Recovery of phosphorus compounds and iron compounds from iron phosphate-containing materials

Abstract

The invention relates to a process for obtaining phosphorus compounds and iron compounds from iron phosphate-containing materials, characterized by i) reacting an iron phosphate-containing material with chlorine gas in the presence of a carbon source at a temperature of 300 to 900°C and ii) removing the formed chlorophosphorus compounds, more particularly phosphorus oxychloride and optionally phosphorus trichloride and iron chloride in an off-gas flow, and iii) branching off from the off-gas flow the iron chloride and iv) separating off the chlorophosphorus compounds.

Description

[0001] Recovery of phosphorus and iron compounds from iron phosphate-containing materials

[0002] The invention relates to a process for the recovery of phosphorus and iron compounds from iron phosphate-containing materials.

[0003] Lithium iron phosphate (LFP) and lithium iron manganese phosphate (LFMP) as well as their modifications, which may be doped with other elements, especially metals, are known as cathode materials - also called cathode active materials (CAM) - for batteries and are preferably used in electric vehicles and stationary batteries.

[0004] Because the lithium-ion battery market is growing rapidly, and each car battery contains between 100 kg and 200 kg of CAM, the amount of valuable components such as lithium, phosphorus, iron, and other ingredients is also large, making the recycling of such used batteries to recover these raw materials very important. Lithium, an element whose demand has increased in recent years, is particularly important here. Also important is the phosphorus it contains, which is considered a critical raw material in many regions of the world.

[0005] During the recycling process, the battery cells are typically mechanically disassembled as far as possible, and the remainder, containing the cathode and anode materials, possibly binders, and other components, is crushed into a mass that is black due to the dark LFP and the carbonaceous, particularly graphite-containing, anode material, and is therefore called "black mass." Due to incomplete technical separation, the black mass may also contain residues of other battery components, such as metals.

[0006] Various approaches for recycling LFP-containing black mass or pure, spent LFP are proposed in the literature. For example, in Qifang Sun et al., Journal of Alloys and Compounds 818, (2020), 153292, the spent LFP-containing material is thermally treated, producing a low-Li material that is to be converted back into LFP by the appropriate addition of Li carbonate and a carbon source. However, the resulting low-Li starting product is very vague, resulting in a correspondingly vague LFP. The same applies to the process according to Lingyu Guan et al. in Renewable Energy, 175 (2021), 559-567, in which the LFP released during recycling, together with special Li, Fe, and P reactants and a carbon source, leads to a mixture of old and new LFP, which is also difficult to specify.

[0007] Other processes oxidize the iron(II) contained in LFP to iron(III) in various ways, such as with hypochlorite, peroxodisulfate, or H2O2 in the presence of acids, and extract the lithium released from the crystal form. The latter is described, for example, in Yang, Yongxia; Meng, Xiangqi; Cao, Hongbin; Lin, Xiao; Liu, Chenming; Sun, Yong; Zhang, Yi; Sun, Zhi, Green Chemistry 20 / 13, (2018), 3121-3133. However, the usually contaminated iron phosphate (FP), which is also produced, can only be used to a limited extent in the production of LFP due to the presence of impurities. Due to the exclusive recovery of lithium in the above-mentioned processes, only a small mass fraction of the LFP used is reused, which means that the issue of LFP and LFMP recycling can be considered unresolved.

[0008] The processes in which lithium is separated from LFP and / or LFMP or a black mass containing them have in common that a proportionally large, more or less pure residue of iron phosphate-containing material remains, which must be further processed.

[0009] The object of the present invention was therefore to find a process for the extraction of phosphorus and iron compounds from iron phosphate-containing materials, which does not require large waste streams and thus enables the recycling of iron phosphate-containing material, regardless of its origin.

[0010] The invention therefore relates to a process for the recovery of phosphorus and iron compounds from iron phosphate-containing materials, characterized in that i) an iron phosphate-containing material is reacted with chlorine gas (Ch) in the presence of a carbon source at a temperature of 300 to 900°C and ii) the chlorophosphorus compounds formed, in particular phosphorus oxychloride and optionally phosphorus trichloride and iron chloride are discharged in the exhaust gas stream, and from the exhaust gas stream iii) the iron chloride, preferably by resublimation and iv) the chlorophosphorus compounds, in particular phosphorus oxychloride and optionally phosphorus trichloride, preferably by condensation, are separated.

