A method for purifying a high viscosity aqueous polymer solution

Abstract

The embodiment of the present application provides a purification method of a high-viscosity polymer aqueous solution, which is used for removing metal ions in the high-viscosity polymer aqueous solution, and comprises the following steps: mixing and dissolving a polymer with water to prepare a to-be-purified aqueous solution of the polymer, wherein the viscosity of the to-be-purified aqueous solution is still greater than 2000 cP when the concentration of the polymer in the to-be-purified aqueous solution is 0.5wt%-2wt%; in a first purification step, exchange resin particles are added into the to-be-purified aqueous solution, the to-be-purified aqueous solution and the exchange resin particles are stirred and filtered to obtain a first filtrate; in a second purification step, new exchange resin particles are added into the first filtrate, the first filtrate and the new exchange resin particles are stirred and filtered to obtain a second filtrate; and the above purification steps are repeated to obtain a target polymer aqueous solution, wherein the concentration of metal ions in the target polymer aqueous solution is less than 500 ppb.

Description

Technical Field

[0001] This application relates to the field of metal ion removal technology, and more particularly to a method for purifying a high-viscosity polymer aqueous solution. Background Technology

[0002] In semiconductor manufacturing processes, metal ions readily diffuse into the silicon lattice during polishing, forming deep-level traps. This can lead to serious device reliability issues such as increased leakage current, charge storage instability, threshold voltage drift, and even dielectric layer breakdown. Therefore, chemical mechanical polishing (CMP) compositions used for intermediate layers and final polishing of silicon wafers have extremely stringent requirements for metal ion purity, typically requiring metal impurities to be controlled below 1 ppm, or even at the ppb level.

[0003] To control the polishing selectivity, surface smoothness, and material removal rate of CMP compositions, functional water-soluble polymers (such as polyacrylic acid, polyvinyl alcohol, or modified cellulose) are typically added. However, these polymers readily introduce metal impurities during synthesis, purification, or storage, and their initial metal content often far exceeds the ppb limits allowed by semiconductor processes. Simultaneously, these polymers typically exhibit high viscosity in aqueous solutions, significantly hindering mass transfer and resulting in a substantial decrease in the efficiency of conventional metal ion removal technologies. In large-scale production scenarios, these problems are further amplified, leading to multiple bottlenecks in traditional methods, including low throughput, high operating costs, and difficulties in media regeneration, severely restricting the stable supply of high-purity CMP compositions. Summary of the Invention

[0004] This application provides a purification method for a high-viscosity polymer aqueous solution. The target polymer aqueous solution obtained through multiple purifications has a metal ion concentration of less than 500 ppb when the polymer concentration in the purified aqueous solution is 2 wt%.

[0005] To achieve the above objectives, the embodiments of this application adopt the following technical solutions: This application provides a purification method for a high-viscosity polymer aqueous solution, used to remove metal ions from the high-viscosity polymer aqueous solution, comprising: mixing and dissolving the polymer with water to prepare an aqueous solution to be purified, wherein the viscosity of the aqueous solution to be purified is still greater than 2000 cP when the concentration of the polymer in the aqueous solution to be purified is 0.5wt%-2wt%; in a first purification step, adding exchange resin particles to the aqueous solution to be purified, stirring the aqueous solution to be purified and the exchange resin particles and filtering to obtain a first filtrate; in a second purification step, adding new exchange resin particles to the first filtrate, stirring the first filtrate and the new exchange resin particles and filtering to obtain a second filtrate; repeating the above purification steps to obtain a target polymer aqueous solution, wherein the concentration of the polymer in the aqueous solution to be purified is 2wt%, and the concentration of metal ions in the target polymer aqueous solution is less than 500 ppb, and the amount of exchange resin particles added in each purification step is equal to 5% to 50% of the ion exchange capacity required to remove metal ions from the aqueous solution to be purified.

[0006] According to some embodiments of this application, the polymer includes at least one of cellulose-based polymers, polyethylene-based polymers, or polysaccharide compounds.

[0007] According to some embodiments of this application, the exchange resin particles are strong acid type cation exchange resin particles.

[0008] According to some embodiments of this application, the particle size of the exchange resin particles ranges from 0.3 mm to 0.9 mm.

[0009] According to some embodiments of this application, at least 90% of the exchange resin particles have a particle size within ±20% of the median particle diameter.

[0010] According to some embodiments of this application, the total amount of the exchange resin particles is determined based on the concentration of metal ions in the aqueous solution to be purified.

[0011] According to some embodiments of this application, in each purification step, the ion exchange capacity utilization of the added exchange resin particles is less than 80%.

[0012] According to some embodiments of this application, the metal in the metal ion includes at least one transition metal, which includes Co, Cr, Fe, Mn, Ni, and Ti.

[0013] According to some embodiments of this application, the stirring time is from 0.1 h to 48 h in each purification step.

[0014] According to some embodiments of this application, the pH value of the target polymer aqueous solution is less than 3, and the purification method further includes: adding a pH adjuster to the target polymer aqueous solution so that the pH value of the adjusted target polymer aqueous solution is greater than 10.

[0015] According to some embodiments of this application, in each purification step, a filtration device is used to filter the aqueous solution to be purified or the filtrate, and the filtration device does not include a filter column.

[0016] According to some embodiments of this application, when the concentration of the polymer in the aqueous solution to be purified is 2 wt%, the concentration of at least 60% of the target metal ions in the target polymer aqueous solution is less than 100 ppb.

[0017] According to some embodiments of this application, when the concentration of the polymer in the aqueous solution to be purified is 2 wt%, the retention rate of the polymer in the target polymer aqueous solution is at least 60%.

[0018] According to some embodiments of this application, the stirring speed is 10 rpm to 2000 rpm in each purification step.

[0019] According to some embodiments of this application, in each purification step, the stirring process alternates between a high-speed stirring phase and a low-speed stirring phase, wherein the stirring speed of the high-speed stirring phase is at least 1.5 times that of the low-speed stirring phase.

[0020] According to some embodiments of this application, in each purification step, the duration of the high-speed stirring phase is 10 s to 10 min, and the duration of the low-speed stirring phase is 10 s to 10 min.

[0021] According to some embodiments of this application, stirring is carried out under temperature-programmed conditions, which include an initial stage, a later stage, and a settling period. In the initial stage of each purification step, the aqueous solution to be purified is maintained at an initial temperature of 35°C to 70°C; and in the later stage of each purification step, the temperature of the aqueous solution to be purified is reduced to a second temperature of 5°C to 30°C.

[0022] According to some embodiments of this application, the initial temperature is at least 10°C higher than the second temperature.

[0023] According to some embodiments of this application, the aqueous solution to be purified or the filtrate is maintained at the initial temperature for 10% to 60% of the time in each purification step.

[0024] According to some embodiments of this application, there is a quiescent period of 10 seconds to 10 minutes between the initial stage and the later stage to allow the exchange resin particles to partially settle. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A flowchart of a purification method for a high-viscosity polymer aqueous solution provided according to an embodiment of this application is shown. Detailed Implementation

[0027] The following description provides specific application scenarios and requirements for this specification, intended to enable those skilled in the art to make and use the contents of this specification. Various partial modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of this specification. Therefore, this specification is not limited to the embodiments shown, but rather to the widest scope consistent with the claims.

[0028] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not restrictive. For example, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” used herein may also include the plural forms. When used in this specification, the terms “comprising,” “including,” and / or “containing” mean that the associated integers, steps, operations, elements, and / or components are present, but do not exclude the presence of one or more other features, integers, steps, operations, elements, components, and / or groups, or that other features, integers, steps, operations, elements, components, and / or groups may be added to the system / method.

