Method for supernormal enrichment of rhenium in waste acid based on calcium polysulfide

Abstract

The invention belongs to the technical field of hydrometallurgy, and particularly relates to a calcium polysulfide-based waste acid rhenium supernormal enrichment method. The method comprises the following steps: 1) respectively preparing a calcium-containing mixed solution and a sulfur-containing mixed solution by taking absolute ethyl alcohol as a solvent; 2) introducing nitrogen into the calcium-containing mixed solution for deoxidation, mixing the deoxidized calcium-containing mixed solution with the sulfur-containing mixed solution, and stirring to obtain a calcium sulfide mixed solution; 3) adding sulfur into the calcium sulfide mixed solution, boiling with water to obtain calcium polysulfide, adding triethanolamine and tetrahydrofuran, stirring, carrying out grain growth, centrifugally separating solids, washing, and annealing to obtain nano calcium polysulfide powder; and 4) adding the nano powder into the waste acid, stirring and reacting, and then filtering and separating to obtain the rhenium sulfide enriched slag. According to the method, specific adsorption and enrichment of rhenium in a waste acid system can be achieved by constructing the stable and effective vulcanizing agent, and the whole method has the advantages of being simple and efficient, low in cost, easy to implement and popularize, wide in raw material source, low in equipment requirement, wide in application range and beneficial to industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a method for super-enriching rhenium in polluted acid based on calcium polysulfide. Background Art

[0002] Rhenium (Re), as a high-value strategic metal, has been widely used in high-tech fields such as aerospace, petrochemicals, and electronic devices due to its excellent performance in ultra-high temperature and high-corrosion environments. It is an indispensable key material in modern industry, national defense and military industry, and strategic emerging industries.

[0003] However, rhenium is sparsely distributed in nature, with no isolated deposits, and its content in the Earth's crust is extremely rare. Currently, proven rhenium resources are only found in countries like Chile, the United States, and Russia. my country's rhenium reserves are relatively low, while demand is high, resulting in a high degree of external dependence. To alleviate this imbalance in rhenium supply and demand, recovering rhenium from secondary sources is gaining increasing attention.

[0004] During the copper smelting process, rhenium typically exists as sulfides (such as ReS and ReS7). As the smelting process progresses, rhenium is oxidized to volatile ReO7, ultimately entering the copper smelting waste acid. Copper smelting waste acid is rich in rhenium and has great development potential as a secondary resource. However, the recovery of rhenium in my country's current copper smelting process faces a series of challenges, such as its strong dispersion, low recovery rate, and lengthy process flow.

[0005] In response to this, the China Patent Office published a patent application on February 18, 2025, for a method for separating rhenium from a rhenium-containing solution using an anion exchange resin. The application is published as CN119464782A. This method uses 1-vinylimidazole, N,N-dimethylformamide, and D314 resin as raw materials to prepare an imidazole-based anion exchange resin, which has a certain selective adsorption capacity for rhenate ions. However, due to the large volume of waste acid, this method suffers from issues such as bulky equipment, high investment costs, and high energy consumption, resulting in poor economic benefits for rhenium recovery.

[0006] On January 24, 2025, the Chinese Patent Office also published a patent application for the construction of a green extraction system and its application in the extraction of rhenium. The application is published as CN119351799A. This method synthesizes multiple functionalized ionic liquids, which are then used as extractants and mixed with diluents in a specific ratio to form an organic phase. The organic and aqueous phases are then mixed at a predetermined ratio to form a multi-element green extraction system, which extracts rhenium under specific experimental conditions. However, this extraction system is costly, highly polluting, and extremely complex, and its organic solvents significantly impact actual production conditions.

