Low-temperature chelation removal process for metal ions in fatty acid amide type surfactant

Abstract

The invention relates to a low-temperature chelation removal process for metal ions in a fatty acid amide type surfactant, and aims to solve the problem that the metal ions are difficult to efficiently chelate and separate under a low-temperature condition in the prior art. The process comprises the following steps: dissolving a fatty acid amide type surfactant in water at 20-30 DEG C to form a homogeneous system; adding a complexing agent system consisting of ethylenediamine disuccinic acid and tricarboxyl potassium isocitrate, a fatty alcohol polyether sulfosuccinate regulator and auxiliaries such as glycerol and sorbitol into the reaction kettle, and stirring and reacting at the temperature of 30-32 DEG C; then interface release and migration of metal ions are strengthened through shearing-standing circulation; introducing a temperature disturbance program to increase the complexing reaction rate, and adjusting the pH to 6.6-7.2 to stabilize the complexing state; and finally, phase separation sedimentation is accelerated through rotational flow induction operation, and a water phase containing complex metal ions is separated out. The process has the advantages of low temperature, high efficiency, high chelating rate, clear layering and small influence on the stability of a surfactant system.

Description

Technical Field

[0001] This invention relates to the technical field of metal ion removal, and in particular to a low-temperature chelation removal process for metal ions in fatty acid amide surfactants. Background Technology

[0002] Fatty acid amide surfactants are a class of nonionic or amphoteric surfactants derived from natural fatty acids and amine derivatives. They possess excellent biodegradability, foam-regulating ability, and emulsifying and dispersing properties, and are widely used in industries such as daily chemicals, textiles, cleaning, oil extraction, and metal processing. However, during their preparation, storage, or application, metal ion contamination is often unavoidable, stemming from impurities in raw materials, ionic components in process water, or equipment corrosion products. The presence of metal ions can not only affect the micelle structure and interfacial properties of surfactants but may also induce undesirable chemical reactions, such as accelerating oxidative degradation, reducing formulation stability, or promoting the precipitation of components, thereby adversely affecting the performance of the final product. Therefore, metal ion removal or chelation steps are typically required in the refining process of surfactant products to ensure product quality and stability in downstream applications.

[0003] For the removal of metal ions from surfactant systems, commonly used techniques include precipitation, membrane separation, ion exchange, and complexation chelation. Among these, complexation chelation is widely used due to its ease of operation, high selectivity, and minimal impact on product structure. Commonly used complexing agents, such as EDTA, DTPA, and NTA (polycarboxyl ligands), can form stable complexes with various metal ions, including copper, nickel, iron, and zinc, achieving separation and enrichment. However, existing complexation techniques still have many limitations. For example, most complexation reactions require relatively high temperatures (typically 50–80°C) to increase the reaction rate and complexation efficiency. However, such high-temperature operations not only increase energy consumption but also easily damage heat-sensitive surfactants, leading to instability in the emulsion system, color changes, or component degradation. On the other hand, metal ions are often enriched at the interface in surfactant micelles or emulsion structures, and have strong hydrophobic interactions or hydrogen bonding with micelles. This makes it difficult for traditional complexing agents to achieve complete dissociation and binding in a short time, thereby reducing the overall chelation efficiency, especially in systems where multiple metals coexist or at low concentrations.

[0004] Therefore, there is an urgent need to develop an improved removal process that is suitable for low-temperature conditions and has both efficient complexation and rapid separation capabilities, in order to meet the practical needs of improving surfactant quality and green manufacturing. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a low-temperature chelation removal process for metal ions in fatty acid amide surfactants.

[0006] A low-temperature chelation removal process for metal ions in fatty acid amide surfactants includes the following steps: S1) Under conditions of 20–30°C, a fatty acid amide surfactant is dissolved in deionized water to form a homogeneous surfactant solution. The surfactant is cocamidopropyl betaine, oleamidopropyl betaine, or a compound of the surfactant and an amphoteric surfactant. The amount of surfactant added is 2–10 wt% of the total mass of the system. S2) Under stirring, a complexing agent and a regulator are added to the surfactant solution. The complexing agent comprises ethylenediamine disuccinic acid and potassium tricarboxyisocitrate in a mass ratio of 1:(0.8-1.2), and the total amount added is 1.5-4 wt% of the total mass of the system. The regulator is fatty alcohol polyether sulfosuccinate, and the amount added is 0.1-0.5 wt%. S3) Maintain the above reaction system at 30°C and stir for 10-30 minutes; S4) After stopping stirring, let it stand for 20 to 40 minutes to separate the aqueous phase and remove the complexed metal ions to form a clear liquid.

