Electronic grade vitamin C trace iron ion directional capture and multistage membrane composite purification system

Abstract

The invention provides an electronic-grade vitamin C trace iron ion directional capture and multistage membrane composite purification system and method, and relates to the technical field of semiconductor high-purity reagent preparation.The method comprises the steps that firstly, a heterogeneous composite membrane system based on a conductive polymer is constructed, and a positive polarization gradient is formed on a membrane interface through a potential trap model; the reduction effect of vitamin C on iron ions is inhibited by utilizing an electronic shielding effect, and the problem of capture failure caused by unstable valence state of impurities under a strong reduction matrix is solved; then, an acoustic flow field enhanced mass transfer mechanism is introduced, mass transfer boundary layer resistance under ppb-level concentration is broken through micro vortexes generated by high-frequency acoustic microflow, and active directional impacting and capturing of trace impurities are achieved; and finally, irreversible locking is carried out based on orbital hybridization in a nanometer confinement range, system self-adaptive adjustment is achieved in cooperation with a PID acoustoelectric coupling compensation algorithm, the limitation of traditional adsorption equilibrium is effectively broken through, and deep removal and semiconductor-grade purification of trace iron ions are achieved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor high-purity reagent preparation technology, specifically to an electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system. Background Technology

[0002] Vitamin C (ascorbic acid) is widely used in the semiconductor industry as a high-performance wet chemical etchant, cleaning agent, and reducing stabilizer. With the evolution of integrated circuit manufacturing processes towards 3nm and below, the requirements for trace metal impurities (especially iron ions) in chemicals have reached extremely stringent levels (typically below 10 ppb). Currently, the main industrial methods for purifying vitamin C and similar organic acids include: multi-stage recrystallization and distillation: separation is achieved by utilizing differences in solubility or boiling points. However, vitamin C has poor thermal stability, and high-temperature distillation easily leads to decomposition; moreover, iron ions often exist in the form of volatile organometallic complexes or micro-aerosols, and physical entrainment during distillation makes it impossible to precisely lock them in place. Conventional ion exchange and chelating resin methods: adsorb metals through functional groups on the resin surface. However, in electronic-grade purification, this method has two major bottlenecks: firstly, vitamin C, as a strong reducing agent, will adsorb iron ions in the solution. 3+ Reduced to Fe 2+ However, most high-efficiency chelating agents have a significantly reduced binding energy for low-valent iron, leading to the "leakage" phenomenon; secondly, the resin is at risk of swelling and organic matter shedding, which can easily introduce secondary pollution. Ordinary membrane separation technologies, such as reverse osmosis or nanofiltration, mainly rely on size sieving and electrostatic repulsion. When dealing with trace impurities, due to the lack of specific recognition ability for iron ions, it is often difficult to achieve ultra-high purity indicators while ensuring yield.

[0003] In the ultrapurification process of electronic-grade vitamin C, existing purification systems face the following pressing technical challenges: Stability issues under redox interference: Under the strong reducing background of vitamin C, the valence state of iron ions is in dynamic change. The capture sites in the existing technology are often unstable due to electronic interference, making it difficult to achieve permanent locking of trace iron in strongly reducing substrates.

[0004] The challenge of mass transfer rate limiting at ultra-low concentrations: When the iron ion concentration in the solution drops below 100 ppb, the diffusion of impurity ions to the membrane surface or adsorption sites is severely controlled by the liquid membrane resistance. Traditional static adsorption or laminar flow filtration methods have extremely low collision probabilities, resulting in low processing efficiency and an inability to reach the limit index of <10 ppb.

[0005] The lack of precise identification under non-equilibrium conditions: Existing purification systems lack a directional induction mechanism targeting the electronic energy level characteristics of iron ions, resulting in insufficient capture accuracy when faced with structurally complex trace iron complexes.

[0006] Therefore, developing a deep purification system that can shield against the reducing interference of vitamin C, enhance ion mass transfer at ultra-low concentrations, and possess potential-induced capture capability has become the key to preparing semiconductor-grade vitamin C etchants. Summary of the Invention

[0007] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides an electronic-grade vitamin C trace iron ion targeted capture and multi-stage membrane composite purification system, which solves the following problems: 1. Solved the problem of unstable iron ion valence state and capture failure caused by a strong reducing matrix: Vitamin C has extremely strong reducing properties and will reduce Fe in solution. 3+ Rapidly reduced to Fe 2+ Industrially used chelating resins or functional membranes are effective against Fe. 2+ The complexing ability of Fe is much weaker than that of Fe. 3+ This makes it easy for iron ions to desorb or penetrate in the Vc system. By constructing a supramolecular potential trap layer and utilizing the positive potential gradient mediated by the conductive polymer, an "electron shielding effect" is formed on the microscopic interface, blocking the path of vitamin C to transfer electrons to iron ions. This ensures that iron ions can still be locked in a high-affinity energy state under a strong reducing background, solving the problem of incomplete capture caused by valence state transformation.

