A green synergistic treatment method for lithium residue

Abstract

The application discloses a kind of green synergic treatment methods of lithium residue, it is related to mineral slag processing technical field.The method includes: lithium residue and aluminum ash are mixed, and reaction precursor is obtained by ball milling treatment;Reaction precursor is carried out reduction reaction under the condition of protective atmosphere and negative pressure, and solid product and smoke containing beryllium, thallium and fluorine are generated;Smoke is collected by condensation trapping, pickling and alkaline washing, and beryllium, thallium and fluorine are efficiently recovered;Condensation trapping is immersed in acid, and then the acid leaching solution is mixed with pickling liquor to obtain mixed acid, adjust pH, and after standing, solid-liquid separation is carried out, to obtain beryllium hydroxide solid and thallium-rich supernatant;Binder and water are added to solid product to form spherical particles, dried, and sintered into ceramsite by solid phase.The application removes gypsum and aluminum nitride by synergistic effect, and realizes harmless treatment of both, prepares calcium-aluminum-silicon resources into ceramsite, and is applied in building material field, not only can improve the comprehensive utilization rate of two kinds of solid waste, but also can reduce environmental pressure.

Description

Technical Field

[0001] This invention relates to the field of slag treatment technology, and more specifically, to a green and synergistic method for treating lithium slag. Background Technology

[0002] Lithium slag is a solid waste generated during the lithium extraction process from lithium ore. Its main components are silicon dioxide and alumina, along with heavy metals such as beryllium and thallium, as well as sulfates. In 2023, lithium slag production reached 15 million tons, with a comprehensive utilization rate of only 30%. The toxic components such as beryllium and thallium in lithium slag not only cause continuous environmental degradation but also pose a serious threat to the survival and development of enterprises. However, from a resource perspective, the chemical composition of lithium slag is similar to that of natural ore, possessing potential chemical activity and utilization value. Sulfuric acid roasting and the sulfuric acid process are core technologies in lithium extraction. During the acidification process, the reaction of excessive sulfuric acid with calcium-containing minerals leads to the production of large amounts of gypsum in the lithium slag. The presence of gypsum is one of the core bottlenecks limiting the resource utilization of lithium slag. Its high content not only degrades the performance of lithium slag-based building materials and ceramics but also easily leads to co-migration with toxic components such as fluorine, beryllium, and thallium, exacerbating the risk of toxic leaching. Currently, lithium slag treatment technologies mainly involve physical blending, low-temperature activation, and high-temperature solidification. However, these methods do not thoroughly treat the gypsum, leading to significant fluctuations in the mechanical properties and volume stability of end materials made from lithium slag, making it difficult to meet industrial-grade product standards. Furthermore, these processes still result in high levels of residual toxic elements and secondary pollution. Existing technologies lack targeted solutions for the removal of gypsum and the harmless treatment of toxic elements in lithium slag, limiting their large-scale application in various fields. Therefore, simultaneously removing gypsum and effectively separating toxic components is a core technological bottleneck that urgently needs to be overcome to achieve high-value conversion of calcium, aluminum, and silicon resources in lithium slag.

[0003] Aluminum ash is a byproduct of aluminum industry production, primarily composed of alumina, silicate minerals, active components (metallic aluminum and aluminum nitride), aluminum fluoride, and soluble salts. The active components react violently with water or humid air, releasing ammonia, hydrogen, and methane, posing a risk of combustion and explosion. Furthermore, the soluble fluorides are environmentally toxic. Wet processing is currently one of the main technologies for the harmless treatment and resource utilization of aluminum ash. Wet processing uses acid and alkali leaching to extract aluminum in ionic form, recovering aluminum salts from the filtrate. However, it suffers from significant aluminum recovery losses and challenging wastewater treatment. Therefore, effectively and safely treating the toxic components in aluminum ash while enabling high-value utilization of alumina and silicate minerals has become a pressing technical problem that needs to be solved.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a green method for the synergistic treatment of lithium slag. Since lithium slag and aluminum ash have complementary compositional characteristics, the gypsum in lithium slag and aluminum nitride in aluminum ash are removed through a synergistic reaction, and beryllium is simultaneously solidified and thallium is removed, thereby achieving the harmless treatment of both. The detoxified products are then prepared into high-strength ceramsite for application in the building materials field. This not only improves the comprehensive utilization rate of the two solid wastes but also reduces environmental pressure.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a green co-processing method for lithium slag, comprising: S1. Lithium slag and aluminum ash are mixed and ball-milled to obtain a reaction precursor; S2. The reaction precursor is placed in the heating zone of a dual-temperature zone heating container and heated under a protective atmosphere and negative pressure to produce solid products and flue gas containing beryllium, thallium and fluorine. S3. The flue gas is condensed and collected in the condensation zone of the dual-temperature zone heating container to obtain beryllium-thallium condensate. The flue gas is then acid-washed and absorbed to obtain beryllium-thallium acid washing solution. The fluorine-containing acidic tail gas discharged after acid washing is collected by alkaline solution to obtain fluoride salt solution. S4. The condensate is subjected to acid leaching, and then the acid leaching solution is mixed and stirred with the pickling solution to obtain a mixed acid solution. The pH of the mixed acid solution is adjusted to 6-9, and after standing, solid-liquid separation is performed to obtain beryllium hydroxide solid and thallium-rich supernatant. S5. Add binder and water to the solid product, mix and form spherical particles, dry and sinter them to form ceramic granules.

[0007] In an optional embodiment, the mass ratio of lithium slag to aluminum ash is (1~10):(3~8). And / or, the ball milling process is performed at a speed of 200~800 rpm for a time of 0.5~24 h.

[0008] In an optional embodiment, the lithium slag is selected from at least one of lepidolite smelting slag and spodumene smelting slag. And / or, the aluminum ash is selected from at least one of primary aluminum ash and secondary aluminum ash.

[0009] In an optional embodiment, the heating reaction temperature is 700~900℃, and the holding time is 0.5~2 h; And / or, the heating reaction is carried out under a protective atmosphere and negative pressure conditions; Preferably, the protective atmosphere includes at least one of nitrogen and argon; Preferably, the negative pressure condition is -0.1~0 MPa.

