Method for removing heavy metals from electroplating waste acid

Abstract

The application discloses a method for removing heavy metals from electroplating waste acid, and belongs to the technical field of wastewater treatment. The method comprises the following steps: S1, filtering electroplating waste acid to obtain pretreated liquid; S2, adjusting the pretreated liquid to be acidic and then performing ultrafiltration to obtain filtered liquid; S3, adsorbing and separating heavy metals and sulfate by using amino imidazole phosphonic acid modified D851 resin; S4, eluting and desorbing the resin to regenerate and recycle; and S5, electrolyzing the sulfate solution to recover high-purity metal elements at a cathode and recover sulfuric acid at an anode. The method realizes efficient and deep removal of heavy metals from electroplating waste acid by a combined process, and simultaneously completes resource recovery of sulfuric acid and metals; the modified resin has strong acid resistance and good cyclic stability, the overall process is stable in operation, and the environmental protection benefit and economic benefit are outstanding, so that the method is suitable for industrial application.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for removing heavy metals from electroplating waste acid. Background Technology

[0002] The electroplating industry generates a large amount of waste acid during workpiece surface treatment. This waste acid mainly originates from the pickling and activation processes before electroplating, and the rinsing and passivation processes after electroplating. It contains high concentrations of sulfates and also contains Cr. 3+ Ni 2+ Cu 2+ Heavy metal ions.

[0003] Currently, the main methods for removing heavy metals from electroplating waste acid solutions include chemical precipitation, electrolysis, and adsorption. Chemical precipitation requires the addition of large amounts of alkali to adjust the pH, generating a large amount of sludge containing heavy metals. Subsequent sludge treatment is difficult and costly, and it cannot recover acid and heavy metal resources. Electrolysis, when directly treating waste acid solutions, suffers from low electrolysis efficiency and severe electrode wear due to interference from impurities in the waste acid, resulting in low purity of recovered heavy metals. Conventional adsorption methods use adsorbents with poor selectivity for chromium and nickel ions, limited adsorption capacity, and difficulty in regenerating the adsorbents, leading to high treatment costs and failing to meet the needs of large-scale industrial processing. Summary of the Invention

[0004] This invention provides a method for removing heavy metals from electroplating waste acid, which can solve the problems of low processing efficiency and resource waste in the prior art.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for removing heavy metals from waste acid solution from electroplating includes the following steps: S1. Filter the electroplating waste acid solution to obtain the pretreated solution; S2. Pass the pretreated waste acid liquid into the pH adjustment tank to adjust it to acidity, obtain pH adjustment liquid, and then ultrafilter to obtain filtrate. S3. Pass the filtrate into an adsorption column containing modified chelating resin for adsorption until the resin is saturated, and then stop and collect the sulfate solution. S4. First, rinse the saturated resin of S3 with eluent to desorb, collect the eluent, and then wash the resin with deionized water until neutral. The sulfate solutions obtained from S5 and S3 are passed into the electrolytic cell to collect the cathode metal element and the anode sulfuric acid solution, respectively. The modified chelating resin is an aminoimidazolidine acid-modified D851 resin.

[0006] Further, in step S1, the filtration device is a bag filter with a diameter of 5–20 μm and a flow rate of 0.5–2.0 m / s.3 / h, pressure is 0.1~0.3MPa.

[0007] Further, in step S2, the substance used to adjust the pH in the pH adjustment tank is a 10% sodium hydroxide solution, and the acidity is pH = 3 to 6.

[0008] Furthermore, in step S2, the ultrafiltration uses a polyethersulfone membrane with a pore size of 0.05–0.2 μm, an operating pressure of 0.2–0.6 MPa, and an operating temperature of 20–45 °C.

[0009] Further, in step S3, the adsorption column has a height-to-diameter ratio of 10:1, a flow rate of 2-10 BV / h, and an adsorption temperature of 10-20℃.

[0010] Further, in step S4, the eluent is a hydrochloric acid solution with a weight percentage of 20% to 30%.

[0011] Furthermore, in step S4, the desorption temperature is 10–20°C and the flow rate is 2–10 BV / h.

[0012] Further, in step S5, the specific parameters of the electrolytic cell are: electrolysis temperature of 40–60°C, and electrolysis current density of 100–200 A / m³. 2 The electrolysis voltage is 5-8V, and the electrolysis time is 8-10h.

[0013] Further, in step S3, the method for preparing the modified chelating resin is as follows: S31. Add D851 resin to anhydrous ethanol for wetting, wash with deionized water, and dry to obtain pretreated resin. S32. Add the pretreated resin to DMF, swell, filter, wash, then add aminoimidazolium phosphonic acid solution, perform hydrothermal reaction, filter, wash, and dry to obtain modified chelating resin.

[0014] Further, in step S31, the ratio of D851 resin to anhydrous ethanol is 10g:100-130mL.

[0015] Furthermore, in step S31, the soaking time is 3 to 4 hours.

[0016] Further, in step S32, the ratio of the pretreatment resin, DMF, and aminoimidazophosphonic acid solution is 10g:100-130mL:40-50mL; the aminoimidazophosphonic acid solution is composed of aminoimidazophosphonic acid and DMF in a ratio of 0.8-1.5g:40mL.

[0017] Furthermore, in step S32, the swelling time is 3-4 hours, the hydrothermal reaction temperature is 90-94°C, and the time is 4-5 hours.

[0018] Further, in step S32, the preparation method of the aminoimidazolidine acid is as follows: S321. Mix 4-iodoimidazole, diethyl phosphite, triphenylphosphine, triethylamine and ethanol, stir and dissolve under nitrogen atmosphere, heat, add palladium acetate, stir to react, filter, wash and dry to obtain intermediate product 1. S322. Add intermediate product 1 and 2-(Boc-amino)bromoethane to acetonitrile, stir and dissolve at room temperature under nitrogen atmosphere, add cesium carbonate, stir at room temperature, filter, evaporate under reduced pressure, purify, evaporate under reduced pressure, cool, and obtain intermediate product 2. S323. Add intermediate product 2 to HBr solution, stir at room temperature under nitrogen atmosphere, wash, and rotary evaporate to obtain aminoimidazolidine.

[0019] Further, in step S321, the ratio of the amounts of 4-iodoimidazole, diethyl phosphite, triphenylphosphine, triethylamine, ethanol, and palladium acetate is 2.9g:4.1g:1.6g:3g:25-30mL:0.3g.

[0020] Furthermore, in step S321, the heating temperature is 70-80°C, and the stirring reaction time is 12-14 hours.

