METHOD AND SYSTEM FOR RECOVERING AND REUSE OF CONDUCTIVE ADDITIVES FOR FLASH Joule HEATING

Abstract

Methods and systems for recovering and reusing conductive additives for flash Joule heating. The conductive additive or flash Joule heated material utilized, such as electronic waste, ore, fly ash, soil, and / or bauxite slag, may be recovered at high recovery yields higher than 85%, and then may be reused for additional flash Joule heating processes. The conductive additive may be separated from the product of the flash Joule heating process, such as by screening or by centrifugation, filtration, and drying.

Description

[0001] Related Applications

[0002] This application claims priority to the following: (1) U.S. Patent Application Serial No. 63 / 420,282, filed October 28, 2022, entitled "Methods And Systems For The Recovery And Reuse Of Conductive Additives For Flash Joule Heating"; (2) PCT Patent Application Serial No. PCT / US23 / 65506, filed April 7, 2023, entitled "Heavy-Metal-Reduced Post-Industrial Waste In Cementitious Materials And Methods Of Making And Using Thereof"; and (3) U.S. Patent Application Serial No. 63 / 589,489, filed October 11, 2023, entitled "Methods For Remediation Of PFAS-Contaminated Soil By Rapid Electrothermal Mineralization".

[0003] The methods and systems of the present invention are also related to PCT Patent Application Serial Nos. PCT / US21 / 52030, PCT / US21 / 52043, PCT / US21 / 52057, and PCT / US21 / 52070, granted to James M. Tour et al., each entitled "Ultrafast Flash Joule Heating Synthesis Methods And Systems For Performing Same", and each filed on September 24, 2021.

[0004] Each of these patent applications is jointly owned by the owner of the present invention and is incorporated herein by reference in its entirety. Technical Field

[0005] The present invention relates to methods and systems for the recovery and reuse of conductive additives for flash joule heating.

[0006] Government Interests

[0007] This invention was made with government support under award numbers FA9550 - 22 - 1 - 0526 awarded by the United States Air Force Office of Scientific Research and W912HZ - 21 - 2 - 0050 awarded by the United States Army Corps of Engineers, Engineer Research and Development Center. The government has certain rights in this invention. Background of the Invention

[0008] Flash Joule heating (FJH), characterized by ultrafast processing durations and ultra - low energy consumption, has emerged as an innovative method for functional material production [Luong 2020; Chen I 2021; Deng I 2022; Stanford 2020] and sustainable waste management [Luong 2020; Algozeeb 2020; Barbhuiya 2021; Wyss 2021; Wyss 2022; Chen II 2021]. For example, the application of the FJH process has been reported for the recovery of precious metals from electronic waste (e - waste), the removal of heavy metals from e - waste, coal fly ash, and contaminated soil, and the recovery of rare earths from coal fly ash, bauxite slag, and e - waste. [Deng 2021; Deng II 2022].

[0009] During the FJH process, when using insulating inorganic or organic materials, conductive additives should be added and mixed with the inorganic materials to ensure good electrical conductivity. Suitable conductive additives include various carbons, metals, etc. Conductive additives typically account for a large portion of the material cost in the FJH process. Therefore, the FJH process generally expects to recycle and reuse conductive additives to reduce material costs.

[0010] Chemical processes can be used to remove conductive additives. For example, for the synthesis of transition metal carbides via flash Joule heating, carbon additives are removed through a calcium etching protocol [Deng I 2022]; for the synthesis of corundum nanoparticles via a pulsed direct - current heating process, carbon additives are removed by calcination in air [Deng III 2022]. However, these processes are energy - consuming, and the carbon additives may not be recyclable and reusable.

[0011] Therefore, there remains a need to recycle and reuse conductive additives for flash Joule heating. Summary of the Invention​

[0012] The present invention relates to methods and systems for recycling and reusing conductive additives for flash Joule heating.

[0013] In a general embodiment, the present invention relates to a method that includes mixing a first material with a conductive additive to form a first mixture. The method further includes subjecting the first mixture to a flash Joule heating process to form a product. The product includes the resulting conductive additive in the first mixture. The resulting conductive additive is selected from the group consisting of: (i) the conductive additive, (ii) a different conductive additive, and (iii) a combination thereof. The method further includes separating at least some of the resulting conductive additive from the product to obtain a recycled conductive additive. The method further includes using the recycled conductive additive in a second flash Joule heating process. The recycled conductive material is mixed with a second material for the second flash Joule heating process. The second material is the same or different from the first conductive material.

[0014] Embodiments of the present invention may include one or more of the following features:

[0015] The resulting conductive additive may include the conductive additive.

[0016] The resulting conductive additive may include the different conductive additive.

[0017] The method may further include separating at least some of a second resulting conductive additive from a second product formed in the second flash Joule heating process to obtain a second recycled conductive additive. The method may further include using the second recycled conductive additive in a third flash Joule heating process. The second recycled conductive additive may be mixed with a third material for the third flash Joule heating process. The third material may be the same or different from the first material and / or the second material.

[0018] For a plurality of additional flash Joule heating processes performed in series, the steps of separating and reusing the recycled conductive additive may be repeated.

[0019] Before performing the second flash Joule heating process, the additional conductive additive may be mixed into the recycled conductive additive and the second material.

[0020] The first material may be prepared from electronic waste, ore, fly ash, soil, and / or bauxite slag.

[0021] The second material can be prepared from electronic waste, ore, fly ash, soil, and / or bauxite slag.

[0022] The first material can be soil.

[0023] The soil is contaminated soil, and the contaminated soil includes contaminants selected from the group consisting of heavy metals, persistent organic pollutants, and polyfluoro- and perfluoroalkyl substances (PFAS).

[0024] The contaminants are heavy metals selected from the group consisting of lead (Pb), arsenic (As), zinc (Zn), cobalt (Co), cadmium (Cd), copper (Cu), mercury (Hg), and nickel (Ni).

[0025] The contaminants can be persistent organic pollutants, and the persistent organic pollutants are selected from the group consisting of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine pesticides, total petroleum hydrocarbons, and PFAS.

[0026] The soil can be contaminated soil including persistent and bioaccumulative contaminants.

[0027] The persistent and bioaccumulative contaminants can include one or more polyfluoro- and perfluoroalkyl substances (PFAS).

[0028] The first material can be fly ash.

