A method for the green co-processing of lithium slag and carbonaceous solid waste

Abstract

This invention discloses a method for the green co-processing of lithium slag and carbonaceous solid waste, relating to the field of slag treatment technology. The method includes: ball milling and mixing lithium slag, carbonaceous solid waste, and magnesium powder to obtain a reaction precursor; heating the reaction precursor under a protective atmosphere and negative pressure to produce solid products and flue gas containing beryllium, thallium, and fluorine; first, absorbing the flue gas containing beryllium, thallium, and fluorine with acid to obtain a beryllium-thallium acid washing solution; then absorbing the remaining fluorine-containing acidic tail gas with alkali to obtain a fluoride salt solution; mixing the solid product with the alkali solution, stirring, heating, washing to neutrality, and drying to obtain a porous material. This method practices the concept of "treating waste with waste," simultaneously solving the problems of gypsum decomposition, detoxification and fixation of toxic components, tail gas purification, and resource utilization through co-processing, achieving deep harmlessness of lithium slag, and significantly improving resource utilization and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of slag treatment technology, and more specifically, to a method for the green co-processing of lithium slag and carbonaceous solid waste. Background Technology

[0002] Lithium slag is an industrial solid waste generated during the production of lithium carbonate from lithium ore through high-temperature roasting and leaching processes. Its main components are silicon dioxide, aluminum oxide, and calcium oxide, and it also contains sulfur, alkali metals, and toxic components such as fluorine, thallium, and beryllium. The toxic components in lithium slag, such as fluorine, beryllium, and thallium, are significant risk sources; therefore, the harmless disposal of lithium slag is crucial. Sulfuric acid roasting and the sulfuric acid process are core technologies in lithium extraction. During acidification, the reaction of excess sulfuric acid with calcium-containing minerals leads to the production of large amounts of gypsum in the lithium slag. However, the negative charge between gypsum layers easily adsorbs heavy metals such as beryllium and thallium, thus increasing the risk of toxic leaching pollution from the lithium slag. The high gypsum content in lithium slag negatively impacts its resource utilization, not only reducing the overall performance of materials but also hindering its large-scale application as a raw material in building materials, ceramics, and adsorption fields. Most lithium slag treatment technologies employ physical blending, low-temperature activation, and high-temperature melting and solidification methods. However, these methods generally fail to completely remove gypsum, leading to unstable performance of products made from lithium slag and poor separation and solidification of toxic components, thus posing a risk of toxic leaching. Currently, technologies for gypsum removal and harmless treatment in lithium slag remain incomplete, resulting in low comprehensive utilization and limited application.

[0003] Carbon-containing solid wastes such as coal gangue and coal gasification slag are mostly by-products of the coal industry. Although they are rich in carbon, silicon dioxide and alumina, their large-scale stockpiling and improper treatment can cause harm to water bodies and soil environments.

[0004] Current technologies for treating lithium slag and carbonaceous solid waste still face bottlenecks such as high costs, incomplete impurity removal, significant environmental risks, and low efficiency in the comprehensive utilization of elements. The efficient removal and targeted separation of toxic components in lithium slag are particularly crucial. Lithium slag and carbonaceous solid waste have certain complementary component characteristics. If they can be synergistically treated to achieve effective separation of toxic components and convert the calcium, aluminum, and silicon resources into functional materials, thereby improving resource utilization, it is a key path to solving environmental problems and achieving resource recycling.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for the green co-processing of lithium slag and carbon-containing solid waste.

[0007] This invention is implemented as follows:

[0008] In a first aspect, the present invention provides a method for the green co-processing of lithium slag and carbonaceous solid waste, comprising:

[0009] S1. Lithium slag, carbon-containing solid waste and magnesium powder are ball-milled and mixed to obtain a reaction precursor;

[0010] S2. The reaction precursor is heated under a protective atmosphere and negative pressure to produce solid products and flue gas containing beryllium, thallium and fluorine.

[0011] S3. The flue gas containing beryllium, thallium and fluorine is first absorbed by acid washing to obtain a beryllium-thallium acid washing solution; then the remaining fluorine-containing acidic tail gas is absorbed by alkali washing to obtain a fluoride salt solution.

[0012] S4. The solid product is mixed with an alkaline solution, stirred and heated, washed until neutral, and dried to obtain a porous material.

[0013] In an optional embodiment, the mass ratio of the lithium slag, the carbonaceous solid waste and the magnesium powder is (80~100):(50~100):(1~10).

[0014] In an optional embodiment, the ball mill rotates at a speed of 200-800 rpm for a time of 1-20 h.

[0015] In an optional embodiment, the lithium slag is selected from any one or both of lepidolite smelting slag and spodumene smelting slag.

