A modification method to mitigate pervaporation membrane fouling in seawater

Abstract

This invention belongs to the field of membrane fouling control, specifically relating to a modified method for mitigating pervaporation membrane fouling in seawater desalination. The method involves immersing the pervaporation membrane in 2% citric acid for two hours to remove residual oil from the membrane surface. Afterward, the surface is rinsed with deionized water to remove any remaining citric acid. The soaked pervaporation membrane is then attached to a membrane module. The membrane module is subsequently immersed in a pre-prepared tannic acid solution for 40-60 seconds. After immersion, the membrane module is removed, its surface is rinsed with deionized water, and then immersed in a prepared ferric chloride solution for 40-60 seconds. Finally, the membrane surface is rinsed with deionized water. Experiments have demonstrated that this method effectively mitigates pervaporation membrane fouling in seawater desalination and has significant practical implications for reducing the cost of seawater desalination.

Description

Technical Field

[0001] This invention belongs to the field of membrane fouling control, specifically relating to a modification method for mitigating pervaporation membrane fouling in seawater. Technical Background

[0002] Pervaporation, as an emerging membrane treatment technology, primarily utilizes the difference in dissolution and diffusion rates of the solutes to be separated within a pervaporation membrane, using vapor pressure difference as the driving force to separate the components in the feed solution. When pervaporation is applied to seawater desalination, brine separation is achieved using a hydrophilic, dense pervaporation membrane. This membrane only allows water molecules to permeate to the permeate side; inorganic salts in seawater cannot permeate to the permeate side. Therefore, the performance of the pervaporation membrane directly affects the desalination efficiency.

[0003] Because seawater contains a large amount of inorganic salt ions such as sodium and magnesium, during the concentration and reduction of seawater in the pervaporation process, these ions accumulate on the surface of the pervaporation membrane due to concentration polarization, causing severe membrane fouling. This fouling increases the resistance to water molecule transport across the membrane, leading to a decrease in membrane flux. Membrane flux refers to the amount of fluid passing through a unit membrane surface area per unit time; therefore, a decrease in membrane flux significantly affects the efficiency of seawater desalination through pervaporation.

[0004] To alleviate membrane fouling issues in seawater desalination processes using pervaporation, research has found that utilizing ferric iron / tannic acid (Fe3+) can be beneficial. Ⅲ / TA) complexes can form a polyphenol coating on the surface of a dense pervaporation membrane. This polyphenol coating contains abundant catechol and galloyl groups, which enhance the hydrophilicity of the membrane surface; Fe Ⅲ The deposition of a polyphenol network on the valley and ridge structures of the pervaporation membrane surface increases the membrane surface roughness. Increased roughness translates to a larger surface area, which facilitates rapid water molecule transport, increases the membrane's water-passing area and provides more water-passing channels. This means a significant increase in the water production per unit time of the dense membrane. Furthermore, the polyphenol coating possesses a three-dimensional stable structure. Compared to other membrane processes such as reverse osmosis, nanofiltration, and ultrafiltration, pervaporation requires lower operating pressures and has less stringent requirements on the modified membrane surface. Therefore, utilizing Fe... Ⅲ The TA-modified pervaporation membrane surface enhances the membrane's antifouling properties, which has practical reference value for alleviating membrane fouling problems in the field of seawater concentration and reduction using pervaporation processes. Summary of the Invention

[0005] The purpose of this invention is to address the membrane fouling problem in seawater concentration and reduction processes during pervaporation, combined with Fe... ⅢBased on the characteristics exhibited by TA complexes in membrane modification, a modification method for mitigating pervaporation membrane fouling in seawater concentration and reduction is proposed.

[0006] like Figure 1 The flowchart shown illustrates a modification method for mitigating pervaporation membrane fouling during seawater concentration and reduction, specifically including the following steps:

[0007] Step 1: Completely immerse the pervaporation membrane in a 2% citric acid solution for two hours, then rinse with deionized water and store it in deionized water.

[0008] Step 2: Prepare 0.24 mmol / L tannic acid solution and 1.44 mmol / L ferric chloride solution respectively;

[0009] Step 3: Attach the pervaporation membrane, which has been soaked in Step 1, onto the membrane module;

[0010] Step 4: Immerse the membrane module with the pervaporation membrane attached in Step 3 in the tannic acid solution prepared in Step 2 for 40s-60s;

[0011] Step 5: Remove the membrane module from Step 4, rinse the membrane surface with deionized water, and then immerse it in the ferric chloride solution prepared in Step 2 for 40-60 seconds.

