A method for recovering indium from a glass panel etching solution

Abstract

The application provides a method for recovering indium from a glass panel etching solution, which can effectively improve the recovery rate of indium from the glass panel etching solution, in particular, can effectively improve the recovery rate of indium from the glass panel etching solution with ultra-low pH, high sulfate and coexistence of multiple impurities, and the purity of the obtained indium is very high.

Description

Technical Field

[0001] This invention belongs to the fields of hydrometallurgy, hazardous waste resource recycling and rare metal purification technology, and specifically relates to a method for recovering indium from glass panel etching solution. Background Technology

[0002] The production process of glass panel touch screens and ITO coating generates a large amount of acidic etching waste liquid. The waste liquid generated in the hydrofluoric acid / sulfuric acid mixed system contains valuable rare metal indium, as well as various impurities such as tin, potassium, sodium, magnesium, aluminum, and iron. The waste liquid is characterized by ultra-low pH, high sulfate content, and coexistence of multiple impurities.

[0003] In a high sulfate environment, indium ions, in addition to existing in the form of single ions (In... 3+ It exists and will also react with sulfate ions (SO4). 2- The ions form mononuclear monocoordinate ions (In(SO4)) through a stepwise complexation and coordination process. + ), mononuclear dual-coordinate ion (In(SO4)2) - ), mononuclear tricoordinate ion (In(SO4)3) 3- This process also generates various hydrated complexes (such as In(H2O)5(SO4)). + In(H2O)4(SO4)2 - Furthermore, the proportions of these complexes change dynamically with variations in pH, temperature, and sulfate concentration, which will significantly affect the effectiveness of indium solvent extraction.

[0004] Currently, the traditional processes for recovering indium from etching solutions in the industry mostly employ mixed clarification tanks, extraction tanks, and conventional extraction, washing, and back-extraction operations using a single-component extractant + diluent, which have many technical drawbacks: (1) Low mass transfer efficiency and slow phase separation rate: Conventional extraction equipment does not have sufficient contact between the two phases. For high sulfate and high acidity systems, the indium extraction loading rate is low, impurities are seriously entrained, and the indium recovery rate is generally lower than 95%. (2) The process equipment is complicated and the stability is poor: different equipment is used for each process, such as extraction, washing, back-extraction, organic phase purification and regeneration. The process flow is complicated, the equipment occupies a large area, the operating parameters are difficult to control uniformly, and the quality of batch products fluctuates greatly. (3) High organic phase loss and poor recyclability: In traditional processes, the organic phase is not thoroughly washed and regenerated, and the accumulation of residual chloride ions and impurities leads to a rapid decline in the saponification rate of the organic phase. Frequent replacement of the organic phase results in high production costs. (4) Insufficient impurity separation precision: It is impossible to effectively remove impurities such as tin and iron entrained in the organic phase, and the final sponge indium obtained by replacement has low purity, which is difficult to reach the 99.9% high purity industrial standard.

[0005] (5) The extraction efficiency decreases under high sulfate system: In a high sulfate environment, indium ions form a variety of complex complex ions with sulfate ions, and single component extractants cannot effectively extract indium, resulting in a significant decrease in the extraction efficiency of indium. Summary of the Invention

[0006] In view of the problems and shortcomings of the existing technology, the present invention provides a method for recovering indium from glass panel etching solution. This method can effectively improve the recovery rate of indium from glass panel etching solution, especially from glass panel etching solution with ultra-low pH, high sulfate and multiple impurities, and the obtained indium has a high purity.

[0007] This invention provides a method for recovering indium from glass panel etching solution, comprising the following steps: S1, take the glass panel etching solution, adjust the pH of the solution to 1.2~1.6 to obtain the pretreatment solution; S2, the pretreated liquid is subjected to countercurrent extraction with the composite extractant, the O / A ratio is controlled at 1:3~5, and the centrifugation speed is 2000~4500 rpm, and the first organic phase is collected; the composite extractant includes P204 and N235, and the volume ratio of P204 to N235 is 15~20:3~5; S3, the first organic phase is countercurrently washed with the first detergent solution, controlling the O / A ratio to be 2~4:1, and the centrifugation speed to be 2000~4500 rpm, and the second organic phase is collected; the first detergent solution includes oxalic acid solution; then the second organic phase is countercurrently washed with the second detergent solution, controlling the O / A ratio to be 3~5:1, and the centrifugation speed to be 2000~4500 rpm, and the third organic phase is collected; the second detergent solution includes ammonium sulfate solution; S4, the third organic phase and the first stripping agent solution are subjected to countercurrent stripping, with O / A ratio controlled at 3~5:1 and centrifugation speed at 2000~4500 rpm, and the first aqueous phase and the fourth organic phase are collected; the first stripping agent solution includes hydrochloric acid solution; S5, zinc powder is added to the first aqueous phase to carry out a displacement reaction. After the reaction is completed, indium is obtained. The fourth organic phase is eluted countercurrently with water, with O / A ratio controlled at 3~5:1 and centrifugation speed at 2000~4500 rpm. The fifth organic phase is collected. Then, the fifth organic phase is regenerated countercurrently with the regenerator solution, with O / A ratio controlled at 10~15:1. The sixth organic phase is collected.

[0008] In the method for recovering indium from glass panel etching solution provided by this invention, through the design of a synergistic extraction system and high-speed countercurrent treatment throughout the entire process, not only are the five core processes of extraction, washing, back-extraction, composite extractant washing, and composite extractant regeneration effectively combined and efficiently completed, but the recovery rate of indium from glass panel etching solution is also significantly improved. In particular, it can also have better processing efficiency and effect for complex etching solution systems with high sulfate and high acidity, poor mass transfer, and serious impurity entrainment. At the same time, it can also effectively regenerate the composite extractant, greatly extend the service life of the composite extractant, and reduce the consumption and production cost of the composite extractant.

[0009] Specifically, in S1, the pH of the glass panel etching solution is first adjusted to 1.2~1.6 to match the optimal extraction acidity range, while inhibiting the co-extraction of iron, aluminum, etc.

