Method for preparing micron-sized zinc metastannate through wet recovery of tin and zinc in electronic waste and synthetic method of 4-hydroxy-1-indanone

Abstract

The invention aims to provide a method for preparing micron-sized zinc metastannate by wet recovery of tin and zinc in electronic wastes and a synthetic method of 4-hydroxy-1-indanone, and belongs to the technical field of metal recycling. According to the method, amino coordination and carboxylic acid chelation are utilized, tin and zinc in the electronic waste are selectively leached out under the mild acidic condition, impurity metals such as iron and copper are retained in residues due to the difference of complexing constants, and metal ion grade separation (selectivity gt and 99%) is achieved. And then, through evaporation-crystallization regulation and control, the Sn-Zn complex is directionally reconstructed into micron-sized zinc metastannate. In indanone synthesis, micron-sized zinc metastannate forms a local protonic acid environment by adsorbing trace moisture in a reaction system, synchronously activates a C = N bond (Lewis acid site catalysis) of an imine substrate and stabilizes a cyclization transition state (hydrogen bond guiding effect), so that the activation energy of [4 + 1] cycloaddition reaction is reduced, reaction equilibrium is driven to move towards a product end, and the yield of indanone is increased. And quantitative conversion of indanone under mild conditions (the yield is 60%) is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of metal recycling, and particularly relates to a method for wet recycling of tin and zinc in electronic waste to prepare micron-scale zinc metastannate and a method for synthesizing 4-hydroxy-1-indanone. Background Art

[0002] The total amounts of tin and zinc in electronic waste are huge. Although traditional acid leaching-precipitation processes can achieve rough metal extraction, they have problems such as relying on the large-scale use of strongly corrosive reagents, difficult selective separation caused by the co-dissolution of multiple metals, and co-pollution of heavy metal leachate and toxic organic substances (such as brominated flame retardants), resulting in significant resource waste and environmental risks. In the end-of-treatment process, pyrometallurgy or simple landfill is mostly used, which not only has a low metal recovery rate (<60%) and limited added value of products, but also is more likely to cause secondary hazards such as soil acidification and groundwater pollution, forming a vicious cycle of "high environmental cost - low economic benefit". Therefore, developing green and low-consumption metal separation technologies and constructing a system for directional recovery and high-value utilization of low-value metals have become the key breakthrough points for improving the resource utilization efficiency of all components of electronic waste.

[0003] In the field of indanone compound synthesis, traditional methods such as polyphosphoric acid cyclization method and Nazarov cyclization reaction have long faced problems such as environmental protection pressure, strong dependence on metal catalysts, or harsh reaction conditions. With the increasing value of 3-aminoindanone compounds in drug development, developing green and efficient synthesis routes has become an urgent need.

[0004] Patent CN107033016B proposed a new strategy for constructing a 3-aminoindanone skeleton using imine derivatives and olefins as raw materials through a dichloropentamethylcyclopentadienylrhodium / manganese acetate catalytic system. Although this method realizes molecular cyclization under mild conditions through a metal-catalyzed [4+1] cycloaddition reaction and avoids the traditional strong acidic environment, the use of precious metal rhodium in the catalytic system significantly increases the raw material cost, and the complex reaction system of multiple components results in limited product yield (about 65-78%). At the same time, the large-scale use of organic solvents conflicts with the concept of green chemistry. This technical route presents a typical "efficiency-cost" balance contradiction between simplifying operation steps and improving atom economy, reflecting the core challenges commonly faced in the development of new indanone synthesis methods. Summary of the Invention

[0005] The object of the present invention is to provide a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate and a method for synthesizing 4-hydroxy-1-indanone. This method utilizes the bifunctional properties of glycine (amino coordination and carboxylic acid chelation) to selectively leach tin and zinc from electronic waste under mild acidic conditions. Subsequently, through evaporation-crystallization regulation, the Sn-Zn complex is directionally reconstructed into micron-sized zinc metastannate (ZnSnO3·nH2O), and the exposed Sn-O-Zn active sites and surface hydroxyl groups in its layered structure endow strong water absorption.

