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    • 专利摘要:
    Procedure for obtaining graphene materials from sludge from wastewater treatment. The present invention relates to the process of obtaining graphene materials consisting of defective graphene containing dopant heteroatoms and graphene materials where metal nanoparticles are supported on these sheets by pyrolysis in the absence of oxygen from sludge from urban wastewater treatment plants or from origin industrial with high organic content. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2678079A1
    申请号:ES201830127
    申请日:2018-02-12
    公开日:2018-08-08
    发明作者:Laura PASTOR ALCAÑIZ；Sílvia DOÑATE HERNÁNDEZ；Javier Eduardo SÁNCHEZ RAMÍREZ；Hermenegildo García Gómez；Josep ALBERO SANCHO；Esther Domínguez Torres
    申请人:Depuracion De Aguas Del Mediterraneo S L；Depuracion De Aguas Del Mediterraneo Sl；
    IPC主号:
    专利说明:

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    PROCEDURE FOR OBTAINING GRAPHENIC MATERIALS FROM FANGES FROM WASTEWATER TREATMENT
    DESCRIPTION
    Field of the Invention
    The present invention belongs to the technical field of new materials and environment, and more specifically to a procedure for obtaining graphene materials where the precursors thereof are sludge generated in the processes of urban wastewater treatment or industrial origin.
    Background of the invention
    Graphene is considered a very promising material in numerous applications ranging from additive in formulations of plastics, paints and other materials, through microelectronics, sensors and reaching biomedicine. This interest in graphene determines that several procedures have been developed for obtaining it.
    Together with the ideal graphene, a large number of related materials have been characterized and prepared that can be generically indicated as graphene materials. Among these types of materials that have some of the structural characteristics that make them similar to graphene are defective graphenes (F. Banhart, J. Kotakoski and AV Krasheninnikov, Acs Nano, 2011, 5, 26-41, LG Cancado, A Jorio, EHM Ferreira, F. Stavale, CA Achete, RB Capaz, MVO Moutinho, A. Lombardo, TS Kulmala and AC Ferrari, Nano Letters, 2011, 11, 3190-3196 and A. Hashimoto, K. Suenaga, A. Gloter, K. Urita and S. lijima, Nature, 2004, 430, 870-873) that are 2D sheets of a thick atom, but where there may be local ordinances other than hexagonal, as well as vacancies of one or more atoms of carbon and holes in the sheet visible by electron microscopy techniques. In addition, there are graphene materials where other elements (doping heteroatoms) are present in smaller proportions (RT Lv and M. Terrones, Materials Letters, 2012, 78, 209218 and XW Wang, GZ Sun, P. Routh, DH Kim, W. Huang and P. Chen, Chemical
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    Society Reviews, 2014, 43, 7067-7098), mainly oxygen, but also nitrogen, sulfur, phosphorus and other elements, as well as combinations of them.
    The preparation of graphenes can be carried out in multiple ways that can be classified according to whether the precursors are molecules that are reacting to give aggregates with a greater number of carbons that end up forming the graphene sheet (bottom-up synthesis routes) or if, on the contrary, it is based on materials that already contain graphene and that can be subjected to delamination and exfoliation treatments (top-down synthetic routes).
    Among the procedures in which graphene materials are obtained by exfoliation, in addition to the use of graphites, some are based on the exfoliation of carbonaceous graphical materials that are obtained by pyrolysis of suitable precursors. In these pyrolysis processes, a precursor is subjected to heating at elevated temperatures in the absence of oxygen for a period of time sufficient for the precursor to undergo a deep structural rearrangement that derives from elimination in the gas phase of small molecules and containing heteroatoms. and leaving a residue with a high carbon content in the solid phase. That carbon residue may, in some cases, contain graphene sheets with imperfect packing and, as a consequence, weak that is susceptible to exfoliation to give rise to graphene materials.
    Not all precursors are suitable for giving this type of exfoliating graffiti carbonaceous materials. Thus, for example, many organic molecules undergo evaporation in the process and are carried away by the evacuation system of the pyrolysis equipment or by the flow that maintains the inert atmosphere in the system. Even high molecular weight macromolecules and molecules break down completely and undergo fragmentation in the pyrolysis process, without giving rise to a significant solid residue that could be graphene. Such is the case, for example, of synthetic polymers such as polystyrene and polyethylene that undergo fragmentation and elimination of the resulting molecules in the gas phase without giving rise to solid graphic carbonaceous residues in appreciable amounts under the conditions of pyrolysis.
