Method for removing metal impurities through electrolytic coupling vacuum distillation of tin benzene sulfonate

Abstract

The invention discloses a method for removing metal impurities through electrolytic coupling vacuum distillation of tin benzene sulfonate. The method comprises the following steps: step 1, preparing a liquid; step 2, preparing an electrolyte; step 3, electrolysis; 4, copper removal and refining; and step 5, vacuum distillation. According to the method, the crude tin is prepared into the electrolyte, the benzene sulfonate is added for electrolysis, the precipitation potential of lead and tin is changed, the impurity lead element with high difficulty is removed, other impurity elements in the crude tin can also be removed, the lead, copper and other impurity elements are further removed by combining copper removal refining and vacuum distillation, and the 5N or 6N standard high-purity tin is obtained. The content of the lead element and the content of the bismuth element are both smaller than 1 ppm, the content of the uranium element and the content of the thorium element are both smaller than 1 ppb, the requirement of a low-alpha-ray-dose material is met, the problem that radioactive alpha-particle impurity elements in crude tin are difficult to remove through an electrolytic method is effectively solved, the use requirement that the high-purity tin serves as a welding flux is met, and the quality of a semiconductor chip is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of high-purity metal materials with low alpha ray dosage for manufacturing electronic parts, and in particular relates to a method for removing metal impurities by electrolysis-coupled vacuum distillation of tin benzenesulfonate. Background Art

[0002] Tin is a low-melting-point metal with a silvery-white luster. It is widely used in electronics, information, electrical appliances, chemicals, metallurgy, building materials, machinery, food packaging and other industries. High-purity tin has excellent properties such as soft texture, low melting point, strong ductility, strong plasticity and non-toxicity. It is mainly used to prepare compound semiconductors, high-purity alloys, ultra-low temperature cooling alloys, superconducting materials, solders, and compound semiconductor dopants and targets and other basic materials.

[0003] With the continuous progress and development of electronic information, the production of printed packaging for semiconductors has also progressed rapidly, and the demand for printed solder paste or related solder paste products has increased significantly. However, in high-density and high-capacity semiconductor devices, the risk of soft errors caused by the influence of α rays from tin materials near semiconductor chips has increased, which has made the quality requirements for such products more stringent, and at the same time, higher requirements have been put forward for the purification technology and process of high-purity tin materials with low α rays, especially the heavy metal impurity elements (such as lead and bismuth) that are prone to α decay must be less than 1ppm, and the radioactive elements (such as uranium and thorium) must be less than 1ppb.

[0004] At present, the main method for preparing high-purity tin is electrolytic refining. In the electrolytic process, the elements that are difficult to remove mainly include lead, iron, copper, arsenic, antimony, bismuth, etc. Among them, the potential of lead, bismuth and copper ions is relatively close to that of tin. It is difficult to purify tin to a higher purity by electrolysis. The existing electrolytic refining technology has a poor effect on the removal of trace impurities such as lead and copper. Combining copper removal refining and vacuum distillation technology can effectively remove lead and copper elements.