[0029] The conductive additive can be selected from the group consisting of elemental carbon, carbon black, graphene, flash graphene, coal, anthracite, coke, metallurgical coke, calcined coke, activated carbon, biochar, natural gas carbon from which its hydrogen atoms have been stripped, activated carbon, impure graphite, plastic waste, carbon coke derived from plastic waste, food waste, carbon coke derived from food waste, biomass, carbon coke derived from biomass, hydrocarbon gas products, metals, and mixtures produced therefrom.

[0030] The conductive additive can be selected from the group consisting of metallurgical coke (metcoke), bituminous activated carbon (BAC), and combinations thereof.

[0031] The conductive additive can be biochar.

[0032] The conductive additive can be fiber and / or graphite.

[0033] The conductive additive can be carbon fiber.

[0034] The metal can be selected from the group consisting of metal particles, metal alloys, and metal carbides.

[0035] The metal can include metal particles, and the metal particles include titanium.

[0036] The metal can be selected from the group consisting of: metal nanoparticles, metal microparticles, metal nanofilaments, and metal centifilaments.

[0037] The metal can include metal carbides, and the metal carbides include tungsten carbide.

[0038] The step of separating at least some of the obtained conductive additive from the product to obtain a recycled conductive additive can be a screening process.

[0039] The step of separating at least some of the obtained conductive additive from the product to obtain a recycled conductive additive can be based on the particle size of the conductive additive and the particle size of the product.

[0040] The separation step can include screening to separate at least some of the obtained conductive additive from the product.

[0041] The step of separating at least some of the obtained conductive additive from the product to obtain a recycled conductive additive can be based on the density difference between the conductive additive and the product. Generally, the carbon additive will float in water. Generally, the metal additive will sink in water.

[0042] The separation step can use a liquid to separate at least some of the obtained conductive additive from the product.

[0043] The liquid can be selected from the group consisting of: water, salts dissolved in water, organic solvents, and ionic liquids.

[0044] The liquid can be water.

[0045] At least some of the obtained conductive additive can float at or near the top surface of the liquid used for separation.

[0046] The conductive additive can be a conductive carbon additive.

[0047] The separation step can include decanting and / or skimming at least some of the obtained conductive additive from the product.

[0048] At least some of the conductive additive sink into the liquid used for separation.

[0049] The conductive additive includes metal.

[0050] The recovery yield of the conductive additive can be at least 85%. The recovery yield of the conductive additive is the weight of the recycled conductive additive recovered from the product divided by the weight of the conductive additive in the first mixture.

[0051] The recovery yield can be at least 90%.

[0052] The recovery yield can be at least 92%.

[0053] The recovery yield can be at least 95%.

[0054] In a further general embodiment, the present invention relates to a system comprising a first source of a first mixture of a first material and a conductive additive. The system further comprises a flash Joule heating system comprising (i) a unit operatively connected to the first source such that the first mixture can flow into the unit and be maintained under compression, (ii) electrodes operatively connected to the pressure unit, and (iii) a flash power source for applying a voltage across the mixture to perform a flash Joule heating process to form a product comprising the resulting conductive additive of the first mixture. The resulting conductive additive is selected from the group consisting of: (i) the conductive additive, (ii) a different conductive additive, and (iii) combinations thereof. The system further comprises a separator for separating some of the resulting conductive additive from the product to obtain a recovered conductive additive. The system further comprises a mixer for mixing the recovered conductive additive with a second material to form a second mixture. The second material is the same or different from the first material. The system further comprises a second source of the second mixture operatively connected to the flash Joule heating system for using the second mixture in the flash Joule heating system.

[0055] Embodiments of the present invention may include one or more of the following features:

[0056] The resulting conductive additive may comprise the conductive additive.

[0057] The resulting conductive additive may comprise the different conductive additive.

[0058] For a plurality of additional Joule heating processes performed in series, the system is operable to repeat the separation and reuse of the recovered conductive additive.

[0059] The system may comprise a second source of additional conductive material. The additional source may be operatively connected to the mixer such that the additional conductive material is mixed with the recovered conductive additive and the second material in the mixer to form the second mixture.

[0060] The first material can be prepared from electronic waste, ore, fly ash, soil, and / or bauxite slag.

[0061] The second material can be prepared from electronic waste, ore, fly ash, soil, and / or bauxite slag.

[0062] The first material can be soil.

[0063] The soil is contaminated soil, and the contaminated soil includes pollutants selected from the group consisting of heavy metals, persistent organic pollutants, and polyfluoro- and perfluoroalkyl substances (PFAS).

[0064] The pollutants are heavy metals selected from the group consisting of lead (Pb), arsenic (As), zinc (Zn), cobalt (Co), cadmium (Cd), copper (Cu), mercury (Hg), and nickel (Ni).

[0065] The pollutants can be persistent organic pollutants selected from the group consisting of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine pesticides, total petroleum hydrocarbons, and PFAS.

[0066] The soil can be contaminated soil including persistent and bioaccumulative pollutants.

[0067] The persistent and bioaccumulative pollutants can include one or more polyfluoro- and perfluoroalkyl substances (PFAS).

[0068] The first material can be fly ash.

[0069] The conductive additive can be selected from the group consisting of elemental carbon, carbon black, graphene, flash graphene, coal, anthracite, coke, metallurgical coke, calcined coke, activated carbon, biochar, natural gas carbon from which its hydrogen atoms have been stripped, activated carbon, impure graphite, plastic waste, carbon coke derived from plastic waste, food waste, carbon coke derived from food waste, biomass, carbon coke derived from biomass, hydrocarbon gas products, metals, and mixtures produced therefrom.

[0070] The conductive additive can be selected from the group consisting of metallurgical coke (metcoke), bituminous activated carbon (BAC), and combinations thereof.

[0071] The conductive additive can be biochar.

[0072] The conductive additive can be fiber and / or graphite.

[0073] The conductive additive can be carbon fiber.

[0074] The metals can be selected from the group consisting of metal particles, metal alloys, and metal carbides.

[0075] The metal may include metal particles, and the metal particles include titanium.

[0076] The metal may be selected from the group consisting of: metal nanoparticles, metal microparticles, metal milliparticles, and metal centiparticles.

[0077] The metal may include metal carbides, and the metal carbides include tungsten carbide.

[0078] The separator may be a sieve.

[0079] The separator is operable to separate at least some of the resulting conductive additive from the product based on the particle size of the conductive additive and the particle size of the product to obtain a recycled conductive additive.

[0080] The separator may include a sieve for separating at least some of the resulting conductive additive from the product based on the particle size of the conductive additive and the particle size of the product.

[0081] The separator is operable to separate at least some of the resulting conductive additive from the product based on the density difference between the conductive additive and the product to obtain a recycled conductive additive.

