A method for regenerating a tributyl phosphate extractant

Abstract

The application discloses a method for regenerating tributyl phosphate extractant, and belongs to the technical field of extraction purification. The method comprises the following steps: mixing aged tributyl phosphate extractant with an aqueous solution of iron ions, stirring and reacting at 25-80 DEG C to form a solid-liquid mixture; the aged tributyl phosphate extractant contains dibutyl phosphate; and the pH value of the aqueous solution of iron ions is less than or equal to 7; and the solid-liquid mixture is subjected to solid-liquid separation to obtain a liquid phase, and the liquid phase is subjected to phase separation by standing to obtain regenerated TBP solvent. The method has a high DBP removal rate, good regeneration effect, can effectively solve the emulsification phenomenon caused by local overalkalization, shorten the phase separation time, reduce the generation of solvent regeneration wastewater, and has important popularization significance.

Description

Technical Field

[0001] This invention belongs to the field of extraction and purification technology, and relates to a method for regenerating tributyl phosphate extractant. Background Technology

[0002] Wet-process phosphoric acid contains various impurities, including Mg. 2+ Al 3+ The presence of impurities, such as other ions, not only directly reduces the purity of wet-process phosphoric acid but also significantly negatively impacts its subsequent applications, thus limiting its use in high-end fields such as food-grade and electronic-grade phosphoric acid. Therefore, further purification and impurity removal are necessary to obtain refined phosphoric acid products with higher added value.

[0003] Currently, common purification methods include solvent extraction, solvent precipitation, chemical precipitation, crystallization, electrodialysis, ion exchange, and physical adsorption. Among these, solvent extraction is the most widely used phosphoric acid purification method in industry due to its advantages of low energy consumption, low pollution, and high effective phosphorus recovery rate. Tributyl phosphate (TBP) is one of the most commonly used extractants in the extraction method for purifying phosphoric acid, effectively separating impurities from the original acid and upgrading it from fertilizer-grade phosphoric acid to industrial and even food-grade phosphoric acid. However, in continuous production processes, some TBP degrades into dibutyl phosphate (DBP), causing solvent aging and a significant decrease in extraction efficiency. Furthermore, aged TBP solvent in the extraction system exacerbates problems such as severe emulsification and difficulty in phase separation, further affecting product purity. Therefore, it is necessary to regenerate aged TBP solvent to restore its extraction performance.

[0004] Current technologies generally use sodium hydroxide (NaOH) solution as an alkali to wash and regenerate aged TBP extractant. This effectively removes major byproducts such as DBP, which are formed from TBP degradation. Theoretically, the higher the concentration of NaOH solution added, the better the DBP removal effect. However, under excessively alkaline conditions, DBP readily undergoes a saponification reaction with NaOH to form corresponding soaps. Most of these soaps have an amphiphilic structure and strong emulsifying ability. They promote the formation of emulsions between the organic and aqueous phases, leading to intensified emulsification, difficulty in phase separation, and impact on subsequent process steps.

[0005] In addition, these alkaline washing and regeneration processes generate a large amount of solvent regeneration wastewater with high organic impurity content, which cannot be discharged or directly recycled. Therefore, a dedicated wastewater treatment unit needs to be set up, which leads to a significant increase in back-end treatment costs. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention aims to provide a method for regenerating tributyl phosphate extractant. This method not only has a high DBP removal rate and good regeneration effect, but also effectively solves the emulsification phenomenon caused by local over-alkaliness, shortens the phase separation time, and reduces the generation of solvent regeneration wastewater.

[0007] This invention provides a method for regenerating tributyl phosphate extractant, comprising the following steps:

[0008] Aged tributyl phosphate extractant is mixed with an iron ion aqueous solution and stirred at 25~80℃ to form a solid-liquid mixture; the aged tributyl phosphate extractant contains dibutyl phosphate, and the pH value of the iron ion aqueous solution is ≤7.

[0009] The solid-liquid mixture is separated into a liquid phase, which is then allowed to stand and separate to obtain a regenerated TBP solvent.

