Methods of recovering metals

Abstract

Methods and apparatuses for recovering metals are disclosed herein. Examples of the methods include immersing a metal compound in a leaching solution comprising a leaching aid to form a slurry; and flowing the slurry through a cavitation field to dissolve at least a portion of the metal compounds.

Description

METHODS OF RECOVERING METALS

[0001] This PCT application claims priority from U.S. Provisional Patent Application No.63 / 563,121 filed March 8, 2024, all of which is incorporated herein by reference in its entirety for all purposes. FIELD

[0002] The present invention is in the field of liquid reactors and in particular the recovery of metals from solids by leaching. BACKGROUND

[0003] A smooth and rapid green transition to net-zero requires a reduction in the use of fossil fuels as energy sources. One of the biggest barriers to net zero is a cost effective and scalable storage of renewable energy to maintain a continuous and reliable supply of energy. Lithium-ion batteries offer the current best-in-practice method for storage. However, the high costs associated with mining these elements may act to hamper or slow further adoption.

[0004] Lithium-ion batteries are used by millions of people globally in their daily lives. Battery cathodes typically are comprised of a transition metal such as cobalt, nickel, and manganese (NMC batteries), and power smartphones and many household appliances and vehicles. Despite the high environmental and economic costs associated with mining these diminishing resources, only 3 - 5 % of lithium-ion batteries are currently recycled.

[0005] Li-ion cathodes have been recycled using high-temperature processes (pyrometallurgy process) or strong inorganic acid solutions to leach the metals (hydrometallurgy process). The hydrometallurgy process may achieve a high recovery rate and purity of the metals, however, the use of these acids is environmentally hazardous, with high risks of soil and water contamination, and may result in atmospheric emissions of nitrogen oxides and corrosive gases and have not been commercially adopted to any extent. Cathode leaching is typically performed using strong inorganic acids, such as sulfuric or hydrochloric acid, with a reducing agent added to facilitate the dissolution of the metallic ions in the acidic solution. The useof these acids is environmentally hazardous, with high risks of soil and water contamination and results in atmospheric emissions of nitrogen oxides and corrosive gases as well as the production of secondary products that are hazardous or have no economic value (e.g., sodium sulfate).

[0006] Conventional recycling techniques typically involve crushing the battery followed by separating the lithium and other metals present in the cathode. Recovery of these metals requires a complex series of processes that include either leaching using chemical solvents to retrieve the lithium, cobalt, and other metals or separation of the copper and magnesium with high temperatures.

[0007] Currently, the cathode leaching step is a bottleneck in the hydrometallurgical recovery of spent LIBs and requires expensive and hazardous inorganic solvents. Recently, Golmohammadzadeh et al., Waste Management 64 (2017) 244–254, reported the recovery of lithium and cobalt from a cathode material employing weak acids such as acetic acid and malic acid at elevated temperatures and in the presence of a reductant (e.g., hydrogen peroxide) using mechanical stirring in a three necked glass reactor immersed in an ultrasonic bath. Unfortunately, the leaching times to realize 80% recovery of the Co and Li are an hour or more even at elevated temperatures.

[0008] Therefore, there is a need in the art to address one or more of these deficiencies.

[0009] This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present disclosure. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present disclosure. SUMMARY

[0010] One objective of the present disclosure is to realize a commercially practicable recovery of transition metals and lithium from compounds (e.g. oxides and phosphates) having one or more transition metals.

[0011] It has been surprisingly discovered that transition, aluminum, and alkali metals may be rapidly leached (dissolved) from metal compounds (e.g., oxides and phosphates) in a leaching solution by flowing a slurry comprised of the metal compounds and leaching solution through one or more transient cavitation fields and in particular collapse (implosion) of the cavitation bubbles. It is believed without being limiting that the leaching is accelerated by the particles being exposed to high energy smaller bubbles implosion in the cavitation field directly, which may be facilitated by forming turbulent / eddy flow at the formation of the cavitation bubbles using, for example, one or more deflectors or flow restrictions in a flow through reactor. Such restriction or deflection may be realized by use of an ultrasonic probe having varying diameters along the axis of a flow tube reactor.

[0012] Depending on the microstructure of the metal compounds, such as those typically displayed by cathode particles it has been discovered that cavitation fields having an average bubble size similar in size (e.g., no larger than 5X, 3X, 2X or 1.5 X) to the metal compounds average particle size are particularly useful. This is believed, without being limiting, to be due to a sufficient amount of cavitation bubbles being of a smaller size that form jets that are able to penetrate the porosity of the secondary particles and effectively cause the comminution of the secondary particles resulting in acceleration of dissolution of primary particles (metals) into the acid solution. The methods may be performed without heating other than rises from ambient (i.e., 20 ℃ to 30 ℃^ to below the boiling point of the acid solution. The methods are desirably performed in a flow through reactor that has a cavitation generating device and a fluid deflection device that causes turbulent flow or eddies within the reactor resulting in increase particle exposure time to the cavitation field within the flowing liquid and particularly at the inception of the cavitation.

[0013] An illustration is a process comprising, immersing a metal compound in a leaching solution comprising a leaching aid to form a slurry; and flowing the slurry through a cavitation field to dissolve at least a portion of the metal compounds. Desirably, the slurry flows through a series of cavitation fields, in which each cavitation field may have the same or similar average bubble size or may have differing average bubble sizes (e.g., the probe vibration frequency of two or more ultrasonic probes may vary ranging for example from 15 kHz to 100kHz).

[0014] According to an aspect of the present disclosure there is provided, which may be used alone or in combination with any other aspects described herein, a method comprising: immersing a metal compound in a leaching solution comprising a leaching aid to form a slurry; and flowing the slurry through a cavitation field to dissolve at least a portion of the metal compounds.

[0015] In an aspect of the disclosure, the leaching solution comprises water.

[0016] In an aspect of the disclosure, the method further comprises adding additional acid during the method.

[0017] In an aspect of the disclosure, the leaching aid comprises a weak acid.

[0018] In an aspect of the disclosure, the acid is a carboxylic acid or a peroxyl acid of the carboxylic acid.

[0019] In an aspect of the disclosure, the cavitation field is provided.

[0020] In an aspect of the disclosure, the method comprises adding an oxidizing agent to the leaching solution.

[0021] In an aspect of the disclosure, the oxidizing agent is hydrogen peroxide.

[0022] In an aspect of the disclosure, from about 0.5% to about 10% vol% oxidizing agent is added to the leaching solution.

[0023] In an aspect of the disclosure, the metal compounds have an average particle size and the cavitation field has an average cavitation bubble size and the average cavitation bubble size / average metal compounds particle size is at most 2.

[0024] In an aspect of the disclosure, the slurry is at a temperature below the leaching solution’s boiling point.

[0025] In an aspect of the disclosure, the solid metal oxide is comprised of lithium and at least one other metal.

[0026] In an aspect of the disclosure, the other metal is comprised of one or more of Al and a transition metal.

[0027] In an aspect of the disclosure, the transition metal is comprised of one or more of Co, Mn and Ni.

[0028] In an aspect of the disclosure, the cavitation field is generated by an ultrasonic probe at least partially immersed in the slurry.

[0029] In an aspect of the disclosure, the ultrasonic probe is disposed within a tubular reactor having a first and second end, an inlet and outlet positioned to flow the slurry through tubular reactor and through the cavitation field generated by the ultrasonic probe.

