Particulate carbon material provided with elemental silver and elemental ruthenium

Abstract

A particulate carbon material that is provided with elemental silver and elemental ruthenium and has an average particle size (d50) in the range of 0.5 to 500 µm, a pore volume in the range of 0.5 to 10 mL / g and a BET surface in the range of 200 to 2000 m² / g.

Description

[0001] Particulate carbon material containing elemental silver and elemental ruthenium

[0002] The invention relates to particulate carbon material containing elemental silver and elemental ruthenium and to an efficient process for its production.

[0003] WO 2021 / 084140 A2 discloses a process for producing a particulate carrier material containing elemental silver and elemental ruthenium, which can be used as an additive for the antimicrobial treatment of a wide variety of materials.

[0004] The object of the invention was to provide a material with a pronounced antimicrobial effect based on a carbon material containing elemental silver and elemental ruthenium.

[0005] The problem can be solved by providing a particulate carbon material equipped with elemental silver and elemental ruthenium with an average particle size (d50) in the range of 0.5 to 500 pm, a pore volume in the range of 0.5 to 10 mL / g and a BET surface area in the range of 200 to 2000 m 2 / g (hereinafter also referred to briefly as "inventive particulate carbon material equipped with elemental silver and elemental ruthenium"). Its silver plus ruthenium weight fraction formed by the elemental silver and the elemental ruthenium can, for example, be in the range of 0.1 to 50 wt.% (wt. %) with a silver:ruthenium weight ratio, for example, in the range of 1 to 2000 parts by weight of silver:1 part by weight of ruthenium.

[0006] The particulate carbon material according to the invention provided with elemental silver and elemental ruthenium consists essentially of carbon particles provided with elemental silver and elemental ruthenium, i.e. it comprises carbon particles provided with elemental silver and elemental ruthenium in a proportion, for example, in the range of 95 to 100 wt.%, in particular 100 wt.%. The possible proportion, which may not exceed 5 wt.%, can be formed by noble metal-free carbon particles. In other words, the particulate carbon material according to the invention provided with elemental silver and elemental ruthenium can in particular consist of 95 to 100 wt.% carbon particles provided with elemental silver and elemental ruthenium and 0 to 5 wt.% noble metal-free carbon particles, wherein the wt.% add up to 100 wt.%.

[0007] The terms "particulate carbon material" and "carbon particles" are used herein. The particulate carbon material or carbon particles are neither carbon nanotubes nor carbon nanofibers. Rather, they may be carbon particles, in particular activated carbon particles. This means that the carbon particles containing elemental silver and elemental ruthenium may be, in particular, carbon particles containing elemental silver and elemental ruthenium, in particular, activated carbon particles containing elemental silver and elemental ruthenium. The carbon particles containing no precious metals may be, in particular, precious metal-free carbon particles, in particular, precious metal-free activated carbon particles.

[0008] The term "average particle size" used herein refers to the volume-average primary particle diameter (d50) determined by laser diffraction. The so-called equivalent circular area diameter (ECAD) can be used as a measure of the particle diameter (cf. RENLIANG XII ET AL: "Comparison of sizing small particles using different technologies," POWDER TECHNOLOGY, ELSEVIER, BASEL (CH), Vol. 132, No. 2-3, June 24, 2003 (2003-06-24), pages 145-153). Laser diffraction measurements can be performed using a suitable particle size measuring device, for example, a Mastersizer 3000 or a Mastersizer 2000 from Malvern Instruments, using the wet determination method. With the wet determination method, particulate samples can be dispersed in ethanol using ultrasound during sample preparation.

[0009] The term "pore volume" is used herein. The pore volume can be determined using mercury porosimetry according to DIN ISO 15901-1:2016 (sample mass 30 mg; mercury surface tension 0.48 N / m; mercury contact angle 141.3°; instrument: Porotec Pascal 140 + 440; measurement method: scanning; initial filling pressure 0.0128 MPa; dilatometer: powder, small volume; sample preparation: 8 h at 110°C under vacuum).

[0010] The term "BET surface area" used herein refers to the specific surface area, which can be determined by BET measurement according to DIN ISO 9277:2014-01 (according to Chapter 6.3.1, static volumetric measurement method, gas used: nitrogen). The invention also relates to a process for producing such a particulate carbon material equipped with elemental silver and elemental ruthenium. Viewed from another perspective, the process can also be understood as a process for equipping a particulate carbon material with elemental silver and elemental ruthenium.In the process according to the invention, the particulate carbon material according to the invention containing elemental silver and elemental ruthenium can be obtained by reducing at least one silver precursor and at least one ruthenium precursor in the presence of aqueously suspended carbon particles, in particular activated carbon particles, followed by separating the resulting solid from the aqueous phase, optionally washing the separated solid with water, and optionally drying the solid. The process according to the invention accordingly comprises the steps of reducing at least one silver precursor and at least one ruthenium precursor in the presence of aqueously suspended carbon particles, in particular activated carbon particles, separating the solid formed during the reduction from the aqueous phase, optionally washing the separated solid with water, and optionally drying the separated and optionally washed solid.During reduction, silver and ruthenium precursors can be reduced sequentially or preferably simultaneously.

