A method for continuously producing elemental arsenic from an arsenic-containing material

Abstract

The application discloses a method for continuously preparing elemental arsenic from arsenic-containing materials. The method comprises the following steps: mixing the arsenic-containing materials with carbon powder to perform reduction roasting, so as to obtain arsenic-containing steam; contacting the arsenic-containing steam with spraying water to perform condensation, so as to obtain slurry containing gamma-state elemental arsenic; and after the slurry containing gamma-state elemental arsenic is subjected to reverse flotation and impurity removal, solid-liquid separation and drying are performed, so as to obtain the elemental arsenic product. The method can not only effectively solve the problems of discontinuous work and low direct yield existing in the collection process of the existing elemental arsenic condenser, but also greatly reduce the content of impurities in the elemental arsenic, and the method is simple, fast, efficient and low in cost, and meets the industrial production.

Description

Technical Field

[0001] This invention relates to a method for preparing elemental arsenic from arsenic-containing materials, specifically a method for continuously producing crude arsenic (high-quality elemental arsenic) containing a small amount of impurities from high-arsenic materials containing various impurities, belonging to the technical field of harmless disposal and resource utilization of arsenic-containing solid waste. Background Technology

[0002] The non-ferrous smelting and environmental remediation processes generate a large amount of high-arsenic materials. For example, the copper, lead and zinc smelting processes produce white smoke ash, and the arsenic sulfide slag, calcium arsenate slag, iron arsenate slag, etc. are generated during the arsenic hazardous waste treatment process.

[0003] Currently, the conventional method for producing high-purity arsenic from high-arsenic materials is to reduce the arsenic-containing components in high-arsenic materials to crude arsenic through reduction roasting, followed by purification of the crude arsenic to high-purity arsenic through vacuum distillation and chlorination reduction. However, this process faces two bottlenecks: first, the continuous and efficient collection of crude arsenic; and second, the separation of impurities during the preparation of high-purity arsenic.

[0004] To address the problem of crude arsenic recovery, existing collection methods primarily utilize the property that arsenic vapor generates α-state elemental arsenic at 280℃ to 460℃, recovering metallic elemental arsenic in the condensation zone within a crystallizer. For example, the elemental arsenic production device designed in Chinese Patent (Announcement No. CN213060988U) requires the condenser temperature to drop below 50℃ before collecting elemental arsenic. Then, the condenser top cover is opened, and finally, large chunks of metallic elemental arsenic condensed on the inner wall of the condenser are dislodged and recovered through vibration or tapping. Clearly, recovering elemental arsenic through a crystallizer not only presents the problem of discontinuous production but also carries the risk of arsenic vapor leakage. Furthermore, to improve the crystallization efficiency of elemental arsenic, the surface area of ​​the condenser needs to be increased. However, the metallic elemental arsenic crystals on the inner wall of the condenser are not easily detached, ultimately leading to a continuous decrease in the surface area of ​​the condenser's inner wall and the accumulation of a thick layer of elemental arsenic crystals. This results in increasingly lower crystallization efficiency and a continuously decreasing direct recovery rate of elemental arsenic. Clearly, improving the collection method of elemental arsenic is essential to increasing the efficiency of the elemental arsenic production process and the recovery rate of elemental arsenic.

[0005] The complexity of high-purity arsenic preparation depends on the composition and content of impurities in the crude arsenic raw material. For example, when high-arsenic materials contain sulfates, the crude arsenic prepared by reduction roasting will contain elemental sulfur impurities. Since the boiling point of elemental sulfur volatilized in the form of S2 is close to that of elemental arsenic during the subsequent vacuum distillation of the crude arsenic to prepare high-purity arsenic, it is difficult to separate from As, resulting in a high sulfur content in the final high-purity arsenic product. Similarly, during the reduction roasting process of high-arsenic materials, impurities such as Sb, Cu, and Pb will also enter the crude arsenic product to varying degrees, increasing the difficulty of subsequent high-purity arsenic preparation. Clearly, if the impurity content can be reduced from the crude arsenic raw material stage, the quality of high-purity arsenic will be greatly improved, and the difficulty of preparing high-purity arsenic will be greatly reduced. Summary of the Invention