[0030] In an aspect of the disclosure, the ultrasonic probe’s length is axially oriented within the tubular reactor’s length.

[0031] In an aspect of the disclosure, the ultrasonic probe has a diameter that varies along the length of the ultrasonic probe that causes cavitation fields at differing points along the ultrasonic probe’s length.

[0032] In an aspect of the disclosure, the tubular reactor comprises one or more deflection devices that cause the slurry when flowed through the tubular reactor to be deflected into the cavitation field.

[0033] In an aspect of the disclosure, each of the one or more deflection devices are independently selected from: protrusions, baffles, and deflections.

[0034] In an aspect of the disclosure, the slurry has a solids loading in excess of the solids’ solubility limit in the leaching solution.

[0035] In an aspect of the disclosure, there are at least two or more ultrasonic probes.

[0036] In an aspect of the disclosure, the two or more probes are vibrated in or out of phase.

[0037] In an aspect of the disclosure, the two or more probes have varying diameters along their length, with the diameters of each probe varying asynchronously, synchronously or combination thereof along their lengths.

[0038] In an aspect of the disclosure, wherein the metal compound is comprised of secondary particles having an average particle size of 2 micrometers to 100 micrometers, the secondary particles being comprised of agglomerated primary particles having an average size of at most 2 micrometers.

[0039] In an aspect of the disclosure, the slurry has a solids loading of the metal compound of 0.1% to 20% by weight.

[0040] In an aspect of the disclosure, wherein flowing of the slurry is through at least two cavitation fields sequentially.

[0041] In an aspect of the disclosure, the flowing of the slurry is through two or more serially connected tubular reactors.

[0042] In an aspect of the disclosure, the method further comprises separating any undissolved metal oxide.

[0043] In an aspect of the disclosure, the average cavitation bubble size / average metal compounds particle size is at most 1.5.

[0044] In an aspect of the disclosure, the metal compound particles are comprised of open porosity having an average pore size and the average cavitation bubble size is no more than 10 times greater than the average pore size of the metal compound particles.

[0045] According to another aspect of the present disclosure there is provided, which may be used alone or in combination with any other aspects described herein, a process for leaching solid metal oxides, the process comprising: exposing the solid metal oxides to a leaching solution comprising an organic acid; and applying ultrasonic waves to the leaching solution at a cavitation frequency to dissolve the solid metal oxides into the leaching solution as metal ions.

[0046] According to another aspect of the present disclosure there is provided, which may be used alone or in combination with any other aspects described herein, a process for leaching solid metal oxides, the process comprising: exposing the solid metal oxides to a leaching solution comprising an organic acid; and applying ultrasonic waves to the leaching solution at a cavitation frequency in a cavitation field to dissolve the solid metal oxides into the leaching solution as metal ions.

[0047] In an aspect of the disclosure, the organic acid is acetic acid.

[0048] In an aspect of the disclosure, the cavitation frequency is about 20-30 kHz

[0049] In an aspect of the disclosure, the leaching solution comprises an oxidizing agent.

[0050] In an aspect of the disclosure, the oxidizing agent is hydrogen peroxide.

[0051] In an aspect of the disclosure, the leaching solution comprises about 0 – about 8 vol% oxidizing agent.

[0052] In an aspect of the disclosure, applying ultrasonic waves occurs for a period of up to about 15 minutes.

[0053] In an aspect of the disclosure, the period is up to about 8 minutes.

[0054] In an aspect of the disclosure, the solid metal oxide comprises one or more of: lithium oxide, cobalt oxide, nickel oxide, manganese oxide, Lithium Cobalt Oxide, Lithium Manganese Oxide, or Lithium Nickel Oxide, as well as phosphates such as Lithium Iron Phosphate.

[0055] In an aspect of the disclosure, applying ultrasonic waves comprises vibrating a sonoprobe at least partially submerged in the leaching solution.

[0056] In an aspect of the disclosure, the sonoprobe is connected to a piezoelectric actuator.

[0057] In an aspect of the disclosure, the process further comprises: exposing the undissolved solid metal oxides and metal phosphate to fresh leaching solution comprising the organic acid; and applying ultrasonic waves to the fresh leaching solution at the cavitation frequency.

[0058] In an aspect of the disclosure, the process further comprises, after applying ultrasonic waves, separating an aqueous solution comprising dissolved metal oxide salts from undissolved solid metal oxides.

[0059] In an aspect of the disclosure, separating occurs via centrifugation.

[0060] According to another aspect of the present disclosure there is provided, which may be used alone or in combination with any other aspects described herein, a reactor for leaching cathodic material into a leaching solution, the device comprising: a reactor wall having a first end and an opposing second end, the reactor wall defining an inner reactor cavity; an inlet, located at or near the first end, configured to receive a mixture of solid cathodic material and the aqueous solution into the inner reactor cavity; an outlet, located at or near the second end, configured to at least partially evacuate the mixture from the inner reactor cavity; and a sonoprobe disposed at least partially within the inner reactor cavity, the sonoprobe configured to apply ultrasonic waves to the leaching solution at a cavitation frequency to dissolve the solid metal oxides into the leaching solution as metal oxide salts.

[0061] In an aspect of the disclosure, the inlet defines an inlet axis, the outlet defines an outlet axis, the sonoprobe defines a sonoprobe axis, and the inlet axis and / or the outlet axis are perpendicular to the sonoprobe axis.

[0062] In an aspect of the disclosure, a distance between an outer surface of the sonoprobe and an inner service of the reactor wall is between about 1.05 to about 3.

[0063] According to another aspect of the present disclosure there is provided, which may be used alone or in combination with any other aspects described herein, a process for leaching metal compounds, such as solid metal oxides, the process comprising: exposing the metal compounds to a leaching solution comprising an organic acid; and applying ultrasonic waves to the leaching solution at a cavitation frequency to dissolve the metal compounds into the leaching solution as metal ions.

[0064] According to another aspect of the present disclosure there is provided, which may be used alone or in combination with any other aspects described herein, a process for leaching metal compounds, such as solid metal oxides, the process comprising: exposing the metal compounds to a leaching solution comprising an organic acid; and applying ultrasonic waves to the leaching solution at a cavitation frequency in a cavitation field to dissolve the metal compounds into the leaching solution as metal ions.

[0065] In an aspect of the disclosure, the organic acid is acetic acid.

[0066] In an aspect of the disclosure, the cavitation frequency is about 20-30 kHz

[0067] In an aspect of the disclosure, the leaching solution comprises an oxidizing agent.

[0068] In an aspect of the disclosure, the oxidizing agent is hydrogen peroxide.

[0069] In an aspect of the disclosure, the leaching solution comprises about 0 – about 8 vol% oxidizing agent.

[0070] In an aspect of the disclosure, applying ultrasonic waves occurs for a period of up to about 15 minutes.

[0071] In an aspect of the disclosure, the period is up to about 8 minutes.

[0072] In an aspect of the disclosure, the metal compounds comprise one or more of: lithium oxide, cobalt oxide, nickel oxide, manganese oxide, Lithium Cobalt Oxide, Lithium Manganese Oxide, or Lithium Nickel Oxide, as well as phosphates such as Lithium Iron Phosphate.