[0010] In S2, a composite extractant system of P204 (di(2-ethylhexyl) phosphate, a cationic extractant) and N235 (trioctyldecyl tertiary amine, an anionic extractant) was used to perform countercurrent extraction on the pretreatment liquid. Compared with the traditional single P204 extractant, which cannot extract In(SO4)2, this method is more efficient. - The present invention addresses the shortcomings of the composite extractant by utilizing the cation exchange mechanism of P204 (extracting In³) + In(SO4) + The ion association mechanism between In³ and N₂35 after protonation under acidic conditions (extraction of In³) + In(SO4)2 - By combining these methods, the etching of indium ions in three forms (In³⁺) in glass etching solutions was achieved. + In(SO4) + In(SO4)2 - Simultaneous capture of indium. This synergistic effect significantly improves the total extraction rate of indium, ensuring efficient recovery of indium from the source. It should be noted that the extraction mechanism of P204 is as follows: (acidic phosphorus extractant, extracting In³ through cation exchange reaction). + In(SO4) + ):In³ + + 3(HA)2 In (HA2)3+ 3H + In(SO4) + + (HA)2 In(SO4) (HA2) + H + The extraction mechanism of N235 is as follows (tertiary amine extractant, protonated under acidic conditions to form R3NH). + In(SO4)2 was extracted via ion association mechanism. - ): R3N+ H+ R3NH + ;2R3NH + + In (SO4)2 - (R3NH)2In(SO4)2, where R3 represents the three substituents attached to the N atom. Furthermore, this step, under higher centrifugal speeds and a specific O / A ratio (O is the oil phase, here the composite extractant; A is the aqueous phase, here the pretreatment solution), can achieve better synergy with the composite extractant, further improving the extraction of indium ions and thus ensuring a high indium recovery rate in the subsequent process.

[0011] In S3, a countercurrent washing process is designed, consisting of a first detergent solution (e.g., oxalic acid solution) and a second detergent solution (e.g., ammonium sulfate solution). Firstly, oxalic acid selectively complexes and removes metallic impurities such as tin, iron, and aluminum. Secondly, ammonium sulfate further washes away entrained sulfate ions. The subsequent two washing steps control the O / A ratio to 2~4:1 (first step, oil phase is the first organic phase, aqueous phase is the first detergent solution) and 3~5:1 (second step, oil phase is the second organic phase, aqueous phase is the second detergent solution), respectively, and maintain relatively high centrifugal speeds. This allows for better integration with the aforementioned two washing steps, thus improving the removal rates of metallic impurities such as tin and iron, as well as sulfate ions. Furthermore, it ensures extremely low indium loss, guarantees high indium retention in the organic phase, and ensures high purity of the final indium product (e.g., sponge indium).

[0012] In S4, back-extraction is performed using acidic solutions such as hydrochloric acid solution, H + The cation exchange reaction of P204 proceeds in reverse (by converting In³) + (Displacement of aqueous phase); Cl - Equal to In³ + Formation of InCl4 - The complexes further promote back-extraction. Simultaneously, N235 exhibits increased protonation under acidic conditions, leading to the association of In(SO4)2... - Also Cl - The process involves displacement and release. Controlling the O / A ratio to 3~5:1 (oil phase as the third organic phase, aqueous phase as the first stripping agent solution) and a high centrifugal speed allows for more efficient stripping and enrichment of indium ions in conjunction with the first stripping agent. This results in extremely low indium content in the stripped organic phase and ensures that the stripping process is less prone to the formation of a third phase or emulsification (high centrifugal speed allows for rapid phase separation, preventing the organic phase from carrying acid or the aqueous phase from carrying organic phase).

[0013] In S5, most of the impurities in the first aqueous phase obtained earlier have been removed, so the indium obtained by directly adding zinc powder to replace it has high purity. However, the fourth organic phase obtained earlier still contains residual Cl. - (from the back-extraction section hydrochloric acid) and a small amount of H + Metal ions. Washing with water can remove Cl... - The concentration is reduced to an acceptable level (typically <0.1 mol / L) to avoid chloride ion accumulation that could degrade the performance of the organic phase. Controlling a specific O / A ratio (oil phase as the fourth organic phase, aqueous phase as water) and a higher centrifugal speed during water washing better matches the washing process, thus enabling more effective chloride removal. - H + Impurities such as metal ions are eliminated, improving the efficiency and effectiveness of water washing. Furthermore, the collected fifth organic phase and regenerator solution, under a specific O / A ratio (oil phase as the fifth organic phase, aqueous phase as the regenerator solution) and a high centrifugal speed, can achieve efficient regeneration of the composite extractant, enabling its recycling, extending its lifespan, and reducing reagent consumption. It should also be noted that each step in S1-S5 is interconnected; their combined effect is what achieves the high indium recovery rate and the regeneration of the composite extractant. Moreover, the specific O / A ratio and high centrifugal speed in each of the extraction, washing, back-extraction, composite extractant washing, and composite extractant regeneration steps ensure a high degree of compatibility with complex raw material systems, making the entire process smoother and simpler, ultimately achieving an ultra-high indium recovery rate and multiple recycling of the composite extractant.

[0014] Preferably, in S1, the pH of the stock solution is adjusted to 1.3-1.6 using a first alkaline solution.

[0015] Preferably, the first alkaline solution includes at least one of sodium hydroxide solution and potassium hydroxide solution. Preferably, when the first alkaline solution is sodium hydroxide solution, its mass concentration is 8-15%. Sodium hydroxide is widely available, inexpensive, highly alkaline, and does not contain additional metal impurities; therefore, it does not introduce Ca²⁺ when used for pH adjustment. + Mg² + Ions that readily form precipitates with oxalic acid or sulfate are avoided, preventing equipment blockage or organic phase contamination and ensuring long-term stable operation of the extraction system. Furthermore, the sodium hydroxide solution has a mass concentration of 8-15%, allowing for stable adjustment, rapid and uniform dispersion, and facilitating automated control.