[0021] Further, in step S322, the ratio of the intermediate product 1, 2-(Boc-amino)bromoethane, acetonitrile, and cesium carbonate is 0.61g:1.18g:3-5mL:4.17g.

[0022] Furthermore, in step S322, the stirring time at room temperature is 12 to 14 hours.

[0023] Further, in step S323, the ratio of intermediate product 2 to HBr solution is 0.16g: 2.3-2.5mL; the HBr solution is prepared by dissolving hydrobromic acid in a 33% aqueous acetic acid solution, and its concentration is 0.25mol / L.

[0024] Furthermore, in step S323, the stirring time at room temperature is 24–48 hours.

[0025] The beneficial effects of this invention are: The S1 filtration step of this invention effectively removes suspended impurities, large particulate precipitates, and mechanical impurities from electroplating waste acid, preventing impurities from clogging equipment pipelines, contaminating ultrafiltration membranes, or occupying adsorption sites of modified chelating resins during subsequent pH adjustment, ultrafiltration, and adsorption steps. This provides a clean and stable raw material foundation for the entire process, ensuring smooth and efficient operation of subsequent steps. S2 first adjusts the pretreated waste acid to acidity, maintaining the stability of heavy metal ions such as chromium, copper, nickel, and iron in the solution and preventing premature hydrolysis and precipitation that would prevent effective adsorption by subsequent resins. Then, the ultrafiltration step further traps tiny colloids, fine impurities, and some large organic molecules in the solution, further purifying the solution and reducing interference from impurities on the adsorption process. Simultaneously, it protects the modified chelating resin in the subsequent adsorption column, extending its service life. S3 uses aminoimidazolium phosphonate-modified D851 resin for adsorption. Its core advantage lies in the fact that the phosphonic acid groups in aminoimidazolium phosphonate not only synergistically exert chelation and electric field adsorption effects with the amino group, efficiently and selectively locking heavy metal ions, but also significantly improve the resin's acid resistance, making it suitable for this process. The process involves creating a safe waste acid environment to reduce the erosion of the resin structure by acidic conditions, thereby improving the resin's recycling performance. After adsorption reaches saturation, the sulfate solution is collected to effectively separate heavy metal ions from sulfate, creating favorable conditions for subsequent sulfuric acid resource recovery. In step S4, the saturated resin is first desorbed with an eluent, which efficiently desorbs the heavy metal ions adsorbed by the resin and collects the eluent for further recycling and reuse of heavy metals. Then, the resin is washed with deionized water until it is neutral, which thoroughly removes residual eluent and impurities from the resin surface, regenerating the resin and allowing it to be reused in the adsorption step. Combined with the excellent recycling performance brought by the phosphonic acid groups, the process significantly reduces operating costs and ensures that the resin can maintain its adsorption efficiency for a long time. In step S5, the sulfate solution collected in step S3 is passed into an electrolytic cell. Through electrolysis, high-purity elemental metals can be obtained at the cathode, realizing the resource recovery of heavy metals and improving the utilization value of waste. At the same time, sulfuric acid solution is recovered at the anode, realizing the recycling and reuse of waste acid. This effectively solves the problem of environmental pollution from electroplating waste acid and achieves efficient resource utilization, balancing environmental and economic benefits. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the present invention for removing heavy metals from electroplating waste acid solution. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0028] A method for removing heavy metals from waste acid solution from electroplating includes the following steps: S1. Filter the electroplating waste acid solution to obtain the pretreated solution; The filtration step effectively removes large particulate impurities, suspended solids, and some insoluble substances from the electroplating waste acid solution through physical interception, resulting in a clarified pretreated solution. This operation not only prevents blockage and wear of subsequent pipelines, pumps, valves, and precision processing units, but also provides stable feeding conditions for subsequent chemical and adsorption treatments, ensuring smooth operation of the entire process.

[0029] S2. Pass the pretreated waste acid liquid into the pH adjustment tank to adjust it to acidity, obtain pH adjustment liquid, and then ultrafilter to obtain filtrate. The above steps adjust the waste acid solution to a specific acidity range, optimizing the existing form of heavy metal ions and reducing hydrogen ion competition, which is beneficial for subsequent adsorption. Ultrafiltration deeply retains colloids, fine particles and macromolecular organic matter, achieving fine purification of the solution. This step significantly protects the core adsorption resin from pollution and poisoning, ensuring the high efficiency and stability of the adsorption process.

[0030] S3. Pass the filtrate into an adsorption column containing modified chelating resin for adsorption until the resin is saturated, and then stop and collect the sulfate solution. The above steps utilize aminoimidazolium phosphonic acid-modified D851 resin for adsorption. Its unique amino and phosphonic acid groups form a multidentate synergistic chelating system, capable of capturing various heavy metal ions such as chromium, copper, nickel, and iron in solution with high capacity and selectivity. This modification significantly enhances the resin's structural stability and adsorption durability in acidic environments, achieving efficient separation of heavy metal ions from the sulfate solution. The resulting purified sulfate solution has low impurity content, creating ideal conditions for subsequent electrolytic recovery of high-purity metals and sulfuric acid.

[0031] S4. First, rinse the saturated resin of S3 with eluent to desorb, collect the eluent, and then wash the resin with deionized water until neutral. Using an eluent allows for efficient desorption of heavy metal ions enriched by the resin, yielding a high-concentration heavy metal eluent that facilitates subsequent centralized recovery or harmless treatment. The resin can regain its adsorption activity after elution and washing, enabling multiple cycles of reuse. This regeneration process fully utilizes the acid resistance and structural stability of the modified resin, significantly reducing operating material costs and demonstrating the process's economic efficiency and sustainability.

[0032] The sulfate solutions obtained from S5 and S3 are passed into the electrolytic cell to collect the cathode metal element and the anode sulfuric acid solution, respectively. Electrolysis of the purified sulfate solution allows for the direct deposition and recovery of high-purity elemental metals at the cathode, achieving the resource-based reuse of heavy metals. Simultaneously, sulfate ions are converted into sulfuric acid at the anode, regenerating and recovering sulfuric acid from the waste acid. This step ultimately completes a dual resource-based closed loop from complex waste acid to high-value metal products and regenerated acid, significantly improving the resource recovery efficiency and environmental benefits of the entire process.

[0033] The modified chelating resin is an aminoimidazolidine acid-modified D851 resin.