[0029] In this application, "X includes at least one of A, B, or C" means that X includes at least A, or X includes at least B, or X includes at least C. That is, X can include any combination of A, B, and C, or any combination of A, B, and C, as well as other possible content / elements. The arbitrary combination of A, B, and C can be A, B, C, AB, AC, BC, or ABC.

[0030] To control the polishing selectivity, surface smoothness, and material removal rate of CMP compositions, functional water-soluble polymers are commonly introduced into them. These polymers (such as modified celluloses like polyacrylic acid, polyvinyl alcohol, hydroxyethyl cellulose, or carboxymethyl cellulose) can optimize polishing performance by adsorbing onto the wafer surface or abrasive particles and modulating interfacial interactions. For example, they can suppress excessive removal of specific materials, improve surface roughness, reduce scratches, and enhance global planarization.

[0031] The aforementioned functional polymers often exhibit high viscosity when formulated into aqueous solutions. This high viscosity significantly restricts molecular diffusion and convective transport, severely hindering the migration of metal ions from the polymer network to the purification medium (such as the resin or membrane surface). The increased mass transfer resistance directly leads to slower metal removal kinetics, resulting in a significant reduction in actual removal efficiency even when using highly efficient adsorbent materials. Furthermore, metal ions in high-viscosity systems may be complexed or encapsulated by functional groups (such as carboxyl and hydroxyl groups) on the polymer chains, further reducing their removability.

[0032] Traditional metal ion removal technologies face significant challenges when processing high-viscosity polymer solutions. Taking ion exchange column processes as an example, high-viscosity polymer solutions can easily cause a sharp increase in system pressure drop when passing through the resin bed, leading to channel blockage or bed compaction. This not only significantly reduces the operating flow rate but can also cause equipment interruptions or even damage. To improve mass transfer efficiency and mitigate the risk of blockage, the solution is usually diluted. However, this not only increases the cost and energy consumption of subsequent concentration processes but may also alter the polymer's conformation, aggregation state, or functional properties, thereby affecting its performance in CMP compositions.

[0033] When scaled up to large-scale industrial production, these problems are amplified. Low throughput means limited processing capacity per unit time, making it difficult to match the continuous, high-volume demand for high-purity slurry in semiconductor production lines.

[0034] In summary, this application provides a method for purifying high-viscosity polymer aqueous solutions. Through multiple purification steps, 5%-50% of the required ion exchange capacity of ion exchange resin particles are added to the aqueous solution to be purified each time. After stirring and adsorption, the solution is filtered to remove metal ions step by step, ultimately obtaining a high-purity filtrate with a metal ion concentration of less than 500 ppb when the polymer concentration in the aqueous solution is 2 wt%. This technical solution overcomes the problems of slow mass transfer and low utilization of resin active sites in high-viscosity polymer aqueous solutions through batch purification. It allows for direct processing of high-viscosity polymer solutions without dilution, maintaining their original properties. Furthermore, this method does not rely on high-precision equipment, requiring only stirring equipment and a filtration device, making it suitable for purifying large-scale high-viscosity polymer aqueous solutions.

[0035] Before describing the specific embodiments in this specification, the application scenario of this specification is first introduced as follows. This application provides a purification method for a high-viscosity polymer aqueous solution. This purification method is used to purify metal ions in a high-viscosity polymer aqueous solution. The metal ions include, but are not limited to, Ag, Al, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sn, Ti, Zn, etc. In some embodiments, the metal ions include at least one transition metal. Transition metals include Co, Cr, Fe, Mn, Ni, and Ti.

[0036] Figure 1 A flowchart illustrating a purification method for a high-viscosity polymer aqueous solution according to an embodiment of this application is shown. Figure 1 As shown, the purification method P100 for high-viscosity polymer aqueous solution may include steps S110, S120, S130 and S140.

[0037] S110: Prepare an aqueous solution of the polymer to be purified by mixing and dissolving the polymer with water, wherein the viscosity of the aqueous solution to be purified is still greater than 2000 cp when the concentration of the polymer in the aqueous solution to be purified is 0.5wt%-2wt%.

[0038] Polymers are those that can form high-viscosity aqueous solutions. Specifically, polymers refer to a class of water-soluble polymers with high molecular weight or strong hydrophilicity. Even at low concentrations, they can fully swell or dissolve in water, forming a highly entangled molecular network structure, which significantly increases the internal frictional resistance of the solution, resulting in high viscosity. These polymers themselves do not necessarily have adhesive properties; their "high viscosity" is mainly reflected in the rheological properties of the solution, and they are often used in applications such as thickening, suspension, slow release, or film formation.

[0039] In this technical solution, the aqueous solution presents an acidic environment during the purification process. Therefore, the polymer needs to remain stable in the acidic aqueous solution. Maintaining stability refers to the polymer maintaining its dissolved state, viscosity properties, and chemical structural integrity.

[0040] The polymers include at least one of cellulose-based polymers, polyethylene-based polymers, or polysaccharide compounds. Cellulose-based polymers include, but are not limited to, sodium carboxymethyl cellulose (CMC-Na), methyl cellulose (MC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), and hydroxypropyl methyl cellulose (HPMC). Polyethylene-based polymers include, but are not limited to, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyethylene oxide (PEO), and polyvinylpyrrolidone (PVP). Polysaccharide compounds include, but are not limited to, carrageenan (CGN), gum arabic (GA), xanthan gum (XG), rhamnolipin gum (RL), gellan gum (GG), pullulan (PUL), hydroxypropyl starch (HPS), chitosan (CS), and propylene glycol alginate (PGA). It should be noted that other polymers that are stable in acidic environments are also within the scope of this protection scheme, but will not be elaborated upon here.

[0041] The polymer is mixed with water and thoroughly dissolved by slow stirring to prepare a homogeneous aqueous solution for purification. It is understood that the water used here is high-purity water (such as deionized water, distilled water, or ultrapure water), which has undergone rigorous treatment to remove metal ions, inorganic salts, organic impurities, and particulate matter. The use of this type of water aims to avoid unintended interactions between foreign ions and the polymer (such as cross-linking, precipitation, or abnormal viscosity changes caused by polyvalent metal ions), thereby ensuring that the polymer maintains stable physicochemical properties and solution homogeneity during dissolution and subsequent purification.

[0042] In the aqueous solution to be purified, the polymer concentration range can be 0.001 wt% to 10 wt%. In some embodiments, the polymer concentration range can be 0.5 wt% to 2 wt%. Further, in the aqueous solution to be purified, the polymer concentration range can be 0.001 wt% to 0.5 wt%, 0.5 wt% to 1 wt%, 1 wt% to 2 wt%, 2 wt% to 3 wt%, 3 wt% to 4 wt%, 4 wt% to 5 wt%, 5 wt% to 6 wt%, 6 wt% to 7 wt%, 7 wt% to 8 wt%, 8 wt% to 9 wt%, or 9 wt% to 10 wt%. It is understood that the above ranges can be arbitrarily combined; for example, in the aqueous solution to be purified, the polymer concentration range can be 3 wt% to 6 wt%. In a preferred embodiment, the polymer concentration range can be 0.5 wt% to 2 wt%.

[0043] In the aqueous solution to be purified, the polymer exhibits very high viscosity even at low concentrations. Specifically, when the polymer concentration in the aqueous solution to be purified is between 0.5 wt% and 2 wt%, the polymer viscosity is greater than 2000 cP. In some embodiments, when the polymer concentration in the aqueous solution to be purified is between 0.5 wt% and 2 wt%, the polymer viscosity is greater than 4000 cP. When the polymer concentration in the aqueous solution to be purified is between 0.5 wt% and 2 wt%, the polymer viscosity is greater than 6000 cP. When the polymer concentration in the aqueous solution to be purified is between 0.5 wt% and 2 wt%, the polymer viscosity is greater than 8000 cP. When the polymer concentration in the aqueous solution to be purified is between 0.5 wt% and 2 wt%, the polymer viscosity is greater than 10000 cP.