[0016] In an optional embodiment, the carbonaceous solid waste is selected from any one or two of coal gangue, black talc slag, coal gasification slag, fly ash, waste activated carbon, and coke dust.

[0017] In an optional embodiment, the heating reaction temperature is 600~900℃, and the holding time is 0.5~2 h.

[0018] In an optional embodiment, the protective atmosphere is at least one of nitrogen and argon.

[0019] In an optional implementation, the negative pressure condition is -0.1 to 0 MPa.

[0020] In an optional embodiment, the pickling is performed using an acidic solution, which includes any one of sulfuric acid, hydrochloric acid, and nitric acid, and the mass concentration of the acidic solution is 1~20wt%.

[0021] In an optional embodiment, the alkaline washing is performed using an alkaline solution, wherein the alkaline solution is any one of potassium hydroxide, sodium hydroxide, calcium hydroxide, and sodium carbonate, and the mass concentration of the alkaline solution is 1~20wt%.

[0022] In an optional embodiment, the solid-liquid ratio of the solid product to the alkaline solution is 1:(1~20) g / ml; the concentration of the alkaline solution is 0.1~30 mol / L; and the stirring and heating temperature is 30~200℃, and the time is 0.1~6 h.

[0023] The present invention has the following beneficial effects:

[0024] This invention provides a green co-processing method for lithium slag and carbon-containing solid waste. The method co-treats lithium slag and carbon-containing solid waste, introducing a small amount of magnesium powder as an initiator. Under a protective atmosphere and negative pressure, the magnesium powder and carbon-containing solid waste jointly participate in the reduction reaction, efficiently removing gypsum components from the lithium slag. The technical principle is that the protective atmosphere forms a barrier, isolating oxygen and moisture, preventing the oxidation of magnesium powder and carbon sources; simultaneously, the negative pressure environment reduces the collision frequency of gas molecules, promoting reactant diffusion. This design not only utilizes the exothermic characteristics of the reaction itself but also achieves dual savings in energy consumption and process cost by shortening the reaction time and lowering the reaction temperature.

[0025] This invention achieves the directional transformation of gypsum and the removal and fixation of toxic components such as fluorine, beryllium, and thallium simultaneously during the reaction through the synergistic treatment of lithium slag and carbon-containing solid waste. Its core mechanism lies in two aspects: First, the gypsum in the lithium slag reacts with the carbon source and magnesium powder to generate nascent calcium oxide and magnesium oxide, which undergo mineral phase reconstruction with silica and alumina in the system, forming a stable structure dominated by anorthite and spinel, thus fixing the toxic components within the crystal lattice. Second, during the reaction, most of the toxic components are converted into volatile substances under a reducing atmosphere, entering the flue gas as compounds and elemental particles, and are thus efficiently separated. Through this dual pathway of solid-phase fixation and gas-phase separation, the deep harmlessness of both types of solid waste is ultimately achieved. In particular, this process simultaneously collects the exhaust gas containing toxic components, not only deeply purifying the waste gas and avoiding environmental pollution, but also realizing the resource recovery of high-value toxic components.

[0026] This invention features a simple and energy-efficient preparation process. It innovatively employs a "waste-to-waste" strategy, simultaneously achieving the harmless treatment of lithium slag while using alkali treatment to prepare porous materials with high specific surface area from the solid products. This method simultaneously transforms the abundant calcium, aluminum, and silicon resources in lithium slag and carbonaceous solid waste into functional materials suitable for catalysis, adsorption, and other fields, significantly improving resource utilization and economic benefits. Attached Figure Description

[0027] 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.

[0028] Figure 1 A process flow diagram of a method for the green co-processing of lithium slag and carbonaceous solid waste provided by the present invention;

[0029] Figure 2 This is an X-ray diffraction pattern of the solid product prepared in Example 1 of the present invention. Detailed Implementation

[0030] 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.

[0031] Please see Figure 1 This invention provides a method for the green co-processing of lithium slag and carbon-containing solid waste, comprising: ball milling and mixing lithium slag, carbon-containing solid waste and magnesium powder to obtain a reaction precursor; heating the reaction precursor under a protective atmosphere and negative pressure to produce a solid product and flue gas containing beryllium, thallium and fluorine; firstly absorbing the flue gas containing beryllium, thallium and fluorine with acid to obtain a beryllium-thallium acid washing solution; then absorbing the remaining fluorine-containing acidic tail gas with alkali to obtain a fluoride salt solution; mixing the solid product with the alkali solution, stirring and heating, washing to neutrality, and drying to obtain a porous material.