[0082] The system may further include a liquid. The separator is operable to separate at least some of the resulting conductive additive from the product using the liquid.

[0083] The liquid may be selected from the group consisting of: water, salts dissolved in water, organic solvents, and ionic liquids.

[0084] The liquid may be water.

[0085] The separator is operable to cause at least some of the resulting conductive carbon additive to float at or near the top surface of the liquid in the separator.

[0086] The conductive additive may be a conductive carbon additive.

[0087] The separator may include a decanter and / or a skimmer for decanting and / or skimming at least some of the resulting conductive additive from the product.

[0088] At least some of the resulting conductive additive may sink into the liquid for separation.

[0089] The conductive material may include a metal.

[0090] The recovery yield of the conductive additive of the system can be at least 85%. The recovery yield of the conductive additive is the weight of the recovered conductive additive recovered from the product divided by the weight of the conductive additive in the first mixture.

[0091] The recovery yield can be at least 90%.

[0092] The recovery yield can be at least 92%.

[0093] The recovery yield can be at least 95%. Description of the Drawings

[0094] Figure 1 Shows the carbon residue after soil remediation using the flash Joule heating (FJH) process. Figure 1 Is the TGA curve of the remediated soil with residual carbon. TGA is carried out in air, where the heating rate is 10 °C min -1 .

[0095] Figures 2A - 2F Shows the separation and reuse of metallurgical coke (metcoke) from soil after remediation by the FJH process. Figure 2A Is a picture of the soil / metallurgical coke mixture before FJH. Figure 2B Is a picture of the soil / metallurgical coke mixture after FJH. Figure 2C Shows the separation of soil and metallurgical coke by screening. Figure 2D Is a picture of the separated soil and metallurgical coke. Figure 2E Is a picture of the soil / metallurgical coke mixture after FJH. (The metallurgical coke is mainly recovered from the previous FJH traces.) Figure 2F Is a picture of the separated soil and metallurgical coke.

[0096] Figures 3A - 3B Shows the Raman spectrum of the metallurgical coke. Figure 3A Is the Raman spectrum of the metallurgical coke raw material. Figure 3B Is the Raman spectrum of the metallurgical coke after FJH and separation. The Raman spectrum shows that after the FJH process, the metallurgical coke is converted into flash graphene.

[0097] Figures 4A - 4B Shows the soil carbon content measurement results. Figure 4A Is the calibration curve of the soil carbon content measurement results. Figure 4B Shows the soil carbon content in the original soil and the treated soil after removing the carbon additive by screening.

[0098] Figures 5A - 5F Shows the separation and reuse of the carbon additive, bituminous activated carbon (BAC).Figure 5A Picture of a mixture of soil and BAC. Figure 5B Picture of a mixture of soil and BAC after FJH. Figure 5C Illustrates the separation of soil and BAC by sieving. Figure 5D Picture of the separated treated soil and recycled BAC. Figure 5E Picture of a mixture of soil and reused BAC after FJH. Figure 5F Picture of the separated treated soil and recycled BAC.

[0099] Figures 6A - 6E Illustrates the recycling of biochar from the treated soil. Figure 6A Picture of the initial biochar before the rapid electrothermal mineralization (REM) process. Figure 6B Picture of the soil / biochar mixture before REM. Figure 6C Picture of the soil / biochar mixture after REM. Figure 6D Picture of the REM soil and biochar dispersion mixture after centrifugation. Figure 6E Picture of the recycled biochar after REM, dispersion, centrifugation, and drying.

[0100] Figures 7A - 7B Illustrates the comparison of biochar with recycled biochar. Figure 7A Is an XRD pattern; and Figure 7B Is a Raman spectrum.

[0101] Figures 8A - 8C Is the TGA result of the soil. Figure 8A Is the original soil (PFAS - contaminated soil). Figure 8B Is the REM - treated soil mixed with biochar. Figure 8C Is the REM - treated soil after removing biochar by centrifugation. The TGA test was carried out in air with a heating rate of 10 °C min -1 .

[0102] Figure 9 Illustrates the PFOA mineralization rate using biochar and recycled biochar as conductive additives after REM treatment. The REM process was carried out once with an input voltage of 100 V and a duration of 1 second. Error bars represent the standard deviation, where N = 3.

[0103] Figures 10A - 10C Illustrates the separation of the conductive additive, metallurgical coke from the soil and its recycling. Figure 10A Picture of the soil / metallurgical coke mixture before the REM process. Figure 10B Picture of the soil / metallurgical coke mixture after the REM process. Figure 10CShows the separation of REM-treated soil and metallurgical coke by sieving.

[0104] Figures 11A - 11B Shows the Raman spectra of metallurgical coke and recycled metallurgical coke. Figure 11A Shows the initial metallurgical coke before REM; and Figure 11B Shows the recycled metallurgical coke after REM.

[0105] Figure 12 Shows the mineralization rate of perfluorooctanoic acid (PFOA, a specific type of PFAS) using metallurgical coke and recycled metallurgical coke as conductive additives after REM treatment. The REM process was carried out once at an input voltage of 100 V and a duration of 1 s. Error bars represent the standard deviation, where N = 3.

[0106] Figures 13A - 13F Shows the separation and reuse of carbon additives. Figure 13A Is a picture of a mixture of coal fly ash (CFA) and metallurgical coke (metcoke). Figure 13B Is a picture of the mixture of CFA and metallurgical coke after flash Joule heating (FJH). Figure 13C Shows the separation of CFA and metallurgical coke by sieving. Figure 13D Is a picture of the separated CFA and the recovered metallurgical coke. Figure 13E Is a picture of the mixture of CFA and the recovered metallurgical coke after FJH. Figure 13F Is a picture of the separated CFA and the recovered metallurgical coke.

[0107] Figure 14 Shows the residual carbon in the CFA sample after sieving separation (TGA curve of purified CFA after removing CB by sieving). TGA was carried out in air with a heating rate of 10 °C / min.

[0108] Figure 15 Is a flowchart of an embodiment of the method of the present invention.

[0109] Figure 16 Is a schematic diagram of an embodiment of the system of the present invention. Detailed Description

[0110] The present invention relates to a method and system for recycling and reusing conductive additives for flash Joule heating.

[0111] During the FJH process, conductive additives can be added and mixed with inorganic materials to ensure good conductivity when using insulating inorganic materials in the FJH process. Based on the physical property differences between the treated inorganic materials (or other materials used in the FJH process) and the carbon conductive additives, they can be separated and the conductive additives can be recovered and reused. Carbon with relatively large particles can be used as the conductive additive, and the carbon additive can be separated from the inorganic materials, such as by a simple and cost-effective sieving process. Various carbon additives with large particles can be used, including metallurgical coke (metcoke) and bituminous activated carbon (BAC). This process is applicable to many inorganic materials (or other materials) with the characteristics of fine powders exemplified by coal fly ash (CFA) and contaminated soil.