[0044] It should be noted that the polymer concentration in the aqueous solution to be purified is positively correlated with the polymer viscosity. That is, as the polymer concentration increases, the degree of entanglement of the molecular chains and the hydrodynamic volume in the aqueous solution increase accordingly, leading to increased frictional resistance within the system and thus a significant increase in viscosity. Under the conditions described in this scheme, when the polymer concentration is in the range of 0.5wt% to 2wt%, the viscosity of the aqueous solution to be purified is still greater than 2000 cP. If the polymer concentration in the aqueous solution to be purified is further increased, the viscosity of the aqueous solution to be purified will continue to rise.

[0045] Metal ions in the aqueous solution to be purified may originate from multiple sources: for example, residual catalyst metals in the polymer raw materials used (such as Co, Ni, Ti, Al, Cr, Fe compounds used in the polymerization reaction), leachings from metal equipment encountered during the production process (such as Fe, Cr, Ni, Cu, Pb, Sn), trace metal impurities contained in the water itself (such as Ca, Mg, Na, K), or pollution introduced from the environment (Zn, Pb, Cu, Fe, Mn, Al).

[0046] The concentration C of metal ions in the aqueous solution to be purified 总 Calculated using the following formula:

[0047] The pH of the aqueous solution to be purified is 6-8. Further, the pH of the aqueous solution to be purified is 6, 7, or 8.

[0048] In this purification method, the aqueous solution to be purified is purified through a purification step to obtain an aqueous solution of the target polymer. When the concentration of the polymer in the aqueous solution to be purified is 2 wt%, the concentration of metal ions in the aqueous solution of the target polymer is less than 500 ppb. The purification step involves adding ion exchange resin particles to the aqueous solution to be purified, stirring the aqueous solution and ion exchange resin particles, and filtering to obtain the aqueous solution of the target polymer. This purification method can be repeated multiple times; that is, if the metal ion concentration does not meet the target requirement after one purification, the above purification steps can be repeated once or multiple times, employing a multi-stage cascade treatment to progressively reduce the metal impurity content.

[0049] Ion exchange resin particles are polymeric materials with ion exchange capabilities. They can remove metal ion impurities from aqueous solutions, thus purifying the solution. Ion exchange resin particles consist of a resin backbone and functional groups. The resin backbone is a highly non-crosslinked, insoluble resin backbone, providing a stable three-dimensional network structure and mechanical strength. The functional groups are exchangeable functional groups covalently bonded to the resin backbone, endowing the ion exchange resin particles with ion exchange capacity.

[0050] The cation exchange resin particles can be either strong acid type cation exchange resin particles or weak acid type cation exchange resin particles. In a particularly preferred embodiment, the cation exchange resin particles are strong acid type cation exchange resin particles. The strong acid type cation exchange resin particles and the weak acid type cation exchange resin particles are described separately below.

[0051] The resin backbone of the strong acid cation exchange resin particles is a cross-linked polystyrene-divinylbenzene copolymer (PS-DVB). Styrene provides a functionalizable aromatic ring structure, while divinylbenzene acts as a cross-linking agent to form a three-dimensional network backbone, endowing the resin with excellent mechanical strength, chemical stability, and porous structure, which is beneficial for ion diffusion and exchange. The functional groups of the strong acid cation exchange resin particles are sulfonic acid groups (–SO3H), covalently introduced through a sulfonation reaction on the benzene ring. These groups exhibit strong acidity and can completely dissociate even at low pH conditions, releasing exchangeable H+. + ion.

[0052] The resin backbone of the weakly acidic cation exchange resin particles is at least one of cross-linked polyacrylic acid-divinylbenzene copolymer and cross-linked polymethacrylic acid-divinylbenzene copolymer. These two types of backbones are formed by free radical copolymerization of monomers containing carboxylic acid functional groups (acrylic acid or methacrylic acid) and cross-linking agent divinylbenzene. Their main chains are naturally rich in carboxylic acid groups (–COOH), which can be directly used as ion exchange sites without additional chemical modification. They have advantages such as simple synthesis process, high density of functional groups, good hydrophilicity and strong selectivity for polyvalent metal cations.

[0053] The functional groups of weakly acidic cation exchange resin particles are at least one of carboxylic acid groups (-COOH) and phosphate groups (-PO3H2). Among these, the carboxylic acid group (-COOH) is the most typical and widely used functional group in weakly acidic resins, and it can effectively dissociate and perform cation exchange under neutral to weakly alkaline conditions. Although the phosphate group (-PO3H2) is slightly more acidic than the carboxylic acid group, it can also be used as a weakly acidic exchange site in specific applications, especially suitable for scenarios requiring the maintenance of a certain exchange capacity at slightly lower pH levels.

[0054] The resin backbone and functional groups of weakly acidic cation exchange resin particles can be combined. For example, the resin backbone is cross-linked polyacrylic acid-divinylbenzene, and the functional group is a carboxylic acid group (-COOH); the resin backbone is cross-linked polymethacrylic acid-divinylbenzene, and the functional group is a carboxylic acid group (-COOH); the resin backbone is cross-linked polyacrylic acid-divinylbenzene, and the functional group is a phosphate group (-PO3H2); the resin backbone is cross-linked polymethacrylic acid-divinylbenzene, and the functional group is a phosphate group (-PO3H2).

[0055] The particle size range of the ion exchange resin particles is 0.3 mm to 0.9 mm. In some embodiments, the particle size range of the ion exchange resin particles is 0.5 mm to 0.8 mm. Further, the particle size range of the ion exchange resin particles is 0.3 mm to 0.4 mm, 0.4 mm to 0.5 mm, 0.5 mm to 0.6 mm, 0.6 mm to 0.7 mm, 0.7 mm to 0.8 mm, or 0.8 mm to 0.9 mm. It is understood that the above-mentioned particle size ranges of the ion exchange resin particles can be arbitrarily combined, for example, the particle size range of the ion exchange resin particles is 0.4 mm to 0.7 mm.

[0056] Within the aforementioned particle size range of the ion exchange resin particles, at least 90% of the particles fall within ±20% of the median particle diameter. In other words, the particle size distribution within the ion exchange resin particles is quite concentrated. If all the ion exchange resin particles are sorted by size and the "median value" (i.e., the median particle size) is found, then at least 90% of the actual particle size falls between 80% and 120% of this median. For example, when the median particle size is 0.5 mm, more than 90% of the particles have a diameter between 0.4 mm and 0.6 mm. This characteristic indicates that the ion exchange resin particles have good particle size uniformity and high batch consistency, which is beneficial for achieving stable hydrodynamic performance and exchange efficiency during ion exchange.

[0057] The total amount of ion exchange resin particles is determined based on the concentration of metal ions in the aqueous solution to be purified. In other words, the required total amount of ion exchange resin particles is not fixed but must be flexibly adjusted according to the concentration of metal ions in the aqueous solution. A higher metal ion concentration means a greater number of ions need to be removed or recovered, thus requiring more ion exchange resin particles to provide sufficient ion exchange sites. Conversely, if the metal ion concentration is low, fewer ion exchange resin particles can be used. This on-demand matching method ensures purification effectiveness while avoiding waste of ion exchange resin particles, improving processing efficiency and economy.

[0058] In this scheme, the total amount of ion exchange resin particles is equal to the ion exchange capacity required to remove metal ions from the aqueous solution. Therefore, the required ion exchange capacity Q of the ion exchange resin particles is... 总 The concentration C of metal ions can be used as a metric. 总 The calculation is performed using the following formula:

[0059] In addition, the required ion exchange capacity Q 总 Alternatively, it can be calculated using the following formula:

[0060] Among them, C V C represents the volumetric exchange capacity of the cation exchange resin particles. When the cation exchange resin particles are strong acid type cation exchange resin particles, then C... v =2mmol / mL, meaning that theoretically, if there are 10 mL of exchange resin particles, the maximum exchange capacity is 2 mmol / mL. Metal ions.

