A method for extracting rhenium from a leach solution of molybdenum concentrate roasting fumes to produce rhenium dioxide

Abstract

The application relates to a method for extracting rhenium from molybdenum concentrate roasting flue gas leaching solution to prepare rhenium dioxide, and belongs to the technical field of rhenium dioxide synthesis. The application aims to solve the technical problem that alkaline desorption solution cannot be directly electrochemically reduced. The method for extracting rhenium from molybdenum concentrate roasting flue gas leaching solution to prepare rhenium dioxide comprises the following steps: (1) preparation of composite modified activated carbon; (2) pretreatment and pH adjustment of the leaching solution; (3) high-selectivity adsorption of the composite modified activated carbon; (4) alkali desorption; (5) acidification pretreatment; and (6) electrochemical selective reduction to prepare ReO2. According to the characteristics of the molybdenum concentrate roasting flue gas leaching solution, the application innovatively proposes a whole-process integrated process of "weak-acid-condition composite modified activated carbon high-selectivity adsorption + alkali desorption + acidification pretreatment + potential control electrochemical selective reduction to prepare ReO2".

Description

Technical Field

[0001] This application relates to the fields of hydrometallurgy and electrochemical synthesis technology, specifically to a method for extracting rhenium from the leaching liquid of molybdenum concentrate roasting flue gas and directly preparing rhenium dioxide. Background Technology

[0002] Rhenium is a highly valuable, high-melting-point rare metal that plays a vital role in cutting-edge scientific fields such as chemical engineering, metallurgy, aerospace, and defense. The mass fraction of rhenium in the Earth's crust is only 1 × 10⁻⁶. -9 There are no independent rhenium minerals in China; rhenium is mainly associated with molybdenite. During the roasting process of molybdenite, rhenium sublimates and enters the flue gas. Some of it enters the flue dust during the dust collection stage, while the rest enters the leaching liquid during the pre-acidification spraying stage. It is estimated that over 70% of the rhenium volatilizes and enters the flue dust leaching liquid. To ensure molybdenum recovery rates, companies often return the flue dust to the roasting system, while the rhenium enters the molybdenum smelting system. Therefore, molybdenite roasting flue gas leaching liquid is an important recovery raw material. Globally, approximately 80% of rhenium is consumed in the manufacture of high-temperature alloys for aero-engines and gas turbines, with high-purity rhenium products reaching prices of tens of thousands of yuan per kilogram. my country's rhenium resources are relatively scarce, with a high dependence on imports. Therefore, the efficient recovery of rhenium from secondary resources is of significant strategic importance.

[0003] Rhenium dioxide (ReO2) is an important oxide form of rhenium, appearing as a black powder. It can be directly used as a catalyst and battery material additive, and is also a key precursor for the preparation of high-purity metallic rhenium powder (via hydrogen reduction: ReO2 + 2H2 → Re + 2H2O). Developing a short-process technology for the direct preparation of ReO2 from the eluent has significant industrial value.

[0004] Chinese Patent Application No. 202011395630.5 discloses a method for separating and extracting rhenium from a rhenium-molybdenum mixed solution and co-producing ferromolybdenum alloy. The method involves adding a molybdate precipitant to the rhenium-molybdenum mixed solution to precipitate molybdate under weakly acidic conditions, followed by solid-liquid separation to obtain molybdenum-rich slag and a rhenium-containing solution. Then, a rhenium precipitant and a flocculant are added to the rhenium-containing solution to flocculate and precipitate rhenium, followed by solid-liquid separation to obtain rhenium-rich slag. The molybdenum-rich slag is then subjected to high-temperature drying and reduction roasting to obtain ferromolybdenum alloy. This method is particularly suitable for the separation and reuse of rhenium and molybdenum in solutions with low molybdenum content and high rhenium content.

[0005] Chinese Patent Application No. 202011545624.3 discloses a method for preparing ammonium perlite from ion-adsorption type molybdenum-rhenium ore, comprising the following steps: First, the ion-adsorption type molybdenum-rhenium ore is crushed and added to a reaction vessel. A first leaching is performed using a leaching agent solution, during which most of the adsorbed rhenium enters the leachate. A second leaching is then performed using the same leaching agent solution to achieve recycling of the leachate. Finally, an ion exchange process is used to recover the rhenium from the leachate and produce the ammonium perlite product. The overall rhenium recovery rate is greater than 60%.

