Recovery of pt-group metals from aqueous-organic solution

Abstract

The invention relates to a method for the isolation and recovery of a Pt-group metal, preferably palladium, from a waste solution which comes from a catalyst process of an industrial method. The Pt-group metal is present in an aqueous-organic solution. Catalyst remnants and further potentially disruptive, in some cases complexing components are to be mentioned as accompanying substances.

Description

[0001] Recovery of Pt group metals from aqueous-organic solution

[0002] The invention relates to a process for isolating and recovering Pt-group metals, preferably palladium, from a waste solution originating from a catalyst process in an industrial process. The Pt-group metal is present in an aqueous-organic solution. Accompanying substances include catalyst residues and other potentially interfering, partially complexing components.

[0003] background

[0004] Due to the great importance of the platinum group metals, especially palladium, in catalytic processes in homogeneous and heterogeneous phases, as well as its sometimes highly fluctuating price at a high level, a large number of processes for the recovery of Pt group metals are known and some are patented or have been patented.

[0005] In addition to the recovery of the Pt groups, metals, especially palladium, the recovery of the ligands or the metal complex is sometimes the focus.

[0006] For example, EP000001834695A1 describes a process for recovering phosphine ligands from transition metal complexes used in homogeneously catalyzed reactions. The phosphine-containing ligands are obtained by contacting the reaction mixture remaining after completion of a homogeneously catalyzed reaction with an oxidizing agent, subsequently extracting the reaction mixture with an organic solvent immiscible with the reaction mixture to separate the resulting transition oxide, and then isolating the oxidized phosphine ligand from the organic solvent separated from the reaction mixture.

[0007] The focus is on the recovery of the phosphine ligands, but oxidizing agents are used, the oxidation products of which must subsequently be reduced. US000007108839B2 describes the recovery of palladium bound to silica gel. The claimed process relates to heterogeneous catalysis or to palladium from homogeneous catalysis, which, however, must first be bound to silica gel.

[0008] Furthermore, processes are known in which activated carbon, which has previously been loaded with EDTA (ethylenediaminetetraacetic acid), binds palladium.

[0009] Some processes are described in which palladium is extracted using organic oximes.

[0010] Extractions with ion exchangers are described, but not all Pd is charged and too many impurities interfere, so that a yield of 100% is never achieved, but is often far below.

[0011] These processes often require the palladium complex to be destroyed through oxidation or intense heating. This is technically and energetically very expensive.

[0012] US000004522760A describes a process for the extraction of palladium resulting from homogeneous catalysis. The palladium or palladium complex is extracted using an alcoholic solution and a nonpolar, aliphatic, organic solvent.

[0013] The application is limited to cases of alcoholic palladium catalyst solutions, which can be purified and separated using the solvents indicated.

[0014] US000004340570A discloses an extraction process for recovering rhodium, which uses EDTA as the final extraction step. The process is complex and produces a number of different extracts, each containing disruptive secondary components that would interfere with the actual extraction step.

[0015] US000004013584A presents a process for the recovery of a spent palladium complex, whereby the palladium is first released by oxidation with chlorine and recovered by various extraction processes and final evaporation.

[0016] In W0002022144338A1 a process is claimed in which palladium is bound under basic conditions by pH adjustment and binding via various bleaching earths, clays, diathomas earths (etc.).

[0017] W0002017198846A1 proposes a process for the aqueous extraction of palladium from organic solution using surfactants or dentrimers, i.e. essentially surface-active substances.

[0018] In W0002004106563A1 a process for the recovery of palladium from a heterogeneous catalytic process is presented , wherein the palladium is bound to activated carbon .

[0019] DE000001935169A claims a process for isolating dissolved palladium in aqueous solution by forming a precipitate in acidic conditions using thiocyanates.

[0020] In RU000002654818C1 an extraction process is presented which allows the extraction of palladium using organic oximes .

[0021] US000004319923A presents a process for precipitating palladium with potassium borohydride in a basic solution, which can then be recovered by filtration. The process represents a series of reduction processes in which the charged palladium species are converted to Pd(O) and then precipitated or bound to activated carbon.

[0022] None of the presented processes is capable of binding Pt-group metals, especially palladium, in a simple manner with high yields from an aqueous-organic solution, whereby the organic component is freely miscible with both water and water-immiscible organic solvents and can thus act as an (unwanted) solubilizer. The presented processes suffer from the fact that several complex process steps using expensive chemicals are always necessary, the yield is insufficient, or an application to organic-aqueous systems that contain an organic solvent such as THF or solvents with comparable mixing properties is not applicable.

