Method for preparing iron phosphate from phosphoric acid waste liquid
By employing pretreatment, impurity removal, and synthesis steps, ferric phosphate is prepared from phosphoric acid waste liquid, solving the problems of traditional treatment processes, achieving efficient resource utilization and low-cost ferric phosphate production, and reducing sludge generation and secondary pollution.
Patent Information
- Application Number
- CN202511775186.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-28
- Publication Date
- 2026-01-23
AI Technical Summary
Traditional phosphoric acid waste liquid treatment processes use acid-base neutralization and precipitation to remove phosphorus, which is difficult to process, has extremely low resource utilization, high cost, and generates a large amount of sludge, resulting in secondary pollution.
Ferric phosphate is prepared from phosphoric acid waste liquid through pretreatment, impurity removal, synthesis and purification steps, including dilution and pH adjustment, addition of PAM for impurity removal, mixing of iron salt and hydrogen peroxide to generate ferric phosphate slurry, and obtaining white ferric phosphate dihydrate powder by filtration and washing.
It effectively reduces the cost of phosphoric acid wastewater treatment, improves the utilization rate of phosphorus resources, reduces raw material costs, ensures the quality of iron phosphate products, and enhances competitiveness in the hazardous waste market.
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Figure CN121376934A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a preparation method of phosphoric iron by using phosphoric acid waste liquid. BACKGROUND
[0002] With the promotion and popularization of new energy vehicles and lithium ion energy storage technology in the global market, the demand for lithium iron phosphate batteries, which are safe and have long cycle life, has increased significantly. Phosphoric iron is one of the important raw materials for preparing lithium iron phosphate. The iron phosphate is a white, white and white monoclinic crystal powder. The commonly used preparation process is co-precipitation, and the technical route is mainly to synthesize by mixing and reacting iron salt and phosphorus salt solution, and adding an oxidizing agent and a pH regulator to promote the precipitation of phosphoric iron. The method is simple in operation, good in product performance and is used as the main production method of phosphoric iron, but the raw material cost accounts for a large proportion.
[0003] In recent years, with the rapid development of the electronic semiconductor industry and the new energy vehicle industry, integrated circuits and the automobile industry have become important sources of phosphoric acid waste liquid, and the waste liquid mainly consists of mixed acid of phosphoric acid and sulfuric acid, and cation impurities such as zinc, aluminum, copper and trivalent chromium ions. The conventional treatment process currently adopts neutralization and precipitation to remove phosphorus. A large amount of sludge is generated by alkali neutralization treatment, which is difficult to treat, has very low resource utilization rate and high disposal cost.
[0004] Therefore, a new efficient and economical preparation process of dihydrate phosphoric iron is needed, which can realize the resource utilization of phosphorus in the phosphoric acid waste liquid and effectively and economically treat the wastewater to realize the full quantization treatment of pollutants. SUMMARY
[0005] The main purpose of the application is to provide a preparation method of phosphoric iron by using phosphoric acid waste liquid, which aims to solve the technical problems of the current traditional phosphoric acid waste liquid treatment process, i.e. the difficulty in treatment, the extremely low resource utilization rate, the high cost, the large amount of sludge generated by neutralization treatment and the secondary pollution.
[0006] To achieve the above purpose, the preparation method of phosphoric iron by using phosphoric acid waste liquid provided by the application comprises the following steps: Step S1, waste phosphoric acid pretreatment, a certain amount of waste phosphoric acid solution is added into a reaction kettle, and pure water is added for dilution, and alkali solution is added dropwise to adjust the ph value of the waste phosphoric acid solution; Step S2, waste phosphoric acid impurity removal, when colloids and precipitates are generated in the reaction solution, PAM is added to purify the impurity metal ions in the waste phosphoric acid solution, and after standing, the supernatant is extracted, and the impurity-removed phosphorus source solution is obtained by filtration; Step S3, iron phosphate synthesis, iron salt solution, hydrogen peroxide and surfactant are added into the waste phosphoric acid solution obtained in step S2, and stirred and mixed uniformly, the molar ratio of iron to phosphorus is controlled at 1:1~1.2:1, the pH value is controlled at 1.6~2.2, heated to 30~60℃, after the reaction is completed, stand for 1~2h, generate iron phosphate slurry, after filtration and washing, obtain iron phosphate filter cake, after repeated filtration and washing of the iron phosphate filter cake, obtain crude iron phosphate filter cake; Step S4, refined iron phosphate, the crude iron phosphate filter cake obtained in step S3 is stirred and mixed with phosphoric acid solution to obtain slurry, the slurry is stirred and heated to 80~90℃, and the crystal transformation is aged to obtain white slurry, after filtration and washing, the refined iron phosphate filter cake is obtained. Step S5, the refined iron phosphate filter cake obtained in step S4 is repeatedly washed and filtered, and finally dried and ground to obtain white iron phosphate powder, which is used as raw material for preparation of subsequent lithium iron phosphate.
