Recovery of Pt-group metals from aqueous organic solutions.

Abstract

The present invention relates to a method for isolating and recovering platinum group metals, preferably palladium, from waste streams generated from catalytic processes in industrial processes. The platinum group metals are present in an aqueous organic solution. Associated materials include catalyst residues and other potentially destructive, partially complexing components.

Description

[Technical Field]

[0001] The present invention relates to a process for the isolation and recovery of Pt-group metals, preferably palladium, from waste streams generated by catalytic processes in industrial processes. The Pt-group metals are present in an aqueous organic solution. The accompanying materials include catalyst residues and other potentially destructive, partially complexing components. [Background technology]

[0002] Due to the great importance of platinum group metals, especially palladium, in catalytic processes in homogeneous and heterogeneous phases, as well as their high and highly variable cost, numerous methods for recovering Pt group metals are known, some of which are patented or pending patent applications.

[0003] In some cases, the focus is on the recovery of the ligand or metal complex in addition to the recovery of the Pt group metal, particularly palladium.

[0004] For example, EP000001834695A1 describes a method for recovering phosphine ligands from transition metal complexes used in homogeneous catalytic reactions. The phosphine-containing ligands are obtained by contacting the reaction mixture remaining after completion of the homogeneous catalytic reaction with an oxidizing agent, then separating the formed transition oxide by extracting the reaction mixture with an organic solvent that is immiscible with the reaction mixture, and then isolating the oxidized phosphine ligand from the organic solvent that has been separated from the reaction mixture.

[0005] The focus is on the recovery of the phosphine ligand, but an oxidizing agent is used and the oxidation product must be subsequently reduced again.

[0006] US000007108839B2 describes the recovery of palladium bound to silica gel. The claimed method relates to a method for obtaining palladium from a heterogeneous or homogeneous catalyst, but the homogeneous catalyst must first be bound to silica gel.

[0007] Furthermore, a process is also known in which activated carbon, which has been previously loaded with EDTA (ethylenediaminetetraacetic acid), binds to palladium.

[0008] Several processes have been described for extracting palladium using organic oximes.

[0009] Extraction methods using ion exchangers have been described, but not all the Pd is loaded and too many impurities interfere, so 100% yields are never achieved and are often far less than that.

[0010] These processes often have in common that the palladium complexes must be destroyed laboriously by oxidation or high heat, which is very costly both from a technical and an energy standpoint.

[0011] US000004522760A describes a process for extracting palladium from homogeneous catalysts: Palladium or a palladium complex is extracted using an alcohol solution and a non-polar aliphatic organic solvent.

[0012] This application is limited to alcoholic palladium catalyst solutions that can be purified and separated using specific solvents.

[0013] US000004340570A discloses an extraction method for recovering rhodium, which is carried out using EDTA as the final extraction step. This method is complex, producing several different extracts, each containing troublesome secondary components that interfere with the actual extraction step.

[0014] US000004013584A presents a method for recovering spent palladium complexes, in which the palladium is first liberated by oxidation with chlorine, and then recovered by various extraction methods and final evaporation.

[0015] WO002022144338A1 claims a process for binding palladium under basic conditions by pH adjustment and binding via various bleaching agents, clays, diatomaceous earth, etc.

[0016] WO002017198846A1 proposes a process for the aqueous extraction of palladium from organic solutions using surfactants or dendrimers, i.e. essentially surface-active substances.

[0017] WO002004106563A1 presents a process for recovering palladium from heterogeneous catalytic processes, in which the palladium is bound to activated carbon.

[0018] DE000001935169A claims a process for isolating palladium dissolved in an aqueous solution by forming a precipitate in acid using thiocyanate.

[0019] RU000002654818C1 presents a process for extracting palladium using organic oximes.

[0020] US000004319923A presents a method for precipitating palladium with potassium borohydride in a basic solution, followed by recovery by filtration. This method represents a sequential reduction process in which charged palladium species are converted to Pd(0), which is then precipitated or bound to activated carbon.

[0021] None of the methods presented allows for the easy binding of Pt group metals, especially palladium, from aqueous organic solutions in high yields, and in these methods the organic components are freely miscible with both water and water-immiscible organic solvents, which can act as (undesirable) solubilizers.

[0022] The presented methods have the drawbacks of always requiring multiple complex process steps using expensive chemicals, of giving insufficient yields, or of not being applicable to organic-aqueous systems containing organic solvents such as THF or solvents with comparable mixing properties.