[0023] Accompanying components such as catalyst residues, catalyst ligands, products, by-products, reactants and / or auxiliary materials from the catalyst process or from the processing of the respective process often interfere with the recovery.

[0024] Due to the presence of THF as a solvent, which is freely miscible with water as well as with strongly non-polar organic solvents such as pentane, hexane, heptane, etc., separation of interfering secondary components is not easily possible.

[0025] The object of the present invention was therefore to provide a process for recovering Pt group metals, in particular palladium, from aqueous-organic solutions in high yields, even in the presence of interfering accompanying substances.

[0026] The object is achieved by a method according to claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

[0027] The present invention therefore provides a process for the recovery of Pt group metals, in particular palladium, from an aqueous-organic solution, comprising the steps of a. providing a metal-containing aqueous-organic solution comprising at least one metal of the Pt group, b. reducing the pH of the solution from a. until the Pt group metal precipitates, c. isolating the Pt group metal precipitated from step b. by extraction or filtration and isolating the Pt group metal-containing filtrate remaining after the extraction or filtration, d. transferring the Pt group metal-containing filtrate remaining after step c. to a Pt group metal-absorbing resin for absorption of the remaining Pt group metal on the Pt group metal-absorbing resin, e. Recovery of Pt group metal from Pt group metal absorbing resin.

[0028] The process described herein allows a simple and cost-effective recovery of Pt group metals, in particular palladium, from catalytic processes with palladium recovery yields of > 80%, preferably > 90% and in particular > 95%.

[0029] According to J.R. Rumble, CRC Handbook of Chemistry and Physics, CRC press Taylor and Francis 98, (2017), Pt-group metals are understood to be six elements from transition groups 8 to 10 and periods 5 and 6 of the Periodic Table of the Elements. These are ruthenium, rhodium, palladium, osmium, iridium, and platinum. All of these elements can be recovered using the process according to the invention. This process is particularly preferred for palladium. The person skilled in the art is aware that any disclosure relating to palladium also applies to the other Pt-group metals.

[0030] According to a preferred embodiment of the process according to the invention, after the precipitation of the Pt group metal, in particular palladium, in step b., the supernatant solution is subjected to oxidation.

[0031] The oxidizing agent, preferably H2O2, is added to this supernatant solution (or suspension). Oxidation with H2O2 lowers the pH to approximately 1.7, which should then be adjusted back to 2.3 (+ / - 0.1 pH units) to improve palladium precipitation before filtration.

[0032] Furthermore, it is possible to filter between pH precipitation and oxidation.

[0033] Thus, according to a further preferred embodiment of the process according to the invention, the filtrate obtained after filtration from step c. is subjected to oxidation. The oxidation step is advantageous because the oxidation causes a portion of the precipitate to re-dissolve. However, from a process engineering perspective, it may be simpler to filter only once and allow the potentially higher concentration for the absorption step, since a single filtration is more cost-effective.

[0034] After filtration (after pH precipitation, oxidation, and pH adjustment), the pH of the filtrate is approximately 2.3. For more effective absorption by the resin in step d., a pH of approximately 4 to 5, preferably 4.2 to 4.7, more preferably 4.4 to 4.6, and most preferably approximately 4.5, should be set. In this pH range, the resin's absorption capacity is significantly better than at pH 2.3.

[0035] Through oxidation, excess cysteine, which masks palladium or other Pt-group metals, is rendered harmless. This occurs through oxidation, for example, with hydrogen peroxide (H2O2), glyoxal, or even atmospheric oxygen, with H2O2 being preferred. Other oxidizing agents known to those skilled in the art can also be used. Oxidation converts the cysteine ​​to cystine, which forms less strong or no longer forms precious metal complexes. This can greatly increase the yield of recovered Pt-group metal, especially palladium.

[0036] In the process according to the invention, the pH of the aqueous-organic Pt-group metal or palladium-containing solution is reduced to a value at which a portion of the Pt-group metal or palladium precipitates as a metal salt or metal complex, in particular as a Pd salt or Pd complex (Pd acetate, phosphine, chloro-, or other complexes or salts). The precipitate is then isolated by filtration or extraction with an organic solvent and can be directly recycled to the originally active catalyst. Alternatively, the Pt-group metal, in particular palladium, can also be isolated from the precipitate by combustion.

