Method for chemical demagnesiumization of phosphate rock

Abstract

The present invention relates to a method for chemical demagnesing of phosphate rock, and belongs to the field of phosphorus chemical technology. The technical problem solved by the present invention is to provide a new method for chemical demagnesing of phosphate rock. The method comprises the following steps: adding an acid solution to the phosphate rock slurry, and then separating the solid and liquid. After the liquid is mixed with a removal agent such as an ion exchange resin or an extractant for reaction, the removal agent is regenerated by a specific method and a by-product is obtained. The method of the present invention is applicable to phosphate rock of any grade and has a wide range of applications. The magnesium element in magnesium-containing phosphate rock is removed by a chemical method, and the removal rate is high, the energy consumption is low, and the process flow is simple. The magnesium ions can be subjected to high-value treatment to obtain products such as ammonium magnesium sulfate, sodium magnesium sulfate, potassium magnesium sulfate or magnesium hydroxide. The product has high purity, the ion exchange resin used has little loss, and can be recycled. The generated demagnesing waste liquid and acid / alkaline regeneration filtrate can be recycled, which not only saves water resources, but also avoids the pollution to the environment caused by sewage discharge, and meets the development concept of green development.

Description

Technical Field

[0001] The invention relates to a method for chemically removing magnesium from phosphate rock, and belongs to the technical field of phosphorus chemical industry. Background Art

[0002] my country boasts vast phosphate rock reserves, ranking second in the world. However, as a non-renewable resource, phosphate rock has become increasingly scarce with industrial development, leaving low- and medium-grade phosphate rock as the majority. Effectively utilizing these low- and medium-grade phosphate rocks is a key challenge in the development of my country's phosphorus chemical industry. These low- and medium-grade phosphate rocks are characterized by low phosphorus content, fine mineral particles that are difficult to separate and select, and high levels of impurities such as magnesium. In particular, the magnesium impurity significantly impacts the quality of phosphoric acid products and increases the complexity and cost of the production process. Therefore, effective and rational processes for removing magnesium from phosphate rock are crucial.

[0003] Phosphate ore demagnesing can be divided into physical and chemical demagnesing. Chemical demagnesing has become the more mainstream demagnesing method due to its higher demagnesing rate and better economic benefits. Chinese invention patent application number 201110237981.8 discloses a method for acid hydrolysis of magnesium-containing phosphate ore. The method uses acid to hydrolyze the magnesium-containing phosphate ore into an acid solution containing water-soluble calcium, magnesium, and phosphoric acid. The resulting phosphoric acid is then used to hydrolyze the phosphate ore to produce Ca(H2PO4)2·H2O solid. H2SO4 then reacts with the water-soluble calcium to form high-purity calcium sulfate whiskers. The magnesium ions are separated by utilizing the reaction of the water-soluble magnesium and phosphorus in the acid solution with NH3 to form a solid MgNH4PO4, thus achieving highly efficient and comprehensive utilization of the acid-hydrolyzed magnesium-containing phosphate ore. This method is complex and prone to secondary pollution and resource waste.

[0004] Chinese invention patent application number 201610980389.X discloses a method for directly preparing magnesium ammonium sulfate by removing magnesium from phosphate rock. This method involves pyrolyzing the phosphate rock and leaching the pyrolysis product with an ammonium sulfate solution. This method separates the magnesium component from the phosphate rock, effectively improving its grade and producing a high-value magnesium ammonium sulfate product. This method increases the added value of phosphate rock processing and can meet the stringent magnesium requirements of nitric acid decomposition. However, this method consumes a lot of energy and places high demands on equipment.

[0005] It can be seen that the existing chemical phosphate rock demagnesium methods generally have problems such as high energy consumption, easy to cause secondary pollution and waste of resources, complex processes, and high equipment requirements. Summary of the Invention

[0006] In view of the above defects, the technical problem solved by the present invention is to provide a new method for chemical demagnesization of phosphate rock.

[0007] The method for chemical demagnesization of phosphate rock of the present invention comprises the following steps:

[0008] (1) Phosphate rock demagnesium: water and phosphate rock powder are mixed to obtain phosphate rock slurry, acid solution is added dropwise to the phosphate rock slurry, the pH of the system is controlled to be 1-4, the reaction temperature is 30-90°C, the liquid-solid mass ratio is 2-5, the reaction is carried out for 1-4 hours, and then the solid-liquid separation is carried out. The solid is washed and dried to obtain refined phosphate rock, and the liquid is magnesium-containing waste liquid;

[0009] (2) demagnesiumization of waste liquid: the magnesium-containing waste liquid in step a is mixed with a removal agent to remove impurity metal ions such as magnesium ions, iron ions and calcium ions in the magnesium-containing filtrate; the removal agent is at least one of an ion exchange resin or an extractant;

[0010] (3) Regeneration reaction: Method 1 or method 2 is used to regenerate the removal agent, wherein method 1 includes the following steps:

[0011] 1a. Mixing a strongly acidic regeneration liquid with the removal agent after the reaction in step (2) to carry out a regeneration reaction to obtain a regeneration liquid and a regenerated removal agent; the strongly acidic regeneration liquid comprises a strong acid, and the strong acid is sulfuric acid, nitric acid or hydrochloric acid;

[0012] 1b. Add strong acid and corresponding strong acid salt to the regeneration liquid in 1a, then cool and freeze crystallize or evaporate and concentrate crystallize to precipitate strong acid magnesium salt crystals. The crystallization mother liquor is the acidic regeneration liquid; return to step 1a and recycle it as the strong acid regeneration liquid;

[0013] 1c, using ultrapure water or sulfuric acid solution to wash the regenerated stripping agent in 1a in multi-stage countercurrent to obtain a regenerated stripping agent, which is returned to step (2) for recycling;

[0014] Method 2 includes the following steps:

[0015] 2a, mixing the weak acid / weak alkaline regeneration liquid with the removal agent after the reaction in step (2), performing a regeneration reaction to obtain a regeneration liquid and a regenerated removal agent;

[0016] 2b. Ammonia gas is introduced into the regeneration liquid in 2a to adjust the pH of the regeneration liquid, and the regeneration liquid is filtered to obtain ferric hydroxide, magnesium hydroxide, calcium hydroxide precipitates and a filtrate;

[0017] 2c. Heat the filtrate in 2b to evaporate the ammonia, then add a weak acid or weak acid ammonium to the solution after ammonia evaporation to obtain the acid / alkaline regeneration solution, which is returned to step 2a for recycling;

[0018] 2d. Use sulfuric acid solution to wash the ammonium ions in the regenerated remover in 2a in a multi-stage countercurrent manner to obtain a regenerated remover, which is returned to step (2) for recycling.

[0019] In one embodiment of the present invention, in step (1), the acid solution is at least one of sulfuric acid, nitric acid, phosphoric acid, fluorosilicic acid, and hydrochloric acid solution; in step (2), the ion exchange resin is a strong acid cation exchange resin, a weak acid cation exchange resin, or a chelating resin; and the extractant is at least one of P204, P507, Cynex272, DNNSA, cyclohexane acid, and versatile carbonic acid.

[0020] In one embodiment of the present invention, in step (2), the mass ratio of ion exchange resin to magnesium-containing waste liquid is 0.1-0.5:1, the stirring intensity is 50-800 rpm, the reaction temperature is 10-90°C, and the removal time is 1-60 min; the volume ratio O / A of the extractant to the magnesium-containing waste liquid is 1-10, the stirring intensity is 50-800 rpm, the reaction temperature is 10-90°C, and multi-stage countercurrent extraction is adopted, with the number of extraction stages being 1-5, preferably 3.

