A pH-responsive separation material, its preparation method, and its application.

Abstract

This invention belongs to the field of oil-water separation materials technology, and particularly relates to a pH-responsive separation material, its preparation method, and its application. The preparation method includes (1) mixing an alkaline solution with a potassium persulfate solution to form a mixed solution; immersing a copper mesh in the mixed solution and removing it; and (2) placing the copper mesh removed in step (1) into an impregnation solution containing octadecylphosphonic acid for further impregnation. The separation material prepared by this method has pH-responsive characteristics, exhibiting different wettability under different pH conditions. It can realize the transformation from a "water-blocking" oil-water separation membrane to an "oil-blocking" oil-water separation membrane. By adjusting the pH, the separation material can achieve bidirectional oil-water separation performance, controllably realizing different oil-water separation methods.

Description

Technical Field

[0001] This invention belongs to the field of oil-water separation materials technology, and particularly relates to a pH-responsive separation material, its preparation method, and its application. Background Technology

[0002] During ship navigation and maintenance, the efficient treatment of oil-water mixtures needs to take into account environmental protection and resource recovery requirements. In traditional micro-fine oil phase separation technology, gravity separation relies on the density difference between oil and water to achieve stratification, and the separation cycle is long, which is difficult to match the needs of continuous ship operation; the sludge scraping method removes floating oil by mechanical means, which poses a risk of secondary pollution from chemical demulsifiers.

[0003] To address the shortcomings of traditional technologies, specialized wetting separation membranes, such as hydrophobic-oleophilic and hydrophilic-oleophobic membranes, have become a research hotspot, enabling efficient oil-water separation in a single mode through interfacial wettability. However, shipboard operations are dynamic and complex, requiring alternating processes for lubricating oil recovery and ballast water treatment. Lubricating oil recovery necessitates "water filtration and oil blocking," while ballast water treatment requires "oil filtration and water blocking." This necessitates frequent disassembly and replacement of existing fixed-wetting separation membranes, resulting in cumbersome operations, interruptions to workflows, and difficulty in meeting practical application requirements. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a pH-responsive separation material, its preparation method, and its application.

[0005] This invention provides the following technical solutions: In a first aspect, the present invention provides a method for preparing a pH-responsive separation material, comprising the following steps: (1) The alkaline solution and potassium persulfate solution are mixed to form a mixture; the copper mesh is immersed in the mixture and then removed; (2) The copper mesh taken out in step (1) is placed in an impregnation solution containing octadecylphosphonic acid for impregnation.

[0006] In one optional embodiment, the concentration of octadecylphosphonic acid in the impregnation solution is 0.0001-0.001M; for example, the concentration of octadecylphosphonic acid in the impregnation solution is any value among 0.0001M, 0.0002M, 0.0004M, 0.0006M, 0.0008M, 0.001M, etc.

[0007] In one optional implementation, the immersion time in step (2) is 1-10s; for example, the immersion time is any value among 1s, 2s, 4s, 6s, 8s, 10s, etc.

[0008] In one optional embodiment, in step (1), the alkaline solution is a solution containing NaOH, and the concentration of the alkaline solution is 0.5-1.5M; In one optional embodiment, the concentration of the potassium persulfate solution is 0.03-0.1M; In one optional embodiment, the volume ratio of the alkaline solution to the potassium persulfate solution is 100:(1-20).

[0009] In one optional implementation, the immersion time in step (1) is 10-50 min.

[0010] In one optional embodiment, the mesh count of the copper mesh is 200-300 mesh; for example, the mesh count of the copper mesh is any value among 200 mesh, 220 mesh, 240 mesh, 260 mesh, 280 mesh, 300 mesh, etc. In one alternative embodiment, the copper mesh comprises copper, red copper, brass, or phosphor bronze.

[0011] Secondly, the present invention provides a pH-responsive separation material prepared by the above-described preparation method.

[0012] Thirdly, the present invention provides a method for preparing a pH-responsive separation material using the above-described preparation method, comprising: adding a pH adjuster to the surface of a copper mesh to adjust the pH.

[0013] In one alternative embodiment, the pH adjuster comprises an alkaline solution and / or an acidic solution; In one optional embodiment, the separating material exhibits superhydrophilic and superoleophobic properties under acidic or alkaline conditions; and superhydrophobic and superoleophilic properties under neutral conditions.

[0014] In one optional embodiment, the alkaline solution comprises a solution containing NaOH; In one alternative embodiment, the acid solution comprises an HCl-containing solution.

