Method for resource utilization of arsenic and antimony-containing alkaline residue
By employing reduction smelting and vacuum volatilization smelting methods, the problem of resource utilization of arsenic-antimony-containing alkaline slag has been solved, achieving efficient separation and recovery of arsenic and antimony, and has broad prospects for industrial application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2023-10-30
- Publication Date
- 2026-06-19
Smart Images
Figure CN117431418B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of comprehensive utilization of arsenic-antimony-containing alkali slag, and particularly to a method for the resource-based, clean, and full-scale utilization of arsenic-antimony-containing alkali slag. Background Technology
[0002] Antimony plays a vital role in photovoltaic material manufacturing, lead-acid energy storage, and machinery manufacturing. Currently, antimony is mainly produced through a process of volatilization smelting, reduction smelting, and alkaline refining. The oxidative refining process generates a large amount of arsenic-containing antimony alkaline slag, with the national antimony smelting industry producing over 20,000 tons per year. This arsenic-containing alkaline slag contains 3-20% arsenic, often in the form of sodium arsenate. Due to the high solubility of sodium arsenate, improper disposal of this arsenic-containing alkaline slag poses a significant risk to the surrounding environment of the smelters.
[0003] Currently, my country extensively uses arsenic-containing crude antimony or arsenic-containing crude antimony oxygen to produce sodium antimonate pyroplatin, generating over 60,000 tons / year of arsenic-containing antimony alkali slag. Simultaneously, some enterprises in my country use alkaline electrowinning processes for antimony smelting, also producing large quantities of arsenic-containing antimony alkali slag annually, which is difficult to utilize cleanly and effectively, placing significant environmental and economic pressure on these enterprises. Currently, efficient, clean, and comprehensive resource utilization technology for arsenic-containing antimony alkali slag is a bottleneck that urgently needs to be overcome in this field.
[0004] Currently, the main method for treating arsenic-antimony-containing alkaline slag is wet precipitation, which first utilizes the difference in water solubility between arsenates and antimonates to separate arsenic and antimony. The resulting arsenic-containing solution is then solidified using calcium and iron salt precipitation and sulfide precipitation. However, practice has shown that calcium salt precipitation is not ideal, requiring large quantities and resulting in only 4-9% arsenic content in the solidified slag. Furthermore, due to the instability of calcium arsenate, the solidified slag still requires storage in a slag plant. Iron salt precipitation, on the other hand, requires significant acidity for pH adjustment under acidic conditions. Moreover, sodium carbonate in the arsenic-antimony-containing alkaline slag can react with calcium salts and acids, making sodium carbonate recovery impossible using either calcium or iron salt precipitation. Some literature reports the use of sulfide precipitation for treating arsenic-antimony-containing alkaline slag, but this method is difficult to separate arsenic and antimony and is costly, limiting its large-scale application. To address this, ZL 200410013369.2 proposed a stepwise crystallization process for preparing sodium arsenate. The sodium arsenate prepared by this process is mainly used as a glass clarifying agent. However, in recent years, the glass industry has widely adopted sodium antimonate as a clarifying agent, making it difficult to find suitable applications for the sodium arsenate prepared by this process. In conclusion, there is an urgent need in this field to develop a new process for the efficient, clean, and complete resource utilization of arsenic-antimony-containing alkali slag. Summary of the Invention
[0005] Addressing the bottlenecks in the resource utilization of arsenic-antimony-containing alkali slag, the present invention aims to provide a method for the resource utilization of arsenic-antimony-containing alkali slag. This method is simple, easy to operate, and can achieve efficient, clean, and full-scale resource utilization of arsenic-antimony-containing alkali slag.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] This invention discloses a method for the resource utilization of arsenic-antimony-containing alkaline slag. The method involves mixing arsenic-antimony-containing alkaline slag, an iron source, and a reducing agent to obtain a mixture, reducing and smelting the mixture, separating FeAs-Sb alloy and alkali-containing molten salt, and then performing volatilization smelting of the FeAs-Sb alloy under vacuum to volatilize the antimony, thereby obtaining antimony powder and FeAs alloy residue.
