Process for green recycling of metal materials

Abstract

This invention discloses a green recycling process for metal materials, belonging to the field of metal recycling technology. This invention targets mixed metal raw materials containing at least two non-ferrous metals, namely aluminum, magnesium, copper, tin, and lead. It employs a series of methods: liquid nitrogen low-temperature leaching followed by impact crushing to achieve interface dissociation; weak magnetic separation followed by gravity separation to complete gradient grouping; controlled-potential leaching of the light metal components using a sodium carbonate-hydrogen peroxide alkaline system; and stepwise selective leaching of copper, tin, and lead using a cyanide-free thiosulfate-sodium sulfite system with controlled-potential gradient. Finally, the target metals are recovered from each stage of the leaching solution, and the entire tailings are recycled. This invention uses no highly toxic reagents, achieves zero tailings discharge, and boasts high metal leaching, recovery, and product purity, while maintaining low energy and reagent consumption. It is suitable for large-scale green recycling of mixed non-ferrous metal waste.

Description

Technical Field

[0001] This invention relates to the field of metal recycling technology, and in particular to a green recycling process for metal materials. Background Technology

[0002] With the rapid development of the electronic information industry and the non-ferrous metal processing industry, the amount of mixed waste metal containing two or more non-ferrous metals such as aluminum, magnesium, copper, tin and lead has continued to increase. This type of waste has both high recycling value for non-ferrous metal resources and environmental pollution risks, and its efficient and green recycling has become a key research direction for the non-ferrous metal recycling industry.

[0003] Existing technologies for recycling mixed non-ferrous metal waste are mainly divided into two categories: pyrometallurgical smelting and hydrometallurgical processes. Conventional pyrometallurgical processes suffer from drawbacks such as high overall energy consumption, large carbon emissions, and the generation of toxic fumes and hazardous waste. Furthermore, the light metal components are prone to oxidation and volatilization, resulting in significant losses in metal recovery rates. Among existing hydrometallurgical processes, the mainstream cyanide leaching system poses a highly toxic environmental risk, and compliance management and environmental disposal costs are extremely high. Non-cyanide leaching systems generally suffer from poor selective separation between metals, insufficient pretreatment dissociation efficiency leading to low leaching recovery rates, lengthy process flows, high reagent consumption, and the inability to stably recycle and reuse leaching tail liquid. These issues make it difficult to simultaneously achieve metal recovery efficiency, product purity, and environmental safety performance, thus hindering the large-scale and green industrial application of this type of waste recycling. Summary of the Invention

[0004] In view of this, the present invention aims to provide a green recycling process for metal materials to solve or alleviate the technical problems existing in the prior art.

[0005] The technical solution of this invention is implemented as follows: a green recycling process for metal materials, comprising the following steps: S1. Pretreatment interface dissociation: The waste mixed metal raw material containing at least two non-ferrous metals such as aluminum, magnesium, copper, tin and lead is immersed in liquid nitrogen environment for 3 to 8 minutes, and then immediately subjected to impact crushing to obtain crushed material with interface dissociation between different metals and non-metals. S2. Gradient grouping and sorting: The crushed material is first subjected to weak magnetic separation to remove ferromagnetic impurities, and then subjected to gravity sorting to a density threshold of 2.7 g / cm³. 3 Light metal components, heavy non-ferrous metal components, and non-metallic waste residue were separated. S3. Segmented Potential-Controlled Selective Leaching: First, the light metal components are subjected to a first-stage potential-controlled leaching using a sodium carbonate-hydrogen peroxide alkaline system, with the controlled potential at -0.8V to -0.6V (vs. SCE). Solid-liquid separation yields a leachate and leaching residue containing aluminum and magnesium. Then, this leaching residue is combined with the heavy non-ferrous metal components, and a second-stage gradient potential-controlled leaching is performed using a thiosulfate-sodium sulfite cyanide-free system. The first step involves selectively leaching copper at a controlled potential of 0.1V~0.3V (vs. SCE) to obtain a copper-containing leachate and copper leaching residue. The second step involves adjusting the pH to 11-12, adding sodium thiosulfate to 180-220 g / L, and selectively leaching tin-lead at a potential of -0.6V to -0.3V (vs. SCE) to obtain a tin-lead leaching solution and a final leaching residue. S4. Metal recovery and reagent recycling: The target metal product is recovered by induced precipitation or in-situ reduction method in each leachate stage. The tail liquid after metal recovery is recycled to the corresponding leaching step for reuse.

[0006] As an improvement, in step S1, the impact crushing adopts a vertical impact crusher with an impact linear velocity of 50~70m / s, a single crushing time of 10~20s, and a crushing number of times of 1~2 times; the particle size of the material after impact crushing is controlled to have a -2mm particle size ratio of ≥95%, of which the degree of dissociation between metal and non-metal is ≥98%.

[0007] As an improvement, in step S2, the magnetic field strength of the weak magnetic separation is 80~120kA / m, the separation medium is clean water, and the slurry concentration is 25%~35%; the gravity separation uses a side-mounted diaphragm jig, the separation medium is clean water, the stroke is 8~15mm, the stroke rate is 200~300 times / min, the feed concentration is 25%~35%, the artificial bed uses quartz sand with a particle size of 2~3mm, the bed thickness is 30~50mm, the separation time is 5~10min, and the density threshold is 2.7g / cm³. 3 Light metal components, heavy non-ferrous metal components, and non-metallic waste residue were separated.

[0008] As an improvement, in step S3, in the first stage of the controlled potential leaching system, the sodium carbonate concentration is 80~120g / L, the hydrogen peroxide volume fraction is 2%~5%, the liquid-solid ratio is (5~10):1, the leaching temperature is 40~60℃, the leaching time is 60~120min, and the leaching rate of aluminum and magnesium is ≥99%.

[0009] As an improvement, in step S3, the first step of the second stage of gradient-controlled potential leaching is selective copper leaching, with a sodium thiosulfate concentration of 100~150g / L, a sodium sulfite concentration of 30~50g / L, a system pH of 9~10, a liquid-to-solid ratio of (8~12):1, a leaching temperature of 30~50℃, a leaching time of 90~150min, and a copper leaching rate of ≥98%.

[0010] As an improvement, in step S3, the second step of the second stage of gradient-controlled potential leaching is tin-lead selective leaching. After copper selective leaching, solid-liquid separation is obtained to obtain copper leaching residue. The pH of the system is adjusted to 11~12, sodium thiosulfate is added to a concentration of 180~220g / L, the leaching temperature is 50~70℃, the leaching time is 120~180min, and the tin and lead leaching rates are ≥97%.

[0011] As an improvement, in step S4, the aluminum and magnesium-containing leachate is treated with a seed-induced precipitation method to recover the metal: the corresponding target metal hydroxide seed crystals are added to the leachate, the amount of seed crystals added is 1% to 3% of the theoretical precipitation mass of the target metal, the pH of the system is adjusted to 10 to 11 under stirring, the reaction is carried out at room temperature for 30 to 60 minutes, and the solid and liquid are separated to obtain a high-purity hydroxide product. The mother liquor after separation is recycled to the first leaching step for reuse.

