Method for treating iron phosphate production wastewater

Abstract

The application discloses a treatment method of iron phosphate production wastewater, and solves the technical problem of difficult treatment of the iron phosphate production wastewater in the prior art. The treatment method of the iron phosphate production wastewater comprises the following steps: (1) adjusting the pH of the wastewater to 2.2-2.5, and then performing solid-liquid separation to obtain first filtrate and first solid; (2) adjusting the pH of the first filtrate to 5.5-6, and then performing solid-liquid separation to obtain second filtrate and second solid; (3) adding a silicon-fluorine adsorbent and a flocculating agent into the second mother liquor, and then performing solid-liquid separation to obtain third filtrate and third solid; (4) performing nanofiltration membrane treatment on the third filtrate to obtain first concentrated water and first produced water; (5) adjusting the pH of the first concentrated water to 9-9.5, adding phosphate, and then performing solid-liquid separation to obtain fourth filtrate and fourth solid; and (6) performing reverse osmosis membrane treatment on the first produced water and the fourth filtrate to obtain second concentrated water and second produced water; and the second concentrated water is rich in ammonium sulfate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of iron phosphate, in particular to the technical field of treatment of wastewater generated in the production of iron phosphate, and more particularly to a treatment method for iron phosphate production wastewater. BACKGROUND

[0002] The use of new energy vehicles such as electric vehicles and fuel cell vehicles can improve current environmental problems to a certain extent. Therefore, the encouragement of national policy for the new energy vehicle industry has led to a rapid increase in the production and sales of electric vehicles in China. The energy storage and power system of electric vehicles mainly uses lithium ion batteries, which have the advantages of high energy, no memory effect, and long service life.

[0003] At present, domestic electric vehicle enterprises mainly use lithium iron phosphate batteries as power batteries. Iron phosphate, lithium carbonate and sugar have always played an important role as the three main materials for making lithium iron phosphate materials. Iron phosphate, as a source of phosphorus and iron, is the most important precursor for the production of lithium iron phosphate.

[0004] The most widely used preparation process for iron phosphate today is as follows:

[0005] (1) Ferrous sulfate (iron source) preparation: purchase iron powder or iron oxide scale, add sulfuric acid to synthesize ferrous sulfate; the tail gas generated in this section is absorbed with liquid alkali; the wastewater produced in this section is waste gas treatment wastewater.

[0006] (2) Pre-dissolution: mix ferrous sulfate, deionized water and phosphoric acid together and stir.

[0007] (3) Oxidation precipitation: add hydrogen peroxide and ammonia water to the pre-dissolved ferrous sulfate solution for oxidation precipitation to obtain iron liquid mother liquor and iron phosphate precipitate. The impurity elements contained in the iron liquid mother liquor will increase over time after multiple uses, at which time the replaced part of the wastewater is called iron phosphate mother liquor wastewater.

[0008] (4) Filter pressing and washing: filter pressing the solid-liquid mixture after oxidation precipitation to extract the mother liquor, which is returned to the oxidation precipitation section of the previous step, and finally washing the filter cake with deionized water to remove the impurities inside. The wastewater generated in this section is iron phosphate washing wastewater.

[0009] (5) Drying: the washed filter cake is transported to the drying process through a line, and flash drying is commonly used. The waste gas generated during the drying process is absorbed with dilute sulfuric acid. This section also generates waste gas treatment wastewater.

[0010] (6) The dried filter cake is crushed and packaged to obtain iron phosphate.

[0011] It can be seen that a large amount of wastewater such as iron phosphate washing wastewater, waste gas treatment wastewater, iron phosphate mother liquor wastewater and the like will be produced in the production process of iron phosphate. According to the pilot production of battery-grade iron phosphate by Guangxi Xinzhi Technology Co., Ltd., it is estimated that about 50 tons of wastewater will be produced per ton of battery-grade iron phosphate, and these wastewaters have the characteristics of low pH, high salinity, containing multiple heavy metals, and high conductivity, which makes it difficult to be economically, efficiently and deeply treated.

