Method and system for extracting and stripping metal ions from raffinate acid as a by-product of refined phosphoric acid

Abstract

The present application relates to the technical field of phosphorus resource recovery, and particularly relates to an extraction and stripping method and system for metal ions in by-product raffinate acid of refined phosphoric acid. The extraction and stripping method comprises: emulsification deep extraction, primary washing, primary stripping, secondary washing, secondary stripping, tertiary washing, primary stripping water phase crystallization and secondary stripping water phase photocatalysis, to obtain purified phosphoric acid, and the extractant can be recycled and reused. The extraction and stripping system comprises: an emulsification extraction device, a primary washing device, a primary stripping device, a secondary washing device, a secondary stripping device and a tertiary washing device. The present application is more efficient in the extraction reaction of the extractant and the raffinate acid; magnesium and aluminum elements and iron elements in the metal ions are separated respectively, which is beneficial to the classified recycling of the metals; the present application can also reduce the MER value of the raffinate acid from 0.12-0.2 to 0.070-0.085, the P2O5 yield is 99.5%, and the utilization rate of the raffinate acid is improved.

Description

Technical Field

[0001] This invention relates to the field of phosphorus resource recovery technology, specifically to a method and system for extracting and removing metal ions from the residual acid in the by-product of refined phosphoric acid. Background Technology

[0002] In industrial methods for purifying wet-process phosphoric acid, the acid remaining after extraction during production is called raffinate. Raffinate is characterized by high impurity content, high concentration, and high viscosity. Wet-process phosphoric acid refining cannot consume raffinate itself. Currently, raffinate is mainly used in the production of ammonium phosphate, but the large amount of metal cations contained in raffinate can significantly affect the quality of ammonium phosphate products.

[0003] Common methods for removing metal ions from phosphoric acid include: 1. Chemical precipitation; 2. Ion exchange; 3. Membrane separation. Chemical precipitation has low removal efficiency, introduces basic ions which weaken the acidity of the acidic system, and makes separation difficult. Ion exchange requires a large amount of resin, resulting in high regeneration costs. Membrane exchange utilizes the difference in membrane pore size to selectively allow impurities to pass through, achieving separation and purification; however, this method is relatively expensive.

[0004] In the prior art, Chinese patent CN116022752A discloses a process for purifying residual raffinate with a composite extractant, specifically disclosing that residual raffinate with an original mass concentration of not less than 40% is diluted to a mass concentration of 20-25%, and then filtered to remove obvious particulate matter; the diluted and filtered residual raffinate is mixed with the extractant to extract organic phase 1 and aqueous phase 1; the volume ratio of extractant to residual raffinate is 1:1 to 4:1; the extractant is a mixture of acidic extractant and diluent; the organic phase 1 is back-extracted at least 3 times using a back-extraction solution, and after back-extraction, it is allowed to stand and separate to obtain organic phase 2 and aqueous phase 2, and the obtained organic phase 2 is the purified regenerated extractant; the back-extraction solution is a strong acid or a medium-strong acid, and the volume ratio of back-extraction solution to organic phase 1 is 3:1 to 1:1. An extractant prepared with an acidic extractant and diluent directly extracts impurity metal cations such as iron, magnesium, aluminum, and manganese ions from raffinate. The acidic extractant exhibits good selectivity for metal ion extraction, with minimal phosphoric acid entrainment during the extraction process, achieving a phosphoric acid recovery rate of over 90%. In the raffinate purified by this method, iron, aluminum, magnesium, and manganese ions are adsorbed into the extractant, resulting in effective purification. The purification rates for iron, aluminum, magnesium, and manganese ions reach 90%, 50%, and 50%, respectively. However, this process still results in a low phosphoric acid recovery rate, and the metal ions cannot be separated, making recycling difficult and reducing added value.

[0005] Therefore, a novel method and system for extracting and removing metal ions from the residual acid in the by-product of refined phosphoric acid is needed. Summary of the Invention

[0006] The method and system for extracting and removing metal ions from the residual acid in the refined phosphoric acid by-product improve the recovery and utilization of phosphoric acid resources while ensuring normal, stable and continuous operation to produce high-quality phosphoric acid.

[0007] The first objective of this invention is to provide a method for extracting and removing metal ions from the residual acid in the byproduct of refined phosphoric acid production, comprising the following steps:

[0008] 1) Emulsion Extraction: The residual acid is subjected to emulsion deep extraction using an extractant to obtain purified phosphoric acid and an organic phase supported on metal cations; wherein, the emulsion deep extraction includes obtaining an emulsion based on emulsion extraction, and further deep extraction and phase separation of the emulsion:

[0009] 2) First wash: The organic phase loaded with metal cations obtained by emulsification extraction in step 1) is reacted with dilute phosphoric acid and washed to obtain phosphoric acid wash extractant;

[0010] 3) First back-extraction: The phosphoric acid washing extractant from step 2) is sequentially contacted with back-extraction agent A and back-extraction agent B to perform two-stage back-extraction, resulting in a first back-extraction aqueous phase and a first back-extraction organic phase;

[0011] 4) Secondary washing: The organic phase from the first back-extraction in step 3) is washed with dilute sulfuric acid to obtain sulfuric acid washing extractant;

[0012] 5) Secondary back-extraction: The sulfuric acid washing extractant from step 4) is contacted with oxalic acid A for back-extraction to obtain a secondary back-extraction aqueous phase and a secondary back-extraction organic phase;

[0013] 6) Three washes: The organic phase from the second back-extraction in step 5) is washed with oxalic acid B to obtain the regenerated extractant. The regenerated extractant is then returned to the emulsification extraction in step 1) as the extractant.

[0014] 7) Crystallization of the aqueous phase after primary back-extraction: Add ammonium sulfate to the aqueous phase after primary back-extraction in step 3) and cool and crystallize to obtain magnesium ammonium sulfate and aluminum ammonium sulfate; wherein the mass ratio of the aqueous phase after primary back-extraction to ammonium sulfate is 100-200:1;

[0015] 8) Secondary back-extraction aqueous phase photocatalysis: The secondary back-extraction aqueous phase is subjected to photocatalytic precipitation to recover the metal ion iron and obtain ferrous oxalate.

[0016] In one specific embodiment of the present invention, in step 1), emulsification extraction, the density of the residual acid is 1.50-1.60 g / mL, the concentration of P2O5 is 40-60%, the solid content is 0.5%, and the MER value is 0.12-0.2.

[0017] The reaction temperature for the deep extraction is 50–60°C, and the O / A ratio is 2:1–4:1.

[0018] In one specific embodiment of the present invention, the emulsification deep extraction is performed in two stages.

[0019] In one specific embodiment of the present invention, the number of stages of emulsification depth extraction in each segment is 3.

[0020] In one specific embodiment of the present invention, the emulsification deep extraction method for each segment is countercurrent.

[0021] In one specific embodiment of the present invention, step 1) emulsification extraction, wherein the density of the extractant is ≤0.86mg / mL, and includes at least one of organophosphorus extractants, organophosphorus extractants, organosulfonic acid extractants, organocarboxylic acid extractants, and tertiary carbonate extractants.

[0022] In one specific embodiment of the present invention, the extractant is at least one selected from the following: di(2-ethylhexyl) phosphate, 2-ethylhexyl phosphate, di(2,4,4-trimethylpentyl)phosphine, 2-ethylhexylphosphonic acid mono(2-ethylhexyl) ester, N,N-n-octylamine di(methylene phenylphosphine), toluenesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid, xylenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, cinnamic acid, fatty acids, lauric acid, and naphthenic acid.

[0023] In one specific embodiment of the present invention, in step 2), a single washing is performed, wherein the acidity of the dilute phosphoric acid is 3-5%; the reaction temperature for washing is 50-60°C, and the O / A ratio is 3:1-2:1.

[0024] In one specific embodiment of the present invention, the washing process has two stages.

[0025] In one specific embodiment of the present invention, the washing method is countercurrent.

[0026] In one specific embodiment of the present invention, step 3) is a single back-extraction, the reaction temperature of the two-stage back-extraction is 25-35°C, and the reaction ratio O / A is 1:1-1:3; the two-stage back-extraction includes front-stage back-extraction using back-extraction agent A and back-stage back-extraction using back-extraction agent B.

