A method for removing arsenic and purifying antimony chloride solution

Abstract

The present invention belongs to the technical field of purification, and particularly relates to a method for removing arsenic and purifying antimony chloride solution. The method includes: 1) adding a copper-antimony alloy to the to-be-treated crude antimony chloride solution containing arsenic in a protective atmosphere, and obtaining a low-arsenic antimony chloride solution after reaction; 2) distilling and concentrating the low-arsenic antimony chloride solution to obtain a high-purity antimony chloride solution. The present invention solves the technical problem of removing impurity arsenic in the preparation process of high-purity antimony. The distillation is carried out under low-temperature conditions, with simple operation, low energy consumption, simple preparation process flow, high production efficiency, easy implementation, no industrial pollution generated, and suitable for industrialization.

Description

Technical Field

[0001] The present invention belongs to the technical field of purification, and particularly relates to a method for removing arsenic and purifying antimony chloride solution. Background Art

[0002] Antimony is an important raw material indispensable in modern industrial production and is widely used in the production of various flame retardant materials, alloys, glass, semiconductor components, pharmaceutical chemicals, national defense and military industries, etc. It plays an extremely important role in ensuring the sustainable development of the national economy and has an irreplaceable strategic role in the development of China's industry. In recent years, with the rapid development of high-tech fields such as semiconductor manufacturing in China, the related research on high-purity antimony in China has attracted great attention. The antimony compounds semiconductors produced from high-purity antimony have good semiconductor properties. Their chemical bonds are mainly covalent bonds, and at the same time contain ionic bonds, forming hybrid bonds, which makes the selection range of basic parameters (band gap and carriers) wider and greatly improves the physical and chemical properties of semiconductor devices. For example, in the article "Antimonene Oxides: Emerging Tunable Direct Bandgap Semiconductor and Novel Topological Insulator" by Zhang Sheng-li, Zhou Wen-han, Ma Yan-dong, et al. in Nano Letters, 2017, 17(6): 3434-3440, it is recorded that antimonene oxides, as emerging tunable direct bandgap semiconductors, cover a wide range from 0 to 2.28 eV and have great potential in the applications of solar cells and photodetectors.

[0003] At present, the main methods for preparing high-purity antimony in China include chlorination distillation method, electrolysis method, vacuum distillation method, etc. However, there are many drawbacks in the process of producing high-purity antimony by the above methods.

[0004] The chlorination distillation method utilizes the boiling point temperature difference of chlorides to separate low-boiling impurities from the main phase of antimony trichloride, so as to achieve the purification effect. However, the existence forms of impurities in the hydrochloric acid medium are very complex, and the removal efficiency of impurity arsenic is relatively low during the distillation process. The residual arsenic content is still 50-500 ppm, and it is difficult to accurately control the arsenic content in the prepared high-purity metallic antimony.

[0005] The invention patent application of a method for producing high-purity antimony by two-stage molten salt electrolysis was published by the China Patent Office on January 28, 2015. The application publication number is CN104313643A, which includes the following steps: adding crushed antimony blocks and molten salt electrolyte to an electrolytic cell, wherein the electrolytic cell has a first graphite electrode and a second graphite electrode; firstly, electrolysis by anode method is performed, wherein the first electrode is set as an anode and the second electrode is set as a cathode. In the anode region, antimony and impurity metals lose electrons and become cations and enter the molten salt. Under the action of electric field and diffusion, they migrate to the cathode surface to obtain electrons, and impurity metals Na, K, Zn, Cd, Fe, Pb, Sn, Cu, and Ni with a standard electrode potential less than that of antimony are removed; then, electrolysis by cathode method is performed, wherein the first electrode is set as a cathode and the second electrode is set as an anode. The reduced antimony element is used as the cathode to remove non-metallic impurity elements As, S, and Bi. However, the technical solution of the invention has the problem that the reduction potentials of As(III) and Sb(III) at the cathode are close, and both will be deposited at the cathode at the same time during the electrolysis process. The impurity control effect in the prepared high-purity antimony is not ideal.