[0006] To address the problems of collecting elemental arsenic and separating impurities in existing technologies, the present invention aims to provide a method for the continuous preparation of elemental arsenic from arsenic-containing materials. This method utilizes the characteristic that high-temperature arsenic vapor crystallizes into γ-state elemental arsenic below 100°C. A spray-water condensation method can be used to continuously cool the high-temperature arsenic vapor and efficiently collect the γ-state elemental arsenic slurry. Then, taking advantage of the difference in hydrophobicity between elemental arsenic and impurities such as sulfur, the impurity components in the elemental arsenic are removed by reverse flotation, thereby obtaining high-quality elemental arsenic. This method solves the technical problems of the inability to continuously condense and collect arsenic vapor and the difficulty in efficiently removing impurities. Furthermore, this method is fast, efficient, low-cost, simple, and easy to operate, meeting the requirements for industrial production.

[0007] To achieve the above technical objectives, the present invention provides a method for the continuous preparation of elemental arsenic from arsenic-containing materials, the method comprising the following steps:

[0008] 1) Arsenic-containing materials are mixed with carbon powder and then subjected to reduction roasting to obtain arsenic-containing vapor;

[0009] 2) Arsenic-containing vapor is condensed upon contact with sprayed water to obtain a slurry containing γ-state elemental arsenic;

[0010] 3) After removing impurities from the slurry containing γ-state elemental arsenic by reverse flotation, solid-liquid separation and drying are performed to obtain the elemental arsenic product.

[0011] Arsenic has three allotropes: α-arsenic, β-arsenic, and γ-arsenic. Arsenic vapor crystallizes at 280°C to 460°C to obtain α-arsenic, which is a close-packed hexagonal crystal with a metallic luster; arsenic vapor crystallizes at 180°C to 200°C to obtain β-arsenic, also known as gray arsenic, with a vitreous luster; and arsenic vapor crystallizes below 100°C to obtain γ-arsenic, which is a black powder. Existing technologies report methods for collecting crude and high-purity arsenic by condensing and recovering α-arsenic in a crystallizer. However, the elemental arsenic generally condenses within the crystallizer, leading to discontinuous production and difficulties in unloading. Furthermore, impurities in the arsenic vapor cannot be effectively removed, resulting in relatively low purity crude arsenic. This invention cleverly utilizes spray water to directly condense and crystallize arsenic vapor, recovering γ-arsenic through a wet process. This allows for continuous arsenic recovery and yields powdered γ-arsenic particles, improving production efficiency. Additionally, the small amount of impurities contained in the powdered γ-arsenic are easily separated by the wet process. For example, since granular γ-arsenic is different from the granular α-arsenic recovered in the crystallizer, granular γ-arsenic can be directly separated from impurities by flotation, taking advantage of the difference in hydrophobicity between elemental arsenic and other impurities. In particular, sulfur, which is difficult to separate, can be separated quickly by taking advantage of the hydrophilic nature of elemental arsenic and the hydrophobic nature of elemental sulfur. This can result in crude arsenic with higher purity, reducing the difficulty of further vacuum distillation to purify arsenic.

[0012] As a preferred embodiment, the arsenic-containing material includes at least one of crude white arsenic, arsenic sulfide slag, and metal arsenate slag. These arsenic-containing materials are all common arsenic-containing solid wastes in smelting and wastewater treatment processes, and are all suitable for the technical solution of this invention.

[0013] As a preferred embodiment, the mass ratio of the arsenic-containing material to the carbon powder is 10:1 to 3. Reduced carbon powder is crucial for controlling the volatilization of arsenic through reduction; therefore, controlling the amount of carbon powder within an appropriate range ensures efficient volatilization of arsenic from the arsenic-containing material. If the proportion of carbon powder is too low, the arsenic volatilization efficiency will be low; if the proportion is too high, the volatilization of impurities such as sulfur and metals will also increase. Therefore, the mass ratio of the arsenic-containing material to the carbon powder is further preferably 10:1.5 to 2.

