Method for preparing iron phosphate from chlorine-process iron phosphate production wastewater

Abstract

The invention discloses a method for preparing iron phosphate from chlorine-process iron phosphate production wastewater, which comprises the following steps: adding iron oxyhydroxide into the chlorine-process iron phosphate production wastewater to obtain filtrate and filter residue; the chlorine-process iron phosphate production wastewater comprises iron ions, hydrogen ions, phosphate ions and chloride ions; aging, washing and drying the filter residues to obtain iron phosphate; and concentrating the filtrate to obtain a ferric chloride solution. According to the method for preparing the iron phosphate from the chlorine-process iron phosphate production wastewater, provided by the invention, under the condition that new impurities are not introduced, iron ions and phosphate ions in the wastewater are recycled, and environment-friendly treatment and resource reutilization of the wastewater are realized.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method for preparing ferric phosphate from chlorine-based ferric phosphate production wastewater. Background Art

[0002] With the rapid development of the new energy battery industry, lithium-ion batteries with lithium iron phosphate as the positive electrode material have the advantages of a wide range of raw material sources, low cost, and outstanding safety performance, and have gradually occupied an increasingly large market share. As the precursor of lithium iron phosphate positive electrode materials, the demand for iron phosphate is also gradually increasing. A large amount of inorganic salt wastewater will be generated during the synthesis, aging, and washing processes of iron phosphate. The wastewater produced by the chlorinated ferric phosphate process mainly contains iron ions, hydrogen ions, chloride ions, phosphate ions, etc. The discharge of wastewater will not only damage the surrounding environment, but also cause waste of resources in the wastewater. Therefore, the harmless and resource-based treatment of chlorinated ferric phosphate production wastewater has become a hot topic in industry research.

[0003] Chinese patent CN115677077 A discloses a wastewater treatment method for ferric chloride phosphate, and the process mainly includes: using calcium hydroxide to adjust the pH value of ferric phosphate production wastewater until flocculation precipitation is formed, pressing filtration to separate the filtrate and the filter residue, evaporating and concentrating the filtrate, crystallizing, granulating, and high-temperature drying to obtain a calcium chloride product. This process can recycle the chloride ions in the wastewater, but other ions (such as phosphate, iron ions, etc.) are formed during the pH adjustment process. The precipitation is not effectively treated; at the same time, the process flow is long, the energy consumption is high, and the cost is high. Summary of the invention

[0004] The present invention aims to solve at least one of the problems in the related art to a certain extent. To this end, the purpose of the present invention is to provide a method for preparing ferric phosphate from wastewater produced by chlorine-based ferric phosphate production, which can achieve the recycling of iron ions and phosphate ions in the wastewater without introducing new impurities, thereby achieving environmentally friendly treatment of the wastewater and resource recycling.

[0005] In order to achieve the above purpose, this application adopts the following technical solutions:

[0006] A method for preparing ferric phosphate from chlorine-based ferric phosphate production wastewater, comprising:

[0007] Adding ferric oxyhydroxide to ferric chlorine phosphate production wastewater to obtain a filtrate and a filter residue; the ferric chlorine phosphate production wastewater includes iron ions, hydrogen ions, phosphate ions and chloride ions;

[0008] Aging, washing and drying the filter residue to obtain iron phosphate;

[0009] The filtrate is concentrated to obtain a ferric chloride solution.

[0010] Furthermore, the chlorinated ferric phosphate production wastewater comprises 0.30wt%-0.52wt% of phosphorus, 0.02wt%-0.06wt% of chlorine and 0.10wt%-0.16wt% of iron; and the pH value of the chlorinated ferric phosphate production wastewater is 1.05-1.15.

[0011] Furthermore, the filter residue is aged with a phosphoric acid solution, and the aging process conditions include: the pH value of the phosphoric acid solution is 1.10-1.20, the aging temperature is 40-80° C., and the aging time is 0.5-2.0 hours.

[0012] Furthermore, the process conditions of the water washing include: the conductivity of the washing liquid is ≤250us / cm.

[0013] Furthermore, the drying process conditions include: a drying temperature of 550-750°C.

[0014] Furthermore, the molar ratio of the added ferric oxyhydroxide to the phosphate ions in the chlorinated ferric phosphate production wastewater is 1.05-1.30:1.