[0011] The process according to the invention is preferably suitable for obtaining chlorophosphorus compounds, in particular phosphorus oxychloride and optionally phosphorus trichloride and chloroiron compounds, in particular iron(II) chloride.

[0012] Iron phosphate and iron phosphate-containing material

[0013] Iron phosphate in the sense of this invention is understood in particular as a compound which consists of at least 97 wt.%, particularly preferably at least 99.5 wt.%, of the elements iron, phosphorus, manganese, aluminum, nickel, titanium and oxygen, in particular of the elements iron, phosphorus, manganese and oxygen and particularly preferably of the elements iron, phosphorus and oxygen. In the crystal structure of the iron phosphate in the sense of this invention, lattice sites of the iron can also be partially occupied by one or more of the above-mentioned metal ions. The iron phosphates can also be present as hydrates. The iron phosphate can preferably be iron(III) phosphate FePO4, in particular FePO4 2H2O, iron(II) phosphate, in particular Fe3(PO4)2 8H2O and iron(III) pyrophosphate, in particular Fe4(P2O?)3, as well as compounds of the general formula Fe x Me yPO4, where Me is understood to mean manganese, aluminum, nickel and titanium, especially manganese, where x is between 0 <x<3 und y zwischen 0<y<2,5 liegt. Besonders bevorzugt kann das Eisenphosphat Eisen(lll)-phosphat FeRCU, insbesondere FePO4'2H2O, Eisen(ll)-phosphat, insbesondere Fes PO^ SFW und Eisen(lll)-pyrophosphat, insbesondere Fe4(P2O?)3 sein.

[0014] As iron phosphate-containing material, a material containing a proportion of 5 to 100 wt.%, preferably 40 to 99 wt.%, in particular 50 to 99 wt.%, particularly preferably 70 to 99 wt.% of iron phosphate is used for the process according to the invention.

[0015] Preferably, a material is used which contains a proportion of 5 to 100 wt.%, preferably 40 to 99 wt.%, in particular 50 to 99 wt.%, particularly preferably 70 to 99 wt.% of at least one iron phosphate from the group consisting of iron(III) phosphate FePO4, iron(II) phosphate, in particular Fe3(PO4)2'8H2O, FePO4'2H2O and iron(III) pyrophosphate, in particular Fe4(P2O?)3 or Fe x Me y PO4, where Me is understood to mean manganese, aluminum, nickel and titanium, especially manganese, and x is between 0 <x<3 und y zwischen 0<y<2,5 liegt.

[0016] Preferably, the proportion of LFP and LFMP in the iron phosphate-containing material is less than 1 wt.%.

[0017] Preferably, the description of the composition of the material used is also possible by determining the weight proportion of certain elements in the iron phosphate-containing material, in each case based on the amount of iron phosphate-containing material, wherein the material used preferably contains:

[0018] 1 to 38 wt% Fe,

[0019] 1 to 30 wt% P,

[0020] 0 to 35 wt% Mn,

[0021] 0 to 35 wt% AI,

[0022] 0 to 35 wt% Ni,

[0023] 0 to 35 wt% Ti,

[0024] 0 to 55 wt.%, preferably 0 to 40 wt.%, in particular 1 to 30 wt.% carbon.

[0025] These amounts can originate from the iron phosphate itself, but also from other components of the material used, such as residues of metallic components or parts of the anode, which may still be present in the black mass even after the Li has been dissolved out. Other doping elements may also be present. The determination of the elemental fractions is preferably carried out using classical methods of elemental analysis.

[0026] The iron phosphate-containing material used preferably has a water content of less than 1 wt.%.

[0027] The iron phosphate-containing material used is preferably obtained as a residue from a reaction of LFP and / or LFMP or a black mass containing them, preferably with H2O2 in the presence of an acid, preferably a C1-C8 carboxylic acid, in particular aliphatic carboxylic acid, particularly preferably acetic acid, whereby the LFP and / or LFMP-containing material has been largely freed of lithium and preferably has a Li content of less than 2 wt.%, in particular less than 1 wt.%, based on the material. Such a reaction preferably takes place at temperatures of 20 to 90°C.