[0010] In some embodiments, the aqueous solution of iron ions contains ferrous ions derived from ferrous sulfate and / or ferrous chloride.

[0011] In some embodiments, the aqueous solution of iron ions contains ferric ions derived from ferric sulfate and / or ferric chloride.

[0012] In some embodiments, the aqueous solution of iron ions contains a pH adjuster to control acidity. The pH adjuster is concentrated sulfuric acid or concentrated hydrochloric acid.

[0013] In some embodiments, the aqueous solution of iron ions is prepared by mixing water-soluble iron salts and water, wherein the mass fraction of iron ions is 2-5%.

[0014] In some embodiments, the mass ratio of the aged tributyl phosphate extractant to the iron ion aqueous solution is 1:1 to 3; and the stirring reaction time is 1 to 3 hours.

[0015] In some embodiments, the solid-liquid separation is performed by filtration, resulting in filtrate and filter residue, wherein the filtrate is allowed to stand and separate into phases, and the filter residue is subjected to combustion treatment.

[0016] In some embodiments, the liquid phase is allowed to stand at room temperature and separate into two phases, with the upper organic phase being regenerated TBP solvent and the lower phase being an aqueous phase.

[0017] In some embodiments, the phase separation is performed using a separatory funnel, and the phases are separated by standing at room temperature for 10-20 minutes.

[0018] In some embodiments, the method further includes: after phase separation, the remaining phase is aqueous, which is replenished with an aqueous solution of iron ions for recycling.

[0019] Compared with existing methods, the regeneration method of tributyl phosphate (TBP) extractant in this invention mainly uses Fe 2+ / Fe 3+ An aqueous solution of iron ions is used as a precipitant, mixed with aged tributyl phosphate extractant (containing dibutyl phosphate-DBP), and stirred at 25-80°C to form a solid-liquid mixture. After solid-liquid separation and phase separation by settling, regenerated TBP solvent is obtained. This invention is the first to replace the traditional alkaline solution with an aqueous solution of iron ions (pH ≤ 7), utilizing Fe... 2+ / Fe 3+ The property of reacting with DBP to form a sparingly soluble solid complex effectively removes DBP from aged TBP solvent, and the resulting solid is easily separated and removed. Using the technical solution of this invention, the DBP content in the regenerated solvent can be reduced to as low as 0.0182%, with a removal rate as high as 97%~99%, meeting the application requirements for production. This invention's embodiments introduce non-alkaline Fe... 2+ / Fe 3+ The solution, through specific washing and regeneration of the old TBP solvent, can not only effectively solve the problem of local over-alkaliness in traditional alkaline solutions, but also alleviate the occurrence of emulsification and reduce the phase separation time.

[0020] Furthermore, the remaining aqueous phase after phase separation in this embodiment of the invention can be supplemented with Fe. 2+ / Fe 3+ The solution is recycled directly, which effectively reduces wastewater generation and alleviates the pressure on downstream solvent regeneration wastewater treatment. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the regeneration method in some embodiments of the present invention;

[0022] Figure 2 The following describes the emulsification of regenerated TBP solvent in some embodiments of the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] Traditional regeneration methods generally include a key step – alkaline washing. Alkaline washing can effectively remove DBP generated from TBP degradation and is relatively simple to operate, possessing a certain degree of technical feasibility. However, this method suffers from problems such as severe emulsification of the TBP extraction system due to degradation, difficulty in phase separation, and excessive solvent regeneration wastewater.

[0025] This invention provides a method for regenerating tributyl phosphate extractant, comprising the following steps:

[0026] Aged tributyl phosphate extractant is mixed with an iron ion aqueous solution and stirred at 25~80℃ to form a solid-liquid mixture; the aged tributyl phosphate extractant contains dibutyl phosphate, and the pH value of the iron ion aqueous solution is ≤7.

[0027] The solid-liquid mixture is separated into a liquid phase, which is then allowed to stand and separate to obtain a regenerated TBP solvent.

[0028] The present invention provides a simple method for regenerating aged TBP solvent, with a high DBP removal rate and excellent regeneration effect, making it highly valuable for industrial applications.

