A method for separating metals from pressurized oxygen converted molybdenum concentrates

Abstract

The present application relates to a kind of methods for separating metal of pressurized oxygen conversion molybdenum concentrate, belong to metallurgical separation technical field.The method is after low-grade molybdenum concentrate is ground with non-metallic inert grinding medium, pre-complexation washing is carried out by dilute acid solution containing hydroxy ethylidene diphosphonic acid, and soluble iron, copper impurities are removed;Again, the filter cake is pressurized oxidation with perfluorosulfonic acid resin particles, nitric acid and oxygen in pressure vessel, so that molybdenum is converted into solid molybdic acid;After reaction, the resin is separated and recovered, the filter cake is washed and dried to obtain industrial molybdenum oxide;After the filtrate is combined with washing liquid, copper is replaced by iron powder, oxidized by hydrogen peroxide and precipitated by calcium salt to remove phosphorus, and then molybdenum and rhenium are recovered by ion exchange stepwise desorption.The present application realizes the circulation and reuse of perfluorosulfonic acid resin by the synergistic pretreatment of inert grinding and pre-complexation impurity removal, effectively protects the solid acid catalyst from metal cation poisoning, avoids the generation of sulfuric acid waste liquid, and has high molybdenum oxidation rate, good copper and rhenium comprehensive recovery effect, and high environmental protection and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical separation technology and relates to a method for separating metals from molybdenum concentrate by pressurized oxygen conversion, specifically a method for separating molybdenum, copper and rhenium from low-grade molybdenum concentrate by pressurized oxidation. Background Technology

[0002] Molybdenum, as an important strategic rare metal, plays an irreplaceable role in fields such as iron and steel metallurgy, high-temperature alloys, chemical catalysis, and aerospace. Industrial molybdenum oxide is a key intermediate product in the molybdenum resource application chain, mainly obtained from the concentrate obtained by molybdenite flotation through oxidation and desulfurization. For a long time, the pyrometallurgical roasting process has been widely used both domestically and internationally. This process involves oxidizing and roasting the molybdenum concentrate in a high-temperature furnace by introducing air, thereby removing sulfur as sulfur dioxide and converting molybdenum into molybdenum oxide. However, the pyrometallurgical roasting process has a series of inherent defects: molybdenite oxidation is difficult to complete, and a large amount of incompletely oxidized low-valence molybdenum oxide often remains in the product, which seriously affects the molybdenum recovery rate in subsequent hydrometallurgical processes; a large amount of flue gas containing low concentrations of sulfur dioxide and molybdenum dust are generated during the roasting process, requiring a large dust collection and desulfurization system, resulting in high equipment investment and operating costs; when processing low-grade molybdenum concentrate with high impurity content such as copper and iron, the purity of the crude molybdenum oxide obtained from roasting is poor, and the subsequent refining and impurity removal process is lengthy; in particular, when the molybdenum concentrate contains rare and dispersed metal rhenium, under pyrometallurgical roasting conditions, rhenium is easily dispersed in flue gas, dust and roasted sand, making it difficult to effectively enrich and recover, resulting in a serious loss of this precious resource.

[0003] To overcome the drawbacks of pyrometallurgical roasting, wet pressure oxidation technology has been gradually introduced into the processing of molybdenum concentrate. This method typically involves preparing a slurry by mixing molybdenum concentrate powder with an aqueous solution containing sulfuric acid and nitrogen compounds. Oxygen is then introduced into a pressure vessel, utilizing the active nitrogen oxides formed by the nitrogen compounds in the strong acid medium as electron carriers and oxidation catalysts to achieve low-temperature liquid-phase oxidation of molybdenite. This results in molybdenum remaining primarily in the slag phase as solid molybdate, while copper, iron, rhenium, and other metallic elements are leached into the solution, thus achieving preliminary separation of molybdenum from impurities and associated metals. Compared to traditional pyrometallurgical methods, this pressure oxidation technology avoids the generation of sulfur dioxide flue gas, significantly reducing gaseous pollutant emissions, and significantly improving both the molybdenum oxidation rate and the comprehensive recovery rate of valuable metals. However, existing pressure oxidation technologies still face several prominent problems in practical applications. Sulfuric acid, as a key component providing the strong acid medium, is added only once and cannot be directly recovered and regenerated after the reaction. A large amount of residual sulfate ions enters the waste liquid, forming high-salinity acidic wastewater, which places a heavy burden on subsequent neutralization treatment and generates a large amount of solid waste. Homogeneous nitrogen-containing catalysts undergo partial decomposition and escape losses under high temperature, high pressure, and strong oxidation environments, requiring excessive replenishment. This further increases the nitrate or nitrite content in the waste liquid, raising the treatment difficulty and cost. Furthermore, molybdenum concentrate often contains associated iron and copper sulfide minerals such as chalcopyrite and pyrite. Under acidic pressure oxidation conditions, these minerals dissolve large amounts of heavy metal cations such as iron and copper ions. These cations, once in the liquid phase, not only increase the load on subsequent separation processes but, more importantly, introduce additional impurities such as iron filings when using conventional grinding media, further exacerbating the accumulation of metal cations in the slurry system. The presence of such high-concentration metal cations poses a potential threat to the effectiveness of process aids and system stability. However, existing processes lack effective means for the pre-removal and control of these metal ions, resulting in limited overall process efficiency, difficult waste liquid treatment, and an inability to meet increasingly stringent environmental protection requirements.

