A complexing extractant for purification of phosphoric acid and a preparation method thereof

Abstract

The application provides a compound extraction agent for phosphoric acid purification and a preparation method thereof, and belongs to the technical field of wet phosphoric acid purification, and comprises the following preparation method: a first part of D100 solvent oil is added into a reaction kettle and heated and stirred, phosphoric acid tri(2-ethylhexyl) ester, butyl phosphoric acid dibutyl ester and a first part of phosphoric acid triisobutyl ester are sequentially added into the reaction kettle to obtain a phosphorus ester-containing mixed solution; molten n-tridecanol is added into the phosphorus ester-containing mixed solution and stirred uniformly, a second part of phosphoric acid triisobutyl ester is premixed with 1,2-octanediol and then added into the reaction kettle, and mixing, cooling, and filtering are continuously performed to obtain the compound extraction agent for phosphoric acid purification. The compound extraction agent can improve the impurity separation selectivity, oil-water phase separation performance, load stability and recycling stability while maintaining the phosphoric acid extraction capacity.

Description

Technical Field

[0001] This invention relates to the field of wet phosphoric acid purification technology, specifically to a compound extractant for phosphoric acid purification and its preparation method. Background Technology

[0002] Wet-process phosphoric acid is typically produced by reacting phosphate rock with inorganic acids. The resulting crude phosphoric acid contains not only phosphoric acid but also metallic impurities such as iron, aluminum, and magnesium, as well as small amounts of suspended solids and organic impurities. To obtain high-purity phosphoric acid, pretreatment, solvent extraction, washing, back-extraction, and concentration are commonly employed to purify the crude phosphoric acid. The extraction capacity of the extractant, impurity selectivity, oil-water phase separation rate, stability of the supported organic phase, and back-extraction performance directly affect the phosphoric acid purification efficiency and the cycle life of the organic phase.

[0003] Patent application CN1657407A discloses a mixed extractant and dilute phosphoric acid dechlorination technology for purifying wet-process phosphoric acid. The mixed extractant is composed of n-butanol, tributyl phosphate, and methyl isobutyl ketone, wherein the volume fraction of n-butanol is 60%-70%, the volume fraction of tributyl phosphate is 20%-30%, and the volume fraction of methyl isobutyl ketone is 10%-20%. This scheme, through the compounding of alcohol, phosphate ester, and ketone solvents, enables the mixed extractant to have certain extraction and impurity removal capabilities at different phosphoric acid concentrations. However, it uses a relatively high proportion of n-butanol as the main component, resulting in relatively large dissolution losses of n-butanol in the aqueous phase and a relatively large burden on subsequent recovery. At the same time, methyl isobutyl ketone is highly volatile, and multi-stage extraction is required during implementation. Therefore, there is still room for further improvement in reducing solvent loss, shortening phase separation time, and improving the cycle stability of the organic phase.

[0004] Patent application CN110357060A discloses a method and apparatus for purifying low-concentration wet-process phosphoric acid production. The extraction organic solvent used is one or more of dibutyl butylphosphonate, dimethylheptyl methylphosphate, diisooctyl isopropylphosphonate, and dibutylphosphonate. Extraction, washing, and back-extraction are completed using at least a three-stage ultrasonic mixer clarification device. This method can improve the extraction and purification effect of low-concentration wet-process phosphoric acid; however, its purification effect largely depends on the multi-stage ultrasonic mixing clarification device and the enhanced washing process.

[0005] Therefore, there is a need to provide a compound extractant for phosphoric acid purification and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0006] In view of this, the present invention provides a compound extractant for phosphoric acid purification and its preparation method, which can improve the impurity separation selectivity, oil-water phase separation performance, loading stability, back-extraction performance and recycling stability of the compound extractant while maintaining the phosphoric acid extraction capacity.

[0007] To achieve the above objectives, the present invention provides a method for preparing a compound extractant for phosphoric acid purification, comprising the following steps:

[0008] Step S1: Add the first part of D100 solvent oil to the reaction vessel, heat and stir, add tri(2-ethylhexyl) phosphate and mix, then add butyl dibutyl phosphate and continue mixing, and finally add the first part of triisobutyl phosphate to obtain a phosphate-containing ester mixture. Step S2: Heat n-tetrazol until completely melted, add it to the phosphate ester mixture, stir evenly, rinse the n-tetrazol melting container with the second part of D100 solvent oil, and add the rinsing solution to the reaction vessel; Step S3: The second part of triisobutyl phosphate and 1,2-octanediol are heated and premixed to obtain a 1,2-octanediol premixed solution, which is added to the reaction vessel. The premixed container is rinsed with the third part of D100 solvent oil, and the rinsing solution is added to the reaction vessel for mixing, cooling, and filtration to obtain a compound extractant for phosphoric acid purification.

