1. A method for removing arsenic in electronic-grade hydrofluoric acid comprises the following steps:

step one, freezing and crystallizing, namely adding 120 parts of 100-plus liquid hydrogen fluoride into a freezing and crystallizing kettle, controlling the cooling rate to be 0.5-1.5 ℃/min, cooling the liquid hydrogen fluoride to be 30-50 ℃ below zero under the condition of slow stirring, and then preserving heat for 5-10h, wherein the stirring rate is 5-15 r/min;

step two, hypergravity separation, wherein the hydrogen fluoride liquid after freezing and crystallization is subjected to hypergravity centrifugal separation, the separation coefficient of the hypergravity centrifugal separation is 150-250g, the centrifugal temperature is minus 15-45 ℃, and the supernatant is separated after centrifugation;

filtering with a filter membrane, namely passing the supernatant obtained by centrifugal separation through a precision filter, and passing through the filter membrane under the pressure of 0.1-0.4Mpa, wherein the filtering temperature is 10-20 ℃ below zero, and the filter membrane is a modified polyvinylidene fluoride microporous membrane, and the preparation method comprises the following steps:

adding 10-20 parts by mass of polyvinylidene fluoride microporous membrane into 120 parts by mass of 100-120 parts by mass of ultrapure water to enable the water to completely immerse the microporous membrane, then heating the water to 70-100 ℃, preserving the heat for 2-10 hours, then reducing the water to 40-60 ℃, adding 2.2-3.8 parts by mass of strong base and 0.5-5 parts by mass of oxidant, uniformly stirring, reacting for 30-60 minutes, taking out the microporous membrane after completion, washing for 3-5 times in the ultrapure water, then placing the microporous membrane into 50-70 parts by mass of anhydrous ethanol, adding 0.05-0.2 part by mass of initiator, stirring for 5-10 minutes, then adding a mixture of 0.1-0.8 part by mass of grafting monomer and 0.01-0.05 part by mass of concentrated sulfuric acid, preserving the heat for 60-80 ℃, stirring, reacting for 2-6 hours, taking out the microporous membrane after completion of the reaction, soaking in 5-10% by mass of glycerol solution for 5-10 hours, cleaning, and drying Drying to obtain a modified polyvinylidene fluoride microporous membrane;

and step four, gasifying the filtered hydrogen fluoride liquid, and absorbing the gasified hydrogen fluoride liquid by using ultrapure water to obtain the electronic grade hydrofluoric acid.

2. The method of claim 1, wherein the step of removing arsenic comprises: the freezing crystallization kettle is made of polyvinylidene fluoride or polytetrafluoroethylene.

3. The method of claim 1, wherein the step of removing arsenic comprises: the strong base is sodium hydroxide or potassium hydroxide.

4. The method of claim 1, wherein the step of removing arsenic comprises: the oxidant is 25-35% of hydrogen peroxide by mass.

5. The method of claim 1, wherein the step of removing arsenic comprises: the initiator is benzoyl peroxide or dicumyl peroxide or methyl ethyl ketone peroxide.

6. The method of claim 1, wherein the step of removing arsenic comprises: the grafting monomer is obtained by mixing allyl amine and 4-propenyl thiosemicarbazide according to the molar ratio of 0.1-0.5: 1.

Background

Electronic grade hydrofluoric acid is also known as high purity hydrofluoric acid. Electronic grade hydrofluoric acid is used as one of key chemical materials for manufacturing integrated circuits, is mainly used for cleaning and corroding chips, and has very important influence on the finished product rate, the electrical property and the reliability of the integrated circuits due to the purity and the cleanliness of the electronic grade hydrofluoric acid.