[0007] Preferably, the total amount of ethylenediamine disuccinic acid and potassium tricarboxyisocitrate added accounts for 2 to 6 wt% of the surfactant solution.

[0008] Preferably, 1-5 wt% of one or more of glycerol, sorbitol, or sodium gluconate is further added to the surfactant solution in step S1.

[0009] Preferably, the mass ratio of the fatty acid amide surfactant to the amphoteric surfactant is (1-2):1, and the amphoteric surfactant is cocamidopropyl carboxybetaine or erucamide carboxymethyl betaine.

[0010] Preferably, 0.05 to 0.5 wt% of sodium polyaspartate or sodium polyglutamate containing carboxylic acid groups is also added to the surfactant solution formed in step S1.

[0011] Preferably, in step S2, the system temperature is maintained at 30–32°C and the stirring time is 15–30 minutes to maintain the stable progress of the complexation reaction.

[0012] Preferably, a shearing and settling step is set between step S2 and step S3, which includes stirring the reaction at 500-700 rpm for 3-5 minutes, then settling the reaction for 2-4 minutes, and repeating the cycle 2-3 times.

[0013] Preferably, in step S3, 0.01 to 0.1 wt% of disodium hydrogen phosphate is added to control the endpoint pH between 6.6 and 7.2.

[0014] Preferably, step S3 sets a temperature disturbance program, which involves first heating the system to 38-40°C and holding it for 5 minutes, then naturally cooling it to 25-27°C.

[0015] Preferably, a cyclone separation operation is set before step S4, in which the reaction liquid is rotated through a cyclone inducer for 3 to 5 minutes and then allowed to stand for stratification.

[0016] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: The low-temperature chelation removal process for metal ions in fatty acid amide surfactants provided by this invention significantly enhances the effective contact and complexation between the complexing agent and metal ions by introducing a shear-settling cycle step during the complexation reaction. Specifically, a shear-settling process is set between steps S2 and S3, with stirring at 500-700 rpm for 3-5 minutes, followed by settling for 2-4 minutes, and this cycle is repeated 2-3 times. During the stirring stage, the metal ions in the complexing agent and surfactant system can form a small and stable dispersion system more quickly under shear action. At this time, the diameter of the complexed particles formed by the metal ions and complexing agent is significantly reduced, further improving their stability and dispersibility. The subsequent settling stage allows the above-mentioned microparticles to slowly aggregate, which is more conducive to the subsequent layer separation process. This periodic shearing and settling synergistic mode is more effective than simple stirring or settling processes in avoiding excessive aggregation or sedimentation of metal complex particles, and promotes the rationality and uniformity of the particle size distribution of the final complexed product. Therefore, the introduction of this process step can further improve the efficiency of the complexation reaction and the removal rate of metal ions under mild conditions. Furthermore, since this shear-holding process achieves good results in a lower temperature range, it avoids the damage to the stability of the surfactant system caused by traditional high temperatures or strong shearing, effectively maintaining the stability of the system itself and significantly reducing energy consumption and processing costs.

[0017] Meanwhile, this invention also incorporates a temperature perturbation program in step S3, where the reaction system is first heated to 38–40°C and maintained for 5 minutes, then naturally cooled to 25–27°C. This temperature perturbation strategy allows the reaction system to experience slight temperature fluctuations within a short period, effectively promoting the kinetic exchange process between the complexing agent molecules and metal ions. The brief heating process significantly increases the molecular thermal energy, enhancing the dispersion and solubility of the reaction components, thereby accelerating the complexation rate between the complexing agent and metal ions. The subsequent natural cooling stage gradually stabilizes the micro-aggregates formed by the complexed substances, resulting in a more concentrated and uniform particle size distribution, which facilitates rapid sedimentation and separation during subsequent stratification operations. Compared to the traditional complexation process under a single constant temperature condition, this temperature perturbation mode significantly improves the dispersion stability and subsequent sedimentation efficiency of the complexed substances in the system, and also avoids the negative impact of prolonged high-temperature operation on the stability of the complex.

