Industrial waste with reduced heavy metals in cementitious materials, and method for producing and using the same

Abstract

Ultra-high speed flash Joule heating method and system, and more particularly, a method and system for removing heavy metals from industrial waste, such as coal fly ash or bauxite residue. The use of the purified industrial waste includes forming a cementitious material comprising the purified industrial waste and cement.

Description

Related Applications

[0001] Cross-reference to related patent applications

[0001] This application claims priority to U.S. Patent Application No. 63 / 328,630, entitled "Removal Of Heavy Metals From Waste And Uses Thereof," filed on April 7, 2022, which is owned in its entirety by the owner of the present invention. This patent application is incorporated herein by reference in its entirety.

Technical Field

[0002]

[0002] The present invention relates to a method and system for ultra-high speed flash joule heating, and more particularly, to a method and system for removing heavy metals from industrial waste (such as coal fly ash or bauxite residue), and to the use of purified industrial waste in cementitious materials.

[0003] Statement regarding research funded by the federal government

[0003] The present invention was made with government support under Award Number FA9550-22-1-0526 awarded by the U.S. Air Force Office of Scientific Research and Award Number W912HZ-21-2-0050 awarded by the U.S. Army Corps of Engineers. The government has certain rights in the invention.

Background Art

[0004] Background

[0004] The growing global demand for materials is continuously increasing greenhouse gas (GHG) emissions. [Daehn 2022]. Building materials are the third largest anthropogenic source of carbon dioxide (CO 2 ) emissions. [Andrew 2019]. For example, the global CO 2Emissions are approximately 1.5 Gt per year, which accounts for about 8% of the total GHG emissions globally [Andrew 2019; Olivier 2016]. Therefore, the cement industry is an important sector for GHG emission reduction strategies [Zhong 2021], and there is renewed interest in alternative raw materials with lower production emissions that replace or partially substitute for the largest volume of construction material, namely ordinary Portland cement (OPC) [Miller 2020].

[0005]

[0005] Among alternative cementitious materials [Miller 2020], coal fly ash (CFA) has been widely investigated and utilized worldwide [Yao 2015]. CFA is the dominant inorganic residue from coal combustion in power plant furnaces, and the global annual production is approximately 750 million tons [Blissett 2012; Sahoo 2016]. CFA mainly consists of oxides of silicon (Si), aluminum (Al), iron (Fe), and calcium (Ca), while containing relatively small amounts of heavy metals such as cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and mercury (Hg) [Fernandez-Turiel 1994; Koukouzas 2011].

[0006]

[0006] Therefore, CFA is classified as a hazardous waste in some countries if the toxic substances exceed the limits; in other countries, it is regulated as non-hazardous under special regulations [EPA 2015]. The improper disposal of CFA is becoming an environmental issue because it may cause water, soil, and air pollution [Yao 2015; Yao 2014]. As a result, due to both economic and environmental reasons, reuse rather than disposal or landfill of CFA is required [Andrew 2019; Blissett 2012].

[0007]

[0007] CFA with a high calcium content has significant cementitious properties [ASTM C618-08 2008] and is useful for the dilution of OPC. [Rafieizonooz 2016; Canpolat 2004]. However, when CFA comes into contact with an aqueous environment such as rainwater, heavy metals may leach from it [Wang N 2020; Praharaj 2002], which has hindered its application in cement. [Yu 2005; Ma 2019]. Therefore, it is necessary to remove toxic elements from CFA before landfill or secondary use.

[0008]

[0008] Most of the prior art methods for heavy metal removal rely on an acid washing process involving the use of inorganic acids [Kashiwakura 2010] or organic acids [Ishaq 2013], both of which have problems of chemical consumption that reduces the value of economic incentives and the generation of a large amount of wastewater flow, causing secondary pollution. [Praharaj 2002; Kashiwakura 2010].

Prior Art Documents

Non-Patent Documents

[0009]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 9

Non-Patent Document 10

Non-Patent Document 11

Non-Patent Document 12

Non-Patent Document 13

Non-Patent Document 14

Non-Patent Document 15

Non-Patent Document 16

Non-Patent Document 17

Non-Patent Document 18

Non-Patent Document 19

Non-Patent Document 20

Summary of the Invention

Problems to be Solved by the Invention

[0010]

[0009] Therefore, the development of cementitious materials with a low carbon footprint is important for reducing greenhouse gas emissions. Furthermore, coal fly ash (CFA) is an attractive diluent additive in cement due to its wide availability and ultra-low cost, but heavy metals in CFA may leach out over a long period. Furthermore, conventional acid washing processes for heavy metal removal have problems of high chemical consumption and a large amount of wastewater flow.

[0011]

[0010] Therefore, there is still a need for improved methods and systems for removing heavy metals from industrial waste (such as coal fly ash and bauxite residues) to obtain waste with reduced heavy metals for use in cementitious materials.

Means for Solving the Problems

[0012]

[0011] The present invention relates to a method and system for ultra-high speed flash joule heating, and more particularly, to a method and system for removing heavy metals from industrial waste (such as coal fly ash or bauxite residue), and to the use of the purified industrial waste in cementitious materials.

[0013]

[0012] Generally, in one embodiment, the present invention features a method of forming a cementitious material. The method includes forming a mixture that includes industrial waste and a conductive additive. The method further includes applying a voltage across the mixture. The voltage is applied in one or more voltage pulses. Each of the one or more voltage pulses has a duration over a predetermined period of time. The application of the voltage removes at least 50 wt% of the heavy metals from the industrial waste to form a purified industrial waste. The method further includes mixing the purified industrial waste with cement to form a cementitious material.

[0014]

[0013] The practice of the present invention may include one or more of the following features.

[0014] The industrial waste may be fly ash.

[0015] The fly ash may be coal fly ash.

[0015]

[0016] The coal fly ash may be C coal fly ash.

[0017] The coal fly ash may be F coal fly ash.

[0018] The industrial waste may be bauxite residue.

[0016]

[0019] The industrial waste may be slag.

[0020] The slag can be selected from the group consisting of boiler slag, furnace slag, tap slag, raker slag, synthetic slag, bottle slag, pit slag, hopper slag, riverbed slag, and combinations thereof.

[0017]

[0021] The industrial waste may be tailings.

[0022] The industrial waste may be silica fume.

[0023] The duration of each of the one or more voltage pulses may be from 1 microsecond to 5 seconds.

[0018]

[0024] The conductive additive may be a carbon source.

[0025] The carbon source may be selected from the group consisting of carbon black, graphene, flash graphene, coal, anthracite, coke, metallurgical coke, calcined coke, activated carbon, biochar, carbon of natural gas from which hydrogen atoms have been removed, furnace black, activated carbon, shungite, plastic waste, carbon char derived from plastic waste, food waste, carbon char derived from food waste, biomass, carbon char derived from biomass, hydrocarbon gas, and mixtures thereof.

[0019]

[0026] The carbon source may be carbon black.

[0027] The carbon source may be metallurgical coke.

[0028] The carbon source may be pyrolysis ash of plastic.

[0020]

[0029] The source of conductivity may include metal flakes.

[0030] The metal flakes may be aluminum flakes.

[0031] The step of forming the mixture may include adding a conductive additive to the industrial waste.

[0021]

[0032] The industrial waste may contain a conductive additive.

[0033] The mixture may have a resistivity of at most 50 Ω.

[0034] The resistivity of the mixture may be from 0.5 Ω to 5 Ω.

[0022]

[0035] The resistivity of the mixture may be 1 Ω to 3 Ω.

[0036] The application of voltage can remove at least 70% by weight of heavy metals from industrial waste to form purified industrial waste.

[0023]

[0037] At least 50% by weight of the heavy metals may be removed from the industrial waste during the application of the first voltage pulse of one or more voltage pulses.

[0038] At least 70% by weight of the heavy metals may be removed from the industrial waste during the application of the first voltage pulse of one or more voltage pulses.

[0024]

[0039] The heavy metals may include one or more metals selected from the group consisting of Al, As, Ba, Be, Bi, B, Ca, Cd, Cs, Cr, Co, Cu, Ga, In, Fe, Pb, Li, Mg, Mn, Ni, P, K, Rb, Se, Si, Ag, Na, Sr, S, Te, Tl, V, Zn, and combinations thereof.

[0025]

[0040] The heavy metals may be one or more metals selected from the group consisting of As, Cd, Co, Ni, Pb, and combinations thereof.

[0041] The method may further include a step of removing residual carbon from the industrial waste after the step of applying voltage across the mixture.

[0026]

[0042] The step of removing the residual carbon may include calcination.

[0043] The calcination step can be carried out in air at a temperature of at least 600 °C for at least 30 minutes.

[0027]

[0044] The calcination step can be carried out in air at a temperature of at least 700 °C for at least 1 hour.

[0045] The step of removing the remaining carbon may include a physical separation step.

[0028]

[0046] The physical separation step may include a step of screening industrial waste after applying a voltage across the mixture.

[0047] The purified industrial waste may be mixed with cement in a weight ratio of about 1:9 to about 1:1.

[0029]

[0048] The purified industrial waste may be mixed with cement in a weight ratio of about 1:4 to about 2:3.

[0049] The purified industrial waste may be mixed with cement in a weight ratio of about 3:7.

[0030]

[0050] The method may be a water-free process.

[0051] The method may not include a pickling step.

[0052] Generally, in another embodiment, the present invention features a cementitious material. The cementitious material includes purified industrial waste. The purified industrial waste has at least 50% by weight less heavy metals compared to the industrial waste before purification. The cementitious material further includes cement.

[0031]

[0053] The implementation of the present invention may include one or more of the following features:

[0054] The purified industrial waste may have at least 70% by weight less heavy metals compared to the industrial waste before purification.

[0032]

[0055] The refined industrial waste may include a step of forming a mixture including industrial waste and a conductive additive that can be produced by a process. The conductive additive may be a carbon source. The process may further include a step of applying a voltage across the mixture. The voltage can be applied in one or more voltage pulses. Each of the one or more voltage pulses may extend over a predetermined period of duration. Application of the voltage can remove at least 50% by weight of heavy metals from the industrial waste to form the refined industrial waste.

[0033]

[0056] Application of the voltage can remove at least 70% by weight of heavy metals from the industrial waste to form the refined industrial waste.

[0057] The cementitious material can be produced by any of the methods described above for forming the cementitious material.

[0034]

[0058] The method for producing the cementitious material may be a process that does not contain water.

[0059] The method for producing the cementitious material may not include a pickling step.

[0035]

[0060] The industrial waste may be fly ash.

[0061] The fly ash may be coal fly ash.

[0062] The coal fly ash may be C coal fly ash.

[0036]

[0063] The coal fly ash may be F coal fly ash.

[0064] The industrial waste may be bauxite residue.

[0065] The industrial waste may be slag.

[0037]

[0066] The slag can be selected from the group consisting of boiler slag, furnace slag, tap slag, ladle slag, synthetic slag, bottle slag, pit slag, cleaning port slag, riverbed slag, and combinations thereof.

[0038]

[0067] The industrial waste may be tailings.

[0068] The industrial waste may be silica fume.

[0069] The cementitious material may contain purified industrial waste and cement in a weight ratio of about 1:9 to about 1:1.

[0039]

[0070] The cementitious material may be purified industrial waste and cement in a weight ratio of about 1:4 to about 2:3.

[0071] The cementitious material may contain purified industrial waste and cement in a weight ratio of about 3:7.