[0006] In the synthesis of indanone, micron-sized zinc metastannate forms a local protonic acid environment by adsorbing trace moisture in the reaction system, synchronously activating the C=N bond of the imine substrate (catalyzed by Lewis acid sites) and stabilizing the cyclization transition state (hydrogen bond guiding effect), reducing the activation energy of the [4+1] cycloaddition reaction, driving the reaction equilibrium to shift towards the product side, and realizing the quantitative conversion of indanone under mild conditions.

[0007] To achieve the above object of the invention, the present invention provides a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate, comprising the following steps: S1. Grind the electronic waste to obtain a pulp; S2. Add an amino acid leaching agent to the pulp, adjust the pH of the pulp to 12-14; stir to leach tin and zinc; S3. After completing the tin and zinc leaching process, filter and collect the leaching liquid; S4. Ultrasonically dissolve the leaching liquid, let it stand, and then dry. When the liquid evaporation amount in the leaching liquid reaches 60%-80% of the initial mass of the leaching liquid, stop evaporation; filter, collect the crystalline solid, wash, and naturally dry to obtain micron-sized zinc metastannate.

[0008] Further, the leaching agent is one or more of glycine, glutamic acid, and histidine.

[0009] Further, in step S2, the concentration of the leaching agent in the pulp is 0.1-1 mol / L.

[0010] Further, during the grinding process, grind the electronic waste until the part with a particle size less than 50 mesh in the material accounts for 90%-98% of the total mass of the ore powder.

[0011] Further, in step S1, the mass concentration of the pulp is 5%-10%.

[0012] Further, in step S2, the stirring time is 1-6 h.

[0013] Further, in step S2, when stirring, the temperature of the pulp is 30°C-35°C.

[0014] The present invention also provides a method for synthesizing 4-hydroxy-1-indanone, wherein micron-sized zinc metastannate is prepared by the above method; the method comprises the following steps: A1. The micron-sized zinc stannate is added to a methanesulfonic acid reagent and stirred to obtain a mixed solution; A2. Add hydroxyphenylpropionic acid into the mixed solution, stir until uniform, then heat to 40°C-45°C, and react for 3-4h; A3. After the reaction is completed, cool to room temperature; neutralize with saturated sodium bicarbonate solution, extract the organic phase with dichloromethane, dry with anhydrous magnesium sulfate, filter and concentrate the organic phase to finally obtain 4-hydroxy-1-indanone.

[0015] Furthermore, in step A1, the amount of the micron-sized zinc metastannate added is 2.0-5.0 wt% of the mass of the methanesulfonic acid reagent.

[0016] Furthermore, in step A2, the mass ratio of the hydroxyphenylpropionic acid to the mixed solution is 1:(10-40).

[0017] The beneficial effects of the present invention are: 1. This application proposes a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate. The method utilizes the bifunctional properties of glycine (amino coordination and carboxylic acid chelation) to selectively leach tin and zinc from electronic waste under mild acidic conditions. Specifically: glycine binds to Sn via NO bidentate coordination. 2+ / Zn 2+ Formation of stable complex (Sn(gly)3 - / Zn(gly)2), while impurity metals such as iron and copper are retained in the residue due to differences in complex constants, achieving metal ion-level separation (selectivity > 99%). Subsequently, through evaporation-crystallization regulation, the Sn-Zn complex is directionally reconstructed into micron-sized zinc metastannate (ZnSnO3·nH2O), and the exposed Sn-O-Zn active sites and surface hydroxyl groups in its layered structure give it strong water absorption.

[0018] 2. The present application proposes a method for synthesizing 4-hydroxy-1-indanone. In the synthesis of indanone, micron-sized zinc metastannate forms a local protonic acid environment by adsorbing trace amounts of water in the reaction system, thereby simultaneously activating the C=N bond of the imine substrate (Lewis acid site catalysis) and stabilizing the cyclization transition state (hydrogen bond directing effect), thereby reducing the activation energy of the [4+1] cycloaddition reaction, driving the reaction equilibrium toward the product end, and achieving quantitative conversion of indanone under mild conditions (yield 60%).