[0028] The residue is preferably obtained over hours to days by continuous extraction of the iron phosphate-containing material.

[0029] Metals, preferably from 0 to 15 wt.%, preferably 0 to 5 wt.%, in particular Al, Cu, Co and Ni, can also be contained in the material used.

[0030] It is preferred that the iron phosphate-containing material used preferably contains less than 10 wt.%, in particular less than 1 wt.%, particularly preferably less than 0.1 wt.% of polymer particles, in particular plastic.

[0031] It is also preferred if the iron phosphate-containing material used contains less than 5 wt.% of PVDF (polyvinylidene fluoride) and / or other binders such as carboxymethylcellulose or alginates. The content of all binders is preferably less than 5 wt.%.

[0032] The VOC content of the iron phosphate-containing material used is preferably less than 1 wt.%, in particular less than 0.1 wt.%, particularly preferably less than 0.01 wt.%. VOCs (volatile organic compounds) are preferably understood to be organic compounds with boiling points in the range of 50 to 260°C at a standard pressure of 101.3 kPa.

[0033] The iron phosphate-containing material used preferably has an average particle size of 0.1 pm to 10 mm. Depending on the size, the particle size can be determined simply by sieving or, for smaller particles, by laser diffraction or laser scattering; the most suitable method is known to the person skilled in the art.

[0034] If the iron phosphate-containing material used has a binder content of greater than 1 wt.%, based on the material, it is preferably dissolved out by treatment with an organic solvent, in particular acetone, ethyl acetate, methyl ethyl ketone, tetrahydrofuran (THF), acetoacetic ester, acetylacetone, dioxane and / or acetic anhydride and mixtures thereof, in order to reduce the content to less than 0.1 wt.%.

[0035] If the iron phosphate-containing material contains a polymer content, especially plastic, of greater than 1 wt.%, it is advantageous to first subject the material to a thermal treatment at a temperature of 300 to 600°C, preferably under an inert gas, in order to reduce the polymer content to less than 0.1 wt.%. A possible binder content of greater than 1 wt.% can be reduced to less than 0.1 wt.% by leaching with organic solvents, or alternatively or additionally, by a thermal treatment at a temperature of 300 to 700°C, preferably under an inert gas.

[0036] In principle, any modification of carbon can be used as a carbon source, such as graphite, soot, coal, coke, activated carbon, but also carbon-containing gases such as carbon monoxide, methane, or phosgene, as well as liquid materials such as polyethylene glycol or various oils, or solid materials such as biowaste or sewage sludge. Sewage sludge is particularly preferred. This preferably contains carbon in a proportion of at least 5 wt.%, preferably 20 to 50 wt.%, based on the dry mass.

[0037] For the purposes of the present invention, the term "sewage sludge" refers to any suspension of finely divided particles of a solid substrate in a liquid. Preferably, the sewage sludge contains a carbon content, expressed as a weight percent elemental carbon, of at least 5 weight percent carbon. In a preferred embodiment, the liquid in which the particles are suspended is wastewater as defined herein. The term "wastewater" refers to all liquids of an aqueous and / or organic nature, or mixtures thereof, that do not meet drinking water quality standards.

[0038] In a particular embodiment, the sewage sludge is present as primary sludge, raw sludge, excess sludge, treated and / or stabilized sewage sludge (aerobic / anaerobic).

[0039] The term "biowaste" refers to all organic waste of animal or plant origin that is generated in a household or factory and can be broken down by microorganisms, soil-dwelling organisms, or enzymes. Examples of such waste include straw, sawdust, waxes, fats, and bird droppings.

[0040] The carbon source can be solid, liquid, or gaseous. The use of a solid carbon source is preferred.

[0041] If the carbon content of the carbon source is less than 70 wt.%, pyrolysis is preferably carried out prior to the reaction with chlorine gas. This is preferably carried out under an inert gas such as nitrogen at temperatures of 250 to 800°C, preferably at 350 to 550°C, until the gas formation of volatile components is less than 1 / 1 kg of carbon source used per hour.