[0005] Therefore, a method for removing metal impurities by electrolysis of tin benzene sulfonate coupled with vacuum distillation is needed. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation in view of the above-mentioned deficiencies of the prior art. The method changes the precipitation potential of lead and tin by making crude tin into an electrolyte and adding benzenesulfonate for electrolysis, thereby removing the difficult impurity lead element. In addition, other impurity elements in the crude tin can also be removed, and then lead, copper and other impurity elements are further removed by combining copper removal refining and vacuum distillation, thereby preparing low α-ray dosage and high-purity tin.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation, characterized in that the method comprises the following steps: Step 1, liquid preparation: heat and melt 2N~4N crude tin, then extract with water to obtain tin beads, then add the tin beads to a dilute sulfuric acid solution and heat to dissolve, and finally perform solid-liquid separation to obtain a stannous sulfate solution; Step 2, preparation of electrolyte: adding concentrated sulfuric acid, benzenesulfonate, resveratrol, naphthol, gelatin, hydroquinone and deionized water to the stannous sulfate solution obtained in step 1 to obtain an electrolyte; the electrolyte comprises the following components: 40g / L~60g / L stannous sulfate, 120g / L~160g / L concentrated sulfuric acid, 8g / L~20g / L benzenesulfonate, 0.03g / L~0.08g / L resveratrol, 0.2g / L~0.5g / L β-naphthol, 1.0g / L~2.5g / L gelatin, 4g / L~6g / L hydroquinone; Step 3: Electrolysis: Add the electrolyte obtained in step 2 into the electrolytic cell, and then use the titanium plate as the cathode and the coarse tin plate as the anode. The cathode current density is 60A / m 2 ~100A / m 2 , the cell voltage is 0.04V~0.06V, and the electrolysis temperature is 20℃~40℃, and cathode tin is obtained on the cathode; Step 4, copper removal and refining: the cathode tin obtained in step 3 is peeled off, then cleaned, and then heated and melted. When it is nearly melted, it is covered with NH4Cl. After all the NH4Cl is volatilized, the slag is removed and cast to obtain an electrolytic tin ingot. Then, stannous sulfide is added to the electrolytic tin ingot, and then heated and stirred. After cooling, the slag is removed and cast to obtain a copper-removed tin ingot. Step 5, vacuum distillation: put the copper-free tin ingot obtained in step 4 into the graphite crucible of the vacuum distillation equipment, then turn on the mechanical pump to evacuate the vacuum distillation equipment, and then turn on the diffusion pump to further evacuate the vacuum. After reaching the vacuum degree requirement, heat the copper-free tin ingot to melt and keep it warm, then release the gas, pour out the molten tin liquid, and obtain high-purity tin after cooling.

[0008] The invention quenches crude tin into tin beads, adds dilute sulfuric acid, heats and dissolves the tin beads, and separates the solid and liquid to obtain a solution whose main salt is stannous sulfate. The invention adopts an electrolyte containing benzenesulfonate to perform electrolysis to change the precipitation potential of lead and tin, thereby removing the impurity lead element which is difficult to remove. In addition, other impurity elements in the crude tin can also be removed. The lead, copper and other impurity elements are further removed by combining copper removal refining and vacuum distillation, thereby preparing tin with low α-ray dosage and high purity.

[0009] The present invention adds concentrated sulfuric acid to the electrolyte to improve the conductivity of the electrolyte and prevent Sn2+ Oxidized to Sn 4+ , benzene sulfonate is added to change the precipitation potential of lead and tin, which is convenient for electrolytic removal of lead and tin. Resveratrol is added to improve the conductivity and stability of the electrolyte, thereby increasing the purity and yield of tin. β-naphthol is added to improve cathode polarization, make the crystal dense and the surface smooth, and prevent the formation of whiskers. Gelatin is added to increase the polarization of metal ions during cathode reduction, which can also refine the grains and improve the density of the coating. Hydroquinone is added as an antioxidant to inhibit the dissolution of Sn in the electrolyte. 2+ Oxidized to Sn 4+ , and inhibit precipitation and settling in the electrolyte, thus preventing the reduction of electrolytic refining efficiency.

[0010] In the copper removal refining of the present invention, when it is close to melting, NH4Cl is used to cover it, a large number of bubbles are generated in the molten pool, and metal oxide slag inclusions are effectively removed. Stannous sulfide is added to the electrolytic tin ingot, and then heated, stirred, and then cooled to efficiently separate and remove copper.

[0011] The above-mentioned method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation is characterized in that the concentration of the dilute sulfuric acid in step 1 is 9 mol / L, and the heating and dissolution is carried out in an oil bath at 90°C to 100°C for 24h to 48h. The present invention ensures that the tin beads are thoroughly dissolved by controlling the concentration of the dilute sulfuric acid and the heating temperature and time.

[0012] The above-mentioned method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation is characterized in that the solid-liquid separation in step 1 adopts a filter press, a polyester bag or a nylon filter bag. When a filter press is used, the filtration pressure is 0.4MPa, the compression pressure is 0.7MPa, the filter cloth is made of polypropylene, and the air permeability of the filter cloth is 100cm 3 / cm 2 / min. The present invention ensures sufficient removal of impurities by controlling the solid-liquid separation device.

[0013] The above-mentioned method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation is characterized in that the benzenesulfonate in step 2 is sodium benzenesulfonate and / or calcium benzenesulfonate. The sodium benzenesulfonate and calcium benzenesulfonate used in the present invention both have strong complexing ability and leveling property, and can change the precipitation potential of lead and tin, and improve the removal effect of lead and tin, and sodium benzenesulfonate is preferred, which has stronger complexing ability and leveling property, and its price is cheaper.

