Method for recovering trisodium phosphate, tripotassium phosphate, iron oxide red and graphite from iron phosphate slag
By recovering trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite from ferric phosphate slag, the problem of high-value utilization of ferric phosphate slag has been solved, achieving efficient and low-cost resource recycling and reducing environmental pollution.
Patent Information
- Application Number
- CN202511508466.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-22
- Publication Date
- 2026-01-02
AI Technical Summary
In the existing technology, there is a lack of effective ways to utilize the iron phosphate slag generated after recycling waste lithium iron phosphate batteries, and traditional sodium and potassium phosphate production methods have problems such as high resource dependence, high cost, and environmental pollution.
Through steps such as pulping, stirring and leaching, liquid-solid separation, countercurrent washing, iron dissolution, roasting, and cooling crystallization, trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite are recovered from ferric phosphate slag, achieving efficient recovery and utilization of multiple valuable components.
It achieves efficient recovery of multiple valuable components in ferric phosphate slag, with advantages of high resource utilization, environmental protection, and low cost. It solves the problem of harmless utilization of ferric phosphate slag and reduces environmental pollution.
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Figure CN121247748A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a method for recovering trisodium phosphate, tripotassium phosphate, red iron oxide and graphite from iron phosphate slag, in particular to a method for recovering trisodium phosphate, tripotassium phosphate, red iron oxide and graphite from iron phosphate slag. BACKGROUND
[0002] With the rapid development of new energy vehicles, energy storage and other fields, the demand for lithium ion batteries is growing explosively. Among them, lithium iron phosphate batteries have occupied an important market share due to their high safety, low cost and long cycle life. However, the service life of lithium iron phosphate batteries is limited, and a large number of waste lithium iron phosphate batteries are generated. If not properly recycled, not only will it waste valuable resources such as lithium, iron and phosphorus, but also the heavy metals and electrolytes contained in the waste lithium iron phosphate batteries will cause serious pollution to the ecological environment such as soil and water. Therefore, the recycling of waste lithium iron phosphate batteries has become a key link in the sustainable development of the new energy industry.
[0003] Currently, the recycling technology for waste lithium iron phosphate batteries mainly focuses on the extraction of lithium elements. Through acid leaching, precipitation and purification processes, lithium can be efficiently recovered. However, a large amount of iron phosphate slag is generated after lithium recovery. The iron phosphate slag contains a high content of phosphate and iron elements. The existing treatment methods are mainly landfill or simple storage. On the one hand, this treatment method cannot fully utilize the phosphorus resources in the iron phosphate slag, which is contrary to the current development concept of "resource recycling"; on the other hand, the phosphate in the iron phosphate slag may seep into groundwater under the action of rainwater, leading to water eutrophication, and the iron elements may accumulate in the soil, causing secondary environmental pollution problems. At the same time, the accumulation of a large amount of iron phosphate slag will also occupy valuable land resources and increase the environmental treatment cost of enterprises. Therefore, how to realize the high-value and harmless utilization of iron phosphate slag has become a difficult problem to be solved in the whole life cycle recycling process of waste lithium iron phosphate batteries.
[0004] Sodium potassium phosphate is an important inorganic chemical raw material, widely used in detergent, food additive, water treatment agent, ceramic industry, metallurgical industry and other fields, with huge market demand. Currently, the main method for producing sodium potassium phosphate in industry is to use phosphate rock as raw material, and to prepare it through multiple processes such as acidolysis, neutralization, purification and crystallization. However, phosphate rock is a non-renewable resource, and its reserves are decreasing with long-term mining, leading to rising production cost of sodium potassium phosphate. At the same time, a large amount of acid wastewater and waste slag will be generated during the acidolysis of phosphate rock, which needs to be treated with a large amount of funds for environmental protection, otherwise it will cause serious harm to the environment. In addition, some studies also use phosphoric acid and sodium hydroxide to prepare sodium potassium phosphate through neutralization reaction, but the production cost of phosphoric acid is high, and a certain amount of energy consumption and pollutants will be generated in the production process, which is not conducive to large-scale industrial application.