[0073] In an aspect of the disclosure, applying ultrasonic waves comprises vibrating a sonoprobe at least partially submerged in the leaching solution.

[0074] In an aspect of the disclosure, the sonoprobe is connected to a piezoelectric actuator.

[0075] In an aspect of the disclosure, the process further comprises: exposing the undissolved metal compounds to fresh leaching solution comprising the organic acid; and applying ultrasonic waves to the fresh leaching solution at the cavitation frequency.

[0076] In an aspect of the disclosure, the process further comprises, after applying ultrasonic waves, separating an aqueous solution comprising dissolved metal compounds, such as metal oxide salts from undissolved metal compounds, such as solid metal oxides.

[0077] In an aspect of the disclosure, separating occurs via centrifugation.

[0078] According to another aspect of the present disclosure there is provided, which may be used alone or in combination with any other aspects described herein, a reactor for leaching cathodic material into a leaching solution, the device comprising: a reactor wall having a first end and an opposing second end, the reactor wall defining an inner reactor cavity;an inlet, located at or near the first end, configured to receive a mixture of solid cathodic material and the aqueous solution into the inner reactor cavity; an outlet, located at or near the second end, configured to at least partially evacuate the mixture from the inner reactor cavity; and a sonoprobe disposed at least partially within the inner reactor cavity, the sonoprobe configured to apply ultrasonic waves to the leaching solution at a cavitation frequency to dissolve the solid metal oxides into the leaching solution as metal oxide salts.

[0079] In an aspect of the disclosure, the inlet defines an inlet axis, the outlet defines an outlet axis, the sonoprobe defines a sonoprobe axis, and the inlet axis and / or the outlet axis are perpendicular to the sonoprobe axis.

[0080] In an aspect of the disclosure, a distance between an outer surface of the sonoprobe and an inner service of the reactor wall is between about 1.05 to about 3.

[0081] Other aspects and features of the disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] FIGURE 1 is a scanning electron micrograph (SEM) of a metal compound particles as is.

[0083] FIGURE 2 is a SEM of metal compound particles treated with transient cavitation in water without acid and reductant.

[0084] FIGURE 3 is a SEM of metal compound particles after acid treatment for 8 minutes by a method described herein.

[0085] FIGURE 4 is a graph comparing leaching efficiency of one of the methods described herein with prior art technology

[0086] FIGURE 5 is a schematic of an apparatus useful to perform one or more methods as described herein.

[0087] FIGURE 6 shows drawings of a reactor useful in performing methods as described herein.

[0088] FIGURE 7 is perspective drawing of a reactor useful in the method.

[0089] FIGURE 8 is a rendering of the modeling of the cavitation of the reactor depicted in Figures 6 and 7.

[0090] FIGURE 9 is a cross-sectional view of a reactor that may be utilized in the flow through tube reactor depicted in Figures 6-8.

[0091] FIGURE 10 are radial and perspective views of a sonic probe that may be utilized in the flow through the tube reactor of Figures 6-8.

[0092] FIGURE 11 are comparative plots of dissolved black mass. DETAILED DESCRIPTION

[0093] One or more illustrative embodiments have been described by way of example. Described herein are processes, apparatuses and methods for one or more of leaching, dissolving, and recycling metal compounds. It will be appreciated that embodiments and examples are provided for illustrative purposes intended for those skilled in the art, and are not meant to be limiting in any way. All references to embodiments, examples, aspects, formulas, solutions, and the like is intended to be illustrative and non-limiting.

[0094] It has been discovered that the reaction (e.g., dissolution) of a solid particulate in a liquid (slurry) may be surprisingly accelerated by passing the particles in the slurry through a cavitation field where the inception and collapse of the cavitation bubbles occur. It has also been surprisingly discovered that the rate of dissolution of electrode metal compounds does not scale with the power (amplitude) inputted into the slurry, with a higher rate of dissolution occurring with a combination of frequency and power inputted to the slurry volume (W / L).

[0095] The process may take place at nearly ambient temperatures and pressure, reducing the costs, risks, complexity of thermal management and energy associated with heating the battery components.

[0096] The term “reactor” refers to a reactor as described herein. Such reactors may comprise flow through a cavitation field. The terms “sonicator”, “sonotrode”, and “ultrasonic probe” are interchangeable and are used to describe devices used to cause transient cavitation induced by ultrasonic vibrations.

[0097] The term “cavitation field” refers to an area where transient cavitation is induced by a suitable means. A proper cavitation field involves the nucleation, growth, oscillation, and collapse of bubbles. The cavitation field may be generated by ultrasonic agitation.

[0098] The term “sonoprobe” refers to an inner part of the ultrasonic probe in a reactor such as described herein. The sonoprobe (e.g., ultrasonic probe) is a piece that vibrates causing the variation of the pressure field of a flowing liquid causing transient cavitation.

[0099] “Black mass” is the term used to describe the intermediate waste (e-waste) which contains valuable metallic components obtained from used batteries during mechanical treatment such as shredding, grinding, heat treatment and density separation to produce a powdered material. The black mass may be a mixture of cathode materials such as the secondary particles described herein and other components used to make a cathode such as electrolytes including a salt (e.g., LiPF6, LiBF4, LiCF3SO3) and organic solvents (e.g., 1,3 dioxane, propylene carbonate- DMF). It is typically difficult to provide a definitive composition of black mass as it may be highly dependent on the source of the battery and the procedure of mechanical disintegration. Lithium metal oxides (LiMeOx) or phosphates are typically used as cathodes covering a metal foil, such as aluminum (Al) foil, and the anode is typically composed of a copper (Cu) foil coated with an anode material such as graphite, but may be comprised of other materials, such as lithium metal or alloy thereof, lithium metal oxide (e.g., lithium titanate), and silicon, silicon alloys and oxides of silicon.

[0100] A polymeric binder, such as polyvinylidene fluoride (PVDF), may be used to bond the cathode particles together and to the foil. A PVDF binder may occuron the surfaces of black mass particles and may hinder its recycling. Generally, the LIBs from different types of cathode materials (e.g., NMCs) are treated by dry mechanical processing consisting of two stages of crushing, sieving, and magnetic separation. The commercially valuable elements found in black mass generally are transition metals such as Co, Ni, Mn, Copper and Iron as well as Al and Li. The active cathode material greatly contributes towards the economic feasibility of LIB recycling processes and is recovered to the so-called black mass in the second stage of recycling, following dismantling. The black mass may also contain graphite, organic binders, and parts of the electrodes depending on the dismantling and processing steps of the recycling process.

[0101] In one illustration, the method comprises immersing a metal compound into a leaching solution to form a slurry. The metal compound may be any metal found in black mass, for example, that is of interest to extract. Metal compounds may be one or more elements found in an electrode, such as a cathode or anode. Examples of suitable cathode materials may include phosphates, fluorophosphates, fluorosulfates, fluorosilicates, spinels, lithium-rich layered oxides, and composite layered oxides. Further examples of suitable cathode materials may include spinel structure lithium metal oxides, layered structure lithium metal oxides, lithium-rich layered structured lithium metal oxides, lithium metal silicates, lithium metal phosphates, metal fluorides, metal oxides, sulfur, metal sulfides, disordered rock salt structures, or any combination thereof. Examples of suitable anode materials may include lithium titanate, graphite, silicon component, and others.

