• 专利附录
  • 专利说明
  • 权利要求
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  • 同族专利
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  • 优先权
    • 专利摘要:
    Procedure for obtaining zerovalent iron nanoparticles. The present invention refers to a process that makes it possible to obtain graphitized zero valence iron nanoparticles from agricultural residues. It is a low-cost process that does not generate waste since it allows the use of all the products and by-products obtained. The procedure comprises the following stages: a) conditioning the agricultural residue by grinding it, mixing it with water and subsequent ultrafiltration, b) hydrothermal carbonization of the permeate obtained in step a) in the presence of an iron salt, c) graphitization in the gas phase of the iron nanoparticles coated with amorphous carbon obtained in the previous step and isolation of the graphitized particles obtained. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2809349A1
    申请号:ES202030780
    申请日:2020-07-27
    公开日:2021-03-03
    发明作者:Font Andrés Fullana；Roca Blanca Calderon
    申请人:Universidad de Alicante；
    IPC主号:
    专利说明:

    [0002] Procedure for obtaining zerovalent iron nanoparticles
    [0004] The present invention relates to a process for producing magnetic iron nanoparticles coated with graphitized carbon using an agricultural residue with a high content of polyphenols. Said particles have application in different fields of industry, such as electrochemistry, renewable energies and elimination of pollutants in water, air and soil.
    [0006] Therefore, this invention focuses on the field of revaluation of agricultural residues for the production of advanced materials with added value.
    [0008] BACKGROUND OF THE INVENTION
    [0010] Zero valence iron nanoparticles (zerovalents) are used in different environmental applications ranging from heavy metal ion removal to biogas production. One of the problems that these types of particles present is that they tend to agglomerate, reducing their effectiveness. In addition, it has been shown that under certain conditions they can re-release the contaminants they had retained into the environment. Current methods of producing zero-valence iron nanoparticles are costly and environmentally inefficient. All this has the consequence that its application on an industrial scale has not yet reached the market.
    [0012] A solution to these problems of agglomeration and release of contaminants is the coating of the nanoparticles with different materials to improve their dispersion in the medium without affecting their reactivity. Among the coatings that can be achieved, one of the most interesting are those of graphitized carbon, which allow the application of nanoparticles for the production of electrodes, as well as environmental decontamination.
    [0014] There are different methods of producing zero valence iron nanoparticles coated with a layer of graphitized carbon. Thus, for example, patent US5472749A describes a method for the synthesis of metallic nanocrystals and their alloys covered by a layer of graphite using a procedure based on the generation of an electric arc. By means of this method, the material to be encapsulated is vaporized by generating an electric arc between a tungsten cathode and an anode of the metal, placing a graphite crucible in the reaction chamber. Said chamber is fed with an inert gas, which serves to drive the nanoparticles formed into the collection chamber.
    [0016] Patent US20080213189A1 describes a method of producing metals and their alloys covered by a layer of graphite by means of a chemical vapor deposition process. The process consists of vaporizing the metal or metals adsorbed on silica, and putting them in contact with a stream of gas rich in carbon, which produces the coating of the metallic particles. The silica is then removed by acid digestion.
    [0018] These methods based on the deposition of carbon at high temperature or using a large amount of electrical energy, although they produce a high quality material, have a very high production cost that makes them unfeasible in environmental applications.
    [0020] Patent US20130343996A1 describes a method for the production of magnetic graphitized nanoparticles with a cobalt and iron core. In this case, the production method is produced in two phases: a first in which iron and cobalt precursors are reacted with a carbohydrate in solution at a temperature between 80-120 ° C for 8 hours, and a second in which the resulting solid is filtered and treated with argon at temperatures between 500-600 ° C.
    [0022] This production method, although it has advantages over carbon deposition in the gas phase, when carried out at low temperatures requires long reaction times, which increases costs and makes it unfeasible for industrial production. In addition, the liquid resulting from the reaction with the carbohydrate generates highly polluting residues due to its content of cobalt, iron and organic matter.