[0032] This invention uses lithium slag and carbonaceous solid waste as main raw materials, employing a "waste-to-waste" approach. The lithium slag and carbonaceous solid waste are co-treated through carbothermal reduction, with a small amount of magnesium powder added as an initiator to synergistically promote the decomposition of gypsum and release active calcium oxide. Under this high-temperature environment, some of the toxic components in the lithium slag, such as fluorine, beryllium, and thallium, are converted into volatile substances and separated. Subsequently, the calcium oxide generated by the reaction undergoes mineral phase reconstruction with components such as alumina and silica in the two solid wastes at high temperature, thereby solidifying the remaining toxic components in a stable crystal lattice, significantly reducing the risk of toxic leaching and achieving efficient detoxification. During the reaction, the generated flue gas containing fluorine, beryllium, and thallium is simultaneously subjected to acid washing and alkali washing for recovery, reducing the pollution of the atmosphere by harmful exhaust gases. The final solid product, after alkali modification, yields a porous material with a high specific surface area, which can be widely used in catalysis, adsorption, and other fields, improving resource utilization and economic benefits.

[0033] The specific steps of the present invention are as follows:

[0034] S1. Lithium slag, carbon-containing solid waste and magnesium powder are ball-milled and mixed to obtain a reaction precursor.

[0035] In this invention, the lithium slag is selected from any one or two of lepidolite smelting slag and spodumene smelting slag. The carbonaceous solid waste is selected from any one or two of coal gangue, black talc slag, coal gasification slag, fly ash, waste activated carbon, and coke dust.

[0036] The lepidolite smelting slag and spodumene smelting slag in this invention mainly contain, but are not limited to, silicon dioxide, alumina, and gypsum, and also explicitly contain toxic and harmful components such as beryllium and thallium. Carbon-containing solid waste has abundant carbon content, silicon dioxide, and alumina.

[0037] The mass ratio of lithium slag, carbon-containing solid waste and magnesium powder is (80~100):(50~100):(1~10), preferably 100:(50~100):(1~8), the ball milling speed is 200~800 rpm, and the time is 1~20 h.

[0038] This invention co-processes lithium slag and carbonaceous solid waste, adding a small amount of magnesium powder as an initiator to lower the subsequent heating temperature. Since lithium slag, carbonaceous solid waste, and magnesium powder are three materials with significantly different properties, ball milling achieves microscopic mixing through mechanical force, ensuring sufficient contact between the components during subsequent heating and avoiding problems such as "local carbon deficiency" or "local magnesium powder excess," thus guaranteeing the synergistic effect of the reaction. During ball milling, the dense structure of the lithium slag is disrupted, reducing particle size (increasing specific surface area), making it easier for harmful components such as beryllium, thallium, and fluorine trapped within to be released in subsequent reactions. The porous structure of the carbonaceous solid waste further develops, providing more active sites for the reduction reaction of magnesium powder. The magnesium powder is dispersed into ultrafine particles through ball milling, reducing agglomeration and improving its reduction efficiency, thereby forming a stable precursor and ensuring process continuity.

[0039] S2. The reaction precursor is heated under a protective atmosphere and negative pressure to produce solid products and flue gas containing beryllium, thallium and fluorine.

[0040] The reaction precursor is placed in a heating container, and a protective atmosphere is introduced into the heating container. The protective atmosphere is at least one of nitrogen and argon. The negative pressure condition is -0.1~0 MPa. The temperature of the heating container is controlled so that the reaction precursor reacts at a temperature of 600~900℃ and the holding time is 0.5~2 h.

[0041] Under a protective atmosphere and negative pressure, magnesium powder and carbonaceous solid waste jointly participate in the reduction reaction. The carbonaceous matter in the solid waste and the magnesium powder reduce the gypsum components in the lithium slag, synergistically promoting the efficient decomposition of the gypsum and releasing active calcium oxide. The protective atmosphere forms a barrier, isolating oxygen and moisture and preventing the oxidation of magnesium powder and carbon sources; simultaneously, the negative pressure environment reduces the collision frequency of gas molecules, promoting reactant diffusion.

[0042] Among them, carbonaceous material acts as a mild reducing agent, reducing the activation energy of gypsum decomposition (avoiding excessively violent local reactions caused by the reduction of magnesium powder alone); magnesium powder acts as a strong reducing agent, further promoting the deep decomposition of gypsum and ensuring that the released calcium oxide is in a highly active state (without a passivation layer, its reactivity is much higher than that of ordinary calcium oxide).

[0043] Subsequently, the calcium oxide generated in the reaction undergoes mineral phase reconstruction with components such as alumina and silicon dioxide in the two solid wastes at high temperature, generating structurally stable silicate minerals. These silicate minerals have a dense three-dimensional crystal lattice structure, and the ionic radius of calcium has a high degree of matching with the crystal lattice, enabling them to form stable crystal structures.

