A method for separating molybdenum and indium by selective extraction from a high-acid high-arsenic solution containing multi-metal impurities

Abstract

This invention provides a method for selectively extracting and separating molybdenum and indium from a high-acid, high-arsenic solution containing polymetallic impurities, belonging to the field of hydrometallurgy and extraction separation technology. The method includes: using Cyanex-272 and TBP to synergistically extract molybdenum, obtaining a molybdenum-loaded organic phase and a raffinate containing indium, iron, and other cations after phase separation; back-extracting the obtained molybdenum-loaded organic phase using an alkaline back-extracting agent to obtain a molybdenum-rich solution; adding iron powder to the obtained raffinate to remove Fe... 3+ Reduced to Fe 2+ After the reaction, the solution is filtered to obtain the reduced solution. The reduced solution is then extracted with a modified P204 organic phase, and after phase separation, an indium-loaded organic phase and a raffinate containing impurities such as iron, cadmium, and arsenic are obtained. The obtained indium-loaded organic phase is back-extracted using an acidic back-extracting agent to obtain an indium-rich solution. This invention forms a complete process flow for the stepwise extraction and separation of molybdenum and indium. The organic phase used has a simple composition, fast phase separation speed, minimal extractant loss, good separation effect of molybdenum and indium, and minimal loss of other cations such as iron during co-extraction, making it easy to industrialize.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgy and extraction separation technology, specifically relating to a method for selectively extracting and separating molybdenum and indium from a high-acid, high-arsenic solution containing polymetallic impurities. Background Technology

[0002] Molybdenum (Mo) and indium (In) are both essential strategic metals for modern high-tech industries. Molybdenum is widely used in alloy steel, catalysts, and electronic components; indium is a crucial material for manufacturing liquid crystal displays (LCDs), thin-film solar cells, and semiconductor components. With declining primary resource grades and increasingly stringent environmental regulations, recovering molybdenum and indium from secondary resources is of great significance. Copper ash (white ash) produced during copper smelting is a key carrier for simultaneously enriching molybdenum and indium, with molybdenum and indium contents reaching 0.2% to 2%. However, copper ash has an extremely complex composition, often accompanied by high concentrations of elements such as arsenic, iron, zinc, and cadmium. Industrially, acid leaching is commonly used to treat copper ash, allowing molybdenum, indium, copper, zinc, cadmium, and arsenic to enter the solution, while lead, bismuth, and silver remain in the slag. The resulting leachate has extremely high acidity (pH often below 0.5) and contains high concentrations of arsenic (up to 10-20 g / L), iron (up to over 10 g / L), and impurities such as cadmium, zinc, and copper, making it a typical complex solution with high arsenic, high acidity, and multiple metals coexisting.

[0003] Achieving selective separation of molybdenum and indium in this specific solution system faces three severe challenges: First, the concentration of the target metal is vastly different from that of impurities. For example, in typical leachates, impurities such as iron, arsenic, zinc, and cadmium often reach concentrations of 10–30 g / L, while the concentrations of molybdenum and indium are only a few hundred mg / L. The extraction system must preferentially identify and capture the low concentration of the target metal in the presence of numerous competing ions. Second, the chemical behaviors of molybdenum, indium, iron, and other cations are highly similar, resulting in an extremely narrow separation window. Under strongly acidic conditions, molybdenum, as a molybdenum acyl cation (MoO2),... 2+ Indium exists in the form of In 3+ Iron exists in the form of Fe. 3+ The three substances exist in the form of their sulfate complexes, and all three are easily co-extracted by conventional acidic phosphorus extractants. A single extractant cannot simultaneously achieve both high extraction rates and high selectivity. Thirdly, the coupling interference effect caused by high iron and high arsenic levels hinders conventional separation methods. Chemical precipitation results in low product purity due to co-precipitation of ferric arsenate; ion exchange methods suffer from resin poisoning due to excessively high solution acidity, leading to a significant decrease in exchange capacity.

[0004] In the field of solvent extraction, acidic phosphorus extractants such as bis(2-ethylhexyl)phosphoric acid (P204) have the ability to extract indium, but when dealing with strongly acidic solutions containing molybdenum and iron, P204 will co-extract molybdenum and iron simultaneously, making it difficult to achieve selective separation of indium from molybdenum and iron. Neutral phosphorus extractants such as tributyl phosphate (TBP) and trialkyl phosphorus oxide (TRPO) have low co-extraction rates for iron and indium, but their extraction ability for molybdenum is limited, with extraction rates typically below 10%. Di(2,4,4-trimethylpentyl)phosphonic acid (Cyanex-272) has a certain extraction ability for molybdenum, but when used alone, it still leads to co-extraction of indium and iron. Some studies have attempted to use TBP and Cyanex-272 in combination, but without modification, the molybdenum extraction rate is still not ideal. If an alkaline extraction system is used, the extractant is usually required to work under alkaline solution conditions. However, copper ash leaching solution is a strongly acidic system. If the solution is adjusted to alkaline, not only will the acid and alkali consumption be large, but the high concentration of iron, arsenic, zinc, and cadmium in the solution will also generate a large amount of colloidal precipitates, entraining and co-precipitating molybdenum and indium.