[0005] In summary, the current waste lithium iron phosphate battery recycling lithium produces phosphorus iron slag lacks effective high-value utilization approach, while the traditional production method of sodium potassium phosphate has high resource dependence, high cost, environmental pollution and other problems. Therefore, developing a kind of phosphorus iron slag resource utilization, and green, low cost of sodium phosphate production technology, has important practical significance and broad application prospect, also in line with the development concept of national energy saving and emission reduction and resource recycling. SUMMARY
[0006] The purpose of the present application is to provide a method for recovering trisodium phosphate, tripotassium phosphate, red iron oxide and graphite from phosphorus iron slag to solve the problems raised in the above background art.
[0007] To solve the above technical problems, the present application provides the following technical solutions:
[0008] The present application provides a method for recovering trisodium phosphate, tripotassium phosphate, red iron oxide and graphite from phosphorus iron slag, comprising the following steps:
[0009] Step 1, beating: phosphorus iron slag is put into a beating equipment, and an appropriate amount of deionized water is added, and the equipment is started to beat, so that the phosphorus iron slag is fully dispersed to form a uniform slurry material; the purpose of beating is to increase the contact area of phosphorus iron slag with subsequent reagents and improve the efficiency of subsequent reaction;
[0010] Step 2, stirring leaching: the slurry material obtained by beating is transferred to a stirring leaching reactor, 32% liquid alkali (sodium hydroxide, potassium hydroxide) is added to the reactor in proportion of 20-40%, then the stirring device is started, the temperature in the reactor is controlled at 25-200 degrees (preferably 90℃), and the stirring leaching time is 30-300 minutes (preferably 120 minutes), so that the liquid alkali fully reacts with the components in the phosphorus iron slag;
[0011] Step 3, first liquid-solid separation: after stirring leaching, the material in the reactor is transported to a liquid-solid separation equipment for liquid-solid separation to obtain a first liquid phase and a first solid phase;
[0012] Step 4, countercurrent washing: the first solid phase is sent to a countercurrent washing device, and hydrochloric acid and deionized water are used for countercurrent washing; the hydrochloric acid is used to neutralize the possible residual alkali and dissolve part of the impurities; the deionized water is used to wash away the soluble substances; through countercurrent washing, the impurities in the first solid phase are further removed, preparing for the subsequent recovery of graphite and red iron oxide;
[0013] Step 5, second liquid-solid separation: after countercurrent washing, the material is subjected to a second liquid-solid separation to obtain a second liquid phase and a second solid phase.
[0014] Step 6, Iron dissolution: The second solid phase is transferred to an iron dissolution reactor, and a suitable iron dissolution reagent (hydrochloric acid or sulfuric acid) is added. The reaction conditions are controlled to dissolve the iron in the second solid phase into the liquid phase, obtaining a solution containing ferrous or ferric ions and a solid phase containing graphite.
[0015] Step 7, Third liquid-solid separation: After the iron dissolution reaction is completed, the material is subjected to a third liquid-solid separation, obtaining a third liquid phase and a third solid phase.
[0016] Step 8, Second reverse flow washing: The third solid phase is subjected to a second reverse flow washing to wash away the remaining iron dissolution reagent and soluble impurities, obtaining a more pure solid phase containing graphite.
[0017] Step 9, Fourth liquid-solid separation: After the second reverse flow washing, a fourth liquid-solid separation is performed, obtaining a fourth liquid phase and a fourth solid phase.
[0018] Step 10, Roasting: The fourth solid phase is sent to a roasting furnace, and the drying temperature is controlled at 90-150 degrees, with a drying time of 60-180 minutes (preferably 120 minutes). The dried graphite is subjected to roasting at 1500-3000 degrees Celsius to further remove impurities, obtaining a high-purity graphite product.
[0019] Step 11, Acid adjustment: The first liquid phase obtained in step 3 is transported to an acid adjustment reactor, and phosphoric acid is slowly added according to the process requirements to adjust the pH value of the solution to 3.5-4.5, so that the components in the solution reach a state suitable for subsequent cooling crystallization.
[0020] Step 12, Cooling crystallization: The acid-adjusted solution is transferred to a cooling crystallization device, and the cooling temperature is controlled at 5-15 degrees, with a cooling time of 20-30 minutes, so that sodium phosphate and potassium phosphate in the solution crystallize and precipitate.