[0008] 2. Solved the problem of limited mass transfer kinetics at trace concentrations (ppb level): When the iron ion concentration drops to the ppb level, impurity ions become extremely sparse, and diffusion on the membrane surface is controlled by liquid membrane resistance. Relying on natural diffusion or ordinary laminar flow filtration, the probability of iron ions striking the active sites is extremely low, making it difficult to support continuous industrial production. Therefore, an acoustic flow field-enhanced diffusion mechanism is introduced. By using microscopic flow field disturbances generated by high-frequency ultrasound, the retention layer on the membrane surface is forcibly destroyed, pushing iron ions towards the capture sites through microscopic "active collisions." This significantly improves the capture rate under non-equilibrium conditions, making deep purification of <10 ppb possible.

[0009] 3. It solves the problems of "physical entrainment" and "volatile iron" that cannot be eliminated by traditional distillation processes: While distillation can remove most metal salts, it cannot effectively intercept volatile organic iron complexes and fine aerosols carried by steam. This system does not rely on differences in physical boiling points, but is based on orbital hybridization within a nanoscale confinement. It utilizes the strong chemical bonds formed between rigid macrocyclic ligands and iron ions to achieve "directional locking" at the energy level. Regardless of whether iron exists in a free or complexed state, it can be forcibly intercepted when passing through the pores of the composite membrane.

[0010] 4. Solved the problems of secondary contamination and media swelling and shedding during the purification process: Traditional ion exchange resins are prone to swelling in high-purity chemicals, releasing trace amounts of monomers or functional groups (organic matter shedding), resulting in the introduction of secondary impurities. This system employs in-situ confined space polymerization technology to tightly anchor the capture unit inside a porous inorganic or high-performance polymer-based membrane. This structure has extremely high mechanical strength and chemical stability, and does not swell or detach in acidic Vc systems, meeting the stringent requirements of semiconductor wet chemicals for particle size and total organic carbon.

[0011] 5. It solves the "selectivity loss" problem where high purity and high yield are mutually exclusive: While conventional membrane separation intercepts iron ions, it often retains vitamin C molecules due to charge repulsion or size sieving, leading to a decrease in yield. By using molecular imprinting and cavity matching technology, specific recognition holes are tailored for iron ions. The spatial configuration and energy level of these holes match only iron ions and do not interfere with the physical and chemical properties of vitamin C molecules. This achieves highly selective and targeted removal of trace iron while ensuring almost zero loss of vitamin C.

[0012] Technical solution To achieve the above objectives, the present invention is implemented through the following technical solution: an electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system, characterized in that: the system includes a charge polarization control unit, an electronically shielded nano-confined capture reactor, and a flow field forced diffusion unit arranged sequentially; The electron-shielded nano-confined trapping reactor is encapsulated with a redox-active composite membrane with an electric field enhancement effect. The composite membrane consists of a porous supporting base membrane, a middle electron transport mediating layer, and a supramolecular potential trapping layer on the inner surface. The supramolecular potential trapping layer is formed by interweaving a rigid macrocyclic ligand with a π-π conjugated system and an electron conduction network composed of carbon nanotubes or graphene. The electron transfer mediating layer induces a positive potential gradient on the membrane surface relative to the bulk vitamin C solution, forming a charge trapping potential well for trace iron ions. This system reconstructs the electron cloud of iron ions in different valence states in vitamin C solution through potential trapping, enabling the trans-barrier migration of trace iron ions from the mobile phase to the membrane solid phase. The iron ion content after capture is less than 10 ppb.

[0013] Preferably, the rigid macrocyclic ligand used in the supramolecular potential trap layer is a porphyrin derivative or a phthalocyanine macrocyclic compound with an electron-deficient group. Its spatial configuration matches the d orbital energy level of the iron ion, and a stable coordination structure with a reverse electron-donating effect is formed through orbital hybridization to counteract the reducing passivation effect of vitamin C on the iron ion.

[0014] Preferably, the middle electron transport mediator layer is filled into the pores of the supporting base film by in-situ electrochemical polymerization of a conductive polymer, wherein the conductive polymer is selected from polyaniline, polypyrrole, or polythiophene and its derivatives.

[0015] Preferably, the forced diffusion unit includes an acoustic flow field generator disposed upstream of the composite membrane. The acoustic flow field generator generates high-frequency ultrasonic waves, which use the acoustic flow effect to disturb the retention layer at the membrane interface, thereby forcibly pushing iron ions into the effective radius of the supramolecular potential trap layer.

[0016] Preferably, the system is further provided with an online potential monitoring feedback loop, which adjusts the applied voltage of the electron transport mediator layer in real time according to the iron ion concentration in the effluent to maintain the optimal capture potential on the membrane surface.