[0102] It has been discovered that the method is particularly suitable for the dissolution of secondary particles comprised of primary particles at least partially sintered together and displaying some open porosity commonly found in battery electrode materials but may be used for primary particles as well and is useful for particles of 5mm, 2mm, 1 mm or 0.5 mm, which may be primary or secondary particles. Illustratively, the method is particularly suited to dissolution and extraction from metal compound particles. In one illustration, the average primary particle size is typically less than 2 micrometers, 1 micrometer, 0.5 micrometer to 5 or 10 nanometers. Commonly, the primary particle is substantially less than 500 nm (average less than or D90 of less than 500 nanometers equivalent spherical diameterby volume or number). Generally, the average primary particle size is at most 20 micrometers, but typically the average primary particle size is at most about 2 micrometers to 0.1 micrometer. The primary particles may agglomerate to form aggregates. Aggregates may be secondary particles, such as those arising from spray drying, which has been at least partially sintered. The porosity generally has the same size range as the primary particles with the porosity being comprised of open porosity that likewise is comprised of pores in the same range as described for the size of the primary particles.

[0103] Suitable diameters of primary particles may be in a range of 0.01-20 µm or any value therebetween (optionally rounded to the nearest 0.001), or any subrange spanning between any two of these values, such as 0.05-2 µm. For example, diameters of 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, 0.095, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.6, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.2, 1.21, 1.22, 1.23, 1.24, 1.25, 1.26, 1.27, 1.28, 1.29, 1.3, 1.31, 1.32, 1.33, 1.34, 1.35, 1.36, 1.37, 1.38, 1.39, 1.4, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, 1.5, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, 1.6, 1.61, 1.62, 1.63, 1.64, 1.65, 1.66, 1.67, 1.68, 1.69, 1.7, 1.71, 1.72, 1.73, 1.74, 1.75, 1.76, 1.77, 1.78, 1.79, 1.8, 1.81, 1.82, 1.83, 1.84, 1.85, 1.86, 1.87, 1.88, 1.89, 1.9, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, 2 µm, and others are considered.

[0104] The particle size of the secondary particles may have an average or median particle size (D50), by volume, from about 1 micrometer (μm), 2 μm, 5 μm, 10 μm or 20 μm to 150 μm, 100 μm, 75 μm or 50 μm. D50 means the particle size (equivalent spherical diameter) in the particle size distribution, where at least 50% by volume of the particles are less than that size.

[0105] Suitable diameters of secondary particles may be in a range of 0.1-200 µm or any value therebetween (optionally rounded to the nearest 0.001), or any subrange spanning between any two of these values, such as 0.05-2 µm. For example, diameters of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200 µm, and others are considered.

[0106] The particle size may be determined by any suitable method such as those known in the art including, for example, laser diffraction or image analysis of micrographs of a sufficient number of particles (~100 to ~200 particles). A representative laser diffractometer is one produced by Microtrac such as the Microtrac S3500. The porosity may be determined by any suitable method such as those known in the art including, for example, gas adsorption techniques, Archimedes method and / or mercury porosimetry.

[0107] Illustratively, the electrode material may be at least one complex oxide of lithium and a metal selected from cobalt (Co), nickel (Ni), and a combination thereof, and 65 more particularly, a compound represented by at least one Formula of LiaA1-bBbD2(wherein, 0.90≤a<l.8 and 0≤b≤0.5); LiaE1-bBbO2-cDc(wherein, 0.90≤a≤l.8, 0≤b≤0.5, 0≤c≤0.05); LiE2-bBbO4-cDc(wherein, 0≤b≤0.5, 0≤c≤0.05); LiaNi1-b-cCobBcDα (wherein, 0.90≤a≤l .8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); LiaNil-b- cCobBcO2-aF^^ (wherein, 0.90≤a≤l.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); LiaNi1-b-cCobBcO2- αFα (wherein, 0.90≤a≤l.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); LiaNi1-b-cMnbBcDα (wherein, 0.90≤a≤l.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); LiaNil-b-cMnbBcO2-αFα(wherein, 0.90≤a≤l.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); LiaNibEcGdO2 (wherein, 0.90≤a≤l.8, 0≤b≤0.9, 0≤c≤0.5, 0.00l≤d≤0.1); LiaNibCocMndGeO2 (wherein, 0.90≤a≤l .8, 0≤b≤0.9, 0≤c≤0.5,0≤d≤0.5); LiaNiGbO2 (wherein, 0.90≤a≤l.8, 0.00l≤b≤0.1.); LiaCoGbO2(wherein, 0.90≤a≤l.8, 0.00l≤b≤0.1); LiaMnGbO2 (wherein, 0.90≤a≤l.8, 0.00l≤b≤0.1); LiaMn2GbO4(wherein, 0.90≤a≤l.8, 0.00l≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O2; LiIO2; LiNiVO4; Li(3-f)J2PO4)3 (wherein 0≤f≤2); Li(3-f)Fe2(PO4)3 (wherein 0≤f≤2); and LiFePO4.

[0108] In the formulae above, A is Ni, Co, manganese (Mn), or a combination thereof; B is aluminum (Al), Ni, Co, Mn, chromium (Cr), iron (Fe), strontium (Sr), vanadium (V), or a combination thereof; D is oxygen (0), fluorine (F), sulfur (S), phosphorus (P), or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, magnesium (Mg), lanthanum (La), Cerium (Ce), Sr, V, or a combination thereof; Q is titanium (Ti), molybdenum (Mo), Mn, or a combination thereof; I is Cr, V, Fe, scandium (Sc), yttrium (Y), or a combination thereof; J is V, Cr, Mn, Co, Ni, copper (Cu), or a combination thereof.

[0109] The leaching aid may be any suitable compound for dissolving or reacting with the metal compound, for example strong or weak acid, oxidizer, or caustic compounds. It has been discovered using weak acid in subsequent separation steps may present advantages with isolation of particular metals. For example, more economically useful compounds may be recovered when precipitating a weak acid’s anion instead of a stronger acid (e.g., acetic acid v. sulfuric acid), using an alkali such as ammonia or hydroxide (e.g., sodium acetate v. sodium sulfate). In some instances, a basic compound may be used when dissolving certain compounds such as those comprised of silicon. Suitable basic compounds include any compound that realizes a pH of above 7.0, such as ammonium, alkali and alkaline earth hydroxides.

[0110] The weak acid may be any compound that is a weak acid displaying a pKa of about 1, 1.5, 2, 2.5 or 3 to 7, 6.5 or 6. For example the weak acid may have a pKa of about 4.76. It will be understood that pKa is the logarithm of the acid disassociation constant in water or mixtures of such compounds. It is also understood that in some cases where multiple carboxylic acid groups are contained in a polymer, the pKa may be difficult to ascertain, but these are contemplated herein. The weak acid may be multifunctional (i.e., 2 or more acids), but generally is comprised of a monofunctional acid. The weak acid may be saturated or unsaturated. The weak acid may be any carboxylic acid such as a natural occurring carboxylic acid. For example,the carboxylic acid may be abietic acid, alginic acid, gallic acid, azelaic acid, caffeic acid, malic acid, pyruvic acid, niacin, citric acid, biotin, abietic acid, cholic resin, pectin, alginic acid, gum rosin (a mixture of naturally occurring natural acids) or combination thereof. The fatty acid may be any fatty acid derived from any animal fat or vegetable oil and may be saturated or unsaturated. Exemplary oils include linseed, palm, coconut, palm, olive, tung, soybean, peanut, sunflower, cotton seed, rapeseed, or combination thereof. Any fatty acid derived from the aforementioned oils and fats may be used (e.g., isostearic acid). In an embodiment, the fatty acid is dimerized to form a dimer, trimer acid or higher polymeric acids. Typically, readily available dimer acids contain some small fraction of monomeric acid, trimer acid and higher polymeric acid.