[0044] Under this high-temperature environment, some of the toxic components originally contained in lithium slag, such as fluorine, beryllium, and thallium, are transformed into volatile substances (i.e. flue gas containing beryllium, thallium, and fluorine) and can be separated.

[0045] Unvolatile trace toxic components (such as heavy metal ions like beryllium) are captured by the lattice structure of silicate minerals during mineral phase reconstruction, solidified within the stable lattice, and cannot be contacted by external leachate, thus significantly reducing the risk of toxic leaching and achieving efficient detoxification.

[0046] S3. The flue gas containing beryllium, thallium and fluorine is first absorbed by acid washing to obtain a beryllium-thallium acid washing solution; then the remaining fluorine-containing acidic tail gas is absorbed by alkali washing to obtain a fluoride salt solution.

[0047] In this invention, by sequentially acid washing and alkaline washing of flue gas containing beryllium, thallium, and fluorine, the flue gas containing beryllium, thallium, and fluorine can be recovered separately, thereby reducing the pollution of the atmospheric environment by harmful exhaust gases.

[0048] Among them, beryllium and thallium in the flue gas are elemental or low-valence oxides, which are readily soluble in acid. During the pickling process, beryllium and thallium react with acid to form soluble salts, which enter the pickling solution, thus achieving the enrichment and recovery of both. In this invention, acid washing is carried out using an acidic solution, which includes any one of sulfuric acid, hydrochloric acid, and nitric acid, with a mass concentration of 1-20 wt%.

[0049] To further separate and recover beryllium and thallium, the pickling solution containing beryllium and thallium can be further treated. The treatment method includes, but is not limited to, adjusting the pH to 6-9 using an alkaline solution. At this time, the beryllium in the pickling solution will react with hydroxide ions to generate beryllium hydroxide and precipitate out. After standing for 0.1-24 hours, solid-liquid separation is performed to obtain beryllium hydroxide solid and thallium-rich supernatant, thereby achieving the separation of beryllium and thallium.

[0050] The remaining tail gas after acid washing is mainly fluorine-containing acidic gas. Alkaline washing can capture fluoride ions to obtain a fluoride salt solution (which can be used to prepare fluorochemical products), realizing the resource utilization of fluorine. At the same time, alkaline washing can neutralize the acidic components in the tail gas, so that the final emission gas meets environmental protection standards. In this invention, alkaline washing is carried out using an alkaline solution, which is any one of potassium hydroxide, sodium hydroxide, calcium hydroxide, and sodium carbonate, with a mass concentration of 1~20wt%.

[0051] S4. The solid product is mixed with an alkaline solution, stirred and heated, washed until neutral, and dried to obtain a porous material.

[0052] In this invention, the solid-liquid ratio of the solid product to the alkaline solution is 1:(1~20) g / ml; the concentration of the alkaline solution is 0.1~30 mol / L; the solid product mainly consists of silicate minerals and amorphous carbon after carbothermic reduction and magnesium powder activation, and OH- is present during the alkaline dissolution process. - Ions attack the silicon-oxygen network of silicate minerals, causing structural disintegration and the formation of pores; at the same time, alkaline conditions can adjust the surface charge properties of solid products and enhance their adsorption performance (such as for heavy metal adsorption and water purification).

[0053] The stirring and heating temperature is 30~200℃, and the time is 0.1~6 h. Stirring and heating can promote full contact between the solid product and the alkaline solution, accelerate the alkaline dissolution reaction rate, shorten the reaction time, and promote the stable formation of the pore structure.

[0054] The subsequent washing process, which aims to neutralize the material, remove residual alkali, protect the material structure, maintain performance stability, and avoid risks in subsequent applications (such as alkali-aggregate reaction and performance degradation). Drying evaporates the moisture, further fixing the pore structure in the solid product, ultimately forming a porous material with a high specific surface area and well-developed pore structure.

[0055] This invention utilizes the calcium aluminum silicate minerals of lithium slag to provide skeletal support, and the residual carbon in carbon-containing solid waste to enhance porosity, thereby achieving "resource upgrading" of both types of solid waste. The product can be widely used in fields such as adsorption, catalysis, and building materials, significantly improving the economic benefits of solid waste disposal.

[0056] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0057] Example 1

[0058] A method for the green co-processing of lithium slag and carbonaceous solid waste includes the following steps:

[0059] (1) The particle size of lepidolite smelting slag and coal gangue is relatively large. The contact area between gypsum in lepidolite smelting slag and carbon component in coal gangue is relatively small. Therefore, it is necessary to process the reaction materials by ball milling in advance. Specifically, lepidolite smelting slag, coal gangue and magnesium powder are mixed in a mass ratio of 100:80:5 and then transferred to a planetary ball mill and ball-milled at 500 rpm for 2 h to obtain the reaction precursor.

