Removal of platinum group metals from organic solution using thiourea-functionalised adsorbers

Abstract

The invention relates to a sorbent comprising a porous carrier, wherein the carrier is coated with an amino-group-containing polymer, wherein the amino-group-containing polymer is modified with aryl isothiocyanate or alkyl isothiocyanate in the side group, and wherein the amino-group-containing polymer comprises 2 to 15 wt.% in the sorbent, based on the total weight of the sorbent. The invention also relates to the removal of platinum group elements (PGE: ruthenium, rhodium, palladium, osmium, iridium, platinum) from organic solutions using the sorbent, and to a method for producing the sorbent.

Description

[0001] Removal of platinum group metals from organic solution using thiourea-functionalized adsorbs

[0002] The invention relates to a sorbent with alkyl or aryl isothiocyanate ligands and to the removal of platinum group elements (PGE: ruthenium, rhodium, palladium, osmium, iridium, platinum) from organic, water-immiscible solutions by binding to the sorbent. The invention further relates to the use of the sorbent for the removal of platinum group elements from organic, water-immiscible solutions and to a process for the preparation of the sorbent.

[0003] background

[0004] Due to the great importance of platinum group metals in catalytic processes in homogeneous and heterogeneous phases, as well as their prices, which fluctuate considerably at high levels, a large number of processes for the recovery of Pt group metals are known and some are patented or have been applied for patent.

[0005] US7,108,839 B2 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.

[0006] In WO2022 / 144 338 Al a process is claimed in which palladium is bound under basic conditions by pH adjustment and binding via various bleaching, clay, diatomaceous earths (etc.).

[0007] WO2017 / 198846 A1 proposes a method for the aqueous extraction of palladium from organic solution using surfactants or dendrimers, essentially surface-active substances. WO002004106563A1 presents a method for recovering palladium from a heterogeneous catalytic process, where the palladium is bound to activated carbon.

[0008] EP 3 186 001 Al of fenbart is a resin with a very high amine concentration in the pores, which can be derivatized with an organic residue that carries Lewis base properties.

[0009] None of the presented methods are able to bind Pt-group metals from an organic solution in a simple manner with high yields.

[0010] The challenge is to provide a wettable absorber (sorbent) that is wetted by the nonpolar solvent in a suitable manner so that the platinum group elements (PGE) trapped in organic compounds can come into contact with the binding sites of the absorber and thus be bound from the liquid phase to the absorber.

[0011] A large number of absorbers (from the applicant and others) were tested for binding capacity and showed only insufficient binding. This observation was made with ruthenium, palladium, and rhodium and appears to be representative of these groups of elements.

[0012] The lack of wettability of the absorbers can be cited as an explanation; this applies in particular to the PVA-based (PVA = polyvinylamine) hydrophilic resins of the applicant instrAction (hydrogels) and commercial resins with polar binding groups, such as Lewatit® TP207 with a di-iminoacetic acid motif (weakly acidic macroporous cation exchange resin on polystyrene with iminodiacetic acid groups for the selective binding of heavy metal cations from weakly acidic to weakly basic solutions). The object of the present invention was therefore to provide a sorbent suitable for recovering Pt-group metals from organic solutions, even in the presence of interfering substances, in high yields and with high capacity.

[0013] Brief description of the invention

[0014] The problem is solved as described in the claims.

[0015] The invention provides a sorbent comprising a porous support coated with an amino group-containing polymer, wherein the amino group-containing polymer is modified in the side group with an aryl or alkyl isothiocyanate, and wherein the amino group-containing polymer comprises 2 to 15 wt.% in the sorbent, based on the total weight of the sorbent.

[0016] According to the invention, the porous support can be an organic or inorganic support.

[0017] According to another aspect of the invention, the amino group-containing polymer is a polyamine.

[0018] In particular, it is preferred that the amino group-containing polymer is polyvinylamine.

[0019] Furthermore, it is preferred that the amino group-containing polymer is cross-linked on the support or in the pores of the support and is not covalently bonded to the support.