[0040]

[0072] Generally, in another embodiment, the present invention features a system for forming a cementitious material. The system includes a source of a mixture containing industrial waste and a conductive additive. The system further includes a cell operably connected to the source, where the mixture can flow into the cell and be held under compression. The system further includes electrodes operably connected to the pressure cell. The system further includes a flash power source for applying a voltage across the mixture. The voltage is applied in one or more voltage pulses. Each of the one or more voltage pulses has a duration over a predetermined period of duration. The application of the voltage removes at least 50% by weight of heavy metals from the industrial waste to form purified industrial waste. The system further includes a collector operably connected to the cell for collecting the purified industrial waste. The system further includes an operable mixer for mixing the collected purified industrial waste with cement to form a cementitious material.

[0041]

[0073] The implementation of the present invention may include one or more of the following features:

[0074] The system can execute a method for forming a cementitious material by utilizing any of the above-described methods for forming a cementitious material.

[0042]

[0075] The method for producing a cementitious material may be a water-free process.

[0076] The method for producing a cementitious material may not include a pickling step.

[0043]

[0077] The cementitious material is any of the cementitious materials of the above-described cementitious materials.

[0078] The industrial waste may be fly ash.

[0044]

[0079] The fly ash may be coal fly ash.

[0080] The coal fly ash may be C coal fly ash.

[0081] The coal fly ash may be F coal fly ash.

[0045]

[0082] The industrial waste may be bauxite residue.

[0083] The industrial waste may be slag.

[0084] The slag can be selected from the group consisting of boiler slag, furnace slag, tap slag, leica slag, synthetic slag, bottle slag, pit slag, cleaning port slag, riverbed slag, and combinations thereof.

[0046]

[0085] The industrial waste may be tailings.

[0086] The industrial waste may be silica fume.

[0087] The duration of each of the one or more voltage pulses may be from 1 microsecond to 5 seconds.

[0047]

[0088] The conductive additive may be a carbon source.

[0089] The carbon source can be selected from the group consisting of carbon black, graphene, flash graphene, coal, anthracite, coke, metallurgical coke, calcined coke, activated carbon, biochar, carbon of natural gas from which hydrogen atoms have been removed, furnace black, activated carbon, shungite, plastic waste, carbon char derived from plastic waste, food waste, carbon char derived from food waste, biomass, carbon char derived from biomass, hydrocarbon gas, and mixtures thereof.

[0048]

[0090] The carbon source may be carbon black.

[0091] The carbon source may be metallurgical coke.

[0092] The carbon source may be pyrolysis ash of plastic.

[0049]

[0093] The source of conductivity may include metal flakes.

[0094] The metal flakes may be aluminum flakes.

[0095] The step of forming the mixture may include adding a conductive additive to industrial waste.

[0050]

[0096] The industrial waste may contain a conductive additive.

[0097] The mixture may have a resistivity of at most 50 Ω.

[0098] The resistivity of the mixture may be 0.5 Ω to 5 Ω.

[0051]

[0099] The resistivity of the mixture may be 1 Ω to 3 Ω.

[0100] The application of voltage can remove at least 70% by weight of heavy metals from the industrial waste to form purified industrial waste.

[0052]

[0101] At least 50% by weight of the heavy metals may be removed from the industrial waste during the application of the first voltage pulse of one or more voltage pulses.

[0102] At least 70% by weight of the heavy metals may be removed from the industrial waste during the application of the first voltage pulse of one or more voltage pulses.

[0053]

[0103] The heavy metals may include one or more metals selected from the group consisting of Al, As, Ba, Be, Bi, B, Ca, Cd, Cs, Cr, Co, Cu, Ga, In, Fe, Pb, Li, Mg, Mn, Ni, P, K, Rb, Se, Si, Ag, Na, Sr, S, Te, Tl, V, Zn, and combinations thereof.

[0054]

[0104] The heavy metals may be one or more metals selected from the group consisting of As, Cd, Co, Ni, Pb, and combinations thereof.

[0105] The system may further include a separator for removing carbon remaining from the industrial waste after the step of applying a voltage across the mixture.

[0055]

[0106] The separator may include a calciner for calcining the industrial waste after the step of applying a voltage across the mixture.

[0107] The calciner may be operable to perform calcination in air at a temperature of at least 600 °C for at least 30 minutes.

[0056]

[0108] The calciner may be operable to perform calcination in air at a temperature of at least 700 °C for at least 1 hour.

[0109] The separator may be a physical separator.

[0057]

[0110] The physical separator may include a sieve.

[0111] The cementitious cement may contain industrial waste and cement purified at a weight ratio of about 1:9 to about 1:1.

[0058]

[0112] The cementitious cement may contain industrial waste and cement purified at a weight ratio of about 1:4 to about 2:3.

[0113] The cementitious cement may contain industrial waste and cement purified at a weight ratio of about 3:7.

Brief Description of the Drawings

[0059]

Figure 1A

[0114] Figures 1A - 1F show the characterization of coal fly ash (CFA). Figure 1A is the XRD pattern of Class C coal fly ash (CFA - C) and Class F coal fly ash (CFA - F). Mullite (PDF15 - 0776) and quartz (PDF33 - 1161) are used as references.

Figure 1B

Figure 1C

Figure 1D

Figure 1E

Figure 1F

Figure 2A

[0115] Figures 2A - 2F show the removal of heavy metals (CFA) in coal fly ash by flash Joule heating (FJH). Figure 2A is a schematic diagram of the FJH process for removing heavy metals in CFA, CB, and carbon black.

Figure 2B

Figure 2C

Figure 2D

Figure 2E

Figure 2F

Figure 3

[0116] Figure 3 shows the heavy metal content in carbon black. The error bars represent the standard deviation for n = 3.

Figure 4

[0117] Figures 4A - 4B show the removal of heavy metals from class C coal fly ash (CFA-C). Figure 4A shows the removal efficiency of heavy metals from CFA-C with varying flash joule heating (FJH) voltage. Figure 4B shows the removal efficiency of heavy metals from CFA-C at a 120V FJH voltage. The error bars in Figures 4A - 4B represent the standard deviation for n = 3.

Figure 5

[0118] Figures 5A - 5D show the improvement of the heavy metal removal efficiency of CFA-C by multiple flash joule heating (FJH) pulses. Figures 5A - 5D show the removal efficiencies of Cd, Co, Ni, and Pb respectively with varying FJH pulses. The error bars represent the standard deviation for n = 3.

Figure 6

[0119] Figures 6A - 6B show the effect of chemical conditions on the FJH process. Figure 6A shows the thermodynamic analysis of the carbon thermal reduction of PbO and the thermal decomposition of PbSO4. Figure 6B shows the relationship between the vapor pressure and temperature of Pb species.

Figure 7

[0120] Figure 7 shows the sample resistance measurement using samples with varying mass ratios of coal fly ash (CFA) and carbon black (CB).

Figure 8

[0121] Figures 8A - 8B show the removal of heavy metals from CFA - F using metallurgical coke (metcoke) as a conductive additive. Figure 8A shows the heavy metal content in the metcoke. Figure 8B shows the flash joule heating (FJH) voltage of 120V and the removal efficiency of heavy metals from CFA - F in 1 second. Error bars represent the standard deviation for n = 3 cases.

Figure 9

[0122] Figures 9A - 9B show the removal of heavy metals from CFA - F using plastic ash as a conductive additive. Figure 9A shows the heavy metal content in the plastic ash. Figure 9B shows the flash joule heating (FJH) voltage of 120V and the heavy metal removal efficiency from CFA - F in 1 second. Error bars represent the standard deviation for n = 3 cases.

Figure 10

[0123] Figures 10A - 10F show the separation and reuse of carbon additives. Figure 10A is a photograph of a mixture of coal fly ash (CFA) and metallurgical coke (metcoke). Figure 10B is a photograph of the mixture of CFA and metcoke after flash joule heating (FJH). Figure 10C shows the separation of CFA and metcoke by sieving. Figure 10D is a photograph of the separated CFA and the recovered metcoke. Figure 10E is a photograph of the mixture of CFA and the recovered metcoke after FJH. Figure 10F is a photograph of the separated CFA and the recovered metcoke.

Figure 11

[0124] Figure 11 shows the remaining carbon in the CFA sample after separation by sieving (TGA curve of purified CFA after CB removal by sieving). TGA was performed in air at a heating rate of 10°C / min.

Figure 12

[0125] Figures 12A - 12B show the characterization of coal fly ash (CFA) after flash Joule heating (FJH). Figure 12A is the XRD pattern of Class F coal fly ash (CFA - F) raw material and CFA - F after FJH. Figure 12B is the XRD pattern of Class C coal fly ash (CFA - C) raw material and CFA - C after FJH. Mullite (PDF15 - 0776) and quartz (PDF33 - 1161) are used as references.

Figure 13

[0126] Figures 13A - 13B show the XRF characterization of coal fly ash (CFA). Figure 13A shows the molar percentages of the major inorganic components of Class C CFA raw material (CFA - C - as - received), CFA - C after flash Joule heating (CFA - C - FJH), and CFA - C after FJH and calcination (CFA - C - FJH - calcined). Figure 13B shows the molar percentages of the major inorganic components of Class F CFA raw material (CFA - F - as - received), CFA - F after FJH (CFA - F - FJH), and CFA - F after FJH and calcination (CFA - F - FJH - calcined). Calcination is carried out in air at 700 °C for 1 hour to remove the residual carbon.

Figure 14

[0127] Figure 14 shows the elemental characterization of coal fly ash (CFA) (XPS full spectrum of Class F CFA (CFA - F - BC) from Boral Cumberland and Class C CFA (CFA - C - CWB) from Charah White Bluff).

Figure 15

[0128] Figures 15A - 15B show the characterization of coal fly ash (CFA) after flash Joule heating (FJH). Figure 15A is the XRD pattern of Class C CFA (CFA - C - CWB) raw material from Charah White Bluff and CFA - C - CWB after FJH. Figure 15B is the XRD pattern of Class F CFA (CFA - F - BC) raw material from Boral Cumberland and CFA - F - BC after FJH. Mullite (PDF15 - 0776) and quartz (PDF33 - 1161) are used as references.

Figure 16

[0129] Figures 16A to 16D show an overview of the flash Joule heating (FJH) process for heavy metal removal. Figure 16A shows the heavy metal content in class C coal fly ash (CFA-C-CWB) collected from color white blast furnace and the removal efficiency by FJH at 120 V for 1 second. Figure 16B shows the heavy metal content in class F coal fly ash (CFA-F-BC) collected from Boral Kalimantan and the removal efficiency by FJH at 120 V for 1 second. Figure 16C is the XRD pattern of bauxite residue (BR) (including an inserted view of the photographs of BR and hematite (PDF02-0919) and calcite (PDF47-1743) used as references). Figure 16D shows the heavy metal content in BR raw material and BR after a single FJH process. The error bars in Figures 16A to 16B and Figure 16D represent the standard deviation for n = 3.

Figure 17

[0130] Figure 17 shows the characterization of BR after FJH (XRD patterns of bauxite residue (BR) raw material and BR after flash Joule heating (FJH)). Hematite (PDF02-0919) and calcite (PDF47-1743) are used as references.

Figure 18A

[0131] Figures 18A to 18F show the application of purified class C coal fly ash (CFA-C) in cement composites. Figure 18A is the TGA curve of CFA-C raw material and a mixture of CFA-C and carbon black (CB) after FJH (including an inserted view of the photographs of the mixture of CFA-C and residual carbon and purified CFA-C after calcination at 700 °C for 1 hour in air).