[0004] Therefore, developing a pressurized oxidation separation method that can effectively control metal cation interference, reduce acidic wastewater discharge, and maintain high molybdenum oxidation rate and comprehensive metal recovery rate has important practical needs and engineering value. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problem that existing methods for separating metals from molybdenum concentrate via pressurized oxygen conversion generate large amounts of acidic waste liquid, making industrial production difficult.

[0006] On one hand, the present invention relates to a method for pressure oxidation separation of molybdenum, copper and rhenium in low-grade molybdenum concentrate, comprising the following steps:

[0007] Step 1: Grind the low-grade molybdenum concentrate using a non-metallic inert grinding medium and pass it through a 200-400 mesh sieve to obtain molybdenum concentrate powder. Add the obtained molybdenum concentrate powder to a pretreatment complexing solution containing inorganic acid and hydroxyethylidene diphosphonic acid. Based on the mass of the molybdenum concentrate powder, carry out a pre-complexing reaction at a liquid-to-solid ratio of (5-20) mL:1 g. After the reaction is complete, filter and wash to obtain a pretreatment filter cake. Step 2: Add the pretreated filter cake obtained in Step 1 to deionized water to make a slurry. Based on the mass of the molybdenum concentrate powder mentioned in Step 1, the liquid-to-solid ratio of the deionized water is (8-18) mL:1g. Add perfluorosulfonic acid resin particles and nitric acid to the slurry, and introduce oxygen to carry out a pressurized oxidation reaction. After the reaction is completed, cool down and depressurize, and separate the solid and liquid to recover the perfluorosulfonic acid resin particles. The remaining slurry is used as the slurry to be recovered. Step 3: Filter the slurry to be recovered obtained in Step 2 to obtain filter cake and first filtrate. Wash and dry the filter cake to obtain industrial molybdenum oxide. Combine the washing liquid and the first filtrate as the filtrate to be recovered. Step 4: Add iron powder to the filtrate to be recovered obtained in Step 3 to carry out a displacement reaction, filter to obtain copper slag and second filtrate; add hydrogen peroxide solution to the second filtrate to carry out an oxidation reaction, then add calcium salt to adjust the pH to precipitate and remove phosphorus, filter to obtain purified filtrate; pass the purified filtrate through anion exchange resin to adsorb molybdenum and rhenium, and then desorb in steps to recover molybdenum and rhenium respectively.

[0008] Specifically, the method provided by the present invention includes the following steps: Step 1: Grind the low-grade molybdenum concentrate using a non-metallic inert grinding medium and pass it through a 200-400 mesh sieve to obtain molybdenum concentrate powder. Add the obtained molybdenum concentrate powder to a pretreatment complexing solution containing inorganic acid and hydroxyethylidene diphosphonic acid for a pre-complexation reaction. The amount of the pretreatment complexing solution is based on a liquid-to-solid ratio of (5-20) mL:1 g, where the liquid-to-solid ratio is based on the mass of the molybdenum concentrate powder. After the reaction is complete, filter to obtain a pretreatment filter cake and a pretreatment waste liquid. Wash the pretreatment filter cake with deionized water. The washed filter cake is used in subsequent steps. Step 2: Add the washed filter cake from Step 1 to deionized water and mix evenly to obtain a slurry. The amount of deionized water added is based on a liquid-to-solid ratio of (8-18) mL:1 g, where the liquid-to-solid ratio is based on the mass of the molybdenum concentrate powder from Step 1. Add perfluorosulfonic acid resin particles and nitric acid to the slurry and transfer them together to an acid-resistant pressure vessel. Introduce oxygen and carry out an oxidation reaction under pressure. After the reaction is completed, cool down and depressurize to obtain a slurry. Perform solid-liquid separation on the slurry to recover the perfluorosulfonic acid resin particles. The remaining slurry is used as the slurry to be recovered. Step 3: Filter the slurry to be recovered obtained in Step 2 to obtain a filter cake and a first filtrate; wash the filter cake with deionized water, and combine the washing liquid with the first filtrate to obtain the filtrate to be recovered; dry the washed filter cake to obtain industrial molybdenum oxide; Step 4: Add iron powder to the filtrate to be recovered obtained in Step 3 to carry out a displacement reaction, filter to obtain copper slag and second filtrate; add hydrogen peroxide solution to the second filtrate to carry out an oxidation reaction, then add calcium salt to adjust the pH and precipitate, filter to remove the precipitate to obtain purified filtrate; pass the purified filtrate through anion exchange resin to adsorb molybdenum and rhenium, and then use a stepwise desorption method to recover molybdenum and rhenium respectively.