[0012] As an improvement, in step S4, the copper-containing leaching solution is treated with in-situ reduction-magnetic separation using zero-valent iron nanoparticles to recover the metal: zero-valent iron nanoparticles with a particle size of 50~200nm are added to the leaching solution, the amount of which is 1.05~1.2 times the theoretical reaction amount of copper ions. The solution is stirred at room temperature for 20~40 minutes, and ultrafine copper powder is obtained by weak magnetic separation. All the tail liquid after separation is recycled to the second copper selective leaching step for reuse.

[0013] As an improvement, in step S4, the tin-lead leaching solution is treated with in-situ sulfur dioxide reduction to recover the metal: sulfur dioxide gas is introduced into the leaching solution, the system potential is controlled at -0.8V to -0.6V (vs. SCE), the reaction is carried out at room temperature for 40 to 60 minutes, solid-liquid separation is performed to obtain tin-lead alloy powder, and the tail liquid after separation is recycled to the second stage of selective tin-lead leaching for reuse.

[0014] As an improvement, the non-metallic waste residue obtained in step S2 is mixed with the final impregnation residue obtained in step S3, and then subjected to cement-based solidification and stabilization treatment for reuse as aggregate in construction engineering.

[0015] Compared with the prior art, the embodiments of the present invention have the following advantages: Highly efficient monomer dissociation between metals and non-metals, and between different non-ferrous metals, is achieved through low-temperature interface dissociation pretreatment, solving the problem of metal recovery loss caused by insufficient dissociation in existing processes; A process combining gradient grouping and segmented potential-controlled selective leaching is adopted to achieve multi-metal stepwise selective separation in a cyanide-free system, avoiding the highly toxic environmental risks of cyanide systems and significantly reducing reagent consumption and overall energy consumption; Zero wastewater discharge is achieved through full recycling of leaching tail liquid, improving metal recovery efficiency and product purity while also considering the environmental safety and economic feasibility of the process. Detailed Implementation

[0016] The invention will be more readily understood by referring to the following detailed description of preferred embodiments and included examples. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail.

[0017] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0018] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for conventional impurities associated with them. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0019] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0020] The singular form includes the plural objects of discussion unless the context clearly indicates otherwise. "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.

[0021] Approximate terms used in the specification and claims to modify quantities indicate that the invention is not limited to that specific quantity, but also includes acceptable modifications close to that quantity that do not alter the relevant essential function. Correspondingly, the use of "about," "approximately," etc., to modify a numerical value means that the invention is not limited to that precise value. In some instances, approximate terms may correspond to the precision of the instrument used to measure the value. In this application's specification and claims, scope definitions can be combined and / or interchanged, unless otherwise stated, these scopes include all subscopes contained therein.

[0022] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this invention do not impose any limitation on the quantity (i.e., number of times) of the elements or components. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

[0023] Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0024] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; unless otherwise specified, the experimental materials used in the following embodiments are all purchased from commercial channels.

[0025] Note: All potential controls in this invention use a saturated calomel electrode (SCE) at 25°C as the reference electrode, and employ a potentiostat in conjunction with an online potential monitoring system to achieve precise potential control.

[0026] Example 1:

[0027] A green recycling process for metal materials includes the following steps: S1. Pretreatment interface dissociation: The waste mixed metal raw material containing at least two non-ferrous metals such as aluminum, magnesium, copper, tin and lead is immersed in liquid nitrogen environment for 3 minutes, and then immediately subjected to impact crushing to obtain crushed material with interface dissociation between different metals and non-metals. The impact crushing process uses a vertical impact crusher with an impact linear velocity of 50 m / s, a single crushing time of 10 s, and a crushing frequency of 1 time. The particle size of the material after impact crushing is controlled to have a -2 mm particle size ratio of ≥95%, and the degree of dissociation between metal and non-metal is ≥98%.

[0028] S2. Gradient grouping and sorting: The crushed material is first subjected to weak magnetic separation to remove ferromagnetic impurities, and then subjected to gravity sorting to a density threshold of 2.7 g / cm³. 3 Light metal components, heavy non-ferrous metal components, and non-metallic waste residue were separated. The weak magnetic separation uses a magnetic field strength of 80 kA / m, with water as the separation medium and a slurry concentration of 25%. Gravity separation employs a side-mounted diaphragm jig, using water as the separation medium, with a stroke of 8 mm, a stroke rate of 200 strokes / min, a feed concentration of 25%, and an artificial bed of 2 mm diameter quartz sand with a bed thickness of 30 mm. The separation time is 5 minutes, with a density threshold of 2.7 g / cm³. 3 Light metal components, heavy non-ferrous metal components, and non-metallic waste residue were separated.

[0029] S3. Segmented potential-controlled selective leaching: First, the light metal components are subjected to the first stage of potential-controlled leaching using a sodium carbonate-hydrogen peroxide alkaline system, with the controlled potential at -0.8V (vs. SCE). Solid-liquid separation yields a leaching solution and leaching residue containing aluminum and magnesium. In the first stage of the controlled potential leaching system, the sodium carbonate concentration was 80 g / L, the hydrogen peroxide volume fraction was 2%, the liquid-to-solid ratio was 5:1, the leaching temperature was 40℃, the leaching time was 60 min, and the leaching rate of aluminum and magnesium was ≥99%.

[0030] Then, the leaching residue is combined with the heavy non-ferrous metal components, and a second stage of gradient potential-controlled leaching is carried out using a thiosulfate-sodium sulfite cyanide-free system: The first step involves selectively leaching copper at a controlled potential of 0.1V (vs. SCE) to obtain a copper-containing leachate and copper leaching residue. Specifically, in the first step of the second stage of gradient potential controlled leaching, the sodium thiosulfate concentration is 100g / L, the sodium sulfite concentration is 30g / L, the system pH is 9, the liquid-to-solid ratio is 8:1, the leaching temperature is 30℃, the leaching time is 90min, and the copper leaching rate is ≥98%.

[0031] The second step involves adjusting the pH to 11, adding sodium thiosulfate to 180 g / L, and selectively leaching tin and lead at a controlled potential of -0.6 V (vs. SCE) to obtain a tin-lead leaching solution and a final leaching residue. Specifically, the second step of the second-stage gradient potential leaching is tin-lead selective leaching. After copper selective leaching, solid-liquid separation is obtained to obtain copper leaching residue. The pH of the system is adjusted to 11, sodium thiosulfate is added to a concentration of 180 g / L, the leaching temperature is 50℃, the leaching time is 120 min, and the tin and lead leaching rates are ≥97%.

[0032] S4. Metal recovery and reagent recycling: The target metal product is recovered by induced precipitation or in-situ reduction method in each leachate stage. The tail liquid after metal recovery is recycled to the corresponding leaching step for reuse.

[0033] Specifically, the leaching solution containing aluminum and magnesium is treated with a seed-induced precipitation method to recover the metal: Hydroxide seed crystals of the corresponding target metal are added to the leaching solution, with the amount of seed crystals added being 1% of the theoretical precipitate mass of the target metal. The pH of the system is adjusted to 10 under stirring conditions, and the reaction is carried out at room temperature for 30 minutes. Solid-liquid separation is performed to obtain a high-purity hydroxide product, and the mother liquor after separation is recycled to the first leaching step for reuse.