[0061] V 树脂 =m / ρ, where m is the actual mass of the ion exchange resin particles after swelling. Correspondingly, V 树脂 ρ represents the actual volume of the ion exchange resin particles after swelling. ρ represents the mass per unit volume of the ion exchange resin particles in a fully swollen, wet, and naturally packed state.

[0062] The agitation of the aqueous solution to be purified with the ion exchange resin particles can be carried out within a mixing container. An impeller is installed within the mixing container. Further, the agitation of the aqueous solution to be purified with the ion exchange resin particles can be carried out using a helical impeller or a double-helical impeller mounted on a central shaft within the mixing container. These impellers have excellent axial flow capability, making them particularly suitable for the uniform mixing of high-viscosity polymer aqueous solutions. The outer diameter of the helical or double-helical impeller is 0.7 to 0.95 times the inner diameter of the mixing container. That is, the impeller rotates almost close to the inner wall of the container, effectively eliminating dead zones, enhancing overall circulation, and promoting uniform dispersion and full contact of the ion exchange resin particles in the viscous system. This improves ion exchange efficiency and avoids local sedimentation or agglomeration, ensuring the stability and reproducibility of the purification process. In some embodiments, the outer diameter of the helical or double-helical impeller is 0.85 to 0.95 times the inner diameter of the mixing container.

[0063] S120: In the first purification step, ion exchange resin particles are added to the aqueous solution to be purified, the aqueous solution to be purified and the ion exchange resin particles are stirred and filtered to obtain the first filtrate.

[0064] In this purification method, the purification steps can be repeated multiple times to ensure that when the concentration of the polymer in the aqueous solution to be purified is 2 wt%, the concentration of metal ions in the target polymer aqueous solution is less than 500 ppb. In the first purification step, ion exchange resin particles are added to the aqueous solution to be purified. The aqueous solution to be purified and the ion exchange resin particles are stirred and filtered to obtain a first filtrate. The ion exchange resin particles are as described above and will not be repeated here.

[0065] After adding ion exchange resin particles, the pH of the aqueous solution to be purified will decrease to 1.5-2.5. For example, after adding ion exchange resin particles, the pH of the aqueous solution to be purified will be 1.5, 2, or 2.5.

[0066] In the first purification step, the amount of ion exchange resin particles added is equal to 5% to 50% of the ion exchange capacity required to remove metal ions from the aqueous solution to be purified. In other words, the amount of ion exchange resin particles added in the first purification step is not based on the ion exchange capacity required to completely remove the metal ions, but rather on a partial addition. This method of addition gradually reduces the metal ion concentration through staged treatment, improving resin utilization efficiency and purification effect, creating more favorable conditions for subsequent purification steps, and ultimately more reliably achieving the high purity target of less than 500 ppb of residual metal ions.

[0067] In some embodiments, the amount of exchange resin particles added in the first purification step is 10% to 40% of the desired ion exchange capacity. In some embodiments, the amount of exchange resin particles added in the first purification step is 10% to 30% of the desired ion exchange capacity. Further, the amount of exchange resin particles added in the first purification step is 5% to 10%, 10% to 20%, 20% to 30%, 30% to 40%, or 40% to 50% of the desired ion exchange capacity. It is understood that the above ranges can be arbitrarily combined.

[0068] In the first purification step, the ion exchange capacity utilization of the added exchange resin particles is less than 80%. For example, if the amount of exchange resin particles is 6.5 mmol, the ion exchange capacity utilization is less than 5.2 mmol. In some embodiments, the ion exchange capacity utilization of the added exchange resin particles is 80%, 70%, 60%, or 50% of the initially added exchange resin particles. It is understood that the utilization rate is the ratio of the consumed exchange capacity to the exchange capacity of the resin initially added for this purification.

[0069] After adding the ion exchange resin particles, the aqueous solution to be purified and the ion exchange resin particles are stirred. The stirring time is from 0.1 h to 48 h. In some embodiments, the stirring time is from 1 h to 40 h. In some embodiments, the stirring time is from 5 h to 20 h. Further, the stirring time is from 0.5 h to 1 h, 1 h to 5 h, 5 h to 10 h, 10 h to 15 h, 15 h to 20 h, 20 h to 25 h, 25 h to 30 h, 30 h to 35 h, 35 h to 40 h, 40 h to 45 h, or 45 h to 48 h. It is understood that the above ranges can be arbitrarily combined.

[0070] The stirring speed ranges from 10 rpm to 2000 rpm. In some embodiments, the stirring speed ranges from 300 rpm to 900 rpm. Furthermore, the stirring speed ranges from 10 rpm to 100 rpm, 100 rpm to 200 rpm, 200 rpm to 300 rpm, 300 rpm to 400 rpm, 400 rpm to 500 rpm, 500 rpm to 600 rpm, 600 rpm to 700 rpm, 700 rpm to 800 rpm, 800 rpm to 900 rpm, 900 rpm to 1000 rpm, 1000 rpm to 1100 rpm, 1100 rpm to 1200 rpm, 1200 rpm to 1300 rpm, 1300 rpm to 1400 rpm, 1400 rpm to 1500 rpm, 1500 rpm to 1600 rpm, 1600 rpm to 1700 rpm, 1700 rpm to 1800 rpm, and 1800 rpm. rpm to 1900 rpm, 1900 rpm to 2000 rpm. It is understood that the above ranges can be arbitrarily combined.

[0071] In some embodiments, during the first purification step, the stirring speed remains constant, for example, maintained at 500 rpm throughout the entire stirring process. In some embodiments, during the first purification step, the stirring process alternates between a high-speed stirring phase and a low-speed stirring phase. When the stirring process alternates between the high-speed and low-speed stirring phases, the stirring speed of the high-speed stirring phase is at least 1.5 times that of the low-speed stirring phase. For example, if the stirring speed is 800 rpm during the high-speed stirring phase, then the stirring speed during the low-speed stirring phase can be 500 rpm, 400 rpm, or 300 rpm.

[0072] In the first purification step, the total stirring time is 0.5 h to 6 h. When the stirring process alternates between high-speed and low-speed stirring phases, the high-speed stirring phase lasts for 10 s to 10 min, and the low-speed stirring phase lasts for 10 s to 10 min. For example, if the total stirring time is 1 h, the high-speed stirring phase lasts for 10 min, and the low-speed stirring phase lasts for 10 min, then the entire stirring process is as follows: 10 min of high-speed stirring followed by 10 min of low-speed stirring, then another 10 min of high-speed stirring followed by 10 min of low-speed stirring, and finally another 10 min of high-speed stirring followed by 10 min of low-speed stirring, thus completing the entire 1 h stirring process.

[0073] In addition to the stirring speed and duration, the stirring temperature is also a crucial factor during the stirring process. Specifically, stirring is conducted under programmed temperature conditions. These programmed temperature conditions include an initial stage, a later stage, and a settling period. In the initial stage of the first purification step, the aqueous solution is maintained at an initial temperature of 35°C to 70°C to reduce solution viscosity, enhance molecular diffusion, and improve the contact efficiency between the exchange resin particles and metal ions, thereby promoting the effective adsorption or exchange of metal ions. In the later stage of the first purification step, the temperature of the aqueous solution to be purified is lowered to a second temperature of 5°C to 30°C, which helps stabilize the polymer and suppress side reactions.