[0016] Preferably, in S1, the stock solution satisfies at least one of the following conditions: (1) The stock solution contains: 80~100g / L of sulfate; (2) The pH of the stock solution is not higher than 0.5, or preferably not higher than 0.1, or preferably not higher than 0.05, or preferably not higher than 0.01.

[0017] Glass etching solutions typically contain high concentrations of sulfate and large amounts of SO4²⁻. - With In³ + Formation of In(SO4)2 - For anionic complexes, P2O4 alone cannot effectively extract them. This invention utilizes a synergistic extraction method combining P2O4 and N235 to simultaneously capture In³⁺. + In(SO4) + and In(SO4)2 - This greatly improves the total extraction rate and effectively solves the problem of high-concentration sulfate systems.

[0018] Preferably, in S1, the glass panel etching solution contains: indium 1.0~1.2 g / L, tin 0.05~0.2 g / L, potassium 0.01~0.05 g / L, sodium 0.01~0.1 g / L, magnesium 0.0005~0.002 g / L, sulfate 80~100 g / L, aluminum 0.001~0.05 g / L, iron 0.001~0.02 g / L, chlorine 0.05~0.1 g / L, and fluorine 0.0002~0.001 g / L.

[0019] Preferably, at least one of the following conditions is satisfied in S2: (1) The number of countercurrent extraction stages is 4 to 7; this number of stages, combined with O / A = 1:3 to 5, is more conducive to improving the total extraction rate and can achieve the optimal balance between equipment investment and extraction efficiency; (2) Countercurrent extraction is carried out using a centrifugal extractor with high gravity. The high gravity centrifugation generates a gravity field of hundreds of times, which disperses the two phases into micron-sized droplets, greatly increases the mass transfer area, and accelerates the extraction equilibrium time. At the same time, rapid phase separation avoids emulsification.

[0020] (3) The composite extractant is also saponified before countercurrent extraction, and the degree of saponification is controlled to be 20-40%; saponification converts part of P2O4 into salt form, and releases H during extraction. + Reduce the pH of the feed solution to avoid a sudden drop that inhibits extraction; control the degree of saponification to 20-40% to stabilize the activity of the organic phase, increase the extraction capacity, and at the same time prevent excessive saponification from causing difficulties in emulsification or back-extraction, thus ensuring long-term recycling. (4) The composite extractant also includes a diluent, and the volume ratio of P204, N235 and diluent is 15~20:3~5:75~82. The diluent adjusts the viscosity and density of the composite extractant as the organic phase, improves its flowability and phase separation performance. This ratio ensures that P204 is the main extractant and N235 is the synergist, and the two work together to capture the three indium forms, while reducing the cost of the extractant, reducing the loss of the organic phase, and facilitating industrial application.

[0021] It should be noted that in the field of solvent extraction, especially when using acidic extractants (such as P204), the degree of saponification refers to the molar percentage of acidic groups in the extractant that are neutralized by alkali (usually NaOH) to form salt. The degree of saponification is calculated (taking sodium hydroxide solution as an example): (Amount of P204 actually neutralized by NaOH ÷ Total amount of P204 in the system) × 100%; P204 molecular formula abbreviation (H2A2) (dimer molecule, acidic phosphorus extractant); Saponification reaction: H2A2 + NaOH = NaHA2 + H2O. The test method for "Amount of P204 actually neutralized by NaOH" is as follows: Before the reaction, the concentration (alkalinity) of sodium hydroxide in the solution is measured; after the reaction, the concentration (alkalinity) of sodium hydroxide in the aqueous phase separated after saponification is measured, and the amount of sodium hydroxide that participated in the reaction is deduced. Based on the reaction formula (saponification reaction formula), the amount of P204 that participated in the saponification is calculated, i.e., the degree of saponification.

[0022] Preferably, a second alkaline solution is used for saponification. Preferably, the specific operation of the saponification process is as follows: (1) Add the second alkaline solution dropwise to the prepared composite extractant at a rate of 50-100 mL / min, and stir at a stirring rate of 120-180 rpm. (2) After the second alkaline solution has been added, continue stirring the reaction for 30-45 minutes; (3) Let stand for 30-60 minutes; (4) Observe the phase interface. After the interface becomes clear, slowly release the lower layer of saponification wastewater (aqueous phase). (5) Next, add water to the organic phase, control O / A = 8~12:1, stir and wash for 8~15 min, and the stirring speed is 120~180 rpm; (6) Let it stand again for 30-60 minutes; (7) Observe the phase interface. After the interface becomes clear, slowly release the lower layer of washing water (aqueous phase). (8) Wash with water 1-2 times until the pH of the wash water is 7-8; (9) After washing, a saponified organic phase (saponified composite extractant) is obtained. The obtained saponified organic phase is a clear and transparent light yellow liquid with no obvious aqueous phase entrainment. In the above saponification treatment steps, in step (1), the state of the organic phase (composite extractant) is closely observed during the drop addition process. If turbidity or emulsification occurs, the drop addition rate is immediately slowed down.

[0023] Preferably, the second alkaline solution includes at least one of sodium hydroxide solution and potassium hydroxide solution. Preferably, when the second alkaline solution is sodium hydroxide solution, its mass concentration is 8-15%.

[0024] Preferably, the diluent includes sulfonated kerosene.

[0025] Preferably, in step S2, after countercurrent extraction of the pretreated feed liquid with the composite extractant, a first raffinate is obtained. The first raffinate is mainly aqueous and is collected and sent to the waste liquid treatment system.

