Sulfidation of a phosphate-containing compound

Abstract

Sulfidation of a phosphate-containing compound is generally described. For example, in some cases, the method comprises heating a feedstock comprising a phosphate-containing compound, a substance comprising sulfur, and a gas-reactive species (e.g., in a reactor) to induce sulfidation of the phosphate-containing compound, producing a phosphorus-containing gas species, a sulfide, and / or a compound comprising sulfur, phosphorus, and oxygen, such as a sulfoapatite, a thiophosphate, and / or a sulfate-phosphate.

Description

[0001] SULFIDATION OF A PHOSPHATE-CONTAINING COMPOUND RELATED APPLICATIONS

[0002] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 63 / 777,249, filed March 25, 2025, and entitled “Sulfidation of Calcium Phosphate Apatite,” which is hereby incorporated herein by reference in its entirety for all purposes.

[0003] TECHNICAL FIELD

[0004] Methods of sulfidation of a phosphate-containing compound are generally described.

[0005] SUMMARY

[0006] Methods of sulfidation of a phosphate-containing compound are generally described. In some cases, the method comprises heating a feedstock (e.g., a rock, ore, and / or mineral) comprising a phosphate-containing compound, a substance comprising sulfur, and a gas-reactive species (e.g., in a reactor) to induce sulfidation of the phosphate-containing compound, producing a phosphorus-containing gas species, a sulfide, and / or a compound comprising sulfur, phosphorus, and oxygen, such as a sulfoapatite, a thiophosphate, and / or a sulfate-phosphate. For example, in certain instances, the method comprises heating a feedstock comprising calcium apatite, disulfur (S2) gas, and graphite in a reactor to induce sulfidation of the calcium apatite, producing (i) a phosphorus-containing gas species and (ii) a sulfide and / or a compound comprising sulfur, phosphorus, and oxygen, such as a sulfoapatite, a thiophosphate, and / or a sulfate-phosphate. In certain cases, the method comprises producing a phosphorus-containing fertilizer, animal feed supplement, ceramic, pharmaceutical, textile, and / or battery from the phosphorus-containing gas species and / or from an additional phosphorus-containing product formed therefrom. The subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and / or a plurality of different uses of one or more systems and / or articles. This Summary introduces a selection of concepts in simplified form that are described further below in the Detailed Description. This Summary neither identifies key or essential features, nor limits the scope, of the claimed subject matter.

[0007] Certain embodiments relate to methods. In some embodiments, the method comprises a. providing a feedstock comprising a phosphate-containing compound to a reactor; b. providing a substance to the reactor, wherein the substance comprises sulfur; and

[0008] 1

[0009] #15070911vlc. heating the feedstock, the substance comprising sulfur, and a gas-reactive species to induce sulfidation of the phosphate-containing compound, producing a phosphorus-containing gas species, a sulfide, and / or a compound comprising sulfur, phosphorus, and oxygen.

[0010] In certain embodiments, the method comprises a. providing a feedstock comprising calcium apatite to a reactor (crucible), wherein the calcium apatite comprises Caio(P04)eX, wherein X is selected from O, Cl, OH, F, or vacancy; b. producing a flow of a gas to the crucible wherein the gas comprises sulfur; and c. heating the reactants in the presence of a carbon compound to induce sulfidation; wherein a sulfide (CaS), sulfoapatite (Caio(P04)eS), and sulfate-apatite (Ca2i-x(PO4)i4-2x(SO4)2x) are produced by the reaction.

[0011] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control. The following Detailed Description references the accompanying drawings which form a part this application, and which show, by way of illustration, specific example implementations. Other implementations may be made without departing from the scope of the disclosure.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figures:

[0014] FIGs. 1A-1D show an induction furnace sulfidation set up and components, in accordance with some embodiments. FIG. 1A shows an image of an induction furnace sulfidation set up, in accordance with some embodiments. FIG. IB shows a simplified diagram of the sulfidation set up of FIG. 1A. FIG. 1C shows a simplified diagram and photo of the susceptor / sample holder designed specifically to hold samples, allow for gas flow of sulfur gas through the samples and create a hot zone for sulfidations, in accordance with

[0015] 2

[0016] #15070911vlsome embodiments. FIG. ID shows a simplified diagram and image during operation of a sulfur boiler designed to control the evaporation rate of sulfur gas that is carried upwards into the hot zone via argon carrier gas, in accordance with some embodiments.

[0017] FIG. 2 shows an image of beta-tricalcium phosphate (Sigma Aldritch 49963) before (left) and after (right) sulfidation at 1400C in an alumina crucible.

[0018] FIG. 3 shows an XRD scan of the beta-tricalcium phosphate of FIG. 2 after sulfidation at 1400C. The scan was conducted using PANalytical X'Pert PRO with a copper Kalpha source and a scan rate of .83 degrees 2theta / minute. Peaks corresponding to Calcium Sulfide, Sulfoapatite, Aluminum Phosphate, and Calcium were identified and matched using HighScore Plus.

[0019] FIG. 4 shows a back-scatter electron image of the obtained product of tricalcium phosphate-magnesium carbonate sulfidation. Electron Dispersive Spectroscopy identified three phases with elemental composition matching calcium sulfide, magnesium-calcium orthophosphate, and a magnesium substituted calcium sulfoapatite.

[0020] FIGs. 5A-5C show the calculated predominance diagrams of pSO2 / pS2 conditions under which TCP (tri-calcium phosphate) is converted into SAp (sulfoapatite) or CaS (calcium sulfide) along with P (phosphorus) as various gas species. FIG. 5A shows the calculated predominance diagram under 1200°C conditions. The stars shows the conditions used for the results in FIGs. 6A-6C. FIG. 5B shows the calculated predominance diagram under 1000°C conditions. FIG. 5C shows the calculated predominance diagram under 800°C conditions.

[0021] FIGs. 6A-6B show powder XRD spectra of TCP after treatment at 1200 °C for 100 minutes with argon gas flow rate of 1 L / minute. FIG. 6A shows the powder XRD spectrum under carbo-sulfidation conditions - sulfidation with added solid graphite, achieving (pSCh / pS2 ) ~= (IO-12, 0.2). These conditions are marked with a star on FIG. 5A. FIG. 6B shows the powder XRD spectrum under sulfidation conditions - only sulfur, pS2 ~= 0.2. FIG. 6C shows the powder XRD spectrum under carbothermic reaction conditions (only graphite), pS2 = 0. Rectangles on the right display phase fraction estimates after Rietveld refinement and the fraction of P “lost” from the solid, believed to be in the gas phase. The product phases, degree of solid conversion, and amount of P volatilized for a sulfidation with a gas reactive species such as graphite were distinctly different from sulfidations and carbothermic reactions.

[0022] 3

[0023] #15070911vlFIG. 7 is a photo showing that sulfur condensed onto the top cap of the furnace tube (actively cooled during experiment). This deposit was partially amorphous with a waxy to gummy like texture.

[0024] DETAILED DESCRIPTION

[0025] Methods of sulfidation of a phosphate-containing compound are generally described. In some cases, the method comprises heating a feedstock (e.g., a rock, ore, and / or mineral) comprising a phosphate-containing compound, a substance comprising sulfur, and a gas-reactive species (e.g., in a reactor) to induce sulfidation of the phosphate-containing compound, producing a phosphorus-containing gas species, a sulfide, and / or a compound comprising sulfur, phosphorus, and oxygen, such as a sulfoapatite, a thiophosphate, and / or a sulfate-phosphate. For example, in certain instances, the method comprises heating a feedstock comprising calcium apatite, disulfur (S2) gas, and graphite in a reactor to induce sulfidation of the calcium apatite, producing (i) a phosphorus-containing gas species and (ii) a sulfide and / or a compound comprising sulfur, phosphorus, and oxygen, such as a sulfoapatite, a thiophosphate, and / or a sulfate-phosphate. In certain cases, the method comprises producing a phosphorus-containing fertilizer, animal feed supplement, ceramic, pharmaceutical, textile, and / or battery from the phosphorus-containing gas species and / or from an additional phosphorus-containing product formed therefrom.