[0010] In an optional embodiment, the temperature of the condensation zone is controlled at 200~300℃, and a ceramic filter screen is placed in the condensation zone to condense and capture the flue gas.

[0011] In an optional embodiment, the ceramic filter screen includes an alumina ceramic filter screen or a silicon carbide ceramic filter screen; And / or, the number of ceramic filters is 3 to 6 and they are evenly distributed in the condensation zone.

[0012] In an optional embodiment, the acid leaching time is 0.1 to 24 hours; And / or, both the pickling and the acid leaching are performed using an acidic solution, the acidic solution including at least one of hydrochloric acid, nitric acid, and sulfuric acid; the mass concentration of the acidic solution is 1~20 wt%. And / or, the pH of the mixed acid solution is adjusted using at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and sodium bicarbonate; And / or, the settling time is 0.1 to 24 hours.

[0013] In an optional embodiment, the alkaline solution includes at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and sodium bicarbonate. And / or, the mass concentration of the alkaline solution is 1~20wt%.

[0014] In an optional embodiment, the amount of the binder added is 1 to 10 wt% of the mass of the solid product. And / or, the binder is any one or two of kaolinite, montmorillonite, pyrophyllite, illite, and diaspore; And / or, the amount of water added is 1 to 10 wt% of the mass of the solid product; And / or, the particle size of the spherical particles is 6~18 mm.

[0015] In an optional embodiment, the drying temperature is 100~110℃ and the time is 10~30 h; And / or, the solid-phase sintering temperature is 1000~1200℃, and the time is 0.2~1 h.

[0016] In an optional embodiment, the bulk density of the ceramsite is 600~1000 kg / m³. 3 The compressive strength of a single particle is 24~40 MPa, and the water absorption rate is 0~10%.

[0017] The present invention has the following beneficial effects: This invention provides a green, co-processing method for lithium slag. Through "waste-to-waste" treatment, it utilizes metallic aluminum and aluminum nitride from aluminum ash to reduce the gypsum component in the lithium slag under a protective atmosphere and negative pressure, efficiently and simultaneously removing both gypsum and aluminum nitride components. The technical principle lies in the protective atmosphere forming a barrier, isolating oxygen and moisture, and preventing the oxidation of elemental aluminum; simultaneously, the negative pressure environment reduces the collision frequency of gas molecules, promoting reactant diffusion. This method fully utilizes the exothermic characteristics of the aluminothermic reaction and, by optimizing reaction conditions (shortening time and lowering temperature), achieves a dual reduction in energy consumption and process costs.

[0018] This invention achieves dual control of fluorine, beryllium, and thallium toxic components through the synergistic reaction of lithium slag and aluminum ash. First, most toxic components are converted into volatile substances at high temperatures and separated with the flue gas. Then, the remaining toxic components, under heating conditions, undergo mineral phase reconstruction with other components in the system (such as silica) through reaction intermediates (alumina and calcium oxide), and are stably fixed within the newly formed minerals. This method significantly reduces the risk of toxic leaching through both "volatile separation" and "lattice fixation." During the reaction, the generated flue gas containing fluorine, beryllium, and thallium is cooled and recovered in stages according to the physical properties of different components, not only recovering the resources of fluorine, beryllium, and thallium but also reducing exhaust gas pollution.

[0019] This invention provides a green and synergistic treatment method for lithium slag, a simple and energy-saving preparation process that achieves the harmless disposal of lithium slag and aluminum ash. The resulting detoxified solid product is further processed into ceramsite for application in the building materials field, efficiently utilizing the calcium, aluminum, and silicon resources in both solid wastes. Furthermore, it cleverly utilizes the residual calcium fluoride in the lithium slag as a flux, reducing sintering energy consumption and improving the performance of the finished product. This method significantly reduces resource waste and improves economic benefits, achieving high-value utilization of lithium slag and aluminum ash. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A process flow diagram of a green synergistic treatment method for lithium slag provided by the present invention; Figure 2 This is an X-ray diffraction pattern of the solid product in Example 1 of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0023] Please see Figure 1 This invention provides a green co-processing method for lithium slag, comprising: S1. Lithium slag and aluminum ash are mixed and ball-milled to obtain a reaction precursor; S2. The reaction precursor is placed in the heating zone of a dual-temperature heating container and heated under a protective atmosphere and negative pressure to produce solid products and flue gas containing beryllium, thallium and fluorine. S3. The flue gas is condensed and collected in the condensation zone of the dual-temperature zone heating container to obtain beryllium-thallium condensate. The remaining flue gas after passing through the condensation zone is again absorbed by acid washing to obtain beryllium-thallium acid washing solution. The fluorine-containing acidic tail gas discharged after acid washing is collected by alkaline solution to obtain fluoride salt solution. S4. The condensate is acid-leached, and then the acid leaching solution is mixed and stirred with the pickling solution to obtain a mixed acid solution. The pH of the mixed acid solution is adjusted to 6-9, and after standing, solid-liquid separation is performed to obtain beryllium hydroxide solid and thallium-rich supernatant. S5. Add binder and water to the solid product, mix and form spherical particles, dry and sinter them in the solid phase to form ceramsite.

[0024] This invention discloses a green and synergistic method for treating lithium slag, utilizing the complementary components in lithium slag and aluminum ash to achieve "waste-to-waste treatment," thereby realizing the harmless treatment of lithium slag and aluminum ash. Specifically, it utilizes metallic aluminum and aluminum nitride in the aluminum ash to reduce the gypsum component in the lithium slag under a protective atmosphere and negative pressure, efficiently and simultaneously removing gypsum and aluminum nitride components, and achieving dual control over toxic components such as fluorine, beryllium, and thallium. First, most toxic components are converted into volatile substances at high temperatures and separated with the flue gas. Then, under heating conditions, the remaining toxic components undergo mineral phase reconstruction with other components in the system (such as silicon dioxide) through reaction intermediates (alumina, calcium oxide), and are stably fixed in the newly formed minerals. This method significantly reduces the risk of toxic leaching through two pathways: "volatile separation" and "lattice fixation." In the reaction process, this invention involves staged cooling and recovery of the generated flue gas containing fluorine, beryllium, and thallium based on the physical properties of different components. This not only recovers the resources of fluorine, beryllium, and thallium and reduces exhaust gas pollution, but also prepares the detoxified solid products into ceramsite, further enhancing the comprehensive utilization value of resources and demonstrating good economic, social, and environmental benefits.

