WO2004054954A1

WO2004054954A1 - Process for the purification of hydroxyaryl-aldhydes and ketones and their use in the production of hydroxyaryl oxime derivatives

Info

Publication number: WO2004054954A1
Application number: PCT/GB2003/004951
Authority: WO
Inventors: Peter Woollven
Original assignee: Cytec Technology Corp.
Priority date: 2002-12-18
Filing date: 2003-11-14
Publication date: 2004-07-01
Also published as: GB0229445D0; AU2003283574A1

Abstract

A process for the purification of hydroxyaryl aldehydes and ketones comprising the following steps; 1) adding a mineral acid to a first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone; 2) washing the mixture obtained in step 1 with water; 3) isolating a second composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone from step 2.

Description

_PROC_ESS _FO_{R T}H_E PURIFICATION OF HYDROXYARYL-ALDHYDES AND KETONES AND THEIR USE _IN THE PRODUCTION OF HYDROXYARYL OXI E DERIVATIVES

The present invention concerns a process for the production hydroxyaryl aldhehydes and hydroxyaryl ketones as precursors for the production of hydroxyaryl oximes.

It is known to extract metals, especially copper, from aqueous solutions containing the metal in the form of, for example, a salt, by contacting the aqueous solution with a solution of a solvent extractant in a water immiscible organic solvent and then separating the solvent phase loaded with metal, i.e. containing at least a part of the metal in the form of a complex. The metal can then be recovered by stripping with a solution of lower pH followed for example, by electrowinning. Most commonly, the aqueous metal-containing solutions for extraction are the result of the acid leaching of ores. However it is known that some metals, especially copper, can be leached from certain ores with ammoniacal solutions. This has the advantage that solutions containing especially high concentrations of copper are derived and that there is little contamination of the solution with iron.

Solvent extractants which have found favour in recent years particularly for the recovery of copper from aqueous solutions include oxime reagents. Of particular importance are the hydroxyaryl oximes, especially o-hydroxyarylaldoximes and o- hyd roxyaryl ketoxi mes .

The hydroxyaryl oximes are often designed to be highly soluble in relatively non- polar solvents. Such hydroxyaryl oximes often are substituted with highly non-polar groups. The hydroxyaryl oximes are generally made by oximation of corresponding hydroxyaryl aldehydes or ketones.

Hydroxyaryl aldhehydes are frequently obtained by formylation of a corresponding hydroxyaryl compound. Hydroxyaryl ketones are frequently obtained from esters of corresponding hydroxyaryl compounds by Fries rearrangement. it is common for certain by-products to be associated with the production of hydroxyaryl aldehydes and ketones. This can result in levels of these by-products being present in the oximes products. These by-products are known to act as modifiers in the metal extraction process. Therefore, it is important to control the levels of such byproducts to ensure consistent performance of the hydroxyaryl oximes in metal extraction. The use of fractional distillation is a known technique used in the purification of many types of organic material in the research laboratory. However, large scale fractional distillation requires specialist manufacturing equipment. It is time consuming to perform, often suffers from yield losses with each stage of operation, can often be inefficient and adds significant capital costs to manufacture. There is therefore a need for improved methods of manufacture of hydroxyaryl aldehydes and ketones. According to a first aspect of the present invention there is provided a process for the purification of hydroxyaryl aldehydes and ketones comprising the following steps:

1 ) adding a mineral acid to a first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone; 2) washing the mixture obtained in step 1 with water;

3) isolating a second composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone from step 2. The first and second compositions comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone may also comprise by-products associated with the methods of production of the hydroxyaryl aldehyde or hydroxyaryl ketone. Typically these byproducts include optionally substituted phenols or O-acylated derivatives of optionally substituted phenols.

Where the first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone also comprises by-products associated with the methods of production of the hydroxyaryl aldehyde or hydroxyaryl ketone, the ratio of by-products to hydroxyaryl aldehyde or hydroxyaryl ketone in the second composition is preferably less than the ratio of by-products to hydroxyaryl aldehyde or hydroxyaryl ketone in the first composition.