[0111] The weak acid may be any carboxylic acid such as mono, dicarboxylic or higher order (e.g., tri or tetra) carboxylic acids (e.g., ascorbic acid and ethylenediaminetetraacetic acid). Illustratively, the carboxylic acid may have linear or branched alkane chains of 1, 2 or 5 to 30, 20 or 15 carbons or mixtures thereof. Examples may include formic acid, acetic acid, butyric acid, valeric acid, hexanoic acid, hexanedioic acid, heptanoic acid, heptanedioic acid, octanoic acid, octanedioic acid, nonanoic acid, nonanedioic acid, decanoic acid, decanedioic acid, 2,3- dimethylbutaneoic acid, 2,3-dimethylbutaneoic acid, 2,3-dimethylbutanedioic, 2,2- dimethylbutaneoic acid, 2,2-dimethylbutanedioic acid, 3-methylheptaneoic acid, 3- methylheptanedioic acid or mixtures thereof.

[0112] The weak acid may be a sterically hindered carboxylic acid with a short and highly branched alkyl chemical structure such as 2,2,3,5- Tetramethylhexanoic acid, 2,4-Dimethyl-2-isopropylpentanoic acid, 2,5-Dimethyl-2- ethylhexanoic acid, 2,2-Dimethyloctanoic acid, or 2,2-Diethylhexanoic acid.

[0113] The weak acid may also be a carboxyl containing: polyether, polyester, polyether-ester, polyamide, conjugated diene polymer or conjugated diene copolymer, polyurethane, polystyrene, polyolefin, silicone or combination thereof. The weak acid may also be a polysaccharide, polypeptide, protein, phosphoric acid, nitrous acid, sulfurous acid, oxalic acid, chromic acid, hydrofluoric acid, hydrogen sulfide or combination of these or any of the aforementioned.

[0114] The acid may be used neat or preferably in solution with water or water-polar solvent solution (e.g., alcohol-water solutions). The concentration of the acid in the solution may be any useful sufficient to solubilize the desired metals up to their solubility limit. Illustratively, the volume ratio of acid / water may be from 0.1, 0.5 or 1 to 3, 4, 5 or 10.

[0115] In some cases, a volume ratio of acid / water of about 0.01-20 or any value therebetween (optionally rounded to the nearest 0.01), or any subrange spanning between any two of these values, such as 1-3 may be used. For example, ratios of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, and others are considered.

[0116] The solution preferably has an oxidizer such as a peroxide, which may include those formed by the mixing of peroxide with a weak acid (described herein) or their corresponding anhydride (e.g., hydrogen peroxide and acetic acid forming peracetic acid). The concentration may be any suitable concentration such as 1% or 2% to 6%, 8% or 10% by volume.

[0117] In some cases, a solution of about 0.01-20 % by volume, or any value therebetween (optionally rounded to the nearest 0.1), or any subrange spanning between any two of these values, such as 2-6%, may be used. For example, solutions of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20% by volume, and others are considered.

[0118] The slurry is comprised of metal compound particles immersed in the leaching solution. Any useful solids loading of the metal compound particles may be used that are commercially practicable. It has been discovered that the dissolution may more rapidly occur at solids loadings of the metal compound in excess of the solubility limit of the metal compound in the particular leaching solution. Generally, the solids loading (grams solids of the metal compound per volume of leachingsolution (g / L) may be the essentially the same as the metal compound’s solubility limit (g / L) or at a ratio of solids loading (g / L) / solubility limit (g / L) of 0.1, 0.25, 0.5, 0.75 to 1.25, 1.5, 1.75, 2, 3, or 5. Illustratively, the solids loading may be from 0.1%, 1%, 2%, or 5% to any practicable such as 50%, 33%, 25% or 20% by volume or weight. Any undissolved metal compound particles may be separated and reinserted alone or with fresh metal compounds to be dissolved with fresh leaching solution (e.g., water, acid, and oxidizer).

[0119] In some cases, solid loading of about 0.1-50 % by volume or weight, or any value therebetween (optionally rounded to the nearest 0.1), or any subrange spanning between any two of these values, such as about 0.1-20% may be used. For example, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, 35, 35.5, 36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5, 40, 40.5, 41, 41.5, 42, 42.5, 43, 43.5, 44, 44.5, 45, 45.5, 46, 46.5, 47, 47.5, 48, 48.5, 49, 49.5, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100%, and others are considered.

[0120] In the method, the slurry is flowed through a cavitation at its collapse as described above. The flow preferably is one that is turbulent or comprised of eddies such that metal compound particles may be exposed to more than one flow through one cavitation field arising from the turbulent / eddies in the flowing slurry and / or a series of cavitation fields. The flowing may occur, for example, by any suitable means using any suitable method to cause flow of a liquid into the cavitation field. In one illustration, the flow may be caused by the cavitation field itself where a sufficient amount of cavitation causes flow of the slurry and the walls of the containment vessel are sufficiently close that slurry results in repeated flow through the cavitation field such as described for Examples A below. Alternatively, the flow may be provided by a stirring radial or axial impeller in conjunction with a cavitation provided by an ultrasonic probe immersed in the slurry or other cavitation device such as described herein.

[0121] Preferably, the flow comprises flowing the slurry into a flow through reactor comprised of one or more cavitation fields and one or more devices for deflecting the slurry into the cavitation field, with the sequential flowing through 2, 3, 4, 5, or 10 or more to any practicable amount of cavitation fields being preferred. Illustratively, a reactor may be comprised of a tube having a wall defining an inner diameter, a length and a first end and second end, an inlet and outlet positioned along the length of the tube for flowing a fluid through at least a portion of the tube, a cavitation generating device that generates a cavitation field within the tube, and at least one fluid deflection device for deflecting the fluid into the cavitation field. Such reactors may be referred to as “tubular reactors”.

[0122] In a particular embodiment (e.g., see Figures 6-10) for applicable illustrations, the cavitation field is provided by an ultrasonic probe and also see, for example, WO2022 / 234502, which is incorporated herein by reference. In these illustrations, the fluid deflection is provided at least in part by the ultrasonic probe’s varying diameter along its axial length within the reactor tube, where the slurry flow is deflected by the constrictions between the ultrasonic probe and the reactor wall causing the flow to deflect into one or more of the modeled cavitation fields (see Figures 6 and 10). The ultrasonic probe is designed to produce a cavitation field with nano scale bubbles formation and collapse.

[0123] In other illustrations, more than one ultrasonic probe having a varying diameter may be axially inserted into the volume of the flow reactor. Such plurality of ultrasonic probes may be vibrated in or out of phase. The plurality of ultrasonic probes may have varying lengths, with the diameters of each probe varying asynchronously, synchronously (largest diameters aligning or being out of phase 180 degrees with the probes being intermeshed being one example) or combination thereof along their lengths.

