to the surface.
5. 5. A process according to claim 3 wherein gold is recovered selectively from a metal-bearing ore containing more than one métal, for example a platinum oxide ore bearing at least both gold and platinum.
6. 6. A process for the dissolution of nickel from a nickel-bearing source material, said process including the step of dissolving the nickel from the nickel-bearing source material with an acidified ferrie chloride solution to form a prégnant digest liquor containing nickel ions in solution.
7. 7. A process according to claim 5 wherein the nickel-bearing source material is a nickel-bearing ore or a processed nickel ore such as tailings or nickel bearing scrap métal.
8. 8. A process according to anyone of claims 6 or 7 wherein the process includes a step of grinding the nickel-bearing source material where the source material is an ore, or a material where the nickel element is not predominantly exposed to the surface.
9. 9. A process according to claim 7 or 8 wherein the nickel-bearing ore is a saprolite nickel latente ore.
10. 10. A process according to claim 7 or 8 wherein the nickel-bearing source material is a native nickel métal ore.
11. 11. A process according to any one of the preceding claims wherein the acidified ferrie chloride solution includes a ratio of from 1:1 to 1:10, preferably a ratio of 1:1 to 1:6 and most preferably a ratio of about 1:1 to 1:4 of an acid and ferrie chloride.
12. 12. A process according to any one of the preceding claims wherein the acid is hydrochloric acid, sulfuric acid, boric acid or nitric acid, preferably hydrochloric acid.
13. 13. A process according to any one of the preceding claims wherein the acid is hydrochloric acid in a concentration of from 0.01 M to 2.0M, preferably 0.02M to 1.0M and more preferably 0.1 M to 0.2M.
14. 14. A process according to any one of the preceding claims wherein the ferrie chloride is in a concentration of from 0.01 M to 2.0M, preferably 0.05M to 1.0M and more preferably 0.08M to 0.4M.
15. 15. A process according to claim 4 or 8 wherein the metal-bearing source material is ground to a size of less than 2.54cm, preferably to a particle size between 100 microns and 2cm.
16. 16. A process according to any one of the preceding claims wherein the température of the process is between 25°C and the atmospheric boiling point of the solution.
17. 17. A process according to any one of the preceding claims wherein the métal is recovered from the prégnant digest liquor with a reducing agent, ion exchange, solvent extraction, electrowinning, multi-stage neutralisation, pyrohydrolysis or sulphidation.
18. 18. A process according to claim 17 wherein the métal is nickel and is recovered from the prégnant digest liquor as a relatively pure nickel métal, or as a compound precipitate such as nickel chloride, nickel sulphate, nickel oxide or a nickel hydroxide, or oxyanionic or organic complex, including as a hydrate.
19. 19. A process according to any one of the preceding claims wherein the métal is recovered with the use of a reducing agent and the nickel recovered as a relatively pure nickel métal.
20. 20. A process according to claim 19 wherein the reducing agent is hydrogen gas or an organic acid, such as oxalic acid, preferably hydrogen gas.
21. 21. A process according to claim 19 or 20 wherein the recovered métal is dried to powder form.
22. 22. A process according to any one of the preceding claims wherein the métal depleted acidified ferrie chloride digest liquor is recycled to treat further ground ore feed in a continuous cycle.