A method for recycling waste lithium aluminosilicate glass-ceramics

Abstract

The present disclosure relates to a recycling method of waste lithium-aluminum-silicon-based glass-ceramics, comprising the following steps: ball milling the waste lithium-aluminum-silicon-based glass-ceramics to obtain glass powder; preparing a hydrofluoric acid solution with a preset concentration as a leaching agent, adding the glass powder into the leaching agent according to a preset liquid-solid ratio, leaching according to a preset leaching temperature and a preset leaching time, and filtering to obtain a leachate; adding a calcium chloride solution to the leachate to dissolve the leachate, and filtering to obtain a conversion solution; extracting the conversion solution, mixing the aqueous phases obtained by two-stage extraction to obtain an extracted conversion solution, mixing the oil phases obtained by two-stage extraction to obtain an extraction solution, back-extracting the extraction solution in a sulfuric acid solution, filtering, and obtaining zirconium sulfate; adjusting the pH of the extracted conversion solution, and filtering to obtain aluminum hydroxide precipitate and a lithium-containing solution.

Description

Technical Field

[0001] This disclosure relates to the field of waste resource recycling, and in particular to a method for recycling waste lithium aluminum silicon microcrystalline glass. Background Technology

[0002] Glass, a material with a history of use spanning thousands of years, is closely intertwined with industrial development and people's lives. Traditional glass mainly includes flat glass and everyday glass, essentially covering all types of glass products used in daily life and production. With the increasing consumer demand for glass products, especially glass packaging and decorative glass, the amount of waste glass generated is also increasing year by year. Waste glass mainly comes from scraps from the production process and normal product waste. According to relevant statistics from the United Nations, waste glass accounts for 7% of solid waste. In urban household waste, waste glass accounts for 4% to 8% in developed countries in Europe and America. The situation in China is also not optimistic, with approximately 10.4 million tons of waste glass generated annually, accounting for about 5% of the total solid waste, and this figure is rising year by year.

[0003] However, waste traditional glass is a low-value waste, which is abundant and difficult to process. Recycling it is not very efficient, and if it is abandoned for recycling and treated directly as raw waste, it will not only harm the environment but also waste resources. Although some traditional glass is treated with metal oxides (such as Li2O, Al2O3, ZrO2, etc.) to meet different usage needs, which increases the value of traditional glass waste to a certain extent, its recycling efficiency is still limited.

[0004] With the advancement of science and technology, glass manufacturing processes have gradually developed, leading to the emergence of new types of glass produced using advanced processes, including optical glass and energy glass. Lithium aluminum silicon glass (also known as lithium aluminum silicon microcrystalline glass) is a new type of high-performance glass. It is a microcrystalline glass with Li₂O-Al₂O₃-SiO₂ as its basic composition. Classified from the perspective of the main crystal, it includes quartz solid solution microcrystalline glass with high light transmittance and zero expansion properties, spodumene solid solution microcrystalline glass, and transparent aluminum-lithium silicon microcrystalline glass. Compared with ordinary glass, lithium aluminum silicon glass has advantages such as good chemical stability, high temperature resistance, high hardness, and high mechanical strength, making it widely used in the electronics industry. Compared with traditional glass waste, lithium aluminum silicon microcrystalline glass has higher recycling value due to its relatively higher content of Li, Al, and Zr. However, there are currently no reports on the recycling of waste lithium aluminum silicon microcrystalline glass. Summary of the Invention

[0005] Based on this, the purpose of this disclosure is to provide a method for recycling waste lithium aluminum silicon-based microcrystalline glass, which realizes the recovery and resource utilization of Li, Al, Zr and Si in waste lithium aluminum silicon-based microcrystalline glass, and prepares the recovered Li, Al, Zr and Si into lithium carbonate, cryolite and zirconium silicate. It has the advantages of high recovery rate, environmentally friendly process and high economic value.

[0006] A method for recycling waste lithium aluminum silicon microcrystalline glass includes the following steps:

[0007] The waste lithium aluminum silicon-based microcrystalline glass was ball-milled to obtain glass powder;

[0008] A hydrofluoric acid solution of a preset concentration is prepared as a leaching agent. The glass powder is added to the leaching agent according to a preset liquid-solid ratio. Leaching is carried out according to a preset leaching temperature and a preset leaching time, and the leachate is obtained by filtration.

[0009] Calcium chloride solution was added to the leachate to dissolve it, and the solution was filtered to obtain the conversion solution.

[0010] The conversion solution is extracted, the aqueous phase obtained from the extraction is mixed to obtain the post-extraction conversion solution, the oil phase obtained from the extraction is mixed to obtain the extract, the extract is back-extracted in sulfuric acid solution, filtered, and zirconium sulfate is obtained.

[0011] The pH of the resulting extraction and conversion solution was adjusted, and the solution was filtered to obtain aluminum hydroxide precipitate and lithium-containing solution.

[0012] The present disclosure discloses a method for recycling waste lithium-aluminum-silicon microcrystalline glass, which realizes the recovery of Li, Al and Zr in waste lithium-aluminum-silicon microcrystalline glass, and has the advantages of high recovery rate and high economic value.

[0013] In one embodiment, the method further includes the following step: adding citric acid and oxalic acid in a preset molar ratio during the ball milling process. Citric acid and oxalic acid can reduce the energy required to break the Si / Al-O bonds on the surface of the waste glass, i.e., reduce the activation energy required for the reaction, and increase the decomposition rate of the transition state complex; and the surface complex formed will change the geometry of the Si / Al-OH bonds, making the waste glass easier to dissolve.

[0014] In one embodiment, the ball milling method is as follows: a preset stainless steel ball group is added to the ball mill, the waste lithium aluminum silicon microcrystalline glass is added to the ball mill according to a preset ball-to-material ratio, and ball milling is performed according to a preset ball milling speed and a preset ball milling time.

