CN114572953B - Method for removing metal impurities in ferrous phosphate acidic solution and application thereof - Google Patents
Method for removing metal impurities in ferrous phosphate acidic solution and application thereof Download PDFInfo
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Abstract
The invention relates to a method for removing metal impurities in ferrous phosphate acidic solution and a preparation method of battery-grade ferric phosphate. The impurity removal method comprises the following steps: will contain Fe 2+ 、PO 4 3‑ Mixing ferrous phosphate acidic solution with metal impurities, a first pH regulator and an adsorbent to prepare a reaction solution, and removing impurities and solids under the condition that the pH value is 1.0-3.0 to prepare ferrophosphorus solution; the adsorbent is amorphous phosphate. The adsorbent is used as an adsorbent and a seed crystal of metal impurities, can strengthen crystallization and precipitation effects while realizing ion selective adsorption, and ensures higher purity and yield of ferric phosphate while deeply removing the metal impurities. In addition, the impurity removal method is simple to operate, low in equipment investment, controllable in quality and easy to industrialize.
Description
Technical Field
The invention relates to the technical field of battery material recovery, in particular to a method for removing metal impurities in ferrous phosphate acidic solution and application thereof.
Background
The lithium iron phosphate battery has the advantages of high specific capacity, multiple cycle times, environmental protection and the like, and is widely applied to the fields of communication base stations, energy storage, power batteries and the like. With the rapid development of new energy automobiles in China, the life cycle of the lithium ion battery is generally 5 years, and the scrapped quantity of the power battery in China reaches 12-17 ten thousand tons along with the time, so that a large amount of retired waste power batteries are required to be recycled. The lithium iron phosphate battery is rich in lithium and ferric phosphate, so that the method has important research value and practical significance in recycling of all components in the retired lithium iron phosphate battery from the aspects of resource recycling and environmental protection.
The titanium ion doping can effectively improve the high-current charge and discharge performance of the commercial lithium iron phosphate battery, and the waste lithium iron phosphate positive electrode powder generally contains titanium (the titanium content is more than 400 ppm). Meanwhile, in the pretreatment process of crushing, sorting and the like of the waste lithium batteries, part of aluminum foil or copper foil small particles can be mixed into the positive electrode powder. Therefore, the method for preparing the battery grade ferric phosphate by recycling the waste lithium iron phosphate anode material by adopting the wet process generally faces the difficult problem of higher content of metal impurities such as aluminum, titanium, copper and the like. In addition, if the directional deep removal of impurities such as aluminum, titanium, copper and the like is not carried out in the process of recycling the lithium iron phosphate battery in a large scale, the uniformity and stability of the quality of the recycled product ferric phosphate are also affected, and the charge and discharge performance of the subsequently prepared lithium iron phosphate battery is indirectly affected. The deep removal of metal impurities has important research value and practical significance.
Hitherto, copper removal processes mainly include two processes of low-acid leaching copper removal and displacement reduction copper removal. The former is that lithium iron phosphate positive electrode powder/iron phosphate slag is selectively dissolved with inorganic acid to remove impurities, and the latter is that acid leaching solution is obtained after acid leaching of the lithium iron phosphate positive electrode powder/iron phosphate slag, and then copper simple substance is precipitated through reduction of iron powder. The aluminum removal process mainly comprises the steps of leaching lithium iron phosphate anode powder by concentrated alkali, selectively dissolving aluminum, and performing iron-aluminum coprecipitation/resin dealumination in pickle liquor.
A method for removing copper and aluminum from ferrous phosphate acid solutions by adding Fe to the solution has been reported 2+ 、PO 4 3- The acidic solution of (2) is supplemented with elemental iron and the pH is adjusted to greater than 3.0 so that copper and aluminum precipitate out while the ferrous component remains in solution. The method can realize deep copper and aluminum removal, but the operation process is difficult to control, and because of K sp (Fe 3 (PO 4 ) 2 )＝1.0×10 -38 Is easy to cause Fe in the pH adjusting process 2+ 、Cu 2+ And Al 3+ Is in fact Fe 2+ And PO (PO) 4 3- The loss of (2) is large.
Or a method for removing titanium from ferrous sulfate acid liquor, wherein the residual titanium content in the solution is large (200-400 ppm) when the pH value of the system is more than 1.5, and the titanium removal is incomplete. Therefore, the recovery rate of the ferric phosphate obtained after the ferrophosphorus pickle liquor is subjected to impurity removal is lower, and the content of impurity titanium is higher.