[0025] Specifically, the specific steps are as follows: S1. Lithium slag and aluminum ash are mixed and ball-milled to obtain the reaction precursor.

[0026] In this invention, the lithium slag is selected from at least one of lepidolite smelting slag and spodumene smelting slag; the aluminum ash is selected from at least one of primary aluminum ash and secondary aluminum ash. This invention utilizes abundant and inexpensive raw materials, has low reaction energy consumption, and saves on process costs.

[0027] The lepidolite smelting slag and spodumene smelting slag in this invention mainly contain, but are not limited to, silicon dioxide, aluminum oxide, and gypsum, and also explicitly contain toxic and harmful components such as beryllium and thallium. The core components of aluminum ash include, but are not limited to, aluminum oxide, metallic aluminum, and aluminum nitride, and also contain small amounts of fluorides, chlorides, and metal oxides such as silicon and iron.

[0028] The mass ratio of lithium slag to aluminum ash is (1~10):(3~8). Mixing according to the above mass ratio can ensure that the component proportions in lithium slag and aluminum ash are appropriate, which is conducive to the complete reduction of gypsum in lithium slag. Preferably, the mass ratio of lithium slag to aluminum ash is 10:(3~8).

[0029] After mixing, ball milling can crush the lithium slag and aluminum ash, making their particle size smaller, which facilitates the full mixing and contact of the lithium slag and aluminum ash, and also facilitates subsequent heating reactions. The ball milling speed is 200~800 rpm, and the ball milling time is 0.5~24 h.

[0030] S2. The reaction precursor is placed in the heating zone of a dual-temperature heating container and heated under a protective atmosphere and negative pressure to produce solid products and flue gas containing beryllium, thallium and fluorine. After the heating reaction, the solid products are collected after the furnace is cooled to room temperature.

[0031] In this invention, a dual-temperature zone heating container is selected as the reaction vessel. The dual-temperature zone heating container includes a heating zone and a condensation zone. The dual-temperature zone heating container can accurately control the temperature of the two independent temperature zones in the same container, and achieve synchronous / asynchronous temperature control of the two independent temperature zones in the same container. Furthermore, the temperature difference between the heating zone and the condensation zone is adjustable and has high stability.

[0032] The reaction precursor undergoes a heating reaction in a heating zone at a temperature of 700–900 °C for a holding time of 0.5–2 h. The heating reaction is carried out under a protective atmosphere and negative pressure conditions. The protective atmosphere includes at least one of nitrogen and argon; the negative pressure conditions are -0.1–0 MPa.

[0033] The raw materials for this invention are lithium slag and aluminum ash. During the heating reaction, metallic aluminum and aluminum nitride in the aluminum ash reduce gypsum in the lithium slag under a protective atmosphere and negative pressure, achieving efficient and simultaneous removal of gypsum and aluminum nitride. For the generated toxic components such as fluorine, beryllium, and thallium, a two-step method is used for control: the first step is high-temperature volatilization separation, converting most of the toxic components into flue gas for discharge; the second step is mineral fixation, where residual toxic components are fixed in the newly formed mineral lattice through mineral phase reconstruction under the action of reaction intermediates (alumina, calcium oxide) and other components in the system (such as silicon dioxide). This dual "volatilization-fixation" mechanism significantly reduces the risk of toxic leaching.

[0034] The protective atmosphere and negative pressure conditions serve two purposes: the protective atmosphere forms a barrier, isolating oxygen and moisture to prevent the oxidation of elemental aluminum; simultaneously, the negative pressure environment reduces the collision frequency of gas molecules, promoting the diffusion of reactants. This method fully utilizes the exothermic nature of the aluminothermic reaction and, by optimizing reaction conditions (shortening time and lowering temperature), achieves a dual reduction in energy consumption and process costs.

[0035] S3. The flue gas is condensed and collected in the condensation zone of the dual-temperature zone heating container to obtain beryllium-thallium condensate. The remaining flue gas after passing through the condensation zone is then acid-washed to obtain beryllium-thallium acid wash solution. The fluorine-containing acidic tail gas discharged after acid washing is collected by alkaline solution to obtain fluoride salt solution.

[0036] This invention targets flue gas containing fluorine, beryllium, and thallium, and performs segmented cooling and recovery based on the physical properties of different components, thereby utilizing the resources of fluorine, beryllium, and thallium and reducing exhaust gas pollution.

[0037] In this invention, a ceramic filter screen is placed in the condensation zone to condense and capture beryllium and thallium particles in the flue gas. The temperature of the condensation zone is controlled between 200 and 300°C. This is because beryllium and thallium in the flue gas mainly exist as oxides or elemental forms, which can rapidly condense into solid particles below 350°C, allowing for efficient capture by the ceramic filter screen. However, considering the possible presence of beryllium chloride (boiling point 520°C) in the flue gas, the condensation temperature must be controlled to be no lower than 180°C (to prevent the hydrolysis of beryllium chloride to generate corrosive hydrogen chloride, which could lead to equipment corrosion) and no higher than 350°C (to ensure sufficient condensation of beryllium and thallium oxides or elemental forms, preventing them from escaping with the flue gas). Therefore, limiting the temperature of the condensation zone to 200-300°C in this invention ensures sufficient condensation of beryllium and thallium-containing components in the flue gas.

[0038] Ceramic filters include alumina ceramic filters or silicon carbide ceramic filters; the number of ceramic filters is 3 to 6 and they are evenly distributed in the condensation zone.