[0029] See Figure 1 , Figure 1 This is a process flow diagram of the regeneration method for aged TBP solvent in some embodiments of the present invention. The embodiments of the present invention first involve the preparation of an aqueous solution of iron ions: water-soluble iron salts are mixed with pure water in a certain mass ratio. The water-soluble iron salts can be completely dissolved under stirring conditions, thus obtaining ferrous ions (Fe²⁺). 2+ Aqueous solution or ferric ions (Fe3+) 3 + Aqueous solution, abbreviated as Fe 2+ / Fe 3+ Solution.

[0030] The water-soluble iron salts mentioned are mainly ferrous sulfate, ferric sulfate, ferrous chloride, and ferric chloride; for example, commercially available ferrous sulfate heptahydrate or ferric sulfate solid. The pure water is water with high purity, produced by methods including distillation, ion exchange, and reverse osmosis, and can further be ultrapure water commonly used in this field; ultrapure water, also known as high-purity water, refers to water in which almost all conductive media have been removed, and non-dissociated colloidal substances, gases, and organic matter have been removed to very low levels. The Fe... 2+ / Fe 3+ In the solution, the preferred iron ion or Fe mass fraction is 2-5%, for example, 2%, 2.5%, 3%, 4%, or 5%. This iron ion concentration range is beneficial for balancing good stability and reactivity. The stirring is an operation well-known to those skilled in the art, typically performed at room temperature (15-25°C). This invention does not impose specific process conditions on the stirring; stirring at room temperature is sufficient. In laboratory preparation of iron ion solutions, stirring is done in a glass beaker.

[0031] The aqueous solution of iron ions described in the embodiments of the present invention has a pH value ≤ 7, and is further weakly acidic (pH 3~7). Some embodiments of the present invention prepare Fe... 3+ In solution, Fe 3+It is prone to hydrolysis, so it is necessary to add pH adjusters such as concentrated sulfuric acid or concentrated hydrochloric acid to control the acidity of the solution (pH≤2) in order to maintain its stability.

[0032] Subsequently, in this embodiment of the invention, the aged TBP solvent is reacted with the obtained Fe... 2+ / Fe 3+ The solutions are mixed at a mass ratio of 1:1~3 and stirred continuously at 25~80℃ for 1~3 hours to achieve reaction regeneration; during the stirring process, Fe 2+ / Fe 3+ It reacts with DBP to form insoluble Fe-DBP solid, forming a solid-liquid mixture.

[0033] The aged TBP solvent is an aged tributyl phosphate extractant containing DBP, which can be derived from the production process of purifying phosphoric acid using conventional extraction methods; its DBP content can be 20,000~50,000 ppm, its TBP content can be 55%~65%, and its density can be 0.88~0.93 g / cm³. 3 The turbidity is between 1.00 and 5.00 NTU. The aged TBP solvent and the obtained Fe... 2+ / Fe 3+ The preferred mass ratio of the solution is 1:1 to 3. The temperature of the reaction regeneration is achieved through conventional heating control, with no special process limitations on heating or cooling. The reaction temperature can be further set at 40 to 80°C, for example, 50°C, 55°C, 60°C, 65°C, 70°C, or 80°C. If the temperature is too low, the coordination reaction is difficult to occur; if the temperature is too high, it is detrimental to the reaction efficiency and economy.

[0034] Fe in the above solvent system 2+ Fe 3+ At a certain temperature, it will undergo a coordination reaction with DBP to form a sparingly soluble coordination compound; the specific reaction formula can be illustrated as follows:

[0035] Fe 2+ +2(C4H9O)2PO(OH)→Fe[(C4H9O)2PO(OH)]2 (1);

[0036] Fe 3+ +3(C4H9O)2PO(OH)→Fe[(C4H9O)2PO(OH)]3 (2).

[0037] Conversely, TBP and Fe 2+ Fe 3+ The conditions for the reaction to occur are extremely harsh, and the reaction will hardly occur even at high temperatures.