[0009] The combined use of triisobutyl phosphate, tri(2-ethylhexyl) phosphate, and dibutyl butyl phosphate is beneficial for forming an environment in the organic phase with phosphorus-containing groups of different polarity, steric hindrance, and hydrophobicity. This allows phosphoric acid molecules to interact with different phosphorus-containing components with varying strengths, thereby maintaining the extraction capacity of phosphoric acid while reducing the entrainment of water and impurities, and avoiding excessive binding of phosphoric acid to a single extraction component, which would increase the difficulty of back-extraction.

[0010] n-Tetrazol mainly regulates the bulk organic phase, which helps to mitigate the local polarity changes caused by phosphoric acid loading, improves the homogeneity of the loaded organic phase, and reduces the tendency to form a third phase and local turbidity. 1,2-Octanediol contains two adjacent hydroxyl groups, and its mechanism of action near the oil-water interface is different from that of n-tetrazol. It is beneficial to generate local disturbances to the interfacial film formed by long-chain alcohols and phosphorus-containing components, and promotes droplet coalescence after stirring is stopped, thereby balancing the stability of the loaded organic phase and the rapid phase separation performance.

[0011] Premixing a portion of triisobutyl phosphate with 1,2-octanediol helps to ensure that the low amount of 1,2-octanediol is uniformly dispersed in the main extraction components before being added to the reactor, reducing the wall adhesion, local enrichment, and uneven dispersion that occur when added directly. Combined with staged feeding, it helps to form a uniform extraction matrix first, and then form phase regulation and interface regulation effects in sequence, thereby improving the compositional uniformity, storage stability, and batch consistency of the compound extractant.

[0012] Preferably, the compound extractant comprises the following components in parts by weight: 440-480 parts of triisobutyl phosphate, 70-90 parts of tri(2-ethylhexyl) phosphate, 60-80 parts of n-tetrazol, 10-16 parts of dibutyl phosphate, 2-4 parts of 1,2-octanediol, and 330-418 parts of D100 solvent oil.

[0013] Preferably, the first part of triisobutyl phosphate accounts for 92%-95% of the total mass of triisobutyl phosphate, the second part of triisobutyl phosphate accounts for 5%-8% of the total mass of triisobutyl phosphate; the first part of D100 solvent oil accounts for 96%-98% of the total mass of D100 solvent oil, and the second part of D100 solvent oil and the third part of D100 solvent oil each account for 1%-2% of the total mass of D100 solvent oil.

[0014] Premixing 1,2-octanediol with a portion of triisobutyl phosphate eliminates the need for additional solubilizers or surfactants. This facilitates the rapid diffusion of 1,2-octanediol throughout the organic phase along with the triisobutyl phosphate, and reduces the risk of increased hydrophilicity and emulsification caused by excessive interface-modifying components.

[0015] Preferably, in step S1, the heating and stirring speed is 230-270 r / min, and the temperature is 38-42℃.

[0016] Preferably, in step S1, the addition time of tris(2-ethylhexyl) phosphate is 3-5 min, and after addition, the mixture is stirred at a speed of 280-320 r / min for 8-12 min; the addition time of dibutyl phosphate is 2-3 min, and after addition, the mixture is stirred for 8-12 min; the addition time of the first part of triisobutyl phosphate is 10-15 min, and after addition, the mixture is stirred for 12-18 min.

[0017] Preferably, in step S2, n-tetrazol is heated to complete melting under a constant temperature water bath at 40-44℃, and the added time of the molten n-tetrazol is 8-10 min; the stirring temperature is 38-42℃, the stirring speed is 280-320 r / min, and the stirring time is 15-25 min.

[0018] Pre-melting n-tetrazol before adding it to the phosphate ester mixture helps reduce the condensation of n-tetrazol on the reactor wall and in the feeding pipeline, allowing it to be evenly distributed in the organic phase, thereby improving the stability of the loaded organic phase.

[0019] Preferably, in step S3, the second part of triisobutyl phosphate and 1,2-octanediol are premixed at 40-44°C and 230-270 r / min for 15-25 min; the 1,2-octanediol premix is ​​added to the reaction vessel at a time of 3-5 min.

[0020] Preferably, in step S3, the mass ratio of the second portion of triisobutyl phosphate to 1,2-octanediol is (7.5-13):1.

[0021] Preferably, in step S3, mixing continues for 40-50 minutes at 38-42°C and 280-320 r / min, followed by cooling to 25-30°C under stirring conditions of 180-220 r / min, and then filtering through organic solvent-resistant filter membranes with pore sizes of 5 μm and 1 μm in sequence.

[0022] The above-mentioned temperature-controlled mixing, cooling and graded filtration work together to help maintain the uniformity and stability of the compound system and remove trace amounts of insoluble matter that may be generated during the preparation process, thereby reducing the possibility of turbidity, precipitation or stratification during storage.