[0018] Furthermore, this invention clarifies that the total addition amount of the complexing agent ethylenediamine disuccinic acid and potassium tricarboxyisocitrate is 2-6 wt% of the surfactant solution mass. This optimized range clarifies the technical boundaries and applicable scope of the complexing agent addition amount. The mass ratio of ethylenediamine disuccinic acid to potassium tricarboxyisocitrate is set at 1:(0.8-1.2), further precisely defining the component ratio range of the compound complexing agent. This ensures the effective utilization efficiency of the complexing agent, enabling efficient chelation and capture of metal ions even at lower dosages. It avoids waste when using excessive amounts of complexing agent and also reduces the negative impact of unreacted complexing agent residue on surfactant performance, thereby ensuring the reliability of the finished surfactant product quality.

[0019] Finally, this invention incorporates a cyclone separation operation before step S4, involving rotation via a cyclone inducer for 3-5 minutes followed by static stratification. Utilizing the cyclone mechanics effect, a centrally stable liquid-liquid stratification region is rapidly formed in the system, causing complexed metal ion particles to quickly aggregate towards the cyclone center and accelerate their settling. Under the cyclone induction effect, the effective settling rate of tiny particles within the system is significantly increased, resulting in a faster and clearer stratification process.

[0020] In summary, this invention significantly improves the low-temperature chelation and removal effect of metal ions in fatty acid amide surfactants through measures such as shear-static cycling, temperature perturbation optimization, limiting the range of complexing agent addition, and cyclone-induced separation. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the embodiments.

[0022] Example 1: This example discloses a low-temperature chelation removal process for metal ions in fatty acid amide surfactants, including the following steps: S1): Weigh out cocamidopropyl betaine (30wt% solution) and cocamidopropyl carboxybenzene (35wt% solution) and mix them at a mass ratio of 1.5:1. Dilute with deionized water to a total concentration of 5wt%. While stirring, add Cu to the solution. 2+ 10mg / L, Ni 2+ A 5 mg / L metal ion simulated solution was used to form a polluting surfactant system. The system mass was set at 200 g.

[0023] Subsequently, 2 wt% each of glycerol and sorbitol were added as chelating aids to improve the compatibility between metal ions and complexation sites; then 0.3 wt% sodium polyaspartate was added to improve the complexation rate and dispersion stability of the system. The mixture was stirred at room temperature (25°C) for 15 minutes to form a homogeneous solution.

[0024] S2): At 30°C, ethylenediamine disuccinic acid (EDDS) and potassium tricarboxyisocitrate (K3-ICA) were added sequentially to the above solution at a mass ratio of 1:1, totaling 3 wt%. To enhance the emulsification and release process of metal ions, 0.3 wt% fatty alcohol polyether sulfosuccinate (AESA) was further added. The reaction was maintained at 31°C with stirring for 20 minutes to allow the metal ions to gradually transfer to the complexing agent phase.

[0025] Between S2 and S3): To enhance the release of metal ions from surfactant micelles, a shearing + settling cycle was used: shearing for 4 minutes at 500 rpm, settling for 3 minutes, and repeating 3 times to promote micelle deconstruction / reconstruction and dynamic transfer of metal ions, thereby improving chelation efficiency.

[0026] S3): Heat the reaction system to 39°C, maintain this temperature for 5 minutes, then allow it to cool naturally to 26°C. Add 0.05 wt% disodium hydrogen phosphate to adjust the pH of the system to 6.9, stabilizing the complex and preventing metal hydrolysis and precipitation. Stir for 15 minutes.

[0027] S4): Transfer to a cyclone inducer and rotate for 4 minutes, then let stand for 30 minutes. The system forms an upper emulsion phase and a lower clear liquid. Metal complexes are enriched in the lower aqueous phase.

