Filter membrane and method for producing same

Abstract

The invention relates to a filtration membrane and a method for manufacturing the same. The filtration membrane includes a porous membrane comprising a polymer and a derivatized polydopamine layer disposed on one or both sides of the porous membrane, wherein the derivatized polydopamine layer is disposed on the porous membrane in the presence of an oxidizing agent. The derivatized polydopamine layer is disposed on the porous membrane in the presence of an oxidizing agent.

Description

Background Technology

[0001] This disclosure relates to a filter membrane and a method for manufacturing the same. In particular, this disclosure applies to the manufacture of high-purity chemicals used in the semiconductor manufacturing industry, as well as the water, food, and pharmaceutical industries.

[0002] In the semiconductor manufacturing industry, liquid-based process chemicals are used throughout the manufacturing process, including photolithography, coating, cleaning, stripping, etching, and chemical mechanical planarization (CMP). These chemicals include, for example, acids, solvents, photoresists, antireflective materials, developers, removers, pastes, and cleaning solutions. As the critical dimensions required for advanced semiconductor devices continue to shrink, providing process chemicals in ultrapure form becomes increasingly important. However, even purified process chemicals typically contain trace amounts of metals, particularly iron, sodium, nickel, copper, calcium, magnesium, and potassium. The presence of metals in process chemicals can be detrimental, for example, causing patterning defects and altering the electrical properties of the resulting devices, thus affecting device reliability and product yield. These metal impurities can originate from raw materials used in the chemical manufacturing process or may be introduced otherwise during manufacturing and packaging processes.

[0003] The reduction of metals and other impurities from process chemicals, feedstocks, and precursors has been routinely achieved through the use of ion exchange and / or filtration processes. Ion exchange purification systems have several drawbacks. Many ion exchange resins possess chemically aggressive functional groups and are incompatible with acid-sensitive feedstocks. The resins are also prone to degradation and leaching of organic impurities, which, like metallic impurities, can lead to quality problems.

[0004] Therefore, there is a desire to develop improved filter membranes, their manufacturing methods, and applications, which address one or more problems associated with the prior art. Furthermore, filtration is an essential part of the manufacturing processes for semiconductor-grade chemicals and formulations to remove particulate impurities. A filtration process capable of simultaneously removing both particulate and ionic impurities is ideal. Summary of the Invention

[0005] A filter membrane includes a porous membrane comprising a polymer and a derivatized polydopamine layer disposed on one or both sides of the porous membrane. The derivatized polydopamine layer is disposed on the porous membrane in the presence of an oxidizing agent.

[0006] A method for coating a porous membrane, the method comprising placing the porous membrane in a solution comprising a dopamine monomer, a buffer, an oxidant, and a solvent in a reactor. The dopamine monomer, buffer, and oxidant are gradually added to the reactor to form a polydopamine layer on the porous membrane. The polydopamine layer is derivatized with an amine, a thiol, a carboxylic acid, or a combination thereof.

[0007] A method for purifying a liquid includes passing the liquid through a filter membrane, wherein the filter membrane comprises a porous membrane; a derivatized polydopamine layer disposed on one or both sides of the porous membrane; wherein the derivatized polydopamine layer is disposed on the porous membrane in the presence of an oxidizing agent. Ionic impurities and particulate impurities are removed from the liquid. Attached Figure Description

[0008] Figures 1 to 3 Bar graphs depicting the removal of metal nanoparticles from untreated membranes and polydopamine-coated membranes are shown respectively. Detailed Implementation

[0009] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. Unless the context otherwise indicates, the singular forms “a / an” and “the” are intended to include both the singular and plural forms.

[0010] Self-polymerization is a process in which monomers form large chain molecules (i.e., polymers) without the need for a chemical initiator. In this case, dissolved oxygen in the solvent is considered to act as an initiator during polymerization. This process can be accelerated by adding a chemical oxidizing agent, which can lead to improved coatings.

[0011] Nominal pore size refers to the approximate size of the pores in a filter or membrane, representing the diameter of the pores from which most particles are expected to be trapped. Unlike absolute pore size, which specifies a precise cutoff value, nominal pore size is a broader indication, typically expressed as the size of the particles that the filter will retain (e.g., 90% or 95%).

[0012] This document discloses filter membranes coated with polydopamine or polydopamine derivatives thereof. Polydopamine or its derivatives form a stable coating on one or both surfaces of the membrane. In one embodiment, an oxidant is added to a precursor solution used to produce polydopamine. The use of the oxidant increases the loading of polydopamine on the membrane, which is associated with improved metal removal capabilities. In another embodiment, the polydopamine membrane is post-functionalized with an amine. This post-functionalization improves the removal of metals from the contents of the contact membrane. These contents may include, for example, acids, solvents, polymers, photoresists, antireflective materials, developers, strippers, slurries, and cleaning solutions.

[0013] This document also discloses a method for coating one or more surfaces of a membrane with a polydopamine layer to form a filter, the method optionally including a step of derivatizing the polydopamine layer. The method includes dissolving a dopamine-containing monomer and a buffer in a solvent to form a reactive solution, and then applying the reactive solution to one or more surfaces of the membrane to form a coating. The buffer promotes the polymerization of the dopamine-containing monomer to form polydopamine.