Figure 18B

Figure 18C

Figure 18D

Figure 18E

Figure 18F

Figure 19

[0132] Figures 19A - 19D show the SEM characterization of class C coal fly ash (CFA - C). Figure 19A is the SEM image of the CFA - C raw material. Figure 19B is the SEM image of the mixture of CFA - C and CB (CFA - C - CB). Figure 19C is the SEM image of CFA - C - CB after FJH (CFA - C - CB - FJH). Figure 19D is the SEM image of CFA - C - CB after FJH and calcination (CFA - C - CB - FJH calcined). Calcination was carried out in air at 700 °C for 1 hour to remove carbon residues.

Figure 20

[0133] Figures 20A - 20B show the measurement of refined coal fly ash (CFA) in the cement composite after 1 - day curing. Figure 20A is the representative stress - strain curve for pure ordinary Portland cement (pure OPC), OPC replaced with 30 wt% raw CFA (OPC / raw CFA), and OPC replaced with 30 wt% refined CFA (OPC / refined CFA). Figure 20B is the compressive strength and modulus of elasticity statistics for pure OPC, OPC / raw CFA, and OPC / refined CFA. Error bars represent the standard deviation for n = 3.

Figure 21

[0134] Figure 21 shows the application of purified Class C coal fly ash (CFA-C) containing carbon residues in cement (stress-strain curves of ordinary Portland cement (OPC) replaced with 5 wt% CFA-C raw material (OPC / raw CFA-C), and OPC replaced with 5 wt% purified CFA-C containing residual carbon black (OPC / purified CFA-C / CB)). Two independent experiments were carried out on two different types of samples.

Figure 22

[0135] Figure 22 shows the application of purified Class F coal fly ash (CFA-F) in cement (stress-strain curves of pure ordinary Portland cement (pure OPC), OPC replaced with 30 wt% raw CFA-F (OPC / raw CFA-F), and OPC replaced with 30 wt% purified CFA-F after removing the carbon remaining by calcination (OPC / purified CFA-F)).

Figure 23

[0136] Figures 23A to 23C show the scale-up of the FJH process. Figure 23A is a photo of the FJH setup using a total capacitance of 0.624 F. Figure 23B is the FJH reaction stage. Figure 23C is the FJH sample size of 3 g per batch.

Figure 24

[0137] Figure 24 shows the design of a continuous FJH reactor.

Figure 25A

[0138] Figures 25A to 25D show the flowchart display and boundary conditions of the life cycle analysis (LCA) model. Figure 25A shows the flowchart display and boundary conditions for the landfill LCA scenario.

Figure 25B

Figure 25C

Figure 25D

Figure 26

[0139] Figures 26A - 26C show the LCA regarding the reuse of coal fly ash (CFA) in cement. Figure 26A shows the comparison of heavy metal emissions. Figure 26B shows the comparison of greenhouse gas (GHG) emissions. Figure 26C shows the comparison of energy consumption.

Figure 27

[0140] Figures 27A - 27C show the environmental impact assessment. Figure 27A shows the percentage of heavy metal emissions of various scenarios normalized to landfill. Figure 27B shows the percentage of greenhouse gas (GHG) emissions of various scenarios normalized to landfill. Figure 27C shows the percentage of energy consumption of various scenarios normalized to landfill.

Figure 28

[0141] Figures 28A - 28D show the comparison of the flash Joule heating (FJH) method using existing methods for heavy metal removal from CFA. Figure 28A shows the water consumption per ton of CFA. Figure 28B shows the material cost per ton of CFA. Figure 28C shows the time consumption. Figure 28D shows the removal efficiency. **DETAILED DESCRIPTION OF THE INVENTION**

[0060]

[0142] The present invention relates to an ultra - high - speed flash Joule heating method and system, and more particularly, to a method and system for removing heavy metals from industrial waste (such as coal fly ash or bauxite residue), and to the use of purified industrial waste in cementitious materials.

[0061]

[0143] In recent years, highly efficient short-burst electric heating has emerged as a high-temperature technology for materials production [Liu S 2022; Liu C 2022; Liu S 2020; Wang C 2020; Cheng 2022; Chen I 2016; Yao 2018] and solid waste management [Barbhuiya 2021]. Chen I 2016 first reported rapid Joule heating for the ultra-fast synthesis of nanoparticles in reduced graphene oxide films. Subsequently, carbon thermal shock has been widely applied to the synthesis of various nanomaterials such as silicon nanoparticles [Chen II 2016], high-entropy alloy nanoparticles [Yao 2018], and single-atom catalysts [Yao 2019] [Jiang 2021]. The FJH process has been used to convert carbon-containing sources into flash graphene [Luong 2020]. In addition to its functional materials synthesis capabilities [Deng I 2022; Chen 2021], the FJH process has been demonstrated to be an efficient method for the sustainable management of carbon-rich wastes such as consumer plastics [Algozeeb 2020; Wyss 2021] and rubber [Advincula 2021]. Using ultra-high temperatures reaching above 3000 °C and ultra-fast processes lasting less than 1 second, the FJH method enables the separation of precious metals by evaporation from electronic waste for urban mines [Deng 2021], the activation of industrial waste for high-yield rare earth element recovery [Deng II 2022], the recycling of photovoltaic silicon waste [Lu 2021], and the recovery of graphite anodes and cathodes of lithium-ion batteries [Cui 2021].

[0062]

[0144] It has been found that the water-free process based on FJH can be utilized to rapidly and efficiently remove heavy metals from CFA, and CFA with such heavy metals removed is widely used in cementitious materials and the like. This means that pickling is not required and thus no secondary aqueous waste streams are generated.

[0063]

[0145] In an embodiment, the FJH process raises the temperature to about 3000 °C within 1 second, enabling removal by evaporation of various heavy metals from CFA with an efficiency of 70 - 90% in the case of As, Cd, Co, Ni, and Pb within a single FJH treatment. The removal efficiency is further increased by repeating 1 - second FJH pulses. The FJH method functions for CFA regardless of type (class F and class C) or geographical origin.

[0064]

[0146] The following disclosure is mainly directed to CFA, but similar FJH strategies can also be applied to the purification of other industrial wastes, such as large - scale bauxite residues (red mud), which further demonstrates the generality of the process for the removal and stabilization of solid waste contamination. "Industrial waste" refers to substances from waste streams in manufacturing processes, examples of which include coal fly ash, bauxite residues (also referred to as slurry forms such as "red mud"), slag (e.g., boiler slag, furnace slag, tap slag, raker slag, synthetic slag, bottle - tapping slag, pit slag, hopper slag, and riverbed slag), tailings, and silica fume.

[0065] Heavy metals in CFA

[0147] CFA is classified into class F CFA (CFA - F) and class C CFA (CFA - C) based on its chemical composition. Both contain SiO 2 、Al 2 O 3 、and Fe 2 O 3 as main components, but CFA - C has a high abundance of CaO [Liu P 2019]. CFA - F was collected from the Appalachian Basin (App) for analysis, and CFA - C was collected from the Powder River Basin (PRB) for analysis, both of which are in the United States. CFA is mostly composed of a glassy phase produced during the coal combustion process 50 [Zhang 2020], and the crystalline components are mainly, according to X - ray diffraction (XRD) analysis, quartz (SiO 2and mullite (aluminum silicate, 3Al 2 O 3 ·2SiO 2 ). See Fig. 1A (plots 101 - 102 correspond to CFA-C and CFA-F, respectively).

[0066]

[0148] In addition to the Ca enrichment in CFA-C, elemental analysis by X-ray photoelectron spectroscopy (XPS) also shows that carbon is abundantly present in CFA-F (Fig. 1B, plots 111 - 122 correspond to CFA-C and CFA-F, respectively), which may be due to incomplete combustion of coal. The morphology of CFA was characterized by a scanning electron microscope (SEM). The particle size of CFA-C was about 1 - 10 μm (Fig. 1C), while CFA-F was about 1 - 8 μm (Fig. 1D).

[0067]

[0149] To evaluate the CFA samples, they were digested with acid. Mixed standards were used (Millipore-Sigma, Periodic Table Mix 1 for ICP; 33 elements; 10 mg L-1, each containing trace amounts of HF in 10% HNO 3 ; Al, As, Ba, Be, Bi, B, Ca, Cd, Cs, Cr, Co, Cu, Ga, In, Fe, Pb, Li, Mg, Mn, Ni, P, K, Rb, Se, Si, Ag, Na, Sr, S, Te, Tl, V and Zn). HNO 3 (67 - 70 wt%, TraceMetal™ grade, Fisher Chemical), HCl (37 wt%, 99.99% trace metal based, Millipore-Sigma), H 2 O 2 (30 wt%, for trace analysis, Millipore-Sigma), and ultrapure water (Millipore-Sigma, ACS reagent for ultratrace analysis) were used for sample digestion. Samples were digested using a modified method from the United States Environmental Protection Agency (EPA). [EPA 1996].

[0068]

[0150] Generally, a sample of about 50 mg was added to 2 mL of HNO 3 (67 - 70%, 1:1 (v:v) with water) at 95 °C for 2 hours. Then, 2 mL of H 2 O 2 (30 wt%, 1:1 (v:v) with water) was added and heated under reflux for 2 hours (95 °C). Then, 1 mL of HCl (37 wt%) and 5 mL of H 2 O were added and heated under reflux for 15 minutes. Then the acidic solution was filtered to remove any undissolved solid particles using a sintered glass funnel (class F). The resulting solution was diluted to within the range of a calibration curve of 1 ppb (part per billion) to 1000 ppb.

[0069]

[0151] The trace heavy metal content was measured by inductively coupled plasma mass spectrometry (ICP - MS). As, Cd, Co, Ni, and Pb were found to be present in CFA - C at As, 59.7 ± 3.3 ppm; Cd, 0.76 ± 0.36 ppm; Co, 15.9 ± 3.8 ppm; Ni, 36.6 ± 8.4 ppm; and Pb, 22.8 ± 1.7 ppm (Figure 1E); and in CFA - F at As, 88.6 ± 43.0 ppm; Cd, 0.62 ± 0.08 ppm; Co, 18.7 ± 5.5 ppm; Ni, 43.5 ± 13.5 ppm; and Pb, 28.3 ± 8.6 ppm (Figure 1F). It is interesting that the heavy metal content in the CFA - F and CFA - C samples was similar even though they were of different types and from different geological origins.

[0070] Removal of heavy metals in CFA by FJH

[0152] For analysis, generally, the CFA was mixed with carbon black (CB) that serves as a conductive additive at about 30 wt%. The mixture 205 was placed in a quartz tube 206, which was connected to a capacitor bank 201. See FIG. 2A (as also shown with the Cu electrode 203, porous Cu 202, and graphite 204). The electrical diagram and setup of the FJH system are similar to those described and shown in Tour's PCT application WO2022 / 067111 (as shown, for example, in FIGS. 6, 13A, 30, and 41A described therein). The resistance of the sample was controlled by the compressive force of the two electrodes; in most of the trials, the resistance was fixed at about 1 Ω. See Table I.

[0071]

Table 1

[0072]

[0153] Resistance that is too high or too low causes a poor FJH reaction: if the resistance is too high, sufficient current is not provided for Joule heating, and if the resistance is too low, sufficient heat is not generated. The detailed conditions for the FJH tested are shown in Table I.

[0073]

[0154] For a typical discharge at 120 V voltage and 1 s discharge time, the current passing through the sample was recorded to be about 120 A at most. See FIG. 2B. The variation in the current curve is due to the change in sample resistance caused by degassing or the intrinsic temperature-dependent resistivity. The discharge of the capacitor results in a sample temperature of up to about 3000 °C in 5 ms (FIG. 2C), followed by rapid cooling. The temperature continued to change during the FJH process due to the variation of the sample resistance and current. Such high temperatures can evaporate heavy metals such as Cd, As, Pb, Co, and Ni according to the relationship between their vapor pressure and temperature. [Lide 2005]. See FIG. 2D (the dotted line 211 means a temperature of 3000 °C). In contrast, the CB conductive additive is converted to graphite-like carbon [Luong 2020], which does not sublime up to about 3600 °C [Abrahamson 1974].