[0039] To prevent some beryllium and thallium from escaping with the flue gas, this invention, after capturing the flue gas in the condensation zone, continues to absorb it through acid washing with an acidic solution. At this point, any escaped beryllium and thallium can be reabsorbed. The acidic solution includes at least one of hydrochloric acid, nitric acid, and sulfuric acid; the mass concentration of the acidic solution is 1-20 wt%.

[0040] Subsequently, the fluoride-containing acidic tail gas discharged after acid washing is collected by an alkaline solution to obtain a fluoride salt solution. The alkaline solution includes at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and sodium bicarbonate; the mass concentration of the alkaline solution is 1~20wt%.

[0041] In this invention, the flue gas containing beryllium, thallium, and fluorine generated from the reaction is sequentially condensed and captured in a condensation zone, then absorbed by acid washing and alkali washing. This allows for the full collection of beryllium, thallium, and fluorine from the flue gas, effectively reducing the pollution of the exhaust gas to the atmosphere.

[0042] S4. The condensate is acid-leached, and then the acid-leaching solution is mixed and stirred with the pickling solution from step S3 to obtain a mixed acid solution. The pH of the mixed acid solution is adjusted to 6-9, and after standing, solid-liquid separation is performed to obtain beryllium hydroxide solid and thallium-rich supernatant.

[0043] The process involves acid leaching of the condensate, which extracts beryllium and thallium from the condensate into a solution to obtain an acid leaching solution containing beryllium and thallium. The acid leaching time is 0.1 to 24 hours. The acidic solution includes at least one of hydrochloric acid, nitric acid, and sulfuric acid. The mass concentration of the acidic solution is 1 to 20 wt%.

[0044] After acid leaching, the leaching solution is mixed with the pickling solution from step S3 to obtain a mixed acid solution. This increases the content of beryllium and thallium in the solution, achieving full recovery of beryllium and thallium. Subsequently, the pH of the mixed acid solution is adjusted to 6-9 using an alkaline solution. At this point, the beryllium in the mixed acid solution reacts with hydroxide ions to produce beryllium hydroxide, which precipitates out. After standing for 0.1-24 hours, solid-liquid separation is performed to obtain beryllium hydroxide solid and thallium-rich supernatant, thus achieving the separation of beryllium and thallium. The alkaline solution includes at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and sodium bicarbonate.

[0045] S5. Add binder and water to the solid product, mix and form spherical particles, dry and sinter them in the solid phase to form ceramsite.

[0046] This invention improves the comprehensive utilization of solid products by processing the detoxified solid products into ceramsite, resulting in significant economic, social, and environmental benefits. The binder is added at 1-10 wt% of the solid product's mass; water is added at 1-10 wt% of the solid product's mass, and the mixture is then formed into spherical particles with a particle size of 6-18 mm.

[0047] The binder is any one or two of kaolinite, montmorillonite, pyrophyllite, illite, and diaspore.

[0048] The drying temperature is 100~110℃, and the time is 10~30 h; The solid-state sintering temperature is 1000~1200℃ and the time is 0.2~1 h.

[0049] The bulk density of expanded clay aggregate is 600~1000 kg / m³ 3 The compressive strength of a single particle is 24~40 MPa, and the water absorption rate is 0~10%.

[0050] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0051] Example 1 A green method for co-processing lithium slag includes the following steps: (1) Lithium mica smelting slag and secondary aluminum ash were mixed at a mass ratio of 10:6, and then placed in a planetary ball mill and ball-milled at 600 rpm for 3 h to obtain the reaction precursor. (2) The reaction precursor was transferred to the left temperature control zone of the dual-temperature zone heating container and heated under an argon atmosphere and a negative pressure of -0.05 MPa. The temperature was 800℃ and the holding time was 0.5 h to obtain solid products and flue gas containing beryllium, thallium and fluorine. (3) The right temperature control zone of the dual-temperature zone heating container is used as the condensation zone. The temperature of the condensation zone is 200℃. Four silicon carbide ceramic meshes are placed at the left, middle and right ends of the zone to condense and capture flue gas containing beryllium, thallium and fluorine, and obtain beryllium-thallium condensate. Then, the flue gas remaining after passing through the condensation zone is acid-washed and absorbed again with 5wt% sulfuric acid to obtain beryllium-thallium acid washing solution. The fluorine-containing acidic gas discharged after acid washing is collected with 10wt% sodium hydroxide solution. (4) The condensate containing beryllium and thallium (i.e., the silicon carbide ceramic mesh containing beryllium and thallium condensate) was placed in 300 mL of 5wt% sulfuric acid and stirred for 5 h to obtain beryllium sulfate and thallium sulfate acid leaching solution. The acid leaching solution was mixed with the above pickling solution containing beryllium and thallium to obtain a mixed acid solution. Then, at room temperature, the alkaline solution (10wt% sodium hydroxide) was added dropwise to the above mixed acid solution by an automatic pH adder while maintaining vigorous mechanical stirring and a constant pH (pH=8.0±0.2). After standing for 5 h, the solid and liquid were separated to obtain beryllium hydroxide solid and thallium-rich supernatant. (5) Based on the mass of the solid product, add 3wt% binder and 8wt% water to the solid product and mix to make spherical particles with a particle size of 12 mm. Dry them in a forced-air drying oven at 100°C for 20 h. Then transfer them to a muffle furnace for solid-phase sintering at 1000°C for 30 min to obtain ceramsite. The reaction procedures in steps (2) and (3) above are carried out simultaneously.

[0052] like Figure 2 The figure shows the X-ray diffraction pattern of the solid product of Example 1 of the present invention. As can be seen from the figure, the phases of the product are mainly composed of anorthite and nepheline, as well as a small amount of alumina, silicon dioxide and calcium fluoride. The gypsum in the lepidolite smelting slag and the aluminum nitride in the aluminum ash have been removed simultaneously.