    [0024] The document: Niu H. et al. ACS Appl. Mater. Interfaces 2012, 4, 1, 286-295, refers to a procedure for obtaining graphitized iron nanoparticles from a starch or glucose solution, characterized by comprising a step of dispersing the previous solution in 0.8 g of Fe 3 O 4 nanoparticles, followed by hydrothermal carbonization around 180 ° C for 4 hours, obtaining iron nanoparticles coated with amorphous carbon and followed by graphitization in the gas phase for 4 hours of the iron nanoparticles coated with amorphous carbon obtained in the previous stage and finally an isolation of the graphitized particles obtained. This process results in very low yields, just 5% by weight of Fe (0).
    [0026] Document EP2383374A1 discloses a process for obtaining graphitized iron nanoparticles from a glucose solution and an iron salt. In the process, there is a hydrothermal carbonization of the graphite precursor at 160-200 ° C and a graphitization in the gas phase of the iron nanoparticles coated with amorphous carbon obtained between 450-700 ° C and in an inert atmosphere.
    [0028] Document EP3659725A1 discloses a process for obtaining graphitized iron nanoparticles from a mixture comprising a source of transition metal and a polybasic organic carboxylic acid with a solvent to form a homogeneous solution, then removing the solvent from the homogeneous solution to obtain a precursor, and subjecting the precursor to high temperature pyrolysis under an inert protective atmosphere or a reducing atmosphere.
    [0030] In view of the foregoing, the processes currently in the literature to obtain zero-valent iron particles have very high production costs, are industrially unfeasible due to their very low yields, or they produce a large amount of waste. There is therefore a need to provide a process for the production of nanoparticles of this type at low costs that enables their application in environmental processes.
    [0032] DESCRIPTION OF THE INVENTION
    [0034] The present invention refers to a process that makes it possible to obtain iron nanoparticles coated with a thin layer (<5 nm) of graphite with high purity, similar to those obtained by deposition or electrical discharge, but at much lower production costs. and carrying out a fully integrated process that does not produce any waste stream, since the products and by-products obtained are used in the same process. In addition, high yields of Fe (0) (<50% by weight of iron) are obtained, thanks to the presence of polyphenols in the process.
    [0035] Therefore, the present invention refers to a process for obtaining graphitized zerovalent iron nanoparticles from agricultural waste containing polyphenols, characterized by comprising the following steps:
    [0036] a) conditioning the agricultural residue by grinding it, mixing it with water and subsequent ultrafiltration, thus obtaining a permeate free of suspended solids and a solid residue,
    [0037] b) hydrothermal carbonization of the permeate obtained in step a) in the presence of an iron salt, obtaining iron nanoparticles coated with amorphous carbon and a residual aqueous stream,
    [0038] c) graphitization in the gas phase of the iron nanoparticles coated with amorphous carbon obtained in the previous step and isolation of the graphitized particles obtained.
    [0040] The agricultural residue used in the process is a carbonaceous material with polyphenol content. The polyphenol content of these residues is essential for the particles produced to have a nanometric size in step b) of the process. Furthermore, these wastes are very difficult to treat in industry given their high content of organic matter, with which the invention presented here provides a solution to this problem and makes it possible to integrate a waste into an industrial process for the production of a product with value added.
    [0042] The combination of polyphenols, graphitization in a reducing medium and magnetic separation that eliminates particles with low Fe (0) content, in the process of the invention, results in high yields of Fe (0).
    [0044] The selection and conditioning of the carbonaceous starting material suitably by ultrafiltration allows to increase the production yield of graphitized iron nanoparticles, increasing the quality of the product obtained. Next, the graphitized iron nanoparticles are synthesized with a method that combines hydrothermal carbonization of an agricultural residue with a high polyphenol content and subsequent graphitization of the product obtained in the gas phase.
    [0046] In a preferred embodiment, the agricultural residue comprises at least 1% by weight of polyphenols with respect to the total volatile solids of the residue, plus preferably between 5 and 20% with respect to total volatile solids.
    [0048] As is known to those skilled in the art, volatile solids (SV) are understood to be the solids that remain after drying the sample but are lost when the residue is calcined at a temperature of between 400 ° C and 900 ° C.
    [0050] In another preferred embodiment, the agricultural residue is alperujo. As is well known to those skilled in the art, alperujo is a by-product of the oil mills during the extraction of olive oil, it is the mixture of: vegetation waters or vegetable water; solid parts of the olive, such as the pit, the mesocarp and the skin; and fatty remains. It is defined as everything that remains of the ground olive if we eliminate the olive oil.
