Method for separating indium from low-concentration indium enrichment liquid based on supercritical extraction

Abstract

The invention relates to the technical field of scattered metal metallurgy, and particularly discloses a method for separating indium from low-concentration indium-enriched liquid based on supercritical extraction, which comprises the following steps: carrying out pH regulation and fluorine ion capture pretreatment on acidic indium-enriched liquid, and then filtering; synthesizing a perfluoroalkylated phosphonate complexing agent, compounding the complexing agent with a cosolvent, and adding a pretreatment solution to pre-complex indium; the indium complex is dynamically extracted and dissolved through supercritical CO2; introducing the indium-loaded CO2 fluid into a hydrochloric acid solution, and applying ultrasonic wave to strengthen reverse extraction to obtain an indium-rich solution; the indium-rich liquid is subjected to electrolytic refining to obtain high-purity indium; and finally, depressurizing and recovering a complexing agent and cosolvent mixture. According to the method, high-selectivity extraction of indium is achieved by synthesizing the perfluoroalkylated phosphonate complexing agent and cooperating with supercritical CO2, impurities are inhibited by combining accurate pH regulation and fluorine capture, the reverse extraction efficiency is enhanced through ultrasonic waves, the indium recovery rate and the impurity removal rate are greatly increased, cyclic utilization of reagents is achieved, and the method is suitable for green recovery of indium resources.

Description

Technical Field

[0001] The present invention relates to the technical field of dispersed metal metallurgy, and in particular to a method for separating indium from a low-concentration indium-enriched solution based on supercritical extraction. Background Art

[0002] Low-concentration indium-enriched solution generally refers to solutions that are initially enriched with indium, such as zinc smelting slag leachate and ITO waste target acid solution. Existing technologies for extracting indium from low-concentration indium-enriched solution generally use two methods. One is the traditional solvent extraction method that relies on extractants such as tributyl phosphate (TBP) or di(2-ethylhexyl) phosphoric acid (P204), which has the following defects:

[0003] 1. High reagent consumption, requiring multi-stage extraction / strip extraction, the organic phase is easily emulsified and deteriorated, and a large amount of kerosene-containing wastewater is generated;

[0004] 2. Poor selectivity, Fe 3+ 、Al 3+ The co-extraction of other impurities is serious, requiring a complex washing process, and the indium recovery rate is only 85-90%;

[0005] 3. There is a concentration limit. The efficiency of the liquid with an indium concentration of less than 200 mg / L drops sharply, and low-grade resources cannot be processed economically.

[0006] The other is traditional supercritical CO2 extraction technology. Although it has environmental advantages compared to solvent extraction, it still has the following problems:

[0007] 1. Conventional phosphine oxide extractants (such as TBP and P350) have low solubility in supercritical CO2 (<0.1 mol%) and poor mass transfer efficiency;

[0008] 2. Fe in acidic system 3+ It is easy to hydrolyze and clog equipment, and trace amounts of fluoride ions (F-) cause surface intergranular corrosion;

[0009] 3. Stripping is difficult. Indium complexes are highly stable in the supercritical phase. Conventional pressure-reduced stripping requires more than 60 minutes, which increases energy consumption.

[0010] Therefore, it is necessary to design a method for separating indium from low-concentration indium-rich solution based on supercritical extraction to solve the problems of low indium recovery rate and low impurity removal rate in existing low-concentration indium-rich solution extraction technology. Summary of the Invention

[0011] In view of this, the present invention proposes a method for separating indium from a low-concentration indium-rich solution based on supercritical extraction, which is used to solve the problems of low indium recovery rate and low impurity removal rate in the existing low-concentration indium-rich solution extraction technology.

