A method for purifying crude selenium by vacuum refining

Abstract

The application discloses a method for refining and purifying crude selenium in a vacuum, and belongs to the field of purification of dispersed metals. The method comprises the following steps: mixing crude selenium raw materials with Pb or Cu to obtain a molten product; and performing vacuum distillation on the molten product to remove volatile matters and obtain refined selenium products with a purity higher than 99%. The method utilizes the difference between saturated vapor pressures to remove metal impurities, and is performed under a vacuum condition, so that the method is green, efficient, low in cost and simple in process.

Description

Technical Field

[0001] This invention belongs to the field of rare and dispersed metal purification technology, specifically relating to a method for vacuum refining and purifying crude selenium. Background Technology

[0002] Selenium is a strategic metal supporting the development of high-tech fields and a key raw material for the preparation of new materials. Crude selenium is mainly extracted through the sulfation roasting of anode mud. After roasting, selenium dioxide is obtained, which is absorbed by water to form a selenite solution. Finally, sulfur dioxide is introduced for reduction to obtain crude selenium powder. The resulting crude selenium has low purity and requires purification processes to obtain refined selenium-grade products. Currently, purification methods for crude selenium include vacuum distillation, zone melting, oxidative volatilization, and combined methods. Vacuum distillation is a highly efficient purification process that, compared with traditional purification processes, has advantages such as a shorter process flow, higher direct metal recovery rate, no need for chemical reagents, and simple operation.

[0003] Patent application CN106946233A discloses a method for vacuum refining and purifying crude selenium. The method mainly involves melting the selenium at 230~350℃, then heating it to 250~400℃ to degas and vacuuming it after complete melting. The resulting selenium melt is then vacuum distilled at 1~20Pa and 500~1000℃ to obtain 99.9% pure selenium. This process requires repeated heating and is quite lengthy.

[0004] Patent application CN116617693A discloses a method for purifying selenium by vacuum distillation. The method mainly involves uniformly mixing crude selenium raw material with elemental sulfur to obtain a mixture, drying it, and then uniformly mixing it with hydrogen peroxide. The resulting material is then vacuum distilled and sulfided for a period of time. After distillation, high-purity selenium ingots with a selenium purity greater than 99.99% can be obtained. This process has high purification efficiency and can purify 99% selenium to more than 99.99%, but the process is lengthy.

[0005] Patent CN115321492A discloses a method for purifying selenium by leaching under normal pressure. The method involves leaching, filtration, reduction, precipitation and washing to obtain 3N refined selenium. The process is relatively complex and uses a large amount of chemical reagents, which puts a certain pressure on the environment. Summary of the Invention

[0006] To address the shortcomings of the prior art, this invention provides a method for vacuum refining and purifying crude selenium.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for vacuum refining and purifying crude selenium includes the following steps:

[0009] (1) The crude selenium raw material is mixed with high-purity metal and melted to obtain the melt product;

[0010] (2) Vacuum distill the molten product to remove the volatiles and obtain the refined selenium product;

[0011] The high-purity metal is Pb or Cu, with a purity greater than 99.9%.

[0012] As a preferred embodiment of the present invention, the crude selenium raw material comprises the following elements in mass percentage: 92~97% Se, 2~5% Te, 0.8~1.2% Pb, 0.5~0.9% Cu, with the balance being trace elements Fe, S, Bi, As and Sb.

[0013] The crude selenium raw material described in this invention contains Te, Pb, Cu, as well as trace elements Fe, S, Bi, As, and Sb. This means that high-purity selenium cannot be purified by vacuum distillation alone using the difference in saturated vapor pressure. Furthermore, adding high-purity metals such as Pb or Cu during vacuum distillation does not purify the selenium.

[0014] In a preferred embodiment of the present invention, the mass ratio of the crude selenium raw material to the high-purity metal is 10:(2-5).

[0015] Adding too much high-purity metal will reduce the selenium recovery rate, while adding too little will reduce the selenium purity. The vacuum refining and purification of crude selenium described in this invention yields refined selenium with a purity of 99.9%~99.98%, and the selenium product recovery rate is 80%~95%.

[0016] In a preferred embodiment of the present invention, the melting temperature is 225-280°C and the melting time is 60-120 min.

[0017] In a preferred embodiment of the present invention, the vacuum distillation pressure is 1-10 Pa, the temperature is 270-320 °C, and the time is 60-120 min.