[0014] In this embodiment, both opposing surfaces of the membrane may be coated with a polydopamine layer to form a filter. If desired, the polydopamine layers on one or both surfaces may be derivatized. membrane

[0015] In embodiments, the membrane may comprise an organic polymer. The organic polymer is preferably a thermoplastic, non-aromatic hydrocarbon polymer having a linear carbon and carbon skeleton molecular structure with only non-aromatic substituents and having a plurality of free hydrogen atoms attached to the carbon atoms of the polymer chain. These polymers can be extruded, blow-molded, or molded to form a membrane. In embodiments, the membrane comprises polyolefins, fluoropolymers, or combinations thereof. Examples of these thermoplastic extrusion-grade or moldable-grade organic polymers are homopolymers of ethylene, propylene, isobutylene, methyl-1-pentene, butene-1, vinyl chloride, vinylidene chloride, and acrylonitrile; interpolymers of the aforementioned monomers; chlorinated polyethylene and chlorinated polypropylene; fluoropolymers, such as polytetrafluoroethylene; perfluoroalkoxy polymers; polyamides, polyimides, polyesters, polystyrene, polysulfones, and blends of the aforementioned monomers and copolymers. Of particular interest are high- and low-density polyethylene, polypropylene, ethylene / propylene copolymers, ethylene / 1-butene copolymers, and blends thereof.

[0016] In this embodiment, the membrane is porous. Based on the total volume of the membrane, it can have a porosity of 10 to 90 volume percentages, preferably 30 to 70 volume percentages. The membrane has a nominal pore size of 0.5 nanometers to 5 micrometers, preferably 5 nanometers to 200 nanometers. These nominal pore sizes are determined by methods such as bubble point or nanoparticle retention tests. Preparation of reactive solutions

[0017] The reaction to form polydopamine can be carried out in a reactor, into which the membrane is then immersed. Preferably, the reactants (monomers containing dopamine and buffers) are added directly to the reactor along with a solvent, where they react to form a polydopamine coating.

[0018] The polydopamine layer is prepared by polymerizing dopamine-containing monomers in a reactive solution using a buffer. Dopamine-containing monomers, a buffer, a solvent, an oxidant, and any other components are added to a reactor to form a reactive solution. The dopamine-containing monomers undergo self-polymerization to form polydopamine.

[0019] Dopamine-containing monomers are typically in the form of salts. In this case, dopamine is preferably present in its protonated form with halide counterions, such as Cl-, Br-, F-, or I- counterions. In a preferred embodiment, the dopamine-containing monomer is dopamine hydrochloride.

[0020] Based on the total weight of the reactive solution, the dopamine-containing monomer is typically present in the reactive solution in an amount of 0.01 to 10 wt%. Based on the total weight of the reactive solution, the dopamine-containing monomer is preferably present in the reactive solution in an amount of 0.02 to 5 wt%, 0.02 to 1 wt%, or 0.05 to 0.20 wt%.

[0021] Buffers are primarily used to adjust the pH of a solution to a range that promotes the self-polymerization of dopamine-containing monomers. Buffers preferably have a pKa between 7.0 and 9.0.

[0022] Examples of buffers include tris buffers (tris(hydroxymethyl)aminomethane), sodium dihydrogen phosphate, potassium dihydrogen phosphate, or combinations thereof. Tris buffers (tris(hydroxymethyl)aminomethane) are preferred buffers. However, they can be substituted for any other buffer with a pKa between 7.0 and 9.0, such as sodium dihydrogen phosphate or potassium dihydrogen phosphate.

[0023] The buffer is typically present in the reactive solution at an amount of 0.01 to 5 wt%, depending on the total weight of the reactive solution. Preferably, the buffer is present in the reactive solution at an amount of 0.01 to 3 wt%, 0.05 to 1 wt%, or 0.10 to 0.30 wt%, depending on the total weight of the reactive solution.

[0024] Oxidants promote an increase in the amount of polydopamine disposed on the membrane surface, especially when compared to reactive solutions without oxidants. This increased dopamine presence enhances the metal removal capacity from the solution contacting the membrane. Oxidants are preferably water-soluble and include, for example, hydrogen peroxide, organic peroxides, nitrates, permanganates, periodates, persulfates, dichromates, chlorates, perborates, or combinations thereof. Examples of suitable oxidants include alkali metal metaperiodates (e.g., sodium metaperiodate, potassium metaperiodate, lithium metaperiodate, or combinations thereof), alkali metal perchlorates (e.g., lithium perchlorate, sodium perchlorate, potassium perchlorate, or combinations thereof), ammonium salts (e.g., ammonium persulfate, ammonium nitrate, ammonium dichromate, ammonium persulfate, ammonium perchlorate, ammonium periodate, or combinations thereof), or combinations thereof.

[0025] In this embodiment, a controlled, gradual addition of the oxidant to the reactive solution yields an improved coating on the membrane compared to adding the oxidant all at once. This is because the oxidant significantly accelerates the coating reaction, potentially leading to the formation of polydopamine particles in the solution rather than deposition on the membrane. By gradually adding the oxidant, the reaction rate can be controlled, thereby maximizing the amount of polydopamine coated onto the filter membrane.