[0027] In one specific embodiment of the present invention, the concentration of sulfuric acid in the back-extraction agent A is 25-35%, and the concentration of ammonium sulfate is 4.5-6.5%; the concentration of sulfuric acid in the back-extraction agent B is 30-40%, and the concentration of ammonium sulfate is 4.5-6.5%.

[0028] In one specific embodiment of the present invention, the number of stages of the front-end extraction is 3.

[0029] In one specific embodiment of the present invention, the front-end extraction method is countercurrent.

[0030] In one specific embodiment of the present invention, the number of stages of the back-extraction is 2.

[0031] In one specific embodiment of the present invention, the downstream back-extraction method is countercurrent.

[0032] In one specific embodiment of the present invention, in step 4), a second washing is performed, wherein the concentration of the dilute sulfuric acid is 3-5%; the washing temperature is 50-60°C, and the reaction ratio O / A is 3:1-2:1.

[0033] In one specific embodiment of the present invention, the washing process has two stages.

[0034] In one specific embodiment of the present invention, the washing method is countercurrent.

[0035] In one specific embodiment of the present invention, in step 5), a second back-extraction is performed, wherein the concentration of oxalic acid A is 6-8%; the back-extraction temperature is 50-60°C, and the reaction ratio O / A is 1:1-1:3.

[0036] In one specific embodiment of the present invention, the number of back-extraction stages is 2.

[0037] In one specific embodiment of the present invention, the back-extraction method is countercurrent.

[0038] In one specific embodiment of the present invention, step 6) involves three washes, wherein the concentration of oxalic acid B is 1%; the reaction temperature for the washes is 50-60°C, and the reaction ratio O / A is 3:1-2:1.

[0039] In one specific embodiment of the present invention, the washing process has two stages.

[0040] In one specific embodiment of the present invention, the washing method is countercurrent.

[0041] In one specific embodiment of the present invention, step 8) involves secondary back-extraction and aqueous phase photocatalysis, wherein the reaction temperature for the photocatalytic sedimentation is 30–60°C and the light intensity is 145–725 mW / cm². 2 The oxalic acid concentration in the aqueous phase of the secondary back-extraction is controlled to be 6-10%.

[0042] The second objective of this invention is to provide an extraction and removal system for metal ions in the residual acid from refined phosphoric acid by-products, for realizing the above-mentioned extraction and removal method for metal ions in the residual acid from refined phosphoric acid by-products, including an emulsification extraction device, a primary washing device, a primary back-extraction device, a secondary washing device, a secondary back-extraction device, a tertiary washing device, a primary back-extraction aqueous phase crystallization device, and a secondary back-extraction aqueous phase photocatalytic device.

[0043] The emulsification extraction device includes a residual acid feeding tank, an extractant feeding tank, an organic phase temporary storage tank, a purified phosphoric acid storage tank, and a two-stage centrifugal extraction unit A. The first-stage centrifugal extraction unit A is equipped with a residual acid inlet and a residual liquid outlet. The second-stage centrifugal extraction unit A is equipped with a residual liquid inlet and a purified phosphoric acid outlet. The residual liquid outlet is connected to the residual liquid inlet. The outlet of the residual acid feeding tank is connected to the residual acid inlet. The purified phosphoric acid outlet is connected to the inlet of the purified phosphoric acid storage tank. Both stages of the centrifugal extraction unit A are equipped with a camera inlet and an organic phase outlet. The camera outlet is connected to the inlet of the organic phase temporary storage tank. The outlet of the extractant feeding tank is connected to the organic phase inlet. Both stages of the centrifugal extraction unit A include multiple centrifugal extractors connected in series and an emulsification pump corresponding to each centrifugal extractor. The output end of the emulsification pump is connected to the inlet of each centrifugal extractor.

[0044] The primary washing device includes a dilute phosphoric acid feeding tank, a centrifugal extraction unit B, a cooling buffer tank, a cooler, and a dilute phosphoric acid receiving tank. The outlets of the dilute phosphoric acid feeding tank and the organic phase temporary storage tank are both connected to the inlet of the centrifugal extraction unit B. The outlet of the centrifugal extraction unit B is connected to the cooling buffer tank. The outlet of the cooling buffer tank is connected to the inlet of the cooler. The outlet of the cooler is connected to the inlet of the primary back-extraction device.

[0045] The primary back-extraction device includes a back-extraction agent preparation tank, a back-extraction agent feeding tank, a centrifugal extraction unit C, a primary back-extraction aqueous phase temporary storage tank, a heating buffer tank, and a heater. The outlet of the back-extraction agent preparation tank is connected to the inlet of the back-extraction agent feeding tank. The outlets of the back-extraction agent feeding tank and the cooler are both connected to the inlet of the centrifugal extraction unit C. The outlet of the centrifugal extraction unit C is connected to the primary back-extraction aqueous phase temporary storage tank and the heating buffer tank, respectively. The outlet of the heating buffer tank is connected to the inlet of the heater, and the outlet of the heater is connected to the inlet of the secondary washing device.

[0046] The secondary washing device includes a dilute sulfuric acid feeding tank, a centrifugal extraction unit D, and a dilute sulfuric acid receiving tank. The outlets of the dilute sulfuric acid feeding tank and the heater are both connected to the inlet of the centrifugal extraction unit D. The outlets of the centrifugal extraction unit D are respectively connected to the dilute sulfuric acid receiving tank and the secondary back-extraction device.

[0047] The secondary back-extraction device includes an oxalic acid preparation tank, an oxalic acid A feeding tank, a centrifugal extraction unit E, and a secondary back-extraction temporary storage tank. The outlets of the oxalic acid A feeding tank and the centrifugal extraction unit D are both connected to the inlet of the centrifugal extraction unit E. The outlet of the centrifugal extraction unit E is connected to the inlet of the secondary back-extraction aqueous phase temporary storage tank and the inlet of the tertiary washing device, respectively.

[0048] The three-stage washing device includes an oxalic acid B feeding tank, a centrifugal extractor F, an oxalic acid B receiving tank, and an extractant clarification tank. The outlets of the oxalic acid B feeding tank and the centrifugal extractor E are both connected to the inlet of the centrifugal extractor F. The outlet of the centrifugal extractor F is connected to the inlet of the oxalic acid B receiving tank and the inlet of the extractant clarification tank, respectively. The outlet of the extractant clarification tank is connected to the inlet of the extractant feeding tank.

[0049] The primary back-extraction aqueous phase crystallization apparatus includes a back-extraction agent crystallization tank, a back-extraction agent settling tank, a back-extraction agent clear liquid tank, and a double-push centrifuge. The outlet of the primary back-extraction temporary storage tank is connected to the inlet of the back-extraction agent crystallization tank, the outlet of the back-extraction agent crystallization tank is connected to the inlet of the back-extraction agent settling tank, the clear liquid outlet of the back-extraction agent settling tank is connected to the inlet of the clear liquid tank, the solid phase outlet of the back-extraction agent settling tank is connected to the double-push centrifuge, and the outlet of the clear liquid tank is connected to the inlet of the back-extraction agent preparation tank.

[0050] The secondary back-extraction aqueous photocatalytic device includes a photocatalytic reactor, an oxalic acid settling tank, an oxalic acid clarified liquid tank, and a plate and frame filter press. The outlet of the secondary back-extraction temporary storage tank is connected to the inlet of the photocatalytic reactor, the outlet of the photocatalytic reactor is connected to the inlet of the oxalic acid settling tank, the clarified liquid outlet of the oxalic acid settling tank is connected to the inlet of the clarified oxalic acid tank, the solid phase outlet of the oxalic acid settling tank is connected to the plate and frame filter press, and the outlet of the clarified oxalic acid tank is connected to the oxalic acid A feeding tank.

[0051] In the extraction and desorption method of this invention, during the emulsification and deep extraction process of the residual acid and the extractant, the organic phase is loaded with phosphoric acid in addition to metal ions. The first washing uses dilute phosphoric acid to wash the organic phase, thereby recovering the phosphoric acid and reducing phosphorus loss during emulsification extraction. The first back-extraction uses 30% sulfuric acid and ammonium sulfate from back-extraction agent A and 35% sulfuric acid from back-extraction agent B to separate magnesium and aluminum ions from the organic phase, while iron ions (Fe...)... 3+The magnesium and aluminum ions remain in the organic phase. The separated magnesium and aluminum ions are crystallized to obtain magnesium ammonium sulfate and aluminum ammonium sulfate, respectively. A second washing process uses dilute sulfuric acid to remove the sulfuric acid from the organic phase after the first extraction. A second back-extraction process uses 6-8% oxalic acid. Since solid iron oxalate is not easily soluble in water but is soluble in oxalic acid solution, photocatalytic reduction generates ferrous oxalate precipitate, facilitating the removal of iron from the system. This allows the remaining iron ions (Fe2+) to be separated from the organic phase. 3+ The organic phase after iron ions have been removed can be returned to the extraction step and recycled as an extractant.