[0012] The relatively mature treatment methods for the iron phosphate production wastewater include precipitation method, stripping method and membrane technology method. Among them, the chemical precipitation method is simple in operation, mature in technology and easy to industrialize, but the reagent consumption is large, and the produced water is difficult to reach the discharge standard due to the influence of the solubility limit of the precipitate, and the precipitate salt has multiple types and complex components, which is difficult to be secondarily utilized. The blowing method has small occupied area, but the cost of the pretreatment reagent used is high, and the stripping tower is easy to scale and has low removal efficiency. The membrane technology method is simple in operation and can realize resource utilization, but the process chain is long, each process easily affects each other, and the damage of fluorine ions in water to the equipment is not considered. SUMMARY

[0013] The main purpose of the present application is to provide a treatment method and system for iron phosphate production wastewater to solve the technical problem of difficult treatment of iron phosphate production wastewater in the prior art.

[0014] In order to achieve the above-mentioned purpose, the present application first provides a treatment method for iron phosphate production wastewater, and the technical scheme is as follows:

[0015] The treatment method for iron phosphate production wastewater comprises the following steps:

[0016] (1) adjusting the pH of the wastewater to 2.2-2.5, and then solid-liquid separation to obtain a first filtrate and a first solid;

[0017] (2) adjusting the pH of the first filtrate to 5.5-6, and then solid-liquid separation to obtain a second filtrate and a second solid;

[0018] (3) adding a silicon-fluorine adsorbent and a flocculating agent to the second filtrate, and then solid-liquid separation to obtain a third filtrate and a third solid;

[0019] (4) performing nanofiltration membrane treatment on the third filtrate to obtain a first concentrated water and a first produced water;

[0020] (5) adjusting the pH of the first concentrated water to 9-9.5, adding a phosphate, and then solid-liquid separation to obtain a fourth filtrate and a fourth solid;

[0021] (6) performing reverse osmosis membrane treatment on the first produced water and the fourth filtrate to obtain a second concentrated water and a second produced water; the second concentrated water is rich in ammonium sulfate.

[0022] As a further improvement of the above treatment method: the iron phosphate production wastewater is any one or mixture of any several of iron phosphate washing wastewater, waste gas treatment wastewater, and iron phosphate mother liquor wastewater.

[0023] As a further improvement of the above treatment method: the pH of the iron phosphate production wastewater is ≤1.5, the ammonia nitrogen concentration is ≥5000 mg / L, the fluoride ion concentration is ≥200 mg / L, the sulfate radical concentration is ≥50000 mg / L, the phosphate radical concentration is ≥850 mg / L, the conductivity is ≥100000 uS / cm, the silicon dioxide is ≥60 mg / L, and the contained ions at least include aluminum ion, iron ion, manganese ion, calcium ion, potassium ion, magnesium ion, and sodium ion.

[0024] As a further improvement of the above treatment method: after the pH adjustment of the first filtrate, the reaction is carried out for 20-30 minutes before the solid-liquid separation treatment.

[0025] As a further improvement of the above treatment method: the adsorbent is polyaluminum sulfate; the flocculant is PAM; after the addition of the silicon fluoride adsorbent, the reaction is carried out for 20-30 minutes before the addition of the flocculant.

[0026] As a further improvement of the above treatment method: the phosphate is ammonium dihydrogen phosphate.

[0027] As a further improvement of the above treatment method: the third filtrate is subjected to ultrafiltration treatment before nanofiltration membrane treatment; and the fourth filtrate is subjected to ultrafiltration treatment before reverse osmosis membrane treatment.

[0028] As a further improvement of the above treatment method: the operation pressure of the nanofiltration membrane treatment is 20-30 bar; and the operation pressure of the reverse osmosis membrane treatment is 120-130 bar.

[0029] As a further improvement of the above treatment method: the pH of the first produced water and the fourth filtrate is adjusted to 6-7 before the reverse osmosis membrane treatment.

[0030] As a further improvement of the above treatment method: further comprising the step of: evaporating the second concentrated water to obtain condensed water for water reuse and fifth solid mainly containing ammonium sulfate.