[0028] Example 2: This example discloses a low-temperature chelation removal process for metal ions in fatty acid amide surfactants, including the following steps: S1): Cocamidopropyl betaine (30wt% solution) and erucamide carboxymethyl betaine (35% solid content) were mixed at a mass ratio of 2:1, diluted with deionized water to prepare a homogeneous solution with a total concentration of 10wt%, and the total mass of the system was 200g. Cu-containing compounds were added to the system. 2+ and Ni 2+The metal ion standard solutions were prepared with initial concentrations of 20 mg / L and 10 mg / L, respectively.

[0029] Subsequently, 2.5 wt% each of glycerol and sorbitol were added as metal chelation solubilizers; at the same time, 0.5 wt% sodium polyglutamate was added to improve the aqueous stability and synergistic adsorption of the complexing agent. The mixture was stirred at 300 rpm and the temperature was maintained at 30°C for 20 minutes to form a homogeneous simulated contamination solution.

[0030] S2): At 32℃, a mixture of ethylenediamine disuccinic acid (EDDS) and potassium tricarboxyisocitrate (K3-ICA) powders was added at a mass ratio of 1:1.2, with a total addition amount of 4 wt% of the total system mass. Simultaneously, 0.5 wt% of fatty alcohol polyether sulfosuccinate (AESA, 30 wt% solution) was introduced as a wetting-transfer aid. The mixture was stirred continuously for 30 minutes to promote the migration of metal ions from the micelles to the complexing agent phase.

[0031] Between S2 and S3): Shear at 700 rpm for 5 minutes + let stand for 4 minutes, repeat 3 times to enhance interfacial desorption and mass transfer by high shear and improve complexation rate.

[0032] S3): Heat to 40℃ and hold for 5 minutes to promote the release and complexation of remaining free metal ions, then cool naturally to 27℃. Add 0.1wt% disodium hydrogen phosphate to the system, adjust the pH to 7.2, and stir for 30 minutes to keep the complexed metal ions in a dissolved state and prevent precipitation.

[0033] S4): The cyclone inducer was run for 5 minutes to induce micelle reconstruction and microemulsion dissociation within the induced phase, followed by standing for 40 minutes. The system was divided into an upper oil phase and a lower clear liquid phase. The lower aqueous phase was collected and analyzed.

[0034] Example 3: This example discloses a low-temperature chelation removal process for metal ions in fatty acid amide surfactants, including the following steps: S1): Oleamidopropyl betaine and cocamidopropyl carboxybetaine were compounded at a mass ratio of 1:1, and deionized water was added to form a surfactant solution with a total concentration of 2 wt% (total mass 200 g). A standard metal ion solution was added to the system until Cu... 2+ 5mg / L, Ni 2+ 2 mg / L.

[0035] Next, add 1 wt% sodium gluconate to enhance the chelating bridging property for metal ion complexation and migration; add 0.05 wt% sodium polyaspartate to promote the formation of a stable complex structure of the chelating agent. Stir for 10 minutes until the system is clear.

[0036] S2): At 30°C, add ethylenediamine disuccinic acid and potassium tricarboxyisocitrate (K3-ICA) in a mass ratio of 1:0.8, with a total addition of 1.5wt%, and add 0.1wt% fatty alcohol polyether sulfosuccinate. Stir continuously for 10 minutes to complete the initial complexation reaction.

[0037] Between S2 and S3): Shear at 500 rpm for 3 minutes, let stand for 2 minutes, and repeat twice to promote the desorption of low-concentration metal ions at the micromicelle interface and their binding with the complexing agent.

[0038] S3): Heat to 38°C and hold for 5 minutes, then cool to 25°C. Slowly add 0.01 wt% disodium hydrogen phosphate, adjust the pH to 6.6, and stir for 10 minutes to stabilize the complex.

[0039] S4): After the cyclone inducer runs for 3 minutes, it is left to stand for 20 minutes to form two phases.

[0040] Comparative Example 1: This comparative example discloses a process for removing metal ions from fatty acid amide surfactants, including the following steps: S1): Cocamidopropyl betaine (30wt% solution) and cocamidopropyl carboxybenzene (35wt% solution) were mixed at a mass ratio of 1.5:1, and diluted with deionized water to 5wt% to form a 200g homogeneous system. Cu was added to the system. 2+ 10mg / L, Ni 2+ A 5 mg / L standard solution of metal ions was used to simulate the contaminated system.