[0020] According to a further aspect of the invention, the polymer containing amino groups comprises 2 to 15 wt.% wt.%, more preferably 3 to 8 wt.%, in which sorbent is included, based on the total weight of the sorbent.

[0021] According to a further aspect of the invention, the aryl isothiocyanate is preferably selected from phenyl isothiocyanate, diphenyl isothiocyanate, phenyl alkyl isothiocyanate, benzohydryl isothiocyanate, cinnamoyl isothiocyanate, and polycondensed aromatic isothiocyanates, as well as mixtures thereof. Furthermore, the aryl isothiocyanate may comprise heteroatoms selected from nitrogen or oxygen and / or substituents on the aromatic ring selected from NO₂, CN, F, CI, or Br, or combinations thereof.

[0022] According to another aspect of the invention, alkyl isothiocyanates can also be used. Preferably, alkyl isothiocyanate alkyl groups from C4 to C6 are used. 12used, whereby the alkyl groups can also be branched or cyclic.

[0023] According to another aspect of the invention, the porous inorganic support is selected from silicon oxide, aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, fluorosil, magnetite, zeolites, silicates, mica, hydroxyapatite, fluoroapatite, metal-organic matrix structures, ceramics, glass or porous glass, or combinations thereof.

[0024] According to a further aspect of the invention, the support is soluble in aqueous alkaline solutions, preferably at a pH > 10, so that only a porous polyamine framework remains, which is insoluble in organic solvents due to cross-linking. However, the cross-linked polyamine framework can swell in organic solvents.

[0025] The organic support is preferably selected from polystyrene, polystyrene-divinylbenzene, polyacrylate, polymethacrylate, polyacrylamide, polyvinyl alcohol, polysaccharides, or mixtures of the aforementioned organic supports.

[0026] The invention further provides the use of the sorbent as described above for the recovery of platinum group metals from organic solutions, wherein the platinum group metals are selected from ruthenium, rhodium, palladium, osmium, iridium and platinum.

[0027] The invention further provides a method for recovering the aforementioned platinum group metals with high yield and high loading, relative to the carrier used.

[0028] The invention further provides a method for producing the sorbent described above, comprising the steps of: a) providing a porous support, b) applying an amino group-containing polymer to the support to coat the support, c) crosslinking the amino group-containing polymer, d) separating a support coated with amino groups, e) modifying the support from step d) by reaction with an aryl or alkyl isothiocyanate.

[0029] According to another embodiment of the method according to the invention, the carrier is an inorganic carrier which is dissolved by alkaline treatment before or after step e).

[0030] Detailed description of the invention

[0031] As mentioned at the beginning, a large number of absorbers exhibit low binding capacity. This observation has been made for ruthenium, palladium, and rhodium and appears to be representative of these groups of elements.

[0032] The poor wettability of the absorbers when using purely organic solvents that are immiscible or only poorly miscible with water, as well as the high polarity of the binding groups on the resin, can be cited as explanations. To overcome this problem, initial attempts were made to improve wettability by introducing lipophilic groups, such as phenyl isothiocyanate. Phenyl isothiocyanate was chosen because of its lipophilicity, which enhances the formation of thioureas, which in turn are very good complexing ligands for PGEs.

[0033] However, this hardly improved the load capacity.

[0034] Surprisingly, it was found that the high concentration and lipophilic derivatization lead to such strong swelling of the coating that the PGEs trapped in partially sterically demanding complexes can no longer enter the swollen pores. This would mean that a large proportion of the binding sites would be sterically blocked, preventing good binding of the PGEs with the desired high capacity.

[0035] The approach according to the invention was therefore to create more space in the pores and to prevent pore closure by swelling (after lipophilic derivatization).

[0036] The invention provides a sorbent comprising a support coated with an amino group-containing polymer, wherein the amino group-containing polymer is modified in the side group with an aryl or alkyl isothiocyanate, and wherein the amino group-containing polymer comprises 2 to 15 wt.%, preferably 3 to 8 wt.%, in the sorbent, based on the total weight of the sorbent.

[0037] According to the invention, the porous support can be an organic or inorganic support.

[0038] According to another aspect of the invention, the amino group-containing polymer is a polyamine.