[0023] Concomitant components such as catalyst residues, catalyst ligands, products, by-products, reactants and / or auxiliary materials from catalytic processes or process steps often present obstacles to recovery.

[0024] The presence of THF as a solvent, which is freely miscible with both water and strong non-polar organic solvents such as pentane, hexane, and heptane, makes it difficult to separate out the interfering trace components. Summary of the Invention [Problem to be solved by the invention]

[0025] It was therefore an object of the present invention to provide a process for recovering platinum group metals, in particular palladium, in high yields from aqueous organic solutions, even in the presence of interfering accompanying substances. [Means for solving the problem]

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

[0027] Accordingly, the present invention provides a method for recovering Pt-group metals from an aqueous organic solution, comprising the steps of: a. providing an aqueous-organic solution containing metals including at least one Pt group metal; lowering the pH of the solution from ba until the Pt-group metal precipitates; c. isolating the Pt-group metal precipitated in step b. by extraction or filtration, and isolating the filtrate containing the Pt-group metal remaining after extraction or filtration; d. transferring the filtrate containing the Pt-group metal remaining after step c. to a Pt-group metal-absorbing resin, thereby absorbing the remaining Pt-group metal onto the Pt-group metal-absorbing resin; e. recovering the Pt-group metal from the Pt-group metal-absorbed resin; The present invention provides a method comprising: [Effects of the Invention]

[0028] The process described herein allows for the simple and cost-effective recovery of Pt-group metals, in particular palladium, from catalytic processes with palladium recovery yields of greater than 80%, preferably greater than 90%, in particular greater than 95%. [Brief explanation of the drawings]

[0029] [Figure 1] Figure 1. DETAILED DESCRIPTION OF THE INVENTION

[0030] According to JR RUMBLE, CRC Handbook of Chemistry and Physics, CRC press Taylor and Francis 98, (2017), the Pt group metals are six elements belonging to subgroups 8-10, periods 5 and 6 of the periodic table of elements. They are ruthenium, rhodium, palladium, osmium, iridium, and platinum. All of these elements can be recovered using the method of the present invention. This method is particularly preferred for palladium. Those skilled in the art will recognize that any disclosure regarding palladium also applies to other Pt group metals.

[0031] According to a preferred embodiment of the method according to the invention, the supernatant solution after precipitating the Pt group metal in step b. is oxidized.

[0032] To this supernatant solution (or suspension) is added an oxidizing agent, preferably H2O2. Oxidation with H2O2 reduces the pH to about 1.7, but the pH should then be readjusted to a value of 2.3 (±0.1 pH units) before filtration to enhance palladium precipitation.

[0033] It is also possible to carry out a filtration between pH precipitation and oxidation.

[0034] Therefore, in a further preferred embodiment of the process according to the invention, said filtrate obtained after filtration in step c. is oxidized.

[0035] The oxidation step is advantageous because some of the precipitated pH precipitate will redissolve through oxidation. However, from a process engineering perspective, it may be easier to perform only one filtration and accept the potentially higher concentration for the absorption step. From a process engineering perspective, performing only one filtration is more cost-effective.

[0036] After filtration (following pH precipitation, oxidation, and pH adjustment), the pH of the filtrate is about 2.3. To make the absorption by the resin in step d more effective, the pH should be set to about pH 4-5, preferably pH 4.2-4.7, more preferably pH 4.4-4.6, and most preferably about pH 4.5. In this pH range, the absorption performance of the resin is significantly improved compared to that at pH 2.3.

[0037] Oxidation detoxifies excess cysteine, which masks palladium or other Pt group metals. This can be accomplished, for example, by oxidation with hydrogen peroxide (HO), glyoxal, or atmospheric oxygen, with HO being preferred. Other oxidizing agents known to those skilled in the art can also be used. Oxidation converts cysteine ​​to cystine, which forms weaker or no precious metal complexes. This can significantly increase the yield of recovered Pt group metals, especially palladium.

[0038] In the method according to the present invention, the pH value of the aqueous organic Pt-group metal or palladium-containing solution is lowered to a value at which a portion of the Pt-group metal or palladium precipitates as a metal salt or complex, in particular a Pd salt or complex (Pd acetate, Pd phosphine, Pd chloro, or other complex or salt). The precipitate can then be isolated by filtration or extraction with an organic solvent and fed directly to a recycling process for the original active catalyst. Alternatively, the Pt-group metal, in particular palladium, can also be isolated from the precipitate by combustion.