[0021] In one embodiment of the present invention, in step (3), step 1a of method 1, when the removing agent is an ion exchange resin, the solid-liquid mass ratio is controlled to be 0.1-0.5, the stirring intensity is 50-800 rpm, the reaction temperature is 0-50°C, and the regeneration time is 60-120 min; when the removing agent is an extractant, the volume ratio O / A is controlled to be 1-10, the stirring intensity is 50-800 rpm, the reaction temperature is 10-90°C, and multi-stage countercurrent stripping is adopted, with the number of extraction stages being 1-5, preferably 3.

[0022] In one embodiment of the present invention, in step (3), step 1a of method 1, the strongly acidic regeneration solution is a mixed solution of 5-60 wt.% sulfuric acid, 0-40 wt.% sulfate and 0-3.0 wt.% magnesium sulfate, wherein the sulfate is one or more of ammonium sulfate, potassium sulfate and sodium sulfate;

[0023] Or the strong acid regeneration solution is a mixed solution of 5-40 wt.% nitric acid, 0-40 wt.% ammonium nitrate and 0-3.5 wt.% magnesium nitrate;

[0024] Or the strong acid regeneration liquid is a mixed solution of 5-25wt.% hydrochloric acid and 0-2.5wt.% magnesium chloride.

[0025] In one embodiment of the present invention, in step (3), in method 1, the strongly acidic regeneration liquid is a mixed solution of 5-60 wt.% sulfuric acid, 0-40 wt.% sulfate and 0-3.0 wt.% magnesium sulfate. After step 1a and before step 1b, a filtration step is further performed, wherein the filtration step is to filter the regeneration liquid in 1a to obtain a precipitated and clarified regeneration liquid.

[0026] In one embodiment of the present invention, in step (3), in method 1, the strongly acidic regeneration solution is a mixed solution of 5-60 wt.% sulfuric acid, 0-40 wt.% sulfate and 0-3.0 wt.% magnesium sulfate, and ammonium magnesium sulfate, potassium magnesium sulfate and sodium magnesium sulfate are crystallized and separated respectively under different cooling conditions, wherein the cooling crystallization temperature of ammonium magnesium sulfate is 15-30°C, and the cooling crystallization temperature of potassium magnesium sulfate and sodium magnesium sulfate is 0-10°C;

[0027] Alternatively, the strongly acidic regeneration solution is a mixed solution of 5-40 wt.% nitric acid, 0-40 wt.% ammonium nitrate and 0-3.5 wt.% magnesium nitrate, and the ammonium magnesium nitrate and calcium ammonium nitrate are precipitated by freezing at a freezing temperature of -25 to 0°C;

[0028] Alternatively, the strong acid regeneration liquid is a mixed solution of 5-25 wt.% hydrochloric acid and 0-2.5 wt.% magnesium chloride, which is concentrated by evaporation and filtered to obtain magnesium chloride and calcium chloride.

[0029] In one embodiment of the present invention, in step (3), in step 1b of method 1, after the acidic regeneration liquid is circulated, iron ions are enriched in the acidic regeneration liquid, and the iron ions are enriched to a concentration of 1 to 35 wt.%. After cooling crystallization or evaporation concentration to precipitate strong acid iron salt crystals, the crystallization mother liquor is returned to step 1a for recycling; the strong acid iron salt is one of ferric sulfate, ammonium ferric sulfate, potassium ferric sulfate, ferric nitrate or ferric chloride.

[0030] In one embodiment of the present invention, in step (3), in step 1c of method 1, when the removing agent is an ion exchange resin, the ion exchange resin is washed with ultrapure water, the amount of ultrapure water used for washing is determined according to the mass of the ion exchange resin to be washed, and the solid-liquid mass ratio is 0.5 to 1.5; the number of washing stages is 3 to 7; when the removing agent is an extractant, the extractant is washed with sulfuric acid, the amount of sulfuric acid used for washing is determined according to the volume of the extractant to be washed, the relative (volume ratio) O / A is 0.5 to 2, and the sulfuric acid concentration is 5 to 30 wt.%; the number of washing stages is 1 to 5;

[0031] In one embodiment of the present invention, in step (3), step 2a of method 2, the weak acid / weak alkaline regeneration liquid is one of 1-6 wt.% oxalic acid or 1-5 wt.% ammonium oxalate; the solid-liquid mass ratio is controlled to be 0.1-0.5, the stirring intensity is 50-800 rpm, the regeneration reaction temperature is 0-50°C, the regeneration time is 60-120 min, and the mass fraction of magnesium ions is enriched to 0.2-0.8 wt.%;

[0032] Step (3), in step 2b of method 2, ferric hydroxide, magnesium hydroxide and calcium hydroxide are sequentially precipitated by adjusting the pH of the regeneration solution, wherein the pH range of the precipitated ferric hydroxide is 3.0 to 4.5, the pH range of the precipitated magnesium hydroxide is 9.0 to 12.5, and the pH of the solution for precipitating calcium hydroxide is greater than 13.5;

[0033] In step (3), in step 2c of method 2, the temperature of ammonia evaporation is 50 to 100° C.;

[0034] In step (3), in step 2d of method 2, the sulfuric acid is 5 to 30 wt.% sulfuric acid. When washing the ion exchange resin, the amount thereof is determined according to the mass of the ion exchange resin to be washed, and the solid-liquid mass ratio is 0.5 to 1.5; the number of washing stages is 3 to 7; when washing the extractant, the amount thereof is determined according to the volume of the extractant to be washed, and the volume ratio O / A is 0.5 to 2; the number of washing stages is 1 to 5.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The magnesium removal filtrate and acid / alkaline regeneration filtrate produced in the present invention can be recycled, which not only saves water resources but also avoids the pollution to the environment caused by sewage discharge, meeting the development concept of green development.

[0037] 2. The present invention adopts ion exchange resin to remove magnesium ions in magnesium-containing waste liquid, and further regenerates the magnesium ions to obtain products such as ammonium magnesium sulfate, sodium magnesium sulfate, potassium magnesium sulfate or magnesium hydroxide. The process is simple, the reaction conditions are mild, the equipment requirements are low, the removal rate and regeneration rate of magnesium ions are high, the magnesium resources in the waste liquid can be fully utilized, the obtained product is high in purity, and the ion exchange resin used is less lost and can be recycled, with good economic benefits and industrial application prospects.

[0038] 3. The present invention uses a chemical method to remove impurities, especially magnesium, from magnesium-containing phosphate ore. Compared with other phosphate ore demagnesium methods, such as flotation and calcination, the present invention has a higher removal rate and significantly reduces the impurity content in the phosphate ore; it also has lower energy consumption and a simpler process flow, which brings greater convenience to subsequent industrial production.

[0039] 4. The present invention filters out calcium sulfate precipitation and centrally treats the iron ions enriched in the regenerated liquid after multiple recycling or adjusts the pH of the regenerated liquid to precipitate iron ions and calcium ions, thereby avoiding the influence of calcium ions and iron ions in the magnesium-containing waste liquid on the removal and regeneration of magnesium ions. At the same time, it does not affect the acid / alkaline regenerated liquid circulation, and the obtained magnesium sulfate salt product and magnesium hydroxide product have high purity.

[0040] 5. The present invention is applicable to phosphate rock of any grade and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a process flow chart of chemical demagnesiumization of phosphate rock according to Examples 1 to 5 of the present invention.