[0012] The present invention proposes a method for separating indium from a low-concentration indium-enriched solution based on supercritical extraction, comprising the following preparation steps:

[0013] Ammonia solution is added to the low-concentration indium-enriched solution and stirred to adjust the pH value to between 2.2 and 2.3, and then sodium fluoride powder is added and stirred for the first time, followed by multi-stage filtration to obtain a pretreated solution;

[0014] Mixing dimethylheptyl methylphosphonate, perfluorohexyl iodide and azobisisobutyronitrile, performing a second stirring and then distilling, collecting the fractions, and cooling to room temperature to obtain a perfluoroalkylated phosphonate complexing agent;

[0015] The perfluoroalkylated phosphonate complexing agent is mixed with ethyl acetate, and then subjected to ultrasonic oscillation to obtain a composite stock solution;

[0016] Injecting the composite reserve solution into the pretreatment solution, and then introducing CO2 to perform supercritical extraction to obtain indium-loaded CO2 fluid;

[0017] Pour the indium-loaded CO2 fluid into a hydrochloric acid solution and perform ultrasonic stripping treatment to obtain an indium-rich hydrochloric acid solution and an indium-depleted CO2 fluid;

[0018] The indium-rich hydrochloric acid solution is subjected to electrolytic refining to obtain high-purity indium.

[0019] Furthermore, the first stirring temperature is 30-40° C., the rotation speed is 100-140 rpm, and the stirring time is 20-40 minutes.

[0020] Furthermore, the multi-stage filtration specifically includes firstly performing pre-filtration using a 10 μm polypropylene filter element, and then performing fine filtration using a 0.45 μm polytetrafluoroethylene membrane.

[0021] Furthermore, the second stirring temperature is 60-80° C., the stirring speed is 200-400 rpm, and the stirring time is 2-6 hours.

[0022] Furthermore, the distillation temperature is 110-120° C., and the vacuum degree is 5-6 kPa.

[0023] Furthermore, the supercritical extraction pressure is 25-35 MPa, the temperature is 50-70° C., the stirring speed is 250-350 rpm, the CO2 flow rate is 1-2 L / min, and the extraction time is 100-140 minutes.

[0024] Furthermore, the ultrasonic stripping treatment has an ultrasonic frequency of 20-30 kHz, a power of 60-100 W, a stripping pressure of 20-40 MPa, a temperature of 40-80° C., and a treatment time of 20-40 minutes.

[0025] Furthermore, the current density of the electrolytic refining is 70-90A / m 2 , voltage is 1-1.4V; electrolysis time is 20-26 hours.

[0026] Furthermore, the de-indiumized CO2 fluid is depressurized and cooled, the oil phase mixture is collected, and ethyl acetate is added to obtain the composite stock solution.

[0027] Furthermore, the decompression cooling is specifically as follows: the decompression of the de-indiumized CO2 fluid is reduced to 6 MPa at a rate of 0.5 MPa / min, and then cooled to 26-30°C.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The perfluoroalkylated phosphonate complex prepared by the present invention has both specific complexing ability for indium and high solubility in supercritical CO2, which greatly improves the extraction rate of indium and thus improves the recovery rate of indium.

[0030] 2. The present invention inhibits Fe by precisely controlling pH 3+ Hydrolysis co-extraction, combined with sodium fluoride to capture Al 3+ / Sn 4+ It forms a stable fluorine complex and greatly improves the impurity removal rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0032] Figure 1 A flow chart of a method for separating indium from a low-concentration indium-rich solution based on supercritical extraction provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, unless there is a conflict, the embodiments of the present disclosure and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0034] like Figure 1As shown, in some embodiments of the present application, a method for separating indium from a low-concentration indium-rich solution based on supercritical extraction includes the following preparation steps:

[0035] Ammonia solution is added to the low-concentration indium-enriched solution and stirred to adjust the pH value to between 2.2 and 2.3, and then sodium fluoride powder is added and stirred for the first time, followed by multi-stage filtration to obtain a pretreated solution;

[0036] Mixing dimethylheptyl methylphosphonate, perfluorohexyl iodide and azobisisobutyronitrile, performing a second stirring and then distilling, collecting the fractions, and cooling to room temperature to obtain a perfluoroalkylated phosphonate complexing agent;

[0037] The perfluoroalkylated phosphonate complexing agent is mixed with ethyl acetate, and then subjected to ultrasonic oscillation to obtain a composite stock solution;

[0038] Injecting the composite reserve solution into the pretreatment solution, and then introducing CO2 to perform supercritical extraction to obtain indium-loaded CO2 fluid;

[0039] Pour the indium-loaded CO2 fluid into a hydrochloric acid solution and perform ultrasonic stripping treatment to obtain an indium-rich hydrochloric acid solution and an indium-depleted CO2 fluid;

[0040] The indium-rich hydrochloric acid solution is subjected to electrolytic refining to obtain high-purity indium.