[0053] Example 2 A green method for co-processing lithium slag includes the following steps: (1) The particle size of lepidolite smelting slag is relatively large, and the contact surface between metallic aluminum and aluminum nitride in primary aluminum ash and gypsum is insufficient. Therefore, it is necessary to crush it in advance. Specifically, lepidolite smelting slag and primary aluminum ash are mixed at a mass ratio of 10:3 and then placed in a planetary ball mill and ball-milled at 500 rpm for 5 h to obtain the reaction precursor. (2) The reaction precursor was transferred to the left temperature control zone of the dual-temperature zone heating container and heated under a nitrogen atmosphere and a negative pressure of -0.04 MPa. The temperature was 850℃ and the holding time was 1 h to obtain a solid product. At the same time, flue gas containing beryllium, thallium and fluorine was generated. (3) The right temperature control zone of the dual-temperature zone heating container is used as the condensation zone. The temperature of the condensation zone is 250℃. Five alumina ceramic meshes are placed at the left, middle and right ends of the zone to condense and capture flue gas containing beryllium, thallium and fluorine, and obtain beryllium-thallium condensate. Then, the flue gas remaining after passing through the condensation zone is acid-washed and absorbed again with 10wt% nitric acid to obtain beryllium-thallium acid washing solution. The fluorine-containing acidic gas discharged after the acid washing is collected with 8wt% calcium hydroxide solution. (4) The condensate containing beryllium and thallium (i.e., the alumina ceramic mesh containing beryllium and thallium) was placed in 200 mL of 10wt% nitric acid and stirred for 8 h to obtain beryllium nitrate and thallium nitrate acid leaching solution. The acid leaching solution was mixed and stirred with the above pickling solution containing beryllium and thallium to obtain a mixed acid solution. Then, at room temperature, the alkaline solution (8wt% calcium hydroxide) was added dropwise to the above mixed acid solution by an automatic pH adder while maintaining vigorous mechanical stirring and a constant pH (pH=7.5±0.2). After standing for 10 h, the solid and liquid were separated to obtain beryllium hydroxide solid and thallium-rich supernatant. (5) Based on the mass of the solid product, add 4.0 wt% binder and 7.5 wt% water to the solid product and mix to make spherical particles with a particle size of 12 mm. Dry them in a forced-air drying oven at 105 °C for 24 h. Then transfer them to a muffle furnace for solid-phase sintering at 1050 °C for 40 min to obtain ceramsite. The reaction procedures in steps (2) and (3) above are carried out simultaneously.

[0054] Example 3 A green method for co-processing lithium slag includes the following steps: (1) The particle size of lepidolite smelting slag is relatively large, and the contact surface between metallic aluminum and aluminum nitride in secondary aluminum ash and gypsum is insufficient. Therefore, it is necessary to crush it in advance. Specifically, lepidolite smelting slag and secondary aluminum ash are mixed at a mass ratio of 10:4 and then placed in a planetary ball mill and ball-milled at 400 rpm for 8 h to obtain the reaction precursor. (2) The reaction precursor was transferred to the left temperature control zone of the dual-temperature zone heating container and heated under nitrogen atmosphere and negative pressure of -0.06 MPa. The temperature was 750℃ and the holding time was 1.2 h to obtain solid product, while generating flue gas containing beryllium, thallium and fluorine. (3) The right temperature control zone of the dual-temperature zone heating container is used as the condensation zone. The temperature of the condensation zone is 220℃. Four silicon carbide ceramic meshes are placed at the left, middle and right ends of the zone to condense and capture flue gas containing beryllium, thallium and fluorine, and obtain beryllium-thallium condensate. Then, the flue gas remaining after passing through the condensation zone is acid washed and absorbed again with 12wt% hydrochloric acid to obtain beryllium-thallium acid washing solution. The fluorine-containing acidic gas discharged after acid washing is collected with 15wt% potassium hydroxide solution. (4) The condensate containing beryllium and thallium (i.e., silicon carbide ceramic mesh containing beryllium and thallium) was placed in 250 mL of 12wt% hydrochloric acid and stirred for 12 h to obtain beryllium chloride and thallium chloride acid leaching solution. The acid leaching solution was mixed and stirred with the above pickling solution containing beryllium and thallium to obtain a mixed acid solution. Then, at room temperature, the alkaline solution (15wt% potassium hydroxide) was added dropwise to the above mixed acid solution by an automatic pH adder while maintaining vigorous mechanical stirring and a constant pH (pH=8.5±0.2). After standing for 6 h, the solid and liquid were separated to obtain beryllium hydroxide solid and thallium-rich supernatant. (5) Based on the mass of the solid product, add 6wt% binder and 8wt% water to the solid product and mix to make spherical particles with a particle size of 16 mm. Dry them in a forced-air drying oven at 108℃ for 18 h. Then transfer them to a muffle furnace for solid-phase sintering at 1150℃ for 20 min to obtain ceramsite. The reaction procedures in steps (2) and (3) above are carried out simultaneously.

[0055] Example 4 A green method for co-processing lithium slag includes the following steps: (1) The particle size of spodumene smelting slag is relatively large, and the contact surface between metallic aluminum and aluminum nitride in secondary aluminum ash and gypsum is insufficient. Therefore, it is necessary to crush it in advance. Specifically, the spodumene smelting slag and secondary aluminum ash are mixed at a mass ratio of 10:5 and then placed in a planetary ball mill and ball-milled at 650 rpm for 4 h to obtain the reaction precursor. (2) The reaction precursor was transferred to the left temperature control zone of the dual-temperature zone heating container and heated under an argon atmosphere and a negative pressure of -0.08 MPa. The temperature was 700℃ and the holding time was 1.4 h to obtain a solid product. At the same time, flue gas containing beryllium, thallium and fluorine was generated. (3) The right temperature control zone of the dual-temperature zone heating container is used as the condensation zone. The temperature of the condensation zone is 260℃. Six alumina ceramic meshes are placed at the left, middle and right ends of the zone to condense and capture flue gas containing beryllium, thallium and fluorine. Then, the remaining flue gas after passing through the condensation zone is acid-washed and absorbed again with 8wt% sulfuric acid to obtain acid washing solution containing beryllium and thallium. The acidic gas containing fluorine discharged after acid washing is collected with 10wt% sodium carbonate. (4) The condensate containing beryllium and thallium (i.e., the alumina ceramic mesh containing beryllium and thallium) was placed in 300 mL of 8wt% sulfuric acid and stirred for 6 h to obtain beryllium sulfate and thallium sulfate acid leaching solution. The acid leaching solution was mixed and stirred with the above pickling solution containing beryllium and thallium to obtain a mixed acid solution. Then, at room temperature, the alkaline solution (10wt% sodium carbonate) was added dropwise to the above mixed acid solution by an automatic pH adder while maintaining vigorous mechanical stirring and a constant pH (pH=7.8±0.2). After standing for 12 h, the solid and liquid were separated to obtain beryllium hydroxide solid and thallium-rich supernatant. (5) Based on the mass of the solid product, add 3wt% binder and 8wt% water to the solid product and mix to make spherical particles with a particle size of 15 mm. Dry them in a forced-air drying oven at 100°C for 20 h. Then transfer them to a muffle furnace for solid-phase sintering at 1080°C for 50 min to obtain ceramsite. The reaction procedures in steps (2) and (3) above are carried out simultaneously.

