A method for preparing metallic arsenic and sulfur fixation by calcium oxide assisted carbothermic reduction of arsenic sulfide residue

Abstract

The application provides a method for preparing metallic arsenic and sulfur fixation by calcium oxide assisted carbothermic reduction of arsenic sulfide residue, comprising: providing a reaction container with a high-temperature zone and a low-temperature zone in communication; reacting arsenic sulfide residue, calcium oxide and a carbon source in the high-temperature zone; the molar ratio of the calcium oxide to arsenic sulfide in the arsenic sulfide residue is not less than 2; the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide residue is not less than 2; the temperature of the high-temperature zone is 750-900 DEG C, the temperature of the low-temperature zone is 650-750 DEG C, and the temperature of the high-temperature zone is higher than that of the low-temperature zone; during the reaction, the generated metallic arsenic transfers to the low-temperature zone, and the generated calcium sulfide stays in the high-temperature zone. The application recovers metallic arsenic and fixes sulfur from arsenic sulfide residue through one-step smelting, avoids the generation of sulfur-containing gas, and improves the recovery rate of the metallic arsenic product.

Description

Technical Field

[0001] This invention belongs to the field of arsenic extraction, and particularly relates to a method for preparing metallic arsenic and fixing sulfur from arsenic slag by carbothermal reduction assisted by calcium oxide. Background Technology

[0002] Industries such as non-ferrous metal smelting and metal ore mining generate large quantities of arsenic sulfide slag, a product of arsenic-containing wastewater treated by sulfide precipitation. Due to its high leaching toxicity and corrosiveness, arsenic sulfide slag is extremely difficult to treat, and improper disposal poses a potential threat to the ecological environment. The common method for treating arsenic sulfide slag is stabilization followed by landfilling; however, this process not only generates large amounts of hazardous waste and poses a risk of secondary pollution, but also wastes valuable metal resources. Therefore, developing efficient and environmentally friendly resource recovery technologies has become an urgent need for the industry.

[0003] Pyrometallurgical processing is one method for recovering arsenic from arsenic sulfide slag, and it is particularly suitable for treating arsenic sulfide slag with high arsenic content. Currently, the pyrometallurgical process for treating arsenic sulfide slag involves first oxidizing it to obtain arsenic trioxide, and then adding a reducing agent for roasting to obtain elemental arsenic. This two-step smelting process increases energy consumption and generates sulfur-containing gases. Furthermore, other existing pyrometallurgical processes face technical bottlenecks such as high processing costs and the potential generation of hazardous waste byproducts during the reaction.

[0004] Therefore, it is necessary to provide a method for preparing metallic arsenic and sulfur fixation from arsenic sulfide slag by calcium oxide-assisted carbothermic reduction, in order to solve the technical problem of how to recover metallic arsenic and fix sulfur from arsenic sulfide slag in a single smelting step. Summary of the Invention

[0005] The main objective of this invention is to provide a method for preparing metallic arsenic and fixing sulfur from arsenic sulfide slag using calcium oxide-assisted carbothermic reduction, aiming to solve the technical problem of how to recover metallic arsenic and fix sulfur from arsenic sulfide slag through a single smelting step.

[0006] To achieve the above objectives, the present invention provides a method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction of arsenic sulfide slag, comprising:

[0007] A reaction vessel is provided, the reaction vessel having a high-temperature zone and a low-temperature zone connected in communication;

[0008] Arsenic sulfide slag, calcium oxide, and carbon source are reacted in the high-temperature zone; the molar ratio of calcium oxide to arsenic sulfide in the arsenic sulfide slag is not less than 2; the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide slag is not less than 2.

[0009] The temperature of the high-temperature zone is 750-900℃, and the temperature of the low-temperature zone is 650-750℃. The temperature of the high-temperature zone is higher than that of the low-temperature zone. During the reaction, the generated metallic arsenic is transferred towards the low-temperature zone, while the generated calcium sulfide remains in the high-temperature zone.

[0010] Furthermore, before the reaction is carried out, the heating rate of the high-temperature zone and the low-temperature zone is 5-15℃ / min; after the reaction is completed, the high-temperature zone and the low-temperature zone are naturally cooled to room temperature.

[0011] Furthermore, the temperature difference between the high-temperature zone and the low-temperature zone is not less than 50°C.

[0012] Furthermore, the reaction vessel includes a horizontally placed tube; one end of the tube is the high-temperature zone, and the other end of the tube is the low-temperature zone.

[0013] Furthermore, the atmosphere of the reaction vessel is one of air, vacuum, or inert gas.

[0014] Furthermore, the carbon source includes at least one of elemental carbon, methane, and carbon monoxide.