The first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone typically comprises more than 40 w/w%, frequently comprises more than 55 w/w% and most often comprises more than 70 w/w% of the hydroxyaryl aldehyde or a hydroxyaryl ketone. Typically, the remainder of the composition comprises by-products associated with the methods of production of the hydroxyaryl aldehyde or hydroxyaryl ketone.

Optionally, in the process of the present invention one or more additional solvents may be present in any of steps 1 to 3. Where an additional solvent is present in any of the steps, preferably the solvent is selected so as not to be detrimental to the overall process. Particularly, where a solvent is used in Step 1 and/or Step 2, preferably the solvent is selected so as to be relatively unreactive towards the mineral acid which is employed.

Solvent which may be present in any of steps 1 to 3 include aliphatic and aromatic hydrocarbon solvents including aliphatic and aromatic hydrocarbons, halogenated solvents including halogenated aliphatic and aromatic hydrocarbons, and nitrated solvents including nitrated aliphatic and aromatic hydrocarbons.

Preferably, the mineral acid is selected to be reactive towards by-products which may be present in the first composition. A mineral acid which is selected to be reactive towards by-products which may be present in the first composition, may be selected for the ability to react directly with the by-products or alternatively may be selected for the ability to facilitate reaction of the by-products. Preferably, the mineral acid is selected such that the by-products undergo a reaction to form species with enhanced water solubility. Mineral acids which may be employed in the process of the present invention include acids of sulphur, particularly sulphuric acid and sulphuric acid / sulphur trioxide mixtures, for example oleum; and acids of phosphorus, particularly phosphoric acid and polyphosphoric acid. Especially preferred mineral acids are sulphuric acid / sulphur trioxide mixtures and polyphosphoric acid.

Often, the quantity of mineral acid which is utilised is related to the concentration of by-products present. The quantity of mineral acid may also be influenced by the stoicheometry of any reaction which takes place between the mineral acid and the byproduct. Although, the quantity of mineral acid employed may be less than a 1 molar equivalent with respect to the by-products, often the quantity of mineral acid employed will be greater than or equal to a 1 molar equivalent with respect to the by-products.

When a molar excess of mineral acid employed, often 1 to 10 molar equivalents are employed, frequently from 2 to 6 molar equivalents and most frequently between 3 and 4, for example 3.5, molar equivalents of mineral acid are employed.

When certain mineral acids are employed, the molar equivalence may be measured with respect to an active component of the mineral acid. For example, when sulphuric acid / sulphur trioxide mixtures are employed, molar equivalency is often measured with respect to the sulphur trioxide present. The hydroxyaryl aldehydes or hydroxyaryl ketones employed in the present invention are substantially water insoluble and preferably have the formula:

Formula (1) wherein

R¹ is hydrogen or an optionally substituted hydrocarbyl group R² is an optionally substituted hydroxyaryl group, and salts thereof.

Whilst the invention is described herein with reference to a compound of Formula (1), it is understood that it relates to said compound in any possible tautomeric forms.

Optionally substituted hydrocarbyl groups which may be represented by R¹ preferably comprise optionally substituted alkyl and aryl groups including combinations of these, such as optionally substituted aralkyl and alkaryl groups.

Examples of optionally substituted alkyl groups which may be represented by R¹ include groups in which the alkyl moieties can contain from 1 to 20, especially from 1 to 4, carbon atoms. A preferred orthohydroxyaryl ketone is one in which R¹ is alkyl, preferably containing up to 20, and especially up to 10, and more preferably up to 3 saturated aliphatic carbon atoms, and most preferably R¹ is a methyl group.

Examples of optionally substituted aryl groups which may be represented by R¹ include optionally substituted phenyl groups. When R¹ is an aryl group, it is preferably an unsubstituted phenyl group.

Optionally substituted hydroxyaryl groups which may be represented by R² include optionally substituted phenols. Preferably R² is an ortho-hydroxyaryl group. Examples of optionally substituted phenols which may be represented by R² include those of formula:

wherein R³ to R⁶ each independently represent H or a Ci to C₂₂, preferably a C₇ to C*i₅, linear or branched alkyl group. Particularly preferably only R⁵ represents a C**-₂₂ alkyl group, most preferably a C₇ to C₁₅ alkyl group, with R³, R⁴ and R⁶ representing H.