[0037] The Pt-containing or palladium-containing filtrate is, after pH adjustment, brought into contact with a Pt-containing or palladium-absorbing resin, which binds the remaining Pt-containing or palladium. This process step can consist of a closed system, such as a stirred reactor, or (under dynamic conditions) a fixed absorber bed through which the Pt-containing or palladium-containing filtrate is pumped. For recovery, the resin can then be incinerated or eluted and regenerated using suitable methods. In the latter case, a concentrated Pt-containing or palladium-containing solution is obtained.

[0038] Resins such as cation exchangers and selective ion exchangers are particularly suitable. However, due to the necessary pH adjustment to 4-5, preferably pH 4.2 to 4.7, more preferably 4.4 to 4.6, and especially preferably approximately pH 4.5, some absorbents that work well under neutral or basic conditions are unsuitable in this case.

[0039] Preferably, in the process according to the invention, the pH of the Pt group metal-containing or palladium-containing aqueous-organic solution in step b. is adjusted to pH -2.3+ / -0.1.

[0040] Controlling the pH is very important in this process, especially with palladium. To precipitate some of the palladium, the pH is adjusted to 2.3 (+ / - 0.1 pH units), as this is the minimum solubility. At both higher and lower pH values, the palladium dissolves again.

[0041] The Pt group metal or palladium-absorbing resin preferably comprises a cation exchanger or selective ion exchanger. It is further preferred that the cation exchanger or selective ion exchanger comprises a polyamine, more preferably polyvinylamine.

[0042] In general, due to the often high salt load, so-called selective ion exchangers are particularly suitable as absorbers. These are those that do not simply exchange two sodium ions for one calcium ion, but have a "chemical" functionality. Commercial resins such as TP207 (imidodiacetic acid, manufacturer Lanxess) or TP214 with thiourea groups (also from Lanxess) would be possible. These were tested and showed a significantly poorer loadability than the polyamine-containing resin (manufacturers: instrAction, MetCap, MetCapT), which is based exclusively on polyamine, preferably polyvinylamine. The background, especially in the case of palladium, is that palladium forms extremely strong amine (“ene”) complexes (log ß2 = 26.9 [Pdfenh] (see Figure 1), from Pure & Appl. Chem., Vol.56, No.4, pp. 491—522, 1984.).

[0043] For this reason, the modified amino resin is preferred in this case (see, for example, WO2016030021A1, WO2017089523A1). In the case of a modified polyamine resin, thiourea-modified resins are preferred.

[0044] The polyamine-containing resin preferably comprises a polyamine supported on an inorganic or organic carrier, more preferably polyvinylamine. The polyamine may also be unsupported and consist essentially only of a cross-linked porous polyamine.

[0045] Examples of amino group-containing polymers or polyamine-containing resins are the following: polyamines, such as any polyalkylamines, e.g. polyvinylamine, polyalkylamine, polyethyleneimine and polylysine etc. Among these, polyalkylamines are preferred, even more preferably polyvinylamine and polyallylamine, with polyvinylamine being particularly preferred.

[0046] The preferred molecular weight of the polyamine is preferably in the range of 5,000 to 50,000 g / mol, which applies in particular to the specified polyvinylamine.

[0047] The porous inorganic support material in particle form is preferably a mesoporous or macroporous support material. The average pore size of the porous support material is preferably in the range of 6 nm to 400 nm, more preferably in the range of 8 to 300 nm, and most preferably in the range of 10 to 150 nm. Furthermore, it is preferred that the porous support material has a pore volume in the range of 30 vol.% to 90 vol.%, more preferably 40 to 80 vol.%, and most preferably 60 to 70 vol.%, in each case based on the total volume of the porous support material. The average pore size and pore volume of the porous support material can be determined by the mercury pore-filling method according to DIN 66133.

[0048] The porous inorganic support material is preferably a particulate material with an average particle size in the range of 5 μm to 2000 μm, more preferably in the range of 10 μm to 1000 μm. The shape of the particles can be spherical, rod-shaped, lenticular, donut-shaped, elliptical, or even irregular, with spherical particles being preferred. The proportion of polymer used in step (a) is in a range of 5 wt.% to 50 wt.%, more preferably 10 to 45 wt.%, and even more preferably 20 to 40 wt.%, in each case based on the weight of the porous inorganic support material without polymer.