[0074]

[0155] The heavy metal content in the solid remaining after FJH was measured by ICP-MS, and its removal efficiency was calculated as follows. The mass of CFA used in FJH is m(CFA), the concentration of heavy metals in CFA is measured as c(CFA), the mass of CB used in FJH is m(CB), the concentration of heavy metals in CB is measured as c(CB), the mass of the solid remaining after FJH (a mixture of CFA and residual carbon) is m(CFA+CB), and considering that the concentration of heavy metals in the remaining solid is measured as c(CFA+CB), the removal efficiency (R) by FJH is calculated using the following equation.

[0075]

Equation

[0076]

[0156] Similarly, when met coke (MC) is used as a conductive additive, the removal efficiency is calculated by the following formula.

[0077]

Equation

[0078]

[0157] When plastic ash (PA) is used as a conductive additive, the removal efficiency is calculated by the following formula.

[0079]

Equation

[0080]

[0158] Furthermore, when BR is used as a raw material, the removal efficiency is calculated by the following formula.

[0081]

Equation

[0082]

[0159] The heavy metal content in CB was 2 - 15% of that in CFA and was a significant amount. Refer to Figure 3. The concentrations of heavy metals in CB were As, about 8.23 ppm; Cd, 0.01 ppm; Co, about 0.34 ppm; Ni, about 1.13 ppm; and Pb, about 2.82 ppm. For comparison, the concentrations of heavy metals in CFA-F were As, about 88.61 ppm; Cd, 0.62 ppm; Co, about 18.72 ppm; Ni, about 43.46 ppm; and Pb, about 28.33 ppm. The concentrations of heavy metals in CFA-C were As, about 59.66 ppm; Cd, 0.76 ppm; Co, about 15.93 ppm; Ni, about 36.57 ppm; and Pb, about 22.84 ppm. Thus, the concentrations of heavy metals in CB were 1.7% - 9.9% of those in CFA-F and 1.4% - 13.8% of those in CFA-C. As a result, the concentrations of heavy metals in CB were statistically significant. Therefore, in the calculation of the removal efficiency, the combined total heavy metal content in CFA and CB was used as the baseline.

[0083]

[0160] A series of FJH voltages in the range of 60 V - 150 V were applied (Figure 2E, plots 221 - 225 for As, Cd, Co, Ni, and Pb respectively) to purify CFA-F. The heavy metal removal efficiency increased from 60 V to 120 V, which might be due to the higher sample temperature caused by the higher FJH voltage. [Deng II 2022].

[0084]

[0161] When using an FJH voltage of 120 V, the heavy metal removal efficiency was 70 - 90% with one FJH pulse. Figure 2F. When the FJH voltage was further increased to 150 V, the removal efficiency did not increase (Figure 2E), which might be due to non-uniform heating under excessive energy input. The evaporated heavy metals were deposited on the sidewall of the quartz tube reactor or on the inside of the sealed chamber to avoid release to the environment.

[0085]

[0162] CFA-C was also used as a starting material. Under a 120 V FJH voltage, the removal efficiency reaches 40 - 80% with a single voltage pulse for typical heavy metals. Figures 4A (plots 401 - 405 for As, Cd, Co, Ni, and Pb) and 4B. Generally, since the physicochemical adsorption method relies on the ability of the adsorbent, the heavy metal removal ability is limited. [Bolan 2014]. In contrast, the FJH process has no limitation in capacity due to its removal mechanism by evaporation. It has been demonstrated that by using multiple FJH pulse reactions, the heavy metal removal efficiency can be increased to >75% for Ni and >85% for Cd, Co, and Pb in the case of CFA-C. Figures 5A - 5D.

[0086]

[0163] According to previous studies, heavy metals in CFA exist in oxidized or natural ore forms. [Koukouzas 2011; Rivera 2017; Liu P 2020]. Depending on the reactivity and thermal stability, heavy metal species may evaporate in their natural form, or undergo thermal decomposition or carbothermal reduction to become other compounds or elemental metals and then evaporate. In any case, the ultra-high temperature by the FJH process is expected to enable the chemical conversion and evaporation of heavy metal species that occur at temperatures much lower than usually 3000°C. Figures 6A (plots 601 - 603 correspond to the reactions shown in equations (5) - (7) below respectively) and 6B (plots 611 - 613 correspond to PbCl 2 , Pb, and PbO respectively). The dashed line 604 in Figure 6A indicates ΔG = 0 kJ·mol -1 .

[0087]

[0164] The heavy metals in CFA are in the form of natural ores or oxides. Depending on the reactivity and thermal stability of these species, there are several scenarios as follows: (1) the heavy metal species evaporate directly; (2) the heavy metal species thermally decompose into other compounds and then evaporate; and (3) the heavy metal compounds are carbothermally reduced to elemental metals and then evaporate. FJH can achieve ultra-high temperatures of up to 3000 °C, which is higher than the temperature required for each of these scenarios. As an example of thermodynamic analysis, different speciations of lead (Pb, PbCl 2 , PbO, PbS, and PbSO 4 ) were used. Pb and PbCl 2 can evaporate directly. PbO can evaporate directly or may be carbothermally reduced to Pb(0) by Equation (5). PbO(s) + C(s) = Pb(s) + CO(g) (5)

[0165] PbS can be converted to PbO by Equation (6). PbS(s) + 1.5O 2 (g) = PbO(s) + SO 2 (g) (6)

[0166] PbSO 4 can be decomposed into PbO by Equation (7). PbSO 4 (s) = PbO(s) + SO 3 (g) (7)

[0167] The changes in Gibbs free energy for these reactions (Equations (5) - (7)) are calculated using the software HSC Chemistry 10. See Figure 6A. All of these reactions are thermodynamically favorable below 2000 °C. Furthermore, the vapor pressure was calculated by varying the temperature for different Pb species. Figure 6B. All of these Pb species have a high vapor pressure below 2000 °C. Since the FJH process can achieve a very high temperature of 3000 °C, all of the above chemical conversion and evaporation processes are likely to be thermodynamically favorable and rapid. Above all, it was concluded that the FJH process is applicable to heavy metal removal regardless of its chemical situation.

[0088]

[0168] In certain embodiments, a CFA to CB mass ratio of about 2:1 is preferred (see Table I), in which case the resistance of the sample was about 1 Ω. See FIG. 7 (Plot 701 shows the sample resistance for varying such mass ratios, and the dashed line 702 shows R = 1 Ω).

[0089]

[0169] In the FJH process, sample resistance is important: if the resistance is too high, the current will not increase as much as heating occurs; in contrast, if the resistance is too low, the sample resembles a conductor and also cannot generate sufficient heat. In some embodiments, a resistance of about 1 Ω has been found to be a preferred resistance for the FJH process.

[0090]

[0170] In addition to CB, other inexpensive carbons can also be used as conductive additives. For example, by using metallurgical coke (met coke) as a conductive additive, the heavy metal removal efficiency from CFA-F is 40 - 90% using one FJH pulse at 120 V. FIGS. 8A - 8B. The heavy metal concentrations in the met coke are as follows: As, below the ICP MS detection limit; Cd, 0.09 ppm; Co, about 7.95 ppm; Ni, about 30.2 ppm; and Pb, about 5.4 ppm. For comparison, the heavy metal concentrations in CFA-F are as follows: As, about 88.61 ppm; Cd, 0.62 ppm; Co, about 18.72 ppm; Ni, about 43.46 ppm; and Pb, about 28.33 ppm. Thus, the heavy metal concentration in CB is 0 - 69% of the heavy metal concentration in CFA-F. As a result, the heavy metal concentration in CB is statistically significant. Again, in the calculation of the heavy metal removal efficiency, the total heavy metal content in the combination of CFA and CB is used as the baseline.

[0091]

[0171] The removal efficiency of heavy metals using met coke as a conductive additive is somewhat lower than that by using CB as an additive. Fig. 2F. Since CB has a conductivity superior to that of met coke (in the case of CB, R of about 1.0 Ω; in the case of met coke, R of about 1.5 Ω), the temperature is expected to be higher when CB is used as the conductive additive. In addition, CB has an even smaller average particle size of about 10 nm, while met coke has an average particle size of <150 μm. The reason for the better heating uniformity when CB is used as the conductive additive is the difference in particle size.

[0092]

[0172] Furthermore, the pyrolysis ash of plastic (plastic ash), which is a by-product of plastic pyrolysis [Anuar Sharuddin 2016], was also used as a conductive additive. Figs. 9A - 9B. The removal efficiency was >60% with a single FJH pulse. Considering the low or negative value of the pyrolysis ash [Menya 2020], the material cost of the FJH purification process is estimated to be close to zero. Under the same FJH parameters, the removal efficiency using met coke or plastic ash is somewhat lower than that using CB as an additive (Fig. 2F). This may be due to the superior conductivity of CB (R of about 1.0 Ω when CB is used as an additive and R of about 3.0 Ω when plastic ash is used as an additive) and the smaller particle size of CB, which allows for higher temperature and more uniform heating. This can be compensated for by increasing the FJH pulse when met coke or plastic ash is used as the conductive additive (Figs. 5A - 5D).

[0093]

[0173] After the FJH treatment process, there is a significant residual carbon content in the remaining solid. The residual carbon can also be removed by calcination, which will be explained below.

[0174] In addition, based on the differences in particle size and density between CFA and carbon, it is possible to separate the residual carbon from CFA using a physical process. As an example, by using met coke, it is shown that purified CFA and met coke can be separated by sieving. CFA has a fine particle size, and met coke with a relatively large size was selected for analysis. A mixture of CFA (about 333 mg) and met coke (about 167 mg) was used. Figure 10A. After FJH, the particle sizes of CFA and met coke remained almost unchanged. Figure 10B. Therefore, the separation of CFA and met coke by sieving was performed. Figure 10C. In a typical process, the recovered mass of met coke was m(recovered met coke) = 154 mg; the recovery yield of met coke in this case was about 92%. Figure 10D.

[0094]

[0175] The recovered met coke can be reused as a conductive additive for further purification of CFA, thereby reducing the FJH purification cost. As shown in Figure 10E, CFA (333 mg) is purified using the recovered met coke (154 mg) containing some new met coke (13 mg) as a conductive additive. After the FJH process and subsequent separation by sieving, met coke was recovered with a mass of m(recovered met coke) = 156 mg, and the recovery yield of met coke was about 93%. Figure 10F.

[0095]

[0176] After the sieving separation process, the residual carbon content (plot 1101) in the treated CFA was reduced to about 3%. See Figure 11 (the dotted line 1102 corresponds to 100 wt%). The residual carbon could be completely removed by calcination in air as described below. The choice of an appropriate carbon removal approach may depend on the landfill or application of the purified CFA.

[0096]

[0177] In addition to trace heavy metals, the major composition of the residual solids was characterized. The crystalline components, according to their XRD patterns, remain quartz and mullite in both CFA-C and CFA-F after FJH. See Figure 12A (plots 1201 - 1202 correspond to CFA-C, FJH, and as-received CFA-C respectively) and Figure 12B (plots 1211 - 1212 correspond to CFA-F, FJH, and as-received CFA-F respectively).