[0015] Furthermore, after adding ferric hydroxide oxide to the chlorinated ferric phosphate production wastewater, the reaction temperature is maintained at 90-105° C.; the reaction time is 2-4 hours; and the stirring speed of the reaction is 100-300 r / min.

[0016] Furthermore, after adding ferric oxyhydroxide to the chlorinated ferric phosphate production wastewater, the reaction product is separated by a solid-liquid separation device to obtain a filtrate and a filter residue; the solid-liquid separation device is a plate and frame filter press.

[0017] Furthermore, the filtrate is concentrated, and the obtained ferric chloride solution is used to return to the chlorinated ferric phosphate production line.

[0018] The above technical solution provided by the embodiment of the present application has the following advantages over the prior art: the present invention uses ferric hydroxide as a wastewater treatment agent, which can realize the recovery and utilization of phosphate ions in the wastewater, and the recovery rate of phosphorus in the chlorinated ferric phosphate production wastewater can reach more than 99.6%; at the same time, ferric hydroxide will not introduce new impurities, and the iron ions introduced during the addition of ferric hydroxide form a ferric chloride solution in the filtrate, which can also be further concentrated and recovered to form a ferric chloride solution for returning to the chlorinated ferric phosphate production line, or for other uses of ferric chloride.

[0019] In the present application, ferric hydroxide can not only recover phosphate ions, but also serve as an alkali source to adjust the pH value of the wastewater, thereby avoiding the pH value adjustment by solvents such as calcium hydroxide or sodium hydroxide in the prior art. The existing pH value adjustment will introduce new impurities and cannot effectively separate the iron phosphate precipitate.

[0020] The wastewater treatment method of the present application is simple and fast. Battery-grade iron phosphate can be obtained with the help of the chlorinated ferric phosphate production line. Chloride ions and iron ions in the wastewater can also be effectively recycled and returned to the chlorinated ferric phosphate production line. No additional wastewater treatment equipment is required, and the production efficiency of chlorinated ferric phosphate can be improved. DETAILED DESCRIPTION

[0021] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Without departing from the spirit and essence of the present invention, modifications or substitutions made to the methods, steps or conditions of the present invention all belong to the scope of protection of the present invention. Unless otherwise specified, the experimental materials, reagents, instruments, etc. used in the present examples are all commercially available; unless otherwise specified, all technical means in the examples of the present invention are conventional means well known to those skilled in the art.

[0022] This application is for the recycling and reuse of wastewater after processing of the chlorinated ferric phosphate production line. The chlorinated ferric phosphate process refers to the use of ferric chloride salt as an iron source and phosphoric acid as a phosphorus source, and the ferric phosphate powder is prepared through synthesis, aging, washing and drying processes. The ferric phosphate produced by the chlorination method has a higher purity and is suitable for the preparation of high-precision chemicals such as electronic materials, catalysts, and metal surface treatment agents. The wastewater produced contains iron ions, hydrogen ions, phosphate ions and chloride ions, and the iron ions are stably present in the form of trivalent iron ions. Specifically, the chlorinated ferric phosphate production wastewater includes 0.30wt%-0.52wt% of phosphorus, 0.02wt%-0.06wt% of chlorine and 0.10wt%-0.16wt% of iron; and the pH value of the chlorinated ferric phosphate production wastewater is 1.05-1.15.

[0023] The present application provides a method for preparing ferric phosphate from chlorine-based ferric phosphate production wastewater, comprising:

[0024] S1: Adding ferric hydroxide oxide to the wastewater from the production of chlorinated ferric phosphate to obtain a filtrate and a filter residue.

[0025] Specifically, the molar ratio of the added ferric hydroxide to the phosphate ions in the chlorinated ferric phosphate production wastewater is 1.05-1.30:1. The reaction of the ferric hydroxide in this step is as follows:

[0026] FeOOH+H3PO4→FePO4·2H2O

[0027] In order to ensure that the phosphate ions are fully reacted and recovered, the molar amount of the iron oxyhydroxide added in the present application is slightly greater than the molar amount of the phosphate ions, and the remaining iron ions are dissolved in the solution under acidic conditions.

[0028] While recovering phosphate ions, ferric hydroxide can also serve as an alkali source to adjust the pH value of wastewater, avoiding the pH adjustment by solvents such as calcium hydroxide or sodium hydroxide in the prior art. The existing pH adjustment method will introduce new impurities and cannot effectively separate the iron phosphate precipitate.