[0038] For the resulting solid-liquid mixture, this embodiment of the invention performs solid-liquid separation such as filtration to obtain filtrate and filter residue. The filtrate is a liquid phase, which can be transferred to a conventional separatory funnel for standing and phase separation, preferably at room temperature for 10-20 minutes, to achieve liquid phase separation in a shorter time; at this time, the upper organic phase (light phase) is the regenerated TBP solvent, and the lower phase is the aqueous phase, which is the remaining iron ion solution.

[0039] The embodiments of this invention are mainly based on the above-described mechanism of action, preferably employing a simple filtration and separation method to precisely remove Fe-DBP solids and DBP from the solid-liquid mixture, thereby regenerating the TBP extractant. Specifically, the regenerated solvent DBP removal rate can reach over 97%.

[0040] The regeneration method of the present invention further includes: for the aqueous phase remaining after phase separation, Fe can be added. 2+ / Fe 3+ The solution is recycled back into the reaction regeneration step. Furthermore, the solid residue, such as filter cake, separated in some embodiments of the present invention can be incinerated. Embodiments of the present invention can effectively reduce the generation of solvent regeneration wastewater and lower costs.

[0041] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention. Unless otherwise specified, the materials used in the embodiments of this invention are commercially available products. The aged TBP solvent is an aged tributyl phosphate extractant containing DBP, which can be derived from the production process of purifying phosphoric acid using conventional extraction methods; its DBP content can be 20,000~50,000 ppm, its TBP content is 55%~65%, and its density is 0.880~0.930 g / cm³. 3 The turbidity is between 1.00 and 5.00 NTU.

[0042] Example 1:

[0043] (1) Fe 2+ Solution preparation:

[0044] 39.72 g of hydrated ferrous sulfate and 360.28 g of ultrapure water were placed in a 1000 mL beaker and stirred continuously until the solid was completely dissolved, thus obtaining Fe=2% Fe. 2+ Solution.

[0045] (2) Reaction regeneration:

[0046] Take 100 g of aged TBP solvent (its TBP content is 63.20%, DBP content is 46183 ppm, and density is 0.895 g / cm³). 3 (Turbidity of 2.84 NTU) and 100 g of prepared Fe 2+The solutions were mixed and stirred at 25 °C for 1 h. The precipitate was separated by filtration, and the liquid phase was transferred to a separatory funnel and allowed to stand for 10 min for phase separation. At this point, the upper light phase was the regenerated TBP solvent, and the lower aqueous phase was the remaining Fe. 2+ Solution.

[0047] In this embodiment, the DBP index of the regenerated TBP solvent and the aged TBP solvent is shown in Table 1; the DBP removal rate in the regenerated TBP solvent is 73.45%.

[0048] Example 2:

[0049] (1) Fe 2+ Solution preparation: Place 99.3 g of hydrated ferrous sulfate and 300.7 g of ultrapure water in a 1000 mL beaker, and stir continuously until the solid is completely dissolved to obtain Fe=5% Fe. 2+ Solution.

[0050] (2) Reaction regeneration: Take 100 g of aged TBP solvent and 200 g of prepared Fe 2+ The solutions were mixed and stirred at 60 °C for 2 h. The precipitate was separated by filtration, and the liquid phase was transferred to a separatory funnel and allowed to stand for 15 min for phase separation. At this point, the upper light phase was the regenerated TBP solvent, and the lower aqueous phase was the remaining Fe. 2+ Solution.

[0051] In this embodiment, the DBP index of the regenerated TBP solvent and the aged TBP solvent is shown in Table 1; the DBP removal rate in the regenerated TBP solvent is 98.96%.

[0052] Example 3:

[0053] (1) Fe 2+ Solution preparation: Place 99.3 g of hydrated ferrous sulfate and 300.7 g of ultrapure water in a 1000 mL beaker, and stir continuously until the solid is completely dissolved to obtain Fe=5% Fe. 2+ Solution.

[0054] (2) Reaction regeneration: Take 100 g of aged TBP solvent and 300 g of prepared Fe 2+ The solutions were mixed and stirred at 80 °C for 3 h. The precipitate was separated by filtration, and the liquid phase was transferred to a separatory funnel and allowed to stand for 20 min for phase separation. At this point, the upper light phase was the regenerated TBP solvent, and the lower aqueous phase was the remaining Fe. 2+ Solution.