    [0052] However, other agricultural residues from the production of coffee, tea, etc. can also be used.
    [0054] In a preferred embodiment, mixing with water in step a), prior to ultrafiltration, is carried out until having a total solids content in the mixture of less than 10% by weight.
    [0056] In a preferred embodiment, the ultrafiltration of step a) is carried out with filters of pore diameter between 70-100 nm.
    [0058] In a preferred embodiment, the hydrothermal carbonization of step b) is carried out by contacting the permeate obtained in step a) with an aqueous solution of an iron salt in a reactor at temperatures between 150 and 275 ° C.
    [0060] Preferably, the iron salt is selected from the list comprising: FeCh, Fe2SO4, FeCl 2 , Fe (NO 3 ) 3 , Fe 2 (SO 4 ) 3 , or combinations thereof.
    [0062] Preferably, between 0.1-1 kg of iron salt / kg of dry matter of the permeate obtained in the previous ultrafiltration step is added (the permeate contains the soluble organic matter).
    [0064] In a preferred embodiment of hydrothermal carbonization, the reaction time of the permeate with the iron salt solution at the indicated temperature is at least 30 minutes.
    [0065] In a preferred embodiment, the gas phase graphitization of the amorphous carbon-coated iron nanoparticles from step c) is carried out at a temperature between 600 and 800 ° C in an inert or reducing atmosphere, for example, nitrogen atmosphere. . This inert or reducing atmosphere can include between 1 and 2% by volume of air or oxygen, preferably 1%. The presence of small amounts of oxygen can help remove non-graphitized carbon.
    [0067] The graphitization is preferably carried out for at least one hour.
    [0069] In a preferred embodiment, the isolation of the graphitized particles of step c) is carried out by means of a magnetic separator that strongly attracts the graphitized particles and does not attract the non-graphitized particles that show less magnetization.
    [0071] In a preferred embodiment, the graphitized zerovalent iron nanoparticles obtained in c) are stabilized by wetting with the residual aqueous stream obtained in b).
    [0073] In a preferred embodiment, the solid residue obtained in step a) is subjected to an anaerobic digestion for the production of biogas and a second solid residue. Preferably, the non-graphitized particles from step c) are used as an additive in anaerobic digestion. The biogas thus obtained can be used as a heating fuel in steps b) and c) and the solid residue obtained in the aerobic digestion can be used as a fertilizer.
    [0075] The process of the invention, as described, takes into account not only the production of the nanoparticles, but also integrates all the waste streams so that it is sustainable from an economic and environmental point of view. For this, a purification treatment of the product obtained is carried out, so that the iron nanoparticles that have not been graphitized are used as an additive for the anaerobic digestion that treats both waste streams and excess agricultural waste. The residues with the presence of polyphenols present problems in anaerobic digestion. However, the addition of carbon with embedded zerovalent iron improves this process substantially. The biogas obtained in the anaerobic digestion is used to heat the stages that require temperature and the digestate can be used preferably as an iron-enriched fertilizer. Both the gases produced in the carbonization and in the activation of the nanoparticles, can be introduced into the digester to become methane by biological methanization, (Schwede, S., et al (2017), Biological syngas methanation via immobilized methanogenic archaea on biochar. Energy Proceed, 105, 823-829) also eliminating the gaseous residues of the process.
    [0077] The nanoparticles obtained by the method of the invention are coated with a thin layer (<5 nm) of graphite and have diameters between 20 and 50 nm.
    [0079] Said nanoparticles have applications, for example, in the field of water treatment, biogas production, electrochemistry and fertilizers.
    [0081] Throughout the description and claims the word "comprise" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and characteristics of the invention will emerge partly from the description and partly from the practice of the invention. The following examples and figures are provided by way of illustration, and are not intended to be limiting of the present invention.
    [0083] BRIEF DESCRIPTION OF THE FIGURES
    [0085] Fig. 1 : TEM (transmission electron microscopy) image of a graphitized zerovalent iron nanoparticle.
    [0087] Fig. 2: TEM image of carbonized impurities with embedded iron nanoparticles that are formed in hydrothermal carbonization (stream (5)). In process c) of the present intention, it serves to eliminate these impurities, in addition to graphitizing the carbon that is around the nanoparticles.
    [0089] Fig. 3: Diagram of the process of the present invention.
