EP4065739A1

EP4065739A1 - Method for recovering gold and/or one or more platinoids present in an acidic aqueous phase

Info

Publication number: EP4065739A1
Application number: EP21705595.3A
Authority: EP
Inventors: Stéphane PELLET-ROSTAING; Guilhem ARRACHART; Raphaël TURGIS; Manuel LEJEUNE; Micheline Draye; Stéphanie MICHEL; Sophie LEGEAI; Fanny MARY; Christian Thomas
Original assignee: TND; Centre National de la Recherche Scientifique CNRS; Universite de Montpellier I; Ecole Nationale Superieure de Chimie de Montpellier ENSCM; Universite de Lorraine; Universite de Montpellier; Universite Savoie Mont Blanc
Current assignee: TND; Centre National de la Recherche Scientifique CNRS; Universite de Montpellier I; Ecole Nationale Superieure de Chimie de Montpellier ENSCM; Universite de Lorraine; Universite de Montpellier; Universite Savoie Mont Blanc
Priority date: 2020-01-23
Filing date: 2021-01-22
Publication date: 2022-10-05
Also published as: FR3106597B1; FR3106597A1; WO2021148758A9; WO2021148758A1

Abstract

The present invention relates to a method for recovering one or more metals M chosen from gold and metals from the platinum group contained in an acidic aqueous phase A1, said method comprising the following steps: (1) extracting the metal(s) M from the acidic aqueous phase A1, said step comprising the following steps (1a) and (1b): (1a) bringing the acidic aqueous phase A1 into contact with a water-immiscible phase A2, whereby, after phase separation, an aqueous phase A1' and a phase A2' comprising the metal(s) M are obtained; subsequently (1b) collecting the phase A2'. (2) recovering the metal(s) M present in the phase A2' as obtained at the end of step (1b). The phase A2 is chosen from a phase A21 comprising a malonamide and an ionic liquid LI, and a phase A22 comprising a functionalised ionic liquid LIF comprising a malonamide group and the recovery step (2) is chosen from: (2') electroplating, and (2") back-extracting, excluding recovering, only the palladium as the metal M when the phase A2 consists of the phase A21.

Description

Process for recovering gold and / or one or more platinoids present in an acidic aqueous phase

Technical area

The present invention relates to the field of the extraction of one or more metals, denoted M, chosen from gold and metals of the platinum group, this or these metals M being contained in an acidic aqueous phase.

It relates more specifically to a process for extracting this or these metals M which comprises bringing the acidic aqueous phase into contact with a particular phase immiscible with water.

The invention also relates to a process for recovering this or these metals M chosen from gold and metals of the platinum group which implements the extraction process which has just been mentioned.

The acidic aqueous phase from which can be extracted, or from which can be recovered, this or these metals M can in particular be a solution resulting from the acid attack of a natural or urban mineral comprising this or these metals M.

The present invention finds an application in particular in the treatment of industrial waste, such as waste electrical and electronic equipment, with a view to recovering the metal or metals M which are present therein.

State of the prior art

The metals of the platinum group, also called platinoids, refer to the elements of the periodic table which are platinum (Pt), palladium (Pd), osmium (Os), iridium (Ir), ruthenium (Ru) and rhodium (Rh).

These platinoids, which have very similar chemical properties, are at the origin of a large number of innovative technologies, including heterogeneous catalysis, homogeneous catalysis and renewable energies. It is in the automotive catalysis sector that the use of platinoids, and in particular palladium, is most important. Palladium is also ubiquitous in the electrical industry and electronic since it is used in motherboards, multilayer capacitors and other printed circuits of components intended for electrical and electronic equipment.

Gold (Au), which is characterized by exceptional physical and chemical properties, is also a key material for innovative technologies. Because of its electrical and thermal conductivity, its resistance to corrosion and its ease of shaping and / or forming alloys, gold is widely used in the field of electricity and electronics. , for example in contacts, connectors or even films used in components of electrical and electronic equipment.

For obvious reasons, the recovery of gold and platinoids, which are in particular contained in such components, is of undeniable interest, both economically, given the high cost of these metals, and from an environmental standpoint.

More generally, the recycling of production waste of these components as well as that of waste electrical and electronic equipment, also called "WEEE" or "D3E", constitute an unconventional and alternative source of access to gold. and platinoids, which is part of an economic and sustainable development approach.

If the pyrometallurgical method is still used, we observe that the hydrometallurgical method is more and more topical to extract and recover the noble metals such as platinoids, gold and silver (Ag) contained in these different wastes.

The recovery of noble metals by the hydrometallurgical route comprises a step of dissolving the production waste and D3E then one or more steps of separation, in particular by liquid / liquid extraction, of the metallic elements.

In the case of platinoids, the dissolving step generally uses a concentrated acidic aqueous solution, such as a solution comprising hydrochloric acid, nitric acid or aqua regia, to achieve complete dissolution of the waste. comprising these platinoids. The acidic aqueous solution containing the dissolved metallic elements is then brought into contact with an organic phase comprising an extractant to obtain the extraction of these metallic elements.

Many extractants of the amines, ketones and sulfur or phosphorus type derivatives have been proposed for extracting palladium dissolved in a solution of nitric acid. However, these extractants are not completely satisfactory in terms of performance and extraction selectivity of palladium vis-à-vis other metal cations. In addition, the stability in a nitric medium of certain extractants is limited.

To remedy these drawbacks, document WO 2016/008932, referenced [1] in the remainder of the present description, proposes a process for the selective extraction of palladium contained in an acidic aqueous solution further comprising nitric acid. and other metal cations. The extraction described in document [1] comprises in particular a step of bringing the acidic aqueous solution into contact with an organic phase comprising a malonamide containing no sulfur atom as extractant, and an organic diluent or solvent. , such as n-heptane or toluene. Among the various malonamides described, N, N'-dimethyl-N, N'-dioctylhexylethoxymalonamide (DMDOHEMA) is more particularly preferred.

Although document [1] indicates that the extraction of palladium from an acidic aqueous solution comprising up to 3 mol / L of nitric acid is efficient and selective, it is observed that only 50% of the Pd initially present in a solution. aqueous comprising 1 mol / L of nitric acid and 9 other metal cations are extracted by means of an organic phase comprising 0.3 mol / L of DMDOHEMA in n-heptane, which corresponds to a distribution coefficient of palladium D _Pd equal to 1. In addition, there is a significant decrease in the selectivity of the extraction of palladium with respect to neodymium S _{Pd / Nd} from an acidic aqueous solution comprising 2 mol / L of nitric acid and more.

In the case of gold, the dissolution step can be carried out by means of hydrochloric acid and the actual extraction is carried out by means of organic phases comprising, as extractant, an amine or a compound comprising sulfur and / or an amide group, this extractant being diluted in a non-polar organic solvent such as an aliphatic solvent. However, the organic solvents which are used as a mixture with these extractants known to extract palladium and gold can be volatile and flammable, which constitutes a significant drawback in terms of industrial and environmental safety.

As an alternative to the use of traditional organic solvents as extraction solvents, it is now proposed to use ionic liquids which are salts having a melting point of less than or equal to 100 ° C and often even lower. at room temperature. Ionic liquids, which typically consist of an organic cation and an organic or inorganic anion, are characterized by high thermal stability, near zero vapor pressure, very low flammability as well as easy recycling, which presents real advantages in terms of industrial implementation.

The extraction of platinoids and / or gold contained in acidic aqueous solutions by means of phases comprising ionic liquids has already been envisaged to date.

Thus, the publication by K. Sasaki et al. ("Extraction of Pd (ll), Rh (lll) and Ru (lll) from HNO ₃ aqueous solution to betainium bis (trifluoromethanesulfony) imide ionic liquid", Dalton Transactions, 2014, 43 (15), 5648-5651), ci -after referenced [2], relates to the extraction of palladium, rhodium and ruthenium contained in aqueous solutions also comprising nitric acid, by means of three different hydrophobic ionic liquids, in this case bis- betainium (trifluoromethanesulfonyl) imide [Hbet] NTf ₂ , trimethylpropylammonium bis- (trifluoromethanesulfonyl) imide [TMPA] NTf ₂ and choline bis (trifluoromethanesulfonyl) imide [choline] NTf ₂ .

However, it is observed that, in publication [2], the acidic aqueous solutions from which the platinoids have been extracted comprise at most 2 mol / L of nitric acid.

IGBN's publication Makertihartha et al. ("Solvent extration of gold using ionic liquid based process", AIP Conférence Proceedings, 2017, 030008, 1-8), hereinafter referenced [3], lists the ionic liquids which have been described by the literature for liquid / liquid gold extraction. According to publication [3], the parameter which is important for optimizing the performance of extraction using ionic liquids is the choice of the anion and the cation forming the ionic liquid.

If, as reported in the publication [3], the potential for extracting certain ionic liquids has been demonstrated, it is observed that in the case where gold is extracted from acidic aqueous solutions, these solutions all comprise acid. hydrochloric.