[0015] In one embodiment, during the leaching step, the preset concentration is 39-41%, the preset liquid-to-solid ratio is (6:1)-(10:1), the preset leaching temperature is 80℃-100℃, and the preset leaching time is 240min-360min. A preset concentration greater than 41% results in excessive material consumption and high production costs; a preset concentration less than 39% leads to a low leaching rate of Li. A preset liquid-to-solid ratio less than 6:1 easily leads to incomplete leaching; a preset liquid-to-solid ratio greater than 10:1 results in waste of leachate. A preset leaching temperature below 80℃ results in incomplete leaching and low production efficiency; a preset temperature above 100℃ results in excessive energy consumption and limited improvement in leaching effect. A preset leaching time that is too short results in incomplete leaching; a preset leaching time that is too long slows down the recovery process and increases recovery costs.

[0016] In one embodiment, a preset extractant, composed of trioctylamine, tributyl phosphate, and sulfonated kerosene, is used to extract the conversion solution at a preset oil-water ratio, preset extraction temperature, and preset extraction time.

[0017] In one embodiment, the volume ratio of trioctylamine, tributyl phosphate, and sulfonated kerosene is 1:1:4. This volume ratio offers high cost-effectiveness. Increasing the proportion of trioctylamine or tributyl phosphate on this basis will improve the extraction effect to some extent, but the cost increase will be greater. Decreasing the proportion of trioctylamine or tributyl phosphate will reduce the extraction effect and affect normal production.

[0018] In one embodiment, the preset oil-water ratio is (2:1) to (3:1), the preset extraction temperature is 25°C to 30°C, and the preset extraction time is 5 min to 8 min. If the preset oil-water ratio is less than 2:1, incomplete extraction may occur. If the preset oil-water ratio is greater than 3:1, on the one hand, the extractant often has excessive extraction capacity, and on the other hand, due to the increased amount of extractant, the extraction process will take longer, affecting production efficiency. If the extraction temperature is below 25°C, the extraction efficiency is low; if the extraction temperature is above 30°C, more energy and time are required for heating, resulting in high energy consumption and affecting production efficiency. If the extraction time is too short, the extraction will end before complete extraction, affecting the yield. If the extraction time is too long, the extraction efficiency will be affected.

[0019] In one embodiment, the preset molar ratio is (1:2) to (1:1). A molar ratio less than 1:2 results in poor activation, while a molar ratio greater than 1:1 increases costs and affects economic efficiency.

[0020] In one embodiment, the preset stainless steel ball group includes stainless steel balls with a radius of 5 mm and stainless steel balls with a radius of 3 mm, and the mass ratio of the stainless steel balls with a radius of 5 mm to that with a radius of 3 mm is (1:2 to 1:1); the preset ball-to-material ratio is (2:1) to (4:1); the preset ball milling speed is 400 r / min to 600 r / min; and the preset ball milling time is 180 min to 240 min. If the ball-to-material ratio is less than 2:1, the amount of material added is too large, exceeding the ball milling capacity, resulting in the inability to achieve the expected ball milling effect; if the ball-to-material ratio is greater than 4:1, it easily leads to waste of ball milling resources; if the ball milling speed is less than 400 r / min, the ball milling speed is slow or even uneven ball milling occurs; if the ball milling speed is greater than 600 r / min, it easily causes the device to lose its crushing function; if the ball milling time is less than 180 min, the material is not completely milled; if the ball milling time is longer than 240 min, the ball milling time is too long, affecting production efficiency.

[0021] In one embodiment, the glass powder has a particle size of 0.2 mm to 0.8 mm. If the particle size is less than 0.2 mm, the grinding is too fine, resulting in low production efficiency; if the particle size is greater than 0.8 mm, the reaction will be incomplete.

[0022] In one embodiment, the aluminum hydroxide precipitate is synthesized with soda ash and hydrofluoric acid to form cryolite. The recovered aluminum hydroxide is further processed into high-purity cryolite. Cryolite has a wide range of industrial applications, including in the electrolytic aluminum industry, glass enamel industry, and pesticide manufacturing. Therefore, further processing aluminum hydroxide into cryolite can increase the value of the recycled material.

[0023] In one embodiment, the zirconium sulfate is reacted with silicon dioxide to generate zirconium silicate. Further preparing zirconium sulfate, which is prone to environmental risks, into zirconium silicate can, on the one hand, avoid potential environmental hazards from the recycled materials; on the other hand, zirconium silicate is a high-quality opacifier that can be used in the production of various building ceramics, craft ceramics, etc., and preparing zirconium sulfate into zirconium silicate can increase the value of the recycled materials.

[0024] In one embodiment, the lithium-containing solution is reacted with soda ash to obtain lithium carbonate. The lithium-containing solution is further processed into lithium carbonate. Lithium carbonate has wide applications in the new energy industry. Crude lithium carbonate can be sold to customers for the preparation of battery-grade lithium carbonate. Similarly, battery-grade lithium carbonate can be prepared in-house and then sold. The preparation of battery-grade lithium carbonate only requires extraction and impurity removal from the lithium-containing solution before preparing lithium carbonate. Therefore, preparing lithium carbonate from the lithium-containing solution can increase the value of the recycled materials.

[0025] In one embodiment, silicon tetrafluoride generated during the leaching step is collected, and the silicon tetrafluoride is reacted with a sodium carbonate solution to generate hydrofluoric acid. The hydrofluoric acid derived from the silicon tetrafluoride is then used to synthesize the cryolite. Collecting the colorless and toxic silicon tetrafluoride gas generated during the leaching process and converting it into hydrofluoric acid for cryolite preparation avoids pollution and allows for resource recovery.

[0026] In one embodiment, silicon tetrafluoride generated during the leaching step is collected, and the silicon tetrafluoride is reacted with a sodium carbonate solution to generate orthosilicic acid. The orthosilicic acid is then heated to obtain silicon dioxide. The silicon dioxide derived from the silicon tetrafluoride is used to synthesize the zirconium silicate. Collecting the colorless and toxic silicon tetrafluoride gas generated during the leaching process and converting it into silicon dioxide for the preparation of zirconium silicate avoids pollution and allows for resource recovery.