[0097]

[0178] X-ray fluorescence (XRF) is also used to quantify compositional changes because the amorphous phase, undetectable by XRD, generally accounts for >60% of the CFA compositions [Chancey 2010]. It has been found that the major composition, including various oxides, changed little after the FJH process, which is attributed to the ultra-fast heating and cooling rates and very short heating durations of the FJH process. See Figure 13A (bars 1301 - 1303 correspond to CFA-C, as-received, CFA-C FJH, and CFA-C FJH calcined respectively) and Figure 13B (bars 1311 - 1313 correspond to CFA-F, as-received, CFA-F FJH, and CFA-F FJH calcined respectively).

[0098] Overview of the FJH process for heavy metal removal

[0179] The above-described analysis demonstrated that FJH functions for various classes of CFA. CFA from different geological origins may vary significantly in their trace heavy metal contents. To demonstrate an overview of the FJH process for heavy metal removal, CFA from different sources were used as feedstocks, including both CFA-C (referred to as CFA-C-CWB) collected from Color White Bluff in the United States and CFA-F (referred to as CFA-F-BC) collected from Borah Volcanic Land.

[0099]

[0180] The main compositions of CFA-F-BC and CFA-C-CWB are quartz and mullite, similar to those from App and PRB. Refer to Figure 14 compared with Figure 1B (plots 1401 - 1402 correspond to CFA-C-CWB and CFA-F-BC respectively); Figure 15A (plots 1501 - 1502 correspond to CFA-C-CWB FJH and as-received CFA-C-CWB respectively) compared with Figure 12A; Figure S14B (plots 1511 - 1512 correspond to CFA-F-BC FJH and as-received CFA-F-BC respectively) compared with Figure 12B. The main heavy metals in CFA-C-CWB and CFA-F-BC were Cd, Co, Ni, and Pb. Figure 16A is for CFA-C-CWB (bars 1601 - 1602 correspond to concentration and removal efficiency respectively), and Figure 16B is for CFA-F-BC (bars 1611 - 1612 correspond to concentration and removal efficiency respectively).

[0100]

[0181] At 120V FJH voltage (Table I), the removal efficiency of heavy metals was 40 - 60% for CFA-C-CWB (Figure 16A) and 40 - 70% for CFA-F-BC (Figure 16B) using one FJH pulse, indicating that the FJH process is a versatile process for CFA from different geological origins.

[0101]

[0182] The FJH purification process can further be extended to other large-scale solid wastes, such as bauxite residue (BR), a by-product of the Bayer process for alumina production. [Deady 2016]. BR is one of the most abundant industrial wastes, with an annual production rate of 150 million tons in addition to the already accumulated 3 billion tons. [OchsenkuhnPetropulu 1996].

[0102]

[0183] BR contains significant amounts of heavy metals. [Service 2020]. BR is a red powder in its dry form (insert figure 1623 in Figure 16C), and XRD shows the main components of hematite and calcite. Figure 16C (circles 1621 and triangles 1622 correspond to hematite and calcite, respectively).

[0103]

[0184] Similar to CFA, BR was mixed with CB and the FJH process was carried out. Table I; and Figure 17 (circles 1701 and triangles 1702 correspond to hematite and calcite, respectively). In BR, hematite and calcite are the main crystalline components. After FJH, as expected by the following equation (8), hematite remained and calcite was reduced. CaCO 3 =CaO+CO 2 (8)

[0185] Abundant heavy metals in BR include Cd, Co, Ni, and Pb. Figure 16D (bars 1631 - 1632 correspond to raw BR and BR FJH, respectively). After the FJH process, the heavy metal concentration was significantly reduced (Figure 16D), which shows an overview of the FJH process for waste pollution removal.

[0104] Application of purified CFA-C in cement composites

[0186] CFA-C containing a high content of CaO (about 22 wt%, Figure 13A) can be used as a cementitious material. [Rafieizonooz 2016; Canpolat 2004]. After the FJH reaction, CFA-C contains about 10 wt% of residual carbon according to thermogravimetric analysis (TGA). Figure 18A (plots 1801 - 1802 correspond to the case of CFA-C and CFA-C-CBFJH, respectively). Before use, the residual carbon was removed by calcination at 700 °C for 1 hour in air (insert figure 1803 in Figure 18A). Note that according to XRF analysis, the calcination process does not change the main composition of CFA-C (Figure 13A). In addition, the FJH and calcination processes do not substantially change the morphology of the CFA-C material as observed by microscopy. See Figures 19A - 19D.

[0105]

[0187] Using refined CFA-C, 30 wt% of the OPC in the cement composite was replaced (referred to as OPC / refined CFA), and pure OPC cement (referred to as pure OPC) and raw CFA-C replaced with 30 wt% of OPC (referred to as OPC / raw CFA) were tested as controls.

[0106]

[0188] Removal of the residual carbon in the CFA after FJH was carried out by calcination at 700 °C for 1 h in air using a furnace (NEY6-160A). The cement used for analysis was type I / II Portland cement. Three cement samples: (a) pure OPC, (b) OPC / raw CFA, and (c) OPC / refined CFA were cast. This mass ratio (CFA:OPC = 3:7) is considered an appropriate amount of CFA for cement-based materials to improve mechanical properties without extending the setting time or retarding strength development. [Thomas 2007]. All cement samples were cast at a water:cement weight ratio of 0.6, removed from the mold after 24 h, and then cured in water for 1 day or 28 days before testing. The dimensions of the cast samples were 25.4 × 25.4 × 50.8 mm as shown in the inset of Fig. 18B, Fig. 1814 3 and had the shape of a rectangular prism. The cured samples were tested in a uniaxial compression apparatus using a loading rate of 1.29 mm / min.

[0107]

[0189] After curing for only 1 day, the compressive strength and elastic modulus of the OPC / refined CFA composite reached 33.4 MPa ± 4.0 MPa and 15.5 GPa ± 2.5 GPa, respectively. These are greater than those of pure OPC at 20.6 MPa and 8.9 GPa, respectively. Figure 20A (plots 2001 - 2003 correspond to pure OPC, OPC / unprocessed CFA, and OPC / refined CFA, respectively), Figure 20B (bars 2011 - 2012 correspond to compressive strength and elastic modulus, respectively), and Table II. That is, the compressive strength of OPC / refined CFA exhibited an increase of about 62% compared to that of pure OPC; the elastic modulus of OPC / refined CFA was about 74% higher than that of pure OPC. Additionally, the performance of OPC / refined CFA was equivalent to that of OPC / unprocessed CFA.

[0108]

Table 2

[0109]

[0190] Typical stress-strain curves 1811 - 1813 of pure OPC, OPC / unprocessed CFA, and OPC / refined CFA after 28 days of curing are shown in Figure 18B. The compressive strength of OPC / refined CFA is 62.8 ± 2.4 MPa, exhibiting an increase of about 51% compared to that of pure OPC. Figure 5C (bar 1821 corresponds to compressive strength); Table II. The elastic modulus of OPC / refined CFA is 25.5 ± 2.6 GPa, which is about 28% greater than that of pure OPC. Figure 5C (bar 1822 corresponds to elastic modulus); Table II. Additionally, the performance of OPC / refined CFA was equivalent to that of OPC / unprocessed CFA. This is probably because the composition of CFA (Figure 13A) as well as the particle size and morphology (Figures 19A - 19D) remained similar except for the reduction in heavy metal content after the FJH refining process.

[0110]

[0191] The applicant has previously shown that appropriate loading of flash graphene into OPC (about 0.15 wt%) increases the compressive strength of the composite material [Luong 2020; Wyss 2021; Advincula 2021]. However, the as-obtained CFA-C / CB after FJH has a high residual carbon content of about 10 wt%. To avoid the calcination process for removing the residual carbon, the as-obtained purified CFA-C / CB was further used to replace 5 wt% OPC with a reference carbon content of about 0.5 wt%. The obtained purified CFA-C / CB replacement cement showed performance similar to that of the raw CFA-C. Figure 21 (plots 2101 - 2102 correspond to OPC / raw CFA-C and OPC / purified CFA-C / CB, respectively). In addition to CFA-C, purified CFA-F was also used to replace 30 wt% OPC. This exhibited equivalent performance compared to pure OPC. Figure 22 (plots 2201 - 2203 correspond to pure OPC, OPC / raw CFA-F, and OPC / purified CFA-F, respectively).

[0111]

[0192] To simulate the leaching conditions of acid rain, three cement pastes made from pure OPC, raw CFA-C, and purified CFA-C were placed in a HNO 3 solution with pH 4, and the heavy metals accumulated over 1 hour to 125 hours were measured. Three types of cement samples were prepared using 0.25 g of solid mass of pure OPC, raw CFA-C, and purified CFA-C. All samples were cast for 24 hours at a water:cement weight ratio of 0.6 and then cured in water for an additional 24 hours. To simulate the conditions of acid rain, the samples were separately placed in 0.0001 M HNO 3 solution (10 mL) with pH 4. The heavy metal content in the leachate after 1 hour, 2 hours, 4 hours, 6 hours, 25 hours, 50 hours, 100 hours, and 125 hours was measured by ICP-MS. The accumulated heavy metal content of the leaching agent was plotted against the leaching time.

[0112]

[0193] As shown in FIG. 18D, the as-received CFA-C (plot 1831) showed significant As leaching of up to about 0.2 ppm; in contrast, the purified CFA-C (plot 1832) showed even less As leaching comparable to that of pure OPC (plot 1833). In addition, pure OPC exhibited the most severe Co (FIG. 18E, plots 1841 - 1843 correspond to as-received CFA-C, purified CFA-C, and OPC, respectively) and Ni (FIG. 18F, plots 1851 - 1853 correspond to as-received CFA-C, purified CFA-C, and OPC, respectively) leaching, while both were substantially reduced in the purified CFA-C. Thus, purified CFA-C may be more environmentally friendly than OPC considering heavy metal leakage, which serves as another incentive for the application of purified CFA in real-world applications.

[0113] Techno-economic analysis and life cycle analysis

[0194] The FJH process for CFA purification has excellent scalability. Removal by heavy metal evaporation may be influenced by the maximum temperature during FJH; thus, maintaining a constant temperature may be important for scaling up the FJH process.

[0114] Scaling rules for the FJH process based on theoretical analysis

[0195] Performing a theoretical analysis of the FJH process demonstrated that the sample mass per batch can be increased by linearly increasing the FJH voltage or the total capacitance.

[0115]

[0196] In the case of the separation process by evaporation, the heavy metal removal efficiency is influenced by the maximum temperature; thus, when scaling up the FJH process, the available temperature across the sample is expected to be important. In the case of the Joule heating process, the heat quantity (Q) is calculated by Equation (9). Q = I 2 Rt (9) where I is the current passing through the sample, R is the resistance, and t is the discharge time.

[0116]

[0197] The heat quantity per unit volume (Q v ) is calculated by Equation (10). Q v =j2ρ e t (10) where j is the current density and ρ e is the electrical resistivity.

[0117]

[0198] The temperature change (ΔT) is proportional to the heat quantity according to Equation (11). Q=C p mΔT (11) where Cp is the heat capacity and m is the mass of the sample.

[0118]

[0199] The above equation can be reformulated per unit volume to Equation (12). Q v =C p ρ m ΔT (12) where ρ m is the density of the sample.

[0119]

[0200] For a specific sample, C p and ρ are constant; therefore, to maintain the same temperature in the FJH, it is important to maintain a constant Q v .

[0201] For a specific sample, the electrical resistivity (ρ e ) is constant; therefore, to maintain a constant Q v when increasing the sample mass, it is necessary to maintain a constant j according to Equation (10).

[0120]

[0202] The charge quantity (q) in the capacitor bank can be calculated by Equation (13). q=CV (13) where C is the capacitance of the capacitor bank and V is the voltage of the capacitor bank.