[0042] Figure 2 This is a process flow chart for chemical demagnesiumization of phosphate rock according to Examples 6 and 8 of the present invention. DETAILED DESCRIPTION

[0043] The method for chemical demagnesization of phosphate rock of the present invention comprises the following steps:

[0044] (1) Phosphate rock demagnesium: water and phosphate rock powder are mixed to obtain phosphate rock slurry, acid solution is added dropwise to the phosphate rock slurry, the pH of the system is controlled to be 1-4, the reaction temperature is 30-90°C, the liquid-solid mass ratio is 2-5, the reaction is carried out for 1-4 hours, and then the solid-liquid separation is carried out. The solid is washed and dried to obtain refined phosphate rock, and the liquid is magnesium-containing waste liquid;

[0045] (2) demagnesiumization of waste liquid: the magnesium-containing waste liquid in step a is mixed with a removal agent to remove impurity metal ions such as magnesium ions, iron ions and calcium ions in the magnesium-containing filtrate; the removal agent is at least one of an ion exchange resin or an extractant;

[0046] (3) Regeneration reaction: Method 1 or method 2 is used to regenerate the removal agent, wherein method 1 includes the following steps:

[0047] 1a. Mixing a strongly acidic regeneration liquid with the removal agent after the reaction in step (2) to carry out a regeneration reaction to obtain a regeneration liquid and a regenerated removal agent; the strongly acidic regeneration liquid comprises a strong acid, and the strong acid is sulfuric acid, nitric acid or hydrochloric acid;

[0048] 1b. Add strong acid and corresponding strong acid salt to the regeneration liquid in 1a, then cool and freeze crystallize or evaporate and concentrate crystallize to precipitate strong acid magnesium salt crystals. The crystallization mother liquor is the acidic regeneration liquid; return to step 1a and recycle it as the strong acid regeneration liquid;

[0049] 1c, using ultrapure water or sulfuric acid solution to wash the regenerated stripping agent in 1a in multi-stage countercurrent to obtain a regenerated stripping agent, which is returned to step (2) for recycling;

[0050] Method 2 includes the following steps:

[0051] 2a, mixing the weak acid / weak alkaline regeneration liquid with the removal agent after the reaction in step (2), performing a regeneration reaction to obtain a regeneration liquid and a regenerated removal agent;

[0052] 2b. Ammonia gas is introduced into the regeneration liquid in 2a to adjust the pH of the regeneration liquid, and the regeneration liquid is filtered to obtain ferric hydroxide, magnesium hydroxide, calcium hydroxide precipitates and a filtrate;

[0053] 2c. Heat the filtrate in 2b to evaporate the ammonia, then add a weak acid or weak acid ammonium to the solution after ammonia evaporation to obtain the acid / alkaline regeneration solution, which is returned to step 2a for recycling. If the weak acid / alkaline regeneration solution is oxalic acid or ammonium oxalate, add oxalic acid or ammonium oxalate accordingly.

[0054] 2d. Use sulfuric acid solution to wash the ammonium ions in the regenerated remover in 2a in a multi-stage countercurrent manner to obtain a regenerated remover, which is returned to step (2) for recycling.

[0055] The novel method for chemical demagnesing of phosphate rock solves the problems of high energy consumption, large wastewater discharge, and low comprehensive utilization of waste liquid in existing chemical demagnesing methods. This method uses medium-strong acid demagnesing to remove impurities such as magnesium from lean ore and fully utilizes the magnesium-containing waste liquid after phosphate rock demagnesing to produce high-value products such as ammonium magnesium sulfate, potassium magnesium sulfate, sodium magnesium sulfate, or magnesium hydroxide. This method offers excellent economic benefits and practical significance.

[0056] Step (1) is to remove magnesium from phosphate rock. Water and phosphate rock powder are mixed and stirred thoroughly to obtain phosphate rock slurry. An acid solution is added dropwise to the phosphate rock slurry. The concentration of the acid solution can be adjusted according to the pH and liquid-solid ratio of the system. The pH of the system is controlled to be 1-4, the reaction temperature is 30-90°C, and the liquid-solid mass ratio is 2-5. The reaction is carried out under uniform stirring for 1-4 hours, and then filtered. The filter cake can be washed and dried to obtain refined phosphate rock, and the filtrate is a magnesium-containing waste liquid.

[0057] Acid solutions commonly used in the art are applicable to the present invention. In a specific embodiment, the acid solution is at least one of sulfuric acid, nitric acid, phosphoric acid, fluorosilicic acid, and hydrochloric acid solutions.

[0058] Step (2) is the demagnesization of the waste liquid, wherein the magnesium-containing waste liquid in step a is mixed with an ion exchange resin / extractant to react and remove impurity metal ions such as magnesium ions, iron ions and calcium ions in the magnesium-containing filtrate.

[0059] The ion exchange resin of the present invention can be any commonly used ion exchange resin in the art. In one embodiment, the ion exchange resin is a strongly acidic cation exchange resin, a weakly acidic cation exchange resin, or a chelating resin. The extractant of the present invention can be any commonly used extractant in the art, including but not limited to at least one of P204 (chemical name: di(2-ethylhexyl)phosphate), P507 (chemical name: 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester), Cynex 272 (chemical name: di(2,4,4-trimethylpentyl) hypophosphorous acid), DNNSA (chemical name: dinonylnaphthalenesulfonic acid), cyclohexane acid, and tertiary carbonic acid.

[0060] In one specific embodiment, in step (2), the mass ratio of ion exchange resin to magnesium-containing waste liquid is 0.1-0.5:1, the stirring intensity is 50-800 rpm, the reaction temperature is 10-90°C, and the removal time is 1-60 min, at which time, the ion exchange reaches equilibrium; the extractant and the magnesium-containing waste liquid (volume ratio) O / A is 1-10, the stirring intensity is 50-800 rpm, the reaction temperature is 10-90°C, and multi-stage countercurrent extraction is adopted, with the number of extraction stages being 1-5, preferably 3.

[0061] Step (3) is the regeneration of the resin / extractant and the treatment of the regeneration liquid. Two methods can be used, wherein method 1 uses a strong acid regeneration liquid to regenerate the resin / extractant, and method 2 uses a weak acid / weak alkaline regeneration liquid to regenerate the resin / extractant.

[0062] In one embodiment of the present invention, the resin / extractant is regenerated using method 1. Specifically, method 1 comprises the following steps:

[0063] 1a. Mixing a strongly acidic regeneration liquid with the magnesium ion-loaded removal agent in step (2) to carry out a regeneration reaction to obtain a regeneration liquid and a regenerated removal agent; the strongly acidic regeneration liquid comprises a strong acid, which is sulfuric acid, nitric acid or hydrochloric acid;

[0064] 1b. Add strong acid and corresponding strong acid salt to the regeneration liquid in 1a, then cool and freeze crystallize or evaporate and concentrate crystallize to precipitate strong acid magnesium salt crystals. The crystallization mother liquor is the acidic regeneration liquid; return to step 1a and recycle it as the strong acid regeneration liquid;

[0065] 1c. The regenerated descaling agent in 1a is washed with ultrapure water / sulfuric acid solution in a multi-stage countercurrent manner to obtain a regenerated descaling agent, which is returned to step (2) for recycling.

[0066] Preferably, in step 1a, when regenerating the ion exchange resin, the solid-liquid mass ratio is controlled to be 0.1-0.5, the stirring intensity is 50-800 rpm, the reaction temperature is 0-50°C, and the regeneration time is 60-120 min. When regenerating the extractant, the phase (volume ratio) O / A is controlled to be 1-10, the stirring intensity is 50-800 rpm, the reaction temperature is 10-90°C, and multi-stage countercurrent stripping is adopted, with the number of extraction stages being 1-5, preferably 3. At this point, the mass fraction of magnesium sulfate / magnesium nitrate / magnesium chloride is enriched to 1.0-6.0 wt.%.