The aim of the present invention is therefore to overcome the operating limitations mentioned above and to provide a process making it possible to efficiently extract gold and / or one or more platinoids, in particular palladium, present in an aqueous phase. acid formed by an aqueous solution comprising an inorganic acid, in particular nitric acid, regardless of the concentration of inorganic acid in this solution and, in particular in the case of nitric acid, that this concentration falls within in the intervals described in documents [1] and [2] or else it is greater than or equal to 3 mol / L.

In addition to being efficient, this process must also be able to make it possible to extract the gold and / or the platinoid (s) with a marked selectivity with respect to the other metals and impurities which are also present in the acidic aqueous solution.

Another aim of the present invention is to provide a process making it possible to efficiently recover gold and / or one or more platinoids, in particular palladium, present in an acidic aqueous phase comprising such an inorganic acid. This recovery process must, moreover, be able to be carried out in a reduced number of stages and to be implemented under conditions which are as gentle as possible, so as to reduce the health and environmental risks.

Disclosure of the invention

The above-mentioned goals and others are achieved, firstly, by a process for extracting one or more metals M chosen from among gold and the metals of the platinum group contained in an acidic aqueous phase A1, this process comprising the following successive steps (la) and (lb):

(Ia) bringing the acidic aqueous phase A1 into contact with a water-immiscible A2 phase, whereby one obtains, after phase separation, an aqueous phase A1 'and an A2' phase comprising the metal (s) M ; then

(lb) a collection of phase A2 '.

In the extraction process according to the invention, phase A2 is chosen from:

- a phase A21 comprising a malonamide and an ionic liquid L1, and

- A phase A22 comprising a functionalized ionic liquid LIF comprising a malonamide group.

The above-mentioned goals and others are achieved, secondly, by a process for recovering one or more metals M chosen from gold and the metals of the platinum group contained in an acidic aqueous phase A1, this method comprising the following successive steps (1) and (2):

(1) extraction of the metal (s) M from the acidic aqueous phase A1 by an extraction process as defined above and specified in the remainder of the present description; and

(2) recovery of the metal (s) M present in phase A2 ′ as obtained at the end of step (1).

In the recovery process according to the invention, phase A2 is chosen from:

- a phase A21 comprising a malonamide and an ionic liquid L1, and

- A phase A22 comprising a functionalized ionic liquid LIF comprising a malonamide group, and the recovery step (2) is chosen from:

(2 ') an electroplating, and (2 ") back-extraction, excluding the recovery of only palladium as metal M when phase A2 is formed by phase A21.

The characteristics common to the extraction and recovery processes which are the subject of the present invention will be described below.

The choice of a phase A2 which comprises a malonamide, either mixed with an ionic liquid (phase A21), or as a functional group of an ionic liquid (phase A22), makes it possible to extract and, where appropriate, to recover, with a high-performance yield, gold and / or one or more platinoids, and in particular palladium, from an acidic aqueous phase A1 which contains it or them, whether this acidic aqueous phase comprises nitric acid or another inorganic acid, such as sulfuric acid, under conditions of industrial safety and optimized environmental safety by using ionic liquids.

In particular, the extraction and recovery processes according to the invention are characterized by extraction performance and, consequently, recovery performance which is in particular much higher than that which can be achieved with an extraction process such as than that described by document [1] which uses an organic phase comprising a malonamide and an organic solvent.

The processes according to the invention also make it possible to extract and recover gold and / or the platinoid (s), and palladium in particular, which are present in an acidic aqueous phase with remarkable selectivity towards vis-à-vis other metals and impurities also present in this acidic aqueous phase A1, in particular vis-à-vis copper and silver.

In a first variant of the processes according to the invention, phase A2 is a phase denoted A21 which comprises a malonamide and an ionic liquid denoted L1.

In other words, in this phase A21, the extractant is formed by the malonamide, the ionic liquid L1 providing the function of diluent or solvent.

In one embodiment of this first variant of the processes according to the invention, the malonamide of phase A21 corresponds to the following formula (I): in which

- R ₁ , R ₂ , R ₃ and R ₄ represent, independently of one another: a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 20 carbon atoms and optionally one or more heteroatoms; or a hydrocarbon-based group, saturated or unsaturated, comprising one or more rings of 3 to 8 carbon atoms, said group possibly being branched and / or comprising one or more heteroatoms; and

- R ₅ represents:

. a hydrogen atom;

. a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 20 carbon atoms and optionally one or more heteroatoms; Where

. a saturated or unsaturated hydrocarbon group comprising one or more rings of 3 to 8 carbon atoms, said group possibly being branched and / or comprising one or more heteroatoms.

In what precedes and in what follows, we mean:

- by "hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 20 carbon atoms and optionally one or more heteroatoms", any group formed from a hydrocarbon chain, linear or branched, which comprises between 1 and 20 atoms of carbon in total, the chain of which may be saturated or, on the contrary, contain one or more double or triple bonds and whose chain may be interrupted by one or more heteroatoms or substituted by one or more heteroatoms or by one or more substituents comprising a heteroatom; - By "hydrocarbon group, saturated or unsaturated, comprising one or more rings of 3 to 8 carbon atoms, said group possibly being branched and / or comprising one or more heteroatoms", any hydrocarbon group comprising one or more rings, each ring comprising between 3 and 8 carbon atoms in total and, where appropriate, a linear or branched hydrocarbon chain. This or these rings and / or the hydrocarbon chain, when it is present, can be saturated or, on the contrary, comprise one or more double or triple bonds, and can comprise one or more heteroatoms or be substituted by one or more heteroatoms or with one or more substituents comprising a heteroatom; and

- by `` heteroatom '', any atom other than a carbon atom or a hydrogen atom, this atom being, for example, a nitrogen atom, an oxygen atom or a phosphorus atom .

In addition, the expression "between ... and ..." which has just been used to define the intervals and which is used in the remainder of the present application, must be understood as defining not only the values of l 'interval, but also the values of the limits of this interval.

In an advantageous embodiment, the malonamide of phase A21 corresponds to formula (I) in which

- R ₁ , R ₂ , R ₃ and R ₄ represent, independently of one another, an alkyl group comprising from 1 to 10 carbon atoms; and

- R ₅ represents a hydrogen atom, an alkyl group comprising from 4 to 16 carbon atoms or an alkoxy group comprising from 4 to 10 carbon atoms.

The malonamide of phase A21 can in particular be:

- N, N, N ', N'-tetrahexylmalonamide (THEMA),

- N, N'-dimethyl-N, N'-dibutyltetradecylmalonamide (DMDBTDMA),

- N, N'-dimethyl-N, N'-dioctylhexylethoxymalonamide (DMDOHEMA),

- N, N'-dimethyl-N, N'-dioctyloctylmalonamide (DMDOOMA),

- N, N'-dimethyl-N, N'-dioctylhexylmalonamide (DMDOHxMA), - N, N'-dimethyl-N, N'-dioctylheptylmalonamide (DMDOHpMA), or

- N, N'-dimethyl-N, N'-dibutyldodecylmalonamide (DMDBDDEMA).

Preferably, the malonamide is chosen from THEMA and DMDOHEMA which respectively correspond to the following semi-developed formulas:

In addition to the malonamide, phase A21 comprises an ionic liquid L1.

If in a preferred embodiment of the first variant of the processes according to the invention, phase A21 comprises only one ionic liquid L1, nothing prevents this phase A21 from comprising two, three, or even more, ionic liquids L1. . As seen above, the ionic liquid L1 comprises an organic cation and an anion. From the point of view of nomenclature, the cation is noted in square brackets and indicated first.

In a particular embodiment, the organic cation of the ionic liquid Ll comprises a nitrogenous group chosen from the group consisting of a quaternary ammonium, cyclic or non-cyclic, a phosphonium, a piperidinium, a pyridinium, a pyrrolidinium, a piperazinium and an imidazolium , it being specified that these nitrogenous groups are respectively symbolized by “A”, “P”, “Pip”, “Py”, “Pyr”, “Piperaz” and “IM”.

In an advantageous embodiment, the organic cation of the ionic liquid L1 comprises a nitrogenous group chosen from the group consisting of a piperidinium, a pyridinium, a pyrrolidinium, a piperazinium and an imidazolium. In a preferred embodiment, the organic cation of the ionic liquid U is chosen from the group consisting of a dialkylpiperidinium, an alkylpyridinium, an N, N'-dialkylpiperazinium and an N, N'-dialkylimidazolium.

In a particular embodiment, the anion of the ionic liquid U is an organic anion.

In an advantageous embodiment, the anion of the ionic liquid U is chosen from bis- (trifluoromethanesulfonyl) imide, symbolized by “NTf ₂ ”, hexafluorophosphate, noted “PF ₆ ”, and bis- (fluorosulfonyl) imide , denoted "N (S0 ₂ F) ₂ " or "FSI". In a preferred embodiment, the anion of the ionic liquid U is bis- (trifluoromethanesulfonyl) imide NTf ₂ , also called bis-trifluorosulfonimide.

