Preparation method and application of a composite modified clay mineral adsorbent for adsorbing dioxins

Abstract

The present application relates to a kind of preparation method and application of composite modified clay mineral adsorbent for adsorbing dioxin, and the preparation method includes the following steps: (1) clay mineral is crushed and sieved, sintering, obtain the clay mineral powder after sintering;(2) the clay mineral powder after sintering and cerium trichloride are mixed into deionized water, citric acid solution is added, obtain the cerium after clay mineral;(3) the cerium after clay mineral, sodium azide and alkali metal element are weighed and mixed uniformly, after temperature treatment, obtain cerium nitride & clay mineral compound;(4) the cerium nitride & clay mineral compound is dispersed into phosphate buffer solution, hafnium oxychloride solution is added, in situ photodeposition method is reacted, obtain composite modified clay mineral.Compared with traditional clay mineral, the composite modified clay mineral prepared in the present application not only has strong adsorption removal efficiency for dioxin, but also has better reusability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of clay minerals, in particular to a preparation method and application of a composite modified clay mineral adsorbent for adsorbing dioxins. BACKGROUND

[0002] Incineration is a mainstream technology for municipal solid waste treatment, which can better achieve the goals of reduction, resource utilization and harmlessness. However, some secondary pollutants such as hydrogen chloride, heavy metals and dioxins will be produced during the incineration process of waste, among which dioxins are considered to be the most toxic compounds. Dioxins are the general term of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), and there are more than 200 isomers according to the number of chlorine atom substitution and the substitution position. The toxicity of dioxins is related to the 8 positions of chlorine atom substitution, and the most concerned is 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (2,3,7,8-TCDD), which is more than 1000 times as toxic as potassium cyanide, and has the properties of carcinogenicity, mutagenicity and teratogenicity. In the "Standard for Pollution Control on Incineration of Domestic Waste" (GB18485-2014), the emission limit of dioxins for domestic waste incineration plants with a capacity of more than 300 t / d is increased to 0.1 ng TEQ / m 3 . Under this background, how to control dioxin emissions has become the focus of incineration technology application.

[0003] Clay minerals are a kind of material that can be used to remove dioxin pollutants, which are usually natural clay minerals or artificially synthesized clay minerals. Traditional clay minerals have insufficient removal effect on dioxins, and the existing technology adds some modified substances to the clay minerals to increase the surface activity, specific surface area and adsorption capacity of the clay minerals to obtain composite clay minerals, thereby improving the adsorption effect of the composite clay minerals on dioxins. However, the composite clay mineral adsorbent prepared in the prior art has the defects of low adsorption efficiency of dioxins, low reusability and complex preparation process, and therefore needs to be improved. SUMMARY

[0004] In view of the problems in the prior art, the purpose of the present application is to provide a method for preparing a dioxin adsorbent by modifying composite clay minerals and application thereof.

[0005] The purpose of the present application is achieved by adopting the following technical solutions:

[0006] In a first aspect, the present application provides a preparation method of a composite modified clay mineral adsorbent for adsorbing dioxins, comprising the following steps:

[0007] (1) crushing and sieving clay minerals to obtain clay mineral powder, then sintering the powder in a high temperature furnace, and obtaining sintered clay mineral powder after the treatment;

[0008] (2) mixing the sintered clay mineral powder and cerium chloride into deionized water, uniformly dispersing at room temperature, then adding citric acid solution drop by drop to form a clay mineral mixture, and then stirring and reacting to obtain cerium-treated clay minerals after drying;

[0009] (3) mixing the cerium-treated clay minerals, sodium azide and alkali metal elements, transferring them to a graphite furnace, purging nitrogen as a protective gas, and obtaining cerium nitride & clay mineral composite after washing and drying;

[0010] (4) dispersing the cerium nitride & clay mineral composite into a phosphate buffer solution, adding hafnium oxychloride solution drop by drop under the protection of nitrogen, and obtaining a composite modified clay mineral after in-situ photodeposition reaction, filtration and drying.

[0011] Preferably, in step (1), the clay minerals are crushed and sieved to 100-200 mesh.

