A method for regenerating waste containing iron phosphate

Abstract

The present invention provides a method for regenerating waste containing iron phosphate, the method comprising: (1) mixing waste containing iron phosphate and an acidic solution, separating solid from liquid, and obtaining an acidic leachate; (2) heating the acidic leachate and preserving the temperature to obtain a slurry containing iron phosphate precipitation; (3) solid-liquid separation of the slurry to obtain regenerated iron phosphate. The regeneration method separates iron phosphate from impurities by heating the acidic leachate and preserving the temperature to obtain the regenerated iron phosphate. The regeneration method has good quality and does not generate ammonia nitrogen wastewater or sodium salt wastewater due to the use of ammonia alkali or sodium alkali, and has good prospects for industrial application.

Description

Technical Field

[0001] The invention relates to the technical field of chemical metallurgy, and in particular to a method for regenerating waste containing iron phosphate. Background Art

[0002] Lithium iron phosphate batteries have developed rapidly in the new energy industry, including new energy vehicles and energy storage, due to their outstanding advantages such as good safety performance, long cycle life and low cost.

[0003] There are many preparation processes for lithium iron phosphate. The three mainstream technologies are solid-phase method based on iron phosphate, solid-phase method based on ferrous oxalate, and liquid-phase method based on ferric nitrate. As the key precursor of the first method, the quality of iron phosphate directly determines the performance of lithium iron phosphate. Iron phosphate is mainly prepared by wet synthesis. During the preparation process, due to abnormal raw material impurities, imbalanced ratios / calcination conditions and other process errors, the impurity / magnetic substance / sulfur content of the finished iron phosphate may exceed the standard, the iron-phosphorus ratio is unqualified, the morphology is abnormal, or there are impurities in the finished iron phosphate. These iron phosphates with abnormal quality cannot enter the downstream lithium iron phosphate battery production. If they are discarded directly, it will cause waste of resources and increase costs. Therefore, the regeneration of iron phosphate waste is of great significance to iron phosphate raw material production companies.

[0004] CN110683528A discloses a method for regenerating waste iron phosphate. The method comprises dissolving the waste iron phosphate with acid, filtering the waste iron phosphate, obtaining a solution containing iron and phosphorus, adjusting the iron-phosphorus ratio in the solution to 1:(0.9-1.02), adding an alkaline solution with stirring, adjusting the pH value to 2.0-2.5, reacting at 85-100°C, separating the solid and the liquid, washing the solid, obtaining an amorphous iron phosphate intermediate, further slurrying the amorphous iron phosphate intermediate, adding phosphoric acid, stirring and heating to convert the amorphous iron phosphate into crystalline iron phosphate. It is believed that the crystalline iron phosphate can be calcined to obtain battery-grade anhydrous iron phosphate.

[0005] CN112320780A discloses a method for recovering iron phosphate waste, which comprises the following steps: dissolving the collected iron phosphate waste in an acid solution and filtering to obtain an acidic leaching solution; adding an oxidant and a surfactant to the acidic leaching solution to obtain an oxidized leaching solution; adjusting the pH of the oxidized leaching solution to 1.0-1.5, filtering to obtain an iron phosphate residue; washing the iron phosphate residue, adding dilute phosphoric acid and stirring, aging and filtering to obtain iron phosphate crystals; washing the iron phosphate crystals and calcining to obtain battery-grade iron phosphate.

[0006] The existing method for recycling waste iron phosphate draws on the conventional two-step preparation process of iron phosphate in principle, that is, firstly, a ferrous source (such as FeSO4·7H2O) and a phosphorus source (such as (NH4)2HPO4) are reacted in an aqueous solution environment in the presence of an oxidant (such as hydrogen peroxide) to generate an amorphous iron phosphate precipitate, and the obtained amorphous iron phosphate precipitate is washed, and then the washed amorphous iron phosphate precipitate is added to a phosphoric acid solution and crystallized at 85-100°C to obtain dihydrate iron phosphate crystals, which are also washed again to remove the entrained free ions.

[0007] In the two-step preparation process, the precipitation of iron phosphate mostly requires the use of ammonia alkali or sodium alkali, and the use of ammonia alkali or sodium alkali brings about the problem of ammonia nitrogen wastewater or sodium salt wastewater treatment; moreover, impurities are easily co-precipitated with iron phosphate, and the impurity removal effect is poor.