[0019] 3. This application innovatively constructs a closed-loop system of "metal recycling - catalytic synthesis" by directing the recovery of low-value metals (such as tin, zinc, etc.) from electronic waste and converting them into high-value catalysts. Replacing the traditional rhodium-based catalyst with a non-precious metal catalytic system can not only solve the economic and environmental dilemmas in the recovery of low-value metals from electronic waste, but also significantly reduce the dependence on precious metals in the synthesis of indanone compounds. At the same time, it reduces the usage of organic solvents and pollution emissions, which is in line with the sustainable development concept of "treating waste with waste".

[0020] The above description is only an overview of the technical solution of this application. In order to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the following specific embodiments of this application are specifically exemplified. Brief Description of the Drawings

[0021] In order to more clearly illustrate the technical solution of this application, the drawings used in this application will be briefly introduced below. Obviously, the following described drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 SEM photographs and EDS energy spectrum diagrams of the micron-sized zinc metastannate prepared in Example 1; among them, (a) backscattered photograph of the product (20μm); (b) backscattered photograph of the product (8μm); (c), (d) elemental surface distribution of the product (20μm); (e) elemental energy spectrum analysis.

[0023] Figure 2 XRD pattern of the micron-sized zinc metastannate prepared in Example 1.

[0024] Figure 3 XRD pattern of the product prepared in Comparative Example 1.

[0025] Figure 4 SEM photographs of the PCBs samples leached for 2h and 3h in Example 12 and Example 1; among them, (a) backscattered photograph of the sample leached for 2h in Example 12; (b) elemental surface distribution map of the sample leached for 2h in Example 12; (c) backscattered photograph of the sample leached for 3h in Example 1; (d) elemental surface distribution map of the sample leached for 3h in Example 1.

[0026] Figure 5 1H nuclear magnetic resonance spectrum of 4-hydroxy-1-indanone synthesized in Example 14. Detailed Description of the Embodiments

[0027] To make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Here, it should also be noted that in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the solution of the present invention are shown in the drawings, while other details less relevant to the present invention are omitted.

[0029] In addition, it should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device.

[0030] The embodiment of the present application provides a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate, which includes the following steps: S1. Grind the electronic waste to obtain pulp; The mass concentration of the pulp is 5%-10%.

[0031] During the grinding process, grind the electronic waste until the part with a particle size less than 50 mesh in the material accounts for 90%-98% of the total mass of the ore powder.

[0032] S2. Add an amino acid-based leaching agent to the pulp, adjust the pH of the pulp to 12-14; stir to leach tin and zinc; During stirring, the temperature of the pulp is 30°C-35°C, and the stirring time is 1-6 h.

[0033] The stirring speed is 100-300 r / min.

[0034] Among them, the leaching agent is one or more of glycine, glutamic acid, and histidine.

[0035] The concentration of the leaching agent in the pulp is 0.1-1 mol / L.

[0036] S3. After completing the tin and zinc leaching process, filter and collect the leaching liquid; S4. Perform ultrasonic dissolution on the leaching liquid, let it stand, and then dry it. When the evaporation amount of the liquid in the leaching liquid reaches 60%-80% of the initial mass of the leaching liquid, stop evaporation; filter, collect the crystalline solid, rinse it, and dry it naturally to obtain micron-sized zinc metastannate.

[0037] The drying temperature is 40°C-60°C to slowly volatilize the water in the leaching liquid.

[0038] During rinsing, use a small amount of ethanol for rinsing.

[0039] The present invention also provides a method for synthesizing 4-hydroxy-1-indanone, using the micron-sized zinc metastannate prepared by the aforementioned method; the method comprises the following steps: A1. Put the micron-sized zinc metastannate into a methanesulfonic acid reagent, stir to obtain a mixed solution; Among them, the addition amount of the micron-sized zinc metastannate is 2.0-5.0 wt% of the mass of the methanesulfonic acid reagent.

[0040] A2. Put hydroxycinnamic acid into the mixed solution, stir until uniform, and then heat to 40°C-45°C and react for 3-4 h; Among them, the mass ratio of hydroxycinnamic acid to the mixed solution is 1:(10-40).

[0041] A3. After the reaction is completed, cool to room temperature; neutralize with saturated sodium bicarbonate solution, extract the organic phase with dichloromethane, dry with anhydrous magnesium sulfate, filter and concentrate the organic phase to finally obtain 4-hydroxy-1-indanone.