[0014] The above-mentioned method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation is characterized in that the material of the cathode in step 3 can also be stainless steel or graphite, the purity of the crude tin plate is 2N~4N, and the crude tin plate is first soaked in a dilute hydrochloric acid solution before electrolysis, then washed, and then covered with a polyester bag. The present invention removes surface impurities by soaking the crude tin plate in a dilute hydrochloric acid solution before electrolysis, and prevents the peeled anode mud from contaminating the electrolyte by covering it with a polyester bag.

[0015] The above-mentioned method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation is characterized in that the cleaning process described in step 4 is: soaking for 2 minutes in 5% HCl by mass fraction, and then rinsing with deionized water. The present invention removes residual lead in the electrolyte by soaking in HCl, thereby ensuring the purity of the electrolytic tin ingot.

[0016] The above-mentioned method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation is characterized in that the surface scum is scraped off with a bamboo stick in time during the casting in step 4. The present invention ensures the purity of the electrolytic tin ingot by scraping off the surface scum.

[0017] The above-mentioned method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation is characterized in that the temperature of heating and stirring in step 4 is 900° C., the time is 30 minutes, and the cooling is cooling to 230° C. By controlling the parameters of heating and stirring and the parameters of cooling, copper can be efficiently separated and removed.

[0018] The above-mentioned method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation is characterized in that the vacuum degree in step 5 is required to be 0.001Pa~10Pa, the temperature of heating and melting is 1000℃~1600℃, and the insulation time is 60min~120min. The present invention prevents oxidation and the introduction of impurities through vacuum degree, maintains a good evaporation rate, controls the parameters through heating, and efficiently separates and removes lead, antimony, and silver.

[0019] The above-mentioned method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation is characterized in that the chemical composition of the high-purity tin in step five meets the standards of 5N or 6N high-purity tin, and the content of lead and bismuth elements is less than 1ppm, and the content of uranium and thorium elements is less than 1ppb, and the high-purity tin meets the requirements of low α-ray dosage materials.

[0020] Compared with the prior art, the present invention has the following advantages: 1. The present invention quenches crude tin into tin beads and adds dilute sulfuric acid to heat and dissolve and separate the solid and liquid to obtain a solution whose main salt is stannous sulfate. The present invention adopts an electrolyte containing benzenesulfonate for electrolysis to change the precipitation potential of lead and tin, thereby removing the impurity lead element which is difficult to remove. In addition, other impurity elements in the crude tin can also be removed. In combination with copper removal refining and vacuum distillation, lead, copper and other impurity elements are further removed, thereby preparing tin with low α-ray dosage and high purity. The problem that it is difficult to remove radioactive α-particle impurity elements in crude tin by electrolysis is effectively solved. The high-purity tin is used as solder, which greatly improves the quality of semiconductor chips.

[0021] 2. The present invention adds concentrated sulfuric acid to the electrolyte to improve the conductivity of the electrolyte and prevent Sn 2+ Oxidized to Sn 4+ , benzene sulfonate is added to change the precipitation potential of lead and tin, which is convenient for electrolytic removal of lead and tin. Resveratrol is added to improve the conductivity and stability of the electrolyte, thereby increasing the purity and yield of tin. β-naphthol is added to improve cathode polarization, make the crystal dense and the surface smooth, and prevent the formation of whiskers. Gelatin is added to increase the polarization of metal ions during cathode reduction, which can also refine the grains and improve the density of the coating. Hydroquinone is added as an antioxidant to inhibit the dissolution of Sn in the electrolyte. 2+ Oxidized to Sn 4+ , and inhibit precipitation and settling in the electrolyte, thus preventing the reduction of electrolytic refining efficiency.

[0022] 3. In the copper removal refining of the present invention, when it is close to melting, it is covered with NH4Cl to generate a large number of bubbles in the molten pool, effectively removing metal oxide slag, and adding stannous sulfide to the electrolytic tin ingot, heating and stirring, and then cooling, so as to efficiently separate and remove copper.