Or a method for selectively recycling copper and aluminum in waste lithium iron phosphate batteries, wherein the copper and aluminum are leached out by leaching lithium iron phosphate anode materials at high temperature by adopting dilute concentration of inorganic acid and oxygen, and ferric phosphate in the lithium iron phosphate anode materials is precipitated and separated in a leaching slag form. The method has better copper and aluminum removal efficiency, but the leaching rate of iron is as high as 4.6%, and the phosphorus iron is damagedThe loss is large; due to K sp (FePO 4 ·2H 2 O)＝1.3×10 -22 ，K sp (Ti(HPO 4 ) 2 ·H 2 O)＝1.0×10 -29 ，Ti(HPO 4 ) 2 ·H 2 O is higher than FePO 4 ·2H 2 O is insoluble. The purity and the yield of the recovered ferric phosphate product are low, and the defects of complex process flow, large high-salt wastewater production amount and the like exist.
Therefore, the titanium in the lithium iron phosphate positive electrode powder/iron phosphate slag is difficult to be selectively dissolved out under the low-acid condition; and under the high acid condition, synchronous dissolution of each component can be caused, and the pH adjustment and precipitation in a high acid system are not thorough for removing titanium, and the ferrophosphorus loss is reduced. Thus, the key to the removal of impurities is still to selectively precipitate titanium, aluminum and copper impurities and to suppress the precipitation of iron.
Disclosure of Invention
Based on the method, the invention provides a method for removing metal impurities in ferrous phosphate acidic solution, which can deeply remove the metal impurities and ensure higher purity and yield of ferric phosphate.
The technical proposal is as follows:
a method for removing metal impurities in ferrous phosphate acidic solution, comprising the following steps:
will contain Fe 2+ 、PO 4 3- Mixing ferrous phosphate acidic solution with metal impurities, a first pH regulator and an adsorbent to prepare a reaction solution, and removing impurities and solids under the condition that the pH value is 1.0-3.0 to prepare ferrophosphorus solution;
the adsorbent is amorphous phosphate.
In one embodiment, the adsorbent is selected from at least one of amorphous iron phosphate, amorphous iron hydroxyphosphate, amorphous aluminum phosphate, amorphous aluminum hydroxyphosphate, amorphous titanium phosphate, and amorphous titanium hydroxyphosphate.
In one embodiment, the adsorbent and the Fe in the acidic solution 2+ The mass ratio of (0.05-0.6): 1.
in one embodiment, the reaction time of the impurity removal reaction is greater than or equal to 2 hours.
In one embodiment, the reaction temperature of the impurity removal reaction is 20 ℃ to 150 ℃.
In one embodiment, the first pH adjuster is selected from at least one of urea, ammonium carbonate, and ammonium bicarbonate.
In one embodiment, the method for removing metal impurities in the ferrous phosphate acidic solution further comprises the step of introducing a protective gas atmosphere into the reaction solution, wherein the protective gas atmosphere is at least one of nitrogen, argon and carbon dioxide.
The invention also provides a preparation method of the battery-grade ferric phosphate, which comprises the following steps:
preparing the ferrophosphorus solution according to the method for removing metal impurities in the ferrous phosphate acidic solution;
and mixing the ferrophosphorus liquid with an oxidant and a second pH regulator to perform oxidation reaction.
In one embodiment, the oxidizing agent is selected from at least one of hydrogen peroxide, air, ozone, or oxygen, and/or
The second pH regulator is at least one selected from ammonia water, ammonium carbonate or ammonium bicarbonate.
In one embodiment, the parameters of the oxidation reaction include: the reaction temperature is 50-100 ℃, the reaction time is 3-10 h, and the pH value of the reaction system is 1.5-2.0.
In one embodiment, after the oxidation reaction is finished, the method further comprises the steps of filtering, collecting filter residues, washing and drying.
In one embodiment, the drying process is performed at a temperature of 500 ℃ to 700 ℃ for a time of 1h to 3h.
The invention has the following beneficial effects:
the invention adopts amorphous phosphate as the adsorbent and seed crystal of metal impurities, can strengthen crystallization and precipitation effects while realizing ion selective adsorption, and the amorphous phosphate has the advantages of porous channels, smaller particle size, large specific surface area and the like, and can improve impurity removal efficiency.