[0026] Preferably, in S3, at least one of the following conditions is met during the countercurrent washing process between the first organic phase and the first detergent solution: (1) The number of countercurrent extraction stages is 2 to 3; this number of stages, combined with high centrifugal speed (super gravity), further improves the removal rate of impurities such as tin and iron and reduces the indium loss rate; (2) Countercurrent extraction is carried out using a centrifugal extractor with high gravity. Centrifugation with high gravity enhances the micro-mixing and mass transfer between the first detergent solution and the supported (indium) organic phase, so that oxalic acid can quickly complex and remove impurities such as tin and iron. At the same time, high-speed centrifugation accelerates the separation of the two phases, avoids emulsion entrainment, and ensures the purity of the organic phase after washing, providing a high-purity supported organic phase for subsequent back-extraction. (3) When the first detergent solution is an oxalic acid solution, the concentration is 0.5~2 mol / L; this concentration range has moderate complexing ability and can efficiently and selectively complex Sn. 4+ Fe³ + Soluble oxalate is formed and enters the aqueous phase, while simultaneously affecting In³ + The complexation is extremely weak. Too low a concentration will result in incomplete impurity removal, while too high a concentration will increase costs and may cause slight elution of indium.

[0027] Preferably, in step S3, after countercurrent washing of the first organic phase and the first detergent solution, a first washing residue is obtained. The first washing residue is mainly aqueous and is collected and sent to the waste liquid treatment system.

[0028] Preferably, in S3, at least one of the following conditions is met during the countercurrent washing process between the second organic phase and the second detergent solution: (1) The number of countercurrent washing stages is 1 to 2; 1 to 2 stages can efficiently remove sulfate ions entrained in the organic phase, and the number of stages is small, the equipment is simplified, the amount of detergent used is low, the production cost is reduced, and the trace loss of indium caused by multi-stage washing can be avoided. (2) Countercurrent washing is performed using a centrifugal extractor with high gravity; high gravity enhances the microscopic mass transfer between the second detergent solution and the organic phase, and accelerates the removal of sulfate by displacement; high-speed centrifugation ensures rapid separation of the two phases, avoids emulsification, and makes the organic phase clean after washing, which is conducive to subsequent back-extraction and organic phase regeneration. (3) When the second detergent solution is an ammonium sulfate solution, the concentration is 0.2~0.8 mol / L; this concentration provides sufficient NH4. + With SO4² - When removing entrained sulfate ions through ion exchange, if the concentration is too low, the removal will be incomplete, while if the concentration is too high, it will waste reagents and may corrode the equipment.

[0029] Preferably, in step S3, after countercurrent washing of the second organic phase and the second detergent solution, a second washing residue is obtained. The second washing residue is mainly aqueous and is collected and sent to the waste liquid treatment system.

[0030] Preferably, in S4, at least one of the following conditions is met during the countercurrent back-extraction process between the third organic phase and the first back-extractant solution: (1) The number of countercurrent back-extraction stages is 4 to 7; 4 to 7 stages of countercurrent back-extraction ensure that indium is fully transferred from the organic phase to the aqueous phase, thereby increasing the back-extraction rate. At the same time, it is also beneficial to enrich the indium concentration in the aqueous phase and increase the indium recovery rate. (2) Countercurrent washing is performed using a centrifugal extractor with high gravity; high gravity enhances the micro-mixing and mass transfer between the first stripping agent solution and the loaded organic phase, accelerating the stripping reaction; high-speed centrifugation quickly separates the phases, avoiding emulsion entrainment, resulting in high stripping efficiency and clear phase separation, ensuring the clean regeneration of the organic phase.

[0031] (3) When the first stripping agent is hydrochloric acid solution, the concentration is 3~7 mol / L; this concentration provides sufficient H+. + Replacement of In³ in organic phase + Meanwhile, Cl - With In³ + Formation of InCl4 - The complex and other compounds synergistically promote back-extraction; if the concentration is too low, back-extraction will be incomplete, and if it is too high, it will corrode the equipment. This range is conducive to achieving efficient and safe back-extraction.

[0032] Preferably, at least one of the following conditions is satisfied in S5: (1) Before adding zinc powder to the first aqueous phase for the displacement reaction, the first aqueous phase is concentrated until the indium concentration in the solution reaches 25~30g / L; preferably, the concentration method is constant temperature evaporation concentration, and the temperature is controlled at 75~85℃; preferably, after concentration, the solution is cooled to room temperature, allowed to stand for 1h, and filtered to remove trace impurities; increasing the indium concentration can reduce the displacement reaction volume, reduce the amount of zinc powder used, and improve the displacement efficiency; constant temperature evaporation (75~85℃) is mild and controllable, and cooling and standing filtration can remove impurities such as calcium and magnesium, ensuring the purity of the subsequent indium (sponge indium); (2) During the replacement reaction of zinc powder added to the first aqueous phase, the reaction temperature is controlled at 40~50℃. Appropriate heating can accelerate the reaction rate and shorten the replacement time. Excessive temperature can easily lead to zinc powder agglomeration or indium re-dissolution. This range takes into account both reaction activity and process stability to ensure that indium is precipitated more completely. (2) The displacement reaction process also involves stirring. The stirring speed is set to 150~200 rpm. Low-speed stirring ensures that the zinc powder is evenly suspended in the solution, increases the solid-liquid contact area, and promotes the displacement reaction. If the speed is too low, the mixing will be uneven, and if it is too high, eddies will easily form, entraining air and causing indium oxidation. (3) The purity of zinc powder is not less than 99.9%, and the average particle size is 150~200 mesh; high-purity zinc powder avoids the introduction of impurities such as lead and cadmium to contaminate the product; fine particle size has a large specific surface area and high reactivity, making the replacement more thorough and more conducive to the sedimentation and separation of indium (sponge indium); (4) Add zinc powder in batches for the displacement reaction, and continue the reaction for 2.0~2.5h. After the reaction is completed, let it stand for no less than 20min. Adding in batches can control the intensity of the reaction and avoid local overheating and splashing; sufficient reaction time ensures complete indium displacement; long standing time allows the sponge indium to settle fully, which facilitates solid-liquid separation and improves the yield. Preferably, after the displacement reaction is completed, filter to obtain primary indium (sponge indium). Preferably, the primary indium is first washed with dilute hydrochloric acid, then repeatedly washed with pure water until neutral, and dried to obtain secondary indium (high-purity sponge indium). Washing with dilute hydrochloric acid is to remove zinc impurities and soluble salts adsorbed on the surface.