[0007] Optionally, in step S1, the mass fraction of phosphoric acid in the waste phosphoric acid solution obtained by adding pure water to dilute the waste phosphoric acid solution is 15%~30%.
[0008] Optionally, in step S1, the alkali solution can be one of sodium hydroxide, sodium carbonate, calcium hydroxide and ammonia solution, and the pH value of the waste phosphoric acid solution is controlled at 3.5~5.5.
[0009] Optionally, in step S3, the iron salt solution is one or more of ferrous chloride, ferrous sulfate or ferrous oxalate, and the surfactant is one of cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate or citric acid.
[0010] Optionally, in step S3, the feeding time is controlled at 10~30min, and stirring is maintained, and the stirring speed is controlled at 500~800rpm / min.
[0011] Optionally, in step S3, the iron phosphate filter cake is washed and filtered for 3~4 times, the first washing is performed using dilute phosphoric acid with a pH value of 2~3, and the subsequent washing is performed using pure water.
[0012] Optionally, in step S4, the concentration of the phosphoric acid solution is 0.5~2mol / L, and the usage amount is 1:2~1:4 of solid to liquid ratio.
[0013] Optionally, in step S4, the stirring speed is 300~500rpm / min, and the crystal transformation aging time is 120~180min.
[0014] Optionally, in the step S5, the refined iron phosphate filter cake is washed and filtered for 2-3 times using pure water.
[0015] Optionally, in the step S5, the drying temperature ranges from 60 to 100 degrees, and the drying time is 8-12 hours. The technical scheme of the present application has the following beneficial effects: The technical scheme of the present application, aiming at the problems of the traditional phosphoric acid waste liquid treatment process, i.e., the difficulty in treatment, the extremely low resource utilization rate, the high cost, the large amount of sludge generated by neutralization treatment, and the secondary pollution, uses low-cost phosphoric acid waste liquid as raw material to prepare low-impurity iron phosphate, thereby effectively reducing the disposal cost of phosphoric acid wastewater, improving the utilization rate of phosphorus resources, reducing the raw material cost, guaranteeing the product quality of iron phosphate, and improving the competitiveness in the hazardous waste market. BRIEF DESCRIPTION OF DRAWINGS
[0016] In order to more clearly illustrate the technical schemes in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.
[0017] Figure 1 The overall step flow chart of the method for preparing iron phosphate from phosphoric acid waste liquid according to an embodiment of the present application.
[0018] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the drawings. DETAILED DESCRIPTION
[0019] The technical schemes in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.
[0020] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly.
[0021] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.
[0022] This invention proposes a method for preparing iron phosphate using phosphoric acid waste liquid.
[0023] like Figure 1 As shown, in one embodiment of the present invention, the method for preparing ferric phosphate from phosphoric acid waste liquid includes the following steps: Step S1: Waste phosphoric acid pretreatment. A certain amount of waste phosphoric acid solution is added to the reactor and diluted with pure water. Alkali solution is added dropwise to adjust the pH value of the waste phosphoric acid solution. Specifically, the phosphoric acid waste liquid mentioned in this invention is produced during the automobile manufacturing process. Its main components are a mixture of phosphoric acid and sulfuric acid, and its main metallic impurity component is aluminum ions.
