Method for green extraction of platinum group metals from solid waste and low-grade ores

Abstract

The application discloses a method for green extraction and recovery of platinum group metals from solid waste and low-grade ores, which is characterized by coupling of direct bioleaching enrichment of sulfides and indirect bioleaching enrichment of oxides, pre-treatment of ball milling, gravity separation and flotation, and post-treatment of impurity removal, adsorption and electrolysis. The method realizes green extraction and recovery of low-content platinum group metals in metal-based solid waste and low-grade ores through a series of processes such as gravity separation, flotation, bioleaching-circulating enrichment, adsorption and electrolysis. In the MBR regeneration tank, the direct leaching enrichment of platinum group metals in sulfides is realized by replacing sulfide materials, the indirect leaching enrichment of platinum group metals in oxides is realized by indirect leaching of oxide materials and regeneration of failed leaching liquid, and the direct leaching enrichment of sulfides and the indirect leaching enrichment of oxides are coupled to realize the synergistic leaching and efficient liquid enrichment of platinum group metals in low-content solid waste and low-grade ores.

Description

Technical Field

[0001] This application belongs to the field of solid waste recycling technology, specifically relating to a method for the green extraction and recovery of platinum group metals from solid waste and low-grade ores. Background Technology

[0002] my country has a large amount of metal-based solid waste, such as non-ferrous tailings slag, iron and steel tailings slag, non-ferrous smelting dust, iron and steel smelting dust, and gold beneficiation tailings, as well as a considerable amount of low-grade gold-bearing ores, such as low-sulfide gold ores, polysulfide gold ores, polymetallic gold ores, gold-bearing copper ores, and gold-bearing iron ores, which contain varying concentrations of gold and other platinum group metals. Because these metal-based solid wastes and gold-bearing ores are diverse in type, complex in structure, and varied in composition, and because the occurrence forms, states, and valence states of gold and other platinum group metals are also very different, coupled with the extremely low concentrations of platinum group metals (1-10 mg / kg), the extraction and recovery of gold and other platinum group metals pose a significant challenge.

[0003] Typically, extraction and recovery technologies for platinum group metals (PGMs) from solid materials mainly include pyrometallurgical and hydrometallurgical processes. However, for metal-based solid wastes and low-grade ores with low PGM content (1-10 mg / kg), the traditional recovery process involves pyrometallurgical enrichment followed by hydrometallurgical separation. First, PGMs are captured through reduction melting to form enriched alloys, and the dust / alloys rich in the target metals are then separated and recovered using hydrometallurgical processes. Pyrometallurgical enrichment requires high-temperature atmospheres, various expensive additives, and complex reaction processes, resulting in high energy consumption, large carbon emissions, and low yields. Alkaline leaching with concentrated NaOH, HCl, or H2SO4, and even direct hydrometallurgical leaching with aqua regia, are plagued by high costs, heavy pollution, and difficulties in impurity removal, posing significant challenges to their industrial commercialization. Green, efficient, and low-carbon extraction technologies for low-content PGMs in metal-based solid wastes and low-grade ores urgently need research. Summary of the Invention

[0004] This application discloses a method for solidifying silty soft soil using activated cementitious materials. It takes the coupling of direct bioleaching enrichment of sulfides and indirect bioleaching enrichment of oxides as its core, ball milling, gravity separation, and flotation as pretreatment, and impurity removal, adsorption, and electrolysis as posttreatment. Through a series of multiple processes such as gravity separation, flotation, bioleaching-circulation enrichment, adsorption, and electrolysis, the green extraction and recovery of low-content platinum group metals in metal-based solid waste and low-grade ores is achieved.

[0005] To solve the above-mentioned technical problems, this application provides the following technical solution:

[0006] A method for the green extraction and recovery of platinum group metals from solid waste and low-grade ores includes the following steps:

[0007] Step S1: After coarse crushing, the low-grade ore is coarsely ground to a particle size of 10-50 mesh. For the coarse mixed tailings, a gravity separation process is used to separate the low-density mud and sand and the high-density platinum group metal pyrite, so as to obtain the coarsely ground low-grade ore and the coarsely separated platinum group metal sulfides.

[0008] Step S2 involves fine grinding and ultrafine ball milling of the coarse-ground low-grade ore and the coarse-particle platinum group metal sulfides after gravity separation to obtain powder with a particle size of 200-800 mesh, which is then subjected to flotation to obtain pyrite enriched material rich in platinum group metals.

[0009] Step S3: Add the platinum group metal-rich pyrite concentrate obtained from flotation to the inorganic salt solution of the MBR and compound it with other energy substrates.

[0010] Step S4: When the concentration of platinum group metals in the regenerated active leaching no longer increases, it indicates that the direct leaching of platinum group metals in pyrite, which serves as the energy substrate, has been completed, and the solid energy substrate in the MBR needs to be replaced.