[0124] The at least one deflection device may be comprised of baffles, protrusions or other inserts into the volume of the flow through reactor to cause the flow of the slurry to increase the residence time of the particles flowing through the cavitation field. In another illustration the cavitation field may be generated by one or more ultrasonic probes orthogonal to the length of the reactor and there are one or more protrusions emanating radially inward from the inner diameter of the reactor oran insert within the volume of the reactor deflecting flow to the walls where the cavitation fields are being generated.

[0125] Any device suitable for imparting cavitation in the slurry may be used such as those known in the art. The cavitation, however, must be comprised of transient (also referred to as “inertial”) cavitation. Transient cavitation is where nano scale bubbles form and collapse under varying levels of pressure experienced in the slurry. Non-inertial cavitation, as occurs in an ultrasonic bath, is insufficient. Non- inertial cavitation is where a bubble merely oscillates in size or shape such as in an ultrasonic bath. Desirably, all of the cavitation is transient. The cavitation average size may be any suitable to accelerate the leaching of the metal compound, but, preferably, the size (equivalent spherical diameter) is within 5, 3, 2, 1 times the average size or maximum bubble size of the cavitation field’s bubbles, which may be determined by any known method such as described in Ultrasonics Sonochemistry 108 (2024) 106957. Illustratively, the average cavitation bubble size is within 50% of the metal compounds’ average particle size.

[0126] The cavitation may be transient cavitation imparted ultrasonically. It is preferred that the cavitation is formed ultrasonically with a suitable method being the direct contact of the vibrating probe and the slurry. The frequency may be any useful such as from 15 kHz to 100 kHz and may vary depending on the metal particle’s size. Multiple frequencies may be employed in the same reactor and may be particularly suited to metal compounds having differing sizes or characteristics such as reintroduction of metal compound particles previously subjected to one or more cavitation field to a slurry having fresh (untreated) metal compound particles.

[0127] In a particular illustration, electrode metal compound particles generally having the characteristics described above (e.g., average secondary particle size of 10 micrometers to 50 micrometers) desirably employ a frequency cavitation field generated from a frequency from 20 kHz, 22 kHz, or 23 kHz to 30 kHz.

[0128] In some cases, a frequency of about 20-30 kHz or any value therebetween (optionally rounded to the nearest 0.1), or any subrange spanning between any two of these values, such as 23-30 kHz may be used. For example,frequencies of 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30 kHz, are considered.

[0129] The dissolution rate, surprisingly, does not scale with power input per unit volume of slurry. Even though the intensity of bubble collapse would increase, with increasing power (amplitude), the rate of dissolution has displayed slower dissolution rates. In other words, it has been surprisingly discovered that the dissolution of metal compound electrode materials, may be dissolved more efficiently at lower power even when employing a weak acid. The power input per unit volume of reactor (W / L) may be any useful, but, desirably is any sufficient to accelerate the dissolution rate and preferably is at a most 5000 W / L, 2000 W / L, 1000 W / L or 500 W / L to any practicable initiate and sustain transient cavitation with 100 W / L in many instances being sufficient.

[0130] In some cases, a power input of about 100-5000 W / L or any value therebetween (optionally rounded to the nearest 0.1), or any subrange spanning between any two of these values, may be used. For example, power inputs of 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 285, 290, 295, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 420, 440, 460, 480, 500, 550, 600, 650, 700, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800, 3900, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900, 5000 W / L, and others are considered.

[0131] In an illustration of a recycling plant employing the method, a leaching unit may start with a mixing tank receiving the black mass and chemicals from oxidizer and acid tanks. The slurry obtained combining black mass (solid) and chemicals (liquid) may then be moved from the mixing tank into a series of sonicators, such as the reactor and ultrasonic probes depicted in Figures 6 to 10. Afterthe dissolution of the metals, the leachate may then be sent into a centrifuge. The centrifuge may have the scope to remove eventual undissolved solids, i.e. undissolved black mass, graphite, or impurities, that are disposed or eventually recirculated to the mixing tank for a second (or greater) passage into the flow through reactors. Further additional acid, acid solution, and reductant may be added during the process, such as when separating and recycling undissolved metal compounds to further dissolve the metal compounds. In some instances, differing solutions may be used in sequential reactors to selectively dissolve and separate differing metals / elements (for example, dissolve Li preferentially from LFP).

[0132] The distance between the sonoprobe and an inner surface of the reactor wall may be varied, for example to create the desired flow and exposure of the particles to the cavitation fields in a flow through reactor. Desirably, as shown in Figure 9, the W / D (wall distance / modules depth) ratio is from 0.1 to 15 and preferably is 1 to 15, or 2 to 15. The sonoprobe to slurry inlet distance may be any useful, but generally is at least about 0.1 cm to 50 cm.

[0133] In some cases, a W / D ratio of about 0.1-20, or any value therebetween (optionally rounded to the nearest 0.1), or any subrange spanning between any two of these values, such as about 2-15, may be used. For example, ratios of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, and others are considered.

[0134] In some cases, a sonoprobe to slurry inlet distance of about 0.1 cm – 50 cm, or any value therebetween (optionally rounded to the nearest 0.1), or any subrange spanning between any two of these values, such as about 2-15, may be used. For example, distances of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, 35, 35.5, 36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5, 40, 40.5, 41, 41.5, 42, 42.5, 43, 43.5, 44, 44.5, 45, 45.5, 46, 46.5, 47, 47.5, 48, 48.5, 49, 49.5, 50 cm, and others are considered.

[0135] The black mass may enter into the reactor as a slurry through an inlet that is aligned perpendicularly to the one or more modules. In some cases, the slurry proceeds perpendicularly to the modules and parallel to the ultrasonic probe.

[0136] The metal compound containing slurry may be at a suitable temperature during dissolution. For example, the slurry may be at a temperature below the leaching solution’s boiling point. The slurry may be at ambient temperature. EXAMPLES

[0137] Examples A:

[0138] Table 1 shows the secondary particle size of the metal compounds used in the Examples (NMC -Li1.05Co0.33Ni0.33Mn0.33O2; LCO – LiCoO2 and LFP LiFeP04). The metal compounds are obtained from MSE SuppliesTM. The particle size is specified by the company and was also confirmed by scanning electron microscopy (SEM). The porosity of each material is also shown in Table 1, which is the reported porosity by the supplier. Table 2 shows the leaching parameters and results for leaching lithium cobalt oxide (LCO) and Table 3 shows the leaching parameters and results for leaching (NMC) for Examples A with the dissolution determined gravimetrically. Table 4 shows the leaching parameters and results for leaching NMC, where the dissolution is determined by ICP-OES of the leachate solution. The data obtained in Tables 2 and 3 are determined gravimetrically from remaining solids filtered from the leachate. Table 4 shows the results from leaching NMC by the same method, where the amount of leached black mass is determined by analysis of the leachate solution. Table 1: Secondary particle size and porosity of metal compounds used in the Examples D10 [μm] D50 [μm] D90 [μm]Porosity %LCO >3 7 <15 20-30% NMC >4 11 <30 28-34% LFP >0.3 1.1 <15 50-65%