[0014] As a preferred embodiment, the reduction roasting conditions are as follows: roasting at 800–1000°C for 2–3 hours under a protective atmosphere. Under these preferred reduction roasting conditions, arsenic oxide or arsenates in high-arsenic materials can be efficiently reduced to arsenic vapor. However, simultaneously, sulfates and metal oxides in the high-arsenic materials are also reduced to elemental sulfur and elemental metals. Since elemental sulfur and other substances are easily removed by subsequent flotation separation, the arsenic recovery rate in arsenic-containing materials can be improved under these preferred reduction roasting conditions. The protective atmosphere is preferably an inert atmosphere or nitrogen.

[0015] As a preferred embodiment, the spray water is deoxygenated water. The main purpose of using deoxygenated water is to prevent the oxidation of elemental arsenic. The deoxygenated water can be deoxygenated at room temperature and can be circulated through a spraying device. When the arsenic concentration in the solution reaches a level suitable for flotation, flotation is performed to remove impurities.

[0016] As a preferred embodiment, in the reverse flotation process, No. 2 oil and / or pine oil are used as frothers, at least one of Z200, methyl isobutyl methanol, and butyl xanthate is used as a collector, and mercaptoacetic acid and / or sodium sulfide is used as a depressant. The preferred collector primarily enhances the flotation of sulfur or sulfides, while the depressant primarily inhibits the flotation of γ-form elemental arsenic. The combined use of both can differentiate the floatability of sulfur impurities from that of γ-form elemental arsenic, achieving efficient flotation separation of the two.

[0017] As a preferred embodiment, in the reverse flotation process, the amount of frother added is 10-20 g / t; the amount of collector added is 10-80 mg / L; and the amount of inhibitor added is 10-200 mg / L.

[0018] As a preferred embodiment, during the reverse flotation process, the mass concentration of the γ-state elemental arsenic slurry is controlled at 35-45%, the pH at 6-8, the potential at 400-450 mV, and the temperature at 20-30℃. More preferably, the stirring speed is 800-1000 rpm, and the flotation time is 15-20 min. Under these preferred flotation conditions, a good separation effect between elemental arsenic and various impurities can be ensured.

[0019] As a preferred embodiment, the drying process employs vacuum drying at a temperature of 50–60°C. Low-temperature vacuum drying helps prevent arsenic oxidation.

[0020] As a preferred method, after solid-liquid separation of the γ-state elemental arsenic slurry, the elemental arsenic filter residue is rinsed with deoxygenated water, and the rinsing is performed more than 3 times.

[0021] Compared with existing technologies, the beneficial technical effects of the present invention are as follows:

[0022] To address the technical challenges of continuous arsenic collection and impurity separation in existing technologies, the key to this invention is the use of arsenic steam-cooled crystallization to recover fine-particle elemental arsenic. This achieves continuous production of elemental arsenic while increasing its recovery rate. Furthermore, the fine-particle elemental arsenic recovered through spray water condensation differs from the blocky elemental arsenic recovered by the crystallizer. In a slurry system containing fine-particle elemental arsenic, the difference in hydrophobicity between elemental arsenic and impurities can be utilized to achieve efficient separation of elemental arsenic and impurities from crude arsenic through flotation, significantly reducing the difficulty of subsequent high-purity arsenic preparation.

[0023] The method for continuous preparation of elemental arsenic from arsenic-containing materials of the present invention is rapid, efficient, low-cost, simple and easy to operate, and meets the requirements of industrial production. Detailed Implementation

[0024] The following examples are intended to further illustrate the present invention, but do not limit the scope of protection of the claims of the present invention.