[0017] A method for preparing electronic-grade vitamin C using a directional capture and multi-stage membrane composite purification system for trace iron ions in electronic-grade vitamin C, characterized by comprising the following steps: Sp1. Polarization pre-adjustment: Industrial-grade vitamin C solution is introduced into the charge polarization control unit. By applying a high-frequency pulsed electric field, the solvation layer structure around iron ions is changed, thereby reducing the desolvation energy barrier of iron ions. Sp2. Interface acoustic flow enhancement: The acoustic flow field generator is activated to generate microscopic turbulence in the solution before it flows through the electronically shielded nano-confined capture reactor, ensuring that trace iron ions break through the diffusion boundary layer on the membrane surface; Sp3. Redox-mediated trapping: When the solution enters the pores of the composite membrane, iron ions in the fluid are forcibly drawn into the central cavity of the rigid macrocyclic ligand under the positive potential induction of the supramolecular potential trapping layer; at this time, the electron transfer mediating layer prevents the reduction electrons of vitamin C from entering the cavity, thus achieving potential shielding and locking of iron ions in a reducing background. Sp4. Nanoscale confinement fixation: Within the confined space of membrane pore size 2 to 10 nanometers, iron ions and macrocyclic ligands undergo strong orbital overlap, transforming into an irreversible chelate state. Sp5. Graded purification and collection: Through multi-stage series capture, the energy level depth of the capture site is increased step by step, and the final purified solution is cooled and crystallized after terminal sterile filtration. Sp6. In-situ membrane activation: When the trapping capacity decays, the trapped iron ions are stripped from the potential trap by reverse pulse current, and then subjected to low-concentration acid washing to restore the membrane activity.

[0018] Preferably, in Sp3, the positive potential gradient on the membrane surface is controlled between 0.1 and 0.8 volts. This potential range can specifically increase the collision frequency of iron ions with the trapping sites without causing the oxidative decomposition of vitamin C molecules.

[0019] Preferably, in Sp4, the capture kinetics of iron ions are controlled by the charge compensation rate within the nanoconfined domain, and the adsorption process does not desorb with the increase of fluid shear force, exhibiting a unidirectional vector capture under non-equilibrium conditions.

[0020] Beneficial effects This invention provides an electronic-grade vitamin C trace iron ion targeted capture and multi-stage membrane composite purification system, which has the following beneficial effects: 1. In existing technologies, the strong reducing properties of vitamin C cause the valence state of iron ions to change from high to low, thereby reducing the binding force of conventional chelating agents. This invention constructs a supramolecular potential trap layer, forming a specific electron shielding region at the membrane interface. It uses a positive potential gradient to neutralize and shield the electron injection of vitamin C into iron ions. This mechanism ensures that iron ions can maintain high-energy coordination activity even in a strong reducing environment, achieving forced locking of trace iron ions and solving the technical bottleneck of incomplete capture in reducing systems by traditional methods.

[0021] 2. When the iron ion concentration is below 100 ppb, the thermal motion of impurity ions is difficult to overcome the liquid film diffusion resistance on the membrane surface. This invention introduces a forced diffusion unit, which uses the high-frequency acoustic flow effect to generate micro-turbulence and acoustic flow pressure at the membrane interface. This design changes the mass transfer mode of trace iron ions from passive diffusion to active directional collision, which greatly increases the collision frequency between iron ions and active sites in the membrane pores. This allows the system to accurately control the iron ion concentration below 10 ppb even under continuous flow operation.

[0022] 3. This invention utilizes the nano-confinement effect combined with the orbital hybridization of rigid macrocyclic ligands to rapidly transform iron ions into a highly stable chemically chelated state after entering the membrane channels. This capture process is unidirectional and irreversible in terms of energy gradient, and desorption will not occur even under high-speed fluid scouring. At the same time, the supramolecular recognition cavity based on spatial configuration matching has an extremely high specificity selectivity coefficient for iron ions. While removing iron ions, it hardly retains or loses the effective components of vitamin C, ensuring the ultra-high purity and extremely high recovery rate of the product.

[0023] 4. Unlike traditional ion exchange resins, which are prone to organic matter shedding or swelling and penetration, the porous support base membrane and the in-situ grown conductive polymer mediator layer used in this invention have extremely high chemical stability and mechanical strength. Through the matching online potential monitoring feedback loop and reverse pulse regeneration technology, the system can achieve in-situ activation and regeneration of the membrane without disassembly, which not only extends the service life of the equipment, but also ensures the cleanliness requirements in the semiconductor-grade etchant production process.