[0023] To achieve the above objectives, the present invention also provides a compound extractant for phosphoric acid purification prepared by the above-described method for preparing the compound extractant for phosphoric acid purification.

[0024] The compound extractant prepared by the method of the present invention maintains the phosphoric acid extraction capability while improving the impurity separation selectivity, oil-water phase performance, loading stability and recycling stability.

[0025] The above-described technical solution of the present invention has at least the following beneficial effects: By forming a composite phosphorus-containing extraction environment using triisobutyl phosphate, tris(2-ethylhexyl) phosphate, and dibutyl butyl phosphate, and by using n-tetrazol and 1,2-octanediol to adjust the organic phase bulk phase and oil-water interface respectively, and by combining n-tetrazol pre-melting, 1,2-octanediol premixing, and staged feeding, it is possible to achieve good phosphoric acid extraction capacity, impurity separation selectivity, organic phase stability, rapid phase separation, low phase entrainment, easy back-extraction, and recycling stability without using tributyl phosphate. Detailed Implementation

[0026] The technical solution will now be clearly and completely described in conjunction with the embodiments of the present invention.

[0027] Example 1 Weigh out 460g of triisobutyl phosphate, 80g of tris(2-ethylhexyl) phosphate, 70g of n-tetrazol, 13g of dibutyl butyl phosphate, 3g of 1,2-octanediol, and 374g of D100 solvent oil, totaling 1000g. Divide the triisobutyl phosphate into two portions of 430g and 30g, and divide the D100 solvent oil into three portions of 364g, 5g, and 5g.

[0028] Add 364g of D100 solvent oil to the reactor, heat it to 40℃ with constant temperature water in the jacket under stirring at 250r / min, and continue stirring for 5min.

[0029] At 40℃ and 250r / min, 80g of tri(2-ethylhexyl) phosphate was added to the reactor over 3-5min, and the stirring speed was increased to 300r / min and stirring was continued for 10min. Then, 13g of dibutyl phosphate was added to the reactor over 2-3min, and stirring was continued for 10min at 40℃ and 300r / min.

[0030] Add 430g of triisobutyl phosphate to the reaction vessel within 10-15 minutes, and continue stirring for 15 minutes at 40℃ and 300r / min to obtain a phosphate-containing ester mixture.

[0031] Add 70g of n-tetrazol to a covered melting vessel and heat and stir at a constant temperature of 42℃ until completely melted. Add the molten n-tetrazol to the phosphate-containing ester mixture over 8-10 minutes and stir at 40℃ and 300 rpm. After addition, rinse the n-tetrazol melting vessel with 5g of D100 solvent oil for 1 minute, then add all the rinsing solution to the reaction vessel and continue stirring for 20 minutes.

[0032] Take another 30g of triisobutyl phosphate and add it to a premixed container with a lid. Heat it in a constant temperature water bath at 42℃ and stir at 250r / min. Add 3g of 1,2-octanediol and stir for 20min at 42℃ and 250r / min to obtain a 1,2-octanediol premix.

[0033] The obtained 1,2-octanediol premix was added to the reactor within 3-5 min. The premix container was rinsed with 5g of D100 solvent oil, and all the rinsing solution was added to the reactor. The mixture was continued to be mixed at 40℃ and 300r / min for 45 min. Then, the material was cooled to 28℃ under stirring at 200r / min. It was then filtered sequentially through organic solvent-resistant filter membranes with pore sizes of 5μm and 1μm to obtain the compound extractant for phosphoric acid purification.

[0034] Example 2 Weigh out 440g of triisobutyl phosphate, 70g of tris(2-ethylhexyl) phosphate, 60g of n-tetrazol, 10g of dibutyl butyl phosphate, 2g of 1,2-octanediol, and 418g of D100 solvent oil, totaling 1000g. Divide the triisobutyl phosphate into two portions of 414g and 26g, and divide the D100 solvent oil into three portions of 408g, 5g, and 5g.

[0035] Add 408g of D100 solvent oil to the reactor, heat it to 39℃ with constant temperature water in the jacket under stirring at 240r / min, and continue stirring for 3min.

[0036] At 39°C and 240 r / min, 70 g of tris(2-ethylhexyl) phosphate was added to the reactor over 3 min, the stirring speed was increased to 280 r / min, and stirring was continued for 8 min; then 10 g of dibutyl phosphate was added to the reactor over 2 min, and stirring was continued for 8 min at 39°C and 280 r / min.

[0037] 414g of triisobutyl phosphate was added to the reaction vessel within 10 min, and the mixture was stirred for 12 min at 39℃ and 280r / min to obtain a phosphate-containing ester mixture.