[0008] In order to achieve green regeneration of iron phosphate waste, a new iron phosphate regeneration method needs to be developed. Summary of the invention

[0009] In view of the problems existing in the prior art, the present invention provides a regeneration method for waste containing iron phosphate. The regeneration method utilizes the characteristics of iron phosphate that it can crystallize and self-purify in an acidic environment, and that alcohol solvents and nucleation promoters can induce crystallization, and develops a method for regenerating waste iron phosphate. The method can regenerate waste iron phosphate into raw material for iron phosphate for batteries, has good impurity removal effect and does not cause problems in the treatment of ammonia nitrogen wastewater or sodium salt wastewater.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] The present invention provides a method for regenerating waste containing iron phosphate, the regeneration method comprising:

[0012] (1) mixing the iron phosphate-containing waste material and the acidic solution, separating the solid from the liquid, and obtaining an acidic leaching solution;

[0013] (2) the acidic leaching solution is heated and kept warm for precipitation to obtain a slurry containing iron phosphate precipitation;

[0014] (3) The slurry is subjected to solid-liquid separation to obtain regenerated iron phosphate.

[0015] The regeneration method provided by the present invention directly performs mixed leaching in an acidic solution and then heats and insulates for precipitation, thereby achieving precipitation and separation of iron phosphate and impurities, avoiding the use of ammonia alkali and / or sodium alkali, solving the problem of ammonia nitrogen wastewater or sodium salt wastewater treatment caused by the use of ammonia alkali and / or sodium alkali, and achieving green regeneration of iron phosphate.

[0016] Preferably, the acidic solution in step (1) comprises any one of sulfuric acid, hydrochloric acid or phosphoric acid, or a combination of at least two of them, wherein typical but non-limiting combinations are: a combination of sulfuric acid and hydrochloric acid, a combination of sulfuric acid and phosphoric acid, a combination of hydrochloric acid and phosphoric acid, and a combination of sulfuric acid, hydrochloric acid and phosphoric acid.

[0017] Preferably, the acidic solution contains H + The concentration is 0.4-12 mol / L, for example, it can be 0.4 mol / L, 0.7 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 2.0 mol / L, 3.0 mol / L, 4.0 mol / L, 6.0 mol / L, 8.0 mol / L, 10.0 mol / L or 12.0 mol / L, etc., preferably 1.0-8 mol / L, but not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0018] The present invention preferably contains H + The concentration is within a specific range to ensure efficient leaching of iron phosphate.

[0019] Preferably, the liquid-to-solid ratio of the mixture is (1-50):1 mL / g, for example, it can be 1:1 mL / g, 3:1 mL / g, 5:1 mL / g, 10:1 mL / g, 20:1 mL / g, 30:1 mL / g, 40:1 mL / g or 50:1 mL / g, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0020] Preferably, the mixing temperature is 20-60°C, for example, it can be 20°C, 25°C, 30°C, 34°C, 38°C, 40°C, 47°C, 52°C, 56°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0021] Preferably, the total iron ion concentration in the acidic leachate is 0.18 to 4.5 mol / L, for example, 0.18 mol / L, 0.2 mol / L, 0.5 mol / L, 0.75 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L or 4.5 mol / L, but not limited to the listed values, other unlisted values ​​within the range are equally applicable. By controlling the above-mentioned hydrogen ion concentration, it is preferred to obtain an acidic leachate with a total iron ion concentration in a specific range, with a high recovery rate of iron and a high purity of the final ferric phosphate product.

[0022] Preferably, the temperature of the heat preservation precipitation in step (2) is 65°C to the boiling point of the acidic leachate, for example, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 105°C or the boiling point of the acidic leachate, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable. It is preferred to use the above temperature in combination with the hydrogen ion concentration in the system, the addition of a nucleation promoter or an alcohol solvent, which is more conducive to forming a precipitation environment for iron phosphate.

[0023] Preferably, before heating in step (2), the acidic leachate and the acidic solution are first mixed to a H+ concentration of 1 to 5 mol / L, for example, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, 4.5 mol / L or 5.0 mol / L, etc., but not limited to the listed values, other unlisted values ​​within the range are also applicable. Preferably, the hydrogen ion concentration in the system is adjusted before heating and heat preservation precipitation to ensure that the system is in a strongly acidic environment, which is conducive to the subsequent separation of iron phosphate precipitation and impurities, and further improves the purity of iron phosphate.