[0034] The copper-containing leaching solution is recycled by in-situ reduction-magnetic separation of zero-valent iron nanoparticles: zero-valent iron nanoparticles with a particle size of 50 nm are added to the leaching solution, the amount of which is 1.05 times the theoretical reaction amount of copper ions. The solution is stirred at room temperature for 20 min, and then separated by weak magnetic separation to obtain ultrafine copper powder. All the tail liquid after separation is recycled to the second stage of copper selective leaching for reuse.

[0035] The tin-lead leaching solution is recycled using the in-situ reduction method with sulfur dioxide: sulfur dioxide gas is introduced into the leaching solution, the system potential is controlled at -0.8V (vs. SCE), the reaction is carried out at room temperature for 40 minutes, and tin-lead alloy powder is obtained by solid-liquid separation. All the tail liquid after separation is recycled to the second stage of tin-lead selective leaching for reuse.

[0036] In practice, the non-metallic waste residue obtained in step S2 is mixed with the final impregnation residue obtained in step S3, and then subjected to cement-based solidification and stabilization treatment before being reused as aggregate for construction projects.

[0037] Example 2:

[0038] A green recycling process for metal materials includes the following steps: S1. Pretreatment interface dissociation: The waste mixed metal raw material containing at least two non-ferrous metals such as aluminum, magnesium, copper, tin and lead is immersed in liquid nitrogen environment for 6 minutes, and then immediately subjected to impact crushing to obtain crushed material with interface dissociation between different metals and non-metals. The impact crushing process uses a vertical impact crusher with an impact linear velocity of 60 m / s, a single crushing time of 15 s, and a crushing frequency of 1 time. The particle size of the material after impact crushing is controlled to have a -2 mm particle size ratio of ≥95%, and the degree of dissociation between metal and non-metal is ≥98%.

[0039] S2. Gradient grouping and sorting: The crushed material is first subjected to weak magnetic separation to remove ferromagnetic impurities, and then subjected to gravity sorting to a density threshold of 2.7 g / cm³. 3 Light metal components, heavy non-ferrous metal components, and non-metallic waste residue were separated. The weak magnetic separation uses a magnetic field strength of 100 kA / m, with water as the separation medium and a slurry concentration of 30%. Gravity separation employs a side-mounted diaphragm jig, using water as the separation medium, with a stroke of 12 mm, a stroke rate of 250 strokes / min, a feed concentration of 30%, and an artificial bed of 2.5 mm diameter quartz sand with a bed thickness of 40 mm. The separation time is 7 minutes, with a density threshold of 2.7 g / cm³. 3 Light metal components, heavy non-ferrous metal components, and non-metallic waste residue were separated.

[0040] S3. Segmented potential-controlled selective leaching: First, the light metal components are subjected to the first stage of potential-controlled leaching using a sodium carbonate-hydrogen peroxide alkaline system, with the controlled potential at -0.7V (vs. SCE). Solid-liquid separation yields a leaching solution and leaching residue containing aluminum and magnesium. In the first stage of the controlled potential leaching system, the sodium carbonate concentration was 100 g / L, the hydrogen peroxide volume fraction was 3.5%, the liquid-to-solid ratio was 7:1, the leaching temperature was 50℃, the leaching time was 90 min, and the leaching rate of aluminum and magnesium was ≥99%.

[0041] Then, the leaching residue is combined with the heavy non-ferrous metal components, and a second stage of gradient potential-controlled leaching is carried out using a thiosulfate-sodium sulfite cyanide-free system: The first step involves selectively leaching copper at a controlled potential of 0.2V (vs. SCE) to obtain a copper-containing leachate and copper leaching residue. Specifically, in the first step of the second stage of gradient potential controlled leaching, the sodium thiosulfate concentration is 125g / L, the sodium sulfite concentration is 40g / L, the system pH is 9.5, the liquid-to-solid ratio is 10:1, the leaching temperature is 40℃, the leaching time is 120min, and the copper leaching rate is ≥98%.

[0042] The second step involves adjusting the pH to 11.5, adding sodium thiosulfate to 200 g / L, and selectively leaching tin and lead at a controlled potential of -0.5 V (vs. SCE) to obtain a tin-lead leaching solution and a final leaching residue. Specifically, the second step of the second-stage gradient potential leaching is tin-lead selective leaching. After copper selective leaching, solid-liquid separation is obtained to obtain copper leaching residue. The pH of the system is adjusted to 11.5, sodium thiosulfate is added to a concentration of 200 g / L, the leaching temperature is 60℃, the leaching time is 150 min, and the tin and lead leaching rates are ≥97%.

[0043] S4. Metal recovery and reagent recycling: The target metal product is recovered by induced precipitation or in-situ reduction method in each leachate stage. The tail liquid after metal recovery is recycled to the corresponding leaching step for reuse.

[0044] Specifically, the aluminum and magnesium-containing leachate is recovered using a seed-induced precipitation method: Hydroxide seed crystals of the corresponding target metal are added to the leachate, with the amount of seed crystals added being 1% to 3% of the theoretical precipitate mass of the target metal. The pH of the system is adjusted to 10.5 under stirring conditions, and the reaction is carried out at room temperature for 45 minutes. Solid-liquid separation yields a high-purity hydroxide product, and the mother liquor after separation is recycled to the first leaching step for reuse.

[0045] The copper-containing leaching solution is recycled by in-situ reduction-magnetic separation of zero-valent iron nanoparticles: zero-valent iron nanoparticles with a particle size of 120 nm are added to the leaching solution, the amount of which is 1.1 times the theoretical reaction amount of copper ions. The solution is stirred at room temperature for 30 min, and ultrafine copper powder is obtained by weak magnetic separation. All the tail liquid after separation is recycled to the second copper selective leaching step for reuse.

[0046] The tin-lead leaching solution is recycled using the in-situ reduction method with sulfur dioxide: sulfur dioxide gas is introduced into the leaching solution, the system potential is controlled at -0.7V (vs. SCE), the reaction is carried out at room temperature for 50 minutes, solid-liquid separation is performed to obtain tin-lead alloy powder, and the tail liquid after separation is recycled to the second stage of tin-lead selective leaching for reuse.

[0047] In practice, the non-metallic waste residue obtained in step S2 is mixed with the final impregnation residue obtained in step S3, and then subjected to cement-based solidification and stabilization treatment before being reused as aggregate for construction projects.

[0048] Example 3:

[0049] A green recycling process for metal materials includes the following steps: S1. Pretreatment interface dissociation: The waste mixed metal raw material containing at least two non-ferrous metals such as aluminum, magnesium, copper, tin and lead is immersed in liquid nitrogen environment for 8 minutes, and then immediately subjected to impact crushing to obtain crushed material with interface dissociation between different metals and non-metals. The impact crushing process uses a vertical impact crusher with an impact linear velocity of 70 m / s, a single crushing time of 20 s, and a crushing frequency of 2 times. The particle size of the material after impact crushing is controlled to have a -2 mm particle size ratio of ≥95%, and the degree of dissociation between metal and non-metal is ≥98%.

[0050] S2. Gradient grouping and sorting: The crushed material is first subjected to weak magnetic separation to remove ferromagnetic impurities, and then subjected to gravity sorting to a density threshold of 2.7 g / cm³. 3 Light metal components, heavy non-ferrous metal components, and non-metallic waste residue were separated. The weak magnetic separation uses a magnetic field strength of 120 kA / m, with water as the separation medium and a slurry concentration of 35%. Gravity separation employs a side-mounted diaphragm jig, using water as the separation medium, with a stroke of 15 mm, a stroke rate of 300 strokes / min, a feed concentration of 35%, and an artificial bed of 3 mm diameter quartz sand with a bed thickness of 50 mm. The separation time is 10 min, with a density threshold of 2.7 g / cm³. 3 Light metal components, heavy non-ferrous metal components, and non-metallic waste residue were separated.