[0021] Step 13, Fifth liquid-solid separation: After the cooling crystallization is completed, a fifth liquid-solid separation is performed, obtaining a fifth liquid phase and a fifth solid phase.
[0022] Step 14, Drying: The fifth solid phase is subjected to drying treatment, and the drying temperature is controlled at 30-40 degrees, with a drying time of 30-45 minutes, obtaining a sodium phosphate and potassium phosphate product.
[0023] Step 15, Iron removal: The third liquid phase obtained in step 7 is transported to an iron removal reactor, and an alkaline substance (lime, sodium hydroxide, potassium hydroxide, liquid ammonia, ammonia water, etc.) is added to react with the iron ions in the solution to form Fe2O3.H2O precipitate, thereby removing iron impurities.
[0024] Step 16, Sixth liquid-solid separation: After the iron removal reaction is completed, a sixth liquid-solid separation is performed, obtaining a sixth liquid phase and a sixth solid phase.
[0025] Step 17, multiple countercurrent washing: the sixth solid phase is subjected to multiple countercurrent washing to wash away the impurity ions adsorbed on the surface of the precipitate, and a relatively pure iron-containing precipitate is obtained.
[0026] Step 18, seventh liquid-solid separation: after multiple countercurrent washing, the seventh liquid-solid separation is performed to obtain a seventh liquid phase and a seventh solid phase.
[0027] Step 19, drying again: the seventh solid phase is sent into a drying device, the drying temperature is controlled to be 80-500 degrees (preferably 350 degrees), and the drying time is 60-180 minutes to obtain an iron oxide red product.
[0028] As an improvement, the liquid-solid separation device in step 3 includes a filter or a centrifuge; the 32% liquid alkali is sodium hydroxide or potassium hydroxide; the first liquid phase is a liquid containing soluble phosphorus, sodium and potassium, and the first solid phase is a solid containing insoluble iron and graphite.
[0029] As an improvement, the second liquid phase in step 5 contains the soluble substances and hydrochloric acid washed away, and the second solid phase is a solid containing iron and graphite.
[0030] As an improvement, the iron-dissolving reagent in step 6 is an acid solution containing hydrochloric acid and sulfuric acid.
[0031] As an improvement, the third liquid phase in step 7 is a blood solution containing iron, and the third solid phase is a solid containing graphite.
[0032] As an improvement, the fourth liquid phase in step 9 is a washing liquid, and the fourth solid phase contains graphite.
[0033] As an improvement, the fifth liquid phase in step 13 contains substances that can be used to prepare snow-melting agent, and the fifth solid phase is sodium phosphate and potassium sodium phosphate crystals.
[0034] As an improvement, the sixth liquid phase in step 16 is a solution after removing iron impurities, and the sixth solid phase includes an iron hydroxide precipitate.
[0035] As an improvement, the seventh liquid phase in step 18 is a washing liquid, and the seventh solid phase is an iron-containing precipitate.
[0036] Compared with the prior art, the present application has the advantages of efficient recycling of various valuable components in iron phosphate slag, high resource utilization rate, environmental protection, low cost, etc. BRIEF DESCRIPTION OF DRAWINGS
[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the following drawings enumerated are only some structural schematic diagrams of the present application, but not all.
[0038] Figure 1 is a flow chart of a method for recovering trisodium phosphate, tripotassium phosphate, red iron oxide and graphite from iron phosphate slag. DETAILED DESCRIPTION
[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.
[0040] The present embodiment is combined with the accompanying drawings Figure 1 A method for recovering trisodium phosphate, tripotassium phosphate, red iron oxide and graphite from iron phosphate slag is described in detail.
[0041] The present embodiment is combined with the accompanying drawings
[0042] Step 1, beating: the iron phosphate slag is put into a beating device, and an appropriate amount of deionized water is added. The device is started to beat the iron phosphate slag, so that the iron phosphate slag is fully dispersed to form a uniform slurry material. The purpose of beating is to increase the contact area of the iron phosphate slag with subsequent reagents and improve the efficiency of subsequent reactions.