According to the test, the impurity removal rate of the titanium, aluminum and copper is higher than 80%, the partial impurity removal rate is higher than 99%, the precipitation rate of trace impurities is increased to more than 80% from about 20% of the original impurity removal rate, and meanwhile, the loss rate of iron is less than 0.8%, so that the purity and the yield of iron phosphate are ensured while the metal impurities are deeply removed.
In addition, the impurity removing method has the advantages of simple operation, less equipment investment, controllable quality, easy industrialization and the like, can generate better economic and social benefits, and has wide application prospect.
Drawings
Fig. 1 is an XRD pattern of battery grade iron phosphate prepared in example 1.
Detailed Description
The invention is described in further detail below with reference to specific embodiments and figures. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The term "and/or," "and/or," as used herein, includes any one of two or more of the listed items in relation to each other, as well as any and all combinations of the listed items in relation to each other, including any two of the listed items in relation to each other, any more of the listed items in relation to each other, or all combinations of the listed items in relation to each other.
Where the terms "comprising," "having," and "including" are used herein, it is intended to cover a non-exclusive inclusion, unless a specifically defined term is used, such as "consisting of … … only," etc., another component may be added.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise. In the description of the present invention, the meaning of "several" means at least one, such as one, two, etc., unless specifically defined otherwise.
The words "preferably," "more preferably," and the like in the present invention refer to embodiments of the invention that may provide certain benefits in some instances. However, other embodiments may be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.
When a range of values is disclosed herein, the range is considered to be continuous and includes both the minimum and maximum values for the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range description features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.
Unless mentioned to the contrary, singular terms may include plural and are not to be construed as being one in number.
In the present invention, "at least one" means any one, any two or more of the listed items.
In the present invention, amorphous means having a structure which is not completely crystalline and is more reactive than having a crystalline structure. For example, amorphous iron phosphate has a non-fully crystalline structure that is more reactive than anhydrous iron phosphate having a crystalline structure.
The raw materials, reagent materials, and the like used in the following embodiments are commercially available products unless otherwise specified.
The technical scheme of the invention is as follows:
a method for removing metal impurities in ferrous phosphate acidic solution, comprising the following steps:
will contain Fe 2+ 、PO 4 3- Mixing ferrous phosphate acidic solution with metal impurities, a first pH regulator and an adsorbent to prepare a reaction solution, and removing impurities and solids under the condition that the pH value is 1.0-3.0 to prepare ferrophosphorus solution;
the adsorbent is amorphous phosphate.
The invention adopts amorphous phosphate as the adsorbent and seed crystal of metal impurities, can strengthen crystallization and precipitation effects while realizing ion selective adsorption, and the amorphous phosphate has the advantages of porous channels, smaller particle size, large specific surface area and the like, and can improve impurity removal efficiency. The ferrophosphorus liquid mainly comprises ferrous iron, phosphate radical and a small amount of metal impurities such as sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, lead, titanium, copper, aluminum and the like, and the specific types correspond to the analysis results of the ICP content of the iron phosphate prepared in the embodiment. The solid obtained by solid-liquid separation has the same component type as the adsorbent, and is accompanied with part of new amorphous titanium phosphate and aluminum phosphate after purification, namely the content of the amorphous titanium phosphate and aluminum phosphate in the purified adsorbent is increased compared with that of the adsorbent.
In one embodiment, the adsorbent is selected from at least one of amorphous iron phosphate, amorphous iron hydroxyphosphate, amorphous aluminum phosphate, amorphous aluminum hydroxyphosphate, amorphous titanium phosphate, and amorphous titanium hydroxyphosphate.
In one embodiment, the adsorbent is amorphous iron phosphate, which can significantly reduce the content of titanium, aluminum and copper, improve the product purity of iron phosphate, and also ensure high yield of iron phosphate.
It is understood that the pH of the impurity removal reaction system includes, but is not limited to: 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 and 3.0. In one embodiment, the first pH adjuster is selected from at least one of urea, ammonium carbonate, and ammonium bicarbonate. By acidity adjustment, metal impurities are promoted to precipitate out in the form of poorly soluble complexes or insoluble complexes.