[0011] The silver and ruthenium precursors mentioned herein are silver and ruthenium compounds. Elemental silver and ruthenium, respectively, can be produced from the silver and ruthenium compounds by reduction.

[0012] Examples of suitable silver compounds include silver acetate, silver sulfate and preferably silver nitrate.

[0013] Examples of suitable ruthenium compounds include ruthenium oxalate, ruthenium acetate and especially ruthenium nitrosyl nitrate.

[0014] Particularly preferably, a combination of silver nitrate and ruthenium nitrosyl nitrate is used as a combination of precursor compounds in the process according to the invention.

[0015] The activated carbon particles used in the reduction process are, in particular, activated carbon particles with an average particle size (d50) in the range of 0.5 to 400 pm, a pore volume in the range of 0.5 to 10 mL / g and a BET surface area in the range of 300 to 3000 m 2 / g. The activated carbon particles can be of various types, for example pyrolytically produced activated carbon or, in particular, those from natural sources such as wood, peat, fruit shells, walnut shells, apricot shells, date shells, coconut shells, and the like. They can be activated carbon exhibiting combustion behavior characterized by a weight loss of 50% after 25 to <28 minutes, with the weight loss being determined by TGA (thermogravimetric analysis) of a small (approximately 8 to 16 mg) powder sample of the respective activated carbon in an air atmosphere at a starting temperature of 200°C and a heating rate of 20°C per minute. The 100% starting weight of approximately 8 to 16 mg is determined at the starting temperature of 200°C. Activated carbons made from wood or peat are examples of activated carbons with such combustion behavior.Examples include commercially available activated carbons such as Norit® SX Plus, manufactured by Cabot Corporation, Alpharetta, Georgia, and Acticarbone® 3S and Acticarbone® CXV, manufactured by Calgon Carbon Corporation, Moon Township, Pennsylvania. Other activated carbons exhibit poorer combustion performance, which may be characterized by a weight loss of 50% after >28 minutes, e.g., >28 to 35 minutes, where the weight loss is determined by the same TGA measurement method and under the same conditions as mentioned above. If the 50% weight loss lasts longer than 35 minutes, the temperature is maintained at 800°C and not increased above it. Coconut shell activated carbon is an example of such a type of activated carbon with poor combustion performance. Examples are commercially available activated carbon types such as Desorex® C33 special and Carbopal® CCP 90 FF special, both manufactured by Donau Carbon GmbH, Frankfurt, Germany.

[0016] The reduction taking place in the process according to the invention can be carried out either at an acidic pH in the range from 1 to 4, preferably from 1 to 2, and at a temperature in the range from 70 to 100°C, preferably from 70 to 90°C, with formic acid or at an acidic pH in the range from 1 to 4, preferably from 1 to 2, and at a temperature in the range from 10 to 40°C, preferably from 15 to 35°C, with hydrazine or at a basic pH in the range from 9 to 14, preferably from 9 to 12, and at a temperature in the range from 10 to 40°C, preferably from 15 to 35°C, with a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates.

[0017] Hydrazine can be used as such, but preferably as hydrazine hydrate with a

[0018] Hydrazine content ranges from 30 to 65 wt.%. When working at basic pH, hydrazine can also be used as a hydrazinium salt, for example, hydrazinium sulfate.

[0019] Hydrazine hydrate is preferred.

[0020] Hypophosphites and formates are mentioned here. These are salts, especially alkali salts, alkaline earth salts, and ammonium salts (NH4 salts). Sodium hypophosphite and potassium hypophosphite, respectively, and sodium formate and potassium formate are preferred.

[0021] The reducing agent(s) are used in the process according to the invention in the amount or more stoichiometrically required for the complete reduction of the silver and ruthenium precursors to elemental silver and elemental ruthenium, but preferably in no more than 110% (hydrazine as reducing agent) or in no more than 200% (formic acid, sodium borohydride, hypophosphites or formates as reducing agents) of the stoichiometrically required amount. Using hydrazine as an example, this means: 1 mol of the reducing agent hydrazine can deliver 4 mol of reducing electrons and accordingly releases 1 mol of N2 during a reduction; accordingly, for example, the reduction of 1 mol of Ag + 0.25 mol hydrazine and for the reduction of 1 mol Ru 3+ 0.75 mol hydrazine.

[0022] In the following, four embodiments of the process according to the invention for producing the particulate carbon material according to the invention equipped with elemental silver and elemental ruthenium are disclosed.

[0023] In a first and preferred embodiment, the manufacturing method according to the invention comprises the successive steps:

[0024] (1a) Providing an aqueous suspension comprising water, carbon particles, in particular activated carbon particles, at least one silver precursor and at least one ruthenium precursor, (2a) Contacting the aqueous suspension at a pH in the range of 1 to 4 and at a temperature in the range of 70 to 100°C with formic acid or at a pH in the range of 1 to 4 and at a temperature in the range of 10 to 40°C with hydrazine,

[0025] (3) Separating the solid formed from the aqueous phase,

[0026] (4) optionally washing the separated solid with water, and

[0027] (5) if necessary, drying the solid.