[0007] To achieve economical and efficient recovery of rhenium from waste acid, researchers have used chemical precipitation to enrich rhenium in waste acid. This method is suitable for waste acid containing low concentrations of rhenium and is simple to operate, but it consumes a large amount of conventional reagents, and the small amount of precipitated product makes precipitation recovery difficult. In response to this, the present invention proposes a method for using calcium polysulfide to achieve extraordinary enrichment of rhenium in copper smelting waste acid. This method has the characteristics of low energy consumption, simple process, high yield, and fast separation rate. It reduces reagent consumption by 45%, increases the rhenium recovery rate to over 99.95%, and increases the sedimentation rate by 3-5 times compared to traditional processes. It is particularly suitable for industrial waste acid systems with complex components. Summary of the Invention

[0008] In order to solve the problems of high enrichment and recovery cost of rhenium in waste acid, low economic benefits, and low enrichment degree of rhenium in waste acid due to co-precipitation of impurities, the present invention provides a method for extraordinary enrichment of rhenium in waste acid based on calcium polysulfide.

[0009] The main objectives of the present invention are:

[0010] 1. Improve the economic benefits of rhenium enrichment and recovery in waste acid;

[0011] Second, a simple, efficient and low-cost method is used to enrich rhenium in waste acid;

[0012] 3. The enrichment and recovery process is highly selective and can effectively avoid the influence of impurities.

[0013] To achieve the above objectives, the present invention adopts the following technical solutions.

[0014] A method for the extraordinary enrichment of rhenium in polluted acid based on calcium polysulfide,

[0015] The method comprises:

[0016] 1) using anhydrous ethanol as a solvent to prepare a calcium-containing mixed solution and a sulfur-containing mixed solution respectively;

[0017] 2) passing nitrogen through the calcium-containing mixed solution to deoxygenate it, and then mixing the deoxygenated calcium-containing mixed solution with the sulfur-containing mixed solution and stirring to obtain a calcium sulfide mixed solution;

[0018] 3) adding sulfur to the calcium sulfide mixture and boiling it in water for reaction, then adding triethanolamine and tetrahydrofuran, centrifuging and separating the solids, and washing and drying them in sequence to obtain nano powder;

[0019] 4) adding the nanopowder to the waste acid and stirring for reaction, and then filtering and separating to obtain rhenium sulfide-enriched slag.

[0020] As a preference,

[0021] Step 1) The calcium-containing mixed solution is an ethanol solution of calcium chloride and / or calcium nitrate and / or calcium acetate;

[0022] Step 1) The calcium ion concentration in the calcium-containing mixed solution is 0.01 to 0.05 mol / L;

[0023] In step 1), the sulfur-containing mixed solution is an ethanol solution of sodium sulfide and / or L-cysteine ​​and / or 1-thioglycerol.

[0024] As a preference,

[0025] The nitrogen flow time in step 2) is 10 to 20 minutes.

[0026] As a preference,

[0027] When the calcium-containing mixed solution and the sulfur-containing mixed solution are mixed in step 2), the molar ratio of S to Ca is controlled to be (0.2-5):1; and the stirring time after the mixing in step 2) is 10-16 hours.

[0028] As a preference,

[0029] Step 3) The amount of sulfur added is 10-20 g / L, the reaction time is 20-40 min, and the reaction temperature is 40-60° C. Step 3) The amount of triethanolamine added is 5-20 g / L calcium sulfide mixed solution;

[0030] Step 3) The amount of tetrahydrofuran added is 50-200 mL / L calcium sulfide mixture;

[0031] As a preference,

[0032] Step 4) The stirring reaction is controlled at a temperature of 50 to 60° C. and a reaction time of 15 to 30 minutes.

[0033] The core of the technical solution of the present invention lies in using a wet chemical co-precipitation method to prepare the sulfiding agent. Triethanolamine is used to inhibit its crystal growth, and tetrahydrofuran is used to promote the precipitation of calcium polysulfide in the solution, thereby preparing nanoscale calcium polysulfide particles. This allows the calcium polysulfide particles to be more evenly dispersed in the waste acid during the subsequent sulfidation precipitation process, which is more conducive to capturing trace amounts of rhenium in the waste acid. Furthermore, the prepared calcium polysulfide can release sulfur ions only at an extremely slow rate in the waste acid solution, which can avoid the overflow of excessive hydrogen sulfide gas and reduce pollution. Furthermore, the rhenium content in the precipitated enriched slag is higher, with almost no precipitation of other metal elements. During the nanoparticle preparation stage of the preparation process, the sulfur concentration in the sulfur-containing solution, the calcium-sulfur ratio in the solution, the amount of sulfur added, the calcium polysulfide reaction time, the triethanolamine concentration, and the precipitation rate are all factors that affect the quality of the sulfidation enriched slag.