[0008] The method provided by this invention first involves uniformly mixing arsenic-antimony-containing alkaline slag, iron slag, and reducing agent, followed by reduction smelting to obtain a lower layer of FeAs-Sb alloy and an upper layer of alkali-containing molten salt. After separation, the obtained FeAs-Sb alloy is placed in a vacuum volatilization furnace for vacuum volatilization smelting. After smelting, FeAs alloy and elemental antimony are obtained respectively.
[0009] The inventors discovered that arsenic-antimony-containing alkaline slag mainly consists of sodium arsenate, sodium antimonate, and sodium carbonate, sometimes containing small amounts of sodium hydroxide and sodium sulfate. Under reducing conditions, sodium arsenate and sodium antimonate can be reduced to their metallic state. Furthermore, the reduction process also yields sodium carbonate products, which can float on the surface of the molten metal along with the sodium salts in the arsenic-antimony slag, thus regenerating sodium salts such as sodium carbonate. Simultaneously, because iron can form stable intermetallic compounds with arsenic, such as FeAs, Fe2As, Fe3As2, FeSb2, and Fe3Sb2, and in the Fe-Sb-As system, iron preferentially forms FeAs intermetallic compounds with As, and antimony does not dissolve in FeAs. Due to its high density, chemical stability, and low leaching toxicity, FeAs can be used as a counterweight in equipment manufacturing.
[0010] Therefore, in this invention, arsenic-antimony-containing alkaline slag, iron slag, and reducing agent are directly mixed during operation and subjected to high-temperature reduction smelting. The sodium salts such as sodium carbonate produced during smelting are located in the upper layer of the melt. After slag removal, the sodium carbonate molten salt is regenerated, while the lower layer of the melt yields a FeAs-Sb alloy.
[0011] In FeAs-Sb alloys, Sb and FeAs are immiscible, and the FeAs alloy is stable and does not easily decompose, remaining in the FeAs alloy form even at high temperatures. However, antimony has a high vapor pressure at high temperatures, and FeAs and Sb can be separated simply by heating and volatilizing. In production, to reduce the volatilization temperature of Sb and reduce volatilization energy consumption, vacuum volatilization can be used. By reducing the vacuum level of the system, antimony can be volatilized at low temperatures. Therefore, this invention places the obtained FeAs-Sb alloy in a vacuum volatilization furnace to selectively volatilize Sb under specific conditions. The FeAs alloy remains in the volatilization residue, while Sb enters the gas phase and is finally collected by recondensing into a solid phase in a condenser, achieving efficient separation of FeAs and Sb. The collected FeAs alloy is stable and has low leaching toxicity, and can be directly sold as a counterweight material. The volatilized Sb has high purity and can also be sold directly. Overall, the method for resource utilization of arsenic-antimony-containing alkaline slag disclosed in this invention has a simple process, good raw material adaptability, is clean and environmentally friendly, and has high social and economic value, and has great application potential.
[0012] In a preferred embodiment, the iron source is selected from iron and / or iron-containing compounds.
[0013] In this invention, the iron and / or iron-containing compounds can be selected from pure iron or pure iron-containing compounds, or iron-containing waste, such as iron-containing dust and / or iron-containing solid waste, wherein pure iron is selected from iron powder and / or iron ingots.
[0014] In a preferred embodiment, the molar ratio of iron in the iron source to arsenic in the arsenic-antimony-containing alkaline slag is 1–1.5:1. The inventors have found that controlling the molar ratio of iron in the iron source to arsenic in the arsenic-antimony-containing alkaline slag within this range yields the best results. If insufficient iron is added, As cannot be completely fixed into FeAs alloy, and a large amount of As remains in the system. During vacuum volatilization, As volatilizes along with antimony, resulting in a low arsenic fixation rate. If excessive iron is added, the excess Fe forms FeSb2 intermetallic compound with Sb, which reduces the antimony volatilization rate, thus reducing the antimony recovery rate and resulting in poor arsenic-antimony separation.