[0049] If the porous support material is an inorganic material or comprises an inorganic material, the inorganic material is preferably an inorganic mineral oxide selected from the group consisting of silicon oxide, aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, fluorosil, magnetite, zeolites, silicates (e.g., diatomaceous earth), mica, hydroxyapatite, fluoroapatite, metal-organic basic structures, ceramics, glass, porous glass (e.g., Trisoperl), metals, e.g., aluminum, silicon, iron, titanium, copper, silver, and gold, graphite, and amorphous carbon. The inorganic porous support material is particularly preferably a silicon dioxide or aluminum oxide, in particular silicon dioxide. The silicon dioxide is preferably silica gel.

[0050] If the support is an organic support, the porous support material is preferably selected from the group consisting of polyalkyl, preferably having an aromatic unit in the side chain (i.e. bonded to the polyalkyl chain), polyacrylate, polymethacrylate, polyacrylamide, polyvinyl alcohol, polysaccharides (e.g. starch, cellulose, cellulose esters, amylose, agarose, Sepharose, manganese, xanthan and dextran), and mixtures thereof. Most preferably, the organic polymer is polystyrene or a derivative of polystyrene, which is preferably a copolymer of polystyrene (or derivative of polystyrene) and divinylbenzene. If the organic polymer carries an aromatic unit, this is preferably in sulfonated form. In a very particularly preferred embodiment of the present invention, the organic polymer is a sulfonated crosslinked poly-styrene-co-divinylbenzene) or a derivative thereof.

[0051] However, the polyamine-containing resin can also consist essentially only of a cross-linked polyamine, i.e. it can have no carrier. Such resins are obtainable by coating an inorganic carrier, for example silica, with the polyamine, cross-linking the polyamine and then dissolving the inorganic carrier under alkaline conditions, preferably at a pH > 10. This essentially leaves behind a pure polyamine framework which has the inverse pore structure of the dissolved inorganic carrier. "Essentially" in this case means that only unavoidable residues of, for example, inorganic carrier material can still be present in the porous particles, the proportion of which, however, is preferably less than 2000 ppm, even more preferably 1000 ppm and most preferably 500 ppm.

[0052] In other words , it is preferred that the porous particles of the crosslinked polymer are substantially free of an inorganic material , such as the material of the inorganic support material .

[0053] This pure, cross-linked polyamine can be in the form of a hydrogel, which is preferred according to the invention. A hydrogel is understood here as a solvent (preferably water)-containing but solvent-soluble polymer whose molecules are chemically linked, e.g., by covalent or ionic bonds, or physically linked, e.g., by intertwining of the polymer chains, to form a three-dimensional network. Due to incorporated polar (preferably hydrophilic) polymer components, they swell in the solvent (preferably water), increasing in volume considerably, but without losing their physical cohesion.

[0054] Simple ion exchange resins (here cation exchangers) are unsuitable because the competition with the high salt load (including NaCl >5 wt%) prevents the palladium from binding to the resin.

[0055] Furthermore, it is preferred that the Pt group metal or palladium precipitated in step c. be isolated by combustion or recycled for direct use in catalytic processes. Combustion usually takes place at temperatures > 400°C to 800°C, preferably approximately 600°C.

[0056] Likewise, the recovery of the Pt-group metal or palladium from the Pt-group metal or palladium-absorbing resin is achieved by combustion. This means that the Pt-group metal or palladium remaining in the residue (effluent) after extraction or precipitation is bound to the resin, which is then preferably subjected to combustion. At temperatures > 400°C to 800°C, the organic resin burns, and the Pt-group metal or palladium can be recovered as an oxide.

[0057] The Pt group-containing metal or palladium-containing aqueous-organic solution is preferably an aqueous THF solution. The aqueous THF solution may also comprise other organic solvents, for example linear or cyclic alkyl compounds, linear, branched, and cyclic alkyl alcohols, toluene, benzene, DMF, DMA, or other organic solvents, as well as mixtures thereof.

[0058] The aqueous-organic solution may contain other ingredients, such as salts such as carbonates, halides, phosphates, sulfates, borates, etc. Furthermore, the aqueous-organic solution may contain complexing or non-complexing organic components from the catalyst process itself or other sources. These include, in particular, homo- or heterocyclic compounds, amino acids or their degradation products. Likewise, fluorine or fluorine compounds as well as phosphorus and phosphate compounds may be included. For the purposes of the invention, it is preferred if the Pt-group metal or the palladium-absorbing resin is pH-stable in the range of pH

[0059] 1.5 to 5, more preferably pH 4.2 to 4.7, even more preferably pH 4.4 to 4.6, and especially preferably approximately pH 4.5. Many resins are therefore ruled out as alternatives.