CN103991847A discloses a preparation method of electronic grade hydrofluoric acid, which comprises the following steps: introducing industrial anhydrous hydrogen fluoride liquid and pure water into a rectifying tower to form hydrofluoric acid with a first concentration; then adding hydrogen peroxide solution to oxidize arsenic and silicon impurities in the solution, and then rectifying the solution; condensing the hydrogen fluoride gas obtained by rectification into hydrogen fluoride liquid, carrying out first filtration, absorbing the hydrogen fluoride liquid into hydrofluoric acid with a second concentration by using pure water, and carrying out second filtration to obtain an electronic grade hydrofluoric acid product; absorbing the tail gas with pure water to prepare industrial hydrofluoric acid. The preparation method is simple in preparation process, no extra impurity is introduced, the prepared electronic-grade hydrofluoric acid reaches the semiconductor equipment and material international standard SEMI-C7, the yield is high, the cost is low, and the electronic-grade hydrofluoric acid and the analytically pure hydrofluoric acid can be prepared by one production process.

CN103830926B discloses a rectifying tower for producing electronic grade hydrofluoric acid, wherein only a stripping section on a tower body of the rectifying tower is provided with a hand hole for maintenance. Among the above-mentioned scheme, cancelled traditional rectifying column and all set up the scheme of hand hole at rectifying section and stripping section, avoided the junction of hand hole and rectifying column body can't reach fine seamless bonding, formed the leakage point, prevented that outside impurity from getting into the interior pollution electron level hydrofluoric acid of rectifying column, guaranteed the quality of product.

CN101570318B relates to a method for producing electronic grade hydrofluoric acid, which comprises the following steps: (1) preheating the metered anhydrous hydrofluoric acid raw material, and performing rough distillation to remove low-boiling-point substances; (2) absorbing hydrofluoric acid discharged from the outlet of the condenser after the rough distillation into 48-49% of aqueous hydrofluoric acid solution by using ultrapure water; (3) distilling the absorbed hydrofluoric acid semi-finished product by a fluoroplastic resin sub-boiling distiller, gasifying the hydrogen fluoride liquid to generate ultra-pure electronic-grade hydrofluoric acid gas, condensing to obtain 48-49% aqueous hydrofluoric acid solution, and leaving high-boiling-point substances and heavy metals at the bottom of the sub-boiling distiller; (4) and (3) carrying out secondary filtration on the hydrofluoric acid semi-finished product discharged from the fluoroplastic resin sub-boiling distiller, and finally carrying out automatic filling to prepare a 48% ultra-pure hydrofluoric acid finished product. The method of the invention makes full use of the different boiling points of the anhydrous hydrofluoric acid and the impurities in the anhydrous hydrofluoric acid to remove different impurities, especially silicon, at different temperatures, so that the impurity content of the obtained ultra-pure hydrofluoric acid is reduced to the minimum.

Hydrogen fluoride contains arsenic and other metal impurities from the raw fluorite ore, which have a severe impact on electronic device performance; the other metal impurities are generally removed by a rectification method, and the arsenic is removed by a hydrogen peroxide oxidation method, a potassium permanganate oxidation method and an electrochemical oxidation method, wherein the corrosivity of HF is aggravated by the byproduct water of the hydrogen peroxide oxidation method, secondary metal pollution is caused by the byproduct manganese dioxide of the potassium permanganate method, and the reaction diffusivity and uniformity of the electrochemical oxidation method are limited, so that various defects and limitations exist.

Disclosure of Invention

In order to solve the problems, the invention provides a method for removing arsenic in electronic-grade hydrofluoric acid. The method of the invention separates out arsenic trifluoride by freezing, and then realizes high-efficiency solid-liquid separation by super-gravity centrifugation and precise filtration, thereby achieving the purpose of removing arsenic impurities. The melting point data for arsenic trifluoride and hydrogen fluoride are shown in the following table:

	melting Point (. degree.C.)	Boiling point (. degree.C.)
			Arsenic trifluoride	-8.5	63
Hydrogen fluoride	-83.7	19.54