When R¹ or R² is substituted, the substituent(s) should be such as not to affect the process of the present invention. Suitable substituents include halogen, nitro, cyano, hydrocarbyl, such as C*ι-₂₀-alkyl, especially Cι-₁₀-alkyl; hydrocarbyloxy, such as C**- ₂o-alkoxy, especially C*ι-₁₀-alkoxy; hydrocarbyloxycarbonyl, such as C**-₂o-alkoxycarbonyl, especially C*ι-₁₀-alkoxycarbonyl; acyl, such as C*ι-₂₀-alkylcarbonyl and arylcarbonyl, especially C**-₁₀-alkylcarbonyl and phenylcarbonyl; and acyloxy, such as Ci-₂0-alkylcarbonyloxy and arylcarbonyloxy, especially C^o-alkylcarbonyloxy and phenylcarbonyloxy. There may be more than one substituent in which case the substituents may be the same or different.

In many embodiments, when an orthohydroxyaryl ketone is employed, the orthohydroxyaryl ketone is a 5-(C₈ to C₁₄ alkyl)-2-hydroxyacetophenone, particularly 5-nonyl-2-hydroxyacetophenone.

In many embodiments, when an orthohydroxyaryl aldehyde is employed, the orthohydroxyarylaldehyde is a 5-(C₈ to C₁₄ alkyl)-2-hydroxybenzaldehyde, particularly 5-nonyl-2-hydroxybenzaldehyde.

Typically, by-products which may be associated with the production of the preferred aldehydes or ketones are optionally substituted phenols of formula:

and/or O-acylated derivatives of optionally substituted phenols of formula:

Formula (3)

where R⁷ is an optionally substituted hydrocarbyl group and R³ to R⁶ are as hereinbefore defined above. Optionally, the first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone may be prewashed with a basic solution. Such pre-washing may be effective in removing at least a portion of the unwanted by-products.

In certain preferred processes, the washing of a first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone with a basic solution may serve to provide a 5 purified hydroxyaryl aldehyde or a hydroxyaryl ketone.

More preferably, the first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone is prewashed with a basic solution prior to step 1.

Basic solution suitable for pre-washing the first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone include aqueous solutions of alkali metal 0 hydroxides or alkali earth metal hydroxides and aqueous solutions of hydroxides of ammonia and amines particularly ammonium hydroxide.

Often, the concentration and quantity of basic solution which is utilised is related to the concentration of by-products present. The concentration and quantity of basic solution may also be influenced by the stoicheometry of any reaction which takes place 5 between the basic solution and the by-product. . Typically, when. the basic solution is an aqueous solution of sodium hydroxide, from 4 to 8 wt% sodium hydroxide solution is employed.

Hydroxaryl aldehydes and hydroxaryl ketones obtained by the process of the present invention find particular use in processes for of manufacture of hydroxyaryl o oximes. According to a second aspect of the present invention there is provided a process for the production of a hydroxyaryl oxime comprising the following steps:

3) isolating a second composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone from step 2;

4) reacting hydroxylamine or a salt thereof with the hydroxyaryl aldehyde or hydroxyaryl ketone obtained in step 3 to produce a hydroxyaryl oxime from said hydroxyaryl aldehyde or hydroxyaryl ketone.

The mineral acid and the first and second composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone can be as described before in the first aspect of the present invention.

The hydroxyaryl oxime produced by the process of the present invention are substantially water insoluble and preferably have the formula:

Formula (4) wherein R¹ is hydrogen or an optionally substituted hydrocarbyl group

R² is an optionally substituted hydroxyaryl group, and salts thereof.

R¹ and R² can be as described above in the first aspect of the present invention.

Optionally, in the process of the present invention the first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone may be prewashed with a basic solution. Such pre-washing may be effective in removing at least a portion of the unwanted byproducts. The basic solution can be as described in the first aspect of the present invention.

The process of the present invention results in hydroxyaryl oxime compositions which have reduced levels of unwanted by-products and which have an impurity profile which is determined by the method of production. Such compositions are considered novel.

According to a third aspect of the present invention there is provided a composition comprising a hydroxyaryl oxime obtainable by a process comprising the following steps: 1) adding a mineral acid to a first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone;

2) washing the mixture obtained in step 1 with water;

4) reacting hydroxylamine or a salt thereof with the hydroxyaryl aldehyde or hydroxyaryl ketone obtained in step 3 to produce the hydroxyaryl oxime from said hydroxyaryl aldehyde or hydroxyaryl ketone.

