Electrothermal chlorination and carbochlorination system and method for selective metal recovery

Abstract

Metal recovery and separation systems and methods, more particularly electrothermal chlorination (ETC) and electrothermal carbochlorination (ETCC) methods and systems for selective metal extraction, such as extraction of key metals from waste streams. Alternatively, other oxidizing agents, such as fluorine, bromine or iodine, may be used in place of or in combination with chlorine. Further, or other reducing agents, such as a metal (0), such as tin (0), and H2 (H2 included in argon, such as 1% to 5% by volume of H2 in argon, may be used in place of or in combination with carbon. Embodiments of the invention may utilize ETC to selectively recover In from ITO-containing waste, and utilize ETC in combination with ETCC to recover Ta from capacitor waste.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of U.S. Patent Application No. 63 / 415,384, filed on October 12, 2023, entitled "Metal Recovery And Separation Systems And Methods", by James M. Tour et al., which is commonly owned by the owners of the present invention and is hereby incorporated by reference in its entirety.

[0003] This application also claims the benefit of U.S. Patent Application No. 18 / 263,831, filed on August 1, 2023, entitled "Ultrafast Flash Joule Heating Synthesis Methods And Systems For Performing Same", by James M. Tour et al. ("Tour’831 Application"), which is the U.S. §371 national stage of PCT Patent Application No. PCT / US22 / 14923, filed on February 2, 2022, entitled "Ultrafast Flash Joule Heating Synthesis Methods And Systems For Performing Same", which in turn claims the priority of U.S. Patent Application No. 63 / 144,862, filed on February 2, 2021. All of these patent applications are commonly owned by the owners of the present invention. The Tour‘831 Application is hereby incorporated by reference in its entirety. Technical field

[0004] The present invention relates to metal recovery and separation systems and methods, and more particularly to electrothermal chlorination and electrothermal carbothermal chlorination methods and systems for selective metal extraction, such as the extraction of critical metals from waste material streams.

[0005] Government interests

[0006] This invention was made with government support under Award No. R1A330-416000, awarded by the United States Air Force Office of Scientific Research; Award No. W912HZ-21-2-0050, awarded by the United States Engineer Research and Development Center for the United States Army Corp of Engineer; and Award No. HR00112290122, awarded by the Defense Advanced Research Projects Agency, United States Department of Defense. The government has certain rights in this invention. BACKGROUND OF THE INVENTION

[0007] There is an urgent and growing need for metals for applications in electronics, superalloys, and renewable energy systems [Reck 2012; Sovacool 2020]. In principle, metals are infinitely recyclable. However, due to limitations in social behavior, product design, and recycling technologies, current metal recycling is often inefficient. In the category of urban mining, the recovery of critical elements from electronic waste (e-waste) is crucial for the circular economy, which can simultaneously prevent disruptions in the critical materials supply chain and also mitigate the environmental impact of waste disposal. It is estimated that over 45 million tons of e-waste are generated annually and are growing at ~9% per year [Ghosh 2015]. E-waste has become a huge environmental problem because it contains heavy metals and plastics [Ogunseitan 2009]. However, e-waste is also a valuable resource because it has high levels of valuable metals [Chauhan 2018], including base metals (such as Cu, Al, and Fe), precious metals (such as Au, Ag, and Pt), rare earth metals (Sc, Y, and the La group), and critical metals (such as Ga, In, Ta), which are essential for electronic platforms but are currently difficult to obtain due to political and economic controls.

[0008] Critical metals, including Ga, In, and Ta, are widely used in semiconductor, display, and capacitor technologies and are thus essential for modern electronics. For example, tantalum (Ta) is widely used as tantalum capacitors in mobile phones and computers [Matsuoka 2004]. Due to the limited production rate of Ta, the price of Ta has increased sharply. Therefore, the recovery of Ta from e-waste is crucial for achieving a sustainable Ta supply chain. For Ga, its production in 2012 was estimated to be ~270 tons [Salazar 2013].

[0009] Ga has traditionally been recovered from by-products of alumina and zinc production [Dutrizac 2000; Fang 1996]. The increasing demand for Ga requires the exploration of new resources and extraction methods. Ga is mainly used as a semiconductor in electronic devices in the form of gallium arsenide (GaAs), and partly gallium nitride (GaN), aluminum gallium indium phosphide (AlGaInP), aluminum gallium arsenide (AlGaAs), etc. Recycling Ga from e-waste will compensate for the increasing Ga consumption in consumer electronics.

[0010] For In, which is also a rare metal, it is mainly recovered from the by-product residues in the production processes of lead and zinc. Currently, In is mainly used to produce indium tin oxide (ITO) films that have both transparency and conductivity, and thus is a key component of transparent electrodes in displays, touchscreens, photovoltaic cells, and smart windows. With the increasing demand for personal electronic products, the consumption of In is experiencing a sharp increase. Therefore, recycling In from consumer electronic waste is crucial for a sustainable In supply chain.

[0011] The chlorination process is used in extractive metallurgy for metal separation, which is industrially used to separate titanium (Ti) from its ores [Jena 1997]. By reacting various metals or metal compounds with chlorinating agents to form metal chlorides, the differences in properties such as volatility and solubility of the metal chlorides allow for the separation of metals [Xing 2020]. Commercially, chlorination is carried out using a fluidized bed [Niu 2013], which typically operates at 900 to 1300 °C [Gleser’353 patent]. The available temperature range limits its wide application. Therefore, the chlorination process is applied to several cases, such as Ti and magnesium (Mg) [Xing 2020]. In addition, the slow heating and cooling processes inevitably reduce the efficiency of the chlorination process.

[0012] Similarly, rare earth elements (REEs) are key materials in modern electronics, clean technology, alloys, and catalysts [Cheisson 2019]. The leaching of REE minerals in concentrated aqueous acid solutions followed by two-phase solvent extraction has become the main scenario for the large-scale production of REEs [Cheisson 2019]. Although REE minerals are not rare, their separation from each other remains very difficult. There are several difficulties in mining from natural ores: (1) the production of low-value mixed rare earth concentrates, which are 60 - 70% Ce and La, both of which have near-zero value and hinder the separation of the more desirable critical REEs (including Nd, Pr, Dy, Tb, and Sc); (2) iron, silicon, and aluminum oxides impede high recovery rates and pure products; (3) the co-concentration of actinides is extremely intractable. Uranium (U) can be sold, but thorium (Th) is produced at a 3:1 ratio compared to U. The enrichment of Th and U beyond certain levels is illegal in the United States. Backmixing into tailings is an environmental burden. If a method could recover the lanthanides while leaving the actinides in the feedstock, this would be significant, but no such solution currently exists.

[0013] Therefore, if a technology could selectively recover Nd, Pr, Dy, Tb, and Sc while leaving Ce and La, as well as actinides and other impurities, this would be highly advantageous.

[0014] REE separation is generally divided into primary separation (separation of REEs from other impurity elements) and secondary separation (separation of individual REEs) [Xie 2014]. The presence of metal impurities in the REE-containing leachate affects the efficiency of subsequent separation of REEs by methods such as solvent extraction and ion exchange [Xie 2014; Judge 2020; Zhang 2021]. Therefore, it is usually necessary to remove impurities before REE separation [Judge 2020].

[0015] The compositions of ores and secondary waste materials typically vary significantly from one another depending on their sources, and thus the impurities in the leachate also vary significantly in terms of type and content [Judge 2020]. The main impurities include Al, Si, Fe, Ca, Mg, Zn, Co, Ni, Cr, Cu, etc. Many techniques, including solvent extraction, ion exchange or adsorption, and selective precipitation, have been widely used to remove impurities from the leachate [Judge 2020]. The applicable approach clearly depends on the type and content of the impurities, as well as the target application of the REEs. For example, for iron-containing solutions, acidic extractants such as di-(2-ethylhexyl) phosphoric acid (D2EHPA) can selectively extract REEs at a suitable extractant concentration and organic phase / water phase ratio [Ye 2019]. For Al impurities, a large amount can be removed by selective precipitation by adjusting the pH of the leachate [Silva 2019]. Ca and Mg impurities generally do not co-extract with REEs, with an upper tolerance limit of 1500 ppm [Li 2019]. Thus, Ca and Mg are not particularly problematic in REE extraction. For Cu and Zn, they generally do not co-extract with REEs during cationic solvent extraction or ion exchange processes [Li 2019; Lou 2019].