[0023] 4. The method proposed in the present invention solves the problem that it is difficult to make the crude tin reach a Pb and Bi content below 1 ppm using the existing high-purity tin preparation technology, and can meet the quality requirements of semiconductor tin solder.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a process flow chart of the electrolysis of tin benzenesulfonate coupled with vacuum distillation to remove metal impurities. DETAILED DESCRIPTION

[0026] Figure 1 The process flow chart of the present invention is to remove metal impurities by electrolysis of tin benzene sulfonate coupled with vacuum distillation, from Figure 1It can be seen that the present invention first heats the crude tin to melt and extracts it with water to obtain tin beads, adds the tin beads to a dilute sulfuric acid solution, heats to dissolve, and then performs solid-liquid separation to obtain a stannous sulfate solution, electrolyzes the stannous sulfate solution to obtain cathode tin, adds stannous sulfide to the cathode tin for copper removal and refining to obtain a copper-removing tin ingot, and vacuum distills the copper-removing tin to obtain high-purity tin.

[0027] Example 1 This embodiment includes the following steps: Step 1, liquid preparation: Place 2N crude tin in a crucible and heat it in a muffle furnace to melt it, then extract it with water to obtain tin beads, then add 23g of tin beads to 25mL of 9mol / L dilute sulfuric acid solution and heat it in a 90℃ oil bath to dissolve for 36h until the tin no longer dissolves, pour out the solution, and heat it with 50mL of deionized water together with the residue to extract the remaining stannous sulfate, finally combine the two parts of the solution and use a filter press with a filtration pressure of 0.4MPa and a compression pressure of 0.7MPa. The filter cloth is made of polypropylene and has an air permeability of 100cm 3 / cm 2 / min to perform solid-liquid separation to obtain stannous sulfate solution; Step 2: Preparation of electrolyte: Add concentrated sulfuric acid, sodium benzenesulfonate, resveratrol, naphthol, gelatin, hydroquinone and deionized water to the stannous sulfate solution obtained in step 1 to obtain 1000 mL of electrolyte; the electrolyte comprises the following components: 40 g / L stannous sulfate, 120 g / L concentrated sulfuric acid, 8 g / L sodium benzenesulfonate, 0.03 g / L resveratrol, 0.2 g / L β-naphthol, 1.0 g / L gelatin, and 4 g / L hydroquinone; Step 3: Electrolysis: Add the electrolyte obtained in step 2 into the electrolytic cell, and then use the titanium plate as the cathode. Soak the crude tin plate with a purity of 2N in a dilute hydrochloric acid solution, then wash it, and then put on a polyester bag as the anode. At an inter-electrode distance of 50mm and a cathode current density of 60A / m 2 , the cell voltage is 0.04V, the electrolysis temperature is 20°C, and cathode tin is obtained on the cathode; Step 4, copper removal and refining: the cathode tin obtained in step 3 is peeled off, soaked in HCl with a mass fraction of 5% for 2 minutes, then rinsed with deionized water, and then heated to melt. When it is close to melting, it is covered with NH4Cl. After the NH4Cl is completely volatilized, the slag is removed and cast, and the surface scum is scraped off with a bamboo piece in time during the casting process to obtain a 30g electrolytic tin ingot, and then stannous sulfide is added to the electrolytic tin ingot with a stoichiometric ratio of copper to stannous sulfide of 1:2, and the temperature is raised to 900°C for heating and stirring for 30 minutes. After cooling to 230°C, the scum is removed and cast, and the surface scum is scraped off with a bamboo piece in time during the casting process to obtain a copper-removed tin ingot; Step 5: Vacuum distillation: The copper-free tin ingot obtained in step 4 is placed in a graphite crucible of a vacuum distillation device, and then a mechanical pump is turned on to evacuate the vacuum distillation device to 15Pa, and then a diffusion pump is turned on to further evacuate the vacuum. After the vacuum degree reaches 0.01Pa, the copper-free tin ingot is heated to 1150°C to melt and kept warm for 100min, and then the gas is released, and the molten tin liquid is poured out, and high-purity tin is obtained after cooling.

[0028] The high-purity tin prepared in this example was subjected to glow discharge mass spectrometry (GDMS) detection. The results are shown in Table 1, and the unit is ppm, wherein 4NSn (99.99) represents a tin sample with a purity of 4N, 5NSn (99.999) represents a tin sample with a purity of 5N, and 6NSn (99.9999) represents a tin sample with a purity of 6N.