[0005] Therefore, developing a method for the sequential selective extraction and separation of molybdenum and indium under conditions of high acidity, high arsenic, high iron, high cadmium, high zinc, and low concentration of the target metal is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a method for selective extraction and separation of molybdenum and indium from a highly acidic, high-arsenic solution containing multiple metal impurities. This solution is strongly acidic and contains high levels of impurities such as arsenic, iron, and cadmium, with low concentrations of the target metal. The method combines a co-extraction system of saponified Cyanex-272 and TBP, iron powder reduction, and a saponified P204 extraction system. Through a specific sequence of steps, molybdenum and indium are separated in stages.

[0007] To achieve the above objectives, the main technical solution of the present invention is as follows:

[0008] A method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities includes the following steps:

[0009] (1) Modified bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex-272) and tributyl phosphate (TBP) co-extraction of molybdenum: The pH of the acidic solution containing molybdenum, indium, iron and polymetallic impurities was adjusted to -1.5~0.5; extraction was performed using a mixed organic phase containing modified Cyanex-272 and TBP, and after phase separation, a molybdenum-loaded organic phase and a raffinate containing indium, iron and other cations were obtained.

[0010] (2) Back-extraction of molybdenum: The molybdenum-loaded organic phase obtained in step (1) is back-extracted using an alkaline back-extraction agent with a pH of 7.5~13.0. Molybdenum enters the aqueous phase in the form of oxyanions to obtain a molybdenum-rich solution. The organic phase can be regenerated and returned to step (1) for use.

[0011] (3) Iron powder reduction: Add iron powder to the raffinate obtained in step (1) to reduce Fe 3+ Reduced to Fe 2+ After the reaction, the solution was filtered to obtain the reduced solution.

[0012] (4) Modified P204 extraction of indium: Adjust the pH of the reduced solution obtained in step (3) to 0.0~2.5, extract with modified P204 organic phase, and obtain indium-loaded organic phase and raffinate containing impurities such as iron, cadmium and arsenic after phase separation.

[0013] (5) Indium back-extraction: The indium-loaded organic phase obtained in step (4) is back-extracted using an acidic back-extraction agent with a concentration of 1~7 mol / L to obtain an indium-rich solution.

[0014] Preferably, in step (1), the acidic solution is an acidic leaching solution of copper ash, wherein the content of arsenic is 10~20 g / L, the content of iron is 10~15 g / L, the content of cadmium is 10~25 g / L, the content of zinc is 10~30 g / L, the content of molybdenum is 200~1000 mg / L, the content of indium is 200~1000 mg / L, and the pH value is -0.5~0.5.

[0015] Preferably, in step (1), the pH value is -1.0 to 0.2.

[0016] Preferably, in step (1), the modified Cyanex-272 is obtained by partial saponification pretreatment of Cyanex-272 with alkali, which can convert some of its dimers into monomers or ionic states with higher activity, and the degree of saponification is controlled at 5%~50%. Under strongly acidic conditions, this co-extraction system revolves around MoO2. 2+ The formation of highly stable mixed coordination complexes significantly enhances molybdenum extraction, while the competitive hydrogen bonding of TBP to the Cyanex-272 hydroxyl groups and steric hindrance greatly inhibits Fe extraction. 3+ In 3+ Co-extraction of isocations. Further, the volume concentration of modified Cyanex-272 in the organic phase is 5%~40%, the volume concentration of TBP is 5%~25%, and the total volume concentration of the extractant does not exceed 50% of the total volume of the organic phase; wherein the volume ratio (O / A) of the organic phase to the aqueous phase is 1:8~8:1.

[0017] In the co-extraction system, Cyanex-272 is the main active component for molybdenum extraction, while TBP mainly inhibits the co-extraction of indium, iron, and other cations. The preferred volume concentrations of both are 10%–20%. If the Cyanex-272 concentration is too low, the molybdenum extraction rate will be insufficient; if the TBP concentration is too low, the effect of inhibiting the co-extraction of indium, iron, and other cations will be limited. The total concentration of both is preferably 20%–35%, which ensures a high molybdenum extraction rate while keeping the co-extraction rate of indium, iron, and other cations at a low level.

[0018] Preferably, in step (1), the alkali used for modifying Cyanex-272 and modifying P204 in step (4) is independently selected from at least one of sodium hydroxide, potassium hydroxide, ammonia, and sodium carbonate, and the saponification temperature is 10~80 ℃ and the saponification time is 20~120 minutes.

[0019] Preferably, in step (1), the extraction temperature is 15~65 ℃, the extraction time is 5~25 minutes, and the extraction stage is 1~5 stages.

[0020] Preferably, in step (2), the alkaline back-extraction agent is selected from ammonia water, ammonium carbonate, sodium carbonate or sodium hydroxide solution.

[0021] Preferably, in step (2), the back-extraction temperature is 15~80 ℃, the back-extraction time is 3~25 minutes, and the number of back-extraction stages is 1~5.