A method for removing arsenic in electronic-grade hydrofluoric acid comprises the following steps:

step one, freezing and crystallizing, namely adding 120 parts of 100-plus liquid hydrogen fluoride into a freezing and crystallizing kettle, controlling the cooling rate to be 0.5-1.5 ℃/min, cooling the liquid hydrogen fluoride to be 30-50 ℃ below zero under the condition of slow stirring, and then preserving heat for 5-10h, wherein the stirring rate is 5-15 r/min;

step two, hypergravity separation, wherein the hydrogen fluoride liquid after freezing and crystallization is subjected to hypergravity centrifugal separation, the separation coefficient of the hypergravity centrifugal separation is 150-250g, the centrifugal temperature is minus 15-45 ℃, and the supernatant is separated after centrifugation;

filtering with a filter membrane, namely passing the supernatant obtained by centrifugal separation through a precision filter, and passing through the filter membrane under the pressure of 0.1-0.4Mpa, wherein the filtering temperature is 10-20 ℃ below zero, and the filter membrane is a modified polyvinylidene fluoride microporous membrane, and the preparation method comprises the following steps:

adding 10-20 parts by mass of polyvinylidene fluoride microporous membrane into 120 parts by mass of 100-120 parts by mass of ultrapure water to enable the water to completely immerse the microporous membrane, then heating the water to 70-100 ℃, preserving the heat for 2-10 hours, then reducing the water to 40-60 ℃, adding 2.2-3.8 parts by mass of strong base and 0.5-5 parts by mass of oxidant, uniformly stirring, reacting for 30-60 minutes, taking out the microporous membrane after completion, washing for 3-5 times in the ultrapure water, then placing the microporous membrane into 50-70 parts by mass of anhydrous ethanol, adding 0.05-0.2 part by mass of initiator, stirring for 5-10 minutes, then adding a mixture of 0.1-0.8 part by mass of grafting monomer and 0.01-0.05 part by mass of concentrated sulfuric acid, preserving the heat for 60-80 ℃, stirring, reacting for 2-6 hours, taking out the microporous membrane after completion of the reaction, soaking in 5-10% by mass of glycerol solution for 5-10 hours, cleaning, and drying Drying to obtain a modified polyvinylidene fluoride microporous membrane;

and step four, gasifying the filtered hydrogen fluoride liquid, and absorbing the gasified hydrogen fluoride liquid by using ultrapure water to obtain the electronic grade hydrofluoric acid.

The freezing crystallization kettle is made of polyvinylidene fluoride or polytetrafluoroethylene.

The strong base is sodium hydroxide or potassium hydroxide.

The oxidant is 25-35% of hydrogen peroxide by mass.

The initiator is benzoyl peroxide or dicumyl peroxide or methyl ethyl ketone peroxide.

The grafting monomer is obtained by mixing allyl amine and 4-propenyl thiosemicarbazide according to the molar ratio of 0.1-0.5: 1.

The invention discloses a method for removing arsenic in electronic-grade hydrofluoric acid, which separates out arsenic trifluoride by freezing, and then realizes high-efficiency solid-liquid separation by super-gravity centrifugation and precise filtration to achieve the aim of removing arsenic impurities; the modified polyvinylidene fluoride microporous membrane adopted by the invention has a certain adsorption effect on arsenic trifluoride by forming carbon-carbon double bonds on the surface of the polyvinylidene fluoride microporous membrane under the action of strong alkali and an oxidant and then carrying out graft copolymerization with a grafting monomer, and the prepared modified polyvinylidene fluoride microporous membrane can increase the flux of liquid hydrogen fluoride and improve the filtration efficiency; the method of the invention has high efficiency and has obvious advantages compared with other methods for removing arsenic in electronic-grade hydrofluoric acid.

Detailed Description

The invention is further illustrated by the following specific examples:

example 1

A method for removing arsenic in electronic-grade hydrofluoric acid comprises the following steps:

step one, freezing and crystallizing, namely adding 100kg of liquid hydrogen fluoride into a freezing and crystallizing kettle, controlling the cooling rate to be 0.5 ℃/min, cooling the liquid hydrogen fluoride to be 30 ℃ below zero under the condition of slow stirring, and then preserving heat for 5h, wherein the stirring rate is 5 r/min;

step two, hypergravity separation, namely, performing hypergravity centrifugal separation on the hydrogen fluoride liquid after freezing and crystallization, wherein the separation coefficient of the hypergravity centrifugal separation is 150g, the centrifugal temperature is 15 ℃ below zero, and supernatant is separated after centrifugation;