[0060] (2) The reaction precursor was placed in a heating container and heated under a nitrogen atmosphere and a pressure of -0.05 MPa at a temperature of 900℃ for 0.5 h. Then the product was cooled to obtain a solid product.

[0061] (3) During the heating reaction, 200 mL of 5wt% nitric acid was used to collect the generated tail gas containing beryllium and thallium to obtain beryllium nitrate and thallium nitrate washing solution. Then, the remaining fluoride-containing acidic tail gas was treated with 200 mL of 8wt% sodium hydroxide to recover the fluoride salt solution.

[0062] (4) The solid product in step (2) is mixed with 8 mol / L potassium hydroxide solution at a solid-liquid ratio of 1:5 (g / mL), stirred and heated at 60°C for 3 h, and then washed until neutral and dried to obtain a porous material.

[0063] Steps (2) and (3) above are performed simultaneously.

[0064] like Figure 2 The figure shows the X-ray diffraction pattern of the product after high-temperature reaction in Example 1 of the present invention. As can be seen from the figure, the phase of the solid product is mainly composed of anorthite and spinel, and the gypsum in the lepidolite smelting slag has been removed.

[0065] Example 2

[0066] A method for the green co-processing of lithium slag and carbonaceous solid waste includes the following steps:

[0067] (1) The particle size of lepidolite smelting slag is relatively large. The carbon components of gypsum and coal gasification slag are not in sufficient contact. Therefore, the reaction materials need to be ball-milled and mixed in advance. Specifically, lepidolite smelting slag, coal gasification slag and magnesium powder are mixed in a mass ratio of 100:60:3 and then transferred to a planetary ball mill and ball-milled at 300 rpm for 5 h to obtain the reaction precursor.

[0068] (2) The reaction precursor was placed in a heating container and heated under an argon atmosphere and a pressure of -0.04 MPa at a temperature of 800℃ for 1 h. Then the product was cooled to obtain a solid product.

[0069] (3) During the heating reaction, 350 mL of 15wt% hydrochloric acid was used to collect the generated tail gas containing beryllium and thallium to obtain beryllium chloride and thallium chloride acid washing solution. Then, the remaining fluoride-containing acidic tail gas was treated with 300 mL of 8wt% potassium hydroxide to recover the fluoride salt solution.

[0070] (4) The solid product in step (2) is mixed with 10 mol / L sodium hydroxide solution at a solid-liquid ratio of 1:12 (g / mL), stirred and heated at 80°C for 2 h, and then washed until neutral and dried to obtain a porous material.

[0071] Steps (2) and (3) above are performed simultaneously.

[0072] Example 3

[0073] A method for the green co-processing of lithium slag and carbonaceous solid waste includes the following steps:

[0074] (1) The particle size of lepidolite smelting slag and coke chips is relatively large. The gypsum and carbon components are not in sufficient contact. Therefore, the reaction materials need to be ball-milled and mixed in advance. Specifically, lepidolite smelting slag, coke chips and magnesium powder are mixed in a mass ratio of 100:90:6 and then transferred to a planetary ball mill and ball-milled at 450 rpm for 3 h to obtain the reaction precursor.

[0075] (2) The reaction precursor was placed in a heating container and heated under a nitrogen atmosphere and a pressure of -0.06 MPa at a temperature of 750℃ for 1.2 h. Then the product was cooled to obtain a solid product.

[0076] (3) During the heating reaction, 250 mL of 13.5 wt% sulfuric acid was used to collect the generated tail gas containing beryllium and thallium to obtain beryllium sulfate and thallium sulfate washing solution. Then, the remaining fluoride-containing acidic tail gas was treated with 300 mL of 10 wt% calcium hydroxide to recover the fluoride salt solution.

[0077] (4) The solid product in step (2) is mixed with a 12 mol / L sodium carbonate solution at a solid-liquid ratio of 1:8 (g / mL), stirred and heated at 100°C for 4 h, and then washed until neutral and dried to obtain a porous material.

[0078] Steps (2) and (3) above are performed simultaneously.

[0079] Example 4

[0080] A method for the green co-processing of lithium slag and carbonaceous solid waste includes the following steps:

[0081] (1) The particle size of spodumene smelting slag and black talc slag is relatively large, and the contact area between gypsum and carbon components is relatively small. Therefore, the reaction materials need to be ball-milled and mixed in advance. Specifically, spodumene smelting slag, black talc slag and magnesium powder are mixed in a mass ratio of 100:70:8 and then transferred to a planetary ball mill and ball-milled at 550 rpm for 5 h to obtain the reaction precursor.

[0082] (2) The reaction precursor was placed in a heating container and heated under an argon atmosphere and a pressure of -0.08 MPa at a temperature of 700℃ for 1.5 h. Then the product was cooled to obtain a solid product.