[0039] After readjusting the pH, the Pt-group metal-containing or palladium-containing filtrate is contacted with a Pt-group metal- or palladium-absorbing resin, which binds the remaining Pt-group metal or palladium. This step can consist of a closed system, such as a stirred reactor, or a fixed absorption bed through which the Pt-group metal- or palladium-containing filtrate is pumped (under dynamic conditions). For recovery, the resin can then be regenerated by incineration or leaching using an appropriate method. In the latter case, a concentrated Pt-group metal- or palladium-containing solution is obtained.

[0040] Resins such as cation exchangers and selective ion exchangers are particularly suitable, however, some absorbents that work well under neutral or basic conditions are excluded in this case, since the pH value must be adjusted to pH 4-5, preferably pH 4.2-4.7, more preferably pH 4.4-4.6, and particularly preferably to about pH 4.5.

[0041] In the method of the present invention, the pH value of the Pt group metal-containing or palladium-containing aqueous organic solution in step b is preferably adjusted to pH-2.3±0.1.

[0042] Control of the pH value is particularly important in this process, especially for palladium. To precipitate some of the palladium, the pH value is set at 2.3 (±0.1 pH units), since at this value its solubility is at a minimum. At higher or lower pH values, the palladium dissolves again.

[0043] The resin that absorbs the Pt group metal or palladium preferably comprises a cation or selective ion exchanger. It is also preferred that the cation or selective ion exchanger comprises a polyamine, more preferably polyvinylamine.

[0044] Because salt loadings are often high, selective ion exchangers are generally the most suitable sorbents—that is, sorbents that have a chemical function beyond simply exchanging two sodium ions for one calcium ion. Commercially available resins, such as TP207 (imidodiacetic acid, manufactured by Lanxess) or TP214 (also manufactured by Lanxess) with thiourea groups, may also be considered. These resins have been tested and shown to have significantly poorer loading capacity than polyamine-based resins (manufacturers: instrAction, MetCap, MetCapT) based solely on polyamines, preferably polyvinylamines. This is due to the formation of extremely strong amine (en) complexes, particularly in the case of palladium (log β2 = 26.9 [Pd(en)2] (see Figure 1), Pure & Appl. Chem., Vol. 56, No. 4, pp. 491–522, 1984).

[0045] For this reason, in this case, unmodified amino resins are preferred (see, for example, WO2016030021A1, WO2017089523A1). In the case of modified polyamine resins, resins modified with thiourea are preferred.

[0046] The polyamine-containing resin preferably comprises a polyamine, more preferably a polyvinylamine, supported on an inorganic or organic support. The polyamine may also be unsupported and consist essentially of a crosslinked porous polyamine.

[0047] Examples of the polymer containing an amino group or the resin containing a polyamine include polyamines, such as any polyalkylamines (e.g., polyvinylamine, polyalkylamine, polyethyleneimine, polylysine, etc.). Among these, polyalkylamines are preferred, polyvinylamine and polyallylamine are more preferred, and polyvinylamine is particularly preferred.

[0048] The preferred molecular weight of the polyamine is preferably in the range of 5,000 to 50,000 g / mol, this applies in particular to the polyvinylamines mentioned above.

[0049] The particulate porous inorganic support material 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, the pore volume of the porous support material is preferably in the range of 30 vol% to 90 vol%, more preferably in the range of 40 to 80 vol%, and most preferably in the range of 60 to 70 vol%, based on the total volume of the porous support material. The average pore size and pore volume of the porous support material can be measured by the mercury pore filling method in accordance with DIN 66133.

[0050] The porous inorganic support material is preferably a granular 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 may be spherical, rod-like, lenticular, donut-like, ellipsoidal, or even irregular, with spherical particles being preferred. The proportion of polymer used in step (a) is in the range of 5% to 50% by weight, more preferably 10% to 45% by weight, and even more preferably 20% to 40% by weight, in each case based on the weight of the porous inorganic support material without polymer.