[0029] Table 1

[0030] It can be seen from Table 1 that the chemical composition of the high-purity tin prepared by electrolytic refining coupled with vacuum distillation technology in this embodiment meets the standard of 5N high-purity tin, and the content of lead and bismuth is less than 1ppm, and the content of uranium and thorium is less than 1ppb, indicating that the prepared high-purity tin meets the requirements of low α-ray dose materials.

[0031] In this embodiment, the benzenesulfonate may also be calcium benzenesulfonate, or sodium benzenesulfonate and calcium benzenesulfonate.

[0032] In this embodiment, the cathode may also be made of stainless steel or graphite.

[0033] Example 2 This embodiment includes the following steps: Step 1, liquid preparation: 3N crude tin is placed in a crucible, and heated in a muffle furnace to melt, and then water-extracted to obtain tin beads, and then 28g of tin beads are added to 30mL of a 9mol / L dilute sulfuric acid solution and heated in an oil bath at 100°C for 24h until the tin no longer dissolves, the solution is poured out, and 50mL of deionized water is used to heat the residue together to extract the remaining stannous sulfate, and finally the two parts of the solution are combined and solid-liquid separation is performed using a polyester bag to obtain a stannous sulfate solution; Step 2: Preparation of electrolyte: Add concentrated sulfuric acid, sodium benzenesulfonate, resveratrol, naphthol, gelatin, hydroquinone and deionized water to the stannous sulfate solution obtained in step 1 to obtain 1000 mL of electrolyte; the electrolyte comprises the following components: 50 g / L stannous sulfate, 140 g / L concentrated sulfuric acid, 14 g / L sodium benzenesulfonate, 0.05 g / L resveratrol, 0.35 g / L β-naphthol, 1.7 g / L gelatin, and 5 g / L hydroquinone; Step 3: Electrolysis: Add the electrolyte obtained in step 2 into the electrolytic cell, and then use the titanium plate as the cathode. Soak the crude tin plate with a purity of 3N in a dilute hydrochloric acid solution, then wash it, and then put on a polyester bag as the anode. At an inter-electrode distance of 60mm and a cathode current density of 80A / m 2 , the cell voltage is 0.05V, the electrolysis temperature is 25°C, and cathode tin is obtained on the cathode; Step 4, copper removal and refining: the cathode tin obtained in step 3 is peeled off, soaked in HCl with a mass fraction of 5% for 2 minutes, then rinsed with deionized water, and then heated to melt. When it is close to melting, it is covered with NH4Cl. After the NH4Cl is completely volatilized, the slag is removed and cast, and the surface scum is scraped off with a bamboo piece in time during the casting process to obtain a 30g electrolytic tin ingot, and then stannous sulfide is added to the electrolytic tin ingot with a stoichiometric ratio of copper to stannous sulfide of 1:2, and the temperature is raised to 900°C for heating and stirring for 30 minutes. After cooling to 230°C, the scum is removed and cast, and the surface scum is scraped off with a bamboo piece in time during the casting process to obtain a copper-removed tin ingot; Step 5: Vacuum distillation: The copper-free tin ingot obtained in step 4 is placed in a graphite crucible of a vacuum distillation device, and then a mechanical pump is turned on to evacuate the vacuum distillation device to 15 Pa, and then a diffusion pump is turned on to further evacuate the vacuum. After the vacuum degree reaches 0.67 Pa, the copper-free tin ingot is heated to 1200°C to melt and kept warm for 70 minutes, and then the gas is released, and the molten tin liquid is poured out, and high-purity tin is obtained after cooling.

[0034] The high-purity tin prepared in this example was subjected to glow discharge mass spectrometry (GDMS) detection. The results are shown in Table 2, in ppm, where 4NSn (99.99) represents a tin sample with a purity of 4N, 5NSn (99.999) represents a tin sample with a purity of 5N, and 6NSn (99.9999) represents a tin sample with a purity of 6N.

[0035] Table 2

[0036] It can be seen from Table 2 that the chemical composition of the high-purity tin prepared by electrolytic refining coupled with vacuum distillation technology in this embodiment meets the standard of 5N high-purity tin, and the content of lead and bismuth is less than 1ppm, and the content of uranium and thorium is less than 1ppb, indicating that the prepared high-purity tin meets the requirements of low α-ray dose materials.