In one embodiment, the adsorbent and the Fe in the acidic solution 2+ The mass ratio of (0.05-0.6): 1. the adsorbents can selectively adsorb specific cations, strengthen crystallization and precipitation effects and effectively improve impurity removal effects. The mass ratio in the range is more beneficial to deeply removing metal impurities (particularly aluminum, titanium and copper) and ensuring higher purity and yield of the ferric phosphate. If the addition amount of the adsorbent is lower than the range of the invention, the impurity removal (especially aluminum, titanium and copper) efficiency is greatly reduced, so that the purity of the ferric phosphate is insufficient; if the amount of the adsorbent is higher than the range of the present invention, the yield of iron phosphate is greatly reduced. Understandably, the adsorbent and the Fe in the acidic solution 2+ Including but not limited to: 0.05: 1. 0.06: 1. 0.07: 1. 0.08: 1. 0.09: 1. 0.1: 1. 0.12: 1. 0.15: 1. 0.18: 1. 0.2: 1. 0.22: 1. 0.25: 1. 0.28: 1. 0.3: 1. 0.32: 1. 0.35: 1. 0.38: 1. 0.4: 1. 0.42: 1. 0.45: 1. 0.48: 1. 0.5: 1. 0.52: 1. 0.55: 1. 0.58:1 and 0.6:1.
in one embodiment, the reaction time of the impurity removal reaction is greater than or equal to 2 hours. The reaction time in the range is more beneficial to deeply removing aluminum, titanium and copper, and simultaneously ensuring higher purity and yield of the ferric phosphate.
It is understood that the reaction time of the impurity removal reaction includes, but is not limited to, the following: 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h, 16h, 16.5h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h and 25h. Preferably, the reaction time of the impurity removal reaction is 2-10 hours, so that the method can deeply remove aluminum, titanium and copper, ensure higher purity and yield of ferric phosphate and is more economical.
In one embodiment, the reaction temperature of the impurity removal reaction is 20 ℃ to 150 ℃. The reaction temperature in the range is more beneficial to deeply removing aluminum, titanium and copper and ensuring higher purity and yield of ferric phosphate. If the temperature is higher than the range of the invention, the impurity removal efficiency is greatly reduced, so that the purity and the yield of the ferric phosphate are insufficient; and the temperature is lower than the range of the invention, which also reduces the impurity removal efficiency. It is understood that the reaction temperature of the impurity removal reaction includes, but is not limited to, the following: 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃,70 ℃, 75 ℃,80 ℃,85 ℃,90 ℃,95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃, and 150 ℃. Preferably, the reaction temperature of the impurity removal reaction is 20-100 ℃. Further, the reaction temperature of the impurity removal reaction is 30-80 ℃.
In one embodiment, the impurity removal reaction further comprises a step of introducing a protective gas atmosphere into the reaction liquid, wherein the protective gas atmosphere is at least one of nitrogen, argon and carbon dioxide. The protective gas can avoid Fe 2+ Oxidized, the method is more beneficial to deeply removing aluminum, titanium and copper, and simultaneously can ensure higher purity and yield of the ferric phosphate.
In one embodiment, the manner of removing solids is filtration.
The invention also provides a preparation method of the battery-grade ferric phosphate, which comprises the following steps:
preparing the ferrophosphorus solution according to the method for removing metal impurities in the ferrous phosphate acidic solution;
and mixing the ferrophosphorus liquid with an oxidant and a second pH regulator to perform oxidation reaction.
The ferrophosphorus solution reacts with the oxidant so that ferrous iron therein is oxidized to ferric iron, forming ferric phosphate.
In one embodiment, the oxidizing agent is selected from at least one of hydrogen peroxide, air, ozone, or oxygen. The amount of the oxidizing agent to be added is sufficient to oxidize the ferrous iron. When the oxidant is air or ozone, the oxidant is introduced into the ferrophosphorus liquid, and the ferrophosphorus liquid reacts with the oxidant, so that ferrous iron is oxidized into ferric iron, and ferric phosphate is formed.
In one embodiment, the second pH adjuster is selected from at least one of ammonia, ammonium carbonate, or ammonium bicarbonate. Through acidity adjustment, the solubility of the ferric phosphate is reduced, so that the ferric phosphate is precipitated and separated out, and the yield is improved.
In one embodiment, the parameters of the oxidation reaction include: the reaction temperature is 50-100 ℃, the reaction time is 3-10 h, and the pH value of the reaction system is 1.5-2.0.