[0006] Chinese Patent Application No. 201110042349.8 discloses a method for preparing ammonium perrhenate from waste liquid containing molybdenum and rhenium. The method involves adding hydrogen peroxide to the waste liquid containing molybdenum and rhenium until the solution turns yellow, then adding a mixing agent until the pH of the solution reaches 6-7. The solution is then separated by pressure filtration, and the filtrate is collected. The filtrate is then passed through a resin exchange column for adsorption. Adsorption is stopped when the concentration of rhenium in the effluent remains constant. The solution is eluted with NH3·H2O, and the collected eluent is concentrated by heating at 98-100°C. After cooling and crystallization, ammonium perrhenate is obtained. The mixing agent is a mixture of calcium hydroxide and calcium oxide in a weight ratio of 5:1. This invention uses molybdenum and rhenium waste liquid, especially molybdenum roasting flue gas absorption liquid, as raw material, which increases the enrichment of rhenium by nearly 20 times. Ammonia water is determined as the eluent for rhenium, with a rhenium elution rate of more than 98% and a rhenium recovery rate of more than 93%. The purity of ammonium perrhenate product can reach more than 99.5%.

[0007] Chinese patent application number 201911081505.4 discloses a method for selective flotation separation of molybdenum and rhenium ions in an alkaline leaching solution. The method involves adjusting the pH of an alkaline leaching solution containing molybdenum and rhenium ions to 7.1-12, then adding an organic modified activated carbon collector and a surfactant composed of triethylenetetramine, tetraethylenepentamine, methyl violet 10B and cocamidopropyl betaine, followed by aeration flotation. The foam product is a rhenium-rich component, and the remaining liquid is a molybdenum-rich solution.

[0008] The aforementioned existing technologies have the following shortcomings:

[0009] (1) Insufficient selectivity for molybdenum-rhenium separation: Conventional methods are difficult to achieve efficient separation of molybdenum and rhenium under weakly acidic conditions, and ordinary adsorption materials have poor selectivity.

[0010] (2) Limited performance of adsorption materials: Ordinary activated carbon has low adsorption selectivity for rhenium, and the adsorption rate of rhenium is low in the presence of impurities such as molybdenum and iron. Furthermore, no composite modified activated carbon specifically designed for rhenium recovery from leaching solutions has been found.

[0011] (3) Complex process flow: Traditional process requires multiple steps of "adsorption → desorption → concentration → crystallization", which is energy-intensive and has a long cycle.

[0012] (4) Single product form: Existing technologies mostly focus on the preparation of ammonium perrhenate / potassium perrhenate, and there are no reports on short-process technology for directly preparing ReO2 from the eluent. Summary of the Invention

[0013] In view of this, this application provides a method for extracting rhenium from the leaching liquid of molybdenum concentrate roasting flue gas to prepare rhenium dioxide, solving the problem that alkaline desorption liquid cannot be directly electrochemically reduced.

[0014] The first aspect of this application provides a method for preparing rhenium dioxide by extracting rhenium from the leaching liquid of molybdenum concentrate roasting flue gas, comprising the following steps:

[0015] (I) Preparation of Composite Modified Activated Carbon: Pretreated coconut shell activated carbon was placed in tartaric acid solution for the first modification. After the reaction, it was filtered, and the activated carbon was washed with deionized water until the pH of the washing solution was neutral to remove free tartaric acid from the surface. After drying, tartaric acid-modified activated carbon was obtained. The tartaric acid-modified activated carbon was placed in FeSO4 solution for the second modification. After the reaction, it was filtered, and the activated carbon was washed with deionized water until the washing solution was colorless and free of Fe. 2+ The residue was dried to obtain composite modified activated carbon;

[0016] (ii) Pretreatment and pH adjustment of the eluent: The pH of the eluent is adjusted to 4.0-5.0 with alkaline solution, stirred and filtered to obtain the pretreated eluent;

[0017] (III) High Selectivity Adsorption of Composite Modified Activated Carbon: The pretreated eluent was subjected to adsorption treatment. Under pH 4-5 conditions, the positively charged surface of the activated carbon reacted with the negatively charged ReO4. - Electrostatic attraction is generated, resulting in adsorption-saturated composite modified activated carbon;

[0018] (iv) Alkaline desorption: The adsorption-saturated composite modified activated carbon is desorbed to obtain an alkaline desorption solution;

[0019] (v) Acidification pretreatment: Dilute sulfuric acid is added to the alkaline desorption solution at room temperature, stirred, tartaric acid is added, and the pH of the solution is adjusted to 1.0~2.0 to obtain the acidified rhenium-containing solution;

[0020] (vi) Electrochemical selective reduction to prepare ReO2: The acidified rhenium-containing solution is placed in an electrolytic cell for electrochemical reduction, and after washing and drying, rhenium dioxide is obtained.