[0112] Carbon Residue after FJH Process

[0113] After the FJH treatment process, there is a significant residual carbon content in the remaining solid. For example, for soil remediation by FJH, the contaminated soil is mixed with the carbon additive at a mass ratio of 2:1. After the FJH purification process, according to thermogravimetric analysis (TGA), the mass of the residual carbon is about 27 wt%, as Figure 1 shown. During the FJH process, the decomposable components in the soil are decomposed. Therefore, in the TGA measurement, most of the weight loss is attributed to the residual carbon.

[0114] Recycling and Reuse of Soil

[0115] Soil contaminated with heavy metals / persistent organic pollutants

[0116] The FJH process can be used to remediate soil contaminated with pollutants such as heavy metals, including lead (Pb), arsenic (As), zinc (Zn), cobalt (Co), cadmium (Cd), copper (Cu), mercury (Hg) and nickel (Ni), and persistent organic pollutants (POPs), such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, organochlorine pesticides, total petroleum hydrocarbons and PFAS. The FJH process for remediating such multiple pollutants in contaminated soil can also be referred to as the high-temperature electrothermal (HET) process.

[0117] The residual carbon in the soil after the FJH process (HET process) can be separated by sieving based on the particle size difference between the soil and the introduced carbon. Taking metallurgical coke as an example, the separation of the treated soil and the residual metallurgical coke is achieved, with a carbon recovery yield of about 92%. Figures 2A - 2D 。

[0118] The particle size of metallurgical coke is larger than that of the soil. Figure 2A 。After the FJH process, the particle size of the metallurgical coke is still larger than that of the soil. Figure 2BTherefore, the soil and metallurgical coke are separated by sieving. Figures 2C - 2D For example, the mass of the mixture of soil and metallurgical coke is m(soil) = 334 mg, and m(metallurgical coke) = 166 mg. After FJH, the remaining mass of soil and metallurgical coke is m(soil + metallurgical coke, FJH) = 445 mg. After sieving separation, purified soil with a mass of m(purified soil) = 293 mg and recycled metallurgical coke with a mass of m(recycled metallurgical coke) = 152 mg are obtained, resulting in a recovery yield of metallurgical coke of approximately 92%. It is believed that approximately 8% of the mass loss is due to consumption during the FJH process.

[0119] The recycled metallurgical coke is converted into flash graphene ( Figures 3A - 3B ), and the flash graphene has better conductivity and can be reused for the FJH process ( Figures 2E - 2F ), thus significantly reducing material consumption. For example, the above recycled metallurgical coke (152 mg) and some fresh metallurgical coke (14 mg) are then used as conductive additives for the second FJH process. Figure 2E After a similar sieving separation, metallurgical coke with a mass of m(recycled metallurgical coke) = 155 mg is recovered ( Figure 2F ), resulting in a recovery yield of metallurgical coke of approximately 93%. This shows that simple sieving recycling can significantly reduce the consumption of conductive additives.

[0120] After separating the carbon conductive additive, the soil carbon content in the original soil and the treated soil is measured. Figures 4A - 4B The carbon content in the treated soil is approximately 3.5%, which is comparable to the original soil (approximately 3.7%). The residual carbon additive can compensate for the loss of organic carbon during the FJH process, resulting in similar total carbon contents in the treated soil and the original soil.

[0121] Other inexpensive carbon additives (such as bituminous activated carbon (BAC)) can also be used for separation. Figures 5A - 5F The FJH process uses a mixture of soil (approximately 200 mg) and BAC (approximately 100 mg). Figure 5A After the FJH purification and sieving process ( Figures 5B - 5C ), the mass of the recycled BAC is m(recycled BAC) = 95.5 mg ( Figure 5D ), resulting in a BAC recovery yield of approximately 95.5%.

[0122] The recycled BAC can be reused for additional FJH treatments. To prove this, the recycled BAC (95.5 mg) and some new BAC (4.5 mg) are used as conductive additives to purify another batch of soil (200 mg). Figure 5EAfter the FJH process and subsequent separation by sieving, BAC was recovered, where the mass was m(recovered BAC) = 93.2 mg( Figure 5F ), resulting in a BAC recovery yield of approximately 93.2%.

[0123] PFAS - contaminated soil

[0124] The FJH process can be used to remediate soils contaminated with persistent and bioaccumulative pollutants, such as soils contaminated with per - and polyfluoroalkyl substances (PFAS). The FJH process for remediating such soils contaminated with persistent and bioaccumulative pollutants (such as soils contaminated with per - and polyfluoroalkyl substances (PFAS) ("PFAS - contaminated soil")) can also be referred to as the rapid electrothermal mineralization (REM) process.

[0125] In such a process, the PFAS - contaminated soil is mixed with a conductive additive, such as biochar, to ensure proper conductivity. After the FJH process (REM process), the carbon additive used can be separated from the soil mixture and then reused for the next batch of soil remediation. For example, perfluorooctanoic acid (PFOA) is a specific type of PFAS. For the PFOA - contaminated soil and biochar, m(soil) = 400 mg and m(biochar) = 200 mg. Figures 6A - 6B After the REM process, the remaining mass of the mixture is m(mixture, REM) = 476 mg. Figure 6C After centrifugation, filtration, and drying( Figure 6D showing the case where biochar 601 floats and soil 602 sinks), purified REM - treated soil with m(purified soil) = 307 mg and recycled biochar with m(recycled biochar) = 169 mg were obtained. Figure 6E .

[0126] Biochar is flash - Joule heated to enhance its conductivity and then used as a conductive additive. Figures 7A - 7B A comparison between biochar and recycled biochar is shown, where lines 701 - 702 are the XRD patterns of biochar and recycled biochar respectively( Figure 7A ); and where lines 701 - 702 are the Raman spectra of biochar and recycled biochar respectively( Figure 7B ). No significant compositional differences were found between them, thus demonstrating the efficiency of the biochar recycling process. In this case, biochar was pre - flash - evaporated before use to convert it into graphene, and the graphene was used as a conductive additive.