As examples of ionic liquids L1, the following compounds may be mentioned:

- ethylbutylpiperidinium bis- (trifluoromethanesulfonyl) imide, symbolized by [EBPip] NTf ₂ , of formula: lebis- (trifluoromethanesulfonyl) ethyloctylpiperidinium imide, symbolized by [EOPip] NTf ₂ , of formula: - lebis- (trifluoromethanesulfonyl) imide of N-octyl- N-methylimidazolium, symbolized by [OMIM] NTf ₂ , of formula:

In a second variant of the processes according to the invention, phase A2 is a phase called A22 which comprises an ionic liquid which can be qualified as functionalized ionic liquid, denoted LIF, since this ionic liquid LIF comprises a functional group, in l species a malonamide group.

In other words, in this phase A22, the functionalized ionic liquid LIF performs not only the function of organic solvent or diluent but also that of extractant.

In one embodiment of this second variant of the processes according to the invention, phase A22 can be constituted by the functionalized ionic liquid LIF, that is to say, that it can comprise only the functionalized ionic liquid LIF.

In another embodiment, phase A22 can comprise the functionalized ionic liquid LIF in admixture with one or more ionic liquids L1.

The functionalized ionic liquid LIF comprises an organic cation, an anion as well as a malonamide group.

In a particular embodiment, the organic cation of the LIF functionalized ionic liquid comprises a nitrogenous group chosen from the group consisting of a piperidinium, a pyridinium, a pyrrolidinium, a piperazinium and an imidazolium.

In an advantageous embodiment, the organic cation of the LIF functionalized ionic liquid is chosen from the group consisting of a dialkylpiperidinium, an alkylpyridinium, an N, N'-dialkylpiperazinium and an N, N'-dialkylimidazolium.

In a particular embodiment, the anion of the functionalized ionic liquid LIF is chosen from bis- (trifluoromethanesulfonyl) imide, hexafluorophosphate and bis (fluorosulfonyl) imide.

In an advantageous embodiment, the anion of the functionalized ionic liquid LIF is bis- (trifluoromethanesulfonyl) imide NTf ₂ . In a particular embodiment, the malonamide group of the LIF functionalized ionic liquid of phase A22 corresponds to the following formula (II): in which

- R ₁ , R ₂ , R ₃ and R ₄ represent, independently of each other:

. a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 20 carbon atoms and optionally one or more heteroatoms; Where . a hydrocarbon-based group, saturated or unsaturated, comprising one or more rings of 3 to 8 carbon atoms, said group possibly being branched and / or comprising one or more heteroatoms; and

- R 'represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 2 to 12 carbon atoms and optionally one or more heteroatoms, the malonamide group being linked by a covalent bond (materialized by the dotted line) to the cation organic ionic liquid functionalised LIF.

The functionalized ionic liquid LIF comprising the malonamide group can be synthesized according to the following reaction scheme: With reference to this reaction scheme, the first step is to synthesize malonamide by reacting diethyl malonate with a secondary amine. The alkylation of malonamide is then carried out from a dibromo compound. The alkylated malonamide thus obtained is then reacted with an amine, such as methylimidazole or ethylpiperidine, to form the quaternary amine. The functionalized ionic liquid LIF is then obtained by exchange of the halide anion (Br) with the bis- (trifluoromethanesulfonyl) imide anion NTf ₂ -.

By way of example of ionic liquids functionalized LIF, there may be mentioned the following compound: - lebis- (trifluoromethanesulfonyl) imide of 1- (6- (dibutylamino) -5-

(dibutylcarbamoyl) -6-oxohexyl) -1-ethylpiperidin-1-ium, of the formula:

In one embodiment of the extraction and recovery processes according to the invention, according to their first or second variant, the acidic aqueous phase A1 is a solution resulting from the acid attack, typically by one or more inorganic acids, of a natural ore or an urban ore comprising one or more metals M chosen from gold (Au) and the metals of the platinum group such as platinum (Pt), palladium (Pd), osmium (Os) , iridium (Ir), ruthenium (Ru) and rhodium (Rh). By “urban ore” is meant the source which comes in particular from the recycling of industrial and domestic waste such as waste electrical and electronic equipment, also called “WEEE” or “D3E”. In a particular embodiment, the acidic aqueous phase A1 comprises at least one inorganic acid chosen from the group consisting of nitric acid, sulfuric acid and hydrochloric acid.

In an advantageous embodiment, the acidic aqueous phase A1 comprises at least nitric acid.

In a preferred embodiment, the inorganic acid of the aqueous acidic phase A1 is nitric acid.

In a particular embodiment, the acidic aqueous phase A1 has a total molar concentration of inorganic acid (s) of at least 0.1 mol / L, advantageously of at least 1 mol / L.

The total molar concentration of inorganic acid (s) is preferably between 3 mol / L and 7 mol / L.

In a more particularly advantageous embodiment of the processes according to the invention, the metal or metals M are chosen from palladium and gold.

As already mentioned above, the present invention relates, secondly, to a process for recovering one or more metals M chosen from gold and the metals of the platinum group contained in an acidic aqueous phase A1, this process recovery comprising the following successive steps (1) and (2):

(1) extraction of the metal (s) M from the acidic aqueous phase A1 by an extraction process as defined above, this extraction step (1) comprising the following successive steps (la) and (lb):

(Ia) bringing the acidic aqueous phase A1 into contact with a water-immiscible A2 phase, whereby, after phase separation, an aqueous phase A1 ′ and an A2 ′ phase comprising the metal (s) M are obtained ; then

(lb) a collection of phase A2 '; and

(2) recovery of the metal (s) M present in phase A2 ′ as obtained at the end of step (lb). In the recovery process according to the invention, phase A2 is chosen from:

- a phase A21 comprising a malonamide and an ionic liquid L1, and

(2 ') an electroplating, and

(2 ") back-extraction, excluding the recovery of only palladium as metal M when phase A2 is formed by phase A21.

In this recovery process according to the invention, the extraction step (1) is carried out by the extraction process as defined above, it being specified that the advantageous and preferential characteristics of this step (1) of extraction, such as those relating to the metals M and to the compositions of the acidic aqueous phase A1 as well as of the phases A21 and A22, can be taken alone or in combination.

The inventors have demonstrated the fact that both step (2 ″) of back-extraction of the metal (s) M and step (2 ′) of electrodeposition of the metal (s) M are particularly efficient and make it possible to recover quantitatively the or the metals M which have been previously extracted from the acidic aqueous phase A1.

As indicated above, the recovery step (2) is chosen from:

(2 ') an electroplating, and

Thus, when the recovery step (2) is carried out by carrying out an electrodeposition step (2 '), it is possible to recover, from the acidic aqueous phase A1 in which they are contained, one or more several M metals chosen from Au, Pt, Pd, Os, Ir, Ru and Rh, regardless of the A2 phase implemented in the extraction step (1), that this extraction step (1) or formed by an A21 phase comprising a malonamide and an ionic liquid U or by an A22 phase comprising a functionalized ionic liquid LIF comprising a malonamide group. When the extraction step (1) is carried out with a phase A2 formed by a phase A22 and the recovery step (2) is carried out by the implementation of a de-extraction step (2 "), it is also possible to recover one or more metals M chosen from Au, Pt, Pd, Os, Ir, Ru and Rh from the acidic aqueous phase A1 in which this or these metals M are contained.

When the extraction step (1) is implemented with a phase A2 formed by a phase A21 and the recovery step (2) is performed by the implementation of a back-extraction step (2 "), it is possible to recover, from the acidic aqueous phase A1 in which they are contained, one or more metals M chosen from Au, Pt, Pd, Os, Ir, Ru and Rh, with the exclusion of palladium alone. other words, in this particular configuration of steps (1) and (2 ") implementing a phase A21, it is possible to recover either a (single) metal M chosen from Au, Pt, Os, Ir, Ru and Rh , or at least two M metals chosen from Au, Pt, Pd, Os, Ir, Ru and Rh. Thus, in this configuration, the palladium can be back-extracted together with one or more of these other M metals.

In particular, and as will be seen in the examples described below, the recovery process according to the invention makes it possible to jointly extract or deposit jointly, to co-extract or to co-deposit, gold and palladium .

This finding is all the more surprising since the back-extraction step (2 ″) just like the electrodeposition step (2 ′) can be carried out directly with the phase A2 ′ as obtained at the end of the phase. step (lb), that this phase A2 ′ further comprises a malonamide and an ionic liquid originating from phase A21 or else a functionalized ionic liquid LIF comprising a malonamide group and, where appropriate, an ionic liquid originating from phase A22.

The recovery process according to the invention therefore has a particularly advantageous implementation advantage from an industrial standpoint, with a number of steps which is particularly limited in the case where the recovery step (2) is formed by one step. (2 ') of electroplating. In a particular embodiment, step (2 ") of back-extraction of the recovery process according to the invention comprises the following successive steps (2" a) and (2 "b):

(2 "a) contacting phase A2 'with an aqueous phase A3, whereby, after phase separation, a phase A2" and an aqueous phase A3' comprising the metal (s) M are obtained; then (2 "b) a collection of phase A3 '.

