Method for preparing electronic grade phosphoric acid by coupling membrane separation with ion exchange resin

Abstract

The invention discloses a method for preparing electronic-grade phosphoric acid by coupling membrane separation with ion exchange resin, and aims to solve the technical problems that impurities are not thoroughly removed, the purity is difficult to reach the standard and the process energy consumption is high in the preparation of the electronic-grade phosphoric acid. The specific method mainly comprises the following steps: carrying out pretreatments of removing readily oxidizable substances on food-grade phosphoric acid, separating the treated food-grade phosphoric acid through a nanofiltration membrane to remove most metal cations and part of anion impurities, and deeply adsorbing residual trace impurities through ion exchange resin with a specific function, and carrying out vacuum concentration, and carrying out terminal ultrafiltration to remove particles to obtain a phosphoric acid product meeting the electronic grade standard. The method is high in purification efficiency, low in process energy consumption and high in production efficiency, and can be applied to industrial production of electronic-grade phosphoric acid on a large scale.

Description

Technical Field

[0001] This invention relates to the field of electronic chemical material preparation technology, specifically to a method for preparing electronic-grade phosphoric acid for use in the semiconductor, display panel and other electronic industries, and particularly to a purification process coupled with membrane separation and ion exchange resin. Background Technology

[0002] Electronic-grade phosphoric acid is a core material for emerging industries such as semiconductor chip manufacturing, photovoltaic cell packaging, and electronic component cleaning. Its purity directly determines the performance and reliability of downstream products, especially with stringent limits on metal ions, non-metallic impurities, and particles. Currently, the domestic electronic-grade phosphoric acid market relies heavily on imports, primarily because domestic purification technology struggles to overcome the bottleneck of efficiently removing complex impurities from thermal phosphoric acid. During the thermal phosphoric acid preparation process, raw phosphate rock and production equipment introduce various difficult-to-treat impurities, mainly including easily oxidizable substances such as phosphorous acid and hypophosphite, metal ions such as Fe, Cr, Ni, Na, Mg, Al, Ca, and Cu, non-metallic anions such as Cl⁻, SO₄²⁻, and NO⁻, as well as trace amounts of organic matter and colloidal particles. These impurities interact strongly with the phosphoric acid system; some metal ions easily form stable complexes, while non-metallic impurities are highly soluble in phosphoric acid, making deep separation difficult with conventional processes. Furthermore, the impurity content is mostly in the ppm to ppb range, orders of magnitude lower than the stringent limits for electronic-grade products, further increasing the purification difficulty.

[0003] Among existing methods for preparing electronic-grade phosphoric acid, distillation is energy-intensive, causes severe equipment corrosion, and is less effective at separating trace ionic impurities; solvent extraction requires large amounts of organic solvents, posing a risk of solvent residue and making subsequent separation difficult; membrane separation technology has been attempted for phosphoric acid purification due to its simplicity and lack of secondary pollution, but single nanofiltration membranes can only remove some large molecular impurities and high-valence metal ions; while ion exchange resins can deeply adsorb metal ions, they are easily contaminated and their adsorption capacity decreases when directly processing high-concentration industrial phosphoric acid, leading to reduced purification efficiency. None of these methods can simultaneously meet the requirements of high purity, low energy consumption, and large-scale industrial production. Therefore, there is an urgent need to develop a method for preparing electronic-grade phosphoric acid that can synergistically leverage the advantages of membrane separation and ion exchange resins to achieve deep removal of complex impurities while meeting the requirements of large-scale production and environmental friendliness. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by proposing a method for preparing electronic-grade phosphoric acid using membrane separation coupled with ion exchange resin. This method innovatively couples membrane separation and ion exchange processes in a specific sequence, achieving a stepwise, deep removal of impurity ions and significantly extending the lifespan of the ion exchange resin, thereby enabling the stable and economical preparation of electronic-grade phosphoric acid.

