Method for removing perfluorinated compounds from a source of drinking water

Abstract

The application discloses a method for removing perfluorinated compounds in drinking water sources and belongs to the technical field of drinking water treatment. 2 The method comprises the following steps: taking the drinking water source as raw water and injecting the raw water into an electrolytic cell, then adding a supporting electrolyte to stir and dissolve the raw water to obtain an electrolyte; connecting a modified titanium plate as an anode and a polished titanium plate as a cathode to the positive and negative poles of a constant-voltage direct-current power supply respectively, and stirring the electrolyte at a current density of 20-100 mA / cm 2, a rotating speed of 350-400 r / min, and an electrode spacing of 1-2 cm for 3 h of electrochemical oxidation treatment, and then filtering to remove the perfluorinated compounds in the drinking water source.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of drinking water treatment, and particularly relates to a method for removing perfluorinated compounds in a drinking water source. BACKGROUND

[0002] Drinking water is an indispensable resource in people's daily life, and the quality of a drinking water source directly determines the quality of drinking water, which is directly related to the health and safety of people drinking water. Perfluorinated compounds are a kind of refractory organic matter. Since perfluorinated compounds are persistent and bioaccumulative, such pollutants have been frequently detected in drinking water sources in various places, which can have a certain impact on human health. Electrochemical oxidation is a new process of complex chemical oxidation technology, and the main purpose is to produce strong oxidizing free radicals (·OH) and other oxidizing active substances in the solution to oxidize and degrade organic pollutants in the solution to remove them. Electrochemical oxidation has been proven to be able to decompose and mineralize perfluorinated compounds, but the performance of the electrode material, especially the anode material, in the electrochemical oxidation process affects the removal efficiency of perfluorinated compounds in drinking water sources, which needs to be further improved. SUMMARY

[0003] The purpose of the present application is to provide a method for removing perfluorinated compounds in a drinking water source to solve the problems in the background art.

[0004] The purpose of the present application can be achieved by the following technical solutions:

[0005] A method for removing perfluorinated compounds in a drinking water source, comprising the following steps:

[0006] The drinking water source is injected into an electrolytic cell as raw water, and then a supporting electrolyte is added and stirred to dissolve, to obtain an electrolyte. A modified titanium plate is used as an anode, and a polished titanium plate is used as a cathode, which are respectively electrically connected to the positive and negative electrodes of a constant voltage direct current power supply, with an electrode spacing of 1-2 cm. The electrolyte is subjected to electrochemical oxidation treatment for 3 h under stirring at a current density of 20-100 mA / cm 2 , and a rotation speed of 350-400 r / min, and then filtered to remove perfluorinated compounds in the drinking water source.

[0007] Further, the supporting electrolyte is any one of sodium sulfate and sodium chloride, and the amount of the supporting electrolyte in the raw water is 0.2-0.5 mol / L; preferably, the supporting electrolyte is sodium chloride.

[0008] Further, the modified titanium plate is prepared by the following steps:

[0009] Step S1, the pretreated substrate is put into a deposition chamber, vacuumized to 20-50Pa, then methane and hydrogen are inputted according to a total flow rate of 400sccm, the methane concentration is controlled to be 4%, the tungsten hot wire is heated to 2200-2400℃ for carbonization treatment for 2h;

[0010] Step S2, the pretreated substrate is raised to the middle of the two rows of tungsten hot wires, the pretreated substrate is heated to 750-850℃ by the tungsten hot wires, the carbonization treatment is continued under the conditions of step S1 for 0.5h, then the methane concentration is reduced to 2%, and borane is inputted, first deposited at a borane concentration of 4000ppm for 1.5-2h, then deposited at a borane concentration of 2000ppm for 4-6h;

[0011] Step S3, after the deposition is completed, the methane and borane are stopped, the temperature is reduced to room temperature, finally the hydrogen is stopped to restore to normal pressure, and the modified titanium plate is obtained after discharging.

[0012] Further, the pretreated substrate is prepared by the following steps:

[0013] The surface of the titanium plate is cleaned with lye to remove oil stains and impurities on the surface of the titanium plate, then the titanium plate is put into an oxalic acid solution with a concentration of 15wt%, and soaked in a constant-temperature water bath at 90℃ for 2h, then washed with distilled water for 2 times, the surface of the titanium plate presents a concave-convex gray pitted surface, the nucleation driving force of the diamond is improved, the nucleation density is increased, then the titanium plate is transferred into a diamond acetone suspension liquid for ultrasonic treatment for 30-40min to improve the nucleation density of the diamond, then ultrasonic cleaned with distilled water for 30s, and dried to obtain the pretreated substrate.

[0014] Further, the content of the diamond particles in the diamond acetone suspension liquid is 4-6g / 100mL, and the size of the diamond particles is 0.5-0.6μm.