[0029] In this step, after adding ferric hydroxide to the chlorine-based ferric phosphate production wastewater, the reaction temperature is maintained at 90-105°C; the reaction time is 2-4 hours; the reaction stirring speed is 100-300r / min, so that the ferric hydroxide and the phosphate ions are fully mixed and reacted to obtain ferric phosphate precipitation. The reaction temperature and stirring speed can ensure that the ferric hydroxide and the phosphate ions in the wastewater fully react.

[0030] After sufficient reaction, the reaction product is separated by solid-liquid separation equipment to obtain filtrate and filter residue; the solid-liquid separation equipment can specifically be a plate-frame filter press.

[0031] S2: Aging, washing and drying the filter residue to obtain battery-grade iron phosphate.

[0032] It should be noted that the filter residue in this application is the ferric phosphate precipitate. After obtaining the ferric phosphate precipitate, the ferric phosphate precipitate can be aged, washed and dried with the help of the chlorinated ferric phosphate production line, without the need to set up a separate processing device. In fact, the chlorinated ferric phosphate production line is already equipped with aging, washing and drying process devices, and this application directly transfers the precipitate generated in step S1 to the aging, washing and drying workshop in the chlorinated ferric phosphate production line. The aging, washing and drying described below in this application are also the equipment and process conditions in the chlorinated ferric phosphate production line.

[0033] Specifically, in the aging process, a phosphoric acid solution is used to age the filter residue, and the aging process conditions include: the pH value of the phosphoric acid solution is 1.10-1.20, the aging temperature is 40-80°C, and the aging time is 0.5-2.0 hours. The present application performs aging treatment on the generated iron phosphate in order to improve the stability of the iron phosphate. After the aging treatment, the amorphous lattice in the iron phosphate can be changed into a stable form, so that the performance of the iron phosphate is more stable.

[0034] Specifically, the process conditions of the water washing include: the conductivity of the washing liquid is ≤250us / cm. The washing liquid here refers to the washing of the aged iron phosphate with deionized water. The solution after the iron phosphate is washed with deionized water is the washing liquid. In the water washing process, the conductivity of the washing liquid needs to be monitored in real time to ensure that its conductivity is less than or equal to 250us / cm. The purpose of this is to ensure that the metal ions in the iron phosphate are fully washed and removed, and the content of metal impurities is controlled to be reduced to below the standard requirements of battery-grade iron phosphate, thereby improving the purity of battery-grade iron phosphate.

[0035] Specifically, the iron phosphate after washing is dried and used as battery-grade iron phosphate, just like the iron phosphate prepared in the chlorine-based iron phosphate production process. The drying process conditions include: a drying temperature of 550-750° C. The iron phosphate after drying and dehydration meets the battery grade.

[0036] The present application uses ferric hydroxide as a wastewater treatment agent, which can realize the recycling of phosphate ions in the wastewater. There is no need to separately adjust the pH value of the wastewater, and there is no need to introduce new impurities. The phosphate ions in the wastewater can be fully recovered, and there is no need to set up a separate treatment device and production line during the recovery process. It only needs to return the precipitate to the chlorinated ferric phosphate production line and use the existing aging, water washing and drying equipment for treatment. This realizes the recycling of wastewater and further improves the production efficiency of chlorinated ferric phosphate.

[0037] S3: Concentrate the filtrate to obtain a ferric chloride solution. The order of step S2 and step S3 of the present application can be interchanged or performed simultaneously.

[0038] The mass fraction of phosphorus in the filtrate after solid-liquid separation in step S1 is 0.001wt%-0.0015wt%. It can be seen that phosphate ions have been fully recovered with a small amount of residues, and the recovery rate of phosphorus in wastewater can reach more than 99.6%.

[0039] The filtrate is further concentrated, and the obtained ferric chloride solution is used to return to the chlorinated ferric phosphate production line. This application is aimed at treating the wastewater generated by the chlorinated ferric phosphate process, and the chlorinated ferric phosphate process refers to the use of ferric chloride salt as the iron source and phosphoric acid as the phosphorus source, and the ferric phosphate powder is prepared through synthesis, aging, washing, and drying processes. The filtrate after removing the filter residue from the wastewater of this application is basically free of phosphate ions, and after concentration, it can continue to be used as a raw material for the chlorinated ferric phosphate process.