[0034] This technology uses calcium polysulfide composite reagent as a waste acid system treatment agent, which is characterized by: the calcium polysulfide undergoes controllable dissociation in an acidic medium, decomposing and releasing S x 2- 、S 2- , HS - The polysulfide active groups react selectively with rhenate and arsenite in the waste acid to form ReS2 and As2S3 composite precipitates. The As2S3 precipitate acts as a crystal nucleus carrier, adsorbing rhenium species and inducing a heterogeneous coprecipitation effect, achieving efficient rhenium enrichment. Simultaneously, calcium ions in the system react with sulfate to form calcium sulfate microcrystals, which reduce colloidal stability through surface charge neutralization. The synergistic effects of physical trapping during microcrystal growth and the formation of a three-dimensional bridging structure promote the aggregation of nano-sized sulfide particles, increasing sedimentation rates by 3-5 times compared to traditional processes and reducing solid-liquid separation time to 1 / 3 of that of traditional processes, ultimately achieving efficient separation and recovery of rhenium.

[0035] As for the selection of calcium source, the solute in the calcium-containing mixed solution can be selected as calcium chloride and / or calcium nitrate and / or calcium ethoxide, but the best one is calcium chloride, whose solution has the advantage of being easy to precisely control, because calcium chloride, compared with other calcium sources, can avoid the output and precipitation of impurities in the process of forming calcium polysulfide and producing nanoparticle precipitation, ensuring the stable performance of the prepared sulfiding agent. On the other hand, the calcium concentration should not be too high. Excessive calcium concentration can easily lead to excessive reaction, affecting the nucleation and growth process of the nanoparticles, and thus affecting the particle size and distribution of the nanoparticles. If the concentration is too low, the ions in the solution will not be fully contacted, affecting the purity and yield of calcium polysulfide.

[0036] Regarding the selection of a sulfur source, the optimal sulfur source in the sulfur-containing mixed solution is also a mixture of sodium sulfide and 1-thioglycerol. Compared to other sources, the mixture of sodium sulfide and 1-thioglycerol can quickly dissociate sulfur ions and react quickly with calcium ions. The main byproducts produced can be easily separated from the target product through conventional washing, centrifugation, and other operations. At the same time, it is also necessary to control the calcium ion concentration after the calcium-containing mixed solution and the sulfur-containing mixed solution are mixed between 0.005 and 0.05 mol / L, also to avoid excessive calcium content that can easily lead to an overly violent reaction.

[0037] In the subsequent reaction process, the present invention requires effective deoxidation and reaction in a protective atmosphere to effectively prevent the oxidation of sulfur ions and ensure that the reaction produces calcium sulfide as expected. At the same time, the long stirring reaction time in step 2) provides sufficient time and opportunity for the ions to effectively collide, ensuring the uniformity of the system and facilitating the slow crystallization of calcium sulfide nanoparticles, forming a regular crystal structure and reducing crystal defects. Subsequently, an appropriate amount of sulfur powder is added for a water boiling reaction, and the calcium sulfide is converted into calcium polysulfide after water boiling. The reaction equation of the water boiling reaction is:

[0038]

[0039] For the construction of polysulfide nanopowder, the present invention also innovatively adds triethanolamine. The amount of capping agent triethanolamine added directly affects the dispersibility of the nanoparticles. An appropriate amount of triethanolamine can form a weak adsorption layer on the surface of the particles, providing a certain amount of steric hindrance to prevent excessive agglomeration of the particles, thereby controlling the particle size to about 30nm. After the nanoparticles are formed in the solution, tetrahydrofuran is added to reduce the solubility of the nanoparticles in the mixed solvent, causing the particles to aggregate and form a turbid liquid, thereby achieving the separation and collection of the nanoparticles by filtration. However, it should be noted that if the concentration of tetrahydrofuran is too low, the nanoparticles are difficult to dissolve, resulting in a reduced yield; if the concentration is too high, it will cause excessive agglomeration of the nanoparticles and may also introduce too many organic impurities.