[0024] Step S2: Waste phosphoric acid purification. When colloids and precipitates are generated in the reaction solution, PAM is added to purify the impurity metal ions in the waste phosphoric acid solution. After standing, the supernatant is extracted and filtered to obtain the purified phosphoric acid source solution. Specifically, in step 2, the mass fraction of PAM added is 0.2% to 0.3%.
[0025] Specifically, polyacrylamide (PAM) is a linear water-soluble polymer compound and one of the most widely used water-soluble polymers. Polyacrylamide has good biocompatibility and high viscosity, and is well miscible with common surfactants. Its degree of polymerization can reach 10,000–90,000, with a corresponding molecular weight of 1.5 million–6 million. Its coagulation effect lies in its strong adsorption to colloidal surfaces, forming bridges between colloidal particles.
[0026] Step S3: Iron phosphate synthesis. Iron salt solution, hydrogen peroxide, and surfactant are added to the waste phosphoric acid solution obtained in step S2. The mixture is stirred and mixed evenly. The iron-phosphorus molar ratio is controlled at 1:1 to 1.2:1, and the pH value is controlled at 1.6 to 2.2. If the pH value of the solution is too high, the iron salt will be converted into iron hydroxide colloid and adsorb other impurity ions in the solution, resulting in a decrease in the purity of the subsequent product. The mixture is heated to 30℃ to 60℃. After the reaction is complete, it is allowed to stand for 1 to 2 hours to generate iron phosphate slurry. After filtration and washing, iron phosphate filter cake is obtained. The iron phosphate filter cake is repeatedly filtered and washed several times to obtain crude iron phosphate filter cake. Step S4, refining the iron phosphate, the crude iron phosphate filter cake obtained in step S3 is mixed with a phosphoric acid solution to obtain a slurry, the slurry is stirred and heated to 80-90℃, and the white slurry is obtained by crystal transformation and aging, and the refined iron phosphate filter cake is obtained by filtration and washing; Step S5, the refined iron phosphate filter cake obtained in step S4 is repeatedly washed and filtered, and finally dried and ground to obtain white iron phosphate powder, which is used as raw material for preparation of lithium iron phosphate.
[0027] Specifically, in step S1, the mass fraction of phosphoric acid in the waste phosphoric acid solution obtained by diluting the waste phosphoric acid solution with pure water is 15%-30%.
[0028] Specifically, in step S1, the alkali solution can be one of sodium hydroxide, sodium carbonate, calcium hydroxide and ammonia solution, and the pH value of the waste phosphoric acid solution is controlled at 3.5-5.5.
[0029] Specifically, in step S3, the iron salt solution is one or more of ferrous chloride, ferrous sulfate or ferrous oxalate, and the surfactant is one of cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate or citric acid.
[0030] Specifically, in step S3, the feeding time is controlled at 10-30 min, and the stirring speed is controlled at 500-800 rpm / min.
[0031] Specifically, in step S3, the iron phosphate filter cake is washed and filtered for 3-4 times, the first washing is performed with dilute phosphoric acid with a pH value of 2-3, and the subsequent washing is performed with pure water.
[0032] Specifically, in step S4, the concentration of the phosphoric acid solution is 0.5-2 mol / L, and the amount used is 1:2-1:4 of solid to liquid.
[0033] Specifically, in step S4, the stirring speed is 300-500 rpm / min, and the crystal transformation and aging time is 120-180 min.
[0034] Specifically, in step S5, the refined iron phosphate filter cake is washed and filtered for 2-3 times, and pure water is used for washing.
[0035] Specifically, in step S5, the drying temperature is 60-100 degrees, the drying time is 8-12 h, and the surface attached water is removed.
[0036] Example 1 Take 20 ml of waste phosphoric acid into a 500 ml beaker, filter the impurities with filter paper, then add 31.88 g of ferrous sulfate heptahydrate (calculated according to the molar ratio of Fe:P = 1.05:1), dilute with pure water to 200 ml, add 0.02% of cationic surfactant CTAB, a total of 0.04 g, stir until completely dissolved.
[0037] Place the beaker in a 60°C constant temperature water bath, slowly add 27% hydrogen peroxide (excess added according to the molar ratio of H2O2:Fe = 1.3:1), continue stirring for 10 minutes.