[0067] The strong acid regeneration liquid can be conventional in the art. In a specific embodiment, the strong acid regeneration liquid is a mixed solution of 5-60 wt.% sulfuric acid, 0-40 wt.% sulfate, and 0-3.0 wt.% magnesium sulfate, wherein the sulfate is one or more of ammonium sulfate, potassium sulfate, and sodium sulfate. In another specific embodiment, the strong acid regeneration liquid is a mixed solution of 5-40 wt.% nitric acid, 0-40 wt.% ammonium nitrate, and 0-3.5 wt.% magnesium nitrate. In another specific embodiment, the strong acid regeneration liquid is a mixed solution of 5-25 wt.% hydrochloric acid and 0-2.5 wt.% magnesium chloride.

[0068] When the strongly acidic regeneration solution is a mixed solution of 5-60 wt.% sulfuric acid, 0-40 wt.% sulfate, and 0-3.0 wt.% magnesium sulfate, a filtration step is performed after step 1a and before step 1b. The filtration step comprises filtering the regeneration solution in step 1a to obtain a precipitated and clarified regeneration solution. The clarified regeneration solution is then subjected to step 1b. The regenerated calcium ions combine with sulfate ions in the regeneration solution to form calcium sulfate. Calcium sulfate has extremely low solubility in this strongly acidic regeneration solution, so the precipitate removed by filtration is calcium sulfate precipitate.

[0069] In step 1b, a strong acid and a corresponding strong acid salt are added to the regeneration liquid in 1a. The added strong acid salt is an industrial-grade strong acid salt, and the added strong acid is a concentrated acid. The corresponding strong acid and strong acid salt are added according to the type of acid in the strong acid regeneration liquid. For example, when the strong acid regeneration liquid includes sulfuric acid, the added strong acid is concentrated sulfuric acid, and the strong acid salt is sulfate. When the strong acid regeneration liquid includes nitric acid, the added strong acid is concentrated nitric acid, and the strong acid salt is nitrate. When the strong acid regeneration liquid includes hydrochloric acid, the added strong acid is concentrated hydrochloric acid, and the strong acid salt is hydrochloride. The mass of the added strong acid is determined according to the mass of the waste liquid to be treated and the magnesium content in the waste liquid, and the mass of the consumed strong acid and strong acid salt is calculated by the mass balance of the magnesium salt obtained. Preferably, the strong acid salt is at least one of an ammonium salt, a potassium salt or a sodium salt, preferably an ammonium salt.

[0070] After adding strong acid and strong acid salt, crystals are precipitated by cooling and freezing crystallization or evaporation and concentration crystallization.

[0071] In some embodiments, the strongly acidic regeneration liquid is a mixed solution of 5-60 wt.% sulfuric acid, 0-40 wt.% sulfate and 0-3.0 wt.% magnesium sulfate, and ammonium magnesium sulfate, potassium magnesium sulfate and sodium magnesium sulfate are crystallized and separated respectively under different cooling conditions, wherein the cooling crystallization temperature of ammonium magnesium sulfate is 15-30°C, and the cooling crystallization temperature of potassium magnesium sulfate and sodium magnesium sulfate is 0-10°C.

[0072] In other embodiments, the strongly acidic regeneration liquid is a mixed solution of 5-40 wt.% nitric acid, 0-40 wt.% ammonium nitrate and 0-3.5 wt.% magnesium nitrate, and the ammonium magnesium nitrate and calcium ammonium nitrate are precipitated by freezing at a freezing temperature of -25 to 0°C.

[0073] In other embodiments, the strong acid regeneration solution is a mixed solution of 5-25 wt.% hydrochloric acid and 0-2.5 wt.% magnesium chloride, which is concentrated by evaporation and filtered to obtain magnesium chloride and calcium chloride.

[0074] The regenerated liquid after cooling and freezing crystallization or evaporation and concentration crystallization can be returned to step 1a for recycling, and the regenerated liquid can be recycled more than 100 times.

[0075] Furthermore, after the acidic regeneration liquid is circulated, iron ions are enriched in the acidic regeneration liquid, and the iron ions are enriched to a concentration of 1 to 35 wt.%. After cooling and crystallization or evaporation and concentration to precipitate strong acid iron salt crystals, the crystallization mother liquor is returned to step 1a for recycling; the strong acid iron salt is ferric sulfate, ammonium ferric sulfate, potassium ferric sulfate, ferric nitrate or ferric chloride.

[0076] In some embodiments of the present invention, in step (3), step 1c of method 1, the amount of ultrapure water / sulfuric acid solution used for washing is determined according to the mass of the ion exchange resin / extractant to be washed. When ultrapure water is used to wash the resin, the solid-liquid mass ratio is 0.5-1.5, and the number of washing stages is three to seven. When sulfuric acid is used to wash the extractant, the amount of sulfuric acid used for washing is determined according to the volume of the extractant to be washed, the relative (volume ratio) O / A is 0.5-2, the sulfuric acid concentration is 5-30 wt.%, and the number of washing stages is one to five.

[0077] In another embodiment of the present invention, the resin / extractant is regenerated using method 2. Specifically, method 2 comprises the following steps:

[0078] 2a. Mixing the weak acid / weak alkaline regeneration liquid with the magnesium ion-loaded removal agent (i.e., ion exchange resin / extraction agent) in step (2) to perform a regeneration reaction to obtain a regeneration liquid and a regenerated removal agent;

[0079] 2b. Ammonia gas is introduced into the regeneration liquid in 2a to adjust the pH of the regeneration liquid, and the regeneration liquid is filtered to obtain ferric hydroxide, magnesium hydroxide, calcium hydroxide precipitates and a filtrate;

[0080] 2c. Heat the filtrate in 2b to evaporate the ammonia, then add a weak acid or weak acid ammonium to the solution after ammonia evaporation to obtain the acid / alkaline regeneration solution, which is returned to step 2a for recycling;

[0081] 2d. Use sulfuric acid solution to wash the ammonium ions in the regenerated remover in 2a in a multi-stage countercurrent manner to obtain a regenerated remover, which is returned to step (2) for recycling.

[0082] In some embodiments of the present invention, in step 2a, the weak acid / weak alkaline regeneration liquid is one of 1-6 wt.% oxalic acid or 1-5 wt.% ammonium oxalate; when regenerating the ion exchange resin, the solid-liquid mass ratio is controlled to be 0.1-0.5, the stirring intensity is 50-800 rpm, the regeneration reaction temperature is 0-50°C, and the regeneration time is 60-120 min; when regenerating the extractant, the phase (volume ratio) O / A is controlled to be 1-10, the stirring intensity is 50-800 rpm, the reaction temperature is 10-90°C, and multi-stage countercurrent stripping is adopted, with the number of extraction stages being 1-5, preferably 3. At this point, the mass fraction of magnesium ions is enriched to 0.2-0.8 wt.%.

[0083] In some embodiments of the present invention, in step 2b, ferric hydroxide, magnesium hydroxide, and calcium hydroxide are sequentially precipitated by adjusting the pH of the regeneration solution, wherein the pH range of the precipitated ferric hydroxide is 3.0 to 4.5, the pH range of the precipitated magnesium hydroxide is 9.0 to 12.5, and the pH of the solution for precipitating calcium hydroxide is greater than 13.5;

[0084] In some embodiments of the present invention, in step 2c, the temperature of ammonia evaporation is 50-100°C; the added oxalic acid / ammonium oxalate is industrial grade oxalic acid / ammonium oxalate; and the regenerated liquid after ammonia evaporation and addition of oxalic acid / ammonium oxalate can be returned to step (3) method 2a for recycling.