[0083] (3) During the heating reaction, 250 mL of 8.5 wt% hydrochloric acid was used to collect the generated tail gas containing beryllium and thallium to obtain beryllium chloride and thallium chloride acid washing solution. Then, the remaining fluoride-containing acidic tail gas was treated with 250 mL of 10 wt% sodium hydroxide for alkaline washing to recover the fluoride salt solution;

[0084] (4) The solid product in step (2) is mixed with 5 mol / L ammonium bicarbonate solution at a solid-liquid ratio of 1:6 (g / mL), stirred and heated at 120°C for 5 h, and then washed until neutral and dried to obtain a porous material.

[0085] Steps (2) and (3) above are performed simultaneously.

[0086] Example 5

[0087] A method for the green co-processing of lithium slag and carbonaceous solid waste includes the following steps:

[0088] (1) The particle size of spodumene smelting slag is relatively large, and the gypsum in it does not have sufficient contact with the carbon component in the waste activated carbon. Therefore, the reaction materials need to be ball-milled and mixed in advance. Specifically, the spodumene smelting slag, waste activated carbon and magnesium powder are mixed in a mass ratio of 100:85:4 and then transferred to a planetary ball mill and ball-milled at 350 rpm for 6 h to obtain the reaction precursor.

[0089] (2) The reaction precursor was placed in a heating container and heated under an argon atmosphere and a pressure of -0.1 MPa. The temperature was 650℃ and the holding time was 2 h. Then the product was cooled to obtain a solid product.

[0090] (3) During the heating reaction, 150 mL of 8.0 wt% sulfuric acid was used to collect the generated tail gas containing beryllium and thallium to obtain beryllium sulfate and thallium sulfate washing solution. Then, the remaining fluoride-containing acidic tail gas was treated with 150 mL of 12 wt% sodium carbonate for alkaline washing to recover the fluoride salt solution;

[0091] (4) The solid product in step (2) is mixed with 16 mol / L sodium hydroxide solution at a solid-liquid ratio of 1:20 (g / mL), stirred and heated at 150°C for 6 h, and then washed until neutral and dried to obtain a porous material.

[0092] Steps (2) and (3) above are performed simultaneously.

[0093] Comparative Example 1

[0094] A method for the green co-processing of lithium slag and carbon-containing solid waste is provided. The process steps are basically the same as those in Example 1. The main difference is that the mass ratio of lithium mica smelting slag, coal gangue and magnesium powder in step (1) of Example 1 is reduced to 100:10:1, while other conditions remain unchanged.

[0095] Comparative Example 2

[0096] A method for the green co-processing of lithium slag and carbon-containing solid waste is provided. The process steps are basically the same as those in Example 2. The main difference is that the heating temperature in step (2) of Example 2 is changed to 200℃ and the holding time is 10 min, while other conditions remain unchanged.

[0097] Comparative Example 3

[0098] A method for the green co-processing of lithium slag and carbon-containing solid waste is basically the same as that in Example 4. The main difference is that the heating temperature in step (4) of Example 4 is changed to 500℃, while other conditions remain unchanged.

[0099] Comparative Example 4

[0100] A method for the green co-processing of lithium slag and carbon-containing solid waste is provided. The process steps are basically the same as those in Example 5. The main difference is that the argon atmosphere in step (2) of Example 5 is changed to an air atmosphere, under normal pressure conditions, while other conditions remain unchanged.

[0101] Comparative Example 5

[0102] A method for the green co-processing of lithium slag and carbon-containing solid waste is basically the same as that in Example 5, except that the magnesium powder in step (1) of Example 5 is replaced with steel slag.

[0103] Comparative Example 6

[0104] A method for the green co-processing of lithium slag and carbon-containing solid waste is basically the same as that in Example 5, except that the carbon-containing solid waste in step (1) of Example 5 is replaced with marble tailings.

[0105] Experimental Example

[0106] The solid products and porous materials obtained from the green co-processing method for lithium slag and carbonaceous solid waste provided in the above embodiments and comparative examples were subjected to performance testing. The removal rates of fluorine, beryllium, and thallium in the solid products were determined using ion chromatography and inductively coupled plasma mass spectrometry (ICP-MS). The toxic leaching concentrations of fluorine, beryllium, and thallium in the solid products were also determined using ion chromatography and ICP-MS. The specific surface area of ​​the porous materials was determined using a specific surface area measurement method. The test results are shown in Table 1.

[0107] Table 1. Statistical table of performance test results of solid products and porous materials of different examples

[0108]

[0109] As can be seen from the table above, the thallium removal rate in the solid products of Examples 1-5 of the present invention is as high as 90% or more, and the leaching content of fluorine and beryllium toxicity is lower than the national leaching toxicity standard, and the thallium content is lower than the local standard.

