阅读说明：本技术 具有选择性吸附银离子的过滤膜的制备方法 (Preparation method of filtering membrane capable of selectively adsorbing silver ions ) 是由 陈晨 弓晓晶 郭冰 于 2021-08-27 设计创作，主要内容包括：本发明涉及过滤膜的技术领域,尤其涉及一种具有选择性吸附银离子的过滤膜的制备方法。将碳纳米管薄膜进行双面等离子清洗,然后浸泡在饱和碳酸氢钠里,水浴60℃磁力搅拌2h后取出,碳膜发泡分层,用去离子水清洗后浸泡在含有纳米二氧化硅的乙醇溶液中,超声震荡,最后拿出干燥即可获得整体镶嵌纳米二氧化硅的碳纳米管过滤膜。本发明制备的过滤膜可用于净水领域和工业废水的过滤,主要用于去除自来水和污水中的银离子,碳纳米管稳定的化学性能和巨大的比表面积使得它有很好的吸附性能,可以作为良好的过滤介质,配合上纳米二氧化硅的对银离子的吸附性,使得过滤膜可以选择性的去除液体中的银离子。(The invention relates to the technical field of filtering membranes, in particular to a preparation method of a filtering membrane capable of selectively adsorbing silver ions. And (2) carrying out double-sided plasma cleaning on the carbon nanotube film, then soaking the carbon nanotube film in saturated sodium bicarbonate, carrying out magnetic stirring for 2 hours in a water bath at 60 ℃, taking out the carbon nanotube film, foaming and layering the carbon film, cleaning the carbon nanotube film with deionized water, soaking the carbon nanotube film in an ethanol solution containing nano silicon dioxide, carrying out ultrasonic oscillation, and finally taking out and drying the carbon nanotube film to obtain the carbon nanotube filter membrane with the nano silicon dioxide embedded integrally. The prepared filter membrane can be used for the field of water purification and the filtration of industrial wastewater, is mainly used for removing silver ions in tap water and wastewater, has good adsorption performance due to the stable chemical property and the large specific surface area of the carbon nano tube, can be used as a good filter medium, and can be matched with the adsorption of nano silicon dioxide on the silver ions, so that the filter membrane can selectively remove the silver ions in liquid.)

1. A preparation method of a filter membrane capable of selectively adsorbing silver ions is characterized by comprising the following steps:

firstly, putting the carbon nano tube film into a plasma cleaning machine, and carrying out double-sided cleaning treatment to obtain a hydroxylated carbon nano tube film;

secondly, soaking the carbon nano tube film in the first step in a saturated sodium bicarbonate solution, stirring in a constant-temperature water bath magnetic stirrer, washing the surface with deionized water, and drying after washing to obtain a layered carbon nano tube film;

and thirdly, soaking the layered carbon nano tube film in an ethanol solution in which the silica sol is dissolved, carrying out water bath ultrasonic treatment, and finally taking out and drying to obtain the filtering membrane capable of selectively adsorbing silver ions.

2. The method for preparing a filtration membrane having a selective adsorption of silver ions according to claim 1, wherein the carbon nanotube film has a thickness of 15 to 25 μm and a pore size of 70 to 100 nm.

3. The method for preparing a filtration membrane having selective adsorption of silver ions according to claim 1, wherein said plasma cleaning machine is under the treatment conditions of power 70w for 100 s.

4. The method for preparing the filtering membrane capable of selectively adsorbing the silver ions according to claim 1, wherein the conditions of the thermostatic waterbath magnetic stirrer are that the water bath temperature is 70 ℃, the time is 2 hours, and the rotating speed is 400 rpm.

5. The method for preparing a filtration membrane having a selective adsorption of silver ions according to claim 1, wherein the thickness of the foam after soaking in a saturated sodium bicarbonate solution is 3 to 5 mm.

6. The method for preparing a filtration membrane having a selective adsorption of silver ions according to claim 1, wherein the drying temperature in the second step is 50 ℃ and the drying temperature in the third step is 50 ℃.

7. The method for preparing a filtration membrane having a selective adsorption of silver ions according to claim 1, wherein the volume ratio of the ethanol solution in which the silica sol is dissolved is, absolute ethanol: silica sol = 50: 1.

8. the preparation method of the filtering membrane capable of selectively adsorbing silver ions according to claim 1, wherein the water bath ultrasonic treatment conditions are that the water bath temperature is 40 ℃, the time is 30min, and the power is 560W.