[0074] The initial temperature can range from 35°C to 70°C. In some embodiments, the initial temperature can range from 50°C to 70°C. Further, the initial temperature range can be 35°C to 40°C, 40°C to 45°C, 45°C to 50°C, 50°C to 55°C, 55°C to 60°C, 60°C to 65°C, or 65°C to 70°C. It is understood that the above ranges can be arbitrarily combined.

[0075] The second temperature range can be from 5°C to 30°C. In some embodiments, the second temperature range can be from 10°C to 20°C. Further, the second temperature range can be 5°C to 10°C, 10°C to 15°C, 15°C to 20°C, 20°C to 25°C, or 25°C to 30°C. It is understood that the above ranges can be arbitrarily combined.

[0076] It is understandable that the initial temperature is at least 10°C higher than the second temperature. For example, the initial temperature is 60°C and the second temperature is 30°C.

[0077] The aqueous solution to be purified is maintained at the initial temperature for 10% to 60% of the time in the first purification step. That is, in the first purification step, the aqueous solution to be purified is maintained at the initial temperature for 10% to 60% of the total stirring time, and for the remaining 40% to 90% of the time, the aqueous solution to be purified is maintained at the second temperature.

[0078] A 10-second to 10-minute settling period is introduced between the initial and later stages to allow partial sedimentation of the ion exchange resin particles. In other words, a 10-second to 10-minute settling period is intentionally introduced between the initial high-temperature stage and the later cooling stage, during which stirring is paused to allow the ion exchange resin particles to partially settle under gravity. This brief settling helps alleviate mass transfer resistance caused by uneven particle suspension in the high-viscosity polymer solution.

[0079] After stirring, the aqueous solution to be purified is filtered using a filtration device. The filtration device may include a vibrating screen, a plate and frame filter, a filter cartridge, or a filter bag. Different filtration devices are used depending on the volume of the aqueous solution to be purified. When the volume of the aqueous solution to be purified is small, such as 10L, a filter cartridge or filter bag is used. When the volume of the aqueous solution to be purified is large, such as 100L, a vibrating screen or a plate and frame filter is used.

[0080] The filter bags can have a pore size of 60-100 mesh. The filter cartridges can have a pore size of 1-40 μm. The vibrating screens can have a pore size of 60-100 mesh. The filter cloth used in plate and frame filters can have a pore size of 60-100 mesh.

[0081] After filtration, the first filtrate is obtained. The first filtrate contains polymer and water, but does not contain ion exchange resin particles (the ion exchange resin particles have been filtered out).

[0082] S130: In the second purification step, new exchange resin particles are added to the first filtrate, the first filtrate and the new exchange resin particles are stirred and filtered to obtain the second filtrate.

[0083] The second purification step is a repetition of the first purification step. That is, all steps in the second purification step are the same as in the first purification step, such as the purification process, the utilization rate of the ion exchange capacity of the exchange resin particles, the stirring time, stirring speed, stirring temperature, settling period, and filtration. The difference is that the exchange resin particles used in the second purification step are new.

[0084] In the second purification step, new cation exchange resin particles are added to the first filtrate. The first filtrate and cation exchange resin particles are stirred and filtered to obtain the first filtrate. The cation exchange resin particles are those that have not previously come into contact with the aqueous solution to be purified; these are the new cation exchange resin particles. The type of cation exchange resin particles added in the second purification step can be the same as or different from those added in the first purification step. For example, if strong acid cation exchange resin particles are added in the first purification step, strong acid cation exchange resin particles are also added in the second purification step. As another example, if strong acid cation exchange resin particles are added in the first purification step, weak acid cation exchange resin particles are added in the second purification step.

[0085] After adding ion exchange resin particles, the pH of the first filtrate will decrease to 1.5-2.5. For example, after adding ion exchange resin particles, the pH of the first filtrate will be 1.5, 2, or 2.5.

[0086] In the second purification step, the amount of exchange resin particles added is equal to 5% to 50% of the ion exchange capacity required to remove metal ions from the aqueous solution to be purified. In some embodiments, the amount of exchange resin particles added in the second purification step is 10% to 40% of the required ion exchange capacity. In some embodiments, the amount of exchange resin particles added in the second purification step is 10% to 30% of the required ion exchange capacity. Further, the amount of exchange resin particles added in the second purification step is 5% to 10%, 10% to 20%, 20% to 30%, 30% to 40%, or 40% to 50% of the required ion exchange capacity. It is understood that the above ranges can be arbitrarily combined.

[0087] It is understandable that the amount of ion exchange resin particles added in the second purification step can be the same as or different from the amount added in the first purification step. For example, the amount of ion exchange resin particles added in the second purification step may be 30% of the required ion exchange capacity, while the amount added in the first purification step may be 35%. As another example, the amount of ion exchange resin particles added in the second purification step may be 30% of the required ion exchange capacity, while the amount added in the first purification step may be 30%.

[0088] In the second purification step, the purification process, the utilization rate of the ion exchange capacity of the ion exchange resin particles, the stirring time, the stirring speed, the stirring temperature, the settling period, and the filtration are the same as in the first purification step, and will not be repeated here.

[0089] After filtration, a second filtrate was obtained. The second filtrate contained polymer and water, but no ion exchange resin particles (the ion exchange resin particles had been filtered out).

[0090] After the first and second purification steps, if the concentration of the polymer in the aqueous solution to be purified is 2 wt%, and the concentration of metal ions in the second filtrate is less than 500 ppb, then the third and fourth purification steps are not performed, and the second filtrate is used as the target polymer aqueous solution. In this case, the total amount of exchange resin particles added in the first and second purification steps equals the ion exchange capacity required to remove metal ions from the aqueous solution to be purified.

[0091] S140: Repeat the above purification steps to obtain an aqueous solution of the target polymer, wherein when the concentration of the polymer in the aqueous solution to be purified is 2 wt%, the concentration of metal ions in the aqueous solution of the target polymer is less than 500 ppb.

[0092] If the concentration of the polymer in the aqueous solution to be purified is 2 wt%, and the concentration of metal ions in the second filtrate is greater than 500 ppb, then a third purification step is performed. The third purification step is a repetition of either the first or second purification step. That is, all steps in the third purification step are the same as in the first and second purification steps, such as the purification process, the utilization rate of the ion exchange capacity of the exchange resin particles, the stirring time, the stirring speed, the stirring temperature, the settling period, and filtration. The difference is that the exchange resin particles used in the third purification step are new.

[0093] In the third purification step, new exchange resin particles are added to the second filtrate. The second filtrate and exchange resin particles are stirred and filtered to obtain the third filtrate. The exchange resin particles in this third purification step are those that have not previously come into contact with the aqueous solution to be purified; these are the new exchange resin particles. The type of exchange resin particles added in the third purification step can be the same as or different from those added in the first and second purification steps; this will not be elaborated upon here.

[0094] After adding ion exchange resin particles, the pH of the third filtrate will decrease to 1.5-2.5. For example, after adding ion exchange resin particles, the pH of the third filtrate will be 1.5, 2, or 2.5.

[0095] In the third purification step, the amount of exchange resin particles added is equal to 5% to 50% of the ion exchange capacity required to remove metal ions from the aqueous solution to be purified. In some embodiments, the amount of exchange resin particles added in the third purification step is 10% to 40% of the required ion exchange capacity. In some embodiments, the amount of exchange resin particles added in the third purification step is 10% to 30% of the required ion exchange capacity. Further, the amount of exchange resin particles added in the third purification step is 5% to 10%, 10% to 20%, 20% to 30%, 30% to 40%, or 40% to 50% of the required ion exchange capacity. It is understood that the above ranges can be arbitrarily combined.

[0096] It is understandable that the amount of exchange resin particles added in the third purification step can be the same as or different from the amount of exchange resin particles added in the first and second purification steps, which will not be elaborated here.

