A method and application for solvent-induced enhanced catalytic thermal desorption of organic pollutants from soil.

Abstract

This invention discloses a method and its application based on solvent-induced enhanced catalytic thermal desorption of organic pollutants from soil. A Cu-Mn-Ce / diatomite catalyst is prepared using refined diatomite as a carrier, wherein the copper-manganese-cerium composite oxide is the active component of the catalyst, potassium hydroxide is used as the complexing agent, and citric acid solution is used as the inducing solvent. The refined diatomite, potassium hydroxide, and the precursor solution of the catalytic active component are added to a polytetrafluoroethylene hydrothermal reactor, and the catalyst is prepared by stirring, hydrothermal synthesis, and drying. This method applies solvent-induced enhanced catalytic thermal desorption technology to soil remediation of contaminated sites. It not only significantly reduces the energy consumption of soil thermal desorption and eliminates the need for exhaust gas harmless treatment, but also features a simple process, high cost-effectiveness, and strong application and promotion value.

Description

Technical Field

[0001] This invention relates to a novel method for inducing thermal desorption of organic polluted soil and its application, belonging to the fields of environmentally friendly catalytic materials and soil remediation. Background Technology

[0002] With industrial and urbanization development, soil pollution has gradually attracted people's attention. Organic pollutants in the soil pose a serious threat to human health and environmental safety. Currently, methods for treating soil pollution include physical, chemical, and biological methods. Physical methods mainly include technologies such as thermal desorption, volatilization, leaching, and adsorption; chemical methods include technologies such as oxidation-reduction, acid-base neutralization, and complexation; biological methods mainly include technologies such as microbial degradation and phytoremediation. However, these methods all have some drawbacks, such as high energy consumption, high cost, low efficiency, and difficulty in adapting to complex environments.

[0003] Thermal desorption is a commonly used method for treating soil pollution. Its principle is to desorb organic pollutants from the soil into the gas or liquid phase by raising the soil temperature. However, as research into thermal desorption technology deepens, its high energy consumption and the generation of secondary pollutants are unavoidable problems in its application. Future research on thermal desorption technology will focus more on reducing desorption temperatures, lowering energy consumption, and improving desorption efficiency; and on evolving from single remediation technologies to remediation technologies that combine with multiple treatment methods, and ultimately, integrated remediation technologies.

[0004] Therefore, improving the efficiency and reducing the energy consumption of thermal desorption technology has become a key focus of research. In recent years, catalytic oxidation technology has been widely used in soil pollutant treatment. By mixing a catalyst with soil, the catalyst can catalyze the oxidation and decomposition of organic pollutants under specific temperature and oxygen conditions, thereby improving the efficiency of thermal desorption and reducing energy consumption. However, existing catalysts have some problems in soil application, such as low activity, poor stability, and significant impact on the soil. Therefore, there is an urgent need to develop a new, efficient, stable, and low-cost soil thermal desorption technology. Summary of the Invention

[0005] The purpose of this invention is to address the current status and existing problems of soil thermal desorption, and to propose a method for enhancing the catalytic thermal desorption of organic pollutants in soil based on solvent induction. Another purpose of this invention is to provide a method for preparing the above-mentioned catalyst and inducing solvent. A third purpose of this invention is to provide the above-mentioned method for thermal desorption of organic pollutants using a catalyst.

[0006] A catalyst for the thermal desorption of organic pollutants from soil based on solvent-induced enhancement is provided. The catalyst uses diatomaceous earth as a support, copper-manganese-cerium composite oxide as the active component of the catalyst, potassium hydroxide as a complexing agent, and citric acid solution as the inducing catalytic solvent.

[0007] Based on the support, the mass percentage of the catalyst active component in the support is 1% to 15%; the mass ratio of copper oxide, manganese dioxide and cerium oxide in the active component is 1:(1~10):(1~10).

[0008] The carrier described in the technical solution of this invention is diatomaceous earth with a particle size of 20-60 mesh; the concentration of the citric acid solution is 5wt%-15wt%.