It is understood that the temperature of the oxidation reaction includes, but is not limited to,: 50 ℃, 52 ℃, 55 ℃, 60 ℃, 62 ℃, 65 ℃, 67 ℃,70 ℃, 72 ℃, 75 ℃,80 ℃, 82 ℃,85 ℃, 87 ℃,90 ℃, 92 ℃,95 ℃, 96 ℃, 98 ℃, and 100 ℃. The time of the oxidation reaction includes, but is not limited to: 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h and 10h. The pH of the oxidation reaction system includes, but is not limited to: 1.5, 1.6, 1.7, 1.8, 1.9 and 2.0.
In one embodiment, after the oxidation reaction is finished, the method further comprises the steps of filtering, collecting filter residues, washing and drying.
In one embodiment, the drying process is performed at a temperature of 500 ℃ to 700 ℃ for a time of 1h to 3h. It is understood that the temperature of the drying process includes, but is not limited to,: 500 ℃, 525 ℃, 550 ℃, 575 ℃, 600 ℃, 625 ℃, 650 ℃, 675 ℃ and 700 ℃. The time of the drying process includes, but is not limited to: 1h, 1.5h, 2h, 2.5h and 3h.
The preparation method of the battery-grade ferric phosphate has the advantages of simple operation, less equipment investment, controllable quality, easy industrialization and the like, can generate better economic and social benefits, and has wide application prospect.
Further description will be given below with reference to specific examples and comparative examples.
It will be appreciated that ferrous phosphate acidic solutions may vary somewhat in elemental composition, but the metal removal methods disclosed herein are applicable to a wide variety of ferrous phosphate acidic systems, and for ease of description of the invention, the elemental content analysis of ferrous phosphate used in the following examples and comparative examples is as follows (calculated as the total mass of acidic solution):
in addition to the above elements, trace amounts of silicon, sulfur, chromium, manganese, cadmium, lead elements, and a large amount of lithium elements are contained.
Example 1
1200g of Fe-containing alloy 2+ 、PO 4 3- And an acidic solution of metal impurities, 25g of amorphous iron phosphate (adsorbent: ferrous ion mass ratio 0.39:1) were mixed, and nitrogen was introduced into the slurry, and the slurry temperature was adjusted to 30 ℃. The final slurry ph=1.5 was slowly adjusted with ammonium bicarbonate and the reaction time was controlled for 3.0h. After the reaction is finished, filtering, washing, regulating the pH=1.8 of the purifying liquid by using ammonia water with the mass concentration of 25%, mixing with 60g of hydrogen peroxide with the mass concentration of 30%, reacting for 5.0h at 90 ℃, filtering, washing and dehydrating for 2.0h at 600 ℃ to obtain the battery grade ferric phosphate with the yield of 99.4%.
XRD test is carried out on the prepared ferric phosphate to obtain a diffraction pattern shown in figure 1, and the diffraction pattern is compared with a standard card of a corresponding product, so that the product obtained in the embodiment is proved to be ferric phosphate.
The iron phosphate prepared above is detected by atomic emission spectrometry (ICP), and the impurity contents are calculated relative to the mass of the iron phosphate, wherein the contents of impurities such as sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are all less than 10ppm, and the contents of impurities such as titanium, copper and aluminum are respectively 20ppm, 1ppm and 12ppm.
Example 2
2000g of Fe-containing alloy 2+ 、PO 4 3- And an acidic solution of metal impurities, 5.5g of amorphous aluminum hydroxyphosphate (adsorbent: ferrous ion mass ratio 0.05:1) were mixed, and argon was introduced into the slurry, and the slurry temperature was adjusted to 80 ℃. The final slurry ph=2.5 was slowly adjusted with urea and the reaction time was controlled for 5.0h. After the reaction is finished, filtering, washing, regulating the pH=1.5 of the purifying liquid by using ammonium bicarbonate with the mass concentration of 20%, introducing oxygen into the solution, controlling the oxygen partial pressure to be 2.5MPa, reacting at 80 ℃ for 7.0h, filtering, washing and dehydrating at 550 ℃ for 2h to obtain the battery-grade ferric phosphate with the yield of 98.9%.
The iron phosphate prepared above was detected by atomic emission spectrometry (ICP), and the impurity contents were calculated with respect to the mass of the iron phosphate, and the contents of the impurities sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were all less than 10ppm, and the contents of the impurities titanium, copper, and aluminum were 28ppm, 3ppm, and 15ppm, respectively.