[0051] When the porous carrier material is or contains 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, zeolite, silicate (e.g., diatomaceous earth), mica, hydroxyapatite, fluoroapatite, metal-organic framework, ceramics, glass, porous glass (e.g., Trisoperl), metal (e.g., aluminum, silicon, iron, titanium, copper, silver, gold), graphite, and amorphous carbon. In particular, the inorganic porous carrier material is preferably silica or alumina, and more preferably silica. Silica is preferably silica gel.

[0052] When the support is an organic support, the porous support material is preferably selected from the group consisting of polyalkyls (preferably those with aromatic units in the side chains (i.e., those attached to polyalkyl chains)), polyacrylates, polymethacrylates, polyacrylamides, polyvinyl alcohols, polysaccharides (e.g., starch, cellulose, cellulose esters, amylose, agarose, sepharose, mannan, xanthan, dextran), and mixtures thereof. The most preferred organic polymers are polystyrene or derivatives of polystyrene, preferably copolymers of polystyrene (or derivatives of polystyrene) and divinylbenzene. When the organic polymer contains aromatic units, the aromatic units are preferably sulfonated. In a particularly preferred embodiment of the present invention, the organic polymer is a sulfonated cross-linked polystyrene-divinylbenzene copolymer or a derivative thereof.

[0053] However, the polyamine-containing resin may essentially consist of crosslinked polyamine, i.e., may be free of a carrier. Such a resin can be obtained by coating an inorganic carrier, for example, silica, with a polyamine, crosslinking the polyamine, and then dissolving the inorganic carrier under alkaline conditions, preferably at a pH greater than 10. This leaves essentially a pure polyamine skeleton with an inverted pore structure of the dissolved inorganic carrier. In this case, "essentially" means that, for example, only unavoidable residues of the inorganic carrier material may still be present in the porous particles, but the proportion is preferably less than 2000 ppm, more preferably less than 1000 ppm, and most preferably less than 500 ppm.

[0054] In other words, the porous particles of crosslinked polymer are preferably essentially free of inorganic materials, such as inorganic support materials.

[0055] This pure crosslinked polyamine can exist in the form of a hydrogel, which is preferred in the present invention. Here, a hydrogel is a polymer that contains a solvent (preferably water) but is soluble in the solvent, and its molecules are chemically (e.g., by covalent or ionic bonds) or physically (e.g., by entanglement of polymer chains) linked to form a three-dimensional network. Due to the incorporated polar (preferably hydrophilic) polymer component, the polymer component swells in the solvent (preferably water), resulting in a significant increase in volume, but without losing the cohesive strength of the material.

[0056] Simple ion exchange resins (cation exchange resins in this case) are not suitable because competition with high salt loads (including NaCl (greater than 5 wt%)) prevents binding of palladium to the resin.

[0057] Furthermore, the Pt group metal or palladium precipitated in step c is preferably isolated by combustion or recycled and directly used in the catalytic process. Combustion is typically carried out at temperatures above 250°C to above 400°C.

[0058] Similarly, Pt-group metals or palladium are recovered from the Pt-group metal or palladium-absorbed resin by combustion. This means that the Pt-group metal or palladium still present in the residue (effluent) after extraction or precipitation is bound to the resin and then preferably subjected to combustion. At temperatures above 250°C to above 400°C, the organic resin is combusted and the Pt-group metal or palladium can be recovered as oxide.

[0059] The aqueous organic solvent containing a Pt group metal or palladium is preferably a THF solution, which may contain other organic solvents, such as linear or cyclic alkyl compounds, linear, branched, and cyclic alkyl alcohols, toluene, benzene, DMF, DMA, or other organic solvents, and mixtures thereof.

[0060] The aqueous organic solution may contain further components such as salts, which may be, for example, carbonates, halides, phosphates, sulfates, borates, etc. Furthermore, the aqueous organic solution may contain complexing or non-complexing organic components from the catalytic process itself or from other sources. These include, in particular, monocyclic or heterocyclic compounds, amino acids, or their decomposition products. Fluorine or fluorine compounds as well as phosphorus and phosphate compounds may also be present.

[0061] In the context of the present invention, it is preferred that the Pt group metal or palladium absorption resin be pH stable in the range of pH 1.5 to 5, more preferably pH 4.2 to 4.7, even more preferably pH 4.4 to 4.6, and most preferably pH 4.5, thus ruling out many resins as alternatives.

[0062] Similar to the recovery of Pt-group metals or palladium from the precipitation step above, recovery of Pt-group metals or palladium from steps c. and e. is achieved by combustion at temperatures greater than 400° C., which effectively removes organic components.