[0026] In this embodiment, one or more of the dopamine monomer, buffer, and oxidant may be gradually added to the reactive solution. Excessively high reagent concentrations (especially oxidant concentrations) can lead to very rapid polydopamine formation, resulting in the precipitation of small polydopamine particles in the solution. This reduces the amount of polydopamine successfully coated onto the membrane. Gradual addition of one or more of the dopamine monomer, buffer, and oxidant keeps the reagent concentrations within an optimal range, maximizing slow, controlled deposition of polydopamine onto the membrane and minimizing rapid particle formation.

[0027] In one embodiment, the buffer and dopamine-containing monomer are added to the reactor over a period of 1 to 12 hours, preferably 4 to 8 hours. In another embodiment, the oxidant is added to the reactor over a period of 2 to 24 hours, preferably 12 to 16 hours.

[0028] In the embodiments, the molar ratio of electrons accepted by the oxidant (if used) to electron-donating dopamine-containing monomers is 2:1 to 8:1, preferably 3:1 to 5:1. Based on the total weight of the reactive solution, the oxidant (if used) is typically present in the solution in an amount of 0.001 wt% to 10 wt%. More preferably, based on the total weight of the reactive solution, the amount is 0.01 wt% to 5 wt%, or 0.1 wt% to 0.5 wt%.

[0029] The solvent present in the reactive solution should be capable of dissolving the dopamine-containing monomer and any other solid components in the solution. The solvent forms the balance of the reactive solution. Examples of suitable solvents are water, organic solvents such as alcohols, or combinations thereof. Particularly preferred solvents include ethanol and / or water.

[0030] The solvent is typically present in the reactive solution at an amount of 90 to 99.99 wt%, based on the total weight of the reactive solution. Preferably, the solvent is present in the reactive solution at an amount of 95 to 99.99 wt%, 98 to 99.90 wt%, or 99.50 to 99.85 wt%, based on the total weight of the reactive solution.

[0031] In the embodiments, dopamine monomers, oxidants, and buffers (which adjust the pH to a range where dopamine will self-polymerize), along with any other components, are dissolved in a solvent in the reactor to form a reaction solution. A color change indicates that self-polymerization has begun. For example, observing a change in color to light orange, and then beginning to darken, eventually turning black, indicates that polymerization of high molecular weight polydopamine has occurred. The reaction solution is stirred for a period of 0.5 hours to 96 hours, preferably 5 to 80 hours, and more preferably 10 to 30 hours, at a temperature of 10°C to 50°C, preferably 18°C ​​to 40°C, to form a polydopamine coating solution.

[0032] The membrane to be coated with the polydopamine layer is preferably hydrophobic and needs to be pre-wetted with a water-miscible organic solvent, followed by rinsing (e.g., washing) with water to remove the solvent. Examples of such water-miscible solvents are alcohols (e.g., methanol, ethanol, isopropanol, ethylene glycol, or combinations thereof), ketones (e.g., acetone, methyl ethyl ketone, cyclohexanone, or combinations thereof), acetonitrile, dimethyl sulfoxide, tetrahydrofuran, glycerol, N-methyl-2-pyrrolidone, etc., or combinations thereof.

[0033] After rinsing with water, the membrane is immersed in a polydopamine-containing solution in a reactor or other container. The membrane can be introduced into the reactive solution once the components are mixed together or at any time after the start of polymerization. The polydopamine-containing solution is in contact with the membrane for 2 to 20 hours, preferably 8 to 19 hours, and more preferably 12 to 16 hours, to promote polydopamine deposition on the membrane. The coated membrane is referred to as a polydopamine-coated membrane.

[0034] In one embodiment, both sides of the membrane can be coated with polydopamine. In another embodiment, one side of the membrane can be covered with a removable mask before immersion in the reactive solution. After the polydopamine layer is applied to the membrane, the mask can be removed, allowing the membrane to be coated on only one surface. During this coating process, the polydopamine in the container or reactor can be gently stirred. When deposition is complete, the remaining solution is discarded, leaving the polydopamine-coated membrane. The polydopamine-coated membrane is washed with water to remove any trace amounts of the reactive solution and other loose particles. Derivatization of polydopamine

[0035] In the embodiments, the polydopamine-coated film can be functionalized after polymerization to form a polydopamine derivative. The derivatized polydopamine can exhibit improved metal removal from the contents of a container. Functionalizing agents that can be used to functionalize polydopamines include, for example, primary amines, secondary amines, tertiary amines, moieties containing carboxylic acids functionalized with amines and / or thiols, or combinations thereof. Amines can be, for example, linear or cyclic amines. Preferred amines are primary amines, secondary amines, or combinations thereof.

[0036] Examples of primary amines include methylamine, ethylamine, propylamine, ethylenediamine, monoethanolamine, etc., or combinations thereof. Examples of secondary amines include dialkylamines, such as dimethylamine, diethylamine, dipropylamine, dibutylamine, diethanolamine, etc., or combinations thereof.

[0037] In the examples, amine-functionalized carboxylic acids can be used as functionalizing agents. Compared to functionalizing agents that contain only primary or secondary amines, the carboxylic acid present in these functionalizing agents promotes additional metal removal capabilities. Examples include aminopolycarboxylic acids (APCAs), such as iminodiacetic acid, aspartic acid, ethylenediaminetetraacetic acid, hyaluronic acid, etc., or combinations thereof.