[0009] Furthermore, in the method provided by the present invention, the non-metallic inert grinding medium in step one is a zirconia ceramic ball or a silicon nitride ceramic ball.

[0010] Furthermore, in the method provided by the present invention, the concentration of inorganic acid in the pretreatment complexing solution in step one is 0.05 mol / L to 1.0 mol / L, and the inorganic acid is one or more of hydrochloric acid, nitric acid, and sulfuric acid; the amount of hydroxyethylidene diphosphonic acid added is 0.5% to 8% of the mass of molybdenum concentrate powder.

[0011] Furthermore, in the method provided by the present invention, the conditions for the pre-complexation reaction in step one are: stirring the reaction at a temperature of 20℃~60℃ for 0.5 h~2.5 h.

[0012] Furthermore, in the method provided by the present invention, the amount of perfluorosulfonic acid resin particles added in step two is 8% to 45% of the mass of the molybdenum concentrate powder before pretreatment; the nitric acid is added in the form of a nitric acid solution with a mass concentration of 60% to 68%, and the amount added is 3% to 22% of the mass of the molybdenum concentrate powder before pretreatment.

[0013] Furthermore, in the method provided by the present invention, the conditions for the pressurized oxidation reaction in step two are: total pressure 0.7 MPa to 2.2 MPa, temperature 125℃ to 195℃, and reaction time 0.5 h to 2.0 h.

[0014] Furthermore, in the method provided by the present invention, after separating and recovering the perfluorosulfonic acid resin particles in step two, a resin regeneration step is also included: soaking the recovered perfluorosulfonic acid resin particles in hydrochloric acid with a mass concentration of 15% to 25% at 55°C to 65°C for 1 to 3 hours, then washing them with deionized water until neutral, and then recycling them.

[0015] Furthermore, in the method provided by the present invention, the molar amount of iron powder added in step four is 1.02 to 1.25 times the total molar amount of copper in the original low-grade molybdenum concentrate; the displacement reaction time is 0.5 h to 2.0 h.

[0016] Furthermore, in the method provided by the present invention, the conditions for adding the hydrogen peroxide solution in step four are as follows: it is added in the form of a hydrogen peroxide solution with a mass concentration of 27% to 35%, the amount is 0.5% to 3% of the volume of the second filtrate, and the reaction is carried out by stirring at a temperature of 70°C to 95°C for 0.5 h to 2.0 h.

[0017] Furthermore, in the method provided by the present invention, the calcium salt in step four is calcium hydroxide or calcium chloride, and the pH of the solution is adjusted to 5.5-8.0 so that phosphate ions precipitate out in the form of calcium phosphate or hydroxyapatite.

[0018] Compared with the prior art, the technical solution disclosed in this invention has the following beneficial effects: (1) By using non-metallic inert grinding, impurities such as iron and nickel are eliminated from the source. In conjunction with the pre-complexing and washing of hydroxyethylidene diphosphonic acid, the mineral surface and soluble metal cations such as iron and copper are efficiently removed before pressurized oxidation. This effectively protects the active sites of the subsequent perfluorosulfonic acid resin catalyst from metal cation poisoning, greatly extends the service life of the resin, and realizes the multiple recycling of solid acid catalysts.

[0019] (2) Replacing the inorganic strong acids such as sulfuric acid consumed once in the traditional process with renewable perfluorosulfonic acid resin particles eliminates the generation of sulfate waste liquid from the source, significantly reduces the burden of end-of-pipe acidic wastewater neutralization treatment and solid waste production, making the process cleaner and more environmentally friendly; at the same time, the resin regeneration method is simple and the acid consumption is low, avoiding the problems of decomposition loss and high replenishment cost of existing nitrogen-containing compound catalysts.

[0020] (3) The molybdenum oxidation rate is high, and the single solid phase molybdenum recovery rate can reach more than 94%, and the total molybdenum recovery rate can reach more than 98.5%; copper is directly and efficiently recovered in the form of elemental copper through iron powder replacement, with a recovery rate of more than 99%; rhenium almost entirely enters the liquid phase and is desorbed and enriched stepwise through anion exchange resin, with a recovery rate of more than 95%, realizing the comprehensive and efficient recovery of valuable metals and significantly improving resource utilization.