[0027] In one embodiment, the calcium chloride solution is a hydrochloric acid solution of calcium chloride. The acidic environment prevents the formation of aluminum hydroxide.

[0028] The beneficial effects of this disclosure are as follows:

[0029] 1. The recovery of Li, Al, Zr, and Si from waste lithium-aluminum-silicon microcrystalline glass was achieved;

[0030] 2. The resource utilization of Li, Al, Zr, and Si recovered from waste lithium-aluminum-silicon microcrystalline glass has been achieved. Specifically, the recovered Li, Al, Zr, and Si are used to prepare lithium carbonate, cryolite, and zirconium silicate. Lithium carbonate has wide applications in the new energy industry; crude lithium carbonate can be sold externally, while refined lithium carbonate has a higher value. Cryolite has a wide range of industrial applications and can be used in the electrolytic aluminum industry, glass enamel industry, and pesticide manufacturing. Zirconium silicate is a high-quality opacifier that can be used in the production of various building ceramics, craft ceramics, etc.

[0031] 3. By ball milling waste lithium-aluminum-silicon glass-ceramics, the Si-O bonds in the glass-ceramics are broken through physical processes such as interparticle collisions, increasing surface defects and specific surface area, thereby enhancing its reactivity. Specifically, after ball milling waste lithium-aluminum-silicon glass-ceramics using a planetary ball mill, processes such as microstructure collapse, lattice distortion, and chemical bond breaking occur, resulting in increased reactivity. The integrity and order of the silicate structure in the mechanically activated waste lithium-aluminum-silicon glass-ceramics are effectively reduced, giving the raw material higher reactivity.

[0032] 4. By adding citric acid and oxalic acid during ball milling, the energy required to break the Si / Al-O bonds on the surface of waste glass is reduced, that is, the activation energy required for the reaction is reduced, and the decomposition rate of the transition state complex is increased; and the surface complex formed will change the geometry of the Si / Al-OH bonds, making the waste glass easier to dissolve;

[0033] 5. Through the combined action of ball milling and organic acids, the microstructure of waste lithium aluminum silicon-based glass-ceramics collapses, the lattice is distorted, and chemical bonds are broken, increasing the reactivity and facilitating subsequent recycling.

[0034] 6. By collecting silicon tetrafluoride produced during hydrofluoric acid leaching and allowing it to undergo an incomplete hydrolysis reaction with sodium carbonate solution to produce hydrofluoric acid and orthosilicic acid, the hydrofluoric acid is used in the preparation of cryolite, while the orthosilicic acid is decomposed to prepare silicon dioxide, and the obtained silicon dioxide is used in the preparation of zirconium silicate; this disclosure achieves the harmlessness and resource utilization of silicon tetrafluoride through the aforementioned method, and greenly and efficiently transforms harmful substances into valuable products;

[0035] 7. Zr in the conversion solution is separated by using a pre-prepared extractant made of trioctylamine, tributyl phosphate and sulfonated kerosene, and zirconium sulfate is obtained by three extractions;

[0036] 8. The recycling method for waste lithium aluminum silicon microcrystalline glass disclosed herein has a high recycling rate and is environmentally friendly, possessing great economic value and environmental benefits.

[0037] To better understand and implement this disclosure, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0038] Figure 1 The XRD test results of waste lithium aluminum silicon microcrystalline glass of type 1 and type 2 selected for this disclosure;

[0039] Figure 2 This is a flowchart of a method for recycling waste lithium aluminum silicon microcrystalline glass as described in Example 1;

[0040] Figure 3 The image shown is a SEM image of the waste lithium-aluminum-silicon microcrystalline glass described in Example 1 before activation.

[0041] Figure 4 The image shows the activated waste lithium-aluminum-silicon microcrystalline glass described in Example 1.

[0042] Figure 5 The XRD results are for the high-purity cryolite prepared in Examples 1-3. Detailed Implementation

[0043] This disclosure discloses a method for recycling waste lithium-aluminum-silicon microcrystalline glass, applicable to common waste lithium-aluminum-silicon microcrystalline glass containing SiO2, Al2O3, Li2O, and ZrO2. In the following embodiments, this disclosure exemplifies two common types of waste lithium-aluminum-silicon microcrystalline glass (Type 1 and Type 2). This application implements the recycling method of this disclosure for Type 1. The component content (wt%) of Type 1 and Type 2 is shown in Table 1 below, and the XRD test results of Type 1 and Type 2 are shown below. Figure 1 As shown, the diffraction peaks of the microcrystalline glass of type 1 and type 2 are consistent, and the composition of the material is the same.

[0044] Table 1 Component content of Model 1 and Model 2

[0045] Components <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[B2O3]]> <![CDATA[Li2O]]> <![CDATA[Na2O]]> MgO <![CDATA[ZrO2]]> Model 1 60 24 0.5 4.4 6.9 0.7 3.5 Model 2 60.1 23.8 0.5 4.2 7.1 0.9 3.4

[0046] Example 1

[0047] This embodiment provides a method for recycling waste lithium aluminum silicon-based microcrystalline glass, such as... Figure 2 As shown, it includes the following steps:

[0048] A certain amount of waste lithium-aluminum-silicon microcrystalline glass was added to a planetary ball mill, along with stainless steel balls at a ball-to-material ratio of 2:1. The stainless steel ball group consisted of stainless steel balls with a radius of 5 mm and those with a radius of 3 mm, with a mass ratio of 1:2. The milling was carried out at a speed of 400 r / min for 180 min. During the milling process, a mixture of citric acid and oxalic acid at a molar ratio of 1:2 and a concentration of 1 mol / L was added to the planetary ball mill. After milling, glass powder with a particle size of 0.2 mm to 0.8 mm was obtained. The aforementioned steps are for activating the waste lithium-aluminum-silicon microcrystalline glass; SEM images before and after activation can be found in [reference needed]. Figure 3 and Figure 4 It is easy to see that its structure becomes more porous after activation. During the activation process, on the one hand, physical actions such as interparticle collisions break the Si-O bonds in the waste lithium aluminum silicon microcrystalline glass, increasing its surface defects and specific surface area, and improving its reactivity. On the other hand, citric acid and oxalic acid can reduce the energy required to break the Si / Al-O bonds on the surface of the waste glass, that is, reduce the activation energy required for the reaction and increase the decomposition rate of the transition state complex. Furthermore, the surface complexes formed will change the geometry of the Si / Al-OH bonds, making the waste glass easier to dissolve. Through the combined action of ball milling and organic acids, the microstructure of the waste lithium aluminum silicon microcrystalline glass collapses, the lattice is distorted, and the chemical bonds are broken, increasing the reactivity and facilitating subsequent recycling.