[0031] To achieve the above object, the application further provides a treatment system for iron phosphate production wastewater, and the technical scheme is as follows:

[0032] The treatment system for iron phosphate production wastewater comprises:

[0033] A first reaction tank for adjusting the pH of the wastewater and precipitating to obtain a first solid-liquid mixture;

[0034] a first filtering device for filtering the first solid-liquid mixture to obtain a first filtrate and a first solid;

[0035] a second reaction tank for adjusting the pH of the first filtrate and precipitating to obtain a second solid-liquid mixture;

[0036] a second filtering device for filtering the second solid-liquid mixture to obtain a second filtrate and a second solid;

[0037] a third reaction tank for reacting the second filtrate with a silicon-fluorine adsorbent and a flocculant to obtain a third solid-liquid mixture;

[0038] a third filtering device for filtering the third solid-liquid mixture to obtain a third filtrate and a third solid;

[0039] a nanofiltration membrane device for treating the third filtrate to obtain a first concentrated water and a first product water;

[0040] a fourth reaction tank for adjusting the pH of the first concentrated water and reacting with a phosphate to obtain a fourth solid-liquid mixture;

[0041] a fourth filtering device for filtering the fourth solid-liquid mixture to obtain a fourth filtrate and a fourth solid;

[0042] a reverse osmosis membrane device for treating the first product water and the fourth filtrate to obtain a second concentrated water and a second product water.

[0043] As a further improvement of the above treatment system, it further comprises a first feeding device for adding an alkaline adjusting agent, a second feeding device for adding a silicon-fluorine adsorbent, a third feeding device for adding a flocculant, a fourth feeding device for adding a phosphate, and a fifth feeding device for adding an acidic adjusting agent.

[0044] As a further improvement of the above treatment system, the first filtering device, the second filtering device, the third filtering device, and the fourth filtering device adopt any one of a plate-and-frame filter device, a belt filter press, and a ceramic filter device.

[0045] As a further improvement of the above treatment system, the nanofiltration membrane device and the reverse osmosis membrane device adopt a disc-and-tube membrane module or a spiral-wound membrane module.

[0046] As a further improvement of the above treatment system, it further comprises a fifth reaction tank, and the pH of the first product water and the fourth filtrate is adjusted to be weakly acidic in the fifth reaction tank before entering the reverse osmosis membrane device.

[0047] As a further improvement of the above treatment system, it further comprises a first ultrafiltration device, and the third filtrate is treated by the first ultrafiltration device before entering the nanofiltration membrane device.

[0048] As a further improvement of the above-mentioned treatment system, it further comprises a second ultrafiltration device, and the fourth filtrate is treated by the second ultrafiltration device before entering the reverse osmosis membrane device.

[0049] As a further improvement of the above-mentioned treatment system, it further comprises an evaporation crystallization device, and the evaporation crystallization device is used for evaporating the second concentrated water to obtain condensed water and a fifth solid.

[0050] As a further improvement of the above-mentioned treatment system, it further comprises a wastewater storage tank, and the wastewater storage tank is used for storing any one or a mixture of any several of the phosphatic iron washing wastewater, the waste gas treatment wastewater and the phosphatic iron mother liquor wastewater.

[0051] In the treatment method and the treatment system of the present application, firstly, a plurality of valuable solids can be recovered, including: the first solid is mainly phosphatic iron, which can be used as an iron source and a phosphorus source for synthesizing phosphatic iron; the second solid is mainly iron hydroxide adsorbed with fluoride ions, which can be used as an iron source for synthesizing phosphatic iron; the fourth solid can be used as a compound fertilizer; and the fifth solid is ammonium sulfate with high purity, which can be used as industrial-grade ammonium sulfate. Secondly, through a specific pollutant removal sequence, the use of reagents is reduced, the energy consumption and the loss of the membrane treatment device are significantly reduced, a plurality of precipitated salts with high purity and convenient secondary utilization are obtained, and the wastewater is reused up to the standard. It can be seen that the treatment method of the present application has simple process, and economic, efficient and deep treatment of the phosphatic iron production wastewater can be realized by using conventional equipment, the investment and operation cost are low, it is green and environmentally friendly, the technical problem of difficult treatment of the phosphatic iron production wastewater in the prior art is effectively solved, and the present application has strong practicability.