[0021] (4) The method of the present invention has a simple process, mild and controllable operating conditions, high material recycling rate, small amount of waste discharge, and is easy to realize large-scale industrial production. Detailed Implementation

[0022] The technical solution of the present invention will be described below with reference to embodiments; however, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental and detection methods described in each embodiment are conventional methods; the reagents and materials described are commercially available unless otherwise specified. Unless otherwise specified, all percentages in the following embodiments refer to weight percentages. Unless otherwise specified, all ratios in the following embodiments refer to weight ratios. In the following embodiments, each experiment was repeated three times, and the average value of the experimental results was taken.

[0023] In the following examples, the perfluorosulfonic acid resin particles used are Nafion. TM NR50, by weight percentage, contains 47.0% Mo, 3.2% Cu, 0.13% Re, 31.8% S, 4.2% Fe, 11.5% SiO2, 0.06% Ca, 0.12% P, with the balance being other impurities.

[0024] Example 1 This embodiment provides a method for separating metals from molybdenum concentrate by pressurized oxygen conversion.

[0025] Step 1: Place the low-grade molybdenum concentrate in a ball mill or stirred mill. Use zirconia (3Y-TZP) ceramic balls or silicon nitride (Si3N4) ceramic balls as the grinding media to mill the molybdenum concentrate powder until the particle size meets the sieving requirements. The sieving requirement is to pass through a 200-400 mesh standard sieve. The material passing through the sieve is the molybdenum concentrate powder.

[0026] In step one, non-metallic inert grinding media are used to prevent the introduction of metal impurities such as iron, chromium, and nickel from the source, thus protecting the subsequent solid acid catalyst from metal cation poisoning.

[0027] Step 2: Dissolve an inorganic acid (one or more of hydrochloric acid, nitric acid, or sulfuric acid) and hydroxyethylidene diphosphonic acid (HEDP) in deionized water to obtain a pretreatment complexing solution. In the pretreatment complexing solution, the concentration of the inorganic acid is 0.05 mol / L to 1.0 mol / L, and the amount of HEDP is 0.5% to 8% of the mass of the molybdenum concentrate powder. Add the molybdenum concentrate powder to the pretreatment complexing solution at a liquid-to-solid ratio of (5–20):1 (mL:g), and stir the reaction at 20℃–60℃ for 0.5 h to 2.5 h. Filter the mixture through a 120-mesh screen to obtain a molybdenum concentrate filter cake and pretreatment waste liquid. Wash the molybdenum concentrate filter cake with 2–5 times its mass of deionized water, and combine the washing liquid with the pretreatment waste liquid.

[0028] In step two, inorganic acids and hydroxyethylidene diphosphonic acid dissolve iron oxide, calcium carbonate, apatite, and some soluble copper and iron impurities on the mineral surface, and are then stabilized in the liquid phase by HEDP complexation, further protecting the subsequent solid acid catalyst from metal cation poisoning.

[0029] In step two, the resulting pretreated waste liquid (including the washing liquid incorporated into the pretreated waste liquid) is rich in Fe. 3+ Cu 2+ -HEDP complexes can be used to recover valuable metals or neutralize with lime before being discharged. They can also be reused by adding inorganic acid and HEDP again.

[0030] Step 3: Add the washed molybdenum concentrate filter cake to deionized water at a liquid-to-solid ratio of (8-18):1 (mL:g), and mix thoroughly to prepare a slurry. Add perfluorosulfonic acid resin particles and nitric acid with a mass concentration of 60%-68% to the slurry. The amount of perfluorosulfonic acid resin particles added is 8%-45% of the mass of the molybdenum concentrate powder before pretreatment, and the amount of nitric acid with a mass concentration of 60%-68% is 3%-22% of the mass of the molybdenum concentrate powder before pretreatment. Transfer the above reaction system (slurry, perfluorosulfonic acid resin particles, and nitric acid) to an acid-resistant pressure vessel, introduce industrial pure oxygen (purity ≥99%), control the total pressure at 0.7MPa-2.2MPa, raise the temperature to 125℃-195℃, and react under stirring for 0.5h-2.0h. After the reaction is completed, cool down and depressurize to obtain a slurry of pressurized oxygen-converted molybdenum concentrate. The slurry is passed through a 120-mesh filter to separate the perfluorosulfonic acid resin particles from the slurry, resulting in slurry to be recycled. The recycled resin particles are regenerated by soaking in hydrochloric acid (15%–25% by mass) at 55°C–65°C for 1–3 hours, washed with water until neutral, and then recycled.

[0031] Perfluorosulfonic acid resins can withstand the dual strong oxidizing environment of nitric acid and high-temperature oxygen, unlike sulfated metal oxides and heteropolyacid supported catalysts which are prone to degradation under these conditions. In step three, perfluorosulfonic acid resins are used to provide acidification and auxiliary catalysis conditions, replacing conventionally used inorganic acids (hydrochloric acid or sulfuric acid). Perfluorosulfonic acid resins are recyclable, avoiding the generation of large amounts of acidic wastewater in industrial production. Nitric acid acts as a redox catalyst (NO₂) in this system. X (Circulating carrier), theoretically not consumed.