Technical Field

The invention relates to a filtering membrane, in particular to a preparation method of a filtering membrane capable of selectively adsorbing silver ions.

Background

Heavy metal contamination has become a serious worldwide problem threatening life and even human survival. Industrial waste water associated with automotive manufacturing, electroplating, metal purification, galvanizing, coating, painting, chemical, electronic, pharmaceutical and battery manufacturing is the most common source of heavy metal contamination. Silver has been widely used in many industrial applications due to its many advantages, such as antibacterial, antifungal, antiviral, anti-inflammatory, anti-angiogenic and anti-cancer, as well as high electrical conductivity and sensitivity. However, excessive silver released from industrial products (such as coins, detergents, textiles, toys, pig's products, cosmetics, and medical devices) can pose risks to human health and the environment; therefore, the removal of such elements from wastewater is an important goal.

The carbon nano tube is a seamless tubular structure formed by winding graphene, has a hollow inner cavity and a layered structure, a large specific surface area, high thermal stability and chemical stability, and has unique advantages as a novel adsorption material. It has wide application in material science and chemistry, certain adsorption capacity to many substances, and good development prospect in treating environmental pollution as adsorbent. The ability to use Carbon Nanotubes (CNTs) to produce robust membrane-like structures can lead to a wide range of applications in separation technology, especially considering the selectivity and adsorption characteristics of the carbon nanotube surface, and thus the use of carbon nanotube membranes for filtration separation is an important development. In order to make the carbon nano tube film selectively adsorb substances, the selectivity of the filtering membrane can be improved by changing the chemical property and the physical property of the surface of the membrane, by electrochemical oxidation-reduction reaction, or by adding compatible adsorptive substances into the membrane.

Disclosure of Invention

The invention aims to solve the defects and provides a preparation method of a filtering membrane capable of selectively adsorbing silver ions, which is characterized in that carbon nano tubes are prepared into a thin film, the thin film is subjected to plasma treatment to make the thin film hydrophilic, then saturated sodium bicarbonate solution is soaked to change the physical appearance of the thin film, and finally nano silicon dioxide particles are embedded in the thin film, so that the filtering membrane has specific adsorption and can selectively adsorb the silver ions, and the filtering membrane is a promising adsorption material.

In order to overcome the defects in the background art, the technical scheme adopted by the invention for solving the technical problems is that the preparation method of the filtering membrane with the function of selectively adsorbing silver ions comprises the following steps:

firstly, putting the carbon nano tube film into a plasma cleaning machine, and carrying out double-sided cleaning treatment to obtain a hydroxylated carbon nano tube film;

secondly, soaking the carbon nano tube film in the first step in a saturated sodium bicarbonate solution, stirring in a constant-temperature water bath magnetic stirrer, washing the surface with deionized water, and drying after washing to obtain a layered carbon nano tube film;

and thirdly, soaking the layered carbon nano tube film in an ethanol solution in which the silica sol is dissolved, carrying out water bath ultrasonic treatment, and finally taking out and drying to obtain the filtering membrane capable of selectively adsorbing silver ions.

According to another embodiment of the invention, the carbon nanotube film further comprises a film thickness of 15-25 μm and an aperture of 70-100 nm.

According to another embodiment of the present invention, the plasma cleaning machine further comprises a power 70w and a time 100 s.

According to another embodiment of the invention, the conditions of the thermostatic waterbath magnetic stirrer are that the temperature of the waterbath is 70 ℃, the time is 2h and the rotating speed is 400 rpm.

According to another embodiment of the present invention, further comprising the step of foaming the foam to a thickness of 3 to 5mm after soaking in the saturated sodium bicarbonate solution.

According to another embodiment of the present invention, further comprising the drying temperature in the second step is 50 ℃ and the drying temperature in the third step is 50 ℃.

According to another embodiment of the present invention, the volume ratio of the ethanol solution dissolved with the silica sol is, absolute ethanol: silica sol = 50: 1.

according to another embodiment of the invention, the water bath ultrasonic treatment conditions are that the water bath temperature is 40 ℃, the time is 30min and the power is 560W.