filtering with a filter membrane, namely passing the supernatant obtained by centrifugal separation through a precision filter, and passing through the filter membrane under the pressure of 0.1Mpa, wherein the filtering temperature is 10 ℃ below zero, and the filter membrane is a modified polyvinylidene fluoride microporous membrane, and the preparation method comprises the following steps:

adding 10kg of polyvinylidene fluoride microporous membrane into 100kg of ultrapure water, completely immersing the microporous membrane in water, heating the water to 70 ℃, keeping the temperature for 2h, reducing the water temperature to 40 ℃, adding 2.2kg of strong base and 0.5kg of oxidant, uniformly stirring, reacting for 30min, taking out the microporous membrane after the reaction is finished, washing for 3 times in the ultrapure water, then placing the microporous membrane into 50kg of absolute ethyl alcohol, adding 0.05kg of initiator, stirring for 5min, adding a mixture of 0.1kg of grafting monomer and 0.01kg of concentrated sulfuric acid, keeping the temperature to 60 ℃, stirring for reacting for 2h, taking out the microporous membrane after the reaction is finished, soaking the microporous membrane in 5% glycerol solution by mass for 5h, cleaning and drying to obtain the modified polyvinylidene fluoride microporous membrane;

and step four, gasifying the filtered hydrogen fluoride liquid, and absorbing the gasified hydrogen fluoride liquid by using ultrapure water to obtain the electronic grade hydrofluoric acid.

The material of the freezing crystallization kettle is polyvinylidene fluoride.

The strong base is sodium hydroxide.

The oxidant is 25% of hydrogen peroxide by mass.

The initiator is benzoyl peroxide.

The grafting monomer is obtained by mixing allyl amine and 4-propenyl thiosemicarbazide according to the molar ratio of 0.1: 1.

Example 2

A method for removing arsenic in electronic-grade hydrofluoric acid comprises the following steps:

step one, freezing and crystallizing, namely adding 110kg of liquid hydrogen fluoride into a freezing and crystallizing kettle, controlling the cooling rate to be 1 ℃/min, cooling the liquid hydrogen fluoride to be 40 ℃ below zero under the condition of slow stirring, and then preserving heat for 8h, wherein the stirring rate is 10 r/min;

step two, hypergravity separation, namely, performing hypergravity centrifugal separation on the hydrogen fluoride liquid after freezing and crystallization, wherein the separation coefficient of the hypergravity centrifugal separation is 200g, the centrifugal temperature is 35 ℃ below zero, and supernatant is separated after centrifugation;

filtering with a filter membrane, namely passing the supernatant obtained by centrifugal separation through a precision filter, and passing through the filter membrane under the pressure of 0.25Mpa, wherein the filtering temperature is 15 ℃ below zero, and the filter membrane is a modified polyvinylidene fluoride microporous membrane, and the preparation method comprises the following steps:

adding 15kg of polyvinylidene fluoride microporous membrane into 110kg of ultrapure water, completely immersing the microporous membrane in water, heating the water to 80 ℃, keeping the temperature for 6h, reducing the water temperature to 50 ℃, adding 2.8kg of strong base and 2.5kg of oxidant, uniformly stirring, reacting for 40min, taking out the microporous membrane after the reaction is finished, washing for 4 times in the ultrapure water, then placing the microporous membrane into 60kg of absolute ethyl alcohol, adding 0.1kg of initiator, stirring for 8min, adding a mixture of 0.5kg of grafting monomer and 0.03kg of concentrated sulfuric acid, keeping the temperature to 70 ℃, stirring, reacting for 4h, taking out the microporous membrane after the reaction is finished, soaking the microporous membrane in 8% glycerol solution by mass for 8h, cleaning, and drying to obtain the modified polyvinylidene fluoride microporous membrane;

and step four, gasifying the filtered hydrogen fluoride liquid, and absorbing the gasified hydrogen fluoride liquid by using ultrapure water to obtain the electronic grade hydrofluoric acid.

The material of the freezing crystallization kettle is polytetrafluoroethylene.

The strong base is potassium hydroxide.