[0139] A sonotrode, composed of a piezoelectric generator and an ultrasonic probe (sonoprobe) was used to generate ultrasounds at 20 kHz in a 400 ml borosilicate beaker containing an acid solution (about 200 ml having black mass powder (NMC - Li1.05Co0.33Ni0.33Mn0.33O2 or LCO – LiCoO2) suspended therein (slurry) in the presence of an oxidizing agent (hydrogen peroxide 30% v / v, VWR Chemicals) and acetic acid (glacial acetic acid diluted as noted with Milli-QTM water) as noted in Tables 2-4. The cavitation field developed engulfed the entire slurry volume and created substantial agitation within the slurry volume in the beaker causing the slurry to repeatedly flow through the cavitation field due to the deflections from the wall of the beaker arising from the small size of the beaker. The average size of the secondary NM cathode particles prior to any treatment is shown in Figure 1 and is about 10 micrometers with the average primary particle size being about an order of magnitude less with at least a portion of the open porosity at the surface being a similar size as the primary particles. The probe input energy is about 2000 W / L. Figure 2 corresponds to the cathode particles after being treated in water (no acid or hydrogen peroxide) reflecting the original particle microstructure and morphology. Figures 1 and 2 have been reproduced from Canciani, et al. "On the effect of cavitation on particles in leaching processes: implications to battery recycling." Environmental Advances 17 (2024): 100570, incorporated herein by reference.

[0140] Figure 3 shows the particles after being treated as in Run 3 of Table 4. Characterization techniques may include any suitable techniques known in the art such as Scanning Electron Microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDX), Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), Mercury porosimetry and micrographic image analysis techniques.Table 2: Examples A (Dissolution of LCO determined gravimetrically): run  Water / Acid Solid / liq  H2O2  time  Ampli‐ dissolved  [ml / ml]  [g / L]  vol%  [min]  tude  LiCoO2 [g / L]  1  3  24.51  2.00  3.00  100.00  15.29 2  2  24.10  2.47  3.00  100.00  14.46 3  3  105.00  0.00  3.00  100.00  5.00 4  3  99.51  2.50  3.00  100.00  13.17 5  3  99.02  2.50  3.00  50.00  22.68 6  3  18.78  2.50  3.00  50.00  8.54 7  3  19.00  2.50  3.00  100.00  10.67 8  3  19.00  2.50  5.00  100.00  11.33 9  3  19.00  2.50  10.00  100.00  16.67 10  2  24.71  4.94  3.00  100.00  13.41 11  3  18.13  2.75  13.00  100.00  10.27 12  3  1.34  2.50  15.00  100.00  0.90 13  3  1.37  2.50  15.00  100.00  0.88 14  3  0.17  2.50  10.00  100.00  0.09 15  0  25.70  6.10  3.00  100.00  13.14 16  0  25.70  6.10  5.00  100.00  7.95 17  0  25.70  6.10  10.00  100.00  13.36 18  3  18.20  2.50  12.00  100.00  10.27 19  3  24.88  2.50  12.00  100.00  24.46 20  3  30.00  2.50  10.00  100.00  10.49 21  3  9.93  2.50  2.00  100.00  4.85 22  3  9.80  2.50  5.00  100.00  7.32 23  3  10.56  2.50  8.00  100.00  9.02 24  3  9.80  2.50  12.00  100.00  8.05 25  3  9.76  2.50  15.00  100.00  8.22 26  3  9.76  2.50  15.00  50.00  8.44 Table 3: Examples A (Dissolution of NMC determined gravimetrically)Table 4. Examples A (Dissolution of LCO determined by ICP-OES) Test Water / Acid Solid / liq H2O2 time Amplitud Dissolved LCO [ml / ml] [g / L] vol% [min] e [g / L] 1 pure water 40 3 10 100 0 2 1 40 3 10 100 11.16 3 3 40 3 10 100 15.77 4 pure acid 40 3 10 100 2.08 5 3 10 3 10 100 9.28 6 3 20 3 10 100 12.93 7 3 30 3 10 100 14.60 8 3 50 3 10 100 16.93 9 3 60 3 10 100 17.88 10 3 70 3 10 100 18.53 11 3 80 3 10 100 19.13 12 3 40 0 10 100 0 13 3 40 1.5 10 100 11.36 14 3 40 0 10 100 18.27 15 3 40 4.5 10 100 18.67 16 3 40 6 10 100 20.31 17 3 40 3 1 100 1.90 18 3 40 3 2 100 2.94 19 3 40 3 3 100 4.14 20 3 40 3 4 100 6.48 21 3 40 3 5 100 7.73 22 3 40 3 6 100 10.12 23 3 40 3 7 100 11.22 24 3 40 3 8 100 12.18 25 3 40 3 9 100 12.71

[0141] Figure 4 shows the leaching efficiency at the NMC black mass solids loading of 40g / L. The efficiency plot shows that the solubility limit of the metals ~35g / L is reached in about 8 minutes (Ultrasonic induced cavitation “transient” enhanced), whereas similarly reported conventional leaching with aid by sonication bath is below 20% even after 15 or 20 minutes under similar loadings of black mass, acid and hydrogen peroxide (“Literature” as recited in Figure 4 refers to Xiao, et al., Green Chem.2021, 23, 8519, DOI: 10.1039 / d1gc02693c, incorporated herein byreference). The improvement, without being limiting in any way, is believed to be due to the injection of the leaching solution into the porosity of the particles as a result of direct exposure to microjets due to implosion of finer cavitation bubbles (transient cavitation) at cavitation inception and re-exposure from the agitation caused by the probe being directly inserted into the slurry as well as the particle morphology of the cathodic particles (secondary particles comprised of sintered primary oxide particles and porosity between the primary particles).

[0142] LFP is dissolved in the same manner as described above A at 100% amplitude, ~24 g / L solids loading (5.2 grams LFP), 8.6 water / acid (g / g), for 10 minutes. The method selectively dissolves the more desired Li when dissolving LFP. The dissolution efficiency of Li is greater than 94%, Fe is less than 0.5 % and P is less than 2.5%, which is desirable in retrieving the Li while retaining the iron phosphate, which may be recycled directly to form new LFP. Examples B:

[0143] A pilot-scale ultrasonic flow through reactor is shown in Figures 5 to 10, the experimental set-up is shown in Figure 5 showing a flow loop through a reservoir and the reactor, the residence time is computed as the actual process time multiplied by the ratio between the processed volume and the reactor volume. LCO and NMC and LFP (LiFePO4) electrode metal compounds were tested. Figure 8 also shows the results of a computation fluid dynamic simulation of the cavitation bubble distribution in the flow through reactor. Any suitable software may be utilized such as those available commercial and described by P. Guida, et. al., Chemical Engineering Journal Advances, Volume 12, 15 November 2022, 100362, incorporated herein by reference. The operational parameters are shown in Table 5.

[0144] Table 5: Operational Parameters of the Example B reactor.Free volume in the reactor  4 [L] Power input per reactor  2 [kW] Power per liter  0.5 [kw / L] Solids load  Table 6 [g / L] H2O2 / Solvent vol%  4 [%] Acetic Acid / Water   3 (ml / ml)

[0145] The slurry with the metal compound (NMC, LCO or LFP-LiFePO4) with the acid and hydrogen peroxide is inserted tangentially and further water is inserted axially protecting the probe. The slurry after passing through the reactor exits at the top after passing through multiple cavitation fields with the flow being disrupted by the ultrasonic probe, believing to cause without being limited to eddy currents prolonging the exposure to the cavitation bubbles inception.