    [0090] EXAMPLES
    [0092] In the following, the invention will be illustrated by an example of the process of the invention.
    [0094] Example 1: Procedure for obtaining graphitized zerovalent particles by the method of the invention
    [0096] In stage 1, the raw material used as the carbonaceous phase in the process is conditioned. In this case, alperujo was used. Said residue was triturated and mixed with water until the production of a fluid aqueous suspension with a total solids content of less than 10% by weight. This suspension (1) was stored in a tank (101) (see figure 3). The aqueous phase was separated from the solid phase by using ultrafiltration equipment (102) with a pore between 70-100 nm, thus obtaining a permeate (2) and solid residue (3). The permeate (2), which must be free of suspended solids and containing soluble organic matter, was taken to the autoclave reactor (104). The solid waste stream (3) was passed to the waste storage tank before going on to its subsequent treatment in an anaerobic digester.
    [0098] The next stage of the procedure consisted of hydrothermal carbonization of the permeate obtained in stage 1. In this stage, the iron nanoparticles coated with amorphous carbon are produced. To this end, the ultrafiltered stream of permeate (2) from the block for conditioning the raw material by ultrafiltration (102) was introduced into the reactor (104), with a solution of iron chloride (FeCh) (4) found in a reservoir (103). Preferably, the ratio between the dissolution of the salt and the ultrafiltered stream was 0.5 kg of salt / kg of dry matter of the permeate obtained. The reaction was carried out in the stirred autoclave reactor (104) at 225 ° C for a time of 30 minutes. Under these conditions, zerovalent iron nanoparticles with an average size of 50 nm were obtained, covered with a thin layer of amorphous carbon (less than 5 nm). The reaction product (5) was filtered in unit (105), obtaining two streams: one of carbon-coated nanoparticles (7) that were brought to the activation phase and a residual aqueous stream (8).
    [0100] This was followed by the graphitization of the nanoparticles in the gas phase and the removal of the non-graphitizable carbon. For this, the stream (7) from the reactor (104) previously filtered in the filtration unit (105), it was introduced into an oven (106) at a temperature of 700 ° C for one hour in an inert or reducing atmosphere, preferably with nitrogen. After completion of the reaction, a stream of water was used to extract the solid product from the oven. In addition, water has the function of stabilizing highly reactive nanoparticles and preventing their spontaneous reaction with air. The water used comes from the aqueous phase from the previous filtration stage (8). Once the nanoparticles were stabilized in the mixer (107), the mixture (10) of nanoparticles and water was led to a magnetic separator (108) from which two streams emerged, one formed by the graphitized magnetic nanoparticles (11) strongly attracted by the magnet and another current formed by carbon agglomerates with iron nanoparticles whose magnetization / weight ratio is low (12). This stream (12) was used as an additive in the anaerobic digestion of the solid residue (3) obtained in the first stage.
    [0102] Finally, the treatment of waste streams and their integration in the process were carried out. The aqueous streams from the process (3 and 12) were treated in an anaerobic digester (109) from which biogas was obtained, which was used both for heating the reactor (104) for hydrothermal carbonization, and for the furnace of graphitization (106). A part of the original residue of alperujo (13) was used to increase the production of biogas (a part of the stream (7) could also be used to improve the quality of the biogas obtained in the digester). A pasty solid residue (15) was also obtained from the digester that can be used as a fertilizer. The properties of fertilizers are improved by the fact that they contain iron nanoparticles. The gas (6) produced in the autoclave reactor (104) is bubbled into the anaerobic digester (109), eliminating the possible polluting gases HCl, NOx or SO 2 produced during carbonization and improving the quality of the biogas by conversion of the monoxide carbon to methane.
    权利要求:
    Claims (19)
    [1]
    1. Procedure for obtaining graphitized zerovalent iron nanoparticles from agricultural waste containing polyphenols, characterized by comprising the following steps:
    a) conditioning the agricultural residue by grinding it, mixing it with water and subsequent ultrafiltration, thus obtaining a permeate free of suspended solids and a solid residue,
    b) hydrothermal carbonization of the permeate obtained in step a) in the presence of an iron salt, obtaining iron nanoparticles coated with amorphous carbon and a residual aqueous stream,
    c) graphitization in the gas phase of the iron nanoparticles coated with amorphous carbon obtained in the previous step and isolation of the graphitized particles obtained.