[0049] Next, a 40% hydrofluoric acid solution was prepared as the leaching agent. Glass powder was added to the leaching agent at a liquid-to-solid ratio of 6:1, and leaching was carried out at 80°C for 240 minutes. The gas generated during the leaching process (mainly silicon tetrafluoride gas) was collected, and the gas was reacted with sodium carbonate solution to obtain hydrofluoric acid and orthosilicic acid. The hydrofluoric acid was collected and temporarily stored, while the orthosilicic acid was further prepared into silicon dioxide by means of heating and decomposition. The silicon dioxide was collected and temporarily stored. After the leaching was completed, the leachate was obtained by filtration. During the leaching process, the following reactions occur: LiAlSi2O6 + 12HF == AlF3(s) + LiF(s) + 2SiF4(g) + 6H2O. Additionally, sodium oxide and zirconium oxide in the waste lithium-aluminum-silicon glass-ceramics also react with hydrofluoric acid. Therefore, during leaching, Al, Li, and Zr in the lithium-aluminum-silicon glass-ceramics are converted into AlF3 precipitate, LiF precipitate, and ZrF4 precipitate (i.e., the aforementioned leachates). Na in the lithium-aluminum-silicon glass-ceramics is converted into NaF and dissolved in hydrofluoric acid, while Si in the lithium-aluminum-silicon glass-ceramics is converted into colorless and toxic SiF4 gas. Therefore, by combining this leaching step with filtration, the mixture of Al, Li, and Zr, Na, and Si can be initially separated.

[0050] Next, a calcium chloride hydrochloric acid solution is added to the leachate to dissolve it, and the solution is filtered to obtain the conversion solution. In this step, the reactions involved in the dissolution process include: 2LiF + CaCl2 = 2LiCl + CaF2(s); 2AlF3 + 3CaCl2 = 2AlCl3 + 3CaF2(s); ZrF4 + 2CaCl2 = ZrCl4 + 2CaF2(s). Therefore, the components of the aforementioned conversion solution include LiCl, AlCl3 and ZrCl4. The contents of the main valuable metal components in the conversion solution are shown in Table 2 below.

[0051] Table 2 shows the content of major valuable metals in the conversion solution of Example 1.

[0052] Components Al Li Zr g / L 14.6 3.4 4.3

[0053] Next, an extractant prepared by mixing trioctylamine, tributyl phosphate, and sulfonated kerosene in a volume ratio of 1:1:4 was used to perform a two-stage extraction on the aforementioned conversion solution at an oil-to-water ratio of 2:1. The extraction time was 5 minutes, and the extraction temperature was 25°C. The aqueous phases obtained from the two-stage extraction were mixed to obtain the post-extraction conversion solution, which contained LiCl and AlCl3. The oil phases obtained from the two-stage extraction were mixed to obtain the extract, which contained ZrCl4. The zirconium extraction rate after the two-stage extraction was 99.2%. The extract was then back-extracted in a sulfuric acid solution, with a zirconium back-extraction rate of 96.23%. The solution was filtered to obtain zirconium sulfate. Because zirconium sulfate poses a significant environmental risk, therefore... Further preparing zirconium sulfate into zirconium silicate can avoid potential environmental hazards from the recycled materials. Furthermore, zirconium silicate is a high-quality opacifier that can be used in the production of various building ceramics and craft ceramics. Preparing zirconium sulfate into zirconium silicate increases the value of the recycled materials. The method for preparing zirconium silicate involves reacting zirconium sulfate with silicon dioxide. During the preparation of zirconium silicate, silicon dioxide obtained from silicon tetrafluoride gas in the leaching step can be used to achieve resource recovery of the recycled materials obtained in the leaching step. The zirconium silicate prepared in this embodiment meets the requirements of the standard "JC / T1094-2009 Zirconium Silicate for Ceramic Use," and its dry basis test results are shown in Table 3 below.

[0054] Table 3. Dry basis test results of zirconium silicate prepared in Example 1

[0055] <![CDATA[ZrSiO4]]> <![CDATA[TiO2]]> <![CDATA[Fe2O3]]> 99.83％ 0.08％ 0.09％

[0056] The pH of the extraction-conversion solution was adjusted using soda ash until no precipitate formed. The solution was then filtered to obtain aluminum hydroxide precipitate and a lithium-containing solution. The filtered aluminum hydroxide precipitate, soda ash, and HF were reacted to synthesize high-purity cryolite (Na3AlF6). The XRD results of the high-purity cryolite prepared in this example are as follows: Figure 5 As shown, it has a good crystal form and no obvious impurity peaks. The preparation principle is: 12HF + 3Na2CO3 + 2Al(OH)3 = 2Na3AlF6 + 3CO2 + 9H2O. Cryolite has a wide range of industrial applications and can be used in the electrolytic aluminum industry, glass enamel industry, and pesticide manufacturing. Therefore, further preparing aluminum hydroxide into cryolite can improve the value of the recycled material. In the process of preparing cryolite, HF obtained from silicon tetrafluoride gas in the leaching step can be used to realize the resource utilization of the recycled material obtained in the leaching step.