    One of the raw materials for the production of graphene materials is sludge, which is the by-product from the different stages of
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    decontamination of urban wastewater and industrial activities. Its production results from the combination of several phenomena: Growth of microorganisms, accumulation of suspended material and accumulation of non-biodegradable organic matter. Mud is also referred to as waste from septic tanks and other industrial facilities during the treatment of water and waste.
    In the treatment of wastewater, urban sludge and industrial sludge are distinguished. Urban sludge is generated during the treatment of wastewater of domestic origin and has an organic matter content of around 70%. Industrial sludge is generated during the treatment of industrial waters and waste, its characteristics depend on the industrial activities developed and some of them may also have a high content in organic matter.
    On the other hand, at the industrial level there are other sources of sludge generation with a high content in organic matter, which are formed in the treatment of industrial wastewater or in the treatment of various industrial or agro-food waste. These sludges can be subjected to various processes, with anaerobic digestion and composting being the most common. In the case of anaerobic waste digestion, biogas is generated and a digested sludge of industrial origin.
    There is an interest in the valorization of sludge produced in wastewater treatment processes of both domestic and industrial origin.
    Patent CN106348274A describes the preparation of graphene from biomass using agricultural and forestry waste as a carbon source. The method specifically comprises the following stages:
    (1) add the crushed waste and forest waste biomass to a reaction boiler with water, perform a hydrothermal reaction, cool to room temperature after completion of the reaction, filter, wash and dry to obtain biological solid carbon;
    (2) mix the alkali with the biological carbon obtained in step (1), grind sufficiently, mix evenly and heat and calcine in the presence of protective gas; Y
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    (3) soak a sample obtained after calcination in step (2) with an acidic liquid to remove a by-product, filter, wash the solid obtained with water until the washing liquid is neutral and dry, thus obtaining graphene of A small number of layers.
    According to the method, the process is simple, the yield is high, the reaction conditions are smooth, simple equipment, respectful of the environment, and the biomass, when coming from agricultural and forest residues, is available at low cost and in sufficient quantities.
    Although with the above method graphene can be prepared using lignocellulosic biomass as a raw material, the preparation cycle is long, requires a pretreatment of the biomass and involves the massive use of chemical reagents. In addition, intermediate thermal reactions in aqueous medium at 180 ° C temperatures are necessary in the methodology used, causing significant additional energy consumption. On the other hand, the material obtained must be washed and separated using chemical compounds such as sulfuric acid, ethanol, potassium hydroxide, hydrochloric acid and metric acid that cause the generation of large volumes of liquid waste that require proper treatment before discharge, increasing production costs of graphene.
    In summary, the graphene preparation method described in document CN106348274A can be expensive, time-consuming due to the previous treatment of the sample, it requires high amounts of thermal energy, large volumes of expensive reagents and potential contaminants are necessary, all of which hinders its scalability for graphene industrial production.
    Description of the invention
    The present invention solves the problems existing in the state of the art by means of obtaining graphene materials from wastewater treatment by-products (sludge).
    The present invention describes the process for obtaining graphene materials consisting of defective graphenes containing doping heteroatoms and graphene materials where metal nanoparticles are supported on these
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    pyrolysis sheets in the absence of sludge oxygen from urban or industrial wastewater purification stations with high organic content.
    In a first aspect of the invention, the process for obtaining graphene materials from sludge and sludge from wastewater treatment comprises the following steps:
    a) Pyrolysis of by-products from wastewater treatment in the absence of oxygen at temperatures between 700 and 1500 ° C.
    b) Dispersion of the residue obtained in a solvent and exfoliation of the material.
    c) Decantation of the residues that settle spontaneously or after centrifugation at speeds below 8000 RPM.
    d) Recovery of the grapheic material of the liquid phase.