[0041] Specifically, the indium concentration in the low-concentration indium-enriched solution is preferably 200 mg / L;

[0042] Specifically, an ammonia solution was added to the low-concentration indium-enriched solution and stirred. When the pH value was adjusted to between 2.2 and 2.3, 0.8 mol / L ammonia solution was pumped into the low-concentration indium-enriched solution at a rate of 5 L / min through a metering pump until the pH value was adjusted to between 2.2 and 2.3. During this period, the temperature was maintained at 25°C and stirring was continued.

[0043] Specifically, the molar amount of the sodium fluoride powder is the Al in the low-concentration indium-enriched solution. 3+ and Sn 4+ 1.05 times the total molar amount.

[0044] Specifically, dimethylheptyl methylphosphonate, perfluorohexyl iodide, and azobisisobutyronitrile were mixed under nitrogen, wherein the molar ratio of dimethylheptyl methylphosphonate to perfluorohexyl iodide was 1:1.1, and the mass ratio of dimethylheptyl methylphosphonate to azobisisobutyronitrile was 100:1.

[0045] Specifically, the mass ratio of the perfluoroalkylated phosphonate complexing agent to ethyl acetate when mixed is 1:4, and the ultrasonic oscillation time is preferably 10 minutes.

[0046] Specifically, the molar ratio of the composite stock solution to the molar ratio of indium ions in the low-concentration indium-enriched solution is 4:1.

[0047] Specifically, the concentration of the hydrochloric acid solution is 1 mol / L.

[0048] It can be understood that the perfluoroalkylated phosphonate complex prepared by the present invention has both specific complexing ability for indium and high solubility in supercritical CO2, which greatly improves the extraction rate of indium and thus improves the recovery rate of indium.

[0049] It is understandable that the present invention suppresses Fe by precisely controlling pH. 3+ Hydrolysis co-extraction, combined with sodium fluoride to capture Al 3+ / Sn 4+ It forms a stable fluorine complex and greatly improves the impurity removal rate.

[0050] In some embodiments of the present application, the first stirring temperature is 30-40°C, the rotation speed is 100-140 rpm, and the stirring time is 20-40 minutes; the first stirring temperature is preferably 35°C, the rotation speed is preferably 120 rpm, and the stirring time is preferably 30 minutes.

[0051] It is understandable that adding sodium fluoride (NaF) powder to the solution and stirring at 35±2°C for 30 minutes can eliminate the dual hidden dangers through the directional capture and stable complexation of fluoride ions: on the one hand, the impurity ions (Al, Sn, etc.) in the feed solution are concentrated. 3+ / Sn 4+ ) is converted into water-soluble and stable hexafluoroaluminate (AlF6 3- ) or hexafluorostannate (SnF6 2- ) complex, completely blocking its competitive complexation with indium in the subsequent supercritical extraction, thereby improving indium selectivity; on the other hand, it permanently fixes the free fluoride ion (F - ) to eliminate the risk of intergranular corrosion of supercritical high-pressure equipment (especially stainless steel seals) caused by fluorine, and ensure the long-term and safe operation of the system.

[0052] In some embodiments of the present application, the multi-stage filtration is specifically performed by first using a 10 μm polypropylene filter element for pre-filtration, and then using a 0.45 μm polytetrafluoroethylene membrane for fine filtration.

[0053] Specifically, a two-stage filter connected in series is used for multi-stage filtration, the first stage is a 10 μm polypropylene filter element for pre-filtration; the second stage is a 0.45 μm polytetrafluoroethylene (PTFE) membrane filter for fine filtration.