[0026] Phosphorus (P) is an element which is used in the agricultural sector in the form of fertilizers and animal feed stocks. Approximately 95% of the world phosphate rock production is consumed in fertilizer manufacturing. Economic recovery of phosphates is generally limited to naturally concentrated phosphate mineral deposits. Occasionally natural concentrations are enough to be used as mined; generally, however, the ore is low grade and must be concentrated for economic utilization.

[0027] Apatite may be a major potential resource of P for use in the manufacturing of e.g., nitrogen-phosphorus-potassium (NPK) fertilizers, animal feed supplements, ceramics, pharmaceuticals, textiles and batteries. The sedimentary phosphorites make a large contribution to the world production of phosphate. Phosphate minerals occurring in the primary environment include calcium apatites: mainly fluor-apatite (Caio(P04)eF2), hydroxyapatite (Caio(P04)e(OH)2), and carbonate-hydroxy-apatite (Caio(P04,C03)e(OH)2).

[0028] Because of the increasing demand on phosphate rock for fertilizers, it may be useful to mine and process low grades of phosphate deposits. Most of these low-grade deposits are

[0029] 4

[0030] #15070911vlof sedimentary phosphates and the rest are of different origins. These deposits typically occur in the form of ore bodies in one thick bed, or several successive beds intercalated with non-phosphatic materials.

[0031] Physical as well as thermal treatment techniques may be used for concentrating the run-of-mine phosphates. Several techniques may be used in the manufacture of industrial phosphoric acid. The so-called thermal process may have a very large energy consumption. Wet process phosphoric acid (WPA) may be produced by a chemical reaction of the phosphate rock with a mineral acid. Due to the presence of impurities in the raw material the phosphoric acid produced by these methods typically contains many chemical species, including compounds comprising radioactive elements. Some of these compounds may be detrimental to the quality of the acid for its end uses in fertilizers or food industries.

[0032] There is a need for improved methods of extracting phosphate from phosphate ores, including methods that do not produce toxic byproducts.

[0033] Certain embodiments relate to methods. In some embodiments, the method comprises providing a feedstock to a reactor. According to certain embodiments, the feedstock comprises a rock and / or an ore, such as an iron ore, an apatite phosphate ore, a sedimentary phosphorite, and / or a phosphate rock. According to some embodiments, the feedstock comprises a mineral, such as monazite. In accordance with some embodiments, the feedstock comprises beta-tricalcium phosphate (Cas PC ). In certain embodiments, the feedstock comprises a primary phosphate source and / or a secondary phosphate source. In accordance with some embodiments, the feedstock comprises an impurity of an extraction stream (e.g., a primary and / or secondary mineral extraction stream). In some embodiments, the feedstock comprises metallurgical slag. According to some embodiments, the feedstock comprises an industrial waste. In some cases, the feedstock comprises bones. For example, certain of the systems and methods used herein can make use of the bones of animals as feedstocks.

[0034] In certain instances, the feedstock is not pretreated prior to being provided to the reactor and / or prior to being heated (e.g., with a substance comprising sulfur and a gas-reactive species). For example, in some instances, the feedstock does not undergo calcination, dehalogenation, dephosphorization, and / or sulfidative sintering prior to being provided to the reactor and / or prior to being heated (e.g., with a substance comprising sulfur and a gas-reactive species). For example, in some cases, the feedstock does not undergo

[0035] 5

[0036] #15070911vldephosphorization prior to being provided to the reactor and / or prior to being heated (e.g., with a substance comprising sulfur and a gas-reactive species).

[0037] In certain instances, the feedstock comprises a phosphate-containing compound. In some cases, the phosphate-containing compound comprises an inorganic phosphate. For example, in some instances, the inorganic phosphate comprises a compound-comprising phosphate that does not include carbon. In some embodiments, the phosphate-containing compound and / or inorganic phosphate comprises a metal phosphate, such as an alkali metal phosphate, an alkaline earth metal phosphate, a transition metal phosphate, and / or a rare earth metal phosphate. For example, in some cases, the phosphate-containing compound and / or inorganic phosphate comprises a calcium phosphate.

[0038] In accordance with some embodiments, the phosphate-containing compound comprises an apatite. In some embodiments, the phosphate-containing compound comprises calcium apatite. According to some embodiments, the calcium apatite comprises Caio(P04)eX, wherein X is selected from O, Cl, OH, F, or vacancy.

[0039] According to certain embodiments, the phosphate-containing compound comprises aMwOv■ bP2O5or aMwOv■ bP2O5■ cMqXrwhere M is a metal cation, X is a non-metal anion or polyatomic anion, and a, b, c, w, v, q, and r are each independently a number. For example, in some cases, the phosphate-containing compound comprises:

[0040] • an oxide-phosphate slag and / or glass;

[0041] • a phosphate apatite, such as Mio(P04)eX2 where M is a metal such as Ca, Sr, Pb, and / or Na, X is an anion, such as F, Cl, OH, O, S, CO3, and / or SO4;

[0042] • an orthophosphate, such as My(P04)zwhere M is a metal and y and z are numbers, such as K3PO4, FePO4, Fe3P20s, and / or LiFePO4; and / or

[0043] • a pyrophosphate and / or metaphosphate, such as:

[0044] o My(P20?)z = My(PO3.5)2z (where M is a metal and y and z are numbers) o My(P2Oe)z = My(PO3)2z (where M is a metal and y and z are numbers) According to some embodiments, the phosphate-containing compound is a solid and / or a liquid.

[0045] In some embodiments, greater than or equal to 0.1 wt%, greater than or equal to 0.5 wt%, greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 3 wt%, greater than or equal to 5 wt%, greater than or equal to 7 wt%, greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 45 wt%, greater than or equal to 50 wt%,

[0046] 6

[0047] #15070911vlgreater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt% of the feedstock is made up of the phosphate-containing compound. In certain cases, less than or equal to 100 wt%, less than or equal to 95 wt%, less than or equal to 90 wt%, less than or equal to 85 wt%, less than or equal to 80 wt%, less than or equal to 75 wt%, less than or equal to 70 wt%, less than or equal to 65 wt%, less than or equal to 60 wt%, less than or equal to 55 wt%, less than or equal to 50 wt%, less than or equal to 45 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, less than or equal to 15 wt%, less than or equal to 10 wt%, or less than or equal to 5 wt% of the feedstock is made up of the phosphate-containing compound. Combinations of these ranges are also possible (e.g., greater than or equal to 1 wt% and less than or equal to 100 wt%, greater than or equal to 15 wt% and less than or equal to 100 wt%, greater than or equal to 15 wt% and less than or equal to 45 wt%, or greater than or equal to 80 wt% and less than or equal to 100 wt%). In some instances, 100 wt% of feedstock is made up of the phosphate-containing compound.

[0048] In some cases, the method comprises providing a substance to the reactor. For example, in certain embodiments, the substance is generated in situ and / or the substance is added to the reactor (e.g., through a flow of gas). In some embodiments, the substance comprises a solid, a liquid (e.g., molten), and / or a gas. In some cases, the substance comprises a fluid (e.g., a gas and / or a liquid). For example, in certain embodiments, the substance comprises a gas.