[0005] Specifically, this invention provides a method for preparing electronic-grade phosphoric acid using membrane separation coupled ion exchange resin, the method comprising the following steps: S1: Mix food-grade phosphoric acid and reducing substances in a certain proportion and react them evenly; S2: The pretreated phosphoric acid obtained in S1 is pumped into the nanofiltration membrane system. The operating pressure, temperature and membrane flux are controlled to remove most of the metal cations and anions. The permeate is collected to obtain the preliminary purified phosphoric acid solution 1. S3: The primary purified phosphoric acid solution 1 obtained in S2 is sequentially passed into a cation exchange resin column and a mixed ion exchange resin column, and the flow rate is controlled to further adsorb the residual anion and cation impurities to obtain phosphoric acid solution 2. S4: Distill the phosphoric acid solution 2 obtained in step S3 under reduced pressure to a mass concentration of 85%-90%; S5: Filter the phosphoric acid solution obtained in step S4 using a terminal filter to obtain electronic-grade phosphoric acid product.

[0006] The food-grade thermal phosphoric acid raw material mentioned in step S1 has a mass concentration of approximately 70-80 wt%. This food-grade phosphoric acid contains easily oxidizable substances, cationic impurities, and anionic impurities. The easily oxidizable substances, such as phosphorous acid and hypophosphite, contain approximately 100-500 ppm. The cationic impurities include Na, Mg, Al, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, and Sb, with each ion containing 1-5000 ppb. The anionic impurities include Cl... - SO4 2- NO3 - The content of each ion is 1~30ppm.

[0007] The reducing agent mentioned in step S2 is 30-35 wt% electronic grade hydrogen peroxide, and the amount added is 0.001-0.01% of the weight of phosphoric acid. The reaction time is 1-6 hours and the temperature is 30-40℃.

[0008] The nanofiltration membrane mentioned in step S2 includes any one of NE8040-ARM, ESNA1-LF2-LD, DK8040F30, NF8040C-34D, and NF4040C-34D; Filtration is achieved by controlling the operating pressure, temperature, and membrane flux of the nanofiltration membrane system; specifically, the operating pressure is 2 MPa~4 MPa, the temperature is 30~40℃, and the flux is controlled at 15-25 L / (m²). 2 ·h).

[0009] Nanofiltration membranes, due to their combination of charge repulsion and pore size sieving effects, can strongly repel anions with the same charge (such as Cl-). - SO4 2- NO3- (etc.), while simultaneously hindering high-valence cations (such as Mg) through electrostatic interactions. 2+ Al 3+ Ca 2+ Cr 3+ Mn 2+ Fe 3+ Ni 2+ Cu 2+ Zn 2+ As 3+ The nanofiltration membrane system of this invention allows for the efficient removal of impurity ions from phosphoric acid by filtering out most of the ion clusters formed by cations and anions or particles bound to other substances through the pore size sieving effect. The total amount of anions can be reduced to 10 ppm, and the total amount of cations to 1 ppm.

[0010] The resin used in the cation exchange resin column in step S3 includes any one of D860, SK1BH, 9126, ZG107, and MTS9570, with a column pass rate of 3~12 BV / h.

[0011] The resin used in the cation exchange resin column in step S3 is pretreated before column chromatography. The pretreatment method is as follows: first, the resin is rinsed with ultrapure water and then rinsed with alcohol. After soaking in alcohol for 2-4 hours, it is rinsed with ultrapure water. Alcohol treatment can effectively remove the organic solvents and oligomers remaining in the resin during the synthesis process, so as to avoid contamination of the product. The resin is then rinsed with a 1-2% (w / w) electronic grade HCl solution, and then soaked in a 1-2% (w / w) electronic grade HCl solution for 10-12 hours before being rinsed with ultrapure water. Acid washing is to further remove inorganic impurities such as metal ions from the resin and to transform the resin into the H-type cationic resin required for the experiment.

[0012] In the following preferred embodiment, the resin used in the cation exchange resin column in step S3 requires fine pretreatment. The specific method is as follows: first, the resin is rinsed with ultrapure water, then rinsed with ethanol at a flow rate of 4 BV / h, with a volume of about 5 times the resin volume. After soaking for 4 hours, it is rinsed with ultrapure water. Then, 2% electronic grade HCl solution is passed through the resin at a flow rate of 2 BV / h, with a volume of about 3 times the resin volume. After soaking for 12 hours, it is rinsed with ultrapure water.