[0121]

[0203] Assuming that all the charges in the capacitor bank are discharged within time t, the current (I) passing through the sample can be calculated by Equation (14). I = q / t (14)

[0204] As a result, the current density (j) can be calculated by Equation (15). j = I / s = CV / st (15) Wherein, S is the cross-sectional area of the sample.

[0122]

[0205] In the case of a cylindrical sample, which is usually the case in the FJH apparatus used in the tests performed and described herein, the mass (m) can be calculated by Equation (16). m = ρ m SL (16) Wherein, ρ m is the density of the sample, S is the cross-sectional area of the sample, and L is the length of the sample.

[0123]

[0206] For a specific sample type, the density (ρ m ) is maintained the same.

[0207] In summary, Equation (17) for determining the current density can be obtained. j = CVρ m L / mt (17)

[0208] As the inventors described above, when increasing the mass (m) of the sample, the current density (j) passing through the sample can be maintained constant (generally, maintained constant). This can be achieved by the following measures: (1) increasing the FJH voltage (V), and / or (2) increasing the capacitance (C).

[0124] Scale-up to gram scale per batch

[0209] By constructing the FJH system with a large capacitance of C = 0.624 F, a maximum sample mass of 3 g per batch was demonstrated. See FIGS. 23A - 23C.

[0125]

[0210] In this first-generation FJH setup, the capacitor bank consisted of ten aluminum electrolytic capacitors (450 V, 6 mF, Mouser #80-PEH200YX460BQU2) with a total capacitance of C 0 = 0.06 F. In small-scale experiments, for a sample mass of m0 = 0.15 g, an FJH voltage of V 0 = 120 V and a capacitance of C 0 = 0.06 F were used. Next, the upscaling of FJH to a mass of m1 = 3 g was demonstrated. A second-generation FJH setup was constructed using a larger capacitance of C1 = 0.624 F. Figure 23A. According to Equation (16), Equation (18) is obtained. m 1 / m 0 = C 1 V 1 / C 0 V 0 (18)

[0211] For a mass of m1 = 3 g and C1 = 0.624 F, an FJH voltage of V1 = 250 V was used and thus basically fitted using Equation (18). Further adjustment of the FJH process, including the conductive additive content, FJH voltage, and FJH time, can be utilized when scaling up the process.

[0126] Scale-up and continuous process

[0212] By using a 3D-printed automation system, the applicant's research laboratory achieved a production rate of more than 10 kg / day of flash graphene (from met coke). This system was constructed for the process of converting the carbon source discovered by the applicant into flash graphene. [Luong 2020]. The flash temperature in that process was 3100 °C.

[0127]

[0213] Therefore, the FJH process can be integrated using scale-up technologies for continuous processing. Figure 24. The FJH process can be integrated using industrially available processes for continuous operation using belt rollers. As shown in Figure 24, a sheet metal belt 2401 controlled by a tension roller 2402 can be used to convert the CFA raw material 2403. A doctor blade 2404 can be used to control the thickness and compactness of the CFA raw material. During FJH, since the sheet metal is not an excellent electrical conductor along its length, the current may be concentrated where the electrodes 2405-2406 (each having connectors 2407-2408 to a power source) are arranged. The FJH zone can be installed in a vacuum chamber 2409 to collect volatile substances. Clean CFA can be collected by a collector 2410 (a doctor blade 2411 can be used to control the thickness and other sizing of the cleaned CFA).

[0128] Energy consumption and cost

[0214] The energy consumption and cost of the FJH purification process were investigated. Joule heating is a highly efficient technology with an operating coefficient close to 1.0 because almost all of the electrical energy directly targets sample heating. This is in stark contrast to conventional furnaces that rely on heat conduction to heat the sample, causing a reduction in energy efficiency. Due to the ultra-high heating and cooling rates and short processing times within 1 second, the FJH process for heavy metal removal from CFA has an estimated electricity consumption of approximately 532 kWh / ton, or $21 / ton (using industrial electricity rates).

[0129]

[0215] The material cost can be minimized by recovering and reusing the conductive additive or by using low-cost conductive additives or low-value carbon such as plastic ash.

[0130] Life cycle analysis

[0216] Performed a life cycle analysis (LCA) from production to use for comparison to examine the resulting environmental impacts and energy requirements of CFA disposal, compared to the reuse of raw or purified CFA as an alternative cementitious material. The LCA further confirmed the value of the present invention, including considering the newly established FJH and partial replacement strategies, as well as the reduction of GHG emissions and heavy metal emissions due to their energy consumption requirements. This analysis was performed based on the requirements of ISO14044.

[0131]

[0217] This analysis covered three main processes: raw material production, feedstock preparation, and landfill. Transportation was considered in the landfill process, and the process at the experimental scale was assumed for FJH without applying further scaling. The functional unit considered was 1 ton of cementitious material. The complete life cycle inventory is shown in Tables III - VII below. The direct energy input for the FJH process was experimentally measured, and the cumulative requirements and impacts were calculated using values from the ISO-compliant Argonne National Laboratory GREET LCA database or the literature.

[0132] Description of scenarios and system boundaries

[0218] The following four scenarios were considered: (a) landfill (using pure OPC as cement for the useful life, with CFA and plastic ash landfilled), (b) direct replacement (using an OPC - raw CFA composite as cement for the useful life, with plastic ash landfilled), (b) FJH - separation - replacement (purifying CFA by FJH, followed by removing the remaining carbon by separation, and using an OPC - purified CFA composite as cement for the useful life), and (d) FJH - replacement (purifying CFA by FJH without removing the remaining carbon and using an OPC - purified CFA - plastic ash composite as cement for the useful life). See Figures 25A - 25D.

[0133]

[0219] In all scenarios, 1 ton of cementitious material for service life is used as the baseline, and the flow of all other materials is normalized according to the cementitious material. See Table III.

[0134]

Table 3

[0135]

[0220] Landfill of Scenario 1: In this scenario (Figure 25A), pure OPC (1 ton) is used for the service life in cement, and CFA (0.47 ton) and plastic ash (0.23 ton) are landfilled. It should be noted here that the masses of CFA and plastic ash are assigned according to their consumption in the FJH-separation-replacement scenario. See the details in Scenario 3 below.

[0136]

[0221] Direct replacement of Scenario 2: In this scenario (Figure 25B), the application of cement in which OPC is replaced by 30 wt% of raw CFA (Figures 18B - 18C) is used. Thus, in this scenario, OPC (0.7 ton) is mixed with raw CFA (0.3 ton) for the service life in cement. In this scenario, plastic ash (0.23 ton) and a part of CFA (0.17 ton) are landfilled to supplement the material consumption in Scenario 3 (detailed below). The energy consumption of landfilling is the same as that in Scenario 1 above.

[0137]

[0222] FJH-separation-replacement of Scenario 3: In this scenario (Figure 25C), plastic ash is used as the conductive additive. CFA (0.47 tons) is mixed with 33 wt% plastic ash (0.23 tons), and 0.7 tons are subjected to FJH to remove heavy metals, resulting in a purified CFA-plastic ash mixture (0.33 tons). The remaining carbon in the purified CFA-plastic ash mixture is separated by sieving (Figures 10A - 10F) to obtain purified CFA (0.3 tons). In the cement application by the inventors (Figures 18B - 18C), OPC is replaced with 30 wt% of the purified CFA. Thus, OPC (0.7 tons) is mixed with the purified CFA (0.3 tons) as the effective life in the cement. In this scenario, the materials are not landfilled.

[0138]

[0223] FJH - substitution in Scenario 4: In this scenario (Figure 25D), plastic ash is used as the conductive additive. CFA (0.07 tons) is mixed with 33 wt% plastic ash (0.04 tons), and 0.11 tons are subjected to FJH to remove heavy metals, thereby obtaining a purified CFA-plastic ash mixture (0.05 tons). Using the cement application in Figure 21, OPC is replaced with 5 wt% of the purified CFA-plastic ash without performing a separation process. Thus, OPC (0.95 tons) is mixed with the purified CFA-plastic ash (0.05 tons) for the effective life in the cement. In this scenario, a portion of CFA (0.4 tons) and plastic ash (0.19 tons) are landfilled to supplement the material consumption in Scenario 3 described above.

[0139] Life cycle inventory

[0224] Table IV summarizes the environmental impacts such as GHG emissions, heavy metal emissions, and energy consumption requirements related to the production, processing, and landfilling of raw materials, and further explanations of the values are shown below.

[0140]

Table 4

[0141]

[0225] Production of materials: The GHG emissions (849.50 kg / ton) and energy consumption (4581 MJ / ton) for OPC are from the Argonne GREET model. The GHG emissions (10.1 kg / ton) and energy consumption (199 MJ / ton) for CFA are from the literature. [Teixeira 2016]. Since the GHG emissions and energy consumption of plastic ash are not available, biomass ash data is used as a substitute for its similar process (GHG emissions at 0.028 kg / ton, energy consumption at 5.94 MJ / ton). [Teixeira 2016].

[0142]

[0226] Useful life as cement: It is assumed that heavy metal release to the surrounding environment occurs during the useful life of the cement. Heavy metal release is defined as the total elution content of As, Co, and Ni. The elution content of As, Co, and Ni in the cement reaches a plateau according to the acid elution experiment (Figures 18D - 18F); therefore, the eluted heavy metal content at 125 hours is used as the heavy metal release during the useful life of the cement. Therefore, the heavy metal releases of pure OPC, raw CFA, and purified CFA are evaluated as 2.25 g / ton, 1.88 g / ton, and 0.94 g / ton, respectively. When a mixture of cement composites is used, the heavy metal release is normalized according to its mass ratio. Therefore, the heavy metal releases of OPC replaced with 30 wt% raw CFA, OPC replaced with 30 wt% purified CFA, and OPC replaced with 5% purified CFA are calculated as 2.14 g / ton, 1.85 g / ton, and 2.18 g / ton, respectively.

[0143]

[0227] Landfill: Assume that heavy metal release occurs in the landfill of CFA. The heavy metal release from the CFA landfill is defined as the total elution content of As, Co, and Ni, which is assigned as the plateau content at 125 hours in the acid elution experiment, i.e., 1.88 g / ton (Figs. 18D - 18F). The heavy metal release from the landfill of plastic ash is not considered in this analysis. Since CFA is mostly composed of inorganic substances and plastic ash is mostly composed of graphitized carbon that is very stable in the environment, it is assumed here that there is no GHG emission during the landfill of CFA and plastic ash. Energy input is required for the landfill of CFA and plastic ash. According to recent literature [Nabav - Pelesaraei 2017], the energy consumption for landfill is approximately 19.6 MJ / ton, including human labor, diesel fuel, transportation vehicles, electricity, etc. This energy is assigned to the energy consumption of the landfill of CFA and plastic ash.

[0144]

[0228] Processing - mixing: Energy input is required for the mixing process, including the mixing of raw CFA and plastic ash for FJH and the mixing of unrefined or refined CFA and OPC for cement. Mixing is carried out using an electrically driven powder mixer, which is assumed to consume 9.432 MJ / ton of energy. There is no GHG emission and heavy metal release in the mixing process.

[0145]

[0229] Processing - FJH: The energy consumption for FJH is estimated to be 2901.6 MJ / ton. Since heavy metals are collected in the FJH process, there is no heavy metal release in this step.

[0146]

[0230] Processing - separation by sieving: Separation is assumed to be carried out using an industrial vibrating sieve. For a typical shaker, the capacity is estimated to be m = 0.034 tons according to its volume. The powder is 80W. If the processing time is assumed to be 0.5 hours, the energy consumption for separation is estimated to be about 4 MJ / ton. The separation process has no heavy metal or GHG emissions.