The invention has the beneficial effects that:

1. according to the invention, the carbon nanotube film is subjected to plasma treatment, and hydroxyl is grafted on the surface of the film, so that the hydrophilicity is improved, and the carbon nanotube film can absorb water and filter a solution;

2. according to the invention, the carbon nanotube film is soaked in a saturated sodium bicarbonate solution, so that the carbon nanotube film is layered to form a cavity, which is beneficial to the selective adsorption of silver ions;

3. according to the invention, the carbon nanotube film is combined with the nano silicon dioxide, and the nano silicon dioxide grows inside and outside the film to perform specific adsorption on silver ions;

4. the carbon nano tube filtering membrane prepared by the invention has excellent mechanical property and can react with Ag⁺Has specific adsorption and separation capacity, and is a promising adsorption material;

5. the method has the advantages of simple process, convenient operation, mild conditions, large adsorption capacity of the prepared product, selective adsorption of silver ions and excellent biological compatibility.

Drawings

The invention is further illustrated with reference to the following figures and examples.

FIG. 1 is a schematic view of a filtration apparatus;

FIG. 2 is an SEM image of the surface of the carbon nanotube after plasma treatment;

FIG. 3 is a layered carbon nanotube film after soaking in saturated sodium bicarbonate;

fig. 4 is an SEM image of the carbon nanotube filtration membrane on which nano-silica has grown.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The preparation method of the filtering membrane with the selective adsorption of the silver ions comprises the steps of preparing a carbon nano tube into a thin film, carrying out plasma treatment on the thin film to make the thin film hydrophilic, soaking a saturated sodium bicarbonate solution to change the physical appearance of the thin film, and finally inlaying nano silicon dioxide particles in the thin film to make the filtering membrane have specific adsorption and can selectively adsorb the silver ions, so that the filtering membrane is a promising adsorption material.

Example 1:

in the example, the carbon nanotube film is put into a plasma cleaning machine for double-sided treatment, then is soaked in a saturated sodium bicarbonate solution, is stirred in a constant-temperature water bath magnetic stirrer, is cleaned with deionized water on the surface, is dried, is soaked in an ethanol solution in which nano silica sol is dissolved, is subjected to water bath ultrasonic treatment, and is finally taken out and dried, so that the filtering membrane capable of selectively adsorbing silver ions is obtained.

The filter membrane with the function of selectively adsorbing silver ions specifically comprises the following steps:

preparing a hydroxylated carbon nanotube film in step (1): the thickness of the carbon nano tube film selected at this time is 15-25 μm, and the aperture is 70-100 nm. The specific experimental steps are as follows: cutting the carbon nanotube film into a shape and a size which accord with the filter, and then fixing the carbon nanotube film in a tray, wherein the parameters of the plasma cleaning machine are as follows: the power is 70w, the cleaning time is 100s, after one side is cleaned, the operation is taken out and repeated, and double-side plasma cleaning is carried out, so that the hydroxylated carbon nanotube film is obtained.

Step (2) preparation of saturated sodium bicarbonate solution: sufficient solid sodium bicarbonate was added to the deionized water until no more dissolution occurred and the resulting supernatant was a saturated sodium bicarbonate solution.

Step (3) preparation of the layered carbon nanotube film: soaking the carbon nanotube film cleaned by the double-sided plasma in a saturated sodium bicarbonate solution, and carrying out constant-temperature water bath magnetic stirring under the following experimental conditions: the water bath temperature is 60 ℃, the time is 2h, and the rotating speed is 400 rpm. And after the treatment is finished, taking out the carbon nano tube film, enabling the visible film to be blown up to form a layered structure, washing two surfaces of the film by using deionized water, cleaning residual solute to prevent residual sodium carbonate crystals on the surface after drying, and drying in a drying oven at 50 ℃ to obtain the layered carbon nano tube film.

Step (4), preparation of nano silicon dioxide solution: weighing 50ml of absolute ethyl alcohol, then sucking 1ml of nano-silica sol by using a rubber head dropper, dropping the nano-silica sol into the absolute ethyl alcohol, and carrying out ultrasonic treatment in an ultrasonic instrument for 30min to uniformly disperse the nano-silica sol, thereby obtaining a nano-silica solution.

Growing nano silicon dioxide particles on the carbon nanotube film: soaking the dried layered carbon nanotube film in a nano silicon dioxide solution, and carrying out constant-temperature water bath ultrasonic treatment under the following treatment conditions: the water bath temperature is 40 ℃, the time is 30min, and the power is 560 w. And taking out the carbon nano tube film after the treatment is finished, and drying the carbon nano tube film in a drying oven at 50 ℃ to obtain the carbon nano tube film with the nano silicon dioxide.