    The absence of oxygen during the pyrolysis process is essential, since its presence at temperatures and in the conditions of the thermal treatment causes the combustion of organic matter, resulting in the formation of no graffiti carbonaceous residue. This absence can be achieved by carrying out the pyrolysis process in an atmosphere that does not contain this chemical element or under ford. When working in an atmosphere that does not contain oxygen, the pyrolysis system may be subject to a slight overpressure with respect to atmospheric pressure in order to prevent the entry of atmospheric oxygen into the system.
    The pyrolysis temperature is another important variable that influences the content of heteroatoms that remain in the residue, the density of defects and the packing of the graphene sheets that are formed. The process of deep structural reorganization that leads to the graffiti of the precursor organic matter begins to be observed at temperatures of around 700 ° C, being already notable in many cases at temperatures of 900 ° C. As the temperature rises, as a general rule, materials with a higher percentage of carbon and lower defect density result. This favors the packing of graphene sheets, which determines that the exfoliation process may be less efficient. It is known that, due to its high crystallinity, the direct exfoliation of graphite to graphene from a single layer by ultrasonic treatment does not take place with appreciable performance in most solvents.
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    In another aspect of the present invention the precursor materials of the graphene materials are organic compounds of diverse nature in the form of a complex mixture that are found in wastewater and that accumulate in the sludge generated in the sedimentation process. These organic compounds of natural origin can be accompanied by synthetic polymers that are used as coagulants, as well as metal compounds that can be added to favor coagulation or that may be present in industrial waters. These sludges can be used as graphene precursors, either after undergoing a drying process or containing a percentage of moisture.
    Mud grains generated in the depuration process and containing organic matter and that may have been subjected to anaerobic digestion processes for the fermentation and decomposition of a certain percentage of organic matter to biogas or other biological transformations can also be used as graphene precursors. They can also undergo pyrolysis to form graphene sludge and sludge from the sewage treatment of farms and livestock farms, agri-food industries and agroforestry industries.
    Another aspect of the invention is the possibility of carrying out the process under the flow of a gas not containing oxygen, so that a certain flow of the inert gas circulates through the pyrolysis system that drags and separates from the system any molecule that can pass the gas phase. As inert gases nitrogen and argon can be used, among others, and this stream may or may not contain a certain proportion of hydrogen, which contributes to the process reducing environment and reduces the oxygen content and heteroatoms that remain in the carbonaceous residue. At pyrolysis temperatures, particularly when certain transition metals such as Co, Ni and Cu are present, the hydrogen reacts with the heteroatoms present in the sample subjected to pyrolysis and forms hydrogenated molecules such as H2O, NH3, SH2, etc. which migrate to the gas phase and reduce the heteroatom content of the resulting carbonaceous residue. This pyrolysis is carried out with a flow of H2 and an inert gas selected from N2, Ar, He, CO2 or combinations of two or more of the above gases in any proportion.
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    In this way, the presence of hydrogen or other reducing reagent can affect the resulting graphene material, its structure, heteroatom content and properties.
    Another aspect of the invention relates to the fact that when the pyrolysis is carried out in vain, it is necessary to work at very low pressures, lower than 10-3 Torr, which ensure that during the pyrolysis period the oxygen exposure of the carbonaceous residue is very limited so that combustion does not occur.
    Another aspect of the invention relates to the exfoliation of material, which is carried out in step b) of the process by ultrasonic treatment or by mechanical agitation with high shear power. After pyrolysis, the carbonaceous material can generate graphene with high efficiency by treatment, among other ways described, with ultrasound of the carbonaceous residue to give rise to its exfoliation and separation in graphene sheets. In this way, the graphene material can be separated from other amorphous carbon forms or from the inorganic material that may be part of the sludge. Thus, when treating a dispersion of the carbonaceous residue with ultrasound in water or organic solvents known in the state of the art such as alcohols, amides, aromatic compounds and others, a persistent graphene dispersion is generated which does not settle by gravity or by centrifugation at low revolutions. .
    The material that settles after the dispersion of graphene in the liquid medium can be separated from the graphene material that remains in the suspension. This sedimentation can be favored and accelerated by centrifugation or other means. After the purification of the graphene material, it can be recovered by filtration, centrifugation at high revolutions higher than 8000 rpm or by evaporation of the liquid phase. The cycle of i) redispersion by sonication, ii) separation by sedimentation and iii) recovery of graphene can be carried out several times to achieve a better quality of the graphene material.