[0009] In some preferred technical solutions, the mass percentage of the catalyst active component in the support is 5% to 10%; the mass ratio of copper oxide, manganese dioxide and cerium oxide in the active component is 1:(2 to 4):(1 to 2).

[0010] A method for preparing the above-mentioned catalyst, the method of which is as follows:

[0011] (1) Preparation of colloidal solution of active component

[0012] Copper salt, manganese salt, cerium salt and potassium permanganate were added to deionized water and stirred. At the same time, potassium hydroxide solution was added to make the pH of the reaction system 7-9, so as to obtain a colloidal solution of the active component.

[0013] (2) Catalyst preparation

[0014] The carrier and the colloidal solution of the active component prepared in step (1) are successively transferred to a polytetrafluoroethylene hydrothermal reactor for hydrothermal reaction. The mixture obtained after the reaction is placed in a forced-air drying oven for heat preservation and drying to obtain the catalyst.

[0015] (3) Preparation of inducing solvent

[0016] Based on the mass of deionized water, citric acid accounts for 5-15% of the mass of deionized water.

[0017] In the above preparation method: the copper salt mentioned in step (1) is copper nitrate trihydrate, the manganese salt is manganese nitrate, the cerium salt is cerium nitrate hexahydrate, and potassium permanganate is used as an oxidant.

[0018] In the above preparation method: the hydrothermal reaction temperature in step (2) is 80~190℃, the hydrothermal time is 8~24h; the drying temperature is 80~120℃; the drying time is 3~10h.

[0019] A method for thermal desorption of organic polluted soil using the above-mentioned catalyst is described. The method uses air as a carrier gas to bring the catalyst, inducing solvent and polluted soil into contact and perform thermal desorption. During the desorption process, the organic pollutants undergo decomposition reaction under the synergistic effect of the catalyst and inducing solvent. At the same time, the decomposed gas and the inducing solvent gas are separated and removed from the soil, thus completing the thermal desorption process of organic polluted soil.

[0020] In the above-mentioned method for thermal desorption of soil, the mass ratio of the catalyst, the inducing solvent and the contaminated soil is (0.05~0.2):(0.1~0.5):1.

[0021] In the above-mentioned method for thermal desorption of soil, the desorption temperature is 150~190°C and the desorption time is 10~20 min.

[0022] In the above-mentioned method for thermal desorption of soil, the organic pollutant is trichlorobenzene and / or dichlorophenol.

[0023] The thermal desorption experimental conditions and results of this invention: 5g of soil containing 5% trichlorobenzene or 5% dichlorophenol was placed in a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10mm, and hot air at 150~190℃ was introduced for performance evaluation. The soil heating temperature was also 150~190℃, and the amount of catalyst used was 0.5g. After thermal desorption at 190°C for 20min, the desorption efficiency of trichlorobenzene and dichlorophenol reached over 99%.

[0024] Beneficial effects:

[0025] The catalyst prepared by this invention has the following advantages:

[0026] (1) The inducing solvent used can decompose when heated to a certain temperature, and the catalyst can be recycled and reused without damaging the soil medium, which is in line with the concept of green and environmentally friendly materials.

[0027] (2) The inducing solvent and the catalyst have a synergistic effect, which can enhance the activity of the catalyst, thereby ensuring the efficient removal of trichlorobenzene and dichlorophenol, and also reducing the thermal desorption temperature of trichlorobenzene and dichlorophenol;

[0028] (3) The final products of the decomposition of pollutants in the soil are carbon dioxide, water and a small amount of hydrogen chloride, which can be directly discharged with simple treatment.

[0029] (4) K in the catalyst + It enhances the catalytic performance of manganese and cobalt active components, improves the selectivity of the active components of the catalyst for catalytic oxidation of chlorobenzene and o-xylene CO2, and the potassium salt formed after the catalytic reaction remains in the soil as potassium fertilizer to provide nutrients to the soil.