[0110] In Comparative Example 1, the removal rates of fluorine, beryllium, and thallium in the solid product were only 34.2%, 4.3%, and 52.3%, respectively, with toxic leaching contents of 74.6 mg / L, 0.32 mg / L, and 0.012 mg / L. Due to the relatively low content of reducing medium, gypsum in the lepidolite smelting slag could not be completely removed. The residual gypsum in the material not only affected the adsorption performance but also had a synergistic adsorption effect on toxic components such as beryllium and thallium, affecting the removal rates of beryllium and thallium and increasing the toxic leaching concentration. Furthermore, the low magnesium powder content increased energy consumption and cost. Therefore, the mass ratio of lepidolite smelting slag, coal gangue, and magnesium powder needs to be adjusted to a suitable range.

[0111] In Comparative Example 2, the removal rates of fluorine, beryllium, and thallium in the solid product were only 28.6%, 3.4%, and 43.1%, respectively, with toxic leaching concentrations of 62.3 mg / L, 0.28 mg / L, and 0.017 mg / L. Due to the low reaction temperature, the migration rate of sulfur was significantly reduced, leading to its enrichment at the reaction interface. Sulfur preferentially combined with unreacted calcium ions to form calcium sulfide (rather than further oxidation to sulfur dioxide). Simultaneously, the diffusion coefficient of carbon decreased under low-temperature conditions, resulting in insufficient contact between reactants and hindering the complete reduction and decomposition of gypsum. This process reduced the removal efficiency of toxic elements such as fluorine, beryllium, and thallium from the desulfurized gypsum, thereby increasing the leaching concentration of these toxic elements in the solid product. Therefore, the reaction temperature needs to be adjusted to a suitable range.

[0112] The removal rates of fluorine, beryllium, and thallium in the solid product of Comparative Example 3 were 44.5%, 14.1%, and 97.5%, respectively, with toxic leaching contents of 1.36 mg / L, 0.00083 mg / L, and 0.00072 mg / L. Although gypsum was removed from the spodumene smelting slag, the removal rate of toxic components was high and the toxic leaching concentration did not exceed the standard. However, during the alkali treatment, the excessively high heating temperature caused the porous material's framework to collapse, the pore size distribution to widen, and the pore structure to become disordered, resulting in a reduction in specific surface area to 83 m². 2 / g. Therefore, the heating temperature needs to be adjusted to a suitable range during the alkali treatment process.

[0113] The removal rates of fluorine, beryllium, and thallium in the solid product of Comparative Example 4 were 21.3%, 4.5%, and 43.5%, respectively, with toxic leaching concentrations of 65.3 mg / L, 0.42 mg / L, and 0.16 mg / L. Because the carbon source in the coal gasification slag is easily oxidized and consumed under air atmosphere, its reducing activity decreases, and the gypsum fails to react fully. This residual gypsum not only degrades the pore structure of the porous material but also forms a synergistic leaching effect with the heavy metals thallium and beryllium, causing the toxic leaching concentration to exceed the standard. Secondly, under normal pressure conditions, this reaction requires increased reaction temperature and time to maintain, which significantly increases the reaction energy consumption.

[0114] In Comparative Example 5, when steel slag replaced magnesium powder, the removal rates of fluorine, beryllium, and thallium (32.6%, 5.6%, and 53.6%, respectively) were low, while the corresponding toxic leaching concentrations (12.1 mg / L, 0.032 mg / L, and 0.014 mg / L, respectively) remained at relatively high levels. The reason for this is that the large amount of iron oxide in steel slag competitively reduces the carbon source in the carbon-containing solid waste, consuming the carbon intended for reducing gypsum. This results in insufficient carbon and incomplete reduction and decomposition of gypsum, thus affecting the removal efficiency of fluorine, beryllium, and thallium and posing a leaching risk. Simultaneously, the reaction is not exothermic enough, requiring external heating to maintain, leading to a significant increase in energy consumption. Therefore, steel slag has limitations in both reactivity and thermal effect.

[0115] The removal rates of fluorine, beryllium, and thallium in the solid product of Comparative Example 6 were 27.2%, 4.8%, and 48.3%, respectively, with toxic leaching concentrations of 28.4 mg / L, 0.072 mg / L, and 0.028 mg / L. Compared with carbonaceous solid waste, marble tailings, a solid waste without reducing components, although having a certain solidification effect on toxic components, cannot effectively remove gypsum due to its lack of reducing ability. This results in low removal efficiency and insufficient stability of toxic elements, and the continued risk of toxic leaching.