[0054] It can be understood that the present invention achieves dual protection through a gradient interception mechanism: the first-level pre-filtration efficiently removes micron-sized precipitates (such as Fe(OH)3 colloids and NaAlF6 flocs) generated by pH control and fluorination reaction to prevent clogging of subsequent precision equipment; the second-level PTFE membrane fine filtration completely intercepts submicron-sized particles (<0.5μm) and colloidal residues, ensuring that the pretreatment liquid reaches the ultra-low solid content (≤1ppm) required for supercritical system feed, eliminating the risk of high-pressure valve wear and scaling on the inner wall of the extraction kettle, and ensuring the stability of supercritical phase mass transfer.

[0055] In some embodiments of the present application, the second stirring temperature is 60-80°C, the stirring speed is 200-400 rpm, and the stirring time is 2-6 hours; the second stirring temperature is preferably 70°C, the stirring speed is preferably 300 rpm, and the stirring time is preferably 4 hours.

[0056] Specifically, dimethylheptyl methylphosphonate, perfluorohexyl iodide and azobisisobutyronitrile are added to a glass reactor protected by nitrogen, magnetic stirring is turned on at 200-400 rpm, the oil bath is heated to 60-80° C., and the reaction is carried out for 2-6 hours.

[0057] In some embodiments of the present application, the distillation temperature is 110-120° C., and the vacuum degree is 5-6 kPa; the distillation temperature is preferably 110° C., and the vacuum degree is preferably 5 kPa.

[0058] Specifically, after stirring, the reaction solution is transferred to a short-range molecular distillation device, distilled at a vacuum degree of 5-6 kPakPa and a temperature of 110-120° C., and a fraction at 160-180° C. is collected.

[0059] It can be understood that the present invention achieves three goals simultaneously through low-temperature, high-vacuum rapid separation: efficient cutting of the target product perfluoroalkylated phosphonate (boiling range 160-180°C) and the separation of high-boiling-point raw materials (>250°C) / low-boiling-point by-products (<100°C) components, completing mass transfer within 5 seconds to avoid thermal decomposition of the perfluoroalkyl chain (CF bond); and at the same time, deeply removing residual free radical initiators and iodinated impurities to obtain a high-purity F-P350 complexing agent of >99%, thereby ensuring the selectivity and mass transfer efficiency of the supercritical extraction process from the source.

[0060] In some embodiments of the present application, the pressure of the supercritical extraction is 25-35 MPa, the temperature is 50-70°C, the stirring speed is 250-350 rpm, the CO2 flow rate is 1-2 L / min, and the extraction time is 100-140 minutes; the pressure of the supercritical extraction is preferably 30 MPa, the temperature is preferably 60°C, the stirring speed is preferably 200 rpm, the CO2 flow rate is preferably 1.5 L / min, and the extraction time is preferably 120 minutes.

[0061] Specifically, during supercritical extraction, the pretreatment liquid is pumped into a 50L high-pressure extraction kettle (material: 316L stainless steel), the compound reserve liquid is injected below the liquid surface through a high-pressure syringe, the kettle body is closed, the system is started, and liquid food-grade CO2 is introduced to a pressure of 30MPa in the kettle; the circulating water bath is heated to 60°C; the turbine agitator is turned on at 300pm; the CO2 flow rate is controlled to 1.5L / min (standard state), and dynamic extraction is performed for 120 minutes.

[0062] In some embodiments of the present application, the ultrasonic frequency of the ultrasonic stripping treatment is 20-30kHz, the power is 60-100W, the stripping pressure is 20-40MPa, the temperature is 40-80°C, and the treatment time is 20-40 minutes; the ultrasonic frequency of the ultrasonic stripping treatment is preferably 28kHz, the power is preferably 80W, the stripping pressure is preferably 30MPa, the temperature is preferably 60°C, and the treatment time is preferably 30 minutes.

[0063] Specifically, half the volume of 1.0 mol / L hydrochloric acid solution is pre-loaded into the titanium alloy stripping kettle, and the indium-loaded CO2 fluid is introduced into the stripping kettle through a high-pressure pipeline, and the ultrasonic transducers (frequency 20-30 kHz, power 60-100 W) evenly distributed at the bottom of the kettle are simultaneously turned on; the stripping system pressure is maintained at 20-40 MPa and the temperature is 40-80°C; after stripping for 20-40 minutes, the ultrasonic wave is turned off, and the kettle is allowed to stand for 5 minutes to separate into layers; the aqueous phase is discharged from the valve at the bottom of the kettle to obtain the indium-rich hydrochloric acid solution.