[0147] Assessment of life cycle impacts

[0231] In the LCA, the environmental impacts were classified into three midpoint indicators including heavy metal emissions (Table V), GHG emissions (Table VI), and energy consumption (Table VII).

[0148]

[0232] Two environmental impacts, namely heavy metal emissions and GHG emissions, as well as energy consumption were analyzed. First, the FJH-separation-replacement scenario has the least heavy metal emissions as expected (Figure 26A and Table V), and a reduction of about 41% is demonstrated compared to the landfill scenario. See Figure 27A.

[0149]

Table 5

[0150]

[0233] The direct replacement scenario also shows a reduction of about 22% in heavy metal emissions because the heavy metal leakage of CFA is lower than that of OPC. Figures 18D - 18F. Second, regarding GHG emissions, the landfill scenario includes a huge amount of CO 2 emissions of 854 kg / 1 ton of cementitious material, most of which is from OPC production. Figure 26B and Table VI.

[0151]

Table 6

[0152]

[0234] All other scenarios using partial replacement of OPC with CFA show a reduction in GHG emissions, i.e., a reduction of about 30% for direct replacement, about 30% for FJH or burn-replacement, and about 5% for FJH-replacement compared to landfilling. Figure 27B.

[0153]

[0235] Finally, the direct replacement scenario has the lowest energy consumption at 3310 MJ / ton, which represents a reduction of about 29% compared to landfilled material. Figure 26C, Figure 27C, and Table VII.

[0154]

Table 7

[0155]

[0236] Scenarios using the FJH purification process demonstrate a slight decrease in energy consumption of about 1% for FJH-separation-replacement and a slight increase of about 2% for FJH-replacement due to the highly energy-efficient FJH process as discussed above (Figure 27C). Thus, the energy consumption of the FJH process is balanced by the reduction in OPC consumption.

[0156]

[0237] Thus, among other advantages of the present invention, LCA from production to use has demonstrated that the reuse of CFA in cement can reduce heavy metal emissions by 41% and GHG emissions by 30% compared to current waste management methods (landfilling).

[0157] Comparison with previous methods

[0238] Furthermore, comparisons were performed using the present invention and existing methods (Table VIII) for the removal of heavy metals from CFA such as bioleaching [Seidel 2001], elution using inorganic acids [Xu 2001] or organic acids [Pangayao 2014], chemical extraction with alkaline leachates [Harris 1983] or chelating agents [Harris 1983].

[0158]

Table 8

[0159]

[0239] FJH is a water - free process, while bio or chemical processes consume large amounts of water. Fig. 28A. The chemical leaching method uses large amounts of chemicals such as acids, bases, and chelating agents, so the material cost is higher than that of bioleaching and the FJH process. Fig. 28B. The FJH process enables rapid treatment within seconds, which is faster than slow leaching processes. Fig. 28C. As a conclusion, the heavy - metal removal efficiency of the FJH process is similar to the removal efficiency of inorganic acid leaching, and both of these are superior to other processes. Fig. 28D.

[0160]

[0240] Therefore, compared with the prior art, the present invention utilizes the FJH strategy with a single 1 - second FJH pulse for the removal of toxic heavy metals from CFA with a high removal efficiency of 70 - 90%. When preparing cement from purified CFA and replacing 30 wt% of OPC, it showed an enhanced strength of about 51% and an elastic modulus of about 28% compared to that of pure OPC. The simulated acid - rain leaching experiment showed that the cement from purified CFA exhibited less heavy - metal leakage than raw CFA, indicating that it is superior to pure OPC. LCA from production to use clarified that the reuse of CFA in cement can reduce heavy - metal emissions by 41% and GHG emissions by 30% compared to the current waste - management method (landfill). Due to the rapid treatment process and ultra - high heating and cooling rates, the FJH process is highly energy - efficient, and the estimated electrical cost is about $21 per ton for CFA treatment. The FJH strategy can also be applied to remove the contamination of other wastes such as BR. The continuous industrial scale - up of the FJH process makes it even more attractive in large - scale industrial waste - pollution removal and stabilization.

[0161]

[0241] While embodiments of the present invention have been shown and described, modifications thereof can be made by those skilled in the art without departing from the essence and teachings of the present invention. The described embodiments and examples provided herein are merely illustrative and not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the present invention. The scope of protection is not limited by the above description, but is limited only by the following claims, which include all equivalents of the subject matter of the claims.

[0162]

[0242] The disclosures of all patents, patent applications, and publications cited herein are incorporated by reference in their entirety to the extent that they provide exemplary, procedural, or other details supplementary to those described herein.

[0163]

[0243] Quantities and other numerical data can be presented herein in a range format. Such a range format is used merely for convenience and brevity and should be interpreted flexibly as including not only the numerical values explicitly recited as the limits of the range, but also all 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 approximately 1 to 4.5 should be interpreted as including not only the explicitly recited limits of approximately 1 to 4.5, but also individual numerical values such as 2, 3, 4, and sub-ranges such as 1 to 3, 2 to 4, etc. The same principle applies to ranges reciting only one numerical value such as "less than approximately 4.5", which range should be interpreted as including all of the values and ranges recited above. Further, such interpretation should apply regardless of the width of the range or the characteristics being described.

[0164]

[0244] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the subject matter of this disclosure, representative methods, devices, and materials are described herein.

[0165]

[0245] In accordance with longstanding patent law convention, the terms “a” and “an,” as used in this application, including in the claims, mean “one or more.”

[0166]

[0246] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and the like used in this specification and the claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and the appended claims are approximations that may vary depending upon the desired properties sought to be obtained by the subject matter of this disclosure.

[0167]

[0247] As used herein, the terms “about” and “substantially” when referring to a value or amount of mass, weight, time, volume, concentration, or percentage, mean in some embodiments a variation of ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, such as is appropriate in carrying out the disclosed method.

[0168]

[0248] As used herein, the terms “substantially perpendicular” and “substantially parallel” mean, in some embodiments, within ±10° of the perpendicular and parallel directions, in some embodiments, within ±5° of the perpendicular and parallel directions, in some embodiments, within ±1° of the perpendicular and parallel directions, and in some embodiments, within ±0.5° of the perpendicular and parallel directions.

[0169]

[0249] As used herein, the term “and / or” when used in the context of a list of items refers to the items being 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 any and all combinations and sub - combinations of A, B, C, and D.

[0170] References

[0250] PCT International Patent Publication No. WO 2022 / 067111, entitled “Ultrafast Flash Joule Heating Methods And System For Performing Same,” to J. M. Tour, et al., filed September 24, 2021 (the “Tour ’111 PCT Application”).

[0251] Abrahamson, J., “Graphite sublimation temperatures, carbon arcs and crystalline erosion,” Carbon, 1974, 12, 111 - 141 (“Abrahamson 1974”).

[0252] Advincula, P. A., et al., “Flash graphene from rubber waste,” Carbon, 2021, 178, 649 - 656 (“Advincula 2021”).

[0253] Algozeeb, W. A., et al., “Flash graphene from plastic waste,” ACS Nano, 2020, 14, 15595-15604 (“Algozeeb 2020”).

[0254] Andrew, R. M., “Global CO 2 emissions from cement production, 1928-2018,” Earth Syst. Sci. Data, 2019, 11, 1675-1710 (“Andrew 2019”).

[0255] Anuar Sharuddin, S. D., et al., “A review on pyrolysis of plastic wastes,” Energy Convers. Manag., 2016, 115, 308-326 (“Anuar Sharuddin 2016”).

[0256] ASTM C618-08, “Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete,” Annual Book of ASTM Standards (West Conshohocken) 2008 (“ASTM C618-08 2008”).

[0257] 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”).

[0258] Blissett, R. S., et al., “A review of the multi-component utilisation of coal fly ash,” Fuel, 2012, 97, 1-23 (“Blissett 2012”).

[0259] Bolan, N., et al., “Remediation of heavy metal(loid)s contaminated soils - To mobilize or to immobilize?” J. Hazard. Mater., 2014, 266, 141-166 (“Bolan 2014”).

[0260] Canpolat, F., et al., “Use of zeolite, coal bottom ash and fly ash as replacement materials in cement production,” Cem. Conc. Res., 2004, 34, 731-735 (“Canpolat 2004”).

[0261] Chancey, R. T., et al., “Comprehensive phase characterization of crystalline and amorphous phases of a Class F fly ash,” Cem. Concr. Res., 2010, 40, 146-156 (“Chancey 2010”).

[0262] Chen, W. et al., “Millisecond conversion of metastable 2D materials by flash Joule heating,” ACS Nano, 2021, 15, 1282-1290 (“Chen 2021”).

[0263] Chen, Y., et al., “Ultra-fast self-assembly and stabilization of reactive nanoparticles in reduced graphene oxide films,” Nat. Commun., 2016, 7, 12332 (“Chen I 2016”).

[0264] Chen, Y., et al., “Rapid, in situ synthesis of high capacity battery anodes through high temperature radiation-based thermal shock,” Nano Lett., 2016, 16, 5553-5558 (“Chen II 2016”).

[0265] Cheng, Y., et al., “Electric current aligning component units during graphene fiber Joule heating,” Adv. Funct. Mater., 2022, 32, 2103493 (“Cheng 2022”).

[0266] Cui, B., et al., “Waste to wealth: Defect-rich Ni-incorporated spent LiFePO 4 for efficient oxygen evolution reaction,” Sci. China Mater., 2021, 64, 2710-2718 (“Cui 2021”).

[0267] Daehn, K., et al., “Innovations to decarbonize materials industries,” Nat. Rev. Mater., 2002, 7, 275-294 (“Daehn 2022”).

[0268] Deady, E. A., et al., “A review of the potential for rare-earth element resources from European red muds: examples from Seydisehir, Turkey and Parnassus-Giona, Greece,” Mineral. Mag., 2016, 80, 43-61 (“Deady 2016”).

[0269] 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”).

[0270] Deng, B., et al., “Rare earth elements from waste,” Sci. Adv., 2022, 8, eabm3132 (“Deng II 2022”).

[0271] Deng, B., et al., “Urban mining by flash Joule heating,” Nat. Commun., 2021, 12, 5794 (“Deng 2021”).

[0272] Environmental Protection Agency, “Hazardous and Solid Waste Management System; Disposal of Coal Combustion Residuals From Electric Utilities; Final Rule,” Federal Register, Vol. 80, No. 74 (April 17, 2015): 21301 (“EPA 2015”).

[0273] Environmental Protection Agency, “Method 3050B: Acid Digestion of Sediments, Sludges, and Soils,” Revision 2, Washington, DC, 1996 (“EPA 1996”).

[0274] Fernandez-Turiel, J. L., et al., “Mobility of heavy metals from coal fly ash,” Environ. Geol., 1994, 23, 264-270 (“Fernandez-Turiel 1994”).

[0275] Harris, W. R., et al., “Time-dependent leaching of coal fly ash by chelating agent,” Environ. Sci. Technol., 1983, 17, 139-145 (“Harris 1983”).

[0276] Ishaq, M., et al., L”eaching capabilities of iodine monochloride (ICl) and diethylenetriamine pentaacetic acid (DPTA) at different concentrations and pH for some major and trace metals from coal and coal fly ash,” Arabian J. Geosci., 2013, 6, 4109-4118 (“Ishaq 2013”).

[0277] ISO 14044:2006, “Environmental Management -- Life Cycle Assessment --Requirements and Guidelines, 2006 (“ISO 14044”).

[0278] Jiang, R., et al., “Ultrafast synthesis for functional nanomaterials,” Cell Rep. Phys. Sci., 2021, 2, 100302 (“Jiang 2021”).