[0097] In the third purification step, the purification process, the utilization rate of the ion exchange capacity of the ion exchange resin particles, the stirring time, the stirring speed, the stirring temperature, the settling period, and the filtration are the same as in the first and second purification steps, and will not be described in detail here.

[0098] After filtration, a third filtrate was obtained. The third filtrate contained polymer and water, but no ion exchange resin particles (the ion exchange resin particles had been filtered out).

[0099] If the concentration of the polymer in the aqueous solution to be purified is 2 wt%, and the concentration of metal ions in the third filtrate is less than 500 ppb, then the fourth purification step is not performed, and the third filtrate is used as the target polymer aqueous solution. In this case, the total amount of exchange resin particles added in the first, second, and third purification steps is equal to the ion exchange capacity required to remove metal ions from the aqueous solution to be purified.

[0100] If the concentration of the polymer in the aqueous solution to be purified is 2 wt%, and the concentration of metal ions in the third filtrate is greater than 500 ppb, then a fourth purification step is performed. The fourth purification step is a repetition of either the first, second, or third purification step. That is, all steps in the fourth purification step are the same as in the first, second, and third purification steps, such as the purification process, the utilization rate of the ion exchange capacity of the exchange resin particles, the stirring time, stirring speed, stirring temperature, settling period, and filtration. The difference is that the exchange resin particles used in the fourth purification step are new.

[0101] In the fourth purification step, new ion exchange resin particles are added to the third filtrate. The third filtrate and ion exchange resin particles are stirred and filtered to obtain the fourth filtrate. The ion exchange resin particles in this fourth purification step are those that have not previously come into contact with the aqueous solution to be purified; these are the new ion exchange resin particles. The type of ion exchange resin particles added in the fourth purification step can be the same as or different from those added in the first, second, and third purification steps, which will not be elaborated here. Furthermore, the total amount of ion exchange resin particles added in the first, second, third, and fourth purification steps equals the ion exchange capacity required to remove metal ions from the aqueous solution to be purified.

[0102] After adding ion exchange resin particles, the pH of the fourth filtrate will decrease to 1.5-2.5. For example, after adding ion exchange resin particles, the pH of the fourth filtrate will be 1.5, 2, or 2.5.

[0103] In the fourth purification step, the amount of exchange resin particles added is equal to 5% to 50% of the ion exchange capacity required to remove metal ions from the aqueous solution to be purified. In some embodiments, the amount of exchange resin particles added in the fourth purification step is 10% to 40% of the required ion exchange capacity. In some embodiments, the amount of exchange resin particles added in the fourth purification step is 10% to 30% of the required ion exchange capacity. Further, the amount of exchange resin particles added in the fourth purification step is 5% to 10%, 10% to 20%, 20% to 30%, 30% to 40%, or 40% to 50% of the required ion exchange capacity. It is understood that the above ranges can be arbitrarily combined.

[0104] It is understandable that the amount of exchange resin particles added in the fourth purification step can be the same as or different from the amount of exchange resin particles added in the first, second, and third purification steps.

[0105] In the fourth purification step, the purification process, the utilization rate of the ion exchange capacity of the ion exchange resin particles, the stirring time, the stirring speed, the stirring temperature, the settling period, and the filtration are the same as in the first, second, and third purification steps, and will not be described in detail here.

[0106] After filtration, an aqueous solution of the target polymer was obtained. The aqueous solution of the target polymer contained polymer and water, but did not contain ion exchange resin particles (the ion exchange resin particles had been filtered out).

[0107] If the desired concentration of less than 500 ppb is not achieved subsequently, purification can continue until this target concentration is reached. It should be noted that, generally, after repeating the purification steps four times, the metal ions in the aqueous solution to be purified can be effectively removed, achieving the desired concentration of less than 500 ppb when the polymer concentration in the aqueous solution is 2 wt%.

[0108] The target polymer aqueous solution comprises a polymer and water. The polymer retention rate is at least 60% compared to the aqueous solution to be purified. In some embodiments, the polymer retention rate is at least 70% compared to the aqueous solution to be purified. Further, the polymer retention rates are 60%, 70%, 80%, 90%, 95%, and 100% compared to the aqueous solution to be purified.

[0109] In some embodiments, at least 60% of the target metal ions in the target polymer aqueous solution have a concentration of less than 100 ppb. That is, among multiple metal ions, 60% of the target metal ions have a concentration of less than 100 ppb. For example, the target metal ions in the target polymer aqueous solution include ten metal ions: Co, Cr, Fe, Mn, Ni, Ti, Ag, Al, Ca, and K. Among these, the concentrations of six metal ions—Co, Cr, Fe, Mn, Ni, and Ti—are all less than 100 ppb. Here, "target metal ion" refers to a specific metal ion that is detected and confirmed to be present in the target polymer aqueous solution and needs to be removed or controlled.

[0110] Since acidic solutions are prone to bacterial growth, a pH adjuster can be added to the target polymer aqueous solution after purification to make the pH value of the adjusted target polymer aqueous solution greater than 10.

[0111] pH adjusters can be bases or their salts. Specifically, pH adjusters can be organic bases, inorganic bases, or combinations thereof. Among them, organic bases can be quaternary ammonium hydroxides (e.g., tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH)), piperazine, pyrazine, guanidines (e.g., guanidine carbonate, guanidine hydrochloride, arginine, creatine), imidazole, triazole, methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, ethylenediamine, monoethanolamine, diethanolamine, aminoethylethanolamine, linear primary diamines (e.g., butane-1,4-diamine, pentane-1,5-diamine, hexane-1,6-diamine, heptane-1,7-diamine, octane-1,8-diamine) or combinations thereof. Inorganic bases include alkali metal hydroxides (e.g., potassium hydroxide, sodium hydroxide, lithium hydroxide), alkaline earth metal hydroxides (e.g., magnesium hydroxide, calcium hydroxide, beryllium hydroxide), alkali metal carbonates (e.g., potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, lithium bicarbonate), alkaline earth metal carbonates (e.g., magnesium carbonate, calcium carbonate, beryllium carbonate), alkali metal phosphates (e.g., tripotassium phosphate, trisodium phosphate, dipotassium phosphate, disodium phosphate), alkaline earth metal phosphates (e.g., magnesium phosphate, calcium phosphate, beryllium phosphate), ammonium carbonate, ammonium bicarbonate, ammonium hydroxide, ammonia, or combinations thereof. Preferably, the pH adjuster is an inorganic base. In a particularly preferred embodiment, the pH adjuster is selected from alkali metal hydroxides, alkaline earth metal hydroxides, ammonium hydroxide, ammonium carbonate, ammonia, and combinations thereof. In a particularly preferred embodiment, the pH adjuster is ammonia.

[0112] With the adjustment of a pH adjuster, the target polymer aqueous solution has a suitable pH value. In some embodiments, the target polymer aqueous solution has a pH value greater than 10, i.e., the target polymer aqueous solution is alkaline. In some embodiments, the target polymer aqueous solution has a pH value of 10 or 11.

[0113] The following are specific examples of compositions designed according to the above content of this disclosure. It should be understood that the following examples are merely illustrative of the purification method for high-viscosity polymer aqueous solutions disclosed above, and the specific implementation methods and parameters used are only one or more of the numerous parameters and methods described above. Those skilled in the art can use other parameters to purify the materials according to the above methods without departing from the core spirit of the disclosure.

[0114] In the following embodiments, the concentration of metal ions was measured in the following manner: The metal ion content in aqueous solutions was determined using inductively coupled plasma mass spectrometry (ICP-MS). Before testing, all samples were filtered through a filter membrane to remove residual exchange resin particles. Subsequently, ultrapure nitric acid was added to the samples for acidification, ensuring complete dissolution of the metal ions and eliminating potential matrix interference from the high-viscosity polymer matrix. The acidified samples were then diluted appropriately with ultrapure water to bring the concentration of the analyte within the linear range of the instrument calibration curve.