[0042] The following lists some specific examples. It should be noted that the examples described below are exemplary and are only used to explain the present application and cannot be construed as a limitation to the present application. For those where specific technologies or conditions are not indicated in the examples, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0043] Example 1 A method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate, comprising the following steps: S1. Crush the electronic waste (waste printed circuit board) to a particle size less than 50 mesh to obtain a material; then add water to the material and stir to obtain a pulp with a concentration of 5%; S2. Add glycine to the pulp to make the concentration of glycine 0.5 mol / L; then add sodium hydroxide to adjust the pH of the pulp to 14; thereafter, stir at 30°C for 3 h to leach tin and zinc; S3. After completing the tin and zinc leaching process, filter and collect the leaching liquid; measure the concentrations of tin and zinc by ICP-OES and calculate the leaching rates of tin and zinc.

[0044] S4. Ultrasonically dissolve the leaching liquid for 0.5 h, let it stand for 3 h, then place it in a constant temperature drying oven, set at 50°C, slowly evaporate the water in the solution. When the evaporation amount of the liquid reaches 60% of the initial mass of the leaching liquid, stop evaporation, filter, collect the crystalline solid, rinse with a small amount of ethanol, and dry naturally to obtain micron-sized zinc metastannate (ZnSnO3·nH2O).

[0045] Examples 2-4 and Comparative Examples 1-5 Examples 2-4 and Comparative Examples 1-5 provide a method for wet recovery of tin and zinc from electronic waste to prepare zinc metastannate at the micron scale. Compared with Example 1, the difference lies in that in step S2, the dosage of glycine is different, as shown in Table 1 specifically. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0046] Table 1 Dosage of glycine and experimental results in Examples 2-4 and Comparative Examples 1-5 As can be seen from Table 1, the dosage of glycine has a significant impact on the leaching of tin and zinc and the yield of zinc metastannate at the micron scale. When the glycine concentration is increased from 0.1 mol / L to 1 mol / L (Examples 1-4), the leaching rate of tin increases from 80% to 90%, the leaching rate of zinc remains at 93-94%, and the yield of the micron product increases from 57% to 66%, indicating that appropriately increasing the glycine concentration can synergistically promote metal leaching and product synthesis.

[0047] However, excessive glycine (>1 mol / L) has a negative impact: when the concentration reaches 3 mol / L (Comparative Example 5), although the tin leaching rate remains at 86%, the zinc leaching rate drops sharply from 94% to 84%, resulting in a sharp reduction in the product yield to 12%. In addition, the absence of glycine (Comparative Example 1) completely inhibits the leaching of tin and the formation of the product, proving its indispensability as a key complexing agent.

[0048] The experimental results show that the optimal dosage range of glycine is 0.1-1 mol / L. At this time, the zinc / tin leaching balance is optimal, the yield can reach more than 55%, and it also has good economic feasibility.

[0049] Figure 1 Figure for the scanning electron microscope test and energy spectrum analysis of the zinc metastannate at the micron scale prepared in Example 1. It can be seen that the product is in the shape of cubes with different sizes, and most of the particle sizes are in the range of 3-5 µm. According to the energy spectrum analysis, the main components of the precipitated metal product obtained are tin, zinc, oxygen, sodium, etc. Among them, the mass percentages are approximately 31.13% for tin, 21.15% for zinc, 36.64% for oxygen, 10.33% for sodium, and 0.75% for copper. Through the observation window (the scales are 20 µm and 8 µm respectively), it can be observed that the zinc metastannate at the micron scale has a complete crystal form, and a single crystal is in the shape of a cube, and the edge length of the cube is in the range of 3-5 µm.

[0050] Figure 2XRD pattern of the micron-sized zinc stannate prepared in Example 1. It can be seen from the pattern that the diffraction peaks shown can be respectively attributed to the diffraction peaks at 19.8°, 22.5°, 32.7°, 52.6° and 57.7°, corresponding to the (111), (200), (220), (420) and (422) crystal planes of ZnSn(OH)6 respectively. The characteristic peaks of ZnSn(OH)6 match well with the standard card, and the peak shape is relatively sharp, indicating that ZnSn(OH)6 has good crystallinity and high purity. While the characteristic peaks of ZnO are very weak and the peak shape is relatively wide, indicating that the crystallinity of ZnO is not high and the content is small, and its main source is the decomposition of ZnSn(OH)6 under vacuum drying conditions.

