A method for fractional extraction of noble metals and monoacids from phosphoric acid-based etching solutions.

Abstract

This invention proposes a method for the graded extraction of precious metals and monoacids from phosphoric acid-based etching solutions. The method includes the following steps: S1, mixing capsules and phosphoric acid-based etching solutions to perform a first reaction, obtaining a first precipitate, separating the first precipitate, and recovering phosphoric acid; S2, then performing a second reaction to obtain a second precipitate, separating the second precipitate, and recovering the precious metals; wherein the capsules have a core-shell structure, comprising a core and an outer shell from the inside out. The core comprises polyethyleneimine and alginate, and the outer shell comprises calcium carbonate, sodium alginate, and chitosan. This invention requires no external intervention; the simultaneous recovery of two resources can be achieved by deploying a single capsule, offering significant advantages such as ease of operation, low cost, high recovery efficiency, and environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of resource recycling technology, and in particular to a method for graded extraction of precious metals and monoacids from phosphoric acid etching solutions. Background Technology

[0002] Phosphoric acid-based etching solutions are widely used in etching processes in industries such as LCD panels, semiconductors, and precision metal processing. A typical composition includes phosphoric acid (50%–80%), acetic acid (5%–15%), nitric acid (1%–5%), dissolved metal ions, and small amounts of precious metals. With repeated use, metal ions accumulate in the etching solution, reducing its etching performance and eventually rendering it waste.

[0003] Currently, the main technical problems with the treatment methods for phosphoric acid-based etching waste liquid are as follows: (1) Precious metal recovery and acid recovery are mutually restrictive In existing technologies, the recovery of precious metals typically employs chemical precipitation or electrolysis. Chemical precipitation involves adding sulfides or reducing agents to the waste liquid, causing the precious metals to precipitate as sulfides or in elemental form. However, this method suffers from poor selectivity, and the waste liquid often contains large quantities of base metals (Al). 3+ Fe 3+ Cu 2+ Phosphoric acid co-precipitates with precious metals, resulting in low purity of the recovered product and high subsequent refining costs. Electrolysis requires controlling the cathode potential to achieve selective deposition, which involves large equipment investment, high energy consumption, and the high-concentration phosphoric acid system corrodes the electrodes, affecting long-term operational stability.

[0004] On the other hand, phosphoric acid recovery often employs diffusion dialysis or solvent extraction. While diffusion dialysis can recover free acid, it cannot simultaneously process dissolved metal ions; solvent extraction introduces organic solvents, posing a risk of secondary pollution, and the co-extraction of precious metal ions by the extractant can lead to the dispersion and loss of precious metals.

[0005] (2) The processing flow is complex and requires multiple independent procedures. To simultaneously recover acid and precious metals, existing technologies typically employ a multi-stage process: first, a neutralizing agent is used to adjust the pH to precipitate metal ions; then, the precipitate is acid-dissolved and separated; finally, the acid and metal are recovered separately. This staged treatment method is cumbersome, requires large equipment footprint, consumes a lot of chemicals, and requires precise control for staged dosing, increasing operational difficulty and labor costs.

[0006] (3) Insufficient utilization of phosphoric acid resources Most treatment methods neutralize phosphoric acid as waste or only recover it as low-value crude phosphoric acid. As a non-renewable resource, the direct discharge or underutilization of phosphoric acid results in a serious waste of phosphorus resources. A few technologies attempt to convert phosphoric acid into phosphate products, but these typically require additional conversion steps and equipment.

[0007] (4) Difficulty in separating precious and base metals The concentration of precious metals in etching wastewater is relatively low (typically tens to hundreds of mg / L), while the concentration of base metals can reach tens of thousands of mg / L. Existing precipitation methods are insufficient to separate precious and base metals, as precious metals are often lost due to entrainment by base metal hydroxides or phosphates, resulting in low recovery rates.