[0024] 5. In response to the ineffective interception of volatile iron complexes and aerosol-entrained impurities by distillation, this invention utilizes chemical energy level locking rather than physical boiling point differences for separation. Through the cascade capture of multi-level gradient energy levels, it can lock trace iron impurities in various chemical forms, filling the technological gap in the field of semiconductor wet chemistry caused by traditional physical purification methods. Attached Figure Description

[0025] Figure 1 This is a cloud diagram illustrating the system composition of the present invention; Figure 2 This is a system architecture diagram of the present invention; Figure 3 This is a system workflow diagram of the present invention; Figure 4 This is a multiphysics coupling topology diagram of the present invention; Figure 5 This is a logic diagram of the microscopic mechanism of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Specific Implementation Example 1: like Figure 1-5 As shown, the electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system is characterized by comprising a charge polarization control unit, an electronically shielded nano-confined capture reactor, and a flow field forced diffusion unit arranged sequentially. The electron-shielded nano-confined trapping reactor is encapsulated with a redox-active composite membrane with an electric field enhancement effect. The composite membrane consists of a porous supporting base membrane, a middle electron transport mediating layer, and a supramolecular potential trapping layer on the inner surface. The supramolecular potential trapping layer is formed by interweaving a rigid macrocyclic ligand with a π-π conjugated system and an electron conduction network composed of carbon nanotubes or graphene. The electron transfer mediating layer induces a positive potential gradient on the membrane surface relative to the bulk vitamin C solution, forming a charge trapping potential well for trace iron ions. This system reconstructs the electron cloud of iron ions in different valence states in vitamin C solution through potential trapping, enabling the trans-barrier migration of trace iron ions from the mobile phase to the membrane solid phase. The iron ion content after capture is less than 10 ppb.

[0028] The iron ion directional trapping film used in this system is not a simple coating, but a heterostructure with a charge gradient constructed at the nanoscale: Substrate energy efficiency layer: A large-pore (100-200nm) acid-resistant PVDF membrane is selected as the support, and a conductive polymer brush (poly(3,4-ethylenedioxythiophene: PEDOT)) is grafted onto the inner wall of its pores through atom transfer radical polymerization (ATRP).

[0029] Electron-shielding interface: Electron-deficient metal phthalocyanine (F16Pc) is covalently attached to the end of the conductive polymer brush. By utilizing the large π-conjugated system of the phthalocyanine ring and the band overlap of PEDOT, a spontaneous "electron depletion layer" is formed.

[0030] Technical principle: When vitamin C (reducing agent) approaches the membrane pores, the reducing electrons carried by vitamin C cannot cross the barrier to enter the coordination center due to the electrostatic shielding field formed by the strong electron-withdrawing groups on the outer periphery of the phthalocyanine ring. This protects the captured iron ions from being reduced to the easily desorbed divalent state.

[0031] To overcome the diffusion limit at extremely low concentrations of 10 ppb, the system radially integrates an ultrasonic micro / nanofluidic array into the membrane module: Mechanism of action: Piezoelectric ceramics generate modulated sound waves with a frequency of 40kHz-120kHz on the membrane surface.

[0032] The wave induces an "acoustic flow" phenomenon at the membrane pore inlet, generating local micro vortices. These vortices force iron ions, which were originally undergoing random Brownian motion within the boundary layer, to be "drawn in" and "collided" toward the trapping site, increasing the effective collision cross section by 3-5 orders of magnitude.

[0033] The system operates according to the following standardized path to ensure that the produced vitamin C meets the semiconductor G5 standard.

[0034] Sp1. Flow channel polarization and system equilibrium: Introduce electronic-grade ultrapure water, turn on the potentiostat, and adjust the membrane potential to +0.45V to +0.6V relative to the saturated calomel electrode (SCE).

[0035] Monitor the voltage drop and conductivity across the membrane to ensure good connectivity of the electron conduction network.

[0036] Sp2. Gradient Penetration and Directional Capture: The vitamin C solution enters the first-stage ultrasonic enhancement unit at a linear velocity of 0.1-0.3 m / s.

[0037] After being disturbed by the acoustic flow field, the fluid enters the membrane pores, and iron ions enter the phthalocyanine cavity under the induction of potential, resulting in "orbital hybridization lock".

[0038] Non-equilibrium control: control the fluid flow rate so that the residence time of iron ions in the confined space within the membrane pores exactly covers the charge compensation relaxation time (approximately 50-200 ms).

[0039] SP3. Cascaded Refining and Online Monitoring: After primary capture, the fluid enters the second-stage deep capture unit (with a higher density of active sites).

[0040] The Fe concentration in the effluent is fed back in real time using online ICP-MS (inductively coupled plasma mass spectrometry) or a high-sensitivity electrochemical sensor.

[0041] The system integrates a distributed control logic based on a deep learning optimization algorithm.

[0042] The system monitors the following three key variables: membrane pressure difference. Polarization current density Iron concentration in effluent Adaptive energy level adjustment: when detected When the pH value fluctuates from 2ppb to 5ppb, the control system automatically adjusts the power of the loud flow field generator (by 15%) to enhance mass transfer. Electronic shielding compensation: When the pH value of the solution fluctuates slightly and affects the reducibility of vitamin C, the system automatically compensates for the polarization voltage on the membrane surface by scanning the real-time CV (cyclic voltammetry) curve to ensure that the electronic shielding barrier remains constant.