[0040] The beneficial effects of the present invention are:

[0041] The present invention can achieve specific adsorption and enrichment of rhenium in a contaminated acid system by constructing a stable and effective sulfiding agent. The overall method is simple and efficient, and is low in cost, easy to implement and promote. It has a wide range of raw material sources, low equipment requirements, a wide range of applications, and is conducive to industrial application. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only a portion of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0043] Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all methods known to those skilled in the art.

[0044] Example 1

[0045] A method for the extraordinary enrichment of rhenium in polluted acid based on calcium polysulfide,

[0046] The method comprises:

[0047] 1) Prepare 0.01 mol / L CaCl2 ethanol solution and 0.01 mol / L Na2S ethanol solution;

[0048] 2) nitrogen was passed through the CaCl2 ethanol solution for 10 minutes to deoxygenate the solution, and then the deoxygenated CaCl2 ethanol solution and the Na2S ethanol solution were mixed in an equal ratio of 1:1 by volume and stirred for 10 hours to obtain a calcium sulfide mixture;

[0049] 3) adding 5 g / L sulfur to the calcium sulfide mixture at a ratio of 50 mL / L of the calcium sulfide mixture, boiling the mixture for 20 minutes, adding triethanolamine to achieve grain growth, adding tetrahydrofuran dropwise, centrifuging to separate the solid, ultrasonically cleaning the solid with anhydrous ethanol, and drying the solid; 4) adding the nanopowder to the waste acid at a ratio of 1 g / L of the waste acid, stirring to react for 20 minutes, and then filtering and separating to obtain the rhenium sulfide-enriched slag.

[0050] The rhenium concentration in the waste acid before the nanopowder was added and stirred in step 4) was characterized and recorded as the initial Re content. The rhenium concentration in the waste acid after the nanopowder was added and stirred in step 4) was characterized and recorded as the residual Re content. The precipitation efficiency was calculated as ((initial Re content - residual Re content) / initial Re content) × 100%.

[0051] The characterization results show that this example achieved a rhenium precipitation efficiency of 95.83%.

[0052] Example 2

[0053] A method for the extraordinary enrichment of rhenium in polluted acid based on calcium polysulfide,

[0054] The method comprises:

[0055] 1) Prepare 0.01 mol / L Ca(NO3)2 ethanol solution and 0.01 mol / L Na2S ethanol solution;

[0056] 2) nitrogen was passed through the Ca(NO3)2 ethanol solution for 10 minutes to deoxygenate the solution, and then the deoxygenated Ca(NO3)2 ethanol solution and the Na2S ethanol solution were mixed in an equal ratio of 1:1 by volume and stirred for 10 hours to obtain a calcium sulfide mixture;

[0057] 3) 5 g / L sulfur was added to the calcium sulfide mixture at a ratio of 50 mL / L, and the mixture was boiled in water for 20 minutes. Triethanolamine was then added to achieve grain growth, and tetrahydrofuran was added dropwise, followed by centrifugation to separate the solid. The solid was ultrasonically cleaned with anhydrous ethanol and dried. The resulting nanopowder was characterized, and the average particle size was 300 ± 5 nm.

[0058] 4) adding the nanopowder to the waste acid at a ratio of 1 g / L of waste acid, stirring and reacting for 20 minutes, and then filtering and separating to obtain rhenium sulfide-enriched slag.

[0059] The rhenium concentration in the waste acid before the nanopowder was added and stirred in step 4) was characterized and recorded as the initial Re content. The rhenium concentration in the waste acid after the nanopowder was added and stirred in step 4) was characterized and recorded as the residual Re content. The precipitation efficiency was calculated as ((initial Re content - residual Re content) / initial Re content) × 100%.

[0060] The characterization results show that this example achieved a rhenium precipitation efficiency of 93.28%.