[0024] Preferably, the acidic leaching solution and the alcohol solvent are mixed before the heating in step (2). Preferably, the alcohol solvent is added before the heating and heat preservation precipitation to adjust the solvent environment of the iron phosphate, promote the separation of the iron phosphate and impurities, and obtain battery-grade regenerated iron phosphate.

[0025] Preferably, the alcohol solvent comprises any one of methanol, ethanol, propanol or isopropanol or a combination of at least two thereof, wherein typical but non-limiting combinations are: a combination of methanol and ethanol, a combination of methanol and propanol, a combination of ethanol and propanol, a combination of methanol, ethanol and propanol, a combination of methanol, ethanol and isopropanol, and a combination of methanol, ethanol, propanol and isopropanol.

[0026] Preferably, the amount of the alcohol solvent added is 5-100% of the volume fraction of the acidic leaching liquid, for example, it can be 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%, etc., but is not limited to the listed values, and other values ​​not listed in this range are also applicable. It is further preferred that the amount of the alcohol solvent added is within the above range, which is more conducive to the formation of iron phosphate precipitation.

[0027] Preferably, before the heating in step (2), the acidic leaching solution and the nucleation promoter are mixed.

[0028] The present invention further preferably adds a nucleation promoter to further enhance the precipitation of iron phosphate in a strongly acidic system.

[0029] Preferably, the nucleation promoter includes any one or a combination of at least two of isobarbital iron phosphate, monoclinic iron phosphate, orthorhombic iron phosphate, α-quartz iron phosphate (also called hexagonal iron phosphate), monoclinic iron phosphate dihydrate or orthorhombic iron phosphate dihydrate, wherein typical but non-limiting combinations are a combination of isobarbital iron phosphate and monoclinic iron phosphate, a combination of orthorhombic iron phosphate and monoclinic iron phosphate, a combination of monoclinic iron phosphate dihydrate and orthorhombic iron phosphate, and a combination of α-quartz iron phosphate and orthorhombic iron phosphate dihydrate.

[0030] Preferably, before mixing the nucleation promoter and the acidic leaching solution, the nucleation promoter is firstly ground. The present invention further firstly grinds the nucleation promoter, so as to facilitate the regulation of the particle size and morphology of the iron phosphate.

[0031] Preferably, the added molar amount of the nucleation promoter is 0.01 to 10 times the total molar amount of iron in the solution before precipitation, for example, it can be 0.01 times, 0.1 times, 0.5 times, 1 times, 2 times, 3 times, 4 times, 5 times, 8 times or 10 times, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable. It is further preferred that the added amount of the nucleation promoter is within the above range, which is conducive to promoting the precipitation of iron phosphate and better avoiding impurity entrainment.

[0032] The acid solution, alcohol solvent and nucleation promoter supplemented in the present invention can be added simultaneously, or one or at least two can be added selectively, preferably all three are added simultaneously, which has a better regulating effect.

[0033] Preferably, the solid phase after the solid-liquid separation in step (3) is washed.

[0034] Preferably, the washing comprises washing with water.

[0035] Preferably, after the washing in step (3), the solid phase is further ground and calcined in sequence. The present invention further adds the grinding and calcining steps to better control the size of the final ferric phosphate product and further optimize the purity of the product.

[0036] Preferably, the grinding method comprises any one of ball milling, stirred milling or sand milling, or a combination of at least two of them, wherein typical but non-limiting combinations include a combination of stirred milling and sand milling, a combination of stirred milling and ball milling, and a combination of stirred milling, ball milling and sand milling.

[0037] Preferably, the grinding reaches a scale of an average particle size of 2 to 6 μm, such as 2 μm, 3 μm, 4 μm, 5 μm or 6 μm, etc., but not limited to the listed values, and other values ​​not listed in the range are also applicable, and the particle size is below 15 μm, such as 15 μm, 14 μm, 13 μm, 12 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm or 4 μm, etc., but not limited to the listed values, and other values ​​not listed in the range are also applicable. It can better meet the requirements for iron phosphate particle size and specific surface area when preparing lithium iron phosphate positive electrode materials.