[0039] In particular, it is preferred that the amino group-containing polymer is polyvinylamine.

[0040] Furthermore, the amino group-containing polymer is cross-linked in the pores of the porous support. The amino group-containing polymer is preferably non-covalently bonded to the porous support.

[0041] According to a further aspect of the invention, the polymer containing amino groups comprises 2 to 15 wt.%, more preferably 3 to 8 wt.%, of the sorbent, based on the total weight of the sorbent.

[0042] It was surprisingly found that a reduced amount of deposited amino-containing polymer, compared to known absorbers (see, e.g., EP 3 186 001 Al of fenbart), exhibits better loading capacity for precious metals from purely organic solvents than absorbers with a higher polymer content. This is an unexpected observation, as previous studies had found that the loading capacity of absorbers with heavy metals increased almost linearly with the immobilized amount of amino-containing polymer and thus the number of binding groups.

[0043] According to a further aspect of the invention, the aryl isothiocyanate is selected from phenyl isothiocyanate, diphenyl isothiocyanate, phenyl alkyl isothiocyanate, benzohydryl isothiocyanate, cinnamoyl isothiocyanate, and polycondensed aromatic isothiocyanates, as well as mixtures thereof. Furthermore, the aryl isothiocyanate may comprise heteroatoms selected from nitrogen or oxygen and / or substituents on the aromatic ring selected from NO₂, CN, F, Gl, or Br, or combinations thereof.

[0044] According to a further aspect of the invention, alkyl isothiocyanates can also be used. Preferably, alkyl isothiocyanates with alkyl groups from C4 to C12 are used, wherein the alkyl groups can also be branched or cyclic. According to a further aspect of the invention, the porous inorganic support is selected from silicon oxide, aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, Fluorosil, magnetite, zeolites, silicates, mica, hydroxyapatite, fluoroapatite, metal-organic matrix structures, ceramics, glass or porous glass, or combinations thereof.

[0045] The organic support is preferably selected from polystyrene, polystyrene-divinylbenzene, polyacrylate, polymethacrylate, polyacrylamide, polyvinyl alcohol, polysaccharides, or mixtures of the aforementioned organic supports.

[0046] The invention further provides the use of the sorbent as described above for the recovery of platinum group metals from organic solutions, wherein the platinum group metals are selected from ruthenium, rhodium, palladium, osmium, iridium and platinum.

[0047] The invention further provides a method for recovering the aforementioned platinum group metals in high yield and provides a method for producing the sorbent described above, comprising the steps of: a) providing a porous support, b) applying an amino group-containing polymer to the support to coat the support, c) crosslinking the amino group-containing polymer, d) separating a support coated with amino groups, e) coating the support from step d) with an aryl or alkyl isothiocyanate.

[0048] According to a further embodiment of the invention, the porous support is an inorganic support, preferably silica gel, which dissolves under alkaline conditions, preferably at a pH value > 10. Dissolution can take place before or after step e).

[0049] According to the invention, the coating and crosslinking preferably take place in a stirred reactor, for example, a Lödige mixer. This has the advantage over crosslinking in suspension that the crosslinking can be carried out simply in the pores of the already partially crosslinked polymer and in non-critical water. Crosslinking occurs almost predominantly in the pores of the porous support material, and simultaneously, the solvent water is removed during crosslinking, so that step b) and consequently step c) can be repeated in the same apparatus. Steps b) and c) can be repeated until the desired degree of coating and density of amino groups is achieved. Preferably, coating and crosslinking are carried out at least twice; however, it can also be carried out three, four, or more times. Two coating and crosslinking steps are most preferred.

[0050] The concentration of amino groups should be drastically reduced compared to the prior art, so that the concentration of amino groups of the sorbent according to the invention, determined by titration, is 80 to less than 600 pmol / mL, more preferably at least 120-580 pmol / mL, most preferably 150-500 pmol / mL.