[0028] The sequence of steps (1a) to (5) are consecutive steps, and they can be directly consecutive steps without intermediate steps. In step (1a) of the first embodiment of the process according to the invention, an aqueous suspension comprising water, carbon particles, in particular activated carbon particles, at least one silver precursor, and at least one ruthenium precursor is provided.

[0029] The aqueous suspension can be prepared by adding carbon particles, in particular activated carbon particles, to an aqueous solution of the at least one silver precursor and the at least one ruthenium precursor and suspending them therein.

[0030] However, the procedure is preferably carried out by adding the silver precursor and the ruthenium precursor—preferably each as an aqueous solution—simultaneously or in any desired order (overlapping, alternating, or successively) to an initial aqueous suspension of carbon particles, in particular activated carbon particles. It is particularly preferred that an aqueous solution of both precursors (of the at least one silver precursor and of the at least one ruthenium precursor) is added to an initial aqueous suspension of carbon particles, in particular activated carbon particles. The addition preferably takes place slowly, for example, over a period of 2 or more hours, for example 3 to 5 hours.

[0031] Generally, mixing is carried out during and after the addition, for example by stirring. Mixing after the addition can expediently extend over a period of, for example, 8 to 120 hours, in particular 24 to 120 hours.

[0032] Addition and mixing can be carried out at elevated temperatures, for example, in the range of 60 to 90°C. It may also be expedient to carry out the mixing at a pH of the aqueous suspension that is within the pH range prevailing in the subsequent step (2a); for this purpose, a suitable agent for adjusting the pH accordingly can be added.

[0033] The weight fraction of the carbon particles, in particular activated carbon particles, of the aqueous suspension provided in step (1a) of the first embodiment of the process according to the invention can, for example, be in the range from 5 to 30 wt.%.

[0034] The silver weight fraction of the aqueous suspension provided in step (1a) of the first embodiment of the process according to the invention can, for example, be in the range from 0.01 to 2.5 wt.%, while the ruthenium weight fraction can, for example, be in the range from 0.01 to 0.13 wt.%. The aqueous suspension provided in step (1a) of the first embodiment of the process according to the invention is characterized by a weight ratio, for example, in the range from 1 to 2000 parts by weight of silver to 1 part by weight of ruthenium, and is generally significantly favored by silver. This silver:ruthenium weight ratio is also found in the product obtained after completion of step (5).

[0035] In addition to carbon particles, in particular activated carbon particles and the precious metal precursors, the aqueous suspension provided in step (1a) of the first embodiment of the process according to the invention generally comprises only water and, if appropriate, the agent used for pH adjustment.

[0036] In step (2a) of the first embodiment of the process according to the invention, the aqueous suspension provided in step (1a) is contacted with formic acid at a pH in the range from 1 to 4, preferably from 1 to 2, and at a temperature in the range from 70 to 100°C, preferably from 70 to 90°C, or with hydrazine at a pH in the range from 1 to 4, preferably from 1 to 2, and at a temperature in the range from 10 to 40°C, preferably from 15 to 35°C. If necessary, an appropriate pH and a corresponding temperature of the aqueous suspension can first be adjusted. The acidic pH can be adjusted, for example, with acetic acid. The formic acid or hydrazine is used in the amount stoichiometrically necessary for the complete reduction of the silver and ruthenium precursors to elemental silver and elemental ruthenium, as mentioned above.Preferably, the formic acid is added to the aqueous suspension in concentrated form or in the form of, for example, an 80 to <100 wt.% aqueous solution, or the hydrazine as such or in aqueous dilution with a hydrazine concentration, for example, in the range of 65 to <100 wt.%. The addition is preferably carried out slowly, for example, over a period of 2 or more hours, for example 3 to 5 hours. Mixing generally takes place during and after the addition, for example by stirring, for example over a period of 2 to 24 hours, in particular 4 to 8 hours.

[0037] In a second and particularly preferred embodiment, the production process according to the invention comprises the successive steps: (1b) providing an aqueous suspension comprising water, carbon particles, in particular activated carbon particles, at least one silver precursor and at least one ruthenium precursor, (2b) contacting the aqueous suspension at a pH in the range from 9 to 14 and at a temperature in the range from 10 to 40°C with a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates,

[0038] (3) Separating the solid formed from the aqueous phase,

[0039] (4) optionally washing the separated solid with water, and

[0040] (5) if necessary, drying the solid.

[0041] The sequence of steps (1b) to (5) are consecutive steps and can be directly consecutive steps without intermediate steps.

[0042] Step (1b) of the second embodiment of the process according to the invention does not differ from step (1a) of the first embodiment of the process according to the invention or proceeds analogously to step (1a); in this respect, reference is made to the above-mentioned information regarding step (1a); it should merely be pointed out that here too it may be expedient to carry out the mixing at a pH of the aqueous suspension which lies within the pH range prevailing in the subsequent step - here (2b); for this purpose, a suitable agent for adjusting the pH accordingly may be added.