Other characteristics and advantages of the invention will appear better on reading the examples which follow and which relate to the synthesis of a functionalized ionic liquid LIF comprising a malonamide group as well as to tests which demonstrate the ability phases A21 and A22 in extracting the palladium and / or gold from acidic aqueous phases A1 in which they are present.

It is specified that these examples, which are described in particular in relation to the appended FIGS. 1 to 8, are given only by way of illustration of the subjects of the invention and do not in any way constitute a limitation of these subjects.

Brief description of the drawings

Figure 1 illustrates the influence of the molar concentration of nitric acid (denoted [HNO ₃ ] and expressed in mol / L) in an acidic aqueous phase A1 comprising palladium Pd on the distribution coefficient of this Pd (denoted by D _Pd ) when this Pd is extracted from said acidic aqueous phase A1 by means of an A21 phase comprising 0.1 M of DMDOHEMA in [EBPip] NTf ₂ .

Figure 2 illustrates the influence of the molar concentration of nitric acid (denoted [HNO3] and expressed in mol / L) in an acidic aqueous phase A1 comprising Pd on the distribution coefficient of this Pd (denoted by D _Pd ) when this Pd is extracted from said acidic aqueous phase A1 by means of an A21 phase comprising 0.1 M of DMDOHEMA in [EOPip] NTf ₂ .

FIG. 3 illustrates the influence of the molar concentration of DMDOHEMA (denoted [DMDOHEMA] and expressed in mmol / L or mM) in a phase A21 comprising, in addition, [EBPip] NTf ₂ or [EOPip] NTf ₂ as ionic liquid , on the distribution coefficient of Pd (denoted by D _Pd ) during extractions of this Pd from an acidic aqueous phase A1 in which it is contained by means of said phase A21.

Figure 4 illustrates the influence of the mass concentration of Pd (noted [Pd] and expressed in g / L) contained in an acidic aqueous phase A1 on the distribution coefficient of this Pd (noted D _Pd ) when this Pd is extracted of said acidic aqueous phase A1 by means of an A21 phase comprising 0.1 M of DMDOHEMA in [EBPip] NTf ₂ .

FIG. 5 illustrates the change in the mass concentration of Pd extracted (denoted [Pd] extr and expressed in g / L) of an acidic aqueous phase A1 as a function of the initial mass concentration of Pd (denoted [Pd] mi and expressed in g / L) present in this acidic aqueous phase A1 when this Pd is extracted therefrom by means of a phase A21 comprising 0.1 M of DMDOHEMA in [EBPip] NTf ₂ .

FIG. 6 is a histogram showing the evolution of the distribution coefficients of Pd, Ag and Cu (respectively denoted D _Pd , D _Ag and D _Cu ) as a function of the initial mass concentrations of Pd, Ag and Cu (respectively denoted [Pd], [Ag] and [Cu] and expressed in mmol / L or mM) present in an acidic aqueous phase A1 when these Pd, Ag and Cu are extracted therefrom by means of an A21 phase comprising 0.1 M of DMDOHEMA in [EBPip] NTf ₂ .

Figure 7 illustrates the curves obtained in cathodic voltammetry showing the evolution of the current density (noted j and expressed in mA.cm ^-2 ) as a function of the potential (noted E and expressed in V vs Ag ^{+ l} / Ag) applied , under an inert atmosphere, to a system comprising the glassy carbon cathode in two reference Pd solutions, one comprising 0.5 g / L of Pd in [EBPip] NTf ₂ (curve represented by a continuous line) and l another comprising 0.5 g / L of Pd in a mixture of 0.1 M of DMDOHEMA in [EBPip] NTf ₂ (curve represented by a broken line).

Figure 8 illustrates the curves obtained in cathodic voltammetry showing the evolution of the current density (noted j and expressed in mA.cm- ² ) as a function of the potential (noted E and expressed in V vs Ag ^{+ I} / Ag) applied , under an inert atmosphere, to the system comprising the glassy carbon cathode in the reference solution comprising 0.5 g / L of Pd in a mixture of 0.1 M of DMDOHEMA in [EBPip] NTf ₂ (curve represented by a broken line) and in a phase A2 ′ comprising the Pd obtained from extractions carried out by means of a particular phase A21 (curve represented by a continuous line).

Detailed description of particular embodiments 1. Synthesis of a functionalized ionic liquid LIF comprising a malonamide group

The LIF functionalized ionic liquid comprising a malonamide group which has been synthesized is 1- (6- (dibutylamino) -5- (dibutylcarbamoyl) -6-oxohexyl) -1-ethylpiperidin-1-ium bis- (trifluoromethanesulfonyl) imide. This ionic liquid was synthesized from N, N, N ', N'-tetrabutylmalonamide by the implementation of steps 1.1. to 1.3. described below.

1.1. Synthesis of N, N, N ', N'-tetrabutylmalonamide

The reaction implemented for the synthesis of N, N, N ', N'-tetrabutylmalonamide is as follows:

The operating protocol followed for the synthesis of N, N, N ', N'-tetrabutylmalonamide is as follows: in a Teflon microwave reactor, diethyl malonate (21.10 g; 20 mL; 0.131 mol; 1 eq.) And dibutylamine (68.10 g; 89 mL; 0.526 mol; 4 eq.). The mixture is then heated at 180 ° C. in a microwave for 2 h (first at 550 W for 15 min then at 300 W for 1 h 45). After cooling, the colorless solution is transferred to a flask and the excess dibutylamine is distilled off under vacuum. The residue is then washed with 50 mL of reverse osmosis water and then extracted with 100 mL of ethyl acetate. The organic phase is washed with 100 mL of an aqueous HCl solution (1 N) and then twice with 100 mL of reverse osmosis water before to be dried over magnesium sulfate MgS04. After evaporation, the residue is purified by chromatography on a silica column, first with cyclohexane (100) then with a cyclohexane / ethyl acetate mixture (60/40).

The N, N, N ', N'-tetrabutylmalonamide obtained is in the form of a very slightly yellow oil (30.79 g; 0.094 mol; yield of 72%).

The characterization data for N, N, N ', N'-tetrabutylmalonamide are as follows:

¹ H NMR _{(CDCl 3} ; 400.13 MHz; 25 ° C) δ (ppm): 0.90 (t, 6H, ³ J = 7.3 Hz, NCH ₂ CH ₂ CH ₂ CH ₃ ); 0.94 (t, 6H, ³ J = 7.3Hz, NCH ₂ CH ₂ CH ₂ CH ₃ ); 1.25-1.36 (m, 8H, NCH ₂ CH ₂ CH ₂ CH ₃ ); 1.48-1.58 (m, 8H, NCH ₂ CH ₂ CH ₂ CH ₃ ); 3.28-3.35 (m, 8H, NCH ₂ CH ₂ CH ₂ CH ₃ ); 3.43 (s, 2H,

NC (O) CH ₂ C (O) N).

1.2. Synthesis of 2- (4-bromobutyl) - N, N, N ', N'-tetrabutylmalonamide

The reaction implemented for the synthesis of 2- (4-bromobutyl) - N, N, N ', N'-tetrabutylmalonamide is as follows:

The operating protocol followed for the synthesis of 2- (4-bromobutyl) - N, N, N ', N'-tetrabutylmalonamide is as follows: in a first 100 mL flask, sodium hydride NaH (60 % in oil) (0.499 g; 0.028 mol; 1.1 eq.) previously washed three times with 20 mL of anhydrous cyclohexane, then with 80 mL of freshly distilled 2-methyltetrahydrofuran. The mixture is then placed at 0 ° C. In a second flask, the N, N, N ', N'-tetrabutylmalonamide (6.17 g; 0.019 mol; 1 eq.) Are introduced as well as 20 mL of 2-methyltetrahydrofuran under argon. The malonamide solution is also placed at 0 ° C, then added very slowly to the solution of NaH by cannula. At the end of the addition, the resulting solution is stirred at 0 ° C. under argon until the evolution of gas has completely disappeared. Dibromobutane (12.24 g; 0.056 mol; 3 eq.) Is then added. The mixture is allowed to return to ambient temperature and is heated at 80 ° C. for 24 h under argon. After cooling, 2 ml of ethanol are added and the mixture is concentrated on a rotary evaporator. The residue obtained is dissolved in 100 ml of ethyl acetate. The organic phase is washed three times with 100 mL of reverse osmosis water. The ethyl acetate is evaporated off and the oil obtained is purified by chromatography on a silica column, first with cyclohexane (100) then with a cyclohexane / ethyl acetate mixture (90/10).

The 2- (4-bromobutyl) - N, N, N ', N'-tetrabutylmalonamide obtained is in the form of a very slightly yellow oil (8.73 g; 0.018 mol; yield of 94%).