[0052] The present application will be further described below in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages of the present application will be partially given in the following description, partially will become obvious from the following description, or will be understood by those skilled in the art through the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0053] The accompanying drawings, which form a part of the present application, are used to aid in the understanding of the present application and the content provided by the accompanying drawings and the related description in the present application can be used to explain the present application, but do not constitute improper limitations on the present application.

[0054] Figure 1 It is a structure schematic view of one embodiment of the treatment system for the phosphatic iron production wastewater of the present application.

[0055] The related marks in the above-mentioned accompanying drawings are as follows:

[0056] 100 - wastewater storage tank, 211 - first reaction tank, 212 - first filtration device, 221 - second reaction tank, 222 - second filtration device, 231 - third reaction tank, 232 - third filtration device, 610 - first ultrafiltration device, 300 - nanofiltration membrane device, 241 - fourth reaction tank, 242 - fourth filtration device, 620 - second ultrafiltration device, 251 - fifth reaction tank, 400 - reverse osmosis membrane device, 500 - evaporation crystallization device, 710 - first feeding device, 720 - second feeding device, 730 - third feeding device, 740 - fourth feeding device, 750 - fifth feeding device. DETAILED DESCRIPTION

[0057] The present application will be described in detail below with reference to the drawings. Those skilled in the art will be able to implement the present application based on these descriptions. Before the present application is disclosed with reference to the drawings, it is to be particularly noted that the present application is not limited to the specific embodiments disclosed below, but encompasses all embodiments that will become apparent to those skilled in the art in light of the description.

[0058] The technical solutions and technical features provided in each part of the present application, including the following description, can be combined with each other without conflict.

[0059] In addition, the embodiments of the present application involved in the following description are generally only a part of the embodiments of the present application, not all. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments in the present application without creative labor should be within the scope of protection of the present application.

[0060] Regarding the terms and units in the present application. The terms "include", "have" and any variations thereof in the specification and claims of the present application and related parts are intended to cover non-exclusive inclusion.

[0061] Figure 1 Structure diagram of an embodiment of the iron phosphate production wastewater treatment system of the present application.

[0062] As shown in Figure 1 The iron phosphate production wastewater treatment system includes a wastewater storage tank 100, a first reaction tank 211, a first filtration device 212, a second reaction tank 221, a second filtration device 222, a third reaction tank 231, a third filtration device 232, a first ultrafiltration device 610, a nanofiltration membrane device 300, a fourth reaction tank 241, a fourth filtration device 242, a second ultrafiltration device 620, a fifth reaction tank 251, a reverse osmosis membrane device 400, an evaporation crystallization device 500, a first feeding device 710, a second feeding device 720, a third feeding device 730, a fourth feeding device 740, and a fifth feeding device 750.

[0063] The wastewater storage tank 100 is used for storing any one or a mixture of any several of iron phosphate washing wastewater, waste gas treatment wastewater and iron phosphate mother liquor wastewater.

[0064] The first reaction tank 211 is used for adjusting the pH of the wastewater and precipitating to obtain a first solid-liquid mixture;

[0065] The first filter device 212 is used for filtering the first solid-liquid mixture and obtaining a first filtrate and a first solid;

[0066] The second reaction tank 221 is used for adjusting the pH of the first filtrate and precipitating to obtain a second solid-liquid mixture;

[0067] The second filter device 222 is used for filtering the second solid-liquid mixture and obtaining a second filtrate and a second solid;

[0068] The third reaction tank 231 is used for reacting the second filtrate with a silicon-fluorine adsorbent and a flocculant to obtain a third solid-liquid mixture;

[0069] The third filter device 232 is used for filtering the third solid-liquid mixture and obtaining a third filtrate and a third solid; the third filtrate is treated by the first ultrafiltration device 610 and then enters the nanofiltration membrane device 300;

[0070] The nanofiltration membrane device 300 is used for treating the third filtrate and obtaining a first concentrated water and a first product water;

[0071] The fourth reaction tank 241 is used for adjusting the pH of the first concentrated water and reacting with a phosphate to obtain a fourth solid-liquid mixture;

[0072] The fourth filter device 242 is used for filtering the fourth solid-liquid mixture and obtaining a fourth filtrate and a fourth solid; preferably, the fourth filtrate is treated by the second ultrafiltration device 620 and then enters the reverse osmosis membrane device 400;

[0073] The reverse osmosis membrane device 400 is used for treating the first product water and the fourth filtrate and obtaining a second concentrated water and a second product water; preferably, the pH of the first product water and the fourth filtrate is adjusted to be weakly acidic in the fifth reaction tank 251 and then enters the reverse osmosis membrane device 400.