[0030] Therefore, the synergistic thermal desorption technology described in this invention can be regarded as a novel theoretical technology. Its principle is based on catalytic oxidation as the main method and solvent induction as the auxiliary method. The method of using solvent induction to enhance catalysis is used to optimize thermal desorption, which can effectively reduce the thermal desorption temperature and efficiency. It can not only significantly reduce the energy consumption of soil thermal desorption and reduce the cost of industrial thermal desorption, but also the catalyst component preparation process is simple, the cost is low, the cost performance is high, and it has strong application and promotion value. Attached Figure Description

[0031] Figure 1 This is a diagram of the experimental setup.

[0032] Figure 2 The graph shows the effect of the catalyst prepared in Example 1 on the removal rate of trichlorobenzene.

[0033] Figure 3 The graph shows the effect of the catalyst prepared in Example 1 on the removal rate of dichlorophenol. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto:

[0035] Example 1

[0036] (1) Preparation of colloidal solution of active component

[0037] Weigh 1.51g of copper nitrate trihydrate, 0.775g of manganese nitrate hexahydrate, 0.79g of potassium permanganate, and 1.63g of cerium nitrate hexahydrate and add them to 23.53g of deionized water. While stirring at room temperature, add potassium hydroxide to adjust the pH of the mixture to 7. After stirring for 30 minutes, the precursor of the active component is obtained. The mass ratio of copper oxide, manganese dioxide, and cerium oxide in the active component is 1:2:1.

[0038] (2) Preparation of catalyst and inducing solvent

[0039] Based on the quality of diatomaceous earth, and according to the mass percentage of active component to carrier mass of 5%, 100g of diatomaceous earth with a particle size of 20 mesh was weighed and transferred together with the ion solution of active component precursor obtained in step (1) into a 200ml polytetrafluoroethylene hydrothermal reactor. After hydrothermal reaction at 150℃ for 12h, it was taken out and cooled to room temperature. The precipitate was placed in a forced-air drying oven and kept at 100℃ for 4h to dry, thus obtaining the thermal desorption catalyst for organic polluted soil.

[0040] Weigh 5g of citric acid and add it to 95g of deionized water, then stir well at room temperature.

[0041] (3) Desorption efficiency test

[0042] Five grams of soil containing 5% trichlorobenzene and 5% dichlorophenol were respectively placed into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10 mm. 0.25 g of catalyst, 0.5 g of inducing solvent, and contaminated soil were mixed thoroughly and then introduced into the reaction device for performance evaluation. The thermal desorption temperature was 150–190 °C, and the air carrier gas flow rate was 400 mL / min. After thermal desorption at 190 °C for 20 min, the desorption efficiencies for trichlorobenzene and dichlorophenol were 99.4% and 99.1%, respectively. Figure 1 As shown.

[0043] Example 2

[0044] (1) Preparation of colloidal solution of active component

[0045] Weigh 1.51g of copper nitrate trihydrate, 1.1625g of manganese nitrate hexahydrate, 1.185g of potassium permanganate, and 1.63g of cerium nitrate hexahydrate and add them to 21.95g of deionized water. While stirring at room temperature, add potassium hydroxide to adjust the pH of the mixture to 8. After stirring for 30 minutes, the precursor of the active component is obtained. The mass ratio of copper oxide, manganese dioxide, and cerium oxide in the active component is 1:3:1.

[0046] (2) Preparation of catalyst and inducing solvent

[0047] Based on the quality of diatomaceous earth, and with the active component accounting for 7.5% of the carrier mass, 100g of diatomaceous earth with a particle size of 40 mesh was weighed and transferred together with the active component precursor ion solution obtained in step (1) into a 200ml polytetrafluoroethylene hydrothermal reactor. After hydrothermal reaction at 170℃ for 18h, it was taken out and cooled to room temperature. The precipitate was placed in a forced-air drying oven and kept at 110℃ for 6h to dry, thus obtaining a thermal desorption catalyst for organic polluted soil.

[0048] Weigh 10g of citric acid and add it to 90g of deionized water, then stir well at room temperature.