    [2]
    2. Process according to claim 1, wherein the agricultural residue comprises at least 1% by weight of polyphenols with respect to total volatile solids.
    [3]
    3. Process according to claim 1 or 2, where the agricultural residue is alperujo.
    [4]
    4. Process according to any of the preceding claims, wherein the mixing with water from stage a) prior to ultrafiltration is carried out until having a content of total solids in the mixture of less than 10% by weight.
    [5]
    5. Process according to any of the preceding claims, wherein the ultrafiltration of step a) is carried out with filters with a pore diameter between 70-100 nm.
    [6]
    6. Process according to any of the preceding claims, wherein the hydrothermal carbonization of step b) is carried out by contacting the permeate with an aqueous solution of an iron salt in a reactor at temperatures between 150 and 275 ° C. .
    [7]
    7. Process according to claim 6, where the iron salt is selected from the list comprising: FeCh, Fe2SO4, FeCh, Fe (NO 3 ) 3 , Fe 2 (SO 4 ) 3 , or combinations thereof.
    [8]
    8. Process, according to any of the preceding claims 6 or 7, where between 0.1-1 kg of iron salt / kg of dry matter of the permeate obtained after ultrafiltration of step a) is added.
    [9]
    9. Process according to any of the preceding claims 6 to 8, wherein the reaction time of the permeate with the iron salt solution at the indicated temperature is at least 30 minutes.
    [10]
    10. Process according to any of the preceding claims, wherein the gas phase graphitization of the iron nanoparticles coated with amorphous carbon from step c) is carried out at a temperature between 600 and 800 ° C in an inert or reducing atmosphere .
    [11]
    11. Process according to claim 10, where the graphitization is carried out for at least one hour.
    [12]
    12. Process according to claim 10 or 11, where the inert or reducing atmosphere includes 1% by volume of air or oxygen.
    [13]
    13. Process according to any of the preceding claims, wherein the isolation of the graphitized particles of step c) is carried out by means of a magnetic separator that strongly attracts the graphitized particles and does not attract the non-graphitized particles that present less magnetization .
    [14]
    14. Process according to any of the preceding claims, wherein the graphitized zerovalent iron nanoparticles obtained in c) are stabilized by wetting with the residual aqueous stream obtained in b).
    [15]
    15. Process according to any of the preceding claims, wherein the residue obtained in step a) is subjected to anaerobic digestion for the production of biogas and a second solid residue.
    [16]
    16. Process according to claim 15, where the non-graphitized particles from step c) are used as an additive in anaerobic digestion.
    [17]
    17. Process according to any of the preceding claims 15 to 16, wherein the biogas obtained from aerobic digestion is used as fuel for heating in stages b) and c).
    [18]
    18. Process according to any of the preceding claims 15 to 17, wherein a part of the agricultural residue containing starting polyphenols and / or a part of the iron nanoparticles coated with amorphous carbon obtained in step b) are used in the digestion anaerobic.
    [19]
    19. Process according to any of the preceding claims 15 to 18, wherein the solid residue obtained in the aerobic digestion is used as a fertilizer.
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    同族专利:
    公开号 | 公开日
    WO2022023596A1|2022-02-03|
    ES2809349B2|2021-07-06|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    EP2383374A1|2010-04-29|2011-11-02|BASF Corporation|Nano-particles containing carbon and a ferromagnetic metal or alloy|
    EP3659725A1|2017-07-28|2020-06-03|China Petroleum & Chemical Corporation|Carbon-coated transition metal nanocomposite material, and preparation and use thereof|
    CN109277078A|2018-10-25|2019-01-29|广东轻工职业技术学院|A kind of tea polyphenols modified graphene loaded nano-iron material and its preparation method and application|
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    优先权:
    申请号 | 申请日 | 专利标题
    ES202030780A|ES2809349B2|2020-07-27|2020-07-27|PROCEDURE FOR OBTAINING ZEROVALENT IRON NANOPARTICLES|ES202030780A| ES2809349B2|2020-07-27|2020-07-27|PROCEDURE FOR OBTAINING ZEROVALENT IRON NANOPARTICLES|
    PCT/ES2021/070506| WO2022023596A1|2020-07-27|2021-07-12|Method for obtaining zerovalent iron nanoparticles|
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