[0012] Step 6: Remove the membrane module from Step 5 and rinse the membrane surface with deionized water;

[0013] Step 7: Use the pervaporation membrane obtained in Step 6 for seawater concentration and reduction through pervaporation, and observe the antifouling performance of the pervaporation membrane.

[0014] The membrane assembly in step three is a plate with a built-in hollow grid, used to fix the pervaporation membrane so that the front of the pervaporation membrane is in contact with the solution and the back is kept dry.

[0015] The beneficial effects of this invention are as follows:

[0016] This invention utilizes ferric chloride solution and tannic acid solution to form a polyphenol coating on the surface of a pervaporation membrane. The polyphenol coating alters the surface properties of the pervaporation membrane, enhancing its antifouling performance in seawater concentration and reduction. This invention provides a modification method to mitigate pervaporation membrane fouling during seawater desalination, effectively improving the antifouling performance of pervaporation membranes in seawater treatment.

[0017] This invention only requires ferric chloride and tannic acid as modifying agents, and the amount of reagents consumed is low. Compared with other modification methods, it can significantly reduce the modification cost; moreover, the modification process is simple to operate and takes little time. Attached Figure Description

[0018] Figure 1This is a process flow diagram of the present invention.

[0019] Figure 2 This is a graph comparing the flux of the modified membrane and the unmodified membrane under the concentration and reduction experiment in this invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this does not limit the scope of protection of the present invention.

[0021] This invention utilizes the complexation of ferric chloride solution and tannic acid solution on the surface of a pervaporation membrane to form a polyphenol coating. This can alleviate membrane fouling problems in pervaporation membranes during seawater concentration and reduction.

[0022] The pervaporation membrane was completely immersed in a 2% citric acid solution for two hours, then rinsed with deionized water and stored in deionized water. A 0.24 mmol / L tannic acid solution and a 1.44 mmol / L ferric chloride solution were prepared, and the pervaporation membrane immersed in deionized water was attached to the membrane module to ensure that the front side of the membrane could contact the modification solution during the immersion modification process, while the back side did not contact the modification solution.

[0023] Furthermore, the membrane module with the pervaporation membrane attached is immersed in the prepared tannic acid solution for 40-60 seconds. After the time is up, the membrane module is removed and the membrane surface is rinsed with deionized water. Then, the membrane module is immersed in the prepared ferric chloride solution for 40-60 seconds. After the time is up, the membrane module is removed and the membrane surface is rinsed with deionized water. The membrane module is then stored in deionized water.

[0024] Furthermore, pervaporation seawater concentration and reduction experiments were conducted on both modified and unmodified membranes, and the membrane antifouling performance was observed by monitoring changes in membrane flux; the differences exhibited by the two methods are shown in [see figure]. Figure 2 Throughout the entire experimental period, the flux of the modified membrane was consistently higher than that of the unmodified membrane at the same time point, indicating that the modified membrane has superior antifouling performance.

[0025] The experimental results show that the present invention achieves this by attaching Fe to the membrane surface. Ⅲ The TA complex method improves the antifouling performance of the pervaporation membrane, which can alleviate membrane fouling problems in pervaporation experiments for seawater concentration and reduction.

[0026] The above description is merely an embodiment of the present invention. It should be noted that those skilled in the art can make appropriate improvements and modifications without departing from the design principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A modification method for mitigating pervaporation membrane fouling in seawater desalination, characterized in specific ways. The steps are as follows: Step 1: Completely immerse the pervaporation membrane in a 2% citric acid solution for two hours, then rinse with deionized water and store it in deionized water. Step 2: Prepare 0.24 mmol / L tannic acid solution and 1.44 mmol / L ferric chloride solution respectively; Step 3: Attach the pervaporation membrane, which has been soaked in Step 1, onto the membrane module; Step 4: Immerse the membrane module with the pervaporation membrane attached in Step 3 in the tannic acid solution prepared in Step 2 for 40s-60s; Step 5: Remove the membrane module from Step 4, rinse the membrane surface with deionized water, and then immerse it in the ferric chloride solution prepared in Step 2 for 40-60 seconds. Step 6: Remove the membrane module from Step 5 and rinse the membrane surface with deionized water; Step 7: Use the pervaporation membrane obtained in Step 6 for concentration and volume reduction in seawater desalination via pervaporation, and observe the antifouling performance of the pervaporation membrane.

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