阅读说明：本技术 一种硅粉的提纯方法 (Method for purifying silicon powder ) 是由 周星 曾领才 田兴 李敏 李良 于 2021-10-21 设计创作，主要内容包括：本发明提供了一种硅粉的提纯方法,包括如下步骤：S1去除所述硅粉中的金属粉末和有机物；S2将氟化钠溶于无机酸后,采用所述无机酸对所述硅粉进行酸洗；S3采用溶液Ⅰ清洗所述硅粉；S4采用离子尖端放电法去除所述硅粉中的金属离子；S5采用溶液Ⅱ进一步去除所述硅粉中的金属离子；S6采用水对所述硅粉进行漂洗后烘干即得。本发明提供的硅粉的提纯方法,以去除硅片切割时产生的硅粉中的杂质,回收硅粉,节约资源,降低生产成本。而且该方法可将硅粉中的杂质的含量降低至ppm级,从而满足单晶提拉的要求。(The invention provides a method for purifying silicon powder, which comprises the following steps: s1, removing metal powder and organic matters in the silicon powder; s2, dissolving sodium fluoride in inorganic acid, and carrying out acid washing on the silicon powder by using the inorganic acid; s3, cleaning the silicon powder by using the solution I; s4, removing metal ions in the silicon powder by an ion tip discharge method; s5, further removing metal ions in the silicon powder by using a solution II; and S6, rinsing the silicon powder by water and drying to obtain the silicon powder. The method for purifying the silicon powder provided by the invention is used for removing impurities in the silicon powder generated during silicon wafer cutting, recovering the silicon powder, saving resources and reducing the production cost. And the method can reduce the content of impurities in the silicon powder to ppm level, thereby meeting the requirement of pulling the single crystal.)

1. The method for purifying the silicon powder is characterized by comprising the following steps of:

s1, removing metal powder and organic matters in the silicon powder;

s2, dissolving sodium fluoride in inorganic acid, and carrying out acid washing on the silicon powder by using the inorganic acid;

s3, cleaning the silicon powder by using the solution I;

s4, removing metal ions in the silicon powder by an ion tip discharge method;

s5, further removing metal ions in the silicon powder by using a solution II and cation exchange resin;

s6, rinsing the silicon powder by water and drying the silicon powder to obtain the silicon powder;

the solution I comprises tartrate, citrate and EDTA;

in the solution I, the content of tartrate is 4.5-5.5 wt%;

in the solution I, the content of citrate is 7.5-8.5 wt%;

in the solution I, the content of EDTA is 1.5-2.5 wt%;

the solution II comprises tartrate, citrate and EDTA;

in the solution II, the content of tartrate is 0.5-1.5 wt%;

in the solution II, the content of citrate is 0.5-1.5 wt%;

in the solution II, the content of EDTA is 0.25-0.75 wt%.

2. The method of purifying silicon powder according to claim 1, wherein:

in the step S1, removing metal powder and organic matters in the silicon powder by using an ethanol aqueous solution dissolved with a surfactant;

the surfactant comprises sodium isethionate.

3. The method of purifying silicon powder according to claim 2, wherein:

in the step S1, adding the silicon powder into the ethanol aqueous solution, stirring at 40-42 ℃ for 30min, and then performing suction filtration to remove metal powder and organic matters in the silicon powder;

the rotating speed of the stirring is 100-200 r/min.

4. The method of purifying silicon powder according to claim 1, wherein:

the inorganic acid comprises hydrochloric acid and nitric acid;

the content of hydrochloric acid in the inorganic acid is 9-11 wt%;

the content of nitric acid in the inorganic acid is 25-35 wt%;

the content of sodium fluoride in the inorganic acid is 2.5-3.5 wt%.

5. The method of purifying silicon powder according to claim 1, wherein:

in the S3, the pH value of the solution I is 3.8-4.2.

6. The method of purifying silicon powder according to claim 1, wherein:

in the S3, the temperature of the solution I is 40-42 ℃.

7. The method of purifying silicon powder according to claim 1, wherein:

in S4, the current and voltage used in the ion tip discharge method are 450-550A and 36V, respectively.

8. The method of purifying silicon powder according to claim 1, wherein:

the pH value of the solution II is 5.8-6.5.