[0016] For secondary separation, ion exchange or solvent extraction is the most suitable commercial technique for REE separation [Gupta 1992]. Because the chemical properties of rare earth ions in aqueous solutions are similar, the separation degree in the solvent extraction process is often poor, and the separation factor per stage is usually only 2 to 10 [Adachi 1999]. Therefore, up to hundreds of stages of mixers and settlers can be assembled to achieve the necessary separation and purity of REEs [Xie 2014]. In addition, the ion exchange process is not suitable for industrial production because significant separation requires a very long time [Uda 2000]. Summary of the Invention

[0017] The present invention relates to metal recovery and separation systems and methods, and more particularly to electrothermal chlorination and electrothermal carbothermal chlorination methods and systems for selective metal extraction (such as extracting critical metals from waste material streams).

[0018] Generally, in one embodiment, the present invention features a method for selectively recovering at least one metal from two or more metals in a material. The method includes mixing the material with an oxidant to form a mixture. The material includes two or more metals. The method further includes subjecting the mixture to a flash Joule heating process. The method further includes separating and selectively recovering at least one or more first metals from the two or more metals in the material and at least one or more second metals from the two or more metals in the material.

[0019] Embodiments of the present invention may include one or more of the following features:

[0020] The oxidizing agent may be selected from chlorine reagents, fluorine reagents, bromine reagents, iodine reagents, and combinations thereof.

[0021] The oxidizing agent may include a chlorine reagent.

[0022] The chlorine reagent may be selected from halide salts, ammonium chloride, and combinations thereof.

[0023] The chlorine reagent may be sodium chloride.

[0024] The chlorine reagent may be Cl2.

[0025] The flash Joule heating process may include an electrothermal chlorination process.

[0026] The flash Joule heating process may be carried out at a temperature of 630 °C to 830 °C.

[0027] The first one or more metals may include In.

[0028] The flash heating process may be carried out at a temperature greater than 1240 °C.

[0029] The first one or more metals may include metals selected from Sn and Mn. The second one or more metals may include metals selected from Au and Cr.

[0030] The step of subjecting the mixture to a flash Joule heating process may include subjecting the mixture to a first flash Joule heating process at a first temperature to form a first product. The step of subjecting the mixture to a flash Joule heating process may include subjecting the first product to a first evaporation process to form a first residual product. The step of subjecting the mixture to a flash Joule heating process may include subjecting the first residual product to a second flash Joule heating process at a second temperature.

[0031] The second temperature may be greater than the first temperature.

[0032] The first flash Joule heating process may include a first electrothermal chlorination process. The second flash Joule heating process may include a second electrothermal chlorination process.

[0033] The first flash Joule heating process may be carried out at a temperature of 630 °C to 830 °C. The second flash Joule heating process may be carried out at a temperature higher than 1240 °C.

[0034] The first evaporation process may form an evaporation phase.

[0035] The evaporation phase may include a compound containing In.

[0036] The first residual product may include a compound containing a metal selected from Sn, Mn, Au, and Cr.

[0037] The second flash Joule heating process may form a second product.

[0038] A second evaporation process may be performed on the second product to form a second residual product.

[0039] The second residual product may include a compound containing a metal selected from Au and Cr.

[0040] The second evaporation process may form a second evaporation phase.

[0041] The second evaporation phase may include a compound containing a metal selected from Sn and Mn.

[0042] The step of performing a flash Joule heating process on the mixture may include a second flash Joule heating process to form a second residual product. The step of performing a flash Joule heating process on the mixture may include performing a second evaporation process on the second product to form a second residual product. The step of performing a flash Joule heating process on the mixture may include performing a third flash Joule heating process on the second residual product at a third temperature.

[0043] The second temperature may be greater than the first temperature. The third temperature may be greater than the second temperature.

[0044] The material may be waste.

[0045] The waste may be post-consumer electronic waste.

[0046] The waste may be post-industrial waste.

[0047] The post-industrial waste may be selected from fly ash, bauxite residue, ore, mining tailings, and dredged mud.

[0048] The e-waste may include indium tin oxide (ITO).

[0049] The waste may be electrode waste.

[0050] The electrode waste may include a compound selected from In2O3, SnO2, Au, MnO, Cr2O3, and combinations thereof.

[0051] The mixture may further include a reducing agent.

[0052] The reducing agent may be selected from a carbon source, a metal(0) source, H2, and combinations thereof.

[0053] The reducing agent may include a metal(0) source.

[0054] The metal(0) source may include a tin(0) source.

[0055] The reducing agent may include H2.

[0056] The reducing agent may include H2 in argon or nitrogen (N2).

[0057] The reducing agent may contain 1% to 5% by volume of H2 in argon or nitrogen (N2).

[0058] The reducing agent may include a carbon source.

[0059] The flash Joule heating process may include an electrothermal carbothermal chlorination process.

[0060] The flash Joule heating process may form a first product. A first evaporation process may be performed on the first product to form a first residual product. The method may further include mixing a reducing agent with the first residual product to form a second mixture. The method may further include performing a second flash Joule heating process on the second mixture.

[0061] Before the step of performing the second flash Joule heating process, the method may treat the first residual product. The treatment may be selected from aqueous treatment, aqueous acid treatment, and aqueous base treatment.

[0062] Treatment of the first residual product may increase the purity of one or more metals recovered from the first residual product.

[0063] The reducing agent may be selected from a carbon source, a metal(0) source, H2, and combinations thereof.

[0064] The reducing agent may include a metal(0) source.

[0065] The metal(0) source may include a tin(0) source.

[0066] The reducing agent may include H2.

[0067] The reducing agent may include H2 in argon or nitrogen (N2).

[0068] The reducing agent may be 1% to 5% by volume of H2 in argon or nitrogen (N2).

[0069] The reducing agent may include a carbon source.

[0070] The flash Joule heating process on the mixture may include an electrothermal chlorination process. The second flash Joule heating process on the second mixture may include an electrothermal carbothermal chlorination process.

[0071] The first evaporation process may form a first evaporation phase.

[0072] The first evaporation phase may include a compound containing a metal selected from Fe, Ni, Mn, Cu, and combinations thereof.

[0073] The first residue may include a compound containing a metal selected from Si, Ta, and combinations thereof.

[0074] The second flash Joule heating process may form a second product.

[0075] A second evaporation process may be performed on the second product to form a second residue.

[0076] The second residue may include a compound containing Ta.

[0077] The second evaporation process may form a second evaporation phase.

[0078] The second evaporation phase may include a compound containing Si.

[0079] The material may be waste.

[0080] The waste may be post-consumer electronic waste.

[0081] The waste may be post-industrial waste.

[0082] The post-industrial waste may be selected from fly ash, bauxite residue, ore, mining tailings, and dredged mud.

[0083] The waste may include Ta.

[0084] The waste may be capacitor waste.

[0085] The capacitor waste may include compounds selected from Fe2O3, NiO, MnO, CuO, SiO2, Ta2O5, and combinations thereof.

[0086] The method may selectively recover at least one of the two or more metals from the material with a selectivity of at least 70 wt% purity of the at least one metal.

[0087] The selectivity may be at least 90 wt%.

[0088] The selectivity may be at least 95 wt%.

[0089] The selectivity may be at least 97 wt%.

[0090] The selectivity may be at least 99 wt%.

[0091] The selectivity may be at least 99.999 wt%.

[0092] Typically, in another embodiment, the invention features a system for selectively recovering at least one metal from two or more metals. The system includes a source of a mixture of a material and an oxidizing agent. The material includes two or more metals. The system further includes a cell operably connected to the source such that the mixture can flow into the cell and be maintained under compression. The system further includes an electrode operably connected to the pressure cell. The system further includes a flash power source for applying a voltage across the mixture to effect a flash Joule heating process on the mixture. The system is configured and operable to perform any of the above methods to separate and selectively recover at least one or more first metals from two or more metals of the material from at least one or more second metals of the two or more metals of the material.

[0093] Embodiments of the invention may include one or more of the following features:

[0094] The source of the mixture may include the material, the oxidizing agent, and a reducing agent.

[0095] The system may include a second source containing a reducing agent.