The characterization data for 2- (4-bromobutyl) - N, N, N ', N'-tetrabutylmalonamide are as follows:

¹ H NMR _{(CDCl 3} ; 400.13 MHz; 25 ° C) δ (ppm): 0.82 (t, 6H, ³ J = 7.3 Hz, NCH ₂ CH ₂ CH ₂ CH ₃ ); 0.87 (t, 6H, 1 / = 7.3Hz, NCH ₂ CH ₂ CH ₂ CH ₃ ); 1.16-1.28 (m, 8H, NCH ₂ CH ₂ CH ₂ CH ₃ ); 1.36-1.47 (m, 10H, NCH ₂ CH ₂ CH ₂ CH ₃ and CH ₂ CH ₂ CH ₂ CH ₂ Br); 1.80 (m, 4H, CH ₂ CH ₂ CH ₂ CH ₂ Br and CH ₂ CH ₂ CH ₂ CH ₂ Br); 3.09-3.20 (m, 8H, NCH ₂ CH ₂ CH ₂ CH ₃ ); 3.32 (t, 2H, CH ₂ CH ₂ CH ₂ CH ₂ Br, ³ J = 6.8Hz); 3.41 (t, 1H, NC (O) CHC (O) N, ³ J = 6.6Hz).

1.3. Synthesis of 1- (6- (dibutylamino) -5- (dibutylcarbamoyl) -6-oxohexyl) -1-ethylpiperidin-1- ium bis- (trifluoromethanesulfonyl) imide

The reaction carried out for the synthesis of l- (6- (dibutylamino) -5- (dibutylcarbamoyl) -6- oxohexyl) -1-ethylpiperidin-1-ium bis- (trifluoromethanesulfonyl) imide is as follows:

In a 100 mL flask, are introduced N-ethylpiperidine (4.28 g; 5.2 mL; 0.037 mol; 2 eq.), 2- (4-bromobutyl) - N, N, N ', N' -tetrabutylmalonamide (8.73 g; 0.018 mol; 1 eq.) and acetonitrile (25 mL). The mixture is then heated under argon for 48 to 72 h, the progress of the reaction being followed by thin layer chromatography (TLC) plate. The mixture is then allowed to cool and the excess N-ethylpiperidine and acetonitrile are evaporated off in vacuo. The residue is taken up in 25 ml of reverse osmosis water. The aqueous solution is then washed three times with 50 ml of diethyl ether and then heated to 75 ° C. in the presence of activated carbon (10% by weight). After cooling, the mixture is filtered through Celite and the solution obtained is used directly in the anion metathesis step. The L1NTF2 salt (5.10 g; 0.018 mmol; 1 eq.) Is added to the previous solution. After 3 h of stirring, the two-phase mixture is transferred to a separating funnel. The organic phase is washed three times with 50 ml of reverse osmosis water (silver nitrate test on the washing waters). Then 1 g of activated carbon (approx. 10% by weight) is added and the mixture is heated at 75 ° C overnight. After cooling, the mixture is passed through neutral alumina. The solvent is evaporated off and then the functionalized ionic liquid LIF is dried at 80 ° C. under vacuum for 24 h.

The 1- (6- (dibutylamino) -5- (dibutylcarbamoyl) -6-oxohexyl) -1-ethylpiperidin-1-ium bis- (trifluoromethanesulfonyl) imide obtained is an ionic liquid functionalized LIF which is in the form of a very viscous colorless oil (11.43 g; 0.014 mol; yield of 82%). The characterization data of 1- (6- (dibutylamino) -5- (dibutylcarbamoyl) -6-oxohexyl) -1-ethylpiperidin-1-ium bis- (trifluoromethanesulfonyl) imide are as follows:

¹ H NMR _{(CDCl 3} ; 400.13 MHz; 25 ° C) d (ppm): 0.84 (t, 6H, ³ J = 7.3 Hz, NCH ₂ CH ₂ CH ₂ CH ₃ ); 0.88 (t, 6H, ³ V = 7.3 Hz, NCH ₂ CH ₂ CH ₂ CH _3); 1.18-1.30 (m, 11H, NCH ₂ CH ₂ CH ₂ CH ₃ and NCH ₂ CH ₃ ); 1.37 (q, 2H, (CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ ) _cyde , 1 / = 8.0Hz); 1.40-1.51 (m, 8H, NCH ₂ CH ₂ CH ₂ CH ₃ ); 1.59-1.68 (m, 4H, CH ₂ CH ₂ CH ₂ CH ₂ N); 1.78-1.86 (m, 6H,

(CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ ) _Cycie and CH ₂ CH ₂ CH ₂ CH ₂ N); 3.11-3.15 (m, 6H, CH ₂ CH ₂ CH ₂ CH ₂ N and (CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ ) _cycie ); 3.18-3.27 (m, 8H, NCH ₂ CH ₂ CH ₂ CH ₃ ); 3.31 (q, 2H, NCH ₂ CH ₃ , ³ J = 7.1 Hz); 3.46 (t, 1H, NC (O) CHC (O) N, ³ J = 6.2Hz).

¹⁹ F NMR (CDCI ₃ ; 376.49 MHz; 25 ° C) d (ppm): -78.74 (s, CF ₃ )

2. Methods for evaluating the extracting and de-extracting properties

The efficiency of extraction, or back-extraction, is evaluated by determining the percentage of extraction, or back-extraction, which is calculated from the distribution coefficient of the species in solution.

This measurement of the distribution coefficient of the species in solution is carried out by inductively coupled plasma optical emission spectrometry (in English, Inductively Coupled Plasma - Optic Emission Spectrometry or ICP-OES).

The distribution coefficient of a metallic element M, denoted DM, between phase A2 ′ and acidic aqueous phase A1 ′ is determined by the following equation: with [M] _{A2 '} = concentration of the metallic element M in phase A2' after extraction (in mg / L)

[M] _{A1 '} = concentration of the metallic element M in the aqueous phase A1' after extraction (in mg / L)

[M] _A1 = concentration of the metallic element M in the acidic aqueous phase A1 before extraction (in mg / L)

V _{A1 '} = V _A1 = volume of the aqueous phase A1' or A1 (in mL) V _{A2 '} = V _A2 = volume of phase A2' or A2 (in mL)

The extraction percentage, noted E (%), is determined by the following equation: with [M] A2 = concentration of the metallic element M in phase A2 'after extraction (in mg / L)

[M] AI - concentration of the metallic element M in the acidic aqueous phase A1 before extraction (in mg / L)

DM = distribution coefficient of the metallic element M

V _A1 = V _{A1 '} volume of the aqueous phase A1 or A1' (in mL)

V _A2 = V _{A2 '} volume of phase A2 or A2' (in mL)

The percentage of back-extraction, noted Desex (%), is determined by the following equation: with [M] _A3 , ⁼ concentration of the metallic element M in the aqueous phase A3 'after back-extraction (in mg / L)

[M] _{A2 '} = concentration of the metallic element M in phase A2' after extraction and before back-extraction (in mg / L)

The selectivity of the extraction of the metal M1 with respect to the metal M2, denoted SMI / M2, is determined by the following equation: with D _M1 = distribution coefficient of the metallic element M1, and D _M2 = distribution coefficient of the metallic element M2.

3. Operating protocols Protocol for the preparation of the aqueous acidic phases A1

The acidic aqueous phases A1 are prepared by dissolving the following metal salts, which are introduced directly into an acid solution comprising the inorganic acid under consideration (nitric acid or sulfuric acid) in deionized water:

- for Pd: Pd (NO ₃ ) ₂ , _X H ₂ O

- forAu: AuCl ₃

- forAg: AgNO ₃

- for Cu: Cu (NO ₃ ) ₂ , 2,5H ₂ O

Phases A21

Extraction and recovery tests were carried out using different A21 phases comprising a malonamide and an ionic liquid U chosen from the compounds listed below:

Malonamides

- N, N'-dimethyl-N, N'-dioctylhexylethoxymalonamide (DMDOHEMA)

- N, N, N ', N'-tetrahexylmalonamide (THEMA)

Ionic liquids U

- lebis- (trifluoromethanesulfonyl) ethylbutylpiperidinium imide [EBPip] NTf ₂

- lebis- (trifluoromethanesulfonyl) ethyloctylpiperidinium imide [EOPip] NTf ₂

Phases A22

Extraction and recovery tests were carried out using different A22 phases comprising a functionalized ionic liquid LIF and an ionic liquid U chosen from the compounds listed below:

LIF functionalized ionic liquid

- lebis- (trifluoromethanesulfonyl) imide of l- (6- (dibutylamino) -5- (dibutylcarbamoyl) -6-oxohexyl) -1-ethylpiperidin-1-ium, the synthesis of which has been described above and which will be referred to as TSIL

Ionic liquids U

- lebis- (trifluoromethanesulfonyl) ethyloctylpiperidinium imide [EOPip] NTf ₂ Extraction and back-extraction protocols

The extractions are carried out by bringing the acidic aqueous phase A1 into contact with the A2 phase considered in a volume ratio between the acidic aqueous phase A1 and the A2 phase (V _A1 / V _A2 ) of between 0.1 and 100, in particular of the order of 1 or 2. Phases A1 and A2 are brought into contact for 1 h at 25 ° C. then centrifuged for 5 min at 4000 rpm at 20 ° C. then separated. The extraction kinetics show that thermodynamic equilibrium is reached after 30 min.