[0038] In the embodiments, polydopamine can be derivatized using a functionalizing agent containing both thiols and carboxylic acids. An example of a functionalizing agent containing both thiols and carboxylic acids is mercaptosuccinic acid. Functionalizing agents containing both thiols and amines can also be used to facilitate the removal of metals from the contents of a container.

[0039] In the embodiments, functionalized agents containing sulfonic acid groups, amines, and / or thiols may also be used to facilitate the removal of metals from the contents of the container. Examples of such functionalized agents are aminosulfonic acids, 3-mercapto-1-propanesulfonic acids, or combinations thereof.

[0040] Amines can be added to the amination solution in one step or in batches as hydrochloride salts rather than free bases. For example, dimethylamine hydrochloride can be used instead of dimethylamine, or more preferably a mixture of both (dimethylamine and dimethylamine hydrochloride) to adjust the pH to the desired range.

[0041] In a preferred embodiment, during the functionalization of the polydopamine-coated membrane, an acid is added to the amination solution (if the amine is used for the functionalization of the polydopamine coating) to adjust the pH to an optimal range. pH adjustment allows for the use of higher concentrations of amine, which would otherwise result in an excessively high pH and dissolution of the polydopamine coating if left unadjusted. The acid can be an inorganic acid such as hydrochloric acid, but can also be an aminocarboxylic acid, aminophosphonic acid, or aminosulfonic acid; all of these acids provide additional functionality to the membrane through co-deposition with the free alkali amine.

[0042] The derivatization of the polydopamine coating is preferably performed after the polydopamine coating has been formed on the film. Before immersing the polydopamine-coated film therein, the functionalizing agent can be dissolved in a second solvent. The second solvent is preferably water, an alcohol, or a combination thereof. A preferred alcohol is ethanol. A preferred second solvent is water.

[0043] In one embodiment, the functionalizing agent is present in the solution at an amount of 0.01 to 10 wt% based on the total weight of the functionalized solution. In another embodiment, the functionalizing agent is present in the solution at an amount of 0.5 to 5.0 wt% based on the total weight of the functionalized solution.

[0044] In a preferred embodiment, the membrane with the polydopamine coating is then exposed to an amine. Amination of the polydopamine coating is optional but provides a substantial improvement in metal removal performance. The polydopamine-coated membrane is immersed in an aqueous amine solution and stirred for 12-16 hours. Dimethylamine was found to be the amine with the most significant improvement in metal removal performance.

[0045] An optional pickling step can be used to remove residual metals that may impair membrane performance. The membrane is immersed in a dilute aqueous solution of acid (e.g., hydrochloric acid), preferably at the trace metal level, and stirred for several hours. A water-miscible alcohol (e.g., isopropanol) can be used as a co-solvent. The pickling step can be performed after the polydopamine coating step, after the amination step, or after both steps.

[0046] After the acid washing step, the membrane can be thoroughly washed with water before use. If the membrane is used to purify non-aqueous solvents or formulations, residual water should be removed by drying at high temperature or by rinsing with a non-aqueous solvent to displace the water. A drying / thermal curing step can optionally be performed after the water washing step, which will improve the stability of the derivatized coating. The membrane is dried at 50°C to 100°C, more preferably 70°C to 80°C. The drying time is 2 to 16 hours, or more preferably 3 to 12 hours. In the embodiments, the drying step is performed under vacuum, at an absolute pressure of 0.001 to 0.50 atmospheres, or more preferably 0.005 to 0.10 atmospheres.

[0047] Derivatized polydopamine coatings can exhibit a stronger overall ability to extract ionic impurities from solutions filtered using polydopamine-coated membranes. In examples, derivatized polydopamine coatings can extract at least 5 wt%, preferably at least 10 wt%, and more preferably 15 wt% more ionic impurities than underivatized polydopamine coatings of the same thickness.

[0048] Membranes can then be used in filtration processes to remove ionic impurities from the fluid passing through them. The removal of ionic particles and nanoparticles can be achieved using dead-end filtration (where the fluid flows directly into the membrane at a right angle) and cross-flow filtration (where the fluid passes tangentially across the membrane surface).

[0049] The polydopamine and its derivatives, as well as their manufacturing methods, described in detail in this article, are illustrated by the following non-limiting examples. Example Example 1

[0050] A UPE membrane sample (with a diameter of 47 mm and a nominal pore size of 50 nm) was weighed to determine a baseline mass (25.4 mg), placed in a PFA (perfluoroalkoxy) filter holder, and rinsed with 200 g of isopropanol (IPA) at a rate of approximately 3 g / min. The filter holder is a mesh with 1-2 mm diameter pores to allow fluid passage and is held within a PFA housing having inlet and outlet ends for fluid flow. The sample was then rinsed with 200 g of deionized (DI) water to displace the IPA. The filter membrane sample was then removed and placed in a 120 mL low-density polyethylene (LDPE) bottle, to which 112.06 g of DI water, 4.09 g of 15 mg / mL tris buffer (tris(hydroxymethyl)aminomethane) solution, and 4.03 g of 15 mg / mL dopamine hydrochloride solution were added. The bottle was placed on a roller and rolled overnight. The membrane was then removed, washed several times with DI water, and dried in a vacuum oven at 50°C. The final mass was 26.8 mg, indicating that 1.4 mg of polydopamine had been coated onto the membrane.