The mineral acid, the first and second composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone, the hydroxyaryl oximes and optional washing with basic solution can be as described before in the first and second aspect of the present invention.

According to a fourth aspect of the present invention, there is provided a process for the extraction of a metal from solution in which an acidic solution containing a dissolved metal is contacted with a solvent extraction composition comprising a water immiscible organic solvent and a solvent extractant, whereby at least a fraction of the metal is extracted into the organic solution, characterised in that the solvent extractant is a composition comprising a hydroxyaryl oxime obtainable by a process comprising the following steps: 0 1) adding a mineral acid to a first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone;

2) washing the mixture obtained in step 1 with water;

3) isolating a second composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone from step 2; 5 4) reacting hydroxylamine or a salt thereof with the hydroxyaryl aldehyde or hydroxyaryl ketone obtained in step 3 to produce the hydroxyaryl oxime from said hydroxyaryl aldehyde or hydroxyaryl ketone.

Metals that may be extracted in the process according to the third aspect of the present invention include copper, cobalt, nickel, manganese and zinc, most preferably o copper.

The hydroxyaryl oxime and the process by which it is obtainable are as herein described before.

Organic solvents which may be present in the solvent extraction composition include any mobile organic solvent, or mixture of solvents, which is immiscible with water 5 and is inert under the extraction conditions to the other materials present. Preferably the organic solvent has a low aromatic hydrocarbon content.

Preferred organic solvents are hydrocarbon solvents which include aliphatic, alicyclic and aromatic hydrocarbons and mixtures thereof as well as chlorinated hydrocarbons such as trichloroethylene, perchloroethylene, trichloroethane and chloroform.

Highly preferred organic solvents having a low aromatics content include solvents and solvent mixtures where the amount of aromatic hydrocarbons present in the organic solvent is less than 30%, usually around 23% or less, often less than 5%, and frequently less than 1%.

Examples of suitable hydrocarbon solvents include ESCAID 110, ESCAID 115, ESCAID 120, ESCAID 200, and ESCAID 300 commercially available from Exxon (ESCAID is a trade mark), SHELLSOL D70 and D80 300 commercially available from Shell (SHELLSOL is a trade mark), and CONOCO 170 commercially available from Conoco (CONOCO is a trade mark). Suitable solvents are hydrocarbon solvents include high flash point solvents and solvents with a high aromatic content such as SOLVESSO 150 commercially available from Exxon (SOLVESSO is a trade mark).

More preferred are solvents with a low aromatic content. Certain suitable solvents with a low aromatic content, have aromatic contents of <1% w/w, for example, hydrocarbon solvents such as ESCAID 110 commercially available from Exxon (ESCAID is a trade mark), and ORFOM SX 10 and ORFOM SX11 commercially available from Phillips Petroleum (ORFOM is a trade mark). Especially preferred, however on grounds of low toxicity and wide availability, are hydrocarbon solvents of relatively low aromatic content such as kerosene, for example ESCAID 100 which is a petroleum distillate with a total aromatic content of 23% commercially available from Exxon (ESCAID is a trade mark), or ORFOM SX7, commercially available from Phillips Petroleum (ORFOM is a trade mark).

In many embodiments, the solvent extraction composition comprises at least 30%, often at least 45% by weight, preferably from 50 to 95% w/w of water-immiscible hydrocarbon solvent.

The aqueous acidic solution from which metals are extracted by the process of the third aspect of the present invention often has a pH in the range of from -1 to 7, preferably from 0 to 5, and most preferably from 0.25 to 3.5. Preferably, when the metal to be extracted is copper pH values of less than 3 chosen so that the copper is extracted essentially free of iron, cobalt or nickel. The solution can be derived from the leaching of ores or may be obtained from other sources, for example metal containing waste streams such as from copper etching baths.

