Method for screening activated carbon to remove manganese through catalytic oxychlorination

Abstract

The invention provides a method for screening activated carbon to catalyze chlorine oxidation to remove manganese, and belongs to the technical field of water treatment, catalysis and computational chemistry. The method for screening the activated carbon for catalytic manganese removal comprises the following steps: acquiring different physicochemical characteristic indexes of different activated carbon, wherein the physicochemical characteristic indexes are obtained by performing physicochemical characterization on the activated carbon; manganese removal efficiency indexes of different activated carbon are obtained, wherein the manganese removal efficiency indexes are obtained through tests of activated carbon catalytic oxychlorination manganese removal; performing correlation analysis on different physicochemical characteristic indexes and manganese removal efficiency indexes of different activated carbon, and determining a decisive index of activated carbon catalytic oxychlorination manganese removal according to a Pearson's correlation coefficient; performing linear regression fitting on at least one index in the decisive indexes and a manganese removal efficiency index to obtain a fitting coefficient; and screening out target activated carbon suitable for catalytic manganese removal according to the fitting coefficient, and predicting the catalytic oxychlorination manganese removal efficiency of the target activated carbon.

Description

Technical Field

[0001] The present disclosure belongs to the fields of water treatment, catalysis, and computational chemistry, and particularly relates to a method for screening activated carbon for catalytic manganese removal by chlorine oxidation. Background Art

[0002] Manganese (Mn) is a transition metal element with multiple oxidation states, and Mn(II) is one of its most common stable oxidation states. In water, especially in a more reducing environment (such as groundwater), Mn(II) is the main manganese form, and its excessive concentration can have many adverse effects on human health and the ecological environment. Powdered activated carbon, as an adsorbent material with a rich pore structure and a large specific surface area, has been widely used in the field of water treatment. However, the application research on powdered activated carbon materials in catalytic removal of Mn(II) in water is not deep enough, especially the relationship between the pore structure, surface functional groups, chlorine attenuation and other influencing factors of powdered activated carbon materials and the catalytic rate is not clear. Therefore, it is urgent to deeply explore the influence of these factors on Mn(II) removal, determine the key influencing factors, so as to screen out powdered activated carbon materials with high catalytic performance for manganese removal by chlorine oxidation, improve the rate of catalytic removal of Mn(II) in water by powdered activated carbon, and provide more effective technical means for solving the problem of Mn(II) pollution in water bodies. Summary of the Invention

[0003] In view of the above technical problems, the present disclosure provides a method for screening activated carbon for catalytic manganese removal by chlorine oxidation, in order to at least partially solve the above technical problems. For this, the technical solutions provided by the present disclosure are as follows.

[0004] According to an embodiment of the present disclosure, a method for screening activated carbon for catalytic manganese removal is provided, including: obtaining different physicochemical characteristic indexes of different activated carbons, where the physicochemical characteristic indexes are obtained by physicochemical characterization of the activated carbons; obtaining the manganese removal efficiency indexes of different activated carbons, where the manganese removal efficiency indexes are obtained by testing the catalytic manganese removal by chlorine oxidation of the activated carbons; performing a correlation analysis on the different physicochemical characteristic indexes and the manganese removal efficiency indexes of different activated carbons to determine the decisive indexes for catalytic manganese removal by chlorine oxidation of the activated carbons; performing a linear regression fitting on at least one of the decisive indexes and the manganese removal efficiency indexes to obtain a fitting coefficient; screening out target activated carbons suitable for catalytic manganese removal by chlorine oxidation according to the fitting coefficient, and predicting the catalytic manganese removal efficiency of the target activated carbons.

[0005] In the embodiment of the present disclosure, by obtaining different physicochemical characteristic indexes of different activated carbons and the manganese removal efficiency indexes obtained by testing the application of catalytic chlorine oxidation to manganese removal in the activated carbons, and performing analysis to screen out higher target activated carbons for catalytic manganese removal by chlorine oxidation, thereby improving the manganese removal efficiency of the target activated carbons, and also providing a direction for the structural design of the activated carbons and guiding the production of the activated carbons. Description of the Drawings

[0006] Figure 1 Schematic flow chart of the method for screening activated carbon for catalytic manganese removal in the embodiments of the present disclosure;

[0007] Figure 2 Schematic flow chart of the treatment method for raw water containing Mn(II) in the embodiments of the present disclosure;