[0011] Step S5: Slowly add hydrogen peroxide and one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, and ammonia to the high-concentration platinum group metal enrichment leachate produced by the biological cycle leaching. Stir at 80℃-90℃ until the pH of the enrichment solution rises to 2.5-4.0 and keep warm for 15-45 minutes. Then centrifuge, filter, and press filter to remove iron-based precipitates and collect the low-iron platinum group metal enrichment solution.

[0012] Step S6: Extract and separate platinum group metals from the low-iron platinum group metal enrichment solution using anion-targeted adsorption resin.

[0013] Optionally, in step S1, the slurry concentration in the gravity separation process is 20%-50% (w / v), the centrifugal speed is 800-1500 rpm, the residence time is 2-6 seconds, and the temperature is 20℃-50℃, to obtain pyrite material with a density of 4.5-5.0 and a platinum group metal content of 2.0-10 g / ton, with a platinum group metal recovery rate of 50%-85%.

[0014] Optionally, in step S2, the flotation process is carried out at room temperature, with a solid-liquid ratio of 10%-35% and a residence time of 0.5-4 hours. The activator is copper nitrate, copper chloride, or copper sulfate, added at 200-1000 g / ton; the frother is No. 2 oil, No. 4 oil, or eucalyptus oil, added at 200-1000 g / ton; the dispersant is water glass, sodium tripolyphosphate, or sodium dodecyl sulfate, added at 500-2500 g / ton; butyl xanthate 200-800 g / ton; ethyl thiocyanate 200-1000 g / ton; collector (Y89) 200-800 g / ton; the density of the platinum group metal pyrite enrichment is 5.0-6.0, and the platinum group metal recovery rate is 60%-90%.

[0015] Optionally, in step S3, the membrane pore size of the MBR is 0.1-0.5 micrometers, and the pyrite enrichment material is compounded with thiosulfate, ferrous sulfate, sulfur, and waste sulfur paste.

[0016] Optionally, in step S3, the pyrite concentration is 2%-15% (w / v), the ratio of pyrite to the compound energy substrate is 1-10; the cultivation temperature is 20-40℃, the stirring speed is 30-150 rpm, the aeration rate is 0.10-1.0 reactor volume / min, and the inoculum concentration of pyrite-oxidizing bacteria is 3%-15%, then 0.5-2.0 reactor volumes of active leachate are extracted daily via membrane. The active leachate characteristics are: pH 0.5-2.0, Fe... 2+ Concentration 200-1000 mg / L, Fe 3+ Concentrations: 500-2500 mg / L, amino acid concentration: 100-500 mg / L, extracellular polymeric substance concentration: 200-1000 mg / L, gold and other platinum group metals concentration: 1-5 mg / L.

[0017] Optionally, in step S3, the oxide enriched material rich in platinum group metals obtained by flotation is added to the leaching tank and reacted with the active leachate to achieve indirect leaching of the oxide enriched material; the indirect leaching temperature is 20-40℃, the leaching time is 1-4 hours, the solid-liquid ratio is 10%-50%, the stirring speed is 25-100 rpm, and the concentration of gold and other platinum group metals in the leaching solution is 5-50 mg / L.

[0018] Optionally, in step S4, when replacing the solid energy substrate in the MBR, membrane pumping is paused. The mud-water mixture in the MBR is separated from the solid energy substrate and bacterial solution by low-speed centrifugation and macroporous membrane filtration. The bacterial solution is returned to the MBR, while the pyrite after direct leaching of platinum group metals is discharged. New pyrite rich in platinum group metals and compound energy substrate are added to the MBR for a new batch of direct leaching and production of active leachate. The regenerated active leachate is used for indirect bioleaching of a new batch of oxide material. The pyrite used for direct leaching to extract platinum group metals is replaced 2-4 times. After 4-8 batches of indirect leaching to extract platinum group metals from oxides, the enriched leachate containing a high concentration of platinum group metals is opened for the separation and purification of platinum group metals.

[0019] Optionally, in step S5, the effective concentration of hydrogen peroxide is 30%, and the amount added is 1%-5%; the stirring speed is 30-120 rpm.

[0020] Optionally, in step S6, a gold-absorbing resin is used to specifically adsorb and separate gold in the enrichment solution, and a resin for adsorbing platinum group metals is used to specifically adsorb and separate platinum group metals in the enrichment solution.

[0021] Optionally, the dosage of the targeted adsorption resin is 20%-40%, the adsorption temperature is 20℃-50℃, the adsorption time is 6-12 hours, and the resin saturation gold loading is 50-150 g / L.

[0022] The advantages of this application are:

[0023] 1. In the MBR regeneration tank, direct leaching enrichment of platinum group metals in sulfides is achieved by replacing sulfide materials, and indirect leaching enrichment of platinum group metals in oxides is achieved by indirect leaching of oxide materials and regeneration of spent leaching liquid. The coupling of direct leaching enrichment of sulfides and indirect leaching enrichment of oxides achieves synergistic leaching and high-efficiency liquid phase enrichment of platinum group metals in low-content solid waste and low-grade ore.