[0056] Example 5 A green method for co-processing lithium slag includes the following steps: (1) The particle size of spodumene smelting slag is relatively large, and the contact surface between metallic aluminum and aluminum nitride in secondary aluminum ash and gypsum is insufficient. Therefore, it is necessary to crush it in advance. Specifically, the spodumene smelting slag and secondary aluminum ash are mixed at a mass ratio of 10:8 and then placed in a planetary ball mill and ball-milled at 800 rpm for 6 h to obtain the reaction precursor. (2) Load an appropriate amount of the reaction precursor into a ceramic boat, and then transfer it to the left temperature control zone of the dual-temperature zone heating container. The reaction is carried out under nitrogen atmosphere and negative pressure of -0.1 MPa. The temperature is 900℃ and the holding time is 0.8 h to obtain a solid product. At the same time, flue gas containing beryllium, thallium and fluorine is generated. (3) The right temperature control zone of the dual-temperature zone heating container is used as the condensation zone. The temperature of the condensation zone is 280℃. Three silicon carbide ceramic meshes are placed at the left, middle and right ends of the zone to condense and capture the flue gas containing beryllium, thallium and fluorine. Then, the flue gas remaining after passing through the condensation zone is acid-washed and absorbed again with 5wt% sulfuric acid to obtain an acid washing solution containing beryllium and thallium. The acidic gas containing fluorine discharged after acid washing is collected with 8wt% sodium hydroxide. (4) The condensate containing beryllium and thallium (i.e., silicon carbide ceramic mesh containing beryllium and thallium) was placed in 400 mL of 15wt% nitric acid and stirred for 10 h to obtain beryllium nitrate and thallium nitrate acid leaching solution. The acid leaching solution was mixed and stirred with the above pickling solution containing beryllium and thallium to obtain a mixed acid solution. Then, at room temperature, an alkaline solution (8wt% sodium hydroxide) was added dropwise to the above mixed acid solution using an automatic pH adder while maintaining vigorous mechanical stirring and a constant pH (pH=8.2±0.2). After standing for 10 h, solid-liquid separation was performed to obtain beryllium hydroxide solid and thallium-rich supernatant. (5) Based on the mass of the solid product, add 3wt% binder and 8wt% water to the solid product and mix to make spherical particles with a particle size of 15.6 mm. Dry them in a forced-air drying oven at 105℃ for 20 h. Then transfer them to a muffle furnace for solid-phase sintering at 1040℃ for 35 min to obtain ceramsite. The reaction procedures in steps (2) and (3) above are carried out simultaneously.

[0057] Comparative Example 1 A green method for co-processing lithium slag includes the following steps: The mass ratio of lepidolite smelting slag to secondary aluminum ash in step (1) of Example 1 was adjusted to 10:1, and the rest was the same as in Example 1.

[0058] Comparative Example 2 A green method for co-processing lithium slag includes the following steps: The heating temperature of the lithium mica smelting slag and primary aluminum ash in step (2) of Example 2 was reduced to 300℃ and kept at that temperature for 1 h. The rest was the same as in Example 2.

[0059] Comparative Example 3 A green method for co-processing lithium slag includes the following steps: In step (2) of Example 4, the argon atmosphere was changed to air, the negative pressure was changed to normal pressure, and the rest was the same as in Example 4.

[0060] Comparative Example 4 A green method for co-processing lithium slag includes the following steps: In step (5) of Example 5, the solid-state sintering temperature was raised to 1800℃ and held for 5 h, and the rest was the same as in Example 5.

[0061] Comparative Example 5 A green method for co-processing lithium slag includes the following steps: In Example 5, step (3) involving the placement of a silicon carbide ceramic mesh in a condensation zone was omitted. Instead, flue gas containing beryllium, thallium, and fluorine was directly absorbed by acid washing with 5wt% sulfuric acid to obtain a beryllium-thallium-containing acid washing solution. The fluorine-containing acidic gas discharged after acid washing was collected using 8wt% sodium hydroxide. Step (4) was adjusted as follows: at room temperature, an alkaline solution (8wt% sodium hydroxide) was added dropwise to the above acid washing solution using an automatic pH adder while maintaining vigorous mechanical stirring and a constant pH (pH=8.2±0.2). After standing for 10 h, solid-liquid separation was performed to obtain beryllium hydroxide solid and thallium-rich supernatant.

[0062] Comparative Example 6 This comparative example is basically the same as Example 5, except that aluminum ash is replaced with red mud in this comparative example.

[0063] Experimental Example 1 The products of each stage of the methods provided in the above embodiments and comparative examples were tested.