[0063] Furthermore, it has been found to be advantageous to adjust the pH value of the Pt-group metal or palladium-absorbing resin to preferably pH 4 to 5, more preferably pH 4.4 to 4.6, and particularly preferably about pH 4.5 in step d to absorb the remaining Pt-group metal or palladium onto the Pt-group metal or palladium-absorbing resin. This improves the separation of the Pt-group metal or palladium from the Pt-group metal or palladium-absorbing resin. This improves the absorption onto the Pt-group metal or palladium-absorbing resin. [Example]

[0064] Hereinafter, the present invention will be described in more detail with reference to embodiments, which should not be regarded as limiting the protection scope of the present invention, but merely serve to provide a better understanding.

[0065] Example 1: The pH of the aqueous organic solution containing palladium is adjusted to 2.3±0.1 with 35% HCl under vigorous stirring. The precipitate is filtered off. The proportion of palladium in the precipitate relative to the total amount of dissolved palladium is 68%.

[0066] Example 2: Oxidation of the supernatant To 250 mL of the supernatant of the palladium THF aqueous solution (pH 2.3) from Example 1, 25 mL of H2O2 (35% aqueous solution) is added with stirring, and the mixture is stirred at room temperature for 2 hours. The pH of the solution is then adjusted to 2.3 using 5 M HCl and 5 M NaOH. The resulting precipitate is separated from the supernatant under vacuum using a Por4 filter.

[0067] Example 3: The pH of the filtrate (40 ml) from Example 1 is adjusted to about 4.5 using 5 M sodium hydroxide solution. The aqueous-organic solution containing palladium is then mixed with 2 g of palladium complexing absorption resin T425 (manufacturer: instrAction GmbH) and shaken for 30 minutes. If necessary, the pH of the solution is maintained at about 4.5 by further adding 35% HCl or 5 M NaOH.

[0068] The absorbent resin is removed by filtration, and the amount of palladium bound from the filtrate is greater than 90%.

[0069] Example 4: Palladium is recovered from the palladium-containing filter residues of Examples 1 and 2 and from the palladium-containing absorption resin of Example 3 by combustion at temperatures above 400°C.

[0070] Example 5: The pH value of the filtrate from Example 1 is adjusted to 4.5±0.1 and then pumped through a cartridge containing a palladium complexing absorption resin (MetCap, MetCApT, InstAction GmbH, cross-linked polyvinylamine resin) until breakthrough occurs. The effluent is collected and analyzed for palladium.

[0071] The palladium-containing absorbent resin is then combusted, thereby isolating the palladium.

[0072] To summarize, two different procedures are possible: Method I (double filtration) 1. Prepare an aqueous-organic solution containing a Pt group metal or palladium. 2. Adjust the pH value to 2.3 using HCl (e.g., a 30% solution). 3. The precipitate is separated by filtration. 4. Add H2O2 to the filtrate (e.g., 35% H2O2 aqueous solution, 2.5% by volume relative to the original solution). 5. Adjust the pH value to 2.3 using NaOH (e.g., 50% solution). 6. Filter the precipitate. 7. Adjust the pH value to 4.5 using NaOH (e.g., 50% solution). 8. The filtrate containing the Pt-group metal or palladium remaining after step 7 is transferred to a Pt-group metal or palladium absorbing resin, and the remaining Pt-group metal or palladium is absorbed onto the Pt-group metal or palladium absorbing resin.

[0073] Method II (single filtration) 1. Providing an aqueous-organic solution containing a Pt group metal or palladium. 2. Adjust the pH value to 2.3 (for example with HCl (30% solution)). 3. Add H2O2 to the filtrate (e.g., 35% H2O2 aqueous solution, 2.5% by volume relative to the initial solution). 4. Adjust the pH value to 2.3 using NaOH (e.g., 50% solution). 5. Filter the precipitate. 6. Adjust the pH value to 4.5 using NaOH (e.g., 50% solution). 7. The filtrate containing the Pt-group metal or palladium remaining after step 7 is transferred to a Pt-group metal or palladium absorbing resin, and the remaining Pt-group metal or palladium is absorbed onto the Pt-group metal or palladium absorbing resin.