    In this way, the graphene materials result from subjecting the sludge that constitutes waste from the wastewater treatment of different origins and with a different degree of drying to pyrolysis in the absence of oxygen at temperatures above 700 ° C and typically in the range between 900 and 1200 ° C, subsequent ultrasonic exfoliation or sufficient agitation and purification eliminating residues that do not disperse and settle in the process.
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    Another aspect of the invention relates to the fact that the dispersions obtained in step b) contain monolayers of graphenes, particles of several layers of graphenes with stacking or combinations thereof.
    Another aspect of the invention relates to the fact that steps b) and c) of the process can be carried out repeatedly depending on the purity of the desired material. The resulting graphene materials can be kept in suspension, for example, in water or they can be separated from the liquid phase by high speed centrifugation (greater than 8000 rpm), by filtration or by evaporation of the liquid phase. Dry graphene materials can be redispersed again almost completely or completely by sonication in the appropriate solvent.
    Another aspect of the invention relates to the fact that the graphene material obtained is doped with oxygen, nitrogen, sulfur, phosphorus, boron or combinations thereof in a content of less than 10%.
    Another aspect of the invention relates to the fact that the graphene material obtained contains on its surface nanoparticles of iron, aluminum or silicon and their oxides. The graphene materials obtained in the pyrolysis of sludge may contain adsorbed small particles of nanometric size of other non-carbonaceous material and which is also formed in the pyrolysis process. This is due to the adsorption capacity that characterizes graphene and the possible presence in the mud of inorganic material, typically metal ions, that do not evaporate in the pyrolysis process.
    In this way the inorganic material is secreted in a different phase and remains adsorbed on the graphene surface as it is formed in the pyrolysis process. A typical case is the formation of iron nanoparticles on graphene, due to the possible iron content of graphene precursor sludge. Once the material is formed, these metal nanoparticles can be oxidized spontaneously by exposure to the environment forming metal oxide nanoparticles or they can be converted into other metal compounds, such as sulfides, by suitable treatments.
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    These metals can also react at pyrolysis temperatures with the carbon present in the medium forming nanoparticles of metal carbides on the graphene surface. This type of graphene materials with metal nanoparticles are typically formed in sludges that contain a high content of metals, such as certain sludges of industrial origin or sludge generated in the treatment of urban wastewater that has undergone coagulation and flocculation processes with metal salts
    Graphene materials obtained in the pyrolysis of sludge can be characterized by the usual techniques in the state of the art that demonstrate 2D morphology (electron microscopy), the nature of the mono- or few layers of the material (atomic force microscopy), the presence of oxygen and other heteroatoms (elemental analysis and X-ray photoelectronic spectroscopy, XPS), the sp2 nature of carbon atoms (13C NMR in solid state, XPS and Raman spectroscopy), the presence of network defects (Raman spectroscopy), the existence of supported metal nanoparticles and the distribution of their sizes (transmission electron microscopy, XPS, X-ray diffraction, elemental analysis), among many other techniques that may include UV-Vis absorption spectroscopy (transparency and light absorption ), oxygen thermogravimetry (inorganic waste), constant temperature gas adsorption (specific area measurement), conductivity measurements d electrical (specific and superficial electrical resistance), among other possible.
    The graphene materials described herein may have different applications such as additives of plastic materials, paints, asphalts, ceramics and other fields. In particular, those materials containing Fe nanoparticles have been tested as catalysts in processes of relevance for wastewater purification, presenting many of the characteristics that are expected for graphenes supporting nanoparticles
    Brief description of the figures
    Figure 1. Raman spectra recorded for the solid sample of the graphene material resulting from the pyrolysis of the primary sedimentation sludge in three different regions using a 532 nm laser as a source of excitation and measuring the spectrum in 3 ^ 3 mm regions.
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    Figure 2. Images of transmission electron microscopy of the particles present in a methanol suspension resulting from the dispersion of the graphene material obtained in the pyrolysis of the primary sludge from the urban wastewater treatment of the city of Murcia.