[0015] Furthermore, the molar ratio of calcium oxide to arsenic sulfide in the arsenic sulfide slag is 3-4:1; the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide slag is 2-4:1.

[0016] Furthermore, the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide slag is 3-4:1.

[0017] Furthermore, the reaction time is not less than 0.5 h.

[0018] Furthermore, the reaction time is 0.5-2.5 h.

[0019] Compared with the prior art, the present invention has at least the following advantages:

[0020] This invention enables the recovery of metallic arsenic and sulfur fixation from arsenic sulfide slag through a single smelting step. The invention involves reacting arsenic sulfide slag, calcium oxide, and a carbon source in a high-temperature zone. The metallic arsenic generated from the reaction is transferred to a low-temperature zone, while the calcium sulfide generated remains in the high-temperature zone. This method efficiently recovers metallic arsenic while avoiding the generation of sulfur-containing gases.

[0021] This invention uses calcium oxide to fix sulfur in arsenic sulfide slag, which can further ensure the recovery rate of metallic arsenic products. Calcium oxide not only has high sulfur fixation efficiency and can promote the formation of metallic arsenic, but also has little impact on the purity of metallic arsenic products. In addition, the method of recovering metallic arsenic and fixing sulfur from arsenic sulfide slag using calcium oxide and carbon source is short and low-cost. It solves the problems of energy waste and process complexity in the traditional pyrometallurgical treatment of arsenic sulfide slag by oxidation followed by reduction, as well as the high cost of other recovery methods. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a photograph of the metallic arsenic product in Example 1 of the present invention;

[0024] Figure 2 This is a SEM image of the metallic arsenic product in Example 1 of the present invention;

[0025] Figure 3 The image shows the XRD pattern of the metallic arsenic product in Example 1 of this invention.

[0026] Figure 4 This is a photograph of the roasting residue in Example 1 of the present invention;

[0027] Figure 5 This is a SEM image of the roasted slag in Example 1 of the present invention;

[0028] Figure 6 This is the XRD pattern of the roasted slag in Example 1 of the present invention.

[0029] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0032] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0033] This invention provides a method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag, comprising:

[0034] A reaction vessel is provided, the reaction vessel having a high-temperature zone and a low-temperature zone connected in communication.

[0035] Arsenic sulfide slag, calcium oxide, and carbon source are reacted in the high-temperature zone. During the reaction, the temperature of the high-temperature zone is 750-900℃, and the temperature of the low-temperature zone is 650-750℃. The temperature of the high-temperature zone is greater than that of the low-temperature zone. The temperature difference between the high-temperature zone and the low-temperature zone is not less than 50℃, and the temperature difference between the high-temperature zone and the low-temperature zone is further 50-250℃.

[0036] For example, when the carbon source contains elemental carbon or carbon monoxide, the following reaction occurs in the high-temperature zone of the present invention:

[0037] As2S3+ 3CaO + 2C = 2As + 3CaS + CO(g) + CO2(g);

[0038] As2S3+ 3CaO + 3CO(g) = 2As + 3CaS + 3CO2(g).

[0039] In this invention, the arsenic sulfide slag, the calcium oxide, and the metallic arsenic generated from the reaction of the carbon source are transferred to the low-temperature zone, specifically from the high-temperature zone to the low-temperature zone, and the metallic arsenic product is collected after condensation. The arsenic sulfide slag, the calcium oxide, and the calcium sulfide generated from the reaction of the carbon source remain in the high-temperature zone.

[0040] In this invention, the transfer of some or all of the metallic arsenic to the low-temperature zone can be understood as the transfer of metallic arsenic generated by the reaction of the arsenic sulfide slag, the calcium oxide, and the carbon source to the low-temperature zone; the retention of some or all of the calcium sulfide in the high-temperature zone can be understood as the retention of the calcium sulfide generated by the reaction of the arsenic sulfide slag, the calcium oxide, and the carbon source in the high-temperature zone.

[0041] For example, the temperature of the high-temperature zone can be 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, or any range consisting of any two of these values; the temperature of the low-temperature zone can be 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, or any range consisting of any two of these values.

[0042] For example, the temperature difference between the high-temperature zone and the low-temperature zone can be 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, or any range of any two of these values.

[0043] After the reaction is completed, the high-temperature zone and the low-temperature zone are cooled down to room temperature by natural cooling. Then, metallic arsenic products are collected in the low-temperature zone and calcined slag containing calcium sulfide is collected in the high-temperature zone.

