Flexible electrocatalytic membrane for removing nitrate from water, preparation method and use thereof

Patent metadata

Field	Value
Publication number	US-11565953-B2
Application number	US-202015930454-A
Country	US
Kind code	B2
Filing date	May 13, 2020
Priority date	Dec 25, 2019
Publication date	Jan 31, 2023
Grant date	Jan 31, 2023

Abstract

A flexible electrocatalytic membrane for removing nitrate from water, a preparation method and use thereof are provided. The method of the present invention includes dropwise adding an aramid fiber solution into deionized water to prepare an aramid nanofiber sol, then reacting an ethanol solution containing 3,4-ethylenedioxythiophene and ferric nitrate with the aramid nanofiber sol to prepare a conductive aramid nanofiber sol, and finally dropwise adding MXene nanosheets ultrasonically pretreated by a tetramethylammonium hydroxide solution into the conductive aramid nanofiber sol to prepare the flexible electrocatalytic membrane. The prepared flexible electrocatalytic membrane possesses good mechanical strength and flexibility, and can not only effectively remove nitrate but also avoid failure of electrocatalytic materials due to surface fouling in the process of electrocatalytic reduction of nitrate, and thus has a long service life.

First claim

What is claimed is:

1. A method of preparing a flexible electrocatalytic membrane for removing nitrate from water, comprising the following steps:
(1) preparation of an aramid nanofiber sol:
fracturing an aramid textile yarn to obtain a fractured aramid textile yarn, adding the fractured aramid textile yarn into dimethyl sulfoxide for stirring to obtain a first solution, followed by adding potassium hydroxide into the first solution to obtain a second solution, and continuously stirring the second solution until an aramid fiber in the fractured aramid textile yarn is completely dissolved to obtain an aramid fiber solution, dropwise adding the aramid fiber solution into deionized water to obtain a third solution, stirring the third solution for a period of time and then centrifuging the third solution to obtain a supernatant comprising the aramid nanofiber sol;
(2) preparation of a conductive aramid nanofiber sol:
dissolving 3,4-ethylenedioxythiophene and ferric nitrate in ethanol for stirring uniformly to obtain a mixed solution; adding the mixed solution into the aramid nanofiber sol prepared in step (1) to obtain a fourth solution, and performing a reaction on the fourth solution for 1 hour to 3 hours at 40° C. to 50° C. to obtain the conductive aramid nanofiber sol; and
(3) preparation of the flexible electrocatalytic membrane:
adding MXene nanosheets into a tetramethyl ammonium hydroxide solution to obtain a fifth solution, performing an ultrasonic treatment on the fifth solution in an ice bath for 1 hour to 2 hours to obtain an ultrasonically treated MXene nanosheet solution, and then dropwise adding the ultrasonically treated MXene nanosheet solution into the conductive aramid nanofiber sol prepared in step (2) to obtain a sixth solution, stirring the sixth solution for 1 hour to 2 hours and then carrying out a suction filtration on the sixth solution to obtain the flexible electrocatalytic membrane.

2. The method of preparing the flexible electrocatalytic membrane for removing nitrate from water of claim 1 , wherein the aramid textile yarn, the dimethyl sulfoxide, and the deionized water in step (1) are used in an amount ratio of 1 g:(300-800) mL:(2000-3000) mL.

3. The method of preparing the flexible electrocatalytic membrane for removing nitrate from water of claim 1 , wherein a mass ratio of the aramid textile yarn to the potassium hydroxide in step (1) is 1:(0.8-2).

4. The method of preparing the flexible electrocatalytic membrane for removing nitrate from water of claim 1 , wherein in step (2), a mass ratio of the 3,4-ethylenedioxythiophene to the ferric nitrate is 1:(1.5-3), and a volume ratio of the mixed solution to the aramid nanofiber sol is 1:(3-5).

5. The method of preparing the flexible electrocatalytic membrane for removing nitrate from water of claim 1 , wherein the MXene nanosheets and the conductive aramid nanofiber sol in step (3) are used in an amount ratio of 1 g:(0.5-2) L.

6. A flexible electrocatalytic membrane prepared using the method of claim 1 .

7. A method of using the flexible electrocatalytic membrane of claim 6 in an electrocatalytic reduction of nitrate, comprising the steps of:
placing the flexible electrocatalytic membrane as a cathode in a first container and connecting the cathode to a negative electrode of a direct current power supply, and
placing a graphite rod as an anode in a second container and connecting the anode to a positive electrode of the direct current power supply;
wherein
a water inlet is provided at a top of the first container, and a water outlet is provided at a bottom of the first container;
the first container communicates with the second container through a communicating pipe, and a proton exchange membrane is provided on the communicating pipe; and
the first container contains a first nitrate solution, the second container contain a second nitrate solution, and an initial concentration of the first nitrate solution is equal to an initial concentration of the second nitrate solution.

8. The method of claim 7 , wherein a pH value of each of the first nitrate solution and the second nitrate solution is 6-9, the initial concentration of each of the first nitrate solution and the second nitrate solution is 1-10 mg/L, a cathode voltage of the direct current power supply is 0.6 V to 1.0 V, and a water permeability of the flexible electrocatalytic membrane is 50-150 L/(m 2 ·h·bar).

9. The flexible electrocatalytic membrane of claim 6 , wherein the aramid textile yarn, the dimethyl sulfoxide, and the deionized water in step (1) are used in an amount ratio of 1 g:(300-800) mL:(2000-3000) mL.

10. The flexible electrocatalytic membrane of claim 6 , wherein a mass ratio of the aramid textile yarn to the potassium hydroxide in step (1) is 1:(0.8-2).

11. The flexible electrocatalytic membrane of claim 6 , wherein in step (2), a mass ratio of the 3,4-ethylenedioxythiophene to the ferric nitrate is 1:(1.5-3), and a volume ratio of the mixed solution to the aramid nanofiber sol is 1:(3-5).

12. The flexible electrocatalytic membrane of claim 6 , wherein the MXene nanosheets and the conductive aramid nanofiber sol in step (3) are used in an amount ratio of 1 g:(0.5-2) L.

Assignees

• Univ Tongji
• Univ Tianjin Polytechnic

Inventors

• Wang Zhiwei
• Li Yang
• Zhang Hongwei
• Wang Jie
• Wang Xueye

Classifications

• C02F2001/46133

  characterised by the material · CPC title

• C02F1/46109

  Electrodes · CPC title

• C02F1/4676 Primary

  by electroreduction · CPC title

• C02F2201/46115

  Electrolytic cell with membranes or diaphragms · CPC title

• C02F2101/163

  Nitrates · CPC title