[0033] Preferably, in step S5, during the countercurrent elution of the fourth organic phase with water, the number of countercurrent elution stages is 1 to 3. Using 1 to 3 stages of countercurrent elution can efficiently remove residual chloride ions and acidic impurities from the fourth organic phase. Within this range, combined with high centrifugal speed, it is even more beneficial to improve the chloride ion removal rate, providing pure material for subsequent organic phase regeneration and ensuring stable saponification.

[0034] Preferably, in S5, at least one of the following conditions is met during the countercurrent regeneration process of the fifth organic phase and the regenerator solution: (1) The number of countercurrent regeneration stages is 2 to 3; 2 to 3 stages of countercurrent regeneration allow the regenerator to come into full contact with the organic phase, ensuring that residual chloride ions and acidic impurities in the organic phase are fully neutralized and removed, while also facilitating precise control of the degree of regeneration. (2) The regenerator solution includes a third alkaline solution; using an alkaline solution as a regenerator can neutralize the residual acid in the organic phase and convert P204 into a salt form, restoring its extraction activity.

[0035] Preferably, the third alkaline solution includes at least one of sodium hydroxide solution and potassium hydroxide solution. Preferably, when the third alkaline solution is sodium hydroxide solution, its mass concentration is 8-15%. Sodium hydroxide converts P2O4 into sodium soap form, which is more conducive to restoring its extraction activity. A concentration of 8-15% can achieve stable regeneration, stably maintain the composite extractant within a suitable saponification rate range, and extend its service life.

[0036] Preferably, after S5, the process further includes the operation of returning the sixth organic phase to the countercurrent extraction process of S2 for recycling; The sixth organic phase is a regenerated composite extractant.

[0037] In summary, the present invention has the following advantages over the prior art: (1) The synergistic extraction of cationic extractant (P204) + anionic extractant (N235) combined with high centrifugal speed (super gravity) to enhance the rapid mixing and mass transfer of the two phases and precise phase separation is suitable for complex etching solution systems with high sulfate ions, and effectively improves the recovery rate of indium. (2) The five core processes of extraction, washing, back-extraction, washing of compound extractant and regeneration of compound extractant are all carried out with high centrifugal speed. That is, the entire core process can be carried out using a super gravity centrifugal extractor. The equipment is simple and the process is concise, which solves the problem of mismatch between multiple equipment in the traditional process. The degree of automation is high and it is suitable for continuous industrial production. (3) Combining high centrifugal speed (super gravity) washing with multi-stage purification, trace impurities such as tin, iron, and chlorine are thoroughly removed, and the finished sponge has high and stable indium purity; (4) The composite extractant can be recycled multiple times, which greatly reduces the cost of extractant procurement and waste liquid treatment. (5) Achieve efficient recovery of indium resources in etching waste liquid, centralized harmless treatment of waste liquid, no secondary pollution, and meet the policy requirements for the resource utilization of industrial solid waste and hazardous waste. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0039] Example 1 Take the glass panel etching solution. The solution composition is: indium 1.1204 g / L, tin 0.0846 g / L, potassium 0.0115 g / L, sodium 0.0105 g / L, magnesium 0.0005 g / L, sulfate 92.56 g / L, aluminum 0.0024 g / L, iron 0.0015 g / L, chlorine 0.0703 g / L, fluorine 6.0733 mg / L, and the pH of the solution is 0.008.

[0040] Treat the glass panel etching solution according to the following steps: S1, take the glass panel etching solution, adjust the pH of the solution to 1.5, and obtain the pretreatment solution; S2, prepare a composite extractant with a volume ratio of 18% P2O4 + 4% N235 + 78% sulfonated kerosene; saponify the prepared composite extractant with 10% sodium hydroxide solution, controlling the saponification rate of the organic phase to 30%, and set aside; use a centrifugal extractor to perform 5-stage countercurrent extraction with the pretreated liquid and the saponified composite extractant, controlling O / A = 1:4 and the centrifugation speed to 3500 rpm, collect the first organic phase, and collect the first raffinate and send it to the waste liquid treatment system; S3, the first organic phase and the first detergent solution are countercurrently washed using a centrifugal extractor with a centrifugal extractor, controlling the O / A ratio at 3:1 and the centrifugation speed at 3500 rpm. The second organic phase is collected, and the resulting first washing residue is collected and sent to the waste liquid treatment system. The first detergent solution is a 1 mol / L oxalic acid solution. Next, the second organic phase and the second detergent solution are countercurrently washed using a centrifugal extractor with a centrifugal extractor, controlling the O / A ratio at 4:1 and the centrifugation speed at 3500 rpm. The third organic phase is collected, and the resulting second washing residue is collected and sent to the waste liquid treatment system. The second detergent solution is a 0.5 mol / L ammonium sulfate solution. S4, the third organic phase and the first stripping agent solution are subjected to 5-stage countercurrent stripping using a centrifugal extractor with O / A ratio controlled at 4:1 and centrifugation speed at 3500 rpm. The first aqueous phase and the fourth organic phase are collected. The first stripping agent solution is a 4 mol / L hydrochloric acid solution. S5. The first aqueous phase is placed in a constant-temperature evaporation device and concentrated at 80℃ until the indium concentration in the solution reaches 28g / L. After concentration, it is naturally cooled to room temperature and allowed to stand for 1 hour. Trace impurities are removed by filtration to obtain a clear, high-purity indium-containing mother liquor. The clear, high-purity indium-containing mother liquor is then introduced into a reaction vessel, and the system temperature is kept constant at 45℃ with a stirring speed of 180rpm. 99.99% high-purity zinc powder with an average particle size of 180 mesh is added in batches and the reaction is continued for 2.2 hours. After the reaction is completed, it is allowed to stand for 30 minutes to achieve complete displacement and sedimentation of indium. The displaced material is filtered to obtain preliminary sponge indium. First, dilute hydrochloric acid is used to wash away the zinc impurities and soluble salts adsorbed on the surface, and then it is repeatedly washed with pure water until neutral. Finally, vacuum drying is performed to obtain the high-purity sponge indium product. The fourth organic phase and water were subjected to two-stage countercurrent elution using a centrifugal extractor with O / A ratio controlled at 4:1 and centrifugation speed at 3500 rpm. The fifth organic phase was collected. Then, the fifth organic phase and the regenerator solution were subjected to countercurrent regeneration using a centrifugal extractor with O / A ratio controlled at 12:1. The sixth organic phase was collected. The sixth organic phase (regenerated composite extractant) was returned to the countercurrent extraction process of S2 for recycling.