[0042] Sewage sludge is particularly preferred as a carbon source.

[0043] Preferably, the chloride content in the carbon source, in particular based on its dry weight, is less than 1 wt.%.

[0044] If the iron phosphate-containing material used, for example because it originates as a residue from the Li depletion of LFP and / or LFMP or in particular a black mass containing them, already contains at least part of the carbon source, then it particularly preferably contains 1 to 55 wt.%, preferably 1 to 40 wt.%, in particular 1 to 30 wt.% of carbon, in particular graphite and / or carbon black.

[0045] The sum of iron phosphate and carbon, based on the iron phosphate-containing material, is preferably more than 70 wt.%, preferably more than 80 wt.%, particularly preferably more than 90 wt.%. The iron phosphate-containing material preferably contains a molar carbon-to-phosphorus ratio of greater than or equal to 1.5, preferably from 1.5 to 20, particularly preferably from 1.5 to 10, in particular from 1.5 to 5, most preferably from 1.5 to 4.

[0046] If the material used contains less than 1.5 mol of carbon per 1 mol of phosphorus, based on the iron phosphate contained in the material, it is preferable to add enough carbon to the material before the reaction to achieve the desired ratio.

[0047] reactor

[0048] The material to be used in the process according to the invention is preferably introduced into a reactor, which is preferably provided with a layer resistant to the reaction conditions to be established. Preferred reactor materials are reactors coated with nickel or graphite, or reactors made of quartz. Tubular reactors such as rotary tube reactors or other reactors can also be used. Particular preference is given to reactors that allow movement of the material during the reaction in order to ensure the most effective contact between the material and the chlorine gas. Fluidized bed reactors, rotary tube reactors, or a reaction in an extruder with screw propulsion are preferred.

[0049] In the case of a tubular reactor, the reactor length is preferably 0.2 to 40 m. The residence time in the reactor during the reaction generally depends on the temperature and the possibility of contact between the material and chlorine gas. The residence time in the reactor can range from one minute to 10 hours, for example. The process according to the invention can be operated as a batch or continuously.

[0050] Procedure:

[0051] Step i)

[0052] The reaction preferably takes place in the absence of air. Any air present in the reactor is preferably displaced by an inert gas, such as nitrogen, at the start of the reaction.

[0053] The reaction with chlorine gas takes place at a temperature of 300 to 900°C, in particular at 350 to 800°C. If the process is operated at a temperature of 300 to 320°C, it is advantageous to expel any iron chloride that has not completely escaped from the reactor by subsequently increasing the temperature to 350 to 400°C. The temperature increase preferably takes place after the content of phosphorus compounds in the exhaust gas, measured using a gas-phase IR spectrometer calibrated accordingly in weight percent, is less than 0.1 wt.%, in particular less than 0.01 wt.%.

[0054] The chlorine gas can be brought into contact with the material in various ways. Preferably, chlorine is passed over or through the material, whereby the material is preferably agitated during the reaction for effective conversion. This can take place in a rotary kiln or in a paddle dryer in which the material is agitated. The chlorine gas can also be passed through the material, which can be achieved, for example, in a fluidized bed or fixed bed. If necessary, the material can first be shaped for this purpose, for example by compacting or pelletizing. The reactor preferably has an outlet for the exhaust gas stream. The exhaust gas stream contains the gaseous reaction products, volatile constituents of the material, and excess chlorine gas, which can all be discharged from the reaction chamber.

[0055] The reaction is preferably terminated when the proportion of phosphorus compounds, preferably measured using a gas phase IR spectrometer calibrated accordingly in weight percent, is less than 0.1 wt.%, in particular less than 0.01 wt.%.

[0056] Step ii)

[0057] In addition to the chlorophosphorus compounds, in particular phosphorus oxychloride and possibly phosphorus trichloride, the exhaust gas stream also contains gaseous iron(III) chloride and possibly also AlCh, if aluminum is contained in the material used.