[0049] In some instances, the substance comprises sulfur. According to certain embodiments, the substance comprising sulfur comprises a gas, a solid, and / or a liquid, such as molten sulfur. In some cases, the substance comprising sulfur comprises a fluid (e.g., a gas and / or a liquid, such as a gas comprising sulfur and / or molten sulfur). In some embodiments, the substance comprising sulfur comprises a gas comprising sulfur. In certain instances, the substance comprising sulfur and / or the gas comprising sulfur comprises disulfur (S2), carbon disulfide (CS2), aluminum sulfide, silicon sulfide, and / or gallium sulfide. For example, in some instances, the substance comprising sulfur comprises S2 gas.

[0050] In some embodiments, the method comprises providing the substance and / or the gas comprising sulfur at a flow rate of greater than or equal to 100 sscm (standard cubic centimeters per minute), greater than or equal to 150 sscm, greater than or equal to 200 sscm, greater than or equal to 250 sscm, greater than or equal to 300 sscm, greater than or equal to

[0051] 7

[0052] #15070911vl350 sscm, greater than or equal to 400 sscm, greater than or equal to 500 sscm, greater than or equal to 600 sscm, greater than or equal to 700 sscm, greater than or equal to 800 sscm, greater than or equal to 900 sscm, greater than or equal to 1,000 sscm, greater than or equal to 2,000 sscm, greater than or equal to 3,000 sscm, greater than or equal to 4,000 sscm, greater than or equal to 5,000 sscm, greater than or equal to 6,000 sscm, greater than or equal to 7,000 sscm, greater than or equal to 8,000 sscm, or greater than or equal to 9,000 sscm, In certain embodiments, the method comprises providing the substance and / or the gas comprising sulfur at a flow rate of less than or equal to 10,000 sscm, less than or equal to 9,500 sscm, less than or equal to 9,000 sscm, less than or equal to 8,500 sscm, less than or equal to 8,000 sscm, less than or equal to 7,500 sscm, less than or equal to 7,000 sscm, less than or equal to 6,500 sscm, less than or equal to 6,000 sscm, less than or equal to 5,500 sscm, less than or equal to 5,000 sscm, less than or equal to 4,500 sscm, less than or equal to 4,000 sscm, less than or equal to 3,500 sscm, less than or equal to 3,000 sscm, less than or equal to 2,500 sscm, less than or equal to 2,000 sscm, less than or equal to 1,500 sscm, or less than or equal to 1,000 sscm. Combinations of these ranges are also possible (e.g., greater than or equal to 100 sscm and less than or equal to 10,000 sscm, greater than or equal to 500 sscm and less than or equal to 4,000 sscm, or greater than or equal to 400 sscm and less than or equal to 1,000 sscm).

[0053] In accordance with certain embodiments, the method comprises providing the substance and / or the gas comprising sulfur at a partial pressure of greater than or equal to 0.01 atm, greater than or equal to 0.02 atm, greater than or equal to 0.03 atm, greater than or equal to 0.04 atm, greater than or equal to 0.05 atm, greater than or equal to 0.07 atm, greater than or equal to 0.1 atm, greater than or equal to 0.15 atm, greater than or equal to 0.2 atm, greater than or equal to 0.25 atm, greater than or equal to 0.3 atm, greater than or equal to 0.35 atm, greater than or equal to 0.4 atm, greater than or equal to 0.45 atm, greater than or equal to 0.5 atm, greater than or equal to 0.6 atm, greater than or equal to 0.7 atm, greater than or equal to 0.8 atm, or greater than or equal to 0.9 atm. In some embodiments, the method comprises providing the substance and / or the gas comprising sulfur at a partial pressure of less than or equal to 1 atm, less than or equal to 0.95 atm, less than or equal to 0.9 atm, less than or equal to 0.85 atm, less than or equal to 0.8 atm, less than or equal to 0.75 atm, less than or equal to 0.7 atm, less than or equal to 0.65 atm, less than or equal to 0.6 atm, less than or equal to 0.55 atm, less than or equal to 0.5 atm, less than or equal to 0.4 atm, less than or equal to 0.3 atm, less than or equal to 0.2 atm, or less than or equal to 0.1 atm.

[0054] 8

[0055] #15070911vlCombinations of these ranges are also possible (e.g., greater than or equal to 0.01 atm and less than or equal to 1 atm or greater than or equal to 0.05 atm and less than or equal to 0.5 atm).

[0056] According to some embodiments, the substance (e.g., the substance comprising sulfur) comprises a first substance and a second substance. In some cases, the first substance comprises a substance comprising sulfur, such as any substance comprising sulfur disclosed herein, such as a gas comprising sulfur. In certain instances, the second substance comprises a gas, such as an inert carrier gas, such as argon. For example, in some cases, the substance comprises a gas comprising sulfur (a first substance) and an inert carrier gas, such as argon (a second substance).

[0057] According to some embodiments, the method comprises providing a gas-reactive species to the reactor. For example, in certain embodiments, the gas-reactive species is generated in situ and / or the gas-reactive species is added to the reactor (e.g., through a flow of gas). Without wishing to be bound by theory, it is believed that, in some embodiments, the gas-reactive species enhances selectivity of sulfidation, by allowing for physical separation of gaseous and solid / liquid sulfides.

[0058] As used herein, a “gas-reactive species” is a species that is reactive to produce a product that is (1) reactive and (2) in the gas phase. One example of a gas-reactive species is a species that reacts (e.g., with oxygen or sulfur) to form a gaseous species that is reactive under the reaction conditions (e.g., in the reactor during performance of the method(s) described herein). For example, in some cases, solid carbon is a gas-reactive species, as it may react with oxygen to form reactive carbon monoxide gas and / or reactive carbon dioxide gas. As another example, in certain instances, chlorine gas is a gas-reactive species, as it is a species that is reactive in the gas phase. A species that does not form a gas phase (e.g., in the reaction conditions) is not a gas-reactive species. Similarly, a species that does form a gas phase but is inert and non-reactive (e.g., in the reaction conditions) (such as argon) would not be a gas-reactive species.

[0059] In accordance with some embodiments, the gas-reactive species comprises a carbon-containing compound (such as a carbon-containing gas species), a carbonyl-containing compound (such as a carbonyl-containing gas species), carbon monoxide, carbon dioxide, carbonyl sulfide, carbon fluoride, carbon chloride, carbon iodide, carbon bromide, silicon sulfide, aluminium sulfide, gallium sulfide, an arsenide, magnesium and / or a volatile compound comprising magnesium, calcium and / or a volatile compound comprising calcium,

[0060] 9

[0061] #15070911vlsodium, potassium, and / or lithium. For example, in certain cases, the gas-reactive species comprises a carbon-containing compound. In some cases, the carbon-containing compound comprises carbon in a zero oxidation state. For example, according to some embodiments, the gas-reactive species and / or carbon-containing compound comprises graphite. In some instances, the gas-reactive species is a solid, such as carbon, graphite, and / or a carbide.

[0062] According to some embodiments, the gas-reactive species comprises a reducing agent. In certain embodiments, the reducing agent comprises an electron donor.

[0063] In accordance with some embodiments, the gas-reactive species has greater affinity for oxygen than the phosphorus does and / or than the sulfur does. For example, in certain instances, the gas-reactive species has greater affinity for oxygen than the phosphorus does and than the sulfur does.