[0008] Therefore, developing a graded extraction method that can simultaneously and efficiently recover phosphoric acid and precious metals, and which is simple to operate and does not require complex equipment, has significant industrial application value and environmental significance. Summary of the Invention

[0009] In view of this, the present invention proposes a method for the fractional extraction of precious metals and monoacids from phosphoric acid-based etching solutions. This method utilizes a phosphoric acid-based etching solution and a capsule reaction to recover phosphoric acid and precious metals. The capsule has a core-shell structure, with the outer shell containing calcium carbonate, sodium alginate, and chitosan, and the inner core containing polyethyleneimine and alginate. The strong acidity of the etching solution itself drives the outer shell to undergo acid neutralization and react with calcium phosphate precipitation, achieving phosphoric acid recovery. Simultaneously, the outer shell automatically disintegrates upon pH increase, exposing the inner core for selective adsorption of precious metal ions, thereby achieving the sequential fractional extraction of phosphoric acid and precious metals. This invention requires no external intervention; the simultaneous recovery of two resources can be achieved by deploying a single capsule, offering significant advantages such as ease of operation, low cost, high recovery efficiency, and environmental friendliness.

[0010] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a method for graded extraction of precious metals and monoacids from phosphoric acid etching solution, comprising the following steps: S1, mixing capsules and phosphoric acid etching solution, performing a first reaction to obtain a first precipitate, separating the first precipitate, and recovering phosphoric acid; S2. Then, a second reaction is carried out to obtain a second precipitate. The second precipitate is separated to recover the precious metal. The capsule has a core-shell structure, consisting of a core and an outer shell from the inside out. The core comprises polyethyleneimine and alginate, and the outer shell comprises calcium carbonate, sodium alginate, and chitosan.

[0011] The outer shell is composed of a ternary composite of calcium carbonate, sodium alginate, and chitosan, with each component complementing the others and being indispensable.

[0012] Calcium carbonate undergoes a neutralization reaction in a strongly acidic phosphoric acid system. This reaction achieves three objectives simultaneously: First, it rapidly consumes the free acid in the etching solution, raising the pH from 0.2-0.5 to around 3.0; second, it converts soluble phosphate ions in the solution into insoluble calcium phosphate precipitates, realizing the resource recovery of phosphoric acid; and third, the CO2 gas released in the reaction generates a micro-explosion effect inside the shell, promoting the formation of micro-cracks in the shell and creating conditions for subsequent disintegration.

[0013] Chitosan molecules contain a large number of amino groups, and these amino groups are converted by H... + Protonation to -NH3 + The polymer chains extend due to electrostatic repulsion, but at this point, the overall structure of the outer shell remains intact because the calcium carbonate has not yet been completely consumed. When the calcium carbonate raises the pH of the waste liquid to 2.5-3.5, the protonation degree of chitosan reaches a critical value, the interlayer forces of the polyelectrolyte complex (sodium alginate-chitosan) are disrupted, and the outer shell undergoes macroscopic disintegration. This pH-responsive disintegration mechanism ensures that the core is only exposed after the acidity decreases, avoiding the failure of PEI in a strongly acidic environment.

[0014] Sodium alginate reacts with Ca in aqueous solution 2+ Cross-linking forms a calcium alginate gel network, providing mechanical strength to the shell. Simultaneously, sodium alginate and chitosan form a polyelectrolyte complex through electrostatic interactions. The difference in swelling behavior of this complex at different pH values ​​forms the structural basis for the time-series control in this scheme.

[0015] The core is a three-dimensional network structure formed by cross-linking polyethyleneimine and alginate. In a weakly acidic environment of pH 3-4, the amino groups on PEI are protonated, and the positively charged -NH3 groups... + PEI adsorbs noble metal complexes in solution in anionic form through electrostatic interactions, while unprotonated nitrogen atoms coordinate and chelate with noble metal ions to form stable five- or six-membered ring complexes. This dual "electrostatic + coordination" mechanism endows PEI with extremely high noble metal selectivity.

[0016] Alginate forms a stable three-dimensional gel network through ionic and covalent cross-linking, anchoring PEI in the network to prevent PEI from dissolving in the aqueous phase, while maintaining the accessibility of active sites to noble metal ions.

[0017] This invention uses calcium carbonate to raise the pH of the waste liquid from 0.2 to 3.0, which falls precisely within the chitosan disintegration trigger window (pH 2.5~3.5). If the pH is too low, the chitosan solubility is insufficient, preventing disintegration; if the pH is too high, the chitosan disintegrates too quickly, potentially exposing the core prematurely. The optimal pH range for PEI adsorption of precious metals is 3~10. Calcium carbonate raises the pH of the waste liquid to 3.0, precisely bringing PEI into its optimal working state. If the pH is too low (<2), although PEI can adsorb anionic complexes through electrostatic interactions, the PEI molecular chains are not fully extended, the stability of the calcium alginate gel decreases, and the overall adsorption effect significantly declines; if the pH is too high (>5), phosphate ions may form precipitates, interfering with the adsorption process.