[0041] In S2 above, the saponification process is performed as follows: (1) Add the second alkaline solution (10% sodium hydroxide solution) dropwise to the prepared composite extractant at a rate of 80 mL / min and stir at a stirring rate of 150 rpm. (2) After the second alkaline solution has been added, continue stirring the reaction for 38 minutes; (3) Let stand for 45 min; (4) Observe the phase interface. After the interface becomes clear, slowly release the lower layer of saponification wastewater (aqueous phase). (5) Next, add water to the organic phase, control O / A=10:1, stir and wash for 10 min at a stirring speed of 150 rpm; (6) Let it stand again for 45 minutes; (7) Observe the phase interface. After the interface becomes clear, slowly release the lower layer of washing water (aqueous phase). (8) Wash with water 1-2 times until the pH of the wash water is 7-8; (9) After washing, a saponified organic phase (saponified composite extractant) is obtained. The obtained saponified organic phase is a clear and transparent light yellow liquid with no obvious aqueous phase entrainment. In the above saponification treatment steps, in step (1), the state of the organic phase (composite extractant) is closely observed during the drop addition process. If turbidity or emulsification occurs, the drop addition rate is immediately slowed down.

[0042] Example 2 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S1, the pH of the solution is adjusted to 1.1 using a first alkaline solution; the rest is the same as in embodiment 1.

[0043] Example 3 In the process of processing the glass panel etching solution, this embodiment differs from Embodiment 1 in that, in S1, the pH of the solution is adjusted to 1.7 using a first alkaline solution; the rest is the same as in Embodiment 1.

[0044] Example 4 In the process of processing the glass panel etching solution, this embodiment differs from Embodiment 1 in that, in S2, the saponification degree of the composite extractant is 18%; the rest is the same as in Embodiment 1.

[0045] Example 5 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S2, the saponification degree of the composite extractant is 43%; the rest is the same as in embodiment 1.

[0046] Example 6 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S2, the volume ratio of the components in the composite extractant is 20% P2O4 + 2% N235 + 78% sulfonated kerosene; the rest is the same as in embodiment 1.

[0047] Example 7 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S2, the volume ratio of the components in the composite extractant is 16% P2O4 + 6% N235 + 78% sulfonated kerosene; the rest is the same as in embodiment 1.

[0048] Example 8 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S2, the number of countercurrent extraction stages is 3; the rest is the same as in embodiment 1.

[0049] Example 9 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S3, during the countercurrent washing process of the second organic phase and the second detergent solution, the number of countercurrent washing stages is 3; the rest is the same as in embodiment 1.

[0050] Comparative Example 1 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S2, the volume ratio of the components in the composite extractant is 18% P2O4 + 82% sulfonated kerosene; the rest is the same as in embodiment 1.

[0051] Comparative Example 2 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S2, during countercurrent extraction, the O / A ratio is controlled to be 1:6; the rest is the same as in embodiment 1.

[0052] Comparative Example 3 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S2, during countercurrent extraction, the centrifugation speed is controlled at 4800 rpm; the rest is the same as in embodiment 1.

[0053] Comparative Example 4 In the process of processing the glass panel etching solution, this embodiment differs from Embodiment 1 in that, in S3, the step of countercurrent washing of the first organic phase and the first detergent solution is omitted; the rest is the same as Embodiment 1.

[0054] Comparative Example 5 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S4, during the countercurrent extraction, the centrifugal speed is controlled at 1700 rpm; the rest is the same as in embodiment 1.

[0055] Comparative Example 6 In the process of processing the glass panel etching solution, the difference between this embodiment and embodiment 1 is that in S4, during the countercurrent back-extraction process, the O / A ratio is controlled to be 5:1; the rest is the same as in embodiment 1.

[0056] Comparative Example 7 In the process of processing the glass panel etching solution, this embodiment differs from Embodiment 1 in that step S3 is omitted; the rest is the same as Embodiment 1.

[0057] Test case 1. Experimental Construction Method The indium recovery rate and the number of times the composite extractant could be recycled were tested in the above embodiments and comparative examples: (1) Indium recovery rate: Calculate the recovery rate of indium (initial sponge indium product) obtained in step S5 above: η 总 =m 成品海绵铟中In质量 / (V 原蚀刻液 ×C 原液In )×100%; In the formula: V 原蚀刻液 Volume of raw material etching solution added, in L; C 原液In Initial concentration of indium in the stock solution, g / L; m 成品In Net weight of metallic indium in the dried sponge indium product, in grams.

[0058] (2) Indium purity: w In =(m In / m 海绵铟 )×100% In the formula, w In The mass fraction of indium, i.e., its purity, is m. In m is the mass of indium in the sponge indium. 海绵铟 This represents the total mass of the indium sponge sampled.

[0059] (2) Number of cycles of the compound extractant: The saponification rate, indium loading capacity, phase separation state, and emulsification status are used as four indicators to determine the organic phase's scrapping criteria.

[0060] 1) Under the same process conditions, the saturated indium loading of the composite extractant after recycling decreases by >10% compared to the initial saturated indium loading; the calculation method for the saturated indium loading of the composite extractant is as follows: C org = V A / V O *(C0- Ce); In the above formula, V A C is the volume of the aqueous phase, in mL or L; C0 is the initial indium concentration in the aqueous phase, in g / L; C e V represents the residual indium concentration in the aqueous phase after reaction equilibrium, expressed in g / L. O The volume is the oil phase, in mL or L; C org The indium concentration in the oil phase after equilibrium is expressed in g / L. The above formula is the saturated indium loading calculated after the composite extractant (oil phase) and the original extract (aqueous phase) have been fully mixed and reacted to equilibrium.