The de-extractions are carried out by bringing phase A2 'into contact with aqueous phase A3 in a volume ratio between aqueous phase A3 and phase A2' (V _A3 / V _{A2 '} ) which is between 0.1 and 100, in particular of the order of 1 to 5. Phases A2 ′ and A3 are brought into contact and kept under stirring for 1 h at 25 ° C. then centrifuged for 5 min at 4000 rpm at 20 ° C. then separated. The extraction kinetics show that thermodynamic equilibrium is reached after 30 min.

Evaluation of extraction and back-extraction properties

The extracting properties of the A2 phases (A21 and A22) and de-extracting of the A3 phases were evaluated by measuring the distribution coefficients of the species in solution, by optical emission spectrometry by inductively coupled plasma (in English, Inductively Coupled Plasma - Optic Emission Spectrometry or ICP-OES).

Electroplating protocols

The electrochemical measurements and the electrodeposition experiments were carried out, in certain cases, in an inert atmosphere (argon, H ₂ O, O ₂ <1 ppm), in a glove box (BAG) marketed under the name Labstar by the company MBraun.

When the measurements were carried out outside BAG, the water content of the deposit solutions was determined by coulometric Karl Fischer assay using a reference coulometer 831 KF from the company Metrohm.

The various tests, carried out from 60 ° C. to 110 ° C., were carried out with a conventional assembly with 3 electrodes connected to a reference potentiostat SP-300 from the company BioLogic. The reference electrode developed in the laboratory is a reference Ag ^{+ I} / Ag (0.01 M AgCF ₃ SO ₃ in BMICF ₃ SO ₃ ). This electrode has the advantage of keeping a fixed potential, unlike the pseudo-references conventionally used in an ionic liquid medium. The counter electrode is a glassy carbon electrode.

The tests were carried out on three substrates: mainly on vitreous carbon (Cv), titanium (Ti) and 304L stainless steel (stainless steel) but also on Al, Ni, Cu and Fe, in potentiostatic mode.

The cyclic voltammetry was carried out with a speed of 5 mV / s, starting from the free potential towards cathode potentials. The quantities of Coulomb applied for the deposits are 1 C / cm ² , the area of each electrode being 0.5 cm ² .

The morphology of the deposits was analyzed using a reference scanning electron microscope (SEM) Vega3 from the company Tescan and the chemical analysis EDX with the reference software Esprit 1.9.

The identification of the species present in the phases studied is carried out using the Bragg-Brentano geometry diffractometer of reference D8 ADVANCE from the company Bruker. The wavelength l used is that corresponding to the line K _α1 of copper, ie λ = 1.5405 Å. The diffractograms are analyzed using EVA software from Bruker.

4. Experimental results

Example A: Extraction and recovery of Pd from an acidic aqueous phase A1 with an A21 phase comprising a malonamide and an ionic liquid U

A.1 Pd extraction

A.1.1 To determine the influence of the molar concentration of inorganic acid in the aqueous acid phase A1 on the extraction performance, a series of extractions were carried out by bringing the phases A1 and A21 into contact (with a ratio Following VAI / VA2I = 1):

Phase A1: 500 ppm of Pd in a nitric acid solution of varying concentration, between 0.1 M and 7 M Phase A21: 0.1 M of DMDOHEMA as malonamide

[EBPip] NTf ₂ or [EOPip] NTf ₂ as ionic liquid U It is specified that the unit "M" mentioned below and below corresponds to the abbreviation of the International System unit "mol / THE".

Referring to Figures 1 and 2, which illustrate the evolution of the distribution coefficient D _Pd as a function of the molar concentration of nitric acid in the aqueous acid phase A1, it is observed that the extraction of Pd by a mixture comprising, on the one hand, DMDOHEMA and, on the other hand, either [EBPip] NTf ₂ or [EOPip] NTf ₂ as ionic liquid, is obtained with distribution coefficients D _Pd which are very clearly greater than 1. These coefficients of D _Pd distribution even reach a maximum of 32 for the DMDOHEMA + [EBPip] NTf ₂ mixture and 18 for the DMDOHEMA + [EOPip] NTf ₂ mixture for a nitric acid [HNO3] concentration of 3 M.

It can in particular be observed that the extraction performance of a phase A21 comprising a malonamide diluted in an ionic liquid U are very much greater than that of a phase comprising this same malonamide diluted in an organic solvent.

Indeed, by way of comparison, the extraction of Pd from the same acidic aqueous phase A1 comprising 3 M nitric acid by means of an organic phase formed by a mixture comprising 0.1 M of DMDOHEMA and heptane results in a distribution coefficient D _Pd of a value of 0.62.

A.1.2 To determine the influence of the molar concentration of malonamide in phase A2, in this case A21, on the extraction performance, a series of extractions was carried out by bringing phases A1 and A21 into contact ( with a VAI / VA2I ratio = 1) following:

Phase A1: 500 ppm Pd in 3M nitric acid solution

Phase A21: DMDOHEMA of variable concentration, between 5 mM and

100 mM, as malonamide [EBPip] NTf ₂ or [EOPip] NTf ₂ as ionic liquid U As shown in Figure 3, the extraction performance of Pd from the acidic aqueous phase A1 comprising 500 ppm of Pd in 3M nitric acid se characterized by D _Pd distribution coefficients are greater than 1, even in cases where the extractions are carried out with very low concentrations of DMDOHEMA, in this case from 15 mM.

A slightly more marked extraction performance is also observed when the malonamide DMDOHEMA is diluted in [EBPip] NTf ₂ as ionic liquid L1.

A.1.3 To determine the influence of the mass concentration of Pd contained in the acidic aqueous phase A1 on the extraction performance, a series of extractions was carried out by bringing the phases A1 and A21 into contact (with a VAI ratio / VA2I = 1) following:

Phase A1: Pd of variable concentration, being established between 0.5 g / L and 8 g / L, in a 3 M nitric acid solution Phase A21: 0.1 M of DMDOHEMA and [EBPip] NTf ₂

As shown in figure 4, the extraction performance is obtained with distribution coefficients D _Pd which are greater than 1, even in the case where the initial concentration of Pd is very high, typically 8 g / L.

FIG. 5 shows that the saturation of phase A21 is not reached, even for an initial mass concentration of Pd of 8 g / L.

The extraction of the Pd contained in the acidic aqueous phase A1 by means of the A21 phase comprising a malonamide and an ionic liquid, in this case DMDOHEMA and [EBPip] NTf ₂ , is efficient, even in the case where the acidic aqueous phase A1 has a high mass concentration of Pd.

A.1.4 To evaluate the extraction performance of a phase A21 comprising a malonamide other than DMDOHEMA, in this case THEMA, a series of extractions was carried out by bringing phases A1 and A21 into contact (with a VAI / VA2I ratio = 1) following:

Phase A1: 500 ppm or 1000 ppm Pd in 3M nitric acid solution

Phase A21: 0.25 M or 0.5 M of THEMA as malonamide [EBPip] NTf ₂ or [EOPip] NTf ₂ as ionic liquid L1 The calculated values of the distribution coefficients of Pd D _{Pd as} well as the extraction percentages E (%) are reported in Table 1 below. [Table 1]

Table 1 As shown by the data in Table 1, the extraction of Pd by an A21 phase comprising, on the one hand, THEMA and, on the other hand, either [EBPip] NTf ₂ or [EOPip] NTf ₂ as liquid ionic, is obtained with D _Pd distribution coefficients which are also much greater than 1, with a more marked performance when the THEMA malonamide is mixed with [EOPip] NTf ₂ as ionic liquid L1. A.2 Pd recovery

The Pd which has been extracted by the various phases A21 comprising DMDOHEMA or THEMA as malonamide and an ionic liquid L1 is contained in phase A21 ′. The Pd can then be recovered from this phase A2 ′ either by back-extraction or by electrochemical means, in this case by electrodeposition. A.2.1 By back-extraction

The Pd can be back-extracted from phase A2 'by bringing this phase A2' into contact with an aqueous phase A3, whereby one obtains, after phase separation, a phase A2 "and an aqueous phase A3 'comprising the metal (s) M.

The aqueous phase A3 can advantageously comprise a complexing agent. This complexing agent can be a sulfur-based compound such as a thiourea, a thiosulphate or a metabisulphite, or a polycarboxylic acid such as oxalic acid, hydroxyethylene diamine triacetic acid (HEDTA), ethylene diamine acid. tetra acetic (EDTA) or diethylene triamine penta acetic acid (DTPA).

The aqueous phase A3 can in particular be formed by a thiourea solution at a concentration of 0.1 mol / L, or alternatively by a solution of diethylene triamine penta acetic acid (DTPA) at a concentration of 0.5 M.

The recovery of the Pd can be obtained by bringing the aqueous phase A3 of back-extraction into contact with the phase A2 'considered in a volume ratio between the aqueous phase A3 and the phase A2' (V _A3 / V _{A2 '} ) of between 1 and 5.