[0041] Then add 2 wt% each of glycerol and sorbitol, and 0.3 wt% sodium polyaspartate, stir until homogeneous, maintain the system temperature at 25°C, and stir for 15 minutes.

[0042] S2): At 30°C, add ethylenediamine disuccinic acid and potassium tricarboxyisocitrate (mass ratio 1:1, total addition 3wt%), and add 0.3wt% fatty alcohol polyether sulfosuccinate. Maintain the temperature at 31°C and stir for 20 minutes.

[0043] S3): This comparative example omits the shear-settling cycle step in Example 1. After completing S2, proceed directly to S3. Heat to 39°C and hold for 5 minutes, then allow to cool naturally to 26°C. Add 0.05wt% disodium hydrogen phosphate to adjust the pH to 6.9 and stir for 15 minutes.

[0044] S4): After rotating the cyclone inducer for 4 minutes, let it stand for 30 minutes to separate the lower clear liquid.

[0045] Comparative Example 2: This comparative example discloses a process for removing metal ions from fatty acid amide surfactants, including the following steps: S1) Configuration of a metal-containing surfactant system: Under constant temperature water bath conditions, deionized water was heated to 25°C. 190.6 g of deionized water was placed in a 250 mL three-necked flask, and the stirring speed was set to 300 rpm. 8.33 g of cocamidopropyl betaine (30 wt% solution) and 5.56 g of cocamidopropyl carboxybetaine (35 wt% solution) were added sequentially at a mass ratio of 1.5:1, resulting in a total mass of 200 g and a surfactant mass fraction of 5 wt%.

[0046] Add a standard solution of metal ions to the system to control Cu 2+ The concentration is 10 mg / L, Ni 2+ A concentration of 5 mg / L was used to simulate a metal contamination system.

[0047] Continue adding 4.0g (2wt%) of glycerol, 4.0g (2wt%) of sorbitol, and 0.6g (0.3wt%) of sodium polyaspartate. Maintain the temperature at 25℃ and stir for 15 minutes to form a homogeneous contamination system.

[0048] S2) Reaction of complexing agents and functional additives: Add 3.0 g of ethylenediamine disuccinic acid (EDDS) and 3.0 g of potassium tricarboxyisocitrate (K3-ICA) to the above system in a mass ratio of 1:1, with the total addition amount accounting for 3 wt% of the system mass. Then add 2.0 g of fatty alcohol polyether sulfosuccinate (AESA, 30 wt% solution), equivalent to 0.6 g of the effective component, accounting for 0.3 wt% of the total mass. Stir the reaction continuously at 30 °C for 20 minutes.

[0049] Between S2 and S3) Shear-hold cycle operation: A high-speed shearing device was used to shear and stir at 500 rpm for 4 minutes, followed by standing for 3 minutes. This process was repeated 3 times to enhance the desorption process of metal ions from surfactant micelles.

[0050] S3) Complexation stabilization treatment under conditions without temperature rise or fall disturbance: The reaction system under stirring was maintained at a constant temperature of 30°C without heating or cooling, and stirring was continued at this temperature for 15 minutes. Then, 0.1 g (0.05 wt%) of disodium hydrogen phosphate was added to adjust the pH to 6.9, and stirring was continued for 10 minutes to stabilize the complex.

[0051] S4) Swirl-induced separation: The mixed solution was transferred to a cyclone induction device, the rotation speed was set to 800 rpm, and the solution was run for 4 minutes before being stopped and allowed to stand for 30 minutes to separate into layers. The clear lower layer was collected through the bottom valve for analysis of metal residues.

[0052] Comparative Example 3: This comparative example discloses a process for removing metal ions from fatty acid amide surfactants, including the following steps: S1) Configuration of a metal-containing surfactant system: 8.33 g of cocamidopropyl betaine (30 wt% solution) and 5.56 g of cocamidopropyl carboxybetaine (35 wt% solution) were mixed at a mass ratio of 1.5:1, and deionized water was added to a total mass of 200 g to form a homogeneous system with a surfactant concentration of 5 wt%.