[0127] According to the TGA results, for the original soil, its weight loss was caused by the decomposition of organic compounds, accounting for approximately 7 wt%.Figure 8A After mixing with biochar and treatment by REM, the soil weight loss increased to approximately 18 wt%, which was caused by the oxidation of carbon in the biochar. Figure 8B After removing the biochar by centrifugation and drying, the weight loss of the REM soil decreased to a low value of approximately 5 wt%, thus demonstrating that most of the biochar in the soil had been successfully removed. Figure 8C 。

[0128] The biochar was separated from the soil by dispersion and centrifugation, with a recycling rate of approximately 85 wt% ( Figures 6A - 6E 、7A - 7B and 8A - 8C), and reused in a second REM process with performance comparable to PFAS mineralization ( Figure 9 ). Figure 9 There was a negligible change in the PFOA mineralization rate (approximately 94%) when using either biochar or recycled biochar as the conductive additive, indicating the efficiency of reusing recycled biochar in the REM process.

[0129] Similarly, when using metallurgical coke as the conductive additive, approximately 91 wt% could be recycled by simple sieving after REM ( Figures 10A - 10C and 11A - 11B), and then reused with similar performance ( Figure 12 ). For example, soil contaminated with PFOA was mixed with metallurgical coke, where m(soil) = 400 mg and m(metallurgical coke) = 200 mg. Figure 10A After the REM process, the remaining mass of the mixture was m(mixture, REM) = 473 mg. Figure 10B After sieving separation, purified REM - treated soil with m(purified soil) = 287 mg and recycled metallurgical coke with m(recycled metallurgical coke) = 186 mg were obtained. Figure 10C The recycling yield of the metallurgical coke was calculated to be approximately 93 wt%. Figures 11A - 11B The Raman spectra in show that the initial metallurgical coke was transformed into crystalline flash graphene during the REM process. When the recycled metallurgical coke was used as the conductive additive, the PFOA mineralization rate could also reach a comparable value of approximately 91%, indicating the efficiency of reusing recycled metallurgical coke in the REM process. Figure 12 This significantly reduced the material consumption in the REM process, but more processing was required.

[0130] Recycling and Reuse of CFA

[0131] Based on the differences in particle size and density between coal fly ash (CFA) and carbon, physical processes can also be used to separate the residual carbon in CFA. Taking metallurgical coke as an example, the separation of purified CFA and metallurgical coke by screening is shown. CFA has a finer particle size, and metallurgical coke with a relatively larger particle size is utilized for analysis. A mixture of CFA (about 333 mg) and metallurgical coke (about 167 mg) was used. Figure 13A After FJH, the particle sizes of CFA and metallurgical coke remained almost unchanged. Figure 13B Therefore, CFA and metallurgical coke were separated by screening. Figure 13C In a typical process, the mass of the recovered metallurgical coke was m(recovered metallurgical coke) = 154 mg; it was a recovery yield of about 92% of the metallurgical coke. Figure 13D 。

[0132] The recovered metallurgical coke can be reused as a conductive additive to further purify CFA, which reduces the cost of FJH purification. The recovered metallurgical coke (154 mg) and some new metallurgical coke (13 mg) were used as conductive additives to purify CFA (333 mg), as Figure 13E After the FJH process and subsequent separation by screening, metallurgical coke with a mass of m(recovered metallurgical coke) = 156 mg was recovered, and the metallurgical coke recovery yield was about 93%. Figure 13F 。

[0133] After the screening separation process, the residual carbon content (curve 1401) in the treated CFA was reduced to about 3%. See Figure 14 (The dashed line 1402 represents 100 wt%). By calcining in air, the residual carbon can be completely removed. The selection of an appropriate carbon removal method may depend on the landfill or application of the purified CFA.

[0134] Similarly, other inexpensive carbon additives (such as bituminous activated carbon (BAC)) can also be used for separation. Figure 10A - 1 0F. Similar to metallurgical coke, BAC with a relatively larger particle size was utilized for analysis. A mixture of CFA (about 200 mg) and BAC (about 100 mg) was used. Figure 10A After FJH, the particle sizes of CFA and BAC remained unchanged. Figure 10B Therefore, CFA and BAC were separated by screening. Figure 10C In a typical process, the mass of the recovered BAC was m(recovered BAC) = 95 mg; it was a recovery yield of about 95% of the BAC. Figure 10D.

[0135] The recycled BAC can be reused for additional FJH treatment. To demonstrate this, the recycled BAC (154 mg) and some fresh BAC (5.5 mg) were used as conductive additives to purify CFA (200 mg). Figure 10E. After the FJH process and subsequent separation by sieving, BAC with a mass of m (recycled BAC) = 94 mg was recovered, and the BAC recovery yield was approximately 94%. Figure 10F.

[0136] Separation Process

[0137] Table I below reflects a summary of the recovery and reuse of the conductive additives in the examples discussed and described above.

[0138] Table I

[0139] Recovery and Reuse of Conductive Additives

[0140]

[0141]

[0142] Except for the soil and biochar examples, the separation processes utilized were based on sieving to separate the conductive carbon additives from the products obtained from the FJH process. The yield percentages of such sieving provided a recovery yield of at least 90%, and in some embodiments at least 92%, and in still other embodiments at least 95%. The separation processes for the soil and biochar examples utilized centrifugation and drying and achieved a recovery yield of at least 85%.

[0143] Additional and extra separation processes can be utilized to separate the conductive additives from the products obtained from the FJH process. For example, separation can be based on the particle size of the conductive additives and the particle size of the products obtained from the FJH process. This can be sieving or other processes for separating materials based on material size. Further by way of example, separation can be based on the density difference between the conductive additives and the products obtained from the FJH process. This can include using a liquid (such as water) to separate the conductive additives from the products obtained from the FJH process. This can further include a conductive additive that can float at or near the top surface of the liquid used for separation while the products obtained from the FJH process sink in the liquid (or vice versa). This can further include decanting and / or skimming the conductive additive (or the products obtained from the FJH process).

[0144] Additional Utilization and Advantages

[0145] Figure 15is a flowchart of an embodiment of the method of the present invention. In step 1501, the method mixes a first material with a conductive additive to form a first mixture. In step 1502, the method performs a flash Joule heating process on the first mixture to form a product. The product includes at least some of the conductive additive in the first mixture. In step 1503, the method separates at least some of the conductive additive from the product to obtain a recovered conductive additive. In step 1504, the method uses the recovered conductive additive in a second flash Joule heating process. A conductive material is mixed with a second material for the second flash Joule heating process. The second material is the same as or different from the first material.