    Figure 3. Raman spectra recorded for the solid sample of the graphene material resulting from pyrolysis of sludge from the digester in two different regions using a 532 nm laser as a source of excitation and measuring the spectrum in regions of 3 ^ 3 ^ m.
    Figure 4. Images of electron microscopy of the graphene material sample obtained in the pyrolysis of sludge from a biodigester. The presence of metallic nanoparticles is clearly shown in the image with greater magnification.
    Figure 5. Elemental composition determined by electron microscopy of the sample whose image corresponds to Figure 4. Note that the sample holder is a Cu grid coated with carbon and that the Cu detected in the measurement must be due to the grid.
    DESCRIPTION OF EMBODIMENTS
    Having described the present invention, it is further illustrated by the following examples.
    Example 1. Graphene doped with N and with defects obtained by pyrolysis of primary sedimentation sludge in the treatment of urban wastewater.
    10 grams of sludge formed in the process of decanting-flocculation of urban wastewater (in particular from an urban wastewater treatment plant) were used, which were previously dried in an oven at 60 oC for 8 h with a residual humidity around at 10%, which were introduced into a crucible of 50 ml of porcelain capacity forming a uniform bed and of the lowest possible thickness. The crucible containing the sludge was placed in the central part of a horizontal tubular quartz electric oven of 20 cm in diameter and whose ends protrude from the oven about 10 cm so that these ends do not reach
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    warm to the temperatures of the central part. The oven was closed with teflon seals that fit tightly and a nitrogen flow of 10 ml * min-1 was established. The oven heating was programmed so that the temperature rose to 5 oC * min-1 up to 900 oC (about 3 h), maintaining the temperature of 900 oC for another 3 h.
    After this time, the oven heating stopped, allowing it to cool spontaneously below 150 oC (approximately 2 h), while maintaining the flow of inert argon gas. The resulting grayish residue was dispersed in a 200 ml capacity vessel containing 100 ml of water at room temperature and an ultrasonic treatment (750 W, 60 min) was carried out using an ultrasonic generator whose tip is inserted into the center of the aqueous phase. After this time, the suspension was decanted, eliminating the large particles present in the sludge residue. Then, the suspension was placed in a suitable container for use in an ultracentrifuge and the dispersion was centrifuged at increasing speeds. Rotational speeds below 2000 rpm cause a sediment of unwanted particles that are removed, remaining with the liquid phase that contains the graphene material.
    The weight obtained from graphene was 1.4 g. The graphene material characterization results obtained in the present example are shown in Figures 1 and 2.
    The suspension can be centrifuged in a second cycle at higher speeds up to 8000 rpm, separating the decanted material. The liquid phase can be subjected to lyophilization or another procedure to obtain dry graphene material that is susceptible to elemental analysis.
    Analytical data show that, along with carbon, other heteroatoms are also present in the graphene material sample. Among them, the most abundant are oxygen and nitrogen, but other elements are also detected in smaller quantities such as sulfur and phosphorus.
    An analogous procedure can be carried out at temperatures in the range of 700 to 1200 oC, with a decrease in the proportion of N being observed as the temperature increases. Table 1 summarizes the data obtained.
    Table 1. Main analytical data of the graphene material resulting from the pyrolysis of primary sludge from an urban wastewater treatment plant.
     Temperature (oC)  Performance with respect to the initial weight Content (%) in C N
     900  14 47 9
     1000  11 51 8
     1100  9 55 7
     1200  3 78 1
    Example 2: Graphene materials obtained by pyrolysis of sludge from 5 digesters used in biogas generation processes.
    A procedure similar to that described in example 1 is followed, using the same equipment, but it started from a sludge from a biodigester that produces anaerobic fermentation of part of the organic matter generating methane and carbon dioxide among other gases.
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    In this way a graphene material was obtained in a yield of 7%, lower than that obtained in example 1. This lower yield is in accordance with the lower organic matter content of this sludge. Figures 3 to 5 present characterization data of this graphene material.
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    The presence of metal nanoparticles supported on graphene sheets can be seen in the electron microscopy images of Figure 4. These nanoparticles have iron in their composition, as established by the scanning technique of energy dispersion coupled to the scanning microscopy equipment as indicated in Figure 5.