[0051] Examples 5 - 6 and Comparative Examples 6 - 8 Examples 5 - 6 and Comparative Examples 6 - 8 provide a method for the wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc stannate. Compared with Example 1, the difference lies in the different pulp concentrations, as shown in Table 2 specifically. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0052] Table 2 Pulp concentrations and experimental results of Examples 5 - 6 and Comparative Examples 6 - 8 As can be seen from Table 2, the pulp concentration has an obvious effect on the leaching rates of tin and zinc in electronic waste and the yield of micron-sized zinc stannate. When the pulp concentration increases from 5% to 10%, the leaching rates of tin and zinc gradually decrease from 85% and 93% to 80% and 86% respectively, and at the same time the product yield decreases from 60% to 50%. It shows that high pulp concentration inhibits the metal leaching efficiency and product synthesis.

[0053] When the concentration is further increased to 12% (Comparative Example 7) and 20% (Comparative Example 8), the leaching rate and yield deteriorate sharply (the tin leaching rate drops to 59% and the yield is only 14%), probably because the pulp viscosity is too high, resulting in hindered diffusion of reactants or insufficient solid-liquid contact.

[0054] It should be noted that when the pulp concentration is lower than 5% (4% in Comparative Example 6), all indicators are the same as those in Example 1 (5%), indicating that there is no obvious negative impact on the concentration change below this critical value. Through comprehensive analysis, the comprehensive performance is optimal when the pulp concentration is controlled in the range of 5% - 10%. Too high will lead to a significant decrease in yield, and too low is not conducive to economic efficiency.

[0055] Examples 7 - 8 Compared with Example 1, the difference lies in that in step S2, different leaching agents are used, and the others are roughly the same as those in Example 1 and will not be elaborated here.

[0056] Table 3 Types of leaching agents and experimental results of Examples 7-8 and Comparative Example 1 As can be seen from the above table: The type of stannous zinc leaching agent plays a key role in the leaching rate of tin and the synthesis of micron-sized zinc metastannate. When glycine, glutamic acid, or histidine is used as the leaching agent (Examples 1, 7, 8), the leaching rate of tin exceeds 82%, and more than 60% of the target product can be stably formed; while when no leaching agent is added (Comparative Example 1), the leaching rate of tin is 0, and the product cannot be formed either.

[0057] It should be noted that the leaching rate of zinc remains at a high level of more than 87% with or without the agent, indicating that the leaching process of zinc may mainly depend on other reaction conditions rather than the leaching agent. Different amino acid-based agents have similar effects on tin leaching (slightly lower for glutamic acid and slightly higher for histidine), suggesting that this type of agent may promote the dissolution of tin and product synthesis through a similar complexation mechanism.

[0058] In addition, Figure 3 Figure 12 is the XRD pattern of the sample prepared in Comparative Example 1. It can be seen that the diffraction peaks of the leached sample can be attributed to the diffraction card Zn5(OH)6(CO3)2 (PDF#72-1100) in the ICDD powder diffraction database. Among them, the diffraction peaks at 12.9°, 22.3°, 24.7°, 27.8°, 31.2°, 32.6°, 36.1°, and 60.7° correspond to the (200), (111), (310), (311), (220), (021), (221), and (223) crystal planes of Zn5(OH)6(CO3)2, respectively. The source of Zn5(OH)6(CO3)2 is mainly due to the deliquescence of Zn(OH)2 and its reaction with CO2. It can be proved that in the absence of amino acid-based leaching agents, the leaching process of zinc may mainly depend on other reaction conditions rather than the stannous zinc leaching agent.