Thus, for the THEMA / LI system, a quantitative back-extraction could be demonstrated with a solution of 0.1 M of thiourea and a volume ratio V _A3 / VA2 'of 5.

A.2.2 Electrochemically

A preliminary study carried out on a solution of [EBPip] NTf ₂ in an inert atmosphere shows the possibility of depositing Pd for potentials between -0.5 V vs Ag ^{+ I} / Ag and -1.5 V vs Ag ^{+ I} / Ag, with homogeneous deposits of Pd at E = -0.7 V vs Ag ^{+ I} / Ag in the case of Cv, and at E = -IV vs Ag ^{+ I} / Ag in the case of Ti and stainless steel 304L.

Figure 7 illustrates the cathode part of the voltammograms obtained (T = 60 ° C, v = 5 mV / s, substrate Cv, inert atmosphere):

- in a first reference Pd solution comprising 0.5 g / L of PdCl ₂ in [EBPip] NTf ₂ , and

- in a second reference Pd solution comprising 0.5 g / L of PdCl ₂ in a mixture comprising 0.1 M of DMDOHEMA and [EBPip] NTf ₂ .

With reference to the curves in FIG. 7, it is observed that the presence of DMDOHEMA in a phase comprising Pd and the ionic liquid [EBPip] NTf ₂ causes a shift of the Pd reduction wave towards more negative potentials, characteristic of the formation of a metal complex between Pd (II) and DMDOHEMA. It should be noted that this shift is observed regardless of the substrate (Cv, Ti or 304L stainless steel).

In the presence of DMDOHEMA, it is possible to deposit Pd for potentials ranging from E = -0.5 V vs Ag ^{+ I} / Ag to E = -1.7 V vs Ag ^{+ I} / Ag, with homogeneous deposits of Pd obtained at E = -0.9 V vs Ag ^{+ I} / Ag in the case of Cv, and at E = -1.4 V vs Ag ^{+ I} / Ag in the case of Ti and 304L stainless steel.

FIG. 8 illustrates the cathode part of the voltammograms obtained (T = 60 ° C, v = 5 mV / s, substrate Cv, inert atmosphere):

- in the second reference Pd solution comprising 0.5 g / L of PdCl ₂ in [EBPip] NTf ₂ , and

- in a phase A2 'such as from the extractions described in point A.1 above and carried out from an acidic aqueous solution A1 comprising 0.5 g / L of Pd, by means of phase A21 comprising 0 , 1 M of DMDOHEMA and [EBPip] NTf ₂ .

FIG. 8 shows the presence of the reduction signal towards -IV vs Ag ^{+ I} / Ag during the scanning towards negative potentials which reflects the fact that after the extraction step, the deposition of Pd is possible without that the quality of this deposit is not impacted.

The Pd can be deposited on the 3 substrates by applying a potential corresponding to the most negative peak confirmed by an EDX chemical analysis.

A SEM analysis of the deposits obtained shows that their morphology is different depending on the substrate used, cracked deposits being obtained in the case of Ti.

Identical studies carried out with [EOPip] NTf ₂ instead of [EBPip] NTf ₂ show that the variation in the length of the alkyl chain does not influence the possibility of recovering Pd by electrodeposition, whether on Cv, Ti and 304L stainless steel substrates. Example B: Extraction and recovery of Pd from an acidic aqueous phase A1 comprising other metallic elements by an A21 phase comprising a malonamide and an ionic liquid U

B.1 Extraction of Pd

B.1.1 The selectivity of the extraction of Pd with respect to other metal cations, in particular metal cations which are likely to be present in acidic aqueous solutions as obtained from production waste and / or of waste electrical and electronic equipment D3E, is assessed by carrying out a series of extractions by bringing phases A1 containing Pd, Ag and Cu into contact with phase A21 (with a ratio VAI / VA2I = 1):

Phase A1: [Pd] = 5 mM, [Cu] variable (5, 50 and 500 mM) and [Ag] variable (5 and

50 mM) in a 3 M nitric acid solution Phase A21: 0.1 M of DMDOHEMA and [EBPip] NTf ₂

Referring to the histogram of FIG. 6, it is observed that the extraction of Pd by means of phase A21 comprising the DMDOHEMA and [EBPip] NTf ₂ mixture is carried out, not only efficiently in the presence of other metallic elements, but also particularly selectively with respect to these other metallic elements, here Ag and Cu.

This observation is observed even in the case where these other metallic elements are present in a mass concentration which is 10 times, or even 100 times, greater than that of Pd.

B.1.2 The extraction performance of an A21 phase comprising, on the one hand, DMDOHEMA as malonamide and, on the other hand, either [EBPip] NTf ₂ or [EOPip] NTf ₂ as ionic liquid, were evaluated. by means of a series of extractions carried out by bringing the following phases A1 and A21 into contact (with a ratio V _A1 / V _A21 = 1):

Phase A1: [Ag] = 6677 mg / L, [Cu] = 29734 mg / L and [Pd] = 483 mg / L in 3M nitric acid solution

Phase A21: 0.1 M of DMDOHEMA mixed with [EBPip] NTf ₂ or [EOPip] NTf ₂ The results of Table 2 show that the Pd is extracted efficiently and selectively with respect to Cu and Ag, regardless of the ionic liquid used in phase A21.

The calculated values of the distribution coefficients of Pd, Ag and Cu (DM), their respective extraction percentages E (%) and the extraction selectivities of Pd with respect to other elements (SP _C I / M) are reported in Table 2 below:

Table 2

The results of Table 2 show that the Pd is extracted efficiently and selectively with respect to Cu and Ag, regardless of the ionic liquid U used in phase A21.

B.2 Pd back-extraction

The Pd can be back-extracted from the phases A2 'resulting from the extractions carried out in paragraph B.1.1 with [Pd] = 5 mM, [Ag] = 50 mM and [Cu] = 500 mM, by bringing these phases A2' into contact. with the following aqueous phases A3 (with a ratio V _A3 / V _{A2 '} = 1):

- a 0.1 M thiourea solution, and

- a 0.5 M DTPA solution. The calculated values of the desex extraction percentages (%) are reported in Table 3 below.

Table 3

Example C: Extraction and recovery of Pd and Au from an acidic aqueous phase A1 comprising another metallic element by an A21 phase comprising a malonamide and an ionic liquid U

C.1 Joint extraction of Pd and Au

C.1.1 To evaluate the performance of joint extraction of Pd and Au by means of a phase A21 comprising a malonamide and an ionic liquid L1, a series of extractions was carried out by bringing the phases A1 and A21 into contact (with a VAI / VA2I ratio = 1) following:

Phase A1: Au, Cu and Pd, in the concentrations indicated in Table 4 below, in a 3 M nitric acid solution Phase A21: 0.1 M of DMDOHEMA as malonamide [EBPip] NTf ₂ or [ EOPip] NTf ₂ as ionic liquid Ll

The calculated values of the distribution coefficients of Pd, Au and Cu (DM), their respective extraction percentages E (%) and the extraction selectivities of Pd and Au with respect to other elements (S _{Pd / M} and S _{Au / M} ) are reported in Table 4 below:

Table 4

As shown in Table 4, Au and Pd are jointly extracted (co-extracted) with a slightly more pronounced selectivity for Au. The performance of extraction and selectivity of Pd and Au with respect to Cu are better with phase A21 comprising DMDOHEMA and [EBPiP] NTf ₂ as ionic liquid L1.

C.1.2 To evaluate the performance of joint extraction of Pd and Au by means of a phase A21 comprising a malonamide and an ionic liquid L1, a series of extractions was carried out by bringing the phases A1 and A21 into contact (with a VAI / VA2I ratio = 1) following: Phase A1: Au, Cu and Pd, in the concentrations indicated in table 5 below, in a 0.1 M sulfuric acid solution Phase A21: 0.1 M of DMDOHEMA as malonamide

[EBPip] NTf ₂ or [EOPip] NTf ₂ as ionic liquid Ll The calculated values of the distribution coefficients of Pd, Au and Cu (DM), their respective extraction percentages E (%) and the extraction selectivities of Pd and Au with respect to the other elements (S _{Pd / M} and S _{Au / M} ) are shown in table 5 below:

Table 5

As shown in Table 5, the extraction by means of phase A21 comprising a malonamide and an ionic liquid U is efficient, with a preferential extraction for Au. If the extraction performances are lower than those obtained in paragraph C.1.1 above, from an acidic aqueous phase A1 comprising nitric acid (3 M), it is nevertheless observed that the copper is very little extracted and that we have selectivities of Pd and Au with respect to Cu which are advantageous for co-extracting these two precious metals from an acidic aqueous solution comprising, in addition, copper. C.2 Recovery of Pd and Au

C.2.1 Electrochemically

Electroplating tests were carried out using phases A2 ′ as obtained from the extractions carried out in paragraph C.1 above.

In all of these tests, a metallic deposit was obtained, whether on Cv, Ti or 304L stainless steel.