9. The method of purifying silicon powder according to claim 1, wherein:

the temperature of the solution II is 40-42 ℃.

10. The method of purifying silicon powder according to claim 1, wherein:

and the step S6 includes the step of rinsing the silicon powder by water until the pH value of the water is neutral and then drying the silicon powder.

Technical Field

The invention relates to the field of material recovery, in particular to the field of recovery and purification of silicon powder.

Background

After monocrystalline silicon and polycrystalline silicon rods for photovoltaic power generation are cut into silicon wafers, a large amount of silicon powder is generated. If the silicon powder is directly discarded as solid waste, the environment is polluted, and simultaneously, the waste of resources is caused. And the silicon powder is recovered and can be recycled by being used as a raw material for preparing monocrystalline silicon or polycrystalline silicon. However, since many impurities such as metallic nickel, iron, copper, zinc, and nickel silicide fall from the diamond wire when the diamond wire cuts the silicon wafer, the content of metallic and non-metallic impurities in the silicon powder generated when the diamond wire cuts the silicon wafer is high. When the single crystal silicon or the polycrystalline silicon is prepared by adopting the pulling method, the growth of the seed crystal is interfered, so that the silicon powder is required to be purified and then can be used as a raw material for preparing the single crystal silicon or the polycrystalline silicon for regeneration and recycling.

Disclosure of Invention

The invention aims to provide a method for purifying silicon powder, which is used for removing impurities in the silicon powder generated during silicon wafer cutting, recovering the silicon powder, saving resources and reducing production cost.

In order to achieve the purpose, the invention adopts the following technical means:

a method for purifying silicon powder comprises the following steps:

s1, removing metal powder and organic matters in the silicon powder;

s2, dissolving sodium fluoride in inorganic acid, and carrying out acid washing on the silicon powder by using the inorganic acid;

s3, cleaning the silicon powder by using the solution I;

s4, removing metal ions in the silicon powder by an ion tip discharge method;

s5, further removing metal ions in the silicon powder by using a solution II and cation exchange resin;

s6, rinsing the silicon powder by water and drying the silicon powder to obtain the silicon powder;

the solution I comprises tartrate, citrate and EDTA;

in the solution I, the content of tartrate is 4.5-5.5 wt%;

in the solution I, the content of citrate is 7.5-8.5 wt%;

in the solution I, the content of EDTA is 1.5-2.5 wt%;

the solution II comprises tartrate, citrate and EDTA;

in the solution II, the content of tartrate is 0.5-1.5 wt%;

in the solution II, the content of citrate is 0.5-1.5 wt%;

in the solution II, the content of EDTA is 0.25-0.75 wt%.

Preferably, in S1, metal powder and organic matter in the silicon powder are removed by using an ethanol aqueous solution in which a surfactant is dissolved;

preferably, the surfactant comprises sodium isethionate.

Preferably, in the step S1, the silicon powder is added into the ethanol aqueous solution, stirred at 40-42 ℃ for 30min and then filtered, so as to remove metal powder and organic matters in the silicon powder;

the rotating speed of the stirring is 100-200 r/min.

Preferably, the inorganic acid includes hydrochloric acid and nitric acid;

preferably, the content of hydrochloric acid in the inorganic acid is 9-11 wt%;

preferably, the content of nitric acid in the inorganic acid is 25-35 wt%;

preferably, the content of sodium fluoride in the inorganic acid is 2.5-3.5 wt%.

Preferably, in the S3, the pH value of the solution I is 3.8-4.2.

Preferably, in the S3, the temperature of the solution I is 40-42 ℃.

Preferably, in S4, the current used in the ion tip discharge method is 450-550A, and the voltage is 36V.

Preferably, the pH value of the solution II is 5.8-6.5.

Preferably, the temperature of the solution II is 40-42 ℃.

Preferably, the step S6 includes rinsing the silicon powder with water until the pH of the water is neutral, and drying the silicon powder. Compared with the prior art, the invention has the following technical effects:

the method for purifying the silicon powder provided by the invention is used for removing impurities in the silicon powder generated during silicon wafer cutting, recovering the silicon powder, saving resources and reducing the production cost. And the method can reduce the content of impurities in the silicon powder to ppm level, thereby meeting the requirement of pulling the single crystal.