[0059] Examples 9-10 and Comparative Examples 9-11 Examples 9-10 and Comparative Examples 9-11 provide a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate. Compared with Example 1, the difference is that the pH of the pulp is different, as shown in Table 4 specifically. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0060] Table 4 pH of the pulp and experimental results in Examples 9-10 and Comparative Examples 9-11 Based on the data comparison in Table 4, the following conclusions can be drawn: The pH of the pulp significantly affects metal leaching and product synthesis by regulating the dissociation state of glycine. When pH ≥ 12 (Examples 1, 9, 10), glycine is fully dissociated into the deprotonated form (Gly - ) under strong alkaline conditions (pKa ≈ 9.6), and its complexing ability is enhanced, keeping the tin leaching rate at 83% - 85% and stably forming zinc metastannate on the micron scale (yield ≥ 42%). As the pH decreases to 11 and below (Comparative Examples 9 - 11), the degree of dissociation of glycine drops sharply (close to the isoelectric point), losing the complexing ability for tin (the tin leaching rate drops to 0%), and at the same time, the zinc leaching rate and product yield also collapse due to the weakened complexing effect.

[0061] It is worth noting that the leaching rate of zinc is more sensitive to pH than that of tin (when pH = 14 → 10, the zinc leaching rate drops sharply from 93% to 31%). It is speculated that the dissolution of zinc is more dependent on the complexing drive provided by OH - , while tin may still have a certain reactivity under partial dissociation conditions.

[0062] Examples 11 - 13 and Comparative Examples 12 - 14 Examples 11 - 13 and Comparative Examples 12 - 14 provide a method for the wet recovery of tin and zinc from electronic waste to prepare zinc metastannate on the micron scale. Compared with Example 1, the difference lies in that in step S2, the stirring reaction time is different (i.e., the leaching time is different), as shown in Table 5 specifically. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0063] Table 5 Stirring reaction time and experimental results of Examples 11 - 13 and Comparative Examples 12 - 14 As can be seen from Table 5: The leaching time has a significant regulatory effect on the metal leaching efficiency and product yield. The surface morphologies of the PCB samples leached for 2 h / 3 h are as Figure 4 shown. When the reaction time is controlled within 2 - 6 h, the tin leaching rate (≥80%), zinc leaching rate (≥85%), and zinc metastannate yield (≥50%) all reach relatively good levels, indicating that the reaction requires sufficient time to complete the metal complexation and crystallization processes.

[0064] However, too long a time (Comparative Example 13, 24 hours) will cause a sharp drop in the tin and zinc leaching rates (tin leaching rate 61%, zinc leaching rate 42%), and the product completely disappears (yield 0%). It is speculated that side reactions in the alkaline environment (such as metal hydroxide precipitation or product decomposition) may dominate. In addition, insufficient leaching time (such as 0.5 hours, Comparative Example 14) can partially leach the metals (tin 72%, zinc 81%), but the product yield is only 41%, indicating that the synthesis reaction requires a certain kinetic time to complete the crystal nucleus growth and assembly.

[0065] It should be noted that the leaching rate of zinc is more sensitive to time (for example, the zinc leaching rate drops from 94% to 82% at 7 hours), probably because it is more susceptible to reverse reaction or oxidation.

[0066] As Figure 4 shown, it can be found that when leaching for 2 h / 3 h, the tin covering the surface of nickel and copper begins to dissolve, the layered wrapping of tin is opened, and at the same time other metals (such as copper, nickel, etc.) do not dissolve, proving that the amino acid-based reagent has selectivity for the leaching of tin.

[0067] Example 14 Application of micron-sized zinc metastannate in the synthesis of 4-hydroxy-1-indanone, the specific steps are as follows: A1. Weigh 5 g of methanesulfonic acid reagent, and then weigh 0.2 g of the micron-sized zinc metastannate prepared in Example 1, put it into methanesulfonic acid, and stir for 20 min to obtain a mixed solution.

[0068] A2. Let the mixed solution obtained in step A1 stand at room temperature for 30 min, put 0.52 g of 1-hydroxyphenylpropionic acid into the above solution to obtain a mixed solution, and stir until uniform. Then, slowly heat to 40 °C and react for 4 h.

[0069] A3. After the reaction is completed, cool to room temperature. Neutralize with saturated sodium bicarbonate solution, extract the organic phase with dichloromethane, and dry with anhydrous magnesium sulfate. Filter and concentrate the organic phase to finally obtain 4-hydroxy-1-indanone.

[0070] Comparative Example 15 Compared with Example 14, the difference is that in step A1, micron-sized zinc metastannate is not used, and the others are substantially the same as in Example 14, which will not be elaborated here.