[0037] Example 3 This embodiment includes the following steps: Step 1, liquid preparation: 4N crude tin is placed in a crucible, and heated in a muffle furnace to melt, and then water-extracted to obtain tin beads, and then 33g of tin beads are added to 36mL of a 9mol / L dilute sulfuric acid solution and heated in a 90°C oil bath to dissolve for 48h until the tin no longer dissolves, the solution is poured out, and 50mL of deionized water is used to heat the residue together to extract the remaining stannous sulfate, and finally the two parts of the solution are combined and solid-liquid separation is performed using a nylon filter bag to obtain a stannous sulfate solution; Step 2: Preparation of electrolyte: Add concentrated sulfuric acid, sodium benzenesulfonate, resveratrol, naphthol, gelatin, hydroquinone and deionized water to the stannous sulfate solution obtained in step 1 to obtain 1000 mL of electrolyte; the electrolyte comprises the following components: 60 g / L stannous sulfate, 160 g / L concentrated sulfuric acid, 20 g / L sodium benzenesulfonate, 0.08 g / L resveratrol, 0.5 g / L β-naphthol, 2.5 g / L gelatin, and 6 g / L hydroquinone; Step 3: Electrolysis: Add the electrolyte obtained in step 2 into the electrolytic cell, and then use the titanium plate as the cathode. Soak the 4N pure tin plate in a dilute hydrochloric acid solution, then wash it, and then put on a polyester bag as the anode. When the inter-electrode distance is 80mm and the cathode current density is 100A / m 2 , the cell voltage is 0.06V, the electrolysis temperature is 40°C, and cathode tin is obtained on the cathode; Step 4, copper removal and refining: the cathode tin obtained in step 3 is peeled off, soaked in HCl with a mass fraction of 5% for 2 minutes, then rinsed with deionized water, and then heated to melt. When it is close to melting, it is covered with NH4Cl. After the NH4Cl is completely volatilized, the slag is removed and cast, and the surface scum is scraped off with a bamboo piece in time during the casting process to obtain a 30g electrolytic tin ingot, and then stannous sulfide is added to the electrolytic tin ingot with a stoichiometric ratio of copper to stannous sulfide of 1:2, and the temperature is raised to 900°C for heating and stirring for 30 minutes. After cooling to 230°C, the scum is removed and cast, and the surface scum is scraped off with a bamboo piece in time during the casting process to obtain a copper-removed tin ingot; Step 5: Vacuum distillation: The copper-free tin ingot obtained in step 4 is placed in a graphite crucible of a vacuum distillation device, and then a mechanical pump is turned on to evacuate the vacuum distillation device to 15Pa, and then a diffusion pump is turned on to further evacuate the vacuum. After the vacuum degree reaches 0.5Pa, the copper-free tin ingot is heated to 1300°C to melt and kept warm for 60 minutes, and then the gas is released, and the molten tin liquid is poured out, and high-purity tin is obtained after cooling.

[0038] The high-purity tin prepared in this example was subjected to glow discharge mass spectrometry (GDMS) detection. The results are shown in Table 3, and the unit is ppm, wherein 4NSn (99.99) represents a tin sample with a purity of 4N, 5NSn (99.999) represents a tin sample with a purity of 5N, and 6NSn (99.9999) represents a tin sample with a purity of 6N.

[0039] Table 3

[0040] As can be seen from Table 3, the lead content in the high-purity tin prepared by electrolytic refining coupled with vacuum distillation technology in this embodiment does not meet the standard of 6N high-purity tin, but meets the standard of 5N high-purity tin, and the other chemical components all meet the standard of 6N high-purity tin, and the lead and bismuth contents are both less than 1ppm, and the uranium and thorium contents are both less than 1ppb, indicating that the prepared tin meets the requirements of low α-ray dosage materials.