[0057] Crude lithium carbonate is prepared by adding soda ash to the lithium-containing solution. Lithium carbonate has wide applications in the new energy industry, and the crude lithium carbonate can be sold to customers for the preparation of battery-grade lithium carbonate. Similarly, battery-grade lithium carbonate can also be prepared and sold. The preparation of battery-grade lithium carbonate only requires extraction and impurity removal from the lithium-containing solution before preparing lithium carbonate. Therefore, preparing lithium carbonate from the lithium-containing solution can increase the value of the recycled material. The reaction principle is: 2LiCl + Na2CO3 = 2NaCl + Li2CO3(s). The crude lithium carbonate prepared using the lithium-containing solution of this disclosure, after washing, meets the requirements of GB / T 11075-2013 "Lithium Carbonate". The dry basis test results of the crude lithium carbonate in this embodiment are shown in Table 4 below.

[0058] Table 4. Dry basis test results of crude lithium carbonate prepared in Example 1

[0059] <![CDATA[Li2CO3]]> Na Fe Ca Mg <![CDATA[Cl - ]]> <![CDATA[SO4 2- ]]> 99.305％ 0.08％ 0.07％ 0.2％ 0.015％ 0.02％ 0.31％

[0060] Example 2

[0061] This embodiment provides a method for recycling waste lithium aluminum silicon microcrystalline glass, including the following steps:

[0062] A certain amount of waste lithium-aluminum-silicon microcrystalline glass was added to a planetary ball mill, along with stainless steel balls at a ball-to-material ratio of 4:1. The stainless steel ball group consisted of stainless steel balls with a radius of 5 mm and those with a radius of 3 mm, with a mass ratio of 1:1. The milling was carried out at 600 r / min for 240 min. During the milling process, a mixture of citric acid and oxalic acid at a molar ratio of 1:1 and a concentration of 1 mol / L was added to the planetary ball mill. After milling, glass powder with a particle size of 0.2 mm to 0.8 mm was obtained. The aforementioned steps are an activation process for the waste lithium-aluminum-silicon microcrystalline glass. It is easy to see that after activation, its structure... The structure becomes more porous. During the activation process, on the one hand, physical actions such as interparticle collisions break the Si-O bonds in the waste lithium aluminum silicon-based glass-ceramics, increasing its surface defects and specific surface area, and improving its reactivity. On the other hand, citric acid and oxalic acid can reduce the energy required to break the Si / Al-O bonds on the surface of the waste glass, that is, reduce the activation energy required for the reaction and increase the decomposition rate of the transition state complex. Furthermore, the surface complexes formed will change the geometry of the Si / Al-OH bonds, making the waste glass easier to dissolve. Through the combined action of ball milling and organic acids, the microstructure of the waste lithium aluminum silicon-based glass-ceramics collapses, the lattice is distorted, and the chemical bonds are broken, increasing the reactivity and facilitating subsequent recycling.

[0063] Next, a 40% hydrofluoric acid solution was prepared as the leaching agent. Glass powder was added to the leaching agent at a liquid-to-solid ratio of 6:1, and leached at 70°C for 180 minutes. The gas generated during the leaching process (mainly silicon tetrafluoride gas) was collected, and the gas was reacted with sodium carbonate solution to obtain hydrofluoric acid and orthosilicic acid. The hydrofluoric acid was collected and temporarily stored, while the orthosilicic acid was further prepared into silicon dioxide by means of heating and decomposition. The silicon dioxide was collected and temporarily stored. After the leaching was completed, the leachate was obtained by filtration. During the leaching process, the following reactions occur: LiAlSi2O6 + 12HF == AlF3(s) + LiF(s) + 2SiF4(g) + 6H2O. Additionally, sodium oxide and zirconium oxide in the waste lithium-aluminum-silicon glass-ceramics also react with hydrofluoric acid. Therefore, during leaching, Al, Li, and Zr in the lithium-aluminum-silicon glass-ceramics are converted into AlF3 precipitate, LiF precipitate, and ZrF4 precipitate (i.e., the aforementioned leachates). Na in the lithium-aluminum-silicon glass-ceramics is converted into NaF and dissolved in hydrofluoric acid, while Si in the lithium-aluminum-silicon glass-ceramics is converted into colorless and toxic SiF4 gas. Therefore, by combining this leaching step with filtration, the mixture of Al, Li, and Zr, Na, and Si can be initially separated.

[0064] Next, a calcium chloride hydrochloric acid solution is added to the leachate to dissolve it, and the solution is filtered to obtain the conversion solution. In this step, the reactions involved in the dissolution process include: 2LiF + CaCl2 = 2LiCl + CaF2(s); 2AlF3 + 3CaCl2 = 2AlCl3 + 3CaF2(s); ZrF4 + 2CaCl2 = ZrCl4 + 2CaF2(s). Therefore, the components of the aforementioned conversion solution include LiCl, AlCl3 and ZrCl4. The contents of the main valuable metal components in the conversion solution are shown in Table 5 below.

[0065] Table 5. Content of major valuable metals in the conversion solution of Example 2

[0066] Components Al Li Zr g / L 14.52 3.35 4.25

[0067] Next, an extractant prepared by mixing trioctylamine, tributyl phosphate, and sulfonated kerosene in a volume ratio of 1:1:4 was used to perform a two-stage extraction on the aforementioned conversion solution at an oil-water ratio of 2:1. The extraction time was 8 minutes, and the extraction temperature was 30°C. The aqueous phases obtained from the two-stage extraction were mixed to obtain the post-extraction conversion solution, which contained LiCl and AlCl3. The oil phases obtained from the two-stage extraction were mixed to obtain the extract, which contained ZrCl4. The zirconium extraction rate after the two-stage extraction was 99.8%. The extract was then back-extracted in a sulfuric acid solution, with a zirconium back-extraction rate of 99.23%. The solution was filtered to obtain zirconium sulfate. Because zirconium sulfate poses a significant environmental risk, therefore... Further preparing zirconium sulfate into zirconium silicate can avoid potential environmental hazards from the recycled materials. Furthermore, zirconium silicate is a high-quality opacifier that can be used in the production of various building ceramics and craft ceramics. Preparing zirconium sulfate into zirconium silicate increases the value of the recycled materials. The method for preparing zirconium silicate involves reacting zirconium sulfate with silicon dioxide. During the preparation of zirconium silicate, silicon dioxide obtained from silicon tetrafluoride gas in the leaching step can be used to achieve resource recovery of the recycled materials obtained in the leaching step. The zirconium silicate prepared in this embodiment meets the requirements of the standard "JC / T1094-2009 Zirconium Silicate for Ceramic Use," and its dry basis test results are shown in Table 6 below.