Example 3
800g of Fe-containing alloy 2+ 、PO 4 3- And metal impurities, 20g of amorphous titanium hydroxyphosphate (adsorbent: ferrous ion mass ratio 0.47:1), and carbon dioxide was introduced into the slurry, and the slurry temperature was adjusted to 50 ℃. The final slurry ph=2.0 was slowly adjusted with ammonium carbonate and the reaction time was controlled for 4.0h. After the reaction is finished, filtering, washing, adjusting the pH=2.0 of the purifying liquid by using ammonium carbonate with the mass concentration of 20%, introducing oxygen into the solution, controlling the oxygen partial pressure to be 2MPa, reacting for 5 hours at 85 ℃, filtering, washing and dehydrating for 1.5 hours at 650 ℃ to obtain the battery-grade ferric phosphate with the yield of 98.7%.
The iron phosphate prepared above was detected by atomic emission spectrometry (ICP), and the impurity contents were calculated with respect to the mass of the iron phosphate, and the contents of the impurities sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were all less than 10ppm, and the contents of the impurities titanium, copper, and aluminum were 25ppm, 2ppm, and 13ppm, respectively.
Example 4
4000g of Fe-containing alloy 2+ 、PO 4 3- Metal impurities40g of amorphous iron hydroxyphosphate (adsorbent: ferrous ion mass ratio of 0.19:1) and carbon dioxide was introduced into the slurry, and the slurry temperature was adjusted to 70 ℃. The final slurry ph=2.0 was slowly adjusted with ammonium bicarbonate and the reaction time was controlled to 3.0h. After the reaction is finished, filtering, washing, adjusting the pH=1.8 of the purifying liquid by using 20% ammonium carbonate, mixing with 230g of 30% hydrogen peroxide with mass concentration, reacting for 7.0h at 70 ℃, filtering, washing and dehydrating for 3.0h at 600 ℃ to obtain the battery grade ferric phosphate with the yield of 98.7%.
The iron phosphate prepared above was detected by atomic emission spectrometry (ICP), and the impurity contents were calculated with respect to the mass of the iron phosphate, and the contents of the impurities sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were all less than 10ppm, and the contents of the impurities titanium, copper, and aluminum were 20ppm, 1ppm, and 17ppm, respectively.
Example 5
4000g of Fe-containing alloy 2+ 、PO 4 3- And metal impurities, 64g of amorphous iron hydroxyphosphate, 64g of titanium phosphate (adsorbent: ferrous ion mass ratio is 0.39:1), and nitrogen is introduced into the slurry, and the temperature of the slurry is adjusted to 70 ℃. The final slurry ph=2.0 was slowly adjusted with urea and the reaction time was controlled for 3.0h. After the reaction is finished, filtering, washing, adjusting the pH=1.8 of the purifying liquid by using ammonium carbonate with the mass concentration of 20%, introducing oxygen into the solution, controlling the oxygen partial pressure to be 1.5MPa, reacting for 9.0h at 95 ℃, filtering, washing and dehydrating for 2.5h at 680 ℃ to obtain the battery-grade ferric phosphate with the yield of 99.2%.
The iron phosphate prepared above was detected by atomic emission spectrometry (ICP), and the impurity contents were calculated with respect to the mass of the iron phosphate, and the contents of the impurities sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were all less than 10ppm, and the contents of the impurities titanium, copper, and aluminum were 20ppm, 1ppm, and 14ppm, respectively.
Example 6
The ferrous phosphate acidic solution was treated in the same procedure and process as in example 1, except that no protective gas was introduced during the impurity removal step, and the other operations were the same as in example 1.
The yield of the prepared ferric phosphate was 90.3%. The content of impurities is calculated relative to the mass of the ferric phosphate by atomic emission spectrometry (ICP), and the content of impurities such as sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead is less than 20ppm, and the content of impurities such as titanium, copper and aluminum is 18ppm, 1ppm and 10ppm respectively.
Example 7
The ferrous phosphate acidic solution was treated according to the same procedure and process as in example 1 except that the reaction temperature in the impurity removal step was 150 c, and the other operations were the same as in example 1.
The yield of the prepared ferric phosphate was 86.7%. The content of impurities is calculated relative to the mass of the ferric phosphate by atomic emission spectrometry (ICP), and the content of impurities such as sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead is less than 20ppm, and the content of impurities such as titanium, copper and aluminum is 40ppm, 5ppm and 18ppm respectively.