[0053] A standard solution of metal ions was added under stirring conditions to make Cu 2+ The concentration is 10 mg / L, Ni 2+ The concentration was 5 mg / L. Add 4.0 g of glycerol, 4.0 g of sorbitol, and 0.6 g of sodium polyaspartate, and stir for 15 minutes to form a homogeneous solution.

[0054] S2) Complexing agent addition reaction (insufficient addition amount): 1.0 g of ethylenediamine disuccinic acid (EDDS) and 1.0 g of potassium tricarboxyisocitrate (K3-ICA) were added in a 1:1 mass ratio, for a total addition of 2.0 g, accounting for 1 wt% of the total mass. Simultaneously, 0.6 g of fatty alcohol polyether sulfosuccinate (AESA) (30 wt% solution) was added, representing 0.18 g of the effective component, accounting for 0.09 wt%. The mixture was stirred continuously at 30°C for 20 minutes.

[0055] Between S2 and S3) Shear-hold cycle operation: Shear and stir at 500 rpm for 4 minutes, let stand for 3 minutes, and repeat 3 times.

[0056] S3) Temperature disturbance and pH adjustment treatment: Heat the system to 39°C and hold for 5 minutes, then allow it to cool naturally to 26°C. Add 0.1 g (0.05 wt%) of disodium hydrogen phosphate, adjust the pH to 6.9, and stir for 15 minutes.

[0057] S4) Swirl-induced separation: The cyclone inducer was set to 800 rpm and stopped after running for 4 minutes. It was then allowed to stand for 30 minutes to separate into layers, and the lower aqueous phase was collected to determine the residual metal ions.

[0058] Comparative Example 4: This comparative example discloses a process for removing metal ions from fatty acid amide surfactants, including the following steps: S1) Configuration of a metal-containing surfactant system: Weigh 8.33g (30wt%) of cocamidopropyl betaine and 5.56g (35wt%) of cocamidopropyl carboxybenzene, and add them to deionized water at a mass ratio of 1.5:1 to prepare a surfactant solution with a mass of 200g and a concentration of 5wt%.

[0059] Then add copper ion standard solution (Cu) 2+ 10 mg / L, Ni 2+ 5 mg / L), 4.0 g glycerol, 4.0 g sorbitol, and 0.6 g sodium polyaspartate were stirred at 25°C for 15 minutes to form a homogeneous system.

[0060] S2) Complexing agent addition reaction: Add 3.0g of ethylenediamine disuccinic acid and 3.0g of potassium tricarboxyisocitrate (mass ratio 1:1, addition amount 3wt%), add 2.0g of fatty alcohol polyether sulfosuccinate (30wt% solution), equivalent to 0.6g of effective component (0.3wt%), and stir continuously at 31℃ for 20 minutes.

[0061] Between S2 and S3) Shear-hold cycle operation: Shear and stir at 500 rpm for 4 minutes, let stand for 3 minutes, and repeat 3 times.

[0062] S3) Temperature disturbance and pH adjustment treatment: Heat to 39°C and hold for 5 minutes, then allow to cool naturally to 26°C. Add 0.1g (0.05wt%) of disodium hydrogen phosphate to adjust the pH to 6.9, and stir for 15 minutes.

[0063] S4) No swirling flow induction, only natural settling and stratification: Without performing vortex induction, the reaction system was left to stand in a static environment for 30 minutes to observe the stratification. The lower aqueous phase was collected by siphoning for subsequent detection of residual metal ions.

[0064] Detection method: The residual concentration of metal ions was detected using inductively coupled plasma optical emission spectrometry (ICP-OES), and the specific detection method is as follows: 1. Sample collection and pretreatment: Lower aqueous phase separation: After completing step S4, the lower aqueous phase of all systems is extracted as the sample to be tested by cyclone-induced separation or static sedimentation.

[0065] Pre-filtration: The lower aqueous phase is filtered through a 0.45μm microporous membrane to remove any micelles, precipitates, or particles that may remain in the system.

[0066] Acidification preservation: Add high-purity nitric acid (1% volume fraction) to the filtered sample, acidify, and seal for preservation to stabilize the metal complex and prevent adsorption or precipitation.