[0064] In certain embodiments, the gas-reactive species is not carbon dioxide (CO2). In certain embodiments, the gas-reactive species is not carbon monoxide (CO). In certain embodiments, the gas-reactive species is not chlorine gas (Ch). In certain embodiments, the gas-reactive species is not hydrogen gas (H2). In certain embodiments, the gas-reactive species is not hydrogen sulfide (H2S). According to some embodiments, the gas-reactive species is not H2O gas.

[0065] In some cases, the method does not include use of carbon dioxide (CO2). In some cases, the method does not include use of carbon monoxide (CO). In some cases, the method does not include use of chlorine gas (Ch). In some cases, the method does not include use of hydrogen gas (H2). In some cases, the method does not include use of hydrogen sulfide (H2S). According to some embodiments, the method does not include use of H2O gas.

[0066] In accordance with certain embodiments, the gas-reactive species comprises a first gas-reactive species (e.g., any gas-reactive species disclosed herein, such as a carbon-containing gas-reactive species) and a second gas-reactive species (e.g., any gas-reactive species disclosed herein, such as a reducing agent). For example, in some cases, the gas-reactive species comprises a carbon-containing species as a first gas-reactive species and a reducing agent (e.g., an iron-containing species) as a second gas-reactive species. For example, in certain instances, a carbon-containing species is dissolved in an iron-containing species.

[0067] In certain embodiments, the method comprises heating the reactor, the feedstock, the substance comprising sulfur, and / or the gas-reactive species. For example, in some cases, the method comprises heating the feedstock, the substance comprising sulfur, and the gas-

[0068] 10

[0069] #15070911vlreactive species. For example, in some instances, the method comprises heating the feedstock, the substance comprising sulfur, and the gas-reactive species in the reactor.

[0070] In some embodiments, the method comprises heating (e.g., the reactor, the feedstock, the substance comprising sulfur, the gas-reactive species, and / or combinations thereof, such as a combination of the feedstock, the substance comprising sulfur, and the gas-reactive species) at greater than or equal to 500 °C, greater than or equal to 550 °C, greater than or equal to 600 °C, greater than or equal to 650 °C, greater than or equal to 700 °C, greater than or equal to 750 °C, greater than or equal to 800 °C, greater than or equal to 850 °C, greater than or equal to 900 °C, greater than or equal to 950 °C, greater than or equal to 1,000 °C, greater than or equal to 1,100 °C, greater than or equal to 1,200 °C, greater than or equal to 1,300 °C, greater than or equal to 1,400 °C, greater than or equal to 1,500 °C, greater than or equal to 1,600 °C, greater than or equal to 1,700 °C, greater than or equal to 1,800 °C, or greater than or equal to 1,900 °C. In accordance with some embodiments, the method comprises heating (e.g., the reactor, the feedstock, the substance comprising sulfur, the gas-reactive species, and / or combinations thereof, such as a combination of the feedstock, the substance comprising sulfur, and the gas-reactive species) at less than or equal to 2000 °C, less than or equal to 1,950 °C, less than or equal to 1,900 °C, less than or equal to 1,800 °C, less than or equal to 1,700 °C, less than or equal to 1,600 °C, less than or equal to 1,500 °C, less than or equal to 1,400 °C, less than or equal to 1,300 °C, less than or equal to 1,200 °C, less than or equal to 1,100 °C, less than or equal to 1,000 °C, less than or equal to 900 °C, less than or equal to 800 °C, less than or equal to 700 °C, or less than or equal to 600 °C. Combinations of these ranges are also possible (e.g., greater than or equal to 500 °C and less than or equal to 2000 °C or greater than or equal to 1,000 °C and less than or equal to 1,500 °C). According to some embodiments, the method comprises heating using an induction furnace and / or electrical furnace.

[0071] In some cases, the method comprises heating the feedstock, the substance comprising sulfur, and the gas-reactive species (e.g., in the reactor) to induce sulfidation of the phosphate-containing compound. According to certain embodiments, the method comprises producing a phosphorus-containing gas species, a sulfide, and / or a compound comprising sulfur, phosphorus, and oxygen, such as a sulfoapatite, a thiophosphate, and / or a sulfatephosphate. For example, in accordance with certain embodiments, the method comprises heating the feedstock, the substance comprising sulfur, and the gas-reactive species (e.g., in the reactor) to induce sulfidation of the phosphate-containing compound, producing a

[0072] 11

[0073] #15070911vlphosphorus-containing gas species, a sulfide, and / or a compound comprising sulfur, phosphorus, and oxygen, such as a sulfoapatite, a thiophosphate, and / or a sulfate-phosphate. In accordance with some embodiments, producing a phosphorus-containing gas species, a sulfide, and / or a compound comprising sulfur, phosphorus, and oxygen, such as a sulfoapatite, a thiophosphate, and / or a sulfate-phosphate comprises producing (i) the phosphorus-containing gas species and (ii) the sulfide and / or the compound comprising sulfur, phosphorus, and oxygen, such as a sulfoapatite, a thiophosphate, and / or a sulfate-phosphate. In some embodiments, the method comprises producing a sulfoapatite and / or a sulfateapatite.

[0074] According to certain embodiments, the method comprises producing a phosphorus-containing gas species. A non-limiting example of a phosphorus-containing gas species is P4O10 (or (P20s)2), P4O6 (or P20s)2), pure phosphorus, and / or a phosphorus sulfide. In some cases, the phosphorus-containing gas species reacts with a component of the reactor (e.g., the crucible) and / or a chemical sink (e.g., any chemical sink disclosed herein) to form an additional phosphorus-containing product. For example, in some instances, the phosphorus-containing gas species reacts with aluminum in the crucible to form aluminum phosphate. As another example, in certain cases, the phosphorus-containing gas species reacts with a magnesium carbonate chemical sink to form magnesium-calcium orthophosphate.

[0075] In some embodiments, the phosphorus-containing gas species and / or the additional phosphorus-containing product is relatively pure (e.g., at least 80 wt%, at least 85 wt%, at least 90 wt%, at least 95 wt%, at least 97 wt%, at least 98 wt%, at least 99 wt%, or 100 wt% pure). In certain embodiments, the phosphorus-containing gas species and / or the additional phosphorus-containing product is relatively free (e.g., less than 5 wt%, less than 4 wt%, less than 3 wt%, less than 2 wt%, less than 1 wt%, less than 0.5 wt%, less than 0.1 wt%, or 0 wt%) of toxic impurities (e.g., phosphogypsum) and / or radioactive impurities. In some cases, the phosphorus-containing gas species and / or the additional phosphorus-containing product comprises 0 wt% of toxic impurities and / or radioactive impurities.

[0076] In accordance with certain embodiments, the method comprises producing a sulfide. In some embodiments, the sulfide comprises a metal sulfide, such as an alkali metal sulfide, an alkaline earth metal sulfide, a transition metal sulfide, and / or a rare earth metal sulfide. For example, in some cases, the sulfide comprises a calcium sulfide. In some instances, the sulfide comprises an element, such as a metal, from the phosphate-containing compound. In

[0077] 12

[0078] #15070911vlcertain cases, the sulfide comprises an element, such as a metal, that was chemically bound to a phosphate anion in the phosphate-containing compound.

[0079] According to some embodiments, the method comprises producing a compound comprising sulfur, phosphorus, and oxygen, such as a sulfoapatite, a thiophosphate, and / or a sulfate-phosphate.