[0051] The mass of the amino group-containing polymer can be determined by the increase in tapped density compared to the support material according to DIN 53194. The total volume of the pores [V] of the porous support material can be determined by the solvent absorption capacity (CAC) of the porous support material. Likewise, the pore volume [Vol. %] can also be determined. These values ​​represent the volume of the freely accessible pores of the support material, as only this can be determined by the solvent absorption capacity. The solvent absorption capacity indicates the volume of solvent required to completely fill the pore space of one gram of dry sorbent (preferably stationary phase). Suitable solvents include pure water or aqueous media, as well as organic solvents such as dimethylformamide.If the sorbent expands in volume upon wetting (swelling), the amount of solvent added is automatically recorded. To measure the CTE (Combined Volumetric Extraction Rate), a precisely weighed quantity of dry sorbent is moistened with an excess of a good wetting solvent, and excess solvent is removed from the intergranular volume by centrifugation. The solvent within the pores of the sorbent remains. The mass of the retained solvent is determined by weighing and converted to volume using the density. The CTE of a sorbent is reported as volume per gram of dry sorbent (mL / g).

[0052] The coating of the amino group-containing polymer on the porous support material is preferably in the form of a hydrogel. In this context, a hydrogel is understood to be a solvent-containing (preferably water) but insoluble polymer in organic solvents, whose molecules are chemically linked, e.g., by covalent or ionic bonds, or physically, e.g., by entanglement 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) with a considerable increase in volume, without losing their chemical cohesion. It is known from prior art that some hydrogels irreversibly lose their properties when dried.In the present application, however, the hydrogels do not lose their properties, as they are chemically and mechanically stabilized by the porous support material. However, pure hydrogels are only of very limited use in lipophilic, purely organic solvents that are immiscible or only slightly miscible with water. They do not swell under these conditions, which greatly reduces the accessibility of potential binding sites. If these amino-containing hydrogels are further modified with polar groups such as bromoacetic acid (diimidoacetic acid), internal salt formation can occur, which further increases their polarity and makes them even less accessible to organic solvents.

[0053] The porous support material is preferably a mesoporous or macroporous support material. The mean pore size of the porous support material is preferably in the range of 6 nm to 400 nm, more preferably in the range of 10 to 300 nm, and most preferably in the range of 20 to 150 nm. A pore size in the specified range is important to ensure that the binding capacity is sufficiently high. If the pore size is too small, the amino group-containing polymer on the surface of the porous support material can clog the pores, and the internal volume of the pores will not be filled with amino group-containing polymer. Furthermore, it is preferred that the porous support material has a pore volume in the range of 30 to 90 vol.%, more preferably 40 to 80 vol.%, and most preferably 60 to 70 vol.%. -% exhibits , each in relation to the total volume of the porous support material .

[0054] The mean pore size of the porous substrate material can be determined by the pore filling method with mercury according to DIN 66133.

[0055] The porous support material can comprise or consist of an organic polymer, an inorganic material, or a composite material of organic polymers and inorganic materials. To provide a sorbent exhibiting high sorbent stability over a pH range of 0 to 14, it is preferred that the porous support material be an organic polymer. For the purposes of this invention, sorbent stability means that the sorbent does not lose its chemical and physical properties within the aforementioned pH range of 0 to 14.

[0056] Preferably, the organic polymer for the porous support material is selected from the group consisting of polyalkyl, preferably with 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, manan, xanthan gum, and dextran), and mixtures thereof. Most preferably, the organic polymer is polystyrene or a polystyrene derivative, preferably a copolymer of polystyrene (or a polystyrene derivative) and divinylbenzene. If the organic polymer contains an aromatic unit, this is preferably sulfonated. In a particularly preferred

[0057] In one embodiment of the present invention, the organic polymer is a sulfonated cross-linked poly(styrene-co-divinylbenzene) or a derivative thereof.

[0058] 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 dioxide, aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, fluorosil, magnetite, zeolites, silicates (e.g., diatomaceous earth), mica, hydroxyapatite, fluoroapatite, metal-organic matrix structures, ceramics, glass, porous glass (e.g., Trisoperl), metals (e.g., aluminum, silicon, iron, titanium, copper, silver, and gold), graphite, and amorphous carbon. Particularly preferably, the inorganic porous support material is silicon dioxide or aluminum oxide, especially silicon dioxide. The silicon dioxide is preferably silica gel.