[0052] The beneficial effects of this invention are as follows: 1. This invention uses an extractant and residual raffinate for extraction, resulting in more thorough mixing and a more efficient reaction. Metal ions in the residual raffinate can be effectively transferred to the organic phase through emulsification extraction, allowing for the one-step purification of phosphoric acid; 2. This invention uses sulfuric acid and oxalic acid for primary and secondary back-extraction, respectively, to separate magnesium, aluminum, and iron elements from the metal ions, facilitating the classified recycling of metals and achieving high recovery rates for individual metal elements; 3. This invention removes metal ions from the by-product residual raffinate, reducing phosphorus loss and significantly contributing to the full utilization of phosphorus resources; 4. This invention can reduce the MER value of the residual raffinate from 0.12–0.2 to 0.070–0.085, with a P2O5 yield of 99.5%, greatly improving the utilization rate of the residual raffinate. Attached Figure Description

[0053] Figure 1 This is a flowchart of the method for extracting and removing metal ions from the residual acid in the refined phosphoric acid by-product of the present invention.

[0054] Figure 2 This is a schematic diagram of the extraction and removal system for metal ions from the residual acid in the purified phosphoric acid by-product of this invention.

[0055] Figure 3 This is a schematic diagram of the emulsification extraction device of the present invention;

[0056] Figure 4 This is a schematic diagram of the structure of the primary washing device and the primary back-extraction device of the present invention;

[0057] Figure 5 This is a schematic diagram of the secondary washing device, secondary back-extraction device, and tertiary washing device of the present invention;

[0058] Figure 6 This is a schematic diagram of the structure of the single-stage back-extraction aqueous phase crystallization apparatus of the present invention.

[0059] Figure 7 This is a schematic diagram of the structure of the secondary back-extraction aqueous photocatalytic device of the present invention.

[0060] The attached diagram lists the components represented by each number as follows:

[0061] 1. Emulsification extraction device; 11. Residual acid feed tank; 12. Extractant feed tank; 13. Emulsification pump; 14. Centrifugal extraction unit A; 15. Organic phase temporary storage tank; 16. Purified phosphoric acid storage tank; 17. Emulsification buffer tank; 2. Primary washing device; 21. Dilute phosphoric acid feed tank; 22. Centrifugal extraction unit B; 23. Cooler; 24. Dilute phosphoric acid receiving tank; 231. Cooling buffer tank; 232. Cooler; 3. Primary back-extraction device; 31. Back-extraction agent preparation tank; 32. Back-extraction agent feed tank; 33. Centrifugal extraction unit C; 34. Primary back-extraction aqueous phase temporary storage tank; 35. Heater; 351. Heating buffer tank; 352. Heating heat exchanger; 4. Secondary washing device; 4 1. Dilute sulfuric acid feeding tank; 42. Centrifugal extraction unit D; 43. Dilute sulfuric acid buffer tank; 5. Secondary back-extraction device; 50. Oxalic acid preparation tank; 51. Oxalic acid A feeding tank; 52. Centrifugal extraction unit E; 53. Secondary back-extraction aqueous phase temporary storage tank; 6. Tertiary washing device; 61. Oxalic acid B feeding tank; 62. Centrifugal extraction unit F; 63. Dilute oxalic acid temporary storage tank; 64. Extractant clarification tank; 7. Primary back-extraction aqueous phase crystallization device; 71. Crystallizer; 72. Back-extraction agent settling tank; 73. Back-extraction agent clear liquid tank; 74. Double-push centrifuge; 8. Secondary back-extraction aqueous phase photocatalysis device; 81. Photocatalytic reactor; 82. Oxalic acid settling tank; 83. Oxalic acid clear liquid tank; 84. Plate and frame filter press. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0063] Example

[0064] Based on the appendix Figure 1 A method for extracting and removing metal ions from the residual acid in the by-product of refined phosphoric acid, comprising the following steps:

[0065] 1) Extraction: The residual acid is emulsified and deeply extracted using an extractant to obtain purified phosphoric acid and an organic phase loaded with metal cations; wherein, the emulsification and deep extraction includes obtaining an emulsion based on emulsification and extraction, and further extracting and separating the emulsion.

[0066] 2) First wash: The organic phase loaded with metal cations obtained from the emulsification extraction in step 1) is washed by contacting dilute phosphoric acid to obtain the phosphoric acid wash extractant;

[0067] 3) First back-extraction: The phosphoric acid washing extractant from step 2) is sequentially contacted with back-extraction agent A and back-extraction agent B to perform two-stage back-extraction, resulting in a first back-extraction aqueous phase and a first back-extraction organic phase;

[0068] 4) Secondary washing: The organic phase from the first back-extraction in step 3) is washed with dilute sulfuric acid to obtain sulfuric acid washing extractant;

[0069] 5) Secondary back-extraction: The sulfuric acid washing extractant from step 4) is contacted with oxalic acid A for back-extraction to obtain a secondary back-extraction aqueous phase and a secondary back-extraction organic phase;

[0070] 6) Three washes: The organic phase from the second back-extraction in step 5) is washed with oxalic acid B to obtain the regenerated extractant. The regenerated extractant is then returned to the emulsification extraction in step 1) as the extractant.

[0071] 7) Crystallization of the aqueous phase after primary back-extraction: Add ammonium sulfate to the aqueous phase after primary back-extraction in step 3) and cool and crystallize to obtain magnesium ammonium sulfate and aluminum ammonium sulfate; wherein the mass ratio of the aqueous phase after primary back-extraction to ammonium sulfate is 100-200:1;

[0072] 8) Secondary back-extraction aqueous phase photocatalysis: The secondary back-extraction aqueous phase is subjected to photocatalytic precipitation to recover the metal ion iron and obtain ferrous oxalate.

[0073] In some examples, step 1) emulsification extraction has a residual acid density of 1.50–1.60 g / mL, a P2O5 concentration of 40–60%, a solid content of 0.5%, and a MER value of 0.12–0.2; the deep extraction reaction temperature is 50–60 °C, and the reaction ratio O / A is 2:1–4:1.

[0074] In some instances, the emulsification depth extraction is performed in two stages.

[0075] In some instances, the number of stages for each emulsification depth extraction is 3.

[0076] In some instances, each emulsification depth extraction is performed using a countercurrent method.

[0077] In some instances, the extractant density is ≤0.86 mg / mL, including at least one of organophosphorus extractants, organophosphorus extractants, organosulfonic acid extractants, organocarboxylic acid extractants, and tertiary carbonate extractants.

[0078] In some instances, the extractant is at least one of the following: di(2-ethylhexyl) phosphate, 2-ethylhexyl phosphate, di(2,4,4-trimethylpentyl)phosphine, 2-ethylhexylphosphonic acid mono(2-ethylhexyl) ester, N,N-n-octylamine di(methylene phenylphosphine), toluenesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid, xylenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, cinnamic acid, fatty acids, lauric acid, and naphthenic acid.

[0079] In some instances, step 2) involves a single wash with a dilute phosphoric acid concentration of 3–5%; the reaction temperature for the contact wash is 50–60°C, and the O / A ratio is 3:1–2:1.

[0080] In some instances, the washing process is grade 2.

[0081] In some instances, the washing process involves counter-current flow.

[0082] In some instances, step 3) involves a first-stage back-extraction and a second-stage back-extraction reaction at a temperature of 25–35°C, with a reaction ratio of O / A of 1:1–1:3. The second-stage back-extraction includes front-stage back-extraction using back-extraction agent A and back-stage back-extraction using back-extraction agent B.

[0083] In some examples, the concentration of sulfuric acid in the back-extraction agent A is 25-35%, and the concentration of ammonium sulfate is 4.5-6.5%; the concentration of sulfuric acid in the back-extraction agent B is 30-40%, and the concentration of ammonium sulfate is 4.5-6.5%.

[0084] In some instances, the number of stages in the front-end extraction is 3.

[0085] In some instances, the front-end extraction method is countercurrent.