[0080] In accordance with certain embodiments, the method comprises producing a sulfatephosphate. In some cases, the sulfate-phosphate comprises a compound containing both distinct and separate sulfate anions (SO42) and phosphate anions (PO43), rather than a single linked hybrid ion. For example, in certain instances, the sulfate-phosphate comprises M(SO4)x(PO4)y(where M is a metal cation and x and y are both numbers), wherein both the sulfate and phosphate species coexist in the crystal lattice. In some embodiments, the sulfate-phosphate comprises a metal sulfate-phosphate, such as an alkali metal sulfate-phosphate, an alkaline earth metal sulfate-phosphate, a transition metal sulfate-phosphate, and / or a rare earth metal sulfate-phosphate. For example, in some cases, the sulfate-phosphate comprises a calcium sulfate-phosphate. In some instances, the sulfate-phosphate comprises an element, such as a metal, from the phosphate-containing compound. In certain cases, the sulfate-phosphate comprises an element, such as a metal, that was chemically bound to a phosphate anion in the phosphate-containing compound.

[0081] In accordance with certain embodiments, the method comprises producing a sulfoapatite. In some cases, the sulfoapatite comprises sulfide (S2) anions and phosphate anions both associating with the same cation. In some embodiments, the sulfoapatite comprises a metal sulfoapatite, such as an alkali metal sulfoapatite, an alkaline earth metal sulfoapatite, a transition metal sulfoapatite, and / or a rare earth metal sulfoapatite. For example, in some cases, the sulfoapatite comprises a calcium sulfoapatite. In some instances, the sulfoapatite comprises an element, such as a metal, from the phosphate-containing compound. In certain cases, the sulfoapatite comprises an element, such as a metal, that was chemically bound to a phosphate anion in the phosphate-containing compound.

[0082] In accordance with certain embodiments, the method comprises producing a thiophosphate. In some cases, the thiophosphate comprises a phosphorus surrounded by a mix of sulfur and oxygen. For example, in certain instances, the thiophosphate comprises a P5+bonded to one or more sulfur atoms and one or more oxygen atoms. In some embodiments, the thiophosphate comprises a metal thiophosphate, such as an alkali metal thiophosphate, an alkaline earth metal thiophosphate, a transition metal thiophosphate, and / or

[0083] 13

[0084] #15070911vla rare earth metal thiophosphate. For example, in some cases, the thiophosphate comprises a calcium thiophosphate. In some instances, the thiophosphate comprises an element, such as a metal, from the phosphate-containing compound. In certain cases, the thiophosphate comprises an element, such as a metal, that was chemically bound to a phosphate anion in the phosphate-containing compound.

[0085] In some embodiments, the sulfide and / or the compound comprising sulfur, phosphorus, and oxygen (such as a sulfoapatite, a thiophosphate, and / or a sulfate-phosphate) are solids.

[0086] According to certain embodiments, the method comprises producing CaS, Caio(P04)eS, and / or Ca2i-x(PO4)i4-2x(SO4)2x, where x is a number. For example, in some cases, the method comprises producing CaS, Caio(P04)eS, and Ca2i-x(PO4)i4-2x(SO4)2x, where x is a number.

[0087] In certain cases, the method comprises producing a phosphorus-containing fertilizer, an animal feed supplement, a ceramic, a pharmaceutical, a textile, and / or a battery from the phosphorus-containing gas species and / or from an additional phosphorus-containing product formed therefrom (e.g., by reaction with the crucible and / or a chemical sink). For example, in some instances, the method further comprises producing a phosphorus-containing fertilizer from the phosphorus-containing gas species and / or from an additional phosphorus-containing product formed therefrom (e.g., by reaction with the crucible and / or a chemical sink), such as a nitrogen-phosphorus-potassium (NPK) fertilizer.

[0088] According to some embodiments, the method comprises removing at least a portion of the phosphorus from the feedstock. For example, in some cases, the method comprises removing at least a portion of the phosphorus from the feedstock to mine the phosphorus from the feedstock, to remove a phosphorus impurity from the feedstock, and / or for a waste recycling process. In certain instances, the method can be used to mine phosphorus from feedstock even when the feedstock has low levels of phosphorus.

[0089] In some cases, the method comprises removing at least 10 wt%, at least 20 wt%, at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt%, at least 99 wt%, or at least 99.9 wt% of the phosphorus from the feedstock. In certain embodiments, the method comprises removing less than or equal to 100 wt%, less than or equal to 99.9 wt%, less than or equal to 99 wt%, less than or equal to 95 wt%, less than or equal to 90 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than

[0090] 14

[0091] #15070911vlor equal to 40 wt%, less than or equal to 30 wt%, or less than or equal to 20 wt% of the phosphorus from the feedstock. Combinations of these ranges are also possible (e.g., at least 10 wt% and less than or equal to 100 wt%, at least 50 wt% and less than or equal to 100 wt%, or at least 80 wt% and less than or equal to 100 wt%). In some cases, the method comprises removing 100 wt% of the phosphorus from the feedstock.

[0092] In accordance with some embodiments, the method comprises providing a chemical sink to the reactor. In some embodiments, the chemical sink comprises a reactor phase additive. In certain embodiments, the chemical sink comprises magnesium carbonate, magnesium oxide, potassium oxide, sodium oxide, potassium carbonate, sodium carbonate, aluminum oxide, silicon dioxide, and / or iron. For example, according to some embodiments, the chemical sink comprises magnesium carbonate (MgCCh).

[0093] In certain embodiments, the method comprises heating the chemical sink. For example, in some cases, the method comprises heating the reactor, the feedstock, the substance comprising sulfur, the gas-reactive species, and / or the chemical sink, such as at the temperatures disclosed herein for heating the reactor, feedstock, the substance comprising sulfur, and / or the gas-reactive species. For example, in some instances, the method comprises heating the feedstock, the substance comprising sulfur, the gas-reactive species, and the chemical sink (e.g., at the temperatures disclosed herein for heating the reactor, feedstock, the substance comprising sulfur, and / or the gas-reactive species).

[0094] In some embodiments, the chemical sink reacts with one or more reagents and / or products in the crucible and / or reactor to form an additional product. For example, in some cases wherein the chemical sink comprises magnesium (e.g., magnesium carbonate), the method comprises producing magnesium-calcium orthophosphate (MgsCasP^ie) and / or magnesium substituted sulfoapatite.

[0095] In certain embodiments, the reactor comprises a crucible. According to some embodiments, the crucible comprises aluminum, such as alumina. In certain cases, the crucible or a component thereof (e.g., aluminum) reacts with one or more reagents and / or products in the crucible to form an additional product. For example, in some instances where the crucible comprises aluminum (e.g., alumina), the method further produces aluminum phosphate.

[0096] In some embodiments, the method comprises determining the form of phosphorus in the feedstock (e.g., in an iron ore). For example, in some cases, the method comprises

[0097] 15

[0098] #15070911vldetermining the form of phosphorus in the feedstock based on what conditions can be used (e.g., mild or aggressive) to sulfidize the phosphate-containing compound.

[0099] In some embodiments, the method comprises controlling the phase of one or more (e.g., all) products, the distribution of phosphorus between them, and / or the speciation of phosphorus (e.g., when in the gas phase) by controlling one or more of the following conditions:

[0100] • Sulfidation potential (e.g., by controlling gas flow conditions, sulfur vapor, gas- reactive species presence, and / or mode of gas-reactive species delivery, such as CO, CS2, solid carbon, and / or carbon dissolved in iron);

[0101] • Temperature;

[0102] • Presence of another reducing agent such as reduced iron;

[0103] • Collector phases for collection of P in the solid phase, facilitating sulfide matte, and / or X-anion management; and / or

[0104] • Catalysis of P gas species conversion.