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    Example 3: Graphenes obtained by pyrolysis of secondary sludge from urban wastewater.
    10 g of secondary sludge generated in the treatment of urban wastewater was subjected to pyrolysis using the same equipment described in example 1 and carrying out the treatment at 900 ° C obtaining graphenes with properties similar to those shown in example 1, but with a yield of 8%.
    Example 4: Graphenes obtained by pyrolysis of mixed sludge from mixing primary and secondary sludge in the purification of urban wastewater.
    The pyrolysis was carried out under the conditions of Example 3 using a mixed primary and secondary sludge that was mixed prior to the graphene generation process, obtaining a graphene material as shown in Figure 2 in a yield of 9% by weight .
    Example 5: Graphenes obtained by pyrolysis of thickened sludge generated in the purification of urban wastewater.
    The pyrolysis was carried out using an oven as described in example 1 at 900 ° C, avoiding the presence of oxygen by means of a vacuum pump that maintains the system at a pressure of 10-3 Torr and using as a precursor a formed sludge in the thickener and characterized by a high iron content. Under these conditions a graphene similar to that shown in Figure 4 was obtained and whose main characteristic is the presence of iron nanoparticles deposited on the graphene. The yield of the graphene material was 15% by weight.
    Example 6: Graphenes obtained by pyrolysis of digested dehydrated sludge.
    The pyrolysis process by heating in an electric oven at 900 oC under vacuum was carried out in this example with sludge from a digester and which have been dehydrated before being subjected to heat treatment. The graphene material is similar to that obtained in example 2, but with a yield of 12% with respect to the weight of the precursor and where the presence of nanoparticles constituted by iron and its oxides is also observed.
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    Example 7: Graphene materials obtained by pyrolysis of sludge from the treatment of waste and the purification of sewage from livestock facilities of pigs.
    The slurries generated in pig farms are also suitable sludge for the preparation of graphene materials by pyrolysis at 900 ° C under a stream of inert gas (argon) according to the procedure described in example 1 to generate a susceptible residue. if exfoliated in graphene sheets with a yield of 15%.
    Example 8: Graphene materials obtained by pyrolysis of sludge from the treatment of waste and from the purification of wastewater from cattle facilities of cattle.
    The sludge generated in the treatment of wastewater and waste from the cattle industry (Bovine), are suitable sludge after a stage of dehydration for the preparation of graphene materials. The process used is similar to example 7 where the dried sludge is subjected to a pyrolysis process at temperatures between 800-1000 ° C under a stream of inert gas (argon) to generate a residue that can be exfoliated in graphene sheets with a yield of 13%
    Example 9: Graphene materials obtained by pyrolysis of sludge from waste treatment and sewage treatment of livestock facilities of sheep.
    The sludge generated in the treatment of wastewater and waste from the livestock industry (sheep), are suitable sludge for the preparation of graphene materials. The procedure is by pyrolysis thereof at temperatures between 800-1000 ° C under a stream of inert gas (argon) to generate a residue capable of being exfoliated in graphene sheets with a yield of 12%.
    Example 10: Graphene materials obtained by pyrolysis of sludge from the purification of wastewater from the agri-food industry of fruit juices.
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    The agri-food industry and especially those of fruit juices produce a large amount of waste, these residues once treated (dehydrated) are suitable for the preparation of graphene materials by pyrolysis of the same at temperatures between 800-1000oC under an argon current for generate a residue that can be exfoliated in graphene sheets with a yield of 10%.
    Example 11: Graphene materials obtained by pyrolysis of sludge from septic tanks.
    There is a large number of rural homes and industries that do not have a direct connection to the sewerage network being necessary for the treatment of wastewater generated, the use of septic tanks. In septic tanks biological sludge is produced that must be managed before its final disposition. Once treated, these sludges are suitable for the preparation of graphene materials by pyrolysis at temperatures between 800-1000 ° C under a stream of inert gas (argon) to generate a residue that can be exfoliated in graphene sheets with a yield of eleven%.