Example 2:

in the example, the carbon nanotube film is put into a plasma cleaning machine for double-sided treatment, then is soaked in a saturated sodium bicarbonate solution, is stirred in a constant-temperature water bath magnetic stirrer, is cleaned with deionized water on the surface, is dried, is soaked in an ethanol solution in which nano silica sol is dissolved, is subjected to water bath ultrasonic treatment, and is finally taken out and dried, so that the filtering membrane capable of selectively adsorbing silver ions is obtained.

The filter membrane with the function of selectively adsorbing silver ions specifically comprises the following steps:

preparing a hydroxylated carbon nanotube film in step (1): the thickness of the carbon nano tube film selected at this time is 15-25 μm, and the aperture is 70-100 nm. The specific experimental steps are as follows: cutting the carbon nanotube film into a shape and a size which accord with the filter, and then fixing the carbon nanotube film in a tray, wherein the parameters of the plasma cleaning machine are as follows: the power is 70w, the cleaning time is 100s, after one surface is cleaned, the operation is taken out and repeated, and double-surface plasma cleaning is carried out to obtain a hydroxylated carbon nano tube film;

step (2) preparation of saturated sodium bicarbonate solution: adding sufficient solid sodium bicarbonate to deionized water until no more solid sodium bicarbonate can be dissolved, and collecting supernatant as saturated sodium bicarbonate solution;

step (3) preparation of the layered carbon nanotube film: soaking the carbon nanotube film cleaned by the double-sided plasma in a saturated sodium bicarbonate solution, and carrying out constant-temperature water bath magnetic stirring under the following experimental conditions: the temperature of the water bath is 70 ℃, the time is 2h, and the rotating speed is 400 rpm. Taking out the carbon nano tube film after the treatment is finished, enabling the visible film to be blown up to form a layered structure, then washing two surfaces of the film by deionized water, cleaning residual solute to prevent residual sodium carbonate from crystallizing on the surface after drying, and drying in a drying oven at 50 ℃ to obtain the layered carbon nano tube film;

step (4), preparation of nano silicon dioxide solution: measuring 100ml of absolute ethyl alcohol, then sucking 1ml of nano-silica sol by using a rubber head dropper, dropping the nano-silica sol into the absolute ethyl alcohol, and carrying out ultrasonic treatment in an ultrasonic instrument for 30min to uniformly disperse the nano-silica sol to obtain a nano-silica solution;

growing nano silicon dioxide particles on the carbon nanotube film: soaking the dried layered carbon nanotube film in a nano silicon dioxide solution, and carrying out constant-temperature water bath ultrasonic treatment under the following treatment conditions: the water bath temperature is 40 ℃, the time is 30min, and the power is 560 w. And taking out the carbon nano tube film after the treatment is finished, and drying the carbon nano tube film in a drying oven at 50 ℃ to obtain the carbon nano tube film with the nano silicon dioxide.

Example 3:

in the example, the carbon nanotube film is put into a plasma cleaning machine for double-sided treatment, then is soaked in a saturated sodium bicarbonate solution, is stirred in a constant-temperature water bath magnetic stirrer, is cleaned with deionized water on the surface, is dried, is soaked in an ethanol solution in which nano silica sol is dissolved, is subjected to water bath ultrasonic treatment, and is finally taken out and dried, so that the filtering membrane capable of selectively adsorbing silver ions is obtained.

The filter membrane with the function of selectively adsorbing silver ions specifically comprises the following steps:

preparing a hydroxylated carbon nanotube film in step (1): the thickness of the carbon nano tube film selected at this time is 15-25 μm, and the aperture is 70-100 nm. The specific experimental steps are as follows: cutting the carbon nanotube film into a shape and a size which accord with the filter, and then fixing the carbon nanotube film in a tray, wherein the parameters of the plasma cleaning machine are as follows: the power is 70w, the cleaning time is 100s, after one surface is cleaned, the operation is taken out and repeated, and double-surface plasma cleaning is carried out to obtain a hydroxylated carbon nano tube film;

step (2) preparation of saturated sodium bicarbonate solution: adding sufficient solid sodium bicarbonate to deionized water until no more solid sodium bicarbonate can be dissolved, and collecting supernatant as saturated sodium bicarbonate solution;

