Nano Ca3Mn2O7 / Mn3O4 composite material as well as preparation method and application thereof

Abstract

The invention discloses a nano Ca3Mn2O7 / Mn3O4 composite material and a preparation method and application thereof.The preparation method comprises the following steps that a certain amount of MnCl2. 4H2O and a certain amount of CaO2 are taken and placed in a mortar, grinding is conducted for 10-20 min at the temperature of 20-40 DEG C to obtain a solid mixture, then the solid mixture is transferred into an air dry oven to be subjected to a solid-phase reaction for 1-2 h at the temperature of 80-100 DEG C, and after the solid product is cooled to the room temperature, the nano Ca3Mn2O7 / Mn3O4 composite material is obtained; and washing with water and ethanol for multiple times, and carrying out blast drying to obtain the Ca3Mn2O7 / Mn3O4 composite material. The Ca3Mn2O7 / Mn3O4 composite material prepared by the invention is a green, efficient and low-cost catalyst, not only can effectively catalyze persulfate to degrade organic pollutants, but also can solve the problems of acidification caused by persulfate and secondary pollution caused by sulfate residues. In addition, the method is short in technological process and easy to operate, and has wide application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental functional materials and organic polluted site remediation, and relates to a nano Ca3Mn2O7 / Mn3O4 composite material and a preparation method and application thereof. Background Art

[0002] With the optimization and adjustment of my country's industrial structure, a large number of organic pollution sites have been left behind in cities and surrounding areas after the relocation or closure of industrial enterprises, which poses a serious threat to the ecological environment and human health. Therefore, seeking green and efficient remediation methods has always been a hot topic at home and abroad. Commonly used methods for remediation of organic pollution sites include physical, chemical and biological remediation technologies. Among these technologies, chemical oxidation remediation technology based on persulfate is widely used in the remediation of organic pollution sites due to its advantages such as good remediation effect, short cycle and moderate cost.

[0003] Persulfate (PS) can be activated by transition metal oxides, alkali, heat, light, ultrasound, etc. to produce highly active free radicals, thereby achieving efficient removal of organic pollutants. Transition metal oxides have the advantages of being easily available, low-cost, and easy to operate, and are currently the most commonly used persulfate activators. Among them, manganese-based oxides (MnO x ) has the advantages of high catalytic activity, wide pH range, low toxicity, high natural abundance, environmental friendliness, low cost and large-scale preparation. It has been widely used as an activator for PS.

[0004] Common MnO x Activators include Mn3O4, Mn2O3, MnO2, etc. However, similar to other transition metal oxides, MnO x When activated PS oxidation technology is used to repair organic contaminated sites, it can also cause environmental acidification and sulfate ion (SO4 2- ) residues, resulting in the deterioration of environmental quality, which greatly limits the further promotion and application of this technology in the field of contaminated site remediation.

[0005] Regarding the above SO4 2- To solve the problem of residual, some scholars have proposed adding calcium ions (Ca 2+ ) is an effective solution because Ca 2+ Can be used with SO4 2- The reaction generates stable CaSO4 precipitation, which alleviates the MnO x The secondary hazards caused by activated PS oxidation technology. At the same time, recent studies have shown that Ca 2+ Adding can promote MnO x Activated PS system to degrade organic pollutants. 2+ Doping into MnOx Calcium-doped MnO x The strategy of activators came into being, and it was proposed that the development of calcium-doped manganese oxide activators is an effective way to overcome the shortcomings of existing technologies. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a nano-Ca3Mn2O7 / Mn3O4 composite material and a preparation method thereof.

[0007] Another object of the present invention is to provide an application of the above-mentioned nano-Ca3Mn2O7 / Mn3O4 composite material.

[0008] The technical solution of the present invention is as follows:

[0009] A nanometer Ca3Mn2O7 / Mn3O4 composite material and a preparation method thereof, comprising the following steps: taking a certain amount of MnCl2·4H2O and a certain amount of CaO2, placing them in a mortar, grinding and mixing them uniformly to obtain a solid mixture, then transferring the solid mixture to a blast drying oven for solid phase reaction, cooling the solid product to room temperature, washing it with water and ethanol for several times, and blast drying it to obtain the Ca3Mn2O7 / Mn3O4 composite material.