[0105] In some embodiments, the method comprises using mild sulfidation conditions (e.g., a lower temperature and / or a lower PS2 / PSO2 ratio). In certain embodiments, the method comprises using aggressive or intense sulfidation conditions (e.g., a higher temperature and / or a higher PS2 / PSO2 ratio, such as lower pSCh and / or higher S2). In some cases, mild sulfidation conditions are the temperature and PS2 / PSO2 ratio that produce sulfoapatite, while aggressive or intense sulfidation conditions are the temperature and PS2 / PSO2 ratio that produce calcium sulfide and phosphorus-containing gas.

[0106] Table 1 shows non-limiting examples of various possible product phase distributions.

[0107] Table 1. Non-limiting examples of various possible product phase distributions Treatment Final phases

[0108] Solid / Liquid Solid / Liquid Gas Gas species? Temp + 1 2

[0109] aMwOv■ bP2O5■ cMqXrS + M, S P, O, { / : / £ {P,O,S,C,X}}

[0110] (possibly C) S, C,

[0111] X

[0112] M, S M, P, O, X 0, s, { / : / £ {O,S,C,X}}

[0113] C, X

[0114] M, P, S, O, 0, s, { / : / £ {O,S,C,X}} X C, X

[0115]

[0116] 16

[0117] #15070911vlIn some embodiments, multiple elements are present for M (e.g., Mi and M2). In some such embodiments, the distribution of Mi and M2 across the phases (and their association with P) can also be varied, as shown in Table 2. In some cases, Table 2 is also applicable to a mixed-phase input.

[0118] Table 2. Non-limiting examples of various possible distributions of Mi and M2 across the phases.

[0119] aMwOlt> bPtOs■ cM<tXrTreatment Final phases

[0120] M = M2Solid / Uquid 1 Solid / Uquicf 2 Gas Gas species?

[0121] M2, S P, 0 ()•: !' & J Temp + , S, G x

[0122] OR

[0123] S + M2, S Mz, B 0, X 0, S, C. X r s CX}: 1 aMlwOv- bP2O5• cMt(Xr(possibly C) Mv S M2, P, 0.. X 0, s, q X ? y c {<9,

[0124] + M2O !>■ ■■ ’ / C-:

[0125]

[0126] Mx, M-., P, S, 0, X 0, S, G X

[0127] According to certain embodiments, the feedstock comprises a calcium phosphate apatite. In some such embodiments, mild sulfidation conditions (e.g., a combination of low gas-reactive species, low temperature, and sulfur gas) will achieve conversion to a mixed Ca-P-O-S solid product in the form of sulfoapatite, while more aggressive sulfidation conditions will fully sulfidize Ca to CaS and volatilize the P into the gas phase where, depending on the aforementioned conditions it may form pure P species, P-sulfides, or be collected by a receptor phase.

[0128] In accordance with some embodiments, the feedstock comprises iron ore. In some such embodiments, the phosphorus is present in the iron ore as either small calcium apatite grains or as iron phosphates itself. In some cases, these two different forms of bound phosphate may behave differently under the same sulfidization conditions determined by the relative stability of the two. For example, in certain instances, iron phosphate would convert to iron sulfide and P liberated to the gas phase or a receptor phase under relatively mild sulfidation conditions, whereas P in calcium phosphate apatite may require much more aggressive conditions to break down. In some instances, the method is applied to both forms to remove P present in both ores. In some cases, the method can also be used as a methodology of determining the form of phosphate present in the ore based on whether it is effective by mild sulfidation treatment.

[0129] In accordance with certain embodiments, the feedstock comprises lithium iron phosphate (LiFePC ). In some such embodiments, there is a mixed M (metal) orthophosphate. In some cases, mild sulfidation conditions would result in FeS and Li-Fe-P- 17

[0130] #15070911vlO slag, because while Fe has a higher sulfide affinity than Li or P, solution effects will partially dissolve it. In some instances, more moderate sulfidation conditions will result in FeS and LiPCU, full segregation of the phosphate to one of the cations. In some cases, more intense sulfidation would likely result in full / partial sulfidation of all elements resulting in Li-Fe sulfide phase and gaseous P products. Such a methodology could be applied to the recycling of lithium iron phosphate batteries, in accordance with some embodiments.

[0131] In certain embodiments, the feedstock comprises REEs (rare earth elements) / actinides in apatite. In some such embodiments, the REEs and actinides are concentrated in apatite ores. In some embodiments, the method comprises selectively converting these metals to sulfides while retaining calcium phosphates. In some cases, more intense sulfidation conditions would result in a mixed M-P-O-S thiophosphate phase. In certain cases, even more intense conditions would eventually achieve volatilization of P into the gas phase. In some instances, the method may be applied to the selective extraction of dilute rare earths from REE rich apatite ores or the purification of said ores by selective removal of radioactive or toxic elements, for example prior to conversion to fertilizer.

[0132] According to some embodiments, the method comprises a continuous process.

[0133] According to certain embodiments, the method comprises a batch- wise process.

[0134] In accordance with certain embodiments, the method further comprises electrolysis. In accordance with some embodiments, the reaction is in a liquid phase.

[0135] In some cases, the method does not involve reduction of the phosphate-containing compound to phosphorus, which may be energy and / or carbon intensive. In certain instances, the method does not involve the dilution of the phosphate-containing compound and / or the complete dissolution of the phosphate-containing compound into acid, which may be water and / or waste intensive.

[0136] In some embodiments, the disclosed method allows for controlled conversion of calcium (oxy / hydroxy / fluor-) apatite (Caio(P04)eX, X=O,C1,OH,F, vacancy) to sulfides (CaS), sulfoapatites (Caio(P04)eS), and sulfate-apatites (Ca2i-x(PO4)i4-2x(SO4)2x) via sulfidation. In some cases, it uses gas flow conditions, sulfur vapor and the presence of carbon to control the gas atmosphere’s sulfidizing potential (pSO2 / pS2). Along with temperature and collector phases, these three levers control the equilibrium and kinetic conditions, in accordance with certain embodiments. Variation of these conditions determines the product, and consequently, the degree of liberation of the phosphate, according to some embodiments.

[0137] 18

[0138] #15070911vlIn certain embodiments, the disclosed method comprises reacting calcium apatites with sulfur gas in a sulfidation process to produce calcium sulfide, calcium sulfoapatite, and calcium sulfate- substituted apatite. In certain cases, control of process conditions such as sulfur atmosphere, carbon presence, temperature and receptor phases determine the end products and as a result the degree of liberation of phosphate from the calcium. In some instances, the applications of the disclosed method are towards novel extraction of phosphate from apatite phosphate ores for fertilizer applications, novel forms of phosphate fertilizer, and phosphate impurity removal in other mineral extraction processes in which apatite occurs as gangue.

[0139] According to some embodiments, the method disclosed herein can be applied to the extraction and / or conversion of phosphate locked in primary or secondary phosphate sources - for the creation of phosphate products or intermediates, for example for fertilizer applications. Additionally, in some instances, the methods disclosed herein can be applied to the purification / separation of apatite impurities in other primary and secondary mineral extraction streams, for example to recover and liberate calcium compounds. According to certain embodiments, the method disclosed herein does this by in-situ converting the (oxy / hydroxy / fluor-) apatite structure into various end products (sulfides, sulfoapatites, sulfateapatites), which can be tailored to suit physical separation needs and / or create new viable forms of phosphate products for end use applications or intermediates for further processing.