[0025] Example 1

[0026] 10 kg of high-arsenic slag (elemental composition: As: 28.75%, Mg: 10.27%, S: 0.75%, Sb: 0.24%), mainly composed of arsenate complex salts, was mixed with 1.5 kg of carbon powder and placed in a reduction furnace for reduction roasting at 800℃ under an inert atmosphere. The arsenic vapor generated during reduction roasting was introduced into a spraying device and condensed and crystallized in the deoxygenated water sprayed on it. When the concentration of elemental arsenic slurry in the spray liquid at the bottom of the spraying device reached 35%, it was pumped into a flotation device for flotation. During flotation, 10 g / t of No. 2 oil, 30 mg / L of butyl xanthate, and 50 mg / L of mercaptoacetic acid were added sequentially to the slurry. Simultaneously, the slurry pH was controlled at 6.0, the potential at 450 mV, the stirring speed at 1000 rpm, the slurry temperature at 30℃, and the flotation time at 20 min. After separating impurities from the foam layer, the slurry was vacuum filtered, and the elemental arsenic filter residue was washed three times with deoxygenated water. The washed elemental arsenic was then vacuum dried at 60℃. The direct recovery rate of arsenic was calculated to be 85% after weighing. Samples were sent for ICP-MS analysis to determine the content of various components in the elemental arsenic, as shown in Table 1.

[0027] Table 1. Content (%) of each component in elemental arsenic

[0028]

[0029] Comparative Example 1

[0030] 10 kg of high-arsenic slag (elemental composition: As: 28.75%, Mg: 10.27%, S: 0.75%, Sb: 0.24%), mainly composed of arsenate double salts, was mixed with 1.5 kg of carbon powder and placed in a reduction furnace. Reduction roasting was carried out at 800℃ under an inert atmosphere. The arsenic vapor generated during reduction roasting was directly condensed and recovered as α-state elemental arsenic in a crystallizer. The elemental arsenic collected from the inner wall of the crystallizer was weighed. The direct recovery rate of arsenic was calculated to be only 65%. Simultaneously, samples were sent for ICP-MS analysis to determine the content of various components in the elemental arsenic, as shown in Table 2. Comparing Tables 1 and 2, it can be seen that the technical solution proposed in this patent significantly reduces the content of various impurities in the elemental arsenic product, with the most significant reduction in the content of elemental sulfur impurities.

[0031] Table 2. Content (%) of various impurities in elemental arsenic

[0032]

[0033] Comparative Example 2

[0034] 10 kg of high-arsenic slag (elemental composition: As: 28.75%, Mg: 10.27%, S: 0.75%, Sb: 0.24%), mainly composed of arsenate complex salts, was mixed with 1.5 kg of carbon powder and placed in a reduction furnace for reduction roasting at 800℃ under an inert atmosphere. The arsenic vapor generated during reduction roasting was introduced into a spraying device and condensed and crystallized in the deoxygenated water sprayed on it. When the concentration of elemental arsenic slurry in the spray liquid at the bottom of the spraying device reached 35%, it was pumped into a flotation device for flotation. During flotation, 10 g / t of No. 2 oil, 30 mg / L of butyl xanthate, and 50 mg / L of mercaptoacetic acid were added sequentially to the slurry. Simultaneously, the slurry pH was controlled at 3.0, the potential at 150 mV, the stirring speed at 1000 rpm, the slurry temperature at 30℃, and the flotation time at 20 min. After separating impurities from the froth layer, the slurry was vacuum filtered, and the elemental arsenic filter residue was washed three times with deoxygenated water. The washed elemental arsenic was vacuum dried at 60°C, weighed, and the direct recovery rate of arsenic was calculated to be 75%. Samples were sent for ICP-MS analysis to determine the content of various components in the elemental arsenic, as shown in Table 3. Analysis of Example 1 and Comparative Example 2 shows that under suboptimal flotation pH and potential conditions, some elemental arsenic product is lost in the foam layer, leading to a decrease in the direct recovery rate of elemental arsenic. However, the content of impurities in the elemental arsenic does not change significantly.