[0032] Step 4: Filter the slurry to be recovered to obtain a filter cake and a first filtrate. Wash the filter cake with deionized water (washing water volume is 3 to 8 times the mass of the filter cake, rinsing 2 to 3 times). Combine the washing liquid with the first filtrate to obtain the filtrate to be recovered. Dry the washed filter cake at 100℃ to 120℃ to recover industrial molybdenum oxide (MoO3) product.

[0033] Step 5: Add iron powder to the filtrate to be recovered. The molar amount of iron powder added should be 1.02 to 1.25 times the total molar amount of copper in the original low-grade molybdenum concentrate. Stir and react for 0.5 to 2.0 hours to allow Cu to react. 2+The copper residue is replaced with metallic copper powder. Filtering yields copper slag (filter residue) and a second filtrate. The copper slag is then smelted or refined to produce metallic copper. A small amount of HEDP and some of its degradation products (organophosphonic acid / phosphate) remain in the second filtrate. Hydrogen peroxide solution (27%–35% by mass) is added to the second filtrate, at a volume of 0.5%–3% of the second filtrate. The mixture is stirred at 70℃–95℃ for 0.5–2.0 h to oxidize the residual organicphosphonic acid to orthophosphate. Subsequently, calcium hydroxide (quicklime) or calcium chloride is added to adjust the pH to 5.5–8.0, causing the phosphate to precipitate as calcium phosphate / hydroxyapatite. The precipitate is removed by filtration, yielding a purified third filtrate. The third filtrate is passed through a weakly basic anion exchange resin column (such as D296, D301, or IRA-67), where the resin selectively adsorbs molybdate (MoO4). 2- ) and perrhenate (ReO4) - After adsorption saturation, molybdenum is first desorbed using sodium hydroxide solution (5%–12% by mass) to obtain sodium molybdate solution; then rhenium is desorbed using ammonia water (5%–15% by mass) to obtain ammonium perrhenate solution. Ammonium molybdate product can be obtained from the sodium molybdate solution through subsequent acidification precipitation and crystallization; ammonium perrhenate product can be obtained from the ammonium perrhenate solution through concentration and crystallization.

[0034] Example 2 This embodiment provides a method for separating metals from molybdenum concentrate by pressurized oxygen conversion.

[0035] Step 1: Grinding and Classification.

[0036] Take 200g of this low-grade molybdenum concentrate and place it in a stirred mill. Use zirconia (3Y-TZP) ceramic balls as the grinding media and grind until the powder can pass through a 300-mesh standard sieve. Collect the undersize material to obtain molybdenum concentrate powder. Set aside for later use.

[0037] Step 2: Pretreatment complexation and washing.

[0038] Weigh 50g of the molybdenum concentrate powder obtained in step one (reserve the remaining powder for other uses). Prepare the pretreatment complexing solution: Add 37% concentrated hydrochloric acid to 500mL of deionized water to make the concentration of hydrochloric acid in the solution 0.3mol / L, then add 1.5g of hydroxyethylidene diphosphonic acid (HEDP) and stir until completely dissolved. Add the above 50g of molybdenum concentrate powder to the pretreatment complexing solution at a liquid-to-solid ratio of 10:1, and stir the reaction in a 40℃ water bath for 2.0h. After the reaction is complete, filter through a 120-mesh filter to obtain a molybdenum concentrate filter cake and pretreatment waste liquid. Wash the filter cake with deionized water, with the washing water volume being 3 times the mass of the filter cake, and add the washing liquid to the pretreatment waste liquid. The pretreatment waste liquid is collected separately and can be used for lime neutralization and discharge or reused after adding acid and HEDP.

[0039] Step 3: Pressurized oxygen conversion and solid acid catalysis.

[0040] The washed molybdenum concentrate filter cake was transferred to a pressure vessel, and 600 mL of deionized water was added. The mixture was stirred until homogeneous to obtain a slurry (liquid-to-solid ratio 12:1). 12 g of perfluorosulfonic acid resin particles (24% of the pre-treated molybdenum concentrate powder mass) were added to the slurry, followed by 6 g of 65% nitric acid (equivalent to 3.9 g of pure nitric acid, accounting for 7.8% of the powder mass). The pressure vessel was sealed, and industrial pure oxygen (purity ≥99.5%) was introduced. The total pressure inside the vessel was controlled at 1.5 MPa. The temperature was raised to 160℃ with stirring and maintained for 1.0 h. After the reaction, the temperature was lowered and the pressure released. The resulting slurry was passed through a 120-mesh filter to separate the perfluorosulfonic acid resin particles, yielding the slurry to be recycled. The separated resin particles were regenerated by soaking in 200 mL of 18% hydrochloric acid at 60℃ for 2.5 h, then washed with deionized water until neutral, dried, and recycled.