[0055] In this embodiment, the DBP index of the regenerated TBP solvent and the aged TBP solvent is shown in Table 1; the DBP removal rate in the regenerated TBP solvent is 99.02%.

[0056] Example 4:

[0057] (1) Fe 2+ Solution preparation: Place 99.3 g of hydrated ferrous sulfate and 300.7 g of ultrapure water in a 1000 mL beaker, and stir continuously until the solid is completely dissolved, yielding 400 g of Fe. 2+ Solution (Fe=5%).

[0058] (2) Reaction regeneration: Take 100 g of aged TBP solvent and 200 g of prepared Fe 2+ The solutions were mixed and stirred at 60 °C for 2 h. The precipitate was separated by filtration, and the liquid phase was transferred to a separatory funnel and allowed to stand for 10 min for phase separation. At this point, the upper light phase was the TBP solvent from the first cycle of regeneration, and the lower phase was Fe from the first cycle of regeneration. 2+ Prepare the solution for two cycles.

[0059] (3) Fe 2+ Solution recycling: The Fe solution from one cycle... 2+ Solution supplementation of Fe 2+ After the solution (Fe=5%) reached 200 g, it was recycled again with 100 g of aged TBP solvent. The mixture was stirred at 60 °C for 2 h, and the precipitate was separated by filtration. The liquid phase was transferred to a separatory funnel and allowed to stand for 10 min for phase separation. At this point, the upper light phase was the regenerated TBP solvent from the second cycle, and the lower phase was the Fe from the second cycle. 2+ The solution is prepared for three cycles. The above steps are repeated to remove Fe. 2+ The solution is recycled 3 times.

[0060] In this embodiment, Fe is recycled. 2+ The effect of the solution on the solvent regeneration of aged TBP is shown in Table 1. The solvent regeneration of TBP after 3 cycles is shown in Table 1. Figure 2 a.

[0061] Example 5:

[0062] (1) Fe 3+ Solution preparation:

[0063] 47.62 g of hydrated ferric sulfate was dissolved in 432.38 g of pure water, and 20 g of concentrated sulfuric acid was slowly added dropwise while stirring continuously until the solid was completely dissolved, thus obtaining Fe. 3+ Solution (Fe=2%).

[0064] (2) Reaction regeneration:

[0065] Take 100 g of aged TBP solvent and 200 g of prepared Fe 3+ The solutions were mixed and stirred at 60 °C for 2 h. The precipitate was separated by filtration, and the liquid phase was transferred to a separatory funnel and allowed to stand for 10 min for phase separation. At this point, the upper light phase was the regenerated TBP solvent, and the lower aqueous phase was Fe. 3+Solution.

[0066] In this embodiment, the DBP index of the regenerated TBP solvent and the aged TBP solvent is shown in Table 1; the DBP removal rate in the regenerated TBP solvent is 99.59%.

[0067] Comparative Example 1:

[0068] (1) Preparation of alkaline solution: Place 10 g NaOH and 990 g pure water in 2000 mL and stir continuously until the solid is completely dissolved to obtain a 1% NaOH solution.

[0069] (2) Regeneration: Take 400 g of solvent in a beaker and heat it to 70-80 °C. Stir constantly and slowly add the prepared 1% NaOH solution dropwise to the solvent. During the dropwise addition, use pH test paper to check the pH value of the solvent in time. Stop adding alkali solution when pH=6-7. Stop stirring after 1 min. Place the solvent in a separatory funnel and let it stand. After a clear interface appears, perform phase separation. The upper light phase is the alkali solution regenerated TBP solvent, and the lower heavy phase is the solvent regeneration wastewater. The solvent regeneration wastewater contains 50 g (accounting for 11% of the total material).

[0070] In this comparative example, the DBP index of the alkaline-regenerated TBP solvent and the aged TBP solvent is shown in Table 1; the DBP removal rate in the alkaline-regenerated TBP solvent is 98.33%.