[0085] In some embodiments of the present invention, in step 2d, the sulfuric acid is 5-30 wt.% sulfuric acid. When washing the resin, the amount thereof is determined according to the mass of the ion exchange resin to be washed, and the solid-liquid mass ratio is 0.5-1.5; the number of washing stages is three to seven; when washing the extractant, the amount thereof is determined according to the volume of the extractant to be washed, and the relative ratio (volume ratio) O / A is 0.5-2; and the number of washing stages is one to five.

[0086] The specific embodiments of the present invention are further described below in conjunction with examples, but the present invention is not limited to the scope of the examples.

[0087] Example 1

[0088] (1) 500 g of high-magnesium phosphate rock with a particle size of 40-120 mesh was mixed with water to form a phosphate rock slurry with a water content of 35%, which was preheated to 80° C. Sulfuric acid solution was added dropwise to the phosphate rock slurry, and the mixture was stirred at 500 rpm for 4 h. The pH of the reaction system was controlled to 3 and the liquid-solid ratio was controlled to 3 by controlling the addition rate and amount of sulfuric acid. After the reaction was completed, the mixture was filtered, and the filter cake was washed with ultrapure water until neutral, and then dried to obtain refined phosphate rock. The filtrate was magnesium-containing waste liquid.

[0089] (2) 334.06 g of the magnesium-containing filtrate from step (1) was added to a reactor, and 100.02 g of Sinco-430 ion exchange resin preheated to 50° C. was added to the reactor and mixed. The removal reaction was carried out at 50° C. and 500 rpm for 15 minutes, at which point the exchange reached equilibrium. The filtrate after magnesium ion removal was returned to step (1) for recycling. The removal reaction experimental data is shown in Table 1.

[0090] (3) 379 g of 40 wt.% sulfuric acid-24 wt.% ammonium sulfate-1.5 wt.% magnesium sulfate acidic regeneration solution was taken and regenerated in a reactor at 25° C. and 500 rpm under the reaction conditions. The reaction time was 90 min, at which time the exchange reached equilibrium.

[0091] (4) Filter the regeneration liquid enriched with magnesium ions in step (3) to remove the calcium sulfate precipitate.

[0092] (5) Add industrial-grade ammonium sulfate and 98 wt.% sulfuric acid to the filtrate from step (4), then stir at 500 rpm for 60 min, cool and crystallize to a temperature of 18°C, filter, and dry to obtain 17.3 g of solid, which is magnesium ammonium sulfate hexahydrate. The filtrate can be returned to step (3) for recycling. The regeneration reaction experimental data are shown in Table 1.

[0093] (6) Wash the ammonium ions carried by the ion exchange resin regenerated in step (3) with 100 g of ultrapure water in a multi-stage countercurrent manner at room temperature. The washed ion exchange resin can be returned to step (2) for recycling.

[0094] The results of the analysis showed that the removal rate of magnesium ions by the ion exchange resin reached over 80%, and the regeneration rate of magnesium ions reached over 70%.

[0095] Table 1 Example 1 Removal reaction experimental data analysis

[0096] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 100.02 334.06 0.5776 1.9295 After the reaction 95.87 337.54 0.1061 0.3580

[0097] Table 2 Analysis of experimental data of regeneration reaction in Example 1

[0098] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 94.70 378.90 0.3114 1.1798 After the reaction 73.52 396.43 0.5904 2.3407

[0099] Example 2

[0100] (1) 400 g of phosphate rock powder was mixed with water to obtain phosphate rock slurry. Sulfuric acid solution was added dropwise at a temperature of 80°C and a rotation speed of 500 rpm. The pH of the system was controlled to be 3 and the liquid-to-solid ratio was 3. The reaction was carried out for 4 h. The filter cake and filtrate were then filtered. The filter cake was washed with ultrapure water until neutral and then dried to obtain refined phosphate rock. The filtrate was the magnesium-containing waste liquid.

[0101] (2) Weigh 343.23 g of the magnesium-containing waste liquid in step (1) and mix it with 100.67 g of Sinco-430 ion exchange resin in a reactor, and carry out a removal reaction under the reaction conditions of 50° C. and 400 rpm for 20 min. Then, filter to obtain the resin loaded with magnesium ions and the magnesium-removed filtrate, which can be returned to step (1) for recycling.

[0102] (3) Weigh 454.69 g of 40 wt.% sulfuric acid-24 wt.% ammonium sulfate-1.2 wt.% magnesium sulfate acidic regeneration liquid and the ion exchange resin loaded with magnesium ions in step (2) are mixed and stirred in a reactor for reaction at a reaction temperature of 20° C., a rotation speed of 500 rpm, and a reaction time of 80 min, at which time the ion exchange reaches equilibrium, and then the ion exchange resin and the regeneration liquid are separated.

[0103] (4) Filter the regeneration liquid enriched with magnesium ions in step (3) to remove the calcium sulfate precipitate.

[0104] (5) Concentrated sulfuric acid and industrial-grade ammonium sulfate were added to the filtrate in step (4), stirred at 400 rpm for 60 min, cooled and crystallized to a temperature of 15° C., filtered to obtain a filter cake and a filtrate, and then dried to obtain 21.39 g of a solid, which is magnesium ammonium sulfate hexahydrate. The filtrate can be returned to step (3) for recycling.

[0105] (6) Wash the ammonium ions carried by the ion exchange resin regenerated in step (3) with 100 g of ultrapure water in a multi-stage countercurrent manner at room temperature. The washed ion exchange resin can be returned to step (2) for recycling.

[0106] The results of the analysis showed that the removal rate of magnesium ions in magnesium-containing wastewater by the ion exchange resin reached over 80%, and the regeneration rate of magnesium ions reached over 90%.

[0107] Table 3 Example 2 Removal Reaction Experimental Data Analysis

[0108] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 100.67 339.23 0.5842 1.9818 After the reaction 99.01 339.47 0.0972 0.3298

[0109] Table 4 Analysis of experimental data of regeneration reaction in Example 2

[0110] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 98.12 454.69 0.2424 1.1021 After the reaction 97.45 444.80 0.5831 2.5936

[0111] Example 3

[0112] (1) 600 g of phosphate rock powder was stirred and mixed with water at a speed of 500 rpm to obtain phosphate rock slurry, and sulfuric acid solution was added dropwise to the system. The reaction temperature was controlled to be 80 ° C, the pH was 3, and the liquid-solid ratio was 3. The reaction was carried out for 4 hours, and then the filter cake and filtrate were obtained by filtration. The filter cake was washed with ultrapure water until neutral, and dried to obtain refined phosphate rock. The filtrate was a magnesium-containing waste liquid.

[0113] (2) 500.17 g of the magnesium-containing waste liquid in step (1) was mixed with 144.43 g of Sinco-430 ion exchange resin in a reactor, and a removal reaction was carried out under the reaction conditions of 50° C. and 450 rpm for 25 min. The resin loaded with magnesium ions and a magnesium-removed filtrate were then filtered to obtain the magnesium-removed filtrate, which was returned to step (1) for recycling.