[0034] In some embodiments, in step S1, the filtration device is a bag filter with a diameter of 5–20 μm and a flow rate of 0.5–2.0 m / s. 3 The flow rate is 0.1-0.3 MPa per hour, and the pressure is 0.1-0.3 MPa. Within this parameter range, large particulate impurities can be effectively removed without clogging the filter bag. If the flow rate or pressure is too high, it can easily cause insufficient filtration and damage to the filter bag, while if it is too low, the treatment efficiency will be low and the operating cost will be high.

[0035] In some embodiments, in step S2, the substance used to adjust the pH in the pH adjustment tank is a 10% sodium hydroxide solution, and the acidity is pH = 3 to 6. This pH range can stabilize the form of heavy metal ions, ensure the adsorption effect, and avoid excessive consumption of alkali solution; if the pH is too high, it will easily lead to hydrolysis and precipitation of heavy metals, and if the pH is too low, the resin adsorption capacity will decrease and the removal effect will be poor.

[0036] In some embodiments, in step S2, the ultrafiltration uses a polyethersulfone membrane with a pore size of 0.05–0.2 μm, an operating pressure of 0.2–0.6 MPa, and an operating temperature of 20–45°C. These conditions can efficiently retain colloids and minute impurities, protecting the subsequent resin; excessively high pressure or temperature can damage the ultrafiltration membrane and increase energy consumption, while excessively low pressure or temperature will result in insufficient ultrafiltration flux and poor purification effect.

[0037] In some embodiments, in step S3, the adsorption column has a height-to-diameter ratio of 10:1, a flow rate of 2–10 BV / h, and an adsorption temperature of 10–20°C. These conditions ensure sufficient contact between the liquid and the resin and balanced adsorption; too high a flow rate will lead to incomplete adsorption and too fast penetration, while too low a flow rate will result in low processing efficiency; too high a temperature will reduce the adsorption capacity, while too low a temperature will result in poor liquid flowability.

[0038] In some embodiments, in step S4, the eluent is a hydrochloric acid solution with a weight percentage of 20% to 30%. This concentration of hydrochloric acid can efficiently desorb heavy metals without damaging the resin skeleton; if the acid concentration is too high, it can easily damage the resin structure and reduce the cycle life, while if it is too low, the desorption will be incomplete and the resin regeneration will be incomplete.

[0039] In some embodiments, in step S4, the desorption temperature is 10–20°C and the flow rate is 2–10 BV / h. These conditions enable mild and sufficient desorption and regeneration; excessively high temperatures can damage the acid-resistant groups of the resin and reduce its cycle performance, while excessively low temperatures result in a slow desorption rate; excessively high flow rates lead to insufficient desorption, while excessively low flow rates result in excessively long regeneration times.

[0040] In some embodiments, in step S5, the specific parameters of the electrolytic cell are: an electrolysis temperature of 40–60°C and an electrolysis current density of 100–200 A / m. 2The electrolysis voltage is 5–8V, and the electrolysis time is 8–10h. These parameters ensure uniform metal deposition, high purity, and stable sulfuric acid recovery. Excessive current or voltage can lead to loose metal, increased side reactions, and a sharp increase in energy consumption, while insufficient current or voltage results in incomplete electrolysis and low recovery efficiency.

[0041] In some embodiments, the method for preparing the modified chelating resin in step S3 is as follows: S31. Add D851 resin to anhydrous ethanol for wetting, wash with deionized water, and dry to obtain pretreated resin. D851 resin is a conventional commercial chelating resin with a single active site and limited coordination ability. It is easily affected by acid corrosion in strongly acidic electroplating waste acid systems, exhibiting poor structural stability, low adsorption capacity, insufficient selectivity for heavy metal ions, and poor recyclability. This invention first uses anhydrous ethanol to impregnate the D851 resin. Ethanol can fully wet the resin surface, swell some of the pore structure, and simultaneously dissolve and remove small-molecule organic impurities, pore-forming agents, and surface contaminants remaining from resin production and storage. After washing and drying with deionized water, the resin pore structure is further stabilized, and the surface active sites are activated. This yields a clean, structurally uniform pretreated resin with fully exposed active sites, providing a stable carrier for the subsequent uniform loading and grafting reaction of aminoimidazolium phosphonate, preventing impurities from occupying adsorption sites or hindering modifier diffusion, and ensuring a sufficient and uniform subsequent modification reaction.

[0042] S32. Add the pretreated resin to DMF, swell, filter, wash, then add aminoimidazolium phosphonic acid solution, perform hydrothermal reaction, filter, wash, and dry to obtain modified chelating resin.

[0043] The above steps first involve swelling the pretreated resin in DMF. DMF, as a strongly polar aprotic solvent, deeply opens the internal pores of the resin, significantly increasing the diffusion depth and contact area of ​​the modifier. Subsequently, an aminoimidazolium phosphonic acid solution is added and a hydrothermal reaction is initiated. The high-temperature hydrothermal environment promotes the amide reaction between the amino groups of aminoimidazolium phosphonic acid and the carboxyl groups of the resin, simultaneously introducing imidazole coordination groups and phosphonic acid groups onto the resin backbone. This significantly enhances the resin's chelating ability and selectivity for heavy metal ions. Simultaneously, the introduction of phosphonic acid groups greatly improves the resin's acid resistance in strongly acidic systems, reduces the damage to the resin structure caused by acid etching, and improves the resin's recyclability and service life. Ultimately, a modified chelating resin with high adsorption capacity, good selectivity, strong acid resistance, and reusability is obtained.

[0044] In some embodiments, in step S31, the ratio of D851 resin to anhydrous ethanol is 10g:100-130mL. This ratio ensures sufficient resin wetting and complete removal of impurities. Excessive ethanol usage will result in solvent waste and increased costs, while insufficient ethanol usage will lead to inadequate resin wetting and difficulty in removing residual impurities.

[0045] In some embodiments, the impregnation time in step S31 is 3 to 4 hours. This time range ensures that the resin swells sufficiently and surface impurities are removed completely. If the time is too long, the preparation cycle will be prolonged and efficiency will be reduced; if the time is too short, the resin will not be sufficiently activated and the subsequent modification effect will be affected.

[0046] In some embodiments, in step S32, the ratio of the pretreated resin, DMF, and aminoimidazolidinedionate solution is 10g:100-130mL:40-50mL; the aminoimidazolidinedionate solution is composed of aminoimidazolidinedionate and DMF in a ratio of 0.8-1.5g:40mL. This ratio ensures uniform loading of the modifier and appropriate chelation sites. Excessive dosage or concentration can lead to reagent waste and resin agglomeration, while insufficient dosage results in inadequate modification and limited improvement in acid resistance and adsorption performance.