[0008] Figure 3 Relationship diagram between the physicochemical characteristic indexes and manganese removal efficiency indexes of different carbon materials in the embodiments of the present disclosure;

[0009] Figure 4 Linear fitting diagram of the specific surface area of carbon materials and the catalytic Mn(II) removal rate in the embodiments of the present disclosure;

[0010] Figure 5 Linear fitting diagram of the surface functional groups of carbon materials and the catalytic Mn(II) removal rate in the embodiments of the present disclosure;

[0011] Figure 6 Linear fitting diagram of the catalytic Mn(II) removal rate of carbon materials and the chlorine decay rate in the embodiments of the present disclosure. Detailed Description of the Embodiments

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is obvious that one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.

[0013] Mn(II) is one of the common Mn forms in water. Long-term drinking of water with excessive Mn(II) may cause health problems such as nervous system damage and cognitive dysfunction, and at the same time, it will also harm the growth and reproduction of aquatic organisms. Secondly, the residual Mn(II) in the factory water will continue to transform and deposit on the pipe wall after entering the pipe network, causing yellow water and black water in the pipe network when the hydraulic conditions change. Therefore, developing an efficient method for removing Mn(II) from water has important practical significance.

[0014] At present, the methods for removing Mn(II) from water mainly include chemical precipitation method, ion exchange method, adsorption method, oxidation method, etc. Among them, the oxidation method has received extensive attention due to its advantages such as simple operation and high removal rate. Chlorine oxidation is one of the commonly used oxidation methods. Through the redox reaction between chlorine and Mn(II), Mn(II) is converted into water-insoluble Mn(IV) oxide, thereby achieving the removal of Mn(II). However, the traditional chlorine oxidation method has some limitations, such as slow reaction rate, low utilization rate of chlorine, and the removal rate of Mn(II) needs to be further improved, etc.

[0015] Powdered activated carbon not only has good adsorption performance, but also exhibits certain catalytic activity under certain conditions. However, the mechanism of activated carbon-catalyzed chlorine oxidation for manganese removal is not yet clear. In particular, the relationship between the pore structure, surface functional groups of powdered activated carbon materials, and factors such as chlorine rate decay and the catalytic rate is not clear, resulting in room for further improvement in the performance of existing activated carbon-catalyzed chlorine oxidation for manganese removal. In addition, there are a variety of current powdered activated carbon types, and the selection of carbon materials for efficient Mn(II) removal will directly determine the treatment cost and efficiency.

[0016] In response to this, the present disclosure uses the method of computational chemistry. By using the physical and chemical characteristic indexes of activated carbon and the manganese removal efficiency indexes obtained from the test of activated carbon-catalyzed chlorine oxidation applied to manganese removal, to screen out high-efficiency target activated carbon suitable for catalytic chlorine oxidation for manganese removal, clarify the mechanism of activated carbon for manganese removal, and provide solutions for improving the manganese removal efficiency of activated carbon, the activated carbon structure design and production.

[0017] Figure 1 It is a schematic flow chart of the method for screening activated carbon for catalytic manganese removal in the embodiments of the present disclosure.

[0018] As Figure 1 shown, the method for screening activated carbon for catalytic manganese removal in the present disclosure includes: Step S1 - Step S5.

[0019] Step S1: Obtain different physical and chemical characteristic indexes of different activated carbons, and the physical and chemical characteristic indexes are obtained through physical and chemical characterization of the activated carbon.

[0020] Step S2: Obtain the manganese removal efficiency indexes of different activated carbons, and the manganese removal efficiency indexes are obtained through the test of activated carbon-catalyzed chlorine oxidation for manganese removal.

[0021] Step S3: Conduct a correlation analysis on different physical and chemical characteristic indexes and manganese removal efficiency indexes of different activated carbons to determine the decisive indexes for activated carbon-catalyzed chlorine oxidation for manganese removal.

[0022] Step S4: Perform linear regression fitting on at least one of the decisive indexes and the manganese removal efficiency indexes to obtain the fitting coefficient.

[0023] Step S5: Select the target activated carbon suitable for catalytic oxidation of manganese by chlorine according to the fitting coefficient, and predict the catalytic oxidation efficiency of the target activated carbon for manganese removal by chlorine.