[0068] Table 6. Dry basis test results of zirconium silicate prepared in Example 2

[0069] <![CDATA[ZrSiO4]]> <![CDATA[TiO2]]> <![CDATA[Fe2O3]]> 99.85％ 0.07％ 0.08％

[0070] The pH of the extraction-conversion solution was adjusted using soda ash until no precipitate formed. The solution was then filtered to obtain aluminum hydroxide precipitate and a lithium-containing solution. The filtered aluminum hydroxide precipitate, soda ash, and HF were reacted to synthesize high-purity cryolite (Na3AlF6). The XRD results of the high-purity cryolite prepared in this example are as follows: Figure 5 As shown, it has a good crystal form and no obvious impurity peaks. The preparation principle is: 12HF + 3Na2CO3 + 2Al(OH)3 = 2Na3AlF6 + 3CO2 + 9H2O. Cryolite has a wide range of industrial applications and can be used in the electrolytic aluminum industry, glass enamel industry, and pesticide manufacturing. Therefore, further preparing aluminum hydroxide into cryolite can improve the value of the recycled material. In the process of preparing cryolite, HF obtained from silicon tetrafluoride gas in the leaching step can be used to realize the resource utilization of the recycled material obtained in the leaching step.

[0071] Crude lithium carbonate is prepared by adding soda ash to the lithium-containing solution. Lithium carbonate has wide applications in the new energy industry, and the crude lithium carbonate can be sold to customers for the preparation of battery-grade lithium carbonate. Similarly, battery-grade lithium carbonate can also be prepared and sold. The preparation of battery-grade lithium carbonate only requires extraction and impurity removal from the lithium-containing solution before preparing lithium carbonate. Therefore, preparing lithium carbonate from the lithium-containing solution can increase the value of the recycled material. The reaction principle is: 2LiCl + Na2CO3 = 2NaCl + Li2CO3(s). The crude lithium carbonate prepared using the lithium-containing solution of this disclosure, after washing, meets the requirements of GB / T 11075-2013 "Lithium Carbonate". The dry basis test results of the crude lithium carbonate in this embodiment are shown in Table 7 below.

[0072] Table 7. Dry basis test results of crude lithium carbonate prepared in Example 2.

[0073] <![CDATA[Li2CO3]]> Na Fe Ca Mg <![CDATA[Cl - ]]> <![CDATA[SO4 2- ]]> 99.205％ 0.08％ 0.07％ 0.25％ 0.015％ 0.03％ 0.35％

[0074] Example 3

[0075] This embodiment provides a method for recycling waste lithium aluminum silicon microcrystalline glass, including the following steps:

[0076] A certain amount of waste lithium-aluminum-silicon microcrystalline glass was added to a planetary ball mill, along with stainless steel balls at a ball-to-material ratio of 4:1. The stainless steel ball group consisted of stainless steel balls with a radius of 5 mm and those with a radius of 3 mm, with a mass ratio of 1:1. The milling was carried out at 600 r / min for 240 min. During the milling process, a mixture of citric acid and oxalic acid at a molar ratio of 1:1 and a concentration of 1 mol / L was added to the planetary ball mill. After milling, glass powder with a particle size of 0.2 mm to 0.8 mm was obtained. The aforementioned steps are an activation process for the waste lithium-aluminum-silicon microcrystalline glass. It is easy to see that after activation, its structure... The structure becomes more porous. During the activation process, on the one hand, physical actions such as interparticle collisions break the Si-O bonds in the waste lithium aluminum silicon-based glass-ceramics, increasing its surface defects and specific surface area, and improving its reactivity. On the other hand, citric acid and oxalic acid can reduce the energy required to break the Si / Al-O bonds on the surface of the waste glass, that is, reduce the activation energy required for the reaction and increase the decomposition rate of the transition state complex. Furthermore, the surface complexes formed will change the geometry of the Si / Al-OH bonds, making the waste glass easier to dissolve. Through the combined action of ball milling and organic acids, the microstructure of the waste lithium aluminum silicon-based glass-ceramics collapses, the lattice is distorted, and the chemical bonds are broken, increasing the reactivity and facilitating subsequent recycling.

[0077] Next, a 40% hydrofluoric acid solution was prepared as the leaching agent. Glass powder was added to the leaching agent at a liquid-to-solid ratio of 6:1, and leached at 70°C for 180 minutes. The gas generated during the leaching process (mainly silicon tetrafluoride gas) was collected, and the gas was reacted with sodium carbonate solution to obtain hydrofluoric acid and orthosilicic acid. The hydrofluoric acid was collected and temporarily stored, while the orthosilicic acid was further prepared into silicon dioxide by means of heating and decomposition. The silicon dioxide was collected and temporarily stored. After the leaching was completed, the leachate was obtained by filtration. During the leaching process, the following reactions occur: LiAlSi2O6 + 12HF == AlF3(s) + LiF(s) + 2SiF4(g) + 6H2O. Additionally, sodium oxide and zirconium oxide in the waste lithium-aluminum-silicon glass-ceramics also react with hydrofluoric acid. Therefore, during leaching, Al, Li, and Zr in the lithium-aluminum-silicon glass-ceramics are converted into AlF3 precipitate, LiF precipitate, and ZrF4 precipitate (i.e., the aforementioned leachates). Na in the lithium-aluminum-silicon glass-ceramics is converted into NaF and dissolved in hydrofluoric acid, while Si in the lithium-aluminum-silicon glass-ceramics is converted into colorless and toxic SiF4 gas. Therefore, by combining this leaching step with filtration, the mixture of Al, Li, and Zr, Na, and Si can be initially separated.