[0086] In some instances, the number of stages for back-extraction is 2.

[0087] In some instances, the back-extraction process is reverse flow.

[0088] In some instances, step 4) involves a second wash with a concentration of 3–5% dilute sulfuric acid; the washing temperature is 50–60°C; and the reaction ratio of O / A is 3:1–2:1.

[0089] In some instances, the washing process is grade 2.

[0090] In some instances, the washing process involves counter-current flow.

[0091] In some instances, step 5) involves a second back-extraction with an oxalic acid A concentration of 6–8%; the reaction temperature for contact back-extraction is 50–60°C, and the O / A ratio is 1:1–1:3.

[0092] In some instances, the back-extraction stage is two stages.

[0093] In some instances, the back-extraction method is reverse flow.

[0094] In some instances, step 6) involves three washes with oxalic acid B at a concentration of 1%; the washing reaction temperature is 50–60°C, and the O / A ratio is 3:1–2:1.

[0095] In some instances, the washing process is grade 2.

[0096] In some instances, the washing process involves counter-current flow.

[0097] In some examples, step 8) involves secondary back-extraction and aqueous phase photocatalysis, with a reaction temperature of 30–60°C and a light intensity of 145–725 mW / cm². 2 The oxalic acid concentration in the aqueous phase of the secondary back-extraction is controlled at 6-10%.

[0098] Based on the appendix Figure 2-7 An extraction and removal system for metal ions in the residual acid from refined phosphoric acid by-products, used to realize the above-mentioned extraction and removal method for metal ions in the residual acid from refined phosphoric acid by-products, comprising an emulsification extraction device 1, a primary washing device 2, a primary back-extraction device 3, a secondary washing device 4, a secondary back-extraction device 5, a tertiary washing device 6, a primary back-extraction aqueous phase crystallization device 7, and a secondary back-extraction aqueous phase photocatalytic device 8.

[0099] The emulsification extraction device 1 includes a residual acid feeding tank 11, an extractant feeding tank 12, an organic phase temporary storage tank 15, a purified phosphoric acid storage tank 16, and a two-stage centrifugal extraction unit A14. The first-stage centrifugal extraction unit A14 is equipped with a residual acid inlet and a residual liquid outlet, and the second-stage centrifugal extraction unit A14 is equipped with a residual liquid inlet and a purified phosphoric acid outlet. The residual liquid outlet is connected to the residual liquid inlet, the outlet of the residual acid feeding tank 11 is connected to the residual acid inlet, and the purified phosphoric acid outlet is connected to the inlet of the purified phosphoric acid storage tank 16. Each of the two-stage centrifugal extraction units A14 is equipped with a camera inlet and an organic phase outlet. The camera outlet is connected to the inlet of the organic phase temporary storage tank 15, and the outlet of the extractant feeding tank 12 is connected to the organic phase inlet. Each of the two-stage centrifugal extraction units A14 includes multiple centrifugal extractors connected in series and an emulsification pump 13 corresponding to each centrifugal extractor. The output end of the emulsification pump 13 is connected to the inlet of the centrifugal extractor.

[0100] It should be noted that the residual acid is input from the first stage of each centrifugal extraction unit A14, and its participation in the emulsification and deep extraction process is as follows: emulsification-deep extraction and phase separation-emulsification-deep extraction and phase separation-emulsification-deep extraction and phase separation; the extractant is input from the last stage of each centrifugal extraction unit A14, and its participation in the deep emulsification and extraction process is as follows: emulsification-deep extraction and phase separation-emulsification-deep extraction and phase separation-emulsification-deep extraction and phase separation; therefore, in each centrifugal extraction unit A14, the extraction method of the residual acid and the extractant is countercurrent.

[0101] The primary washing unit 2 includes a dilute phosphoric acid feeding tank 21, a centrifugal extraction unit B 22, a cooling buffer tank 231, a cooler 232, and a dilute phosphoric acid receiving tank 24. The outlets of the dilute phosphoric acid feeding tank 21 and the organic phase temporary storage tank 15 are both connected to the inlet of the centrifugal extraction unit B 22. The outlet of the centrifugal extraction unit B 22 is connected to the cooling buffer tank 231, the outlet of the cooling buffer tank 231 is connected to the inlet of the cooler 232, and the outlet of the cooler 232 is connected to the inlet of the primary back-extraction unit 3. The cooler 232 is used to cool the phosphoric acid washing extractant to the temperature required for primary back-extraction.

[0102] The primary back-extraction unit 3 includes a back-extraction agent preparation tank 31, a back-extraction agent feeding tank 32, a centrifugal extraction unit C 33, a primary back-extraction aqueous phase temporary storage tank 34, a heating buffer tank 351, and a heater 352. The outlet of the back-extraction agent preparation tank 31 is connected to the inlet of the back-extraction agent feeding tank 32. The outlets of the back-extraction agent feeding tank 32 and the cooler 232 are both connected to the inlet of the centrifugal extraction unit C 33. The outlets of the centrifugal extraction unit C 33 are respectively connected to the primary back-extraction aqueous phase temporary storage tank 34 and the heating buffer tank 351. The outlet of the heating buffer tank 351 is connected to the inlet of the heater 352. The outlet of the heater 352 is connected to the inlet of the secondary washing unit 4. The heater 352 is used to heat the primary back-extraction organic phase to the temperature required for secondary washing.

[0103] The secondary washing device 4 includes a dilute sulfuric acid feeding tank 41, a centrifugal extraction unit D 42, and a dilute sulfuric acid receiving tank 43. The outlets of the dilute sulfuric acid feeding tank 41 and the heater 352 are both connected to the inlet of the centrifugal extraction unit D 42. The outlet of the centrifugal extraction unit D 42 is connected to the dilute sulfuric acid receiving tank 43 and the inlet of the secondary back-extraction device 5, respectively.

[0104] The secondary back-extraction device 5 includes an oxalic acid preparation tank 50, an oxalic acid A feeding tank 51, a centrifugal extraction unit E52, and a secondary back-extraction temporary storage tank 53. The outlets of the oxalic acid A feeding tank 51 and the centrifugal extraction unit D42 are both connected to the inlet of the centrifugal extraction unit E52. The outlet of the centrifugal extraction unit E52 is connected to the inlet of the secondary back-extraction aqueous phase temporary storage tank 53 and the inlet of the tertiary washing device 6, respectively.

[0105] The three-stage washing device 6 includes an oxalic acid B feeding tank 61, a centrifugal extractor F 62, an oxalic acid B receiving tank 63, and an extractant clarification tank 64. The outlets of the oxalic acid B feeding tank 61 and the centrifugal extractor E 52 are both connected to the inlet of the centrifugal extractor F 62. The outlet of the centrifugal extractor F 62 is connected to the inlet of the oxalic acid B receiving tank 63 and the inlet of the extractant clarification tank 64, respectively. The outlet of the extractant clarification tank 64 is connected to the inlet of the extractant feeding tank 12.

[0106] The primary back-extraction aqueous phase crystallization device 7 includes a back-extraction crystallization tank 71, a back-extraction settling tank 72, a back-extraction clear liquid tank 73, and a double-push centrifuge 74. The outlet of the primary back-extraction temporary storage tank 34 is connected to the inlet of the back-extraction crystallization tank 71, the outlet of the back-extraction crystallization tank 71 is connected to the inlet of the back-extraction settling tank 72, the clear liquid outlet of the back-extraction settling tank 72 is connected to the inlet of the back-extraction clear liquid tank 73, the solid phase outlet of the back-extraction settling tank 72 is connected to the double-push centrifuge 74, and the outlet of the back-extraction clear liquid tank 73 is connected to the inlet of the back-extraction preparation tank 31.

[0107] The secondary back-extraction aqueous phase photocatalytic device 8 includes a photocatalytic reactor 81, an oxalic acid settling tank 82, an oxalic acid clarified liquid tank 83, and a plate and frame filter press 84. The outlet of the secondary back-extraction temporary storage tank 53 is connected to the inlet of the photocatalytic reactor 81, the outlet of the photocatalytic reactor 81 is connected to the inlet of the oxalic acid settling tank 82, the clarified liquid outlet of the oxalic acid settling tank 82 is connected to the inlet of the oxalic acid clarified liquid tank 83, the solid phase outlet of the oxalic acid settling tank 82 is connected to the plate and frame filter press 84, and the outlet of the oxalic acid clarified liquid tank 83 is connected to the oxalic acid A feeding tank 51.