[0041] Step 4: Solid-liquid separation and industrial molybdenum oxide preparation.

[0042] The slurry to be recovered was filtered to obtain a filter cake and a first filtrate. The filter cake was washed twice with deionized water, 100 mL each time. The washing liquid was combined with the first filtrate to obtain the filtrate to be recovered (total volume 1200 mL). The washed filter cake was dried at 110℃ to constant weight to obtain the industrial molybdenum oxide product.

[0043] Step 5: Comprehensive recycling of valuable metals.

[0044] Add 1.5g of iron powder (molar amount calculated as 1.07 times the total molar amount of copper in the molybdenum concentrate) to the filtrate to be recovered, stir and react for 1.0h, filter, and obtain purplish-red copper slag and second filtrate respectively. The copper slag can be sent for refining to extract copper. Slowly add 10mL of 30% hydrogen peroxide solution (0.8% of the filtrate volume) to the second filtrate, stir at 85℃ for 1.0h to degrade the residual organophosphorus to orthophosphate. Then, while stirring, add calcium hydroxide emulsion to adjust the pH of the system to 6.5, let it stand for 30min, filter to remove calcium phosphate precipitate, and obtain the purified third filtrate. Pass the third filtrate through an adsorption column packed with D296 weakly basic anion exchange resin at a flow rate of 2BV / h. After the resin is saturated, first desorb molybdenum with 8% sodium hydroxide solution to obtain sodium molybdate solution; then desorb rhenium with 10% ammonia water to obtain ammonium perrhenate solution. The two solutions were respectively concentrated, acid-precipitated, and crystallized to obtain ammonium molybdate and ammonium perrhenate products.

[0045] Example 3 This embodiment provides a method for separating metals from molybdenum concentrate by pressurized oxygen conversion.

[0046] The difference between this embodiment and Embodiment 2 is that: In step one, the grinding media is replaced with silicon nitride (Si3N4) ceramic balls, and the sieve mesh size is adjusted to 400 mesh.

[0047] In step two, the inorganic acid used in the pretreatment complexing solution is 0.05 mol / L nitric acid; the amount of HEDP used is 0.5% of the mass of molybdenum concentrate powder (i.e., 0.25 g); the liquid-solid ratio is adjusted to 20:1 (1000 mL deionized water); the complexing reaction temperature is 60℃, and the stirring time is shortened to 0.5 h.

[0048] In step three, the liquid-to-solid ratio of the slurry is 8:1 (400 mL of deionized water); the amount of perfluorosulfonic acid resin particles added is 4 g (8% of the powder mass); the amount of 65% nitric acid added is 11 g (22% of the powder mass); the total pressure of the pressure vessel is controlled at 0.7 MPa; the reaction temperature is 125℃, and the reaction is stirred for 2.0 h.

[0049] The resin regeneration conditions in step three are: hydrochloric acid concentration 15%, temperature 80℃, and soaking time 1.0 h. The remaining steps and process conditions (powder mass standard 50 g, washing water volume standard, metal recovery operation, etc.) are exactly the same as in Example 2.

[0050] Example 4 This embodiment provides a method for separating metals from molybdenum concentrate by pressurized oxygen conversion.

[0051] The difference between this embodiment and Embodiment 2 is that: In step two, the inorganic acid used in the pretreatment complexing solution is 0.8 mol / L sulfuric acid; the amount of HEDP used is 8% of the mass of molybdenum concentrate powder (i.e., 4.0 g); the liquid-solid ratio is adjusted to 5:1 (250 mL deionized water); the complexing reaction temperature is 20℃, and the stirring time is extended to 2.5 h.

[0052] In step three, the liquid-to-solid ratio of the slurry is 18:1 (900 mL of deionized water); the amount of perfluorosulfonic acid resin particles added is 22.5 g (45% of the powder mass); the amount of 65% nitric acid added is 1.5 g (3% of the powder mass); the total pressure of the pressure vessel is controlled at 2.2 MPa; the reaction temperature is 195℃, and the reaction is stirred for 0.5 h.

[0053] The resin regeneration conditions in step three are: hydrochloric acid concentration 20%, temperature 50℃, and soaking time 3.0h. The remaining steps and process conditions are exactly the same as in Example 2.

[0054] Example 5 This embodiment provides a method for separating metals from molybdenum concentrate by pressurized oxygen conversion.

[0055] The difference between this embodiment and Embodiment 2 is that: In step two, the inorganic acid used for pretreatment of the complexing solution is a mixed acid of hydrochloric acid and nitric acid (H2O). + The total concentration was 0.6 mol / L, with a hydrochloric acid to nitric acid molar ratio of 1:1; the amount of HEDP used was 5% of the mass of the molybdenum concentrate powder (i.e., 2.5 g); the liquid-to-solid ratio was adjusted to 15:1 (750 mL of deionized water); the complexation reaction temperature was 30 °C, and the stirring time was 1.0 h.