[0024] 2. With the coupling of direct bioleaching enrichment of sulfides and indirect bioleaching enrichment of oxides as the core, ball milling, gravity separation and flotation as pretreatment, and impurity removal, adsorption and electrolysis as posttreatment, the green extraction and recovery of low-content platinum group metals in metal-based solid waste and low-grade ores is achieved through a series of multiple processes such as gravity separation, flotation, bioleaching-circulation enrichment, adsorption and electrolysis. Detailed Implementation

[0025] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] This application provides a method for the green extraction and recovery of platinum group metals from solid waste and low-grade ores, specifically including the following steps:

[0027] Step S1: After coarse crushing, the low-grade ore is coarsely ground to a particle size of 10-50 mesh. For the coarse mixed tailings, a gravity separation process is used to separate the low-density mud and sand and the high-density platinum group metal pyrite, resulting in coarsely ground low-grade ore and coarsely separated platinum group metal sulfides.

[0028] The gravity separation process involves a slurry concentration of 20%-50% (w / v), a centrifugal speed of 800-1500 rpm, a residence time of 2-6 seconds, and a temperature of 20℃-50℃, yielding pyrite material with a density of 4.5-5.0 and a platinum group metal content of 2.0-10 g / ton, with a platinum group metal recovery rate of 50%-85%.

[0029] In step S2, the low-grade ore after coarse grinding and the coarse-particle platinum group metal sulfides after gravity separation are finely ground and ultrafine ball milled to obtain powder with a particle size of 200-800 mesh. For fine powder tailings, flue dust and other solid waste materials, there is no need to grind them again, and they can be directly floated to obtain pyrite enriched material rich in platinum group metals.

[0030] The flotation process is carried out at room temperature, with a solid-liquid ratio of 10%-35% and a residence time of 0.5-4 hours. The activator is copper nitrate, copper chloride, or copper sulfate, added at 200-1000 g / ton; the frother is No. 2 oil, No. 4 oil, or eucalyptus oil, added at 200-1000 g / ton; the dispersant is water glass, sodium tripolyphosphate, or sodium dodecyl sulfate, added at 500-2500 g / ton; butyl xanthate 200-800 g / ton, ethyl thiocyanate 200-1000 g / ton, and collector (Y89) 200-800 g / ton. The harvested material is enriched with platinum group metals (PGMs), with a PGM enrichment factor of 3-10 times, a PGM density of 5.0-6.0, and a PGM recovery rate of 60%-90%.

[0031] Step S3: The pyrite enriched material rich in platinum group metals obtained by flotation is added to the inorganic salt solution of MBR (membrane pore size 0.1-0.5 micrometers) and compounded with other energy substrates.

[0032] The energy substrates include thiosulfate, ferrous sulfate, sulfur, and waste sulfur paste.

[0033] The concentration of pyrite was 2%-15% (w / v), and the ratio of pyrite to the compound energy substrate was 1-10. Under the conditions of a culture temperature of 20-40℃, a stirring speed of 30-150 rpm, an aeration rate of 0.10-1.0 reactor volume / min, and a pyrite-oxidizing bacteria inoculum concentration of 3%-15%, 0.5-2.0 reactor volumes of active leachate were extracted daily via membrane extraction. The active leachate characteristics were: pH 0.5-2.0, Fe... 2+ Concentration 200-1000 mg / L, Fe 3+ The concentrations are as follows: 500-2500 mg / L for amino acids, 100-500 mg / L for extracellular polymers, 200-1000 mg / L for gold and other platinum group metals, and 1-5 mg / L for gold and other platinum group metals. The oxide-rich material obtained from flotation is added to the leaching tank and reacts with the activated leachate to achieve indirect leaching of the oxide-rich material. The indirect leaching temperature is 20-40℃, the leaching time is 1-4 hours, the solid-liquid ratio is 10%-50%, the stirring speed is 25-100 rpm, and the concentration of gold and other platinum group metals in the leachate is 5-50 mg / L.

[0034] Step S4: When the concentration of platinum group metals in the regenerated active leaching no longer increases, it indicates that the direct leaching of platinum group metals in pyrite, which serves as the energy substrate, has been completed, and the solid energy substrate in the MBR needs to be replaced.

[0035] During the replacement of the solid energy substrate, membrane pumping is paused. The mud-water mixture in the MBR is separated from the solid energy substrate and bacterial solution through low-speed centrifugation and macroporous membrane filtration. The bacterial solution is returned to the MBR, while the pyrite after direct leaching of platinum group metals (PGMs) is discharged. New pyrite rich in PGMs and compound energy substrates are added to the MBR for new (multiple) batches of direct leaching and production (regeneration) of active leachate. The regenerated active leachate is used for indirect bioleaching of new (multiple) batches of oxide feedstock. The pyrite used for direct leaching to extract PGMs is replaced 2-4 times, and after 4-8 batches of indirect leaching to extract PGMs from oxides, the enriched leachate containing a high concentration of PGMs (100-500 mg / L) is opened for the separation and purification of PGMs. The entire bioleaching-cycle enrichment process is then restarted.