Detailed Description

Reference will now be made in detail to the embodiments of the present invention, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The following examples are illustrative only and are not to be construed as limiting the invention.

The invention provides a method for purifying silicon powder. The silicon powder is a product generated after the silicon wafer is cut by the diamond wire. The silicon powder contains a lot of impurities and needs to be provided for preparing monocrystalline silicon by monocrystalline pulling. Because the cutting cooling liquid adopted during the cutting of the silicon wafer contains sulfuration, sulfonation or esterification of various animal fats, the silicon powder generated during the cutting of the silicon wafer contains a plurality of organic matters. Therefore, the organic film in the silicon powder should be removed first. In certain embodiments of the invention, an aqueous alcohol solution of a surfactant is used to clean the organic film in the silicon powder. Specifically, in the alcohol aqueous solution of the surfactant, the content of alcohol is 80 wt%; the content of the surfactant in the alcohol aqueous solution was 5 wt%. The temperature of the alcohol water solution is 40-42 ℃ when cleaning, and the activity of the surfactant is strongest at the temperature. And adding the silicon powder into the alcohol aqueous solution, stirring at the speed of 150r/min for 30min, and performing suction filtration to remove metal powder and organic matters in the silicon powder. The suction filtration liquid can be continuously recycled after being adsorbed by activated carbon. The surfactant is preferably sodium isethionate. The sodium isethionate can increase the solubility of organic matter in aqueous alcohol solution, thereby removing the organic matter. And dissolving sodium fluoride in inorganic acid, and carrying out acid washing on the silicon powder by using the inorganic acid. The inorganic acid is a mixed solution of hydrochloric acid and nitric acid. The inorganic acid can thoroughly dissolve nickel powder and other metal impurities in the silicon powder. And the sodium fluoride dissolved in the inorganic acid can dissolve the nickel silicide film on the surface of the silicon powder. However, metal ions still adsorb on the surface of the silicon powder cleaned by the inorganic acid, so that a strong complex water washing method is adopted to remove the metal ions. Specifically, the silicon powder is cleaned by adopting a solution I which comprises high-concentration tartrate, citrate and EDTA, has the pH value of 3.8-4.2 and the temperature of 40-42 ℃ so as to remove most metal ions. The strong complexing water washing can prevent the metal ions from hydrolyzing to generate hydroxide precipitate or generate metal glue. And then further removing the metal ions by adopting an ion tip discharge method. Under the action of high voltage and large current, metal ions on the surface of the silicon powder directionally migrate to a cathode region and are discharged and reduced into elemental metal at the tip of the cathode. And finally, removing trace metal ions adsorbed on the surface of the silicon powder by weak complexing water washing and weak acidic cation exchange resin. And rinsing the silicon powder until the pH of the eluate is about 7, and performing suction filtration and drying to obtain a finished product.

Example 1

Dissolving alcohol and hydroxyethyl sodium sulfonate in deionized water to obtain an alcohol water solution dissolved with a surfactant. Wherein, the content of the alcohol is 80wt percent, and the content of the hydroxyethyl sodium sulfonate is 4.5wt percent. And (3) keeping the temperature of the alcohol water solution between 40 and 42 ℃, adding the silicon powder, stirring at the speed of 100 revolutions per minute for 30min, then carrying out vacuum filtration on the silicon powder, and cleaning the silicon powder by using inorganic acid with 9 wt% of hydrochloric acid, 25 wt% of nitric acid and 2.5 wt% of sodium fluoride. The temperature of the inorganic acid is 30-40 ℃. When cleaning, the silicon powder is added into the inorganic acid and stirred for 30min at the speed of 150 revolutions per minute. After acid washing treatment, after vacuum filtration, the silicon powder is washed by strong complexing water by using a solution I which comprises 4.5 wt% of tartrate, 7.5 wt% of citrate and 1.5 wt% of EDTA, has a pH value of 3.8 and is at a temperature of 40-42 ℃ so as to remove most metal ions. During cleaning, the silicon powder is added into the solution I, stirred for 30min and then placed into a rectifier to carry out point discharge on metal ions under the condition of 36V/450A.