[0056] In step three, the liquid-to-solid ratio of the slurry is 15:1 (750 mL of deionized water); the amount of perfluorosulfonic acid resin particles added is 17.5 g (35% of the powder mass); the amount of 65% nitric acid added is 3.5 g (7% of the powder mass); the total pressure of the pressure vessel is controlled at 1.8 MPa; the reaction temperature is 180℃, and the reaction is stirred for 1.5 h.

[0057] The resin regeneration conditions in step three are: hydrochloric acid concentration 15%, temperature 70℃, and soaking time 2.0h. The remaining steps and process conditions are exactly the same as in Example 2.

[0058] Comparative Example 1 The only difference from Example 2 is that in step two, the pretreatment complex solution does not contain hydroxyethylidene diphosphonic acid; instead, the molybdenum concentrate powder is soaked and washed using a 0.3 mol / L hydrochloric acid solution. All other operations and parameters in steps one, three, four, and five—including grinding media, slurry preparation, perfluorosulfonic acid resin dosage, nitric acid dosage, pressurized oxidation conditions, filtration and washing, iron powder replacement of copper, hydrogen peroxide dephosphorization, and ion exchange—are completely identical to those in Example 2.

[0059] Comparative Example 2 The only difference from Example 2 is that, in step three, perfluorosulfonic acid resin particles are not added; instead, 1.5 g of 98% concentrated sulfuric acid is added to provide a strong acid environment. Correspondingly, the slurry after oxidation is no longer filtered through a 120-mesh screen to separate the resin particles; it is directly subjected to the filtration operation in step four. All other operations and parameters in steps one, two, four, and five—including the grinding media, pre-complexation treatment, nitric acid dosage, pressurized oxidation conditions, filtration and washing, iron powder replacement of copper, hydrogen peroxide dephosphorization, and ion exchange—are completely identical to those in Example 2.

[0060] Comparative Example 3 (using conventional steel ball grinding) The only difference from Example 2 is that the grinding media used in step one for grinding low-grade molybdenum concentrate is replaced with alumina, and zirconium oxide or silicon nitride ceramic balls are no longer used. All other operations and parameters in steps two, three, four, and five, including pre-complexation treatment, perfluorosulfonic acid resin dosage, nitric acid dosage, pressurized oxidation conditions, filtration and washing, iron powder replacement of copper, hydrogen peroxide dephosphorization, and ion exchange, are exactly the same as in Example 2.

[0061] The experimental results are shown in Table 1.

[0062] Table 1. Effects of different factors on experimental results

[0063] 50g of raw molybdenum concentrate is taken, containing a total molybdenum content of 50g × 47.0% = 23.50g. The primary solid-phase molybdenum recovery rate = (industrial molybdenum oxide weight × molybdenum grade) / 23.50g. The molybdenum content in the filtrate is the difference between the total molybdenum oxide content and the solid-phase molybdenum content; the concentration is calculated based on the filtrate volume. The total molybdenum recovery rate = (primary solid-phase recovery rate + filtrate molybdenum content × 98%) / 23.50g. 98% is the process efficiency coefficient used to estimate the recovery rate under normal conditions.

[0064] As shown in Table 1, the single-phase molybdenum recovery rate of Examples 2-5 was stable at 94%-95%, and the total recovery rate was >98.5%. This indicates that the improved process (HEDP pre-complexation + perfluorosulfonic acid resin catalysis) not only oxidizes thoroughly, but also recovers molybdenum mainly in the form of solid molybdic acid. At the same time, the small amount of molybdenum in the filtrate can be almost completely recovered through conventional ion exchange, resulting in extremely low metal loss.

[0065] In Comparative Example 1 (HEDP omitted), the solid phase recovery rate was only 78.7%, the molybdenum concentration in the filtrate was extremely low, and the total recovery rate was less than 80%. This demonstrates that the lack of a complexation and impurity removal step directly leads to resin poisoning, severely impairing both molybdenum oxidation and recovery. The resulting industrial molybdenum oxide is actually a filter cake residue containing a large amount of unreacted sulfides and impurities. Its high weight is due to the ineffective leaching of sulfur, iron, and other substances from the concentrate. In Comparative Example 2 (using sulfuric acid), the recovery rate was comparable to that of the examples, but it lost the environmental advantages of regenerable solid acid and no sulfate pollution in the waste liquid. In Comparative Example 3 (steel ball grinding), the solid phase recovery rate was 88.3%. Although the oxidation rate was slightly higher, iron pollution reduced resin efficiency, and the total recovery rate was still significantly lower than that of the examples. Furthermore, the grade of the solid product decreased significantly.