[0024] In the embodiments of the present disclosure, by obtaining different physical and chemical characteristic indexes of different activated carbons and the manganese removal efficiency indexes obtained from the test of applying catalytic oxidation of chlorine by activated carbon to manganese removal, and performing correlation analysis, the decisive indexes with relatively high correlation with catalytic oxidation of chlorine by activated carbon for manganese removal can be determined. Further, at least one of the decisive indexes is linearly regressed and fitted with the manganese removal efficiency index to obtain a fitting coefficient to clarify the relationship between the decisive index and the manganese removal efficiency, so as to determine the target activated carbon suitable for catalytic oxidation of chlorine for manganese removal according to the fitting coefficient, improve the catalytic oxidation efficiency of the target activated carbon for manganese removal by chlorine, and also provide a solution for future production and / or design of activated carbon with higher catalytic activity.

[0025] According to the embodiments of the present disclosure, in step S1, the sources of the activated carbon include at least one of woody (such as coconut shell, fruit shell, wood), coal-based (such as anthracite, bituminous coal), petroleum coke, peat, bone char (such as animal bone char), synthetic carbon-based materials (such as resin-based, carbon fiber), bamboo charcoal, crops (such as rice husk, straw), and other biomass materials that can form activated carbon can also be used, which will not be elaborated here. After being crushed and ground, activated carbon with a particle size less than 10 - 1000 mesh (i.e., 10 μm - 2000 μm) is obtained, and activated carbon with a lower particle size and higher catalytic activity can also be used. Further, the activated carbon can be commercially available activated carbon, activated carbon converted from biomass, ultrasonically strengthened activated carbon, or activated carbon secondarily activated by steam. Obtaining ultrasonically strengthened activated carbon includes: performing ultrasonic treatment on a suspension made of activated carbon and water, where the power of the ultrasonic treatment is 150 - 2000 W, the frequency is 20 - 100 kHz, and the time is 1 min - 60 min. Obtaining activated carbon secondarily activated by steam includes: placing the activated carbon in an inert reactor, introducing steam to activate at 800 - 900 °C for 0.5 - 1.5 h, where the reactor can be a tubular furnace, and the flow rate of the steam is 1 - 100 mL / min.

[0026] According to an embodiment of the present disclosure, in step S1, the physical and chemical characteristic indexes of the activated carbon can be stored in a database, and these data can be retrieved from the database before analysis. These data can be stored in the database in the form of a table. The physical and chemical characteristic indexes include physical characteristic indexes and chemical characteristic indexes; among them, the physical characteristic indexes include at least one of the specific surface area, micropore specific surface area, small mesopore specific surface area, and pore size contribution rate; the pore size contribution rate represents the ratio of the sum of the micropore specific surface area and the small mesopore specific surface area to the specific surface area, that is, (micropore specific surface area + small mesopore specific surface area) / specific surface area. The specific surface area of the activated carbon is mainly contributed by the specific surface areas of micropores and small mesopores. Among them, the micropore pore size range is 0-2 nm, and the small mesopore pore size range is 2-5 nm. The chemical characteristic indexes include at least one of the total functional group content, hydroxyl functional group content, carboxyl functional group content, and lactone group functional group content. The physical and chemical characteristic indexes can be obtained by performing physical and chemical characterization on the activated carbon. The methods of physical and chemical characterization can include, for example, non-local density functional theory (NLDFT), Boehm titration method, Fourier transform infrared spectroscopy (FT-IR), etc.

[0027] According to an embodiment of the present disclosure, in step S2, the manganese removal efficiency indexes include the manganese removal rate index and the chlorine attenuation rate index. Among them, both the manganese removal rate index and the chlorine attenuation rate index are used to measure the effect of activated carbon-catalyzed manganese removal. The manganese removal rate index and the chlorine attenuation rate index can be obtained by measuring the concentrations of manganese and chlorine in the water body before and after the activated carbon-catalyzed chlorine oxidation of manganese removal reaction.