The concentration of metal, particularly copper, in the aqueous acidic solution will vary widely depending for example on the source of the solution. Where the solution is derived from the leaching of ores, the metal concentration is often up to 75g/l and most often from 1 to 40g/l. Where the solution is a waste stream, the metal concentrations can vary from 0.5 to 2g/l for a waste water stream, to somewhat higher for those from other waste streams, for example Printed Circuit Board waste streams, and can be up to 150g/l, usually from 75 to 130g/l.

Preferred solvent extraction compositions are those where the organic solvent solutions may contain the hydroxyaryl oxime in an amount approaching 100% ligand, but typically the hydroxyaryl oxime will be employed at about 10 to 40% by weight. Highly preferred solvent extraction compositions are those comprising an organic solvent with a total aromatic content of around 23% or less and one or more hydroxyaryl oxime selected from 5-(C₈ to C₁₄ alkyl)-2-hydroxyacetophenone oximes, particularly 5-nonyl-2- hydroxyacetophenone oxime, and 5-(C₈ to C₁₄ alkyl)-2-hydroxybenzaldoximes, particularly 5-nonyl-2-hydroxybenzaldoxime, in a total amount of between 5 to 40% by weight.

The process of the third aspect of the present invention can be carried out by contacting the solvent extractant composition with the aqueous acidic solution. Ambient or elevated temperatures, such as up to 75°C can be employed if desired. Often a temperature in the range of from 5 to 60°C, and preferably from 15 to 40°C, is employed. The aqueous solution and the solvent extractant are usually agitated together to maximise the interfacial areas between the two solutions. The volume ratio of solvent extractant to aqueous solution are commonly in the range of from 20:1 to 1:20, and preferably in the range of from 5:1 to 1 :5. In many embodiments, to reduce plant size and to maximise the use of solvent extractant, organic to aqueous volume ratios close to 1 :1 are maintained by recycle of one of the streams.

After contact with the aqueous acidic solution, the metal can be recovered from the solvent extractant by contact with an aqueous acidic strip solution.

The aqueous strip solution employed in the process according to the third aspect of the present invention is usually acidic, commonly having a pH of 2 or less, and preferably a pH of 1 or less, for example, a pH in the range of from -1 to 0.5. The strip solution commonly comprises a mineral acid, particularly sulphuric acid, nitric acid or hydrochloric acid. In many embodiments, acid concentrations, particularly for sulphuric acid, in the range of from 130 to 200g/l and preferably from 150 to 180g/l are employed. When the extracted metal is copper, preferred strip solutions comprise stripped or spent electrolyte from a copper electro-winning cell, typically comprising up to 80g/l copper, often greater than 20g/l copper and preferably from 30 to 70g/l copper, and up to 220g/l sulphuric acid, often greater than 120g/l sulphuric acid, and preferably from 150 to 180g/l sulphuric acid.

The volume ratio of organic solution to aqueous strip solution in the process of the third aspect of the present invention is commonly selected to be such so as to achieve transfer, per litre of strip solution, of up to 50g/l of metal, especially copper into the strip solution from the organic solution. In many industrial copper electrowinning processes transfer is often from 10g/l to 35g/l, and preferably from 15 to 20g/l of copper per litre of strip solution is transferred from the organic solution. Volume ratios of organic solution to aqueous solution of from 1 :2 to 15:1 and preferably from 1 :1 to 10:1, especially less than 6:1 are commonly employed.

Both the separation and stripping process can be carried out by a conventional batch extraction technique or column contactors or by a continuous mixer settler technique. The latter two techniques are generally preferred as they involve recycling of the stripped organic phase in a continuous manner, thus allowing the one volume of organic reagent to be repeatedly used for metal recovery.

A preferred embodiment of the fourth aspect of the present invention comprises a process for the extraction of a metal from aqueous acidic solution in which: in step 1 , the solvent extraction composition comprising a hydroxyaryl oxime is first contacted with the aqueous acidic solution containing metal, in step 2, separating the solvent extraction composition containing metal-solvent extractant complex from the aqueous acidic solution; in step 3, contacting the solvent extraction composition containing metal-solvent extractant complex with an aqueous acidic strip solution to effect the stripping of the metal from the water immiscible phase; in step 4, separating the metal-depleted solvent extraction composition from the loaded aqueous strip solution.