step (3) preparation of the layered carbon nanotube film: soaking the carbon nanotube film cleaned by the double-sided plasma in a saturated sodium bicarbonate solution, and carrying out constant-temperature water bath magnetic stirring under the following experimental conditions: the water bath temperature is 80 ℃, the time is 2h, and the rotating speed is 400 rpm. Taking out the carbon nano tube film after the treatment is finished, enabling the visible film to be blown up to form a layered structure, then washing two surfaces of the film by deionized water, cleaning residual solute to prevent residual sodium carbonate from crystallizing on the surface after drying, and drying in a drying oven at 50 ℃ to obtain the layered carbon nano tube film;

step (4), preparation of nano silicon dioxide solution: measuring 100ml of absolute ethyl alcohol, then sucking 1ml of nano-silica sol by using a rubber head dropper, dropping the nano-silica sol into the absolute ethyl alcohol, and carrying out ultrasonic treatment in an ultrasonic instrument for 30min to uniformly disperse the nano-silica sol to obtain a nano-silica solution;

growing nano silicon dioxide particles on the carbon nanotube film: soaking the dried layered carbon nanotube film in a nano silicon dioxide solution, and carrying out constant-temperature water bath ultrasonic treatment under the following treatment conditions: the water bath temperature is 40 ℃, the time is 30min, and the power is 560 w. And taking out the carbon nano tube film after the treatment is finished, and drying the carbon nano tube film in a drying oven at 50 ℃ to obtain the carbon nano tube film with the nano silicon dioxide.

Example 4:

in the example, the carbon nanotube film is put into a plasma cleaning machine for double-sided treatment, then is soaked in a saturated sodium bicarbonate solution, is stirred in a constant-temperature water bath magnetic stirrer, is cleaned with deionized water on the surface, is dried, is soaked in an ethanol solution in which nano silica sol is dissolved, is subjected to water bath ultrasonic treatment, and is finally taken out and dried, so that the filtering membrane capable of selectively adsorbing silver ions is obtained.

The filter membrane with the function of selectively adsorbing silver ions specifically comprises the following steps:

preparing a hydroxylated carbon nanotube film in step (1): the thickness of the carbon nano tube film selected at this time is 15-25 μm, and the aperture is 70-100 nm. The specific experimental steps are as follows: cutting the carbon nanotube film into a shape and a size which accord with the filter, and then fixing the carbon nanotube film in a tray, wherein the parameters of the plasma cleaning machine are as follows: the power is 70w, the cleaning time is 100s, after one surface is cleaned, the operation is taken out and repeated, and double-surface plasma cleaning is carried out to obtain a hydroxylated carbon nano tube film;

step (2) preparation of saturated sodium bicarbonate solution: adding sufficient solid sodium bicarbonate to deionized water until no more solid sodium bicarbonate can be dissolved, and collecting supernatant as saturated sodium bicarbonate solution;

step (3) preparation of the layered carbon nanotube film: soaking the carbon nanotube film cleaned by the double-sided plasma in a saturated sodium bicarbonate solution, and carrying out constant-temperature water bath magnetic stirring under the following experimental conditions: the temperature of the water bath is 70 ℃, the time is 2h, and the rotating speed is 400 rpm. Taking out the carbon nano tube film after the treatment is finished, enabling the visible film to be blown up to form a layered structure, then washing two surfaces of the film by deionized water, cleaning residual solute to prevent residual sodium carbonate from crystallizing on the surface after drying, and drying in a drying oven at 50 ℃ to obtain the layered carbon nano tube film;

step (4), preparation of nano silicon dioxide solution: measuring 200ml of absolute ethyl alcohol, then sucking 1ml of nano-silica sol by using a rubber head dropper, dropping the nano-silica sol into the absolute ethyl alcohol, and carrying out ultrasonic treatment in an ultrasonic instrument for 30min to uniformly disperse the nano-silica sol to obtain a nano-silica solution;

growing nano silicon dioxide particles on the carbon nanotube film: soaking the dried layered carbon nanotube film in a nano silicon dioxide solution, and carrying out constant-temperature water bath ultrasonic treatment under the following treatment conditions: the water bath temperature is 40 ℃, the time is 30min, and the power is 560 w. And taking out the carbon nano tube film after the treatment is finished, and drying the carbon nano tube film in a drying oven at 50 ℃ to obtain the carbon nano tube film with the nano silicon dioxide.