[0038] Add 65 ml of 3 mol / L ammonia solution drop by drop, adjust the pH of the system to 1.83, maintain 60°C stirring reaction for 2 hours, generate light yellow iron phosphate precipitate.
[0039] After the reaction is completed, use a Buchner funnel to filter, collect the crude iron phosphate filter cake; wash the filter cake with pure water for 4 times (300 ml of water each time), filter until the filtrate is clear; place the washed filter cake in a 60°C oven to dry for 12 hours, obtain 21.46 g of crude iron phosphate product. (The drying step is required for sending the intermediate product to the detection composition, and actual process does not need to be dried.) Take 4 g of the initial iron phosphate powder (dry powder) and mix it with 40 ml of 0.5 mol / L dilute phosphoric acid, place it in a 90°C water bath and stir for 1 hour.
[0040] Separate the solid by suction filtration, wash it with pure water for 2 times (30 ml of water each time), dry it in a 60°C oven for 12 hours after suction filtration, obtain 3.72 g of white powdery iron phosphate dihydrate product.
[0041] Example Two Take 20 ml of waste phosphoric acid into a 500 ml beaker, filter the impurities with filter paper, then dilute with pure water to 100 ml, add 65 ml of 3 mol / L ammonia solution drop by drop until the ph value is 3.5. Use 37.7 ml of 3 mol / L ammonia solution, the solution becomes a white viscous colloidal solution. Add 0.5 ml of PAM to promote aluminum phosphate precipitation, filter the solution, a total of 133 ml.
[0042] Take 100 ml of the filtrate into a 500 ml beaker, filter the impurities with filter paper, then add 17.4 g of ferrous sulfate heptahydrate (calculated according to the molar ratio of Fe:P = 1.05:1), dilute with pure water to 200 ml, add 0.02% of cationic surfactant CTAB, a total of 0.04 g, stir until completely dissolved.
[0043] Place the beaker in a 60°C constant temperature water bath, slowly add 27% hydrogen peroxide (excess added according to the molar ratio of H2O2:Fe = 1.3:1), continue stirring for 10 minutes.
[0044] Dropwise add 3 mol / L ammonia solution, adjust the pH of the system to 1.83, maintain 60°C stirring reaction for 2 hours, generate light yellow iron phosphate precipitate.
[0045] After the reaction is completed, use a Buchner funnel to filter, collect the crude iron phosphate filter cake; first wash the filter cake with dilute phosphoric acid with ph=3, (water volume 100ml) filter until the filtrate is clear; then wash the filter cake with pure water for 2 times (water volume 100ml for the first time, water volume 150ml for the second time), filter until the filtrate is clear; the washed filter cake is placed in a 60°C oven and dried for 12h to obtain 12.61g of crude iron phosphate product. (The drying step is required for sending the intermediate product to the detection composition, and the actual process does not need to be dried.) Take 4g of crude iron phosphate powder (dry powder) and mix with 40ml of 0.5mol / L dilute phosphoric acid, place in a 90°C water bath and stir for 2 hours; separate the solid by filtration, wash with 60°C pure water for 2 times (water volume 150ml each time), filter and dry in a 60°C oven for 12h to obtain 3.58g of white powder iron phosphate dihydrate product.
[0046] Example 2 is compared with Example 1, the difference is that the waste phosphoric acid pretreatment impurity removal step is added, and dilute phosphoric acid is used instead of pure water for the first washing, which can effectively remove aluminum impurities. Compared with the original waste phosphoric acid, the aluminum removal rate is 86%, and the aluminum in the waste phosphoric acid is reduced to 0.03%, reaching the standard line of iron phosphate product.
[0047] The products obtained in Example 1 and Example 2 are sent to a professional testing agency for testing, and the product testing data is shown in Table 1: Table 1
[0048] Specifically, the present application uses low-cost waste phosphoric acid as raw material to prepare low-impurity iron phosphate, which can effectively reduce the disposal cost of phosphoric acid wastewater, improve the utilization rate of phosphorus resources, reduce the cost of raw materials, and ensure the quality of iron phosphate products, thereby improving the competitiveness in the hazardous waste market.