[0013] The anion exchange resin used in the mixed ion exchange resin column in step S3 includes any one of DB6150, D201, ZGA351, and AER140, and the cation exchange resin of the resin column includes any one of D860, SK1BH, 9126, ZG107, and MTS9570, which can reduce the content of a single anion to below 0.05 ppm.

[0014] The mixed ion exchange resin column mentioned in step S3 is composed of anion exchange resin and cation exchange resin in a volume ratio of 1:(1-3).

[0015] In step S4, the reduced pressure distillation method controls the temperature at 70-80℃ and the vacuum degree at -0.095MPa to -0.098MPa, concentrating the solution to a mass concentration of 85%-90%.

[0016] The size of the filter element in the terminal filter mentioned in step S5 is 0.01-0.1 μm.

[0017] The technical solution of this invention is used to achieve Cl - Content less than 0.05 ppm, SO4 2- Content less than 0.05 ppm, NO3 - The content is less than 0.05 ppm, and the total anion content is less than 0.1 ppm.

[0018] The content of each cation is less than 20 ppb, and the total cation content is less than 50 ppb. The cations include any one or more combinations of Li, Na, Mg, Al, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Sr, Sb, Ba, Ta, and Pb.

[0019] The beneficial effects of this invention are as follows: This invention employs a combined process of "membrane separation pre-removal + ion exchange deep purification" to achieve highly efficient impurity removal. Utilizing the high rejection rate of nanofiltration membranes for divalent and higher-valent metal cations and macromolecular impurities, most impurities in food-grade phosphoric acid are pre-removed, reducing the processing load on subsequent ion exchange resins. Then, residual metal cation and anionic impurities are deeply adsorbed using a specific type of cation exchange resin and a mixed-bed exchange resin. Finally, reduced-pressure concentration and a terminal filter ensure that the product's phosphoric acid content and particulate matter content meet the requirements for electronic-grade phosphoric acid. This method leverages the high efficiency and low consumption advantages of membrane separation while utilizing the deep purification capabilities of ion exchange, overcoming the shortcomings of single-process methods and achieving the dual goals of highly efficient impurity removal and reduced process costs.

[0020] The technical solution of this invention can reduce the total anion content in electronic-grade phosphoric acid to 0.1 ppm, the total cation content to less than 50 ppb, and the particles larger than 0.1 μm to less than 100 pcs / ml. Detailed Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to the examples. The following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0022] Example 1: S1: Add 33wt% electronic-grade hydrogen peroxide to a reactor containing 75wt% food-grade phosphoric acid. The amount added is about 1 / 15000 of the weight of phosphoric acid. Heat to 35℃ and stir for 2 hours. S2: The phosphoric acid obtained in S1 is pumped into a nanofiltration membrane system equipped with an NE8040-ARM membrane, with the operating pressure controlled at 2 MPa, temperature at 35℃, and flux at 18 L / (m³). 2 •h), collect the permeate to obtain a preliminary purified phosphoric acid solution 1; S3: Pack D860 cation exchange resin into a cation exchange resin column. First, rinse the resin with ultrapure water, then rinse it with ethanol at a flow rate of 4 BV / h, using approximately 5 times the resin volume. Soak for 4 hours, then rinse with ultrapure water. Next, pass 2% electronic grade HCl solution through the resin at a flow rate of 2 BV / h, using approximately 3 times the resin volume. Soak for 12 hours, then rinse with ultrapure water for later use. Mix the D860 cation exchange resin refined according to the above pretreatment method with DB6150 anion exchange resin at a volume ratio of 2.5:1 to prepare a mixed ion exchange resin, then pack it into a mixed ion exchange resin column. Pass the primary purified phosphoric acid solution 1 sequentially through the above cation exchange resin column and the mixed ion exchange resin column at a flow rate of 8 BV / h to obtain phosphoric acid solution 2. S4: Phosphoric acid solution 2 is subjected to vacuum distillation at a temperature of 70℃ and a vacuum degree of -0.095MPa, and concentrated to a mass concentration of 85.5%.