[0049] (3) Desorption efficiency test

[0050] Five grams of soil containing 5% trichlorobenzene and 5% dichlorophenol were respectively loaded into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10 mm. 0.5 g of catalyst, 1.5 g of inducing solvent, and contaminated soil were mixed thoroughly and then introduced into the reaction device for performance evaluation. The thermal desorption temperature was 150–190 °C, and the air carrier gas flow rate was 400 mL / min. After thermal desorption at 190 °C for 20 min, the desorption efficiencies for trichlorobenzene and dichlorophenol were 99.5% and 99.2%, respectively.

[0051] Example 3

[0052] (1) Preparation of colloidal solution of active component

[0053] Weigh 1.51g of copper nitrate trihydrate, 1.55g of manganese nitrate hexahydrate, 1.58g of potassium permanganate, and 3.26g of cerium nitrate hexahydrate and add them to 23.7g of deionized water. While stirring at room temperature, add potassium hydroxide to adjust the pH of the mixture to 9. After stirring for 30 minutes, the precursor of the active component is obtained. The mass ratio of copper oxide, manganese dioxide, and cerium oxide in the active component is 1:4:2.

[0054] (2) Preparation of catalyst and inducing solvent

[0055] Based on the quality of diatomaceous earth, and with the active component accounting for 10% of the carrier mass, 100g of diatomaceous earth with a particle size of 40 mesh was weighed and transferred together with the active component precursor ion solution obtained in step (1) into a 200ml polytetrafluoroethylene hydrothermal reactor. After hydrothermal reaction at 190℃ for 24h, it was taken out and cooled to room temperature. The precipitate was placed in a forced-air drying oven and kept at 120℃ for 8h to dry, thus obtaining a thermal desorption catalyst for organic polluted soil.

[0056] Weigh 15g of citric acid and add it to 85g of deionized water, then stir well at room temperature.

[0057] (3) Desorption efficiency test

[0058] Five grams of soil containing 5% trichlorobenzene and 5% dichlorophenol were respectively loaded into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10 mm. One gram of catalyst, 2.5 grams of inducing solvent, and contaminated soil were mixed thoroughly and then introduced into the reaction device for performance evaluation. The thermal desorption temperature was 150–190 °C, and the air carrier gas flow rate was 400 mL / min. After thermal desorption at 190 °C for 20 min, the desorption efficiencies for trichlorobenzene and dichlorophenol were 99.6% and 99.3%, respectively.

[0059] Comparative Example 1

[0060] (1) Preparation of precursor solution of active component

[0061] Except that potassium permanganate was not added during the preparation of the active component precursor solution, the other conditions were the same as in Example 1;

[0062] (2) Catalytic activity test

[0063] 5g of soil containing 5% trichlorobenzene and dichlorophenol were respectively loaded into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10mm, and the thermal desorption temperature was 150~190℃. The desorption efficiency of trichlorobenzene and dichlorophenol after 20min of thermal desorption at 190℃ was 79.2% and 76.3%, respectively.

[0064] (3) Comparison effect

[0065] Compared with Example 1, the desorption rates of trichlorobenzene and dichlorophenol decreased by 20.2% and 22.8%, respectively. If potassium permanganate is not added as an oxidant during the preparation of the active component precursor solution, the catalyst will not have redox properties, resulting in reduced activity.

[0066] Comparative Example 2

[0067] (1) Preparation of precursor solution of active component

[0068] Except that potassium hydroxide was not added during the preparation of the active component precursor solution, the other conditions were the same as in Example 2;

[0069] (2) Catalytic activity test

[0070] 5g of soil containing 5% trichlorobenzene and dichlorophenol were respectively loaded into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10mm, and the thermal desorption temperature was 150~190℃. The desorption efficiency of trichlorobenzene and dichlorophenol after 20min of thermal desorption at 190℃ was 80.4% and 79.6%, respectively.

[0071] (3) Comparison effect

[0072] Compared with Example 2, the desorption rates of trichlorobenzene and dichlorophenol decreased by 19.1% and 19.6%, respectively. If potassium hydroxide is not added as a complexing agent during the preparation of the active component precursor solution, the catalyst activity decreases.