[0015] Further, the distance between the tungsten hot wire and the pretreated substrate is 5-6mm.

[0016] Further, the cooling rate is 3-4℃ / min; the smaller cooling rate can reduce the internal stress of the modified titanium plate, thereby improving the service life of the modified titanium plate.

[0017] The beneficial effects of the present application are as follows:

[0018] The present application adopts the modified titanium plate as the anode and the titanium plate as the cathode, and removes the perfluorinated compounds in the drinking water source by the method of electrochemical oxidation, the perfluorinated compounds in the drinking water source are directly oxidized by the anode or indirectly oxidized by the active free radicals generated by the anode, the method has a high removal rate, and the method also has the advantages of mild treatment conditions, no secondary pollution and high efficiency;

[0019] The present application takes common titanium plate as base material, etches the titanium plate using oxalic acid solution after alkali cleaning to remove impurities, etches and roughens the surface of the titanium plate to present uneven gray pitted surface, then performs ultrasonic treatment in diamond acetone suspension to load a large amount of diamond microcrystals on the roughened surface of the titanium plate to obtain a pretreated substrate, which is beneficial to the deposition of diamond on the surface of the pretreated substrate; then a hot-wire chemical vapor deposition method is used to perform carbonization treatment on the pretreated substrate under the condition of tungsten carbide hot wire, to increase the carbon concentration on the surface of the pretreated substrate and form an extremely thin and dense titanium carbide layer on the surface of the pretreated substrate, then a boron-doped diamond film layer is deposited in a short time with a high boron doping amount, which can not only inhibit the further formation of titanium carbide to affect the density of the titanium carbide layer, but also reduce the residual stress of the titanium carbide layer, thereby improving the bonding performance of the boron-doped diamond film layer and the titanium plate; then the boron doping amount is reduced to deposit a conventional boron-doped diamond film layer, to form a continuous and dense boron-doped diamond film layer; the modified titanium plate prepared by the present application has the advantages of wide working potential window, high chemical stability and long service life as an anode. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0021] Embodiment 1

[0022] The present embodiment provides a modified titanium plate, which is prepared by the following steps:

[0023] In step S1, the surface of the titanium plate is cleaned using alkali solution to remove oil stains and impurities on the surface of the titanium plate, then the titanium plate is immersed in oxalic acid solution with a concentration of 15wt% under the condition of 90℃ constant temperature water bath for 2h, taken out and washed with distilled water for 2 times, then transferred into diamond acetone suspension with a concentration of 4g / 100mL for ultrasonic treatment for 30min, wherein the size of the diamond particles is 0.5μm, then washed with distilled water for 30s, dried to obtain a pretreated substrate; the pretreated substrate is placed in a deposition chamber, vacuumized to 50Pa in the deposition chamber, then methane and hydrogen are introduced according to a total gas flow of 400sccm, and the methane concentration is controlled to be 4%, the tungsten hot wire is heated to 2200℃ for carbonization treatment for 2h;

[0024] Step S2, the pre-processed substrate is raised to the middle of the two rows of tungsten hot wires, the distance between the tungsten hot wires and the pre-processed substrate is 5 mm, the pre-processed substrate is heated to 750℃ by the tungsten hot wires, the carbonization treatment under the condition of step S1 is continued for 0.5 h, then the methane concentration is reduced to 2%, and borane is introduced, first deposited for 1.5 h at a borane concentration of 4000 ppm, and then deposited for 4 h at a borane concentration of 2000 ppm;

[0025] Step S3, after the deposition is completed, the methane and borane are stopped, the temperature is reduced to room temperature at a rate of 3℃ / min, finally the hydrogen is stopped and the pressure is returned to normal, and the modified titanium plate is obtained after discharging.

[0026] Example 2

[0027] The example provides a modified titanium plate, which is prepared by the following steps:

[0028] Step S1, the surface of the titanium plate is cleaned with lye to remove oil stains and impurities on the surface of the titanium plate, then the titanium plate is put into an oxalic acid solution with a concentration of 15wt%, soaked in a constant temperature water bath at 90℃ for 2 h, taken out and washed with distilled water for 2 times, then transferred into a diamond acetone suspension solution of 5g / 100mL and ultrasonically treated for 35 min, wherein the size of the diamond particles is 0.6μm, then ultrasonically cleaned with distilled water for 30 s, dried, and a pre-processed substrate is obtained; the pre-processed substrate is put into a deposition chamber, vacuumized to an air pressure of 30Pa in the deposition chamber, then methane and hydrogen are introduced according to a total gas flow of 400sccm, the methane concentration is controlled to be 4%, the tungsten hot wires are heated to 2300℃ for carbonization treatment for 2 h;