[0015] In a preferred embodiment, the reducing agent is selected from carbonaceous reducing agents and / or non-carbonaceous reducing agents. The carbonaceous reducing agent is selected from at least one of natural gas, pulverized coal, heavy oil, diesel oil, waste engine oil, biodiesel, waste edible oil, and biomass carbon. The non-carbonaceous reducing agent is hydrogen.
[0016] In a preferred embodiment, the amount of reducing agent is 1.05 to 2.5 times the sum of the theoretical amounts required to reduce both arsenic and antimony in the arsenic-antimony-containing alkaline slag to elemental form and to reduce iron in the iron slag to elemental form.
[0017] In a preferred embodiment, the reduction melting temperature is 1000–1200°C.
[0018] The inventors discovered that the temperature of reduction smelting needs to be controlled within the range of this invention. If the temperature of reduction smelting is too low, the fluidity of the alloy phase and slag phase will become poor, a large amount of gas cannot be effectively discharged, and the alloy and slag will be difficult to separate.
[0019] In a preferred embodiment, the reduction smelting time is 1 to 4 hours.
[0020] In a preferred embodiment, after the reduction smelting is completed, a lower layer of FeAs-Sb alloy and an upper layer of alkali-containing molten salt are obtained, which are then separated to obtain FeAs-Sb alloy and alkali-containing molten salt respectively.
[0021] In a preferred embodiment, the alkali-containing molten salt is returned to the crude antimony refining or sodium pyroantimonate preparation process.
[0022] In a preferred embodiment, the temperature of the volatilization smelting is 650–950°C. In this invention, controlling the volatilization smelting temperature within this range yields the optimal separation effect. If the vacuum volatilization temperature is too low, the saturated vapor pressure of antimony is low, and the volatilization rate is slow, making efficient separation of Sb and FeAs impossible. If the vacuum volatilization temperature is too high, FeAs will gradually decompose, and some As will volatilize into the antimony condensate, resulting in a poorer arsenic-antimony separation effect.
[0023] In a preferred embodiment, the volatilization melting time is 1 to 6 hours.
[0024] In a preferred embodiment, the vacuum degree of the volatile melting is less than 2000 Pa.
[0025] In a preferred embodiment, the FeAs-Sb alloy is placed in a vacuum volatilization furnace, which is connected to a condensing chamber. The volatilization melting is carried out in a vacuum environment to volatilize the antimony. The antimony is collected through the condensing chamber. After the volatilization melting is completed, antimony powder is obtained in the condensing chamber and FeAs alloy residue is obtained in the vacuum volatilization furnace.
[0026] In a further preferred embodiment, the temperature of the condensation chamber is less than 100°C, preferably 60–95°C.
[0027] Beneficial effects
[0028] The method of this invention first mixes arsenic-antimony-containing alkaline slag and iron slag with a reducing agent and then performs reduction smelting to obtain FeAs-Sb alloy and alkali-containing molten salt. The alkali-containing molten salt can be returned as an additive to the crude antimony refining or sodium antimonate pyroplating process, while the FeAs-Sb alloy is placed in a vacuum volatilization furnace for vacuum volatilization smelting. After smelting, FeAs alloy and elemental antimony are obtained separately. This invention's novel "reduction smelting-vacuum volatilization smelting" process for treating arsenic-antimony-containing alkaline slag not only achieves efficient separation of arsenic and antimony from the slag, yielding FeAs alloy and metallic antimony respectively. The FeAs alloy obtained by this invention has stable properties and can be used in industrial counterweights and other fields to achieve large-scale arsenic disposal, while the obtained metallic antimony can be sold directly as a product or further refined to obtain refined antimony. This process achieves clean, efficient, and resource-based full utilization of arsenic-antimony-containing alkaline slag, with significant socio-economic benefits and a very broad prospect for industrial application. Attached Figure Description
[0029] Figure 1 XRD pattern of FeAs-Sb alloy obtained by reduction melting in Example 1.
[0030] Figure 2 Example 1: XRD pattern of antimony powder collected by vacuum volatilization and condensation of FeAs-Sb alloy. Detailed Implementation
[0031] The following examples are intended to further illustrate the present invention, but not to limit it.