[0096] BRIEF DESCRIPTION OF THE DRAWINGS

[0097] Figure 1A-1H Shows the thermodynamics and apparatus of the electrothermal chlorination method. Figure 1A Shows the critical reaction temperatures (T 临界 ) for chlorination and carbothermal chlorination of various metal oxides. Figure 1B Shows a schematic of the electrothermal chlorination process, where metal chlorides or metal oxychlorides evaporate and deposit on a quartz tube. Figure 1C Shows the current curve at 60 V, a resistance of ~1 Ω, and a pulse 1 duty cycle of 10%. Figure 1C The inset of is an enlarged current curve. Figure 1D Is a photograph of the carbon paper heater before (top) and during (bottom) electrical heating. Figure 1E Shows the temperature curve of the carbon paper heater at different voltage inputs. Figure 1F Shows the maximum temperature and heating / cooling rate of the carbon paper heater at different voltage inputs. Figure 1G Shows the simulated average temperature curve of the sample and gas. Figure 1G The inset of shows the simulated cross-sectional temperature distribution at t = 0.6 s and 4 s. Figure 1H Shows the correlation of the sample and gas temperature vs. the carbon paper heater temperature (T 加热器 ).

[0098] Figure 2 It is a schematic diagram of an electrothermal chlorination and carbothermal chlorination system.

[0099] Figure 3A-3B It shows the power supply system, Figure 3A It shows the electrical diagram of the system, Figure 3B It shows a photo of the power supply system.

[0100] Figure 4A-4B It shows the simulated geometry and boundary conditions. Figure 4A It shows the 3D framework of the simulation configuration. Figure 4B It shows the cross-section of the simulation.

[0101] Figure 5 It shows the simulated temperature distributions at different times from 0.1 s to 4 s.

[0102] Figure 6 It shows the simulated temperature distributions at t = 4 s at different carbon heater temperatures (T 加热器 ).

[0103] Figure 7A-7I It shows the selective recovery of In from waste containing ITO. Figure 7A It shows the calculated ΔG vs. temperature for the chlorination of In2O3 and SnO2. Figure 7B It shows the maximum temperature (T max ) of the carbon paper heater vs. voltage input with a duty cycle of 5%. Figure 7C It is a photo of the ITO raw material (bottom), volatiles (middle), and residue (top). Figure 7D It shows the Raman spectra of the ITO raw material, InCl3 volatile product, and SnO2 residue. Figure 7E It shows the XRD patterns of the ITO raw material (PDF#01 - 089 - 4597), InCl3 volatile product (PDF#01 - 0170), and SnO2 residue (PDF#00 - 021 - 1250). Figure 7F It shows the purity and yield of the product vs. voltage input. Figure 7G It shows the main metal composition in the TCE waste. Figure 7H It shows the ΔG vs. temperature for the chlorination reactions of the main components in the TCE waste, where the TCE waste includes In2O3, MnO, SnO2, Au, and Cr2O3. The dashed line indicates ΔG = 0 kJ·mol -1 . Figure 7I It shows the recovery yield and purity of In from the TCE waste. Figure 7F , Figure 7G and Figure 7I The error bars in represent the standard deviation, where N = 3.

[0104] Figure 8 Shows the temperature curves of the carbon paper heater under different voltage inputs.

[0105] Figure 9A-9B Shows the chlorination of In2O3 through the ETC process. Figure 9A Is a photo of the In2O3 raw material (bottom) placed on the carbon paper heater and the InCl3 volatiles deposited on the quartz tube. Figure 9B Is the Raman spectra of the In2O3 raw material, commercial InCl3, and the obtained InCl3 volatiles.

[0106] Figure 10 Shows the scheme for separating In from TCF waste.

[0107] Figure 11A-11B Shows the separation of In from TCF waste through the ETC process. Figure 11A Shows the elemental compositions of the raw material and volatiles under different voltage inputs. Figure 11B Shows the elemental compositions of the raw material and residues under different voltage inputs.

[0108] Figure 12A-12I Shows the selective recovery of Ta from Ta capacitor waste. Figure 12A Shows the main metals present in Ta capacitor waste. Figure 12B Shows ΔG vs. temperature for the chlorination reactions of the main metals in Ta capacitor waste, which includes Ta2O5, SiO2, CuO, Fe2O3, NiO, and MnO. Figure 12C Shows ΔG vs. temperature for the carbothermal chlorination of Ta2O5 and SiO2. Figure 12D Shows the kinetics of the carbothermal chlorination of Ta2O5 and SiO2. The slope of the fitting curve according to the Arrhenius equation is the activation energy of the reaction, where the activation energy is SiO2 = 53.6 kJ mol -1 and Ta2O5 = 31.6 kJ mol -1 . Figure 12E Shows the EDS spectra of the first-step volatiles (bottom) and the second-step volatiles (top). Figure 12E The inset is a photo of the volatiles condensed on the quartz tube; the lower inset is for step 1 chlorination and the upper inset is for step 2 carbothermal chlorination. Figure 12F Shows the percentage of metal content in the Ta capacitor raw material, step 1 volatiles and residues, and step 2 volatiles and residues. Figure 12G Shows the product purity and yield under different electrothermal chlorination and carbothermal chlorination conditions. The first row represents the first-step ETC parameters and the second row represents the second-step ETCC parameters. Figure 12HShows the XRD patterns of as-deposited volatiles and calcined volatiles. The reference PDF of Ta2O5 (01-082-9637) is shown. Figure 12I Shows the Raman spectra of Ta2O5 raw material, as-deposited volatiles, and calcined volatiles. Figure 12A and 12G The error bars in represent the standard deviation, where N = 3.

[0109] Figure 13A-13B Shows the chlorination of Ta2O5 via the ETC process. Figure 13A Shows the photos of Ta2O5 raw material (bottom) and the sample after chlorination. Figure 13B Shows the XRD pattern of the residue after the ETC process.

[0110] Figure 14A-14C Shows the carbothermal chlorination of Ta2O5 via the ETCC process. Figure 14A Shows the photos of the mixture of Ta2O5 and C (bottom) and the volatiles deposited on the quartz tube after the ETCC process. Figure 14B Shows the XRD patterns of the as-deposited volatiles on the quartz tube and the volatiles after calcination at 800 °C. Figure 14C Shows the Raman spectra of Ta2O5 raw material, as-deposited volatiles, and calcined volatiles.

[0111] Figure 15A-15C Shows the carbothermal chlorination of the mixture of Ta2O5 and SiO2 via the ETCC process. Figure 15A Shows the photos of the mixture of Ta2O5, SiO2, and C (bottom) and the volatiles deposited on the quartz tube (top) after the ETCC process. Figure 15B Shows the XRD patterns of the as-deposited volatiles on the quartz tube and the volatiles after calcination. Figure 15C Shows the Raman spectra of Ta2O5 raw material, as-deposited volatiles, and the calcined sample.

[0112] Figure 16 Shows the scheme for separating Ta from Ta capacitor waste via two-step ETC and ETCC processes. Note that a short rinsing step with water before step 2 can remove a small amount of residual metal chlorides from the desired Ta2O3 and SiO2.

[0113] Figure 17A-17E Shows the characterization of the volatiles and residue in the first-step ETC. Figure 17A Shows the XRD patterns of the TCW raw material, residue, and volatiles. Figure 17B Shows the EDS spectrum of the residue. Figure 17C Shows the EDS spectrum of the volatiles. Figure 17DShows the SEM images and EDS elemental maps of the residue. Figure 17E Shows the SEM images and EDS elemental maps of the volatile matter.

[0114] Figure 18A-18C Shows the characterization of the residue of the second-step ETCC. Figure 18A Shows the XRD pattern of the residue. Figure 18B Shows the EDS spectrum of the residue. Figure 18C Shows the SEM images and EDS elemental maps of the residue.

[0115] Figure 19A-19F Shows the scaling rules and magnification demonstrations. Figure 19A Shows the photos of the carbon paper heaters at the same voltage input of 100V, with sizes of 2×6 cm 2 , 3×9 cm 2 and 4×12 cm 2 (W / L)(S are 2, 3, and 4 respectively). Figure 19B Shows the carbon paper heater temperature map vs. voltage input and carbon heater length. The aspect ratio of the carbon paper heater is fixed at 3. Figure 19C Shows the simulated average temperature curves of samples with different carbon heater scales. The carbon heater temperature is fixed at 1200 °C. Figure 19C The inset shows the simulated temperature distributions for S = 2 and 4. Figure 19D Shows the variation of T with the carbon paper heater scale 99 with time and sample mass. Figure 19E Shows the photos of the original capacitor waste (top) placed on the carbon heater with a size of 3×9 cm 2 and the volatile matter (bottom) deposited on the quartz tube after the second-step ETCC reaction. Figure 19F Shows the purity and yield of the Ta product recovered from the enlarged batch.