The oxidant is 30% of hydrogen peroxide by mass.

The initiator is dicumyl peroxide.

The grafting monomer is obtained by mixing allyl amine and 4-propenyl thiosemicarbazide according to the molar ratio of 0.3: 1.

Example 3

A method for removing arsenic in electronic-grade hydrofluoric acid comprises the following steps:

step one, freezing and crystallizing, namely adding 120kg of liquid hydrogen fluoride into a freezing and crystallizing kettle, controlling the cooling rate to be 1.5 ℃/min, cooling the liquid hydrogen fluoride to 50 ℃ below zero under the condition of slow stirring, and then preserving heat for 10h, wherein the stirring rate is 15 r/min;

step two, hypergravity separation, namely, performing hypergravity centrifugal separation on the hydrogen fluoride liquid after freezing and crystallization, wherein the separation coefficient of the hypergravity centrifugal separation is 250g, the centrifugal temperature is 45 ℃ below zero, and supernatant is separated after centrifugation;

filtering with a filter membrane, namely passing the supernatant obtained by centrifugal separation through a precision filter, and passing through the filter membrane under the pressure of 0.4Mpa, wherein the filtering temperature is 20 ℃ below zero, and the filter membrane is a modified polyvinylidene fluoride microporous membrane, and the preparation method comprises the following steps:

adding 20kg of polyvinylidene fluoride microporous membrane into 120kg of ultrapure water, completely immersing the microporous membrane in water, heating the water to 100 ℃, preserving the heat for 10 hours, reducing the water temperature to 60 ℃, adding 3.8kg of strong base and 5kg of oxidant, uniformly stirring, reacting for 60 minutes, taking out the microporous membrane after the reaction is finished, washing for 5 times in the ultrapure water, then placing the microporous membrane into 70kg of absolute ethyl alcohol, adding 0.2kg of initiator, stirring for 10 minutes, adding a mixture of 0.8kg of grafting monomer and 0.05kg of concentrated sulfuric acid, preserving the heat for 80 ℃, stirring for reacting for 6 hours, taking out the microporous membrane after the reaction is finished, soaking the microporous membrane in 10% glycerol solution by mass for 10 hours, cleaning and drying to obtain the modified polyvinylidene fluoride microporous membrane;

and step four, gasifying the filtered hydrogen fluoride liquid, and absorbing the gasified hydrogen fluoride liquid by using ultrapure water to obtain the electronic grade hydrofluoric acid.

The material of the freezing crystallization kettle is polyvinylidene fluoride.

The strong base is potassium hydroxide.

The oxidant is 35% hydrogen peroxide by mass.

The initiator is methyl ethyl ketone peroxide.

The grafting monomer is obtained by mixing allyl amine and 4-propenyl thiosemicarbazide according to the molar ratio of 0.5: 1.

The content of arsenic in the electronic grade hydrofluoric acid prepared in the above example is obtained by ICP-MS8900 test, and the flux test of the prepared modified polyvinylidene fluoride microporous membrane to liquid hydrogen fluoride is performed according to the method in HYT 110-2008, and the test results are shown in the following table:

	arsenic (ng/L)	Flux (L/cm)2）
			Example 1	24	397
Example 2	19	405
			Example 3	18	421

Comparative example 1

A method for removing arsenic in electronic-grade hydrofluoric acid comprises the following steps:

step one, freezing and crystallizing, namely adding 100kg of liquid hydrogen fluoride into a freezing and crystallizing kettle, controlling the cooling rate to be 0.5 ℃/min, cooling the liquid hydrogen fluoride to be 30 ℃ below zero under the condition of slow stirring, and then preserving heat for 5h, wherein the stirring rate is 5 r/min;

step two, hypergravity separation, namely, performing hypergravity centrifugal separation on the hydrogen fluoride liquid after freezing and crystallization, wherein the separation coefficient of the hypergravity centrifugal separation is 150g, the centrifugal temperature is 15 ℃ below zero, and supernatant is separated after centrifugation;

and step three, gasifying the supernatant, and absorbing the gasified supernatant by ultrapure water to obtain the electronic grade hydrofluoric acid.