[0032] Example 1
[0033] Step 1: 1000 kg of arsenic-antimony alkaline slag containing 17% arsenic and 23.7% antimony, produced by an antimony refining reverberatory furnace, is mixed evenly with 128 kg of iron powder and 145 kg of coal powder. The above materials are then subjected to reduction smelting at 1000℃ for 4 hours. After the reduction is completed, 675.82 kg of molten salt containing Na2CO3 and 534.61 kg of FeAs-Sb alloy are obtained. The molten salt containing Na2CO3 can be directly returned to the antimony refining reverberatory furnace for use.
[0034] Step two: The FeAs-Sb alloy obtained in Step one was placed in a vacuum volatilization furnace. Under conditions of 900℃ and 1000Pa vacuum, the temperature of the antimony condensation chamber was set to 95℃, and vacuum volatilization was carried out for 1 hour. After volatilization, 302.11 kg of volatilization residue and 232.50 kg of antimony were obtained. Analysis showed that the residue was a FeAs alloy with an arsenic content of 56.21% and an iron content of 42.47%.
[0035] The entire process achieves a direct antimony recovery rate of 98.10% and an arsenic fixation rate as high as 99.89%. Arsenic is retained in the stable volatile residue FeAs, and antimony is recovered in elemental form.
[0036] Example 2
[0037] Step 1: 1000 kg of arsenic-antimony crystalline alkaline slag containing 17% arsenic and 23.7% antimony, obtained from the mother liquor crystallization process during the production of sodium pyroantimonate from antimony flue ash, is mixed evenly with 185 kg of Fe₂O₃ and 250 kg of charcoal. The mixture is then subjected to reduction smelting at 1200℃ for 2 hours. After reduction, 610.59 kg of molten salt containing NaOH and Na₂CO₃ and 535.94 kg of FeAs-Sb alloy are obtained. The molten salt containing NaOH and Na₂CO₃ can be returned as an auxiliary agent for the preparation of sodium pyroantimonate or used as a solvent in the antimony refining reverberatory furnace.
[0038] Step two: The FeAs-Sb alloy obtained in Step one was placed in a vacuum volatilization furnace. Under conditions of 650℃ and 50 Pa vacuum, the temperature of the antimony condensation chamber was set to 60℃, and vacuum volatilization was carried out for 6 hours. After volatilization, 310.07 kg of volatilization residue and 226.08 kg of antimony were obtained. Analysis showed that the residue was a FeAs alloy, with an arsenic content of 54.54% and an iron content of 41.73%.
[0039] The entire process achieves a direct antimony recovery rate of 95.39% and an arsenic fixation rate as high as 99.47%. Arsenic is retained in the stable volatile residue FeAs, and antimony is recovered in elemental form.
[0040] Example 3
[0041] Step 1: 1000 kg of arsenic-antimony-containing alkaline slag, obtained by crystallization from stibnite alkaline electrodeposition depletion solution (containing 18.94% arsenic and 24.80% antimony), is mixed evenly with 261.25 kg of goethite slag containing 54.19% iron. The mixture is then heated at 1100°C and 120 m³ of hot water is introduced into the melt. 3 The reduction smelting process under natural gas conditions lasted for 1 hour, yielding 624.38 kg of molten salt containing Na2CO3 and 577.64 kg of FeAs-Sb alloy. The Na2CO3-containing molten salt can be recycled as an additive in the antimony refining reverberatory furnace.
[0042] Step two: The FeAs-Sb alloy obtained in Step one was placed in a vacuum volatilization furnace at a temperature of 950℃ and a vacuum degree of 0.1 Pa. The temperature of the antimony condensation chamber was set to 80℃, and vacuum volatilization was carried out for 2 hours. After volatilization, 332.21 kg of volatilization residue and 245.43 kg of antimony were obtained. Analysis showed that the residue was FeAs alloy with an arsenic content of 56.85% and an iron content of 42.61%.