[0018] The shell design ensures that chitosan only disintegrates after calcium carbonate has completed most of the acid neutralization reaction. This sequence guarantees that: most of the phosphoric acid has been converted into calcium phosphate precipitate, completing phosphoric acid recovery; the pH of the waste liquid has been raised to the optimal operating range of PEI; and the PEI core is exposed under low-stress conditions, avoiding degradation in strong acids.

[0019] Based on the above technical solutions, the precious metal further includes gold or palladium.

[0020] Based on the above technical solution, the mass ratio of calcium carbonate, sodium alginate and chitosan in the shell is further 1:(1~3):(1~3).

[0021] Based on the above technical solutions, the alginate further includes one or more of sodium alginate, potassium alginate, or ammonium alginate.

[0022] Based on the above technical solution, the mass ratio of polyethyleneimine to alginate in the core is further 1:(0.2~3).

[0023] Based on the above technical solution, the preparation method of the capsule further includes: A1, dissolving polyethyleneimine and alginate in water, adding a crosslinking agent to obtain the core; A2. The kernel is sequentially immersed in sodium alginate solution and chitosan solution, calcium carbonate is added, and after drying, a capsule is obtained.

[0024] Based on the above technical solutions, the crosslinking agent further includes at least one of glutaraldehyde or epichlorohydrin.

[0025] Based on the above technical solutions, the mass ratio of the core to the shell is further 1:(1~3).

[0026] Based on the above technical solution, the recovery of phosphoric acid further includes: reacting the first precipitate with sulfuric acid to collect phosphoric acid.

[0027] Based on the above technical solution, the recovery of precious metals further includes: eluting the core loaded with precious metals using a hydrochloric acid solution of thiourea to collect the precious metals.

[0028] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention utilizes the strong acidity of the etching solution to drive the neutralization reaction of calcium carbonate in the shell and the pH response disintegration of chitosan, automatically realizing the graded extraction of "first recovering phosphoric acid and then recovering precious metals". The entire process only requires one capsule to be added, without the need for segmented drug addition, electricity or pH adjustment, and is simple to operate and has extremely low energy consumption.

[0029] (2) The outer shell converts phosphoric acid into calcium phosphate precipitate for recycling, while the core selectively adsorbs precious metal ions after the outer shell disintegrates. Both high-value resources are recovered simultaneously in one treatment, avoiding the problems of phosphoric acid being neutralized and wasted, and precious metals being co-precipitated and diluted, thus realizing the full resource utilization of waste liquid.

[0030] (3) The shell protects the core from damage in a strong acid environment. After the pH is raised to a suitable range, it automatically disintegrates and releases the core, so that the adsorption of precious metals can be carried out under optimal conditions. Moreover, the core can be reused after being washed and regenerated. The material is cheap and readily available, the process is simple, and it is easy to promote industrialization. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] In the following specific embodiments, the composition of the etching waste liquid includes 62.5 wt% H3PO4, 10.8 wt% HAc, 1.2 wt% HNO3, and Al. 3+ 3.2wt%, Au 110 mg / L, Pd 35 mg / L, Cu 2+ 0.5 mg / L; The capsules have a particle size of 500~600 μm and a shell thickness of 50~70 μm.

[0033] In the following specific embodiment, the method for preparing the hydrochloric acid solution of thiourea is as follows: In a fume hood, about 800 mL of deionized water is added to a beaker, and 3.81 g of weighed thiourea is slowly added. The mixture is magnetically stirred until completely dissolved, and the resulting solution is a colorless, clear, and transparent liquid. While stirring, slowly add 4.17 mL of concentrated hydrochloric acid (12 mol / L). Wash the beaker wall with a small amount of deionized water and continue stirring for 2-3 minutes to ensure the solution is thoroughly mixed. Transfer the solution to a 1 L volumetric flask, dilute to the mark with deionized water, tighten the stopper, and invert the flask to mix thoroughly, thus obtaining a thiourea hydrochloric acid solution.