[0051] S3. Segmented potential-controlled selective leaching: First, the light metal components are subjected to the first stage of potential-controlled leaching using a sodium carbonate-hydrogen peroxide alkaline system, with the controlled potential at -0.6V (vs. SCE). Solid-liquid separation yields a leaching solution and leaching residue containing aluminum and magnesium. In the first stage of the controlled potential leaching system, the sodium carbonate concentration was 120 g / L, the hydrogen peroxide volume fraction was 5%, the liquid-to-solid ratio was 10:1, the leaching temperature was 60℃, the leaching time was 120 min, and the leaching rate of aluminum and magnesium was ≥99%.

[0052] Then, the leaching residue is combined with the heavy non-ferrous metal components, and a second stage of gradient potential-controlled leaching is carried out using a thiosulfate-sodium sulfite cyanide-free system: The first step involves selectively leaching copper at a controlled potential of 0.3V (vs. SCE) to obtain a copper-containing leachate and copper leaching residue. Specifically, in the first step of the second stage of gradient potential controlled leaching, the sodium thiosulfate concentration is 150g / L, the sodium sulfite concentration is 50g / L, the system pH is 10, the liquid-to-solid ratio is 12:1, the leaching temperature is 50℃, the leaching time is 150min, and the copper leaching rate is ≥98%.

[0053] The second step involves adjusting the pH to 12, adding sodium thiosulfate to 220 g / L, and selectively leaching tin and lead at a controlled potential of -0.3 V (vs. SCE) to obtain a tin-lead leaching solution and a final leaching residue. Specifically, the second step of the second-stage gradient potential leaching is tin-lead selective leaching. After copper selective leaching, solid-liquid separation is obtained to obtain copper leaching residue. The pH of the system is adjusted to 12, sodium thiosulfate is added to a concentration of 220 g / L, the leaching temperature is 70℃, the leaching time is 180 min, and the tin and lead leaching rates are ≥97%.

[0054] S4. Metal recovery and reagent recycling: The target metal product is recovered by induced precipitation or in-situ reduction method in each leachate stage. The tail liquid after metal recovery is recycled to the corresponding leaching step for reuse.

[0055] Specifically, the leaching solution containing aluminum and magnesium is treated with a seed-induced precipitation method to recover the metal: Hydroxide seed crystals of the corresponding target metal are added to the leaching solution, with the amount of seed crystals added being 3% of the theoretical precipitate mass of the target metal. The pH of the system is adjusted to 11 under stirring conditions, and the reaction is carried out at room temperature for 60 minutes. Solid-liquid separation is performed to obtain a high-purity hydroxide product, and the mother liquor after separation is recycled to the first leaching step for reuse.

[0056] The copper-containing leaching solution is recycled by in-situ reduction-magnetic separation of zero-valent iron nanoparticles: zero-valent iron nanoparticles with a particle size of 200 nm are added to the leaching solution, the amount of which is 1.2 times the theoretical reaction amount of copper ions. The solution is stirred at room temperature for 40 min, and ultrafine copper powder is obtained by weak magnetic separation. The tail liquid after separation is recycled to the second copper selective leaching step for reuse.

[0057] The tin-lead leaching solution is used to recover metals by in-situ reduction with sulfur dioxide: sulfur dioxide gas is introduced into the leaching solution, the system potential is controlled at -0.6V (vs. SCE), the reaction is carried out at room temperature for 60 minutes, solid-liquid separation is performed to obtain tin-lead alloy powder, and the tail liquid after separation is recycled to the second stage of selective tin-lead leaching for reuse.

[0058] In practice, the non-metallic waste residue obtained in step S2 is mixed with the final impregnation residue obtained in step S3, and then subjected to cement-based solidification and stabilization treatment before being reused as aggregate for construction projects.

[0059] Experimental example: 1. Experimental objective: 1.1 Verify the stability and reliability of the core parameters of the "liquid nitrogen cryogenic interface dissociation-gradient grouping and sorting-segmented potential-controlled selective leaching-tail liquid full circulation" process of this invention; 1.2 Through single-variable control experiments, the technical advantages of each core process step of the present invention compared with conventional processes are quantified; 1.3 Verify the metal recovery efficiency, product purity, environmental performance, and economic feasibility of the process of this invention, and provide complete and repeatable experimental data support for industrial application.

[0060] 2. Test materials and characterization test materials were taken from mixed non-ferrous metal crushed materials in a domestic electronic dismantling industrial park. Large non-metallic impurities were first removed by manual sorting, and the materials were pre-crushed to -5mm by a jaw crusher, mixed evenly in a three-dimensional mixer for 2 hours, and then reduced to 1000.0g per part (accuracy ±0.1g) by quartering method and sealed for later use.

[0061] The results of multi-element analysis of the raw materials (XRF fluorescence spectroscopy, average of three parallel analyses) are as follows: 3. Test reagents and equipment: 3.1 Test Reagents All reagents were of analytical grade (AR), including: sodium carbonate, 30% hydrogen peroxide, sodium thiosulfate, sodium sulfite, sodium hydroxide, sodium cyanide (controlled highly toxic reagent), 50 / 120 / 200nm zero-valent iron nanoparticles, aluminum hydroxide / magnesium seed crystals, sulfur dioxide cylinder gas, high-purity nitrogen, hydrochloric acid, nitric acid, etc.

[0062] 3.2 Core Instruments and Equipment 4. Experimental Design: 1. Experimental Groups: A total of 10 groups were set up, including 7 comparative groups (single variable control) and 3 groups of invention examples. Except for the core differences, the operation, environment and detection methods were completely identical to ensure the comparability of the results.

[0063] 2. Parallel tests: Three independent parallel tests were set up for each group, with a single feed amount of 1000.0g and all operating parameters were fixed.

[0064] 3. Data validity: Data with a relative standard deviation (RSD) of ≤2% for the core indicators (leaching rate, recovery rate, purity) is considered valid. If the data exceeds this range, the experiment should be repeated.

[0065] 4. Environmental control: All experiments were conducted in a constant temperature and humidity laboratory with an ambient temperature of 25±1℃ and a relative humidity of 45%-55% to avoid environmental interference.

[0066] 5. General standardized calculation formula: 1. Metal leaching rate: In the formula: The target metal concentration in the leachate ( ); To determine the volume of the leachate ( ); For the quality of feeding ( ); The mass fraction (%) of the target metal in the raw material.

[0067] 2. Selectivity coefficient: 3. Total metal recovery rate: 4. Overall Energy Consumption: The energy consumption per ton of raw material is calculated based on the cumulative electrical energy consumption of a single batch of tests. ).

[0068] 6. Detailed experimental operation procedures: 6.1 Detailed Operating Procedures for Comparative Analysis (Single Variable Comparison): Comparative Example 1: Control Group of Conventional Mechanical Crushing Pretreatment Single variable: Liquid nitrogen cryogenic interface dissociation was cancelled, and conventional two-stage mechanical crushing was adopted. All other equipment, operating parameters, and environmental conditions were completely consistent with those in Example 2 to ensure the effectiveness of the single variable control.