According to a fifth aspect of the present invention, there is provided a process for 0 the extraction of a metal from solution in which an aqueous ammoniacal solution containing a dissolved metal is contacted with a solvent extraction composition comprising a water immiscible organic solvent and a solvent extractant, whereby at least a fraction of the metal is extracted into the organic solution, characterised in that the solvent extractant is a composition comprising a hydroxyaryl oxime obtainable by a 5 process comprising the following steps:

1) adding a mineral acid to a first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone;

2) washing the mixture obtained in step 1 with water;

3) isolating a second composition comprising a hydroxyaryl aldehyde or a o hydroxyaryl ketone from step 2;

Metals that may be extracted in the process according to the fourth aspect of the 5 present invention include copper, cobalt, nickel, manganese and zinc, most preferably copper.

The solvent extractant, the processes by which the hydroxyaryl oxime are obtainable and the water immiscible organic solvent are as herein described before. The aqueous ammoniacal solution from which metals are extracted by the process of the fifth aspect of the present invention often has a pH in the range of from 7 to 12, preferably from 8 to 11 , and most preferably from 9 to 10. The solution can be derived from the leaching of ores, particularly chalcocite ores, or may be obtained from other

5 sources, for example metal containing waste streams such as from copper etching baths.

Preferred solvent extraction compositions are those where the organic solvent solutions may contain the hydroxyaryl oxime in an amount approaching 100% ligand, but typically the hydroxyaryl oxime will be employed at about 10 to 40% by weight. Highly preferred solvent extraction compositions are those comprising an organic solvent with a 0 total aromatic content of around 23% or less and one or more hydroxyaryl oximes selected from 5-(C₈ to C₁₄ alkyl)-2-hydroxyacetophenone oximes, particularly 5-nonyl-2- hydroxyacetophenone oxime, and 5-(C₈ to C₁₄ alkyl)-2-hydroxybenzaldoximes, particularly

5-nonyl-2-hydroxybenzaldoxime, in a total amount of between 5 to 40% by weight.

The concentration of metal, particularly copper, in the aqueous ammoniacal 5 solution will vary widely depending for example on the source of the solution. Where the solution is derived from the leaching of ores, the metal concentration is often up to 75g/l and most often from 1 to 40g/l. Where the solution is a waste stream, the metal concentrations can vary from 0.5 to 2g/l for a waste water stream, to somewhat higher for those from other waste streams, for example Printed Circuit Board waste streams, and o can be up to 150g/l, usually from 75 to 130g/l.

The process of the fourth aspect of the present invention can be carried out by contacting the solvent extractant composition with the aqueous ammoniacal solution. Ambient or elevated temperatures can be employed, often a temperature in the range of from 15 to 60°C, and preferably from 30 to 50°C, is employed. The aqueous solution and 5 the solvent extractant are usually agitated together to maximise the interfacial areas between the two solutions. The volume ratio of solvent extractant to aqueous solution are commonly in the range of from 20:1 to 1:20, and preferably in the range of from 5:1 to 1:5. In many embodiments, to reduce plant size and to maximise the use of solvent extractant, organic to aqueous volume ratios close to 1:1 are maintained by recycle of o one of the streams.

After contact with the aqueous ammoniacal solution, the metal can be recovered from the solvent extractant by contact with an aqueous strip solution having a pH lower than that from which the metal was extracted.

Alternatively, after contact with the aqueous ammoniacal solution, the metal can 5 be recovered from the solvent extractant by contact with aqueous ammoniacal strip solution, particularly aqueous ammoniacal ammonium carbonate solution. The use of aqueous ammoniacal ammonium carbonate solution as a stripping solution is particularly suited to the recovery of metals in the form of metal carbonates, for example Nickel. When an aqueous strip solution having a pH lower than that from which the metal was extracted is employed as a strip solution in the process according to the fourth aspect of the present invention, the aqueous strip solution is usually acidic and is as described for the strip solution in the process of the third aspect of the present invention. When the extracted metal is copper, preferred strip solutions comprise stripped or spent electrolyte from a copper electro-winning cell, typically comprising up to 80g/l, often greater than 40g/l copper and preferably from 50 to 70g/l copper, and up to 220g/l sulphuric acid, often greater than 120g/l sulphuric acid, and preferably from 150 to 180g/l sulphuric acid. The volume ratio of organic solution to aqueous strip solution in the process of the fourth aspect of the present invention is commonly selected to be such so as to achieve transfer, per litre of strip solution, of up to 50g/l of metal, especially copper into the strip solution from the organic solution. In many industrial copper electrowinning processes transfer is often from 10g/l to 35g/l, and preferably from 15 to 20g/l of copper per litre of strip solution is transferred from the organic solution. Volume ratios of organic solution to aqueous solution of from 1:2 to 15:1 and preferably from 1:1 to 10:1 , especially less than 6:1 are commonly employed.