[0010] In a preferred embodiment of the present invention, the mass ratio of MnCl2·4H2O to CaO2 is 2:1-3.

[0011] In a preferred embodiment of the present invention, the grinding temperature is 20-40°C and the grinding time is 10-20 minutes.

[0012] In a preferred embodiment of the present invention, the temperature of the solid phase reaction is 80-100°C, and the reaction time is 1-2 h.

[0013] In a preferred embodiment of the present invention, the blast drying temperature is 70-90° C., and the drying time is 4-6 h.

[0014] Another technical solution of the present invention is as follows:

[0015] The nano-Ca3Mn2O7 / Mn3O4 composite material prepared by the above preparation method is used in treating organically contaminated groundwater.

[0016] Another technical solution of the present invention is as follows:

[0017] A method for treating organically contaminated groundwater, wherein the nano-Ca3Mn2O7 / Mn3O4 composite material is used as a catalyst to catalyze persulfate to degrade organic pollutants in groundwater.

[0018] In a preferred embodiment of the present invention, the persulfate is sodium persulfate.

[0019] The beneficial effects of the present invention are:

[0020] 1. The nano-Ca3Mn2O7 / Mn3O4 composite material prepared by the present invention can effectively activate persulfate to generate a large number of free radicals and efficiently degrade refractory organic pollutants in water.

[0021] 2. The nano-Ca3Mn2O7 / Mn3O4 composite material prepared by the present invention can release Ca 2+ , remove SO4 produced by persulfate oxidation process 2- , reduce secondary pollution.

[0022] 3. The nano-Ca3Mn2O7 / Mn3O4 composite material prepared by the present invention is alkaline in water and can neutralize the H generated in the persulfate oxidation process. + , reducing secondary pollution caused by acidification. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope photograph (SEM) of the nano-Ca3Mn2O7 / Mn3O4 composite material prepared in embodiment 1 of the present invention.

[0024] Figure 2 This is the X-ray diffraction pattern (XRD) of the nano-Ca3Mn2O7 / Mn3O4 composite material prepared in embodiment 1 of the present invention.

[0025] Figure 3 This is a SEM-EDS scan of the nano-Ca3Mn2O7 / Mn3O4 composite material prepared in embodiment 1 of the present invention.

[0026] Figure 4 This is a diagram showing the effects of treating aniline in water using different systems in Example 2 of the present invention.

[0027] Figure 5 It is the pH value of the aqueous solution under different system treatments in Example 3 of the present invention.

[0028] Figure 6 SO4 in aqueous solution treated by different systems in Example 4 of the present invention 2- concentration. DETAILED DESCRIPTION

[0029] Example 1

[0030] MnCl2·4H2O and CaO2 are placed in a mortar at a mass ratio of 2:1; the solid mixture is ground at 25°C for 15 minutes to obtain a solid mixture, and then the solid mixture is transferred to a forced air drying oven and subjected to solid phase reaction at 90°C for 1 hour. After the solid product is cooled to room temperature, it is washed with water and ethanol for 3 times respectively, and placed in a forced air drying oven for drying at 80°C for 4 hours to obtain the Ca3Mn2O7 / Mn3O4 composite material.

[0031] Depend on Figure 1 The scanning electron microscope (SEM) image of the nano-Ca3Mn2O7 / Mn3O4 composite material shows that the Ca3Mn2O7 / Mn3O4 composite material is amorphous nanoparticles with obvious agglomeration phenomenon.

[0032] Depend on Figure 2 The X-ray diffraction pattern (XRD) of the nano-Ca3Mn2O7 / Mn3O4 composite material shows that this material is a composite material of Ca3Mn2O7 and Mn3O4.

[0033] Figure 3 The SEM-EDS scanning diagram of the nano-Ca3Mn2O7 / Mn3O4 composite material prepared in Example 1 of the present invention also shows that this material is a composite material of Ca3Mn2O7 and Mn3O4.

[0034] Example 2

[0035] Experiment with the following groups.