[0043] The entire process achieves a direct antimony recovery rate of 98.96% and an arsenic fixation rate as high as 99.71%. Arsenic is retained in the stable volatile residue FeAs, and antimony is recovered in elemental form.
[0044] Example 4
[0045] Step 1: 1000 kg of arsenic-alkali slag (containing 9.61% arsenic and 24.15% antimony) from antimony smelting is mixed evenly with 107.75 kg of commercial Fe₂O₃ and 120 kg of starch. The mixture is then placed at 1050℃ for reduction smelting for 3 hours. After reduction, 658.37 kg of molten salt containing NaOH and Na₂CO₃ and 412.55 kg of FeAs-Sb alloy are obtained. The molten salt containing NaOH and Na₂CO₃ can be directly returned to antimony refining for use.
[0046] Step two: The FeAs-Sb alloy obtained in Step one was placed in a vacuum volatilization furnace. Vacuum volatilization was carried out at 700℃ and 2000 Pa, with the antimony condensation chamber temperature set to 80℃ for 6 hours. After volatilization, 187.61 kg of volatilization residue and 224.94 kg of antimony were obtained. Analysis showed that the residue was a FeAs alloy, with an arsenic content of 51.12% and an iron content of 40.20%.
[0047] The total antimony recovery rate is 93.14%, and the arsenic fixation rate is as high as 99.79%. The arsenic is retained in the stable volatile residue FeAs, and the antimony is recovered in elemental form.
[0048] Comparative Example 1 (insufficient iron added)
[0049] Comparative Example 1 is basically the same as Example 1, except that the mass of iron powder is only 100 kg.
[0050] After vacuum volatilization, the mass of the volatilization residue was 232.64 kg, with arsenic content of 57.01%, iron content of 42.57%, and antimony content of 0.42%. The mass of antimony was 272.21 kg, with an arsenic content of 13.51%, an arsenic fixation rate of only 78.31%, and an antimony recovery rate of 99.30%.
[0051] The arsenic fixation rate in Comparative Example 1 was low because the amount of Fe added during the reduction process was insufficient, which could not completely fix As into FeAs alloy. A large amount of active As remained in the system, which volatilized along with antimony during the vacuum volatilization process, resulting in a low arsenic fixation rate.
[0052] Comparative Example 2 (Reduction Melting Temperature Too Low)
[0053] Comparative Example 2 is basically the same as Example 1, except that the reduction melting temperature is 900°C.
[0054] After reduction smelting, the melt contains a large number of bubbles, and the metallic and slag phases are mixed without a clear boundary layer. The alloy phase cannot be discharged separately through the drain port of the reduction smelting furnace. The melt has high viscosity and poor fluidity, making it impossible to effectively separate the slag and alloy phases. This makes it impossible to carry out vacuum volatilization of the alloy.
[0055] The reduction temperature of Comparative Example 2 was too low, resulting in poor fluidity of the alloy phase and slag phase, a large amount of gas could not be effectively discharged, and the alloy and slag were difficult to separate.
[0056] Comparative Example 3 (too much iron added)
[0057] Comparative Example 3 is basically the same as Example 4, except that the mass of the commercial Fe2O3 is 123 kg.
[0058] After vacuum volatilization, the mass of the volatilization residue was 244.70 kg, and the residue contained 39.19% arsenic, 35.19% iron, and 25.63% antimony. The mass of antimony was 175.97 kg, the arsenic fixation rate was 99.79%, and the antimony recovery rate was only 74.87%.
[0059] The antimony direct recovery rate of Comparative Example 3 was low because too much Fe was added, which caused the excess Fe to form FeSb2 intermetallic compound with Sb, which reduced the volatilization rate of antimony and thus reduced the direct recovery rate of antimony, resulting in poor arsenic-antimony separation.
[0060] Comparative Example 4 (Vacuum evaporation temperature too low)
[0061] Comparative Example 4 is basically the same as Example 4, except that the temperature at which the alloy volatilizes is 600°C.