An isolating membrane is arranged between a cathode chamber and an anode chamber in the rectifier, and metal ions are in the anode chamber. The anode chamber takes inert insoluble titanium as an anode and is connected with the anode of a direct current power supply. The cathode chamber is filled with a stainless steel needle (the surface of the stainless steel needle is 99% encapsulated and insulated, and only the needle point is exposed without encapsulation) which is connected with the cathode of a direct current power supply. Under the action of high voltage and large current, metal ions migrate from the anode chamber to the cathode chamber, obtain electrons at the tip of the stainless steel needle, and are reduced into metal simple substances to be settled. Under the action of high voltage and large current, metal ions directionally migrate to the cathode region and are discharged at the tip of the cathode to be reduced into elemental metal. The equipment can treat 98-99% of metal ions. And (4) carrying out vacuum filtration on the silicon powder, and then washing with weak complexing water. The weak complexing water washing solution II contains 0.5 wt% of tartrate, 0.5 wt% of citrate, 0.25 wt% of EDTA, 5.8 of pH value and 40-42 deg.C. And adding the silicon powder into the solution II, and stirring for 30 min. And after the remaining trace metal ions are exchanged by weak acid cation exchange resin, rinsing the silicon powder until the pH value is about 7, and performing suction filtration and drying to obtain a finished product.

After treatment by this example, the metal impurities in the silicon powder can be reduced from 500ppm to 5 ppm.

Example 2

Dissolving alcohol and hydroxyethyl sodium sulfonate in deionized water to obtain an alcohol water solution dissolved with a surfactant. Wherein, the content of the alcohol is 80wt percent, and the content of the hydroxyethyl sodium sulfonate is 5.5wt percent. And (3) keeping the temperature of the alcohol water solution between 40 and 42 ℃, adding the silicon powder, stirring at the speed of 200 revolutions per minute for 30min, then carrying out vacuum filtration on the silicon powder, and cleaning the silicon powder by using inorganic acid with the hydrochloric acid content of 11 wt%, the nitric acid content of 35 wt% and the sodium fluoride content of 3.5 wt%. The temperature of the inorganic acid is 30-40 ℃. When cleaning, the silicon powder is added into the inorganic acid and stirred for 30min at the speed of 150 revolutions per minute. After acid washing treatment, after vacuum filtration, the silicon powder is washed by strong complexing water by using a solution I which comprises 5.5 wt% of tartrate, 8.5 wt% of citrate and 2.5 wt% of EDTA, has a pH value of 4.2 and is at a temperature of 40-42 ℃ so as to remove most metal ions. And during cleaning, adding the silicon powder into the solution I, stirring for 30min, then putting into a rectifier, and carrying out point discharge on metal ions under the condition of 36V/550A.

An isolating membrane is arranged between a cathode chamber and an anode chamber in the rectifier, and metal ions are in the anode chamber. The anode chamber takes inert insoluble titanium as an anode and is connected with the anode of a direct current power supply. The cathode chamber is filled with a stainless steel needle (the surface of the stainless steel needle is 99% encapsulated and insulated, and only the needle point is exposed without encapsulation) which is connected with the cathode of a direct current power supply. Under the action of high voltage and large current, metal ions migrate from the anode chamber to the cathode chamber, obtain electrons at the tip of the stainless steel needle, and are reduced into metal simple substances to be settled. Under the action of high voltage and large current, metal ions directionally migrate to the cathode region and are discharged at the tip of the cathode to be reduced into elemental metal. The equipment can treat 98-99% of metal ions. And (4) carrying out vacuum filtration on the silicon powder, and then washing with weak complexing water. The weak complexing water washing solution II contains 1.5 wt% of tartrate, 1.5 wt% of citrate, 0.75 wt% of EDTA, 6.5 of pH value and 40-42 of temperature. And adding the silicon powder into the solution II, and stirring for 30 min. And after the remaining trace metal ions are exchanged by weak acid cation exchange resin, rinsing the silicon powder until the pH value is about 7, and performing suction filtration and drying to obtain a finished product.

After treatment by this example, the metal impurities in the silicon powder can be reduced from 500ppm to 8 ppm.