[0006] The vacuum distillation method for preparing high-purity metallic antimony uses industrial pure antimony ingots (2N) as raw materials, in which the arsenic content is 100ppm to 1000ppm. During the vacuum distillation process, arsenic is dissolved in the antimony matrix to form an arsenic-antimony alloy phase, which significantly reduces its saturated vapor pressure, making it difficult to quickly remove arsenic from the metallic antimony ingot by vacuum distillation. This process needs to be repeated many times to achieve the effect of deep arsenic removal. In addition, the separation coefficients of arsenic and antimony are similar, and regional smelting is also difficult to purify quickly.

[0007] In recent years, my country has increased its support for the research of high-purity metallic antimony. The newly released national standard for high-purity antimony (GB / T10117-2021) has re-regulated the content standards of typical impurities such as arsenic, lead and tin in high-purity antimony, especially the impurity arsenic that has a great impact on the purity of high-purity antimony in actual production. The newly announced national standard reduces the impurity arsenic content in 6N high-purity antimony from the original 0.3ppm to 0.1ppm, which poses a huge challenge to the existing domestic high-purity antimony production process. Therefore, a new technology for deep removal of arsenic from crude antimony chloride to prepare high-purity SbCl3 is studied to promote the scale and standardization of high-purity antimony production of 6N and above, which is of great strategic significance to the country's layout of the development of the semiconductor industry. Summary of the invention

[0008] The invention aims at solving the technical problem that arsenic inclusion in the existing high-purity antimony production process causes the purity of metallic antimony to be substandard, and provides a method for removing arsenic from an antimony chloride solution and purifying it.

[0009] The objects of the present invention are:

[0010] 1. It can simply and effectively realize the preparation of high-purity antimony chloride solution;

[0011] II. It is possible to quickly and effectively obtain high-purity antimony trichloride with a purity of more than 3N;

[0012] III. Through refined treatment, ultra-high-purity antimony trichloride with a purity of 5N and above can be obtained.

[0013] To achieve the above object, the present invention adopts the following technical solutions.

[0014] A method for purifying arsenic from an antimony chloride solution

[0015] The method includes:

[0016] 1) In a protective atmosphere, adding a copper-antimony alloy to the arsenic-containing crude antimony chloride solution to be treated, and obtaining a low-arsenic antimony chloride solution after the reaction;

[0017] 2) Distilling and concentrating the low-arsenic antimony chloride solution to obtain a high-purity antimony chloride solution.

[0018] Preferably,

[0019] The protective atmosphere in step 1) is a nitrogen atmosphere, and nitrogen is continuously introduced into the solution system during the reaction in step 1).

[0020] Preferably,

[0021] The reaction temperature in step 1) is controlled at 30-90 °C;

[0022] Stirring is carried out during the reaction, the stirring speed is controlled at 100-500 rpm, and the reaction time is 30-120 min.

[0023] Preferably,

[0024] The stoichiometric ratio of the copper content in the copper-antimony alloy in step 1) to the arsenic content in the arsenic-containing crude antimony chloride solution to be treated is (10-40):1.

[0025] Preferably,

[0026] The distillation temperature in step 2) is controlled at 160-180 °C during the distillation and concentration.

[0027] Preferably,

[0028] During the distillation and concentration process, the distilled gas sample contacts a heat source, the temperature of the heat source is controlled at ≥250 °C, and the distillation is terminated until no arsenic mirror is generated when the distilled gas sample contacts the heat source.

[0029] Preferably,

[0030] The high-purity antimony chloride solution obtained after the distillation and concentration in step 2) is subjected to secondary distillation and condensation to obtain high-purity antimony chloride.

[0031] Preferably,

[0032] The temperature of the secondary distillation is controlled at 220 - 240 °C.

[0033] Preferably,

[0034] In the condensation process, two-stage recovery is carried out. First, liquid antimony chloride is recovered at 160 - 180 °C, and then the liquid antimony chloride is cooled to ≤70 °C to recover high-purity antimony chloride.

[0035] Unless otherwise specified, the antimony chloride mentioned in the present invention is antimony trichloride (SbCl3).