[0074] The evaporation crystallization device 500 is used for evaporating the second concentrated water and obtaining condensed water and a fifth solid; preferably, the evaporation crystallization device 500 adopts an MVR evaporator.

[0075] The first feeding device 710 is used for adding an alkaline adjusting agent into the first reaction tank 211, the second reaction tank 221 and the fourth reaction tank 241; the second feeding device 720 is used for adding a silicon-fluorine adsorbent into the third reaction tank 231; the third feeding device 730 is used for adding a flocculating agent into the third reaction tank 231; the fourth feeding device 740 is used for adding a phosphate into the fourth reaction tank 241; and the fifth feeding device 750 is used for adding an acidic adjusting agent into the fifth reaction tank 251.

[0076] The first filtering device 212, the second filtering device 222, the third filtering device 232 and the fourth filtering device 242 adopt any one of a plate-and-frame filtering device, a belt filter device and a ceramic filtering device.

[0077] A stirrer is arranged in each of the first reaction tank 211, the second reaction tank 221, the third reaction tank 231, the fourth reaction tank 241 and the fifth reaction tank 251.

[0078] The nanofiltration membrane device 300 and the reverse osmosis membrane device 400 adopt a disc-and-tube membrane module or a roll membrane module.

[0079] One embodiment of the method for treating the iron phosphate production wastewater of the present application is to use the treatment system described above, and specifically includes the following steps:

[0080] The method for treating the iron phosphate production wastewater, characterized by comprising the following steps:

[0081] (1) Adjusting the pH of the wastewater to be 2.2-2.5, and then performing solid-liquid separation to obtain a first filtrate and a first solid; the iron phosphate production wastewater is any one or a mixture of any several of iron phosphate washing wastewater, waste gas treatment wastewater and iron phosphate mother liquor wastewater. This step is realized by using the wastewater storage tank 100, the first reaction tank 211, the first filtering device 212 and the first feeding device 710 described above.

[0082] (2) Adjusting the pH of the first filtrate to be 5.5-6, reacting for 20-30 minutes, and then performing solid-liquid separation to obtain a second filtrate and a second solid. This step is realized by using the second reaction tank 221, the third filtering device 232 and the first feeding device 710 described above.

[0083] (3) Adding a silicon-fluorine adsorbent into the second filtrate, reacting for 20-30 minutes, then adding a flocculating agent, and then performing solid-liquid separation to obtain a third filtrate and a third solid; the silicon-fluorine adsorbent is polyaluminum sulfate, and the flocculating agent is PAM; by the combination of polyaluminum sulfate and PAM, the silicon-fluorine can be maximally adsorbed, and the best flocculating effect can be achieved. This step is realized by using the third reaction tank 231, the third filtering device 232, the second feeding device 720 and the third feeding device 730 described above.

[0084] (4) sequentially performing ultrafiltration treatment and nanofiltration membrane treatment on the third filtrate to obtain first concentrated water and first product water. The step is realized by using the first ultrafiltration equipment 610 and the nanofiltration membrane equipment 300 described above.

[0085] (5) adjusting the pH of the first concentrated water to 9-9.5, adding phosphate, and then performing solid-liquid separation to obtain fourth filtrate and fourth solid; the phosphate is ammonium dihydrogen phosphate, which can supplement phosphate in water without introducing cations that are not in water, and the phosphate reacts with ammonium and magnesium ions in water to form ammonium magnesium phosphate, and reacts with manganese ions to form manganese phosphate, thereby removing magnesium ions and manganese ions. The step is realized by using the fourth reaction tank 241, the fourth filtration equipment 242, the first feeding equipment 710 and the fourth feeding equipment 740 described above.