[0028] According to an embodiment of the present disclosure, in step S2, the activated carbon-catalyzed chlorine oxidation of manganese removal includes: after mixing the activated carbon with the manganese-containing water body evenly, adding a chlorine oxidant and adjusting the pH to carry out the catalytic chlorine oxidation reaction to achieve the removal of manganese in the water body. Among them, the chlorine oxidant is selected from sodium hypochlorite or liquid chlorine; during the catalytic chlorine oxidation reaction process, the reaction system is fully mixed by stirring or aeration. After the reaction is completed, the separation of the activated carbon and the water body to be tested can be achieved by solid-liquid separation methods, such as one or more of gravity sedimentation, filtration separation, and centrifugal separation. The temperature of the catalytic chlorine oxidation reaction is 0-50 °C, preferably 5-35 °C (i.e., close to the temperature of natural water bodies), and the pH is adjusted to 6.5-9. The dosage of the activated carbon and available chlorine varies with the concentration of Mn(II) in the manganese-containing water body to be treated. For example, the concentration of manganese in the water body is 0.05-1000 mg / L, the concentration of the activated carbon is 1-1000 mg / L, and the concentration of available chlorine in the water body is 1-1000 mg / L. By optimizing the temperature, pH value, and reaction time of the activated carbon-catalyzed chlorine oxidation of manganese removal, the oxidation conversion of Mn(II) is accelerated, the efficient removal of Mn(II) in water is achieved, and a better Mn(II) removal rate and effect are obtained.

[0029] According to an embodiment of the present disclosure, in step S3, a correlation analysis is performed on different physical and chemical characteristic indexes and manganese removal efficiency indexes of different activated carbons to determine the decisive indexes for catalytic manganese removal by activated carbon, including: performing a correlation analysis on different physical characteristic indexes, different chemical characteristic indexes, and manganese removal efficiency indexes of different activated carbons to obtain Pearson correlation coefficients; and determining the decisive indexes from the physical characteristic indexes, chemical characteristic indexes, and manganese removal efficiency indexes according to the Pearson correlation coefficients. Among them, the decisive indexes include at least one of the chlorine attenuation rate index, specific surface area, small mesopore specific surface area, pore size contribution rate, and micropore specific surface area. For example: performing a correlation analysis on different physical characteristic indexes (such as specific surface area, small mesopore specific surface area, etc.) of different activated carbons and the manganese removal rate to obtain the Pearson correlation coefficient reflecting the correlation degree between the physical characteristic index and the manganese removal rate, and then being able to determine the decisive index related to the manganese removal rate from the physical characteristic indexes. For example, the decisive index is the total specific surface area of the activated carbon. Similarly, the chemical characteristic indexes can also adopt the same method, and the correlation characteristic indexes can also be determined therefrom.

[0030] According to an embodiment of the present disclosure, the decisive indexes are determined from the physical characteristic indexes, chemical characteristic indexes, and manganese removal efficiency indexes according to the Pearson correlation coefficient. Specifically, for example: a preset Pearson correlation coefficient threshold (such as 0.9 - 1) is set, and the physical characteristic indexes, chemical characteristic indexes, and / or manganese removal efficiency indexes above the preset Pearson correlation coefficient threshold are determined as the decisive indexes of the activated carbon.

[0031] Furthermore, through analysis, it is found that in some embodiments, there is a positive correlation between the manganese removal rate index and the chlorine attenuation index, that is, the greater the chlorine attenuation rate, the higher the manganese removal rate. In addition, in some embodiments, there is also a correlation between the physical characteristic indexes and the chemical characteristic indexes. For example, the chlorine attenuation rate is positively correlated with the specific surface area of the activated carbon. The larger the specific surface area, the faster the chlorine attenuation rate.

[0032] According to an embodiment of the present disclosure, in steps S4 and S5, the target activated carbon suitable for catalytic chlorine oxidation manganese removal is selected according to the fitting coefficient, including: selecting the target activated carbon suitable for catalytic chlorine oxidation manganese removal according to the magnitude of the fitting coefficient, where the fitting coefficient is the correlation coefficient R 2 . For example: when the fitting coefficient of the decisive index and the manganese removal efficiency index in the linear fitting is a positive number or the larger the value, it indicates that the larger the value of the decisive index, the more beneficial it is to improve the catalytic chlorine oxidation manganese removal efficiency of the activated carbon. Therefore, the activated carbon corresponding to the maximum value of the decisive index can be selected as the target activated carbon, and the catalytic chlorine oxidation manganese removal efficiency of the target activated carbon can be determined. The target activated carbon has a high specific surface area and a rich pore structure, making it have high catalytic performance. Subsequently, the target activated carbon is applied to catalytic manganese removal, obtaining a high manganese removal efficiency and using less amount of the target activated carbon.