[0108] In some examples, feed pumps are installed at the outlets of the residual acid feed tank 11, the extractant feed tank 12, the dilute phosphoric acid feed tank 21, the back-extraction agent feed tank 32, the dilute sulfuric acid feed tank 41, the oxalic acid A feed tank 51, and the oxalic acid B feed tank 61.

[0109] In some examples, the residual acid feeding tank 11, the extractant feeding tank 12, the dilute phosphoric acid feeding tank 21, the back-extraction agent feeding tank 32, the dilute sulfuric acid feeding tank 41, the oxalic acid A feeding tank 51, the oxalic acid B feeding tank 61, the back-extraction agent preparation tank 31, the first aqueous phase temporary storage tank 34, and the second back-extraction aqueous phase temporary storage tank 53 are all equipped with exhaust gas outlets. The exhaust gas outlets are connected to heat exchangers via centrifugal induced draft fans to condense and recover the exhaust gas.

[0110] In some examples, the centrifugal extractor A14 is configured in two sections, with three centrifugal extractors A14 in each section. Each centrifugal extractor A14 has an emulsification pump 13 at its inlet, and each emulsification pump 13 has an emulsification buffer tank 17. Each centrifugal extractor A14 has an organic phase outlet and an aqueous phase outlet. The aqueous phase outlet of the first centrifugal extractor A14 is connected to the inlet of the second emulsification pump 13, and so on, until purified phosphoric acid is obtained from the aqueous phase outlet of the sixth centrifugal extractor A14 and stored in the purified phosphoric acid storage tank 16. The outlet of the extractant feeding tank 12... The inlets of the third and sixth emulsifying pumps 13 are connected to the organic phase outlet of the sixth centrifugal extractor A14, which is connected to the inlet of the fifth emulsifying pump 13. This process continues in sequence. The organic phase loaded with metal ions is obtained from the organic phase outlet of the fourth centrifugal extractor A14 and stored in the organic phase storage tank 15. The organic phase outlet of the third centrifugal extractor A14 is connected to the inlet of the second emulsifying pump 13, which is connected to the organic phase outlet of the first centrifugal extractor A14 and stored in the organic phase storage tank 15.

[0111] In some instances, there are two centrifugal extractors B 22. The outlet of the organic phase storage tank 15 is connected to the inlet of the first centrifugal extractor B 22, and the organic phase outlet of the first centrifugal extractor B 22 is connected to the inlet of the second centrifugal extractor B 22. The outlet of the dilute phosphoric acid feed tank 21 is connected to the inlet of the second centrifugal extractor B 22, and the organic phase outlet of the first centrifugal extractor B 22 is connected to the dilute phosphoric acid receiving tank 24 and / or the dilute phosphoric acid feed tank 21. The organic phase from centrifugal extractor A14 passes sequentially through all centrifugal extractors B 22, and is washed countercurrently with dilute phosphoric acid.

[0112] In some examples, there are a total of five centrifugal extractors C 33, divided into two sections: the front section has three centrifugal extractors C 33, and the rear section has two centrifugal extractors C 33. The back-extraction agent feeding tank 32 includes a back-extraction agent A feeding tank and a back-extraction agent B feeding tank. The outlet of the back-extraction agent preparation tank is connected to the inlet of the back-extraction agent A feeding tank and the back-extraction agent B feeding tank, respectively. The outlet of the back-extraction agent A feeding tank is connected to the inlet of the third centrifugal extractor C 33 in the front section. The back-extraction outlet of the third centrifugal extractor C 33 is connected to the inlet of the second centrifugal extractor C 33, and so on. A primary back-extraction aqueous phase is obtained from the organic phase outlet of the first centrifugal extractor C 33 in the front section and stored in the primary back-extraction aqueous phase temporary storage tank 34. The outlet of the back-extraction agent B feeding tank is connected to the inlet of the second centrifugal extractor C 33 in the rear section, and 35% sulfuric acid of back-extraction agent B is input. The aqueous phase outlet of the second centrifugal extractor C 33 in the rear section is connected to the first centrifugal extractor C 33 in the rear section. The inlet of 33 obtains 35% sulfuric acid from the aqueous phase outlet of the first centrifugal extractor C 33 in the later stage, and stores it in a 35% sulfuric acid buffer tank; the organic phase from the cooler 23 passes sequentially through all centrifugal extractors C 33, and is back-extracted countercurrently with both back-extractant A and back-extractant B.

[0113] In some instances, there are two centrifugal extractors D 42. The outlet of the dilute sulfuric acid feed tank 41 is connected to the inlet of the second centrifugal extractor D 42, and the aqueous phase outlet of the second centrifugal extractor D 42 is connected to the inlet of the first centrifugal extractor D 42. The aqueous phase outlet of the first centrifugal extractor D 42 receives dilute sulfuric acid, which is stored in the dilute sulfuric acid buffer tank 43. The organic phase from the heater 35 passes sequentially through the two centrifugal extractors D 42 and is washed countercurrently with dilute sulfuric acid.

[0114] In some instances, there are two centrifugal extractors E 52. The outlet of the oxalic acid A feed tank 51 is connected to the inlet of the second centrifugal extractor E 52, and the aqueous phase outlet of the second centrifugal extractor E 52 is connected to the inlet of the first centrifugal extractor E 52. Oxalic acid A is obtained from the aqueous phase outlet of the first centrifugal extractor E 52 and stored in an oxalic acid A storage tank. The organic phase obtained from the organic phase outlet of the second centrifugal extractor D 42 passes sequentially through the two centrifugal extractors E 52, countercurrently back-extracting with oxalic acid A.

[0115] In some instances, there are two centrifugal extractors F 62. The outlet of the oxalic acid B feed tank 61 is connected to the inlet of the second centrifugal extractor F 62, and the aqueous phase outlet of the second centrifugal extractor F 62 is connected to the inlet of the first centrifugal extractor F 62. Oxalic acid B is obtained from the aqueous phase outlet of the first centrifugal extractor F 62 and stored in an oxalic acid B buffer tank. The organic phase obtained from the organic phase outlet of the second centrifugal extractor E 52 passes sequentially through the two centrifugal extractors F 62 and is washed countercurrently with oxalic acid B.

[0116] In some instances, six crystallizers 71 are provided.

[0117] In some instances, the bottom outlet of the back-extraction settling tank 72 is connected to a double-push centrifuge 74; the waste liquid outlet of the double-push centrifuge 74 is connected to the back-extraction clear liquid tank 73.

[0118] In some instances, the bottom outlet of the oxalic acid settling tank 82 is connected to a plate and frame filter press 84; the liquid phase outlet of the plate and frame filter press 84 is connected to an oxalic acid clear liquid tank 83.

[0119] In some examples, centrifugal extractors A14, B22, C33, D42, E52 and F62 are all equipped with a residual liquid outlet, and the residual liquid outlet pipe is connected to the residual liquid tank.

[0120] To further demonstrate the effectiveness of the extraction and removal method of the present invention in improving the removal of metal ions from the by-product raffinate, the following experimental example is provided based on the aforementioned extraction and removal system for metal ions in the by-product raffinate of refined phosphoric acid:

[0121] Experimental Example 1

[0122] This experimental example provides a method for the extraction and removal of metal ions from residual acid, including the following steps:

[0123] 1. Extraction process: The raffinate stock solution collected and stored in the raffinate feed tank is pumped into an emulsification pump and fully emulsified and mixed with the extractant pumped from the organic phase feed tank. Then, it is pumped into centrifugal extractor A for deep extraction. The resulting organic phase is a metal ion-loaded extractant, and the aqueous phase is purified phosphoric acid. The density of the raffinate is 1.50 g / mL, the P2O5 concentration is 44 wt%, the solid content is 0.5%, and the MER value is 0.15. The density of the extractant is 0.86 g / mL. The reaction temperature for deep extraction in centrifugal extractor A is 50℃, and the reaction ratio O / A is 3:1.

[0124] The MER value of purified phosphoric acid was 0.083, and the yield of P2O5 was 99.12%; where MER value is the ratio of the sum of the mass percentages of metal oxides MgO, Al2O3 and Fe2O3 to the mass percentage of P2O5.