[0023] S5: The phosphoric acid solution obtained in step S4 is filtered through a terminal filter equipped with a 0.1µm filter element to reduce the particle size of the phosphoric acid and finally obtain an electronic-grade phosphoric acid product that meets the specifications.

[0024]

[0025] Example 2: S1: Add 33wt% electronic-grade hydrogen peroxide to a reactor containing 75wt% food-grade phosphoric acid. The amount added is about 1 / 15000 of the weight of phosphoric acid. Heat to 35℃ and stir for 2 hours. S2: The phosphoric acid obtained in S1 is pumped into a nanofiltration membrane system equipped with an ESNA1-LF2-LD membrane. The operating pressure is controlled at 4 MPa, the temperature at 35 °C, and the flux at 25 L / (m²·h). The permeate is collected to obtain a preliminary purified phosphoric acid solution 1. S3: ZGC107 is loaded into a cation exchange resin column. First, the resin is rinsed with ultrapure water, then rinsed with ethanol at a flow rate of 4 BV / h, using approximately 5 times the resin volume. After soaking for 4 hours, it is rinsed with ultrapure water. Next, 2% electronic grade HCl solution is passed through the resin at a flow rate of 2 BV / h, using approximately 3 times the resin volume. After soaking for 12 hours, it is rinsed with ultrapure water and set aside. The D860 cation exchange resin purified according to the above pretreatment method is mixed with ZGA351 anion exchange resin at a volume ratio of 1.8:1 to prepare a mixed ion exchange resin, which is then loaded into a mixed ion exchange resin column. Primary purified phosphoric acid solution 1 is passed sequentially through the above cation exchange resin column and the mixed ion exchange resin column at a flow rate of 10 BV / h to obtain phosphoric acid solution 2. S4: Phosphoric acid solution 2 was subjected to vacuum distillation at a temperature of 80℃ and a vacuum degree of -0.098MPa, and concentrated to a mass concentration of 87.3%.

[0026] S5: The phosphoric acid solution obtained in step S4 is filtered through a terminal filter equipped with a 0.1µm filter element to reduce the particle size of the phosphoric acid and finally obtain an electronic-grade phosphoric acid product that meets the specifications.

[0027]

[0028] Example 3: S1: Add 33wt% electronic-grade hydrogen peroxide to a reactor containing 75wt% food-grade phosphoric acid. The amount added is about 1 / 15000 of the weight of phosphoric acid. Heat to 35℃ and stir for 2 hours. S2: Pump the phosphoric acid obtained in S1 into a nanofiltration membrane system equipped with an NF4040C-34D membrane, controlling the operating pressure at 2 MPa, temperature at 35℃, and flux at 15 L / (m³). 2 •h), collect the permeate to obtain a preliminary purified phosphoric acid solution 1; S3: SK1BH is loaded into a cation exchange resin column. First, the resin is rinsed with ultrapure water, then rinsed with ethanol at a flow rate of 4 BV / h, using approximately 5 times the resin volume. After soaking for 4 hours, it is rinsed with ultrapure water. Next, 2% electronic grade HCl solution is passed through the resin at a flow rate of 2 BV / h, using approximately 3 times the resin volume. After soaking for 12 hours, it is rinsed with ultrapure water and set aside. The ZGC107 cation exchange resin purified according to the above pretreatment method is mixed with DB6150 anion exchange resin at a volume ratio of 2.8:1 to prepare a mixed ion exchange resin, which is then loaded into a mixed ion exchange resin column. Primary purified phosphoric acid solution 1 is passed sequentially through the above cation exchange resin column and the mixed ion exchange resin column at a flow rate of 10 BV / h to obtain phosphoric acid solution 2. S4: Phosphoric acid solution 2 is subjected to vacuum distillation at a temperature of 70℃ and a vacuum degree of -0.095MPa, and concentrated to a mass concentration of 85.1%.