[0116] Figure 20 Shows the simulation of the temperature distributions at different scales at t = 4 s for 2D magnification. The carbon paper heater temperature is fixed at 1200 °C.

[0117] Figure 21 Shows the simulation of the temperature distributions of the enlarged sample (S = 4) at different times from 1 s to 60 s. The carbon heater temperature is fixed at 1200 °C.

[0118] Figure 22A-22C Shows the 3D magnification of the ETC process. Figure 22A Shows the simulated temperature distributions at different scales. Figure 22B Shows the simulated average temperature curves of samples with different carbon heater scales. The carbon paper heater temperature is fixed at 1200 °C. Figure 22CShows T varying with the size of the carbon paper heater 99 and the normalized sample mass over time.

[0119] Figure 23A-23B Shows the magnification of the ETC process for separating In from ITO. Figure 23A Shows a photograph of the ITO feedstock (top) and the volatiles deposited on the quartz tube (bottom). Figure 23B Shows the purity and yield of the In product in different batches.

[0120] Figure 24A-24F Shows the magnification of the two-step process for recovering Ta from TCW. Figure 24A Shows a photograph of the TCW feedstock (top) and the volatiles deposited on the quartz tube obtained during the first-step chlorination process (bottom). Figure 24B Shows a photograph of the mixture of the first-step residue and C (top) and the volatiles deposited on the quartz tube obtained during the second-step carbothermal chlorination process (bottom). Figure 24C Shows the XRD patterns of the second-step deposited volatiles and the volatiles after calcination. Figure 24D Shows the Raman spectra of the second-step deposited volatiles and the volatiles after calcination. Figure 24E Shows the EDS spectrum of the second-step deposited volatiles. Figure 24F Shows the SEM image and EDS elemental mapping of the volatiles. Detailed Description of the Invention

[0121] The present invention relates to metal recovery and separation systems and methods, and more particularly to electrothermal chlorination and electrothermal carbothermal chlorination methods and systems for selective metal extraction, such as extracting critical metals from waste material streams.

[0122] As used herein, "selective" or "selectivity" means that the method / system recovers and separates a metal (or group of metals) into a component of the metal (or group of metals) having a purity of at least 70 wt%. In some embodiments, the selectivity can be at least 90 wt% purity, in further embodiments, the selectivity can be at least 95 wt% purity, in further embodiments, the selectivity can be at least 97 wt% purity, in further embodiments, the selectivity can be at least 99 wt% purity, and in still further embodiments, the selectivity can be at least 99.999% purity.

[0123] Electrothermal chlorination and carbothermal chlorination

[0124] Embodiments of the present invention include innovative electrothermal chlorination and carbothermal chlorination methods and systems for the selective extraction of critical metals from waste material streams. Such methods and systems utilize programmable pulsed current inputs to provide precise control of temperature and reaction duration during chlorination. This level of control can be used to achieve thermodynamic and kinetic selectivity for the desired metals. These methods and systems have broad applicability, including, for example, selectively recovering indium from waste materials containing indium tin oxide and recovering tantalum from spent tantalum capacitors. Additionally, these methods and systems can be scaled. Due to their compact reactor design and rapid processing capabilities, the methods offer a variety of applications in metal recycling, refining, and process intensification.

[0125] Thermodynamics and apparatus

[0126] A thermodynamic analysis of the chlorination of 34 metal oxides using chlorine (Cl2) as the chlorinating agent was performed, covering representative metals in the s, p, and d blocks. The thermodynamic analysis was carried out using the software HSC Chemistry 10. The direct chlorination of metal oxides is considered to follow the following reaction:

[0127] MO x + xCl2 = MCl 2x + x / 2O2 (1)

[0128] The carbothermal chlorination of metal oxides is considered to follow the following reaction:

[0129] MO x + xCl2 + xC = MCl 2x + xCO (2)

[0130] Calculations are carried out at a standard pressure of 1 atm. 34 metal oxides and their corresponding chlorides, covering representative metals in the s, p, and d blocks, including Li2O / LiCl, Na2O / NaCl, K2O / KCl, BeO / BeCl2, MgO / MgCl2, CaO / CaCl2, B2O3 / BCl3, Al2O3 / AlCl3, Ga2O3 / GaCl3, In2O3 / InCl3, SiO2 / SiCl4, GeO2 / GeCl4, SnO2 / SnCl4, PbO / PbCl2, TiO2 / TiCl4, ZrO2 / ZrCl4, HfO2 / HfCl4, V2O5 / VCl5, Nb2O5 / NbCl5, Ta2O5 / TaCl5, Cr2O3 / CrCl3, MoO3 / MoCl5, WO3 / WCl6, MnO / MnCl2, Fe2O3 / FeCl3, CoO / CoCl2, NiO / NiCl2, PdO / PdCl2, PtO2 / PtCl2, CuO / CuCl2, Ag2O / AgCl, ZnO / ZnCl2, CdO / CdCl2, and HgO / HgCl2. First, the thermodynamic favorability of direct chlorination reactions is considered; if it is unfavorable, carbothermal chlorination is considered, in which carbon reduces the metal oxide to a lower-valent metal oxide or metal(0) that can react with chlorine to form the desired metal chloride. Alternatively, as a substitute or supplement to chlorine, other oxidants such as fluorine, bromine, or iodine can be used. Additionally, or as a substitute or supplement to carbon, other reductants such as metal(0) (e.g., tin(0)) and H2 (including H2 in argon or nitrogen (N2), such as 1% to 5% H2 by volume in argon or nitrogen (N2)) can be used. A mixture with less than 5% H2 in argon is below the explosion limit of H2 and is thus safer.

[0131] These metals can be classified into several categories, such as Figure 1A as shown in, showing the critical reaction temperatures (T 临界 ) for the chlorination and carbothermal chlorination of various metal oxides:

[0132] (i) Direct chlorination is favorable at any temperature > 0 °C: Li, Na, K, Ca, Pb, Co, Pt, Ag, Zn, Cd, and Hg.

[0133] (ii) Direct chlorination is favorable only at temperatures above a specific value (lower limit): Mg (1870 °C), Al (2220 °C), Ga (875 °C), In (630 °C), Ge (1010 °C), Sn (1250 °C), Mn (830 °C), Fe (1230 °C), and Ni (1680 °C).

[0134] (iii) Direct chlorination is favorable only at temperatures below a specific value (upper limit): Mg (460 °C), Ni (870 °C), Pd (1930 °C), Cu (1370 °C).

[0135] (iv) Direct chlorination is unfavorable at any temperature: Be, B, Si, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W.

[0136] (v) Carbothermal chlorination is favorable at any temperature > 0 °C: Be, B, Si, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W.

[0137] The chlorination reaction equation (1) and the carbothermal chlorination reaction equation (2) were calculated, and these reactions can be divided into four groups:

[0138] (i) The chlorination reaction is favorable at any temperature.

[0139] (ii) The chlorination reaction is favorable with a lower temperature threshold.

[0140] (iii) The chlorination reaction is favorable with an upper temperature threshold.

[0141] (iv) The chlorination reactions are unfavorable at any temperature, but their carbothermal chlorination reactions are favorable, where carbon acts as a reducing agent and the reduced metal reacts with chlorine.

[0142] This analysis determines the limits of conventional chlorination reactions. First, the temperatures required for chlorination reactions can range from 400 to 2400 °C, so many metal oxides cannot be chlorinated using conventional heating methods that typically operate at 1500 °C. Second, the temperature difference between metal oxides in the reactions is narrow, requiring precise temperature control to ensure selectivity based on reactivity differences. Third, for chlorination reactions with the same reactivity trend, they cannot be separated based on thermodynamics alone.

[0143] To address these obstacles, direct electric heating can be used for electrothermal chlorination (ETC) or electrothermal carbothermal chlorination (ETCC). See Figure 1B-1H ; Figure 2 . Different from conventional furnaces that heat samples by thermal convection, metal oxide precursors are loaded on a carbon paper heater and heated by thermal conduction. As Figure 3A-3B shown, the electrical system is used to deliver a programmable DC input to the carbon paper heater ( Figure 1C ), which enables it to heat up and cool down quickly ( Figure 1D ). The temperature of the carbon paper heater can be precisely regulated by changing the voltage input, achieving a wide temperature range from 400 to 2500 °C. Figure 1E(With curves 101 - 108 for 140V, 120V, 100V, 80V, 60V, 50V, 40V, and 30V respectively).