[0071] Table 1. TBP solvent properties before and after regeneration

[0072]

[0073] Furthermore, the alkaline solution regenerates the TBP solvent and Fe. 2+ See the solvent emulsification of TBP during solution regeneration. Figure 2 Fe 2+ TBP solvent after solution regeneration ( Figure 2 a) It is significantly clearer than the TBP solvent after alkaline regeneration ( Figure 2 b).

[0074] As can be seen from the above embodiments, the embodiments of the present invention utilize Fe for the first time. 2+ / Fe 3+ The property of reacting with DBP to form a sparingly soluble solid complex effectively removes DBP from aged TBP solvent, and the resulting solid is easily separated and removed. Using the technical solution of this invention, the DBP content in the regenerated solvent can be reduced to as low as 0.0182%, with a removal rate as high as 97%~99%, and the turbidity of the regenerated solvent is below 3.00 NTU, meeting the application requirements for production. This invention's embodiments introduce non-alkaline Fe... 2+ / Fe 3+The solution, through specific washing and regeneration of old TBP solvent, can not only effectively solve the problem of local over-alkaliness in traditional alkaline solutions, but also alleviate emulsification and reduce phase separation time, which has important implications for widespread application.

[0075] Furthermore, the remaining aqueous phase after phase separation in this embodiment of the invention can be supplemented with Fe. 2+ / Fe 3+ The solution is recycled directly, which effectively reduces wastewater generation and alleviates the pressure on downstream solvent regeneration wastewater treatment.

[0076] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention. The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of various ranges, the endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for regenerating a tributyl phosphate extractant, characterized in that, Includes the following steps: Aged tributyl phosphate extractant is mixed with an iron ion aqueous solution and stirred at 25~80℃ to form a solid-liquid mixture; the aged tributyl phosphate extractant contains dibutyl phosphate, and the pH value of the iron ion aqueous solution is ≤7. The solid-liquid mixture is separated into a liquid phase, which is then allowed to stand and separate to obtain a regenerated TBP solvent.

2. The method for regenerating the tributyl phosphate extractant according to claim 1, characterized in that, The aqueous solution of iron ions contains ferrous ions derived from ferrous sulfate and / or ferrous chloride.

3. The method for regenerating the tributyl phosphate extractant according to claim 1, characterized in that, The aqueous solution of iron ions contains ferric ions derived from ferric sulfate and / or ferric chloride.

4. The method for regenerating the tributyl phosphate extractant according to claim 3, characterized in that, The aqueous solution containing iron ions includes a pH adjuster to control acidity. The pH adjuster is concentrated sulfuric acid or concentrated hydrochloric acid.

5. The method for regenerating the tributyl phosphate extractant according to any one of claims 1-4, characterized in that, The iron ion aqueous solution is prepared by mixing water-soluble iron salt and water, wherein the mass fraction of iron ions is 2-5%.

6. The method for regenerating the tributyl phosphate extractant according to any one of claims 1-4, characterized in that, The mass ratio of the aged tributyl phosphate extractant to the iron ion aqueous solution is 1:1~3; the stirring reaction time is 1~3h.

7. The method for regenerating the tributyl phosphate extractant according to any one of claims 1-4, characterized in that, The solid-liquid separation method is filtration, which yields filtrate and filter residue. The filtrate is allowed to stand and separate into two phases, and the filter residue is subjected to combustion treatment.

8. The method for regenerating the tributyl phosphate extractant according to any one of claims 1-4, characterized in that, The liquid phase was allowed to stand at room temperature and then separated into two phases: the upper organic phase was the regenerated TBP solvent, and the lower phase was the aqueous phase.

9. The method for regenerating the tributyl phosphate extractant according to claim 8, characterized in that, The phase separation is carried out using a separatory funnel, and the phases are separated by standing at room temperature for 10-20 minutes.

10. The method for regenerating the tributyl phosphate extractant according to any one of claims 1-4, characterized in that, The method further includes: after phase separation, the remaining phase is aqueous, and iron ion aqueous solution is added for recycling.

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