When ammoniacal ammonium carbonate solution is employed as a strip solution in the process of the fourth aspect of the present invention, the ammoniacal ammonium carbonate solution may contain excess ammonia and is preferably stronger than the ammoniacal ammonium carbonate solution used to leach the ore. The concentration of the solution used to recover the metal from the loaded organic phase is preferably in the ranges of NH₃ : 210 to 300 gl^"1, CO₂ : 150 to 250 gl^"1. Preferably, the solution strength is close to NH₃ : 270 gl^"1, CO₂ : 230 gl^"1. The contact between the loaded organic phase the ammoniacal ammonium carbonate solution may be carried out at any appropriate temperature and pressure. Preferably this step is conducted at atmospheric pressure and at a temperature in the range of 20°C to 50°C.

It is preferred that the metal loaded organic phase is contacted with the ammoniacal ammonium carbonate solution for a period of between 30 seconds to 60 minutes. Most preferably the content time is for a period of about 3 minutes.

When the process of the invention is applied to the operation of a continuous counter current mixer-settler apparatus, the organic/aqueous ratio in the stripping cells is preferably in the range of 6:1 to 10:1. This contrasts with the preferred organic/aqueous range in the extraction cells (where comparable organic agents may be used) of 1:1 to 1.2:1.

When the metal to be recovered is Nickel, it is preferred that the nickel loaded organic phase is stripped in a stripping cell at a temperature of about 40°C. The metal that separates into the aqueous phase can be recovered as a metal carbonate by any conventional manner. For example, basic nickel carbonate can readily be recovered by distillation. Nickel can also be recovered effectively from aqueous ammonium carbonate solution by hydrogen reduction under pressure. The recovery technique preferably allows for the NH₃ and CO₂ components of the strip liquor to be recycled to the metal loaded organic stripping stage.

A preferred embodiment of the fifth aspect of the present invention comprises a process for the extraction of a metal from aqueous ammoniacal solution in which: in step 1 , the solvent extraction composition comprising a hydroxyaryl oxime is first contacted with the aqueous ammoniacal solution containing metal, in step 2, separating the solvent extraction composition containing metal-solvent extractant complex from the aqueous ammoniacal solution; in step 3, contacting the solvent extraction composition containing metal-solvent extractant complex with an aqueous strip solution of lower pH than the ammoniacal solution to effect the stripping of the metal from the water immiscible phase; 0 in step 4, separating the metal-depleted solvent extraction composition from the loaded lower pH aqueous solution.

The metal can be recovered from the aqueous strip solution by conventional methods, for example by electrowinning.

A further preferred embodiment of the fifth aspect of the present invention 5 comprises a process for the extraction of a metal from aqueous ammoniacal solution in which: in step 1 , the solvent extraction composition comprising a hydroxyaryl oxime is first contacted with the aqueous ammoniacal solution containing metal, in step 2, separating the solvent extraction composition containing metal-solvent o extractant complex from the aqueous ammoniacal solution; in step 3, contacting the solvent extraction composition containing metal-solvent extractant complex with an aqueous ammoniacal strip solution, particularly aqueous an ammoniacal ammonium carbonate solution, to effect the stripping of the metal from the water immiscible phase; 5 in step 4, separating the metal-depleted solvent extraction composition from the loaded aqueous ammoniacal solution.