[0036] For the present invention, the core lies in constructing a primary battery system in the crude solution system. The present invention specifically selects a copper-antimony alloy, and it is necessary to ensure that the antimony content in the alloy is 5 - 30 wt%. Since in the antimony chloride solution, when arsenic exists in the form of AsO + A primary battery structure can be formed due to the potential difference between the alloy phase region and the copper-rich region in the copper-antimony alloy. Among them, the copper-antimony phase micro-region in the alloy powder is negatively charged, which can promote the selective adsorption of arsenic ions in the solution. To avoid side reactions, the purity of the copper-antimony alloy also needs to reach 2N (99.0%) or above. The copper-antimony alloy powder is an intermetallic compound, and its potential changes. Compared with pure copper powder, the doping of antimony elements can effectively reduce the loss of Sb 3+ in the solution. Introducing a copper-antimony alloy powder with a purity of 2N or above can avoid introducing too many impurity elements. At the same time, the antimony in the copper-antimony alloy plays a crucial role in stably capturing As elements. When the antimony content is too low, As cannot be stably captured and removed, and the potential difference cannot be effectively formed. When the antimony content is too high, the primary battery effect of copper will be reduced, and the reaction efficiency is low and the removal is incomplete. It is also necessary to control the stoichiometric ratio of the copper content in the copper-antimony alloy to the arsenic content in the arsenic-containing crude antimony chloride solution to be treated. In the present invention, the stoichiometric ratio means that for every 1 mol of arsenic element in the crude antimony chloride solution, 1.0 mol of copper needs to be provided by the copper-antimony alloy. If the stoichiometric ratio is too small, the reaction is incomplete and the efficiency is low. If the stoichiometric ratio is too high, the loss of antimony elements in the crude antimony chloride solution will increase, and side reactions are likely to occur.

[0037] In addition, the mesh number of the copper-antimony alloy powder should preferably be 100 - 800 meshes. If the powder is too fine, the alloy powder will float on the upper layer, and the displacement reaction cannot proceed fully. If the powder is too coarse, the powder will sink to the bottom, and the arsenic removal effect of the upper layer solution is poor, and the displacement reaction cannot proceed fully. Therefore, the above powder particle size range is the best particle size range.

[0038] The introduction of the copper-antimony alloy can react with AsO in the crude antimony chloride solution to be treated +Cooperate to form a copper-antimony primary battery system. After the copper-antimony alloy is added to the solution, copper is the anode of the primary battery and antimony is the cathode. During the oxidation of copper, electrons are given out, forming a negative electrostatic field on the surface of the alloy particles, selectively adsorbing AsO + , and during the process, the reaction conditions are controlled to accelerate the arsenic removal process and make the displacement reaction process more sufficient, achieving the purpose of deep arsenic removal.

[0039] It specifically includes the following reactions:

[0040] Anode reaction:

[0041] Cu + Cl - = CuCl + e -

[0042] Cathode reaction:

[0043]

[0044] AsO + + 2H + + 3e - = As + H2O

[0045] Alloying side reaction:

[0046] Sb + 2Cu = Cu2Sb

[0047] 2As + 5Cu = As2Cu5

[0048] During the above reaction process, it can be clearly seen that after the primary battery system is formed, copper is converted into copper chloride and consumed. At the same time, antimony and arsenic are formed on the surface of the copper-antimony alloy. The formation of these two elements then undergoes an alloying side reaction with the copper on the copper-antimony alloy to fix arsenic and antimony, reduce impurity interference, and improve the purity of the subsequent obtained antimony chloride. That is, an actual process similar to displacement occurs, replacing the arsenic and antimony in the crude solution with the copper in the copper-antimony alloy. The antimony in the copper-antimony alloy can, on the one hand, effectively inhibit the reduction loss of antimony in the solution, and on the other hand, can also spontaneously terminate the reaction to a certain extent and prevent the formed antimony from falling off, because antimony is more likely to stably combine in the alloy phase region and can spread and grow to a certain extent to coat the outside of the copper-arsenic alloy phase for fixation.