[0022] Preferably, in step (3), iron powder is added to Fe 3+ Reduced to Fe 2+ The reason is: Fe 2+ With a large hydration radius and low charge density, it has a much weaker affinity for acidic phosphorus extractants than Fe. 3+ This allows for the complete separation of iron and indium in subsequent extraction. Additionally, the reduction product of iron powder, Fe... 2+ Since the iron powder is an existing component in the raffinate from step (1), adding iron powder will not introduce Fe into the solution. 2+ Other cations or anions besides iron. Further, the amount of iron powder added is 0.8 to 2.5 times the theoretically calculated mass required to reduce ferric iron, and the reduction conditions are stirring at 15 to 70 °C for 10 to 90 minutes to reduce ferric iron in the solution to ferrous iron.

[0023] Preferably, in step (4), the pH value is 0.2 to 1.4.

[0024] Preferably, in step (4), the modified P204 is obtained by partial saponification of P204 with alkali, with the degree of saponification controlled at 10%~70%. Sodium ions replace some of the acidic hydrogen, which buffers the acidity changes in the aqueous phase during extraction, significantly improving the extraction driving force and saturation capacity of indium; simultaneously, Fe... 2+ The affinity for modified P204 is extremely weak, and it is basically not extracted. Furthermore, the volume concentration of the modified P204 in the organic phase is 10%~45%, and the degree of saponification is 10%~70%; wherein the volume ratio (O / A) of the organic phase to the aqueous phase is 1:8~8:1.

[0025] Preferably, in step (4), the extraction temperature is 15~60 ℃, the extraction time is 3~25 minutes, and the extraction stage is 1~5 stages.

[0026] Preferably, in step (5), the acidic back-extraction agent is selected from hydrochloric acid, sulfuric acid or nitric acid solution, and its concentration is 1~7 mol / L.

[0027] Preferably, in step (5), the back-extraction temperature is 15~65 ℃, the back-extraction time is 3~30 minutes, and the number of back-extraction stages is 1~5.

[0028] Preferably, the organic phase described in steps (1) and (4) has a diluent independently selected from sulfonated kerosene, n-heptane, n-hexane, or aromatic hydrocarbon solvents.

[0029] The technical principle of the above method is as follows:

[0030] Under strongly acidic conditions (pH -1.5~0.5), particularly in the acidic leaching solution of copper flue gas as described in this invention, molybdenum exists as a molybdenum acyl cation (MoO2). 2+ It exists as a small amount of neutral molybdate molecules (H2MoO4); iron exists as ferric ions (Fe3+). 3+ Indium exists as a trivalent cation (In) and its sulfate complexes. 3+ Arsenic, zinc, cadmium, etc., exist in the form of cations or oxygen-containing anions, respectively.

[0031] In step (1), when modified Cyanex-272 is used in combination with TBP, the following synergistic effects occur:

[0032] After partial saponification pretreatment with alkali, the P-OH portion of the dimer of Cyanex-272 is converted into PO-Na. + The dimer structure is opened, releasing active monomers and significantly enhancing the activity of MoO2. 2+ Cation exchange capacity. The use of TBP causes the P=O in it to preferentially form intermolecular hydrogen bonds with the P-OH in Cyanex-272, consuming the cation exchange capacity that would otherwise be formed with Fe.3+ In 3+ The free sites for coordination significantly reduce the co-extraction rate of indium and iron. The aforementioned saponification activation effect, addition synergistic effect, and steric hindrance effect keep the molybdenum extraction rate above 95%, while the co-extraction rate of cations such as iron and indium drops below 5%.

[0033] Extraction of MoO2 2+ The reaction equation is shown in equation (1):

[0034] MoO2 2+ (aq) +2(HA) 2(org) → MoO2(HA2) 2(org) +2H + (aq) (1)

[0035] In step (3), the principle of using iron powder to reduce the raffinate obtained in step (1) is as follows:

[0036] Fe in the raffinate 3+ It possesses strong oxidizing and coordinating abilities, causing severe interference during subsequent indium extraction with P204. Adding iron powder to the raffinate triggers a displacement reaction to generate Fe. 2+ Fe 2+ It has a larger hydration radius and lower charge density, making it less likely to form anionic sulfate complexes, and its affinity for P2O4 is much weaker than that for Fe. 3+ Therefore, Fe 3+ Reduced to Fe 2+ Afterwards, it can effectively suppress its co-extraction behavior in subsequent extraction processes.

[0037] The equation for the reduction of ferric iron by iron powder is shown in equation (2):

[0038] 2Fe 3+ + Fe → 3Fe 2+ (2)

[0039] In step (4), the principle of using modified P204 to extract indium is as follows:

[0040] The P2O4 obtained after partial saponification pretreatment with alkali has some of its acidic hydrogen replaced by sodium ions, etc., and H2O is released during cation exchange in the extraction process. + Reducing pH levels effectively buffers changes in the aqueous phase acidity, allowing the extraction process to proceed under more stable pH conditions, significantly improving the extraction driving force and saturation capacity of indium. Under pH conditions of 0.0–2.5, In… 3+ The reaction with modified P204 produces an extract that enters the organic phase, while Fe... 2+ At this acidity, the affinity for modified P204 is extremely weak, resulting in a very low extraction rate. Since the Fe2O3 was already extracted in the previous step...3+ Reduced to Fe 2+ Furthermore, arsenic, zinc, cadmium, and other elements in the solution are essentially not extracted under these pH conditions, thus enabling efficient recovery of indium.