[0058] Step iii)

[0059] At a reaction temperature of 300 to 320°C, the proportion of ferric chloride in the exhaust stream is generally still comparatively small and only increases after a temperature increase to 350 to 600°C. Iron(I) chloride and also AlCl3, if the material used contains aluminum, can be separated from the exhaust stream and separated from each other, preferably by resublimation on surfaces of different temperatures. If the ferric chloride is present together with AlCl3 in the exhaust stream, the respective chlorides can also be fractionally resublimated on different surfaces at different temperatures due to their sufficiently different boiling points, thus allowing them to be separated very cleanly.

[0060] Preferred deposition temperatures for FeCh are less than or equal to 307°C, in particular between 150 and 300°C, and for AICI3 less than or equal to 150°C, in particular between 110 and 149°C.

[0061] The iron recovered by the process according to the invention in the form of iron(II) chloride can optionally be separated from adhering chlorophosphorus compounds. This can be done by treatment with acid such as sulfuric acid, preferably concentrated sulfuric acid, or by a thermal drying step or in another manner known to the person skilled in the art. Preferably, the iron chloride isolated from the iron(II) chloride in step iii) is reacted with sulfuric acid, whereby any chlorophosphorus compounds present are released and then optionally condensed.

[0062] It can then be converted into the desired raw material form of iron, for example, for the production of LFP and / or LFMP. Examples include iron sulfate, iron nitrate, iron phosphate, or various forms of iron oxide.

[0063] Alternatively, the iron chloride can be introduced directly as a gas stream into an aqueous medium containing sulfuric acid or nitric acid, even without being separated by resublimation, thereby resulting in the formation of the corresponding iron(II) sulfates or nitrates. If necessary, a suitable reducing agent is used in the reaction to obtain iron(II) sulfate, iron(II) nitrate, or iron(II) phosphate.

[0064] However, the separation of iron chloride from the exhaust stream by resublimation is preferred. Step iv)

[0065] In the process according to the invention, the chlorophosphorus compounds, preferably the phosphorus oxychloride and any phosphorus trichloride also formed, can be removed from the exhaust gas stream, preferably by means of a condenser, and any excess chlorine gas can be recycled.

[0066] Phosphorus oxychloride, which is gaseous at reaction temperature, and any phosphorus trichloride that may also be formed are separated from the exhaust stream using a condenser. Typically, a mixture of phosphorus oxychloride and phosphorus trichloride is formed, which can be further separated by distillation. This allows the phosphorus components to be recovered in a very pure form.

[0067] The process according to the invention is preferably characterized in that the exhaust gas stream derived from step ii) contains phosphorus trichloride and this is converted into phosphorus pentachloride as phosphorus trichloride-containing chlorophosphorus compounds from step iv) or after separation therefrom with chlorine gas at a temperature of 20 to 160°C.

[0068] A molar chlorine / phosphorus trichloride ratio of 1:20 is preferred.

[0069] The process according to the invention is preferably used for the recovery of phosphorus compounds in the form of chlorophosphorus compounds, in particular in the form of a mixture of phosphorus oxychloride and phosphorus trichloride.

[0070] Phosphorus oxychloride can be converted into polyphosphoric acid or phosphoric acid via a hydrolysis step, from which their salts are produced by neutralization as required, which can then be reused to produce LFP and / or LFMP.

[0071] Phosphorus oxychloride and phosphorus trichloride are usually present in the exhaust gas stream in a weight ratio of 10 to 1 to 1 to 10.

[0072] The chlorophosphorus compounds from the process according to the invention can be converted into phosphorus trichloride, the preferred starting material for phosphorus pentachloride formation, by conducting the process preferably above 500°C. It is also preferred to conduct the process at a carbon / phosphorus ratio greater than 3 mol / mol. In this way, the phosphorus trichloride / phosphorus oxychloride ratio can be increased to greater than 1.

[0073] If the process according to the invention is operated without a stoichiometric excess of chlorine and thus there is little to no chlorine in the exhaust gas stream, the exhaust gas stream containing the chlorophosphorus compounds, in particular phosphorus oxychloride and optionally phosphorus trichloride, can also be introduced into an aqueous solution, preferably after it has been freed from iron chloride, in order to obtain the corresponding acids of phosphorus, such as phosphoric acid esters and phosphonic acids, from which further phosphorus derivatives can then be produced if necessary.