[0049] To achieve the above process, in addition to selecting and controlling the copper-antimony alloy material, it is also necessary to control the solution system to a certain extent. When purifying a common crude antimony chloride solution, the concentration of hydrogen chloride is extremely high because low-concentration hydrogen chloride cannot inhibit the hydrolysis of antimony trichloride. Therefore, high-concentration hydrogen chloride is required to inhibit it, and it may even be as high as more than 10 M. However, the existence form of arsenic is different at different hydrogen chloride concentrations. The present invention needs to control the concentration of hydrogen chloride in the crude antimony chloride solution within the range of 3-8 mol / L to ensure that arsenic exists in the form of AsO + This is conducive to the progress of the galvanic cell reaction, and a higher hydrochloric acid concentration is beneficial to the distillation and removal of residual arsenic. In addition, under the above conditions of high hydrochloric acid concentration, it is a highly reducing environment. At this time, the galvanic cell system formed by the coordination of copper will only give one electron. From the perspective of potential, the potential for forming Cu + is about -1 V, and the potential for forming Cu 2+ is 0.34 V, while the potential of arsenic is only about 0.24 V. Therefore, the above hydrogen chloride concentration in combination with the galvanic cell system can effectively achieve the removal of arsenic. Otherwise, it may even have the reverse effect of "removing copper with arsenic".

[0050] In addition, during the reaction process of step 1) of the technical solution of the present invention, it needs to be carried out in a closed protective atmosphere, and nitrogen is continuously introduced into the solution system. This is because trace amounts of toxic gases such as AsH3 and SbH3 may be generated during the replacement process, and introducing nitrogen can bring the toxic gases into the tail gas absorption device. In addition, through nitrogen replacement in a closed environment, the oxidation of arsenic and antimony can be avoided. Once arsenic and antimony become pentavalent arsenate and antimonate, it will increase the difficulty of removal. Similarly, the above phenomenon can also be used as a characterization parameter for the subsequent distillation and concentration process in step 2). Because nitrogen can reduce the concentration of arsine, but there will still be a small amount of residue that combines intermolecularly with the residual arsenic compounds and is removed during the distillation and concentration process. In this process, the distillation gas is characterized to verify whether the removal of arsenic compounds is complete, so as to avoid excessive distillation and concentration resulting in the crystallization and precipitation of antimony chloride on the surface of the copper-antimony alloy, causing losses. During the reaction process, it is necessary to control the temperature, stirring speed, and reaction time because too low a reaction temperature will reduce the replacement efficiency, while too high a reaction temperature will cause the volatilization of hydrochloric acid and water, destroying the control of hydrochloric acid concentration during the replacement process. If the stirring speed is too low, the copper-antimony alloy powder does not contact the solution sufficiently, affecting the replacement efficiency; if the stirring speed is too high, the solution is prone to splashing during the replacement reaction, making it inconvenient to operate. If the replacement time is too short, the replacement reaction is incomplete, affecting the arsenic removal efficiency; if the replacement time is too long, it affects the production cycle.

[0051] For the high-purity antimony trichloride solution obtained after concentration, crystallization after actually filtering and removing solid impurities already has a relatively high purity, but it is more preferable to further purify it. During the purification process, antimony trichloride is evaporated at 220-240 °C and then condensed, which can reduce high-boiling impurities. However, direct condensation also has certain defects. Because the aforementioned arsenic mirror test actually has a certain detection limit, it is difficult to detect when the arsenic content is extremely low. But actually, it can only stably reach 3N purity at this time because intermolecular forces will cause some arsenic to be always difficult to effectively remove. And the present invention further adopts a two-stage condensation recovery method, which can further separate and remove arsenic compounds, so that the product purity can stably reach more than 5N.