Comparative example 1
The ferrous phosphate acidic solution was treated according to the same procedure and process as in example 1 except that anhydrous ferric phosphate was used as the adsorbent, and the other operations were the same as in example 1.
The yield of the prepared ferric phosphate is 99.3%. The content of impurities is calculated relative to the mass of the ferric phosphate by atomic emission spectrometry (ICP), and the content of impurities such as sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead is less than 20ppm, and the contents of impurities such as titanium, copper and aluminum are 560ppm, 210ppm and 1250ppm respectively.
Comparative example 2
The ferrous phosphate acidic solution was treated according to the same procedure and process as in example 1 except that ammonium bicarbonate was used to adjust the pH to 4.0 in the impurity removal step, and the other operations were the same as in example 1.
The yield of the prepared iron phosphate was 81.3%. The content of impurities is calculated relative to the mass of the ferric phosphate by atomic emission spectrometry (ICP), and the content of impurities such as sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead is less than 20ppm, and the contents of impurities such as titanium, copper and aluminum are respectively 350ppm, 130ppm and 830ppm.
Comparative example 3
The ferrous phosphate acidic solution was treated according to the same procedure and process as in example 1 except that phosphoric acid was used to adjust the pH to 0.5 in the impurity removal step, and the other operations were the same as in example 1.
The yield of the prepared ferric phosphate was 98.8%. The content of impurities is calculated relative to the mass of the ferric phosphate by atomic emission spectrometry (ICP), and the content of impurities such as sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead is less than 20ppm, and the contents of impurities such as titanium, copper and aluminum are 430ppm, 340ppm and 1150ppm respectively.
Comparative example 4
The ferrous phosphate acidic solution was treated in accordance with the same procedure and process as in example 1 except that the amorphous ferric phosphate was added at 38.3 (adsorbent: ferrous ion mass ratio of 0.6:1), the reaction time in the impurity removal step was 1.5h, and the other operations were the same as in example 1.
The yield of the prepared ferric phosphate was 99.7%. The content of impurities is calculated relative to the mass of ferric phosphate by atomic emission spectrometry (ICP), and the content of impurities such as sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead is less than 20ppm, and the contents of impurities such as titanium, copper and aluminum are 180ppm, 3ppm and 1080ppm respectively.
Comparative example 5
The ferrous phosphate acidic solution was treated according to the same procedure and process as in example 1 except that no adsorbent was added in the impurity removal step, and the other operations were the same as in example 1.
The yield of the prepared ferric phosphate was 87.5%. The content of impurities is calculated relative to the mass of the ferric phosphate by atomic emission spectrometry (ICP), and the content of impurities such as sodium, magnesium, silicon, sulfur, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead is less than 20ppm, and the contents of impurities such as titanium, copper and aluminum are 380ppm, 6ppm and 1240ppm respectively.
Analysis of results:
the methods for removing metal impurities in ferrous phosphate acidic solutions provided in examples 1 to 5 can guarantee higher purity and yield of ferric phosphate while deeply removing metal impurities.
As is clear from the comparison between the results of example 1 and example 6, in example 6, the impurity removal step was performed without introducing a non-oxidizing gas, and the yield of iron phosphate was greatly lowered although the metal impurity content was greatly lowered.
As is clear from a comparison between the results of example 1 and example 7, the reaction temperature in the impurity removal step of example 7 was 150℃and the metal impurity content was greatly reduced, but the iron phosphate yield was also greatly reduced.
As is clear from the results of comparative example 1 and comparative example 1, the amorphous iron phosphate was replaced with anhydrous iron phosphate in the impurity removal step of comparative example 1, and the iron phosphate yield was substantially unchanged, but most of the titanium, copper and aluminum impurities were not removed, and the object of the present invention was not achieved.
As is clear from the results of comparative examples 1 and 2, in comparative example 2, the ph=4.0 of the final slurry was adjusted in the impurity removal step, and although most of the metal impurities were removed, the yield of iron phosphate was greatly lowered, and the object of the present invention was not achieved.
As is clear from the results of comparative example 1 and comparative example 3, the ph=0.5 of the final slurry was adjusted in the impurity removal step of comparative example 3, and the iron phosphate yield was substantially unchanged, but most of the titanium, copper and aluminum impurities were not removed, and the object of the present invention was not achieved.