[0041] Example 4 This embodiment includes the following steps: Step 1, liquid preparation: Place 4N crude tin in a crucible and heat it in a muffle furnace to melt it, then extract it with water to obtain tin beads, then add 33g of tin beads to 36mL of 9mol / L dilute sulfuric acid solution and heat it in a 95℃ oil bath to dissolve it for 36h until the tin no longer dissolves, pour out the solution, and heat it with 50mL of deionized water together with the residue to extract the remaining stannous sulfate, finally combine the two parts of the solution and use a filter press with a filtration pressure of 0.4MPa and a compression pressure of 0.7MPa. The filter cloth is made of polypropylene and has an air permeability of 100cm 3 / cm 2 / min to perform solid-liquid separation to obtain stannous sulfate solution; Step 2: Preparation of electrolyte: Add concentrated sulfuric acid, sodium benzenesulfonate, resveratrol, naphthol, gelatin, hydroquinone and deionized water to the stannous sulfate solution obtained in step 1 to obtain 1000 mL of electrolyte; the electrolyte comprises the following components: 60 g / L stannous sulfate, 160 g / L concentrated sulfuric acid, 40 g / L sodium benzenesulfonate, 0.1 g / L resveratrol, 0.8 g / L β-naphthol, 3.2 g / L gelatin, and 6 g / L hydroquinone; Step 3: Electrolysis: Add the electrolyte obtained in step 2 into the electrolytic cell, and then use the titanium plate as the cathode. Soak the 4N pure tin plate in a dilute hydrochloric acid solution, then wash it, and then put on a polyester bag as the anode. When the inter-electrode distance is 80mm and the cathode current density is 100A / m 2 , the cell voltage is 0.06V, the electrolysis temperature is 35°C, and cathode tin is obtained on the cathode; Step 4, copper removal and refining: the cathode tin obtained in step 3 is peeled off, soaked in HCl with a mass fraction of 5% for 2 minutes, then rinsed with deionized water, and then heated to melt. When it is close to melting, it is covered with NH4Cl. After the NH4Cl is completely volatilized, the slag is removed and cast, and the surface scum is scraped off with a bamboo piece in time during the casting process to obtain a 30g electrolytic tin ingot, and then stannous sulfide is added to the electrolytic tin ingot with a stoichiometric ratio of copper to stannous sulfide of 1:2, and the temperature is raised to 900°C for heating and stirring for 30 minutes. After cooling to 230°C, the scum is removed and cast, and the surface scum is scraped off with a bamboo piece in time during the casting process to obtain a copper-removed tin ingot; Step 5: Vacuum distillation: The copper-free tin ingot obtained in step 4 is placed in a graphite crucible of a vacuum distillation device, and then a mechanical pump is turned on to evacuate the vacuum distillation device to 15Pa, and then a diffusion pump is turned on to further evacuate the vacuum. After the vacuum degree reaches 0.1Pa, the copper-free tin ingot is heated to 1300°C to melt and kept warm for 60min, and then the gas is released, and the molten tin liquid is poured out, and high-purity tin is obtained after cooling.

[0042] The high-purity tin prepared in this example was subjected to glow discharge mass spectrometry (GDMS) detection. The results are shown in Table 4, in ppm, where 4NSn (99.99) represents a tin sample with a purity of 4N, 5NSn (99.999) represents a tin sample with a purity of 5N, and 6NSn (99.9999) represents a tin sample with a purity of 6N.

[0043] Table 4

[0044] It can be seen from Table 4 that the chemical composition of the high-purity tin prepared by electrolytic refining coupled with vacuum distillation technology in this embodiment meets the standard of 6N high-purity tin, and the content of lead and bismuth is less than 1ppm, and the content of uranium and thorium is less than 1ppb, indicating that the prepared high-purity tin meets the requirements of low α-ray dose materials.

[0045] Example 5 The difference between this embodiment and embodiment 4 is that: the mechanical pump is turned on to evacuate the vacuum distillation equipment to 10Pa, and then the diffusion pump is turned on to further evacuate the vacuum. After the vacuum degree reaches 0.001Pa, the copper-removing tin ingot is heated to 1000°C to melt and keep warm for 120 minutes.

[0046] Example 6 The difference between this embodiment and embodiment 4 is that: the mechanical pump is turned on to evacuate the vacuum distillation equipment to 15Pa, and then the diffusion pump is turned on to further evacuate the vacuum. After the vacuum degree reaches 10Pa, the copper-removing tin ingot is heated to 1600°C to melt and keep warm for 60 minutes.