[0114] (3) Weigh 573.13 g of 30 wt.% sulfuric acid regeneration liquid and the ion exchange resin loaded with magnesium ions in step (2) and stir and react in a reactor at a reaction temperature of 25° C., a rotation speed of 450 rpm, and a reaction time of 90 min, at which time the ion exchange reaches equilibrium, and then separate the ion exchange resin and the regeneration liquid.

[0115] (4) Filter the regeneration liquid enriched with magnesium ions in step (3) to remove the calcium sulfate precipitate.

[0116] (5) Add concentrated sulfuric acid and industrial-grade ammonium sulfate to the filtrate in step (4), stir at a speed of 450 rpm for 60 min, cool and crystallize to a crystallization temperature of 15° C., filter to obtain a filter cake and a filtrate, dry the filter cake to obtain magnesium ammonium sulfate hexahydrate, and the filtrate can be returned to step (3) for recycling.

[0117] (6) After the ion exchange resin has been circulated once, 100 g of ultrapure water is used to wash the ammonium ions carried by the regenerated ion exchange resin in step (3) in a seven-stage countercurrent wash at room temperature. The washed ion exchange resin can be returned to step (2) for recycling.

[0118] The results of the analysis showed that the removal rate of magnesium ions in magnesium-containing waste liquid by the ion exchange resin reached over 80%, and the regeneration rate of magnesium ions reached over 85%.

[0119] Table 5: Data analysis of removal reaction experiment in Example 3

[0120] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 144.43 500.17 0.5799 2.9005 After the reaction 143.38 501.33 0.1144 0.5736

[0121] Table 6 Analysis of experimental data of regeneration reaction in Example 3

[0122] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 143.38 573.13 0 0 After the reaction 143.01 578.55 0.3508 2.0294

[0123] Example 4

[0124] (1) 500 g of high-magnesium phosphate rock with a particle size of 40-120 mesh was mixed with water to form a phosphate rock slurry with a water content of 35%, which was preheated to 80° C. Sulfuric acid solution was added dropwise to the phosphate rock slurry, and the mixture was stirred at 500 rpm for 4 h. The pH of the reaction system was controlled to 3 and the liquid-solid ratio was controlled to 3 by controlling the addition rate and amount of sulfuric acid. After the reaction was completed, the mixture was filtered, and the filter cake was washed with ultrapure water until neutral, and then dried to obtain refined phosphate rock. The filtrate was magnesium-containing waste liquid.

[0125] (2) 455.95 g of the magnesium-containing filtrate from step (1) was added to a reactor, and 136.77 g of Sinco-430 ion exchange resin preheated to 50° C. was added to the reactor and mixed. The removal reaction was carried out at 50° C. and 500 rpm for 15 min, at which point the exchange reached equilibrium. The filtrate after magnesium ion removal was returned to step (1) for recycling.

[0126] (3) 545.90 g of a 30 wt.% sulfuric acid-1.8 wt.% magnesium sulfate acidic regeneration solution was reacted with the ion exchange resin loaded with magnesium ions in step (2) in a reactor at 25° C. and 550 rpm for 90 minutes, at which point the exchange reached equilibrium. The ion exchange resin and the regeneration solution were then separated.

[0127] (4) Filter the regeneration liquid enriched with magnesium ions in step (3) to remove the calcium sulfate precipitate.

[0128] (5) Add industrial-grade ammonium sulfate and concentrated sulfuric acid to the filtrate in step (4), then stir at 500 rpm for 60 min, cool and crystallize to a crystallization temperature of 15° C., filter, and dry to obtain magnesium ammonium sulfate hexahydrate. The filtrate can be returned to step (3) for recycling.

[0129] (6) After the ion exchange resin has been circulated once, 100 g of ultrapure water is used to wash the ammonium ions carried by the regenerated ion exchange resin in step (3) in a seven-stage countercurrent wash at room temperature. The washed ion exchange resin can be returned to step (2) for recycling.

[0130] The results of the analysis showed that the removal rate of magnesium ions by the ion exchange resin reached over 80%, and the regeneration rate of magnesium ions reached over 75%.

[0131] Table 7 Example 4 Removal reaction experimental data analysis

[0132] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 136.77 455.95 0.5804 2.6465 After the reaction 136.48 455.37 0.1155 0.5262

[0133] Table 8 Example 4 Regeneration reaction experimental data analysis

[0134] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 136.48 545.90 0.3600 1.9653 After the reaction 135.89 540.71 0.6677 3.6103

[0135] Example 5

[0136] (1) 400 g of high-magnesium phosphate rock powder was stirred with water at 80° C. to form a phosphate slurry. The stirring intensity was 500 rpm and the reaction time was 4 h. Sulfuric acid solution was added dropwise to the phosphate slurry. The pH of the reaction system was controlled to be 3 and the liquid-solid ratio was controlled to be 3 by controlling the dripping speed and amount of sulfuric acid. After the reaction was completed, the filter cake was washed with ultrapure water until neutral, and then dried to obtain refined phosphate rock. The filtrate was magnesium-containing waste liquid.

[0137] (2) 320.47 g of the magnesium-containing filtrate from step (1) was added to a reactor, and 95.88 g of Sinco-430 ion exchange resin preheated to 55° C. was added to the reactor and mixed. The removal reaction was carried out at 55° C. and 550 rpm for 20 min, at which point the exchange reached equilibrium. The filtrate after magnesium ion removal was returned to step (1) for recycling.

[0138] (3) 340.31 g of 35 wt.% nitric acidic regeneration solution was subjected to a regeneration reaction in a reactor at 20° C. and 550 rpm with the ion exchange resin loaded with magnesium ions in step (2). The reaction time was 120 min, at which time the exchange reached equilibrium.

[0139] (4) Adding industrial-grade ammonium nitrate and concentrated nitric acid to the regeneration liquid enriched with magnesium ions in step (3), stirring at 500 rpm for 60 min, and freezing and crystallizing at a freezing temperature of -15°C to obtain ammonium magnesium nitrate. The regeneration liquid after freezing treatment can be returned to step (3) for recycling.

[0140] (6) After the ion exchange resin has been circulated, 100 g of ultrapure water is used to wash the ammonium ions carried by the regenerated ion exchange resin in step (3) in a multi-stage countercurrent manner. The washing temperature is room temperature. The washed ion exchange resin can be returned to step (2) for recycling.

[0141] The results of the analysis showed that the removal rate of magnesium ions by the ion exchange resin reached over 80%, and the regeneration rate of magnesium ions reached over 85%.

[0142] Table 9 Example 5 Removal Reaction Experimental Data Analysis

[0143] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 95.88 320.47 0.5821 1.8655 After the reaction 95.89 320.96 0.0915 0.2937

[0144] Table 10 Analysis of experimental data of regeneration reaction in Example 5

[0145] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 95.89 340.31 0 0 After the reaction 96.01 339.57 0.3945 1.3396

[0146] Example 6

[0147] (1) 420 g of high-magnesium phosphate rock powder was stirred with water at 80° C. to form a phosphate slurry. The stirring intensity was 500 rpm and the reaction time was 4 h. Sulfuric acid solution was added dropwise to the phosphate slurry. The pH of the reaction system was controlled to be 3 and the liquid-solid ratio was controlled to be 3 by controlling the dripping speed and amount of sulfuric acid. After the reaction was completed, the mixture was filtered, and the filter cake was washed with ultrapure water until neutral, and then dried to obtain refined phosphate ore. The filtrate was magnesium-containing waste liquid.