As is clear from the results of comparative examples 1 and 4, in the impurity removal step of comparative example 4, even if the mass ratio of the amount of the adsorbent to the ferrous ions has reached the upper limit, the reaction time was 1.5 hours, the impurity removal reaction was incomplete, and most of the impurities of titanium, copper and aluminum were not removed, although the yield of iron phosphate was substantially unchanged, and the object of the present invention was not achieved.
As is clear from the results of comparative examples 1 and 5, the iron phosphate yield was greatly lowered without adding an adsorbent in the impurity removing step of comparative example 5, and most of the impurities of titanium, copper and aluminum were not removed, thereby failing to achieve the object of the present invention.
In summary, the amorphous phosphate is adopted as the adsorbent and the seed crystal of the metal impurities in the ferrous phosphate acidic solution, the removal rate of the impurities of titanium, aluminum and copper is higher than 80 percent under the specific acidity condition, the partial removal rate is higher than 99 percent, the precipitation rate of trace impurities is raised from about 20 percent to more than 80 percent, and meanwhile, the loss rate of iron is less than 0.8 percent.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples merely represent a few embodiments of the present invention, which facilitate a specific and detailed understanding of the technical solutions of the present invention, but are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. It should be understood that, based on the technical solutions provided by the present invention, those skilled in the art may obtain technical solutions through logic analysis, reasoning or limited experiments, which are all within the scope of protection of the appended claims. The scope of the patent is therefore intended to be covered by the appended claims, and the description and drawings may be interpreted as illustrative of the contents of the claims.
Claims (9)
1. A method for removing metal impurities in an acidic ferrous phosphate solution, comprising the steps of:
will contain Fe 2+ 、PO 4 3- Mixing ferrous phosphate acidic solution with metal impurities, a first pH regulator and an adsorbent to prepare a reaction solution, introducing protective gas atmosphere into the reaction solution, and removing impurities under the condition that the pH value is 1.0-3.0 to obtain a ferrophosphorus solution;
the reaction time of the impurity removal reaction is more than or equal to 2 hours, and the reaction temperature is 50-100 ℃;
the adsorbent is selected from at least one of amorphous ferric phosphate, amorphous ferric phosphate hydroxide, amorphous aluminum phosphate hydroxide, amorphous titanium phosphate and amorphous titanium phosphate hydroxide;
the protective gas atmosphere is at least one of nitrogen, argon and carbon dioxide.
2. The method of removing metallic impurities from an acidic ferrous phosphate solution according to claim 1, wherein the pH is 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0.
3. The method for removing metallic impurities from an acidic solution of ferrous phosphate according to claim 1, wherein said adsorbent and Fe in said acidic solution 2+ The mass ratio of (0.05-0.6): 1.
4. the method for removing metallic impurities from an acidic solution of ferrous phosphate according to claim 3, wherein said adsorbent and Fe in said acidic solution 2+ The mass ratio of (3) is as follows: 0.05: 1. 0.06: 1. 0.07: 1. 0.08: 1. 0.09: 1. 0.1: 1. 0.12: 1. 0.15: 1. 0.18: 1. 0.2: 1. 0.22: 1. 0.25: 1. 0.28: 1. 0.3: 1. 0.32: 1. 0.35: 1. 0.38: 1. 0.4: 1. 0.42: 1. 0.45: 1. 0.48: 1. 0.5: 1. 0.52: 1. 0.55: 1. 0.58:1 or 0.6:1.
5. the method for removing metal impurities from an acidic ferrous phosphate solution according to claim 1, wherein the reaction time of the impurity removal reaction is as follows: 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h, 16h, 16.5h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h or 25h.
6. The method for removing metal impurities from an acidic ferrous phosphate solution according to claim 1, wherein the reaction time of the impurity removal reaction is 2 to 10 hours.
7. The method for removing metal impurities from an acidic ferrous phosphate solution according to claim 1, wherein the impurity removal reaction is performed at a temperature of 50 ℃, 55 ℃, 60 ℃, 65 ℃,70 ℃, 75 ℃,80 ℃,85 ℃,90 ℃,95 ℃ or 100 ℃.
8. The method for removing metal impurities from an acidic ferrous phosphate solution of claim 1, wherein the first pH adjustor is selected from at least one of urea, ammonium carbonate, and ammonium bicarbonate.
9. The method for removing metal impurities from an acidic ferrous phosphate solution according to claim 1, wherein the means for removing solids is filtration.
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