[0146] The dissolution of the LCO and NMC approach the solubility in less than 10 minutes of residence time for Examples B as shown in Table 6.

[0147] Table 6: Dissolution of LCO, NMC, and LFP Solid load [g / L] Expected Residence time Dissolved BM solubility [g / L] [min] [g / L] LCO 20 ~15-19 7.5 14.55NMC 30 ~35 4.7 29.38*LFP 27 Not determined 9 1.1 g / L**

[0148] Comparative Examples 1 and 2

[0149] Comparative Example 1: Leaching is performed on NMC at ~40 g / L loading in a 400 ml beaker stirred only with a magnetic stir bar with an acetic acid concentration of 25% v / v in water, H₂O₂ concentration 3% v / v in water. A plot of the leaching is shown in Figure 11 compared to the leaching by Examples A-B. Each of the Examples A-B plotted in Figure 11 used the same leaching solution and solids loading except for Examples B, which used 30 g / L.

[0150] Comparative Example 2: Leaching of LFP is performed in the same manner as described above for Examples A with stirring with a magnetic stir bar only(without sonication) at ~24 g / L solids loading (5.2 grams LFP), 8.6 water / acid (g / g), for 24 hours. The method likewise selectively dissolves the more desired Li, but takes more than 2 orders of magnitude longer to do so.

[0151] The plots of Figure 11 show the leaching efficiency of differing methods. The leaching arising from direct ultrasonic agitation where the slurry flows through the cavitation field’s inception is particularly effective and is on the order of less than 8 minutes to realize essentially full dissolution to the solubility limit of the metals being leached and is substantially faster than that reported using reactors immersed in an ultrasonic bath. Likewise, it is noted, that the power of Examples B is substantially less than Examples A, yet surprisingly the leaching efficiency is substantially improved by using Example’s B reactor, which is believed, without being limiting, due to, at least in part, the creation of turbulent flow or eddies within the flow reactor that cause the slurry particles to be exposed to the multiple cavitation fields at the bubble inception.

[0152] Examples A-B dissolve the metal oxides faster and results in a leaching efficiency of 100% after only 2 or 8 minutes to the solubility limit of a weak acid and hydrogen peroxide solution. This is at least an order of magnitude than reported in the literature such as described by Xiao, et al., Green Chemistry 2021, 23 (21), 8519-8532 for similar cathode materials. This much slower rate may be due to the lack of acoustic cavitation generated by the ultrasonic waves or exposure to the cavitation field at inception.

[0153] The leaching of various metal compounds and in particular electrode metal compounds such as LCO, LFP (lithium iron phosphate) and NMC metal compounds have been dissolved more than order an of magnitude faster than reported in the prior art. The reduced leaching time results in several advantages compared to traditional leaching techniques: Modularity: the capacity of the recycling system can be extended by increasing the number of modules instead of developing larger equipment; Flexibility: the startup time of the recycling system is very limited, so that it can work intermittently depending on the quantity of metal compounds available at a given time; Small footprint: The system is continuous, requires shorter residence times and occupies at least 10x less space than necessary for the dissolution rates reported in the prior art; and Low environmental impact: The process adopts a mildorganic acid while competitors rely on more hazardous media such as sulfuric acid. The energy consumption of the process is surprisingly more effective at particular lower power inputs, resulting in cost advantages related to waste treatment and energy management.

[0154] What has been described is merely illustrative of the application of the principles of the disclosure. However, it will be apparent to a person skilled in the art that a number of variations and modifications can be made without departing from the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method comprising:immersing a metal compound in a leaching solution comprising a leaching aid to form a slurry; and flowing the slurry through a cavitation field to dissolve at least a portion of the metal compounds.

2. The method of claim 1, wherein the leaching solution comprises water.

3. The method of claim 1, further comprising adding additional acid duringthe method.

4. The method of claim 1, wherein the leaching aid comprises a weak acid.

5. The method of claim 1, wherein the acid is a carboxylic acid or a peroxylacid of the carboxylic acid.

6. The method of claim 1, wherein the cavitation field is provided.

7. The method of claim 1, wherein the method comprises adding an oxidizingagent to the leaching solution.

8. The method of claim 7, wherein the oxidizing agent is hydrogen peroxide.

9. The method of claim 7, wherein from about 0.5% to about 10% vol%oxidizing agent is added to the leaching solution.

10. The method of claim 1, wherein the metal compounds have an averageparticle size and the cavitation field has an average cavitation bubble size and the average cavitation bubble size / average metal compounds particle size is at most 2.

11. The method of claim 1, wherein the slurry is at a temperature below theleaching solution’s boiling point.

12. The method of claim 1, wherein the solid metal oxide is comprised oflithium and at least one other metal.

13. The method of claim 12, wherein the other metal is comprised of one ormore of Al and a transition metal.

14. The method of claim 13, wherein the transition metal is comprised of oneor more of Co, Mn and Ni.

15. The method of claim 1, wherein the cavitation field is generated by anultrasonic probe at least partially immersed in the slurry.

16. The method of claim 15, wherein the ultrasonic probe is disposed within atubular reactor having a first and second end, an inlet and outlet positioned to flow the slurry through tubular reactor and through the cavitation field generated by the ultrasonic probe.

17. The method of claim 15, wherein the ultrasonic probe’s length is axiallyoriented within the tubular reactor’s length.

18. The method of claim 15, wherein the ultrasonic probe has a diameter thatvaries along the length of the ultrasonic probe that causes cavitation fields at differing points along the ultrasonic probe’s length.

19. The method of claim 16, wherein the tubular reactor comprises one ormore deflection devices that cause the slurry when flowed through the tubular reactor to be deflected into the cavitation field.

20. The method of claim 19, wherein each of the one or more deflectiondevices are independently selected from: protrusions, baffles, and deflections.

21. The method of claim 1, wherein the slurry has a solids loading in excess ofthe solids’ solubility limit in the leaching solution.

22. The method of claim 15, wherein there are at least two or more ultrasonicprobes.

23. The method of claim 22, wherein the two or more probes are vibrated in orout of phase.

24. The method of claim 22, wherein the two or more probes have varyingdiameters along their length, with the diameters of each probe varying asynchronously, synchronously or combination thereof along their lengths.

25. The method of claim 1, wherein the metal compound is comprised ofsecondary particles having an average particle size of 2 micrometers to 100 micrometers, the secondary particles being comprised of agglomerated primary particles having an average size of at most 2 micrometers.

26. The method of claim 1, wherein the slurry has a solids loading of the metalcompound of 0.1% to 20% by weight.

27. The method of claim 1, wherein flowing of the slurry is through at leasttwo cavitation fields sequentially.

28. The method of claim 16, wherein the flowing of the slurry is through twoor more serially connected tubular reactors.

29. The method of claim 1, further comprising separating any undissolvedmetal oxide.

30. The method of claim 10, wherein the average cavitation bubblesize / average metal compounds particle size is at most 1.5.

31. The method of claim 1, wherein the metal compound particles arecomprised of open porosity having an average pore size and the average cavitation bubble size is no more than 10 times greater than the average pore size of the metal compound particles.

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