[0047] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation, characterized in that: The method comprises the following steps: Step 1, liquid preparation: heat and melt 2N~4N crude tin, then extract with water to obtain tin beads, then add the tin beads to a dilute sulfuric acid solution and heat to dissolve, and finally perform solid-liquid separation to obtain a stannous sulfate solution; Step 2, preparation of electrolyte: adding concentrated sulfuric acid, benzenesulfonate, resveratrol, naphthol, gelatin, hydroquinone and deionized water to the stannous sulfate solution obtained in step 1 to obtain an electrolyte; the electrolyte comprises the following components: 40g / L~60g / L stannous sulfate, 120g / L~160g / L concentrated sulfuric acid, 8g / L~20g / L benzenesulfonate, 0.03g / L~0.08g / L resveratrol, 0.2g / L~0.5g / L β-naphthol, 1.0g / L~2.5g / L gelatin, 4g / L~6g / L hydroquinone; Step 3: Electrolysis: Add the electrolyte obtained in step 2 into the electrolytic cell, and then use the titanium plate as the cathode and the coarse tin plate as the anode. The cathode current density is 60A / m 2 ~100A / m 2 , the cell voltage is 0.04V~0.06V, and the electrolysis temperature is 20℃~40℃, and cathode tin is obtained on the cathode; Step 4, copper removal and refining: the cathode tin obtained in step 3 is peeled off, then cleaned, and then heated and melted. When it is nearly melted, it is covered with NH4Cl. After all the NH4Cl is volatilized, the slag is removed and cast to obtain an electrolytic tin ingot. Then, stannous sulfide is added to the electrolytic tin ingot, and then heated and stirred. After cooling, the slag is removed and cast to obtain a copper-removed tin ingot. Step 5, vacuum distillation: put the copper-free tin ingot obtained in step 4 into the graphite crucible of the vacuum distillation equipment, then turn on the mechanical pump to evacuate the vacuum distillation equipment, and then turn on the diffusion pump to further evacuate the vacuum. After reaching the vacuum degree requirement, heat the copper-free tin ingot to melt and keep it warm, then release the gas, pour out the molten tin liquid, and obtain high-purity tin after cooling.

2. The method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation according to claim 1, characterized in that: The concentration of the dilute sulfuric acid in step 1 is 9 mol / L, and the heating and dissolving is carried out in an oil bath at 90° C. to 100° C. for 24 h to 48 h.

3. The method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation according to claim 1, characterized in that: The solid-liquid separation in step 1 is carried out by using a filter press, a polyester bag or a nylon filter bag. When using a filter press, the filtration pressure is 0.4MPa, the compression pressure is 0.7MPa, the filter cloth is made of polypropylene, and the air permeability of the filter cloth is 100cm 3 / cm 2 / min.

4. The method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation according to claim 1, characterized in that: The benzenesulfonate described in step 2 is sodium benzenesulfonate and / or calcium benzenesulfonate.

5. The method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation according to claim 1, characterized in that: The material of the cathode in step three can also be stainless steel or graphite. The purity of the crude tin plate is 2N~4N. The crude tin plate is soaked in a dilute hydrochloric acid solution before electrolysis, then washed, and then covered with a polyester bag.

6. The method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation according to claim 1, characterized in that: The cleaning process in step 4 is: soaking in 5% HCl for 2 minutes, and then rinsing with deionized water.

7. The method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation according to claim 1, characterized in that: During the casting process described in step 4, use a bamboo stick to scrape off the surface scum in time.

8. The method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation according to claim 1, characterized in that: The temperature of the heating and stirring in step 4 is 900° C., the time is 30 min, and the cooling is to 230° C.

9. The method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation according to claim 1, characterized in that: The vacuum degree in step five is required to be 0.001Pa~10Pa, the heating and melting temperature is 1000℃~1600℃, and the insulation time is 60min~120min.

10. The method for removing metal impurities by electrolysis of tin benzenesulfonate coupled with vacuum distillation according to claim 1, characterized in that: The chemical composition of the high-purity tin in step 5 meets the standard of 5N or 6N high-purity tin, and the content of lead and bismuth elements are both less than 1ppm, and the content of uranium and thorium elements are both less than 1ppb. The high-purity tin meets the requirements of low α-ray dosage materials.

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