[0029] S5: The phosphoric acid solution obtained in step S4 is filtered through a terminal filter equipped with a 0.1µm filter element to reduce the particle size of the phosphoric acid and finally obtain an electronic-grade phosphoric acid product that meets the specifications.

[0030]

[0031] Comparative Example 1: S1: Add 33wt% electronic-grade hydrogen peroxide to a reactor containing 75wt% food-grade phosphoric acid. The amount added is about 1 / 15000 of the weight of phosphoric acid. Heat to 35℃ and stir for 2 hours. S2: The phosphoric acid obtained in S1 is pumped into a nanofiltration membrane system equipped with an ESNA1-LF2-LD membrane. The operating pressure is controlled at 4 MPa, the temperature at 35 °C, and the flux at 25 L / (m²·h). The permeate is collected to obtain a preliminary purified phosphoric acid solution 1. S3: Pack ZGC107 into a cation exchange resin column, rinse the resin with ultrapure water and set aside; mix D860 cation exchange resin and ZGA351 anion exchange resin at a volume ratio of 1.8:1 to prepare a mixed ion exchange resin, and then pack it into a mixed ion exchange resin column; pass the primary purified phosphoric acid solution 1 through the above cation exchange resin column and the mixed ion exchange resin column at a flow rate of 10 BV / h to obtain phosphoric acid solution 2. S4: Phosphoric acid solution 2 was subjected to vacuum distillation at a temperature of 80℃ and a vacuum degree of -0.098MPa, and concentrated to a mass concentration of 87.3%.

[0032] S5: The phosphoric acid solution obtained in step S4 is filtered through a terminal filter equipped with a 0.1µm filter element to reduce the particle size of the phosphoric acid and finally obtain an electronic-grade phosphoric acid product that meets the specifications.

[0033]

[0034] Comparative Example 2: S1: Add 33wt% electronic-grade hydrogen peroxide to a reactor containing 75wt% food-grade phosphoric acid. The amount added is about 1 / 15000 of the weight of phosphoric acid. Heat to 35℃ and stir for 2 hours. S2: SK1BH is loaded into a cation exchange resin column. First, the resin is rinsed with ultrapure water, then rinsed with ethanol at a flow rate of 4 BV / h, using approximately 5 times the resin volume. After soaking for 4 hours, it is rinsed with ultrapure water. Next, 2% electronic grade HCl solution is passed through the resin at a flow rate of 2 BV / h, using approximately 3 times the resin volume. After soaking for 12 hours, it is rinsed with ultrapure water and set aside. The ZG107 cation exchange resin and DB6150 anion exchange resin, which have been purified according to the above pretreatment method, are mixed at a volume ratio of 2.8:1 to prepare a mixed ion exchange resin, which is then loaded into a mixed ion exchange resin column. The phosphoric acid solution obtained in step S1 is passed sequentially through the above cation exchange resin column and the mixed ion exchange resin column at a flow rate of 10 BV / h to obtain phosphoric acid solution 1. S3: Phosphoric acid solution 1 is subjected to vacuum distillation at a temperature of 70℃ and a vacuum degree of -0.095MPa, and concentrated to a mass concentration of 85.1%.

[0035] S4: The phosphoric acid solution obtained in step S3 is filtered through a terminal filter equipped with a 0.1µm filter element to reduce the particle size of the phosphoric acid and finally obtain an electronic-grade phosphoric acid product that meets the specifications.

[0036]

[0037] The preparation methods and products disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the raw materials and process parameters, based on the content of this document. The above description is merely a preferred embodiment of this invention, but the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing electronic-grade phosphoric acid using membrane separation coupled ion exchange resin, characterized in that, Includes the following steps: S1: Mix food-grade phosphoric acid and reducing substances in a certain proportion and react them evenly; S2: Pump the pretreated phosphoric acid obtained in S1 into the nanofiltration membrane filtration system, collect the permeate to obtain a preliminary purified phosphoric acid solution 1; S3: Pass the primary purified phosphoric acid solution 1 obtained in S2 sequentially into a cation exchange resin column and a mixed ion exchange resin column to obtain phosphoric acid solution 2; S4: Distill the phosphoric acid solution 2 obtained in step S3 under reduced pressure to a mass concentration of 85%-90%; S5: Filter the phosphoric acid solution obtained in step S4 using a terminal filter to obtain electronic-grade phosphoric acid product.