[0043] In step (1b) it is particularly useful to work with an activated carbon with an inherently basic pH value, for example with the activated carbon Ceca 2SW from Chemviron.

[0044] In step (2b) of the second embodiment of the process according to the invention, the aqueous suspension provided in step (1b) is contacted with a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites, and formates at a pH in the range from 9 to 14, preferably from 9 to 12, and at a temperature in the range from 10 to 40°C, preferably from 15 to 35°C. If necessary, an appropriate pH and an appropriate temperature of the aqueous suspension can first be adjusted. The basic pH can be adjusted with a strong base, in particular with alkali hydroxide, especially sodium or potassium hydroxide. The reducing agent is used in the amount or more stoichiometrically necessary for the complete reduction of the silver and ruthenium precursors to elemental silver and elemental ruthenium, as mentioned above.Preferably, the reducing agent is added to the aqueous suspension in the form of an aqueous solution. The addition is preferably carried out slowly, for example, over a period of 2 or more hours, for example, 3 to 5 hours. Generally, mixing is continued during and after the addition, for example, by stirring, for example, over a period of 2 to 24 hours, in particular 4 to 8 hours.

[0045] In a third embodiment, the manufacturing method according to the invention comprises the successive steps:

[0046] (1c) providing an aqueous suspension having a pH in the range of 9 to 14 comprising water, carbon particles, in particular activated carbon particles and a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates,

[0047] (2c) contacting the aqueous suspension at a pH in the range of 9 to 14 and at a temperature in the range of 10 to 40°C (i) with an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor or (ii) with an aqueous solution comprising at least one silver precursor and then with an aqueous solution comprising at least one ruthenium precursor or (iii) with an aqueous solution comprising at least one ruthenium precursor and then with an aqueous solution comprising at least one silver precursor,

[0048] (3) Separating the solid formed from the aqueous phase,

[0049] (4) optionally washing the separated solid with water, and

[0050] (5) if necessary, drying the solid.

[0051] The sequence of steps (1c) to (5) are consecutive steps and can be directly consecutive steps without intermediate steps.

[0052] In step (1c) of the third embodiment of the process according to the invention, an aqueous suspension having a pH in the range from 9 to 14, preferably 9 to 12, comprising water, carbon particles, in particular activated carbon particles, and a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites, and formates is provided. The aqueous suspension can be prepared by adding carbon particles, in particular activated carbon particles, to an aqueous solution of the reducing agent and suspending them therein. However, the process is preferably carried out by adding the reducing agent—preferably as an aqueous solution—to an initial aqueous suspension of carbon particles, in particular activated carbon particles. The basic pH can be adjusted with a strong base, in particular with alkali hydroxide, specifically sodium or potassium hydroxide.Generally, mixing is carried out during and after addition, for example by stirring, for a period of 1 to 2 hours.

[0053] The weight fraction of the carbon particles, in particular activated carbon particles, of the aqueous suspension provided in step (1c) of the third embodiment of the process according to the invention can, for example, be in the range from 5 to 30 wt.%.

[0054] The weight fraction of the reducing agent in the aqueous suspension provided in step (1c) of the third embodiment of the process according to the invention may, for example, be in the range from 0.5 to 10 wt.%.

[0055] In addition to carbon particles, in particular activated carbon particles and the reducing agent, the aqueous suspension provided in step (1c) of the third embodiment of the process according to the invention generally comprises only water and, if appropriate, base used for pH adjustment.

[0056] In step (1c) it is particularly useful to work with an activated carbon with an inherently basic pH value, for example with the activated carbon Ceca 2SW from Chemviron.

[0057] In step (2c) of the third embodiment of the process according to the invention, the aqueous suspension provided in step (1c) is contacted at a pH in the range from 9 to 14, preferably from 9 to 12, and at a temperature in the range from 10 to 40°C, preferably from 15 to 35°C, (i) with an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor, or (ii) with an aqueous solution comprising at least one silver precursor and subsequently with an aqueous solution comprising at least one ruthenium precursor, or (iii) with an aqueous solution comprising at least one ruthenium precursor and subsequently with an aqueous solution comprising at least one silver precursor. The one reducing agent is used in the amount stoichiometrically necessary for the complete reduction of the silver and ruthenium precursors to elemental silver and elemental ruthenium, as mentioned above.Variant (i) is preferred.

[0058] The precious metal weight fraction formed from silver and / or ruthenium in the aqueous precious metal precursor solutions used according to variants (i), (ii), or (iii) in step (1c) of the third embodiment of the process according to the invention can, for example, range from 1 to 40 wt.%. The process is carried out with a weight ratio, for example, in the range of 1 to 2000 parts by weight of silver:1 part by weight of ruthenium, and the storage is generally significantly in favor of silver. This silver:ruthenium weight ratio is also found in the product obtained after completion of step (5).

[0059] Generally, mixing is carried out during and after addition, for example by stirring, for a period of 2 to 24 hours, in particular 4 to 8 hours.