[0043] Step 2, agitation leaching: the slurry material obtained by beating is transferred to an agitation leaching reactor. 20-40% of 32% liquid alkali (sodium hydroxide, potassium hydroxide) is added to the reactor, and then the stirring device is started. The temperature in the reactor is controlled at 25-200 degrees (preferably 90°C), and the agitation leaching time is 30-300 minutes (preferably 120 minutes), so that the liquid alkali fully reacts with the components in the iron phosphate slag.
[0044] Step 3, first liquid-solid separation: after agitation leaching is completed, the material in the reactor is transported to a liquid-solid separation device for liquid-solid separation to obtain a first liquid phase and a first solid phase.
[0045] Step 4, countercurrent washing: the first solid phase is sent to a countercurrent washing device, and hydrochloric acid and deionized water are used for countercurrent washing. The hydrochloric acid is used to neutralize possible residual alkali and dissolve part of the impurities. The deionized water is used to wash away the soluble substances. Through countercurrent washing, the impurities in the first solid phase are further removed, and preparation is made for subsequent recovery of graphite and red iron oxide.
[0046] Step 5, second liquid-solid separation: after countercurrent washing is completed, the material is subjected to a second liquid-solid separation to obtain a second liquid phase and a second solid phase.
[0047] Step 6, Iron dissolution: The second solid phase is transferred to the iron dissolution reactor, and a suitable iron dissolution reagent (hydrochloric acid or sulfuric acid) is added. The reaction conditions are controlled to dissolve the iron in the second solid phase into the liquid phase, obtaining a solution containing ferrous or ferric ions and a solid phase containing graphite.
[0048] Step 7, Third liquid-solid separation: After the iron dissolution reaction is completed, the material is subjected to a third liquid-solid separation, obtaining a third liquid phase and a third solid phase.
[0049] Step 8, Second reverse flow washing: The third solid phase is subjected to a second reverse flow washing to wash away the remaining iron dissolution reagent and soluble impurities, obtaining a more pure solid phase containing graphite.
[0050] Step 9, Fourth liquid-solid separation: After the second reverse flow washing, a fourth liquid-solid separation is performed, obtaining a fourth liquid phase and a fourth solid phase.
[0051] Step 10, Roasting: The fourth solid phase is sent to a roasting furnace, and the drying temperature is controlled at 90-150 degrees, with a drying time of 60-180 minutes (preferably 120 minutes). The dried graphite is subjected to roasting at 1500-3000 degrees Celsius to further remove impurities, obtaining a high-purity graphite product.
[0052] Step 11, Acid adjustment: The first liquid phase obtained in step 3 is transported to an acid adjustment reactor, and phosphoric acid is slowly added according to the process requirements to adjust the pH value of the solution to 3.5-4.5, so that the components in the solution reach a state suitable for subsequent cooling crystallization.
[0053] Step 12, Cooling crystallization: The acid-adjusted solution is transferred to a cooling crystallization device, and the cooling temperature is controlled at 5-15 degrees, with a cooling time of 20-30 minutes, so that sodium phosphate and potassium phosphate in the solution crystallize and precipitate.
[0054] Step 13, Fifth liquid-solid separation: After the cooling crystallization is completed, a fifth liquid-solid separation is performed, obtaining a fifth liquid phase and a fifth solid phase.
[0055] Step 14, Drying: The fifth solid phase is subjected to drying treatment, and the drying temperature is controlled at 30-40 degrees, with a drying time of 30-45 minutes, obtaining a sodium phosphate and potassium phosphate product.
[0056] Step 15, Iron removal: The third liquid phase obtained in step 7 is transported to an iron removal reactor, and an alkaline substance (lime, sodium hydroxide, potassium hydroxide, liquid ammonia, ammonia water, etc.) is added to react with the iron ions in the solution to form Fe2O3.H2O precipitate, thereby removing iron impurities.
[0057] Step 16, Sixth liquid-solid separation: After the iron removal reaction is completed, a sixth liquid-solid separation is performed, obtaining a sixth liquid phase and a sixth solid phase.
[0058] Step 17, multiple countercurrent washing: the sixth solid phase is subjected to multiple countercurrent washing to wash away the impurity ions adsorbed on the surface of the precipitate, and a relatively pure iron-containing precipitate is obtained.