[0078] Next, a calcium chloride hydrochloric acid solution is added to the leachate to dissolve it, and the solution is filtered to obtain the conversion solution. In this step, the reactions involved in the dissolution process include: 2LiF + CaCl2 = 2LiCl + CaF2(s); 2AlF3 + 3CaCl2 = 2AlCl3 + 3CaF2(s); ZrF4 + 2CaCl2 = ZrCl4 + 2CaF2(s). Therefore, the components of the aforementioned conversion solution include LiCl, AlCl3 and ZrCl4. The contents of the main valuable metal components in the conversion solution are shown in Table 8 below.

[0079] Table 8. Content of major valuable metals in the conversion solution of Example 3

[0080] Components Al Li Zr g / L 14.51 3.37 4.2

[0081] Next, an extractant prepared by mixing trioctylamine, tributyl phosphate, and sulfonated kerosene in a volume ratio of 1:1:4 was used to perform a two-stage extraction on the aforementioned conversion solution at an oil-water ratio of 2:1. The extraction time was 8 minutes, and the extraction temperature was 30°C. The aqueous phases obtained from the two-stage extraction were mixed to obtain the post-extraction conversion solution, which contained LiCl and AlCl3. The oil phases obtained from the two-stage extraction were mixed to obtain the extract, which contained ZrCl4. The zirconium extraction rate after the two-stage extraction was 99.8%. The extract was then back-extracted in a sulfuric acid solution, with a zirconium back-extraction rate of 99.23%. The solution was filtered to obtain zirconium sulfate. Because zirconium sulfate poses a significant environmental risk, therefore... Further preparing zirconium sulfate into zirconium silicate can avoid potential environmental hazards from the recycled materials. Furthermore, zirconium silicate is a high-quality opacifier that can be used in the production of various building ceramics and craft ceramics. Preparing zirconium sulfate into zirconium silicate increases the value of the recycled materials. The method for preparing zirconium silicate involves reacting zirconium sulfate with silicon dioxide. During the preparation of zirconium silicate, silicon dioxide obtained from silicon tetrafluoride gas in the leaching step can be used to achieve resource recovery of the recycled materials obtained in the leaching step. The zirconium silicate prepared in this embodiment meets the requirements of the standard "JC / T1094-2009 Zirconium Silicate for Ceramic Use," and its dry basis test results are shown in Table 9 below.

[0082] Table 9. Dry basis test results of zirconium silicate prepared in Example 3

[0083] <![CDATA[ZrSiO4]]> <![CDATA[TiO2]]> <![CDATA[Fe2O3]]> 99.83％ 0.07％ 0.1％

[0084] The pH of the extraction-conversion solution was adjusted using soda ash until no precipitate formed. The solution was then filtered to obtain aluminum hydroxide precipitate and a lithium-containing solution. The filtered aluminum hydroxide precipitate, soda ash, and HF were reacted to synthesize high-purity cryolite (Na3AlF6). The XRD results of the high-purity cryolite prepared in this example are as follows: Figure 5 As shown, it has a good crystal form and no obvious impurity peaks. The preparation principle is: 12HF + 3Na2CO3 + 2Al(OH)3 = 2Na3AlF6 + 3CO2 + 9H2O. Cryolite has a wide range of industrial applications and can be used in the electrolytic aluminum industry, glass enamel industry, and pesticide manufacturing. Therefore, further preparing aluminum hydroxide into cryolite can improve the value of the recycled material. In the process of preparing cryolite, HF obtained from silicon tetrafluoride gas in the leaching step can be used to realize the resource utilization of the recycled material obtained in the leaching step.

[0085] Crude lithium carbonate is prepared by adding soda ash to the lithium-containing solution. Lithium carbonate has wide applications in the new energy industry, and the crude lithium carbonate can be sold to customers for the preparation of battery-grade lithium carbonate. Similarly, battery-grade lithium carbonate can also be prepared and sold. The preparation of battery-grade lithium carbonate only requires extraction and impurity removal from the lithium-containing solution before preparing lithium carbonate. Therefore, preparing lithium carbonate from the lithium-containing solution can increase the value of the recycled material. The reaction principle is: 2LiCl + Na2CO3 = 2NaCl + Li2CO3(s). The crude lithium carbonate prepared using the lithium-containing solution of this disclosure, after washing, meets the requirements of GB / T 11075-2013 "Lithium Carbonate". The dry basis test results of the crude lithium carbonate in this embodiment are shown in Table 10 below.

[0086] Table 10. Dry basis test results of crude lithium carbonate prepared in Example 3

[0087] <![CDATA[Li2CO3]]> Na Fe Ca Mg <![CDATA[Cl - ]]> <![CDATA[SO4 2- ]]> 99.325％ 0.08％ 0.07％ 0.13％ 0.015％ 0.03％ 0.35％

[0088] The beneficial effects of this disclosure are as follows:

[0089] 1. The recovery of Li, Al, Zr, and Si from waste lithium-aluminum-silicon microcrystalline glass was achieved;

[0090] 2. The resource utilization of Li, Al, Zr, and Si recovered from waste lithium-aluminum-silicon microcrystalline glass has been achieved. Specifically, the recovered Li, Al, Zr, and Si are used to prepare lithium carbonate, cryolite, and zirconium silicate. Lithium carbonate has wide applications in the new energy industry; crude lithium carbonate can be sold externally, while refined lithium carbonate has a higher value. Cryolite has a wide range of industrial applications and can be used in the electrolytic aluminum industry, glass enamel industry, and pesticide manufacturing. Zirconium silicate is a high-quality opacifier that can be used in the production of various building ceramics, craft ceramics, etc.

[0091] 3. By ball milling waste lithium-aluminum-silicon glass-ceramics, the Si-O bonds in the glass-ceramics are broken through physical processes such as interparticle collisions, increasing surface defects and specific surface area, thereby enhancing its reactivity. Specifically, after ball milling waste lithium-aluminum-silicon glass-ceramics using a planetary ball mill, processes such as microstructure collapse, lattice distortion, and chemical bond breaking occur, resulting in increased reactivity. The integrity and order of the silicate structure in the mechanically activated waste lithium-aluminum-silicon glass-ceramics are effectively reduced, giving the raw material higher reactivity.