[0062] After vacuum volatilization, the mass of the volatilization residue was 315.47 kg, with arsenic content of 30.28%, iron content of 23.90%, and antimony content of 45.81%. The antimony mass was 107.14 kg, the arsenic fixation rate was 99.40%, and the antimony recovery rate was only 44.36%.
[0063] The antimony direct recovery rate of Comparative Example 4 is relatively low because the vacuum evaporation temperature is low, the saturated vapor pressure of antimony is low, and the evaporation rate is slow, making it impossible to achieve efficient separation of Sb and FeAs.
[0064] Comparative Example 5 (Vacuum evaporation temperature too high)
[0065] Comparative Example 5 is basically the same as Example 4, except that the temperature at which the alloy volatilizes is 1100°C.
[0066] After vacuum volatilization, the mass of the volatilization residue was 137.44 kg, and the residue contained 20.15% arsenic, 48.93% iron, and 2.11% antimony. The condensed antimony powder obtained contained 9.33% arsenic.
[0067] The arsenic content in the condensed antimony powder collected in Comparative Example 5 was as high as 9% or more. Compared with Example 4, arsenic and antimony separation was not performed because the temperature of vacuum volatilization was too high, which caused FeAs to gradually decompose in the later stage of vacuum volatilization, and some As volatilized into the antimony condensed dust, thus failing to achieve the effect of arsenic and antimony separation.
Claims
1. A method for the resource utilization of arsenic-antimony-containing alkaline slag, characterized in that: Arsenic-antimony alkali slag, iron source and reducing agent are mixed to obtain a mixture. The mixture is reduced and smelted, separated to obtain FeAs-Sb alloy and alkali molten salt. The FeAs-Sb alloy is volatilized and smelted in a vacuum environment to volatilize antimony and obtain antimony powder and FeAs alloy residue. The molar ratio of iron in the iron source to arsenic in the arsenic-antimony-containing alkaline slag is 1~1.5:1; The temperature of the volatilization melting is 650~950℃, the time of the volatilization melting is 1~6h, and the vacuum degree of the volatilization melting is less than 2000 Pa.
2. The method for resource utilization of arsenic-antimony-containing alkaline residue according to claim 1, characterized in that: The iron source is selected from iron and / or iron-containing compounds.
3. The method for resource utilization of arsenic-antimony-containing alkaline slag according to claim 1, characterized in that: The reducing agent is selected from carbonaceous reducing agents and / or non-carbonaceous reducing agents. The carbonaceous reducing agent is selected from at least one of natural gas, pulverized coal, heavy oil, diesel oil, waste engine oil, biodiesel, waste edible oil, and biomass carbon. The non-carbonaceous reducing agent is hydrogen.
4. The method for resource utilization of arsenic and antimony containing alkaline residue according to claim 1, characterized in that: The amount of reducing agent is 1.05 to 2.5 times the sum of the theoretical amounts required to reduce both arsenic and antimony in arsenic-antimony alkali slag to elemental form and to reduce iron in iron slag to elemental form.
5. The method for resource utilization of arsenic-antimony-containing alkaline slag according to claim 1, characterized in that: The reduction smelting temperature is 1000~1200℃, and the reduction smelting time is 1~4 h.
6. The method for resource utilization of arsenic-antimony-containing alkaline slag according to claim 1, characterized in that: After the reduction smelting is completed, a lower layer of FeAs-Sb alloy and an upper layer of alkali-containing molten salt are obtained. They are then separated to obtain FeAs-Sb alloy and alkali-containing molten salt, respectively.
7. The method for resource utilization of arsenic and antimony containing alkaline residue according to claim 1, characterized in that: The FeAs-Sb alloy is placed in a vacuum volatilization furnace, which is connected to a condensing chamber. Antimony is volatilized and melted in a vacuum environment. Antimony is collected through the condensing chamber. After the volatilization and melting are completed, antimony powder is obtained in the condensing chamber and FeAs alloy residue is obtained in the vacuum volatilization furnace.
8. The method for resource utilization of arsenic and antimony containing alkaline residue according to claim 7, characterized in that: The temperature of the condensation chamber is less than 100°C.