[0036] PS group: At a temperature of 25°C and without adjusting the pH of the reaction system, 200 mL of 10 mg / L aniline solution was added to the reactor, and then sodium persulfate was added to a concentration of 1.0 g / L. After 4 hours of reaction, the water sample was taken out and filtered through a 0.22 μm organic filter membrane. The residual aniline concentration in the sample was detected by high performance liquid chromatography and the degradation efficiency was calculated. Figure 4 As shown, the degradation rate of aniline after 4 h was less than 10%;

[0037] Ca3Mn2O7@Mn3O4 group: under the condition of temperature of 25°C and without adjusting the pH of the reaction system, 200 mL of 10 mg / L aniline solution was added to the reactor, and then Ca3Mn2O7 / Mn3O4 prepared in Example 1 was added to a dosage of 0.25 g / L. After reacting for 4 h, a water sample was taken out, filtered through a 0.22 μm organic filter membrane, and the residual aniline concentration in the sample was detected by high performance liquid chromatography and the degradation efficiency was calculated; Figure 4 As shown, the degradation rate of aniline was 25% after 4 h;

[0038] Ca3Mn2O7@Mn3O4 / PS group: At a temperature of 25°C and without adjusting the pH of the reaction system, 200 mL of a 10 mg / L aniline solution was added to the reactor, and then Ca3Mn2O7 / Mn3O4 (0.25 g / L) and sodium persulfate (1.0 g / L) prepared in Example 1 were added respectively. After reacting for 4 h, a water sample was taken out and filtered through a 0.22 μm organic filter membrane. The residual aniline concentration in the sample was detected by a high performance liquid chromatograph and the degradation efficiency was calculated; Figure 4 As shown, the degradation rate of aniline after 4 hours was 95.6%.

[0039] Example 3

[0040] Experiment with the following groups.

[0041] PS group: At 25°C and without adjusting the pH of the reaction system, add 200 mL of 10 mg / L aniline solution to the reactor, and then add sodium persulfate to a concentration of 1.0 g / L. After reacting for 4 h, measure the pH value of the solution with a pH meter; Figure 5 As shown, the pH of the solution after 4 h was 3.73;

[0042] Ca3Mn2O7@Mn3O4-0.25 group: At 25°C and without adjusting the pH of the reaction system, 200 mL of 10 mg / L aniline solution was added to the reactor, and then Ca3Mn2O7 / Mn3O4 prepared in Example 1 was added to a dosage of 0.25 g / L. After reacting for 4 h, the pH value of the solution was measured with a pH meter; Figure 5 As shown, the pH of the solution after 4 h was 9.52;

[0043] Ca3Mn2O7@Mn3O4-0.25 / PS group: At 25°C and without adjusting the pH of the reaction system, 200 mL of 10 mg / L aniline solution was added to the reactor, and then Ca3Mn2O7 / Mn3O4 (0.25 g / L) and sodium persulfate (1.0 g / L) prepared in Example 1 were added. After reacting for 4 h, the pH value of the solution was measured with a pH meter; Figure 5 As shown, the pH of the solution after 4 h was 4.98;

[0044] Ca3Mn2O7@Mn3O4-0.5 / PS group: At 25°C and without adjusting the pH of the reaction system, 200 mL of 10 mg / L aniline solution was added to the reactor, and then Ca3Mn2O7 / Mn3O4 (0.50 g / L) and sodium persulfate (1.0 g / L) prepared in Example 1 were added. After reacting for 4 h, the pH value of the solution was measured with a pH meter; Figure 5 As shown, the pH of the solution after 4 h was 7.23;

[0045] Ca3Mn2O7@Mn3O4-1.0 / PS group: At 25°C and without adjusting the pH of the reaction system, 200 mL of 10 mg / L aniline solution was added to the reactor, and then Ca3Mn2O7 / Mn3O4 (1.0 g / L) and sodium persulfate (1.0 g / L) prepared in Example 1 were added. After reacting for 4 h, the pH value of the solution was measured with a pH meter; Figure 5 As shown, the pH of the solution after 4 h was 7.91.

[0046] Example 4

[0047] Experiment with the following groups.