[0116] In summary, this invention provides a green co-processing method for lithium slag and carbon-containing solid waste. This method involves co-treating lithium slag and carbon-containing solid waste, introducing a small amount of magnesium powder as an initiator. Under a protective atmosphere and negative pressure, the magnesium powder and carbon-containing solid waste participate in the reduction reaction, efficiently removing gypsum components from the lithium slag. The technical principle is that the protective atmosphere forms a barrier, isolating oxygen and moisture, preventing the oxidation of magnesium powder and carbon sources; simultaneously, the negative pressure environment reduces the collision frequency of gas molecules, promoting reactant diffusion. This design not only utilizes the exothermic characteristics of the reaction itself but also achieves dual savings in energy consumption and process cost by shortening the reaction time and lowering the reaction temperature. This invention, through the co-processing of lithium slag and carbon-containing solid waste, simultaneously achieves the directional conversion of gypsum and the removal of toxic components such as fluorine, beryllium, and thallium during a high-temperature reaction. The core mechanism lies in two aspects: First, the gypsum in the lithium slag reacts with the carbon source and magnesium powder to generate nascent calcium oxide and magnesium oxide, which undergo mineral phase reconstruction with silica and alumina in the system, forming a stable structure dominated by anorthite and spinel, thus fixing the toxic components in the crystal lattice. Second, during the reaction, most of the toxic components are converted into volatile substances under a reducing atmosphere, entering the flue gas in the form of compounds and elemental particles, and are thus efficiently separated. Through the dual pathways of solid-phase fixation and gas-phase separation, the deep harmlessness of both types of solid waste is ultimately achieved. In particular, the process simultaneously collects the tail gas containing toxic components, which not only deeply purifies the waste gas and avoids environmental pollution, but also realizes the resource recovery of high-value toxic components. The preparation process of this invention is simple and energy-efficient, and innovatively adopts a "waste-to-waste" strategy, achieving the harmless treatment of lithium slag while preparing porous materials with high specific surface area from the solid products through alkali treatment. This method simultaneously transforms abundant resources such as calcium, aluminum, and silicon from lithium slag and carbon-containing solid waste into functional materials suitable for catalysis, adsorption, and other fields, significantly improving resource utilization and economic benefits.

[0117] 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 method for the green co-processing of lithium slag and carbonaceous solid waste, characterized in that, It includes: S1. Lithium slag, carbon-containing solid waste and magnesium powder are ball-milled and mixed to obtain a reaction precursor, wherein the mass ratio of lithium slag, carbon-containing solid waste and magnesium powder is (80~100):(50~100):(1~10). S2. The reaction precursor is heated under a protective atmosphere and negative pressure to produce a solid product and flue gas containing beryllium, thallium and fluorine; the protective atmosphere is at least one of nitrogen and argon; the negative pressure is -0.1~0 MPa, the heating reaction temperature is 600~900℃, and the holding time is 0.5~2 h. S3. The flue gas containing beryllium, thallium and fluorine is first absorbed by acid washing to obtain a beryllium-thallium acid washing solution; then the remaining fluorine-containing acidic tail gas is absorbed by alkali washing to obtain a fluoride salt solution. S4. The solid product is mixed with an alkaline solution, stirred and heated, washed until neutral, and dried to obtain a porous material.

2. The method for green co-processing of lithium slag and carbonaceous solid waste according to claim 1, characterized in that, The ball mill operates at a speed of 200-800 rpm for 1-24 hours.

3. The method for green co-processing of lithium slag and carbonaceous solid waste according to claim 1, characterized in that, The lithium slag is selected from any one or both of lepidolite smelting slag and spodumene smelting slag.

4. The method for green co-processing of lithium slag and carbonaceous solid waste according to claim 1, characterized in that, The carbon-containing solid waste is selected from any one or two of the following: coal gangue, black talc slag, coal gasification slag, fly ash, waste activated carbon, and coke dust.

5. The method for green co-processing of lithium slag and carbonaceous solid waste according to claim 1, characterized in that, The pickling is performed using an acidic solution, which includes any one of sulfuric acid, hydrochloric acid, and nitric acid, and the mass concentration of the acidic solution is 1~20wt%.

6. The method for green co-processing of lithium slag and carbonaceous solid waste according to claim 1, characterized in that, The alkaline washing is performed using an alkaline solution, which is any one of potassium hydroxide, sodium hydroxide, calcium hydroxide, and sodium carbonate, and the mass concentration of the alkaline solution is 1~20wt%.

7. The method for green co-processing of lithium slag and carbonaceous solid waste according to claim 1, characterized in that, The solid-liquid ratio of the solid product to the alkaline solution is 1:(1~20)g / ml; the concentration of the alkaline solution is 0.1~30 mol / L; the stirring and heating temperature is 30~200℃, and the time is 0.1~6 h.

Images