[0140] Some phosphate extraction from calcium (oxy / hydroxy / fluor-) apatite for fertilizer applications requires large volumes of water and acid and produces high volume toxic waste products such as phosphogypsum. This process is called the wet acid process. In some instances, the method disclosed herein solves this problem by converting the apatite into useable and / or more extractable forms while minimizing the dilution that occurs, thereby minimizing the volume of waste and degree of re-concentration for valuable end products. Some methods for phosphate extraction involve reduction to elemental phosphorus then reoxidation to phosphoric acid (sometimes used for higher purity chemical applications). The reduction, then re-oxidation is an energetically costly process that the method disclosed herein avoids, in accordance with certain embodiments, by separating the phosphate via sulfidation which does not completely reduce the phosphate.

[0141] Calcium (oxy / hydroxy / fluor-) apatite is a common gangue / impurity in other mineral extraction pathways (both primary and secondary). Of note, in existing iron production and

[0142] 19

[0143] #15070911vlrecycling, ineffective physical separation of phosphate impurities in source material results in phosphorus contamination in later iron products that must be removed. In some embodiments, the method disclosed herein allows for the segregation then improved physical separation of the phosphate earlier on in an extraction pathway.

[0144] Finally, in certain cases, the sulfoapatites and sulfate-apatite products themselves are potential novel forms of phosphate fertilizer. Climate change and growing populations both pose challenges to global agriculture. Some phosphate fertilizers produced via the wet acid process are water soluble often leading towards run-off, causing overapplication and eutrophication in local water sources. Modified apatite products could help meet the call for more slow-release fertilizers, in accordance with certain embodiments. Furthermore, in some instances, the sulfur present in these products would also be beneficial as sulfur has been shown to be a positive additive for agriculture.

[0145] In certain embodiments, the method disclosed herein provides new tools to drive or prevent sulfidation of apatite such as carbon presence, receptor phases, and higher temperatures. The more aggressive sulfidation conditions that these provide allow for example the sulfidation of the oxygen associated with calcium itself and thereby liberation of phosphate, according to some embodiments.

[0146] In accordance with certain embodiments, this method of phosphate extraction avoids the reduction of phosphate to P (energy / carbon intensive) and it avoids the dilution of the phosphate via complete dissolution into acid (“volumetrically” / water / waste intensive).

[0147] In some embodiments, the method of producing sulfoapatites and sulfate-apatite disclosed herein utilizes more levers and more rigorous methodology for precise control of the product and degree of conversion, and allows to form phases in conditions that had not been observed before.

[0148] Methods

[0149] According to certain embodiments, the method disclosed herein allows for controlled conversion of calcium (oxy / hydroxy / fluor-) apatite (Caio(P04)eX, X=O, Cl, OH, F, vacancy) to sulfides (CaS), sulfoapatites (Caio(P04)eS), and sulfate-apatites (Ca2i-x(PO4)i4-2x(SO4)2x) via sulfidation. In some cases, it uses gas flow conditions, sulfur vapor and the presence of carbon to control the gas atmosphere’s sulfidizing potential (PSO2 / PS2). Along with temperature and collector phases, these three levers control the equilibrium and kinetic conditions, in certain instances. Variation of these conditions determines the product, and as

[0150] 20

[0151] #15070911vla consequence, the degree of liberation of the phosphate, in accordance with some embodiments.

[0152] The following examples are intended to illustrate certain embodiments of the present invention, but do not exemplify the full scope of the invention.

[0153] EXAMPLE 1

[0154] A. Sulfidation of tricalcium phosphate in an alumina crucible

[0155] 0.3 grams of beta-tricalcium phosphate (Ca3(PO4)2), a proxy for calcium (oxy / hydroxy / fluor-) apatite was reacted with sulfur gas at 1400C, under argon flow rate of 500sccm, in the presence of graphite, in an alumina crucible, for 40 minutes with an estimated inlet sulfur gas partial pressure of 0.1-0.4 atm. This experiment was conducted in an induction furnace outfitted with components designed specifically for sulfidations, (see FIGs. 1A, IB, 1C, and ID). The color change was noted from white to grey / pink / brownish powder (see FIG. 2). The product was analyzed via X-ray Diffraction and showed the presence of calcium sulfide, calcium sulfoapatite, and aluminum phosphate (see FIG. 3).

[0156] Results described herein show that the sulfidation conditions could be made aggressive enough such that sulfur substituted oxygen directly associated with calcium in the tricalcium phosphate, resulting in the partial release of phosphate and formation of calcium sulfide, sulfoapatite, and some aluminum phosphate from gaseous phosphate reacting with the crucible material.

[0157] Without wishing to be bound by theory, it is believed that the following reactions were achieved in this example:

[0158] 10 / 3 Ca3(PO4)2(s) + 11 / 12 S2(g) Caio(P04)6S(S) + P40e(g) C

[0159]

[0160] a3(PO4)2(s) + 9 / 2 S2(g) 3 CaS(S)+ 4 SO2(g) + 2 PS(g) 2 Ca3(PO4)2(s) + 3 MgCO3(S) + 3 S2(g) Ca3Mg3(PO4)4(s) + 3 CaS(S) + 3 SO2(g) + 3 CO(g) However, without wishing to be bound by theory, it is also believed that the following reactions may have been achieved in this example:

[0161] 3.33 C

[0162]

[0163] a3(PO4)2+ 0.75S2Caio(P04)6S + 0.5 SO2+ P2O5

[0164] Ca3(PO4)2+ 2.25 S

[0165]

[0166] 23 CaS+ 1.5 SO2+ P2O5

[0167] This example indicated a wide range of options in controlling the distribution of phosphate with the sulfoapatite acting not solely as end product but also as an intermediate. The presence of carbon and higher temperature facilitated this work.

[0168] 21

[0169] #15070911vlB, Sulfidation of tricalcium phosphate with magnesium carbonate receptor

[0170] 0.5 grams of beta-tricalcium phosphate (Cas PC ), a proxy for calcium (oxy / hydroxy / fluor-) apatite was mixed with 0.55 grams of magnesium carbonate (MgCCh) and reacted with sulfur gas at 1100 °C, under argon flow rate of 700 seem, in a graphite crucible, for about 40 minutes, with an estimated inlet sulfur gas partial pressure of 0.05-0.15 atm. The product was analyzed using scanning electron microscopy and electron dispersive spectroscopy. This analysis revealed the formation of calcium sulfide (CaS), magnesiumcalcium orthophosphate (MgsCasP^ie) and magnesium substituted sulfoapatite (see FIG. 4). This experiment further innovates how sulfidation can be used to form sulfides and sulfoapatite and as a result shift the association of phosphate. In particular, the use of the receptor phase of magnesium carbonate showed how receptor phase additives may be used to influence the thermodynamic favorability of the reaction and may be used as a sink for the liberated phosphate.

[0171] EXAMPLE 2

[0172] TCP (tri-calcium phosphate) was treated at 1200 °C for 100 min with argon gas flow rate of 1 L / min under various conditions: under carbo-sulfidation conditions - sulfidation with added solid graphite, achieving (pSCh / pS2 ) ~= (IO-12, 0.2) (FIG. 6A), under sulfidation conditions - only sulfur, pS2 ~= 0.2 (FIG. 6B), and under carbothermic reaction conditions (only graphite), pS2 = 0 (FIG. 6C).

[0173] IR gas analysis measured % CO<g) in reactor off gas during the carbo-sulfidation reaction. This concentration, along with the controlled pS2 was used to calculate that loglO(pS02)= -12, using reaction [1], Based on the predominance diagram in FIGs. 5A-5C, it was believed that PS<g) was created.

[0174] SO2 (g) + 2 C(S) --> 2 CO(g) + Vi S2(g) [1]

[0175] The total CO(g) measured over the experiment was compared to the total loss of P from the solid, and this indicated that P was not bound to O while in the gas phase.