[0064] (1) Removal rate of fluorine, beryllium and thallium in solid products: The test methods include ion chromatography and inductively coupled plasma mass spectrometry; (2) Toxicity leaching concentrations of fluorine, beryllium, and thallium in solid products: Test methods include ion chromatography and inductively coupled plasma mass spectrometry; (3) Recovery rates of fluorine, beryllium, and thallium in exhaust gas: The test methods include ion chromatography and inductively coupled plasma mass spectrometry; (4) Bulk density of expanded clay: The test methods include the bulk density tester method and the water filling method; (5) Compressive strength of expanded clay: The test methods include cylinder compressive strength test and cubic compressive strength test; (6) Water absorption rate of ceramsite: The test methods include atmospheric pressure immersion method and vacuum pumping method.

[0065] The results of the removal rates and toxicity leaching concentrations of fluorine, beryllium, and thallium in the solid products are shown in Table 1. The national standard used is the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification" (GB 5085.3-2017); the local standard used is the "Emission Standard for Thallium Pollutants in Industrial Wastewater" (DB 44 / 1989-2017). The results of the recovery rates of fluorine, beryllium, and thallium in the exhaust gas, as well as the bulk density, compressive strength, and water absorption of the ceramsite, are shown in Table 2.

[0066] Table 1. Statistical results of removal rates and toxicity leaching concentrations of fluorine, beryllium, and thallium in solid products.

[0067] Table 2. Statistical results of fluorine, beryllium, and thallium recovery rates and performance indicators of ceramsite in exhaust gas.

[0068] As can be seen from Tables 1 and 2, the removal rate of thallium in the solid products of Examples 1-5 of the present invention is greater than 97%, and the leaching concentrations of fluorine and beryllium toxicity are both lower than the national hazardous waste identification standards, and the thallium concentration is lower than the local standards.

[0069] The removal rates of fluorine, beryllium, and thallium in the solid product of Comparative Example 1 were 4.2%, 7.3%, and 45.3%, respectively, with toxic leaching concentrations of 21.6 mg / L, 0.042 mg / L, and 0.012 mg / L, respectively. Because the secondary aluminum ash contained relatively little reducing agent (metallic aluminum and aluminum nitride), it could not completely reduce the gypsum in the lepidolite smelting slag. The remaining gypsum not only had a synergistic adsorption effect on fluorine, beryllium, and thallium, reducing the removal rate and increasing the toxic leaching concentration, but also affected the performance of the ceramsite, increasing its water absorption to 25.8% and reducing its flexural strength to 11.8 MPa. Therefore, the mass ratio of lepidolite smelting slag to secondary aluminum ash needs to be adjusted to a suitable range.

[0070] The removal rates of fluorine, beryllium, and thallium in the solid product of Comparative Example 2 were 6.2%, 5.3%, and 37.8%, respectively, with toxic leaching concentrations of 26.1 mg / L, 0.053 mg / L, and 0.021 mg / L, respectively. Since the melting point of elemental aluminum, the reducing agent in primary aluminum ash, is 660℃, and it remains solid at 300℃, the contact area with gypsum is reduced, leading to incomplete reaction of the gypsum and consequently affecting the removal rate of toxic components and increasing the risk of toxic leaching. Furthermore, at lower reaction temperatures, gypsum reacts more readily with metallic aluminum and aluminum nitride to generate the byproduct calcium sulfide, which reduces the content of anorthite in the sintered product, causing the ceramsite strength to drop to 13.1 MPa and the water absorption rate to increase to 18.2%. Therefore, the heating reaction temperature of lepidolite smelting slag and primary aluminum ash needs to be adjusted to a suitable range.

[0071] In Comparative Example 3, the removal rates of fluorine, beryllium, and thallium in the solid product were only 5.2%, 7.5%, and 42.4%, respectively, while their toxic leaching concentrations were as high as 32.3 mg / L, 0.037 mg / L, and 0.018 mg / L, all exceeding the standards. This indicates that treatment under air atmosphere and negative pressure conditions failed to achieve effective detoxification and stabilization. The reasons for this are mainly twofold: First, the elemental aluminum in the aluminum ash is easily oxidized in air, leading to a loss of reducing activity and resulting in gypsum residue. The residual gypsum decomposes during subsequent sintering to produce sulfur dioxide, causing the ceramsite to bubble and crack (compressive strength drops to 10.4 MPa, water absorption increases to 20.5%), and the dissolved SO4... 2- Will with Tl + Be 2+ First, soluble complexes are formed, triggering synergistic leaching. Second, to maintain the reaction under normal pressure, the temperature and time need to be increased, leading to a significant increase in energy consumption.

[0072] Comparative Example 4 showed that the compressive strength of the ceramsite was 12.6 MPa. Due to accelerated atomic diffusion at high temperatures, abnormal grain growth occurred, forming coarse equiaxed or columnar crystal structures. The grain size increased significantly, but the compressive strength actually decreased. Although high temperatures may promote partial densification, excessively high temperatures not only consume a lot of energy but also exacerbate liquid phase volatilization, leading to a rebound in porosity and an increase in water absorption to 19.8%. Furthermore, the large temperature difference between the inside and outside of the green body at high temperatures can easily cause thermal stress concentration, leading to deformation or cracking. Therefore, the solid-state sintering temperature needs to be adjusted to a suitable range.

[0073] In Comparative Example 5, the recovery rates of fluorine, beryllium, and thallium in the exhaust gas were only 42.5%, 36.7%, and 53.2%, respectively. During the exhaust gas treatment, due to the lack of silicon carbide ceramic mesh in the condensation zone, some flue gas containing beryllium, thallium, and fluorine remained in the pipeline, resulting in low recovery rates of fluorine, beryllium, and thallium. This not only reduced the utilization value of high-value toxic components but also may cause secondary pollution.

[0074] In Comparative Example 6, after replacing aluminum ash with solid waste red mud, the removal rates of fluorine, beryllium, and thallium in the solid products were relatively low, at 6.8%, 7.3%, and 48.3%, respectively, and the leaching concentrations of beryllium and thallium toxicity exceeded national and local standards, respectively. Furthermore, other solid wastes such as marble tailings, phosphogypsum, and quartz sludge showed similar effects to red mud. Although these materials possess a certain degree of solidification ability, due to the lack of reducing substances, under high-temperature conditions, the gypsum only removes water molecules, forming anhydrite. Subsequent solid-phase sintering processes generate large amounts of sulfur dioxide gas, easily causing cracking of the ceramsite.