[0036] Step S5: Slowly add hydrogen peroxide (effective concentration 30%, addition amount 1%-5%) and one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, and ammonia (concentration 0.5-2.0M) to the high-concentration platinum group metal enriched leachate produced by biological cycle leaching. Stir at 80℃-90℃ (30-120 rpm) until the pH of the enriched solution rises to 2.5-4.0 and keep warm for 15-45 minutes. Then centrifuge, filter, and press filter to remove iron-based precipitates and collect the low-iron platinum group metal enriched solution (total iron concentration 0.2-1.0 g / L).

[0037] Among them, the low-iron enrichment solution uses cation exchange resin to further remove Fe. 3+ Al 3+ Pb 2+ Ca 2+ Mg 2+ Impurities such as metal ions. Resin impurity removal process: resin concentration 15%-30% (v / v), adsorption temperature 20℃-50℃, adsorption time 0.5-2.5 hours, stirring speed 20-80 rpm, residual concentration of iron and aluminum 20-100 mg / L, residual concentration of calcium and magnesium 40-200 mg / L. Centrifugation, filtration, and pressure filtration are used to separate the resin and collect the purified enriched solution. The saturated resin that has adsorbed impurities is regenerated with concentrated acid and washed with water before being reused for impurity removal in the low-iron enriched solution.

[0038] Step S6: Extract and separate platinum group metals from the low-iron platinum group metal enrichment solution using anion-targeted adsorption resin.

[0039] The process involves using gold-absorbing resins to specifically adsorb and separate gold from the enrichment solution, and using resins specifically designed for adsorbing platinum group metals (PGMs) to specifically adsorb and separate PMMs from the enrichment solution. The targeted adsorption resin dosage is 20%-40%, the adsorption temperature is 20℃-50℃, the adsorption time is 6-12 hours, and the resin saturation gold (PGM) loading is 50-150 g / L. The desorption process uses sulfuric acid concentrations of 2%-10% and thiourea concentrations of 2%-10%, with a desorption temperature of 20℃-50℃ and a desorption time of 2-6 hours. The average desorption rate of PMMs is 80%-95%, and the PMM concentration in the enrichment solution is 15-60 g / L. The enrichment solution is then electrolyzed to produce elemental PMMs or alloys with a purity ≥90%. The desorbed targeted resin is regenerated in an alkaline solution and washed with water until neutral before reuse.

[0040] The following detailed description of the method for green extraction and recovery of platinum group metals from solid waste and low-grade ore provided in this application is illustrated by specific embodiments 1-3. Example 1

[0041] Example 1 provides a method for the green extraction and recovery of platinum group metals from solid waste and low-grade ores, specifically including the following steps:

[0042] Step S1: The zinc-lead beneficiation tailings are separated from the sludge and platinum group metal-containing pyrite through a gravity separation process. The gravity separation process uses a slurry concentration of 20% (w / v), a centrifugal speed of 1500 rpm, a residence time of 2 seconds, and a temperature of 20°C. The collected pyrite material has a density of 4.5 and a platinum group metal content of 10 g / ton, with a platinum group metal recovery rate of 81%.

[0043] Step S2: Platinum group metal sulfides are obtained by ultrafine ball milling to obtain powder with a particle size of 600 mesh, which is then enriched by flotation. The flotation process is carried out at room temperature, with a solid-liquid ratio of 25% and a residence time of 4 hours. The activator is a mixture of copper nitrate and copper chloride, added at 1000 g / ton; the frother is a mixture of oil No. 2 and oil No. 4, added at 500 g / ton; the dispersant is water glass, added at 1000 g / ton; butyl xanthate 400 g / ton; ethyl thiocyanate 500 g / ton; and collector (Y89) 350 g / ton. The harvested platinum group metal enriched material has a enrichment factor of 3.6 times, a density of 5.5, and a platinum group metal recovery rate of 84%.