[0115] Calibration curves were established using multi-element standard solutions, and internal standard elements were used to correct for instrument drift and matrix effects. All tests were performed under trace metal analysis conditions, and the detection limits of the methods used for the target metal ions were below 1 ppb. Test results are expressed in ppb (parts per billion, i.e., micrograms of metal contained in one kilogram of solution). The resin particles used in the following experiments were strongly acidic cation exchange (SAC) particles, gel type.

[0116] Example 1 Polymer: Hydroxyethyl cellulose (HEC) Viscosity of the aqueous solution: 50,000 cp The polymer's molecular weight Mw = 1,000,000 Purification steps: 1) Dissolution: Polymer powder and water were added to a stirred tank and stirred to dissolve, preparing an aqueous solution with a polymer concentration of 1 wt%; 2) Exchange resin particles were washed with ultrapure water and filtered dry; 3) The exchange resin particles were poured into the stirred aqueous solution and samples were taken at 3h, 6h, and 12h of stirring, respectively, at a stirring speed of 600 rpm. The exchange resin particles were filtered off, and the concentration of metal ions was measured. The specific results are listed in Table 1. ppb represents parts per billion, and ND indicates not detected. After purification by stirring, the polymer concentration of aqueous solutions E1-E3 was 0.9 wt%. For comparison with aqueous solutions E1-E3, aqueous solution A1 was also diluted to 0.9 wt%.

[0117] Here, "first" indicates the first purification step.

[0118] Table 1

[0119] in conclusion: 1) The method in this scheme can effectively remove various metal ions from high-viscosity polymer aqueous solutions, thereby achieving effective purification of metal ions in high-viscosity polymers; Example 2 Polymer: Hydroxypropyl methylcellulose (HPMC) Viscosity of the aqueous solution: 86,000 cp The polymer's molecular weight Mw = 820,000 Purification steps: 1) Dissolution: Polymer powder and water were added to a stirred tank and stirred to dissolve, preparing an aqueous solution with a polymer concentration of 2 wt%; 2) Exchange resin particles were washed with ultrapure water and drained; 3) Exchange resin particles were added to the stirred aqueous solution and stirred for 3 hours at a stirring speed of 600 rpm; 4) After stirring, the exchange resin particles were filtered out using a filter device, and then the concentration of metal ions was measured; 5) Exchange resin was added again and stirred for 24 hours at a stirring speed of 600 rpm; 6) The exchange resin particles were filtered out using a filter device, and then the concentration of metal ions was measured. Specific results are listed in Table 2. After purification by stirring, the polymer concentration in aqueous solutions E4 and E5 was 1 wt%, and for comparison with aqueous solutions E4 and E5, aqueous solution A2 was also diluted to 1 wt%.

[0120] Wherein, "first" represents the first purification step, and "second" represents the second purification step, wherein the amount of ion exchange resin added each time is equal to 5%-50% of the ion exchange capacity required to remove metal ions from the aqueous solution to be purified.

[0121] Table 2

[0122] in conclusion: 1) The method in this scheme can effectively remove various metal ions from high-viscosity polymer aqueous solutions, thereby achieving effective purification of metal ions in high-viscosity polymers; Example 3 Polymer: Hydroxypropyl starch Viscosity of aqueous solution: 9,800 cp The polymer's molecular weight, Mw, is 1,800,000. Purification steps: 1) Dissolution: Polymer powder and water were added to a stirred tank and stirred to dissolve, preparing an aqueous solution with a polymer concentration of 1 wt%; 2) Exchange resin particles were washed with ultrapure water and drained; 3) Exchange resin particles were added to the stirred aqueous solution and stirred for 3 hours at a stirring speed of 400 rpm; 4) After stirring, the exchange resin particles were filtered out using a filter; 5) New exchange resin particles were added and stirring was continued for 3 hours at a stirring speed of 400 rpm; 6) The above steps were repeated once more to obtain the target polymer aqueous solution; 7) The exchange resin particles in the target polymer aqueous solution were filtered out using a filter. In the above steps, the concentration of metal ions in the aqueous solution obtained in each purification step was measured. The specific results are listed in Table 3. After purification by stirring, the polymer concentration of aqueous solutions E6-E8 was 1 wt%, and for comparison with aqueous solutions E6-E8, aqueous solution A3 was also diluted to 1 wt%.

[0123] Wherein, the first represents the first purification step, the second represents the second purification step, and the third represents the third purification step. The amount of ion exchange resin added each time is equal to 5%-50% of the ion exchange capacity required to remove metal ions from the aqueous solution to be purified.

[0124] Table 3

[0125] in conclusion: 1) The method in this scheme can effectively remove various metal ions from high-viscosity polymer aqueous solutions, thereby achieving effective purification of metal ions in high-viscosity polymers; 2) Stirring for 3 hours can achieve a good purification effect; 3) This method is applicable to the purification of metal ions in large-scale high-viscosity polymer aqueous solutions.

[0126] Example 4 Polymer: Polyacrylamide (PAM) Viscosity of the aqueous solution: 4000 cp The polymer's molecular weight Mw = 4,000,000 Purification steps: 1) Dissolution: Polymer powder and water were added to a stirred tank and stirred to dissolve, preparing an aqueous solution with a polymer concentration of 1 wt%; 2) Exchange resin particles were washed with ultrapure water and drained; 3) Exchange resin particles were poured into the stirred aqueous solution and stirred for 40 min at a stirring speed of 500 rpm; 4) After stirring, the exchange resin particles were filtered out using a filter; 5) New exchange resin particles were added and stirring was continued for 40 min at a stirring speed of 500 rpm; 6) The above steps were repeated 3 times to obtain the target polymer aqueous solution; 7) The exchange resin particles in the target polymer aqueous solution were filtered out using a filter. In the above steps, the concentration of metal ions in the aqueous solution obtained in each purification step was measured. The specific results are listed in Table 4. After purification by stirring, the polymer concentration of aqueous solutions E9-E11 was 1 wt%, and for comparison with aqueous solutions E9-E11, aqueous solution A4 was also diluted to 1 wt%.

[0127] Wherein, the first represents the first purification step, the second represents the second purification step, and the third represents the third purification step. The amount of ion exchange resin added each time is equal to 5%-50% of the ion exchange capacity required to remove metal ions from the aqueous solution to be purified.

[0128] Table 4

[0129] in conclusion: The method described in this scheme can effectively remove various metal ions from low-viscosity polymer aqueous solutions, and achieve effective purification of metal ions in high-viscosity polymers.

[0130] Example 5 Polymer: Carboxymethyl cellulose (CMC), molecular weight Mw approximately 1,100,000. Aqueous solution viscosity approximately 43,000 cP. The polymer powder and deionized water were added to a stirred tank and stirred at room temperature to dissolve, preparing an aqueous solution with a polymer concentration of 1 wt%. First, the strong acid cation exchange resin particles were pretreated: the resin particles were thoroughly washed with ultrapure water to remove surface impurities, and then filtered to remove excess water for later use. Subsequently, the exchange resin particles were added to the stirred aqueous solution, with the amount of exchange resin particles corresponding to approximately 15% of the theoretical ion exchange capacity of the metal ions in the aqueous solution.

[0131] Sample A6 was stirred at 300 rpm for 3 hours at room temperature, repeated three times. Fresh resin was added after each cycle as described for the sample. Sample E12 was stirred at 300 rpm for 10 minutes at room temperature. Subsequently, the stirring speed was alternated between high and low speed stages.