[0049] The above is only a preferred embodiment of the present application, and does not limit the patent scope of the present application, any equivalent structural transformation made under the inventive concept of the present application, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.
Claims
1. A method for preparing iron phosphate using phosphoric acid waste liquid, characterized by, The method comprises the following steps: Step S1, waste phosphoric acid pretreatment, a certain amount of waste phosphoric acid solution is added into a reaction kettle, and pure water is added for dilution, and alkali solution is added dropwise to adjust the pH value of the waste phosphoric acid solution; Step S2, waste phosphoric acid impurity removal, when colloids and precipitates are generated in the reaction solution, PAM is added to purify the impurity metal ions in the waste phosphoric acid solution, and after standing, the supernatant is extracted, and the phosphorus source solution after impurity removal is obtained by filtration; Step S3, iron phosphate synthesis, iron salt solution, hydrogen peroxide and surfactant are added to the waste phosphoric acid solution obtained in step S2, and stirred and mixed uniformly, the molar ratio of iron to phosphorus is controlled to be 1:1~1.2:1, the pH value is controlled to be 1.6~2.2, heated to 30~60℃, after the reaction is completed, stand for 1~2h, generate iron phosphate slurry, after filtration and washing, obtain iron phosphate filter cake, after repeated filtration and washing of the iron phosphate filter cake, obtain crude iron phosphate filter cake; Step S4, refined iron phosphate, the crude iron phosphate filter cake obtained in step S3 is stirred and mixed with phosphoric acid solution to obtain slurry, the slurry is stirred and heated to 80~90℃, and the crystal transformation is aged to obtain white slurry, after filtration and washing, refined iron phosphate filter cake is obtained; Step S5, the refined iron phosphate filter cake obtained in step S4 is repeatedly washed and filtered, and finally dried and ground to obtain white iron phosphate powder, which is used as raw material for preparation of lithium iron phosphate.
2. The method for preparing iron phosphate using phosphoric acid waste liquid according to claim 1, characterized by, In step S1, the mass fraction of phosphoric acid in the waste phosphoric acid solution obtained by adding pure water to dilute the waste phosphoric acid solution is 15%~30%.
3. The method for preparing iron phosphate using phosphoric acid waste liquid according to claim 1, characterized by, In step S1, the alkali solution can be one of sodium hydroxide, sodium carbonate, calcium hydroxide and ammonia solution, and the pH value of the waste phosphoric acid solution is controlled to be 3.5~5.
5.
4. The method for preparing iron phosphate using phosphoric acid waste liquid according to claim 1, characterized in that, In step S3, the iron salt solution is one or more of ferrous chloride, ferrous sulfate or ferrous oxalate, and the surfactant is one of cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate or citric acid.
5. The method for preparing iron phosphate using phosphoric acid waste liquid according to claim 1, characterized in that, In step S3, the feeding time is controlled to be 10~30min, and stirring is maintained, and the stirring speed is controlled to be 500~800rpm / min. 6.The method for preparing iron phosphate using phosphoric acid waste liquid according to claim 1, characterized in that, In step S3, the iron phosphate filter cake is washed and filtered for 3~4 times, the first washing is performed using dilute phosphoric acid with a pH value of 2~3, and the subsequent washing is performed using pure water. 7.The method for preparing iron phosphate using phosphoric acid waste liquid according to claim 1, characterized in that, In step S4, the concentration of the phosphoric acid solution is 0.5~2mol / L, and the usage amount is solid-liquid ratio 1:2~1:
4. 8.The method for preparing iron phosphate using phosphoric acid waste liquid according to claim 1, characterized in that, In step S4, the stirring speed is 300~500rpm / min, and the crystal transformation aging time is 120~180min. 9.The method for preparing iron phosphate using phosphoric acid waste liquid according to claim 1, characterized in that, In step S5, the refined iron phosphate filter cake is washed and filtered for 2~3 times, and pure water is used for washing. 10.The method for preparing iron phosphate using phosphoric acid waste liquid according to claim 1, characterized in that, In step S5, the drying temperature is 60~100℃, and the drying time is 8~12h.