[0061] Example 3

[0062] A method for the extraordinary enrichment of rhenium in polluted acid based on calcium polysulfide,

[0063] The method comprises:

[0064] 1) Prepare 0.01 mol / L CaCl2 ethanol solution and 0.01 mol / L 1-thioglycerol ethanol solution;

[0065] 2) nitrogen was passed through the CaCl2 ethanol solution for 10 minutes to deoxygenate the solution, and then the deoxygenated CaCl2 ethanol solution was mixed with the 1-thioglycerol ethanol solution in a volume ratio of 1:1 and stirred for 10 hours to obtain a calcium sulfide mixture;

[0066] 3) 5 g / L sulfur was added to the calcium sulfide mixture at a ratio of 50 mL / L, and the mixture was boiled in water for 20 minutes. Triethanolamine was then added to achieve grain growth, and tetrahydrofuran was added dropwise, followed by centrifugation to separate the solid. The solid was ultrasonically cleaned with anhydrous ethanol and dried. The resulting nanopowder was characterized, and the average particle size was 300 ± 5 nm.

[0067] 4) adding the nanopowder to the waste acid at a ratio of 1 g / L of waste acid, stirring and reacting for 20 minutes, and then filtering and separating to obtain rhenium sulfide-enriched slag.

[0068] The rhenium concentration in the waste acid before the nanopowder was added and stirred in step 4) was characterized and recorded as the initial Re content. The rhenium concentration in the waste acid after the nanopowder was added and stirred in step 4) was characterized and recorded as the residual Re content. The precipitation efficiency was calculated as ((initial Re content - residual Re content) / initial Re content) × 100%.

[0069] The characterization results show that this example achieved a rhenium precipitation efficiency of 91.77%.

[0070] Example 4

[0071] A method for the extraordinary enrichment of rhenium in polluted acid based on calcium polysulfide,

[0072] The method comprises:

[0073] 1) Prepare 0.01 mol / L CaCl2 ethanol solution and 0.01 mol / L L-cysteine ​​ethanol solution;

[0074] 2) nitrogen was passed through the CaCl2 ethanol solution for 10 minutes to deoxygenate, and then the deoxygenated CaCl2 ethanol solution and the L-cysteine ​​ethanol solution were mixed in an equal ratio of 1:1 by volume and stirred for 10 hours to obtain a calcium sulfide mixture;

[0075] 3) 5 g / L sulfur was added to the calcium sulfide mixture at a ratio of 50 mL / L, and the mixture was boiled in water for 20 minutes. Triethanolamine was then added to achieve grain growth, and tetrahydrofuran was added dropwise, followed by centrifugation to separate the solid. The solid was ultrasonically cleaned with anhydrous ethanol and dried. The resulting nanopowder was characterized, and the average particle size was 300 ± 5 nm.

[0076] 4) adding the nanopowder to the waste acid at a ratio of 1 g / L of waste acid, stirring and reacting for 20 minutes, and then filtering and separating to obtain rhenium sulfide-enriched slag.

[0077] The rhenium concentration in the waste acid before the nanopowder was added and stirred in step 4) was characterized and recorded as the initial Re content. The rhenium concentration in the waste acid after the nanopowder was added and stirred in step 4) was characterized and recorded as the residual Re content. The precipitation efficiency was calculated as ((initial Re content - residual Re content) / initial Re content) × 100%.

[0078] The characterization results show that this example achieved a rhenium precipitation efficiency of 94.35%.

[0079] Examples 5 to 16

[0080] A method for the extraordinary enrichment of rhenium in polluted acid based on calcium polysulfide,

[0081] The method comprises:

[0082] 1) preparing CaCl2 ethanol solution and Na2S ethanol solution;

[0083] 2) nitrogen is passed through the CaCl2 ethanol solution to deoxygenate it, and then the deoxygenated CaCl2 ethanol solution and the Na2S ethanol solution are mixed in an equal ratio of 1:1 by volume and stirred to obtain a calcium sulfide mixture;

[0084] 3) adding 5 g / L sulfur to the calcium sulfide mixture and boiling it in water for reaction, then adding triethanolamine to achieve grain growth and adding tetrahydrofuran dropwise, centrifuging and separating the solids, ultrasonically cleaning with anhydrous ethanol, and drying;

[0085] 4) adding the nanopowder to the waste acid at a ratio of 1 g / L of waste acid, stirring and reacting for 20 minutes, and then filtering and separating to obtain rhenium sulfide-enriched slag.