[0038] Preferably, the calcination temperature in step (3) is 500-750°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C or 750°C, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0039] Preferably, the calcination time is 2 to 10 h, for example, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0040] Preferably, the precipitated liquid obtained by the solid-liquid separation in step (3) is returned to step (1) for recycling.

[0041] The present invention has no special restrictions on solid-liquid separation, and any method known to those skilled in the art for solid-liquid separation may be used, and may also be adjusted according to the actual process, such as centrifugal separation, filtration separation, or sedimentation separation.

[0042] As a preferred technical solution of the present invention, the regeneration method comprises the following steps:

[0043] (1) Mix the iron phosphate-containing waste and H at a liquid-to-solid ratio of (1-50): 1 mL / g + An acid solution with a concentration of 0.4 to 12 mol / L is mixed and leached at 20 to 60° C. After the mixed leaching, solid-liquid separation is performed to obtain an acidic leaching solution with a total iron ion concentration of 0.18 to 4.5 mol / L;

[0044] (2) adding any one or a combination of at least two of an acidic solution, an alcohol solvent or a nucleation promoter to the acidic leachate, heating the solution and keeping the temperature within a range of 65° C. to the boiling point of the acidic leachate to obtain a slurry containing iron phosphate precipitate;

[0045] When the acid solution is added, it is mixed into the system. +The concentration is 1 to 5 mol / L; when an alcohol solvent is added, the amount of the alcohol solvent added is 5 to 100% of the volume fraction of the acidic leaching liquid; when a nucleation promoter is added, the molar amount of the nucleation promoter added is 0.01 to 10 times the total molar amount of iron in the solution before precipitation;

[0046] (3) The solid phase obtained by solid-liquid separation of the slurry is then washed to obtain regenerated iron phosphate.

[0047] Further preferably, the liquid phase obtained by solid-liquid separation of the slurry is distilled to recover the alcohol solvent and the acidic solution, and the alcohol solvent can preferably be circulated to the heat preservation precipitation step; the acidic solution is circulated to the mixed leaching step; or the liquid phase obtained by solid-liquid separation of the slurry is directly returned to the mixed leaching step for the treatment of the next batch of iron phosphate-containing waste.

[0048] Further preferably, after washing, the solid phase obtained by solid-liquid separation of the slurry can be firstly ground to a particle size of 2 to 6 μm on average and the particle size is less than 15 μm, and then calcined at 500 to 750° C. for 2 to 10 hours to obtain regenerated iron phosphate. The particle size and product purity of the final regenerated iron phosphate can be further preferably controlled.

[0049] Compared with the prior art, the present invention has at least the following beneficial effects:

[0050] (1) The regeneration method of the iron phosphate-containing waste provided by the present invention can effectively ensure the quality of the regenerated iron phosphate, wherein the purity of the regenerated iron phosphate obtained is preferably above 99.9%, the recovery rate of phosphorus is above 67%, even as high as above 95%, and the recovery rate of iron is above 67%, even as high as above 95%;

[0051] (2) The method for regenerating waste containing iron phosphate provided by the present invention does not cause the problem of ammonia nitrogen wastewater or sodium salt wastewater generated by the use of ammonia alkali or sodium alkali, thereby realizing the green regeneration of iron phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a flow chart of the regeneration method of iron phosphate-containing waste provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0053] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0054] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0055] As a specific embodiment of the present invention, a method for regenerating waste containing iron phosphate is provided, such as Figure 1As shown, the regeneration method comprises the following steps:

[0056] (1) Mix the iron phosphate-containing waste and H at a liquid-to-solid ratio of (1-50): 1 mL / g + An acid solution with a concentration of 0.4 to 12 mol / L is mixed and leached at 20 to 60° C. After the mixed leaching, solid-liquid separation is performed to obtain an acidic leaching solution with a total iron ion concentration of 0.18 to 4.5 mol / L;

[0057] (2) After adding any one or a combination of at least two of an acidic solution, an alcohol solvent or a nucleation promoter to the acidic leaching solution ( Figure 1 The dotted line indicates that any one of them or a combination of at least two or more can be added), the temperature is raised and kept in a range of 65°C to the boiling point of the acidic leaching solution for precipitation to obtain a slurry containing iron phosphate precipitation;

[0058] When the acid solution is added, it is mixed into the system. + The concentration is 1 to 5 mol / L; when an alcohol solvent is added, the amount of the alcohol solvent added is 5 to 100% of the volume fraction of the acidic leaching liquid; when a nucleation promoter is added, the molar amount of the nucleation promoter added is 0.01 to 10 times the total molar amount of iron in the solution before precipitation;

[0059] (3) The solid phase obtained by solid-liquid separation of the slurry is then washed to obtain regenerated iron phosphate.