[0038] Add 60g of n-tetrazol to a covered melting vessel and heat and stir at a constant temperature of 41°C until completely melted. Add the molten n-tetrazol to the phosphate-containing ester mixture within 8 minutes and stir at 39°C and 280 rpm. After the addition is complete, rinse the n-tetrazol melting vessel with 5g of D100 solvent oil for 1 minute, then add all the rinsing solution to the reaction vessel and continue stirring for 15 minutes.

[0039] Take another 26g of triisobutyl phosphate and add it to a premixed container with a lid. Heat it in a constant temperature water bath at 41℃ and stir at 240r / min. Add 2g of 1,2-octanediol and stir for 15min at 41℃ and 240r / min to obtain a 1,2-octanediol premix.

[0040] The obtained 1,2-octanediol premix was added to the reactor within 3 min. The premix container was rinsed with 5 g of D100 solvent oil, and all the rinsing solution was added to the reactor. The mixture was continued to be mixed at 39 °C and 280 r / min for 40 min. Then, the material was cooled to 25 °C under stirring at 180 r / min. It was then filtered sequentially through organic solvent-resistant filter membranes with pore sizes of 5 μm and 1 μm to obtain the compound extractant for phosphoric acid purification.

[0041] Example 3 Weigh out 480g of triisobutyl phosphate, 90g of tris(2-ethylhexyl) phosphate, 80g of n-tetrazol, 16g of dibutyl butyl phosphate, 4g of 1,2-octanediol, and 330g of D100 solvent oil, totaling 1000g. Divide the triisobutyl phosphate into two portions of 450g and 30g, and the D100 solvent oil into three portions of 320g, 5g, and 5g.

[0042] Add 320g of D100 solvent oil to the reactor, heat it to 41℃ with jacketed constant temperature water under stirring at 270r / min, and continue stirring for 8min.

[0043] At 41℃ and 270r / min, 90g of tri(2-ethylhexyl) phosphate was added to the reactor over 5min, and the stirring speed was increased to 320r / min and stirring was continued for 12min. Then, 16g of dibutyl phosphate was added to the reactor over 3min, and stirring was continued for 12min at 41℃ and 320r / min.

[0044] 450g of triisobutyl phosphate was added to the reaction vessel within 15 minutes, and the mixture was stirred for 18 minutes at 41℃ and 320r / min to obtain a phosphate-containing ester mixture.

[0045] Add 80g of n-tetrazol to a covered melting vessel and heat and stir at a constant temperature of 43℃ until completely melted. Add the molten n-tetrazol to the phosphate-containing ester mixture within 10 minutes and stir at 41℃ and 320 rpm. After the addition is complete, rinse the n-tetrazol melting vessel with 5g of D100 solvent oil for 1 minute, then add all the rinsing solution to the reaction vessel and continue stirring for 25 minutes.

[0046] Take another 30g of triisobutyl phosphate and add it to a premixed container with a lid. Heat it in a constant temperature water bath at 43℃ and stir at 270r / min. Add 4g of 1,2-octanediol and stir at 43℃ and 270r / min for 25min to obtain a 1,2-octanediol premix.

[0047] The obtained 1,2-octanediol premix was added to the reactor within 5 min. The premix container was rinsed with 5 g of D100 solvent oil, and all the rinsing solution was added to the reactor. The mixture was continued to be mixed at 41 °C and 320 r / min for 50 min. Then, the material was cooled to 30 °C under stirring at 220 r / min. The mixture was then filtered through organic solvent resistant filter membranes with pore sizes of 5 μm and 1 μm to obtain the compound extractant for phosphoric acid purification.

[0048] Example 4 Weigh out 450g of triisobutyl phosphate, 75g of tris(2-ethylhexyl) phosphate, 65g of n-tetrazol, 12g of dibutyl phosphate, 2.5g of 1,2-octanediol, and 395.5g of D100 solvent oil, totaling 1000g. Divide the triisobutyl phosphate into two portions of 422g and 28g, and the D100 solvent oil into three portions of 385.5g, 5g, and 5g.

[0049] Add 385.5g of D100 solvent oil to the reactor, heat it to 40℃ with jacketed constant temperature water under stirring at 245r / min, and continue stirring for 4min.

[0050] At 40℃ and 245r / min, 75g of tris(2-ethylhexyl) phosphate was added to the reactor over 4min, the stirring speed was increased to 290r / min, and stirring was continued for 9min; then 12g of dibutyl phosphate was added to the reactor over 2min, and stirring was continued for 9min at 40℃ and 290r / min.

[0051] 422g of triisobutyl phosphate was added to the reaction vessel within 12 minutes, and the mixture was stirred for 14 minutes at 40℃ and 290r / min to obtain a phosphate-containing ester mixture.

[0052] Add 65g of n-tetrazol to a covered melting vessel and heat and stir at a constant temperature of 42℃ until completely melted. Add the molten n-tetrazol to the phosphate-containing ester mixture within 9 minutes and stir at 40℃ and 290 rpm. After the addition is complete, rinse the n-tetrazol melting vessel with 5g of D100 solvent oil for 1 minute, then add all the rinsing solution to the reaction vessel and continue stirring for 18 minutes.