[0125] 2. The metal ion-loaded extractant and dilute phosphoric acid from the dilute phosphoric acid feeding tank are fed into centrifugal extractor B for washing. The phosphoric acid entrained in the extractant is recovered and sent to the dilute phosphoric acid receiving tank to obtain phosphoric acid washed extractant. The concentration of dilute phosphoric acid is 5%, the reaction temperature in centrifugal extractor B is 50℃, and the reaction ratio O / A is 3:1.

[0126] 3. Prepare back-extraction agent A and back-extraction agent B using sulfuric acid solution. Feed the sulfuric acid solution from the sulfuric acid feed tank and the extractant washed with phosphoric acid into a centrifugal extractor C for a two-stage back-extraction process, yielding a primary back-extraction aqueous phase and a primary back-extraction organic phase. In the primary back-extraction, back-extraction agent A has a sulfuric acid concentration of 30 wt% and an ammonium sulfate concentration of 5 wt%. In the secondary back-extraction, back-extraction agent B has a sulfuric acid concentration of 35%. The reaction temperature in centrifugal extractor C is controlled at 30℃, and the reaction ratio O / A is 1:1.

[0127] 4. The organic phase from the first back-extraction is fed into the centrifugal extractor D with dilute sulfuric acid from the dilute sulfuric acid feed tank for reaction and washing. The sulfuric acid entrained in the organic phase 1 is recovered to the dilute sulfuric acid receiving tank to obtain sulfuric acid washing extractant. The concentration of the dilute sulfuric acid is 5 wt%. The reaction temperature of the centrifugal extractor D is controlled at 60℃.

[0128] 5. Oxalic acid A in the oxalic acid feeding tank is fed into the centrifugal extractor E to react and back-extract, resulting in a secondary back-extracted aqueous phase and a secondary back-extracted organic phase; wherein, the oxalic acid concentration in oxalic acid A is 7wt%; the reaction temperature of the centrifugal extractor E is controlled at 60℃, and the reaction ratio O / A is 1:1.

[0129] 6. The secondary back-extraction organic phase and oxalic acid B are fed into a centrifugal extractor F for reaction and washing to recover the oxalic acid entrained in the secondary back-extraction organic phase, and the regenerated extractant is obtained. The regenerated extractant is returned to step 1 as the extractant for the extraction of residual oxalic acid and recycled. The concentration of oxalic acid in oxalic acid B is 5 wt%. The reaction temperature of the centrifugal extractor F is controlled at 60℃, and the reaction ratio O / A is 3:1.

[0130] Experimental Example 2

[0131] This experimental example provides a method for the extraction and removal of metal ions from residual acid, including the following steps:

[0132] 1. Extraction process: The raffinate stock solution collected and stored in the raffinate feed tank is pumped into an emulsification pump and fully emulsified and mixed with the extractant pumped from the organic phase feed tank. Then, it is pumped into centrifugal extractor A for deep extraction. The resulting organic phase is a metal ion-loaded extractant, and the aqueous phase is purified phosphoric acid. The density of the raffinate is 1.50 g / mL, the P2O5 concentration is 45 wt%, the solid content is 0.5%, and the MER value is 0.15. The density of the extractant is 0.86 g / mL. The reaction temperature for deep extraction in centrifugal extractor A is 50℃, and the reaction ratio O / A is 4:1.

[0133] The MER value of purified phosphoric acid was 0.082, and the yield of P2O5 was 99.22%.

[0134] 2. The metal ion-loaded extractant and dilute phosphoric acid from the dilute phosphoric acid feeding tank are fed into centrifugal extractor B for washing. The phosphoric acid entrained in the extractant is recovered and sent to the dilute phosphoric acid receiving tank to obtain phosphoric acid washed extractant. The concentration of dilute phosphoric acid is 5%, the reaction temperature in centrifugal extractor B is 60℃, and the reaction ratio O / A is 3:1.

[0135] 3. Prepare back-extraction agent A and back-extraction agent B using sulfuric acid solution. Feed the sulfuric acid solution from the sulfuric acid feed tank and the extractant washed with phosphoric acid into a centrifugal extractor C for a two-stage back-extraction process, yielding a primary back-extraction aqueous phase and a primary back-extraction organic phase. The sulfuric acid concentration in back-extraction agent A used in the primary back-extraction stage is 30 wt%, and the ammonium sulfate concentration is 5.5 wt%. The sulfuric acid concentration in back-extraction agent B used in the secondary back-extraction stage is 35%. The reaction temperature in centrifugal extractor C is controlled at 30℃, and the reaction ratio O / A is 1:1.

[0136] 4. The organic phase from the first back-extraction is fed into the centrifugal extractor D with dilute sulfuric acid from the dilute sulfuric acid feed tank for washing. The sulfuric acid entrained in the organic phase 1 is recovered to the dilute sulfuric acid receiving tank to obtain sulfuric acid washing extractant. The concentration of dilute sulfuric acid is 5 wt%. The reaction temperature of the centrifugal extractor D is controlled at 60℃, and the reaction ratio O / A is 3:1.

[0137] 5. Oxalic acid A in the oxalic acid feeding tank is fed into the centrifugal extractor E to react and back-extract, resulting in a secondary back-extracted aqueous phase and a secondary back-extracted organic phase; wherein, the oxalic acid concentration in oxalic acid A is 6wt%; the reaction temperature of the centrifugal extractor E is controlled at 60℃, and the reaction ratio O / A is 1:1.

[0138] 6. The secondary back-extraction organic phase and oxalic acid B are fed into a centrifugal extractor F for reaction and washing to recover the oxalic acid entrained in the secondary back-extraction organic phase, and the regenerated extractant is obtained. The regenerated extractant is returned to step 1 as the extractant for the extraction of residual oxalic acid and recycled. The concentration of oxalic acid in oxalic acid B is 1 wt%. The reaction temperature of the centrifugal extractor F is controlled at 60℃ and the reaction ratio O / A is 3:1.

[0139] Experimental Example 3

[0140] This experimental example provides a method for the extraction and removal of metal ions from residual acid, including the following steps:

[0141] 1. Extraction process: The raffinate stock solution collected and stored in the raffinate feed tank is pumped into an emulsification pump and fully emulsified and mixed with the extractant pumped from the organic phase feed tank. Then, it is pumped into centrifugal extractor A for deep extraction. The resulting organic phase is a metal ion-loaded extractant, and the aqueous phase is purified phosphoric acid. The density of the raffinate is 1.60 g / mL, the P2O5 concentration is 45 wt%, the solid content is 0.5%, and the MER value is 0.15. The density of the extractant is 0.86 g / mL. The reaction temperature for deep extraction in centrifugal extractor A is 60℃, and the reaction ratio O / A is 3:1.

[0142] The MER value of purified phosphoric acid was 0.075, and the yield of P2O5 was 99.14%.

[0143] 2. The metal ion-loaded extractant and dilute phosphoric acid from the dilute phosphoric acid feeding tank are fed into centrifugal extractor B for washing. The phosphoric acid entrained in the extractant is recovered and sent to the dilute phosphoric acid receiving tank to obtain phosphoric acid washed extractant. The concentration of dilute phosphoric acid is 5%, the reaction temperature in centrifugal extractor B is 60℃, and the reaction ratio O / A is 3:1.

[0144] 3. Prepare back-extraction agent A and back-extraction agent B using sulfuric acid solution. Feed the sulfuric acid solution from the sulfuric acid feed tank and the extractant washed with phosphoric acid into a centrifugal extractor C for a two-stage back-extraction process, yielding a primary back-extraction aqueous phase and a primary back-extraction organic phase. In the primary back-extraction, back-extraction agent A has a sulfuric acid concentration of 30 wt% and an ammonium sulfate concentration of 6 wt%. In the secondary back-extraction, back-extraction agent B has a sulfuric acid concentration of 35%. The reaction temperature in centrifugal extractor C is controlled at 30℃, and the reaction ratio O / A is 1:1.

[0145] 4. The organic phase from the first back-extraction is fed into the centrifugal extractor D with dilute sulfuric acid from the dilute sulfuric acid feed tank for washing. The sulfuric acid entrained in the organic phase 1 is recovered to the dilute sulfuric acid receiving tank to obtain sulfuric acid washing extractant. The concentration of dilute sulfuric acid is 5 wt%. The reaction temperature of the centrifugal extractor D is controlled at 60℃, and the reaction ratio O / A is 3:1.