[0052] The beneficial effects of the present invention are as follows:

[0053] 1) The present invention solves the technical difficulty of removing impurity arsenic in the preparation process of high-purity antimony;

[0054] 2) The distillation is carried out under low-temperature conditions, with simple operation and low energy consumption;

[0055] 3) The preparation process flow is simple, the production efficiency is high, it is easy to implement, no industrial pollution is generated, and it is suitable for industrialization. Description of the Drawings

[0056] Figure 1 It is the XRD characterization result of the solid product (filter cake) obtained by filtration and separation in Example 1 of the present invention;

[0057] Figure 2 It is the XRD characterization result of the product in Example 2 of the present invention;

[0058] Figure 3 It is the SEM characterization result of the product in the embodiment of the present invention, Figure 2 (a) corresponds to the product in Example 1, Figure 2 (b) corresponds to the product in Example 3;

[0059] Figure 4 It is the EDS characterization result of the product in Example 3 of the present invention. Detailed Embodiments

[0060] The following further clearly and detailedly describes the present invention in conjunction with specific embodiments and the accompanying drawings of the specification. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are usually only part of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0061] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available or raw materials that can be obtained by those skilled in the art; unless otherwise specified, the methods used in the embodiments of the present invention are all methods mastered by those skilled in the art.

[0062] Unless otherwise specified, the copper-antimony alloy used in the present invention is a commercially available 320-mesh copper-antimony alloy with a purity of 2N.

[0063] Unless otherwise specified, since the raw stibium chloride solution to be treated used in the present invention has multiple sources and different batches, the arsenic content and antimony content in the raw stibium chloride solution to be treated need to be characterized before each experiment for calculating the arsenic removal rate and antimony loss rate.

[0064] Examples 1-6

[0065] A method for arsenic removal and purification of stibium chloride solution

[0066] The method includes:

[0067] 1) In a nitrogen atmosphere, add a copper-antimony alloy to the raw stibium chloride solution containing arsenic, continuously introduce nitrogen into the solution system during the reaction, and obtain a low-arsenic stibium chloride solution after the reaction;

[0068] 2) Distill and concentrate the low-arsenic stibium chloride solution at 160 °C, automatically sample and characterize the distillate gas every 5 minutes. Using the distillate gas sampling to contact the heat source, the heat source controls the temperature ≥ 250 °C, and distill until no arsenic mirror is produced when the distillate gas sampling contacts the heat source, then a high-purity stibium chloride solution is obtained.

[0069] The high-purity stibium chloride solution is distilled at 225 °C and condensed and crystallized at room temperature to recover a high-purity stibium chloride product (SbCl3 molten salt).

[0070] The specific reaction parameters of each group are shown in the following table.

[0071] Copper content Stoichiometric ratio Temperature HCl concentration Stirring speed Reaction time Example 1 80wt% 16 90℃ 6mol / L 400rpm 120min Example 2 80wt% 8 90℃ 6mol / L 400rpm 120min Example 3 80wt% 28 90℃ 6mol / L 400rpm 120min Example 4 80wt% 16 90℃ 8mol / L 400rpm 120min Example 5 80wt% 16 90℃ 6mol / L 100rpm 120min Example 6 80wt% 16 90℃ 6mol / L 400rpm 60min

[0072] In the table: the copper content is the copper content in the copper-antimony alloy; the stoichiometric ratio is the stoichiometric ratio of the copper content in the copper-antimony alloy to the arsenic content in the raw stibium chloride solution containing arsenic; the temperature is the reaction temperature in step 1); the HCl concentration is the hydrogen chloride concentration in the raw stibium chloride solution in step 1); the stirring speed is the stirring speed controlled during the reaction in step 1); the reaction time is the reaction duration in step 1). The arsenic content, arsenic removal rate and antimony loss rate in the treated high-purity stibium chloride solution are characterized and calculated, and the following results are obtained.