[0029] Step S2, the pre-processed substrate is raised to the middle of the two rows of tungsten hot wires, the distance between the tungsten hot wires and the pre-processed substrate is 6 mm, the pre-processed substrate is heated to 800℃ by the tungsten hot wires, the carbonization treatment under the condition of step S1 is continued for 0.5 h, then the methane concentration is reduced to 2%, and borane is introduced, first deposited for 2 h at a borane concentration of 4000 ppm, and then deposited for 5 h at a borane concentration of 2000 ppm;

[0030] Step S3, after the deposition is completed, the methane and borane are stopped, the temperature is reduced to room temperature at a rate of 4℃ / min, finally the hydrogen is stopped and the pressure is returned to normal, and the modified titanium plate is obtained after discharging.

[0031] Example 3

[0032] The example provides a modified titanium plate, which is prepared by the following steps:

[0033] Step S1, the surface of the titanium plate is cleaned with alkaline solution to remove oil stains and impurities on the surface of the titanium plate, then the titanium plate is added into an oxalic acid solution with a concentration of 15wt%, and soaked in a constant temperature water bath at 90℃ for 2h, then washed with distilled water for 2 times, then transferred into a diamond acetone suspension solution with a concentration of 6g / 100mL, and ultrasonically treated for 40min, wherein the size of the diamond particles is 0.6μm, then washed with distilled water for 30s, and dried to obtain a pretreated substrate; the pretreated substrate is placed in a deposition chamber, vacuumized to 50Pa, then methane and hydrogen are introduced according to a total flow rate of 400sccm, the methane concentration is controlled to be 4%, and the tungsten hot wire is heated to 2400℃ for carbonization treatment for 2h;

[0034] Step S2, the pretreated substrate is raised to the middle of the two rows of tungsten hot wires, the distance between the tungsten hot wires and the pretreated substrate is 6mm, the pretreated substrate is heated to 850℃ by the tungsten hot wires, and the carbonization treatment is continued for 0.5h under the conditions of step S1, then the methane concentration is reduced to 2%, and borane is introduced, first deposited at a borane concentration of 4000ppm for 2h, then deposited at a borane concentration of 2000ppm for 6h;

[0035] Step S3, after the deposition is completed, the methane and borane are stopped, the temperature is reduced to room temperature at a rate of 4℃ / min, and finally the hydrogen is stopped to restore to normal pressure, and the modified titanium plate is obtained after discharging.

[0036] Comparative Example 1

[0037] The difference between this comparative example and Example 3 is that in step S2, the borane concentration is always 2000ppm for 8h of deposition treatment, and the other steps are the same.

[0038] Comparative Example 2

[0039] The difference between this comparative example and Example 3 is that in step S2, first deposited at a borane concentration of 4000ppm for 6h, then deposited at a borane concentration of 2000ppm for 1h, and the other steps are the same.

[0040] Example 4

[0041] The present example provides a method for removing perfluorinated compounds in drinking water sources, comprising the following steps:

[0042] The drinking water source is used as raw water and injected into an electrolytic cell, then sodium sulfate is added to the raw water according to a dosage of 0.2mol / L, stirred and dissolved to obtain an electrolyte; the modified titanium plate prepared in Example 1 is used as an anode, and a polished titanium plate is used as a cathode, which are respectively electrically connected to the positive and negative electrodes of a constant voltage direct current power supply, and the electrode spacing is 1cm, the current density is 20mA / cm 2, the stirring speed is 350 r / min, the electrolyte is electrochemically oxidized for 3 hours, and the removal of the perfluorinated compound in the drinking water source is completed after filtration.

[0043] Example 5

[0044] The example provides a method for removing perfluorinated compounds in a drinking water source, including the following steps:

[0045] The drinking water source is injected into an electrolytic cell as raw water, then sodium chloride is added to the raw water in an amount of 0.4 mol / L, stirred and dissolved to obtain an electrolyte; the modified titanium plate prepared in Example 2 is used as an anode, and the polished titanium plate is used as a cathode, which are respectively electrically connected to the positive and negative electrodes of a constant-voltage direct-current power supply, the electrode spacing is 1.5 cm, the current density is 60 mA / cm 2 , the stirring speed is 380 r / min, the electrolyte is electrochemically oxidized for 3 hours, and the removal of the perfluorinated compound in the drinking water source is completed after filtration.