[0053] Take another 28g of triisobutyl phosphate and add it to a premixed container with a lid. Heat it in a constant temperature water bath at 42℃ and stir at 245r / min. Add 2.5g of 1,2-octanediol and stir for 18min at 42℃ and 245r / min to obtain a 1,2-octanediol premix.

[0054] The obtained 1,2-octanediol premix was added to the reactor within 4 min. The premix container was rinsed with 5 g of D100 solvent oil, and all the rinsing solution was added to the reactor. The mixture was continued to be mixed at 40 °C and 290 r / min for 43 min. Then, the material was cooled to 27 °C under stirring at 190 r / min. The mixture was then filtered through organic solvent resistant filter membranes with pore sizes of 5 μm and 1 μm to obtain the compound extractant for phosphoric acid purification.

[0055] Example 5 Weigh out 470g of triisobutyl phosphate, 85g of tris(2-ethylhexyl) phosphate, 75g of n-tetrazol, 15g of dibutyl phosphate, 3.5g of 1,2-octanediol, and 351.5g of D100 solvent oil, totaling 1000g. Divide the triisobutyl phosphate into two portions of 440g and 30g, and the D100 solvent oil into three portions of 341.5g, 5g, and 5g.

[0056] Add 341.5g of D100 solvent oil to the reactor, heat it to 41℃ with jacketed constant temperature water under stirring at 260r / min, and continue stirring for 6min.

[0057] At 41℃ and 260r / min, 85g of tri(2-ethylhexyl) phosphate was added to the reactor over 5min, and the stirring speed was increased to 310r / min and stirring was continued for 11min. Then, 15g of dibutyl phosphate was added to the reactor over 3min, and stirring was continued for 11min at 41℃ and 310r / min.

[0058] 440g of triisobutyl phosphate was added to the reaction vessel within 14 min, and the mixture was stirred for 17 min at 41℃ and 310 r / min to obtain a phosphate-containing ester mixture.

[0059] Add 75g of n-tetrazol to a covered melting vessel and heat and stir at a constant temperature of 43°C until completely melted. Add the molten n-tetrazol to the phosphate-containing ester mixture within 10 minutes and stir at 41°C and 310 rpm. After the addition is complete, rinse the n-tetrazol melting vessel with 5g of D100 solvent oil for 1 minute, then add all the rinsing solution to the reaction vessel and continue stirring for 23 minutes.

[0060] Take another 30g of triisobutyl phosphate and add it to a premixed container with a lid. Heat it in a constant temperature water bath at 43℃ and stir at 260r / min. Add 3.5g of 1,2-octanediol and stir at 43℃ and 260r / min for 23min to obtain a 1,2-octanediol premix.

[0061] The obtained 1,2-octanediol premix was added to the reactor within 5 min. The premix container was rinsed with 5 g of D100 solvent oil, and all the rinsing solution was added to the reactor. The mixture was continued to be mixed at 41 °C and 310 r / min for 48 min. Then, the material was cooled to 29 °C under stirring at 210 r / min. It was then filtered through organic solvent resistant filter membranes with pore sizes of 5 μm and 1 μm to obtain the compound extractant for phosphoric acid purification.

[0062] Example 6 Weigh out 455g of triisobutyl phosphate, 78g of tris(2-ethylhexyl) phosphate, 68g of n-tetrazol, 11g of dibutyl phosphate, 2.8g of 1,2-octanediol, and 385.2g of D100 solvent oil, totaling 1000g. Divide the triisobutyl phosphate into two portions of 427g and 28g, and divide the D100 solvent oil into three portions of 375.2g, 5g, and 5g.

[0063] Add 375.2g of D100 solvent oil to the reactor, heat it to 39℃ with jacketed constant temperature water under stirring at 230r / min, and continue stirring for 7min.

[0064] At 39°C and 230 r / min, 78 g of tris(2-ethylhexyl) phosphate was added to the reactor over 4 min, and the stirring speed was increased to 285 r / min and stirring was continued for 10 min. Subsequently, 11 g of dibutyl phosphate was added to the reactor over 2 min, and stirring was continued for 10 min at 39°C and 285 r / min.

[0065] 427g of triisobutyl phosphate was added to the reaction vessel within 13 minutes, and the mixture was stirred for another 16 minutes at 39℃ and 285r / min to obtain a phosphate-containing ester mixture.

[0066] Add 68g of n-tetrazol to a covered melting vessel and heat and stir at a constant temperature of 41°C until completely melted. Add the molten n-tetrazol to the phosphate-containing ester mixture within 9 minutes and stir at 39°C and 285 rpm. After the addition is complete, rinse the n-tetrazol melting vessel with 5g of D100 solvent oil for 1 minute, then add all the rinsing solution to the reaction vessel and continue stirring for 21 minutes.