[0064] In some embodiments of the present application, the current density of the electrolytic refining is 70-90A / m 2 , voltage is 1-1.4V; electrolysis time is 20-26 hours; the current density of the electrolytic refining is 80A / m 2 , voltage is 1.2V; electrolysis time is 24 hours.

[0065] Specifically, an indium-rich hydrochloric acid solution is injected into the anode chamber; 0.1 mol / L dilute hydrochloric acid is injected into the cathode chamber; the current density and cell voltage are controlled for electrolysis, and sponge indium is precipitated at the cathode; the sponge indium at the cathode is scraped and washed three times with ultrapure water; and high-purity indium ingots are obtained by vacuum drying at 60°C and 10kPa.

[0066] In some embodiments of the present application, the de-indiumized CO2 fluid is depressurized and cooled, the oil phase mixture is collected, and ethyl acetate is added to obtain the composite stock solution.

[0067] In some embodiments of the present application, the decompression cooling is specifically: reducing the pressure of the de-indiumized CO2 fluid to 6 MPa at a rate of 0.5 MPa / min, and then cooling to 26-30°C; the cooling temperature is preferably 28°C.

[0068] Specifically, the de-indiumized CO2 fluid enters the separation kettle and is pressurized to 6 MPa at a rate of 0.5 MPa / min; the circulating cold water is cooled to 28°C, the bottom valve of the separation kettle is opened, the oil phase mixture (containing 98% of the initial reagent) is collected, and 2% fresh ethyl acetate is added to obtain the composite stock solution.

[0069] Example 1

[0070] S1. Add an ammonia solution to the low-concentration indium-enriched solution and stir. When the pH value is adjusted to between 2.2 and 2.3, pump 0.8 mol / L ammonia solution into the low-concentration indium-enriched solution at a rate of 5 L / min through a metering pump until the pH value is adjusted to between 2.2 and 2.3. During this period, maintain the temperature at 25° C. and continue stirring.

[0071] S2, adding Al in the low concentration indium enriched solution to the solution 3+ +Sn 4+ The total molar amount of sodium fluoride powder was 1.05 times, the temperature was raised to 30°C, and the mixture was stirred at 100 rpm for 20 minutes. After the reaction mixture was pre-filtered through a 10 μm polypropylene filter element, and then finely filtered through a 0.45 μm polytetrafluoroethylene (PTFE) membrane filter to obtain a pre-treated solution.

[0072] S3. In a nitrogen-protected glass reactor, dimethylheptyl methylphosphonate and perfluorohexyl iodide were added in a molar ratio of 1:1.1, and then 1% by weight of dimethylheptyl methylphosphonate and azobisisobutyronitrile were added. Magnetic stirring was turned on and the stirring speed was maintained at 200 rpm. The oil bath was heated to 60°C and the reaction was carried out for 2 hours. The reaction solution was transferred to a short-path molecular distillation apparatus and distilled at a vacuum degree of 5 kPa and a temperature of 110°C. The 160-180°C fraction was collected and cooled to room temperature to obtain a perfluoroalkylated phosphonate complexing agent.

[0073] S4. Mix the perfluoroalkyl phosphonate complexing agent and ethyl acetate in a mass ratio of 1:4, and ultrasonically vibrate for 10 minutes to obtain a composite stock solution.

[0074] S5. Pump the pretreatment liquid into the high-pressure extraction kettle, and inject the composite reserve solution under the liquid surface through a high-pressure syringe. The molar amount of the composite reserve solution is 4 times the molar amount of indium in the pretreatment liquid. Close the kettle body and introduce liquid food-grade CO2 to the pressure in the kettle to 25MPa; heat the circulating water bath to 50°C; turn on the turbine agitator at 250rpm; control the CO2 flow rate to 1L / min, and perform dynamic extraction for 100 minutes to obtain a CO2 fluid loaded with indium.