[0073] Comparative Example 3

[0074] (1) Preparation of catalyst and inducing solvent

[0075] Except for not using an inducing solvent, the other conditions are the same as in Example 3;

[0076] (2) Catalytic activity test

[0077] 5g of soil containing 5% trichlorobenzene and dichlorophenol were respectively loaded into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10mm, and the thermal desorption temperature was 150~190℃. The desorption efficiency of trichlorobenzene and dichlorophenol after 20min of thermal desorption at 190℃ was 83.4% and 81.2%, respectively.

[0078] (3) Comparison effect

[0079] Compared with Example 3, the desorption rates of trichlorobenzene and dichlorophenol decreased by 16.2% and 18.1%, respectively. The catalytic activity of the catalyst decreased if citric acid was not used as the inducing solvent.

Claims

1. A catalyst for solvent-induced enhanced catalytic thermal desorption of organic pollutants from soil, characterized in that: Diatomaceous earth was used as a carrier, copper-manganese-cerium composite oxide was used as the active component of the catalyst, potassium hydroxide was used as a complexing agent, and citric acid solution was used as an inducing catalytic solvent. Based on the support, the mass percentage of the catalyst active component in the support is 1% to 15%; the mass ratio of copper oxide, manganese dioxide and cerium oxide in the active component is 1:(1~10):(1~10).

2. The catalyst according to claim 1, characterized in that: The particle size of diatomaceous earth is 20-60 mesh; the concentration of citric acid solution is 5wt%-15wt%.

3. The catalyst according to claim 1, characterized in that... The active component of the catalyst accounts for 5% to 10% of the mass of the support; among which, the mass ratio of copper oxide, manganese dioxide and cerium oxide in the active component is 1:(2 to 4):(1 to 2).

4. A method for preparing the catalyst according to claim 1, characterized in that: The catalyst is prepared as follows: (1) Preparation of colloidal solution of active component Copper salt, manganese salt, cerium salt and potassium permanganate were added to deionized water and stirred. At the same time, potassium hydroxide solution was added to make the pH of the reaction system 7-9, so as to obtain a colloidal solution of the active component. (2) Preparation of catalyst The carrier and the colloidal solution of the active component prepared in step (1) are successively transferred to a polytetrafluoroethylene hydrothermal reactor for hydrothermal reaction. The mixture obtained after the reaction is placed in a forced-air drying oven for heat preservation and drying to obtain the catalyst. (3) Preparation of inducing solvent Based on the mass of deionized water, citric acid accounts for 5-15% of the mass of deionized water.

5. The preparation method according to claim 4, characterized in that: The copper salt mentioned in step (1) is copper nitrate trihydrate, the manganese salt is manganese nitrate, the cerium salt is cerium nitrate hexahydrate, and potassium permanganate is used as an oxidant.

6. The preparation method according to claim 4, characterized in that: The hydrothermal reaction temperature in step (2) is 80~190℃, and the hydrothermal time is 8~24h; the drying temperature is 80~120℃, and the drying time is 3~10h.

7. A method for thermal desorption of organic polluted soil using the catalyst described in claim 1, characterized in that: This method uses air as a carrier gas to bring the catalyst, inducing solvent, and contaminated soil into contact and perform thermal desorption. During the desorption process, the organic pollutants undergo decomposition reactions under the synergistic effect of the catalyst and inducing solvent. At the same time, the decomposed gases and the inducing solvent gases are separated and removed from the soil, thus completing the thermal desorption process of organically contaminated soil.

8. The method according to claim 7, characterized in that: The mass ratio of the catalyst, inducing solvent, and contaminated soil is (0.05~0.2):(0.1~0.5):

1.

9. The method according to claim 7, characterized in that: The desorption temperature is 150~190°C, and the desorption time is 10~20 min.

10. The method according to claim 8, characterized in that: The organic pollutants mentioned are trichlorobenzene and / or dichlorophenol.

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