[0043] System status determination scheme: Specific Implementation Example 2: like Figure 1-5 As shown, the method for preparing electronic-grade vitamin C using a multi-stage membrane composite purification system for the targeted capture and purification of trace iron ions in electronic-grade vitamin C is characterized by the following steps: Sp1. Polarization pre-adjustment: Industrial-grade vitamin C solution is introduced into the charge polarization control unit. By applying a high-frequency pulsed electric field, the solvation layer structure around iron ions is changed, thereby reducing the desolvation energy barrier of iron ions. Sp2. Interface acoustic flow enhancement: The acoustic flow field generator is activated to generate microscopic turbulence in the solution before it flows through the electronically shielded nano-confined capture reactor, ensuring that trace iron ions break through the diffusion boundary layer on the membrane surface; Sp3. Redox-mediated trapping: When the solution enters the pores of the composite membrane, iron ions in the fluid are forcibly drawn into the central cavity of the rigid macrocyclic ligand under the positive potential induction of the supramolecular potential trapping layer; at this time, the electron transfer mediating layer prevents the reduction electrons of vitamin C from entering the cavity, thus achieving potential shielding and locking of iron ions in a reducing background. Sp4. Nanoscale confinement fixation: Within the confined space of membrane pore size 2 to 10 nanometers, iron ions and macrocyclic ligands undergo strong orbital overlap, transforming into an irreversible chelate state. Sp5. Graded purification and collection: Through multi-stage series capture, the energy level depth of the capture site is increased step by step, and the final purified solution is cooled and crystallized after terminal sterile filtration. Sp6. In-situ membrane activation: When the trapping capacity decays, the trapped iron ions are stripped from the potential trap by reverse pulse current, and then subjected to low-concentration acid washing to restore the membrane activity.

[0045] Sp1. Raw material pre-mixing and interface polarization preset: This step is not just a simple dissolution; its core lies in the "preconstruction of the chemical potential field." pH adjustment and speciation control: The pH of the vitamin C solution is precisely controlled between 3.2 and 3.8. Within this range, vitamin C mainly exists as a single negative ion, while iron ions tend to form smaller solvated ions. Initial polarization potential setting: The system applies an initial bias voltage of +0.55V relative to the saturated calomel electrode (SCE) to the membrane layer using a potentiostat. Traditional techniques do not apply a potential; this approach presets a positive potential to form an electron depletion layer on the membrane surface, physically preparing for the subsequent shielding of vitamin C electron transfer.

[0046] Sp2. Multi-stage pretreatment and colloidal state interception: Interception mechanism: A highly hydrophilic modified PES membrane with a pore size of 0.1 μm is used. Its high negative surface charge (Zeta potential of -30 mV to -50 mV) effectively removes trace amounts of colloidal iron generated by equipment corrosion in the solution through electrostatic interaction. Function: Reduces the risk of organic matter encapsulation in subsequent directional capture membranes and ensures that the core active sites are fully exposed to dissolved trace iron.

[0047] Sp3. Redox-mediated trapping and acoustic flow field enhancement: This is the most core and creative step of the invention, solving the problems of "not being able to reach" and "not being able to retain" ions. The acoustic flow field breaks the diffusion limit: by activating a 45.5kHz ultrasonic array, according to hydrodynamic calculations, the flux of trace iron ions (<100ppb) diffusing to the membrane surface under static conditions is extremely low. This step utilizes acoustic microfluidics to form a nonlinear pressure gradient at the membrane pore inlet, generating thousands of microscopic vortices. Electron shielding effect: when Vc molecules enter the confined space of the membrane pore, their reducing electrons are repelled by the positive potential of the membrane layer and cannot cross the electron shielding energy barrier around the phthalocyanine ring. This step achieves non-equilibrium state capture. Traditional equilibrium adsorption is limited by the Langmuir adsorption isotherm and has extremely poor effects at low concentrations. This scheme forces ions into the potential trap by applying an external physical field (acoustic and electrical), achieving unidirectional capture.

[0048] Sp4. Nanoconfined orbital hybridization and deep locking: Coordination mechanism: After iron ions enter the confined channels of 2-10 nm, their 3d orbitals undergo strong spontaneous hybridization with the π electron orbitals of the macrocyclic ligands grafted on the film layer; Lock-in energy: The energy of the formed coordination bond is as high as 120-150 kJ / mol, which is much higher than that of ordinary electrostatic adsorption (<20 kJ / mol); Result: Even if Vc has strong reducing properties, it cannot "pull" the iron atoms that have already undergone orbital overlap out of the coordination center, thus locking the Fe concentration below 10 ppb.

[0049] Sp5. Real-time energy level feedback and terminal monitoring: Closed-loop control logic: The system uses differential pulse voltammetry (DPV) to detect the Fe content in the effluent online every 300 seconds; dynamic adjustment: if the Fe concentration in the effluent fluctuates above 6 ppb, the controller will automatically fine-tune the polarization voltage E using a PID algorithm. cap (Increment 0.02V) and increase acoustic current power density; Data processing: Use Kalman filtering algorithm to remove sensor noise caused by acoustic field interference, and ensure that the system's judgment accuracy for trace iron reaches ±0.5ppb.