[0047] In some embodiments, in step S32, the swelling time is 3-4 hours, and the hydrothermal reaction temperature is 90-94°C for 4-5 hours. A swelling time of 3-4 hours allows for sufficient opening of the resin pores, facilitating modifier diffusion. Excessive swelling time reduces production efficiency, while insufficient swelling time prevents adequate pore opening and hinders modifier penetration. The hydrothermal reaction conditions ensure stable grafting of aminoimidazolium phosphonate and complete reaction. Excessive temperature or time can damage the resin skeleton and functional groups, while insufficient temperature or time results in incomplete grafting and poor resin acid resistance and cycling performance.

[0048] In some embodiments, the preparation method of the aminoimidazolidine acid in step S32 is as follows: S321. Mix 4-iodoimidazole, diethyl phosphite, triphenylphosphine, triethylamine and ethanol, stir and dissolve under nitrogen atmosphere, heat, add palladium acetate, stir to react, filter, wash and dry to obtain intermediate product 1. The above steps use ethanol as the reaction medium and nitrogen atmosphere as the inert protective atmosphere. 4-Iodoimidazole, as an aryl iodide derivative, has good leaving property of the iodine atom in its molecule. Under the catalysis of palladium acetate catalyst, palladium acetate and triphenylphosphine form an active catalytic system, activating the aryl carbon-iodine bond in 4-iodoimidazole. Triethylamine, as an acid-binding agent, can promptly neutralize the hydrogen iodide generated during the reaction, avoiding the influence of acidic protons on catalyst activity and forward reaction. Diethyl phosphite, as a nucleophile, has a phosphine atom with a lone pair of electrons, which can undergo a nucleophilic substitution reaction with the activated aryl carbon, realizing the coupling connection between the phosphonate group and the imidazole ring, generating intermediate 1 containing an imidazole ring and a diethyl phosphonate group. After the reaction, the catalyst and insoluble impurities are removed by filtration, and the purified intermediate 1 is obtained after washing and drying.

[0049] S322. Add intermediate product 1 and 2-(Boc-amino)bromoethane to acetonitrile, stir and dissolve at room temperature under nitrogen atmosphere, add cesium carbonate, stir at room temperature, filter, evaporate under reduced pressure, purify, evaporate under reduced pressure, cool, and obtain intermediate product 2. The above steps constitute a nucleophilic substitution reaction. Acetonitrile is used as a polar aprotic solvent, and a nitrogen atmosphere prevents the product and reactants from being oxidized. The nitrogen atom on the imidazole ring of intermediate 1 has a lone pair of electrons, exhibiting nucleophilicity, and can act as a nucleophilic center to attack the bromoethyl carbon in the 2-(Boc-amino)bromoethane molecule. Cesium carbonate, as a basic reagent, can promote the nucleophilic activity of the imidazole nitrogen atom in intermediate 1 on the one hand, and neutralize the hydrobromic acid generated in the reaction on the other hand, thus promoting the reaction to proceed in the forward direction. The two undergo a nucleophilic substitution reaction at room temperature, causing the bromoethyl chain to attach to the nitrogen atom of the imidazole ring, while retaining the Boc (tert-butyloxycarbonyl) protecting group. After the reaction is completed, the generated cesium carbonate salt impurities are removed by filtration, the acetonitrile solvent is removed by vacuum evaporation, and unreacted raw materials and byproducts are removed by purification. After vacuum distillation and cooling again, intermediate 2 containing an imidazole ring, a diethyl phosphonate group, and a Boc protected amino group is obtained.

[0050] S323. Add intermediate product 2 to HBr solution, stir at room temperature under nitrogen atmosphere, wash, and rotary evaporate to obtain aminoimidazolidine.

[0051] The above steps constitute the deprotection reaction of the Boc protecting group. A nitrogen atmosphere is used to prevent the deprotected amino group from being oxidized. The Boc protecting group in intermediate product 2 is sensitive to acid. HBr solution, as a strong acid reagent, can hydrolyze the Boc group to remove the Boc protecting group and release the free amino group. At the same time, HBr solution can promote the hydrolysis of the diethyl phosphonate group introduced in intermediate product 1, converting it into the phosphonic acid group in the target product. After the reaction is completed, by washing, the byproducts such as tert-butyl bromide and ethanol generated in the reaction, as well as excess HBr, are removed. The water and residual impurities in the system are removed by rotary evaporation, and finally the target product containing amino, imidazole and phosphonic acid groups is obtained.

[0052] In some embodiments, in S321, the ratio of 4-iodoimidazole, diethyl phosphite, triphenylphosphine, triethylamine, ethanol, and palladium acetate is 2.9g:4.1g:1.6g:3g:25-30mL:0.3g. This ratio ensures complete formation of intermediate 1 with minimal side reactions. An excessively high proportion of raw materials can easily generate impurities and reduce product purity, while an excessively low proportion will result in incomplete reaction and a decreased yield of intermediate 1.

[0053] In some embodiments, in S321, the heating temperature is 70–80°C, and the stirring reaction time is 12–14 h. These conditions ensure a mild and complete reaction with a high yield of intermediate product 1. Excessive temperature or time can easily lead to the formation of byproducts and damage to the product structure, while excessively low temperature or time results in incomplete reaction and a low yield.

[0054] In some embodiments, in S322, the ratio of intermediate product 1, 2-(Boc-amino)bromoethane, acetonitrile, and cesium carbonate is 0.61 g: 1.18 g: 3-5 mL: 4.17 g. This ratio ensures the smooth progress of the substitution reaction and high purity of intermediate product 2. An excessively high proportion of raw materials can introduce impurities and increase the difficulty of post-processing, while an excessively low proportion will result in incomplete reaction and decreased grafting efficiency.

[0055] In some embodiments, in S322, the stirring time at room temperature is 12-14 hours. This time allows for the full formation of intermediate product 2 and complete reaction. Too long a time will prolong the synthesis cycle and reduce efficiency, while too short a time will result in incomplete reaction and affect the structure and properties of subsequent products.

[0056] In some embodiments, in S323, the ratio of intermediate product 2 to HBr solution is 0.16 g: 2.3–2.5 mL; the HBr solution is prepared by dissolving hydrobromic acid in a 33% aqueous acetic acid solution, and its concentration is 0.25 mol / L. This dosage and concentration can gently remove the Boc protecting group to obtain high-purity aminoimidazolidine phosphate. If the acid amount or concentration is too high, it will easily damage the product structure; if it is too low, the deprotection will be incomplete and the product activity will be insufficient.