[0073] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Arsenic content (ppm) 38.4 155 2.37 3.47 40.2 52.7 Arsenic removal rate 91.6％ 65.9％ 99.2％ 90.1％ 91.2％ 88.4％ Antimony loss rate 5.8％ 4.9％ 8.7％ 6.3％ 5.7％ 5.8％

[0074] Various tests were performed on the filter cake obtained by filtration and separation after the replacement reaction in step 1) of Examples 1 to 6 and the condensation crystal product. Figure 1 This is the XRD test result of the product in Example 2. Figure 2 The XRD test results of the filter cake in Example 1 clearly show that the copper-arsenic stoichiometric ratio in the copper-antimony alloy powder affects the replacement process and has an impact on the arsenic removal efficiency. When the copper-arsenic stoichiometric ratio is relatively low, the replacement products at the end of the reaction are mainly arsenic and antimony. When the copper-arsenic stoichiometric ratio increases, in addition to antimony and arsenic, side reactions occur in the solution to form arsenic-copper intermetallic compounds Cu2Sb and As2Cu5. The occurrence of side reactions greatly improves the arsenic removal efficiency in the antimony chloride solution. Figure 3 The SEM image shown shows that the structure of the replacement reaction product is composed of spherical particles of different sizes, which is the key to deep arsenic removal in antimony chloride solution. It is worth noting that the concentration of hydrochloric acid also plays an important role in the efficiency of arsenic removal, and the increase of hydrochloric acid promotes the side reaction. Figure 4 The EDS spectrum analysis of the surface structure of the product of Example 1 shows that the copper-arsenic intermetallic compound is formed on the surface of the spherical particles. This shows that the removal of arsenic in the solution is divided into two parts, namely, the main reaction of displacement to generate arsenic element and the side reaction to generate the copper-arsenic intermetallic compound, thereby achieving the purpose of efficient arsenic removal. The SbCl3 molten salt products obtained in each example are characterized, and the characterization results are shown in the following table.

[0075] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Arsenic content (ppm) 11.5 50.6 0.61 1.22 14.3 17.9 Purity grade 3N 3N 5N 4N 4N 3N

[0076] It can be clearly seen from the above characterization results that the high-purity antimony chloride molten salt prepared in the present invention can basically stably reach a purity level of 3N.

[0077] Comparative Example 1

[0078] The same experimental operation was performed on the experimental group based on Example 3, except that different copper-antimony alloys were used for the experiment. The experimental results are shown in the following table.

[0079] Copper content (wt%) 60 70 80 90 95 99.9 Arsenic content (ppm) 97.4 76.2 2.37 10.6 16.6 2.21 Arsenic removal rate 52.6％ 87.9％ 99.2％ 96.1％ 97.7％ 99.4％ Antimony loss rate 2.1％ 4.9％ 8.7％ 9.3％ 9.7％ 22.8％

[0080] In the table: Copper content refers to the copper content in copper-antimony alloy.

[0081] From the above results, it can be seen that with the increase of copper content, the arsenic removal rate generally shows an upward trend, but the antimony loss rate also shows a great upward trend, and when the copper content is 60wt% (the balance is antimony and inevitable impurities, about 40wt% antimony content), the arsenic removal rate is extremely low. It can be seen that in the technical solution of the present invention, the arsenic removal effect and the actual industrial implementation effect also need to consider the antimony loss, and the optimal copper-antimony alloy should control the copper content to 70-95wt%.

[0082] Comparative Example 2

[0083] The same experimental operation was performed on the experimental group based on Example 3, except that the concentration of hydrogen chloride in the crude antimony chloride solution to be treated was adjusted for the experiment. The experimental results are shown in the following table.

[0084] HCl concentration (mol) 2 3 6 8 10 12 Arsenic content (ppm) 63.6 51.2 2.37 6.93 16.2 10.8 Arsenic removal rate 89.13％ 93.6％ 99.2％ 98.6％ 71.6％ 81.7％

[0085] In the table: HCl concentration is the concentration of hydrogen chloride in the crude antimony chloride solution to be treated in step 1).

[0086] It can be clearly seen from the above results that, considering the influence of the original arsenic content in the actual treated liquid, the arsenic removal rate of the present invention generally shows a phenomenon of first increasing and then decreasing with the increase of hydrogen chloride concentration, especially when the HCl concentration reaches 10 mol / L, the arsenic removal rate drops drastically. This is mainly because the HCl concentration affects the existence form of arsenic in the treated liquid, and AsO + Ions are the most suitable form of arsenic to be removed by the technical solution of the present invention, and have a great impact on the actual effect of the solution. Therefore, technicians believe that the concentration of hydrogen chloride should be controlled at 3-8 mol / L.