[0146] Figure 16 is a schematic diagram of an embodiment of the system of the present invention. The system includes a source 1601 of a first mixture of a first material and a conductive additive. The system further includes a flash Joule heating system 1602. Such a flash Joule heating system can include (i) a unit operably connected to the first source such that the first mixture can flow into the unit and be held under compression, (ii) electrodes operatively connected to the pressure unit, and (iii) a flash power source for applying a voltage across the mixture to perform a flash Joule heating process to form a product that includes at least some of the conductive additive of the first mixture. The system further includes a separator 1803 for separating some of the conductive additive from the product to obtain a recovered conductive additive. The system further includes a mixer 1604 for mixing the recovered conductive additive with a second material to form a second mixture. The second material is the same as or different from the first material. The system further includes a second source 1605 of the second mixture, the second source being operably connected to the flash Joule heating system 1602 for using the second mixture in the flash Joule system. It should be noted that the flash Joule heating 1602 system can have multiple reactors for performing flash Joule heating such that the system can perform flash Joule heating on the first mixture from source 1601 in the same or different reactors as it performs flash Joule heating on the second mixture from source 1602. In addition, the source 1801 of the first mixture can be the same as the source 1605 of the second mixture.

[0147] These methods and systems for recycling and reusing conductive additives for FJH can be used in various FJH processes, including recovering precious metals from electronic waste, removing heavy metals from electronic waste and coal fly ash, removing heavy metals and organic pollutants from contaminated soil for soil remediation, recovering rare earths from coal fly ash, bauxite slag, and electronic waste, etc. Separating and recycling the conductive additives from the treated materials can be used to reduce the material costs of the FJH process. The conductive additives can be separated and recycled through a simple and energy-saving process such as sieving.

[0148] In addition to waste reduction and resource recovery, FJH has been used to synthesize various functional nanomaterials, including transition metal carbide nanocrystals, silicon carbide, corundum nanoparticles, molybdenum disulfide, boron nitride, etc. Recycling and reusing the conductive additives can also be used for the separation and purification of these materials.

[0149] Previously, the process of separating residual carbon additives using FJH-treated inorganic materials usually involved chemical processes such as calcium etching or calcination. The separation process (such as sieving) has the following advantages: (1) The sieving process is a physical process, so the energy consumption is extremely low. In contrast, chemical processes involve high-temperature treatments with high energy consumption; (2) The carbon additives can be recovered and reused with a high yield of >95%; in contrast, chemical processes usually etch the carbon, so they cannot be reused. In addition, the sieving process for recycling and reusing conductive additives is scalable.

[0150] Although the embodiments of the present invention have been shown and described, those skilled in the art can modify them without departing from the spirit and teachings of the present invention. The embodiments described herein and the examples provided are merely exemplary and are not intended to be restrictive. Many variations and modifications of the present invention disclosed herein are possible and within the scope of the present invention. The scope of protection is not limited by the above description, but only by the following claims, and the scope includes all equivalents of the subject matter of the claims.

[0151] The disclosures of all patents, patent applications, and publications cited herein are incorporated herein by reference in their entirety as long as they provide supplementary exemplary, procedural, or other details described herein.

[0152] Quantities and other numerical data may be presented herein in a range format. It should be understood that the use of such range formats is merely for convenience and brevity and should be interpreted flexibly as including not only the numerical values explicitly recited as the limitations of the range but also all the individual numerical values or sub-ranges subsumed within that range as if each numerical value and sub-range were explicitly recited. For example, a numerical range of about 1 to about 4.5 should be interpreted as including not only the explicitly listed limits of 1 to about 4.5 but also the individual numbers (such as 2, 3, 4) and sub-ranges such as 1 to 3, 2 to 4, etc. The same principle applies to ranges listing only one numerical value, such as "less than about 4.5", which should be interpreted as including all of the above values and ranges. Moreover, this interpretation should apply regardless of the breadth of the range or the nature of the property being described.

[0153] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the presently disclosed subject matter belongs. Although any methods, devices, and materials similar or equivalent to those described herein may be used in the practice or testing of the presently disclosed subject matter, representative methods, devices, and materials are now described.

[0154] Following long-standing patent law convention, the terms "a / an" and "the" when used in this application (including the claims) mean "one or more".

[0155] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, etc. used in the specification and claims should be understood to be modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and the appended claims are approximations that may vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter.

[0156] As used herein, when referring to values or amounts of mass, weight, time, volume, concentration, or percentage, the terms "about" and "substantially" mean encompassing variations of ±20% in some embodiments, ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, ±0.5% in some embodiments, and ±0.1% in some embodiments from the specified amount, as such variations are suitable for carrying out the disclosed methods.

[0157] As used herein, the terms “substantially perpendicular” and “substantially parallel” are meant to encompass the following variations: in some embodiments, within ±10° of the perpendicular and parallel directions, respectively; in some embodiments, within ±5° of the perpendicular and parallel directions, respectively; in some embodiments, within ±1° of the perpendicular and parallel directions, respectively; and in some embodiments, within ±0.5° of the perpendicular and parallel directions, respectively.

[0158] As used herein, when used in the context of a list of entities, the term “and / or” refers to the entities present individually or in combination. Thus, for example, the phrase “A, B, C, and / or D” includes A, B, C, and D individually, but also includes any and all combinations and sub - combinations of A, B, C, and D.

[0159] References

[0160] PCT International Patent Publication No. WO 2022 / 067111, entitled “Ultrafast Flash Joule Heating Methods And System For Performing Same,” granted to J.M. Tour et al. on September 24, 2021 (the “Tour’111 PCT Application”).

[0161] Algozeeb, W.A. et al., “Flash graphene from plastic waste,” ACS Nano, 2020, 14, 15595 - 15604 (“Algozeeb 2020”).

[0162] Barbhuiya, N.H. et al., “The Future of flash graphene for the sustainable management of solid waste,” ACS Nano, 2021, 15, 15461 - 15470 (“Barbhuiya 2021”).

[0163] Chen, W. et al., “Millisecond conversion of metastable 2D materials by flash Joule heating,” ACS Nano, 2021, 15, 1282 - 1290 (“Chen I 2021”).

[0164] Chen, W. et al., “Ultrafast and controllable phase evolution by flash Joule heating,” ACS Nano, 2021, 15, 11158 - 11167 (Chen II 2021”).

[0165] Deng, B. et al., “Phase controlled synthesis of transition metal carbide nanocrystals by ultrafast flash Joule heating,” Nat. Commun., 2022, 13, 262 (“Deng I 2022”).

[0166] Deng, B. et al., “Rare earth elements from waste,” Sci. Adv., 2022, 8, eabm3132 (“Deng II 2022”).