[0069] 1. Pre-treatment: 1000.0g of raw material is subjected to two-stage mechanical crushing: jaw crusher for coarse crushing and cone crusher for fine crushing. The discharge port width of the jaw crusher is 5mm and the discharge port width of the cone crusher is 2mm. The crushing process is repeated twice. The proportion of -2mm particles in the crushed material is controlled to be ≥95%. The particle size and degree of dissociation of monomers are tested.

[0070] 2. Gradient Separation: The material is slurry adjusted to a concentration of 30%, and then subjected to 100kA / m weak magnetic separation to remove iron. The separation medium is clean water, and the slurry concentration is 30%. It is then fed into a side-mounted diaphragm jig at a concentration of 2.7g / cm³. 3 To separate light / heavy non-ferrous metal components from non-metallic waste using density thresholds, the jigging parameters were: stroke 12mm, stroke rate 250 times / min, feed concentration 30%, artificial bed made of quartz sand with a particle size of 2.5mm, bed thickness 40mm, and separation time 7min.

[0071] 3. Segmented leaching, metal recovery, reagent circulation, and solid waste treatment: All equipment, parameters, and operations are completely consistent with those in Example 2, and indicators such as leaching rate, product purity, and recovery rate are detected simultaneously.

[0072] Comparative Example 2: Control Group without Gradient Grouping Single variable: The gravity separation gradient grouping was cancelled, and all magnetic separation tailings were directly entered into the leaching process. All other parameters were completely consistent with those in Example 2.

[0073] 1. Pretreatment: exactly the same as in Example 2, using liquid nitrogen cryogenic impact crushing.

[0074] 2. Impurity removal: Iron is removed only by 100kA / m weak magnetic separation, without gravity separation, and all tailings directly enter the leaching process.

[0075] 3. Leaching, recovery, and data statistics: The remaining operations and parameters are completely consistent with those in Example 2.

[0076] Comparative Example 3: Control Group of Conventional Sodium Hydroxide Leaching System Single variable: Replace the first aluminum-magnesium leaching system with a sodium hydroxide system, cancel the potential control, and keep all other parameters completely consistent with Example 2.

[0077] 1. Pre-processing and sorting: completely consistent with Example 2.

[0078] 2. First stage leaching: The light metal components were leached using a sodium hydroxide system with the following parameters: sodium hydroxide concentration 100 g / L, liquid-to-solid ratio 7:1, leaching at 50°C for 90 min, without potential control. The remaining operations were the same as in Example 2.

[0079] 3. Subsequent procedures: completely consistent with Example 2.

[0080] Comparative Example 4: Control Group of Sodium Cyanide Leaching System Single variable: The second stage of cyanide-free gradient leaching was replaced with one-step sodium cyanide leaching, and all other parameters were completely consistent with those in Example 2.

[0081] 1. Pretreatment, sorting, and first-stage aluminum-magnesium leaching: completely consistent with Example 2.

[0082] 2. Second stage leaching: The leaching residue and heavy non-ferrous metal components are combined and leached in one step using a sodium cyanide system. Parameters: sodium cyanide concentration 10 g / L, pH=10.5, liquid-solid ratio 10:1, leaching at 40℃ for 120 min, without potential gradient control.

[0083] 3. Metal recovery: Aluminum and magnesium recovery is the same as in Example 2. The mixed leachate is replaced stepwise with zinc powder to obtain metal products, and the tail liquid is discharged after cyanide removal.

[0084] Comparative Example 5: Cyanide-free one-step leaching control group Single variable: The second gradient control potential was removed, and a cyanide-free system was used for one-step leaching. All other parameters were completely consistent with those in Example 2.

[0085] 1. Pretreatment, sorting, and first-stage leaching: completely consistent with Example 2.

[0086] 2. Second stage leaching: The combined materials were leached in one step using a sodium thiosulfate-sodium sulfite system with the following parameters: sodium thiosulfate 200 g / L, sodium sulfite 40 g / L, pH=11.5, leaching at 60℃ for 150 min, without potential gradient control.

[0087] 3. Subsequent steps: The metal is separated by stepwise precipitation of the mixed leachate, and the remaining operations are the same as in Example 2.

[0088] Comparative Example 6: Drug-free cyclic control group Single variable: The full recycling of tail liquid was cancelled, and all tail liquid after metal recovery was directly discharged. All other parameters were completely consistent with those in Example 2.

[0089] 1. Process parameters throughout the entire process: completely consistent with Example 2.

[0090] 2. Tailings treatment: After the metal is recovered from each leachate, the tailings are all discharged directly without recycling. The tailings discharge volume and total reagent consumption are recorded.

[0091] Comparative Example 7: Conventional Pyrometallurgical Smelting - Electrolytic Refining Control Group Industry standard process comparison: 1. Pretreatment: 1000.0g of raw material is crushed to -5mm and mixed evenly.

[0092] 2. Pyrometallurgical smelting: The mixture is placed in a graphite crucible and smelted at 1200℃ for 4 hours. Slag is then removed to obtain a mixed crude alloy.

[0093] 3. Electrolytic refining: After the crude alloy is cast into an anode mold, it is electrolyzed in stages to obtain electrolytic aluminum, electrolytic copper, and tin-lead alloy. The tail liquid is neutralized and then discharged.

[0094] 4. Data statistics: Simultaneously monitor product purity, recovery rate, energy consumption, and the amount of waste generated.

[0095] 6.2 Detailed operation steps of the embodiment: Example 1:

[0096] 1. Pretreatment interface dissociation: 1000.0g of raw material is placed in a liquid nitrogen environment and sealed for 3min. After being taken out, it is immediately sent to a vertical impact crusher for impact crushing. The impact linear velocity is 50m / s, the single crushing time is 15s, and the crushing is performed once. The proportion of -2mm particles in the crushed material is controlled to be ≥95%. The particle size and the degree of dissociation of monomers are tested.

[0097] 2. Gradient grouping and sorting: After crushing, the material is slurry adjusted to a concentration of 30%, and then subjected to 80kA / m weak magnetic separation to remove ferromagnetic impurities. The sorting medium is clean water, and the slurry concentration is 30%. The material is then fed into a bypass diaphragm jig at a concentration of 2.7g / cm³. 3 The density threshold separation method separates light metal components, heavy non-ferrous metal components, and non-metallic waste residue. The jigging parameters are: stroke 8mm, stroke rate 200 times / min, feed concentration 30%, artificial bed using quartz sand with a particle size of 2mm, bed thickness 30mm, and separation time 5min.

[0098] 3. Segmented potentiometric selective leaching: First stage aluminum-magnesium leaching: Light metal components are added to a sodium carbonate-hydrogen peroxide system with the following parameters: sodium carbonate 80 g / L, hydrogen peroxide volume fraction 2%, liquid-to-solid ratio 5:1, leaching at 40℃, potential -0.8V (vs. SCE), stirring at 300 r / min for 60 min, and the leaching rate is detected by solid-liquid separation.

[0099] The second stage of selective copper leaching: the leaching residue and heavy non-ferrous metal components were combined and a sodium thiosulfate-sodium sulfite system was added. The parameters were: sodium thiosulfate 100 g / L, sodium sulfite 30 g / L, pH=9, liquid-solid ratio 8:1, leaching at 30℃ and potential 0.1V (vs. SCE) for 90 min, and solid-liquid separation detection was performed.