[0035] Table 3. Content (%) of various impurities in elemental arsenic

[0036]

[0037] Comparative Example 3

[0038] 10 kg of high-arsenic slag (elemental composition: As: 28.75%, Mg: 10.27%, S: 0.75%, Sb: 0.24%), mainly composed of arsenate complex salts, was mixed with 1.5 kg of carbon powder and placed in a reduction furnace for reduction roasting at 800℃ under an inert atmosphere. The arsenic vapor generated during reduction roasting was introduced into a spraying device and condensed and crystallized in the deoxygenated water sprayed on it. When the concentration of elemental arsenic slurry in the spray liquid at the bottom of the spraying device reached 35%, it was pumped into a flotation device for flotation. During flotation, 5 g / t of No. 2 oil, 7 mg / L of butyl xanthate, and 10 mg / L of mercaptoacetic acid were added sequentially to the slurry. Simultaneously, the slurry pH was controlled at 6.0, the potential at 450 mV, the stirring speed at 1000 rpm, the slurry temperature at 30℃, and the flotation time at 20 min. After separating impurities from the froth layer, the slurry was vacuum filtered, and the elemental arsenic filter residue was washed three times with deoxygenated water. The washed elemental arsenic was vacuum dried at 60°C, weighed, and the direct recovery rate of arsenic was calculated to be 85%. Samples were sent for ICP-MS analysis to determine the content of various components in the elemental arsenic, as shown in Table 4. Analysis of Example 1 and Comparative Example 3 shows that under non-optimal flotation reagent conditions, the impurity content in elemental arsenic increased, especially the content of elemental sulfur impurities increased significantly.

[0039] Table 4. Content (%) of various impurities in elemental arsenic

[0040]

[0041] Example 2

[0042] 10 kg of copper smelting white flue dust (specific composition: Cu: 5.42%, As: 31.78%, Bi: 2.50%, Zn: 2.335%, Pb: 8.44%) was mixed with 2.0 kg of carbon powder and placed in a reduction furnace for reduction roasting under an inert atmosphere at 1000℃. The arsenic vapor generated during reduction roasting was passed into a spraying device and condensed and crystallized in the deoxygenated water sprayed on it. When the concentration of elemental arsenic slurry in the spray liquid at the bottom of the spraying device reached 40%, it was pumped into a flotation device for flotation. During flotation, 5 g / t of terpineol, 50 mg / L of Z-200, and 100 mg / L of sodium sulfide were added sequentially to the slurry. Simultaneously, the slurry pH was controlled at 7.0, the potential at 500 mV, the stirring speed at 1000 rpm, the slurry temperature at 30℃, and the flotation time at 15 min. After separating impurities from the foam layer, the slurry was vacuum filtered, and the elemental arsenic filter residue was washed three times with deoxygenated water. The washed elemental arsenic was vacuum dried at 60℃, weighed, and the direct recovery rate of arsenic was calculated to be 82%. Samples were sent for ICP-MS analysis to determine the content of various components in the elemental arsenic, as shown in Table 5.

[0043] Table 5. Content (%) of various impurities in elemental arsenic

[0044]

[0045] Comparative Example 4

[0046] 10 kg of copper smelting white flue dust (specific composition: Cu: 5.42%, As: 31.78%, Bi: 2.50%, Zn: 2.335%, Pb: 8.44%) was mixed with 2.0 kg of carbon powder and placed in a reduction furnace for reduction roasting at 700℃ under an inert atmosphere. The arsenic vapor generated during reduction roasting was passed into a spraying device and condensed and crystallized in deoxygenated water. When the concentration of elemental arsenic slurry in the spray liquid at the bottom of the spraying device reached 40%, it was pumped into a flotation device for flotation. During flotation, 5 g / t of terpineol, 50 mg / L of Z-200, and 100 mg / L of sodium sulfide were added sequentially to the slurry. Simultaneously, the slurry pH was controlled at 7.0, the potential at 500 mV, the stirring speed at 1000 rpm, the slurry temperature at 30℃, and the flotation time at 15 min. After separating impurities from the foam layer, the slurry was vacuum filtered, and the elemental arsenic filter residue was washed three times with deoxygenated water. The washed elemental arsenic was vacuum dried at 60°C, weighed, and the direct recovery rate of arsenic was calculated to be 43%. Samples were sent for ICP-MS analysis to determine the content of various components in the elemental arsenic, as shown in Table 6. Comparing Example 2 and Comparative Example 1, it can be seen that when the reduction roasting temperature is not within the appropriate range, the recovery rate of elemental arsenic will also decrease significantly.