[0044] Step S3: The pyrite concentrate rich in platinum group metals obtained from flotation is added to the inorganic salt solution of an MBR (membrane pore size 0.25 μm) and compounded with sodium thiosulfate (1.5%) and sulfur (1.5%). Under the following conditions: pyrite concentration 15% (w / v), culture temperature 30℃, stirring speed 50 rpm, aeration rate 0.2 reactor volumes / min, and pyrite-oxidizing bacteria inoculum concentration 10%, 1.0 reactor volume of active leachate is extracted daily via the membrane. The active leachate characteristics are: pH 0.8, Fe... 2+ Concentration 500 mg / L, Fe 3+ The concentrations of the zinc-lead smelting flue dust oxides enriched with platinum group metals (PGMs) were 1000 mg / L, amino acid concentration 210 mg / L, extracellular polymeric substance concentration 270 mg / L, and gold and other PGMs concentration 2.4 mg / L. Indirect leaching of the oxide enrichment was achieved by adding the PGM-rich zinc-lead smelting flue dust oxides obtained from flotation to an extraction tank and reacting them with activated leachate. The indirect leaching temperature was 30℃, the leaching time was 3 hours, the solid-liquid ratio was 15%, the stirring speed was 60 rpm, and the concentration of gold and other PGMs in the leachate was 22 mg / L.

[0045] Step S4: When the concentration of platinum group metals (PGMs) in the regenerated activated leaching no longer increases, it indicates that the direct leaching of PGMs from the pyrite (the energy substrate) has been completed, and the solid energy substrate in the MBR needs to be replaced. During this process, membrane pumping is paused, and the mud-water mixture in the MBR is separated from the solid energy substrate and the bacterial solution through low-speed centrifugation and macroporous membrane filtration. The bacterial solution is returned to the MBR, while the pyrite after direct leaching of PGMs is discharged. New pyrite rich in PGMs and a compounded energy substrate are added to the MBR for new (multiple) batches of direct leaching and production (regeneration) of activated leaching. The regenerated activated leaching is used for new (multiple) batches of indirect bioleaching of oxide materials. After the pyrite used for direct leaching of PGMs is replaced three times, and after six batches of indirect leaching of PGMs from oxides, a concentrated leachate containing a high concentration of PGMs (260 mg / L) is opened for the separation and purification of PGMs.

[0046] In step S5, hydrogen peroxide (30% effective concentration, 5% addition) and sodium hydroxide (0.5M concentration) are slowly added to the enriched leachate containing high concentrations of platinum group metals produced by the bio-cycle leaching. The mixture is stirred at 90°C (100 rpm) until the pH of the enriched solution reaches 3.0 and is kept at this temperature for 30 minutes. After centrifugation, filtration, and pressure filtration to remove iron-based precipitates, a low-iron platinum group metal enriched solution (total iron concentration 0.6 g / L) is collected. The low-iron enriched solution is further treated with cation exchange resin to remove Fe. 3+ Al 3+ Pb 2+ Ca 2+ Mg 2+Impurities such as metal ions were removed. Resin purification process: resin concentration 10% (v / v), adsorption temperature 25℃, adsorption time 1.0 h, stirring speed 60 rpm. The residual concentrations of iron and aluminum were 80 mg / L, and the residual concentrations of calcium and magnesium were 110 mg / L. The resin was separated by centrifugation, filtration, and pressure filtration, and the purified enriched solution was collected.

[0047] Step S6 involves extracting and separating platinum group metals (PGMs) from a low-iron PGM enrichment solution using anion-targeted adsorption resin. The resin dosage is 30%, the adsorption temperature is 30°C, the adsorption time is 8 hours, and the resin-saturated gold (PGM) loading is 120 g / L. The desorption process involves 5% sulfuric acid and 5% thiourea, at a desorption temperature of 30°C for 6 hours, achieving an average desorption rate of 87% for PGMs and a PGM concentration of 32 g / L in the enrichment solution. The enrichment solution is then electrolyzed to produce elemental PGMs or alloys with a purity of 92%. Example 2

[0048] Example 2 provides a method for the green extraction and recovery of platinum group metals from solid waste and low-grade ore, specifically including the following steps:

[0049] Step S1: The copper ore tailings are separated from the sludge and platinum group metal-containing pyrite through a gravity separation process. The gravity separation process uses a slurry concentration of 25% (w / v), a centrifugal speed of 1200 rpm, a residence time of 2 seconds, and a temperature of 30°C. The collected pyrite material has a density of 4.6 and a platinum group metal content of 11 g / ton, with a platinum group metal recovery rate of 82%.

[0050] In step S2, platinum group metal sulfides are obtained by ultrafine ball milling to obtain powder with a particle size of 400 mesh, which is then enriched by flotation. The flotation process is carried out at room temperature, with a solid-liquid ratio of 20% and a residence time of 5 hours. The activator is a mixture of copper sulfate and copper chloride, added at a rate of 800 g / ton; the frother is No. 2 oil, added at a rate of 600 g / ton; the dispersant is water glass, added at a rate of 600 g / ton; butyl xanthate 500 g / ton; ethyl thiocyanate 400 g / ton; and collector (Y89) 400 g / ton. The harvested platinum group metal enriched material has a enrichment factor of 3.5 times, a density of 5.7, and a platinum group metal recovery rate of 82%.