[0041] The extraction reaction equation is shown in equation (3):

[0042] In 3+ (aq) +3 (HR) 2(org) → InR3·3HR (org) +3H + (aq) (3)

[0043] Steps (1), (3), and (4) in the above scheme must be performed in sequence, based on the following technical basis: Step (1) In a strong acid solution environment, the modified Cyanex-272 and TBP are preferentially used to remove MoO2. 2+ Extracted from solution into the organic phase, allowing In 3+ and Fe 3+ It is retained in the raffinate. After step (1) is completed, step (3) is performed. At this point, the raffinate is basically free of hexavalent molybdenum, and the iron powder specifically reacts with Fe. 3+ The reaction produces Fe 2+ If iron powder reduction is performed before step (1), the MoO2 present in the solution... 2+ Under reducing conditions, it will be partially reduced to low-valence molybdenum oxide, which will not only lead to a decrease in the subsequent molybdenum extraction rate, but also cause irreversible loss of molybdenum.

[0044] If step (4) is performed directly before step (1), that is, indium is extracted from the original solution using modified P204, P204 will be used in the extraction of In. 3+ Simultaneous co-extraction of large amounts of MoO2 2+ and Fe 3+ This makes selective separation of molybdenum from cations such as indium and iron impossible. Therefore, step (4) is performed after step (3). At this point, molybdenum has been removed from the solution, and iron is separated as Fe. 2+ It exists in the form of In. Under conditions of pH 0.0–2.5, In... 3+ The modified P204 was extracted into the organic phase, and Fe 2+ It is basically not extracted.

[0045] In summary, the sequence of steps determined in the technical solution—molybdenum extraction followed by iron powder reduction and then indium extraction—distinguishes from existing technologies that either reduce first and then extract or extract indium first and then molybdenum. The preferential extraction of molybdenum provides the necessary conditions for the subsequent specific reduction of iron powder, while the valence state transformation of iron eliminates interference with indium extraction. These three steps are sequentially linked and none can be omitted.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] This invention employs a binary mixed extractant composed of saponified Cyanex-272 and TBP to preferentially extract molybdenum from complex solutions containing high levels of arsenic, acid, cadmium, iron, and zinc. This is combined with iron powder reduction and saponified P204 for selective indium extraction, forming a complete process for the stepwise extraction and separation of molybdenum and indium. This method utilizes a simple organic phase composition, exhibits rapid phase separation, minimizes extractant loss, achieves excellent molybdenum and indium separation, minimizes co-extraction losses of iron and other cations, has a wide process parameter window, offers high operational flexibility, and is easily industrialized. It is particularly suitable for treating complex secondary resource leachates and waste acids containing molybdenum, indium, and other cations. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a process flow diagram of the method for selectively extracting and separating molybdenum and indium from a high-acid, high-arsenic solution containing polymetallic impurities, provided by the present invention. Detailed Implementation

[0050] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0051] Example 1

[0052] (a) Molybdenum extraction using TBP alone: ​​Take 50 ml of white soot leachate from a copper smelter, with a pH of 0.16. The specific concentrations of each element in the solution are shown in Table 1.

[0053] Table 1. Composition Analysis of White Flue Ash Leachate from a Copper Smelter

[0054]

[0055] Tributyl phosphate (TBP), a neutral extractant, was dissolved in sulfonated kerosene to prepare an organic phase with a TBP volume concentration of 30%. The organic phase and the feed solution were mixed at a volume ratio of 1:1 at 30 °C and placed in a constant-temperature shaker at 280 r / min for 10 minutes. After primary extraction and phase separation by settling, the metal concentration in the aqueous phase was measured, and the extraction rate was calculated. The results are shown in Table 2 below.

[0056] Table 2. Composition analysis of raffinate after extraction with neutral extractant TBP.

[0057]

[0058] Results: The extraction rates were 5.2% for Mo, 1.5% for In, 2.7% for Fe, 0.9% for As, 2.1% for Zn, and 1.3% for Cd. These results indicate that using neutral extractants such as TBP alone results in low extraction rates for each metal, making efficient recovery of molybdenum or indium impossible.

[0059] (b) Co-extraction of molybdenum by TBP and TRPO: 50 mL of the same white soot leachate as in Example 1(a) was taken. Tributyl phosphate (TBP) and trialkyl phosphorus oxide (TRPO) were dissolved in sulfonated kerosene at a volume fraction of 15%, with a total extractant concentration of 30%. The organic phase and the feed solution were mixed at a volume ratio of 1:1 at 30°C and shaken at 280 r / min for 10 minutes. After first-stage extraction and phase separation by settling, the metal concentration in the aqueous phase was measured, and the extraction rate was calculated. The results are shown in Table 3 below.

[0060] Table 3. Composition analysis of raffinate after synergistic extraction with neutral extractants TBP and TRPO.