[0060] Further preferably, in the above specific implementation manner, Figure 1 As shown, the liquid phase obtained by solid-liquid separation of the slurry is distilled to recover the alcohol solvent and the acid solution. The alcohol solvent can preferably be recycled to the heat preservation precipitation step; the acid solution is recycled to the mixed leaching step.

[0061] Further preferably, in the above specific implementation manner, Figure 1 As shown, after washing, the solid phase obtained by solid-liquid separation of the slurry can be ground to a particle size of 2 to 6 μm on average and below 15 μm, and then calcined at 500 to 750° C. for 2 to 10 hours to obtain regenerated iron phosphate. The particle size and product purity of the final regenerated iron phosphate can be further preferably controlled.

[0062] Example 1

[0063] This embodiment provides a method for regenerating waste containing iron phosphate, the regeneration method comprising the following steps:

[0064] (1) Iron phosphate waste (iron content 38%, phosphorus content 18.53%, impurity content 1%, impurities mainly including aluminum, calcium and magnesium) and H were mixed at a liquid-to-solid ratio of 5:1 mL / g. +A sulfuric acid solution with a concentration of 3 mol / L is mixed and leached at 45° C. After the mixed leaching, filtration is performed to obtain an acidic leaching solution with a total iron ion concentration of 1.2 mol / L;

[0065] (2) The acidic leaching solution is placed in a precipitator, and sulfuric acid solution is added to the system. + The concentration is 4 mol / L, and methanol is added, the amount of methanol added is 25% of the volume fraction of the acidic leaching liquid, and the temperature is increased and kept at 75°C for precipitation to obtain a slurry containing iron phosphate precipitation;

[0066] (3) The solid phase obtained by filtering the slurry is then washed with water, ground to a particle size with an average particle size of 3.5 μm and a particle size of less than 15 μm, and calcined at 600° C. for 8 h to obtain regenerated iron phosphate.

[0067] Example 2

[0068] This embodiment provides a method for regenerating waste containing iron phosphate, the regeneration method comprising the following steps:

[0069] (1) Iron phosphate waste (iron content 38%, phosphorus content 18.53%, impurity content 1%, impurities mainly including aluminum, calcium, and magnesium) and H were mixed at a liquid-to-solid ratio of 2:1 mL / g. + A phosphoric acid solution with a concentration of 12 mol / L is mixed and leached at 60° C. After the mixed leaching, filtration is performed to obtain an acidic leaching solution with a total iron ion concentration of 3.35 mol / L;

[0070] (2) the acidic leaching solution is placed in a precipitator, and methanol is added, the amount of methanol added is 50% of the volume fraction of the acidic leaching solution, and at the same time, finely ground monoclinic ferric phosphate dihydrate is added in an amount twice the total molar amount of iron in the acidic leaching solution, and the temperature is raised and kept at 65° C. for precipitation to obtain a slurry containing ferric phosphate precipitation;

[0071] (3) The solid phase obtained by filtering the slurry is then washed with water, ground to a particle size with an average particle size of 2.5 μm and a particle size of less than 14 μm, and calcined at 500° C. for 10 h to obtain regenerated iron phosphate.

[0072] Example 3

[0073] This embodiment provides a method for regenerating waste containing iron phosphate, the regeneration method comprising the following steps:

[0074] (1) Iron phosphate waste (iron content 38%, phosphorus content 18.53%, impurity content 1%, impurities mainly including aluminum, calcium, and magnesium) and H were mixed at a liquid-to-solid ratio of 35:1 mL / g. +A sulfuric acid solution with a concentration of 0.4 mol / L is used for mixed leaching at 20° C. After the mixed leaching, filtration is performed to obtain an acidic leaching solution with a total iron ion concentration of 0.18 mol / L;

[0075] (2) The acidic leaching solution is placed in a precipitator, and sulfuric acid solution is added to the system. + The concentration is 5 mol / L, and methanol is added, the amount of methanol added is 5% of the volume fraction of the acidic leaching liquid, and at the same time, ground orthorhombic ferric phosphate is added in an amount of 5 times the total molar amount of iron in the acidic leaching liquid, and the temperature is raised and kept at 100° C. for precipitation to obtain a slurry containing ferric phosphate precipitation;

[0076] (3) The solid phase obtained by filtering the slurry is then washed with water, ground to a size where the average particle size is 6 μm and the particle size is less than 15 μm, and calcined at 750° C. for 2 h to obtain regenerated iron phosphate.