[0033] The following further elaborates in detail on the method for screening powdered activated carbon materials to catalyze the oxidation of chlorine for removing Mn(II) provided by the present disclosure in combination with specific embodiments and the accompanying drawings.

[0034] In the embodiments of the present disclosure, the pretreatment of the obtained coal-based material and straw activated carbon (PAC) includes: grinding the obtained coal-based material and straw activated carbon (PAC) to fully powderize the raw materials for subsequent screening. Washing the ground activated carbon with ultrapure water to remove pollutants and / or impurities in the powdered activated carbon, thereby purifying the powdered activated carbon. Subsequently, placing the washed powdered activated carbon in an environment at 60°C and drying it at a constant temperature for 12 h to keep the powdered activated carbon in a dry state. Further, screening the dried powdered activated carbon with a 200-mesh sieve to obtain powdered activated carbon with a particle size <200 mesh (75 μm). The activated carbon obtained after screening is stored dry for later use in modification treatment. Among them, the coal-based material is provided by a certain water supply company, and the straw carbon material is purchased from a certain activated carbon company. The method provided by the present disclosure can also be used for the straw carbon material or coal-based material purchased from other companies.

[0035] Figure 2 It is a schematic flow chart of the treatment method for raw water containing Mn(II) in the disclosed embodiments.

[0036] As Figure 2 shown, the activated carbon is screened based on physical characteristic indexes (such as pore structure), chemical characteristic indexes (such as chlorine attenuation), and functional groups to obtain the target activated carbon (abbreviated as "carbon material" in the embodiments). Subsequently, the carbon material is used in combination with available chlorine (sodium hypochlorite) to carry out the manganese removal reaction in water.

[0037] Example 1

[0038] Perform physicochemical characterization on carbon material 1.

[0039] Take 1 L of 25°C aqueous solution (pH = 7.8) containing 0.4 mg / L Mn(II), add 10 mg / L of carbon material 1 (untreated coal-based PAC) and 2.0 mg / L of available chlorine to it simultaneously, mix evenly, after reacting for 60 minutes, filter through a membrane, and use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual Mn(II) concentration in the filtered solution. Calculate the Mn(II) removal rate and chlorine attenuation rate by kinetic fitting. The specific test results and the physicochemical characterization results of carbon material 1 are shown in Tables 1 and 2.

[0040] Example 2

[0041] Perform physicochemical characterization on carbon material 2.

[0042] Take 1 L of an aqueous solution at 25 °C (pH = 7.8) containing 0.4 mg / L of Mn(II). Add 10 mg / L of carbon material 2 (nitric acid-modified coal-based PAC) and 2.0 mg / L of available chlorine to it simultaneously, mix evenly, after reacting for 60 minutes, filter through a membrane, and use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual Mn(II) concentration in the filtered solution. Calculate the Mn(II) removal rate and chlorine decay rate by kinetic fitting. Specifically, the test results and the physicochemical characterization results of carbon material 2 are shown in Table 1 and Table 2.

[0043] Example 3

[0044] Perform physicochemical characterization on carbon material 3.

[0045] Take 1 L of an aqueous solution at 25 °C (pH = 7.8) containing 0.4 mg / L of Mn(II). Add 10 mg / L of carbon material 3 (sodium hydroxide-modified coal-based PAC) and 2.0 mg / L of available chlorine to it simultaneously, mix evenly, after reacting for 60 minutes, filter through a membrane, and use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual Mn(II) concentration in the filtered solution. Calculate the Mn(II) removal rate and chlorine decay rate by kinetic fitting. Specifically, the test results and the physicochemical characterization results of carbon material 3 are shown in Table 1 and Table 2.

[0046] Example 4

[0047] Perform physicochemical characterization on carbon material 4.

[0048] Take 1 L of an aqueous solution at 25 °C (pH = 7.8) containing 0.4 mg / L of Mn(II). Add 10 mg / L of carbon material 4 (steam secondary activation-modified coal-based PAC) and 2.0 mg / L of available chlorine to it simultaneously, mix evenly, after reacting for 60 minutes, filter through a membrane, and use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual Mn(II) concentration in the filtered solution. Calculate the Mn(II) removal rate and chlorine decay rate by kinetic fitting. Specifically, the test results and the physicochemical characterization results of carbon material 4 are shown in Table 1 and Table 2.