[0087] Example 7

[0088] The same experimental operation was performed based on the experimental group of Example 1, except that the high-purity antimony chloride solution was distilled at 225°C, condensed and recovered at 175°C to obtain liquid antimony chloride, and then cooled and crystallized at room temperature to obtain high-purity antimony chloride product (SbCl3 molten salt). Five groups of different liquids to be treated were equally divided and treated according to the scheme of Example 1 and the scheme of this example, and the arsenic content and purity of the SbCl3 molten salt obtained in this example and Example 1 were characterized, and the results are shown in the following table.

[0089] Example 1 Result 1 Result 2 Result 3 Result 4 Result 5 Arsenic content (ppm) 10.6 1.83 13.2 10.1 11.9 Purity grade 3N 4N 3N 3N 3N Example 7 Result 1 Result 2 Result 3 Result 4 Result 5 Arsenic content (ppm) 1.62 0.81 1.86 1.22 1.35 Purity grade 4N 5N 4N 4N 4N

[0090] In the table: the same vertical column represents the same experimental group of liquid to be treated.

[0091] It can be seen from the above characterization results that the purity of the product can be further significantly improved through graded cooling recovery, mainly because the graded cooling recovery process can actually further remove a small amount of arsenic impurities that could not be removed during the distillation concentration process due to intermolecular forces.

Claims

1. A method for purifying arsenic-removed antimony chloride solution, characterized in that, the method comprises: 1) In a protective atmosphere, adding a copper-antimony alloy to the arsenic-containing crude antimony chloride solution to be treated, and obtaining a low-arsenic antimony chloride solution after the reaction; 2) Distilling and concentrating the low-arsenic antimony chloride solution to obtain a high-purity antimony chloride solution; In step 1), the stoichiometric ratio of the copper content in the copper-antimony alloy to the arsenic content in the arsenic-containing crude antimony chloride solution to be treated is (10-40):1, and the antimony content in the copper-antimony alloy is 5-30 wt%; The concentration of hydrogen chloride in the arsenic-containing crude antimony chloride solution to be treated is 3-8 mol / L.

2. A method for purifying arsenic-removed antimony chloride solution according to claim 1, characterized in that, The protective atmosphere in step 1) is a nitrogen atmosphere, and nitrogen is continuously introduced into the solution system during the reaction in step 1).

3. A method for purifying arsenic-removed antimony chloride solution according to claim 1, characterized in that, The reaction temperature in step 1) is controlled at 30-90 °C; Stirring is carried out during the reaction, the stirring speed is controlled at 100-500 rpm, and the reaction time is 30-120 min.

4. A method for purifying arsenic-removed antimony chloride solution according to claim 1, characterized in that, The distillation temperature in step 2) is controlled at 160-180 °C for the distillation and concentration.

5. A method for purifying arsenic-removed antimony chloride solution according to claim 1 or 4, characterized in that, During the distillation and concentration process, the distilled gas sample contacts a heat source, the temperature of the heat source is controlled at ≥250 °C, and the distillation is terminated until no arsenic mirror is generated when the distilled gas sample contacts the heat source.

6. A method for purifying arsenic-removed antimony chloride solution according to claim 1, characterized in that, The high-purity antimony chloride solution obtained after the distillation and concentration in step 2) is subjected to secondary distillation and then condensed to obtain high-purity antimony chloride.

7. A method for purifying arsenic-removed antimony chloride solution according to claim 6, characterized in that, The distillation temperature for the secondary distillation is controlled at 220-240 °C.

8. A method for purifying arsenic-removed antimony chloride solution according to claim 6 or 7, characterized in that, During the condensation process, two-stage recovery is carried out. First, liquid antimony chloride is recovered at 160-180 °C, and then the liquid antimony chloride is cooled to ≤70 °C to recover high-purity antimony chloride.

Images