[0167] Deng, B. et al., “High - surface - area corundum nanoparticles by resistive hotspot - induced phase transformation,” Nat Commun, 2022, 13, 5027 (Deng III 2022).

[0168] Deng, B. et al., “Urban mining by flash Joule heating,” Nat. Commun., 2021, 12, 5794 (“Deng 2021”).

[0169] Luong, D. X. et al., “Gram - scale bottom - up flash graphene synthesis,” Nature, 2020, 577, 647 - 651 (“Luong 2020”).

[0170] Stanford, M. G. et al., “Flash Graphene Morphologies,” ACS Nano, 2020, 14, 13691 - 13699 (“Stanford 2020”).

[0171] Wyss, K.M. et al., "Upcycling end-of-life vehicle waste plastic into flash graphene," Communications Engineering, 2022, 1, 3 ("Wyss 2022").

[0172] Wyss, K.M. et al., "Converting plastic waste pyrolysis ash into flash graphene," Carbon, 2021, 174, 430-438 ("Wyss 2021").

Claims

1. A method, the method comprising: (a) mixing a first material with a conductive additive to form a first mixture; (b) subjecting the first mixture to a flash Joule heating process to form a product, wherein the product comprises the resulting conductive additive in the first mixture, and wherein the resulting conductive additive is selected from the group consisting of (i) the conductive additive, (ii) a different conductive additive, and (iii) a combination thereof; (c) separating at least some of the resulting conductive additive from the product to obtain a recovered conductive additive; and (d) using the recovered conductive additive in a second flash Joule heating process, wherein (i) the recovered conductive material is mixed with a second material for the second flash Joule heating process, and (ii) the second material is the same as or different from the first material.

2. The method according to claim 1, wherein the resulting conductive additive comprises the conductive additive.

3. The method according to claim 1, wherein the resulting conductive additive comprises the different conductive additive.

4. The method according to claim 1, wherein the method further comprises: (a) separating at least some of a second resulting conductive additive from a second product formed in the second flash Joule heating process to obtain a second recovered conductive additive; and (b) using the second recovered conductive additive in a third flash Joule heating process, (i) the second recovered conductive additive is mixed with a third material for the third flash Joule heating process, and (ii) the third material is the same as or different from the first material and / or the second material.

5. The method according to claim 4, wherein for a plurality of additional flash Joule heating processes performed in series, the steps of separating and reusing the recovered conductive additive of claim 4 are repeated.

6. The method according to claim 1, wherein before performing the second flash Joule heating process, the additional conductive additive is mixed into the recovered conductive additive and the second material.

7. The method according to claim 1, wherein the first material is prepared from electronic waste, ore, fly ash, soil, and / or bauxite slag.

8. The method according to claim 7, wherein the second material is prepared from electronic waste, ore, fly ash, soil, and / or bauxite slag.

9. The method according to claim 1, wherein the first material is soil.

10. The method according to claim 9, wherein the soil is contaminated soil, and the contaminated soil comprises contaminants selected from the group consisting of heavy metals, persistent organic pollutants, and polyfluoro- and perfluoroalkyl substances (PFAS).

11. The method according to claim 10, wherein the contaminants are heavy metals selected from the group consisting of lead (Pb), arsenic (As), zinc (Zn), cobalt (Co), cadmium (Cd), copper (Cu), mercury (Hg), and nickel (Ni).

12. The method according to claim 10, wherein the pollutant is a persistent organic pollutant, and the persistent organic pollutant is selected from the group consisting of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine pesticides, total petroleum hydrocarbons, and PFAS.

13. The method according to claim 9, wherein the soil is contaminated soil containing persistent and bioaccumulative pollutants.

14. The method according to claim 13, wherein the persistent and bioaccumulative pollutants comprise one or more per- and polyfluoroalkyl substances (PFAS).

15. The method according to claim 1, wherein the first material is fly ash.

16. The method according to claim 1, wherein the conductive additive is selected from the group consisting of elemental carbon, carbon black, graphene, flash graphene, coal, anthracite, coke, metallurgical coke, calcined coke, activated carbon, biochar, natural gas carbon from which its hydrogen atoms have been stripped, activated carbon, shungite, plastic waste, plastic waste-derived carbon coke, food waste, food waste-derived carbon coke, biomass, biomass-derived carbon coke, hydrocarbon gas products, metals, and mixtures produced therefrom.

17. The method according to claim 16, wherein the conductive additive is selected from the group consisting of metallurgical coke (metcoke), bituminous activated carbon (BAC), and combinations thereof.

18. The method according to claim 16, wherein the conductive additive is biochar.

19. The method according to claim 16, wherein the conductive additive is fiber and / or graphite.

20. The method according to claim 19, wherein the conductive additive is carbon fiber.

21. The method according to claim 16, wherein the metal is selected from the group consisting of metal particles, metal alloys, and metal carbides.

22. The method according to claim 21, wherein the metal comprises metal particles, and the metal particles comprise titanium.

23. The method according to claim 21, wherein the metal is selected from the group consisting of metal nanoparticles, metal microparticles, metal nanomicelles, and metal centimicelles.

24. The method according to claim 21, wherein the metal comprises metal carbides, and the metal carbides comprise tungsten carbide.

25. The method according to claim 1, wherein the step of separating at least some of the obtained conductive additive from the product to obtain a recycled conductive additive is a screening process.

26. The method according to claim 1, wherein the step of separating at least some of the obtained conductive additive from the product to obtain a recycled conductive additive is based on the particle size of the conductive additive and the particle size of the product.

27. The method according to claim 26, wherein the separation step comprises screening to separate at least some of the obtained conductive additive from the product.

28. The method according to claim 1, wherein the step of separating at least some of the resulting conductive additive from the product to obtain a recycled conductive additive is based on a density difference between the conductive additive and the product.

29. The method according to claim 28, wherein the separating step comprises using a liquid to separate at least some of the resulting conductive additive from the product.

30. The method according to claim 29, wherein the liquid is selected from the group consisting of water, salts dissolved in water, organic solvents, and ionic liquids.

31. The method according to claim 29, wherein the liquid is water.

32. The method according to any one of claims 29 to 31, wherein at least some of the resulting conductive additive floats at or near the top surface of the liquid used for separation.

33. The method according to claim 32, wherein the conductive additive is a conductive carbon additive.

34. The method according to any one of claims 29 to 33, wherein the separating step comprises decanting and / or skimming at least some of the resulting conductive additive from the product.

35. The method according to any one of claims 29 to 31, wherein at least some of the resulting conductive additive sinks in the liquid used for separation.