The SEM and EDX analyzes of the deposits obtained show that they are Pd-Au co-deposits. C.2.2 By back-extraction

* Pd and Au can be de-extracted from the phases A2 'resulting from the extractions carried out in paragraph C.1.1 by bringing these phases A2' into contact with the following aqueous phases A3 (with a ratio V _A3 / V _{A2 '} = 1): - a 0.1 M thiourea solution, and a 0.5 M DTPA solution.

The calculated values of the desex extraction percentages (%) for Pd and Au are reported in Table 6 below.

Table 6 * Pd and Au can be de-extracted from the phases A2 'resulting from the extractions carried out in paragraph C.1.2 by bringing these phases A2' into contact with the following aqueous phases A3: a thiourea solution at 0.1 M, and a 0.5 M DTPA solution. The calculated values of the Desex back-extraction percentages (%) for

Pd and Au are specified in Table 7 below.

Table 7 Example D: Extraction and recovery of Pd from an acidic aqueous phase A1 comprising other metallic elements by an A22 phase comprising a functionalized ionic liquid LIF and an ionic liquid U D.1 Extraction of Pd

The extraction performance of an A22 phase comprising, on the one hand, TSIL and, on the other hand, either [EBPip] NTf ₂ or [EOPip] NTf ₂ as ionic liquid, were evaluated by means of a series of extractions carried out by bringing the following phases A1 and A22 (with a V _A1 / V _A22 = 1) into contact: Phase A1: [Ag] = 6677 mg / L, [Cu] = 29734 mg / L and [ Pd] = 483 mg / L in 3M nitric acid solution

Phase A22: 0.1 M TSIL mixed with [EBPip] NTf ₂ or [EOPip] NTf ₂

The calculated values of the distribution coefficients of Pd, Ag and Cu (DM), their respective extraction percentages E (%) and the extraction selectivities of Pd with respect to other elements (SP _C I / M) are reported in Table 8 below:

Table 8 It emerges from the data in Table 8 that the extractions carried out by means of phase A22 comprising TSIL in an ionic liquid U are lower than those carried out by means of a phase A21 comprising DMDOHEMA in the same ionic liquid L1. It may however be noted that more than 80% of the Pd initially present in the acidic aqueous phase A1 can be extracted by a single contact with this phase A22. As previously, this extraction is selective for Pd with respect to Cu and Ag.

D.2 Pd back-extraction

The Pd can be back-extracted from the phases A2 'resulting from the extractions carried out in paragraph D.1 by bringing these phases A2' into contact with the following aqueous phases A3 (with a ratio V _A3 / V _{A2 '} = 1): a solution 0.1 M thiourea, and 0.5 M DTPA solution.

The calculated values of the desex extraction percentages (%) are reported in Table 9 below.

Table 9

Example E: Extraction and recovery of Pd and Au from an acidic aqueous phase A1 comprising another metallic element by a phase A22 comprising a functionalized ionic liquid LIF and an ionic liquid LI

E.1 Joint extraction of Pd and Au To evaluate the performance of joint extraction of Pd and Au by means of an A22 phase comprising, on the one hand, TSIL and, on the other hand, either [EBPip] NTf ₂ or [EOPip] NTf ₂ as ionic liquid , a series of extractions was carried out by bringing the following phases A1 and A22 (with a ratio V _A1 / V _A22 = 1) into contact: Phase A1: Au, Cu and Pd, in the concentrations indicated in table 10 below - below, in a 3 M nitric acid solution Phase A22: 0.1 M TSIL mixed with [EBPip] NTf ₂ or [EOPip] NTf ₂

The calculated values of the distribution coefficients of Pd, Au and Cu (DM), their respective extraction percentages E (%) and the extraction selectivities of Pd and Au with respect to other elements (S _{Pd / M} and S _{Au / M} ) are reported in Table 10 below:

Table 10

With reference to Tables 4 and 10, it is observed that the extraction performances obtained by means of phase A22 comprising TSIL in an ionic liquid U are comparable to those obtained by means of a phase A21 comprising DMDOHEMA in the same liquid ionic Ll. E.2 Joint back-extraction of Pd and Au

The Pd and Au can be de-extracted from the phases A2 'resulting from the extractions carried out in paragraph E.1 by bringing these phases A2' into contact with the following aqueous phases A3 (with a ratio V _A3 / V _{A2 '} = 1): - a 0.1 M thiourea solution, and a 0.5 M DTPA solution.

The calculated values of the Desex back-extraction percentages (%) for Pd and Au are reported in Table 11 below.

Table 11

BIBLIOGRAPHY

[1] WO 2016/008932 A1

[2] K. Sasaki et al., Dalton Transactions, 2014, 43 (15), p. 5648-5651 [3] I.G.B.N. Makertihartha et al., AIP Conférence Proceedings, 2017, 030008, p. 1-8

Claims

1. Process for recovering one or more metals M chosen from gold and metals of the platinum group contained in an acidic aqueous phase A1, this process comprising the following successive steps (1) and (2):

(1) extraction of the metal (s) M from the acidic aqueous phase A1, this extraction step (1) comprising the following successive steps (la) and (lb):

(lb) a collection of phase A2 '; and

(2) recovery of the metal (s) M present in phase A2 ′ as obtained at the end of step (lb), characterized in that phase A2 is chosen from:

- a phase A21 comprising a malonamide and an ionic liquid L1, and

- A phase A22 comprising a functionalized ionic liquid LIF comprising a malonamide group, and in that the recovery step (2) is chosen from:

(2 ') an electroplating, and

2. The recovery process according to claim 1, wherein phase A22 consists of the functionalized ionic liquid LIF, alone or as a mixture with an ionic liquid L1.

3. The recovery process according to claim 1 or 2, wherein the ionic liquid functionalized LIF comprises an organic cation and an anion, the cation. organic being chosen from the group consisting of a piperidinium, a pyridinium, a pyrrolidinium, a piperazinium and an imidazolium.

4. The recovery process according to claim 3, wherein the anion of the LIF functionalized ionic liquid is chosen from bis- (trifluoromethanesulfonyl) imide, hexafluorophosphate and bis (fluorosulfonyl) imide and is advantageously lebis- (trifluoromethanesulfonyl). ) imide.

5. Recovery process according to any one of claims 1 to 4, in which the malonamide group of the ionic liquid LIF functionalized in phase A22 corresponds to the following formula (II): in which

- R ₁ , R ₂ , R ₃ and R ₄ represent, independently of each other:

. a hydrocarbon-based group, saturated or unsaturated, comprising one or more rings of 3 to 8 carbon atoms, said group possibly being branched and / or comprising one or more heteroatoms; and

6. The recovery process according to claim 1, in which the malonamide of phase A21 corresponds to the following formula (I): in which

- R ₁ , R ₂ , R ₃ and R ₄ represent, independently of each other:

- R ₅ represents: a hydrogen atom;

7. The recovery process according to any one of claims 1 to 6, wherein the ionic liquid U comprises an organic cation and an anion, said organic cation comprising a nitrogenous group chosen from the group consisting of a quaternary ammonium, cyclic or not. cyclic, a phosphonium, a piperidinium, a pyridinium, a pyrrolidinium, a piperazinium and an imidazolium.

8. The recovery process according to claim 7, wherein the organic cation of the ionic liquid U is chosen from the group consisting of a piperidinium, a pyridinium, a pyrrolidinium, a piperazinium and an imidazolium and, preferably, from the group consisting of a dialkylpiperidinium, an alkylpyridinium, an N, N'-dialkylpiperazinium and an N, N'-dialkylimidazolium.

9. The recovery process according to claim 7 or 8, wherein the anion of the ionic liquid U is chosen from bis- (trifluoromethanesulfonyl) imide, hexafluorophosphate and bis (fluorosulfonyl) imide and is advantageously bis- ( trifluoromethanesulfonyl) imide.

10. The recovery method according to any one of claims 1 to 9, wherein the step (2 ") of back-extraction comprises:

(2 "a) contacting phase A2 ′ with an aqueous phase A3, the aqueous phase A3 advantageously comprising a complexing agent, whereby one obtains, after phase separation, a phase A2" and an aqueous phase A3 ′ comprising the metal (s) M; then (2 "b) a collection of phase A3 '.

11. Recovery process according to any one of claims 1 to 10, characterized in that the acidic aqueous phase A1 is a solution resulting from the acid attack of a natural or urban ore comprising said metal or metals M.

12. Recovery process according to any one of claims 1 to 11, wherein the aqueous acid phase A1 comprises at least one inorganic acid chosen from the group consisting of nitric acid, sulfuric acid and hydrochloric acid, the inorganic acid being preferably nitric acid.

13. The recovery process according to claim 12, wherein the acidic aqueous phase A1 has a total molar concentration of inorganic acid (s) of at least 0.1 mol / L, advantageously of at least 1 mol / L and is preferably between 3 mol / L and 7 mol / L.

14. The extraction or recovery process according to any one of claims 1 to 13, in which the metal or metals M are chosen from palladium and gold.