[0021] The mechanism is speculated to be that the carboxyl and hydroxyl groups in tartaric acid can react with ReO4. - Complexation occurs, forming activated carbon-tartaric acid-ReO4. -Complexes are formed to improve the adsorption selectivity for rhenium. The iron oxide formed by FeSO4 on the activated carbon surface enhances the adsorption selectivity for oxygen-containing anions (ReO4). - The two modifiers exhibit high affinity, which can further increase the adsorption sites and adsorption strength. Occupying different sites on the activated carbon surface, they synergistically enhance the adsorption selectivity and capacity for rhenium, while the adsorption of molybdenum remains at a low level.

[0022] This application innovatively proposes an integrated process for preparing ReO2, specifically targeting the characteristics of molybdenum concentrate roasting flue gas scrubbing liquid. This process involves "highly selective adsorption of composite modified activated carbon under weakly acidic conditions + alkaline desorption + acidification pretreatment + potential-controlled electrochemical selective reduction." Tartaric acid and FeSO4 composite modified coconut shell activated carbon are used, and through a dual enhancement mechanism of complexation and iron oxide adsorption, the adsorption of ReO2 is significantly improved. - The adsorption selectivity and adsorption capacity were assessed. The pH of the eluent was adjusted to 4-5, and under weakly acidic conditions, the positive charge on the surface of activated carbon was utilized to react with ReO4. - The electrostatic attraction and the specific binding sites provided by the composite modification enable highly selective adsorption of rhenium, while molybdenum exists in the form of polyanions, thus inhibiting adsorption. High-concentration NaReO4 solution (containing residual NaOH) is obtained through efficient desorption using 1-2 mol / L NaOH solution. The alkaline desorption solution is acidified to pH 1.0-2.0 with dilute sulfuric acid, followed by potential-controlled electrochemical selective reduction to obtain high-purity ReO2 precipitate at the cathode, while molybdenum remains in the solution and is not reduced.

[0023] Preferably, in step (i), the activated carbon pretreatment process is as follows: take coconut shell activated carbon, boil it in deionized water for 1 hour, wash it to remove ash and surface oil, and dry it to obtain pretreated coconut shell activated carbon.

[0024] Preferably, in step (i), the specific conditions for the first modification are: modification in a 60°C constant temperature water bath oscillator for 6 hours, with an oscillation rate of 120 r / min.

[0025] Preferably, in step (i), the specific conditions for the second modification are: oscillation modification at room temperature for 3 hours, with an oscillation rate of 150 r / min.

[0026] Preferably, in step (ii), the rinsing solution comprises the following components: rhenium 0.1~1.5g / L, molybdenum 0.1~3g / L, and sulfuric acid 10~200g / L.

[0027] Preferably, in step (iii), the specific conditions for the adsorption treatment are: an adsorption linear velocity of 1~4 m / h at room temperature, and adsorption is stopped when the rhenium concentration in the effluent reaches 10~20% of the original solution concentration.

[0028] Preferably, in step (iv), the specific conditions for the desorption treatment are: using 1~2 mol / L NaOH solution as the desorbent, a desorption linear velocity of 1~3 m / h at 25~60℃, and a desorption time of 1~3 h.

[0029] Preferably, in step (v), the concentration of tartaric acid is 0.05~0.2mol / L.

[0030] Preferably, in step (vi), the specific conditions for the electrochemical reduction are as follows: a diaphragm electrolytic cell is used, the cathode and anode regions are separated by a cation exchange membrane, the cathode is a graphite plate or a titanium plate, the anode is a DSA-coated titanium electrode, the cathode potential is controlled at -0.45~-0.55V, and the current density is 5~15mA / cm². 2 The electrolysis temperature is 25~50℃, the electrolysis time is 2~8 hours, and slow magnetic stirring is used during the electrolysis process.

[0031] Preferably, in step (vi), the specific drying conditions are: vacuum drying at 60~100℃ for 2~6 hours.

[0032] Compared with the prior art, this application has the following advantages:

[0033] (i) Achieving highly selective adsorption under weakly acidic conditions: Under pH 4~5 conditions, the adsorption rate of rhenium by the composite modified activated carbon is ≥93%, and the adsorption rate of molybdenum is <10%, thus achieving efficient separation of rhenium and molybdenum.

[0034] (II) Excellent performance and low cost of adsorption materials: Composite modified activated carbon for ReO4 - Its adsorption selectivity and adsorption capacity are significantly higher than those of ordinary activated carbon; the cost of activated carbon materials is low, about 1 / 5 to 1 / 10 of that of ion exchange resins; it can be recycled 5 to 10 times, further reducing operating costs.

[0035] (III) High desorption efficiency and simple process: 1~2 mol / L NaOH for desorption, NaReO4 solution concentration ≥5 g / L; the desorption solution can be directly used for electrochemical reduction after simple acidification, without the need for additional concentration.