[0046] Example 6

[0047] The example provides a method for removing perfluorinated compounds in a drinking water source, including the following steps:

[0048] The drinking water source is injected into an electrolytic cell as raw water, then sodium chloride is added to the raw water in an amount of 0.5 mol / L, stirred and dissolved to obtain an electrolyte; the modified titanium plate prepared in Example 3 is used as an anode, and the polished titanium plate is used as a cathode, which are respectively electrically connected to the positive and negative electrodes of a constant-voltage direct-current power supply, the electrode spacing is 2 cm, the current density is 100 mA / cm 2 , the stirring speed is 400 r / min, the electrolyte is electrochemically oxidized for 3 hours, and the removal of the perfluorinated compound in the drinking water source is completed after filtration.

[0049] Comparative Example 3

[0050] The comparative example is different from Example 6 in that the polished titanium plate is used as an anode instead of the modified titanium plate prepared in Example 3, and the remaining steps are the same.

[0051] Comparative Example 4

[0052] The comparative example is different from Example 6 in that the modified titanium plate prepared in Comparative Example 1 is used instead of the modified titanium plate prepared in Example 3, and the remaining steps are the same.

[0053] Comparative Example 5

[0054] The comparative example is different from Example 6 in that the modified titanium plate prepared in Comparative Example 2 is used instead of the modified titanium plate prepared in Example 3, and the remaining steps are the same.

[0055] The concentration of perfluorinated compounds in the raw water before and after the treatment of examples 4-6 and comparative examples 3-5 was determined using an ultra-high performance liquid chromatograph-mass spectrometer, the removal rate of each group was calculated and recorded, and the results are shown in table 1:

[0056] Table 1

[0057]

[0058] As can be seen from the data in table 1, the treated drinking water source of examples 4-6 contains lower concentration of perfluorinated compounds and higher removal rate compared with comparative examples 3-5, which indicates that the method of the present application has excellent treatment effect and higher removal efficiency; at the same time, from the data of comparative example 4 and comparative example 5, it can be seen that the modified titanium plate prepared in the present application has excellent electrochemical oxidation performance as an anode.

[0059] It should be noted that in this text, relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual such relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0060] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for removing perfluorinated compounds from a source of drinking water, characterized in that, The method comprises the following steps: The drinking water source is used as raw water to inject into an electrolytic cell, and then a supporting electrolyte is added to stir and dissolve to obtain an electrolyte; The modified titanium plate is connected with the positive pole and the negative pole of a constant voltage direct current power supply as an anode and a cathode respectively, the distance between the electrodes is 1-2 cm, and the electrolyte is subjected to electrochemical oxidation treatment for 3 h under the stirring of a current density of 20-100 mA / cm 2 , a rotating speed of 350-400 r / min, and then the removal of perfluorinated compounds in the drinking water source is completed after filtration. The modified titanium plate is prepared by the following steps: S1, the pretreated substrate is placed in a deposition chamber, vacuumized to 20-50 Pa, then methane and hydrogen are introduced according to a total gas flow of 400 sccm, the methane concentration is controlled to be 4%, the tungsten hot wire is heated to 2200-2400 DEG C for carbonization treatment for 2 h; S2, the pretreated substrate is raised to the middle of the two rows of tungsten hot wires, the pretreated substrate is heated to 750-850 DEG C by the tungsten hot wire, the carbonization treatment is continued for 0.5 h, then the methane concentration is reduced to 2%, and borane is introduced, first deposited at a borane concentration of 4000 ppm for 1.5-2 h, and then deposited at a borane concentration of 2000 ppm for 4-6 h; S3, after the deposition is completed, the methane and borane are stopped, the temperature is reduced to room temperature, finally the hydrogen is stopped, and the pressure is returned to normal, and the modified titanium plate is obtained after discharging.

2. The method of claim 1, wherein the method is used for removing perfluorinated compounds from a drinking water source. The supporting electrolyte is any one of sodium sulfate and sodium chloride, and the amount of the supporting electrolyte in the raw water is 0.2-0.5 mol / L.

3. The method of claim 1, wherein the method is used for removing perfluorinated compounds from a drinking water source. The pretreated substrate is prepared by the following steps: The surface of the titanium plate is cleaned with lye, then the titanium plate is added into an oxalic acid solution with a concentration of 15 wt%, soaked in a 90 DEG C constant temperature water bath for 2 h, washed with distilled water after taking out, then ultrasonically cleaned in a diamond acetone suspension liquid for 30-40 min, then ultrasonically cleaned with distilled water for 30 s, dried, and the pretreated substrate is obtained.

4. The method of claim 3, wherein the water source is a drinking water source. The content of the diamond particles in the diamond acetone suspension liquid is 4-6 g / 100 mL, and the size of the diamond particles is 0.5-0.6 μm.

5. The method of claim 1, wherein the method is used for removing perfluorinated compounds from a drinking water source. The distance between the tungsten hot wire and the pretreated substrate is 5-6 mm.

6. The method of claim 1, wherein the method is used in a drinking water source. The cooling rate is 3-4 DEG C / min.

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