[0148] (2) 336.53 g of the magnesium-containing filtrate from step (1) was added to a reactor, and 101.44 g of Sinco-430 ion exchange resin preheated to 50° C. was added to the reactor and mixed. The removal reaction was carried out at 50° C. and 550 rpm for 20 min until the exchange reached equilibrium. The filtrate after magnesium ion removal was returned to step (1) for recycling.

[0149] (3) 603.06 g of 5 wt.% oxalic acid regeneration solution was reacted with the ion exchange resin loaded with magnesium ions in step (2) in a reactor at 20° C. and 550 rpm for 120 minutes until the exchange reached equilibrium. The magnesium ion-enriched regeneration solution and the ion exchange resin were separated.

[0150] (4) Slowly passing ammonia gas into the regeneration solution enriched with magnesium ions in step (3), stirring continuously, and adjusting the pH of the solution. When the pH is 4.0, ferric hydroxide precipitate is separated. Continue passing ammonia gas, and when the pH is 12.5, magnesium hydroxide precipitate is separated. Further passing ammonia gas can precipitate calcium hydroxide, which is filtered and separated to obtain ferric hydroxide, magnesium hydroxide, calcium hydroxide and a filtrate.

[0151] (5) Heat the filtrate from step (4) to 65°C to evaporate the ammonia in the regeneration liquid for 60 minutes. Add oxalic acid to the regeneration liquid after ammonia evaporation and return it to step (3) for recycling.

[0152] (6) After the cyclic reaction, the ion exchange resin regenerated in step (3) is washed with 100 g of 5 wt.% dilute sulfuric acid in a five-stage countercurrent wash to remove the ammonium ions. The washing temperature is room temperature. The washed ion exchange resin can be returned to step (2) for recycling.

[0153] The removal reaction test data are shown in Table 11, and the regeneration reaction test data are shown in Table 12. Analysis shows that the removal rate of the ion exchange resin for magnesium ions is over 80%, and the regeneration rate of magnesium ions is over 85%.

[0154] Table 11: Data analysis of removal reaction experiment in Example 6

[0155] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 101.44 336.53 0.5799 1.9515 After the reaction 102.51 335.64 0.1040 0.3491

[0156] Table 12: Data analysis of regeneration reaction experiment in Example 6

[0157] Resin mass / g Solution mass / g Magnesium ion content / wt.% Magnesium ion mass / g Before reaction 102.51 603.06 0 0 After the reaction 101.02 605.36 0.2297 1.3905

[0158] Example 7

[0159] The magnesium-containing filtrate after demagnesiumization of phosphate rock was mixed and stirred with different ion exchange resins under the same reaction conditions, that is, the mass ratio of ion exchange resin to waste liquid was 0.25, the stirring intensity was 600 rpm, the reaction temperature was 60°C, the removal time was 60 min, and the ion exchange reached equilibrium. The removal rates of magnesium ions by different ion exchange resins are shown in Table 13.

[0160] Table 13 Removal rate of magnesium ions by different ion exchange resins

[0161] model 732 resin D001 resin D851 resin MTS9570 resin Sinco-430 resin Removal rate 77.5％ 63％ 83.5％ 66％ 85％

[0162] Example 8

[0163] (1) 410 g of high-magnesium phosphate rock powder was stirred with water at 80° C. to form a phosphate slurry. The stirring intensity was 500 rpm and the reaction time was 4 h. Sulfuric acid solution was added dropwise to the phosphate slurry. The pH of the reaction system was controlled to be 3 and the liquid-solid ratio was controlled to be 3 by controlling the dripping speed and amount of sulfuric acid. After the reaction was completed, the mixture was filtered, and the filter cake was washed with ultrapure water until neutral, and then dried to obtain refined phosphate ore. The filtrate was magnesium-containing waste liquid.

[0164] (2) 337.33 g (about 300 ml) of the magnesium-containing filtrate from step (1) was subjected to an extractive demagnesization reaction with 773.38 g (about 900 ml) of fresh extractant at 60° C. and 500 rpm. Multi-stage countercurrent extraction was used with five extraction stages until the extraction reached equilibrium. The filtrate after magnesium ion removal was returned to step (1) for recycling.

[0165] (3) 822.35 g (about 900 ml) of 6 wt.% oxalic acid regeneration liquid and the extractant loaded with magnesium ions in step (2) were subjected to regeneration reaction in a reactor at 60° C. and 550 rpm. Multi-stage countercurrent stripping was adopted with three stripping stages to separate the regeneration liquid enriched with magnesium ions and the extractant.

[0166] (4) Slowly passing ammonia gas into the regeneration solution enriched with magnesium ions in step (3), stirring continuously, and adjusting the pH of the solution. When the pH is 4.0, ferric hydroxide precipitate is separated. Continue passing ammonia gas, and when the pH is 12.5, magnesium hydroxide precipitate is separated. Further passing ammonia gas can precipitate calcium hydroxide, which is filtered and separated to obtain ferric hydroxide, magnesium hydroxide, calcium hydroxide and a filtrate.

[0167] (5) Heat the filtrate from step (4) to 65°C to evaporate the ammonia in the regeneration liquid for 60 minutes. Add oxalic acid to the regeneration liquid after ammonia evaporation and return it to step (3) for recycling.

[0168] (6) After the cyclic reaction, the extractant regenerated in step (3) is washed with 100 g of 5 wt.% dilute sulfuric acid in a five-stage countercurrent wash to remove the ammonium ions. The washing temperature is room temperature. The washed extractant can be returned to step (2) for recycling.

[0169] The extraction rate of the extractant for magnesium ions reaches more than 80%, and the regeneration rate of magnesium ions reaches more than 90%.

Claims

1. A method for chemical demagnesiumization of phosphate rock, characterized in that: The following steps are involved: (1) Phosphate rock demagnesium: Mix water and phosphate rock powder to obtain phosphate rock slurry, add acid solution dropwise to the phosphate rock slurry, control the system pH to 1-4, the reaction temperature to 30-90 ° C, the liquid-solid mass ratio to 2-5, react for 1-4 hours, then separate the solid and liquid, wash and dry the solid to obtain refined phosphate rock, and the liquid is magnesium-containing waste liquid; (2) Removal of magnesium from waste liquid: The magnesium-containing waste liquid in step a is mixed with a removal agent to remove metal ions from the magnesium-containing filtrate; the removal agent is at least one of an ion exchange resin or an extractant; (3) Regeneration reaction: Method 1 or method 2 is used to regenerate the removal agent, wherein method 1 includes the following steps: 1a. Mixing a strong acid regeneration liquid with the removal agent after the reaction in step (2) to carry out a regeneration reaction to obtain a regeneration liquid and a regenerated removal agent; the strong acid regeneration liquid includes a strong acid, and the strong acid is sulfuric acid, nitric acid or hydrochloric acid; 1b. Add strong acid and corresponding strong acid salt to the regeneration liquid in 1a, then cool and freeze crystallize or evaporate and concentrate crystallize to precipitate strong acid magnesium salt crystals. The crystallization mother liquor is the acidic regeneration liquid; return to step 1a and recycle it as the strong acid regeneration liquid; 1c. Use ultrapure water or sulfuric acid solution to wash the regenerated descaling agent in 1a in multi-stage countercurrent to obtain a regenerated descaling agent, which is returned to step (2) for recycling; Method 2 includes the following steps: 2a. Mixing a weak acid / weak alkaline regeneration liquid with the removal agent after the reaction in step (2) to carry out a regeneration reaction to obtain a regeneration liquid and a regenerated removal agent; the weak acid / weak alkaline regeneration liquid is one of 1 to 6 wt.% oxalic acid or 1 to 5 wt.% ammonium oxalate; 2b. Ammonia is introduced into the regeneration liquid in 2a, the pH of the regeneration liquid is adjusted, and the solution is filtered to obtain ferric hydroxide, magnesium hydroxide, and calcium hydroxide precipitates and a filtrate; wherein ferric hydroxide, magnesium hydroxide, and calcium hydroxide are precipitated in sequence by adjusting the pH of the regeneration liquid, wherein the pH range of the precipitated ferric hydroxide is 3.0 to 4.5, the pH range of the precipitated magnesium hydroxide is 9.0 to 12.5, and the pH of the solution of the precipitated calcium hydroxide is greater than 13.5; 2c. Heat the filtrate in 2b to evaporate the ammonia, then add a weak acid or weak acid ammonium to the solution after ammonia evaporation to obtain the acid / alkaline regeneration solution, which is returned to step 2a for recycling; 2d. Use sulfuric acid solution to wash the ammonium ions in the regenerated remover in 2a in a multi-stage countercurrent manner to obtain a regenerated remover, which is returned to step (2) for recycling.