[0074] After completion of the process according to the invention, the residue contains all components of the material used that are non-volatile under reaction conditions or their non-volatile reaction products, particularly in the form of chlorides, as well as unreacted iron phosphate-containing material and unreacted carbon. For further processing of the residue and recovery of valuable materials, the residue can be partially dissolved in water, preferably at a temperature of 10 to 40°C, and separated from insoluble components.

[0075] Insoluble residues from the process according to the invention include, in particular, graphite or other added or existing carbon, provided it was present in the material used, as well as, if applicable, titanium dioxide. The water-soluble components can then, if necessary after determining their possible existence, be separated and isolated from one another in the form of their sulfides, chlorides, phosphates, fluorides, or other precipitated compounds using the classic H2S separation process. Thus, manganese and aluminum, if present in the residue, as well as nickel, can be precipitated as sulfides at different pH values ​​and then, after drying, roasted in air to form the corresponding sulfates. The titanium can be separated in the form of dioxide in the insoluble residue.

[0076] The sulfates obtained can be reused for the production of iron phosphates in the sense of this invention.

[0077] Examples

[0078] Analysis: Analysis for phosphorus compounds, especially POCh and PCI3, is preferably performed using online IR in the exhaust stream. For this purpose, the gas stream from the reactor is passed through a glass cuvette that allows the passage of IR radiation over the widest possible spectral range, for example, by using windows made of a thalium compound. The mass fraction of phosphorus compounds in the exhaust stream can be determined by prior calibration (total evaporation of known PCI3 or POCh mass flows into a nitrogen gas stream with a known volume flow and quantification of characteristic bands in the IR spectrum).

[0079] The stated weight percentages of the various elements were determined using ICP-OES measurements. For this purpose, a weighed amount of the solid is first dissolved in a known amount of an acid, the concentration of the specified elements is determined using an ICP analyzer against a calibration measurement, and the element content in the solid is then calculated from this value.

[0080] Example

[0081] 120g of lithium iron phosphate is stirred with 1 liter of 1 molar acetic acid and 250g of 30% H2O2 for 30 minutes at room temperature. The precipitate is then filtered off with suction, washed three times with water, and dried.

[0082] 55g of the iron phosphate-containing material produced above (with the following analytical data: Fe 36 wt.%, P 21 wt.%, Li < 1 wt.%) are thoroughly mixed with 6.6g of finely ground activated carbon (dry carbon). The water content is <1 wt.%.

[0083] The powder mixture is heated to 600°C in a quartz bowl in a heated tube reactor (made of quartz glass, 120 mm diameter) under a nitrogen stream. The reactor is then switched to a chlorine gas flow of 100 ml / min. It is held at this temperature for 6 hours. After approximately 10 minutes of reaction time, two adsorption bands appear in the IR spectrum of the gas phase at 593 cm. -1 and at 1322 cm -1 , both of which can be assigned to POCI3.

[0084] The resulting iron chloride is separated from the exhaust stream on a surface cooled to 100°C along with some of the resulting POCl3. They are then collected together and reacted with sulfuric acid to form iron sulfate and phosphoryl chloride. The mixture is distilled.

[0085] The obtained iron sulfate can be used to produce new iron phosphate or LFP / LFMP.

[0086] The resulting distillate, consisting of POCl3, can be used in chemical processes, for example, for the production of phosphoric acid esters. POCl3 can also be used to produce polyphosphoric acid or phosphoric acid. Depending on the process, these are possible starting materials for the production of LFP or LFMP.

[0087] A residue of unreacted iron phosphate and excess carbon remains in the shell (total 22g).

Claims

1. A process for the recovery of phosphorus and iron compounds from iron phosphate-containing materials, characterized in that i) an iron phosphate-containing material is reacted with chlorine gas at a temperature of 300 to 900°C in the presence of a carbon source and ii) the chlorophosphorus compounds formed, in particular phosphorus oxychloride and optionally phosphorus trichloride and iron chloride, are discharged in the exhaust gas stream, and iii) the iron chloride and iv) the chlorophosphorus compounds are separated from the exhaust gas stream.