[0061] For example, the test conditions (room temperature and pressure) for testing saturated indium loading are as follows: a. Take 20 mL of oil phase (fresh or recycled composite extractant organic phase) and 80 mL of aqueous phase (pretreated solution after pH adjustment); b. Mix and shake for 20 min, then allow to stand for phase separation; c. Phase separation is terminated when the oil and aqueous phases are essentially separated and no intermediate state remains; d. Measure the concentrations of indium (C0, Ce, Corg) in the pre-extraction aqueous phase, post-extraction aqueous phase, and post-extraction oil phase, respectively; e. Calculate the saturated indium loading using the formula.

[0062] 2) The saponification rate cannot be stably maintained at 28% to 32% under the same amount of alkali added; "under the same amount of alkali added" means that under the same conditions, the same amount of alkali solution is added for the saponification reaction, such as the amount of alkali added in Example 1; 3) The extraction phase separation time of the composite extractant after circulation is more than twice the original initial extraction phase separation time of the composite extractant; The test conditions (at room temperature and pressure) for verifying the phase separation time are as follows: a. Take 25 mL of oil phase (fresh composite extractant organic phase or recycled composite extractant organic phase) and 75 mL of aqueous phase (pretreated solution after pH adjustment); b. Mix and shake for 5 min, then let stand for phase separation; c. The phase separation time is terminated when the oil and aqueous phases are basically separated and there is no intermediate state.

[0063] 4) Continuous emulsification / third phase; The standard conditions (room temperature and pressure) for testing emulsification / third phase formation are: a. Take 25 mL of oil phase (fresh composite extractant organic phase or recycled composite extractant organic phase) and 75 mL of aqueous phase (pretreated solution after pH adjustment); b. Mix and shake for 5 min, then let stand for phase separation; c. The phase separation time is limited to 10 min, and observe the phase separation state.

[0064] If any one of the above conditions 1)-4) is met, the composite extractant is deemed invalid and scrapped.

[0065] Experimental conditions: Each round involves performing steps S2-S5 completely, recording one cycle. Samples are taken every 20 cycles for testing: saturated indium loading in the organic phase of the composite extractant, measured saponification rate, phase separation state, and emulsification status. The effective number of cycles for the composite extractant is calculated according to the aforementioned scrapping standards.

[0066] 2. Experimental Results The indium recovery rates and the number of times the composite extractant was recycled in the above embodiments and comparative examples are recorded in Table 1.

[0067] Table 1. Indium recovery rate and number of times the composite extractant was recycled in the examples and comparative examples.

[0068] As shown in Table 1, the method provided by the present invention can not only effectively improve the recovery rate of indium, but also the obtained primary sponge indium has high purity, and the composite extractant can be recycled more than 189 times.

[0069] The extractant in Comparative Example 1 did not contain N235, i.e., it was a single P204 extractant system, which resulted in a decrease in the total extraction rate and yield.

[0070] In Comparative Example 2, during countercurrent extraction in S2, the O / A ratio was controlled at 1:6, meaning that the oil-water ratio was too small, the aqueous phase was too large, and the extraction was incomplete, resulting in a decrease in the overall yield.

[0071] In Comparative Example 3, during countercurrent extraction in S2, the centrifugation speed was controlled at 4800 rpm. This means that the centrifugation speed was too high, the phase contact time was short, the reaction was incomplete, resulting in low extraction rate and low total yield. Furthermore, the composite extractant was over-sheared, causing certain physical and chemical damage to the composite extractant itself and shortening its lifespan.

[0072] In Comparative Example 4, the step of countercurrent washing of the first organic phase and the first detergent solution in S3 is omitted, which reduces the washing and impurity removal step of the first oxalic acid solution, resulting in a decrease in indium purity and a shortened lifespan of the composite extractant.

[0073] In Comparative Example 5, during countercurrent extraction in S4, the centrifugal speed was controlled at 1700 rpm. If the centrifugal speed was too low, the shearing effect was weak, the reaction was incomplete, the extraction rate decreased, resulting in a decrease in indium recovery rate and a shortened lifespan of the composite extractant.

[0074] In Comparative Example 6, during the countercurrent extraction process in S4, controlling O / A = 5:1 resulted in insufficient aqueous phase and incomplete reaction, which affected the indium recovery rate and also reduced the service life of the composite extractant.

[0075] In Comparative Example 7, step S3 was omitted, meaning there was no purification step at all, which significantly affected the purity, indium recovery rate, and lifespan of the composite extractant.

[0076] Furthermore, comparing Example 1 and Example 2, in Example 2, the pH of the stock solution was adjusted to be too low in S1, i.e., H + An increase in ion concentration shifts the equilibrium reaction to the left, reducing the extraction rate of the main reaction and thus decreasing the indium extraction rate, resulting in a decrease in indium recovery.

[0077] Comparing Example 1 and Example 3, in Example 3, the pH of the stock solution was adjusted too high in S1. Impurity ions such as iron and aluminum were close to the hydrolysis reaction range, which would increase the risk of emulsification and reduce the extraction rate, thus reducing the indium recovery rate.

[0078] Comparing Example 1 and Example 4, in Example 4, the saponification degree of the composite extractant in S2 was low, resulting in insufficient NaHA2 for the displacement reaction, which affected the extraction rate and caused a decrease in the indium recovery rate.

[0079] Comparing Example 1 and Example 5, in Example 5, the saponification degree of the composite extractant in S2 is higher, the viscosity of the organic phase increases, the reaction phase separation time is longer, which also reduces the extraction rate and causes a decrease in the indium recovery rate.