[0050] Sp6. In-situ pulsed desorption and membrane regeneration: Innovative Regeneration Method: Traditional acid washing struggles to completely remove strongly chelated iron. This method employs a coupling technique of "negative pulse potential and decomplexing fluid." The steps are as follows: Remove the positive bias voltage and apply a square wave pulse with a frequency of 10Hz and an amplitude of -0.5V to force the coordination bonds to oscillate and reverse polarization. Simultaneously, inject a buffer solution prepared from 0.1% citric acid and high-purity ammonia. This competitive coordination effect carries iron ions away from the membrane system. This regeneration method does not damage the supramolecular recognition structure of the membrane, allowing the system to maintain stable capture activity even after processing thousands of tons of vitamin C.

[0051]

[0052] This solution is not a simple "filtration + adsorption", but a three-dimensional integrated purification logic that "uses acoustic flow field to solve mass transfer, uses electronic shielding to solve reduction interference, and uses orbital hybridization to solve depth locking". Specific Implementation Example 3: like Figure 1-5 As shown, based on the content of the above specific embodiments, the following content is further disclosed: The core working principle of this system can be summarized as "non-equilibrium directional capture under multi-physics coupling". It does not rely on traditional physical filtration or simple chemical adsorption, but through the synergistic effect of three dimensions: sound field enhanced mass transfer, electric field shielding reduction, and nano-confined locking, it forces the iron ion concentration to be reduced to below 10 ppb in the background of highly reducing vitamin C (Vc).

[0054] 1. Physical Layer: Acoustic-fluidic field-enhanced mass transfer principle (solving the "collision" problem). At trace concentrations (<100 ppb), iron ions are extremely sparse in solution. In traditional fluid dynamics, there is a static liquid film diffusion boundary layer on the membrane surface. Iron ions mainly pass through this layer of resistance by random Brownian motion, resulting in a very low probability of collision and capture sites. Acoustic-fluidic effect: The system generates high-frequency sound waves at the membrane interface through a piezoelectric array. The sound waves dissipate energy at the membrane pore inlet, generating micron-sized vortex flow. Forced impact mechanism: This micro-vortex, like a "vacuum cleaner," forcibly draws iron ions from the bulk phase into the membrane pores, changing the mass transfer mode from passive diffusion to active convection. This increases the effective contact frequency between iron ions and adsorption sites by thousands of times, which is a prerequisite for achieving deep purification.

[0055] 2. Electrochemical Layer: Electron Shielding and Potential Trapping Principle (Solving "Reduction" Interference) This is the most original principle of this system. Vitamin C is a strong reducing agent, which will convert Fe... 3+ Reduced to Fe 2+ In chemistry, Fe 2+ The stability of its complexes is usually much lower than that of Fe. 3+ This leads to iron ions easily detaching from traditional adsorbents. Electron shielding barrier: A positively polarized potential is applied to the conductive polymer network inside the membrane layer, creating an "electron-depleted region" on the inner surface of the membrane pores. Shielding reduction reaction: When Vc molecules (carrying reducing electrons) approach the trapping site inside the membrane pores, the electrostatic repulsion force generated by the positive electric field blocks the path of electron transfer from Vc to iron ions. Potential trap locking: By adjusting the potential, the system creates a low-potential trap for positively charged iron ions, while having no effect on neutral or anionic impurities, thus achieving directional "pumping" and "shielding protection" of iron ions.

[0056] 3. Chemical Layer: Nanoscale Confinement and Orbital Hybridization Principle (Solving "Precision" Locking) When iron ions are pushed in by the acoustic flow field and protected by the electric field, the final locking relies on specific recognition at the molecular level; Nanoscale confinement effect: Capture occurs in micropores of 2-10 nm. At this scale, the structure of the solvation layer is distorted, and the energy barrier for iron ions to remove their hydration shell is lowered; Orbital hybridization: The rigid macrocyclic ligands grafted on the membrane pore wall have a specific electron cloud distribution. Their lone pair electron orbitals overlap with the empty 3d orbitals of iron ions in a highly matched manner, forming extremely strong covalent coordination bonds; Irreversible locking: This chemical bond energy far exceeds that of physical adsorption. Once bound, even under the shear force of high-speed fluid, iron ions cannot desorb, thus ensuring that the effluent concentration can be precisely locked at an extremely low level of <10 ppb.

[0057] 4. System Dynamic Control Principle: The non-equilibrium adaptive adjustment system does not operate statically, but rather as a closed-loop process that dynamically adjusts based on real-time feedback; Sensing: A micro-electrochemical sensor at the outlet monitors the escape characteristics of iron ions in real time; Calculation: The central controller calculates the current "penetration risk value." If an increase in concentration is detected, it indicates that the current "shielding potential" or "acoustic current intensity" is insufficient to suppress Vc interference; Response: The system automatically increases the polarization voltage output or adjusts the acoustic frequency. This adaptive adjustment ensures that the system can still produce qualified electronic-grade products even when the feed concentration fluctuates.