[0144] A diagram of an electrical system for generating pulsed direct current is shown in Figure 3A-3B . A capacitor bank with a total capacitance of 0.624F can achieve a voltage of up to 500V. The capacitors are charged by a DC power supply. A variable frequency drive (VFD) is used to generate a pulsed voltage with a frequency (f) of 0 to 1000Hz (and typically f = 1000Hz is used in the experiments described herein). The duty cycle (or on - state period) is tunable (and typically a duty cycle of 5% or 10% is used in the experiments described herein). The current curves are recorded using a multifunctional I / O (NIUSB - 6009) controlled by LabView. Carbon paper is used as a heater, which is fixed on a graphite block and connected to the electrical system through two graphite electrodes. For carbon paper with dimensions of 1cm × 3cm, the resistance is ∼0.7Ω, which is suitable for Joule heating.

[0145] The ETC process exhibits some unprecedented characteristics, addressing the limitations of traditional furnace - based chlorination processes. First, the high temperature of up to 2500°C enables almost all metal oxide chlorination reactions ( Figure 1A ), greatly broadening the applicability of the chlorination process. Second, the precise temperature controllability obtained by adjusting the voltage input of the electrothermal process ( Figure 1F , with curves 111 - 113 for T max , heating, and cooling respectively) enables the separation of metals with a narrow reaction window. Third, the ultra - fast heating (up to ∼4500°C s -1 ) and cooling (∼500°C s -1 ) rates ( Figure 1F ) result in kinetic selectivity based on differences in reaction rates and activation energies in reactions with similar thermodynamics.

[0146] In the electrothermal chlorination configuration, a metal oxide precursor and Cl2 gas are heated by a carbon paper heater. Simulations are performed to evaluate the details of the sample and gas heating processes. The main purpose of this simulation is to evaluate how the sample and gas temperatures are related to the carbon paper heater temperature. Based on the finite element method (FEM), numerical simulations are performed using the software COMSOL Multiphysics 5.5. Heat transfer at the solid - liquid interface in the heat transfer module is used for time - dependent studies. The geometric configuration, material parameters, and boundary conditions are shown in Figure 4A-4B and Tables I - II.

[0147] Table I

[0148] Geometric parameters of the simulation

[0149] Component Shape Dimension Quartz tube Tube Length: 5*S cm; radius: 1.2*S cm; thickness: 0.1 cm Chlorine Cylinder Length: 5*S cm; radius: (1.2*S - 0.1) cm Carbon paper Membrane Length: 3*S cm; width: 1*S cm; thickness: 0.019 cm Sample Cube Length: (3*S - 1) cm; width: (1*S - 0.2) cm; thickness: 0.21*S cm

[0150] Note: S is the scale factor, representing the size of the simulation, where S = 1, 2, 3, 4 were used in this study.

[0151] Table II

[0152] Material parameters

[0153]

[0154] Note: The temperature-dependent functions are built into the material library of COMSOL.

[0155] The geometry of all components is similar to the real experiment. Based on the experimental measurements during the chlorination reaction, the temperature of the quartz tube wall was set to 320 °C. The inlet gas temperature was set to room temperature (20 °C), and the pressure was set to 1 atm. The flow rate of Cl2 was estimated to be 10 sccm. The experiment measured the maximum temperature of the carbon paper heater at voltage inputs of 60, 80, 100, 120, and 140 V ( Figure 1E-1F ). These values were used as the input for the carbon paper heater temperature, and time-dependent heat transfer (heatertransfer) was performed for the simulation to obtain the temperature distribution. The simulation was carried out at four scales with scale factors (S) of 1, 2, 3, and 4. S = 1 represents the most commonly used experimental conditions, and larger S represents scaled-up experiments.

[0156] The temperature of the carbon paper heater was fixed at T 加热器 = 1141 °C, which is the experimental measurement value at a voltage input of U = 60 V. Figure 1F . The sample temperature was defined as the average temperature of the sample; considering that only the gas close to the sample reacts, the gas temperature was defined as the average temperature of the gas within the diameter of the carbon paper width. It was found that the sample and gas temperatures reached a plateau (∼1141 °C) at ∼4 s ( Figure 1G (with curves 121 - 122 for the sample and gas respectively, and the dashed line 123 represents the carbon paper heater temperature, which was fixed at 1141 °C); Figure 5 ), demonstrating the rapid sample and gas heating ability of the electrothermal process. This is different from the traditional indirect heating process, which may take several hours to reach thermal equilibrium. In addition, by changing T 加热器 , the sample temperature and gas temperature closely followed the T 加热器 pattern ( Figure 1H (with curves 131 - 132 for the sample and gas respectively); Figure 6 ), providing precise controllability of the reaction temperature (it was found that the sample and gas temperatures closely followed the pattern of the carbon paper heater temperature).

[0157] In a typical small-scale experiment, a 1×3 cm 2 carbon paper size is used for a sample mass of 100 mg. The sample is loaded on a carbon paper heater, which is connected to a capacitor bank. The sample is placed in a sealed quartz tube. After purging the system three times, for small-scale samples, Cl2 is introduced at a flow rate of ~20 sccm, and for large-scale samples, Cl2 is introduced at a flow rate of ~40 sccm. Pulse current input brings the carbon paper heater to the desired temperature. As Figure 1G shown, the sample and gas temperatures rapidly follow the heater's pattern. Volatiles are deposited on the quartz tube. Chloride products are usually deliquescent, so the sample sealed in the quartz tube is transferred to a glove box, and then the sample is collected. The detailed experimental conditions of the experiment are shown in Table III.

[0158] Table III

[0159] Reaction conditions for chlorination and carbothermal chlorination

[0160]

[0161] Note: TCE, transparent conductive film; TCW, tantalum capacitor waste.

[0162] Recovery of In from waste containing ITO

[0163] Next, the recovery of critical metals in real-world waste is tested, such as the recovery of In from waste containing ITO and the recovery of Ta from Ta capacitor waste.

[0164] In is a critical metal that has no minerals of its own and is thus usually produced as a by-product of other metallurgical processes, especially zinc (Zn) and copper (Cu) [Frenzel 2017]. In is considered a technology-critical element and is mainly used as indium tin oxide (ITO), which serves as the main waste for In recycling [Virolainen 2011]. ITO consists of 90% In and 10% tin (Sn). The chlorination reaction using Cl2 as a chlorinating agent for In2O3 and SnO2 was analyzed thermodynamically. Figure 7A (With curves 701 - 702 for the chlorination of In2O3 and SnO2 respectively, and the dashed line 703 represents ΔG = 0 kJ mol -1 ). The temperature window of 630 to 1240 °C enables the conversion of In2O3 to InCl3 while SnO2 remains unreacted.

[0165] InCl3 can then be evaporated as a volatile phase, thus separating it from SnO2 based on their volatility differences. The above temperature window corresponds to a voltage input of 90 to 110 V. Figure 7B(The curve 704 with the bottom dotted line 705 and the top dotted line 706 represent T = 630 °C and 1240 °C respectively); Figure 8 (Curves 801 - 805 for 80V, 90V, 1000V, 110V, and 120V respectively).

[0166] First, by controlling the voltage input at 100V, the feasibility of converting In2O3 to InCl3 through the ETC process was demonstrated. Figure 9A-9B . Subsequently, ITO was used as the precursor. After the ETC process, volatile condensates were obtained on the quartz tube, and the residues remained on the carbon paper heater. Figure 7C . X-ray diffraction patterns and Raman spectra indicated that the volatiles were InCl3, while the residues were SnO2. Figure 7D-7E .

[0167] The effect of voltage input on the purity and yield of the product was investigated. Figure 7F (Bars 711 - 712 for purity and yield respectively). As the voltage increased, the yield was improved due to more complete reactions; however, due to the simultaneous chlorination of SnO2, an excessive voltage input of 120V led to a significant decrease in purity. Figure 7B . The optimization results showed a product purity of 99% and a yield of 91% for In products. Figure 7F .

[0168] Next, the In recovery from real-world waste - transparent conductive films (TCFs) was studied. After removing the plastic substrate by calcination, a metal mixture mainly composed of Au, In, Sn, Mn, etc. was obtained. Total quantification showed that In accounted for ~30 wt% of the metal content. Figure 7G . Considering five metals with a content > 1 wt%, including Au, In, Sn, Mn, and Cr. A computational thermodynamic analysis of the chlorination reactions of Au, In2O3, SnO2, MnO, and Cr2O3 was performed. Figure 7H .