[0071] Table 6 Influence of catalytic systems on the synthesis of 4-hydroxy-1-indanone As can be seen from the above table, in the reaction of synthesizing 4-hydroxy-1-indanone from 1-hydroxyphenylpropionic acid, the catalytic system has a significant influence on the product yield.

[0072] When the composite catalytic system of methanesulfonic acid and micron-sized zinc metastannate is used in Example 14, the yield reaches 70%, while the yield of Comparative Example 1 using only methanesulfonic acid is only 9%. This shows that there is a synergistic catalytic effect between micron-sized zinc metastannate and methanesulfonic acid. The possible mechanism is as follows: Methanesulfonic acid, as a protonic acid, catalyzes the dehydration of hydroxyphenylpropionic acid to generate an enoic acid intermediate, and then micron-sized zinc metastannate promotes the intramolecular Friedel-Crafts cyclization reaction through its solid acidic surface. The high specific surface area and abundant acidic sites of the micron material can effectively adsorb and activate the reactants, and at the same time stabilize the cyclization transition state and reduce the energy barrier. Zn in zinc metastannate2+ The carboxylic acid group may be fixed through coordination, promoting the electrophilic attack on the ortho benzene ring, thus efficiently constructing the indanone five-membered ring structure. This acid-base cooperative catalytic mechanism significantly improves the cyclization efficiency, inhibits side reactions, and greatly increases the yield.

[0073] Figure 5 1H NMR spectrum of 4-hydroxy-1-indanone synthesized in Example 14. It can be seen that: at 300 MHz, the deuterated reagent is DMSO, 9.50~1.00 (S, 1H) is an active hydrogen on the hydroxyl group, 7.30~7.50 (t, 1H), 7.00~7.20 (t, J Hz, 1H), and 6.80~6.99 (t, J 1H) are three hydrogens on the benzene ring respectively, and 2.70~3.00 (t, 2H) and 2.40~2.60 (t, 2H) are 4 Hs on the aliphatic five-membered ring respectively.

[0074] Examples 15 - 16 and Comparative Example 16 Examples 15 - 16 and Comparative Example 16 provide the application of micro-sized zinc metatitanate in the synthesis of 4-hydroxy-1-indanone. Compared with Example 14, the difference lies in that in step A1, the mass fraction of micro-sized zinc metatitanate added to the methanesulfonic acid reagent is different, as shown in Table 7 specifically. Other experimental parameters and conditions are basically the same as those in Example 14 and will not be elaborated here.

[0075] Table 7 Mass fraction of micro-sized zinc metatitanate in methanesulfonic acid reagent and experimental results in Examples 15 - 16 and Comparative Example 16 As can be seen from the above table, the mass fraction of micro-sized zinc metatitanate in the methanesulfonic acid reagent needs to reach at least 2% to effectively catalyze the reaction for synthesizing 4-hydroxy-1-indanone. When the dosage is 2%, the yield can reach 61%; when the dosage is optimized to 4% - 5%, significantly higher yields (70% - 72%) can be obtained, which are the most preferred implementation conditions. The extremely low yield (19%) of Comparative Example 16 (1%) proves that dosages below 2% cannot meet the requirements of effective catalysis.

[0076] Examples 17 - 18 and Comparative Examples 17 - 19 Examples 17 - 18 and Comparative Examples 17 - 19 provide the application of micro-sized zinc metatitanate in the synthesis of 4-hydroxy-1-indanone. Compared with Example 14, the difference lies in that in step A2, the mass ratio of 3-(4-hydroxyphenyl)propanoic acid to the methanesulfonic acid mixed solution of micro-sized zinc metatitanate is different, as shown in Table 8 specifically. Other experimental parameters and conditions are basically the same as those in Example 14 and will not be elaborated here.

[0077] Table 8 Influence of the mass ratio of 3-(4-hydroxyphenyl)propanoic acid to the methanesulfonic acid mixed solution of micro-sized zinc metatitanate on the synthesis of 4-hydroxy-1-indanone As can be seen from the data in Table 8, in the synthesis of 4-hydroxy-1-indanone, the mass ratio of the mixed solution of 1-hydroxyphenylpropionic acid and zinc metatungstate in the micron scale significantly affects the product yield.