[0061]

[0062] Results: The extraction rates were 6.48% for Mo, 1.17% for In, and 2.35% for Fe. Compared to Example 1(a) using TBP alone, the molybdenum extraction rate increased from 5.20% to 6.48% when TBP was used in combination with TRPO, but this was still far below the level required for effective recovery. The above comparison indicates that neutral phosphorus extractants, whether used alone or in combination, have very limited extraction capacity for molybdenum and cannot meet the requirements for recovering molybdenum from this acidic solution.

[0063] Example 2

[0064] (a) Preferential extraction of molybdenum using unsaponifiable-modified Cyanex-272: Take 50 mL of the same white soot leachate as in Example 1. Dissolve the extractant Cyanex-272 in sulfonated kerosene to prepare an organic phase with a Cyanex-272 volume concentration of 30%. At 30 °C, mix the organic phase and the feed solution at a volume ratio of 1:1, place in a constant temperature shaker, and shake at 280 r / min for 10 minutes. After first-stage extraction and phase separation by standing, measure the metal concentration in the aqueous phase and calculate the extraction rate. The results are shown in Table 4 below:

[0065] Table 4. Composition analysis of raffinate after Cyanex-272 extraction

[0066]

[0067] Results: The extraction rates were 91.52% for Mo, 22.54% for In, 28.01% for Fe, 5.37% for As, 7.46% for Zn, and 5.49% for Cd. These results indicate that while Cyanex-272 alone achieves a high extraction rate for molybdenum, severe co-extraction with indium, iron, and other cations results in poor selectivity for molybdenum.

[0068] (b) Preferential extraction of molybdenum using saponified Cyanex-272: Take 50 mL of the same white soot leachate as in Example 1. Take Cyanex-272 and slowly add a measured amount of 2 mol / L NaOH solution at 40 °C until the degree of saponification reaches 50%. Stir for 30 minutes to obtain saponified Cyanex-272. Dissolve the modified extractant in sulfonated kerosene to prepare an organic phase with a volume concentration of 15%. At 30 °C, mix the organic phase and the feed solution at a volume ratio of 1:1 and place in a constant temperature shaker. Shake at 280 r / min for 10 minutes. After first-stage extraction and phase separation, measure the metal concentration in the aqueous phase and calculate the extraction rate. The results are shown in Table 5 below:

[0069] Table 5. Composition analysis of raffinate after extraction with saponified modified Cyanex-272.

[0070]

[0071] Results: The Mo extraction rate was 96.40%, the In extraction rate was 9.10%, and the Fe extraction rate was 14.02%. Compared with Example 2(a) (unsaponified Cyanex-272, Mo extraction rate 91.52%, In extraction rate 22.54%, Fe extraction rate 28.01%), the saponification treatment increased the Mo extraction rate from 91.52% to 96.40%, decreased the In co-extraction rate from 22.54% to 9.10%, and decreased the Iron co-extraction rate from 28.01% to 14.02%, indicating that saponification treatment can enhance the extraction efficiency of MoO2 by Cyanex-272. 2+ It has the cation exchange capacity and, to some extent, inhibits the co-extraction of indium and iron. However, when saponified Cyanex-272 is used alone, the co-extraction rate of indium and iron is still too high, which cannot meet the requirements for high selective separation of molybdenum from indium and iron.

[0072] (c) Co-extraction of molybdenum by saponified Cyanex-272 and TBP: Take 50 mL of the same white soot leachate as in Example 1. Take Cyanex-272 and slowly add a measured amount of 2 mol / L NaOH solution at 40 °C to achieve a saponification degree of 50%. Stir for 30 minutes to obtain saponified Cyanex-272. Dissolve the modified extractant and TBP at 15% by volume in sulfonated kerosene, with a total extractant concentration of 30%. At 30 °C, mix the organic phase and the feed solution at a volume ratio of 1:1 and place in a constant temperature shaker. Shake at 280 r / min for 10 minutes. After first-stage extraction and phase separation by standing, measure the metal concentration in the aqueous phase and calculate the extraction rate. The results are shown in Table 6 below:

[0073] Table 6. Composition analysis of raffinate after synergistic extraction with saponified modified Cyanex-272 and TBP.

[0074]

[0075] Results: The extraction rates were 95.50% for Mo, 1.48% for In, and 1.14% for Fe. Compared to the result without TBP (Mo extraction rate 96.40%, In co-extraction rate 9.10%, Fe co-extraction rate 14.02%), the addition of TBP reduced the indium co-extraction rate from 9.10% to 1.48%, the iron co-extraction rate from 14.02% to 1.14%, while maintaining the molybdenum extraction rate above 95%. This indicates that the synergistic use of saponified Cyanex-272 and TBP can significantly suppress the co-extraction of indium and iron while maintaining a high molybdenum extraction rate, achieving highly selective separation of molybdenum from indium and iron.