[0077] Example 4

[0078] This embodiment provides a method for regenerating iron phosphate-containing waste. The difference between the regeneration method and the embodiment 1 is that: + The concentration is 0.3mol / L.

[0079] Example 5

[0080] This embodiment provides a method for regenerating iron phosphate-containing waste. The difference between the regeneration method and the embodiment 1 is that: + The concentration is 15mol / L.

[0081] Example 6

[0082] This embodiment provides a method for regenerating iron phosphate-containing waste. The difference between the regeneration method and the embodiment 1 is that before the temperature is raised in step (2), the acidic leaching solution and the sulfuric acid solution are first mixed to H + The concentration is 6mol / L.

[0083] Example 7

[0084] This embodiment provides a method for regenerating waste containing iron phosphate. The difference between the regeneration method and the embodiment 1 is that sulfuric acid solution is added to the system. + The concentration is 4 mol / L, and methanol and ground monoclinic ferric phosphate dihydrate in an amount of 4 times the total molar amount of iron in the acidic leaching solution are added at the same time. The amount of methanol added is 25% of the volume fraction of the acidic leaching liquid.

[0085] Example 8

[0086] This embodiment provides a method for regenerating waste containing iron phosphate. The regeneration method is different from that of Embodiment 1 only in that methanol is not added.

[0087] Example 9

[0088] This embodiment provides a method for regenerating waste containing iron phosphate. The regeneration method is different from that of Embodiment 2 only in that methanol is not added and only monoclinic iron phosphate dihydrate is added.

[0089] Example 10

[0090] This embodiment provides a method for regenerating waste containing iron phosphate. The regeneration method is different from that of Embodiment 1 only in that no calcination is performed.

[0091] Comparative Example 1

[0092] This comparative example provides a method for regenerating waste containing iron phosphate, and the regeneration method is Example 3 in CN110683528A.

[0093] Test method:

[0094] The purity of the regenerated ferric phosphate was determined by dissolving the ferric phosphate with 6 mol / L hydrochloric acid, analyzing it by ICP-OES, and calculating the recovery rates of iron and phosphorus, respectively, as follows.

[0095] The molar ratio of phosphorus to iron in the ferric phosphate product is determined by ICP-OES analysis to obtain the mass content of iron and phosphorus in the ferric phosphate product, and then converted into an iron-phosphorus molar ratio.

[0096] The formula for calculating the recovery rate of iron is: 1-(volume of liquid after precipitation × iron concentration in liquid after precipitation) / (volume of liquid before precipitation × iron concentration in liquid before precipitation)

[0097] The formula for calculating the phosphorus recovery rate is: 1-(volume of liquid after precipitation × phosphorus concentration in liquid after precipitation) / (volume of liquid before precipitation × phosphorus concentration in liquid before precipitation)

[0098] The test results of the above embodiments are shown in Table 1.

[0099] Table 1

[0100]

[0101] From Table 1, we can see the following points:

[0102] (1) It can be seen from Examples 1 to 3 that the regeneration method of iron phosphate-containing waste provided by the present invention achieves the separation of iron phosphate and impurities, and the regenerated iron phosphate is of good quality, wherein the purity of the regenerated iron phosphate is above 99.92wt%, the recovery rate of iron is above 88%, preferably above 95%, and the recovery rate of phosphorus is above 88%, preferably above 95%;

[0103] (2) Combining Example 1 and Examples 4 to 5, it can be seen that the H + The concentration of is 3 mol / L, compared with 0.3 mol / L and 15 mol / L in Examples 4 to 5, respectively, the recovery rates of iron and phosphorus in Example 1 are both 95%, while the recovery rates of iron and phosphorus in Example 4 are only 74%, respectively, and the recovery rates of iron and phosphorus in Example 5 are only 67%, respectively, which shows that the present invention significantly improves the recovery rates of iron and phosphorus by preferably using an acidic solution with a specific hydrogen ion content;