[0034] In the following specific embodiments, unless otherwise specified, all reagents used are conventional reagents that can be obtained commercially. The polyethyleneimine was purchased from Wuhan Shuer Biotechnology Co., Ltd., with product number 9002-98-6.

[0035] Example 1 This embodiment provides a method for fractional extraction of noble metals and monoacids from phosphoric acid-based etching solutions, comprising the following steps: 1. Capsule preparation Dissolve 10 g of polyethyleneimine and 10 g of sodium alginate in 200 mL of deionized water and stir at room temperature until completely dissolved. Add 0.5 mL of glutaraldehyde (25 wt% aqueous solution) as a crosslinking agent and continue stirring for 1 hour. Drop the mixture into 0.2 M CaCl2 solution using a syringe, allow it to stand for crosslinking for 2 hours, filter, and wash three times with deionized water to obtain the core.

[0036] The mass ratio of polyethyleneimine to sodium alginate in the core is 1:1.

[0037] 100 g of the above-mentioned core was placed in 500 mL of 0.3% (w / v) sodium alginate solution, shaken for 15 minutes for adsorption, filtered, and washed with deionized water. Then it was transferred to 500 mL of 0.3% (w / v) chitosan solution, shaken for 15 minutes for adsorption, filtered, and washed. The above alternating assembly cycle of sodium alginate and chitosan was repeated 4 times, with 2 g of calcium carbonate added each time during the alternating assembly process to ensure that the calcium carbonate was uniformly dispersed in the outer shell layer.

[0038] Finally, the assembled capsules were dried in a 60°C oven for 12 hours to obtain the capsules.

[0039] The mass ratio of calcium carbonate, sodium alginate and chitosan in the outer shell is 1:2:2; the mass ratio of the core to the outer shell is 1:2.

[0040] 2. Phosphoric acid recovery Take 1 L of etching waste liquid and place it in a 2 L glass reactor. Add 15 g of the capsules prepared in step 1, and stir mechanically (200 rpm) at 25°C. After reacting for 60 minutes, filter to separate and obtain the first precipitate.

[0041] Measurements showed that the total phosphorus concentration in the liquid phase decreased from the initial 62.5% to 24.1%, and the phosphoric acid precipitation recovery rate was 61.4%. Simultaneously, the pH of the waste liquid increased from the initial 0.2 to 3.1.

[0042] The first precipitate (calcium phosphate) was mixed with dilute sulfuric acid (20% H2SO4) at a solid-liquid ratio of 1:3 and stirred for 2 hours. The calcium sulfate precipitate was removed by filtration, and the filtrate was concentrated by evaporation to obtain crude phosphoric acid with a mass fraction of 82.3%. After purification by activated carbon adsorption, industrial-grade phosphoric acid (H3PO4 content 85.2%, total metal impurity content <50 ppm) was obtained.

[0043] 3. Precious metal recycling The liquid phase obtained after filtration in step S1 (with the first precipitate removed) was stirred further. At this point, the outer shell had disintegrated after the pH rose to 3.1, exposing the core to the liquid phase.

[0044] The reaction was continued with stirring for 3 hours, during which the polyethyleneimine in the core adsorbed noble metal ions through its amine groups. After the reaction was completed, the core loaded with noble metals (the second precipitate) was obtained by filtration.

[0045] The second precipitate was eluted with a thiourea hydrochloric acid solution at 45°C for 2 hours by shaking, filtered, and the precious metals were collected. The concentration of Au in the eluent was determined to be 105.2 mg / L, and the concentration of Pd was 32.6 mg / L.

[0046] The calculated recovery rates were 97.5% for Au and 94.9% for Pd.

[0047] Example 2 This embodiment provides a method for fractional extraction of noble metals and monoacids from phosphoric acid-based etching solutions, which differs from Embodiment 1 in that: 1. Capsule preparation The mass ratio of calcium carbonate, sodium alginate and chitosan was adjusted to 1:1:1; Alginate is ammonium alginate, and the mass ratio of polyethyleneimine to ammonium alginate is 1:0.2.

[0048] The mass ratio of the core to the shell is 1:1.

[0049] The recovered phosphoric acid concentration was 83.1%, Au recovery rate was 96.2%, and Pd recovery rate was 92.9%.