[0076] Example 3

[0077] (a) Preferential extraction of indium using unsaponified modified P204: Take 50 mL of the same white soot leachate as in Example 1. Dissolve the extractant P204 in sulfonated kerosene to prepare an organic phase with a P204 volume concentration of 30%. At 40 °C, mix the organic phase and the feed solution at a volume ratio of 1:1, place in a constant temperature shaker, and shake at 280 r / min for 10 minutes. After first-stage extraction and phase separation by standing, measure the metal concentration in the aqueous phase and calculate the extraction rate. The results are shown in Table 7 below:

[0078] Table 7. Composition analysis of the raffinate after preferential indium extraction using P204.

[0079]

[0080] Results: The extraction rates were 87.04% for In, 74.26% for Mo, 22.38% for Fe, 3.15% for As, 3.09% for Zn, and 2.17% for Cd. These results indicate that while the extraction rate of indium from the original leachate using unsaponified P2O4 is relatively high, severe co-extraction of molybdenum and iron prevents the selective separation of indium from molybdenum and iron.

[0081] (b) Preferential extraction of indium from saponified P204: Take 50 mL of the same white soot leachate as in Example 1. Dissolve P204 in sulfonated kerosene to prepare an organic phase with a volume concentration of 30%. Slowly add 3 mol / L NaOH solution at 35 °C to achieve a saponification degree of 40%, and stir until homogeneous. Extract for 10 minutes at a ratio of O / A = 1:1 and a temperature of 40 °C. Allow to stand and separate the phases to obtain the indium-loaded organic phase and the raffinate. The results are shown in Table 8 below:

[0082] Table 8. Composition analysis of the residual liquid after indium extraction

[0083]

[0084] Results: The extraction rates were 93.00% for In, 72.96% for Mo, and 20.56% for Fe. Compared to the extraction results of unsaponified modified P204 (In extraction rate 87.04%, Mo extraction rate 74.26%, Fe extraction rate 22.38%), the extraction rate of indium by modified P204 increased from 87.04% to 93.00%, but the co-extraction rate of molybdenum remained as high as 72.96%, and the co-extraction rate of iron remained at 20.56%. These comparisons indicate that although modified P204 has a higher extraction rate for indium, the large-scale co-extraction of molybdenum and iron during indium extraction, coupled with the difficulty in effectively recovering the molybdenum remaining in the raffinate, necessitates indium extraction only after molybdenum extraction.

[0085] Example 4

[0086] Take 50 mL of the same white soot leachate as in Example 1, add 1.5 times the theoretical amount of reduced iron powder, and stir the mixture at 50°C for 30 minutes to react the Fe. 3+ Reduced to Fe 2+ The reduced solution was obtained by filtration, and the pH value of the solution increased from 0.16 to 0.23. The concentrations of various ions in the reduced solution were measured, and the results are shown in Table 9 below:

[0087] Table 9. Composition analysis of the solution after iron powder reduction.

[0088]

[0089] Results: After reduction with iron powder, Fe... 3+ All converted to Fe2+ The total iron concentration increased from 11.48 g / L to 14.72 g / L, an increase of approximately 3.24 g / L. The Mo concentration decreased from 686.26 mg / L to 580.2 mg / L, with approximately 15.5% of the Mo being reduced to molybdenum blue precipitate and removed during filtration. The concentrations of other elements remained essentially unchanged.

[0090] The reduced solution was prepared by dissolving Cyanex-272 (50% saponification degree) and TBP (15% by volume) in sulfonated kerosene to form an organic phase. The solution was extracted at 30 °C and a 1:1 phase ratio for 10 minutes. After standing and phase separation, the concentrations of various metals in the raffinate were measured, and the extraction rate was calculated. The results are shown in Table 10 below.

[0091] Table 10 Extraction results of molybdenum after reduction.

[0092]

[0093] Results: Based on the reduced solution, the Mo extraction rate was 75.00%, the In extraction rate was 1.32%, and the Fe extraction rate was 4.82%. Compared with the results of Mo extraction using modified Cyanex-272 and TBP in Example 2(c) (Mo extraction rate 95.50%, iron co-extraction rate 1.14%), if iron powder reduction was performed before Mo extraction, the Mo extraction rate decreased by 20.50 percentage points, and approximately 15.5% of the Mo was lost as a molybdenum blue precipitate during the reduction stage; simultaneously, the iron co-extraction rate increased from 1.14% to 4.82%, because the iron powder dissolution increased the total iron concentration from 11.48 g / L to 14.72 g / L, and the concentration effect led to an increase in the iron co-extraction rate. Example 4 shows that the iron powder reduction step must be performed after Mo extraction; otherwise, MoO2... 2+ In a reducing environment, it is partially reduced to molybdenum blue, resulting in irreversible loss of molybdenum.

[0094] Example 5

[0095] Take 100 mL of the same white soot leachate as in Example 1. Take Cyanex-272 and slowly add a measured amount of 2 mol / L NaOH solution at 40°C until the saponification degree reaches 50%. Stir for 30 minutes to obtain saponified Cyanex-272. Dissolve the modified extractant and TBP at 15% by volume in sulfonated kerosene, with a total extractant concentration of 30%. At 30°C, mix the organic phase and the feed solution at a volume ratio of 1:1, place in a constant temperature shaker, and shake at 280 r / min for 10 minutes. After first-stage extraction and allowing the phases to separate, measure the metal concentration in the aqueous phase and calculate the extraction rate. The results are shown in Table 11 below.