[0051] Step S3: The pyrite concentrate rich in platinum group metals obtained from flotation is added to the inorganic salt solution of the MBR (membrane pore size 0.25 μm) and compounded with waste sulfur paste (1.5%) and sulfur (1.5%). Under the following conditions: pyrite concentration 12% (w / v), culture temperature 32℃, stirring speed 60 rpm, aeration rate 0.15 reactor volumes / min, and pyrite-oxidizing bacteria inoculum concentration 15%, 1.0 reactor volume of active leachate is extracted daily through the membrane. The active leachate characteristics are: pH 0.8, Fe...2+ Concentration 600 mg / L, Fe 3+ The concentrations of the copper smelting flue dust, rich in platinum group metals, were 1100 mg / L, 230 mg / L (amino acids), 260 mg / L (extracellular polymers), and 3.4 mg / L (gold and other platinum group metals). Oxide enriched material from copper smelting flue dust obtained through flotation and containing platinum group metals was added to a leaching tank and reacted with activated leachate to achieve indirect leaching of the oxide enriched material. The indirect leaching temperature was 35℃, the leaching time was 3.5 hours, the solid-liquid ratio was 16%, the stirring speed was 80 rpm, and the concentration of gold and other platinum group metals in the leachate was 25 mg / L.

[0052] Step S4: When the concentration of platinum group metals (PGMs) in the regenerated activated leaching no longer increases, it indicates that the direct leaching of PGMs from the pyrite (the energy substrate) has been completed, and the solid energy substrate in the MBR needs to be replaced. During this process, membrane pumping is paused, and the mud-water mixture in the MBR is separated from the solid energy substrate and the bacterial solution through low-speed centrifugation and macroporous membrane filtration. The bacterial solution is returned to the MBR, while the pyrite after direct leaching of PGMs is discharged. New pyrite rich in PGMs and a compounded energy substrate are added to the MBR for new (multiple) batches of direct leaching and production (regeneration) of activated leaching. The regenerated activated leaching is used for new (multiple) batches of indirect bioleaching of oxide materials. After the pyrite used for direct leaching of PGMs is replaced four times, and after five batches of indirect leaching of PGMs from oxides, a concentrated leachate containing a high concentration of PGMs (220 mg / L) is opened for the separation and purification of PGMs.

[0053] In step S5, hydrogen peroxide (30% effective concentration, 5% addition) and sodium hydroxide (0.5M concentration) are slowly added to the enriched leachate containing high concentrations of platinum group metals produced by the bio-cycle leaching. The mixture is stirred at 85°C (100 rpm) until the pH of the enriched solution reaches 3.3, and then kept at this temperature for 25 minutes. After centrifugation, filtration, and pressure filtration to remove iron-based precipitates, a low-iron platinum group metal enriched solution (total iron concentration 0.65 g / L) is collected. The low-iron enriched solution is further treated with cation exchange resin to remove Fe. 3+ Al 3+ Pb 2+ Ca 2+ Mg 2+ Impurities such as metal ions were removed. Resin purification process: resin concentration 12% (v / v), adsorption temperature 30℃, adsorption time 1.5 hours, stirring speed 60 rpm. The residual concentrations of iron and aluminum were 85 mg / L, and the residual concentrations of calcium and magnesium were 120 mg / L. The resin was separated by centrifugation, filtration, and pressure filtration, and the purified enriched solution was collected.

[0054] Step S6 involves extracting and separating platinum group metals (PGMs) from a low-iron PGM enrichment solution using anion-targeted adsorption resin. The resin dosage is 35%, the adsorption temperature is 35°C, the adsorption time is 6 hours, and the resin-saturated gold (PGM) loading is 150 g / L. The desorption process involves 6% sulfuric acid and 6% thiourea, at a desorption temperature of 40°C for 8 hours, achieving an average desorption rate of 89% for PGMs and a PGM concentration of 42 g / L in the enrichment solution. The enrichment solution is then electrolyzed to produce elemental PGMs or alloys with a purity of 91%. Example 3

[0055] Example 3 provides a method for the green extraction and recovery of platinum group metals from solid waste and low-grade ore, specifically including the following steps:

[0056] Step S1 involves separating the pyrite-based acid production waste residue into platinum group metal (PGM)-free and PMM-containing materials using a gravity separation process. The gravity separation process uses a slurry concentration of 30% (w / v), a centrifugal speed of 1000 rpm, a residence time of 2 seconds, and a temperature of 35°C. The collected material has a density of 4.2 and a PMM content of 14.3 g / ton, achieving a PMM recovery rate of 65%.

[0057] Step S2: The high-value material containing platinum group metals is subjected to ultrafine ball milling to obtain powder with a particle size of 600 mesh, which is then enriched by flotation. The flotation process is carried out at room temperature, with a solid-liquid ratio of 25% and a residence time of 4 hours. The activator is a mixture of copper sulfate and copper nitrate, added at a rate of 850 g / ton; the frother is No. 2 oil, added at a rate of 500 g / ton; the dispersant is water glass, added at a rate of 500 g / ton; butyl xanthate 500 g / ton; ethyl thiocyanate 400 g / ton; and collector (Y89) 400 g / ton. The harvested platinum group metal enriched material has a enrichment factor of 3.0, a density of 5.6, and a platinum group metal recovery rate of 74%.