[0060] In a fourth embodiment, the manufacturing method according to the invention comprises the successive steps:

[0061] (1d) providing an aqueous suspension having a pH in the range of 1 to 4 comprising water, carbon particles, in particular activated carbon particles and formic acid or hydrazine,

[0062] (2d) contacting the aqueous suspension at a pH in the range of 1 to 4 and at a temperature in the range of 70 to 100°C (in the case of formic acid as reducing agent) or at a temperature in the range of 10 to 40°C (in the case of hydrazine as reducing agent) (i) with an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor or (ii) with an aqueous solution comprising at least one silver precursor and then with an aqueous solution comprising at least one ruthenium precursor or (iii) with an aqueous solution comprising at least one ruthenium precursor and then with an aqueous solution comprising at least one silver precursor,

[0063] (3) Separating the solid formed from the aqueous phase,

[0064] (4) optionally washing the separated solid with water, and

[0065] (5) if necessary, drying the solid.

[0066] The sequence of steps (1d) to (5) are consecutive steps and can be directly consecutive steps without intermediate steps.

[0067] In step (1d) of the fourth embodiment of the process according to the invention, an aqueous suspension having a pH in the range from 1 to 4, preferably from 1 to 2, comprising water, carbon particles, in particular activated carbon particles, and formic acid or hydrazine is provided. The aqueous suspension can be prepared by adding carbon particles, in particular activated carbon particles, to an aqueous solution of formic acid or hydrazine and suspending them therein. However, the procedure is preferably carried out by adding the formic acid or hydrazine—preferably as an aqueous solution—to an initial aqueous suspension of carbon particles, in particular activated carbon particles. The acidic pH can be adjusted, for example, with acetic acid. Mixing generally takes place during and after the addition, for example by stirring, for example over a period of 1 to 2 hours.

[0068] The weight fraction of the carbon particles, in particular activated carbon particles, of the aqueous suspension provided in step (1d) of the fourth embodiment of the process according to the invention can, for example, be in the range from 5 to 30 wt.%.

[0069] The weight fraction of formic acid or hydrazine in the aqueous suspension provided in step (1 d) of the fourth embodiment of the process according to the invention may, for example, be in the range from 0.5 to 10 wt.%.

[0070] In addition to carbon particles, in particular activated carbon particles and formic acid or hydrazine, the aqueous suspension provided in step (1d) of the fourth embodiment of the process according to the invention generally comprises only water and, if appropriate, acid used for pH adjustment.

[0071] In step (2d) of the fourth embodiment of the process according to the invention, the aqueous suspension provided in step (1d) is brought into contact, in the case of formic acid as the reducing agent, at a pH in the range from 1 to 4, preferably from 1 to 2, and at a temperature in the range from 70 to 100°C, preferably from 70 to 90°C, or in the case of hydrazine as the reducing agent, at a pH in the range from 1 to 4, preferably from 1 to 2, and at a temperature in the range from 10 to 40°C, preferably from 15 to 35°C, (i) with an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor, or (ii) with an aqueous solution comprising at least one silver precursor and subsequently with an aqueous solution comprising at least one ruthenium precursor, or (iii) with an aqueous solution comprising at least one ruthenium precursor and subsequently with an aqueous solution comprising at least one silver precursor.The formic acid or hydrazine is used in the stoichiometrically necessary amount or more for the complete reduction of the silver and ruthenium precursors to elemental silver and elemental ruthenium, as mentioned above. Variant (i) is preferred.

[0072] The precious metal weight fraction formed from silver and / or ruthenium in the aqueous precious metal precursor solutions used according to variants (i), (ii), or (iii) in step (1d) of the fourth embodiment of the process according to the invention can, for example, range from 1 to 36 wt.%. The process is carried out with a weight ratio, for example, in the range of 1 to 2000 parts by weight of silver:1 part by weight of ruthenium, and the storage is generally significantly in favor of silver. This silver:ruthenium weight ratio is also found in the product obtained after completion of step (5).

[0073] Generally, mixing is carried out during and after addition, for example by stirring, for a period of 2 to 24 hours, in particular 4 to 8 hours.

[0074] Steps (3) to (5) are the same in all four embodiments of the method according to the invention.

[0075] In step (3), the solid formed in steps (2a), (2b), (2c), or (2d) is separated from the aqueous phase. Examples of suitable solid-liquid separation processes include methods known to those skilled in the art, such as decanting, pressing, filtration, suction filtration, centrifugation, or combinations thereof.

[0076] Step (4) of the process according to the invention is an optional, but generally expedient, step in which the solid separated in step (3) can be washed with water. This can remove water-soluble components. The washing can be carried out, for example, on a suction filter.

[0077] Step (5) of the process according to the invention is an optional, but generally expedient, step in which the solid separated in step (3) and optionally washed in step (4) can be dried. Water and any other volatile components present are removed from the solid obtained after completion of step (3) or step (4). The removal of water can be carried out in the sense of virtually complete removal of water or in the sense of water removal until a desired residual moisture content is reached. For this purpose, the majority of the water can first be removed by conventional methods such as pressing, press filtration, suction filtration, centrifugation, or similar methods, before drying, optionally assisted by reduced pressure, is carried out at temperatures, for example, in the range of 20 to 150°C.