[0096] Table 11. Composition analysis of raffinate after synergistic extraction with modified Cyanex-272 and TBP.

[0097]

[0098] Results: The extraction rates were 96.00% for Mo, 1.34% for In, 1.31% for Fe, 2.26% for As, 1.13% for Zn, and 0.97% for Cd. This indicates that the synergistic extraction of modified Cyanex-272 and TBP, while maintaining a high molybdenum extraction rate, significantly reduced the co-extraction rates of cations such as indium and iron, achieving selective extraction of molybdenum.

[0099] Take 100 mL of the molybdenum extraction solution and add 1.5 times the theoretical amount of reduced iron powder. Stir the mixture at 50 °C for 30 minutes to remove Fe from the solution. 3+ Reduced to Fe 2+ Excess iron powder was removed by filtration, resulting in a reduced solution with pH raised to 0.22. The concentrations of each ion were measured, and the results are shown in Table 12 below.

[0100] Table 12 Composition Analysis of Iron Powder Reduction Solution

[0101]

[0102] Take 50 mL of the reduced solution and use it directly without adjusting the pH. Dissolve P204 in sulfonated kerosene to prepare an organic phase with a volume concentration of 30%. Slowly add 3 mol / L NaOH solution at 35 ℃ to achieve a saponification degree of 40%, and stir until homogeneous. Extract for 10 minutes at a phase ratio of O / A = 1:1 and a temperature of 40 ℃. Allow to stand and separate the phases to obtain the indium-loaded organic phase and the raffinate. The extraction rates of each element and the concentration of the raffinate are shown in Table 13 below:

[0103] Table 13. Composition analysis of raffinate after extraction with modified P204.

[0104]

[0105] Results: The extraction rates were 96.42% for In, 2.53% for Fe, 0.77% for As, 1.62% for Zn, and 0.98% for Cd. The experimental results indicate that iron powder reduction can reduce Fe... 3+ Converted to Fe 2+ Afterwards, although the total iron concentration increased from 11.33 g / L in the raffinate to 14.21 g / L, an increase of approximately 2.88 g / L, iron was mainly produced as Fe. 2+ In its original form, it is not co-extracted in the P204 extraction section, with an extraction rate of only 2.53%. The extraction rate of indium reaches 96.42%, achieving highly selective separation of indium and iron.

[0106] Example 6

[0107] (a) Effect of TBP addition on molybdenum co-extraction: Several 50 mL portions of the same white soot leachate as in Example 1 were taken. With a fixed Cyanex-272 (50% saponification) volume concentration of 15% in the organic phase, TBP volume concentrations of 0%, 5%, 10%, 15%, 20%, and 25% were added to prepare organic phases with different ratios. Extraction was performed at 30 °C and a 1:1 ratio for 10 minutes. The results are shown in Table 14 below:

[0108] Table 14 Extraction results with different amounts of TBP added (Cyanex-272 fixed at 15%)

[0109]

[0110] Results: With a fixed Cyanex-272 concentration of 15%, as the TBP addition increased from 0% to 25%, the molybdenum extraction rate gradually decreased from 96.40% to 94.68%, a decrease of 1.72 percentage points; the indium co-extraction rate decreased from 9.10% to 1.20%, a decrease of 7.90 percentage points; and the iron co-extraction rate decreased from 14.02% to 0.72%, a decrease of 13.30 percentage points. The addition of TBP slightly reduced the molybdenum extraction rate, but the decrease in the indium and iron co-extraction rates was more significant, indicating that the addition of TBP effectively inhibited the co-extraction of indium and iron and improved the system's selectivity for molybdenum.

[0111] (b) Effect of Cyanex-272 addition on molybdenum co-extraction: Several 50 mL portions of the same white soot leachate as in Example 1 were taken. With a fixed TBP volume concentration of 15% in the organic phase, modified Cyanex-272 (50% saponification degree) at volume concentrations of 5%, 10%, 15%, and 20% were added to prepare organic phases with different ratios. Extraction was performed at 30 °C and a 1:1 ratio for 10 minutes. The results are shown in Table 15 below:

[0112] Table 15 Extraction results with different amounts of Cyanex-272 added (TBP fixed at 15%)

[0113]

[0114] Results: With a fixed TBP concentration of 15%, as the amount of Cyanex-272 added increased from 5% to 20%, the molybdenum extraction rate gradually increased from 85.65% to 96.07%, an increase of 10.42 percentage points; the indium co-extraction rate increased from 1.27% to 1.78%, an increase of 0.51 percentage points; and the iron co-extraction rate increased from 0.93% to 1.42%, an increase of 0.49 percentage points. The increase in Cyanex-272 concentration improved the molybdenum extraction rate, but the co-extraction rates of indium and iron also increased slightly. The results of Examples 6(a) and (b) indicate that TBP mainly plays a role in inhibiting the co-extraction of indium and iron in the co-extraction system, while Cyanex-272 is the main active component for molybdenum extraction. The synergistic use of both can maintain a high molybdenum extraction rate while keeping the co-extraction rates of indium and iron within a low range.