[0015] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art: 1. The present invention provides a method for preparing a pH-responsive separation material, comprising: (1) mixing an alkaline solution with a potassium persulfate solution to form a mixed solution; immersing a copper mesh in the mixed solution and removing it; and (2) placing the copper mesh removed in step (1) into an impregnation solution containing octadecylphosphonic acid for impregnation. The separation material prepared by this method has pH-responsive characteristics and different wettability under different pH conditions, enabling the transformation of a "water-blocking" oil-water separation membrane into an "oil-blocking" oil-water separation membrane. By adjusting the pH, the separation material can have bidirectional oil-water separation performance, and different oil-water separations can be controllably achieved.

[0016] Octadecylphosphonic acid (ODPA) contains phosphonic acid groups with unique acid-base properties and high surface binding energy. This invention treats copper mesh with octadecylphosphonic acid. The phosphonic acid groups (-PO(OH)2) of ODPA can form more stable phosphonate bonds with the copper mesh surface. Compared to the weak coordination bonds or physical adsorption formed between stearic acid groups and copper, the phosphonic acid groups of this invention have a higher binding energy with the copper mesh, resulting in a more robust, ordered, and dense monolayer. The self-assembly ability of phosphonic acid groups on the metal surface is superior to existing groups, such as stearic acid groups, sulfonic acid groups, and amino groups. During long-term use, they are less likely to detach under mechanical friction or solvent washing, thus extending the material's service life.

[0017] This invention uses ODPA to modify copper mesh. The ionization state of the phosphonic acid groups in ODPA changes with pH. By utilizing the pH change to alter the ionization state of ODPA molecules, the wettability of the copper mesh surface switches accordingly, achieving a directional transition from superhydrophobic to hydrophobic and hydrophilic properties. It exhibits pH-responsive characteristics, is easy to operate, and is suitable for complex operating conditions, such as the alternating needs of lubricating oil recovery and ballast water treatment in ship oily wastewater. It is also suitable for long-term stable industrial scenarios. Existing methods use solvent methods to control the wettability of copper mesh. This method relies on solvent cleaning, which is a physical stripping process that damages the copper mesh surface, causing irreversible damage and contamination, making it difficult to reuse the copper mesh. Compared with existing methods, this invention is based on a chemical state change rather than physical dissolution. The phosphonic acid groups remain anchored on the copper mesh surface, do not rely on solvent cleaning, do not damage the copper mesh surface or cause molecular detachment, can stably switch the wettability of the copper mesh surface, has a high reusability rate, and improves the service life of the copper mesh.

[0018] Furthermore, this invention utilizes ODPA to treat copper mesh, resulting in a micro-nano composite structure on the surface of the copper mesh. Combined with the low surface energy of phosphonic acid groups, it can effectively resist oil adsorption and bioadhesion, exhibiting anti-fouling and self-cleaning properties.

[0019] 2. The method of using the pH-responsive separation material provided by this invention involves the deprotonation of the phosphonic acid groups in ODPA molecules under alkaline conditions, transforming them into a negatively charged state. Strong electrostatic repulsion occurs between these negative charges, forcing the long alkyl chains of the ODPA molecules from an extended state to a collapsed or bent state. Simultaneously, the negatively charged, hydrophilic phosphonate ion heads are exposed. These two factors work together to increase the surface energy of the material, transforming it from a hydrophobic state to a superhydrophilic / underwater superoleophobic state (i.e., "oil-blocking type").

[0020] Under neutral conditions, the phosphonic acid group of the ODPA molecule is in a protonated state (-PO(OH)). 2The octadecyl group is electrically neutral. At this time, there is no electrostatic repulsion between molecules, and the hydrophobic octadecyl long chain can be closely arranged and stretched on the material surface to form a low surface energy hydrophobic layer, thus exhibiting superhydrophobic / superoleophilic properties (i.e., "water-blocking type").