Example 5:

in the example, the carbon nanotube film is put into a plasma cleaning machine for double-sided treatment, then is soaked in a saturated sodium bicarbonate solution, is stirred in a constant-temperature water bath magnetic stirrer, is cleaned with deionized water on the surface, is dried, is soaked in an ethanol solution in which nano silica sol is dissolved, is subjected to water bath ultrasonic treatment, and is finally taken out and dried, so that the filtering membrane capable of selectively adsorbing silver ions is obtained.

The filter membrane with the function of selectively adsorbing silver ions specifically comprises the following steps:

preparing a hydroxylated carbon nanotube film in step (1): the thickness of the carbon nano tube film selected at this time is 15-25 μm, and the aperture is 70-100 nm. The specific experimental steps are as follows: cutting the carbon nanotube film into a shape and a size which accord with the filter, and then fixing the carbon nanotube film in a tray, wherein the parameters of the plasma cleaning machine are as follows: the power is 70w, the cleaning time is 100s, after one surface is cleaned, the operation is taken out and repeated, and double-surface plasma cleaning is carried out to obtain a hydroxylated carbon nano tube film;

step (2) preparation of saturated sodium bicarbonate solution: adding sufficient solid sodium bicarbonate to deionized water until no more solid sodium bicarbonate can be dissolved, and collecting supernatant as saturated sodium bicarbonate solution;

step (3) preparation of the layered carbon nanotube film: soaking the carbon nanotube film cleaned by the double-sided plasma in a saturated sodium bicarbonate solution, and carrying out constant-temperature water bath magnetic stirring under the following experimental conditions: the water bath temperature is 80 ℃, the time is 2h, and the rotating speed is 400 rpm. And after the treatment is finished, taking out the carbon nano tube film, enabling the visible film to be blown up to form a layered structure, washing two surfaces of the film by using deionized water, cleaning residual solute to prevent residual sodium carbonate crystals on the surface after drying, and drying in a drying oven at 50 ℃ to obtain the layered carbon nano tube film.

Step (4), preparation of nano silicon dioxide solution: measuring 200ml of absolute ethyl alcohol, then sucking 1ml of nano-silica sol by using a rubber head dropper, dropping the nano-silica sol into the absolute ethyl alcohol, and carrying out ultrasonic treatment in an ultrasonic instrument for 30min to uniformly disperse the nano-silica sol, thereby obtaining a nano-silica solution.

Growing nano silicon dioxide particles on the carbon nanotube film: soaking the dried layered carbon nanotube film in a nano silicon dioxide solution, and carrying out constant-temperature water bath ultrasonic treatment under the following treatment conditions: the water bath temperature is 40 ℃, the time is 30min, and the power is 560 w. And taking out the carbon nano tube film after the treatment is finished, and drying the carbon nano tube film in a drying oven at 50 ℃ to obtain the carbon nano tube film with the nano silicon dioxide.

Examples 2, 3, 4, 5 compared to example 1, the temperature of the water bath for soaking saturated sodium bicarbonate and the ratio of absolute ethanol to nanosilica sol were varied, with 5 example volume ratios (absolute ethanol: nanosilica sol) of 50: 1. 100, and (2) a step of: 1. 100, and (2) a step of: 1. 200: 1. 200: 1, the rest operation steps and the manufacturing method are completely the same.

Weighing 0.1g of sodium chloride, 0.1g of potassium chloride and 0.1g of silver nitrate respectively, dissolving the sodium chloride, the potassium chloride and the silver nitrate respectively in 100ml of water to prepare respective solutions, building a filtering device, putting the prepared carbon nanotube filtering membrane on the filtering device, filtering the three solutions respectively, and detecting the peak value change of the absorbance of sodium ions, potassium ions and silver ions in the filtrate by using an ultraviolet spectrophotometer.

The carbon nanotube filtering membranes prepared in the five embodiments are respectively filtered by using sodium chloride solution, potassium chloride solution and silver nitrate solution with the same concentration, and after the filtrate is detected by an ultraviolet spectrophotometer, the peaks of the absorbance positions of sodium ions and potassium ions are slightly reduced, and the peaks of the absorbance positions of silver ions are greatly reduced compared with the solution before filtration, which indicates that the prepared filtering membranes have the selective adsorption capacity for silver ions.

Comparing the experimental results of examples 1 to 5, it was found that as the ratio of absolute ethanol to nano-silica increases, i.e., the concentration of nano-silica in the solution is low, the peak of the absorbance position of silver ions decreases less, i.e., in a certain concentration range, the adsorption capacity for silver ions increases as the concentration of nano-silica increases.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.