[0176] Sulfur deposits collected from the top of the furnace tube (FIG. 7) reacted with water producing H2S <g) and H3PO4 (aq). This agreed with reaction [2], which supported that the phosphorus was condensed as a phosphorus-sulfide from the gas phase.

[0177]

[0178] P2S5(s) + 8 H2O(i) 2 H3PO4(aq) + 5 H2S(g)[2]

[0179] 22

[0180] #15070911vlIt should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific implementations described above. The specific implementations described above are disclosed as examples only.

[0181] While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and / or methods, if such features, systems, articles, materials, and / or methods are not mutually inconsistent, is included within the scope of the present invention.

[0182] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0183] 23

[0184] #15070911vlAs used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0185] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0186] As used herein, “wt%” is an abbreviation of weight percentage.

[0187] Some embodiments may be embodied as a method, of which various examples have been described. The acts performed as part of the methods may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and / or that may involve performing some acts simultaneously, even though the

[0188] 24

[0189] #15070911vlacts are shown as being performed sequentially in the embodiments specifically described above.

[0190] Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

[0191] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

[0192] 25

[0193] #15070911vl

Claims

CLAIMSWhat is claimed is:

1. A method, comprising:a. providing a feedstock comprising a phosphate-containing compound to a reactor; b. providing a substance to the reactor, wherein the substance comprises sulfur; and c. heating the feedstock, the substance comprising sulfur, and a gas-reactive species to induce sulfidation of the phosphate-containing compound, producing a phosphorus-containing gas species, a sulfide, and / or a compound comprising sulfur, phosphorus, and oxygen.

2. The method of claim 1, wherein the gas-reactive species comprises a carbon-containing compound, a carbonyl-containing compound, carbon monoxide, carbon dioxide, carbonyl sulfide, carbon fluoride, carbon chloride, carbon iodide, carbon bromide, silicon sulfide, aluminium sulfide, gallium sulfide, an arsenide, magnesium and / or a volatile compound comprising magnesium, calcium and / or a volatile compound comprising calcium, sodium, potassium, and / or lithium.

3. The method of any preceding claim, wherein the gas-reactive species comprises a carbon-containing compound.

4. The method of any preceding claim, wherein the gas-reactive species comprises graphite.

5. The method of any preceding claim, wherein the substance comprising sulfur comprises a gas comprising sulfur, a solid comprising sulfur, and / or molten sulfur.

6. The method of any preceding claim, wherein the substance comprising sulfur comprises S2 gas.

7. The method of any preceding claim, wherein heating the feedstock, the substance comprising sulfur, and the gas-reactive species comprises heating at greater than or equal to 500 °C and less than or equal to 2000 °C.26#15070911vl8. The method of any preceding claim, wherein producing the phosphorus-containing gas species, the sulfide, and / or the compound comprising sulfur, phosphorus, and oxygen comprises producing (i) the phosphorus-containing gas species and (ii) the sulfide and / or the compound comprising sulfur, phosphorus, and oxygen.

9. The method of any preceding claim, wherein the phosphate-containing compound comprises calcium apatite, wherein the calcium apatite comprises Caio(P04)eX, wherein X is selected from O, Cl, OH, F, or vacancy.

10. The method of any preceding claim, wherein producing the phosphorus-containing gas species, the sulfide, and / or the compound comprising sulfur, phosphorus, and oxygen comprises producing the phosphorus-containing gas species, and wherein the method further comprises producing a phosphorus-containing fertilizer from the phosphorus-containing gas species.

11. The method of any preceding claim, wherein the reactor comprises a crucible.

12. The method of claim 11, wherein the crucible comprises aluminum.

13. The method of claim 12, wherein the method further produces aluminum phosphate.

14. The method of any preceding claim, wherein the feedstock comprises an apatite phosphate ore and / or beta-tricalcium phosphate (Cas PC ).

15. The method of any preceding claim, wherein the substance comprising sulfur comprises a gas comprising sulfur and the method comprises providing the gas comprising sulfur at a partial pressure of greater than or equal to 0.01 atm and less than or equal to 1 atm.

16. The method of any preceding claim, wherein the substance comprising sulfur comprises a gas comprising sulfur and the method comprises providing the gas comprising sulfur at a flow rate of greater than or equal to 100 sscm and less than or equal to 10,000 sscm.27#15070911vl17. The method of any preceding claim, wherein the substance comprises a gas comprising sulfur and an inert carrier gas.

18. The method of any preceding claim, wherein heating the feedstock, the substance comprising sulfur, and the gas-reactive species comprises heating the feedstock, the substance comprising sulfur, the gas-reactive species, and a chemical sink.

19. The method of claim 18, wherein the chemical sink comprises magnesium carbonate, magnesium oxide, potassium oxide, sodium oxide, potassium carbonate, sodium carbonate, aluminum oxide, silicon dioxide, and / or iron.

20. The method of any preceding claim, wherein the method comprises removing at least a portion of the phosphorus from the feedstock.

21. The method of any preceding claim, wherein greater than or equal to 0.1 wt% of the feedstock is made up of the phosphate-containing compound.

22. A method comprising:a. providing a feedstock comprising calcium apatite to a reactor (crucible), wherein the calcium apatite comprises Caio(P04)eX, wherein X is selected from O, Cl, OH, F, or vacancy;b. producing a flow of a gas to the crucible wherein the gas comprises sulfur; andc. heating the reactants in the presence of a carbon compound to induce sulfidation;wherein a sulfide (CaS), sulfoapatite (Caio(P04)eS), and sulfate-apatite (Ca2i-x(PO4)i4-2x(SO4)2x) are produced by the reaction.

23. The method of claim 22, wherein the reaction produces a solid comprising CaS, Caio(P04)eS, and (Ca2i-x(PO4)i4-2x(SO4)2x.

24. The method of claim 22 or 23, wherein the carbon compound comprises graphite.28#15070911vl25. The method of any one of claims 22-24, wherein the heating is performed at 1000C to 1500C.

26. The method of claim 25, wherein the heating uses an induction furnace.

27. The method of any one of claims 22-26, wherein crucible comprises aluminum.

28. The method of claim 27, wherein the reaction further produces aluminum phosphate.

29. The method of any one of claims 22-28, wherein the gas further comprises an argon carrier gas.

30. The method of any one of claims 22-29, wherein the gas is at a flow rate of 400 to lOOOsccm.

31. The method of any one of claims 22-30, wherein the sulfur is at a partial pressure of 0.01-1.0 atm.

32. The method of any one of claims 22-31, further comprising providing magnesium carbonate (MgCCh) to the crucible.

33. The method of claim 32, wherein MgCCh is used as a sink for the phosphate produced by the reaction.

34. The method of claim 33, wherein magnesium-calcium orthophosphate (MgsCasP^ie) and magnesium substituted sulfoapatite are produced by the reaction.

35. The method of any one of claims 22-34, wherein the feedstock comprises betatricalcium phosphate (Cas PC ).

36. The method of any one of claims 22-34, wherein the method comprises a continuous process.29#15070911vl37. The method of any one of claims 22-34, wherein the method comprises a batch-wise process.

38. The method of any one of claims 22-34, wherein the method further comprises electrolysis.

39. The method of claim 38, wherein the reaction is in a liquid phase.

40. The method of any one of claims 22-39, wherein the feedstock comprises apatite phosphate ores.

41. A phosphate fertilizer, wherein the fertilizer comprises a product of the method of any one of claims 22-39.

42. A mineral extraction process, wherein a phosphate impurity removal comprises the method of any one of claims 22-39.30#15070911vl

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