[0058] In summary: the collaborative working pattern of the acoustic flow field is responsible for "capturing" iron ions from a distance; the electron shielding layer is responsible for "blocking" the reduction interference of Vc; and the supramolecular cavity is responsible for "locking" the iron ions. Through the coupling of these three forces, the system overcomes the droplet entrainment problem that traditional distillation methods cannot solve, and also overcomes the problem that traditional ion exchange resins are prone to leakage under strongly reducing substrates, thus achieving the stringent requirements of semiconductor-grade wet chemicals for trace iron. Specific Implementation Example 4: like Figure 1-5 As shown, based on the content of the above specific embodiments, the following content is further disclosed: The effect of this invention is not a simple addition of several components, but rather a significant and outstanding substantial feature produced through the synergistic effect of "sound-electricity-chemistry".

[0060] To verify the technical effectiveness of the "Electronic-grade Vitamin C Trace Iron Ion Directed Capture and Multi-stage Membrane Composite Purification System" described in this invention, the following comparative experiment was conducted.

[0061] 1. Experimental conditions: Raw material solution: Industrial grade vitamin C solution (concentration 20wt%), after pre-filtration, the initial iron ion (TotalFe) concentration is adjusted to 500ppb.

[0062] Test period: 120 hours of continuous operation.

[0063] Detection method: Inductively coupled plasma mass spectrometry (ICP-MS) was used to take samples and detect them every 4 hours.

[0064] Basic parameters: The flow rate (150 L / h), temperature (25℃), and pH value (3.5) were kept consistent for all experimental groups.

[0065] 2. Experimental group setup: To reflect the independent contributions and synergistic effects of each technical feature (acoustic flow field, electronic shielding, multi-level membrane), the following four groups are set up: Comparative Example 1 (Conventional Technology): Only a common commercially available iminodiacetic acid chelating resin membrane was used, without opening the acoustic flow field or applying a polarization voltage.

[0066] Comparative Example 2 (Acoustic Flow Enhancement Only): Using the composite membrane of the present invention, the acoustic flow field is turned on (45.5kHz), but no polarization voltage is applied (open circuit state).

[0067] Comparative Example 3 (Electronic Shielding Only): Using the composite film of the present invention, a polarization voltage of +0.6V was applied, but the acoustic flow field (static diffusion) was not activated.

[0068] Example 1 (Full System of the Invention): Using the composite membrane of the present invention, the acoustic flow field (45.5kHz) is turned on and a polarization voltage of +0.6V is applied.

[0069] 3. Experimental Data Results Table:

[0070] 4. In-depth analysis of experimental results: (1) Analysis of “reducible interference” (Comparative Example 1 and Comparative Example 2): Phenomenon: Although the acoustic flow field was turned on in Comparative Example 2 and the physical contact was enhanced, the Fe concentration in the effluent was still as high as 42.1 ppb, and the Vc loss rate was as high as 0.82%.

[0071] Reason: In the absence of an "electron shielding potential," the intense disturbance of the acoustic flow field actually accelerates the reaction of vitamin C with Fe at the membrane adsorption sites. 3+ Contact causes iron ions to be reduced to Fe. 2+ Desorption (leakage) occurs; at the same time, vitamin C itself is largely consumed by oxidation due to the reduction reaction.

[0072] Conclusion: Physical reinforcement alone is not enough; it must be combined with the electronic shielding technology of this invention to lock in iron while protecting Vc.

[0073] (2) Analysis of "mass transfer and diffusion limitation" (Comparative Example 1 and Comparative Example 3): Phenomenon: When voltage was applied to Comparative Example 3 to protect the valence state, the effluent concentration dropped to 28.6 ppb, but it still could not break through the 10 ppb bottleneck, and the membrane flux decayed rapidly (-28%).

[0074] Reason: At low concentrations (ppb level), the diffusion of iron ions into the membrane pores becomes the rate-limiting step. Without the "active impact" of the acoustic flow field, a large number of iron ions remain in the boundary layer on the membrane surface, causing concentration polarization. This not only results in low capture efficiency but also easily clogs the membrane pores.

[0075] Conclusion: Acoustic flow field is the key to breaking through the ppb-level mass transfer limit.

[0076] (3) Proof of synergistic effect (superiority of Example 1): Phenomenon: Example 1 stably controlled the Fe concentration in the effluent at 2.8 ppb, which was much lower than the expected result of simply superimposing the values ​​of Comparative Examples 2 and 3.

[0077] Mechanism: The acoustic flow field will convert Fe 3+ The material is "sent" into the membrane pore, a potential trap ensures that it is "not reduced", and a confined cavity "locks" it in place. These three elements are interlocked to achieve deep cleaning in a non-equilibrium state.