[0036] (iv) Electrochemical selective reduction: By controlling the cathode potential between -0.45V and -0.55V (relative to a saturated calomel electrode), rhenium is selectively reduced, and the molybdenum content in the product is <0.2%, and the ReO2 purity is ≥99%.

[0037] (v) High added value of products: ReO2 can be used directly as a catalyst, battery material additive, or as a precursor for the preparation of high-purity rhenium metal.

[0038] (vi) Green and environmentally friendly: No toxic reagents are used throughout the process; the electrolyte can be recycled; and there is no wastewater discharge.

[0039] (vii) Short process and low energy consumption: Only a few main steps are required from the eluent to the ReO2 product; no evaporation and concentration steps are required; the conditions are mild and the equipment requirements are low. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 This is a schematic flowchart of the method for preparing rhenium dioxide from the leachate of molybdenum concentrate roasting flue gas according to this application. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] Unless otherwise specified, the experimental methods used in the embodiments of this application are all conventional methods.

[0044] In the following examples, unless otherwise specified, all raw materials can be obtained by commercial purchase or conventional methods.

[0045] (I) Preparation of composite modified activated carbon

[0046] (1) Activated carbon pretreatment

[0047] Take coconut shell activated carbon (iodine value ≥1000, 20-30 mesh), boil it in deionized water for 1 hour, wash it to remove ash and surface oil, and dry it at 105℃ for later use.

[0048] (2) Tartaric acid modification (first stage modification)

[0049] Pretreated coconut shell activated carbon was placed in a 4% (mass fraction) tartaric acid solution with a liquid-to-solid ratio (modifier volume: activated carbon mass) of 8:1~12:1 and modified for 6 hours in a 60℃ constant temperature water bath shaker (oscillation rate 120 r / min). The carboxyl groups (-COOH) and hydroxyl groups (-OH) in the tartaric acid molecules were loaded onto the surface and pores of the activated carbon through chemical bonding or physical adsorption. After the reaction, the carbon was filtered, and washed with deionized water until the pH of the washing solution was neutral to remove free tartaric acid from the surface. The activated carbon was then dried at 105℃.

[0050] (3) FeSO4 modification (second stage modification)

[0051] Activated carbon modified with tartaric acid and dried was placed in a 0.8 mol / L FeSO4 solution (liquid-to-solid ratio 10:1) and subjected to shaking modification for 3 hours at room temperature (25℃) (shaking rate 150 r / min). FeSO4 formed iron oxides and iron sulfides as active components on the surface and in the pores of the activated carbon. After the reaction, the mixture was filtered, and the activated carbon was washed with deionized water until the washing solution was colorless and free of Fe. 2+ The residue (detected with KSCN solution) was dried at 105℃ to obtain composite modified activated carbon.

[0052] The mechanism is speculated to be that the carboxyl and hydroxyl groups in tartaric acid can react with ReO4. - Complexation occurs, forming activated carbon-tartaric acid-ReO4. - Complexes are formed to improve the adsorption selectivity for rhenium. The iron oxide formed by FeSO4 on the activated carbon surface enhances the adsorption selectivity for oxygen-containing anions (ReO4). - The two modifiers exhibit high affinity, which can further increase the adsorption sites and adsorption strength. Occupying different sites on the activated carbon surface, they synergistically enhance the adsorption selectivity and capacity for rhenium, while the adsorption of molybdenum remains at a low level.

[0053] (II) Pretreatment and pH adjustment of the eluent

[0054] The turbulent scrubbing liquid from the sulfuric acid production system of molybdenum concentrate roasting flue gas is mainly composed of rhenium (0.1~1.5 g / L), molybdenum (0.1~3 g / L), and sulfuric acid (10~200 g / L).

[0055] Adjust the pH to 4.0-5.0 (preferably pH 4.5) with an alkaline solution (NaOH or Na₂CO₃). Under this pH condition, metal ions such as iron and copper form hydroxide precipitates, which can be removed by filtration. After stirring for 30-60 minutes, filter the solution using a plate and frame filter press; the filtrate is then ready for adsorption.

[0056] (III) High Selectivity Adsorption of Composite Modified Activated Carbon

[0057] The pretreated eluent was passed through an adsorption column packed with composite modified activated carbon at a linear velocity of 1–4 m / h. Under pH 4–5 conditions, the positively charged surface of the activated carbon reacted with the negatively charged ReO4. - Electrostatic attraction is generated. The surface of the composite modified activated carbon has complexation sites of tartaric acid functional groups and adsorption sites of iron oxides, which attract ReO4. - It has a strong affinity. Molybdenum exists in the form of polymolybdate ions, which have a large molecular weight and large steric hindrance, resulting in significant inhibition of adsorption. The adsorption process belongs to a monolayer chemisorption mechanism.