[0115] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities, characterized in that, Includes the following steps: (1) Modified bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex-272) and tributyl phosphate (TBP) synergistic extraction of molybdenum: The pH of the acidic solution containing molybdenum, indium, iron and polymetallic impurities was adjusted to -1.5~0.5; extraction was performed using a mixed organic phase containing modified Cyanex-272 and TBP, and after phase separation, a molybdenum-loaded organic phase and a raffinate containing indium, iron and other cations were obtained; (2) Back-extraction of molybdenum: The molybdenum-loaded organic phase obtained in step (1) is back-extracted using an alkaline back-extraction agent with a pH of 7.5~13.

0. Molybdenum enters the aqueous phase in the form of oxyanions to obtain a molybdenum-rich solution. The organic phase can be regenerated and returned to step (1) for use. (3) Iron powder reduction: Add iron powder to the raffinate obtained in step (1) to reduce Fe 3+ Reduced to Fe 2+ After the reaction, the solution was filtered to obtain the reduced solution. (4) Modified P204 extraction of indium: Adjust the pH of the reduced solution obtained in step (3) to 0.0~2.5, extract with modified P204 organic phase, and obtain indium-loaded organic phase and raffinate containing iron, cadmium and arsenic impurities after phase separation; (5) Indium back-extraction: The indium-loaded organic phase obtained in step (4) is back-extracted using an acidic back-extraction agent with a concentration of 1~7 mol / L to obtain an indium-rich solution.

2. The method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities according to claim 1, characterized in that, In step (1), the acidic solution is an acidic leaching solution of copper ash, wherein the content of arsenic is 10~20 g / L, the content of iron is 10~15 g / L, the content of cadmium is 10~25 g / L, the content of zinc is 10~30 g / L, the content of molybdenum is 200~1000 mg / L, the content of indium is 200~1000 mg / L, and the pH value is -0.5~0.

5.

3. The method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities according to claim 1, characterized in that, In step (1), the modified Cyanex-272 is obtained by partial saponification pretreatment of Cyanex-272 with alkali, and the degree of saponification is 5%~50%; And / or, the volume concentration of modified Cyanex-272 in the organic phase is 5%~40%, the volume concentration of TBP is 5%~25%, and the total volume concentration of the extractant does not exceed 50% of the total volume of the organic phase; wherein the volume ratio (O / A) of the organic phase to the aqueous phase is 1:8~8:

1. And / or, the volume concentrations of Cyanex-272 and TBP in the organic phase are both 10% to 20%, and the total concentration of both is 20% to 35%.

4. The method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities according to claim 1, characterized in that, In step (1), the pH value is -1.0 to 0.2; And / or, the extraction temperature is 15~65 ℃, the extraction time is 5~25 minutes, and the extraction stage is 1~5 stages.

5. The method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities according to claim 1, characterized in that, In step (2), the alkaline back-extraction agent is selected from one of ammonia water, ammonium carbonate, sodium carbonate or sodium hydroxide solution; And / or, the back-extraction temperature is 15~80 ℃, the back-extraction time is 3~25 minutes, and the number of back-extraction stages is 1~5.

6. The method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities according to claim 1, characterized in that, In step (3), the amount of iron powder added is 0.8 to 2.5 times the mass of iron required for the theoretical reduction of ferric iron, and the reduction conditions are stirring and reacting at 15 to 70 °C for 10 to 90 minutes.

7. The method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities according to claim 1, characterized in that, In step (4), the modified P204 is obtained by partial saponification of P204 with alkali, and the degree of saponification is 10%~70%; And / or, the volume concentration of the modified P204 in the organic phase is 10%~45%, and the degree of saponification is 10%~70%; wherein the volume ratio (O / A) of the organic phase to the aqueous phase is 1:8~8:

1.

8. The method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities according to claim 1, characterized in that, In step (4), the pH value is 0.2~1.4; And / or, the extraction temperature is 15~60 ℃, the extraction time is 3~25 minutes, and the extraction stage is 1~5 stages.

9. The method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities according to claim 1, characterized in that, In step (5), the acidic back-extraction agent is selected from hydrochloric acid, sulfuric acid or nitric acid solution, and its concentration is 1~7 mol / L; And / or, in step (5), the back-extraction temperature is 15~65 ℃, the back-extraction time is 3~30 minutes, and the number of back-extraction stages is 1~5.

10. The method for selective extraction and separation of molybdenum and indium from a highly acidic and highly arsenic solution containing polymetallic impurities according to claim 1, characterized in that, The alkali used in the modified Cyanex-272 in step (1) and the modified P204 in step (4) are independently selected from at least one of sodium hydroxide, potassium hydroxide, ammonia, and sodium carbonate, and the saponification temperature is 10~80 ℃ and the saponification time is 20~120 minutes. And / or, the organic phase described in steps (1) and (4) has a diluent independently selected from sulfonated kerosene, n-heptane, n-hexane or aromatic hydrocarbon solvent.

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