[0100] The second stage of selective tin-lead leaching: sodium thiosulfate was added to the copper leaching residue to bring the concentration to 180 g / L, the pH was adjusted to 11, and leaching was carried out at 50°C and a potential of -0.6 V (vs. SCE) for 120 min. Solid-liquid separation was then performed.

[0101] 4. Metal recovery and reagent recycling: - Aluminum and magnesium recovery: Add 1% theoretical amount of hydroxide seed crystals to the leachate, adjust the pH to 10, react at room temperature for 30 minutes, and obtain high-purity hydroxide through solid-liquid separation. The mother liquor is recycled to the first stage of leaching.

[0102] Copper recovery: 1.05 times the theoretical amount of 50nm zero-valent iron nanoparticles are added to the leaching solution, and the reaction is carried out at room temperature for 20 minutes. Ultrafine copper powder is obtained by weak magnetic separation, and the tail liquid is recycled to the copper leaching process.

[0103] Tin-lead recovery: Sulfur dioxide is introduced into the leaching solution, the potential is controlled at -0.8V (vs. SCE), and the reaction is carried out at room temperature for 40 minutes. The solid and liquid are separated to obtain tin-lead alloy powder, and the tail liquid is recycled to the tin-lead leaching process.

[0104] 5. Solid waste treatment: Non-metallic waste residue is mixed with final leaching residue, and after cement-based solidification and stabilization, it is reused as building aggregate. The amount of waste residue generated is statistically analyzed.

[0105] 6. Data statistics: Real-time measurement of energy consumption, reagent consumption, and tail liquid discharge, and calculation of the overall recovery rate.

[0106] Example 2:

[0107] 1. Pretreatment: 1000.0g of raw material is placed in a liquid nitrogen environment and sealed for 6 minutes. After being taken out, it is immediately sent to a vertical impact crusher for impact crushing. The impact linear velocity is 60m / s, the single crushing time is 15s, and the crushing is performed once. The proportion of -2mm particles in the crushed material is controlled to be ≥95%. The particle size and the degree of dissociation of monomers are tested.

[0108] 2. Sorting: After crushing, the material is slurryed to a concentration of 30%, and then subjected to a 100kA / m weak magnetic separation to remove ferromagnetic impurities. The sorting medium is clean water, and the slurry concentration is 30%. The slurry is then fed into a bypass-type diaphragm jig at a concentration of 2.7g / cm³. 3 The density threshold separation method separates light metal components, heavy non-ferrous metal components, and non-metallic waste residue. The jigging parameters are: stroke 12mm, stroke rate 250 times / min, feed concentration 30%, artificial bed using quartz sand with a particle size of 2.5mm, bed thickness 40mm, and separation time 7min.

[0109] 3. Segmented leaching: First stage aluminum-magnesium leaching: sodium carbonate 100g / L, hydrogen peroxide 3.5%, liquid-to-solid ratio 7:1, leaching at 50℃ and potential -0.7V (vs. SCE) for 90min.

[0110] Selective copper leaching: sodium thiosulfate 125 g / L, sodium sulfite 40 g / L, pH=9.5, liquid-to-solid ratio 10:1, leaching at 40℃ and potential 0.2V (vs. SCE) for 120 min.

[0111] Selective leaching of tin and lead: Add sodium thiosulfate to 200 g / L, pH=11.5, leaching at 60℃ and potential -0.5V (vs. SCE) for 150 min.

[0112] 4. Metal recycling: Aluminum and magnesium recovery: 2% seed crystal addition, pH=10.5, reaction at room temperature for 45 minutes.

[0113] Copper recovery: 120nm zero-valent iron nanoparticles, added at 1.1 times the normal amount, reacted at room temperature for 30 minutes.

[0114] Tin-lead recovery: control potential -0.7V (vs. SCE), react at room temperature for 50 min.

[0115] 5. The remaining operations, solid waste treatment, and data statistics are completely consistent with Example 1.

[0116] Example 3:

[0117] 1. Pretreatment: 1000.0g of raw material is placed in a liquid nitrogen environment and sealed for 8 minutes. After being taken out, it is immediately sent to a vertical impact crusher for impact crushing. The impact line speed is 70m / s, the single crushing time is 15s, and the number of crushing times is 2. The proportion of -2mm particles in the crushed material is controlled to be ≥95%. The particle size and monomer dissociation degree are tested.

[0118] 2. Sorting: After crushing, the material is slurryed to a concentration of 30%, and then subjected to a 120kA / m weak magnetic separation to remove ferromagnetic impurities. The sorting medium is clean water, and the slurry concentration is 30%. The slurry is then fed into a bypass-type diaphragm jig at a concentration of 2.7g / cm³. 3 The density threshold separation method separates light metal components, heavy non-ferrous metal components, and non-metallic waste residue. The jigging parameters are: stroke 15mm, stroke rate 300 times / min, feed concentration 30%, artificial bed using quartz sand with a particle size of 3mm, bed thickness 50mm, and separation time 10min.

[0119] 3. Segmented leaching: First stage aluminum-magnesium leaching: sodium carbonate 120g / L, hydrogen peroxide 5%, liquid-to-solid ratio 10:1, leaching at 60℃ and potential -0.6V (vs. SCE) for 120min.

[0120] Selective copper leaching: sodium thiosulfate 150 g / L, sodium sulfite 50 g / L, pH=10, liquid-to-solid ratio 12:1, leaching at 50℃ and potential 0.3V (vs. SCE) for 150 min.

[0121] Selective leaching of tin and lead: Add sodium thiosulfate to 220 g / L, pH=12, leaching at 70℃ and potential -0.3V (vs. SCE) for 180 min.

[0122] 4. Metal recycling: Aluminum and magnesium recovery: 3% seed crystal addition, pH=11, reaction at room temperature for 60 minutes.

[0123] Copper recovery: 200nm zero-valent iron nanoparticles, 1.2 times the amount added, react at room temperature for 40 minutes.

[0124] Tin-lead recovery: control potential -0.6V (vs. SCE), reaction at room temperature for 60 minutes. 5. The remaining operations, solid waste treatment, and data statistics are completely consistent with Example 1.

[0125] II. Experimental raw data and summary table: All data are the average of three parallel experiments, with RSDs simultaneously labeled.

[0126] Table 1 Summary of pretreatment interface dissociation test data Note: Except for Comparative Example 1, Comparative Examples 2-7 all used the liquid nitrogen cryogenic crushing process of this invention, and the dissociation data showed no significant differences.

[0127] Table 2 Summary of Gradient Grouping and Sorting Test Data Note: Comparative Example 2 did not undergo gravity sorting, and therefore no metal distribution rate data is available. Table 3 Summary of Aluminum-Magnesium Potential-Controlled Leaching Test Data (Section 1) Table 4 Summary of Gradient-Controlled Potential Immersion Test Data for the Second Segment Note: All products have a purity RSD ≤ 0.05% and a total recovery RSD ≤ 0.15%, demonstrating excellent data stability.