[0086] (6) first performing ultrafiltration treatment on the fourth filtrate, then adjusting the pH of the mixture of the ultrafiltrate and the first product water to 6-7, and then performing reverse osmosis membrane treatment to obtain second concentrated water and second product water; the second concentrated water is rich in ammonium sulfate. The step is realized by using the second ultrafiltration equipment 620, the fifth reaction tank 251, the fifth feeding equipment 750 and the reverse osmosis membrane equipment 400 described above.

[0087] (7) performing evaporation treatment on the second concentrated water to obtain condensed water that can be reused as reclaimed water and fifth solid mainly containing ammonium sulfate. The step is realized by using the evaporation crystallization equipment 500 described above.

[0088] The beneficial effects of the treatment method and treatment system for the iron phosphate production wastewater according to the present application will be described below through specific examples.

[0089] The iron phosphate production wastewater used in this example is iron phosphate mother liquor wastewater, and the water quality parameters are shown in Table 1. As can be seen from Table 1, the pH of the iron phosphate production wastewater is ≤1.5, the ammonia nitrogen concentration is ≥5000 mg / L, the fluoride ion concentration is ≥200 mg / L, the sulfate ion concentration is ≥50000 mg / L, the phosphate ion concentration is ≥850 mg / L, the conductivity is ≥100000 uS / cm, the silicon dioxide is ≥60 mg / L, and the ions contained include at least aluminum ions, iron ions, manganese ions, calcium ions, potassium ions, magnesium ions and sodium ions.

[0090] Table 1

[0091]

[0092] (1) Adjust the pH of the wastewater to 2.2-2.5 with ammonia water (i.e. alkaline adjusting agent) to generate white precipitate, and perform solid-liquid separation by the first filtration equipment 212 to obtain first solid which is mainly iron phosphate, and the water quality parameters of the first filtrate obtained by solid-liquid separation are shown in Table 2.

[0093] Table 2

[0094]

[0095] (2) The first filtrate is adjusted to pH 5.5-6 with ammonia water and stirred in the second reaction tank for 20 minutes, so that most of the iron ions, phosphate ions and part of the fluorine ions in the water are removed. The main component of the second solid obtained by solid-liquid separation through the second filtering device 222 is iron hydroxide. Part of the water quality parameters of the second filtrate obtained by solid-liquid separation through the second filtering device 222 are shown in Table 3.

[0096] Table 3

[0097]

[0098] (3) A proper amount of polyaluminum sulfate (i.e. silicon-fluorine adsorbent) is added to the second filtrate in the third reaction tank, and PAM (i.e. flocculant) is added after stirring for 30 minutes, so that most of the silicon and fluorine in the water are removed. The third solid obtained by solid-liquid separation through the third filtering device 232 is solid waste containing silicon and fluorine. Part of the water quality parameters of the third filtrate obtained by solid-liquid separation through the third filtering device 232 are shown in Table 4.

[0099] Table 4

[0100]

[0101] (4) The third filtrate is filtered by the first ultrafiltration device, and then the magnesium ions in the water are concentrated into concentrated water by the nanofiltration membrane device. Under the operating pressure of 20-30 bar, the first concentrated water treated by the nanofiltration membrane device 300 accounts for 20% of the amount of the original water. The water quality test results are shown in Table 5.

[0102] Table 5

[0103]

[0104] (5) A 2.6% ammonium dihydrogen phosphate solution (i.e. phosphate, the dosing amount is controlled according to the molar ratio of magnesium to phosphorus of 1:1) is added to the first concentrated water in the fourth reaction tank, and the pH is adjusted to 9-9.5 with ammonia water to remove calcium, magnesium, manganese and other heavy metal ions in the first concentrated water. Part of the water quality parameters of the fourth filtrate obtained by solid-liquid separation through the fourth filtering device 242 are shown in Table 6.

[0105] Table 6

[0106]

[0107] (6) The fourth filtrate is filtered by the second ultrafiltration equipment, mixed with the first product water in the fifth reaction tank 251, and then adjusted to a pH of 6-7 by sulfuric acid (i.e. an acid regulator). Under the operating pressure of 120-130 bar, the second concentrated water obtained by the reverse osmosis membrane equipment 400 accounts for 30% of the amount of the raw water, and the main component in the second concentrated water is ammonium sulfate. The second product water can be used as recycled water. Some water quality parameters of the second concentrated water are shown in Table 7.