Comparative example 1

Dissolving alcohol and hydroxyethyl sodium sulfonate in deionized water to obtain an alcohol water solution dissolved with a surfactant. Wherein, the content of the alcohol is 80 wt%, and the content of the hydroxyethyl sodium sulfonate is 5 wt%. And (3) keeping the temperature of the alcohol water solution between 40 and 42 ℃, adding the silicon powder, stirring at the speed of 150 revolutions per minute for 30min, then carrying out vacuum filtration on the silicon powder, and cleaning the silicon powder by using inorganic acid with the hydrochloric acid content of 10 wt%, the nitric acid content of 30 wt% and the sodium fluoride content of 3 wt%. The temperature of the inorganic acid is 30-40 ℃. When cleaning, the silicon powder is added into the inorganic acid and stirred for 30min at the speed of 150 revolutions per minute. After acid washing treatment, after vacuum filtration, the silicon powder is washed by strong complexing water by using a solution I which comprises 5 wt% of tartrate, 8 wt% of citrate and 2 wt% of EDTA, has a pH value of 3.8-4.2 and is at a temperature of 40-42 ℃ so as to remove most metal ions. And during cleaning, adding the silicon powder into the solution I, stirring for 30min, then putting into a rectifier, and carrying out point discharge on metal ions under the condition of 36V/500A.

An isolating membrane is arranged between a cathode chamber and an anode chamber in the rectifier, and metal ions are in the anode chamber. The anode chamber takes inert insoluble titanium as an anode and is connected with the anode of a direct current power supply. The cathode chamber is filled with a stainless steel needle (the surface of the stainless steel needle is 99% encapsulated and insulated, and only the needle point is exposed without encapsulation) which is connected with the cathode of a direct current power supply. Under the action of high voltage and large current, metal ions migrate from the anode chamber to the cathode chamber, obtain electrons at the tip of the stainless steel needle, and are reduced into metal simple substances to be settled. Under the action of high voltage and large current, metal ions directionally migrate to the cathode region and are discharged at the tip of the cathode to be reduced into elemental metal. The equipment can treat 98-99% of metal ions. And finally, rinsing the silicon powder until the pH value is about 7, and performing suction filtration and drying to obtain a finished product.

After treatment by this example, the metal impurities in the silicon powder can be reduced from 500ppm to 109 ppm.

Comparative example 2

Dissolving alcohol and hydroxyethyl sodium sulfonate in deionized water to obtain an alcohol water solution dissolved with a surfactant. Wherein, the content of the alcohol is 80 wt%, and the content of the hydroxyethyl sodium sulfonate is 5 wt%. And (3) keeping the temperature of the alcohol water solution between 40 and 42 ℃, adding the silicon powder, stirring for 30min at the speed of 150r/min, then carrying out vacuum filtration on the silicon powder, and cleaning the silicon powder by using inorganic acid with the hydrochloric acid content of 10 wt%, the nitric acid content of 30 wt% and the sodium fluoride content of 3 wt%. The temperature of the inorganic acid is 30-40 ℃. When cleaning, the silicon powder is added into the inorganic acid and stirred for 30min at the speed of 150 revolutions per minute. After acid washing treatment, after vacuum filtration, the silicon powder is washed by strong complexing water by using a solution I which comprises 5 wt% of tartrate, 8 wt% of citrate and 2 wt% of EDTA, has a pH value of 3.8-4.2 and is at a temperature of 40-42 ℃ so as to remove most metal ions. And during cleaning, adding the silicon powder into the solution I, stirring for 30min, and then carrying out vacuum filtration on the silicon powder and washing with weak complexing water. The weak complexing water washing solution II contains 1 wt% of tartrate, 1 wt% of citrate, 0.5 wt% of EDTA, 5.8-6.5 of pH value and 40-42 of temperature. And adding the silicon powder into the solution II, and stirring for 30 min. And after the remaining trace metal ions are exchanged by weak acid cation exchange resin, rinsing the silicon powder until the pH value is about 7, and performing suction filtration and drying to obtain a finished product.

After treatment by this example, the metal impurities in the silicon powder can be reduced from 500ppm to 230 ppm.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.