[0051] After rewetting the polydopamine-coated membrane with propylene glycol methyl ether acetate (PGMEA), the membrane was placed back into the filter holder and rinsed with a PGMEA solution doped with custom multi-element standards containing Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, K, Na, Sn, Ti, and Zn ions (hereinafter referred to as doped PGMEA) at a flow rate of 1.5 g / min. After continuous rinsing for 5 min, 40 min, and 75 min, the doped PGMEA samples were collected, and the metal content was analyzed using an Agilent 7700 single quadrupole inductively coupled plasma mass spectrometer (ICP-MS). The doped PGMEA was continuously rinsed through the filter without recirculation. Samples were collected from the membrane outlet at 5, 40, and 75 min.

[0052] Table 1 shows the results in parts per billion (ppb) and the results for the control sample doped with PGMEA. The results indicate that the amount of each metal in the sample decreased over time (compared to the control). Table 1 Metal Comparison 5 minutes 40 minutes 75 minutes Al 7.752 5.453 7.100 6.827 Ca 7.230 7.284 7.441 7.875 Cr 8.045 6.331 8.168 8.284 Cu 7.056 5.304 7.186 7.785 Fe 6.603 8.008 7.601 7.620 Mg 7.822 5.235 7.311 7.351 Mn 7.414 4.590 6.584 7.037 Ni 7.787 4.247 5.712 6.089 K 7.523 5.423 7.657 7.820 Na 8.269 6.485 8.589 8.538 Sn 4.679 3.453 4.510 4.463 Ti 2.710 1.866 2.360 2.229 Zn 7.737 5.612 7.100 7.211 total 90.627 69.291 87.319 89.129 Example 2

[0053] A UPE membrane sample (with a diameter of 47 mm and a nominal pore size of 50 nm) was weighed to determine a baseline mass (25.7 mg). It was then placed in a PFA filter holder and rinsed with IPA and water in the same manner as described in Example 1. The filter membrane sample was then removed and placed in a 120 mL LDPE bottle, to which 72.06 g of DI water, 4.07 g of 15 mg / mL Tris buffer solution (the same as in Example 1), 4.01 g of 15 mg / mL dopamine hydrochloride solution, and 40.09 g of 6 mg / mL sodium periodate solution were added. The bottle was placed on a roller and tumbled overnight. The membrane was then removed, washed several times with DI water, and dried in a vacuum oven at 50°C. The final mass was 34.5 mg, indicating that 8.8 mg of polydopamine had been coated onto the membrane.

[0054] After rewetting the membrane with propylene glycol methyl ether acetate (PGMEA), the membrane was placed back into the filter holder and rinsed with a solution of doped PGMEA (described in Example 1) at a flow rate of 1.5 g / min. After rinsing continuously for 9 min, 40 min, and 76 min, the doped PGMEA samples were collected, and the metal content was analyzed using an Agilent 7700 single quadrupole inductively coupled plasma mass spectrometer (ICP-MS). The results for the control sample with doped PGMEA and the results obtained after continuous rinsing are shown in Table 2 below. Results are expressed in parts per billion (ppb). Table 2 Metal Comparison 9 minutes 40 minutes 76 minutes Al 7.752 3.625 5.454 5.625 Ca 7.230 1.038 8.391 4.222 Cr 8.045 4.938 6.905 6.902 Cu 7.056 1.860 2.808 3.649 Fe 6.603 4.918 6.649 6.861 Mg 7.822 0.426 2.537 4.489 Mn 7.414 0.276 0.360 0.387 Ni 7.787 0.421 0.563 0.543 K 7.523 0.466 0.420 0.528 Na 8.269 0.421 1.560 2.885 Sn 4.679 2.612 3.514 3.579 Ti 2.710 1.128 1.732 1.724 Zn 7.737 0.366 0.395 0.910 total 90.627 22.495 41.288 42.304 Example 3

[0055] A sample of ultra-high molecular weight polyethylene (UPE) membrane (with a diameter of 47 mm and a nominal pore size of 50 nm) was weighed to determine a baseline mass (24.3 mg). It was then placed in a PFA filter holder and rinsed with IPA and water in the same manner as described in Example 1. The filter membrane sample was then removed and placed in a 120 mL LDPE bottle, to which 112.10 g of DI water, 4.04 g of 15 mg / mL Tris buffer solution from Example 1, and 4.03 g of 15 mg / mL dopamine hydrochloride solution were added. The bottle was left to stand overnight on a roller, after which the polydopamine-coated membrane was removed and washed with DI water. The membrane was then functionalized (amined) by returning it to the bottle with 120.04 g of an aqueous solution containing 20 mg / mL dimethylamine (Fisher Scientific) and 0.5 mg / mL Tris buffer (adjusted to pH 10 with hydrochloric acid). The bottle was placed on a roller and rolled overnight. The membrane was then removed, and the functionalized polydopamine-coated membrane was washed several times with DI water and dried in a vacuum oven at 50°C. The final mass was 24.4 mg, indicating that 0.1 mg of the polydopamine coating remained on the membrane.