2. The method for preparing electronic-grade phosphoric acid using a membrane separation coupled ion exchange resin according to claim 1, characterized in that: The food-grade thermal phosphoric acid raw material mentioned in step S1 has a mass concentration of 70-80 wt%, and the food-grade phosphoric acid contains phosphorous acid and hypophosphoric acid, with a content of 100-500 ppm.

3. The method for preparing electronic-grade phosphoric acid using a membrane separation coupled ion exchange resin according to claim 1, characterized in that: The reducing agent mentioned in step S2 is 30-35 wt% electronic grade hydrogen peroxide, and the amount added is 0.001-0.01% of the weight of phosphoric acid. The reaction time is 1-6 hours and the temperature is 30-40℃.

4. The method for preparing electronic-grade phosphoric acid using a membrane separation coupled ion exchange resin according to claim 1, characterized in that: The nanofiltration membrane mentioned in step S2 includes any one of NE8040-ARM, ESNA1-LF2-LD, DK8040F30, NF8040C-34D, and NF4040C-34D; Filtration is achieved by controlling the operating pressure, temperature, and membrane flux of the nanofiltration membrane system; specifically, the operating pressure is 2 MPa~4 MPa, the temperature is 30~40℃, and the flux is controlled at 15-25 L / (m²). 2 ·h).

5. The method for preparing electronic-grade phosphoric acid using a membrane separation coupled ion exchange resin according to claim 1, characterized in that: The resin used in the cation exchange resin column in step S3 includes any one of D860, SK1BH, 9126, ZGC107, and MTS9570; Column flow rate: 3~12 BV / h.

6. The method for preparing electronic-grade phosphoric acid using a membrane separation coupled ion exchange resin according to claim 5, characterized in that: The resin used in the cation exchange resin column in step S3 is pretreated before passing through the column. The pretreatment method is as follows: first, rinse the resin with ultrapure water, then rinse the resin with alcohol, then soak it in alcohol for 2-4 hours, and then rinse it with ultrapure water. Rinse the resin with a 1-2% (w / w) electronic grade HCl solution, then soak it in a 1-2% (w / w) electronic grade HCl solution for 10-12 hours, and finally rinse it with ultrapure water.

7. The method for preparing electronic-grade phosphoric acid using a membrane separation coupled ion exchange resin according to claim 1, characterized in that: The anion exchange resin used in the mixed ion exchange resin column in step S3 includes any one of DB6150, D201, ZGA351, and AER140, and the cation exchange resin of the resin column includes any one of D860, SK1BH, 9126, ZGC107, and MTS9570.

8. The method for preparing electronic-grade phosphoric acid using a membrane separation coupled ion exchange resin according to claim 7, characterized in that: The mixed ion exchange resin column mentioned in step S3 is composed of anion exchange resin and cation exchange resin in a volume ratio of 1:(1-3). Column flow rate: 3~12 BV / h.

9. The method for preparing electronic-grade phosphoric acid using a membrane separation coupled ion exchange resin according to claim 1, characterized in that: In step S4, the reduced pressure distillation method controls the temperature to 70-80℃ and the vacuum degree to -0.095MPa to -0.098MPa, concentrating to a mass concentration of 85%-90%; in step S5, the filter element size of the terminal filter is 0.01-0.1μm.

10. The method for preparing electronic-grade phosphoric acid using a membrane separation coupled ion exchange resin according to claim 1, characterized in that: The technical solution of this invention is used to achieve Cl - Content less than 0.05 ppm, SO4 2- Content less than 0.05 ppm, NO3 - The content is less than 0.05 ppm, and the total anion content is less than 0.1 ppm; the content of each cation is less than 20 ppb, and the total cation content is less than 50 ppb. The cations include any one or more combinations of Li, Na, Mg, Al, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Sr, Sb, Ba, Ta, and Pb.

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