[0058] Step S3 involves adding the pyrite gold tailings to the inorganic salt solution in the MBR (membrane pore size 0.55 μm) and compounding it with waste sulfur paste (5.0%). The pyrite gold tailings concentration is 10% (w / v), the culture temperature is 35℃, the stirring speed is 40 rpm, the aeration rate is 0.25 reactor volumes / minute, and the inoculum concentration of pyrite oxidizing bacteria is 10%. 1.0 reactor volume of active leachate is extracted daily through the membrane. The active leachate characteristics are: pH 0.7, Fe... 2+ Concentration 500 mg / L, Fe 3+The concentrations of the gold oxide tailings were 1300 mg / L, amino acid concentration 260 mg / L, extracellular polymeric substance concentration 280 mg / L, and gold ion concentration 1.2 mg / L. Indirect leaching of the gold oxide tailings was achieved by adding the tailings to the leaching tank and reacting them with the activated leachate. The indirect leaching temperature was 50℃, the leaching time was 4.5 hours, the solid-liquid ratio was 25%, the stirring speed was 60 rpm, and the gold ion concentration in the leachate was 9.8 mg / L.

[0059] Step S4: When the gold ion concentration in the regenerated activated leaching no longer increases, replace the gold sulfide tailings in the MBR. During this process, membrane pumping is paused, and the mud-water mixture in the MBR is separated from the solid energy substrate and bacterial solution through low-speed centrifugation and macroporous membrane filtration. The bacterial solution is returned to the MBR, and the pyrite after direct leaching is discharged. New gold sulfide tailings and compounded energy substrates are added to the MBR for new (multiple) batches of direct leaching and production (regeneration) activated leaching. The regenerated activated leaching is used for new (multiple) batches of indirect bioleaching of oxide materials. After four batches of direct leaching extraction of gold pyrite tailings and five batches of indirect leaching extraction of oxide gold tailings, a concentrated leachate containing a high concentration of gold ions (54 mg / L) is opened for gold separation and purification.

[0060] In step S5, hydrogen peroxide (effective concentration 30%, addition amount 4%) and sodium hydroxide (concentration 0.4M) are slowly added to the gold-enriched leachate produced by the bio-cycle leaching. The mixture is stirred at 90°C (100 rpm) until the pH of the enriched solution rises to 3.3, and then kept at this temperature for 25 minutes. After centrifugation, filtration, and pressure filtration to remove iron-based precipitates, a low-iron platinum group metal enriched solution (total iron concentration 0.55 g / L) is collected. The low-iron enriched solution is further treated with cation exchange resin to remove Fe. 3+ Al 3+ Pb 2+ Ca 2+ Mg 2+ Impurities such as metal ions were removed. Resin purification process: resin concentration 15% (v / v), adsorption temperature 30℃, adsorption time 2.5 hours, stirring speed 80 rpm. The residual concentrations of iron and aluminum were 95 mg / L, and the residual concentrations of calcium and magnesium were 110 mg / L. The resin was separated by centrifugation, filtration, and pressure filtration, and the purified enriched solution was collected.

[0061] Step S6 involves extracting and separating platinum group metals from a low-iron platinum group metal enrichment solution using anion-targeted adsorption resin. The resin dosage is 35%, the adsorption temperature is 35℃, the adsorption time is 6 hours, and the resin saturation gold loading is 120 g / L. The desorption process involves 6% sulfuric acid and 6% thiourea, a desorption temperature of 40℃, and a desorption time of 8 hours. The average gold desorption rate is 92%, and the gold concentration in the precious metal solution is 19 g / L. Elemental gold is then produced by electrolysis of the precious metal solution with a purity of 93%.