[0080] Comparing Example 1 and Example 6, in Example 6, the amount of N235 decreased, the overall extraction rate decreased, and therefore the indium recovery rate also decreased.

[0081] Comparing Example 1 and Example 7, in Example 7, P204 was reduced, the extraction rate of the main reaction was lowered, and therefore the indium recovery rate also decreased.

[0082] Comparing Example 1 and Example 8, in Example 8, the number of extraction stages was insufficient, and the extraction was not thorough enough, so the indium recovery rate also decreased.

[0083] Comparing Example 1 and Example 9, in Example 9, there are too many extraction stages, which may lead to excessive elution of the target metal and a decrease in indium recovery rate.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention, but such modifications or substitutions are all within the scope of protection of the present invention.

Claims

1. A method for recovering indium from glass panel etching solution, characterized in that, Includes the following steps: S1, take the glass panel etching solution, adjust the pH of the solution to 1.2~1.6 to obtain the pretreatment solution; S2, the pretreated liquid is subjected to countercurrent extraction with the composite extractant, the O / A ratio is controlled at 1:3~5, and the centrifugation speed is 2000~4500 rpm, and the first organic phase is collected; the composite extractant includes P204 and N235, and the volume ratio of P204 to N235 is 15~20:3~5; S3, the first organic phase is countercurrently washed with the first detergent solution, controlling the O / A ratio to be 2~4:1, and the centrifugation speed to be 2000~4500 rpm, and the second organic phase is collected; the first detergent solution includes oxalic acid solution; then the second organic phase is countercurrently washed with the second detergent solution, controlling the O / A ratio to be 3~5:1, and the centrifugation speed to be 2000~4500 rpm, and the third organic phase is collected; the second detergent solution includes ammonium sulfate solution; S4, the third organic phase and the first stripping agent solution are subjected to countercurrent stripping, with O / A ratio controlled at 3~5:1 and centrifugation speed at 2000~4500 rpm, and the first aqueous phase and the fourth organic phase are collected; the first stripping agent solution includes hydrochloric acid solution; S5, add zinc powder to the first aqueous phase to carry out a displacement reaction. After the reaction is completed, indium is obtained. The fourth organic phase is countercurrently eluted with water, with O / A = 3~5:1 and centrifugation speed of 2000~4500 rpm. The fifth organic phase is collected. Then, the fifth organic phase is countercurrently regenerated with the regenerator solution, with O / A = 10~15:

1. The sixth organic phase is collected.

2. The method for recovering indium from glass panel etching solution as described in claim 1, characterized in that: In step S1, the pH of the stock solution is adjusted to 1.2-1.6 using a first alkaline solution.

3. The method for recovering indium from glass panel etching solution as described in claim 1, characterized in that, In S1, the stock solution satisfies at least one of the following conditions: (1) The stock solution contains: 80~100g / L of sulfate; (2) The pH of the stock solution is not higher than 0.5, or preferably not higher than 0.1, or preferably not higher than 0.05, or preferably not higher than 0.

01.

4. The method for recovering indium from glass panel etching solution as described in claim 1, characterized in that, S2 satisfies at least one of the following conditions: (1) The number of countercurrent extraction stages is 4 to 7; (2) Countercurrent extraction was performed using a centrifugal extractor. (3) The composite extractant is also subjected to saponification treatment before countercurrent extraction, and the degree of saponification is controlled to be 20-40%; (4) The composite extractant also includes a diluent, and the volume ratio of P204, N235 and the diluent is 15~20:3~5:75~82.

5. The method for recovering indium from glass panel etching solution as described in claim 1, characterized in that, In step S3, at least one of the following conditions is met during the countercurrent washing process between the first organic phase and the first detergent solution: (1) The number of countercurrent extraction stages is 2 to 3; (2) Countercurrent extraction was performed using a centrifugal extractor. (3) When the first detergent solution is the oxalic acid solution, the concentration is 0.5~1.2 mol / L.

6. The method for recovering indium from glass panel etching solution as described in claim 1, characterized in that, In step S3, at least one of the following conditions is met during the countercurrent washing process between the second organic phase and the second detergent solution: (1) The countercurrent washing stage is 1 to 2 stages; (2) Countercurrent washing was performed using a centrifugal extractor. (3) When the second detergent solution is the ammonium sulfate solution, the concentration is 0.2~0.8 mol / L.

7. The method for recovering indium from glass panel etching solution as described in claim 1, characterized in that, In step S4, at least one of the following conditions must be met during the countercurrent back-extraction process between the third organic phase and the first back-extractant solution: (1) The number of countercurrent extraction stages is 4 to 7; (2) Countercurrent washing was performed using a centrifugal extractor. (3) When the first stripping agent is the hydrochloric acid solution, the concentration is 3~7 mol / L.

8. The method for recovering indium from glass panel etching solution as described in claim 1, characterized in that, At least one of the following conditions must be satisfied in S5: (1) Before adding zinc powder to the first aqueous phase for the displacement reaction, the first aqueous phase is concentrated until the indium concentration in the solution reaches 25~30g / L; (2) During the displacement reaction of adding zinc powder to the first aqueous phase, the reaction temperature is controlled at 40~50℃; (2) The displacement reaction process also involves stirring, with the stirring speed set to 150~200 rpm; (3) The purity of zinc powder shall not be less than 99.9%, and the average particle size shall be 150~200 mesh; (4) Add zinc powder in batches for displacement reaction, and continue the reaction for 2.0~2.5h. After the reaction is completed, let it stand for no less than 20min.

9. The method for recovering indium from glass panel etching solution as described in claim 1, characterized in that: In step S5, during the countercurrent elution process of the fourth organic phase and the water, the number of countercurrent elution stages is 1 to 3.

10. The method for recovering indium from glass panel etching solution as described in claim 1, characterized in that, In step S5, at least one of the following conditions must be met during the countercurrent regeneration process of the fifth organic phase and the regenerator solution: (1) The number of countercurrent regeneration stages is 2 to 3; (2) The regenerator solution includes a third alkaline solution.

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