[0059] If silica gel or a similar material is used as a support, it is also possible, after coating with a linear polymer and crosslinking it to form a three-dimensional network, to remove the support by treatment with a basic solvent, leaving only the three-dimensional polyvinylamine network. The three-dimensional network can be further modified by introducing additional bonding groups.

[0060] Particularly for reasons of use in a wide pH range, especially in the basic range, the porous support material is preferably an organic polymer.

[0061] The porous support material used according to the invention can be of homogeneous or heterogeneous composition and therefore particularly includes materials that are composed of one or more of the above-mentioned materials, for example in multilayer compositions.

[0062] The porous support material is preferably a particulate material with an average particle size in the range of 5 to 2000 pm, more preferably in the range of 10 to 1000 pm. The porous support material can also be a sheet- or fiber-shaped material, such as a membrane or a foam. The outer surface of the porous support material can be flat (sheets, films, discs, membranes, fibrous fabric or non-fibrous fabric) or curved (either concave or convex: spherical, granules, (hollow) fibers, tubes, capillaries).

[0063] As mentioned above, the porous support material is coated with a polymer containing amino groups, which consists of or comprises individual polymer chains. The polymer chains are preferably covalently linked to each other. The amino group-containing polymer is preferably non-covalently linked to the surface of the porous support material.

[0064] The use of a non-covalently surface-bound cross-linked polymer as the amino group-containing polymer on the porous support material also has the following three advantages: (1) flexibility of the polymer, due to its non-covalent bonding to the surface of the porous support material; (2) the cross-linking of the amino group-containing polymer ensures that the film remains on the surface of the porous support material and is not lost during use of the sorbent; (3) the thickness of the amino group-containing polymer on the support material can be chosen to be correspondingly large if the polymer is not covalently bonded to the support material.

[0065] Surprisingly, it was found that the binding capacity of the resins for PGEs improved drastically compared to the original resins (which were very successful in aqueous applications), even though less than a third of the polymer quantity and thus the possible binding sites were introduced.

[0066] The technical shortcomings that prompted the invention were the failure of previously available commercial and proprietary absorbers to bind PGE from purely organic, water-immiscible solutions. The existing resins exhibited insufficient wettability and poor binding behavior of the Pt group metals, resulting in unacceptable yields.

[0067] These solutions became known through our own investigations, as well as literature and patent searches aimed at finding them. This goal was not achieved. The majority of reports on the isolation of platinum group elements use aqueous solutions, not purely organic ones that are immiscible with water.

[0068] The invention makes it possible, compared to the previous state of the art, to obtain PGEs from purely organic solutions that are not miscible with water (e.g. toluene, xylene) effectively, with high yield and using standardized processes such as filtration or stirred tank applications.

[0069] The invention is explained in more detail below using examples, with reference to the figures.

[0070] This shows:

[0071] Figure 1 shows ruthenium absorption as a function of the amount of resin.

[0072] Figure 2 shows the ruthenium absorption kinetics.

[0073] Figure 3 shows a ruthenium absorption from an organic high-boiling solution.

[0074] Figure 4 shows the absorption of palladium from toluene.

[0075] Figure 5 shows a kinetic study of Pd absorption.

[0076] Examples

[0077] Example 1

[0078] Ru from o-Xylene

[0079] Increasing amounts of PEG absorber are added to a solution of 1300 ppm ruthenium in o-xylene and shaken for 16 h at 22°C. The solution is then separated from the resin by filtration, diluted, and analyzed for residual ruthenium using AAS. The result is shown in Figure 1.

[0080] 80-90% of the ruthenium is bound by the PEG-absorbing resin. Within the margin of error, the absorption is therefore almost quantitative.

[0081] Example 2

[0082] 12.5 g absorber resin (silica gel, 200 pm, phenylthiourea-

[0083] Motifs are placed in a 250 mL Erlenmeyer flask and mixed under argon with 50 mL of the ruthenium solution in o-xylene.

[0084] The suspension is shaken at 25°C and 250 pL are taken from time to time for analysis.