[0057] In some embodiments, in S323, the stirring time at room temperature is 24–48 hours. This time ensures complete deprotection reaction and high product purity; too long a time can easily lead to product decomposition, while too short a time will result in insufficient deprotection and difficulty in forming effective chelated functional groups.

[0058] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0059] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0060] The specific composition of the electroplating waste acid solution used in this embodiment and comparative example is as follows: sulfate (calculated as sulfate ions, concentration 18000 mg / L); Cr 3+ Concentration: 60 mg / L; Cu 2+ Concentration: 150 mg / L; Ni 2+ Concentration: 120 mg / L; Fe 3+ Concentration: 100 mg / L; pH=1.2.

[0061] Preparation Example 1

[0062] The method for preparing the modified chelating resin in this preparation example is as follows: S31. Add 10g of D851 resin to 100mL of anhydrous ethanol and soak for 3h. Wash with deionized water and dry to obtain pretreated resin. S32. Add 10g of pretreated resin to 100mL of DMF, allow it to swell for 3 hours, filter, wash, and then add 40mL of aminoimidazophosphonic acid solution. The aminoimidazophosphonic acid solution is composed of aminoimidazophosphonic acid and DMF in a ratio of 0.8g:40mL. Perform a hydrothermal reaction at 90℃ for 4 hours, filter, wash, and dry to obtain the modified chelating resin.

[0063] The preparation method of aminoimidazolidinedionate is as follows: S321. Mix 2.9g of 4-iodoimidazole, 4.1g of diethyl phosphite, 1.6g of triphenylphosphine, 3g of triethylamine and 25mL of ethanol, stir and dissolve under nitrogen atmosphere, heat at 70℃ for 12h, add 0.3g of palladium acetate, stir to react, filter, wash and dry to obtain intermediate product 1. S322. Add 0.61g of intermediate product 1 and 1.18g of 2-(Boc-amino)bromoethane to 3mL of acetonitrile, stir and dissolve at room temperature under nitrogen atmosphere, add 4.17g of cesium carbonate, stir at room temperature for 12h, filter, evaporate under reduced pressure, purify, evaporate under reduced pressure, cool, and obtain intermediate product 2. S323. Add 0.16 g of intermediate product 2 to 2.4 mL of HBr solution. The HBr solution is prepared by dissolving hydrobromic acid in 33% aqueous acetic acid solution with a concentration of 0.25 mol / L. Stir at room temperature for 24 h under nitrogen atmosphere, wash, and rotary evaporate to obtain aminoimidazolidine acid.

[0064] Preparation Example 2

[0065] The method for preparing the modified chelating resin in this preparation example is as follows: S31. Add 10g of D851 resin to 115mL of anhydrous ethanol and soak for 3.5h. Wash with deionized water and dry to obtain pretreated resin. S32. Add 10g of pretreated resin to 115mL of DMF, allow it to swell for 3.5h, filter, wash, then add 45mL of aminoimidazophosphonic acid solution, which is composed of aminoimidazophosphonic acid and DMF in a ratio of 1.2g:40mL. Perform hydrothermal reaction at 92℃ for 4.5h, filter, wash, and dry to obtain modified chelating resin.

[0066] The preparation method of aminoimidazolidinedionate is as follows: S321. Mix 2.9g of 4-iodoimidazole, 4.1g of diethyl phosphite, 1.6g of triphenylphosphine, 3g of triethylamine and 28mL of ethanol, stir and dissolve under nitrogen atmosphere, heat at 75℃ for 13h, add 0.3g of palladium acetate, stir to react, filter, wash and dry to obtain intermediate product 1. S322. Add 0.61g of intermediate product 1 and 1.18g of 2-(Boc-amino)bromoethane to 4mL of acetonitrile, stir and dissolve at room temperature under nitrogen atmosphere, add 4.17g of cesium carbonate, stir at room temperature for 13h, filter, evaporate under reduced pressure, purify, evaporate under reduced pressure, cool, and obtain intermediate product 2. S323. Add 0.16 g of intermediate product 2 to 2.4 mL of HBr solution. The HBr solution is prepared by dissolving hydrobromic acid in 33% aqueous acetic acid solution with a concentration of 0.25 mol / L. Stir at room temperature for 36 h under nitrogen atmosphere, wash, and rotary evaporate to obtain aminoimidazolidine acid.

[0067] Preparation Example 3

[0068] The method for preparing the modified chelating resin in this preparation example is as follows: S31. Add 10g of D851 resin to 130mL of anhydrous ethanol and soak for 4h. Wash with deionized water and dry to obtain pretreated resin. S32. Add 10g of pretreated resin to 130mL of DMF, allow it to swell for 4 hours, filter, wash, and then add 50mL of aminoimidazolidinedionate solution. The aminoimidazolidinedionate solution is composed of aminoimidazolidinedionate and DMF in a ratio of 1.5g:40mL. Perform hydrothermal reaction at 94℃ for 5 hours, filter, wash, and dry to obtain modified chelating resin.

[0069] The preparation method of aminoimidazolidinedionate is as follows: S321. Mix 2.9g of 4-iodoimidazole, 4.1g of diethyl phosphite, 1.6g of triphenylphosphine, 3g of triethylamine and 30mL of ethanol, stir and dissolve under nitrogen atmosphere, heat at 80℃ for 14h, add 0.3g of palladium acetate, stir to react, filter, wash and dry to obtain intermediate product 1. S322. Add 0.61g of intermediate product 1 and 1.18g of 2-(Boc-amino)bromoethane to 5mL of acetonitrile, stir and dissolve at room temperature under nitrogen atmosphere, add 4.17g of cesium carbonate, stir at room temperature for 14h, filter, evaporate under reduced pressure, purify, evaporate under reduced pressure, cool, and obtain intermediate product 2. S323. Add 0.16 g of intermediate product 2 to 2.5 mL of HBr solution. The HBr solution is prepared by dissolving hydrobromic acid in 33% aqueous acetic acid solution with a concentration of 0.25 mol / L. Stir at room temperature for 48 h under nitrogen atmosphere, wash, and rotary evaporate to obtain aminoimidazolidine acid.

[0070] Compare with Example 1

[0071] The only difference between this comparative example and preparation example 1 is that an equal amount of 1-(3-aminopropyl)imidazole was used to replace aminoimidazolium phosphonate. The specific steps are as follows: S31. Add 10g of D851 resin to 100mL of anhydrous ethanol and soak for 3h. Wash with deionized water and dry to obtain pretreated resin. S32. Add 10g of pretreated resin to 100mL of DMF, allow it to swell for 3h, filter, wash, and then add 40mL of 1-(3-aminopropyl)imidazole solution, which is composed of 1-(3-aminopropyl)imidazole and DMF in a ratio of 0.8g:40mL. Perform hydrothermal reaction at 90℃ for 4h, filter, wash, and dry to obtain modified chelating resin.