[0049] Example 5

[0050] Perform physicochemical characterization on carbon material 5.

[0051] Take 1 L of an aqueous solution at 25 °C (pH = 7.8) containing 0.4 mg / L of Mn(II). Add 10 mg / L of carbon material 5 (ultrasonic-treated modified coal-based PAC) and 2.0 mg / L of available chlorine to it simultaneously. Mix evenly. After reacting for 60 minutes, filter through a membrane. Use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual Mn(II) concentration in the filtered solution. Calculate the Mn(II) removal rate and chlorine decay rate by kinetic fitting. Specifically, the test results and the physicochemical characterization results of carbon material 5 are shown in Tables 1 and 2.

[0052] Example 6

[0053] Perform physicochemical characterization on carbon material 6.

[0054] Take 1 L of an aqueous solution at 25 °C (pH = 7.8) containing 0.4 mg / L of Mn(II). Add 10 mg / L of carbon material 6 (coal-based PAC with secondary steam activation followed by ultrasonic treatment) and 2.0 mg / L of available chlorine to it simultaneously. Mix evenly. After reacting for 60 minutes, filter through a membrane. Use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual Mn(II) concentration in the filtered solution. Calculate the Mn(II) removal rate and chlorine decay rate by kinetic fitting. Specifically, the test results and the physicochemical characterization results of carbon material 6 are shown in Tables 1 and 2.

[0055] Example 7

[0056] Perform physicochemical characterization on carbon material 7.

[0057] Take 1 L of an aqueous solution at 25 °C (pH = 7.8) containing 0.4 mg / L of Mn(II). Add 10 mg / L of carbon material 7 (untreated straw PAC) and 2.0 mg / L of available chlorine to it simultaneously. Mix evenly. After reacting for 60 minutes, filter through a membrane. Use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual Mn(II) concentration in the filtered solution. Calculate the Mn(II) removal rate and chlorine decay rate by kinetic fitting. Specifically, the test results and the physicochemical characterization results of carbon material 7 are shown in Tables 1 and 2.

[0058] Example 8

[0059] Perform physicochemical characterization on carbon material 8.

[0060] Take 1 L of an aqueous solution at 25 °C containing 0.4 mg / L of Mn(II) (pH = 7.8), add 10 mg / L of carbon material 8 (steam secondary activated straw PAC) and 2.0 mg / L of available chlorine to it simultaneously, mix evenly, after reacting for 60 minutes, filter through a membrane, and use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual Mn(II) concentration in the filtered solution. Calculate the Mn(II) removal rate and chlorine decay rate by kinetic fitting. Specifically, the test results and the physicochemical characterization results of carbon material 8 are shown in Table 1 and Table 2.

[0061] Example 9

[0062] Carry out physicochemical characterization on carbon material 9.

[0063] Take 1 L of an aqueous solution at 25 °C containing 0.4 mg / L of Mn(II) (pH = 7.8), add 10 mg / L of carbon material 9 (ultrasonic-treated straw PAC) and 2.0 mg / L of available chlorine to it simultaneously, mix evenly, after reacting for 60 minutes, filter through a membrane, and use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual Mn(II) concentration in the filtered solution. Calculate the Mn(II) removal rate and chlorine decay rate by kinetic fitting. Specifically, the test results and the physicochemical characterization results of carbon material 9 are shown in Table 1 and Table 2.

[0064] Example 10

[0065] Carry out physicochemical characterization on carbon material 10.

[0066] Take 1 L of an aqueous solution at 25 °C containing 0.4 mg / L of Mn(II) (pH = 7.8), add 10 mg / L of carbon material 10 (first steam secondary activated and then ultrasonic-treated - straw PAC) and 2.0 mg / L of available chlorine to it simultaneously, mix evenly, after reacting for 60 minutes, filter through a membrane, and use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual Mn(II) concentration in the filtered solution. Calculate the Mn(II) removal rate and chlorine decay rate by kinetic fitting. Specifically, the test results and the physicochemical characterization results of carbon material 10 are shown in Table 1 and Table 2.

[0067] The physicochemical characteristic indexes of different carbon materials in the above Examples 1 - 10, as well as the Mn removal efficiency indexes of different carbon materials for catalytic chlorine oxidation of manganese removal, are shown in Table 1 and Table 2 for the test results.