[0078] After completion of step (5), the particulate carbon material according to the invention equipped with elemental silver and elemental ruthenium is obtained, having an average particle size (d50) in the range of 0.5 to 500 pm, a pore volume in the range of 0.5 to 10 mL / g and a BET surface area in the range of 200 to 2000 m 2 / g. The silver plus ruthenium weight fraction formed by elemental silver and elemental ruthenium can vary within wide limits, for example in the range from 0.1 to 50 wt.%, preferably 1 to 40 wt.%, and at the same time the silver:ruthenium weight ratio can, for example, be in the range from 1 to 2000 parts by weight of silver:1 part by weight of ruthenium. Scanning electron micrographs show that the silver and ruthenium are present on internal surfaces (within pores and / or cavities) and / or on the external surface of the originally silver- and ruthenium-free carbon particles and can, for example, form a discontinuous layer and / or small silver or ruthenium particles (silver or ruthenium islands). The silver and ruthenium are not alloyed but are statistically distributed, and the two precious metals are at least partially in contact with each other.It will be clear to those skilled in the art that the silver and ruthenium on their surface may comprise silver species other than elemental metallic silver and ruthenium species other than elemental metallic ruthenium, for example, corresponding oxides, halides, and / or sulfides. Such species may be formed during or subsequently carrying out the process according to the invention, for example, during storage, use, or further processing of the particulate carbon material according to the invention equipped with elemental silver and elemental ruthenium.

[0079] The particulate carbon material according to the invention, which is provided with elemental silver and elemental ruthenium, is characterized by a dark or black color with a correspondingly low brightness L*, for example, in the range of 35 to 45, which can be problematic for some applications. The brightness L* is L* determined spectrophotometrically at a measurement geometry of d / 8° in the CIEL*a*b* color space (DIN EN ISO / CIE 11664-4:2020-03). The spectrophotometric measurement of the particulate carbon material according to the invention, which is provided with elemental silver and elemental ruthenium, can be carried out on a sample filled to a 1 cm fill level in a colorless glass vessel through the flat glass bottom of the glass vessel placed on the measuring head of the spectrophotometer used.

[0080] If desired, the particulate carbon material according to the invention provided with elemental silver and elemental ruthenium can be further processed to form a brightened particulate material having a brightness L*, for example, in the range from 50 to 85. For the purpose of brightening, the particulate carbon material according to the invention provided with elemental silver and elemental ruthenium can be brought into contact with at least one C1-C4 alkoxide of aluminum, magnesium, calcium, silicon, zinc, zirconium and / or titanium in the presence of an amount of water at least sufficient for the complete hydrolysis of the at least one C1-C4 alkoxide. As stated, a brightened particulate material, i.e. a particulate material with a color, for example a gray color, with a brightness L*, for example, in the range from 50 to 85, can be formed.This brightened particulate material consists of the particulate carbon material according to the invention, which is provided with elemental silver and elemental ruthenium, with a solid present at least in part thereon. Depending on the selection of the at least one C1-C4 alkoxide, the solid is a solid selected from the group consisting of aluminum oxide, aluminum hydroxide, aluminum oxide hydroxide, magnesium oxide, magnesium hydroxide, magnesium oxide hydroxide, calcium oxide, calcium hydroxide, calcium oxide hydroxide, silicon dioxide, silica, zinc oxide, zinc hydroxide, zinc oxide hydroxide, zirconium dioxide, zirconium(IV) oxide hydrates, titanium dioxide, titanium(IV) oxide hydrates, and combinations thereof.

[0081] The particulate carbon material according to the invention, which is provided with elemental silver and elemental ruthenium—optionally brightened as mentioned above—is characterized by a particularly pronounced antimicrobial effect, as can be determined in conventional inhibition zone tests or by determining the minimum inhibitory concentration from growth curves of microorganisms. The invention therefore also relates to the use of the optionally brightened particulate carbon material according to the invention, which is provided with elemental silver and elemental ruthenium, as an additive for the antimicrobial treatment of metal surfaces; coating materials; plasters; molding compounds; plastics in the form of plastic films, plastic parts, or plastic fibers; synthetic resin products; ion exchange resins; silicone products; cellulose-based products; foams; cosmetics; and many others.

[0082] Particularly expedient is the use of the optionally brightened particulate carbon material according to the invention, which is provided with elemental silver and elemental ruthenium, as an additive for the antimicrobial treatment of filter fleeces; of textiles or in textile applications; in health and hygiene applications such as, for example, in face masks, breathing masks and insoles; of products provided with or based on activated carbon, such as plastics provided with activated carbon as an additive, of activated carbon filters which can be used for air or water purification, or of products comprising activated carbon filters.

[0083] The particulate carbon material according to the invention equipped with elemental silver and elemental ruthenium - optionally brightened as mentioned above - can also be used as a heterogeneous catalyst, for example in the catalysis of the formation of hydroxyl radicals within aqueous media allowing bacterial growth.