2. Process according to claim 1, characterized in that the iron chloride is separated from the exhaust gas stream in step iii) by resublimation.

3. Process according to claim 1 or 2, characterized in that the iron chloride isolated from the product in step iii) is reacted with sulfuric acid, whereby any chlorophosphorus compounds present are released and then optionally condensed.

4. Process according to at least one of claims 1 to 3, characterized in that the chlorophosphorus compounds, in particular phosphorus oxychloride and optionally phosphorus trichloride, are separated from the exhaust gas stream in step iv) by condensation.

5. The method according to at least one of claims 1 to 4, characterized in that the iron phosphate consists of at least 97% by weight, particularly preferably at least 99.5% by weight, of the elements iron, phosphorus, manganese, aluminum, nickel, titanium and oxygen, in particular of the elements iron, phosphorus, manganese and oxygen and particularly preferably of the elements iron, phosphorus and oxygen.

6. The method according to at least one of claims 1 to 5, characterized in that as iron phosphate at least one is selected from the group consisting of iron(III) phosphate FePO4, iron(II) phosphate, in particular FePO^FW, in particular Fe3(PO4)2'8H2O and iron(III) pyrophosphate, in particular Fe4(P2O?)3, as well as compounds of the general formula Fe x Me y PO4, where Me is understood to mean manganese, aluminum, nickel and titanium, especially manganese, and x is between 0 <x<3 und y zwischen 0<y<2,5 liegt.

7. The method according to at least one of claims 1 to 6, characterized in that the iron phosphate-containing material used is a material containing a proportion of 5 to 100 wt.%, preferably 40 to 99 wt.%, in particular 50 to 99 wt.%, particularly preferably 70 to 99 wt.% of iron phosphate.

8. The method according to at least one of claims 1 to 7, characterized in that the iron phosphate-containing material used is a material containing a proportion of 5 to 100 wt.%, preferably 40 to 99 wt.%, in particular 50 to 99 wt.%, particularly preferably 70 to 99 wt.% of at least one iron phosphate from the group consisting of iron(III) phosphate FePO4, iron(II) phosphate, in particular FePO4·2H2O, in particular Fe3(PO4)2·8H2O and iron(III) pyrophosphate, in particular Fe4(P2O?)3.

9. Method according to at least one of claims 1 to 8, characterized in that the iron phosphate-containing material used is a material containing 0 to 35 wt.% Mn, calculated as elemental manganese, 0 to 35 wt.% AI, calculated as elemental aluminum, 0 to 35 wt.% Ni, calculated as elemental nickel, 0 to 35 wt.% Ti, calculated as elemental titanium, 0 to 55 wt.%, preferably 0 to 40 wt.%, in particular 1 to 30 wt.% carbon.

10. Process according to at least one of claims 1 to 9, characterized in that the iron phosphate-containing material used is a material containing less than 1 wt.% Li, calculated as elemental lithium.

11. Process according to at least one of claims 1 to 10, characterized in that the carbon source is selected from the group consisting of graphite, soot, coal, coke, activated carbon, carbon monoxide, oils, methane, polyethylene glycol, biowaste, and in particular sewage sludge.

12. Process according to at least one of claims 1 to 11, characterized in that the iron phosphate-containing material contains 1 to 55% by weight, preferably 1 to 40% by weight of carbon, in particular graphite and / or activated carbon and / or carbon black.

13. The method according to at least one of claims 1 to 12, characterized in that the iron phosphate-containing material has a molar carbon-to-phosphorus ratio of greater than or equal to 1.5, preferably from 1.5 to 20, particularly preferably from 1.5 to 10, in particular from 1.5 to 5, very particularly preferably from 1.5 to 4.

14. Process according to at least one of claims 1 to 13, characterized in that the exhaust gas stream discharged in step ii) contains phosphorus oxychloride and phosphorus trichloride, preferably in a weight ratio of 10 to 1 to 1 to 10.

15. The method according to at least one of claims 1 to 14, characterized in that the iron chloride is deposited in step iii) at a temperature of less than or equal to 300°C.

Images