[0128] Table 5 Summary of Metal Product Purity and Overall Recovery Rate Data Table 6 Summary of Environmental and Economic Performance Data (based on processing 1 ton of raw material) III. Conclusions of the Module-by-Module Test: All conclusions are based on the above experimental data, and the technical advantages of the process of this invention are quantitatively analyzed.

[0129] 1. Conclusion of the preprocessing interface dissociation step: 1.1 The dissociation effect of the liquid nitrogen cryogenic impact crushing process of the present invention is better than that of conventional mechanical crushing: the dissociation degree of metal-nonmetal monomers in the example group reached 98.3%-99.1%, and the dissociation degree of non-ferrous metal monomers reached 97.5%-98.6%, which is 15.9-16.7% and 21.2-22.3% higher than that of Comparative Example 1, respectively, and all data RSD≤0.2%, indicating extremely strong stability.

[0130] 1.2 The process of this invention achieves selective dissociation along the metal-nonmetal interface, rather than conventional transgranular crushing, which solves the problem of recovery rate loss caused by metal encapsulation and is the core foundation for efficient operation of subsequent sorting and leaching processes.

[0131] 1.3 Liquid nitrogen immersion for 3-8 minutes can achieve excellent dissociation effect, with a wide parameter window and strong industrial operability. Among them, Example 2 with immersion for 6 minutes has the best effect.

[0132] 2. Conclusion of the gradient grouping and sorting process: 2.1 The gradient grouping process of weak magnetic separation and gravity separation of the present invention achieves efficient pre-separation and impurity removal of light / heavy non-ferrous metals: In the example group, the Al / Mg distribution rate in the light metal component is ≥98.6%, the Cu / Sn / Pb distribution rate in the heavy non-ferrous metal component is ≥97.9%, and the non-metal removal rate is ≥96.4%, which is far superior to Comparative Examples 1 and 2.

[0133] 2.2 Comparative Example 2 did not undergo gradient sorting, and the non-metal removal rate was only 62.7%, resulting in a 53.1% increase in subsequent reagent consumption compared to Example 2. The metal leaching rate and recovery rate decreased significantly, proving that gradient grouping is a key step in reducing reagent consumption and improving leaching efficiency.

[0134] 2.3 The separation process of this invention uses clean water as the medium, without the addition of reagents or the generation of wastewater. It has a short process, low cost, and is far more environmentally friendly than conventional separation processes such as flotation.

[0135] 3. Conclusions on the segmented potential-controlled selective leaching process: 3.1 First Stage Aluminum-Magnesium Leaching: The sodium carbonate-hydrogen peroxide potential-controlled system of this invention achieves ultra-high selectivity leaching. In the example group, the Al / Mg leaching rate is ≥99%, the total impurity leaching rate is ≤0.21%, and the selectivity coefficient reaches a maximum of 665.3, which is 84.3 times higher than that of Comparative Example 3 (conventional sodium hydroxide system). Comparative Example 3, without potential control, resulted in the simultaneous dissolution of 12.64% of heavy non-ferrous metals, leading to a 1.73% decrease in the purity of the aluminum-magnesium product and a 10.9% loss in the recovery rate of heavy non-ferrous metals, proving that potential control is the core to achieving selective separation.

[0136] 3.2 Second-stage gradient-controlled potential leaching: The cyanide-free system of this invention achieves stepwise selective leaching of copper, tin, and lead through potential gradient control. In Example 2, the Cu / SnPb separation coefficient reached 156.2, achieving metal pre-separation in the leaching process and greatly simplifying subsequent purification procedures.

[0137] 3.3 Comparison with Comparative Example 4 (Cyanide Method): Although the leaching method has a high leaching rate, it has no separation effect and uses highly toxic sodium cyanide, generating 125.8 kg / t of hazardous waste, posing an extremely high environmental risk. The cyanide-free system of this invention completely avoids highly toxic agents, generates no hazardous waste, and achieves a leaching rate and recovery rate comparable to the cyanide method, solving the core environmental pain point of the industry.

[0138] 3.4 Comparison with Comparative Example 5 (one-step leaching without cyanide): Comparative Example 5 had no potential gradient control, and Cu and Sn / Pb dissolved simultaneously. The separation coefficient was only 1.01, with no separation effect. Subsequent extraction and stepwise precipitation processes were required, increasing the process complexity by more than 40% and significantly increasing the processing cost. This proves that gradient potential control is the core point for selective metal separation in a cyanide-free system.

[0139] 4. Conclusions on product purity and total recovery rate: 4.1 Product Purity: The recovered aluminum hydroxide from the example group had a purity of ≥99.90%, ultrafine copper powder a purity of ≥99.85%, and tin-lead alloy powder a purity of ≥99.76%, all meeting high-purity product standards and suitable for direct reuse as high-end industrial raw materials, resulting in high added value. Example 2 showed the best product purity, with aluminum hydroxide reaching 99.97% and ultrafine copper powder reaching 99.91%.

[0140] 4.2 Total metal recovery rate: The total Al recovery rate in the example group was ≥98.7%, Cu ≥97.5%, Sn+Pb ≥96.8%, which was basically on par with the highly toxic cyanide method (Comparative Example 4) and the non-recycling process (Comparative Example 6). Compared with the conventional pyrometallurgical method (Comparative Example 7), the Al recovery rate was increased by 4.0% and the Cu recovery rate was increased by 2.0%. Compared with the conventional mechanical crushing process (Comparative Example 1), the Al recovery rate was increased by 6.4-6.9%, achieving a balance between environmental protection and efficient recycling.

[0141] 5. Environmental and economic performance conclusions: 5.1 Environmental Performance: The example group achieved 100% recycling of leaching tail liquid, with zero tail liquid discharge, no use of highly toxic agents, no hazardous waste generation, 100% solid waste resource utilization rate, and no secondary pollution throughout the entire process. In contrast, Comparative Examples 4 and 7 generated 125.8 kg / t and 216.3 kg / t of hazardous waste, respectively, while Comparative Examples 6, 4, and 7 generated 9.7 m³ of hazardous waste each. 3 / t, 1.2m 3 / t, 2.8m 3 / t of wastewater poses extremely high environmental risks.

[0142] 5.2 Economic Performance: 5.2.1 Reagent Cost: The total reagent consumption in Example 2 was 175.2 kg / t, which is 59.1% lower than that of the non-recycling process (Comparative Example 6); 5.2.2 Energy Cost: The overall energy consumption of Example 2 is only 315.4 kW·h / t, which is 83.1% lower than that of conventional pyrometallurgical methods (Comparative Example 7); 5.2.3 Overall Cost: Although the consumption of reagents per unit is higher than that of cyanide, it avoids the control, environmental protection and safety costs of highly toxic reagents. The overall treatment cost is reduced by more than 20% compared with cyanide and more than 45% compared with pyrolysis, and its industrial promotion value is significant.

[0143] IV. Overall Experiment Summary: This experiment, through 7 sets of single-variable comparative experiments and 3 sets of systematic parallel experiments of the invention embodiments, completed a total of 30 effective parallel experiments. All core indicators had RSD ≤ 2%, and the data were real, stable, and repeatable, verifying the reliability, advancement, and industrial feasibility of the green recycling process for metal materials of this invention, as detailed below: 1. The process of this invention solves the problems of poor crushing and dissociation effect and low recovery rate caused by metal encapsulation in the waste mixed non-ferrous metal recycling industry; the problems of high toxicity and high environmental risk of cyanide leaching system; and the problems of high energy consumption, large carbon emissions and serious secondary pollution of pyrometallurgical process.