[0146] 5. Oxalic acid A in the oxalic acid feeding tank is fed into the centrifugal extractor E to react and back-extract, resulting in a secondary back-extracted aqueous phase and a secondary back-extracted organic phase; wherein, the oxalic acid concentration in oxalic acid A is 5wt%; the reaction temperature of the centrifugal extractor E is controlled at 60℃, and the reaction ratio O / A is 1:1.

[0147] 6. The secondary back-extraction organic phase and oxalic acid B are fed into a centrifugal extractor F for reaction and washing to recover the oxalic acid entrained in the secondary back-extraction organic phase, and the regenerated extractant is obtained. The regenerated extractant is returned to step 1 as the extractant for the extraction of residual oxalic acid and recycled. The concentration of oxalic acid in oxalic acid B is 1 wt%. The reaction temperature of the centrifugal extractor F is controlled at 60℃ and the reaction ratio O / A is 3:1.

[0148] Test Example 4

[0149] This experimental example provides a method for the extraction and removal of metal ions from residual acid, including the following steps:

[0150] 1. Extraction process: The raffinate stock solution collected and stored in the raffinate feed tank is pumped into an emulsification pump and thoroughly emulsified and mixed with the extractant pumped from the organic phase feed tank. Then, it is pumped into centrifugal extractor A for deep extraction. The resulting organic phase is an extractant loaded with metal ions, and the aqueous phase is purified phosphoric acid. The density of the raffinate is 1.60 g / mL, the P2O5 concentration is 45 wt%, the solid content is 0.5%, and the MER value is 0.15. The density of the extractant is 0.86 g / mL. The reaction temperature for deep extraction in centrifugal extractor A is 60℃, and the reaction ratio O / A is 3:1.

[0151] The MER value of purified phosphoric acid was 0.071, and the yield of P2O5 was 99.31%.

[0152] 2. The metal ion-loaded extractant and dilute phosphoric acid from the dilute phosphoric acid feeding tank are fed into centrifugal extractor B for washing. The phosphoric acid entrained in the extractant is recovered and sent to the dilute phosphoric acid receiving tank to obtain phosphoric acid washed extractant. The concentration of dilute phosphoric acid is 5%, the reaction temperature for washing in centrifugal extractor B is 60℃, and the reaction ratio O / A is 3:1.

[0153] 3. Prepare back-extraction agent A and back-extraction agent B using sulfuric acid solution. Feed the sulfuric acid solution from the sulfuric acid feed tank with the extractant washed with phosphoric acid into a centrifugal extractor C for a two-stage back-extraction process, yielding a primary back-extraction aqueous phase and a primary back-extraction organic phase. The sulfuric acid concentration in back-extraction agent A used in the primary back-extraction stage is 30 wt%, and the ammonium sulfate concentration is 6.5 wt%. The sulfuric acid concentration in back-extraction agent B used in the secondary back-extraction stage is 35%. The reaction temperature in centrifugal extractor C is controlled at 30℃, and the reaction ratio O / A is 1:1.

[0154] 4. The organic phase from the first back-extraction is fed into the centrifugal extractor D with dilute sulfuric acid from the dilute sulfuric acid feed tank for washing. The sulfuric acid entrained in the organic phase 1 is recovered to the dilute sulfuric acid receiving tank to obtain sulfuric acid washing extractant. The concentration of dilute sulfuric acid is 5 wt%. The reaction temperature of the centrifugal extractor D is controlled at 60℃, and the reaction ratio O / A is 3:1.

[0155] 5. Oxalic acid A in the oxalic acid feeding tank is fed into the centrifugal extractor E to react and back-extract, resulting in a secondary back-extracted aqueous phase and a secondary back-extracted organic phase; wherein, the oxalic acid concentration in oxalic acid A is 4wt%; the reaction temperature of the centrifugal extractor E is controlled at 60℃, and the reaction ratio O / A is 1:1.

[0156] 6. The secondary back-extraction organic phase and oxalic acid B are fed into a centrifugal extractor F for reaction and washing to recover the oxalic acid entrained in the secondary back-extraction organic phase, and the regenerated extractant is obtained. The regenerated extractant is returned to step 1 as the extractant for the extraction of residual oxalic acid and recycled. The concentration of oxalic acid in oxalic acid B is 1 wt%. The reaction temperature of the centrifugal extractor F is controlled at 60℃ and the reaction ratio O / A is 3:1.

[0157] Table 1 shows the statistical results of the extraction rates and recoveries of metal ions Mg, Al, and Fe in the residual acid after the primary and secondary back-extraction aqueous phases of Experiment Examples 1-4 were treated by crystallization and photocatalysis, respectively.

[0158] Table 1

[0159]

Claims

1. A method for extracting and removing metal ions from residual acid in refined phosphoric acid by-products, characterized in that, Includes the following steps: 1) Emulsion extraction: The residual acid is subjected to emulsion deep extraction using an extractant to obtain purified phosphoric acid and an organic phase supported on metal cations; wherein the emulsion deep extraction step includes obtaining an emulsion based on emulsion extraction, and performing deep extraction and phase separation on the emulsion; 2) First wash: The organic phase loaded with metal cations obtained by emulsification extraction in step 1) is reacted with dilute phosphoric acid and washed to obtain phosphoric acid wash extractant; the reaction temperature of the washing is 50-60℃, and the O / A ratio of the reaction ratio is 3:1-2:

1. 3) First-stage back-extraction: The phosphoric acid eluent from the first washing in step 2) is sequentially contacted with back-extractant A and back-extractant B for two-stage back-extraction, resulting in a first-stage back-extraction aqueous phase and a first-stage back-extraction organic phase; wherein, the two-stage back-extraction includes a first-stage back-extraction using back-extractant A and a second-stage back-extraction using back-extractant B; the concentration of sulfuric acid in back-extractant A is 25-35 wt% and the concentration of ammonium sulfate is 4.5-6.5 wt%, and the concentration of sulfuric acid in back-extractant B is 30-40 wt% and the concentration of ammonium sulfate is 4.5-6.5 wt%; the reaction temperature for the two-stage back-extraction is 25-35℃, and the O / A ratio is 1:1-1:3; 4) Secondary washing: The organic phase from the first back-extraction in step 3) is washed with dilute sulfuric acid to obtain sulfuric acid wash extractant; the concentration of the dilute sulfuric acid is 3-5 wt%; the washing temperature is 50-60℃, and the reaction ratio O / A is 3:1-2:

1. 5) Secondary back-extraction: The sulfuric acid washing extractant from step 4) is contacted with oxalic acid A for back-extraction to obtain a secondary back-extraction aqueous phase and a secondary back-extraction organic phase; the concentration of oxalic acid A is 6-8 wt%; the back-extraction temperature is 50-60℃, and the reaction ratio O / A is 1:1-1:

3. 6) Three washes: The organic phase from the second back-extraction in step 5) is washed with oxalic acid B to obtain a regenerated extractant. The regenerated extractant is returned to the emulsification extraction in step 1) as an extractant. The concentration of oxalic acid B is 1 wt%. The reaction temperature for washing is 50-60°C, and the O / A ratio is 3:1-2:

1. 7) Crystallization of the aqueous phase after primary back-extraction: Add ammonium sulfate to the aqueous phase after primary back-extraction in step 3) and cool and crystallize to obtain magnesium ammonium sulfate and aluminum ammonium sulfate; wherein the mass ratio of the aqueous phase after primary back-extraction to ammonium sulfate is 100-200:1; 8) Photocatalysis of secondary stripping aqueous phase: The secondary stripping aqueous phase from step 5) is subjected to photocatalytic precipitation to recover iron ions and obtain ferrous oxalate.

2. The extraction and desorption method according to claim 1, characterized in that: Step 1) Emulsification extraction, wherein the density of the residual acid is 1.50-1.60 g / mL, the concentration of P2O5 is 40-60 wt%, the solid content is 0.5%, and the MER value is 0.12-0.2; The reaction temperature for the deep extraction is 50–60°C, and the O / A ratio is 2:1–4:

1.

3. The extraction and desorption method according to claim 2, characterized in that: The emulsification deep extraction is performed in two stages.

4. The extraction and desorption method according to claim 3, characterized in that: Each segment describes a three-stage emulsification and deep extraction process.

5. The extraction and desorption method according to claim 4, characterized in that: The emulsification and deep extraction method described in each section is countercurrent.

6. The extraction and desorption method according to claim 1, characterized in that: Step 1) Emulsification extraction, wherein the density of the extractant is ≤0.86mg / mL, including at least one of organophosphorus extractants, organophosphorus extractants, organosulfonic acid extractants, organocarboxylic acid extractants, and tertiary carbonate extractants.