2. The method for chemical demagnesization of phosphate rock according to claim 1, characterized in that: In step (1), the acid solution is at least one of sulfuric acid, nitric acid, phosphoric acid, fluorosilicic acid, and hydrochloric acid solution; In step (2), the ion exchange resin is a strongly acidic cation exchange resin, a weakly acidic cation exchange resin or a chelating resin; and the extractant is at least one of P204, P507, Cynex272, DNNSA, cyclohexane acid and tertiary carbonic acid.

3. The method for chemical demagnesization of phosphate rock according to claim 1, characterized in that: In step (2), the mass ratio of the ion exchange resin to the magnesium-containing waste liquid is 0.1 to 0.5:1, the stirring intensity is 50 to 800 rpm, the reaction temperature is 10 to 90°C, and the removal time is 1 to 60 min; the volume ratio O / A of the extractant to the magnesium-containing waste liquid is 1 to 10, the stirring intensity is 50 to 800 rpm, the reaction temperature is 10 to 90°C, and multi-stage countercurrent extraction is adopted, with the number of extraction stages being 1 to 5.

4. The method for chemical demagnesiumization of phosphate rock according to claim 3, characterized in that: The number of extraction stages is 3.

5. The method for chemical demagnesization of phosphate rock according to claim 1, characterized in that: In step (3), in step 1a of method 1, when the removing agent is an ion exchange resin, the solid-liquid mass ratio is controlled to be 0.1-0.5, the stirring intensity is 50-800 rpm, the reaction temperature is 0-50°C, and the regeneration time is 60-120 min; when the removing agent is an extractant, the volume ratio O / A is controlled to be 1-10, the stirring intensity is 50-800 rpm, the reaction temperature is 10-90°C, and multi-stage countercurrent stripping is adopted, with the number of extraction stages being 1-5.

6. The method for chemical demagnesization of phosphate rock according to claim 5, characterized in that: The number of extraction stages is 3.

7. The method for chemical demagnesization of phosphate rock according to claim 1, characterized in that: In step (3), in step 1a of method 1, the strongly acidic regeneration solution is a mixed solution of 5-60 wt.% sulfuric acid, 0-40 wt.% sulfate and 0-3.0 wt.% magnesium sulfate, wherein the sulfate is one or more of ammonium sulfate, potassium sulfate and sodium sulfate; Or the strong acid regeneration solution is a mixed solution of 5-40 wt.% nitric acid, 0-40 wt.% ammonium nitrate and 0-3.5 wt.% magnesium nitrate; Or the strong acid regeneration solution is a mixed solution of 5-25 wt.% hydrochloric acid and 0-2.5 wt.% magnesium chloride.

8. The method for chemical demagnesization of phosphate rock according to claim 7, characterized in that: In step (3), in method 1, the strongly acidic regeneration liquid is a mixed solution of 5-60 wt.% sulfuric acid, 0-40 wt.% sulfate and 0-3.0 wt.% magnesium sulfate. After step 1a and before step 1b, a filtration step is further performed, wherein the filtration step is to filter the regeneration liquid in 1a to obtain a precipitated and clarified regeneration liquid.

9. The method for chemical demagnesiumization of phosphate rock according to claim 7, characterized in that: In step (3), in method 1, the strongly acidic regeneration liquid is a mixed solution of 5-60 wt.% sulfuric acid, 0-40 wt.% sulfate and 0-3.0 wt.% magnesium sulfate, and ammonium magnesium sulfate, potassium magnesium sulfate and sodium magnesium sulfate are crystallized and separated respectively under different cooling conditions, wherein the cooling crystallization temperature of ammonium magnesium sulfate is 15-30°C, and the cooling crystallization temperature of potassium magnesium sulfate and sodium magnesium sulfate is 0-10°C; Alternatively, the strong acid regeneration solution is a mixed solution of 5-40 wt.% nitric acid, 0-40 wt.% ammonium nitrate and 0-3.5 wt.% magnesium nitrate, and the ammonium magnesium nitrate and calcium ammonium nitrate are precipitated by freezing, and the freezing temperature is -25 to 0°C; Alternatively, the strong acid regeneration liquid is a mixed solution of 5-25 wt.% hydrochloric acid and 0-2.5 wt.% magnesium chloride, which is concentrated by evaporation and filtered to obtain magnesium chloride and calcium chloride.

10. The method for chemical demagnesization of phosphate rock according to claim 1, characterized in that: In step (3), in step 1b of method 1, after the acidic regeneration liquid is circulated, iron ions are enriched in the acidic regeneration liquid, and the iron ions are enriched to a concentration of 1 to 35 wt.%. After cooling and crystallization or evaporation and concentration to precipitate strong acid iron salt crystals, the crystallization mother liquor is returned to step 1a for recycling; the strong acid iron salt is one of ferric sulfate, ammonium ferric sulfate, potassium ferric sulfate, ferric nitrate or ferric chloride.

11. The method for chemical demagnesization of phosphate rock according to claim 1, characterized in that: In step (3), in step 1c of method 1, when the removing agent is an ion exchange resin, the ion exchange resin is washed with ultrapure water, and the amount of ultrapure water used for washing is determined according to the mass of the ion exchange resin to be washed, and the solid-liquid mass ratio is 0.5 to 1.5; the number of washing stages is 3 to 7; when the removing agent is an extractant, the extractant is washed with sulfuric acid, and the amount of sulfuric acid used for washing is determined according to the volume of the extractant to be washed, and the volume ratio O / A is 0.5 to 2, and the sulfuric acid concentration is 5 to 30 wt.%; the number of washing stages is 1 to 5.

12. The method for chemical demagnesization of phosphate rock according to claim 1, characterized in that: In step (3), in step 2a of method 2, the solid-liquid mass ratio is controlled to be 0.1-0.5, the stirring intensity is 50-800 rpm, the regeneration reaction temperature is 0-50 °C, the regeneration time is 60-120 min, and the mass fraction of magnesium ions is enriched to 0.2-0.8 wt.%; In step (3), step 2c of method 2, the temperature of ammonia evaporation is 50-100°C; In step (3), step 2d of method 2, the sulfuric acid is 5 to 30 wt.% sulfuric acid. When washing the ion exchange resin, the amount thereof is determined according to the mass of the ion exchange resin to be washed, and the solid-liquid mass ratio is 0.5 to 1.5; the number of washing stages is 3 to 7; when washing the extractant, the amount thereof is determined according to the volume of the extractant to be washed, and the volume ratio O / A is 0.5 to 2; the number of washing stages is 1 to 5.

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