[0132] Specifically, in the high-speed stirring-high-temperature stage, the stirrer speed was adjusted to 600 rpm, and the aqueous solution temperature was raised to approximately 40°C using an external heating system. Stirring was continued for 10 minutes under these conditions to reduce the apparent viscosity of the viscous polymer solution and increase the diffusion rate of metal ions, thereby enhancing the mass transfer efficiency of metal ions to the surface of the ion exchange resin particles. In the subsequent low-speed stirring-low-temperature stage, the stirring speed was reduced to 100 rpm, and the solution temperature was lowered to approximately 15°C using a circulating cooling system. Stirring continued for 20 minutes under these conditions to promote the adsorption equilibrium of metal ions on the exchange resin particles and reduce the desorption of adsorbed metal ions.

[0133] The aforementioned high-speed-high-temperature phase and low-speed-low-temperature phase constitute a complete cycle. In this embodiment, this cycle continues until the total purification time reaches 3 hours. After 3 hours, the original resin particles are replaced with new resin particles according to the method described in the previous sample. The entire 3-hour purification process, which includes alternating changes in stirring speed and temperature, was repeated 3 times, and the results were compared with those of sample A6. The specific measurement results are shown in Table 5.

[0134] As described above, the purified polymer solutions A5 and E12 were finally obtained, their concentration was adjusted to 1 wt%, and then tested.

[0135] Table 5

[0136] in conclusion: Sample E12, which employed an alternating stirring and temperature control scheme, exhibited superior purification results.

[0137] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0138] In summary, after reading this detailed disclosure, those skilled in the art will understand that the foregoing detailed disclosure may be presented by way of example only and may not be restrictive. Although not explicitly stated herein, those skilled in the art will understand that this specification requires various reasonable changes, improvements, and modifications to the embodiments. These changes, improvements, and modifications are intended to be made by this specification and are within the spirit and scope of the exemplary embodiments described herein.

[0139] Furthermore, certain terms in this specification have been used to describe embodiments of this specification. For example, "an embodiment," "an embodiment," and / or "some embodiments" mean that a particular feature, structure, or characteristic described in connection with that embodiment may be included in at least one embodiment of this specification. Therefore, it is to be emphasized and understood that two or more references to "an embodiment" or "an embodiment" or "alternative embodiment" in various parts of this specification do not necessarily refer to the same embodiment. Moreover, specific features, structures, or characteristics may be suitably combined in one or more embodiments of this specification.

[0140] It should be understood that in the foregoing description of the embodiments in this specification, various features are combined in a single embodiment, drawing, or description for the purpose of simplifying the description and to aid in understanding a feature. However, this does not mean that the combination of these features is necessary, and those skilled in the art may extract some features as individual embodiments when reading this specification. That is, the embodiments in this specification can also be understood as an integration of multiple sub-embodiments. It is also valid when each sub-embodiment contains fewer than all the features of a single foregoing disclosed embodiment.

[0141] Every patent, patent application, publication of a patent application, and other material, such as articles, books, specifications, publications, documents, and literature (excluding any related historical examination documents), cited in this disclosure is incorporated herein for all purposes, including, for example, in the specification and claims of this disclosure. However, in the event of any inconsistency or conflict between the descriptions, definitions, and / or terms used in the foregoing and those used in this disclosure, the descriptions, definitions, and / or terms used in this disclosure shall prevail.

[0142] Finally, it should be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments described in this specification. Other modified embodiments are also within the scope of this specification. Therefore, the embodiments disclosed in this specification are merely examples and not limitations. Those skilled in the art can implement the applications described in this specification using alternative configurations based on the embodiments in this specification. Therefore, the embodiments in this specification are not limited to the embodiments precisely described in the applications.

Claims

1. A method for purifying a high-viscosity polymer aqueous solution, used to remove metal ions from the high-viscosity polymer aqueous solution, comprising: The polymer is dissolved in water to prepare an aqueous solution of the polymer to be purified, wherein the viscosity of the aqueous solution is still greater than 2000 cP when the concentration of the polymer in the aqueous solution is 0.5wt%-2wt%. In the first purification step, ion exchange resin particles are added to the aqueous solution to be purified, the aqueous solution to be purified and the ion exchange resin particles are stirred and filtered to obtain the first filtrate; In the second purification step, new exchange resin particles are added to the first filtrate, the first filtrate and the new exchange resin particles are stirred and filtered to obtain the second filtrate. The purification steps described above are repeated to obtain an aqueous solution of the target polymer, wherein when the concentration of the polymer in the aqueous solution to be purified is 2 wt%, the concentration of metal ions in the aqueous solution of the target polymer is less than 500 ppb. The amount of the exchange resin particles added in each purification step is equal to 5% to 50% of the ion exchange capacity required to remove metal ions from the aqueous solution to be purified.

2. The purification method according to claim 1, characterized in that, The polymer includes at least one of cellulose-based polymers, polyethylene-based polymers, or polysaccharide compounds.

3. The purification method according to claim 1, characterized in that, The exchange resin particles are strong acid type cation exchange resin particles.

4. The purification method according to claim 1, characterized in that, The particle size of the exchange resin particles ranges from 0.3 mm to 0.9 mm.

5. The purification method according to claim 4, characterized in that, At least 90% of the exchange resin particles have a particle size within ±20% of the median particle diameter.

6. The purification method according to claim 1, characterized in that, The total amount of the exchange resin particles is determined based on the concentration of metal ions in the aqueous solution to be purified.

7. The purification method according to claim 6, characterized in that, In each purification step, the ion exchange capacity utilization rate of the added exchange resin particles is less than 80%.

8. The purification method according to claim 1, characterized in that, The metal ions include at least one transition metal, which includes Co, Cr, Fe, Mn, Ni, and Ti.

9. The purification method according to claim 1, characterized in that, In each purification step, the stirring time ranged from 0.1 h to 48 h.

10. The purification method according to claim 1, characterized in that, The target polymer aqueous solution has a pH value of less than 3, and the purification method further includes: A pH adjuster is added to the target polymer aqueous solution to make the pH value of the adjusted target polymer aqueous solution greater than 10.

11. The purification method according to claim 1, characterized in that, In each purification step, the aqueous solution to be purified or the filtrate is filtered using a filtration device, and the filtration device does not include a filter column.

12. The purification method according to claim 1, characterized in that, When the concentration of the polymer in the aqueous solution to be purified is 2 wt%, the concentration of at least 60% of the target metal ions in the target polymer aqueous solution is less than 100 ppb.

13. The purification method according to claim 1, characterized in that, When the concentration of the polymer in the aqueous solution to be purified is 2 wt%, the retention rate of the polymer in the target polymer aqueous solution is at least 60%.

14. The purification method according to claim 1, wherein in each purification step, the stirring speed is 10 rpm to 2000 rpm.

15. The purification method according to claim 14, wherein in each purification step, the stirring process alternates between a high-speed stirring phase and a low-speed stirring phase, wherein, The stirring speed of the high-speed stirring stage is at least 1.5 times that of the low-speed stirring stage.

16. The purification method according to claim 15, wherein in each purification step, the duration of the high-speed stirring phase is 10 s to 10 min, and the duration of the low-speed stirring phase is 10 s to 10 min.

17. The purification method according to claim 1, characterized in that, The stirring is carried out under programmed temperature conditions, which include an initial stage, a later stage, and a settling period. At the initial stage of each purification step, the aqueous solution to be purified is maintained at an initial temperature of 35°C to 70°C; and In the later stages of each purification step, the temperature of the aqueous solution to be purified is lowered to a second temperature of 5°C to 30°C.

18. The method according to claim 17, characterized in that, The initial temperature is at least 10°C higher than the second temperature.

19. The method according to claim 17, characterized in that, The aqueous solution to be purified or the filtrate is maintained at the initial temperature for 10% to 60% of the time in each purification step.

20. The method according to claim 17, characterized in that, There is a 10-second to 10-minute settling period between the initial and later stages to allow the exchange resin particles to partially settle.

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