[0056] After rewetting the membrane with propylene glycol methyl ether acetate (PGMEA), it was placed back into the filter holder and rinsed with a PGMEA solution containing 10 ppb of a custom multi-element standard for each metal as described in Example 1 at a flow rate of 1.5 g / min. Samples were collected after 5 min, 40 min, and 75 min, and the metal content was analyzed using an Agilent 7700 single quadrupole inductively coupled plasma mass spectrometer (ICP-MS). Results for the control sample doped with PGMEA and results obtained after continuous rinsing are shown in Table 3 below. Results are in parts per billion (ppb). Table 3 Metal Comparison 5 minutes 40 minutes 75 minutes Al 7.185 2.197 5.752 5.772 Ca 10.989 0.226 18.027 17.127 Cr 9.564 3.135 6.837 7.153 Cu 9.903 2.668 4.201 5.533 Fe 10.656 5.577 8.236 8.414 Mg 9.797 0.060 7.529 8.169 Mn 9.782 0.025 0.050 0.264 Ni 9.372 0.130 0.303 0.339 K 9.827 0.722 10.463 11.484 Na 10.338 3.029 10.836 10.432 Sn 5.325 0.667 2.434 2.786 Ti 2.117 0.115 0.939 0.817 Zn 14.147 0.311 1.560 1.914 total 119.002 18.862 77.168 80.205 Example 4

[0057] A sample of ultra-high molecular weight polyethylene (UPE) membrane filter (with a diameter of 47 mm and a nominal pore size of 50 nm) was weighed to determine a baseline mass (24.9 mg). It was then placed in a PFA filter holder and rinsed with IPA and water in the same manner as described in Example 1. The filter membrane sample was then removed and placed in a 120 mL LDPE bottle, to which 72.09 g of DI water, 4.01 g of 15 mg / mL Tris buffer (Thermo Fisher Scientific), 4.04 g of 15 mg / mL dopamine hydrochloride (Thermo Fisher Scientific), and 40.01 g of 6 mg / mL sodium periodate (Thermo Fisher Scientific) solution were added. The bottle was placed on a roller overnight, after which the membrane was removed and washed with DI water. The membrane was then functionalized by returning it to the bottle along with 120.08 g of an aqueous solution containing 20 mg / mL dimethylamine (Thermo Fisher Scientific) and 0.5 mg / mL Tris buffer (pH adjusted to 10 with hydrochloric acid). The bottle was placed on a roller and tumbled overnight. The membrane was then removed, washed several times with DI water, and dried in a vacuum oven at 50°C. The final mass was 30.3 mg, indicating that 5.4 mg of coating remained on the membrane.

[0058] After rewetting the polydopamine-coated membrane with propylene glycol methyl ether acetate (PGMEA), the membrane was placed back into the filter holder and rinsed with a PGMEA solution doped with custom multi-element standards containing Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, K, Na, Sn, Ti, and Zn ions (hereinafter referred to as doped PGMEA) at a flow rate of 1.5 g / min. After continuous rinsing for 5 min, 40 min, and 75 min, the doped PGMEA samples were collected, and the metal content was analyzed using an Agilent 7700 single quadrupole inductively coupled plasma mass spectrometer (ICP-MS). The results for the control samples of the doped PGMEA, as well as the results obtained after continuous rinsing, are shown in Table 4 below. Results are expressed in parts per billion (ppb). Table 4 Example 5

[0059] A sample of ultra-high molecular weight polyethylene (UPE) membrane filter (with a diameter of 47 mm and a nominal pore size of 50 nm) was weighed to determine a baseline mass (27.7 mg). It was then placed in a PFA filter holder and rinsed with IPA and water in the same manner as described in Example 1. The filter membrane sample was then removed and placed in a 120 mL LDPE bottle with 0.404 g of dopamine hydrochloride, 0.163 g of tris base (from Example 1), and 135.20 g of DI water. The bottle was placed on a roller and tumbled overnight. The membrane was then removed, washed several times with DI water, and dried in a vacuum oven at 50°C. The membrane color was significantly darker than before coating. The final mass was 38.3 mg, indicating that 10.6 mg of polydopamine had been coated onto the membrane.

[0060] A dispersion of maleic anhydride-functionalized iron oxide (II,III) nanoparticles (30 nm, Sigma Aldrich) was diluted to 10 ppb in a 0.1% aqueous solution of Triton X-100 surfactant (Dow). The dispersion was passed through a coated membrane at 0.6 g / min. After sample collection, the remaining dispersion (approximately 400 g) was recycled through a filter for 22 hours (equivalent to approximately two tank turnovers), and another sample was collected at the filter holder outlet. The experiment was repeated using an untreated UPE membrane.

[0061] The iron content of the sample was determined by ICP-MS and compared with an unfiltered control sample to determine the percentage of nanoparticle removal. Results were presented in... Figure 1 As shown in the image. Figure 1 This is a bar graph showing the removal of iron nanoparticles in untreated UPE membranes and polydopamine-coated membranes. Example 6

[0062] A sample of ultra-high molecular weight polyethylene (UPE) membrane filter (with a diameter of 47 mm and a nominal pore size of 20 nm) was weighed to determine a baseline mass (32.3 mg). It was then placed in a PFA filter holder and rinsed with IPA and water in the same manner as described in Example 1. The filter membrane sample was then removed and placed in a 120 mL LDPE bottle along with 0.405 g of dopamine hydrochloride, 0.168 g of the Tris base from Example 1, and 135.01 g of DI water. The bottle was placed on a roller and tumbled overnight. The membrane was then removed, washed several times with DI water, and dried in a vacuum oven at 50°C. The final mass of the polydopamine-coated membrane was 41.7 mg, indicating that 9.4 mg of polydopamine had been coated onto the membrane.