[0018] Compared with existing technologies, the beneficial effects of this invention are as follows: Before vacuum distillation, the crude selenium raw material is smelted with high-purity metal Pb or Cu. Pb or Cu can react with the Te impurities in the crude selenium raw material, and the resulting compound does not volatilize during vacuum distillation. Furthermore, the smelting process does not affect the vacuum distillation purification of selenium, thus achieving the goal of improving the purity of the refined selenium product without reducing the selenium recovery rate. This method is carried out under vacuum conditions and has advantages such as being green, efficient, low-cost, and simple in process. Detailed Implementation

[0019] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0020] Example 1

[0021] A method for vacuum refining and purifying crude selenium includes the following steps:

[0022] (1) 10g of crude selenium raw material (Se mass fraction of 94.52%, Te mass fraction of 3.51%, Pb mass fraction of 0.96%, Cu mass fraction of 0.56%, and the remainder being trace impurity elements Fe, S, Bi, As and Sb) was mixed with 2.5g of high-purity metal Pb and placed in a crucible for melting. The melting temperature was 230℃ and the melting time was 120min. After the melting was completed, the melted product was obtained.

[0023] (2) Place the molten product in a vacuum distillation furnace and perform vacuum distillation under the conditions of system pressure of 1~10Pa, distillation temperature of 280℃ and distillation time of 60min. After distillation, remove the volatiles to obtain the refined selenium product.

[0024] In accordance with the provisions of the People's Republic of China Nonferrous Metals Industry Standard YS / T223-2007, the purity of the selenium product was quantitatively analyzed by ICP-AES and chemical titration, and was found to be 99.912%.

[0025] Example 2

[0026] A method for vacuum refining and purifying crude selenium includes the following steps:

[0027] (1) 10g of crude selenium raw material (Se mass fraction of 95.18%, Te mass fraction of 2.75%, Pb mass fraction of 0.88%, Cu mass fraction of 0.65%, and the remainder being trace impurity elements Fe, S, Bi, As and Sb) was mixed with 3g of high-purity metal Pb and placed in a crucible for melting. The melting temperature was 250℃ and the melting time was 100min. After the melting was completed, the melted product was obtained.

[0028] (2) Place the molten product in a vacuum distillation furnace and perform vacuum distillation under the conditions of system pressure of 1~10Pa, distillation temperature of 300℃ and distillation time of 90min. After the distillation is completed, remove the volatiles to obtain the refined selenium product.

[0029] In accordance with the provisions of the People's Republic of China Nonferrous Metals Industry Standard YS / T223-2007, the purity of the selenium product was quantitatively analyzed by ICP-AES and chemical titration, and was found to be 99.933%.

[0030] Example 3

[0031] A method for vacuum refining and purifying crude selenium includes the following steps:

[0032] (1) 10g of crude selenium raw material (Se mass fraction of 96.18%, Te mass fraction of 2.12%, Pb mass fraction of 1.02%, Cu mass fraction of 0.61%, the remainder being trace impurity elements Fe, S, Bi, As and Sb) was mixed with 4g of high-purity metal Pb and placed in a crucible for melting. The melting temperature was 280℃ and the melting time was 70min. After the melting was completed, the melted product was obtained.

[0033] (2) Place the molten product in a vacuum distillation furnace and perform vacuum distillation under the conditions of system pressure of 1~10Pa, distillation temperature of 320℃ and distillation time of 100min. After the distillation is completed, remove the volatiles to obtain the refined selenium product.

[0034] In accordance with the provisions of the People's Republic of China Nonferrous Metals Industry Standard YS / T223-2007, the purity of the selenium product was quantitatively analyzed by ICP-AES and chemical titration, and was found to be 99.945%.

[0035] Example 4

[0036] A method for vacuum refining and purifying crude selenium includes the following steps:

[0037] (1) 10g of crude selenium raw material (Se mass fraction of 94.52%, Te mass fraction of 3.51%, Pb mass fraction of 0.96%, Cu mass fraction of 0.56%, the rest being trace impurity elements) was mixed with 5g of high-purity metal Cu and placed in a crucible for melting. The melting temperature was 225℃ and the melting time was 120min. After the melting was completed, the melted product was obtained.

[0038] (2) Place the molten product in a vacuum distillation furnace and perform vacuum distillation under the conditions of system pressure of 1~10Pa, distillation temperature of 270℃ and distillation time of 120min. After distillation, remove the volatiles to obtain the refined selenium product.

[0039] In accordance with the provisions of the People's Republic of China Nonferrous Metals Industry Standard YS / T223-2007, the purity of the selenium product was quantitatively analyzed by ICP-AES and chemical titration, and was found to be 99.965%.

[0040] Comparative Example 1

[0041] A method for vacuum refining and purifying crude selenium includes the following steps:

[0042] 10g of crude selenium raw material (Se mass fraction 94.52%, Te mass fraction 3.51%, Pb mass fraction 0.96%, Cu mass fraction 0.56%, the remainder being trace impurity elements) was placed in a vacuum distillation furnace and vacuum distilled under the conditions of system pressure 1~10Pa, distillation temperature 280℃, and distillation time 60min. After distillation, the volatiles were removed to obtain the refined selenium product.