[0169] The temperature window was 630 °C to 830 °C, within which only In2O3 could be chlorinated and separated from other metals by evaporation. Figure 10 . The effect of voltage on the In recycling performance was investigated because voltage is important for In recovery. Figure 7I ; Figure 11A-11B . If the voltage was relatively low, at 100V, it led to a temperature that was not low enough where Au could also be chlorinated, resulting in a lower purity of the In product. If the voltage was too high, at 110V, SnO2 and MnO were also chlorinated and mixed with the desired In product. With an appropriate voltage of 105V, an overall performance of 95% purity and 92% yield of In was obtained. Figure 7IThis confirms the crucial role of precise temperature control in the selective recovery of metals, which are the advantages and benefits of the electrothermal process. All of these are provided without the use of water or acid, so there are no tailings or secondary liquid waste.

[0170] Recovery of Ta from waste containing Ta

[0171] Ta is another technologically critical metal, which is mainly used in electronic devices as capacitors or superalloys [Agrawal 2021]. The annual global production of Ta is ~2000 tons, and 42% of Ta consumption is in the manufacture of Ta capacitors [Angerer 2013]. Discarded Ta capacitors are widely present in small electrical appliances, and they contain up to 45 wt% Ta content, so they are high-grade Ta resources [Niu 2017]. Here, tantalum capacitor waste (TCW) is calcined in air to remove the plastic and resin layers. Subsequently, a fine yellow powder composed of various metal oxides including tantalum pentoxide (Ta2O5) is obtained. After digestion and subsequent ICP-MS measurement, the total quantification of metals in the powder is carried out. Figure 12A The mass ratio of Ta in the waste is ~37.8 wt%, and the other main metal components (>1 wt%) include Si, Mn, Cu, Fe, and Ni.

[0172] First, the thermodynamics of the chlorination reaction of these metal oxides with Cl2 is calculated and analyzed. Figure 12B (where the dashed line represents ΔG = 0 kJ mol -1 ). These metal oxides are divided into two categories. The first category is CuO, Fe2O3, NiO, and MnO, whose chlorination reactions are thermodynamically favorable at specific temperature thresholds (the upper limit for CuO, and the lower limits for Fe2O3, NiO, and MnO). The second category of metals includes Ta2O5 and SiO2, whose chlorination reactions are thermodynamically unfavorable.

[0173] The chlorination of Ta2O5 with Cl2 is carried out experimentally, and it does not react ( Figure 13A-13B ), which is highly consistent with the theoretical analysis. Therefore, for Ta2O5 and SiO2, the thermodynamics of their carbothermal chlorination reactions are analyzed ( Figure 12C , where the dashed line represents ΔG = 0 kJmol -1 ), which shows that both are favorable within the studied temperature range. However, there is a large difference in the Gibbs free energy change (ΔG) between SiO2 and Ta2O5, indicating that there may be kinetic selectivity in their separation.

[0174] Experimentally, Ta2O5 is mixed with carbon (C) and the ETCC reaction is carried out. Figure 14A-14CTa2O5 was successfully converted into volatile products, which were expected to be tantalum oxychloride and could be collected by an evaporation-condensation process.

[0175] Similarly, SiO2 could be converted into volatile products by the ETCC process. The kinetics of the carbothermal chlorination reaction were measured and the rate constants were obtained. For the following reactions:

[0176] SiO2(s) + 2Cl2(g) + 2C(s) = SiCl4(g) + 2CO(g) (3)

[0177] Ta2O5(s) + 5Cl2(g) + 5C(s) = 2TaCl5(g) + 5CO(g) (4)

[0178] By definition, the reaction rate (v) is defined as:

[0179]

[0180] Experimentally, SiO2 (or Ta2O5) was mixed with C according to the stoichiometric ratio and the carbothermal chlorination reaction was carried out. The weight loss was measured at different reaction times (Δt), from which the corresponding Δn(SiO2) (or Δn(Ta2O5)) was obtained. Subsequently, the reaction rate was calculated.

[0181] During the experiment, Cl2 was supplied in excess and SiO2, Ta2O5, and C were solids, so the above carbothermal chlorination reaction could be considered a zero-order reaction. Therefore, the reaction rate constant (k) could be calculated by the following equation:

[0182] k(SiO2)=v(SiO2) (7)

[0183] k(Ta2O5)=v(Ta2O5) (8)

[0184] Assuming that k is independent of temperature, according to the Arrhenius equation, the rate constant as a function of the reaction temperature (T) is given by the following equation:

[0185]

[0186] where A is the pre-exponential factor, E a is the activation energy, and R is the gas constant. Equation (9) can be modified as:

[0187]

[0188] By plotting lnk~1 / T ( Figure 12D , for the curves 1201 - 1202 of Ta2O5 and SiO2 respectively), the activation energy of the carbothermal chlorination reaction was calculated to be Ea (SiO2) = 53.6 kJ mol -1 and E a (Ta2O5) = 31.6 kJ mol -1 。

[0189] The activation energy difference enables the kinetic control of the separation of Ta2O5 and SiO2. To further confirm this, SiO2 and Ta2O5 are mixed in the presence of C and the ETCC reaction is carried out. Figure 15A 。By precisely controlling the voltage at 100 V and the corresponding temperature at ~1050 °C, Ta2O5 is selectively chlorinated and separated from the unreacted residual SiO2 by evaporation. Figure 15B-15C 。

[0190] By utilizing thermodynamic and kinetic selectivity, a two-step process can be used to separate Ta from capacitor waste. Figure 16 。In a typical experiment, the first step is the ETC reaction, where CuO, Fe2O3, NiO, and MnO are converted to their chlorides and evaporated as volatile phases by controlling the electrothermal temperature at ~1230 to 1380 °C. By energy-dispersive spectroscopy (EDS, Figure 12E , bottom; Figure 17A-17E ) and ICP-MS ( Figure 12F , step 1 volatiles) characterization of the volatile phases shows that Cu, Fe, Mn, and Ni are enriched in the volatile components. In contrast, Ta and Si are non-reactive and remain in the residue phase, as confirmed by EDS ( Figure 17B and 17D ) and ICP-MS ( Figure 12F , step 1 residue). (Optional water rinsing can be carried out at this point to remove a small amount of metal chlorides, but it is not necessary)

[0191] Next, in the second-step ETCC reaction, the residue from the first step is mixed with C (usually in the form of carbon black, CB) and reacted. By controlling the electrothermal temperature at ~1050 °C, as demonstrated by EDS ( Figure 12E , top) and ICP-MS ( Figure 12F , step 2 volatiles), most of the Ta2O5 is chlorinated and evaporated and collected as a volatile phase. In contrast, most of the SiO2 remains in the residue phase ( Figure 12F , step 2 residue; Figure 18A-18C ). After optimizing the voltage input and duration of the two-step process, the selective recovery of Ta from capacitor waste is achieved with a purity of 96% and a yield of 88%. Figure 12G(For each of the three different voltages or durations, respectively for bars 1211 - 1212 of purity and yield). The as - obtained Ta product is an amorphous mixture of tantalum oxychloride, which can be easily converted to pure Ta2O5 by gentle calcination in air. Figure 12H-12I 。

[0192] Magnification ability

[0193] Evaluate the scale - up potential of the electrothermal chlorination process. Precise temperature control can play a crucial role in the selective recovery of metals. Therefore, first consider the parameters for determining temperature. Use Figure 3B the system shown in Figure 3A (which has an Figure 3B RC circuit) for analysis. In Joule heating, the heater resistance has an important role, and there is an optimized resistance for the carbon paper heater to provide a preferred energy conversion efficiency from electricity to heat. This value is determined by the power supply system, and in the

[0194] system, the optimized value is determined to be 0.5 ohm to 2 ohms.

[0195]

[0196] where ρ is the resistivity of the carbon heater, and L, W, S, D are the length, width, cross - sectional area, and thickness of the carbon heater, respectively.

[0197] If the D and aspect ratio (L / W) of the carbon paper heater are maintained, the resistance (R) of the carbon paper heater will remain the same. For example, when using a carbon paper heater size of 1×3 cm 2 as used in small - scale experiments, this is represented as the scaling factor (S)=1. The resistance (R1) of this carbon paper heater is ∼0.7 Ω. Scale up this process to S = 2, 3, 4. Figure 19A , for carbon paper heaters 1901 - 1903 respectively (the sizes of carbon paper heaters 1901 - 1903 are 2×6 cm 2 , 3×9 cm 2 and 4×12 cm 2 (W / L)). As expected, according to experimental measurements, the resistances of these samples are the same. The temperatures of carbon paper heaters of different scales were measured at different voltage inputs. Figure 19B . This temperature curve provides guidance on how to adjust the voltage input when scaling up.