[0067] Take another 28g of triisobutyl phosphate and add it to a premixed container with a lid. Heat it in a constant temperature water bath at 41℃ and stir at 230r / min. Add 2.8g of 1,2-octanediol and stir for 20min at 41℃ and 230r / min to obtain a 1,2-octanediol premix.

[0068] The obtained 1,2-octanediol premix was added to the reactor within 4 min. The premix container was rinsed with 5 g of D100 solvent oil, and all the rinsing solution was added to the reactor. The mixture was continued to be mixed at 39 °C and 285 r / min for 46 min. Then, the material was cooled to 26 °C under stirring at 185 r / min. The mixture was then filtered through organic solvent resistant filter membranes with pore sizes of 5 μm and 1 μm to obtain the compound extractant for phosphoric acid purification.

[0069] Example 7 Weigh out 465g of triisobutyl phosphate, 82g of tris(2-ethylhexyl) phosphate, 72g of n-tetrazol, 14g of dibutyl butyl phosphate, 3.2g of 1,2-octanediol, and 363.8g of D100 solvent oil, totaling 1000g. Divide the triisobutyl phosphate into two portions of 435g and 30g, and divide the D100 solvent oil into three portions of 353.8g, 5g, and 5g.

[0070] Add 353.8g of D100 solvent oil to the reactor, heat it to 40℃ with jacketed constant temperature water under stirring at 265r / min, and continue stirring for 5min.

[0071] At 40°C and 265 r / min, 82 g of tris(2-ethylhexyl) phosphate was added to the reactor over 4 min, and the stirring speed was increased to 315 r / min and stirring was continued for 11 min. Then, 14 g of dibutyl phosphate was added to the reactor over 3 min, and stirring was continued for 10 min at 40°C and 315 r / min.

[0072] 435g of triisobutyl phosphate was added to the reaction vessel within 14 minutes, and the mixture was stirred for another 16 minutes at 40℃ and 315r / min to obtain a phosphate-containing ester mixture.

[0073] Add 72g of n-tetrazol to a covered melting vessel and heat and stir at a constant temperature of 42℃ until completely melted. Add the molten n-tetrazol to the phosphate-containing ester mixture within 9 minutes and stir at 40℃ and 315 rpm. After addition, rinse the n-tetrazol melting vessel with 5g of D100 solvent oil for 1 minute, then add all the rinsing solution to the reaction vessel and continue stirring for 22 minutes.

[0074] Take another 30g of triisobutyl phosphate and add it to a premixed container with a lid. Heat it in a constant temperature water bath at 42℃ and stir at 265r / min. Add 3.2g of 1,2-octanediol and stir for 22min at 42℃ and 265r / min to obtain a 1,2-octanediol premix.

[0075] The obtained 1,2-octanediol premix was added to the reactor within 4 min. The premix container was rinsed with 5 g of D100 solvent oil, and all the rinsing solution was added to the reactor. The mixture was continued to be mixed at 40 °C and 315 r / min for 47 min. Then, the material was cooled to 28 °C under stirring at 215 r / min. The mixture was then filtered through organic solvent resistant filter membranes with pore sizes of 5 μm and 1 μm to obtain the compound extractant for phosphoric acid purification.

[0076] The present invention also includes comparative examples and related experiments.

[0077] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that tri(2-ethylhexyl) phosphate and dibutyl phosphate are not added, and 93g of triisobutyl phosphate is used as an equal mass substitute, so that the total amount of triisobutyl phosphate is 553g. Other components and preparation methods are the same as in Example 1, and a compound extractant for phosphoric acid purification is prepared.

[0078] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that 1,2-octanediol is not added, the amount of D100 solvent oil is increased to 377g, the 1,2-octanediol premixing step is not performed, and the other components and preparation methods are the same as in Example 1, thus preparing a compound extractant for phosphoric acid purification.

[0079] Comparative Example 3 Comparative Example 3 has the same composition as Example 1, except that all D100 solvent oil, triisobutyl phosphate, tris(2-ethylhexyl) phosphate, n-tetrazol, dibutyl butyl phosphate, and 1,2-octanediol are added to the reactor at once and mixed at 40°C and 300 r / min for 90 min. The n-tetrazol is not pre-melted, and 1,2-octanediol is not premixed with a portion of triisobutyl phosphate. The mixture is then cooled and filtered to prepare a compound extractant for phosphoric acid purification.