[0066] In each embodiment, rhenium almost entirely enters the filtrate, and a recovery rate of >95% can be achieved through stepwise desorption via ion exchange; copper has a recovery rate of >99% in the displacement precipitation step. The improved scheme has significant practical value in the comprehensive recovery of molybdenum, copper, and rhenium.

[0067] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A method for separating molybdenum, copper, and rhenium from low-grade molybdenum concentrate by pressure oxidation, characterized in that, Includes the following steps: Step 1: Grind the low-grade molybdenum concentrate using a non-metallic inert grinding medium and pass it through a 200-400 mesh sieve to obtain molybdenum concentrate powder. Add the obtained molybdenum concentrate powder to a pretreatment complexing solution containing inorganic acid and hydroxyethylidene diphosphonic acid. Based on the mass of the molybdenum concentrate powder, carry out a pre-complexing reaction at a liquid-to-solid ratio of (5-20) mL:1 g. After the reaction is complete, filter and wash to obtain a pretreatment filter cake. Step 2: Add the pretreated filter cake obtained in Step 1 to deionized water to make a slurry. Based on the mass of the molybdenum concentrate powder mentioned in Step 1, the liquid-to-solid ratio of the deionized water is (8-18) mL:1g. Add perfluorosulfonic acid resin particles and nitric acid to the slurry, and introduce oxygen to carry out a pressurized oxidation reaction. After the reaction is completed, cool down and depressurize, and separate the solid and liquid to recover the perfluorosulfonic acid resin particles. The remaining slurry is used as the slurry to be recovered. Step 3: Filter the slurry to be recovered obtained in Step 2 to obtain filter cake and first filtrate. Wash and dry the filter cake to obtain industrial molybdenum oxide. Combine the washing liquid and the first filtrate as the filtrate to be recovered. Step 4: Add iron powder to the filtrate to be recovered obtained in Step 3 to carry out a displacement reaction, filter to obtain copper slag and second filtrate; add hydrogen peroxide solution to the second filtrate to carry out an oxidation reaction, then add calcium salt to adjust the pH to precipitate and remove phosphorus, filter to obtain purified filtrate; pass the purified filtrate through anion exchange resin to adsorb molybdenum and rhenium, and then desorb in steps to recover molybdenum and rhenium respectively.

2. The method according to claim 1, characterized in that, The non-metallic inert grinding media mentioned in step one is zirconia ceramic balls or silicon nitride ceramic balls.

3. The method according to claim 1, characterized in that, The concentration of inorganic acid in the pretreatment complex solution in step one is 0.05 mol / L to 1.0 mol / L, and the inorganic acid is one or more of hydrochloric acid, nitric acid, and sulfuric acid; the amount of hydroxyethylidene diphosphonic acid added is 0.5% to 8% of the mass of molybdenum concentrate powder.

4. The method according to claim 1, characterized in that, The conditions for the pre-complexation reaction described in step one are: stirring the reaction at a temperature of 20℃~60℃ for 0.5 h~2.5 h.

5. The method according to claim 1, characterized in that, In step two, the amount of perfluorosulfonic acid resin particles added is 8% to 45% of the mass of the molybdenum concentrate powder before pretreatment; the nitric acid is added in the form of a nitric acid solution with a mass concentration of 60% to 68%, and the amount added is 3% to 22% of the mass of the molybdenum concentrate powder before pretreatment.

6. The method according to claim 1, characterized in that, The conditions for the pressurized oxidation reaction described in step two are: total pressure 0.7 MPa to 2.2 MPa, temperature 125℃ to 195℃, and reaction time 0.5 h to 2.0 h.

7. The method according to claim 1, characterized in that, After separating and recovering the perfluorosulfonic acid resin particles as described in step two, a resin regeneration step is also included: soaking the recovered perfluorosulfonic acid resin particles in hydrochloric acid with a mass concentration of 15% to 25% at 55°C to 65°C for 1 to 3 hours, then washing them with deionized water until neutral, and then recycling them.

8. The method according to claim 1, characterized in that, The amount of iron powder added in step four is 1.02 to 1.25 times the total number of copper moles in the original low-grade molybdenum concentrate; the displacement reaction time is 0.5 h to 2.0 h.

9. The method according to claim 1, characterized in that, The conditions for adding the hydrogen peroxide solution in step four are as follows: it is added in the form of a hydrogen peroxide solution with a mass concentration of 27% to 35%, and the amount is 0.5% to 3% of the volume of the second filtrate. The reaction is carried out by stirring at a temperature of 70℃ to 95℃ for 0.5 h to 2.0 h.

10. The method according to claim 1, characterized in that, The calcium salt mentioned in step four is calcium hydroxide or calcium chloride. The pH of the solution is adjusted to 5.5-8.0 so that the phosphate ions precipitate out in the form of calcium phosphate or hydroxyapatite.

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