[0068] Table 1

[0069]

[0070] Table 2

[0071]

[0072] Furthermore, correlation analysis was performed on the physical and chemical characteristic indexes and manganese removal rate indexes of different carbon materials in Table 1 and Table 2 to determine the decisive indexes for the removal of manganese by activated carbon-catalyzed chlorine oxidation.

[0073] Figure 3 This is a relationship diagram of the physical and chemical characteristic indexes and manganese removal rate indexes of different carbon materials in the embodiments of the present disclosure.

[0074] Correlation analysis was carried out on the physical characteristic indexes, chemical characteristic indexes, and manganese removal efficiency indexes of different carbon materials to obtain the Pearson correlation coefficient (such as the values in Figure 3 ); based on the Pearson correlation coefficient (0.9 - 1.0), the decisive indexes were determined from the physical characteristic indexes, chemical characteristic indexes, and manganese removal efficiency indexes. As can be seen from Figure 3 , the decisive indexes for the removal of manganese by activated carbon-catalyzed chlorine oxidation include: chlorine decay rate, micropore specific surface area, small mesopore specific surface area, specific surface area, pore size contribution rate. Among them, the specific surface area of the carbon material mainly benefits from the contribution of its micropores and small mesopores, and the proportion is above 95% in both cases. According to the analysis of the test results, it was found that there is a significant positive correlation between the catalytic Mn(II) removal rate of the carbon material and its specific surface area. In addition, the chlorine decay rate is also positively correlated with the specific surface area, that is, the larger the specific surface area, the faster the chlorine decay rate. Comprehensive analysis shows that a high specific surface area helps to improve the Mn(II) removal effect. However, it was also found that the surface functional groups of the carbon material have no significant effect on the Mn(II) removal rate and chlorine decay rate.

[0075] Furthermore, the relationship between the total specific surface area, total functional groups of different carbon materials and the rate in the experiment of catalytic chlorine oxidation for Mn(II) removal was verified by linear regression fitting analysis, and the specific results are as shown in Figures 4 - 6 .

[0076] As shown in Figures 4 - 6 , the powdered activated carbon with a high specific surface area significantly improved the catalytic effect. Among them, the contribution of the micropore and small mesopore specific surface areas is particularly crucial (as shown in Table 1), and the proportion of micropores and small mesopores in the specific surface area (pore contribution rate) is above 95%; a high specific surface area is more conducive to the catalytic effect, which is an important basis for screening powdered activated carbon materials for catalytic Mn(II) removal. In addition, it can also be found from Figures 4 - 6 that although the content of functional groups changes, it has no obvious effect on the manganese removal rate, indicating that the functional groups are not the main factors affecting the catalytic manganese removal by activated carbon. Thus, Figures 4 to 6 it was verified that the operation of determining the decisive indexes in the foregoing of the present disclosure is accurate and reliable.

[0077] Furthermore, as shown in Figure 4As shown, taking the specific surface area and manganese removal efficiency as decisive indicators as an example, linear regression fitting is performed on the data of the two, and the obtained fitting coefficients show a linear positive correlation. Therefore, the operation of screening the target activated carbon suitable for catalytic chlorine oxidation for manganese removal can include: when the fitting coefficient determined by linear fitting is positive, selecting the activated carbon with the largest specific surface area as the target activated carbon.

[0078] In summary, using the method provided by the present disclosure, it is found that the pore structure richness of the powdered activated carbon material is the key to determining its catalytic activity. The catalytic chlorine oxidation rate of powdered activated carbon for removing Mn(II) is positively correlated with the specific surface area of the powdered activated carbon, and has no significant correlation with the quantity and type of functional groups on the surface of the activated carbon material. In addition, the chlorine decay rate also shows a high positive correlation with the Mn(II) removal rate and the specific surface area of the activated carbon material respectively. Measuring the chlorine consumption rate in the system where powdered activated carbon exists can also be used as a rapid method for judging the Mn(II) oxidation rate of powdered activated carbon. Using the method provided by the present disclosure, powdered activated carbon materials with specific pore structures can be screened, precisely regulating the catalytic chlorine oxidation process for removing Mn(II), significantly increasing the rate of chlorine oxidation of Mn(II), thereby greatly enhancing the removal rate of Mn(II) in water, reducing the reaction time and the dosage of powdered activated carbon, so as to achieve the purpose of cost saving. It provides an efficient and feasible new method for the water treatment field. In addition, the method for screening activated carbon and the operation of catalytic chlorine oxidation for manganese removal in the present disclosure are simple and easy to implement, with good application prospects, and can be widely applied to the treatment of water bodies polluted by Mn(II).

