Method for preparing 5N selenium powder

Abstract

The invention discloses a method for preparing 5N selenium powder, which specifically comprises the following steps: carrying out oxidation treatment on a crude selenium raw material to be treated to obtain selenium dioxide; dissolving the obtained selenium dioxide at normal temperature to obtain a seleninic acid solution; and carrying out cascade reduction reaction on the obtained seleninic acid solution under the action of an external magnetic field to obtain nano-scale selenium powder, and washing and drying the nano-scale selenium powder to obtain the 5N selenium powder. According to the method, the oxidation-reduction potential is controlled to rise in a stepped manner, and the external magnetic field is used for assistance, so that the oxidation-reduction reaction of selenium is adjusted, forward proceeding of the selenium reduction reaction is promoted, the whole preparation process is short, the selenium purity is high, and the direct yield of selenium is high.

Description

Technical Field

[0001] The present invention relates to the field of preparation of high-purity metals, and particularly to a method for preparing 5N selenium powder. Background Art

[0002] Selenium is an important rare and dispersed metal. Due to its excellent properties, it is widely used in the metallurgical industry, new energy, semiconductors, electronics industry, glass, and health care fields. In recent years, with the rapid development of industries such as the electronics industry and new energy, the demand for high-purity selenium materials in the electronics industry and others has shown an explosive growth. Therefore, for the smelting industry, how to further purify the crude selenium extracted from anode slime is of great strategic significance for the further application of selenium products.

[0003] Currently, the mainstream process for selenium purification is through vacuum distillation / oxidative distillation. If high-purity selenium (purity ≧ 99.999%) is to be purified from crude selenium raw materials, the vacuum distillation method is usually combined with the chemical method. Since selenium and tellurium have similar properties, most of the existing technologies require the raw materials to go through a relatively complex pretreatment stage and use the vacuum distillation process to repeatedly purify the raw materials to obtain products that meet the requirements, and the process flow is relatively long. There are also technologies that obtain 5N selenium powder through a two-step method of melting and vapor-phase distillation, but the raw materials used in this method are 4N selenium, which has relatively high requirements for the purity of the raw materials.

[0004] In summary, the existing high-purity selenium purification processes generally have defects such as long process flow, difficult separation of selenium and tellurium, and low direct recovery rate of selenium. Summary of the Invention

[0005] Aiming at the difficulties of the existing technology, the present invention aims to provide a method for preparing 5N selenium powder, overcoming the defects such as long process flow for crude selenium purification, difficult separation of selenium and tellurium, and low direct recovery rate of selenium.

[0006] To achieve the above object, the technical solution of the present invention is: a method for preparing 5N selenium powder, which specifically includes the following steps:

[0007] S1) Oxidize the crude selenium raw material to be processed to obtain selenium dioxide;

[0008] S2) Dissolve the selenium dioxide obtained in S1) at room temperature to obtain a selenious acid solution;

[0009] S3) Perform a stepwise reduction reaction on the selenious acid solution obtained in S2) under the action of an external magnetic field to obtain nanoscale selenium powder, which is washed and dried to obtain 5N selenium powder.

[0010] Further, the oxidation process in S1) is specifically: the oxidation of crude selenium is carried out in an oxidation furnace, the oxidation atmosphere is oxygen, the oxygen flow rate is 2.5 - 15m 3 / h, and the oxidation temperature is 450°C - 600°C.

[0011] Further, the purity of the selenium dioxide is 99% - 99.9%.

[0012] Further, in the step S2), the solvent is pure water, the redox potential during dissolution is 260 - 350 mV; the selenium concentration in the obtained selenious acid solution is 5% - 30%.

[0013] Further, the specific process of the step S3) is as follows: it is carried out under an external magnetic field and assisted by weak ultrasound, the reaction temperature is normal temperature, the external magnetic field strength is: 0.05 T - 0.2 T, and the ultrasonic power is 100 - 400 W;

[0014] The reducing agent used in the stepwise reduction reaction is SO 2 gas.