[0108] Table 7

[0109]

[0110] (7) The second concentrated water is evaporated by the evaporation crystallization equipment 500 to 30%. The salt obtained after evaporation is high-purity ammonium sulfate, which can be used as industrial-grade ammonium sulfate. The mother liquor can be mixed with the second concentrated water and then re-enter the evaporation crystallization equipment 500. After multiple cycles, the content of metal ions such as calcium, magnesium and manganese in the mother liquor will become higher. At this time, the mother liquor is taken out and treated separately. The condensed water and the second product water are used as recycled water.

[0111] In Tables 2-7, the units of each index are the same as those in Table 1.

[0112] The above describes the relevant content of the present application. Those skilled in the art will be able to implement the present application based on these descriptions. Based on the above content of the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

Claims

1. A method for treating iron phosphate production wastewater, characterized by: It comprises the following steps: (1) adjusting the pH of the wastewater to 2.2-2.5, and then performing solid-liquid separation to obtain a first filtrate and a first solid; the first solid is mainly iron phosphate; (2) adjusting the pH of the first filtrate to 5.5-6, and then performing solid-liquid separation to obtain a second filtrate and a second solid; the second solid is mainly iron hydroxide adsorbing fluorine ions; (3) adding a silicon-fluorine adsorbent and a flocculant to the second filtrate, and then performing solid-liquid separation to obtain a third filtrate and a third solid; (4) performing nanofiltration membrane treatment on the third filtrate to obtain a first concentrated water and a first product water; (5) adjusting the pH of the first concentrated water to 9-9.5, adding ammonium dihydrogen phosphate, and allowing the phosphate to react with ammonium ions and magnesium ions in the wastewater to form ammonium magnesium phosphate, and with manganese ions to form manganese phosphate, and then performing solid-liquid separation to obtain a fourth filtrate and a fourth solid; (6) adjusting the pH of the first product water and the fourth filtrate to 6-7; (7) performing reverse osmosis membrane treatment on the combined first product water and fourth filtrate to obtain a second concentrated water and a second product water; the second concentrated water is rich in ammonium sulfate.

2. The method of treating iron phosphate production wastewater according to claim 1, characterized by: The iron phosphate production wastewater is any one or a mixture of any several of iron phosphate washing wastewater, waste gas treatment wastewater, and iron phosphate mother liquor wastewater.

3. The method of claim 1, wherein the method is characterized by: The pH of the iron phosphate production wastewater is ≤1.5, the ammonia nitrogen concentration is ≥5000 mg / L, the fluorine ion concentration is ≥200 mg / L, the sulfate ion concentration is ≥50000 mg / L, the phosphate ion concentration is ≥850 mg / L, the conductivity is ≥100000 uS / cm, the silicon dioxide is ≥60 mg / L, and the ions contained include at least aluminum ions, iron ions, manganese ions, calcium ions, potassium ions, magnesium ions, and sodium ions.

4. The method of treating iron phosphate production wastewater of claim 1, wherein: After adjusting the pH of the first filtrate, the solid-liquid separation treatment is performed after 20-30 minutes of reaction.

5. The method of claim 1, wherein the method is characterized by: The silicon-fluorine adsorbent is polyaluminum sulfate, and the flocculant is PAM; the flocculant is added after 20-30 minutes of reaction after the addition of the silicon-fluorine adsorbent.

6. The method of treating iron phosphate production wastewater of claim 1, wherein: The third filtrate is first subjected to ultrafiltration treatment and then nanofiltration membrane treatment; the fourth filtrate is first subjected to ultrafiltration treatment and then reverse osmosis membrane treatment.

7. The method of claim 1, wherein the method is characterized by: The operating pressure of the nanofiltration membrane treatment is 20-30 bar; the operating pressure of the reverse osmosis membrane treatment is 120-130 bar.

8. The method of claim 1, wherein the method is characterized by: It further comprises the step of performing evaporation treatment on the second concentrated water to obtain condensed water that can be reused as reclaimed water and a fifth solid mainly containing ammonium sulfate.

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