    Example 12: Graphene materials obtained by pyrolysis of residues from agroforestry residues, forages and pastures
    The procedure described is similar to the previous examples, the material is dried at 60 ° C, homogenized and subsequently subjected to a pyrolysis process at temperatures between 800-1000oC under a stream of inert gas (argon) to generate a residue capable of being exfoliated in graphene sheets with a yield of 9%.
    Example 13: Graphene materials obtained by pyrolysis of the organic fraction of urban solid waste (MSW).
    The procedure described is similar to the previous examples, the material is dried at 60 ° C, homogenized and subsequently subjected to a pyrolysis process at temperatures between 800-1000oC under a stream of inert gas (argon) to generate a residue capable of being exfoliated in graphene sheets with a yield of 8%.
    Example 14: Graphene materials obtained by pyrolysis of sludge subjected to the composting process.
    5 The procedure described is similar to the previous examples, the material is oven dried, homogenized and subsequently subjected to a pyrolysis process.
    temperatures between 800-1000oC under a stream of inert gas (argon) to generate a residue that can be exfoliated in graphene sheets with a yield of 10%.
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    Example 15: Graphene materials obtained by pyrolysis of the amyloid residues.
    The procedure described is similar to the previous examples, the material is oven dried, homogenized and subsequently subjected to a pyrolysis process.
    15 temperatures between 800-1000oC under a stream of inert gas (argon) to generate a residue that can be exfoliated in graphene sheets with a yield of 7%.
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    权利要求:
    Claims (9)
    [1]
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    1. Procedure for obtaining graphene materials from sludge
    from wastewater treatment, characterized in that
    It comprises the following stages:
    to. Pyrolysis of by-products from wastewater treatment in the absence of oxygen at temperatures between 700 and 1500 ° C.
    b. Dispersion of the residue obtained in water or other solvent and exfoliation of the material.
    C. Decanting of the residues that settle spontaneously or after centrifugation at speeds below 8000 RPM.
    d. Recovery of the grapheic material of the liquid phase.
    [2]
    2. Procedure for obtaining graphene materials according to claim 1, characterized in that the sludge is obtained from sludge generated in the flocculation-sedimentation process of urban wastewater treatment, sludge formed in the urban wastewater digestion processes, farms livestock, agri-food, agroforestry, sludge obtained in thickening processes, dehydrated sludge and sludge from septic tanks.
    [3]
    3. Procedure for obtaining graphene materials according to claims 1 to 2, characterized in that the pyrolysis is carried out in a vacuum at a lower pressure of 10-3 Torr, with a flow of H2 and an inert gas selected from N2, Ar , He, CO2 or combinations of two or more of the above gases in any proportion.
    [4]
    4. Method according to claims 1 to 3, characterized in that the exfoliation is carried out by ultrasonic treatment or by mechanical agitation with high shear power.
    [5]
    5. Method according to claims 1 to 4, characterized in that steps b) and c) of the process can be carried out repeatedly depending on the purity of the desired material.
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    [6]
    Method according to claims 1 to 5, characterized in that the graphene material obtained is doped with oxygen, nitrogen, sulfur, phosphorus, boron or combinations thereof in a content of less than 10%.
    [7]
    Method according to claims 1 to 6, characterized in that the dispersions obtained in step b) contain graphene monolayers, particles of several layers of graphenes with stacking or combinations thereof.
    [8]
    8. Method according to claims 1 to 7, characterized in that the graphene material obtained contains nanoparticles of other components on its surface.
    [9]
    9. Method according to claim 8 wherein the nanoparticles that are deposited on the graphene sheets are iron, aluminum or silicon or their oxides or carbides.
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    同族专利:
    公开号 | 公开日
    ES2678079B2|2020-03-10|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    ES2471318A1|2012-11-22|2014-06-25|Abengoa Solar New Technologies S.A.|Method for obtaining solid graphene samples or suspensions|
    CN104843685A|2015-04-10|2015-08-19|四川大学|Method for preparation of three-dimensional porous graphene carbon electrode material from livestock excrement|
    CN104795565A|2015-05-11|2015-07-22|内蒙古民族大学|Porous graphene powder rich in heteroatom and preparation method and application thereof|
    CN105060289A|2015-09-21|2015-11-18|中南大学|Method for preparing fewer-layer graphene on basis of biomass waste|
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