[0075] In summary, this invention provides a green synergistic treatment method for lithium slag, based on the synergistic treatment of lithium slag and aluminum ash. Through a "waste-to-waste" approach, it utilizes metallic aluminum and aluminum nitride in the aluminum ash to reduce the gypsum component in the lithium slag under a protective atmosphere and negative pressure, simultaneously removing gypsum and aluminum nitride components. The technical principle lies in: the protective atmosphere forms a barrier, isolating oxygen and moisture, preventing the oxidation of elemental aluminum; simultaneously, the negative pressure environment reduces the collision frequency of gas molecules, promoting reactant diffusion. This method fully utilizes the exothermic characteristics of the aluminothermic reaction and, by optimizing reaction conditions (shortening time and lowering temperature), achieves a dual reduction in energy consumption and process costs. This invention achieves dual control of fluorine, beryllium, and thallium poisoning components through the synergistic reaction of lithium slag and aluminum ash. First, most poisoning components are converted into volatile substances at high temperatures and separated with the flue gas. Then, under heating conditions, the remaining poisoning components undergo mineral phase reconstruction with other components in the system (such as silicon dioxide) through reaction intermediates (alumina, calcium oxide), and are stably fixed in the newly formed minerals. This method significantly reduces the risk of toxic leaching through two approaches: "volatile separation" and "lattice fixation." During the reaction process, the invention utilizes segmented cooling and recovery of the generated fluorine-, beryllium-, and thallium-containing fumes based on the physical properties of different components, not only recovering the resources of fluorine, beryllium, and thallium but also reducing exhaust gas pollution. This invention provides a simple and energy-saving preparation process for the harmless disposal of lithium slag and aluminum ash. The detoxified solid product is further processed into ceramsite for application in the building materials field, efficiently utilizing the calcium, aluminum, and silicon resources in both solid wastes. Furthermore, it cleverly utilizes the residual calcium fluoride in the lithium slag as a flux, reducing sintering energy consumption and improving the performance of the finished product. This method significantly reduces resource waste and improves economic efficiency, achieving high-value utilization of lithium slag and aluminum ash.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A green co-processing method for lithium slag, characterized in that, It includes: S1. Lithium slag and aluminum ash are mixed and ball-milled to obtain a reaction precursor. The mass ratio of lithium slag to aluminum ash is (1~10):(3~8). The ball milling speed is 200~800 rpm and the ball milling time is 0.5~24 h. S2. The reaction precursor is placed in the heating zone of a dual-temperature zone heating container and heated under a protective atmosphere and negative pressure. The metallic aluminum and aluminum nitride in the aluminum ash are used to reduce the gypsum component in the lithium slag under the protective atmosphere and negative pressure, simultaneously removing the gypsum and aluminum nitride components. The heating temperature is 700~900℃, and the holding time is 0.5~2 h. The negative pressure is -0.1~0 MPa, producing solid products and flue gas containing beryllium, thallium, and fluorine. The protective atmosphere is nitrogen or argon. S3. The flue gas is condensed and collected in the condensation zone of the dual-temperature zone heating container. The temperature of the condensation zone is controlled at 200~300℃. A ceramic filter screen is placed in the condensation zone to condense and collect the flue gas, obtaining beryllium-thallium-containing condensate. The remaining flue gas after passing through the condensation zone is then acid-washed to obtain a beryllium-thallium-containing acid wash solution. The fluoride-containing acidic tail gas discharged after acid washing is collected by an alkaline solution to obtain a fluoride salt solution. The ceramic filter screen includes an alumina ceramic filter screen or a silicon carbide ceramic filter screen. The number of ceramic filter screens is 3~6 and they are evenly distributed in the condensation zone. S4. The condensate is subjected to acid leaching, and then the acid leaching solution is mixed and stirred with the pickling solution to obtain a mixed acid solution. The pH of the mixed acid solution is adjusted to 6-9, and after standing, solid-liquid separation is performed to obtain beryllium hydroxide solid and thallium-rich supernatant. S5. Add a binder and water to the solid product, mix to form spherical particles, dry, and sinter in a solid phase to produce ceramsite. The thallium removal rate in the solid product is greater than 97%, and the bulk density of the ceramsite is 600~1000 kg / m³. 3 The compressive strength of a single particle is 24~40 MPa, and the water absorption rate is 0~10%.

2. The method for green co-processing lithium slag according to claim 1, characterized in that, The lithium slag is selected from at least one of lepidolite smelting slag and spodumene smelting slag. And / or, the aluminum ash is selected from at least one of primary aluminum ash and secondary aluminum ash.

3. The method for green co-processing lithium slag according to claim 1, characterized in that, The acid leaching time is 0.1~24 h; And / or, both the pickling and the acid leaching are performed using an acidic solution, the acidic solution comprising at least one of hydrochloric acid, nitric acid, and sulfuric acid, and the mass concentration of the acidic solution being 1-20 wt%. And / or, the pH of the mixed acid solution is adjusted using at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and sodium bicarbonate; And / or, the settling time is 0.1 to 24 hours.

4. The method for green co-processing lithium slag according to claim 1, characterized in that, The alkaline solution includes at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and sodium bicarbonate. And / or, the mass concentration of the alkaline solution is 1~20wt%.

5. The method for green co-processing lithium slag according to claim 1, characterized in that, The amount of the binder added is 1 to 10 wt% of the mass of the solid product; And / or, the binder is any one or two of kaolinite, montmorillonite, pyrophyllite, illite, and diaspore; And / or, the amount of water added is 1 to 10 wt% of the mass of the solid product; And / or, the particle size of the spherical particles is 6~18 mm.

6. The method for green co-processing lithium slag according to claim 1, characterized in that, The drying temperature is 100~110℃, and the time is 10~30 h; And / or, the solid-phase sintering temperature is 1000~1200℃, and the time is 0.2~1 h.

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