[0084] Examples

[0085] Reference Example 1 (Preparation of a cellulose powder containing 18.9 wt% elemental silver and 1.0 wt% elemental ruthenium):

[0086] 75.6 g (445 mmol) of solid silver nitrate and 13.94 g of ruthenium nitrosyl nitrate solution (ruthenium content 19.0 wt%; 26.2 mmol Ru) were dissolved in 416.8 g of deionized water, and the resulting aqueous precursor solution was homogeneously mixed with 211.2 g of cellulose powder (Vitacel® L-600 from J.Rettenmaier und Söhne GmbH & Co KG) to form an orange, freely flowable impregnated particulate material. 705 mL of an aqueous hydrazine solution with a pH of 13.9 [4.19 g (131 mmol) of hydrazine and 81.81 g of a 32 wt% sodium hydroxide solution (654.51 mmol NaOH), balance: water] were added to the freely flowing impregnated particulate material at room temperature at a rate of 30 mL / min with stirring. Over time, a black, homogeneous slurry formed that became increasingly easy to stir. After the addition was complete, stirring was continued for 30 minutes until no more nitrogen release could be observed.The material was then filtered with suction, washed with a total of 1000 mL of water, and dried in a drying cabinet at 105°C / 300 mbar to a residual moisture content of 15 wt. A silver content of 18.9 wt.% was determined by ICP-OES.

[0087] wt.% and a ruthenium content of 1.0 wt.% of the final product (based on 0 wt.% residual moisture). one with 18.7 wt% elemental silver and 0.9

[0088] wt.% elemental ruthenium

[0089] An aqueous solution prepared from 157.2 g of aqueous silver nitrate solution (silver content 36.2 wt%; 528 mmol Ag) and 14.9 g of aqueous ruthenium nitrosyl nitrate solution (ruthenium content 18.7 wt%; 30 mmol Ru) and 1000 mL of water was added over a period of 3 hours (7 mL / min) to a suspension of 240 g of activated carbon (Ceca 2SW) in 3000 mL of deionized water. The pH of the suspension was adjusted to 9 using 32 wt% aqueous sodium hydroxide solution. This suspension was stirred for 2 days at 80 °C. The suspension was then cooled to 35 °C, a solution consisting of 7.7 g of hydrazine hydrate (hydrazine content 64 wt%), 96.5 g of sodium hydroxide, and 400 ml of water was added over a period of 3 hours (3 ml / min), and stirring was continued for a further 4 hours. The material was then filtered off with suction and washed with a total of 20 L of water. The resulting product had a residual water content of 50.8 wt%. A silver content of 18.7 wt% was determined using ICP-OES.-% and a ruthenium content of 0.9 wt.% of the product (based on 0 wt.% residual moisture). 1 and the 2 on their antimicrobial

[0090] In various Erlenmeyer flasks, 30 mL of a culture of methicillin-resistant Staphylococcus aureus (MRSA) in trypticase soy broth (TSB) medium were adjusted to an optical density of 0.05. Subsequently, varying amounts of the product from Reference Example 1, ranging from 1 to 20 mg, were weighed in. The samples were incubated in a shaking incubator at 37°C and 150 rpm. The optical density at a wavelength of 600 nm (OD600) was determined at hourly intervals over a period of 6 hours. Inhibition of bacterial growth was evident by a reduced increase in optical density compared to the control sample. An MRSA culture without the addition of an antimicrobial agent served as the control sample. With complete inhibition of bacterial growth, no increase in optical density was observed.The corresponding sample amount of the product from Reference Example 1 or from Inventive Example 2 was used to calculate the minimum inhibitory concentration. This resulted in a minimum inhibitory concentration of 0.55 mg / mL for the product from Reference Example 1 and a comparatively lower minimum inhibitory concentration of 0.35 mg / mL for the product from Inventive Example 2.

Claims

Patent claims 1. Particulate carbon material endowed with elemental silver and elemental ruthenium, with an average particle size (d50) in the range of 0.5 to 500 pm, a pore volume in the range of 0.5 to 10 mL / g and a BET surface area in the range of 200 to 2000 m² 2 / G.

2. Material according to claim 1 comprising a silver-plus-ruthenium weight fraction formed by the elemental silver and the elemental ruthenium in the range of 0.1 to 50 wt.% with a silver : ruthenium weight ratio in the range of 1 to 2000 parts by weight silver : 1 part by weight ruthenium.

3. Material according to claim 1 or 2, comprising 95 to 100 wt.% of carbon particles equipped with elemental silver and elemental ruthenium and 0 to 5 wt.% of precious metal-free carbon particles, wherein the wt.% add up to 100 wt.%.

4. A method for producing a material according to any of the preceding claims, comprising the steps of: reducing at least one silver precursor and at least one ruthenium precursor in the presence of aqueous suspended carbon particles, in particular activated carbon particles, separating the solid formed in the course of the reduction from the aqueous phase, optionally washing the separated solid with water and optionally drying the separated and optionally washed solid.

5. The method of claim 4, wherein silver and ruthenium precursors are reduced successively or simultaneously.

6. Method according to claim 4 or 5, wherein the at least one silver precursor is selected from the group consisting of silver acetate, silver sulfate and silver nitrate and wherein the at least one ruthenium precursor is selected from the group consisting of ruthenium oxalate, ruthenium acetate and ruthenium nitrosyl nitrate.