[0078] When the ratio is increased from 1:5 (Comparative Example 19) to 1:40 (Example 18), the yield gradually increases from 51% to 81%; when the ratio of the micron material is further increased to 1:50 or 1:100 (Comparative Examples 17-18), the yield stabilizes at 81%, indicating the existence of a saturation effect in the catalytic system. This trend shows that the addition ratio of zinc metatungstate in the micron scale needs to reach a certain threshold (≥1:40) to fully exert its catalytic potential: its high specific surface area and acidic sites may improve the efficiency by adsorbing and activating reactants, promoting dehydration cyclization, and stabilizing the transition state; however, when added in excess, due to the saturation of the utilization rate of active sites or the limitation of dispersion uniformity, the catalytic efficiency no longer increases. In addition, the low yield of Comparative Example 19 (1:5) indicates that when the ratio of the micron material is insufficient, the catalytic active sites cannot fully cover the reactants, resulting in low activation efficiency of the intermediate.

[0079] In summary, the optimized ratio of the micron material needs to balance the density and dispersion of active sites, and 1:40 is the critical saturation point in the current system.

[0080] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate, characterized in that, It includes the following steps: S1. Grind the electronic waste to obtain pulp; S2. Add an amino acid leaching agent to the pulp, adjust the pH of the pulp to 12 - 14; stir to leach tin and zinc; S3. After completing the tin and zinc leaching process, filter and collect the leaching liquid; S4. Perform ultrasonic dissolution on the leaching liquid, let it stand, and then dry. When the liquid evaporation amount in the leaching liquid reaches 60% - 80% of the initial mass of the leaching liquid, stop evaporation; filter, collect the crystalline solid, wash, and naturally dry to obtain micron - sized zinc metastannate.

2. The method for wet recovery of tin and zinc from electronic waste to prepare zinc metastannate at the micron level according to claim 1, characterized in that, The leaching agent is one or more of glycine, glutamic acid, and histidine.

3. The method for wet recovery of zinc metastannate in micron scale from electronic waste according to claim 1, characterized in that, In step S2, the concentration of the leaching agent in the pulp is 0.1 - 1 mol / L.

4. The method for wet recovery of zinc metastannate at the micron level from electronic waste as claimed in claim 1, characterized in that, During the grinding process, grind the electronic waste until the part with a particle size less than 50 mesh in the material accounts for 90% - 98% of the total mass of the ore powder.

5. The method for wet recovery of zinc metastannate in micron scale from electronic waste according to claim 1, wherein In step S1, the mass concentration of the pulp is 5% - 10%.

6. The method for wet recovery of tin and zinc from electronic waste to prepare zinc metastannate on a micron scale according to claim 1, characterized in that, In step S2, the stirring time is 1 - 6 h.

7. The method for wet recovery of tin and zinc from electronic waste to prepare zinc metastannate on a micron scale according to claim 1, characterized in that, In step S2, during stirring, the temperature of the pulp is 30°C - 35°C.

8. A method for synthesizing 4-hydroxy-1-indanone, characterized in that, The micron - sized zinc metastannate obtained by the method according to any one of claims 1 - 7; it includes the following steps: A1. Put the micron - sized zinc metastannate into a methanesulfonic acid reagent, stir to obtain a mixed solution; A2. Put 4 - hydroxyphenylpropionic acid into the mixed solution, stir until uniform, then heat to 40°C - 45°C and react for 3 - 4 h; A3. After the reaction is completed, cool to room temperature; neutralize with saturated sodium bicarbonate solution, extract the organic phase with dichloromethane, dry with anhydrous magnesium sulfate, filter and concentrate the organic phase to finally obtain 4 - hydroxy - 1 - indanone.

9. The synthetic method of 4-hydroxy-1-indanone according to claim 8, wherein, In step A1, the addition amount of the micron - sized zinc metastannate is 2.0 - 5.0 wt% of the mass of the methanesulfonic acid reagent.

10. The synthesis method of 4-hydroxy-1-indanone according to claim 8, characterized in that, In step A2, the mass ratio of 4 - hydroxyphenylpropionic acid to the mixed solution is 1:(10 - 40).

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