[0015] Further, the specific process of the stepwise reduction is as follows: control the feeding rate of the SO 2 gas to be 40 - 150 mL / min. Every time the potential rises by 20 - 25 mV, pure water and selenious acid are replenished into the reactor. The amount of water replenished each time is 40 - 100 mL, and the replenishment amount of selenious acid is 1 - 5 g per liter of water. When the potential rises to 400 - 425 mV, control the feeding rate of sulfur dioxide to be 10 - 40 mL / min. After the potential is stable for 20 - 30 min, stop feeding sulfur dioxide, control the temperature to be 35 - 80 °C, and continue the reaction for 1.5 - 3 h to obtain black selenium powder.

[0016] Further, the purity of the SO 2 gas is 99.99% - 99.9999%.

[0017] Further, the purity of the 5N selenium powder obtained by the method meets the YS / T 816 - 2012 high-purity selenium standard, and the particle size of the selenium powder is uniform, being 100 - 150 nm.

[0018] A 5N selenium powder, which is prepared by the above method.

[0019] The present invention has the following beneficial effects:

[0020] (1) By intermittently replenishing water, the present invention controls the stepwise rise of the redox potential and effectively inhibits the rise of acidity to a certain extent, thereby improving the utilization efficiency of the reducing agent.

[0021] (2) By applying an external magnetic field, first, the diffusion of tetravalent selenium ions and sulfite ions in the solution is accelerated under the action of the Lorentz force, and more free radicals are generated by ultrasonic oscillation. Under the induction of the external magnetic field, through the interaction with the quantum spin state of paramagnetic free radicals, the redox reaction of selenium is regulated, and the forward progress of the selenium reduction reaction is promoted, greatly improving the direct recovery rate of selenium.

[0022] (3) The synergistic induction effect of the external magnetic field and ultrasound can effectively overcome the agglomeration of selenium particles and eliminate the situation of impurity wrapping during the reduction process, which is beneficial to forming selenium nanopowder with uniform particle size. Description of the Drawings

[0023] Figure 1 It is a flowchart of the method for preparing 5N selenium powder by the potentiostatic method of the present invention. Detailed Embodiments

[0024] The technical solution of the present invention will be further described below in conjunction with the drawings and specific embodiments.

[0025] As Figure 1 shown, a method for preparing 5N selenium powder of the present invention specifically includes the following steps:

[0026] S1) Coarse selenium oxidation: Oxidize the coarse selenium raw material to obtain selenium dioxide.

[0027] S2) Selenium dioxide dissolution: Dissolve the selenium dioxide obtained in S1) in pure water to obtain selenious acid solution.

[0028] S3) Magnetic field-induced stepwise reduction: Perform a stepwise reduction reaction on the selenious acid solution under the action of an external magnetic field, and obtain high-purity 5N selenium powder after washing and drying the obtained nano-scale selenium powder.

[0029] Preferably, the coarse selenium oxidation is carried out in an oxidation furnace, the atmosphere in the oxidation furnace is oxygen, the oxygen flow rate is set to 2.5 - 15 m 3 / h, and the oxidation temperature is 450°C - 600°C. Selenium dioxide with a purity of 99% - 99.9% is obtained in this step.

[0030] Preferably, the selenium dioxide dissolution process is carried out at room temperature, and the selenium concentration in the formed selenious acid solution is 5% - 30%, and the oxidation-reduction potential is 260 - 350 mV.

[0031] Preferably, the reducing agent for the stepwise reduction reaction is SO 2 gas, and the gas purity is 99.99% - 99.9999%.

[0032] Preferably, the reduction reaction is carried out under an external magnetic field and assisted by weak ultrasound. The external magnetic field strength is: 0.05 T - 0.2 T, the ultrasound power is 100 - 400 W, and the reaction temperature is room temperature. Through the external magnetic field, first, the diffusion of tetravalent selenium ions and sulfite ions in the solution is accelerated under the action of the Lorentz force to accelerate the forward progress of the oxidation-reduction reaction; second, the interaction of the quantum spin states of paramagnetic free radicals is adjusted and the reaction energy barrier is reduced to improve the reaction efficiency.