[0044] In this invention, the high-temperature zone and the low-temperature zone are independently temperature-controlled; the high-temperature zone and the low-temperature zone are at the same level or arranged opposite each other in the transverse direction. For example, the reaction vessel includes a horizontally placed tube, one end of which is the high-temperature zone and the other end of which is the low-temperature zone.

[0045] In some specific embodiments, the reaction vessel is a multi-temperature zone tube furnace, the main structure of which includes a sealed quartz tube and a heating furnace body sleeved outside the quartz tube. The furnace body has multiple heating zones that are axially distributed and can be independently temperature controlled.

[0046] In this invention, the atmosphere of the reaction vessel is one of air, vacuum, or inert gas; further, the reaction vessel is a vacuum environment or an inert gas environment; when the reaction vessel is a vacuum environment, it means that: before the reaction begins, the inside of the reaction vessel is made into a vacuum state, and the reaction is sealed during the process.

[0047] In this invention, the carbon source includes at least one of elemental carbon, methane, and carbon monoxide; as another embodiment, the carbon source includes at least one of activated carbon, coal, methane, and carbon monoxide.

[0048] In this invention, the main component of the arsenic sulfide slag is arsenic sulfide, and the mass percentage of arsenic sulfide is 60-65%.

[0049] In this invention, the molar ratio of calcium oxide to arsenic sulfide in the arsenic sulfide slag is not less than 2 or not less than 3. In some embodiments, the molar ratio of calcium oxide to arsenic sulfide in the arsenic sulfide slag is 2-5:1; further, the molar ratio of calcium oxide to arsenic sulfide in the arsenic sulfide slag is 2-4:1, 3-5:1, 3-4:1, or 2-3:1.

[0050] In this invention, the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide slag is not less than 2; further, the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide slag is 2-4:1; further, the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide slag is 2-3:1 or 3-4:1. In some specific embodiments of this invention, the carbon source includes elemental carbon, and the molar ratio of elemental carbon to arsenic sulfide in the arsenic sulfide slag is not less than 2, further 2-4:1, further 2-3:1 or 3-4:1; in this case, the carbon source can be at least one of activated carbon and coal. In other specific embodiments of this invention, the carbon source includes or is carbon monoxide, and the molar ratio of carbon monoxide to arsenic sulfide in the arsenic sulfide slag is not less than 3, further 3-4:1.

[0051] In this invention, when the carbon source is solid, the arsenic sulfide slag, the calcium oxide, and the carbon source are ground together and then placed in the high-temperature zone; when the carbon source is gaseous, the arsenic sulfide slag and the calcium oxide are ground together and then placed in the high-temperature zone, and the gaseous carbon source is introduced; before introducing the gaseous carbon source, the reaction vessel can be vacuum-treated.

[0052] In this invention, the reaction time is not less than 0.5 h; further, the reaction time is 0.5-2.5 h; for example, the reaction time can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, or any two of these values.

[0053] In this invention, the reaction time refers to the holding time after both the high-temperature zone and the low-temperature zone have reached their corresponding temperatures. In some embodiments, the heating rate of the high-temperature zone and the low-temperature zone is 5-15℃ / min; for example, the heating rate of the heat treatment can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, or any range of any two of these values.

[0054] This invention introduces calcium oxide, regulates the molar ratio of calcium oxide, carbon source, and arsenic sulfide, and then achieves the generation of metallic arsenic simultaneously with sulfur fixation through a one-step heat-preserving reaction at low cost. The process of this invention is short and low-cost, efficiently obtaining metallic arsenic while effectively fixing sulfur and avoiding secondary pollution. Furthermore, the metallic arsenic obtained by this invention can be applied in optoelectronic materials, alloys, semiconductors, medicine, agriculture, wood preservation, glass, and other fields. The calcium sulfide obtained by this invention can be used as a depilatory agent, insecticide, and in the preparation of luminescent paints and thiourea, demonstrating good environmental and economic benefits.

[0055] The following are specific examples of the present invention:

[0056] In this invention, the recovery rate of metallic arsenic products refers to: (mass of metallic arsenic products ÷ mass of arsenic in arsenic sulfide slag) × 100%; the purity of metallic arsenic products refers to: the atomic percentage of arsenic in metallic arsenic products.

[0057] The arsenic sulfide slag used in all cases of this invention is from the same batch. The main component of the arsenic sulfide slag is arsenic sulfide, accounting for about 63% by mass. The surface elemental composition and content of the arsenic sulfide slag were analyzed by SEM-EDS, and the mass percentage of each element is shown in Table 1.