[0040] It should be noted that the impurity content of the filtrate after the removal of phosphate can also be detected in real time, such as heavy metal content or other impurity content. If the impurity content exceeds the preset value, it can be discharged as secondary wastewater. Compared with the wastewater directly generated by the chlorinated ferric phosphate process, the secondary wastewater has fewer phosphate ions, and its subsequent treatment process can be simpler and more convenient, which can also reduce the difficulty and cost of the chlorinated ferric phosphate process wastewater.

[0041] Specifically, the present application can set the filtrate of the previous batch to be returned to the chlorinated ferric phosphate production line for use as raw materials, and the previous batch refers to the filtrate whose impurity content does not exceed the preset value. The filtrate of the latter batch is treated as secondary wastewater, and the latter batch refers to the filtrate whose impurity content exceeds the preset value; for example, the filtrate of the first 5 batches is returned to the chlorinated ferric phosphate production line, and the filtrate of the 6th batch is treated as secondary wastewater, and so on, with 6 cycles as a complete wastewater treatment cycle. In this way, the problem of excessive metal impurities introduced after the filtrate is recycled for multiple times can be avoided, thereby ensuring the performance stability of the iron phosphate obtained by the chlorinated ferric phosphate production line.

[0042] The main component of the filtrate after removing phosphate is ferric chloride, which can also be used as a water purifier.

[0043] The core of the present application is that the pH value of the wastewater produced by the chlorinated ferric phosphate production is no longer directly adjusted, but iron oxyhydroxide is used as both a wastewater treatment agent and a pH regulator.

[0044] Ferric oxyhydroxide is used as a treatment agent to recycle phosphate ions in wastewater and form iron phosphate precipitates. At the same time, ferric oxyhydroxide does not introduce new impurities. The iron ions introduced during the addition of ferric oxyhydroxide form a ferric chloride solution in the filtrate, which can be further concentrated and recovered to form a ferric chloride solution. The ferric phosphate and ferric chloride solutions obtained during the use of ferric oxyhydroxide as a treatment agent can be returned to the chlorinated ferric phosphate production line, where ferric phosphate can be processed and output as a product of the chlorinated ferric phosphate production line, and ferric chloride can be reused as a raw material for the chlorinated ferric phosphate production line. The entire wastewater treatment process is combined with the chlorinated ferric phosphate production line, eliminating the need for separate treatment equipment and devices, and can improve the production efficiency of chlorinated ferric phosphate.

[0045] Ferric oxyhydroxide is used as a pH regulator to adjust the pH value of wastewater while recovering phosphate ions, avoiding the pH adjustment by solvents such as calcium hydroxide or sodium hydroxide in the prior art. The existing pH adjustment method will introduce new impurities and cannot effectively separate the iron phosphate precipitate.

[0046] The present application is further explained and illustrated by specific embodiments below:

[0047] Example 1

[0048] This embodiment provides a method for preparing ferric phosphate from chlorine-based ferric phosphate production wastewater, comprising:

[0049] 10 tons of chlorinated ferric phosphate production wastewater was obtained, wherein the ferric phosphate wastewater contained 0.30 wt% phosphorus, 0.02 wt% chlorine and 0.10 wt% iron; and the pH value of the chlorinated ferric phosphate production wastewater was 1.15. 142 kg of ferric hydroxide oxide (Fe: 40.12 wt%) was added to the chlorinated ferric phosphate production wastewater according to a Fe:P molar ratio of 1.05:1, the stirring speed was maintained at 100 r / min, the reaction temperature was 105°C, the reaction time was 2 h, and 260 kg of ferric phosphate dihydrate (water content 30.80 w%) and filtrate were obtained by filter press separation.

[0050] The following treatment is performed on the ferric phosphate dihydrate separated by filter pressing: the ferric phosphate dihydrate is returned to the chlorine phosphate production line for aging treatment. Specifically, the ferric phosphate dihydrate is aged with a phosphoric acid solution having a pH value of 1.10, and the phosphoric acid solution is prepared in a ratio of 1:5 between the ferric phosphate dihydrate and the phosphoric acid solution (aging solution), the aging temperature is maintained at 40°C, the aging time is 0.5h, and the aging is completed by filter pressing. The aged ferric phosphate dihydrate is washed with water until the conductivity of the washing liquid is 230us / cm and the washing process is stopped; the washed ferric phosphate dihydrate is dried and dehydrated at a drying and dehydration temperature of 550-750°C to obtain battery-grade iron phosphate.