[0033] Preferably, the specific process of stepwise reduction is as follows: control the 2 introduction rate of SO₂ gas to be 40 - 150 mL / min. Every time the potential increases by 20 - 25 mV, pure water and selenious acid are added to the reactor, and the amount of water added each time is 40 - 100 mL, so as to slow down the rising rate of the potential. When the potential increases to 400 - 425 mV, control the introduction rate of sulfur dioxide to be 10 - 40 mL / min. After the potential is stable for 20 - 30 min, stop introducing sulfur dioxide. Control the temperature to be 35 - 80 °C and continue the reaction for 1.5 - 3 h to obtain black selenium powder;

[0034] Preferably, wash the reduced selenium powder with pure water until it is neutral, and then dry it to obtain nano-scale selenium powder. The purity of the selenium powder meets the YS / T816—2012 high-purity selenium standard, and the particle size of the selenium powder is uniform, being 100 - 150 nm.

[0035] Example 1

[0036] The present invention provides a method for preparing 5N selenium powder by controlling the potential method, which includes the following steps:

[0037] Feed the crude selenium raw material into an oxidation furnace. The purity of the crude selenium is 98.3%. Feed oxygen into the oxidation furnace, and the oxygen flow rate is 9.3 m 3 / h, and the oxidation temperature is 550 °C to obtain selenium dioxide powder. The purity of the selenium dioxide powder is 99.3%;

[0038] Table 1 Component content of selenium dioxide (ppm)

[0039]

[0040] Take 145 g of selenium dioxide and dissolve it in 2 L of pure water to obtain a selenious acid solution. The selenium concentration is 8%, and the oxidation-reduction potential is 300 mV;

[0041] Stir the selenious acid solution with ultrasonic waves. Set the ultrasonic power to 120 W and apply an auxiliary magnetic field with a magnetic field strength of 0.05 T. Feed sulfur dioxide gas into the solution. Control the initial ventilation rate to be 100 mL / min. At this time, as SO₂ 2 is introduced, the potential increases. When the potential increases to 325 mV, add pure water to the beaker to make the potential stable for 10 - 15 min, and then add 5 g of selenious acid. After that, every time the potential increases by 20 mV, continue to add water and selenious acid until the potential increases to 410 mV. Then reduce the sulfur dioxide ventilation rate to 40 mL / min and continue the reaction for 30 min, and then stop introducing sulfur dioxide;

[0042] After heating to 55 °C, a constant-temperature reaction was carried out for 2 h. After washing and drying at 40 °C, selenium powder was obtained. The direct recovery rate of selenium was 87.16%, the purity of the selenium powder was greater than 99.999%, the impurity content met the YS / T 816—2012 high-purity selenium standard, and the particle size of the selenium powder was uniform, being 130 - 150 nm.

[0043] Table 2 Component contents of selenium powder (ppm)

[0044]

[0045] Example 2

[0046] Take 280 g of selenium dioxide and dissolve it in 2 L of pure water to obtain a selenious acid solution with a selenium concentration of 10% and a redox potential of 325 mV.

[0047] The selenious acid solution was stirred ultrasonically with an ultrasonic power set to 200 W, an auxiliary magnetic field was applied with a magnetic field intensity of 0.1 T, and sulfur dioxide gas was introduced into the solution. The ventilation rate was initially controlled at 80 mL / min. At this time, as SO 2 was introduced, the potential increased. When the potential increased to 350 mV, pure water was added to the beaker to stabilize the potential for 10 - 15 min, and 3 g of selenious acid was added. Thereafter, every time the potential increased by 20 mV, more water and selenious acid were added until the potential increased to 415 - 420 mV. Then the sulfur dioxide ventilation rate was reduced to 30 mL / min, and the reaction continued for 30 min. Then the introduction of sulfur dioxide was stopped.

[0048] After heating to 55 °C, a constant-temperature reaction was carried out for 2 h. After washing and drying at 40 °C, selenium powder was obtained. The direct recovery rate of selenium was 89.06%, the purity of the selenium powder was greater than 99.999%, the impurity content met the YS / T 816—2012 high-purity selenium standard Se99.999 grade, and the particle size of the selenium powder was uniform, being 100 - 110 nm.