[0072] Compare with Example 2

[0073] This comparative example uses D851 resin.

[0074] Example 1

[0075] This embodiment provides a method for removing heavy metals from electroplating waste acid solution, including the following steps: S1. Filter the electroplating waste acid solution using a 5μm bag filter, controlling the flow rate at 0.5m / s. 3 / h, pressure 0.1MPa, to obtain pretreated liquid; S2. The pretreated waste acid solution is passed into a pH adjustment tank and the pH is adjusted to 3 with 10% sodium hydroxide solution to obtain a pH adjustment solution. The pH adjustment solution is then subjected to ultrafiltration using a polyethersulfone membrane with a pore size of 0.05 μm, an operating pressure of 0.2 MPa, and an operating temperature of 20℃ to obtain a filtrate. S3. Pass the filtrate into an adsorption column containing modified chelating resin for adsorption (adsorption column height-to-diameter ratio 10:1). Use the modified chelating resin prepared in Preparation Example 1, control the flow rate at 2 BV / h, and the adsorption temperature at 10℃. Stop the adsorption when the resin is saturated and collect the sulfate solution. S4. First, rinse the saturated resin of S3 with an eluent, which is a 20% hydrochloric acid solution by weight. The desorption temperature is 10℃ and the flow rate is 2 BV / h. Collect the eluent. Then wash the resin with deionized water until neutral and set aside. The sulfate solutions obtained from S5 and S3 are fed into an electrolytic cell, with the electrolysis temperature controlled at 40℃ and the electrolysis current density at 100A / m³. 2 The electrolysis voltage was 5V and the electrolysis time was 8h. The cathode metal element and the anode sulfuric acid solution were collected separately. Example 2 This embodiment provides a method for removing heavy metals from electroplating waste acid solution, including the following steps: S1. Filter the electroplating waste acid solution using an 8μm bag filter at a flow rate of 0.8m / s. 3 / h, pressure 0.15MPa, to obtain pretreated liquid; S2. The pretreated waste acid solution is passed into a pH adjustment tank and the pH is adjusted to 4 with 10% sodium hydroxide solution to obtain a pH adjustment solution. The pH adjustment solution is then subjected to ultrafiltration using a polyethersulfone membrane with a pore size of 0.08 μm, an operating pressure of 0.3 MPa, and an operating temperature of 25℃ to obtain a filtrate. S3. Pass the filtrate into an adsorption column containing modified chelating resin for adsorption (adsorption column height-to-diameter ratio 10:1). Use the modified chelating resin prepared in Preparation Example 1, control the flow rate at 4 BV / h, and the adsorption temperature at 12℃. Stop the adsorption when the resin is saturated and collect the sulfate solution. S4. First, rinse the saturated resin of S3 with an eluent, which is a 22% hydrochloric acid solution by weight. The desorption temperature is 12℃ and the flow rate is 4 BV / h. Collect the eluent. Then wash the resin with deionized water until neutral and set aside. The sulfate solutions obtained from S5 and S3 are fed into an electrolytic cell, with the electrolysis temperature controlled at 45℃ and the electrolysis current density at 120A / m³. 2 The electrolysis voltage was 6V and the electrolysis time was 8.5h. The cathode metal element and the anode sulfuric acid solution were collected separately.

[0076] Example 3

[0077] This embodiment provides a method for removing heavy metals from electroplating waste acid solution, including the following steps: S1. Filter the electroplating waste acid solution using a 12μm bag filter, controlling the flow rate at 1.2m / s. 3 / h, pressure 0.2MPa, to obtain pretreated liquid; S2. The pretreated waste acid solution is passed into a pH adjustment tank and the pH is adjusted to 4.5 with 10% sodium hydroxide solution to obtain a pH adjustment solution. The pH adjustment solution is then subjected to ultrafiltration using a polyethersulfone membrane with a pore size of 0.1 μm, an operating pressure of 0.4 MPa, and an operating temperature of 30℃ to obtain a filtrate. S3. Pass the filtrate into an adsorption column containing modified chelating resin for adsorption (adsorption column height-to-diameter ratio 10:1). Use the modified chelating resin prepared in Preparation Example 2, control the flow rate at 6 BV / h, and the adsorption temperature at 14℃. Stop the adsorption when the resin is saturated and collect the sulfate solution. S4. First, rinse the saturated resin of S3 with an eluent, which is a 24% hydrochloric acid solution by weight. The desorption temperature is 14℃ and the flow rate is 6 BV / h. Collect the eluent. Then wash the resin with deionized water until neutral and set aside. The sulfate solutions obtained from S5 and S3 are fed into an electrolytic cell, with the electrolysis temperature controlled at 50℃ and the electrolysis current density at 140A / m³. 2 The electrolysis voltage was 6.5V and the electrolysis time was 9h. The cathode metal element and the anode sulfuric acid solution were collected separately.

[0078] Example 4

[0079] This embodiment provides a method for removing heavy metals from electroplating waste acid solution, including the following steps: S1. Filter the electroplating waste acid solution using a 15μm bag filter, controlling the flow rate at 1.6m / s. 3 At a pressure of 0.25 MPa and a flow rate of / h, a pretreated solution was obtained; S2. The pretreated waste acid solution is passed into a pH adjustment tank and the pH is adjusted to 5 with 10% sodium hydroxide solution to obtain a pH adjustment solution. The pH adjustment solution is then subjected to ultrafiltration using a polyethersulfone membrane with a pore size of 0.15 μm, an operating pressure of 0.5 MPa, and an operating temperature of 35℃ to obtain a filtrate. S3. Pass the filtrate into an adsorption column containing modified chelating resin for adsorption (adsorption column height-to-diameter ratio 10:1). Use the modified chelating resin prepared in Preparation Example 3, control the flow rate at 8 BV / h, and the adsorption temperature at 16℃. Stop the adsorption when the resin is saturated and collect the sulfate solution. S4. First, rinse the saturated resin of S3 with an eluent, which is a 26% hydrochloric acid solution by weight. The desorption temperature is 16℃ and the flow rate is 8 BV / h. Collect the eluent. Then wash the resin with deionized water until neutral and set aside. The sulfate solutions obtained from S5 and S3 are fed into an electrolytic cell, with the electrolysis temperature controlled at 55℃ and the electrolysis current density at 160 A / m³. 2 The electrolysis voltage was 7V and the electrolysis time was 9.5h. The cathode metal element and the anode sulfuric acid solution were collected separately.