[0060] As described above for the recovery of the Pt group metal or palladium from the precipitation step, the recovery of the Pt group metal or palladium from step c. and step e. is carried out by combustion at a temperature of > 400°C to 800°C, preferably approximately 600°C. This efficiently removes organic components.

[0061] Furthermore, it was found that advantageously in step d. the pH value before transferring the remaining Pt-group metal or palladium-containing filtrate to a Pt-group metal or palladium-absorbing resin for absorbing the remaining Pt-group metal or palladium on the Pt-group metal or palladium-absorbing resin to a pH of preferably pH 4 to 5, even more preferably pH 4.4 to 4.6 and particularly preferably approx. pH

[0062] 4.5. This improves absorption on the Pt-group metal or palladium-absorbing resin.

[0063] The invention will now be explained in more detail using exemplary embodiments, although these are not to be considered as limiting the scope of the invention but merely serve to improve understanding.

[0064] Example 1:

[0065] With vigorous stirring, the pH of a palladium-containing aqueous-organic solution is adjusted to a pH of 2.3 + / - 0.1 with 35% HCl. The precipitate is filtered off. The proportion of palladium in the precipitate to the total dissolved palladium is 68%.

[0066] Example 2 : Oxidation of the supernatant solution

[0067] To 250 mL of the supernatant solution of palladium in aqueous THF (pH 2.3) from Example 1, 25 mL of H2O2 (35% in water) are added with stirring and stirred for 2 h at room temperature. The pH of the solution is then adjusted to 2.3 with 5 M HCl and 5 M NaOH. The resulting precipitate is separated from the supernatant using a Per 4 filter under vacuum.

[0068] Example 3:

[0069] The pH of the filtrate (40 ml) from Example 1 is adjusted to approximately 4.5 with 5 M sodium hydroxide solution. 2 g of T425, a palladium-complexing absorber resin (manufacturer: instrAction GmbH), is then added to the palladium-containing aqueous-organic solution and shaken for 30 minutes. The pH of the solution is maintained at approximately 4.5 by further addition of 35% HCl or 5 M NaOH, if necessary.

[0070] The absorber resin is filtered off. The bound amount of palladium in the filtrate is >90%.

[0071] Example 4 :

[0072] The palladium is recovered from the palladium-containing filtration residue from Example 1, Example 2 and the palladium-containing absorber resin from Example 3 by combustion at temperatures >400°C.

[0073] Example 5 :

[0074] The pH of the filtrate from Example 1 is adjusted to 4.5 + / - 0.1 and then pumped through a cartridge containing a palladium-complexing absorber resin (MetCap, MetCApT, InstAction GmbH, cross-linked polyvinylamine resin) until breakthrough occurs. The effluent is collected and analyzed for palladium.

[0075] The palladium-containing absorber resin is then burned to isolate the palladium.

[0076] In summary, two different procedures are possible: Procedure I (2 filtrations)

[0077] 1. Providing an aqueous-organic solution containing Pt groups metal or palladium;

[0078] 2. Adjust the pH to 2.3 with HCl (e.g. 30% solution);

[0079] 3. Separation of the precipitate by filtration;

[0080] 4. Addition of H2O2 to the filtrate (e.g. 35% H2O2 in water; 2.5vol% based on the starting solution);

[0081] 5. Adjust the pH to 2.3 with NaOH (e.g. 50% solution)

[0082] 6. Filtration of the precipitate;

[0083] 7. Adjust the pH to 4.5 with NaOH (e.g. 50% solution);

[0084] 8. Transferring the Pt group metal or palladium-containing filtrate remaining after step 7 to a Pt group metal or palladium-absorbing resin for absorption of the remaining Pt group metal or palladium on the Pt group metal or palladium-absorbing resin;

[0085] Method II (1 filtration)

[0086] 1. Providing an aqueous-organic solution containing Pt groups metal or palladium;

[0087] 2. Adjust the pH value to 2.3 e.g. with HCl (30% solution);

[0088] 3. Addition of H2O2 to the filtrate (e.g. 35% H2O2 in water, 2.5vol% based on the starting solution);

[0089] 4. Adjust the pH to 2.3 with NaOH (e.g. 50% solution);

[0090] 5. Filtration of the precipitate; 6. Adjustment of the pH to 4.5 with NaOH (e.g. 50%

[0091] Solution ) ;

[0092] 7. Transferring the Pt group metal or palladium-containing filtrate remaining after step 7 to a Pt group metal or palladium-absorbing resin for absorption of the remaining Pt group metal or palladium on the Pt group metal or palladium-absorbing resin;

[0093] Comparison of the procedures

[0094] Process II has the disadvantage that, by omitting filtration between pH precipitation and oxidation, the Pt group metal or palladium concentration in the filtrate prior to binding to the resin is somewhat higher than if filtration is retained. The disadvantage is higher resin consumption, which is due to this higher Pt group metal or palladium concentration. However, it is advantageous because of a simplified process with only one filtration step.