[0049] Table 3 Component contents of selenium powder (ppm)

[0050]

[0051] Example 3

[0052] Take 340 g of selenium dioxide and dissolve it in 2 L of pure water to obtain a selenious acid solution with a selenium concentration of 12% and a redox potential of 330 mV.

[0053] The selenious acid solution was stirred ultrasonically with an ultrasonic power set to 250 W, an auxiliary magnetic field was applied with a magnetic field intensity of 0.18 T, and sulfur dioxide gas was introduced into the solution. The ventilation rate was initially controlled at 140 mL / min. At this time, as SO 2Introduce, the potential increases. When the potential increases to 350 mV, add pure water into the beaker to make the potential stable for 10 - 15 min, and then add 3 g of selenious acid. After that, every time the potential increases by 20 mV, continue to add water and selenious acid until the potential increases to 415 - 420 mV. Then reduce the sulfur dioxide ventilation rate to 40 mL / min, continue the reaction for 30 min, and then stop introducing sulfur dioxide;

[0054] After heating to 55 °C, keep the temperature constant and react for 2 h. After washing and drying at 40 °C, selenium powder is obtained. The direct recovery rate of selenium is 83.08%, the purity of the selenium powder is greater than 99.999%, the impurity content meets the YS / T 816—2012 high-purity selenium standard, and the particle size of the selenium powder is uniform, being 130 - 140 nm.

[0055] Table 4 Component contents of selenium powder (ppm)

[0056]

[0057] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing 5N selenium powder, characterized in that: The method specifically comprises the following steps: S1) oxidizing the crude selenium raw material to be treated to obtain selenium dioxide; S2) dissolving the selenium dioxide obtained in S1) at room temperature to obtain a selenious acid solution; S3) subjecting the selenious acid solution obtained in S2) to a step reduction reaction under the action of an external magnetic field to obtain nano-selenium powder, which is then washed and dried to obtain 5N selenium powder.

2. The method according to claim 1, characterized in that The oxidation process in S1) is specifically as follows: the crude selenium is oxidized in an oxidation furnace, the oxidizing atmosphere is oxygen, and the oxygen flow rate is 2.5-15m 3 / h, the oxidation temperature is 450℃~600℃.

3. The method according to claim 2, characterized in that The purity of the selenium dioxide is 99% to 99.9%.

4. The method according to claim 1, characterized in that: The solvent in S2) is pure water, and the redox potential during dissolution is 260-350 mV; the selenium concentration in the obtained selenious acid solution is 5%-30%.

5. The method according to claim 1, characterized in that: The specific process of S3) is: carried out under an external magnetic field and assisted by weak ultrasound, the reaction temperature is room temperature, the external magnetic field strength is: 0.05T~0.2T, and the ultrasonic power is 100~400W; The reducing agent used in the cascade reduction reaction is SO2 gas.

6. The method according to claim 5, characterized in that The specific process of the step reduction is: controlling the introduction rate of SO2 gas to 40-150mL / min, adding pure water and selenious acid to the reactor every time the potential increases by 20-25mV, the amount of water added each time is 40-100mL, and the amount of selenious acid added is 1-5g per liter of water. When the potential increases to 400-425mV, controlling the introduction rate of sulfur dioxide to 10-40mL / min, stopping the introduction of sulfur dioxide after the potential is stable for 20-30min, controlling the temperature to 35-80°C, and continuing the reaction for 1.5-3h to obtain black selenium powder.

7. The method according to claim 5, characterized in that The purity of the SO2 gas is 99.99% to 99.9999%.

8. The method according to claim 1, characterized in that: The purity of the 5N selenium powder obtained by the method meets the YS / T816-2012 high-purity selenium standard, and the particle size of the selenium powder is uniform and is 100-150nm.

9. A 5N selenium powder, characterized in that: The 5N selenium powder is prepared by the method according to any one of claims 1 to 8.

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