[0051] The filtrate from the filter press separation was treated as follows: the phosphorus content in the filtrate was detected, and the test results showed that the phosphorus content in the filtrate was 0.001wt%, indicating that the phosphorus content in the filtrate was very low, and the phosphate ions in the chlorinated ferric phosphate production wastewater had been fully recovered as ferric phosphate. The filtrate was evaporated and concentrated to obtain a ferric chloride solution, which was returned to the chlorinated ferric phosphate production line as a raw material for recycling.

[0052] Example 2

[0053] This embodiment provides a method for preparing ferric phosphate from chlorine-based ferric phosphate production wastewater, comprising:

[0054] 12 tons of chlorinated ferric phosphate production wastewater was obtained, wherein the chlorinated ferric phosphate wastewater contained 0.40 wt% phosphorus, 0.04 wt% chlorine and 0.12 wt% iron; and the pH value of the chlorinated ferric phosphate production wastewater was 1.10. 281 kg of ferric hydroxide oxide (Fe: 40.12 wt%) was added to the chlorinated ferric phosphate production wastewater at a Fe:P molar ratio of 1.30:1, the stirring speed was maintained at 300 r / min, the reaction temperature was 90°C, the reaction time was 4 h, and 420 kg of dihydrate phosphoric acid (water content 31.5 wt%) and filtrate were obtained by filter press separation.

[0055] The following treatment is performed on the ferric phosphate dihydrate separated by filter pressing: the ferric phosphate dihydrate is returned to the chlorine phosphate production line for aging treatment. Specifically, the ferric phosphate dihydrate is aged with a phosphoric acid solution having a pH value of 1.2, and the phosphoric acid solution is prepared in a ratio of 1:5 between the ferric phosphate dihydrate and the phosphoric acid solution (aging solution), and the aging temperature is maintained at 80°C for 2 hours. After aging, filter pressing is performed for separation. The aged ferric phosphate dihydrate is washed with water until the conductivity of the washing liquid is 230us / cm and the washing process is stopped; the washed ferric phosphate dihydrate is dried and dehydrated at a drying and dehydration temperature of 550-750°C to obtain battery-grade iron phosphate.

[0056] The filtrate from the filter press separation was treated as follows: the phosphorus content in the filtrate was detected. The test results showed that the phosphorus content in the filtrate was 0.0012wt%, indicating that the phosphorus content in the filtrate was very low, and the phosphate ions in the chlorinated ferric phosphate production wastewater had been fully recovered as ferric phosphate. The filtrate was evaporated and concentrated to obtain a ferric chloride solution, which was returned to the chlorinated ferric phosphate production line for recycling as a raw material.

[0057] Example 3

[0058] This embodiment provides a method for preparing ferric phosphate from chlorine-based ferric phosphate production wastewater, comprising:

[0059] 15 tons of chlorinated ferric phosphate production wastewater was obtained, wherein the chlorinated ferric phosphate wastewater contained 0.50 wt% phosphorus, 0.06 wt% chlorine and 0.16 wt% iron; and the pH value of the chlorinated ferric phosphate production wastewater was 1.050. 405 kg of ferric hydroxide oxide (Fe: 40.12 wt%) was added to the chlorinated ferric phosphate production wastewater at a Fe:P molar ratio of 1.15:1, the stirring speed was maintained at 300 r / min, the reaction temperature was 90°C, the reaction time was 4 h, and 420 kg of dihydrate phosphoric acid (water content 30 wt%) and filtrate were obtained by filter press separation.

[0060] The following treatment is performed on the ferric phosphate dihydrate separated by filter pressing: the ferric phosphate dihydrate is returned to the chlorine phosphate production line for aging treatment. Specifically, the ferric phosphate dihydrate is aged with a phosphoric acid solution having a pH value of 1.15, and the phosphoric acid solution is prepared in a ratio of 1:5 between the ferric phosphate dihydrate and the phosphoric acid solution (aging solution), and the aging temperature is maintained at 60°C for 1 hour. After aging, filter pressing is performed for separation. The aged ferric phosphate dihydrate is washed with water until the conductivity of the washing liquid is 225us / cm and the washing process is stopped; the washed ferric phosphate dihydrate is dried and dehydrated at a drying and dehydration temperature of 550-750°C to obtain battery-grade iron phosphate.