[0075] S6. Pre-fill half the volume of 1.0 mol / L hydrochloric acid solution into the titanium alloy stripping kettle, introduce the indium-loaded CO2 fluid into the stripping kettle through a high-pressure pipeline, and simultaneously turn on the ultrasonic transducer, set the frequency to 20 kHz, and the power to 60 W; maintain the stripping system pressure at 20 MPa and the temperature at 40°C; after stripping for 20 minutes, turn off the ultrasonic wave, let it stand for 5 minutes to separate the layers, and discharge the aqueous phase from the bottom valve of the kettle to obtain the indium-rich hydrochloric acid solution; introduce the de-indiumized CO2 fluid into the separation kettle, and reduce the pressure to 6 MPa at a rate of 0.5 MPa / min; circulate cold water to cool to 26°C, open the bottom valve of the separation kettle, collect the oil phase mixture, and add 2% fresh ethyl acetate to obtain the composite stock solution.

[0076] S7, inject the indium-rich hydrochloric acid solution into the anode chamber; inject 0.1 mol / L dilute hydrochloric acid into the cathode chamber; control the current density to 70 A / m 2 , voltage 1V, electrolysis for 20 hours, scrape the sponge indium precipitated on the cathode, wash it three times with ultrapure water, and vacuum dry it at 60℃, 10kPa to obtain a high-purity indium ingot.

[0077] Example 2

[0078] S1. Add an ammonia solution to the low-concentration indium-enriched solution and stir. When the pH value is adjusted to between 2.2 and 2.3, pump 0.8 mol / L ammonia solution into the low-concentration indium-enriched solution at a rate of 5 L / min through a metering pump until the pH value is adjusted to between 2.2 and 2.3. During this period, maintain the temperature at 25° C. and continue stirring.

[0079] S2, adding Al in the low concentration indium enriched solution to the solution 3+ +Sn 4+ The total molar amount of sodium fluoride powder was 1.05 times, the temperature was raised to 35°C, and the mixture was stirred at 120 rpm for 30 minutes. After the reaction mixture was pre-filtered through a 10 μm polypropylene filter element, and then finely filtered through a 0.45 μm polytetrafluoroethylene (PTFE) membrane filter to obtain a pretreated solution.

[0080] S3. In a nitrogen-protected glass reactor, dimethylheptyl methylphosphonate and perfluorohexyl iodide were added in a molar ratio of 1:1.1, and then 1% by weight of dimethylheptyl methylphosphonate and azobisisobutyronitrile were added. Magnetic stirring was started and the stirring speed was maintained at 300 rpm. The oil bath was heated to 70°C and the reaction was carried out for 4 hours. The reaction solution was transferred to a short-path molecular distillation apparatus and distilled at a vacuum degree of 5 kPa and a temperature of 110°C. The 160-180°C fraction was collected and cooled to room temperature to obtain a perfluoroalkylated phosphonate complexing agent.

[0081] S4. Mix the perfluoroalkyl phosphonate complexing agent and ethyl acetate in a mass ratio of 1:4, and ultrasonically vibrate for 10 minutes to obtain a composite stock solution.

[0082] S5. Pump the pretreatment liquid into a high-pressure extraction kettle, and inject a composite reserve solution under the liquid surface through a high-pressure syringe. The molar amount of the composite reserve solution is 4 times the molar amount of indium in the pretreatment liquid. Close the kettle body, and introduce liquid food-grade CO2 to a pressure of 30 MPa in the kettle; heat the circulating water bath to 60°C; turn on the turbine stirrer at 300 rpm; control the CO2 flow rate to 1.5 L / min, and perform dynamic extraction for 120 minutes to obtain a CO2 fluid loaded with indium.

[0083] S6. Pre-fill half the volume of 1.0 mol / L hydrochloric acid solution into the titanium alloy stripping kettle, introduce the indium-loaded CO2 fluid into the stripping kettle through a high-pressure pipeline, and simultaneously turn on the ultrasonic transducer, set the frequency to 28 kHz, and the power to 80 W; maintain the stripping system pressure at 30 MPa and the temperature at 60°C; after stripping for 30 minutes, turn off the ultrasonic wave, let it stand for 5 minutes to separate the layers, and discharge the aqueous phase from the bottom valve of the kettle to obtain the indium-rich hydrochloric acid solution; introduce the de-indiumized CO2 fluid into the separation kettle, and reduce the pressure to 6 MPa at a rate of 0.5 MPa / min; circulate cold water to cool to 28°C, open the bottom valve of the separation kettle, collect the oil phase mixture, and add 2% fresh ethyl acetate to obtain the composite stock solution.