The invention is further illustrated, but not limited, by the following examples. Example 1

4-Nonylphenyl acetate (262g) and toluene (370ml) are placed in a 2 litre 3 necked round bottomed flask equipped with a reflux condenser, stirrer, gas scrubber, and addition funnel equipped with its own mechanical stirrer. The system is nitrogen blanketed to avoid flammability hazard and to exclude water. The contents of the flask are heated to reflux while a slurry of aluminium chloride (133.5 g) in toluene (130 ml) is made up in the addition funnel. Once the slurry is homogeneous it is added slowly to the refluxing ester/toluene mixture over a period of 8 hours. Additions are in portions at a declining rate, with most of the slurry being added over the first 2 hours (details of the addition are to be determined). During this addition HCI gas is evolved and is scrubbed out of the exiting nitrogen stream. When addition is complete the mixture is held on reflux a further 2 hours. The reaction mixture is then cooled to 50°C and added slowly to a stirred 2 litre reactor containing 10% hydrochloric acid (500g). The mixture is allowed to stir for 1 hour at 50°C and allowed to settle. The aqueous phase is run off and sent for aluminium recovery. The organic (top) phase is washed with 500 ml water and then with a dilute sodium hydroxide solution (made from 2 grams NaOH pellets in 500 ml water) and then with more water (500 ml). The organic layer is then dehydrated by reflux via a Dean and Stark trap until no more water is removed. The layer is analysed by gas chromatography to establish the nonyl phenol content. It is then cooled to 20°C and 20% Oleum (quantity determined by the nonyl phenol content, 3.5 equivalents of sulphur trioxide per mole nonyl phenol) is added and the mixture is stirred at 20°C for 2 hours. Water (500 ml) is then added with stirring and the resulting mixture is allowed to settle. The lower layer is removed and the top layer is washed with 2X500 ml portions of water, or until the washes are acid free.

The organic layer is transferred to a conventional still (without a fractionating column) of 1 litre capacity and the toluene is stripped off under low vacuum (not below 20mm Hg). The still is then set for high vacuum (7 mm Hg or better) and the main fraction (pure ketone) is distilled over, from 120°C to 170°C.

The distilled ketone is an amber oil 157 grams (60% theory) and has the following typical composition:

2-hydroxy-5-nonylacetophenone 92%

4-nonyl phenol 1%

4-nonylphenyl acetate 4%

Hydrocarbon impurities 3%

Comparison A: Fractional distillation only

Comparison B: Fractional distillation after acetylating during Fries stage

Claims

1. A process for the purification of hydroxyaryl aldehydes and ketones comprising the following steps:

2) washing the mixture obtained in step 1 with water;

3) isolating a second composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone from step 2.

2. A process for the production of a hydroxyaryl oxime comprising the following steps:

3. A composition comprising a hydroxyaryl oxime obtainable by a process comprising the following steps:

1 ) adding a mineral acid to a first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone;

2) washing the mixture obtained in step 1 with water;

4. A process for the extraction of a metal from solution in which an acidic solution containing a dissolved metal is contacted with a solvent extraction composition comprising a water immiscible organic solvent and a solvent extractant, whereby at least a fraction of the metal is extracted into the organic solution, characterised in that the solvent extractant is a composition comprising a hydroxyaryl oxime obtainable by a process comprising the following steps: 1 ) adding a mineral acid to a first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone;

2) washing the mixture obtained in step 1 with water;

0 5. A process for the extraction of a metal from solution in which an aqueous ammoniacal solution containing a dissolved metal is contacted with a solvent extraction composition comprising a water immiscible organic solvent and a solvent extractant, whereby at least a fraction of the metal is extracted into the organic solution, characterised in that the solvent extractant is a composition comprising a hydroxyaryl 5 oxime obtainable by a process comprising the following steps:

2) washing the mixture obtained in step 1 with water;

5 6. A process or composition according to any proceeding claim wherein the hydroxyaryl aldehydes or hydroxyaryl ketones have the formula:

Formula (1 ) o wherein

R¹ is hydrogen or an optionally, substituted hydrocarbyl group R² is an optionally substituted hydroxyaryl group, and salts thereof.

5 7. A process or composition according to any proceeding claim wherein the mineral acid is an acid of sulphur, particularly sulphuric acid and sulphuric acid / sulphur trioxide mixtures, for example oleum; or an acid of phosphorus, particularly phosphoric acid and polyphosphoric acid.

8. A process or composition according to any proceeding claim wherein the first composition comprising a hydroxyaryl aldehyde or a hydroxyaryl ketone is prewashed with a basic solution.