[0080] Example 5

[0081] This embodiment provides a method for removing heavy metals from electroplating waste acid solution, including the following steps: S1. Filter the electroplating waste acid solution using a 20μm bag filter, controlling the flow rate at 2.0m. 3 / h, pressure 0.3MPa, to obtain pretreated liquid; S2. The pretreated waste acid solution is passed into a pH adjustment tank and the pH is adjusted to 6 with a 10% sodium hydroxide solution to obtain a pH adjustment solution. The pH adjustment solution is then subjected to ultrafiltration using a polyethersulfone membrane with a pore size of 0.2 μm, an operating pressure of 0.6 MPa, and an operating temperature of 45℃ to obtain a filtrate. S3. Pass the filtrate into an adsorption column containing modified chelating resin for adsorption (adsorption column height-to-diameter ratio 10:1). Use the modified chelating resin prepared in Preparation Example 3, control the flow rate at 10 BV / h, and the adsorption temperature at 20°C. Stop the adsorption when the resin is saturated and collect the sulfate solution. S4. First, rinse the saturated resin of S3 with an eluent, which is a 30% hydrochloric acid solution by weight. The desorption temperature is 20℃ and the flow rate is 10 BV / h. Collect the eluent. Then wash the resin with deionized water until neutral and set aside. The sulfate solutions obtained from S5 and S3 are fed into an electrolytic cell, with the electrolysis temperature controlled at 60℃ and the electrolysis current density at 200A / m³. 2 The electrolysis voltage was 8V and the electrolysis time was 10h. The cathode metal element and the anode sulfuric acid solution were collected separately.

[0082] Comparative Example 1

[0083] The only difference between this comparative example and Example 1 is that the modified chelating resin prepared in Preparation Example 1 is replaced with the modified chelating resin in Control Example 1.

[0084] Comparative Example 2

[0085] The only difference between this comparative example and Example 1 is that the modified chelating resin prepared in Preparation Example 1 was replaced with the D851 resin in Control Example 2.

[0086] Comparative Example 3

[0087] The only difference between this comparative example and Example 1 is that the ultrafiltration step in S2 is omitted. Specifically: S1. Filter the electroplating waste acid solution using an 8μm bag filter at a flow rate of 0.8m / s. 3 / h, pressure 0.15MPa, to obtain pretreated liquid; S2. Pass the pretreated waste acid solution into the pH adjustment tank and adjust the pH to 4 with 10% sodium hydroxide solution to obtain pH adjustment solution; S3. The pH-adjusting solution was passed into an adsorption column containing modified chelating resin for adsorption (adsorption column height-to-diameter ratio 10:1). The modified chelating resin prepared in Preparation Example 1 was used. The flow rate was controlled at 4 BV / h and the adsorption temperature was 12℃. The adsorption was stopped after the resin was saturated, and the sulfate solution was collected. S4. First, rinse the saturated resin of S3 with an eluent, which is a 22% hydrochloric acid solution by weight. The desorption temperature is 12℃ and the flow rate is 4 BV / h. Collect the eluent. Then wash the resin with deionized water until neutral and set aside. The sulfate solutions obtained from S5 and S3 are fed into an electrolytic cell, with the electrolysis temperature controlled at 45℃ and the electrolysis current density at 120A / m³. 2The electrolysis voltage was 6V and the electrolysis time was 8.5h. The cathode metal element and the anode sulfuric acid solution were collected separately.

[0088] Test case

[0089] (1) Heavy metal removal rate test: The sulfate solution (effluent) collected in S3 was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) to determine the Cr³⁺ content. + Cu² + Ni² + Fe³ + The concentration of heavy metals was measured under the following conditions: ICP-OES RF power 1300W, atomizing gas flow rate 0.8L / min, observation height 12mm, and detection wavelength corresponding to the characteristic wavelength of each heavy metal. The calculation formula is: removal rate (%) = [(influent heavy metal concentration - effluent heavy metal concentration) / influent heavy metal concentration] × 100%.

[0090] (2) Sulfuric acid recovery rate test: The sulfate solution collected at S3 and the sulfuric acid solution collected at S5 anode were taken respectively, and the sulfate concentration was determined by gravimetric method and the sulfuric acid concentration was calculated. The test conditions were: drying temperature 105℃, constant weight time 2h, parallel test 3 times, and the error was controlled within ±0.5%. The calculation formula was recovery rate (%) = [(anode sulfuric acid solution volume × sulfuric acid concentration) / (inlet water sulfate concentration × inlet water volume) × 98 / 96] × 100% (98 is the molar mass of sulfuric acid, and 96 is the molar mass of sulfate). (3) Purity test of metallic elements The metallic element obtained from the S5 cathode was collected, and the content of impurity elements (other heavy metals and non-metals) was determined by ICP-OES. The calculation formula is: purity (%) = [1 - (total mass of impurities / total mass of metallic element)] × 100%.

[0091] (4) Resin regeneration performance test

[0092] The regenerated resin from S4 was reused in the S3 adsorption step for five consecutive cycles, and the average removal rate of heavy metals adsorbed each time was measured. Based on the removal rate of the first adsorption, the ratio of the removal rate of the fifth adsorption to that of the first adsorption was calculated (the higher the ratio, the better the regeneration performance).

[0093] Table 1

[0094] As can be seen from Table 1, Examples 1-5 of the present invention have a positive effect on the Cr content in electroplating waste acid solution. 3+ Cu 2+ Ni 2+ Fe 3+All samples exhibited high removal efficiency, with sulfuric acid recovery rate, metal purity, and resin regeneration performance superior to Comparative Examples 1-3. As the aminoimidazolium phosphonic acid loading gradually increased and process parameters were further optimized, the heavy metal removal rate, sulfuric acid recovery rate, metal purity, and resin regeneration performance of Examples 1-5 showed an overall increasing trend. This indicates that aminoimidazolium phosphonic acid-modified D851 resin can significantly enhance its chelation adsorption capacity and selectivity for heavy metal ions. Simultaneously, the introduction of phosphonic acid groups improves the resin's acid resistance, enabling it to maintain high adsorption efficiency and recyclability even in strongly acidic systems.

[0095] Comparative Example 1 uses aminopropylimidazolium-modified resin without phosphonic acid groups. The heavy metal removal rate, sulfuric acid recovery rate, metal purity and resin regeneration performance are significantly reduced. This indicates that the imidazole group and phosphonic acid group in aminoimidazolium phosphonic acid can form a synergistic coordination effect, which is crucial for improving the heavy metal removal effect, acid resistance and cycle stability.