[0144] 2. This invention achieves the ultimate balance between high efficiency and environmental protection: under the premise of no cyanide, zero tail liquid discharge, and no hazardous waste generation, the Al / Mg leaching rate is ≥99%, the Cu leaching rate is ≥98%, and the Sn / Pb leaching rate is ≥97%. The total metal recovery rate of the whole process is comparable to the mainstream highly toxic cyanide method in the industry and far superior to conventional pyrometallurgical and mechanical crushing-wet processes.

[0145] 3. This invention achieves a balance between selective separation and high added value of products: through segmented controlled potential leaching, aluminum, magnesium, copper, tin, and lead are separated in stages during the leaching process. The recovered products all meet high purity standards and can be directly reused as industrial raw materials, significantly improving the economic value of the recovered products.

[0146] 4. This invention has a strong industrialization capability: it has a wide process parameter window, is simple to operate, has a stable process, reduces overall energy consumption by more than 83% compared to pyrometallurgical methods, reduces reagent consumption by more than 59% compared to non-recycling processes, and has a significantly lower overall processing cost than conventional processes in the industry. It has promotion and application value in the field of waste mixed non-ferrous metal recycling.

[0147] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A green recycling process of metallic materials, characterized in that, Includes the following steps: S1. Pretreatment interface dissociation: The waste mixed metal raw material containing at least two non-ferrous metals such as aluminum, magnesium, copper, tin and lead is immersed in liquid nitrogen environment for 3 to 8 minutes, and then immediately subjected to impact crushing to obtain crushed material with interface dissociation between different metals and non-metals. S2. Gradient grouping separation: the crushed material is first removed from ferromagnetic impurities by weak magnetic separation, and then separated by gravity separation according to the density threshold of 2.7 g / cm 3 The light metal component, the heavy non-ferrous metal component and the non-metal waste residue are separated. S3. Segmented Potential-Controlled Selective Leaching: First, the light metal components are subjected to a first-stage potential-controlled leaching using a sodium carbonate-hydrogen peroxide alkaline system, with the controlled potential at -0.8V to -0.6V (vs. SCE). Solid-liquid separation yields a leachate and leaching residue containing aluminum and magnesium. Then, this leaching residue is combined with the heavy non-ferrous metal components, and a second-stage gradient potential-controlled leaching is performed using a thiosulfate-sodium sulfite cyanide-free system. The first step involves selectively leaching copper at a controlled potential of 0.1V~0.3V (vs. SCE) to obtain a copper-containing leachate and copper leaching residue. The second step involves adjusting the pH to 11-12, adding sodium thiosulfate to 180-220 g / L, and selectively leaching tin-lead at a potential of -0.6V to -0.3V (vs. SCE) to obtain a tin-lead leaching solution and a final leaching residue. S4. Metal recovery and reagent recycling: The target metal product is recovered by induced precipitation or in-situ reduction method in each leachate stage. The tail liquid after metal recovery is recycled to the corresponding leaching step for reuse.

2. The green recycling process of metal materials according to claim 1, characterized in that, In step S1, the impact crushing adopts a vertical impact crusher with an impact linear velocity of 50~70m / s, a single crushing time of 10~20s, and a crushing number of times of 1~2 times. The particle size of the material after impact crushing is controlled to have a -2mm particle size ratio of ≥95%, of which the degree of dissociation between metal and non-metal is ≥98%.

3. The green recycling process of metal materials according to claim 1, characterized in that, In step S2, the magnetic field strength of the weak magnetic separation is 80~120kA / m, the separation medium is clean water, and the slurry concentration is 25%~35%; the gravity separation uses a side-mounted diaphragm jig, the separation medium is clean water, the stroke is 8~15mm, the stroke rate is 200~300 times / min, the feed concentration is 25%~35%, the artificial bed uses quartz sand with a particle size of 2~3mm, the bed thickness is 30~50mm, the separation time is 5~10min, and the density threshold is 2.7g / cm³. 3 Light metal components, heavy non-ferrous metal components, and non-metallic waste residue were separated.

4. The green recycling process of metal materials according to claim 1, characterized in that, In step S3, in the first stage of potential-controlled leaching system, the sodium carbonate concentration is 80~120g / L, the hydrogen peroxide volume fraction is 2%~5%, the liquid-solid ratio is (5~10):1, the leaching temperature is 40~60℃, the leaching time is 60~120min, and the leaching rate of aluminum and magnesium is ≥99%.

5. The green recycling process of metal materials according to claim 1, characterized in that, In step S3, the first step of the second stage of gradient-controlled potential leaching is selective copper leaching, with a sodium thiosulfate concentration of 100~150g / L, a sodium sulfite concentration of 30~50g / L, a system pH of 9~10, a liquid-to-solid ratio of (8~12):1, a leaching temperature of 30~50℃, a leaching time of 90~150min, and a copper leaching rate of ≥98%.

6. The green recycling process of a metal material according to claim 5, characterized in that, In step S3, the second step of the second stage of gradient-controlled potential leaching is tin-lead selective leaching. After copper selective leaching, solid-liquid separation is obtained to obtain copper leaching residue. The pH of the system is adjusted to 11-12, sodium thiosulfate is added to a concentration of 180-220 g / L, the leaching temperature is 50-70℃, the leaching time is 120-180 min, and the tin and lead leaching rates are ≥97%.

7. The green recycling process of metal materials according to claim 1, characterized in that, In step S4, the aluminum and magnesium-containing leachate is treated with a seed-induced precipitation method to recover the metal: Hydroxide seed crystals of the corresponding target metal are added to the leachate, with the amount of seed crystals added being 1% to 3% of the theoretical precipitate mass of the target metal. The pH of the system is adjusted to 10 to 11 under stirring conditions, and the reaction is carried out at room temperature for 30 to 60 minutes. The solid and liquid are separated to obtain a high-purity hydroxide product, and the mother liquor after separation is recycled to the first leaching step for reuse.

8. The green recycling process of metal materials according to claim 1, characterized in that, In step S4, the copper-containing leaching solution is treated with in-situ reduction-magnetic separation using zero-valent iron nanoparticles: zero-valent iron nanoparticles with a particle size of 50~200nm are added to the leaching solution, the amount added is 1.05~1.2 times the theoretical reaction amount of copper ions, the solution is stirred at room temperature for 20~40min, and ultrafine copper powder is obtained by weak magnetic separation. The tail liquid after separation is recycled to the second copper selective leaching step for reuse.

9. The green recycling process of metal materials according to claim 1, characterized in that, In step S4, the tin-lead leaching solution is treated with in-situ sulfur dioxide reduction to recover the metal: sulfur dioxide gas is introduced into the leaching solution, the system potential is controlled at -0.8V to -0.6V (vs. SCE), the reaction is carried out at room temperature for 40 to 60 minutes, solid-liquid separation is performed to obtain tin-lead alloy powder, and the tail liquid after separation is recycled to the second stage of selective tin-lead leaching for reuse.

10. The green recycling process for metal materials according to claim 1, characterized in that, The non-metallic waste residue obtained in step S2 is mixed with the final impregnation residue obtained in step S3, and then subjected to cement-based solidification and stabilization treatment for reuse as aggregate in construction engineering.

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