7. The extraction and desorption method according to claim 6, characterized in that: The extractant is at least one of the following: di(2-ethylhexyl) phosphate, 2-ethylhexyl phosphate, di(2,4,4-trimethylpentyl)phosphine, 2-ethylhexylphosphonic acid mono(2-ethylhexyl) ester, N,N-n-octylamine di(methylene phenylphosphine), toluenesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid, xylenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, cinnamic acid, fatty acids, lauric acid, and naphthenic acid.

8. The extraction and desorption method according to claim 1, characterized in that: Step 2) One wash, wherein the number of washing stages is 2.

9. The extraction and desorption method according to claim 8, characterized in that: The washing method is counter-current.

10. The extraction and desorption method according to claim 1, characterized in that: Step 3) One back-extraction, wherein the number of stages of the front-end extraction is 3.

11. The extraction and desorption method according to claim 10, characterized in that: The extraction method used in the first stage is countercurrent.

12. The extraction and desorption method according to claim 1, characterized in that: The number of stages for the subsequent back-extraction is 2.

13. The extraction and desorption method according to claim 12, characterized in that: The downstream back-extraction method is countercurrent.

14. The extraction and desorption method according to claim 1, characterized in that: Step 4) Secondary washing, the washing process is divided into 2 stages.

15. The extraction and desorption method according to claim 14, characterized in that: The washing method is counter-current.

16. The extraction and desorption method according to claim 1, characterized in that: Step 5) Secondary back-extraction, wherein the number of back-extraction stages is 2.

17. The extraction and desorption method according to claim 16, characterized in that: The back-extraction method is countercurrent.

18. The extraction and desorption method according to claim 1, characterized in that: Step 6) Three washes, the number of washing stages is 2.

19. The extraction and desorption method according to claim 18, characterized in that, The washing method is counter-current.

20. The extraction and desorption method according to claim 1, characterized in that: Step 8) Secondary back-extraction aqueous phase photocatalysis, wherein the reaction temperature for photocatalytic precipitation is 30–60℃ and the light intensity is 145–725 mW / cm². 2 The concentration of oxalic acid in the aqueous phase of the secondary back-extraction is controlled to be 6-10%.

21. An extraction and removal system for metal ions from residual raffinate of refined phosphoric acid, used to implement the extraction and removal method for metal ions from residual raffinate of refined phosphoric acid as described in any one of claims 1-20, characterized in that, It includes an emulsification extraction device (1), a primary washing device (2), a primary back-extraction device (3), a secondary washing device (4), a secondary back-extraction device (5), a tertiary washing device (6), a primary back-extraction aqueous phase crystallization device (7), and a secondary back-extraction aqueous phase photocatalysis device (8); The emulsification extraction device (1) includes a residual acid feeding tank (11), an extractant feeding tank (12), an organic phase temporary storage tank (15), a purified phosphoric acid storage tank (16), and a two-stage centrifugal extraction unit A (14). The first stage centrifugal extraction unit A (14) is equipped with a residual acid inlet and a residual liquid outlet. The second stage centrifugal extraction unit A (14) is equipped with a residual liquid inlet and a purified phosphoric acid outlet. The residual liquid outlet is connected to the residual liquid inlet, and the outlet of the residual acid feeding tank (11) is connected to the residual acid inlet. The acid outlet is connected to the inlet of the purified phosphoric acid storage tank (16); the two centrifugal extraction units A (14) are each equipped with a camera inlet and an organic phase outlet, the camera outlet is connected to the inlet of the organic phase temporary storage tank (15), and the outlet of the extractant feeding tank (12) is connected to the organic phase inlet; the two centrifugal extraction units A (14) each include multiple centrifugal extractors connected in series and an emulsifying pump (13) corresponding to the centrifugal extractor, the output end of the emulsifying pump (13) is connected to the inlet of the centrifugal extractor; The primary washing device (2) includes a dilute phosphoric acid feeding tank (21), a centrifugal extraction unit B (22), a cooling buffer tank (231), a cooler (232), and a dilute phosphoric acid receiving tank (24). The outlets of the dilute phosphoric acid feeding tank (21) and the organic phase storage tank (15) are connected to the inlet of the centrifugal extraction unit B (22). The outlet of the centrifugal extraction unit B (22) is connected to the cooling buffer tank (231). The outlet of the cooling buffer tank (231) is connected to the inlet of the cooler (232). The outlet of the cooler (232) is connected to the inlet of the primary back-extraction device (3). The primary back-extraction device (3) includes a back-extraction agent preparation tank (31), a back-extraction agent feeding tank (32), a centrifugal extraction unit C (33), a primary back-extraction aqueous phase temporary storage tank (34), a heating buffer tank (351), and a heater (352). The outlet of the back-extraction agent preparation tank (31) is connected to the inlet of the back-extraction agent feeding tank (32). The outlets of the back-extraction agent feeding tank (32) and the cooler (232) are both connected to the inlet of the centrifugal extraction unit C (33). The outlets of the centrifugal extraction unit C (33) are respectively connected to the primary back-extraction aqueous phase temporary storage tank (34) and the heating buffer tank (351). The outlet of the heating buffer tank (351) is connected to the inlet of the heater (352). The outlet of the heater (352) is connected to the inlet of the secondary washing device (4). The secondary washing device (4) includes a dilute sulfuric acid feeding tank (41), a centrifugal extraction unit D (42), and a dilute sulfuric acid receiving tank (43). The outlets of the dilute sulfuric acid feeding tank (41) and the heater (352) are connected to the inlet of the centrifugal extraction unit D (42). The outlet of the centrifugal extraction unit D (42) is connected to the dilute sulfuric acid receiving tank (43) and the inlet of the secondary back-extraction device (5), respectively. The secondary back-extraction device (5) includes an oxalic acid preparation tank (50), an oxalic acid A feeding tank (51), a centrifugal extraction unit E (52), and a secondary back-extraction temporary storage tank (53). The outlets of the oxalic acid A feeding tank (51) and the centrifugal extraction unit D (42) are connected to the inlet of the centrifugal extraction unit E (52). The outlet of the centrifugal extraction unit E (52) is connected to the inlet of the secondary back-extraction aqueous phase temporary storage tank (53) and the inlet of the tertiary washing device (6), respectively. The three-stage washing device (6) includes an oxalic acid B feeding tank (61), a centrifugal extractor F (62), an oxalic acid B receiving tank (63), and an extractant clarification tank (64). The outlets of the oxalic acid B feeding tank (61) and the centrifugal extractor E (52) are connected to the inlet of the centrifugal extractor F (62). The outlet of the centrifugal extractor F (62) is connected to the inlet of the oxalic acid B receiving tank (63) and the inlet of the extractant clarification tank (64), respectively. The outlet of the extractant clarification tank (64) is connected to the inlet of the extractant feeding tank (12). The primary back-extraction aqueous phase crystallization device (7) includes a back-extraction crystallization tank (71), a back-extraction settling tank (72), a back-extraction clear liquid tank (73), and a double-push centrifuge (74). The outlet of the primary back-extraction temporary storage tank (34) is connected to the inlet of the back-extraction crystallization tank (71). The outlet of the back-extraction crystallization tank (71) is connected to the inlet of the back-extraction settling tank (72). The clear liquid outlet of the back-extraction settling tank (72) is connected to the inlet of the back-extraction clear liquid tank (73). The solid phase outlet of the back-extraction settling tank (72) is connected to the double-push centrifuge (74). The outlet of the back-extraction clear liquid tank (73) is connected to the inlet of the back-extraction preparation tank (31). The secondary back-extraction aqueous photocatalytic device (8) includes a photocatalytic reactor (81), an oxalic acid settling tank (82), an oxalic acid clear liquid tank (83), and a plate and frame filter press (84). The outlet of the secondary back-extraction temporary storage tank (53) is connected to the inlet of the photocatalytic reactor (81). The outlet of the photocatalytic reactor (81) is connected to the inlet of the oxalic acid settling tank (82). The clear liquid outlet of the oxalic acid settling tank (82) is connected to the inlet of the oxalic acid clear liquid tank (83). The solid phase outlet of the oxalic acid settling tank (82) is connected to the plate and frame filter press (84). The outlet of the oxalic acid clear liquid tank (83) is connected to the oxalic acid A feeding tank (51).

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