[0095] The invention thus represents a simple and effective process for isolating Pt-group metals, in particular palladium, from an aqueous-organic solution, using only simple and inexpensive chemicals and absorbers and established process steps. Both the Pt-group metal or palladium and the catalytically active complex can be isolated in this way. None of the known processes can, according to the known prior art, isolate a Pt-group metal, in particular palladium, from aqueous-organic solutions in which the organic component is freely miscible with both water and non-polar organic solvents.

[0096] The method presented here represents a simple process for the recovery of Pt-group metals, particularly palladium, from an aqueous-organic solution in the presence of a variety of interfering components. By selecting the conditions appropriate to the Pt-group metal or palladium-containing solution, the Pt-group metal or palladium can be recovered in high yield using simple chemicals and low energy consumption. In the presented process, interfering components are either precipitated or inactivated by selecting the pH value, whereby the bond to absorber resins is not or only minimally disturbed.

Claims

Patent claims 1. A process for recovering metals of the Pt group from an aqueous-organic solution, comprising the steps of a. providing a metal-containing aqueous-organic solution comprising at least one metal of the Pt group, b. reducing the pH of the solution from a. until the Pt group metal precipitates, c. isolating the Pt group metal precipitated from step b. by extraction or filtration and isolating the Pt group metal-containing filtrate remaining after the extraction or filtration, d. transferring the Pt group metal-containing filtrate remaining after step c. to a Pt group metal-absorbing resin for absorption of the remaining Pt group metal on the Pt group metal-absorbing resin, e. recovering the Pt group metal from the Pt group metal-absorbing resin.

2. The process according to claim 1, wherein the solution remaining after the precipitation of the Pt group metal in step b. is subjected to oxidation. 3 . Process according to claim 1 , wherein the filtrate obtained after step c . is subjected to oxidation .

4. Process according to claim 2 or 3, wherein the pH of the filtrate or the supernatant solution after the oxidation is adjusted to a pH of 2.3 + / - 0.1 and the precipitate formed is separated off.

5. A process according to any one of the preceding claims, wherein in step d. the pH is adjusted to a pH of 4 to 5 before transferring the remaining Pt group metal-containing filtrate to a Pt group metal-absorbing resin for absorbing the remaining Pt group metal on the Pt group metal-absorbing resin.

6. Process according to one of claims 2 to 5, wherein the oxidation is carried out with hydrogen peroxide (H2O2), glyoxal or atmospheric oxygen.

7. The process according to claim 1, wherein the pH of the Pt group metal-containing aqueous-organic solution in step b. is adjusted to a pH > 2.3 + / - 0.

1.

8. The method according to any one of claims 1 to 7, wherein the Pt group metal-absorbing resin comprises a cation exchanger or selective ion exchanger.

9. A method according to any one of the preceding claims, wherein the Pt group metal-absorbing resin is a polyamine resin or polyvinylamine resin.

10. A process according to any one of the preceding claims, wherein the Pt group metal precipitated in step c. is isolated by combustion or can be used directly for catalytic processes via recycling.

11. A process according to any one of the preceding claims, wherein the recovery of the Pt group metal from the Pt group metal absorbing resin is carried out by combustion.

12. The process according to any one of the preceding claims, wherein the Pt group metal-containing aqueous-organic solution comprises an aqueous THF solution.

13. The process according to claim 12, wherein the aqueous THF solution comprises further organic solvents selected from the group comprising linear or cyclic alkyl compounds, linear, branched and cyclic alkyl alcohols, toluene, benzene, DMF, DMA and mixtures thereof.

14. A process according to any one of the preceding claims, wherein the Pt group metal-absorbing resin is pH-stable in the range of pH 1.5 to 5.

15. A process according to any one of the preceding claims, wherein the Recovery of the Pt group metal from step c. and step e. is carried out by burning at a temperature > 400°C to 800°C.

16. Process according to one of the preceding claims, wherein the Pt group metal is selected from ruthenium, rhodium, palladium, osmium, iridium and platinum.

17. A process according to any one of the preceding claims, wherein the Pt group metal is palladium.

Images