[0084] S7, inject the indium-rich hydrochloric acid solution into the anode chamber; inject 0.1 mol / L dilute hydrochloric acid into the cathode chamber; control the current density to 80 A / m 2 , voltage 1.2V, electrolysis for 24 hours, scrape the sponge indium precipitated on the cathode, wash it three times with ultrapure water, and vacuum dry it at 60℃, 10kPa to obtain a high-purity indium ingot.

[0085] Example 3

[0086] S1. Add an ammonia solution to the low-concentration indium-enriched solution and stir. When the pH value is adjusted to between 2.2 and 2.3, pump 0.8 mol / L ammonia solution into the low-concentration indium-enriched solution at a rate of 5 L / min through a metering pump until the pH value is adjusted to between 2.2 and 2.3. During this period, maintain the temperature at 25° C. and continue stirring.

[0087] S2, adding Al in the low concentration indium enriched solution to the solution 3+ +Sn 4+ The total molar amount of sodium fluoride powder was 1.05 times, the temperature was raised to 40°C, and the mixture was stirred at 140 rpm for 40 minutes. After the reaction mixture was pre-filtered through a 10 μm polypropylene filter element, and then finely filtered through a 0.45 μm polytetrafluoroethylene (PTFE) membrane filter to obtain a pretreated solution.

[0088] S3. In a nitrogen-protected glass reactor, dimethylheptyl methylphosphonate and perfluorohexyl iodide were added in a molar ratio of 1:1.1, and then 1% by weight of dimethylheptyl methylphosphonate and azobisisobutyronitrile were added. Magnetic stirring was turned on and the stirring speed was maintained at 400 rpm. The oil bath was heated to 80°C and the reaction was carried out for 6 hours. The reaction solution was transferred to a short-path molecular distillation apparatus and distilled at a vacuum degree of 10 kPa and a temperature of 120°C. The 160-180°C fraction was collected and cooled to room temperature to obtain a perfluoroalkylated phosphonate complexing agent.

[0089] S4. Mix the perfluoroalkyl phosphonate complexing agent and ethyl acetate in a mass ratio of 1:4, and ultrasonically vibrate for 10 minutes to obtain a composite stock solution.

[0090] S5. Pump the pretreatment liquid into a high-pressure extraction kettle, and inject a composite reserve solution into the liquid surface through a high-pressure syringe. The molar amount of the composite reserve solution is 4 times the molar amount of indium in the pretreatment liquid. Close the kettle body, and introduce liquid food-grade CO2 to a pressure of 35 MPa in the kettle; heat the circulating water bath to 70°C; turn on the turbine agitator at 350 rpm; control the CO2 flow rate to 2 L / min, and perform dynamic extraction for 140 minutes to obtain a CO2 fluid loaded with indium.

[0091] S6. Pre-fill half the volume of 1.0 mol / L hydrochloric acid solution into the titanium alloy stripping kettle, introduce the indium-loaded CO2 fluid into the stripping kettle through a high-pressure pipeline, and simultaneously turn on the ultrasonic transducer, set the frequency to 30 kHz, and the power to 100 W; maintain the stripping system pressure at 40 MPa and the temperature at 80°C; after stripping for 40 minutes, turn off the ultrasonic wave, let it stand for 5 minutes to separate the layers, and discharge the aqueous phase from the bottom valve of the kettle to obtain the indium-rich hydrochloric acid solution; introduce the de-indiumized CO2 fluid into the separation kettle, and reduce the pressure to 6 MPa at a rate of 0.5 MPa / min; circulate cold water to cool to 30°C, open the bottom valve of the separation kettle, collect the oil phase mixture, and add 2% fresh ethyl acetate to obtain the composite stock solution.