[0048] PS group: At 25°C and without adjusting the pH of the reaction system, 200 mL of 10 mg / L aniline solution was added to the reactor, and then sodium persulfate was added to a concentration of 1.0 g / L. After 4 hours of reaction, the water sample was taken out and filtered through a 0.22 μm organic filter membrane. The SO4 in the sample was detected by ion chromatography. 2- concentration; e.g. Figure 6 As shown, after 4 hours, SO4 2- The concentration is 437 mg / L;

[0049] Ca3Mn2O7@Mn3O4-0.25 / PS group: At a temperature of 25°C and without adjusting the pH of the reaction system, 200 mL of 10 mg / L aniline solution was added to the reactor, and then Ca3Mn2O7 / Mn3O4 (0.25 g / L) and sodium persulfate (1.0 g / L) prepared in Example 1 were added respectively. After reacting for 4 h, the water sample was taken out and filtered through a 0.22 μm organic filter membrane. The SO4 in the sample was detected by ion chromatograph. 2- concentration; e.g. Figure 6 As shown, after 4 hours, SO4 2- The concentration is 114 mg / L;

[0050] Ca3Mn2O7@Mn3O4-0.5 / PS group: At 25°C and without adjusting the pH of the reaction system, 200 mL of 10 mg / L aniline solution was added to the reactor, and then Ca3Mn2O7 / Mn3O4 (0.50 g / L) and sodium persulfate (1.0 g / L) prepared in Example 1 were added. After 4 h of reaction, the water sample was taken out and filtered through a 0.22 μm organic filter membrane. The SO4 in the sample was detected by ion chromatograph. 2- concentration; e.g. Figure 6 As shown, after 4 hours, SO4 2- The concentration is 183 mg / L;

[0051] Ca3Mn2O7@Mn3O4-1.0 / PS group: At 25°C and without adjusting the pH of the reaction system, 200 mL of 10 mg / L aniline solution was added to the reactor, and then Ca3Mn2O7 / Mn3O4 (1.0 g / L) and sodium persulfate (1.0 g / L) prepared in Example 1 were added respectively. After reacting for 4 h, the water sample was taken out and filtered through a 0.22 μm organic filter membrane. The SO4 in the sample was detected by ion chromatograph. 2- concentration; e.g. Figure 6 As shown, after 4 hours, SO4 2- The concentration is 199mg / L.

[0052] The above description is only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of the present invention. That is, equivalent changes and modifications made according to the patent scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. The present invention discloses a method for preparing a nano-Ca3Mn2O7 / Mn3O4 composite material, characterized in that: The specific steps are as follows: taking a certain amount of MnCl2·4H2O and a certain amount of CaO2 and placing them in a mortar; grinding and mixing them evenly to obtain a solid mixture, then transferring the solid mixture to a blast drying oven for solid phase reaction, waiting for the solid product to cool to room temperature, washing the sample with water and ethanol, and blast drying to obtain the Ca3Mn2O7 / Mn3O4 composite material.

2. The method for preparing a nano-Ca3Mn2O7 / Mn3O4 composite material according to claim 1, characterized in that: The mass ratio of the MnCl2·4H2O to CaO2 is 2:1-3.

3. The method for preparing a nano-Ca3Mn2O7 / Mn3O4 composite material according to claim 1, characterized in that: The grinding temperature is 20-40°C, and the grinding time is 10-30min.

4. The method for preparing a nano-Ca3Mn2O7 / Mn3O4 composite material according to claim 1, characterized in that: The temperature of the solid phase reaction is 80-100° C., and the reaction time is 1-2 hours.

5. The method for preparing a nano-Ca3Mn2O7 / Mn3O4 composite material according to claim 1, characterized in that: The blast drying temperature is 70-90°C, and the drying time is 4-6h.

6. Application of the nano-Ca3Mn2O7 / Mn3O4 composite material prepared by any preparation method as described in any one of claims 1 to 5 in treating organically contaminated groundwater.

7. A method for treating organically contaminated groundwater, characterized in that: The nanometer Ca3Mn2O7 / Mn3O4 composite material is used as a catalyst to catalyze persulfate to degrade organic pollutants in groundwater.

8. The processing method according to claim 7, characterized in that: The persulfate is sodium persulfate.

9. The processing method according to claim 7, characterized in that: The organic pollutant is aniline.

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