The material of the freezing crystallization kettle is polyvinylidene fluoride.

Comparative example 2

A method for removing arsenic in electronic-grade hydrofluoric acid comprises the following steps:

step one, freezing and crystallizing, namely adding 100kg of liquid hydrogen fluoride into a freezing and crystallizing kettle, controlling the cooling rate to be 0.5 ℃/min, cooling the liquid hydrogen fluoride to be 30 ℃ below zero under the condition of slow stirring, and then preserving heat for 5h, wherein the stirring rate is 5 r/min;

step two, hypergravity separation, namely, performing hypergravity centrifugal separation on the hydrogen fluoride liquid after freezing and crystallization, wherein the separation coefficient of the hypergravity centrifugal separation is 150g, the centrifugal temperature is 15 ℃ below zero, and supernatant is separated after centrifugation;

filtering with a filter membrane, namely passing the supernatant obtained by centrifugal separation through a precision filter, and passing through the filter membrane under the pressure of 0.1Mpa, wherein the filtering temperature is 10 ℃ below zero, and the filter membrane is a polyvinylidene fluoride microporous membrane;

and step four, gasifying the filtered hydrogen fluoride liquid, and absorbing the gasified hydrogen fluoride liquid by using ultrapure water to obtain the electronic grade hydrofluoric acid.

The material of the freezing crystallization kettle is polyvinylidene fluoride.

Comparative example 3

A method for removing arsenic in electronic-grade hydrofluoric acid comprises the following steps:

step one, freezing and crystallizing, namely adding 100kg of liquid hydrogen fluoride into a freezing and crystallizing kettle, controlling the cooling rate to be 0.5 ℃/min, cooling the liquid hydrogen fluoride to be 30 ℃ below zero under the condition of slow stirring, and then preserving heat for 5h, wherein the stirring rate is 5 r/min;

filtering with a filter membrane, namely passing the hydrogen fluoride liquid after freezing and crystallization through a precision filter, and passing the hydrogen fluoride liquid through the filter membrane under the pressure of 0.1Mpa, wherein the filtering temperature is 10 ℃ below zero, and the filter membrane is a modified polyvinylidene fluoride microporous membrane, and the preparation method comprises the following steps:

adding 10kg of polyvinylidene fluoride microporous membrane into 100kg of ultrapure water, completely immersing the microporous membrane in water, heating the water to 70 ℃, keeping the temperature for 2h, reducing the water temperature to 40 ℃, adding 2.2kg of strong base and 0.5kg of oxidant, uniformly stirring, reacting for 30min, taking out the microporous membrane after the reaction is finished, washing for 3 times in the ultrapure water, then placing the microporous membrane into 50kg of absolute ethyl alcohol, adding 0.05kg of initiator, stirring for 5min, adding a mixture of 0.1kg of grafting monomer and 0.01kg of concentrated sulfuric acid, keeping the temperature to 60 ℃, stirring for reacting for 2h, taking out the microporous membrane after the reaction is finished, soaking the microporous membrane in 5% glycerol solution by mass for 5h, cleaning and drying to obtain the modified polyvinylidene fluoride microporous membrane;

and step three, gasifying the filtered hydrogen fluoride liquid, and absorbing the gasified hydrogen fluoride liquid by using ultrapure water to obtain the electronic grade hydrofluoric acid.

The material of the freezing crystallization kettle is polyvinylidene fluoride.

The strong base is sodium hydroxide.

The oxidant is 25% of hydrogen peroxide by mass.

The initiator is benzoyl peroxide.

The grafting monomer is obtained by mixing allyl amine and 4-propenyl thiosemicarbazide according to the molar ratio of 0.1: 1.

The content of arsenic in the electronic grade hydrofluoric acid prepared by the above comparative example and the flux test of the prepared modified polyvinylidene fluoride microporous membrane to liquid hydrogen fluoride were carried out by the example method, and the test results are shown in the following table:

	arsenic (ng/L)	Flux (L/cm)2）
			Comparative example 1	142	-
Comparative example 2	48	214
			Comparative example 3	63	385