[0104] (3) It can be seen from Example 1 and Example 7 that in Example 7, methanol, a nucleation promoter and a sulfuric acid solution are added at the same time. Compared with Example 1 in which monoclinic ferric phosphate dihydrate is not added as a nucleation promoter, the recovery rate of iron and phosphorus in Example 7 is further improved to 97% on the basis of Example 1. Examples 1-2 and Examples 8-9 also have similar situations. This shows that the present invention preferably adopts the method of adjusting pH, adding alcohol solvents and nucleation promoters at the same time, which can better improve the recovery rate of iron and phosphorus;

[0105] (4) It can be seen from Example 1 and Example 10 that calcination can further improve the purity of the ferric phosphate product of the present invention.

[0106] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for regenerating iron phosphate-containing waste, characterized in that: The regeneration method comprises: (1) mixing the iron phosphate-containing waste material and the acidic solution, separating the solid from the liquid, and obtaining an acidic leaching solution; (2) the acidic leaching solution is heated and kept warm for precipitation to obtain a slurry containing iron phosphate precipitation; (3) The slurry is subjected to solid-liquid separation, and the solid phase after the solid-liquid separation is washed to obtain regenerated iron phosphate; Before heating in step (2), the acidic leaching solution and the acidic solution are mixed until H + The concentration is 1 to 5 mol / L, and the acidic leaching solution, alcohol solvent and nucleation accelerator are mixed; After the washing in step (3), the solid phase is further subjected to grinding and calcination in sequence.

2. The regeneration method according to claim 1, characterized in that: The acidic solution in step (1) includes any one of sulfuric acid, hydrochloric acid or phosphoric acid, or a combination of at least two of them.

3. The regeneration method according to claim 1, characterized in that: The acidic solution contains H + The concentration is 0.4~12mol / L.

4. The regeneration method according to claim 1, characterized in that: The liquid-to-solid ratio of the mixture is (1-50):1 mL / g.

5. The regeneration method according to claim 1, characterized in that: The mixing temperature is 20-60°C.

6. The regeneration method according to claim 1, characterized in that: The total iron ion concentration in the acidic leaching solution is 0.18-4.5 mol / L.

7. The regeneration method according to claim 1, characterized in that: The temperature of the heat preservation precipitation in step (2) is 65°C to the boiling point of the acidic leaching solution.

8. The regeneration method according to claim 1, characterized in that: The alcohol solvent includes any one of methanol, ethanol, propanol or isopropanol, or a combination of at least two of them.

9. The regeneration method according to claim 1, characterized in that: The added amount of the alcohol solvent is 5 to 100% of the volume fraction of the acidic leaching liquid.

10. The regeneration method according to claim 1, characterized in that: The nucleation promoter includes any one of isophosphotyrite-type iron phosphate, monoclinic iron phosphate, orthorhombic iron phosphate, α-quartz crystal iron phosphate, monoclinic iron phosphate dihydrate or orthorhombic iron phosphate dihydrate, or a combination of at least two thereof.

11. The regeneration method according to claim 1, characterized in that: Before mixing the nucleation accelerator and the acidic leaching solution, the nucleation accelerator is firstly ground.

12. The regeneration method according to claim 1, characterized in that: The added molar amount of the nucleation promoter is 0.01 to 10 times the total molar amount of iron in the solution before precipitation.

13. The regeneration method according to claim 1, characterized in that: The solid phase after the solid-liquid separation in step (3) is washed.

14. The regeneration method according to claim 1, characterized in that: The washing includes water washing.

15. The regeneration method according to claim 1, characterized in that: The grinding method includes any one of ball milling, stirred milling or sand milling, or a combination of at least two of them.

16. The regeneration method according to claim 1, characterized in that: The grinding reaches a scale in which the average particle size is 2 to 6 μm, and the particle size is below 15 μm.

17. The regeneration method according to claim 1, characterized in that: The calcination temperature in step (3) is 500-750°C.

18. The regeneration method according to claim 1, characterized in that: The calcination time is 2 to 10 hours.

19. The regeneration method according to claim 1, characterized in that: The precipitated liquid obtained by the solid-liquid separation in step (3) is returned to step (1) for recycling.

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