36. The method according to claim 35, wherein the conductive additive comprises a metal.

37. The method according to claim 1, wherein the recovery yield of the conductive additive is at least 85%, wherein the recovery yield of the conductive additive is the weight of the recycled conductive additive recovered from the product divided by the weight of the conductive additive in the first mixture.

38. The method according to claim 37, wherein the recovery yield is at least 90%.

39. The method according to claim 37, wherein the recovery yield is at least 92%.

40. The method according to claim 37, wherein the recovery yield is at least 95%.

41. A system, the system comprising: (a) a first source of a first mixture of a first material and a conductive additive; (b) a flash Joule heating system, the flash Joule heating system comprising (i) a unit operably connected to the first source such that the first mixture can flow into the unit and be held under compression, (ii) electrodes operatively connected to the pressure unit, and (iii) a flash power source for applying a voltage across the mixture to perform a flash Joule heating process to form a product comprising the resulting conductive additive of the first mixture, wherein the resulting conductive additive is selected from the group consisting of (A) the conductive additive, (B) a different conductive additive, and (C) a combination thereof; (c) a separator for separating some of the resulting conductive additive from the product to obtain a recycled conductive additive; (d) A mixer configured to mix the recycled conductive additive with a second material to form a second mixture, where the second material is the same as or different from the first material; and (e) A second source of the second mixture, operably connected to the flash Joule heating system to use the second mixture in the flash Joule heating system.

42. The system according to claim 41, wherein the resulting conductive additive comprises the conductive additive.

43. The system according to claim 41, wherein the resulting conductive additive comprises the different conductive additive.

44. The system according to claim 41, wherein for a plurality of additional Joule heating processes performed in series, the system is capable of operating to repeatedly separate and reuse the recycled conductive additive.

45. The system according to claim 41, wherein (a) The system comprises a second source of additional conductive material, and (b) The additional source is operably connected to the mixer such that the additional conductive material is mixed with the recycled conductive additive and the second material in the mixer to form the second mixture.

46. The system according to claim 41, wherein the first material is prepared from electronic waste, ore, fly ash, soil, and / or bauxite slag.

47. The system according to claim 46, wherein the second material is prepared from electronic waste, ore, fly ash, soil, and / or bauxite slag.

48. The system according to claim 41, wherein the first material is soil.

49. The system according to claim 48, wherein the soil is contaminated soil, and the contaminated soil comprises contaminants selected from the group consisting of heavy metals, persistent organic pollutants, and per- and polyfluoroalkyl substances (PFAS).

50. The system according to claim 49, wherein the contaminants are heavy metals selected from the group consisting of lead (Pb), arsenic (As), zinc (Zn), cobalt (Co), cadmium (Cd), copper (Cu), mercury (Hg), and nickel (Ni).

51. The system according to claim 49, wherein the contaminants are persistent organic pollutants selected from the group consisting of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine pesticides, total petroleum hydrocarbons, and PFAS.

52. The system according to claim 48, wherein the soil is contaminated soil containing persistent and bioaccumulative contaminants.

53. The system according to claim 52, wherein the persistent and bioaccumulative contaminants comprise one or more per- and polyfluoroalkyl substances (PFAS).

54. The system according to claim 41, wherein the first material is fly ash.

55. The system according to claim 41, wherein the conductive additive is selected from the group consisting of: elemental carbon, carbon black, graphene, flash graphene, coal, anthracite, coke, metallurgical coke, calcined coke, activated carbon, biochar, natural gas carbon from which its hydrogen atoms have been stripped, activated carbon, impure graphite, plastic waste, carbon coke derived from plastic waste, food waste, carbon coke derived from food waste, biomass, carbon coke derived from biomass, hydrocarbon gas products, metals, and mixtures thereof.

56. The system according to claim 55, wherein the conductive additive is selected from the group consisting of: metallurgical coke (metcoke), bituminous activated carbon (BAC), and combinations thereof.

57. The method according to claim 55, wherein the conductive additive is biochar.

58. The system according to claim 59, wherein the conductive additive is fiber and / or graphite.

59. The system according to claim 58, wherein the conductive additive is carbon fiber.

60. The system according to claim 55, wherein the metal is selected from the group consisting of: metal particles, metal alloys, and metal carbides.

61. The system according to claim 60, wherein the metal comprises metal particles, and the metal particles comprise titanium.

62. The system according to claim 60, wherein the metal is selected from the group consisting of: metal nanoparticles, metal microparticles, metal nanonano particles, and metal centiparticles.

63. The method according to claim 60, wherein the metal comprises metal carbide, and the metal carbide comprises tungsten carbide.

64. The system according to claim 41, wherein the separator is a sieve.

65. The system according to claim 41, wherein the separator is operable to separate at least some of the resulting conductive additive from the product based on the particle size of the conductive additive and the particle size of the product to obtain a recovered conductive additive.

66. The system according to claim 65, wherein the separator comprises a sieve for separating at least some of the resulting conductive additive from the product based on the particle size of the conductive additive and the particle size of the product.

67. The system according to claim 41, wherein the separator is operable to separate at least some of the resulting conductive additive from the product based on the density difference between the conductive additive and the product to obtain a recovered conductive additive.

68. The system according to claim 67, wherein the system further comprises a liquid, and the separator is operable to separate at least some of the resulting conductive additive from the product using the liquid.

69. The system according to claim 68, wherein the liquid is selected from the group consisting of: water, salts dissolved in water, organic solvents, and ionic liquids.

70. The system according to claim 68, wherein the liquid is water.

71. The system according to any one of claims 68 to 70, wherein the separator is operable to cause at least some of the resulting conductive carbon additive to float at or near the top surface of the liquid in the separator.

72. The system according to claim 71, wherein the conductive additive is a conductive carbon additive.

73. The system according to any one of claims 68 to 72, wherein the separator comprises a decanter and / or a skimmer for decanting and / or skimming off at least some of the resulting conductive additive from the product.

74. The system according to any one of claims 68 to 70, wherein at least some of the resulting conductive additive sinks into the liquid used for separation.

75. The system according to claim 74, wherein the conductive additive comprises a metal.

76. The system according to claim 41, wherein the recovery yield of the conductive additive of the system is at least 85%, wherein the recovery yield of the conductive additive is the weight of the recovered conductive additive recovered from the product divided by the weight of the conductive additive in the first mixture.

77. The system according to claim 76, wherein the recovery yield is at least 90%.

78. The system according to claim 76, wherein the recovery yield is at least 92%.

79. The system according to claim 76, wherein the recovery yield is at least 95%.

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