7. A method according to any one of claims 4 to 6, wherein the activated carbon particles are activated carbon particles with an average particle size (d50) in the range of 0.5 to 400 pm, a pore volume in the range of 0.5 to 10 mL / g and a BET surface area in the range of 300 to 3000 m². 2 / g is involved.

8. A method according to any one of claims 4 to 7, wherein the reduction is carried out either at an acidic pH in the range of 1 to 4 and at a temperature in the range of 70 to 100°C with formic acid, or at an acidic pH in the range of 1 to 4 and at a temperature in the range of 10 to 40°C with hydrazine, or at a basic pH in the range of 9 to 14 and at a temperature in the range of 10 to 40°C with a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates.

9. The method of claim 8 in an embodiment comprising the successive steps: (1a) Providing an aqueous suspension comprising water, carbon particles, in particular activated carbon particles, at least one silver precursor and at least one ruthenium precursor, (2a) Contacting the aqueous suspension with formic acid at a pH in the range of 1 to 4 and a temperature in the range of 70 to 100°C or with hydrazine at a pH in the range of 1 to 4 and a temperature in the range of 10 to 40°C, (3) Separation of the formed solid from the aqueous phase, (4) where appropriate, washing the separated solid, and (5) If necessary, dry the solid.

10. The method of claim 8 in an embodiment comprising the successive steps: (1b) Providing an aqueous suspension comprising water, carbon particles, in particular activated carbon particles, at least one silver precursor and at least one ruthenium precursor, (2b) Contacting the aqueous suspension at a pH in the range of 9 to 14 and at a temperature in the range of 10 to 40°C with a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates, (3) Separation of the formed solid from the aqueous phase, (4) where appropriate, washing the separated solid, and (5) If necessary, dry the solid.

11. The method according to claim 8 in an embodiment comprising the successive steps: (lc) Providing an aqueous suspension with a pH in the range of 9 to 14 comprising water, carbon particles, in particular activated carbon particles and a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates, (2c) Contacting the aqueous suspension at a pH in the range of 9 to 14 and at a temperature in the range of 10 to 40°C (i) with an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor or (ii) with an aqueous solution comprising at least one silver precursor and subsequently with an aqueous solution comprising at least one ruthenium precursor or (iii) with an aqueous solution comprising at least one ruthenium precursor and subsequently with an aqueous solution comprising at least one silver precursor, (3) Separation of the formed solid from the aqueous phase, (4) where appropriate, washing the separated solid, and (5) If necessary, dry the solid.

12. The method of claim 8 in an embodiment comprising the successive steps: (1d) Providing an aqueous suspension with a pH in the range of 1 to 4 comprising water, carbon particles, in particular activated carbon particles and formic acid or hydrazine, (2d) Contacting the aqueous suspension at a pH in the range of 1 to 4 and at a temperature in the range of 70 to 100°C (in the case of formic acid as the reducing agent) or at a temperature in the range of 10 to 40°C (in the case of hydrazine as the reducing agent) (i) with an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor or (ii) with an aqueous solution comprising at least one silver precursor and subsequently with an aqueous solution comprising at least one ruthenium precursor or (iii) with an aqueous solution comprising at least one ruthenium precursor and subsequently with an aqueous solution comprising at least one silver precursor, (3) Separation of the formed solid from the aqueous phase, (4) where appropriate, washing the separated solid, and (5) If necessary, dry the solid.

13. A method according to any one of claims 4 to 12, wherein the particulate carbon material equipped with elemental silver and elemental ruthenium is further processed to a brightened particulate material with a brightness L* in the range of 50 to 85 by reacting it with at least one C1-C4 alkoxide of aluminum, Magnesium, calcium, silicon, zinc, zirconium and / or titanium are brought into contact with an amount of water sufficient to completely hydrolyze the at least one C1-C4 alkoxide.

14. Use of the particulate carbon material equipped with elemental silver and elemental ruthenium according to claims 1 to 3 or produced according to a method of any one of claims 4 to 12 or of the product produced according to the method of claim 13 as an additive for the antimicrobial treatment of metal surfaces; of coating materials; of plasters; of molding compounds; of plastics in the form of plastic films, plastic parts, plastic fibers or of plastics equipped with activated carbon as an additive; of synthetic resin products; of ion exchange resins; of silicone products; of cellulose-based products; of foams; of cosmetics; of filter nonwovens; of textiles; in textile applications; in health and hygiene applications; of face masks; of respiratory masks; of insoles; of products equipped with or based on activated carbon; of activated carbon filters for use in air or water purification; of products comprising activated carbon filters.

15. Use of the particulate carbon material equipped with elemental silver and elemental ruthenium according to claims 1 to 3 or produced according to a method of any one of claims 4 to 12 or of the product produced according to the method of claim 13 as a heterogeneous catalyst in the catalysis of the formation of hydroxyl radicals within aqueous media allowing bacterial growth.

Images