[0058]

[0059] Example 1

[0060] A method for preparing metallic arsenic using arsenic sulfide slag, comprising the following steps:

[0061] S1, Arsenic sulfide slag, calcium oxide and activated carbon powder are ground together to obtain a mixture, and the molar ratio of arsenic sulfide, calcium oxide and carbon is 1:3:2;

[0062] The mixture is placed at one end of a quartz tube and then placed horizontally in a multi-temperature zone tube furnace. The quartz tube is then vacuum treated and sealed. The mixture is placed in the high-temperature zone, and the other end of the quartz tube, which is horizontally opposite to the high-temperature zone, is the low-temperature zone.

[0063] S2, the high-temperature zone is heated to 800℃ at a heating rate of 10℃ / min, and the low-temperature zone is simultaneously heated to 650℃ at a heating rate of 10℃ / min, and then kept at that temperature for 1.5h.

[0064] S3, after the heat preservation ends, the high temperature zone and the low temperature zone are naturally cooled to room temperature, and the roasting residue in the high temperature zone and the metallic arsenic products in the low temperature zone are collected.

[0065] See Figure 1 As shown, metallic arsenic products have a metallic luster; see also Figures 2-3 As shown, the main product of metallic arsenic is metallic arsenic; in this embodiment, the recovery rate of the metallic arsenic product is 99.51%. See also Figures 4-6 As shown, the roasting residue is mainly calcium sulfide.

[0066] The surface elemental composition and content of metallic arsenic products and roasted slag were analyzed by SEM-EDS. The atomic percentage of each element is shown in Table 2.

[0067]

[0068] As can be seen from Table 2, the purity of the metallic arsenic product is extremely high, with a purity of 99.41%; only a small amount of arsenic element remains in the roasting residue.

[0069] Example 2

[0070] A method for preparing metallic arsenic using arsenic sulfide slag, comprising the following steps:

[0071] S1, Arsenic sulfide slag, calcium oxide and activated carbon powder are ground together to obtain a mixture, and the molar ratio of arsenic sulfide, calcium oxide and carbon is 1:3:2;

[0072] The mixture is placed at one end of a quartz tube and then placed horizontally in a multi-temperature zone tube furnace. The quartz tube is then vacuum treated and sealed. The mixture is placed in the high-temperature zone, and the other end of the quartz tube, which is horizontally opposite to the high-temperature zone, is the low-temperature zone.

[0073] S2, the high-temperature zone is heated to 850℃ at a heating rate of 10℃ / min, and the low-temperature zone is simultaneously heated to 650℃ at a heating rate of 10℃ / min, and then kept at that temperature for 2 hours.

[0074] S3, after the heat preservation ends, the high temperature zone and the low temperature zone are naturally cooled to room temperature, and the roasting residue in the high temperature zone and the metallic arsenic products in the low temperature zone are collected.

[0075] In this embodiment, the recovery rate of metallic arsenic products was 99.4%; the purity of metallic arsenic products was 99.37%.

[0076] Example 3

[0077] A method for preparing metallic arsenic using arsenic sulfide slag, comprising the following steps:

[0078] S1, Arsenic sulfide slag, calcium oxide and activated carbon powder are ground together to obtain a mixture, and the molar ratio of arsenic sulfide, calcium oxide and carbon is 1:4:2;

[0079] The mixture is placed at one end of a quartz tube and then placed horizontally in a multi-temperature zone tube furnace. The quartz tube is then vacuum treated and sealed. The mixture is placed in the high-temperature zone, and the other end of the quartz tube, which is horizontally opposite to the high-temperature zone, is the low-temperature zone.

[0080] S2, the high-temperature zone is heated to 800℃ at a heating rate of 10℃ / min, and the low-temperature zone is simultaneously heated to 750℃ at a heating rate of 10℃ / min, and then kept at that temperature for 2 hours.

[0081] S3, after the heat preservation ends, the high temperature zone and the low temperature zone are naturally cooled to room temperature, and the roasting residue in the high temperature zone and the metallic arsenic products in the low temperature zone are collected.

[0082] In this embodiment, the recovery rate of metallic arsenic product was 94.55%; the purity of metallic arsenic product was 99.13%.

[0083] Example 4

[0084] A method for preparing metallic arsenic using arsenic sulfide slag, comprising the following steps:

[0085] S1. Arsenic sulfide slag and calcium oxide are ground and mixed and placed at one end of a quartz tube. After vacuum treatment, carbon monoxide is introduced and the tube is sealed. The molar ratio of arsenic sulfide, calcium oxide and carbon monoxide is 1:3:3. The quartz tube is placed horizontally in a multi-temperature zone tube furnace. The arsenic sulfide slag and calcium oxide are placed in the high-temperature zone, and the other end of the quartz tube opposite the high-temperature zone in the horizontal direction is the low-temperature zone.