[0050] Example 3 This embodiment provides a method for fractional extraction of noble metals and monoacids from phosphoric acid-based etching solutions, which differs from Embodiment 1 in that: 1. Capsule preparation The mass ratio of calcium carbonate, sodium alginate and chitosan was adjusted to 1:3:3; The alginate is potassium alginate, and the mass ratio of polyethyleneimine to ammonium alginate is 1:3.

[0051] The mass ratio of the core to the shell is 1:3.

[0052] The recovered phosphoric acid concentration was 82.1%, Au recovery rate was 95.2%, and Pd recovery rate was 91.3%.

[0053] Comparative Example 1 The difference between this comparative example and Example 1 is that the capsules in this comparative example do not contain chitosan.

[0054] After 30 minutes of reaction, the pH rose from 0.2 to 2.8, and after 60 minutes of reaction, it rose to 3.2, with a phosphoric acid recovery rate of 58.5%.

[0055] However, no obvious disintegration of the shell was observed during the entire reaction process.

[0056] After stirring for another 4 hours, the outer shell still did not disintegrate and the core was not exposed.

[0057] The results showed that the recovery rate of Au was only 12.3% and the recovery rate of Pd was 10.9%.

[0058] When the capsule was cut open after the reaction, the core PEI / sodium alginate was still completely encapsulated and had almost no contact with the waste liquid.

[0059] This is because chitosan is a natural alkaline polysaccharide with a large number of amine groups on its molecular chain. In an acidic environment, these amine groups undergo protonation, leading to strong electrostatic repulsion between the molecular chains and causing the polymer network to expand. Sodium alginate and chitosan form a polyelectrolyte complex through electrostatic interaction. This complex exhibits significant responsiveness to pH changes: the swelling rate is lowest at low pH and increases in a neutral environment.

[0060] After the chitosan is removed from the capsule, the outer shell consists only of CaCO3 and sodium alginate. Although sodium alginate contains CaCO3... 2+ Crosslinking forms a hydrogel network, but it lacks pH-responsive protonated groups, thus failing to exhibit significant volume changes or structural loosening during pH increases. While the consumption of calcium carbonate makes the outer shell more porous, the calcium alginate gel network remains relatively stable in the absence of chitosan, lacking the driving force to cause macroscopic shell rupture. Therefore, the outer shell cannot disintegrate at the preset pH threshold (2.5-3.5), the core remains encapsulated, and PEI is not exposed to the waste liquid, resulting in almost no recovery of the precious metal.

[0061] Comparative Example 2 The difference between this comparative example and Example 1 is that the capsules in this comparative example do not contain calcium carbonate.

[0062] Throughout the reaction, almost no CO2 bubbles were observed to be produced, nor was any white calcium phosphate precipitate formed. Although the outer shell swelled to some extent after the pH slowly rose to 1.2, no significant disintegration occurred.

[0063] The results showed that the phosphoric acid concentration remained essentially unchanged, and the phosphoric acid precipitation recovery rate was only 5.2%. The Au recovery rate was only 18.6%, and the Pd recovery rate was only 19.1%.

[0064] This is because after removing calcium carbonate, the outer shell consists only of a polyelectrolyte complex of sodium alginate and chitosan. While this complex is pH-responsive, its acid-neutralizing capacity is limited, and it cannot withstand the strong acid environment of high-concentration phosphoric acid. The pH of the waste liquid consistently fails to rise to the conditions required for chitosan disintegration (pH 2.5-3.5), resulting in partial swelling of the outer shell but incomplete disintegration. More importantly, the phosphoric acid is not recovered at all.

[0065] Comparative Example 3 The difference between this comparative example and Example 1 is that the capsule in this comparative example has no outer shell.

[0066] The results showed that the recovery rate of Au was only 38.0% and the recovery rate of Pd was only 38.6%.

[0067] This is because, when the outer shell is missing, the core is exposed in an acidic environment, and almost all the amino groups on the PEI molecular chain are protonated. Although this does not completely eliminate its electrostatic adsorption capacity for noble metal anion complexes, the stability of PEI molecules in strong acids is poor. Furthermore, the cross-linked structure of the calcium alginate gel network is disrupted at low pH, leading to the loss of Ca... 2+ As the PEI dissolves from the gel, the core loses its mechanical strength, and the PEI is released from the network.