[0074] Comparison of methods Method II has the disadvantage that the filtration between pH precipitation and oxidation is omitted, so the concentration of Pt group metal or palladium in the filtrate before binding to the resin is slightly higher than when filtration is maintained. Therefore, the disadvantage is that the resin consumption is higher due to this higher Pt group metal or palladium concentration. On the other hand, the advantage is that it is a simplified process with only one filtration step.

[0075] Thus, the present invention provides a simple and effective method for isolating Pt-group metals, particularly palladium, from aqueous-organic solutions using only simple and inexpensive chemicals and absorbents and established process steps. This method allows for the isolation of both the Pt-group metal or palladium and the catalytically active complex. None of the known methods are capable of isolating Pt-group metals, particularly palladium, from aqueous-organic solutions in which the organic components are freely miscible with both water and nonpolar organic solvents.

[0076] The method presented herein is a simple process for recovering Pt-group metals, particularly palladium, from aqueous-organic solutions containing numerous interfering components. By selecting conditions suitable for the Pt-group metal or palladium-containing solution, Pt-group metals or palladium can be recovered in high yields using simple chemicals and low energy consumption. In the presented method, the interfering components are precipitated or inactivated by selecting a pH value so that their binding to the absorbent resin is not inhibited or is not significantly inhibited.

Claims

1. 1. A method for recovering Pt-group metals from an aqueous organic solution, comprising: a. providing an aqueous-organic solution containing metals, including at least one Pt group metal; b. lowering the pH of the solution from a. until the Pt-group metal precipitates; c. isolating the Pt-group metal precipitated in step b. by extraction or filtration, and isolating the filtrate containing the Pt-group metal remaining after extraction or filtration; d. transferring the filtrate containing the Pt-group metal remaining after step c. to a Pt-group metal-absorbing resin, thereby absorbing the remaining Pt-group metal onto the Pt-group metal-absorbing resin; e. Recovering the Pt-group metal from the Pt-group metal-absorbed resin. A method comprising:

2. 2. The method of claim 1, wherein in step b., the supernatant solution after precipitating the Pt-group metal is oxidized.

3. 10. The method of claim 1, wherein the filtrate obtained after step c. is oxidized.

4. 4. The method according to claim 2 or 3, wherein the pH value of the filtrate or the supernatant solution after oxidation is adjusted to 2.3±0.1, and the precipitate formed therein is separated.

5. 5. The method according to claim 1, wherein in step d., the pH value of the filtrate containing the remaining Pt-group metal is adjusted to a pH of 4 to 5 before transferring the filtrate containing the remaining Pt-group metal to the Pt-group metal-absorbing resin so as to absorb the remaining Pt-group metal onto the Pt-group metal-absorbing resin.

6. The oxidation is carried out with hydrogen peroxide (H ２ O ２ 6. The process according to claim 2, wherein the process is carried out using methyl methyl acrylate, glyoxal or atmospheric oxygen.

7. 10. The method of claim 1, wherein the pH value of the Pt-group metal-containing aqueous organic solution in step b. is adjusted to a pH value greater than 2.3±0.

1.

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

9. The method of any one of claims 1 to 8, wherein the Pt group metal-absorbing resin is a polyamine resin or a polyvinylamine resin.

10. 10. The method according to any one of claims 1 to 9, wherein the Pt group metal precipitated in step c. can be isolated by combustion or directly used in catalytic processes via recycling.

11. The method of any one of claims 1 to 10, wherein the Pt-group metal is recovered from the Pt-group metal-absorbed resin by combustion.

12. The method of any one of claims 1 to 11, wherein the Pt group metal-containing aqueous organic solution comprises an aqueous THF solution.

13. 13. The method of claim 12, wherein the aqueous THF solution comprises an additional organic solvent selected from the group comprising linear or cyclic alkyl compounds, linear, branched and cyclic alkyl alcohols, toluene, benzene, DMF, DMA, and mixtures thereof.

14. The method of any one of claims 1 to 13, wherein the Pt-group metal-absorbed resin is pH stable in the range of pH 1.5 to 5.

15. 15. The method of any one of claims 1 to 14, wherein the recovery of the Pt-group metal from steps c and e is carried out by combustion at a temperature of above 250°C to 400°C.

16. The method of any one of claims 1 to 15, wherein the Pt group metal is selected from ruthenium, rhodium, palladium, osmium, iridium and platinum.

17. The method of any one of claims 1 to 16, wherein the Pt group metal is palladium.

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