[0059] Step 18, seventh liquid-solid separation: after multiple countercurrent washing, the seventh liquid-solid separation is performed to obtain a seventh liquid phase and a seventh solid phase.
[0060] Step 19, drying again: the seventh solid phase is sent into a drying device, the drying temperature is controlled to be 80-500 degrees (preferably 350 degrees), and the drying time is 60-180 minutes to obtain an iron oxide red product.
[0061] The liquid-solid separation device in step 3 includes a filter and a centrifuge, and the 32% liquid alkali is sodium hydroxide or potassium hydroxide; the first liquid phase is a liquid containing soluble phosphorus, sodium and potassium, and the first solid phase is a solid containing insoluble iron and graphite.
[0062] The second liquid phase in step 5 contains soluble substances and hydrochloric acid washed down, and the second solid phase is a solid containing iron and graphite.
[0063] The iron-dissolving reagent in step 6 is an acid solution.
[0064] The third liquid phase in step 7 is an iron-containing blood solution, and the third solid phase is a solid containing graphite.
[0065] The fourth liquid phase in step 9 is a washing liquid, and the fourth solid phase contains graphite.
[0066] The fifth liquid phase in step 13 contains substances that can be used to prepare snow-melting agents, and the fifth solid phase is sodium phosphate and potassium sodium phosphate crystals.
[0067] The sixth liquid phase in step 16 is a solution after removing iron impurities, and the sixth solid phase includes an iron hydroxide precipitate.
[0068] The seventh liquid phase in step 18 is a washing liquid, and the seventh solid phase is an iron-containing precipitate.
[0069] In specific implementation, the above steps can be operated. The efficient recycling of various valuable components in the iron phosphate slag is realized, and the method has the advantages of high resource utilization rate, environmental protection, and low cost.
[0070] The above describes the present application and its embodiments, which are not limiting, and the actual protection scope is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.
Claims
1. A method for recovering trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite from ferric phosphate slag, characterized in that, Includes the following steps: Step 1, Pulping: Put the ferric phosphate slag into the pulping equipment, add an appropriate amount of deionized water, start the equipment to pulverize, so that the ferric phosphate slag is fully dispersed and forms a uniform slurry; the purpose of pulverizing is to increase the contact area between the ferric phosphate slag and the subsequent reagents, and improve the efficiency of the subsequent reaction. Step 2, stirring and leaching: Transfer the slurry obtained from pulping to a stirring and leaching reactor. Add 32% liquid alkali to the reactor at a ratio of 20-40%. Then turn on the stirring device, control the temperature inside the reactor at 25-200 degrees Celsius, and stir and leach for 30-300 minutes to allow the liquid alkali to fully react with the components in the ferric phosphate slag. Step 3, First liquid-solid separation: After stirring and soaking, the material in the reactor is transported to a liquid-solid separation device for liquid-solid separation to obtain the first liquid phase and the first solid phase; Step 4, Countercurrent Washing: The first solid phase is fed into a countercurrent washing device and washed countercurrently with hydrochloric acid and deionized water. The hydrochloric acid is used to neutralize any residual alkali and dissolve some impurities. The deionized water is used to wash away soluble substances. Through countercurrent washing, impurities in the first solid phase are further removed, preparing for the subsequent recovery of graphite and iron oxide red. Step 5, Second liquid-solid separation: After countercurrent washing, the material is subjected to a second liquid-solid separation to obtain a second liquid phase and a second solid phase. Step 6, Iron Dissolution: Transfer the second solid phase to the iron dissolution reactor, add a suitable iron dissolution reagent, control the reaction conditions, and dissolve the iron in the second solid phase into the liquid phase to obtain a solution containing ferrous or ferric ions and a solid phase containing graphite. Step 7, Third liquid-solid separation: After the iron dissolution reaction is completed, the material is subjected to a third liquid-solid separation to obtain a third liquid phase and a third solid phase. Step 8: Countercurrent washing again: Perform countercurrent washing on the third solid phase to remove residual iron dissolving reagents and soluble impurities, and obtain a purer graphite-containing solid phase. Step 9, Fourth liquid-solid separation: After countercurrent washing again, a fourth liquid-solid separation