[0096] Comparative Example 2 directly used unmodified D851 resin, and all indicators were the worst, indicating that the original resin had few adsorption sites, poor selectivity, and limited acid resistance and regeneration performance, which could not meet the requirements for deep treatment and resource recovery of electroplating waste acid.

[0097] Comparative Example 3 omitted the ultrafiltration step, resulting in a decrease in the removal and recovery rates of heavy metals. This indicates that ultrafiltration can effectively remove colloids and minute impurities, reducing contamination and occupation of resin adsorption sites, which is beneficial for ensuring adsorption efficiency and process stability.

[0098] In summary, this invention utilizes a combined process of aminoimidazolium phosphonic acid-modified D851 resin, filtration, pH adjustment, ultrafiltration, adsorption, desorption regeneration, and electrolytic resource recovery. This process enables the efficient removal of heavy metals from electroplating waste acid and the simultaneous recovery of sulfuric acid and elemental metals. The resin exhibits strong acid resistance and good regeneration performance. The overall process is stable and has a high resource utilization rate, demonstrating promising prospects for industrial application.

[0099] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for removing heavy metals from electroplating waste acid solution, characterized in that, Includes the following steps: S1. Filter the electroplating waste acid solution to obtain the pretreated solution; S2. Pass the pretreated waste acid liquid into the pH adjustment tank to adjust it to acidity, obtain pH adjustment liquid, and then ultrafilter to obtain filtrate. S3. Pass the filtrate into an adsorption column containing modified chelating resin for adsorption until the resin is saturated, and then stop and collect the sulfate solution. S4. First, rinse the saturated resin of S3 with eluent to desorb, collect the eluent, and then wash the resin with deionized water until neutral. The sulfate solutions obtained from S5 and S3 are passed into the electrolytic cell to collect the cathode metal element and the anode sulfuric acid solution, respectively. The modified chelating resin is an aminoimidazolidine acid-modified D851 resin.

2. The method for removing heavy metals from electroplating waste acid solution according to claim 1, characterized in that, In step S1, the filtration device is a bag filter with a diameter of 5–20 μm and a flow rate of 0.5–2.0 m / s. 3 / h, pressure is 0.1~0.3MPa.

3. The method for removing heavy metals from electroplating waste acid solution according to claim 1, characterized in that, In step S2, the pH-adjusting substance in the pH-adjusting tank is a 10% sodium hydroxide solution, and the acidity is pH = 3 to 6; The ultrafiltration uses a polyethersulfone membrane with a pore size of 0.05–0.2 μm, an operating pressure of 0.2–0.6 MPa, and an operating temperature of 20–45 °C.

4. The method for removing heavy metals from electroplating waste acid solution according to claim 1, characterized in that, In step S3, the adsorption column has a height-to-diameter ratio of 10:1, a flow rate of 2-10 BV / h, and an adsorption temperature of 10-20℃.

5. The method for removing heavy metals from electroplating waste acid solution according to claim 1, characterized in that, In step S3, the modified chelating resin is prepared by: S31. Add D851 resin to anhydrous ethanol for wetting, wash with deionized water, and dry to obtain pretreated resin. S32. Add the pretreated resin to DMF, swell, filter, wash, then add aminoimidazolium phosphonic acid solution, perform hydrothermal reaction, filter, wash, and dry to obtain modified chelating resin.

6. The method for removing heavy metals from electroplating waste acid solution according to claim 5, characterized in that, In step S31, the ratio of D851 resin to anhydrous ethanol is 10g: 100-130mL. In step S31, the soaking time is 3 to 4 hours; In step S32, the ratio of the pretreatment resin, DMF, and aminoimidazolidinedionate solution is 10g: 100-130mL: 40-50mL; the aminoimidazolidinedionate solution is composed of aminoimidazolidinedionate and DMF in a ratio of 0.8-1.5g: 40mL. In step S32, the swelling time is 3-4 hours, the hydrothermal reaction temperature is 90-94°C, and the time is 4-5 hours.

7. The method for removing heavy metals from electroplating waste acid solution according to claim 5, characterized in that, In step S32, the preparation method of the aminoimidazolidine acid is as follows: S321. Mix 4-iodoimidazole, diethyl phosphite, triphenylphosphine, triethylamine and ethanol, stir and dissolve under nitrogen atmosphere, heat, add palladium acetate, stir to react, filter, wash and dry to obtain intermediate product 1. S322. Add intermediate product 1 and 2-(Boc-amino)bromoethane to acetonitrile, stir and dissolve at room temperature under nitrogen atmosphere, add cesium carbonate, stir at room temperature, filter, evaporate under reduced pressure, purify, evaporate under reduced pressure, cool, and obtain intermediate product 2. S323. Add intermediate product 2 to HBr solution, stir at room temperature under nitrogen atmosphere, wash, and rotary evaporate to obtain aminoimidazolidine.

8. The method for removing heavy metals from electroplating waste acid solution according to claim 7, characterized in that, In step S321, the ratio of the amounts of 4-iodoimidazole, diethyl phosphite, triphenylphosphine, triethylamine, ethanol, and palladium acetate is 2.9g:4.1g:1.6g:3g:25-30mL:0.3g; In step S321, the heating temperature is 70-80°C, and the stirring reaction time is 12-14 hours. In step S322, the ratio of the intermediate product 1, 2-(Boc-amino)bromoethane, acetonitrile, and cesium carbonate is 0.61g:1.18g:3-5mL:4.17g; In step S322, the stirring time at room temperature is 12-14 hours; In step S323, the ratio of intermediate product 2 to HBr solution is 0.16g: 2.3-2.5mL; the HBr solution is prepared by dissolving hydrobromic acid in a 33% acetic acid aqueous solution, and its concentration is 0.25mol / L. In step S323, the stirring time at room temperature is 24–48 hours.

9. The method for removing heavy metals from electroplating waste acid solution according to claim 1, characterized in that, In step S4, the eluent is a hydrochloric acid solution with a weight percentage of 20% to 30%; The desorption temperature is 10–20°C, and the flow rate is 2–10 BV / h.

10. The method for removing heavy metals from electroplating waste acid solution according to claim 1, characterized in that, In step S5, the specific parameters of the electrolytic cell are: electrolysis temperature of 40–60°C and electrolysis current density of 100–200 A / m³. 2 The electrolysis voltage is 5-8V, and the electrolysis time is 8-10h.

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