[0063] A dispersion of maleic anhydride-functionalized iron oxide (II,III) nanoparticles (with an average particle size of 30 nm) was diluted to 10 ppb in a 0.1% aqueous solution of Triton X-100 surfactant (Dow Chemical Company). The dispersion was passed through a coated membrane at a rate of 0.6 g / min. After sample collection, the remaining dispersion (approximately 400 g) was recirculated through a filter for 22 hours, and another sample was collected at the filter holder outlet. The experiment was repeated using an untreated control UPE membrane.

[0064] The iron content of the sample was determined by ICP-MS (as detailed in Example 1), and compared with an unfiltered control sample to determine the percentage of nanoparticle removal. Results were presented in... Figure 2 As shown in the image. Figure 2 This is a bar graph showing the reduction in iron nanoparticle removal in untreated UPE membranes and UPE membranes coated with polydopamine. Example 7

[0065] A sample of ultra-high molecular weight polyethylene (UPE) membrane (with a diameter of 47 mm and a nominal pore size of 10 nm) was weighed to determine a baseline mass (32.4 mg). It was then placed in a PFA filter holder and rinsed with IPA and water in the same manner as described in Example 1. The filter membrane sample was then removed and placed in a 120 mL LDPE bottle along with 0.404 g of dopamine hydrochloride, 0.162 g of tris base, and 135.46 g of DI water. The bottle was placed on a roller and tumbled overnight. The membrane was then removed, washed several times with DI water, and dried in a vacuum oven at 50°C. The final mass was 43.8 mg, indicating that 11.4 mg of polydopamine was coated onto the membrane.

[0066] A dispersion of maleic anhydride-functionalized iron oxide (II,III) nanoparticles (average particle size 30 nm) was diluted to 10 ppb in a 0.1% aqueous solution of Triton X-100 surfactant (Dow Chemical Company). The dispersion was initially passed through a coated membrane at 0.6 g / min, but this was reduced to 0.2 g / min due to a high pressure drop (approximately 26 psig). After sample collection, the remaining dispersion (approximately 400 g) was recirculated through a filter for 70 hours, and another sample was collected at the filter holder outlet. The experiment was repeated using an untreated control UPE membrane.

[0067] The iron content of the sample was determined by ICP-MS and compared with an unfiltered control sample to determine the percentage of nanoparticle removal. Results were presented in... Figure 3 As shown in the image. Figure 3 This is a bar graph showing the removal of iron nanoparticles from untreated UPE membranes and UPE membranes coated with polydopamine. Example 8

[0068] A sample of ultra-high molecular weight polyethylene (UPE) membrane (with a diameter of 47 mm and a nominal pore size of 30 nm) was weighed to determine a baseline mass (28.1 mg). It was then placed in a PFA filter holder and rinsed with IPA and water in the same manner as described in Example 1. The filter membrane sample was then removed and placed in a 120 mL LDPE bottle. 48.26 g of DI water, 6.00 g of 15 mg / mL Tris buffer solution (see Example 1), 5.99 g of 15 mg / mL dopamine hydrochloride solution, and 60.38 g of 28 mmol / L sodium periodate solution were added to the bottle. The bottle was left to stand overnight on a roller, after which the membrane was removed and washed with DI water. The membrane was then returned to the bottle along with 120.21 g of an aqueous solution containing 20 mg / mL dimethylamine and 0.5 mg / mL Tris buffer (adjusted to pH 10 with hydrochloric acid). The bottle was placed on a roller and rolled overnight. The membrane was then removed, washed several times with DI water, and dried in a vacuum oven at 50°C. The final mass was 38.6 mg, indicating that 10.5 mg of coating remained on the membrane.

[0069] After rewetting the membrane with propylene glycol methyl ether acetate (PGMEA), it was placed back into the filter holder and rinsed with a PGMEA solution containing 10 ppb of a custom multi-element standard doped with each metal as described in Example 1 at a flow rate of 1.5 g / min. Samples were collected after 8, 42, 77, and 112 minutes, and the metal content of these samples, along with the PGMEA-doped control samples, was analyzed using an Agilent 7700 single quadrupole inductively coupled plasma mass spectrometer (ICP-MS). The results (in ppb) are shown in Table 5 below. Table 5 Example 9

[0070] A sample of ultra-high molecular weight polyethylene (UPE) membrane (with a diameter of 47 mm and a nominal pore size of 30 nm) was weighed to determine a baseline mass (28.7 mg). It was then placed in a PFA filter holder and rinsed with IPA and water in the same manner as described in Example 1. The filter membrane sample was then removed and placed in a 120 mL LDPE bottle, to which 48.05 g of DI water, 6.06 g of 15 mg / mL Tris buffer solution, 6.03 g of 15 mg / mL dopamine hydrochloride solution, and 60.25 g of 28 mmol / L ammonium persulfate solution were added. The bottle was placed on a roller overnight, after which the membrane was removed and washed with DI water. The membrane was then returned to the bottle along with 120.11 g of an aqueous solution containing 20 mg / mL dimethylamine and 0.5 mg / mL Tris buffer (adjusted to pH 10 with hydrochloric acid). The bottle was placed on a roller and rolled overnight. The membrane was then removed, washed several times with DI water, and dried in a vacuum oven at 50°C. The final mass was 30.8 mg, indicating that 2.1 mg of coating remained on the membrane.