[0092] 4. By adding citric acid and oxalic acid during ball milling, the energy required to break the Si / Al-O bonds on the surface of waste glass is reduced, that is, the activation energy required for the reaction is reduced, and the decomposition rate of the transition state complex is increased; and the surface complex formed will change the geometry of the Si / Al-OH bonds, making the waste glass easier to dissolve;

[0093] 5. Through the combined action of ball milling and organic acids, the microstructure of waste lithium aluminum silicon-based glass-ceramics collapses, the lattice is distorted, and chemical bonds are broken, increasing the reactivity and facilitating subsequent recycling.

[0094] 6. By collecting silicon tetrafluoride produced during hydrofluoric acid leaching and allowing it to undergo an incomplete hydrolysis reaction with sodium carbonate solution to produce hydrofluoric acid and orthosilicic acid, the hydrofluoric acid is used in the preparation of cryolite, while the orthosilicic acid is decomposed to prepare silicon dioxide, and the obtained silicon dioxide is used in the preparation of zirconium silicate; this disclosure achieves the harmlessness and resource utilization of silicon tetrafluoride through the aforementioned method, and greenly and efficiently transforms harmful substances into valuable products;

[0095] 7. Zr in the conversion solution is separated by using a pre-prepared extractant made of trioctylamine, tributyl phosphate and sulfonated kerosene, and zirconium sulfate is obtained by three extractions;

[0096] 8. The recycling method for waste lithium aluminum silicon microcrystalline glass disclosed herein has a high recycling rate and is environmentally friendly, possessing great economic value and environmental benefits.

Claims

1. A method for recycling waste lithium aluminum silicon-based microcrystalline glass, characterized in that, Includes the following steps: The waste lithium aluminum silicon-based microcrystalline glass was ball-milled to obtain glass powder; A hydrofluoric acid solution of a preset concentration is prepared as a leaching agent. The glass powder is added to the leaching agent according to a preset liquid-solid ratio. Leaching is carried out according to a preset leaching temperature and a preset leaching time, and the leachate is obtained by filtration. Calcium chloride solution was added to the leachate to dissolve it, and the solution was filtered to obtain the conversion solution. The calcium chloride solution is a hydrochloric acid solution of calcium chloride; The conversion solution is extracted, the aqueous phase obtained from the extraction is mixed to obtain the post-extraction conversion solution, the oil phase obtained from the extraction is mixed to obtain the extract, the extract is back-extracted in sulfuric acid solution, filtered, and zirconium sulfate is obtained. The pH of the resulting extraction and conversion solution was adjusted, and the solution was filtered to obtain aluminum hydroxide precipitate and lithium-containing solution.

2. The method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 1, characterized in that, It also includes the following steps: Citric acid and oxalic acid are added in a preset molar ratio during the ball milling process.

3. The method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 1, characterized in that, The ball milling method is as follows: a preset stainless steel ball group is added to the ball mill, the waste lithium aluminum silicon microcrystalline glass is added to the ball mill according to the preset ball-to-material ratio, and ball milling is performed according to the preset ball milling speed and preset ball milling time.

4. The method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 1, characterized in that, In the leaching step, the preset concentration is 39wt% to 41wt%, the preset liquid-solid ratio is (6:1) to (10:1), the preset leaching temperature is 80℃ to 100℃, and the preset leaching time is 240min to 360min.

5. The method for recycling waste lithium aluminum silicon-based microcrystalline glass according to claim 1, characterized in that, The conversion solution was extracted using a pre-prepared extractant consisting of trioctylamine, tributyl phosphate, and sulfonated kerosene at a pre-prepared oil-water ratio, pre-prepared extraction temperature, and pre-prepared extraction time.

6. The method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 5, characterized in that, The volume ratio of the trioctylamine, the tributyl phosphate, and the sulfonated kerosene is 1:1:

4.

7. A method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 5, characterized in that, The preset oil-water ratio is (2:1) to (3:1), the preset extraction temperature is 25℃ to 30℃, and the preset extraction time is 5min to 8min.

8. A method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 2, characterized in that, The preset molar ratio is (1:2) to (1:1).

9. A method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 3, characterized in that, The preset stainless steel ball group includes stainless steel balls with a radius of 5 mm and stainless steel balls with a radius of 3 mm. The mass ratio of the stainless steel balls with a radius of 5 mm to the stainless steel balls with a radius of 3 mm is (1:2) to (1:1). The preset ball-to-material ratio is (2:1) to (4:1). The preset ball milling speed is 400 r / min to 600 r / min. The preset ball milling time is 180 min to 240 min.

10. A method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 1, characterized in that, The glass powder has a particle size of 0.2 mm to 0.8 mm.

11. A method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 1, characterized in that, The aluminum hydroxide precipitate was then reacted with soda ash and hydrofluoric acid to synthesize cryolite.

12. The method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 1, characterized in that, The zirconium sulfate is reacted with silicon dioxide to produce zirconium silicate.

13. The method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 1, characterized in that, Lithium carbonate is obtained by reacting the lithium-containing solution with soda ash.

14. A method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 11, characterized in that, The silicon tetrafluoride produced in the leaching step is collected, and the silicon tetrafluoride is reacted with sodium carbonate solution to generate hydrofluoric acid. The hydrofluoric acid derived from the silicon tetrafluoride is used to synthesize the cryolite.

15. A method for recycling waste lithium-aluminum-silicon microcrystalline glass according to claim 12, characterized in that, The silicon tetrafluoride produced in the leaching step is collected, and the silicon tetrafluoride is reacted with sodium carbonate solution to generate orthosilicic acid. The orthosilicic acid is heated to obtain silicon dioxide, and the silicon dioxide derived from the silicon tetrafluoride is used to synthesize the zirconium silicate.

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