[0047] Table 6. Content (%) of various impurities in elemental arsenic

[0048]

[0049] Comparative Example 5

[0050] 10 kg of copper smelting white flue dust (specific composition: Cu: 5.42%, As: 31.78%, Bi: 2.50%, Zn: 2.335%, Pb: 8.44%) was mixed with 2.0 kg of carbon powder and placed in a reduction furnace for reduction roasting at 1000℃ under an inert atmosphere. The arsenic vapor generated during reduction roasting was passed into a spraying device and condensed and crystallized in deoxygenated water. When the concentration of elemental arsenic slurry in the spray liquid at the bottom of the spraying device reached 40%, it was pumped into a flotation device for flotation. During flotation, 5 g / t of terpineol and 100 mg / L of sodium sulfide were added sequentially to the slurry, while controlling the slurry pH at 7.0, the potential at 500 mV, the stirring speed at 1000 rpm, the slurry temperature at 30℃, and the flotation time at 15 min. After separating impurities from the froth layer, the slurry was vacuum filtered, and the elemental arsenic filter residue was washed three times with deoxygenated water. The washed elemental arsenic was vacuum dried at 60°C and weighed. The direct recovery rate of arsenic was calculated to be 81%. Samples were sent for ICP-MS analysis to determine the content of various components in the elemental arsenic, as shown in Table 7. Comparing Example 2 and Comparative Example 2, it can be seen that when no collector is added during the flotation process, elemental arsenic and impurities cannot be efficiently separated.

[0051] Table 7. Content (%) of various impurities in elemental arsenic

[0052]

Claims

1. A method for the continuous preparation of elemental arsenic from arsenic-containing materials, characterized in that: Includes the following steps: 1) Arsenic-containing materials are mixed with carbon powder and then subjected to reduction roasting to obtain arsenic-containing vapor; 2) Arsenic-containing vapor is condensed upon contact with sprayed water to obtain a slurry containing γ-state elemental arsenic; 3) After removing impurities from the slurry containing γ-state elemental arsenic by reverse flotation, solid-liquid separation and drying are performed to obtain the elemental arsenic product; In the reverse flotation process, No. 2 oil and / or pine oil are used as frothers, and at least one of Z200, methyl isobutyl methanol, and butyl xanthate is used as a collector, and mercaptoacetic acid and / or sodium sulfide are used as inhibitors. During the reverse flotation process, the mass concentration of the γ-state elemental arsenic slurry is controlled at 35-45%, the pH is 6-8, the potential is 400-450mV, and the temperature is 20-30℃.

2. The method for continuous preparation of elemental arsenic from arsenic-containing materials according to claim 1, characterized in that: The arsenic-containing material includes at least one of crude white arsenic, arsenic sulfide slag, and metal arsenate slag.

3. A method for continuous preparation of elemental arsenic from arsenic-containing materials according to claim 1 or 2, characterized in that: The mass ratio of the arsenic-containing material to the carbon powder is 10:1~3.

4. A method for continuous preparation of elemental arsenic from arsenic-containing materials according to claim 1 or 2, characterized in that: The conditions for reduction calcination are: calcination at 800~1000℃ for 2~3 hours under a protective atmosphere.

5. The method for continuous preparation of elemental arsenic from arsenic-containing materials according to claim 1, characterized in that: The spray water is deoxygenated water.

6. A method for continuously preparing elemental arsenic from arsenic-containing materials according to claim 1, characterized in that: In the reverse flotation process, the amount of frother added is 10~20 g / t; the amount of collector added is 10~80 mg / L; and the amount of inhibitor added is 10~200 mg / L.

7. The method for continuous preparation of elemental arsenic from arsenic-containing materials according to claim 1, characterized in that: The drying process employs vacuum drying at a temperature of 50-60°C.

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