[0086] S2, the high-temperature zone is heated to 800℃ at a heating rate of 10℃ / min, and the low-temperature zone is simultaneously heated to 650℃ at a heating rate of 10℃ / min, and then kept at that temperature for 2 hours.

[0087] S3, after the heat preservation ends, the high temperature zone and the low temperature zone are naturally cooled to room temperature, and the roasting residue in the high temperature zone and the metallic arsenic products in the low temperature zone are collected.

[0088] In this embodiment, the recovery rate of metallic arsenic product was 99.41%; the purity of metallic arsenic product was 99.08%.

[0089] Comparative Example 1

[0090] Compared to Example 1, this comparative example only changed the insulation temperature of the low-temperature zone to 600°C, while keeping other conditions unchanged.

[0091] In this comparative example, the recovery rate of metallic arsenic products was only 66.63%; the purity of metallic arsenic products was 99.45%.

[0092] Analysis example 1

[0093] Compared to Example 1, this analytical example adjusted the heat preservation time to 2 hours and compared the experimental results of arsenic sulfide, calcium oxide, and carbon at different molar ratios, while keeping other conditions unchanged.

[0094] In this analysis, the molar ratios of arsenic sulfide, calcium oxide, and carbon were 1:3:1, 1:3:2, 1:3:3, 1:3:4, 1:1:2, 1:2:2, and 1:4:2, respectively. The corresponding recoveries of metallic arsenic were 21.36%, 99.44%, 99.15%, 98.56%, 18.5%, 92.57%, and 99.78%, respectively, and the corresponding purities of metallic arsenic were 98.39%, 99.61%, 98.68%, 98.21%, 98.02%, 98.58%, and 99.13%, respectively.

[0095] Analysis example 2

[0096] Compared to Example 1, this analytical example only adjusts the heat preservation time, while keeping other conditions unchanged.

[0097] In this analysis, the heat preservation times were 0.5h, 1h, and 2.5h, respectively, with corresponding arsenic metal recovery rates of 95.88%, 95.09%, and 92.31%, and corresponding arsenic metal purity of 99.32%, 99.07%, and 99.57%.

[0098] Analysis example 3

[0099] Compared to Example 2, this analysis example only adjusts the insulation temperature of the high-temperature zone, while keeping other conditions unchanged.

[0100] In this analysis, the heat preservation temperatures in the high-temperature zone were 700℃ and 750℃, respectively, with corresponding arsenic metal recovery rates of 9.25% and 92.68%, and corresponding arsenic metal purities of 98.77% and 98.95%, respectively.

[0101] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag, characterized in that, include: A reaction vessel is provided, the reaction vessel having a high-temperature zone and a low-temperature zone connected in communication; Arsenic sulfide slag, calcium oxide, and carbon source are reacted in the high-temperature zone; the molar ratio of calcium oxide to arsenic sulfide in the arsenic sulfide slag is not less than 2; the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide slag is not less than 2. The temperature of the high-temperature zone is 750-900℃, and the temperature of the low-temperature zone is 650-750℃. The temperature of the high-temperature zone is higher than that of the low-temperature zone. During the reaction, the generated metallic arsenic is transferred towards the low-temperature zone, while the generated calcium sulfide remains in the high-temperature zone.

2. The method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag according to claim 1, characterized in that, Before the reaction is carried out, the heating rate of the high-temperature zone and the low-temperature zone is 5-15℃ / min; after the reaction is completed, the high-temperature zone and the low-temperature zone are naturally cooled to room temperature.

3. The method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag according to claim 1, characterized in that, The temperature difference between the high-temperature zone and the low-temperature zone is not less than 50°C.

4. The method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag according to claim 1, characterized in that, The reaction vessel includes a horizontally placed tube; one end of the tube is the high-temperature zone, and the other end of the tube is the low-temperature zone.

5. The method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag according to claim 1, characterized in that, The atmosphere of the reaction vessel is either vacuum or an inert gas.

6. The method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag according to claim 1, characterized in that, The carbon source includes at least one of elemental carbon, methane, and carbon monoxide.

7. The method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag according to claim 1, characterized in that, The molar ratio of calcium oxide to arsenic sulfide in the arsenic sulfide slag is 3-4:1; the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide slag is 2-4:

1.

8. The method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag according to claim 7, characterized in that, The molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide slag is 3-4:

1.

9. The method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag according to any one of claims 1-8, characterized in that, The reaction time is not less than 0.5 h.

10. The method for preparing metallic arsenic and fixing sulfur from calcium oxide-assisted carbothermic reduction arsenic sulfide slag according to claim 9, characterized in that, The reaction time is 0.5-2.5 h.

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