[0062] The embodiments of this application have been described above, but this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for green extraction of platinum group metals from solid waste and low grade ores, characterized in that, It comprises the following steps: Step S1, after the low-grade ore is coarsely broken, it is coarsely ground to a particle size of 10-50 mesh, and for the coarse particle mixed tailings, the low-density sand and the high-density platinum group-containing pyrite are separated by using the gravity separation process, to obtain the coarsely ground low-grade ore and the gravity separated coarse particle platinum group metal-containing sulfide; Step S2, the coarsely ground low-grade ore and the gravity separated coarse particle platinum group metal-containing sulfide are finely ground and ultra-finely ball milled to obtain a powder with a particle size of 200-800 mesh, and then flotation is performed to obtain a pyrite concentrate rich in platinum group metals; Step S3, the flotation of the rich platinum group metal pyrite rich material is added to the inorganic salt solution of the MBR and compounded with other energy substrates, wherein the pyrite concentration is 2%-15%, the ratio of pyrite to compounded energy substrate is 1-10; the culture temperature is 20-40℃, the stirring speed is 30-150 revolutions / minute, the aeration amount is 0.10-1.0 reactor volume / minute, the sulfur-iron oxidizing bacteria inoculation concentration is 3%-15%, under the condition of 0.5-2.0 reactor volumes of active leachate is extracted through the membrane every day, the active leachate characteristics: pH value 0.5-2.0, Fe 2+ concentration 200-1000mg / L, Fe 3+ concentration 500-2500mg / L, amino acid concentration 100-500 mg / L, extracellular polymer concentration 200-1000mg / L, gold and other platinum group metal concentration 1-5mg / L; Step S4, when the platinum group metal concentration in the regenerated active leachate no longer increases, it indicates that the direct leaching of platinum group metals in the pyrite as an energy substrate has been completed, and the solid energy substrate in the MBR needs to be replaced; Step S5, the high-concentration platinum group metal-rich leaching solution produced by biological leaching is slowly added with hydrogen peroxide and one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, and ammonia water, and stirred at a temperature of 80-90°C until the pH value of the enrichment solution rises to 2.5-4.0 and is kept for 15-45 minutes, then centrifuged, filtered, and pressure-filtered to remove the iron-based precipitate and collect the low-iron platinum group metal-rich solution; Step S6, the platinum group metals in the low-iron platinum group metal-rich solution are extracted and separated by anion targeting adsorption resin.

2. The method of claim 1, wherein, In step S1, the gravity separation process has a pulp concentration of 20%-50%, a centrifugal rotation speed of 800-1500 rpm, a residence time of 2-6 seconds, and a temperature of 20-50°C, to obtain a pyrite material with a density of 4.5-5.0 and a platinum group metal content of 2.0-10 g / ton, with a platinum group metal recovery rate of 50%-85%.

3. The method according to claim 1 or 2, characterized in that, In step S2, the flotation process is carried out at room temperature, with a solid-liquid ratio of 10%-35% and a residence time of 0.5-4 hours; the activator is copper nitrate, copper chloride, or copper sulfate, added in an amount of 200-1000 g / ton; the foaming agent is No. 2 oil, No. 4 oil, or eucalyptus oil, added in an amount of 200-1000 g / ton; the dispersing agent is water glass, sodium tripolyphosphate, or sodium dodecyl sulfate, added in an amount of 500-2500 g / ton; butyl xanthate 200-800 g / ton, ethylthiuram 200-1000 g / ton, and collector 200-800 g / ton; the density of the platinum group metal-containing pyrite concentrate is 5.0-6.0, and the platinum group metal recovery rate is 60%-90%.

4. The method of claim 1, wherein, In step S3, the membrane pore size of the MBR is 0.1-0.5 microns, and other energy substrates include thiosulfate, ferrous sulfate, sulfur, or waste sulfur paste.

5. The method of claim 1, wherein, In step S3, the oxide concentrate rich in platinum group metals obtained by flotation is added to the leaching tank and reacts with the active leachate to achieve indirect leaching of the oxide concentrate; the indirect leaching temperature is 20-40°C, the leaching time is 1-4 hours, the solid-liquid ratio is 1:10-1:2, the stirring speed is 25-100 rpm, and the gold and other platinum group metal concentrations in the leaching solution are 5-50 mg / L.

6. The method of claim 1, wherein, In step S4, when the solid energy substrate in the MBR is replaced, the membrane pumping is suspended, the sludge-water mixture in the MBR is subjected to low-speed centrifugation and macroporous membrane filtration to separate the solid energy substrate and the bacterial liquid, the bacterial liquid is returned to the MBR, the direct leaching sulfuric ore of platinum group metals is discharged, and the MBR is added with new sulfuric ore rich in platinum group metals and compound energy substrate to perform new batch direct leaching and production of active leaching liquid; The indirect biological leaching of oxide materials is performed by using the regenerated active leaching liquid; the sulfuric ore for direct leaching of platinum group metals is replaced for 2-4 times, the platinum group metals in the oxide are extracted by indirect leaching for 4-8 batches, and the enrichment leaching liquid containing high concentration of platinum group metals is opened to separate and purify the platinum group metals.

7. The method of claim 1, wherein, In step S5, the effective concentration of hydrogen peroxide is 30%, the added amount is 1%-5%, and the stirring speed is 30-120 rpm.

8. The method of claim 1, wherein, In step S6, the gold in the enrichment liquid is specifically adsorbed and separated by using a gold adsorption resin, and the platinum group metals in the enrichment liquid are specifically adsorbed and separated by using a platinum group metal adsorption resin.

9. The method of claim 8, wherein, The added amount of the target adsorption resin is 20%-40%, the adsorption temperature is 20-50℃, the adsorption time is 6-12 hours, and the saturated gold loading capacity of the resin is 50-150 g / L.