[0021] Under acidic conditions, ODPA molecules form stable phosphonate bonds (PO-Cu) with copper or copper hydroxide surfaces through their phosphonic acid groups, and the bonds are strong. Under acidic conditions, especially strongly acidic conditions, high concentrations of H+... + It will protonate phosphonate ions and react with metal ions (Cu). 2+ Competitive coordination occurs, thereby weakening or even breaking the chemical bonds (phosphonates). Once the chemical bonds are broken, the binding force between the ODPA molecule and the substrate is reduced from strong chemical bonds to weaker physical adsorption, and it returns to its original hydrophilic state. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a surface morphology diagram of the copper mesh in Embodiment 1 of the present invention without any treatment; Figure 2 This is a surface morphology diagram of the copper mesh after impregnation in step (1) of Embodiment 1 of the present invention; Figure 3 This is a surface morphology diagram of the copper mesh after ODPA treatment in Embodiment 1 of the present invention; Figure 4 This is a test diagram of the contact angle of the copper mesh after impregnation in step (1) of Embodiment 1 of the present invention; Figure 5 This is a test diagram of the contact angle of the copper mesh after ODPA treatment in Embodiment 1 of the present invention. Detailed Implementation

[0025] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0026] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0027] Example 1 This embodiment provides a method for preparing a pH-responsive separation material, including the following steps: (1) Cut a 5cm×5cm copper mesh, and ultrasonically clean it with deionized water and anhydrous ethanol for 15 min in sequence, and then dry it. Mix 1M NaOH solution and 0.05M K2S2O8 solution at a volume ratio of 100:10 to obtain a mixed solution. Immerse the dried copper mesh in the mixed solution for 30 min for etching, take it out, clean it, and dry it for later use. The copper mesh obtained in this step contains Cu(OH)2 on its surface. The copper mesh obtained in this step has superhydrophilic / underwater superoleophobic properties and can be effectively used to separate water and light oil mixtures.

[0028] (2) ODPA and tetrahydrofuran are mixed and dissolved by ultrasound to obtain a tetrahydrofuran solution with a concentration of 0.0002M. The copper mesh taken out in step (1) is placed in the tetrahydrofuran solution containing ODPA for 2s to obtain a copper mesh. The copper mesh has superhydrophobicity and superoleophilicity and can be used to separate mixtures of water and heavy oil.

[0029] Figure 1 This is a surface morphology image of the copper mesh in this embodiment without any treatment, obtained using a metallographic microscope; Figure 2 This is a surface morphology image of the copper mesh after impregnation in step (1), obtained using a metallographic microscope; Figure 3 These are surface morphology images of copper mesh after ODPA treatment, obtained using a scanning electron microscope; from Figures 1 to 3 As can be seen, ODPA does not damage the morphology of the copper mesh surface and forms a film with a micro-nano composite structure on the copper mesh surface.

[0030] Figure 4 These are contact angle test diagrams of the copper mesh after impregnation in step (1). A is the contact angle test result of water droplets, and B is the contact angle test result of oil droplets. Figure 5 These are contact angle test results for copper mesh after ODPA treatment. A shows the water droplet contact angle test results, and B shows the oil droplet contact angle test results. Figure 4 As can be seen, water droplets spread out on the surface of the copper mesh, while oil droplets form spherical shapes, indicating that the copper mesh possesses hydrophilic and oleophobic properties. Figure 5 As you can see, water droplets form spherical shapes on the surface of the copper mesh, while oil droplets spread rapidly on the surface, indicating that the copper mesh has super oleophilic and hydrophobic properties.

[0031] This embodiment also provides a method for using the copper mesh prepared above, including: Take the copper mesh modified with ODPA as described above, add hydrochloric acid solution with pH 3 to its surface, and test the contact angle γ1 after 18 minutes. γ1 is 39.25.

[0032] Take the copper mesh modified with ODPA as described above, add an aqueous solution with pH 7 to the surface of the copper mesh, and test the contact angle γ2 after 18 minutes. The γ2 value is 128.6.

[0033] Take the copper mesh modified with ODPA as described above, add sodium hydroxide solution with pH 11 to the surface of the copper mesh, and test the contact angle γ3 after 18 minutes. The γ3 value is 34.9.

[0034] After solutions with different pH values ​​are dropped onto the surface of the copper mesh of this invention, the hydrophilic and hydrophobic properties of the copper mesh surface are different. Under acidic or alkaline conditions, it has superhydrophilic and superoleophobic properties, and under neutral conditions, it has superhydrophobic and superoleophilic properties. This invention can realize the directional transformation from superhydrophobic to hydrophobic and hydrophilic, and has pH response characteristics.