[0198] As further simulated in the study, when the sample size is enlarged, the sample temperature is regulated by the heater temperature. The heat conduction from the carbon paper heater to the sample is determined by Fourier's law. If it is assumed that the temperature of the sample is uniform during heating and the sample temperature at time t is T 样品 , then the temperature gradient (θ) is defined as:

[0199] θ = T 样品 - T 加热器 (12)

[0200] where T 加热器 is the temperature of the carbon paper heater. Subsequently, the temperature gradient at the initial time (θ0) is:

[0201] θ0 = T 样品,0 - T 加热器 (13)

[0202] where T 样品,0 is the initial temperature of the sample.

[0203] According to the instantaneous heat transfer, the t required for the sample to reach T 样品 can be calculated by the following formula:

[0204]

[0205] where ρ s is the density of the sample, V s is the volume of the sample, c s is the specific heat capacity of the sample, h is the heat transfer coefficient, and A s is the heat transfer area between the carbon paper heater and the sample.

[0206] Considering V s = D s × A s , where D s is the thickness of the sample, the above equation (14) can be modified to:

[0207]

[0208] T 99 is defined as the time required to heat the sample to 99% of the carbon paper heater temperature (T 样品 = 0.99T 加热器 ), which is obtained

[0209]

[0210] For amplification, two cases were considered. The first is to amplify the sample in two dimensions (length and width, denoted as 2D amplification), and the second is to amplify the sample in three dimensions (length, width, and thickness, denoted as 3D amplification).

[0211] First, consider two-dimensional (2D) amplification, which means that the sample length and width are proportionally enlarged according to the size of the carbon paper heater, while the sample thickness remains the same. The temperature curves of the sample at different scales follow a common pattern ( Figure 19C (each of S = 1, 2, 3, 4 in the overlapping graph 1911); Figure 20 ), regardless of the scale.

[0212] T 99 , which again represents the time required to heat the sample temperature to 99% of the carbon paper heater temperature, can be used to quantitatively describe the dependence of the heating cycle on the sample scale. Although the sample mass increases exponentially ( Figure 19D , graph 1921), the time of T 99 is independent of the sample scale factor ( Figure 19D , graph 1922), showing excellent scalability of the electric heating.

[0213] Subsequently, three-dimensional (3D) amplification was analyzed, which means that all three dimensions of the sample are proportionally enlarged according to the size of the carbon paper heater. In this case, as the sample scale increases, the time of T 99 increases synchronously with the sample mass. Figure 21 and 22A -22C. Figure 22B Shows the simulated average temperature curves of the sample, with graphs 2201 - 2204 for different carbon heater scales S = 1, 2, 3, 4 respectively. Figure 22C Shows the time of T 99 and the normalized sample mass varying with the carbon heater scale in graphs 2211 - 2212. However, for the amplified sample, the temperature reaches a plateau within ~1 minute ( Figure 21 ), still superior to indirect heating that may take hours to reach thermal equilibrium. Basically, it was found that for 3D amplification, the temperature equilibrium for larger S requires a longer heating duration, which is determined by the rate of heat transfer. The above results indicate that electric heating is especially good for 2D amplification.

[0214] In addition, electrothermal chlorination was scaled up to the gram scale. A 2-inch (5.08 cm) tube reactor was constructed and a 9 cm × 3 cm (L / W) carbon paper heater was used. The larger reactor was used for ETC of In from ITO at a 1 g scale. Figure 23A . The whole process is the same as the small-scale reaction. After optimization, a comparable 98% purity and 91% yield were obtained (Figure 23B (For three different batches, for the bars 2301 - 2302 of purity and yield respectively), it is almost the same as in the small reactor. Figure 19F (Bars 1931 - 1932 for purity and yield respectively).

[0215] A processing time of 10 minutes is required, corresponding to a productivity of 144 g / day. Subsequently, the scale of the two - step ETC and ETCC processes was increased for the selective recovery of Ta from Ta capacitor waste, also at a 1 g scale ( Figure 19E and 24A -24F), achieving a purity of 95.1%, but the yield decreased due to losses downstream of the tube. Further optimization was carried out by modifying the product collection system. In all cases, unreacted Cl2 can be recycled and reused via typical industrial methods.

[0216] Further utilization

[0217] ETC and ETCC can be used for the selective separation and recovery of technologically critical metals from e - waste. Most methods extract many metals only once and rely on classical wet - chemical methods that are intensive in water, acid, or base, resulting in tailings and toxic secondary waste streams. In embodiments of the present invention, the use of all water and acid is reduced. Compared with conventional chlorination processes, the introduction of electricity realizes advantages including ultra - high temperature, precise temperature control, and kinetic controllability, thereby expanding the scope of chlorination metallurgy. Embodiments of the present invention can selectively recover In from waste containing ITO using ETC, and recover Ta from capacitor waste using ETC in combination with ETCC. Such methods and systems are scalable, revealing the utility of the method for larger quantities. Leveraging thermodynamic and kinetic selectivity in a compact reactor design, ETC and ETCC further presage the possibility of anhydrous and acid - free metal recycling, refining, and stable pricing, while minimizing the need for continued metal mining.

[0218] In addition, the present invention provides metal recovery and separation systems and methods, particularly by combining metal recovery and separation by chlorination methods in a flash Joule heating system and method.

[0219] Although embodiments of the present invention have been shown and described, those skilled in the art can modify them without departing from the spirit and teachings of the present invention. The embodiments and the examples provided herein are merely exemplary and are not intended to be restrictive. Many variations and modifications of the present invention disclosed herein are possible and are within the scope of the present invention. The scope of protection is not limited by the specification set forth above, but only by the appended claims, the scope of which includes all equivalents of the subject matter of the claims.

[0220] The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference in their entireties to the extent that they provide exemplary, procedural, or other details that supplement those set forth herein.

[0221] Quantities and other numerical data may be presented herein in a range format. It is to be understood that such range formats are used merely for convenience and brevity and should be interpreted flexibly to include not only the recited values as the limits of the range, but also all individual values or sub-ranges subsumed within that range as if each individual value and sub-range were explicitly recited. For example, a numerical range of about 1 to about 4.5 should be interpreted to include not only the recited limits of 1 to 4.5, but also individual numbers such as 2, 3, 4 and sub-ranges such as 1 to 3, 2 to 4, etc. The same principle applies to ranges describing only one value, such as “less than about 4.5,” which should be interpreted to include all of the above values and ranges. Moreover, such interpretation shall apply regardless of the width of the range or the nature of the characteristic being described.

[0222] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter of 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 now described.

[0223] In accordance with long-standing patent law practice, the term “a” as used in this application (including the claims) means “one or more.”

[0224] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and the like used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, the numerical parameters set forth in the specification and the appended claims are approximations that may vary depending upon the desired properties sought to be obtained by the subject matter of this disclosure, unless indicated to the contrary.

[0225] As used herein, the terms “about” and “substantially” when referring to a quantity of a value or of mass, weight, time, volume, concentration, or percentage mean encompassing variations of in some embodiments ±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 that such variations are appropriate to practice the disclosed methods.

[0226] As used herein, the terms “substantially vertical” and “substantially parallel” mean variations that in some embodiments are within ±10° of the vertical and parallel directions, respectively, in some embodiments are within ±5° of the vertical and parallel directions, respectively, in some embodiments are within ±1° of the vertical and parallel directions, respectively, and in some embodiments are within ±0.5° of the vertical and parallel directions, respectively.

[0227] As used herein, the term “and / or” when used to list entities means that the entities are present singly or in combination. Thus, for example, the phrase “A, B, C, and / or D” includes A, B, C, and D individually, but also includes any and all combinations and sub-combinations of A, B, C, and D.

[0228] References

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Claims

1. A method for selectively recovering at least one metal from two or more metals from a material, wherein the method comprises: (a) mixing the material with an oxidizing agent to form a mixture, wherein the material comprises two or more metals; (b) subjecting the mixture to a flash Joule heating process; and (c) separating and selectively recovering at least one or more first metals from the two or more metals of the material and at least one or more second metals from the two or more metals of the material.

2. The method of claim 1, wherein the oxidizing agent is selected from chlorine reagents, fluorine reagents, bromine reagents, iodine reagents, and combinations thereof.