[0092] S7, inject the indium-rich hydrochloric acid solution into the anode chamber; inject 0.1 mol / L dilute hydrochloric acid into the cathode chamber; control the current density to 90A / m 2 , voltage 1.4V, electrolysis for 26 hours, scrape the sponge indium precipitated on the cathode, wash it three times with ultrapure water, and vacuum dry it at 60℃ and 10kPa to obtain a high-purity indium ingot.

[0093] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for separating indium from a low-concentration indium-rich solution based on supercritical extraction, characterized in that: The method comprises the following preparation steps: Ammonia solution is added to the low-concentration indium-enriched solution and stirred to adjust the pH value to between 2.2 and 2.3, and then sodium fluoride powder is added and stirred for the first time, followed by multi-stage filtration to obtain a pretreated solution; Mixing dimethylheptyl methylphosphonate, perfluorohexyl iodide and azobisisobutyronitrile, performing a second stirring and then distilling, collecting the fractions, and cooling to room temperature to obtain a perfluoroalkylated phosphonate complexing agent; The perfluoroalkylated phosphonate complexing agent is mixed with ethyl acetate, and then subjected to ultrasonic oscillation to obtain a composite stock solution; Injecting the composite reserve solution into the pretreatment solution, and then introducing CO2 to perform supercritical extraction to obtain indium-loaded CO2 fluid; Pour the indium-loaded CO2 fluid into a hydrochloric acid solution and perform ultrasonic stripping treatment to obtain an indium-rich hydrochloric acid solution and an indium-depleted CO2 fluid; The indium-rich hydrochloric acid solution is subjected to electrolytic refining to obtain high-purity indium.

2. The method for separating indium from a low-concentration indium-rich solution based on supercritical extraction according to claim 1, characterized in that: The first stirring temperature is 30-40° C., the rotation speed is 100-140 rpm, and the stirring time is 20-40 minutes.

3. The method for separating indium from a low-concentration indium-rich solution based on supercritical extraction according to claim 2, characterized in that: The multi-stage filtration specifically includes firstly pre-filtration using a 10 μm polypropylene filter element and then fine filtration using a 0.45 μm polytetrafluoroethylene membrane.

4. The method for separating indium from a low-concentration indium-rich solution based on supercritical extraction according to claim 3, characterized in that: The second stirring temperature is 60-80° C., the stirring speed is 200-400 rpm, and the stirring time is 2-6 hours.

5. The method for separating indium from a low-concentration indium-rich solution based on supercritical extraction according to claim 4, characterized in that: The distillation temperature is 110-120° C., and the vacuum degree is 5-6 kPa.

6. The method for separating indium from a low-concentration indium-rich solution based on supercritical extraction according to claim 5, characterized in that: The supercritical extraction pressure is 25-35 MPa, the temperature is 50-70° C., the stirring speed is 250-350 rpm, the CO2 flow rate is 1-2 L / min, and the extraction time is 100-140 minutes.

7. The method for separating indium from a low-concentration indium-rich solution based on supercritical extraction according to claim 6, characterized in that: The ultrasonic stripping treatment has an ultrasonic frequency of 20-30 kHz, a power of 60-100 W, a stripping pressure of 20-40 MPa, a temperature of 40-80° C., and a treatment time of 20-40 minutes.

8. The method for separating indium from a low-concentration indium-rich solution based on supercritical extraction according to claim 7, characterized in that: The current density of the electrolytic refining is 70-90A / m2, the voltage is 1-1.4V; and the electrolysis time is 20-26 hours.

9. The method for separating indium from a low-concentration indium-rich solution based on supercritical extraction according to claim 8, characterized in that: Also includes: The de-indiumized CO2 fluid is depressurized and cooled, the oil phase mixture is collected, and ethyl acetate is added to obtain the composite stock solution.

10. The method for separating indium from a low-concentration indium-rich solution based on supercritical extraction according to claim 9, characterized in that: The decompression cooling is specifically as follows: the decompression of the de-indiumized CO2 fluid is reduced to 6 MPa at a rate of 0.5 MPa / min, and then cooled to 26-30°C.

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