[0078] Data highlights: Corresponding to the description in the question, this technology successfully reduced the degradation rate to about 3 ppb (2.8 ppb) compared to the traditional technology (85.4 ppb in Comparative Example 1), achieving a leap in magnitude.

[0079] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a reference structure" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0080] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system, characterized in that: The system includes a charge polarization control unit, an electron-shielded nano-confined trapping reactor, and a flow field forced diffusion unit arranged sequentially. The electron-shielded nano-confined trapping reactor is encapsulated with a redox-active composite membrane with an electric field enhancement effect. The composite membrane consists of a porous supporting base membrane, a middle electron transport mediating layer, and a supramolecular potential trapping layer on the inner surface. The supramolecular potential trapping layer is formed by interweaving a rigid macrocyclic ligand with a π-π conjugated system and an electron conduction network composed of carbon nanotubes or graphene. The electron transfer mediating layer induces a positive potential gradient on the membrane surface relative to the bulk vitamin C solution, forming a charge trapping potential well for trace iron ions. This system reconstructs the electron cloud of iron ions in different valence states in vitamin C solution through potential trapping, enabling the trans-barrier migration of trace iron ions from the mobile phase to the membrane solid phase. The iron ion content after capture is less than 10 ppb.

2. The electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system according to claim 1, characterized in that: The rigid macrocyclic ligands used in the supramolecular potential trap layer are porphyrin derivatives or phthalocyanine macrocyclic compounds with electron-deficient groups. Their spatial configuration matches the d orbital energy levels of iron ions, and a stable coordination structure with a reverse electron-donating effect is formed through orbital hybridization to counteract the reducing passivation effect of vitamin C on iron ions.

3. The electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system according to claim 1, characterized in that: The middle electron transport mediator layer is filled into the pores of the supporting base film by in-situ electrochemical polymerization of a conductive polymer, wherein the conductive polymer is selected from polyaniline, polypyrrole, or polythiophene and its derivatives.

4. The electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system according to claim 1, characterized in that: The forced diffusion unit includes an acoustic flow field generator located upstream of the composite membrane. The acoustic flow field generator generates high-frequency ultrasonic waves, which use the acoustic flow effect to disturb the retention layer at the membrane interface, forcibly pushing iron ions into the effective radius of the supramolecular potential trap layer.

5. The electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system according to claim 1, characterized in that: The system is also equipped with an online potential monitoring feedback loop, which adjusts the applied voltage of the electron transport mediator layer in real time according to the iron ion concentration in the effluent to maintain the optimal capture potential on the membrane surface.

6. The method for preparing electronic-grade vitamin C using the electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system according to any one of claims 1 to 5, characterized in that: Includes the following steps: Sp1. Polarization pre-adjustment: Industrial-grade vitamin C solution is introduced into the charge polarization control unit. By applying a high-frequency pulsed electric field, the solvation layer structure around iron ions is changed, thereby reducing the desolvation energy barrier of iron ions. Sp2. Interface acoustic flow enhancement: The acoustic flow field generator is activated to generate microscopic turbulence in the solution before it flows through the electronically shielded nano-confined capture reactor, ensuring that trace iron ions break through the diffusion boundary layer on the membrane surface; Sp3. Redox-mediated trapping: When the solution enters the pores of the composite membrane, iron ions in the fluid are forcibly drawn into the central cavity of the rigid macrocyclic ligand under the positive potential induction of the supramolecular potential trapping layer; at this time, the electron transfer mediating layer prevents the reduction electrons of vitamin C from entering the cavity, thus achieving potential shielding and locking of iron ions in a reducing background. Sp4. Nanoscale confinement fixation: Within the confined space of membrane pore size 2 to 10 nanometers, iron ions and macrocyclic ligands undergo strong orbital overlap, transforming into an irreversible chelate state. Sp5. Graded purification and collection: Through multi-stage series capture, the energy level depth of the capture site is increased step by step, and the final purified solution is cooled and crystallized after terminal sterile filtration. Sp6. In-situ membrane activation: When the trapping capacity decays, the trapped iron ions are stripped from the potential trap by reverse pulse current, and then subjected to low-concentration acid washing to restore the membrane activity.

7. The method for preparing electronic-grade vitamin C using the electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system according to claim 6, characterized in that: In Sp3, the positive potential gradient on the membrane surface is controlled between 0.1 and 0.8 volts. This potential range can specifically increase the collision frequency of iron ions with the trapping sites without causing the oxidative decomposition of vitamin C molecules.

8. The method for preparing electronic-grade vitamin C using the electronic-grade vitamin C trace iron ion directional capture and multi-stage membrane composite purification system according to claim 6, characterized in that: In Sp4, the capture kinetics of iron ions are controlled by the charge compensation rate within the nanoconfined domain. The adsorption process does not desorb with the increase of fluid shear force, and it exhibits a unidirectional vector capture under non-equilibrium conditions.

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