[0035] Example 2 This embodiment provides a method for preparing a pH-responsive separation material, including the following steps: (1) Cut a 5cm×5cm copper mesh, and ultrasonically clean it with deionized water and anhydrous ethanol for 15 min in sequence, and then dry it. Mix 1.2M NaOH solution and 0.05M K2S2O8 solution at a volume ratio of 100:5 to obtain a mixed solution. Immerse the dried copper mesh in the mixed solution for 30 min for etching, take it out, clean it, and dry it for later use. The copper mesh obtained in this step contains Cu(OH)2 on its surface. The copper mesh obtained in this step has superhydrophilic / underwater superoleophobic properties and can be effectively used to separate water and light oil mixtures.

[0036] (2) ODPA and tetrahydrofuran are mixed and dissolved by ultrasound to obtain a tetrahydrofuran solution with a concentration of 0.0008M. The copper mesh taken out in step (1) is placed in the tetrahydrofuran solution containing ODPA for 7s to obtain a copper mesh. The copper mesh has superhydrophobicity and superoleophilicity and can be used to separate mixtures of water and heavy oil.

[0037] Comparative Example 1 This comparative example provides a method for preparing a separation material, which is basically the same as that in Example 1, except that stearic acid is used instead of ODPA.

[0038] Comparative Example 2 This comparative example provides a method for preparing a separation material, which is basically the same as that in Example 1. The main difference is that dodecyl mercaptan and mercaptoundecanoic acid are used instead of ODPA. The concentration of dodecyl mercaptan in the tetrahydrofuran solution containing dodecyl mercaptan and mercaptoundecanoic acid is 0.0003M, and the concentration of mercaptoundecanoic acid is 0.0003M.

[0039] Comparative Example 3 This comparative example provides a method for preparing a separation material, which is basically the same as that in Example 1, except that dodecyl mercaptan is used instead of ODPA.

[0040] Test case This experimental example provides the test results of the service life of the separation materials provided in Example 1 and Comparative Examples 1-3, as follows: A standard oil-water mixture was prepared, comprising water and n-hexane in a 1:1 volume ratio. Under gravity, the oil-water mixture was continuously passed through copper meshes prepared in the examples and comparative examples, with a single pass volume of 500 ml. After passing through, the copper mesh was gently rinsed or soaked with water or ethanol, dried, and the process was repeated 10 times. The contact angle of the copper mesh surface was then measured. This process simulates the change in surface wettability of the copper mesh during use. The degree of change in contact angle before and after the test characterizes the lifespan of the copper mesh. A large change in contact angle indicates a significant change in the surface properties of the copper mesh and a short lifespan, while a small change indicates minimal change in the copper mesh's properties and a long lifespan. The contact angles before and after the test are shown in the table below.

[0041] Table 1. Contact angle and change range before and after copper mesh testing

[0042] Based on the above test results, the copper mesh provided by the present invention shows little change in contact angle before and after the test, indicating that the surface wettability of the copper mesh of the present invention is stable and has a longer service life.

[0043] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0044] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method using a pH-responsive separation material, characterized in that, include: A pH adjuster is added dropwise to the surface of a pH-responsive separation material to adjust the pH; the pH adjuster includes an alkaline solution and / or an acidic solution. Under acidic or alkaline conditions, the separating material exhibits superhydrophilic and superoleophobic properties; under neutral conditions, the separating material exhibits superhydrophobic and superoleophilic properties. The preparation method of the pH-responsive separation material includes the following steps: (1) The alkaline solution and potassium persulfate solution are mixed to form a mixture; the copper mesh is immersed in the mixture and then removed; (2) The copper mesh taken out in step (1) is placed in an impregnation solution containing octadecylphosphonic acid for impregnation.

2. The method according to claim 1, characterized in that, The alkaline solution includes a solution containing NaOH; And / or, the acid solution includes a solution containing HCl.

3. The method according to claim 1, characterized in that, The concentration of octadecylphosphonic acid in the impregnation solution is 0.0001-0.001M.

4. The method according to claim 1, characterized in that, In step (2), the soaking time is 1-10 seconds.

5. The method according to claim 1, characterized in that, In step (1), the alkaline solution is a solution containing NaOH, and the concentration of the alkaline solution is 0.5-1.5M; And / or, the concentration of the potassium persulfate solution is 0.03-0.1M; And / or, the volume ratio of the alkaline solution to the potassium persulfate solution is 100:(1-20).

6. The method according to claim 1, characterized in that, In step (1), the soaking time is 10-50 minutes.

7. The method according to any one of claims 1-5, characterized in that, The copper mesh has a mesh count of 200-300 mesh; And / or, the copper mesh includes copper, copper, brass or phosphor bronze.

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