[0086] The rhenium concentration in the waste acid before the nanopowder was added and stirred in step 4) was characterized and recorded as the initial Re content. The rhenium concentration in the waste acid after the nanopowder was added and stirred in step 4) was characterized and recorded as the residual Re content. The precipitation efficiency was calculated as ((initial Re content - residual Re content) / initial Re content) × 100%.

[0087] The characterization results show that this example achieved a rhenium precipitation efficiency of 95.83%.

[0088] Multiple experimental treatments were carried out with the concentrations of CaCl2 ethanol solution and Na2S ethanol solution (Ca concentration and S concentration), sulfur concentration, nitrogen deoxygenation time (ventilation time), step 2) water boiling time (reaction time), the amount of triethanolamine per liter of calcium sulfide mixture (TEOA amount) and the amount of tetrahydrofuran per liter of calcium sulfide mixture (THF amount) as variables.

[0089] The details are shown in the following table.

[0090]

[0091] The average particle size of the nanopowder obtained in step 3) and the rhenium precipitation efficiency in the treatment process of step 4) in each test group were detected and characterized. The characterization results are shown in the following table.

[0092]

[0093]

[0094] It can be clearly seen from the above Examples 5 to 16 and the test results in the above table that the calcium polysulfide powder prepared by the method of the present invention has a small size, high controllability, and excellent selective precipitation ability. Its application in a rhenium-containing solution can achieve efficient separation of rhenium and other impurities.

Claims

1. A method for the extraordinary enrichment of rhenium in polluted acid based on calcium polysulfide, characterized in that: The method comprises: 1) Using anhydrous ethanol as solvent, prepare a calcium-containing mixed solution and a sulfur-containing mixed solution respectively; 2) nitrogen is passed through the calcium-containing mixed solution to deoxygenate it, and then the deoxygenated calcium-containing mixed solution is mixed with the sulfur-containing mixed solution and stirred to obtain a calcium sulfide mixed solution; 3) After adding sulfur to the calcium sulfide mixture and boiling it in water for reaction, triethanolamine and tetrahydrofuran are added and the solids are separated by centrifugation, and then washed and dried in sequence to obtain nanopowder; 4) Add the nanopowder to the waste acid and stir to react, then filter and separate to obtain rhenium sulfide-enriched slag.

2. The method for super-enrichment of rhenium in polluted acid based on calcium polysulfide according to claim 1, characterized in that: Step 1) the calcium-containing mixed solution is an ethanol solution of calcium chloride and / or calcium nitrate and / or calcium acetate; Step 1) The calcium ion concentration in the calcium-containing mixed solution is 0.01 to 0.05 mol / L; Step 1) The sulfur-containing mixed solution is an ethanol solution of sodium sulfide and / or L-cysteine ​​and / or 1-thioglycerol.

3. The method for super-enrichment of rhenium in polluted acid based on calcium polysulfide according to claim 1, characterized in that: The nitrogen flow time in step 2) is 10 to 20 minutes.

4. The method for super-enrichment of rhenium in polluted acid based on calcium polysulfide according to claim 1, characterized in that: Step 2) When the calcium-containing mixed solution is mixed with the sulfur-containing mixed solution, the molar ratio of S to Ca is controlled to be (0.2-5):1; Step 2) The stirring time after mixing is 10 to 16 hours.

5. The method for super-enrichment of rhenium in polluted acid based on calcium polysulfide according to claim 1, characterized in that: Step 3) The amount of sulfur added is 10-20 g / L, the reaction time is 20-40 min, and the reaction temperature is 40-60°C; Step 3) the amount of triethanolamine added is 5-20 g / L calcium sulfide mixture; In step 3), the amount of tetrahydrofuran added is 50 to 200 mL / L of the calcium sulfide mixture.

6. The method for super-enrichment of rhenium in polluted acid based on calcium polysulfide according to claim 1, characterized in that: In step 4), the stirring reaction is carried out at a temperature of 50-60° C. and a reaction time of 15-30 min.

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