[0080] Performance testing (1) Extraction selectivity and back-extraction performance test Prepare a simulated wet-process phosphoric acid solution, wherein the mass fraction of phosphoric acid is 45.0%, and the Fe content is... 3+ Concentration of 1.50 g / L, Al 3+ Concentration of 1.00 g / L, Mg 2+ The concentration was 0.50 g / L. 100 mL of the compound extractants prepared in Examples 1-7 and Comparative Examples 1-3 were mixed with 100 mL of simulated wet-process phosphoric acid, respectively, at 30℃ and 300 r / min for 10 min. Stirring was stopped, and the mixture was allowed to stand for phase separation. The phosphorus and iron contents in the aqueous phases before and after extraction were measured, and the phosphoric acid extraction rate and iron co-extraction rate were calculated. The phosphorus and iron partition ratios were calculated based on the phosphoric acid extraction rate and iron co-extraction rate, and the phosphorus / iron separation coefficient was calculated. The loaded organic phase was mixed with deionized water at a volume ratio of 1:1, stirred at 40℃ and 300 r / min for 10 min, allowed to stand for phase separation, and the phosphorus content in the back-extracted aqueous phase was measured, and the phosphoric acid back-extraction rate was calculated. The test results are shown in Table 1.

[0081] Table 1. Results of Extraction Selectivity and Back-Extraction Performance Tests

[0082] As shown in Table 1 above, the iron co-extraction rate of the compound extractant prepared in Comparative Example 1 was significantly higher than that in Example 1, while the phosphorus / iron separation coefficient and phosphoric acid back-extraction rate were significantly lower. This indicates that the combined use of tri(2-ethylhexyl) phosphate and dibutyl butyl phosphate with triisobutyl phosphate is beneficial to improving the separation selectivity of phosphoric acid and iron impurities while maintaining the phosphoric acid extraction capacity, and also improves the back-extraction performance. Compared with Example 1, Comparative Example 2 showed little change in phosphoric acid extraction rate and phosphorus / iron separation coefficient, but the phosphoric acid back-extraction rate decreased. This indicates that 1,2-octanediol, in addition to regulating the interface, also plays a certain role in the overall mass transfer state of the compound system. Compared with Example 1, Comparative Example 3 showed a significant decrease in phosphoric acid extraction rate, phosphorus / iron separation coefficient, and phosphoric acid back-extraction rate. This indicates that staged feeding, pre-melting of n-tetrazol, and pre-mixing of 1,2-octanediol are beneficial to forming a uniform and stable compound system.

[0083] (2) Phase separation and storage stability test Timing began after extraction and mixing. The phase separation endpoint was defined as a clear oil-water interface, near-complete disappearance of interfacial flocculents, and no further change in the volume of both phases within 30 seconds. The settling time for phase separation was recorded. After 30 minutes of phase separation, the upper organic phase was collected, and the water content in the organic phase was determined using the Karl Fischer method. The loaded organic phase was allowed to stand at 10℃ for 24 hours, and the presence of a third phase, flocculents, turbidity, or stratification was observed. Unused compound extractants were stored in sealed containers at 5℃ and 40℃ for 30 days, respectively. After being restored to 25℃, the transparency, precipitation, and stratification were observed. The test results are shown in Table 2.

[0084] Table 2. Phase separation and storage stability test results

[0085] As shown in Table 2 above, the compound extractant prepared in Comparative Example 1, compared with Example 1, exhibited significantly increased standing phase separation time and water content in the organic phase, along with slight turbidity and interfacial flocculent matter. This indicates that the composite extraction environment formed by the three phosphorus-containing components is beneficial for improving the flowability of the organic phase and the oil-water phase separation state. Compared with Example 1, Comparative Example 2 showed a prolonged standing phase separation time, increased water content in the organic phase, and the formation of a durable interfacial film. This indicates that n-decithinol can improve the bulk stability of the loaded organic phase, but it is difficult to achieve rapid phase separation when used alone. A low addition amount of 1,2-octanediol is beneficial for disturbing the interfacial film and promoting droplet coalescence. Compared with Example 1, Comparative Example 3 showed significantly increased standing phase separation time and water content in the organic phase, and slight stratification occurred after low-temperature storage. This indicates that premixing and staged feeding are beneficial for improving the uniformity of distribution and storage stability of each component. The test results of Examples 1-7 show that the compound extractants prepared in this scheme all have relatively fast oil-water phase separation rates, low water content in the organic phase, and good loading and storage stability.

[0086] (3) Cyclic use stability test Following the extraction and back-extraction steps described above, the compound extractants prepared in Examples 1-7 and Comparative Examples 1-3 were continuously recycled 10 times. The phosphoric acid extraction rates for the 1st and 10th extractions were measured, and the retention rate of the 10th phosphoric acid extraction rate relative to the 1st phosphoric acid extraction rate was calculated. The test results are shown in Table 3.