is performed to obtain a fourth liquid phase and a fourth solid phase. Step 10, Calcination: The fourth solid phase is fed into the calcination furnace, and the drying temperature is controlled at 90-150 degrees Celsius for 60-180 minutes. The dried graphite is then calcined at 1500-3000 degrees Celsius to further remove impurities and obtain a high-purity graphite product. Step 11, Acid Adjustment: The first liquid phase obtained in Step 3 is transferred to the acid adjustment reactor. Phosphoric acid is slowly added according to the process requirements to adjust the pH value of the solution to 3.5-4.5, so that the components in the solution reach a state suitable for subsequent cooling and crystallization. Step 12, Cooling and Crystallization: Transfer the acidified solution to a cooling and crystallization device, control the cooling temperature to 5-15 degrees Celsius, and the cooling time to 20-30 minutes, so that sodium phosphate and potassium phosphate in the solution crystallize out. Step 13, Fifth Liquid-Solid Separation: After cooling and crystallization, a fifth liquid-solid separation is performed to obtain a fifth liquid phase and a fifth solid phase. Step 14, Drying: Dry the fifth solid phase by controlling the drying temperature at 30-40 degrees Celsius and the drying time at 30-45 minutes to obtain sodium phosphate and potassium phosphate products. Step 15, Iron Removal: The third liquid phase obtained in Step 7 is transported to the iron removal reactor, and an alkaline substance is added to cause the iron ions in the solution to react with lime to form Fe2O3·H2O precipitate, thereby removing iron impurities. Step 16, Sixth Liquid-Solid Separation: After the iron removal reaction is completed, a sixth liquid-solid separation is performed to obtain a sixth liquid phase and a sixth solid phase. Step 17, Multiple countercurrent washing: Perform multiple countercurrent washings on the sixth solid phase to remove impurity ions adsorbed on the precipitate surface and obtain a relatively pure iron-containing precipitate. Step 18, Seventh Liquid-Solid Separation: After multiple countercurrent washings, a seventh liquid-solid separation is performed to obtain a seventh liquid phase and a seventh solid phase. Step 19, Drying again: The seventh solid phase is fed into the drying equipment, and the drying temperature is controlled at 80-500 degrees Celsius and the drying time is 60-180 minutes to obtain the iron oxide red product.
2. The method for recovering trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite from ferric phosphate slag according to claim 1, characterized in that, The liquid-solid separation equipment in step 3 includes a filter and a centrifuge. The first liquid phase is a liquid containing soluble phosphorus, sodium, and potassium, and the first solid phase is a solid containing insoluble iron and graphite.
3. The method for recovering trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite from ferric phosphate slag according to claim 1, characterized in that, The second liquid phase in step 5 contains the washed-off solubles and hydrochloric acid, and the second solid phase is a solid containing iron and graphite.
4. The method for recovering trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite from ferric phosphate slag according to claim 1, characterized in that, The iron-dissolving reagent in step 6 is an acid solution.
5. The method for recovering trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite from ferric phosphate slag according to claim 1, characterized in that, The third liquid phase in step 7 is an iron-containing blood solution, and the third solid phase is a graphite-containing solid.
6. The method for recovering trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite from ferric phosphate slag according to claim 1, characterized in that, The fourth liquid phase in step 9 is a washing liquid, and the fourth solid phase contains graphite.
7. The method for recovering trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite from ferric phosphate slag according to claim 1, characterized in that, The fifth liquid phase in step 13 contains substances that can be used to prepare snow melting agents, and the fifth solid phase is sodium phosphate and potassium sodium phosphate crystals.
8. The method for recovering trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite from ferric phosphate slag according to claim 1, characterized in that, The sixth liquid phase in step 16 is the solution after removing iron impurities, and the sixth solid phase includes ferric hydroxide precipitate.
9. A method for recovering trisodium phosphate, tripotassium phosphate, iron oxide red, and graphite from ferric phosphate slag according to claim 1, characterized in that, The seventh liquid phase in step 18 is a washing liquid, and the seventh solid phase is an iron-containing precipitate.