[0058] Adsorption linear velocity: 1~4 m / h (preferably 2~3 m / h); room temperature (20~35℃); adsorption stops when the rhenium concentration in the effluent reaches 10%~20% of the original concentration. Rhenium adsorption rate: ≥93%; molybdenum adsorption rate: <10%; the separation effect of molybdenum and rhenium is significantly better than that of ordinary activated carbon.

[0059] (iv) Alkali desorption

[0060] A 1-2 mol / L NaOH solution (preferably 1.5 mol / L) was used as the desorbent to desorb saturated composite modified activated carbon, yielding a high-concentration NaReO4 solution (rhenium concentration ≥ 5 g / L). The desorption process was carried out at room temperature to 60°C, with a desorption linear velocity of 1-3 m / h and a desorption time of 1-3 h. Analysis showed that the desorbate contained rhenium concentration ≥ 5 g / L, low molybdenum content (typically < 0.2 g / L), residual NaOH (pH > 12), and trace amounts of As and K as other impurities.

[0061] Desorption principle: Activated carbon·ReO4 - +OH - →Activated carbon·OH+ReO4 - (It enters the solution in the form of NaReO4).

[0062] (v) Activated carbon regeneration

[0063] After desorption, the activated carbon is washed with water until neutral and can be reused in the adsorption process. The activated carbon can be recycled 5-10 times without a significant decrease in adsorption performance.

[0064] (vi) Acidification pretreatment

[0065] At room temperature, sulfuric acid (49-50% by mass) is added to the above alkaline desorption solution (NaReO4+NaOH), stirred for 10-15 min, and 0.05-0.2 mol / L tartaric acid is added to adjust the pH of the solution to 1.0-2.0 (preferably 1.5). In this step, the function of adding tartaric acid is: (1) as a complexing agent to react with trace metal impurities (such as Fe) in the electrolyte. 3+ Cu 2+(1) To form a stable water-soluble complex, avoid its co-deposition on the cathode, thereby ensuring the purity of ReO2 products; (2) Tartrate ions have a certain adsorption effect on the cathode surface, which can inhibit the hydrogen evolution side reaction, improve current efficiency, and facilitate the formation of a dense and uniform deposition layer of ReO2.

[0066] (vii) Electrochemical selective reduction preparation of ReO2

[0067] The acidified rhenium-containing solution (rhenium concentration 5~15 g / L, pH 1.0~2.0) was placed in an electrolytic cell for electrochemical reduction, and a black ReO2 precipitate was obtained at the cathode.

[0068] Cathode reaction equation: ReO4 - + 4H + + 3e - → ReO2↓+ 2H2O

[0069] A diaphragm electrolytic cell is used, with the cathode and anode regions separated by a cation exchange membrane. The cathode is made of graphite or titanium, preferably graphite, and the anode is a DSA-coated titanium electrode. The cathode potential is controlled at -0.45V to -0.55V (relative to a saturated calomel electrode), and the current density is controlled at 5 to 15 mA / cm². 2 The electrolysis temperature is controlled at 25~50℃, and the electrolysis time is adjusted according to the rhenium concentration and the amount processed, generally 2~8 hours. Slow magnetic stirring is used during the electrolysis process.

[0070] The acidified rhenium-containing solution was pumped into the cathode region, and a 0.5 mol / L H₂SO₄ solution was pumped into the anode region to further suppress the co-reduction of molybdenum. The power supply was turned on, and the cathode potential was controlled at -0.45V to -0.55V (relative to the saturated calomel electrode (SCE)). During electrolysis, the rhenium concentration in the solution was periodically sampled and monitored. Electrolysis was stopped when the rhenium concentration dropped below 0.1 g / L.

[0071] The solid-liquid mixture from the cathode region is discharged and centrifuged. The black ReO2 precipitate is washed 3-5 times with deionized water and then vacuum dried at 60-100℃ for 2-6 hours to obtain the ReO2 product. ReO2 product purity: ≥99%, rhenium direct recovery (electrochemical section): ≥85%, molybdenum content in the product: <0.2%.

[0072] The waste liquid after electrolysis can be returned to the desorbent preparation stage or sent to the wastewater treatment system. The washing liquid contains a small amount of ReO2 particles and can be returned to the electrochemical process for further treatment.