[0079] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present disclosure. It should be understood that the above description is only specific embodiments of the present disclosure and is not used to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A method for screening activated carbon for catalytic oxidation of manganese by chlorine, characterized in that, The method includes: Obtaining different physical and chemical characteristic indexes of different activated carbons, where the physical and chemical characteristic indexes are obtained through physicochemical characterization of the activated carbons; Obtaining the manganese removal efficiency indexes of the different activated carbons, where the manganese removal efficiency indexes are obtained through tests of catalytic oxidation of manganese by chlorine using the activated carbons; Performing correlation analysis on the different physical and chemical characteristic indexes and the manganese removal efficiency indexes of the different activated carbons to determine the decisive indexes for catalytic oxidation of manganese by chlorine of the activated carbons; Performing linear regression fitting on at least one of the decisive indexes and the manganese removal efficiency indexes to obtain a fitting coefficient; Selecting target activated carbons suitable for catalytic oxidation of manganese by chlorine according to the fitting coefficient and predicting the catalytic oxidation of manganese by chlorine efficiency of the target activated carbons.

2. The method according to claim 1, wherein The sources of the activated carbons include at least one of wood-based, coal-based, petroleum coke, peat, bone char, synthetic carbon-based materials, bamboo charcoal, and crops; The particle size of the activated carbons is less than 10 - 1000 mesh; The activated carbons are commercially available activated carbons, activated carbons treated by ultrasonic strengthening, or activated carbons secondarily activated by steam.

3. The method according to claim 1, characterized in that, The physical and chemical characteristic indexes include physical characteristic indexes and chemical characteristic indexes; Among them, the physical characteristic indexes include at least one characteristic index of specific surface area, micropore specific surface area, small mesopore specific surface area, and pore size contribution rate; The chemical characteristic indexes include at least one characteristic index of total functional group content, hydroxyl functional group content, carboxyl functional group content, and lactone group functional group content; The manganese removal efficiency indexes include manganese removal rate indexes and chlorine decay rate indexes; Among them, the pore size contribution rate represents the ratio of the sum of the micropore specific surface area and the small mesopore specific surface area to the specific surface area.

4. The method according to claim 1, wherein The catalytic oxidation of manganese by chlorine using the activated carbons includes: After uniformly mixing the activated carbon with the manganese-containing water body, adding a chlorine oxidant and adjusting the pH to carry out a catalytic oxidation reaction of chlorine to achieve the removal of manganese in the water body.

5. The method according to claim 4, wherein The temperature of the catalytic oxidation reaction of chlorine is 0 - 50 °C, and the pH is adjusted to 5.5 - 10; Among them, the concentration of manganese in the water body is 0.05 - 1000 mg / L, the concentration of the activated carbon is 1 - 5000 mg / L, and the concentration of available chlorine in the water body is 0.5 - 2000 mg / L; The chlorine oxidant is selected from sodium hypochlorite or liquid chlorine.

6. The method according to claim 3, characterized in that, Performing correlation analysis on the different physical and chemical characteristic indexes and the manganese removal efficiency indexes of the different activated carbons to determine the decisive indexes for catalytic manganese removal of the activated carbons, including: Performing correlation analysis on the different physical characteristic indexes, different chemical characteristic indexes, and the manganese removal efficiency indexes of the different activated carbons to obtain Pearson correlation coefficients; Based on the Pearson correlation coefficients, determining the decisive indexes of the activity of the activated carbon from the physical characteristic indexes, chemical characteristic indexes, and the manganese removal efficiency indexes.

7. The method according to claim 6, characterized in that, The decisive indexes include at least one of chlorine decay rate index, specific surface area, small mesopore specific surface area, pore size contribution rate, and micropore specific surface area.

8. The method according to claim 3, characterized in that, The manganese removal rate indexes and chlorine decay rate indexes are obtained by measuring the concentrations of manganese and chlorine in the water body before and after the reaction.

9. The method according to any one of claims 1 - 8, characterized in that, The method further includes: Using the target activated carbon for catalytic manganese removal.

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