[0085] The binding of the ruthenium to the absorber is complete after approximately 5 h (Figure 2).

[0086] Example 3

[0087] To a solution of rhodium (~5000 ppm) in a complex mixture of high-boiling organic solvents (e.g., Sasfroth 10® (Sasol South Africa Limited), a mixture of hexan-l-ol (>= 10.00 - < 30.00 %W / W), isomers of pentanol (>= 1.00 - < 30.00 %W / W) and hexanol, cyclohexanol, hexanoic acid, and C10-C13 n-paraffins, boiling range 150.8 - 229.2 °C), increasing amounts of PGE-absorbing resins are added and shaken for 16 h at room temperature. The supernatants are then separated from the resin and analyzed for residual rhodium by AAS. Figure 3 shows the absorption result.

[0088] The rhodium concentration in the filtrates is still approximately 20-35% after incubation with the PEG-selective absorbers, i.e., approximately 65-80% of the available rhodium is bound at one stage.

[0089] Example 4:

[0090] Increasing amounts of the phenylthiourea-containing absorber are added to a 23 ppm palladium solution in toluene and shaken for 16 h at 20°C. The supernatant is then separated from the absorber by filtration and analyzed by AAS. The results of the analysis are shown in the following figure. The absorbance is >90% in all cases and is therefore almost complete within the margin of error (Figure 4).

[0091] Example 5:

[0092] 6.25 g of PEG absorber are weighed into an Erlenmeyer flask and mixed with 50 mL of the palladium solution in toluene.

[0093] The suspension is shaken at 25°C and ~1 mL sample is taken from time to time and analyzed for palladium using AAS.

[0094] The result is shown in Figure 5. The absorption of palladium by the PEG absorber is almost complete and very rapid. Approximately 90% of the palladium is bound in 60 minutes.

[0095] Example 6

[0096] coating

[0097] In a Lödige VT 5 dryer, 800 g of Davisil LC 150 A silica gel (100-300 pm) are placed. The jacket temperature is set to 20 °C. The mixing drum speed is set to 180 rpm. In a separate container, 246 g of PVA polymer solution (polymer content 13%) are diluted with 400 g of deionized water. Then, 6.7 g of ethylene glycol diglycidyl ether (EGDGE) are added to the polymer solution as a crosslinking agent. This mixture is then added to the silica gel in the mixer within 5 minutes. During this process, the temperature rises. The mixer jacket temperature is set to 95 °C. The dryer is then closed, and the pressure is set to 60 mbar. The coated material is dried for 3 hours. The polymer adsorbate is then transferred to a frit with porosity 1 and washed with 3 bed volumes (BV) of deionized water, 3 bed volumes of 1 M NaCOa, and 3 bed volumes of 1 M NaCl. The resin is then vacuum-dried and packaged.1828 g of resin with a residual moisture content of 52.4% are obtained.

[0098] Example 7 - Coating

[0099] In a Lödige VT 5 dryer, 800 g of Davisil LC 150 silica gel (100-300 ml) are placed. The jacket temperature is set to 20 °C. The mixing drum speed is set to 180 rpm. In a separate container, 500.9 g of PVA polymer solution (polymer content 13%) are diluted with 260 g of deionized water. Then, 13.0 g of ethylene glycol diglycidyl ether (EGDGE) are added to the polymer solution as a crosslinking agent. This mixture is then added to the silica gel in the mixer within 10 minutes. During this process, the temperature rises. The mixer jacket temperature is set to 95 °C. The dryer is then closed, and the pressure is set to 60 mbar. The coated material is dried for 3 hours. The product temperature rises to 72.6 °C. The polymer adsorbate is then transferred to a frit with porosity 1 and washed with 3 volumes of deionized water, 3 volumes of 1 M NaCO3, and 3 volumes of 1 M NaCl. The resin is then vacuum-dried and packaged.1575 g of resin with a residual moisture content of 47% are obtained.