[0071] After rewetting the membrane with propylene glycol methyl ether acetate (PGMEA), it was placed back into the filter holder and rinsed with a PGMEA solution containing 10 ppb of a custom multi-element standard doped with each metal as described in Example 1 at a flow rate of 1.4 g / min. Samples were collected after 5 min, 60 min, and 108 min, and the metal content of these samples, along with the PGMEA-doped control samples, was analyzed using an Agilent 7700 single quadrupole inductively coupled plasma mass spectrometer (ICP-MS). The results (in ppb) are shown in Table 6. Table 6 Example 10

[0072] A sample of ultra-high molecular weight polyethylene (UPE) membrane (with a diameter of 47 mm and a nominal pore size of 30 nm) was weighed to determine a baseline mass (25.6 mg). It was then placed in a PFA filter holder and rinsed with IPA and water in the same manner as described in Example 1. The filter membrane sample was then removed and placed in a 120 mL LDPE bottle. 48.07 g of DI water, 6.03 g of 15 mg / mL Tris buffer solution (from Example 1), 6.03 g of 15 mg / mL dopamine hydrochloride solution, and 60.02 g of 28 mmol / L lithium perchlorate solution (oxidant) were added to the bottle. The bottle was left to stand overnight on a roller, after which the membrane was removed and washed with DI water. The membrane was then returned to the bottle along with 120.83 g of an aqueous solution containing 20 mg / mL dimethylamine (amination agent) and 0.5 mg / mL Tris buffer (adjusted to pH 10 with hydrochloric acid). The bottle was placed on a roller and rolled overnight. The membrane was then removed, washed several times with DI water, and dried in a vacuum oven at 50°C. The final mass was 27.2 mg, indicating that 1.6 mg of coating remained on the membrane.

[0073] After rewetting the membrane with propylene glycol methyl ether acetate (PGMEA), it was placed back into the filter holder and rinsed with a PGMEA solution containing 10 ppb of a custom multi-element standard for each metal as described in Example 1 at a flow rate of 1.4 g / min. Samples were collected after 5 min, 50 min, and 125 min, and the metal content of these samples, along with the PGMEA-doped control samples, was analyzed using an Agilent 7700 single quadrupole inductively coupled plasma mass spectrometer (ICP-MS). The results (in ppb) are shown in Table 7 below. Table 7 Metal Comparison 5 minutes 50 minutes 125 minutes Al 10.843 0.146 1.147 3.603 Ca 14.175 0.241 0.490 6.718 Cr 12.098 0.276 2.191 5.527 Cu 10.843 0.095 0.218 0.603 Fe 10.363 0.085 0.920 3.414 Mg 11.843 0.025 0.143 6.709 Mn 11.904 0.010 0.025 2.542 Ni 11.425 0.030 0.079 0.822 K 14.354 0.065 10.233 12.211 Na 19.007 0.090 10.233 13.711 Sn 6.730 0.015 0.514 2.313 Ti 3.296 0.000 0.109 0.713 Zn 14.502 0.040 0.049 0.219 total 151.383 1.118 26.351 59.105

Claims

1. A filtration membrane, comprising: a porous membrane comprising a polymer; a derivatized polydopamine layer disposed on one or both sides of the porous membrane; wherein the derivatized polydopamine layer is disposed on the porous membrane in the presence of an oxidizing agent.

2. The filtration membrane of claim 1, wherein, the polydopamine layer is derivatized with an amine, a thiol, a carboxylic acid, or a combination thereof.

3. The filtration membrane of claim 1, wherein, the polymer comprises a polyolefin or a fluoropolymer.

4. The filtration membrane of claim 1, wherein, the porous membrane has a nominal pore size of 1 to 5000 nanometers.

5. The filtration membrane of claim 2, wherein, the amine is dimethylamine.

6. The filtration membrane of claim 1, wherein, the polydopamine layer has a thickness of 1 to 100 nm.

7. The filtration membrane of claim 1, wherein, the oxidizing agent comprises a periodate, a perchlorate, a persulfate, or a combination thereof.

8. The filtration membrane of claim 1, wherein, the periodate is sodium metaperiodate.

9. A method of coating a porous membrane, the method comprising: placing a porous membrane in a solution comprising a dopamine monomer, a buffer, an oxidizing agent, and a solvent in a reactor; wherein the dopamine monomer, the buffer, and the oxidizing agent are gradually added to the reactor; forming a polydopamine layer on the porous membrane; and derivatizing the polydopamine layer with an amine, a thiol, a carboxylic acid, or a combination thereof.

10. A method of purifying a liquid, the method comprising: passing a liquid through a filtration membrane; wherein the filtration membrane comprises: a porous membrane; a derivatized polydopamine layer disposed on one or both sides of the porous membrane; wherein the derivatized polydopamine layer is disposed on the porous membrane in the presence of an oxidizing agent; and removing ionic and particulate impurities from the liquid.

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