[0073] Example 1

[0074] Preparation of composite modified activated carbon: 1 kg of coconut shell activated carbon (iodine value 1100, 20-30 mesh) was boiled in deionized water for 1 hour, washed, and dried. It was then placed in a 4% (mass fraction) tartaric acid solution at a liquid-to-solid ratio of 10:1 and subjected to constant temperature shaking at 60℃ for 6 hours. After filtration and washing, it was placed in a 0.8 mol / L FeSO4 solution at a liquid-to-solid ratio of 10:1 and subjected to room temperature shaking for 3 hours. After filtration and washing, it was dried at 105℃ to obtain composite modified activated carbon.

[0075] Leachate Pretreatment and Adsorption: 1000 L of turbulent scrubbing solution from a molybdenum smelting plant was taken, containing 0.57 g / L rhenium, 1.2 g / L molybdenum, and 116.8 g / L sulfuric acid. The pH was adjusted to 4.5 with 10% (mass fraction) NaOH solution, stirred for 40 min, and then filtered by plate and frame filter press. The filtrate was passed through an adsorption column packed with 0.5 kg of composite modified activated carbon at a linear velocity of 2.5 m / h. The effluent after adsorption contained 0.03 g / L rhenium (adsorption rate 94.7%) and 1.15 g / L molybdenum (molybdenum adsorption rate 4.2%).

[0076] Alkaline desorption: Saturated activated carbon was desorbed using 1.5 mol / L NaOH solution at 50℃ for 2 h to obtain NaReO4 desorption solution with rhenium concentration of 8.6 g / L, molybdenum concentration of 0.08 g / L, and pH of approximately 13.5.

[0077] Acidification pretreatment: Take 5L of the above desorption solution, slowly add sulfuric acid (49~50% by mass) under stirring, add 0.1mol / L tartaric acid, stir for 10min, and adjust the pH to 1.5.

[0078] Electrochemical selective reduction preparation of ReO2: A membrane electrolyzer was used, with cation exchange membranes separating the anode and cathode regions. Cathode: graphite plate (10cm×10cm×0.5cm); Anode: DSA-coated titanium electrode (10cm×10cm); Cathode potential: -0.50V (relative to a saturated calomel electrode); Current density: 10mA / cm². 2 Electrolysis temperature: 30℃, electrolysis time: 6 hours, stirring: slow magnetic stirring (200 r / min). The electrolyte contains 0.1 mol / L tartaric acid. During electrolysis, black ReO2 precipitate gradually forms on the cathode surface. After electrolysis, the solid-liquid mixture in the cathode area is discharged, centrifuged, the precipitate is washed 5 times with deionized water, and vacuum dried at 60℃ for 5 hours.

[0079] Product testing: ReO2 purity 99.2%, molybdenum content 0.10%.

[0080] Example 2

[0081] Preparation of composite modified activated carbon: 1 kg of coconut shell activated carbon (iodine value 1100, 20-30 mesh) was boiled in deionized water for 1 hour, washed, and dried. It was then placed in a 4% (mass fraction) tartaric acid solution at a liquid-to-solid ratio of 12:1 and modified by constant temperature shaking at 60℃ for 6 hours. After filtration and washing, it was placed in a 0.8 mol / L FeSO4 solution at a liquid-to-solid ratio of 10:1 and modified by shaking at room temperature for 3 hours. After filtration and washing, it was dried at 105℃ to obtain composite modified activated carbon.

[0082] Leachate Pretreatment and Adsorption: 1000 L of turbulent scrubbing solution from a molybdenum smelting plant was taken, containing 1.25 g / L rhenium, 1.5 g / L molybdenum, and 15.2 g / L sulfuric acid. The pH was adjusted to 4.0 with 10% (mass fraction) Na₂CO₃, stirred for 40 min, and then filtered by pressure. The filtrate was passed through an adsorption column packed with 0.5 kg of composite modified activated carbon at a linear velocity of 2.0 m / h, achieving an adsorption rate of 95.2% and a molybdenum adsorption rate of 4.8%.

[0083] Alkaline desorption: Desorption was performed using 1.8 mol / L NaOH solution at a desorption temperature of 60℃ for 2.5 h, resulting in a desorption solution with a rhenium concentration of 11.2 g / L, a molybdenum concentration of 0.10 g / L, and a pH of approximately 13.8.

[0084] Acidification pretreatment: Take 5L of the above desorption solution, slowly add sulfuric acid (49~50% by mass), add 0.2mol / L tartaric acid, stir for 15min, and adjust the pH to 1.0.

[0085] Electrochemical selective reduction preparation of ReO2: Cathode: Titanium plate (10cm×10cm×0.3cm), Anode: DSA-coated titanium electrode, Cathode potential: -0.55V (relative to saturated calomel electrode), Current density: 15mA / cm² 2 Electrolysis temperature: 40℃, electrolysis time: 5 hours, electrolyte contains 0.15mol / L tartaric acid.