[0061] The filtrate from the filter press separation was treated as follows: the phosphorus content in the filtrate was detected. The test results showed that the phosphorus content in the filtrate was 0.0015wt%, indicating that the phosphorus content in the filtrate was very low, and the phosphate ions in the chlorinated ferric phosphate production wastewater had been fully recovered as ferric phosphate. The filtrate was evaporated and concentrated to obtain a ferric chloride solution, which was returned to the chlorinated ferric phosphate production line for recycling as a raw material.

[0062] From Example 1 to Example 3, it can be seen that the recovery rate of phosphate ions in the chlorinated ferric phosphate production wastewater can reach more than 99.6%. The use of ferric hydroxide as a treatment agent can achieve the recycling of phosphate ions in the wastewater to form ferric phosphate precipitation. At the same time, ferric hydroxide does not introduce new impurities. The iron ions introduced during the addition of ferric hydroxide form a ferric chloride solution in the filtrate, and can be further concentrated and recovered to form a ferric chloride solution. The ferric phosphate and ferric chloride solutions obtained during the use of ferric hydroxide as a treatment agent can be returned to the chlorinated ferric phosphate production line, wherein ferric phosphate can be processed and output as a product of the chlorinated ferric phosphate production line, and ferric chloride can be reused as a raw material for the chlorinated ferric phosphate production line. The entire wastewater treatment process is combined with the chlorinated ferric phosphate production line, without the need for separate treatment equipment and devices, and can improve the production efficiency of chlorinated ferric phosphate.

[0063] At the same time, ferric hydroxide is used as a pH regulator to adjust the pH value of the wastewater while recovering phosphate ions, avoiding the pH adjustment by solvents such as calcium hydroxide or sodium hydroxide in the prior art. The existing pH adjustment method will introduce new impurities and cannot effectively separate the iron phosphate precipitate.

[0064] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

1. A method for preparing ferric phosphate from chlorine-based ferric phosphate production wastewater, characterized in that: include: Adding ferric oxyhydroxide to ferric chlorine phosphate production wastewater to obtain a filtrate and a filter residue; the ferric chlorine phosphate production wastewater includes iron ions, hydrogen ions, phosphate ions and chloride ions; Aging, washing and drying the filter residue to obtain iron phosphate; The filtrate is concentrated to obtain a ferric chloride solution.

2. The method for preparing ferric phosphate from chlorinated ferric phosphate production wastewater according to claim 1, characterized in that: The chlorinated ferric phosphate production wastewater comprises 0.30wt%-0.52wt% of phosphorus, 0.02wt%-0.06wt% of chlorine and 0.10wt%-0.16wt% of iron; the pH value of the chlorinated ferric phosphate production wastewater is 1.05-1.

15.

3. The method for preparing ferric phosphate from chlorine-based ferric phosphate production wastewater according to claim 1, characterized in that: The filter residue is aged by using a phosphoric acid solution, and the aging process conditions include: the pH value of the phosphoric acid solution is 1.10-1.20, the aging temperature is 40-80° C., and the aging time is 0.5-2.0 hours.

4. The method for preparing ferric phosphate from chlorinated ferric phosphate production wastewater according to claim 1, characterized in that: The process conditions of water washing include: the conductivity of the washing liquid is ≤250us / cm.

5. The method for preparing ferric phosphate from chlorine-based ferric phosphate production wastewater according to claim 1, characterized in that: The drying process conditions include: a drying temperature of 550-750°C.

6. The method for preparing ferric phosphate from chlorine-based ferric phosphate production wastewater according to claim 1, characterized in that: The molar ratio of the added ferric oxyhydroxide to the phosphate ions in the chlorinated ferric phosphate production wastewater is 1.05-1.30:

1.

7. The method for preparing ferric phosphate from chlorinated ferric phosphate production wastewater according to claim 6, characterized in that: After adding ferric hydroxide oxide to the chlorinated ferric phosphate production wastewater, the reaction temperature is maintained at 90-105°C; the reaction time is 2-4 hours; and the stirring speed of the reaction is 100-300 r / min.

8. The method for preparing ferric phosphate from chlorinated ferric phosphate production wastewater according to claim 1, characterized in that: After adding ferric oxyhydroxide to the chlorinated ferric phosphate production wastewater, the reaction product is separated by a solid-liquid separation device to obtain a filtrate and a filter residue; the solid-liquid separation device is a plate-frame filter press.

9. The method for preparing ferric phosphate from chlorinated ferric phosphate production wastewater according to claim 1, characterized in that: The filtrate is concentrated and the obtained ferric chloride solution is returned to the chlorinated ferric phosphate production line.