[0087] Table 3 Results of Cyclic Use Stability Test

[0088] As shown in Table 3 above, the retention rates of phosphoric acid extraction in the 10th cycle of the compound extractants prepared in Comparative Examples 1-3 were all lower than those in Example 1. Specifically, Comparative Example 1 lacked the complex phosphorus-containing environment formed by tris(2-ethylhexyl) phosphate and dibutyl butyl phosphate, making the interface state and impurity entrainment more prone to change during cycling. Comparative Example 2 lacked the interface regulation effect of 1,2-octanediol, resulting in a decrease in phase separation performance after continuous cycling. Comparative Example 3 did not employ pre-melting of n-tetrazol, pre-mixing with 1,2-octanediol, or staged feeding, leading to poor uniformity of component distribution and a significantly lower cycle retention rate. The test results from Examples 1-7 show that the compound extractants prepared in this scheme can maintain a high phosphoric acid extraction rate during continuous extraction and back-extraction, exhibiting good stability for repeated use.

Claims

1. A method for preparing a compound extractant for phosphoric acid purification, characterized in that, Includes the following steps: Step S1: Add the first part of D100 solvent oil to the reaction vessel, heat and stir, add tri(2-ethylhexyl) phosphate and mix, then add butyl dibutyl phosphate and continue mixing, and finally add the first part of triisobutyl phosphate to obtain a phosphate-containing ester mixture. Step S2: Heat n-tetrazol until completely melted, add it to the phosphate ester mixture, stir evenly, rinse the n-tetrazol melting container with the second part of D100 solvent oil, and add the rinsing solution to the reaction vessel; Step S3: The second part of triisobutyl phosphate and 1,2-octanediol are heated and premixed to obtain a 1,2-octanediol premixed solution, which is added to the reaction vessel. The premixed container is rinsed with the third part of D100 solvent oil, and the rinsing solution is added to the reaction vessel for mixing, cooling, and filtration to obtain a compound extractant for phosphoric acid purification.

2. The method for preparing a compound extractant for phosphoric acid purification according to claim 1, characterized in that, The compound extractant comprises the following components in parts by weight: 440-480 parts of triisobutyl phosphate, 70-90 parts of tri(2-ethylhexyl) phosphate, 60-80 parts of n-tetrazol, 10-16 parts of dibutyl phosphate, 2-4 parts of 1,2-octanediol, and 330-418 parts of D100 solvent oil.

3. The method for preparing a compound extractant for phosphoric acid purification according to claim 1, characterized in that, The first part, triisobutyl phosphate, accounts for 92%-95% of the total mass of triisobutyl phosphate, and the remainder is the second part, triisobutyl phosphate; the first part, D100 solvent oil, accounts for 96%-98% of the total mass of D100 solvent oil, and the remainder consists of the second part and the third part of D100 solvent oil, with the second and third parts each accounting for 1%-2% of the total mass of D100 solvent oil.

4. The method for preparing a compound extractant for phosphoric acid purification according to claim 1, characterized in that, In step S1, the heating and stirring speed is 230-270 r / min, and the temperature is 39-41℃.

5. The method for preparing a compound extractant for phosphoric acid purification according to claim 1, characterized in that, In step S1, the addition time of tris(2-ethylhexyl) phosphate is 3-5 min, and after addition, the mixture is stirred at a speed of 280-320 r / min for 8-12 min; the addition time of dibutyl phosphate is 2-3 min, and after addition, the mixture is stirred for 8-12 min; the addition time of the first part of triisobutyl phosphate is 10-15 min, and after addition, the mixture is stirred for 12-18 min.

6. The method for preparing a compound extractant for phosphoric acid purification according to claim 1, characterized in that, In step S2, n-tetrazol is heated to complete melting in a constant temperature water bath at 41-43℃, and the added time of the molten n-tetrazol is 8-10 min; the stirring temperature is 39-41℃, the stirring speed is 280-320 r / min, and the stirring time is 15-25 min.

7. The method for preparing a compound extractant for phosphoric acid purification according to claim 1, characterized in that, In step S3, the second part, triisobutyl phosphate, is premixed with 1,2-octanediol at 41-43°C and 230-270 r / min for 15-25 min; the 1,2-octanediol premix is ​​added to the reaction vessel at a time of 3-5 min.

8. The method for preparing a compound extractant for phosphoric acid purification according to claim 1, characterized in that, In step S3, the mass ratio of the second portion of triisobutyl phosphate to 1,2-octanediol is (7.5-13):

1.

9. The method for preparing a compound extractant for phosphoric acid purification according to claim 1, characterized in that, In step S3, the mixture is continued for 40-50 minutes at 39-41℃ and 280-320r / min, and then cooled to 25-30℃ under stirring conditions of 180-220r / min. The mixture is then filtered sequentially through organic solvent-resistant filter membranes with pore sizes of 5μm and 1μm.

10. A compound extractant for phosphoric acid purification, characterized in that, It is prepared by the method of any one of claims 1-9 for preparing a compound extractant for phosphoric acid purification.

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