[0100] Example 8: Derivatization with phenyl isothiocyanate to phenyl thiourea

[0101] 200 g of the coated support from Example 6 are placed in a 500 mL three-necked flask equipped with a stirrer and internal thermometer. 300 mL of 2-propanol are then added, the phase is suspended, and the oil bath is heated to 60°C. In a dropping funnel, 12.8 g of phenyl isothiocyanate [103-72-0] are mixed with 25 mL of isopropanol and suspended, then slowly added over 10 minutes. The reaction suspension is then stirred at 60°C for 3 hours. The modified resin is washed with 5 BV of isopropanol and then dried in a stream of air. Product yield: 120 g (residual moisture 4.6%).

[0102] Example 9: Derivatization with phenyl isothiocyanate to phenyl thiourea

[0103] 100 g of the coated support from Example 7 are placed in a 500 mL three-necked flask equipped with a stirrer and internal thermometer. 200 mL of 2-propanol are then added, the phase is suspended, and the oil bath is set to 60°C. In a dropping funnel, 12.8 g of phenyl isothiocyanate [103-72-0] are mixed with 25 mL of isopropanol and suspended, then slowly added over 10 min. The reaction suspension is then stirred at 60°C for 3 h. The modified resin is washed with 5 BV of 2-propanol and then dried in a stream of air. Product: 64.3 g (residual moisture)

[0104] 3.3%) .

Claims

Patent claims 1. A sorbent comprising a porous support, wherein the support is coated with an amino group-containing polymer, wherein the amino group-containing polymer is modified with an aryl or alkyl isothiocyanate in the side group, and wherein the amino group-containing polymer comprises 2 to 15 wt.% in the sorbent, based on the total weight of the sorbent.

2. Sorbens according to claim 1, wherein the porous support is an organic or inorganic support.

3. Sorben according to claim 1 or 2, wherein the polymer containing amino groups is a polyamine.

4. Sorben according to claim 3, wherein the amino group-containing polymer is polyvinylamine.

5. Sorben according to any of the preceding claims, wherein the amino group-containing polymer is cross-linked in the pores of the support or wherein the sorbent consists of a cross-linked amino group-containing polymer.

6. Sorben according to any of the preceding claims, wherein the aryl isothiocyanate is selected from phenyl isothiocyanate, diphenyl isothiocyanate, phenyl alkyl isothiocyanate, benzohydryl isothiocyanate, cinnamoyl isothiocyanate and polycondensed aromatic isothiocyanates, as well as mixtures thereof.

7. Sorben according to any one of claims 1 to 6, wherein the aryl isothiocyanate comprises heteroatoms selected from nitrogen or oxygen and / or substituents on the aromatic compound selected from NO2, CN, F, Gl or Br, or combinations thereof.

8. Sorben according to any of the preceding claims, wherein the alkyl isothiocyanate comprises alkyl groups from C4 to C12, where the alkyl groups can also be branched or cyclic.

9. Sorbens according to any of the preceding claims, wherein the porous inorganic support is selected from silicon oxide, aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, Fluorosil, magnetite, zeolites, silicates, mica, hydroxyapatite, fluoroapatite, metal-organic matrix structures, ceramics, glass or porous glass, or combinations thereof.

10. Sorbens according to any of the preceding claims, wherein the porous organic support is selected from polystyrene, polystyrene-divinylbenzene, polyacrylate, polymethacrylate, polyacrylamide, polyvinyl alcohol, polysaccharides, or mixtures of the aforementioned organic supports.

11. Use of the sorbent according to any one of claims 1 to 10 for the recovery of platinum group metals from organic solutions.

12. Use according to claim 11, wherein the platinum group metals are selected from ruthenium, rhodium, palladium, osmium, iridium and platinum.

13. Use according to claim 11 or 12, wherein an organic solution containing platinum group metal is brought into contact with a sorbent according to claims 1 to 6.

14. A method for producing a sorbent according to any one of claims 1 to 10, comprising the steps of: a) providing a porous support; b) applying an amino group-containing polymer to the support to coat the support; c) crosslinking the amino group-containing polymer in the pores of the porous support; d) separating a support coated with amino groups. e) Modifying the support from step d) by reaction with an aryl or alkyl isothiocyanate .

15. The method of claim 14, wherein the carrier is an inorganic carrier which is dissolved by alkaline treatment before or after step e).

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