3. The method of claim 1, wherein the oxidizing agent comprises a chlorine reagent.

4. The method of claim 3, wherein the chlorine reagent is selected from halide salts, ammonium chloride, and combinations thereof.

5. The method of claim 3, wherein the chlorine reagent is sodium chloride.

6. The method of claim 3, wherein the chlorine reagent is Cl2.

7. The method of any one of claims 3-6, wherein the flash Joule heating process comprises an electrothermal chlorination process.

8. The method of claim 7, wherein the flash Joule heating process is carried out at a temperature between 630 °C and 830 °C.

9. The method of claim 8, wherein the first one or more metals comprise In.

10. The method of claim 7, wherein the flash heating process is carried out at a temperature greater than 1240 °C.

11. The method of claim 10, wherein: (a) the first one or more metals comprise metals selected from Sn and Mn, and (b) the second one or more metals comprise metals selected from Au and Cr.

12. The method of any one of claims 1-6, wherein the step of subjecting the mixture to a flash Joule heating process comprises: (a) subjecting the mixture to a first flash Joule heating process at a first temperature to form a first product; (b) subjecting the first product to a first evaporation process to form a first residual product; and (b) subjecting the first residual product to a second flash Joule heating process at a second temperature.

13. The method of claim 12, wherein the second temperature is greater than the first temperature.

14. The method of any one of claims 12-13, wherein: (a) the first flash Joule heating process comprises a first electrothermal chlorination process; and (b) the second flash Joule heating process comprises a second electrothermal chlorination process.

15. The method of claim 14, wherein: (a) the first flash Joule heating process is carried out at a temperature between 630 °C and 830 °C; and (b) the second flash Joule heating process is carried out at a temperature higher than 1240 °C.

16. The method of any one of claims 12-15, wherein the first evaporation process forms an evaporation phase.

17. The method of claim 16, wherein the evaporation phase comprises a compound containing In.

18. The method of any one of claims 12-17, wherein the first residual product comprises a compound containing metals selected from Sn, Mn, Au, and Cr.

19. The method of claim 18, wherein the second flash Joule heating process forms a second product.

20. The method of claim 19, wherein a second evaporation process is performed on the second product to form a second residual product.

21. The method of claim 20, wherein the second residual product comprises a compound containing a metal selected from Au and Cr.

22. The method of any one of claims 20 - 21, wherein the second evaporation process forms a second evaporation phase.

23. The method of claim 22, wherein the second evaporation phase comprises a compound containing a metal selected from Sn and Mn.

24. The method of any one of claims 12 - 23, wherein the step of subjecting the mixture to a flash Joule heating process comprises: (a) The second flash Joule heating process forms a second residual product; (b) A second evaporation process is performed on the second product to form a second residual product; and (c) A third flash Joule heating process is performed on the second residual product at a third temperature.

25. The method of claim 24, wherein: (a) The second temperature is greater than the first temperature, and (b) The third temperature is greater than the second temperature.

26. The method of any one of claims 1 - 25, wherein the material is a waste.

27. The method of claim 26, wherein the waste is post - consumer electronic waste.

28. The method of claim 26, wherein the waste is post - industrial waste.

29. The method of claim 28, wherein the post - industrial waste is selected from fly ash, bauxite residue, ore, mining tailings, and dredged mud.

30. The method of claim 26, wherein the waste contains indium tin oxide (ITO).

31. The method of claim 26, wherein the waste is electrode waste.

32. The method of claim 31, wherein the electrode waste comprises a compound selected from In2O3, SnO2, Au, MnO, Cr2O3, and combinations thereof.

33. The method of any one of claims 1 - 6, wherein the mixture further comprises a reducing agent.

34. The method of claim 33, wherein the reducing agent is selected from a carbon source, a metal(0) source, H2, and combinations thereof.

35. The method of claim 34, wherein the reducing agent comprises a metal(0) source.

36. The method of claim 35, wherein the metal(0) source comprises a tin(0) source.

37. The method of claim 34, wherein the reducing agent comprises H2.

38. The method of claim 37, wherein the reducing agent comprises H2 in argon or nitrogen (N2).

39. The method of claim 38, wherein the reducing agent comprises H2 in argon or nitrogen (N2) in a volume range between 1% and 5%.

40. The method of claim 34, wherein the reducing agent comprises a carbon source.

41. The method of claim 40, wherein the flash Joule heating process comprises an electrothermal carbothermal chlorination process.

42. The method of any one of claims 1 - 6, wherein: (a) The flash Joule heating process forms a first product; (b) A first evaporation process is performed on the first product to form a first residual product; (c) The method further includes mixing a reducing agent with the first residue to form a second mixture; and (d) The method further includes subjecting the second mixture to a second flash Joule heating process.

43. The method of claim 42, wherein: (a) Before the step of subjecting to the second flash Joule heating process, the first residue is treated, and (b) The treatment is selected from aqueous treatment, aqueous acid treatment, and aqueous base treatment.

44. The method of claim 43, wherein the treatment of the first residue improves the purity of one or more metals recovered from the first residue.

45. The method of any one of claims 42 - 44, wherein the reducing agent is selected from carbon sources, metal(0) sources, H2, and combinations thereof.

46. The method of claim 45, wherein the reducing agent comprises a metal(0) source.

47. The method of claim 46, wherein the metal(0) source comprises a tin(0) source.

48. The method of claim 45, wherein the reducing agent comprises H2.

49. The method of claim 48, wherein the reducing agent comprises H2 in argon or nitrogen (N2).

50. The method of claim 49, wherein the reducing agent comprises H2 in argon or nitrogen (N2) in a volume between 1% and 5%.

51. The method of claim 45, wherein the reducing agent comprises a carbon source.

52. The method of claim 51, wherein: (a) The flash Joule heating process on the mixture includes an electrothermal chlorination process; and (b) The second flash Joule heating process on the second mixture includes an electrothermal carbothermal chlorination process.

53. The method of claim 52, wherein the first evaporation process forms a first evaporation phase.

54. The method of claim 53, wherein the first evaporation phase includes a compound containing a metal selected from Fe, Ni, Mn, Cu, and combinations thereof.

55. The method of any one of claims 52 - 54, wherein the first residue includes a compound containing a metal selected from Si, Ta, and combinations thereof.

56. The method of any one of claims 52 - 55, wherein the second flash Joule heating process forms a second product.

57. The method of claim 56, wherein the second product is subjected to a second evaporation process to form a second residue.

58. The method of claim 57, wherein the second residue includes a compound containing Ta.

59. The method of any one of claims 57 - 58, wherein the second evaporation process forms a second evaporation phase.

60. The method of claim 59, wherein the second evaporation phase includes a compound containing Si.

61. The method of any one of claims 33 - 60, wherein the material is a waste.

62. The method of claim 61, wherein the waste is post - consumer electronic waste.

63. The method of claim 61, wherein the waste is post - industrial waste.

64. The method of claim 63, wherein the post - industrial waste is selected from fly ash, bauxite residue, ore, mining tailings, and dredging sludge.

65. The method of claim 61, wherein the waste contains Ta.

66. The method of claim 61, wherein the waste is capacitor waste.

67. The method of claim 66, wherein the capacitor waste comprises compounds selected from Fe2O3, NiO, MnO, CuO, SiO2, Ta2O5, and combinations thereof.

68. The method of any one of claims 1-67, wherein the method selectively recovers at least one of the two or more metals from the material with a selectivity of at least 70 wt% purity of the at least one metal.

69. The method of claim 68, wherein the selectivity is at least 90 wt%.

70. The method of claim 68, wherein the selectivity is at least 95 wt%.

71. The method of claim 68, wherein the selectivity is at least 97 wt%.

72. The method of claim 68, wherein the selectivity is at least 99 wt%.

73. The method of claim 68, wherein the selectivity is at least 99.999 wt%.

74. A system for selectively recovering at least one of two or more metals, wherein the system comprises: (a) A source containing a mixture of a material and an oxidant, wherein the material contains two or more metals; (b) A unit operably connected to the source such that the mixture can flow into the unit and be maintained under compression; (c) An electrode operably connected to the pressure unit; and (d) A flash power source for applying a voltage across the mixture to subject the mixture to a flash Joule heating process, wherein the system is configured and operable to perform the method of any one of claims 1-73 to separate and selectively recover at least one or more first metals of the two or more metals of the material from at least one or more second metals of the two or more metals of the material.

75. The system of claim 74, wherein the source of the mixture contains the material, the oxidant, and a reducing agent.

76. The system of claim 74, wherein the system includes a second source containing a reducing agent.

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