[0086] Product testing: ReO2 purity 99.1%, molybdenum content 0.12%.

[0087] Example 3

[0088] Preparation of composite modified activated carbon: 1 kg of coconut shell activated carbon (iodine value 1100, 20-30 mesh) was boiled in deionized water for 1 hour, washed, and dried. It was then placed in a 4% (mass fraction) tartaric acid solution at a liquid-to-solid ratio of 8:1 and modified by constant temperature shaking at 60℃ for 6 hours. After filtration and washing, it was placed in a 0.8 mol / L FeSO4 solution at a liquid-to-solid ratio of 10:1 and modified by shaking at room temperature for 3 hours. After filtration and washing, it was dried at 105℃ to obtain composite modified activated carbon.

[0089] Leachate pretreatment and adsorption: 1000 L of turbulent scrubbing solution from a molybdenum smelting plant was taken, containing 0.22 g / L rhenium, 0.8 g / L molybdenum, and 58.9 g / L sulfuric acid. The pH was adjusted to 5.0 with 10% (mass fraction) NaOH, stirred for 30 min, and then filtered by pressure. The filtrate was passed through an adsorption column packed with 0.5 kg of composite modified activated carbon at a linear velocity of 3.0 m / h, with an adsorption rate of 92.3% and a molybdenum adsorption rate of 5.2%.

[0090] Alkaline desorption: Desorption was performed using 1.2 mol / L NaOH solution at a desorption temperature of 40℃ for 1.5 h, resulting in a desorption solution with a rhenium concentration of 5.8 g / L, a molybdenum concentration of 0.05 g / L, and a pH of approximately 13.0.

[0091] Acidification pretreatment: Take 5L of the above desorption solution, slowly add sulfuric acid (49~50% by mass), add 0.05mol / L tartaric acid, stir for 12min, and adjust the pH to 2.0.

[0092] Electrochemical selective reduction preparation of ReO2: Cathode: graphite plate (10cm×10cm×0.5cm), Anode: DSA-coated titanium electrode, Cathode potential: -0.45V (relative to saturated calomel electrode), Current density: 8mA / cm² 2 Electrolysis temperature: 25℃, electrolysis time: 7 hours, electrolyte contains 0.08 mol / L tartaric acid.

[0093] Product testing: ReO2 purity 99.4%, molybdenum content 0.08%.

[0094] Test case

[0095] (1) Effect of activated carbon modification method on adsorption performance

[0096] Experimental conditions: eluent (containing 0.35 g / L rhenium and 6.8 g / L molybdenum), pH=4.5, adsorption linear velocity 2.5 m / h, activated carbon dosage 0.5 kg / L, adsorption at room temperature.

[0097]

[0098] Conclusion: The rhenium adsorption rate of the composite modified activated carbon increased by 23.5 percentage points compared with the unmodified activated carbon and by about 10 percentage points compared with the single modification, with a separation coefficient as high as 320, proving that the composite modification of tartaric acid and FeSO4 produced a significant synergistic enhancement effect.

[0099] (2) Comparison of adsorption effects under different pH conditions

[0100] Experimental conditions: Composite modified activated carbon, rinsing solution as above, other conditions are the same.

[0101]

[0102] Conclusion: pH 4.5 is the optimal choice. Under this condition, impurity ions such as iron and copper can be removed simultaneously by precipitation, eliminating the need for additional impurity removal steps.

[0103] (3) Effect of acidification pH on electrochemical reduction effect

[0104] Experimental conditions: NaReO4 solution (rhenium concentration 8.6 g / L), graphite cathode, DSA anode, cathode potential -0.50 V (relative to saturated calomel electrode), electrolysis time 4 h, room temperature.

[0105]

[0106] Conclusion: pH 1.5 is the optimal choice; pH that is too low or too high is detrimental to yield and purity.

[0107] (4) Effect of cathode potential on selective separation of molybdenum and rhenium

[0108] The acidified solution (Re 8.6 g / L, Mo 0.15 g / L, pH=1.5), graphite cathode, DSA anode, electrolysis time 4 h, room temperature.

[0109]

[0110] Conclusion: By controlling the cathode potential within the range of -0.45V to -0.55V, efficient and selective recovery of rhenium can be achieved, with the molybdenum content in the product controlled below 0.2% and the ReO2 purity ≥99%.