[0043] In accordance with the provisions of the People's Republic of China Nonferrous Metals Industry Standard YS / T223-2007, the purity of the selenium product was quantitatively analyzed by ICP-AES and chemical titration, and was found to be 97.135%.

[0044] Comparative Example 2

[0045] A method for vacuum refining and purifying crude selenium includes the following steps:

[0046] 10g of crude selenium raw material (Se mass fraction 95.18%, Te mass fraction 2.75%, Pb mass fraction 0.88%, Cu mass fraction 0.65%, the remainder being trace impurity elements) was placed in a vacuum distillation furnace and vacuum distilled under the conditions of system pressure 1~10Pa, distillation temperature 300℃, and distillation time 90min. After distillation, the volatiles were removed to obtain the refined selenium product.

[0047] In accordance with the provisions of the People's Republic of China Nonferrous Metals Industry Standard YS / T223-2007, the purity of the selenium product was quantitatively analyzed by ICP-AES and chemical titration, and was found to be 98.513%.

[0048] Comparative Example 3

[0049] A method for vacuum refining and purifying crude selenium includes the following steps:

[0050] 10g of crude selenium raw material (Se mass fraction 96.18%, Te mass fraction 2.12%, Pb mass fraction 1.02%, Cu mass fraction 0.61%, the remainder being trace impurity elements) was placed in a vacuum distillation furnace and vacuum distilled under the conditions of system pressure 1~10Pa, distillation temperature 320℃, and distillation time 100min. After distillation, the volatiles were removed to obtain the refined selenium product.

[0051] In accordance with the provisions of the People's Republic of China Nonferrous Metals Industry Standard YS / T223-2007, the purity of the selenium product was quantitatively analyzed by ICP-AES and chemical titration, and was found to be 98.915%.

[0052] Comparative Example 4

[0053] A method for vacuum refining and purifying crude selenium includes the following steps:

[0054] (1) 10g of crude selenium raw material (Se mass fraction of 94.52%, Te mass fraction of 3.51%, Pb mass fraction of 0.96%, Cu mass fraction of 0.56%, and the remainder being trace impurity elements) was placed in a crucible for melting at a temperature of 230℃ for 120min. After melting was completed, the melted product was obtained.

[0055] (2) Place the molten product in a vacuum distillation furnace and perform vacuum distillation under the conditions of system pressure of 1~10Pa, distillation temperature of 280℃ and distillation time of 60min. After distillation, remove the volatiles to obtain the refined selenium product.

[0056] In accordance with the provisions of the People's Republic of China Nonferrous Metals Industry Standard YS / T223-2007, the purity of the selenium product was quantitatively analyzed by ICP-AES and chemical titration, and was found to be 97.544%.

[0057] Comparative Example 5

[0058] A method for vacuum refining and purifying crude selenium includes the following steps:

[0059] (1) 10g of crude selenium raw material (Se mass fraction is 94.52%, Te mass fraction is 3.51%, Pb mass fraction is 0.96%, Cu mass fraction is 0.56%, and the rest are trace impurity elements) was mixed with 2.5g of high-purity metal Fe and placed in a crucible for melting. The melting temperature was 230℃ and the melting time was 120min. After the melting was completed, the melted product was obtained.

[0060] (2) Place the molten product in a vacuum distillation furnace and perform vacuum distillation under the conditions of system pressure of 1~20Pa, distillation temperature of 280℃ and distillation time of 60min. After the distillation is completed, remove the volatiles to obtain the refined selenium product.

[0061] In accordance with the provisions of the People's Republic of China Nonferrous Metals Industry Standard YS / T223-2007, the purity of the selenium product was quantitatively analyzed by ICP-AES and chemical titration, and was found to be 97.25%.

[0062] In this comparative example, Fe metal was smelted with crude selenium raw material. Fe did not react with Te in the crude selenium raw material, resulting in a decrease in the purity of the refined selenium product.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for vacuum refining and purifying crude selenium, characterized in that, Includes the following steps: (1) The crude selenium raw material is mixed with high-purity metal and melted to obtain the melt product; (2) Vacuum distill the molten product to remove the volatiles and obtain the refined selenium product; The high-purity metal is Pb or Cu with a purity greater than 99.9%; the mass ratio of the crude selenium raw material to the high-purity metal is 10:(2-5); the melting temperature is 225-280℃ and the melting time is 60-120min.

2. The method for vacuum refining and purifying crude selenium as described in claim 1, characterized in that, The crude selenium raw material comprises the following elements by mass percentage: 92-97% Se, 2-5% Te, 0.8-1.2% Pb, 0.5-0.9% Cu, with the balance being trace elements Fe, S, Bi, As and Sb.

3. The method for vacuum refining and purifying crude selenium as described in claim 1, characterized in that, The vacuum distillation process involves a pressure of 1-10 Pa, a temperature of 270-320 °C, and a time of 60-120 min.