[0068] Comparative Example 4 The difference between this comparative example and Example 1 is that the mass ratio of the kernel to the shell in the capsule of this comparative example is 1:10.

[0069] The recovery rate of phosphoric acid precipitation reached 72.3%, while the recovery rate of Au was only 70.4% and the recovery rate of Pd was only 63.4%.

[0070] This is because when the shell is too thick, the total amount of CaCO3 increases significantly, requiring a longer time to deplete the calcium carbonate and raise the pH to the disintegration threshold (2.5-3.5). Due to the large amount of CaCO3, even when the pH reaches the disintegration threshold, the CaCO3 is not completely consumed. The calcium carbonate particles form a physical barrier in the shell, hindering the full expansion and disintegration of the chitosan network. This leads to a significant decrease in precious metal recovery efficiency.

[0071] In summary, this invention proposes a method for the fractional extraction of precious metals and monoacids from phosphoric acid-based etching solutions. This method utilizes a phosphoric acid-based etching solution and a capsule reaction to recover phosphoric acid and precious metals. The capsule has a core-shell structure, with the outer shell containing calcium carbonate, sodium alginate, and chitosan, and the inner core containing polyethyleneimine and alginate. The strong acidity of the etching solution itself drives the outer shell to neutralize and precipitate calcium phosphate, achieving phosphoric acid recovery. Simultaneously, the outer shell automatically disintegrates upon pH increase, exposing the inner core for selective adsorption of precious metal ions, thus achieving the sequential fractional extraction of phosphoric acid and precious metals. This invention requires no external intervention; the simultaneous recovery of two resources can be achieved by deploying a single capsule, offering significant advantages such as ease of operation, low cost, high recovery efficiency, and environmental friendliness.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fractionally extracting noble metals and monoacids from phosphoric acid-based etching solutions, characterized in that, The process includes the following steps: S1, mixing the capsule and the phosphoric acid etching solution, performing a first reaction to obtain a first precipitate, separating the first precipitate, and recovering the phosphoric acid; S2. Then, a second reaction is carried out to obtain a second precipitate. The second precipitate is separated to recover the precious metal. The capsule has a core-shell structure, consisting of a core and an outer shell from the inside out. The core comprises polyethyleneimine and alginate, and the outer shell comprises calcium carbonate, sodium alginate, and chitosan.

2. The method for fractional extraction of noble metals and monoacids from phosphoric acid etching solution as described in claim 1, characterized in that, The precious metals include gold or palladium.

3. The method for fractional extraction of noble metals and monoacids from phosphoric acid etching solution as described in claim 1, characterized in that, The mass ratio of calcium carbonate, sodium alginate and chitosan in the shell is 1:(1~3):(1~3).

4. The method for fractional extraction of noble metals and monoacids from phosphoric acid etching solution as described in claim 1, characterized in that, The alginate includes one or more of sodium alginate, potassium alginate, or ammonium alginate.

5. The method for fractional extraction of noble metals and monoacids from phosphoric acid etching solution as described in claim 4, characterized in that, The mass ratio of polyethyleneimine to alginate in the core is 1:(0.2~3).

6. The method for fractional extraction of noble metals and monoacids from phosphoric acid etching solution as described in claim 1, characterized in that, The preparation method of the capsule includes: A1, dissolving polyethyleneimine and alginate in water, adding a crosslinking agent to obtain the core; A2. The kernel is sequentially immersed in sodium alginate solution and chitosan solution, calcium carbonate is added, and after drying, a capsule is obtained.

7. The method for fractional extraction of noble metals and monoacids from phosphoric acid etching solution as described in claim 6, characterized in that, The crosslinking agent includes at least one of glutaraldehyde or epichlorohydrin.

8. The method for fractional extraction of noble metals and monoacids from phosphoric acid etching solution as described in claim 1, characterized in that, The mass ratio of the core to the outer shell is 1:(1~3).

9. The method for fractional extraction of noble metals and monoacids from phosphoric acid etching solution as described in claim 1, characterized in that, The recovery of phosphoric acid includes reacting the first precipitate with sulfuric acid to collect phosphoric acid.

10. The method for fractional extraction of noble metals and monoacids from phosphoric acid etching solution as described in claim 1, characterized in that, The recovery of precious metals includes: eluting the core loaded with precious metals using a thiourea hydrochloric acid solution, and collecting the precious metals.