[0067] 2. ICP-OES analysis conditions: Instrument model: PerkinElmerOptima8000 or equivalent; Wavelength selection: Cu 2+ The detection wavelength is 324.75nm; Ni 2+ The detection wavelength is 231.60 nm; Standard curve: A working curve was established using five concentration gradient points (0.2–20 mg / L) prepared with national standard metal ion solutions. The linear correlation coefficient R0 was calculated. 2 >0.999.

[0068] Sample introduction method: nebulizer flow rate 0.8 L / min, sampling time 10 s, average data reading 3 times, and the average value is taken as the final result.

[0069] 3. Removal rate calculation: Based on the initial metal concentration C0 and the final residual concentration C1 in each system, the metal ion removal rate (R) is calculated using the following formula:

[0070] The detection results of Examples 1-3 and Comparative Examples 1-4 are shown in Table 1 below.

[0071] Table 1:

[0072] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A low-temperature chelation removal process for metal ions in fatty acid amide surfactants, characterized in that, Includes the following steps: S1) Under conditions of 20–30°C, a fatty acid amide surfactant is dissolved in deionized water to form a homogeneous surfactant solution. The surfactant is cocamidopropyl betaine, oleamidopropyl betaine, or a compound of the surfactant and an amphoteric surfactant. The amount of surfactant added is 2–10 wt% of the total mass of the system. S2) Under stirring, a complexing agent and a regulator are added to the surfactant solution. The complexing agent comprises ethylenediamine disuccinic acid and potassium tricarboxyisocitrate in a mass ratio of 1:(0.8-1.2), and the total amount added is 1.5-4 wt% of the total mass of the system. The regulator is fatty alcohol polyether sulfosuccinate, and the amount added is 0.1-0.5 wt%. S3) Maintain the above reaction system at 30°C and stir for 10-30 minutes; S4) After stopping stirring, let it stand for 20 to 40 minutes to separate the aqueous phase and remove the complexed metal ions to form a clear liquid.

2. The low-temperature chelation removal process for metal ions in fatty acid amide surfactants according to claim 1, characterized in that, The total amount of ethylenediamine disuccinic acid and potassium tricarboxyisocitrate added accounts for 2 to 6 wt% of the surfactant solution mass.

3. The low-temperature chelation removal process for metal ions in fatty acid amide surfactants according to claim 1, characterized in that, In step S1, 1-5 wt% of one or more of glycerol, sorbitol, or sodium gluconate is further added to the surfactant solution.

4. The low-temperature chelation removal process for metal ions in fatty acid amide surfactants according to claim 1, characterized in that, The mass ratio of the fatty acid amide surfactant to the amphoteric surfactant is (1-2):1, and the amphoteric surfactant is cocamidopropyl carboxybetaine or erucamide carboxymethyl betaine.

5. The low-temperature chelation removal process for metal ions in fatty acid amide surfactants according to claim 1, characterized in that, The surfactant solution formed in step S1 also contains 0.05 to 0.5 wt% of sodium polyaspartate or sodium polyglutamate containing carboxylic acid groups.

6. The low-temperature chelation removal process for metal ions in fatty acid amide surfactants according to claim 1, characterized in that, In step S2, the system temperature is maintained at 30–32°C, and the stirring time is 15–30 minutes to ensure the stable progress of the complexation reaction.

7. The low-temperature chelation removal process for metal ions in fatty acid amide surfactants according to claim 1, characterized in that, A shearing and settling step is set between step S2 and step S3, which includes stirring the reaction at 500-700 rpm for 3-5 minutes, then settling the reaction for 2-4 minutes, and repeating the cycle 2-3 times.

8. The low-temperature chelation removal process for metal ions in fatty acid amide surfactants according to claim 1, characterized in that, In step S3, 0.01–0.1 wt% of disodium hydrogen phosphate is added to control the endpoint pH between 6.6 and 7.

2.

9. The low-temperature chelation removal process for metal ions in fatty acid amide surfactants according to claim 1, characterized in that, Step S3 sets the temperature disturbance program, which involves first heating the system to 38-40°C and holding it for 5 minutes, then naturally cooling it to 25-27°C.

10. The low-temperature chelation removal process for metal ions in fatty acid amide surfactants according to claim 1, characterized in that, Before step S4, a cyclone separation operation is set up. The reaction liquid is rotated through a cyclone inducer for 3 to 5 minutes and then allowed to stand for stratification.

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