[0111] (5) Effect of different current densities on ReO2 deposition

[0112]

[0113] Conclusion: Current density 10 mA / cm 2 The preferred option is the one that offers the best overall combination of yield and current efficiency.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing rhenium dioxide by extracting rhenium from the leaching liquid of molybdenum concentrate roasting flue gas, characterized in that, Includes the following steps: (I) Preparation of composite modified activated carbon: The pretreated coconut shell activated carbon was placed in tartaric acid solution for the first modification. After the reaction was completed, the carbon was filtered and washed with deionized water until the pH of the washing solution was neutral to remove the free tartaric acid on the surface. After drying, the activated carbon modified with tartaric acid was obtained. The tartaric acid-modified activated carbon was placed in a FeSO4 solution for a second modification. After the reaction was complete, the carbon was filtered, and then washed with deionized water until the washing solution was colorless and free of Fe. 2+ The residue was dried to obtain composite modified activated carbon; (ii) Pretreatment and pH adjustment of the eluent: The pH of the eluent is adjusted to 4.0-5.0 with alkaline solution, stirred and filtered to obtain the pretreated eluent; (III) High Selectivity Adsorption of Composite Modified Activated Carbon: The pretreated eluent was subjected to adsorption treatment. Under pH 4-5 conditions, the positively charged surface of the activated carbon reacted with the negatively charged ReO4. - Electrostatic attraction is generated, resulting in adsorption-saturated composite modified activated carbon; (iv) Alkaline desorption: The adsorption-saturated composite modified activated carbon is desorbed to obtain an alkaline desorption solution; (v) Acidification pretreatment: Dilute sulfuric acid is added to the alkaline desorption solution at room temperature, stirred, tartaric acid is added, and the pH of the solution is adjusted to 1.0~2.0 to obtain the acidified rhenium-containing solution; (vi) Electrochemical selective reduction to prepare ReO2: The acidified rhenium-containing solution is placed in an electrolytic cell for electrochemical reduction, and after washing and drying, rhenium dioxide is obtained.

2. The method for preparing rhenium dioxide by extracting rhenium from the leaching liquid of molybdenum concentrate roasting flue gas according to claim 1, characterized in that, In step (1), the activated carbon pretreatment process is as follows: take coconut shell activated carbon, boil it in deionized water for 1 hour, wash it to remove ash and surface oil, and dry it to obtain pretreated coconut shell activated carbon.

3. The method for preparing rhenium dioxide from the leachate of molybdenum concentrate roasting flue gas according to claim 1, characterized in that, In step (1), the specific conditions for the first modification are: modification in a 60℃ constant temperature water bath oscillator for 6 hours, with an oscillation rate of 120r / min.

4. The method for preparing rhenium dioxide from the leachate of molybdenum concentrate roasting flue gas according to claim 1, characterized in that, In step (1), the specific conditions for the second modification are: oscillation modification at room temperature for 3 hours, with an oscillation rate of 150 r / min.

5. The method for preparing rhenium dioxide from the leachate of molybdenum concentrate roasting flue gas according to claim 1, characterized in that, In step (ii), the rinsing solution comprises the following components: rhenium 0.1~1.5g / L, molybdenum 0.1~3g / L, and sulfuric acid 50~200g / L.

6. The method for preparing rhenium dioxide by extracting rhenium from the leaching liquid of molybdenum concentrate roasting flue gas according to claim 1, characterized in that, In step (iii), the specific conditions for the adsorption treatment are: the adsorption linear velocity is 1~4 m / h at room temperature, and adsorption is stopped when the rhenium concentration in the effluent reaches 10~20% of the original concentration.

7. The method for preparing rhenium dioxide from the leachate of molybdenum concentrate roasting flue gas according to claim 1, characterized in that, In step (iv), the specific conditions for the desorption treatment are as follows: using 1~2 mol / L NaOH solution as the desorbent, the desorption linear velocity is 1~3 m / h at 25~60℃, and the desorption time is 1~3 h.

8. The method for preparing rhenium dioxide by extracting rhenium from the leaching liquid of molybdenum concentrate roasting flue gas according to claim 1, characterized in that, In step (5), the concentration of tartaric acid is 0.05~0.2 mol / L.

9. The method for preparing rhenium dioxide from the leachate of molybdenum concentrate roasting flue gas according to claim 1, characterized in that, In step (vi), the specific conditions for the electrochemical reduction are as follows: a diaphragm electrolytic cell is used, with the cathode and anode regions separated by a cation exchange membrane; the cathode is a graphite plate or titanium plate; the anode is a DSA-coated titanium electrode; the cathode potential is controlled at -0.45 to -0.55 V; and the current density is 5 to 15 mA / cm². 2 The electrolysis temperature is 25~50℃, the electrolysis time is 2~8 hours, and slow magnetic stirring is used during the electrolysis process.

10. The method for preparing rhenium dioxide from the leachate of molybdenum concentrate roasting flue gas according to claim 1, characterized in that, In step (six), the specific drying conditions are: vacuum drying at 60~100℃ for 2~6 hours.

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