[0279] Kashiwakura, S., et al., “Removal of arsenic in coal fly ash by acid washing process using dilute H 2 SO 4 solvent,” J. Hazard. Mater., 2010, 181, 419-425 (“Kashiwakura 2010”).

[0280] Koukouzas, N., et al., “Heavy metal characterization of CFB-derived coal fly ash,” Fuel Process. Technol., 2011, 92, 441-446 (“Koukouzas 2011”).

[0281] Lide, D. R., CRC Handbook of Chemistry and Physics (CRC Press) 2005 (“Lide 2005”).

[0282] Liu, C., et al., “Air-assisted transient synthesis of metastable nickel oxide boosting alkaline fuel oxidation reaction,” Adv. Funct. Mater., 2020, 10, 2001397-2001404 (“Liu C 2020”).

[0283] Liu, P., et al., “Speciation, distribution, and mobility of hazardous trace elements in coal fly ash: Insights from Cr, Ni, and Cu,” Energy Fuels, 2020, 34, 14333-14343 (“Liu P 2020”).

[0284] Liu, P., et al., “Comprehensive understandings of rare earth element (REE) speciation in coal fly ashes and implication for REE extractability,” Environ. Sci. Technol., 2019, 53, 5369-5377 (“Liu P 2019”).

[0285] Liu, S., et al., “Extreme environmental thermal shock induced dislocation-rich Pt nanoparticles boosting hydrogen evolution reaction,” Adv. Mater., 2022. 34, 2106973-2106979 (“Liu S 2022”).

[0286] Liu, S., et al., “Dislocation-strained IrNi alloy nanoparticles driven by thermal shock for the hydrogen evolution reaction,” Adv. Mater., 2020, 32, 2006034-2006041 (“Liu S 2020”).

[0287] Lu, J., et al., “Millisecond conversion of photovoltaic silicon waste to binder-free high silicon content nanowires electrodes,” Adv. Energy Mater., 2021, 11, 2102103 (“Lu 2021”).

[0288] Luong, D. X., et al., “Gram-scale bottom-up flash graphene synthesis,” Nature, 2020, 577, 647-651 (“Luong 2020”).

[0289] Ma, W., et al., “Performance of chemical chelating agent stabilization and cement solidification on heavy metals in MSWI fly ash: A comparative study,” J. Environ. Manage., 2019, 247, 169-177 (“Ma 2019”).

[0290] Meer, I., et al.. “Removal techniques for heavy metals from fly ash,” J. Mater. Cycles Waste Manag., 2018, 20, 703-722 (“Meer 2018”).

[0291] Menya, E., et al., “Optimization of pyrolysis conditions for char production from rice husks and its characterization as a precursor for production of activated carbon,” Biomass Convers. Biorefin., 2020, 10, 57-72 (“Menya 2020”).

[0292] Miller, S. A., et al., “Environmental impacts of alternative cement binders,” Environ. Sci. Technol. 2020, 54, 677-686 (“Miller 2020”).

[0293] Nabavi-Pelesaraei, A., et al., “Modeling of energy consumption and environmental life cycle assessment for incineration and landfill systems of municipal solid waste management - A case study in Tehran Metropolis of Iran” J. Clean. Prod., 2017, 148, 427-440 (“Nabavi-Pelesaraei 2017”).

[0294] OchsenkuhnPetropulu, M., et al., “Recovery of lanthanides and yttrium from red mud by selective leaching,” Anal. Chim. Acta, 1996, 319, 249-254 (“OchsenkuhnPetropulu 1996”).

[0295] Olivier, J. G. J., et al., “Trends in global CO 2 emissions: 2016 report,” PBL Netherlands Environmental Assessment Agency, 2016 (“Olivier 2016”).

[0296] Pangayao D, et al., “Leaching of chromium from coal ash using citric acid, oxalic acid and gluconic acid by batch leaching procedure,” In: IEEE 2014 International Conference on Humanoid, Nanotechnology, Information Technology, Communication and Control, Environment and Management (HNICEM), 2014 (“Pangayao 2014”).

[0297] Praharaj, T., et al., “Leachability of elements from sub-bituminous coal fly ash from India,” Environ. Int., 2002, 27, 609-615 (“Praharaj 2002”).

[0298] Rafieizonooz, M., et al., “Investigation of coal bottom ash and fly ash in concrete as replacement for sand and cement,” Constr. Build. Mater., 2016, 116, 15-24 (“Rafieizonooz 2016”).

[0299] Rivera, N., et al., “Chemical speciation of potentially toxic trace metals in coal fly ash associated with the Kingston fly ash spill,” Energy Fuels, 2017, 31, 9652-9659 (“Rivera 2017”).

[0300] Sahoo, P. K., et al., “Recovery of metals and other beneficial products from coal fly ash: a sustainable approach for fly ash management,” Int. J Coal Sci. Technol., 2016, 3, 267-283 (“Sahoo 2016”).

[0301] Seidel, A., et al., “Mechanism of bioleaching of coal fly ash by Thiobacillus thiooxidans,” Chem. Eng. J., 2001, 83, 123-130 (“Seidel 2001”).

[0302] Service, R. F., “Red alert,” Science, 2020, 369, 910-911 (“Service 2020”).

[0303] Stanford, M. G., et al., “Flash Graphene Morphologies,” ACS Nano, 2020, 14, 13691-13699 (“Stanford 2020”).

[0304] Teixeira, E. R., et al., “Comparative environmental life-cycle analysis of concretes using biomass and coal fly ashes as partial cement replacement material,” J. Clean. Prod., 2016, 112, 2221-2230 (“Teixeira 2016”).

[0305] Thomas, M., “Optimizing the use of fly ash in concrete,” Portland Cement Association, 2007 (“Thomas 2007”).

[0306] Wang, C. W., et al., “A general method to synthesize and sinter bulk ceramics in seconds,” Science, 2020, 368, 521-526 (“Wang C 2020”).

[0307] Wang, N. N., et al., “Leachability and adverse effects of coal fly ash: A review,” J. Hazard. Mater., 2020, 396, 122725 (“Wang N 2020”).

[0308] Wyss, K. M., et al., “Converting plastic waste pyrolysis ash into flash graphene,” Carbon, 2021, 174, 430-438 (“Wyss 2021”).

[0309] Xu, Y. H., et al., “Leaching of arsenic from coal fly ashes 1. leaching behavior of arsenic and mechanism study,” Toxicol. Environ. Chem., 2001, 81, 55-68 (“Xu 2001”).

[0310] Yao, Y., et al., “High temperature shockwave stabilized single atoms,” Nat. Nanotechnol., 2019, 14, 851-857 (“Yao 2019”).

[0311] Yao, Y., et al., “Carbothermal shock synthesis of high-entropy-alloy nanoparticles,” Science, 2018, 359, 1489-1494 (“Yao 2018”).

[0312] Yao, Z. T., et al., “A comprehensive review on the applications of coal fly ash,” Earth-Sci. Rev., 2015, 141, 105-121 (“Yao 2015”).

[0313] Yao, Z. T., et al., “A review of the alumina recovery from coal fly ash, with a focus in China,” Fuel, 2014, 120, 74-85 (“Yao 2014”).

[0314] Yu, Q., et al., “The leachability of heavy metals in hardened fly ash cement and cement- solidified fly ash,” Cem. Concr. Res., 2005, 35, 1056-1063 (“Yu 2005”).

[0315] Zhang, W. C., et al., “Comprehensive review of rare earth elements recovery from coal-related materials,” Minerals, 2020, 10, 451-478 (“Zhang 2020”).

[0316] Zhong, X. Y., et al., “Global greenhouse gas emissions from residential and commercial building materials and mitigation strategies to 2060,” Nat. Commun., 2021, 12, 6126 (“Zhong 2021”).

Explanation of Symbols

[0171] 201 Capacitor 202 Porous Cu 203 Cu Electrode 204 Graphite 205 CFA + CB 206 Quartz tube 2401 Sheet metal belt 2402 Tension roller 2403 CFA raw material 2404 Doctor blade 2405 Electrode 2406 Porous electrode 2407 Connector to power source 2408 Connector to power source 2409 Vacuum chamber 2410 Collection of cleaned CFA 2411 Doctor blade

Claims

1. 1. A method of forming a cementitious material, comprising: (a) forming a mixture comprising an industrial waste material and a conductive additive; (b) applying a voltage across the mixture; (i) the voltage is applied in one or more voltage pulses; (ii) the duration of each of the one or more voltage pulses is for a predetermined period of time in duration; (iii) applying the voltage removes at least 50% by weight of the heavy metals from the industrial waste to form a purified industrial waste; (c) mixing the refined industrial waste with cement to form a cementitious material; The above method, comprising:

2. 10. The method of claim 1, wherein the industrial waste is selected from the group consisting of fly ash, bauxite residue, slag, tailings, and silica fume.

3. The method of claim 1 or 2, wherein the conductive additive is a carbon source.

4. The method of claim 1 or 2, wherein the conductive source comprises metal flakes.

5. 3. The method of claim 1 or 2, wherein the application of the voltage removes at least 70% by weight of the heavy metals from the industrial waste to form a purified industrial waste.

6. 3. The method of claim 1 or 2, wherein the heavy metals comprise one or more metals selected from the group consisting of Al, As, Ba, Be, Bi, B, Ca, Cd, Cs, Cr, Co, Cu, Ga, In, Fe, Pb, Li, Mg, Mn, Ni, P, K, Rb, Se, Si, Ag, Na, Sr, S, Te, Tl, V, Zn, and combinations thereof.

7. 3. The method of claim 1 or 2, further comprising removing residual carbon from the industrial waste after the step of applying a voltage across the mixture.

8. 8. The method of claim 7, wherein the step of removing the residual carbon comprises a calcination or physical separation step.

9. 3. The method of claim 1 or 2, wherein the refined industrial waste is mixed with the cement in a weight ratio of about 1:9 to about 1:

1.

10. 3. The method of claim 1 or 2, which is a water-free process.

11. 3. The method of claim 1 or 2, which does not include an acid washing step.

12. (a) refined industrial waste having at least 50% less heavy metals by weight compared to the industrial waste prior to refinement; and (b) cement; A cementitious material comprising a refined industrial waste material comprising: (1) forming a mixture comprising an industrial waste material and a conductive additive; and (2) applying a voltage across the mixture; wherein the conductive additive is a carbon source; (A) the voltage is applied in one or more voltage pulses; (B) the duration of each of the one or more voltage pulses is for a predetermined period of time in duration; (C) the application of said voltage removes at least 50% by weight of said heavy metals from said industrial waste to form a purified industrial waste.

13. 13. The cementitious material of claim 12 made by the method of claim 1 or 2.

14. 1. A system for forming a cementitious material, comprising: (a) a source of a mixture containing industrial waste and conductive additives; (b) a cell operatively connected to said source, said cell being adapted to allow said mixture to flow into said cell and be held under compression; (c) an electrode operably connected to the pressure cell; (d) a flash power supply for applying a voltage across the mixture, (i) the voltage is applied in one or more voltage pulses; (ii) the duration of each of the one or more voltage pulses is for a predetermined period of time in duration; (iii) a flash power supply, wherein application of said voltage removes at least 50% by weight of said heavy metals from said industrial waste to form purified industrial waste; (e) a collector operably connected to the cell for collecting the purified industrial waste; and (f) an operable mixer for mixing the collected refined industrial waste with cement to form a cementitious material; The system as described above.

15. 15. The system of claim 14, wherein the method of claim 1 or 2 is utilized to perform the method of forming the cementitious material.

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