[0012] Preferably, in step (1), the clay minerals include, by weight fraction: 10-20 parts of palygorskite, 10-20 parts of illite, 2-6 parts of montmorillonite, and 5-15 parts of chlorite.

[0013] Preferably, in step (1), the sintering temperature in the high temperature furnace is 200-250℃, and the sintering time is 2-4h.

[0014] Preferably, in step (2), the mass ratio of sintered clay mineral powder, cerium chloride and deionized water is 1:0.16-0.24:10-20.

[0015] Preferably, in step (2), the mass fraction of citric acid solution is 10%-20%, and the mass ratio of citric acid solution to clay mineral mixture is 0.3-0.5:1.

[0016] Preferably, in step (2), the stirring reaction is stirred at room temperature for 1-2h.

[0017] Preferably, in step (3), the alkali metal element includes one of lithium, sodium and potassium, and more preferably sodium.

[0018] Preferably, in step (3), the mass ratio of cerium-treated clay minerals, sodium azide and alkali metal elements is 1:0.24-0.36:0.15-0.3.

[0019] Preferably, in step (3), nitrogen is introduced to the furnace to a pressure of 0.5 MPa, the furnace is heated to 550-600 DEG C, and the treatment time is 24-48 h.

[0020] Preferably, in step (3), the washing is washing three times in turn using ethanol and deionized water, and the drying is vacuum drying.

[0021] Preferably, in step (4), the components of the phosphate buffer solution include: 0.24 g / L of potassium dihydrogen phosphate, 1.42 g / L of disodium hydrogen phosphate, 8.0 g / L of sodium chloride, and 0.2 g / L of potassium chloride.

[0022] Preferably, in step (4), the mass fraction of the hafnium oxychloride solution is 4.1%-8.2%.

[0023] Preferably, in step (4), the mass ratio of the cerium nitride & clay mineral compound, the hafnium oxychloride solution, and the phosphate buffer solution is 1:1.8-3.6:100-200.

[0024] Preferably, in step (4), the conditions of the in-situ photodeposition method include: 50 W of xenon lamp irradiation, a stirring speed of 300-500 r / min, and a reaction time of 5-10 h.

[0025] Preferably, in step (4), the washing is washing three times in turn using ethanol and deionized water, and the drying is vacuum drying.

[0026] In a second aspect, the application provides a use of a composite modified clay mineral adsorbent for adsorbing dioxins, wherein the composite modified clay mineral adsorbent is prepared by the method described above and is used for adsorbing dioxins in a waste incineration process.

[0027] The application has the following beneficial effects:

[0028] 1. The application prepares a composite modified clay mineral, which is generated by first generating cerium nitride by an in-situ nitriding method and then generating hafnium phosphate by an in-situ photodeposition method on the basis of a traditional clay mineral, and finally obtaining a hafnium phosphate / cerium nitride & clay mineral compound. Compared with the traditional clay mineral, the composite modified clay mineral prepared by the application not only has a strong adsorption and removal efficiency for dioxins, but also has a better reusability.

[0029] 2、The clay mineral base material used in the present application is mixed with various mineral raw materials, and is subjected to high-temperature sintering treatment in the process of treatment, so as to remove the impurities adsorbed by the clay mineral, and then is mixed with a cerium salt solution, so that the clay mineral adsorbs a large amount of cerium ions, a complexing agent citric acid is added dropwise, and cerium citrate is formed to be adsorbed on the clay mineral, so as to form the cerium-modified clay mineral; then, sodium azide (NaN3) is used as a nitrogen source, and an alkali metal element is used as a fluxing agent, and under the conditions of a certain pressure and temperature, cerium nitride is generated on the clay mineral in situ, that is, a cerium nitride & clay mineral composite is generated.

[0030] 3、In the process of in-situ photodeposition, a phosphate buffer solution is used as a phosphate source, and hafnium oxychloride is used as a hafnium source, and under the irradiation of in-situ light, hafnium phosphate is deposited on the surface of the cerium nitride & clay mineral composite in situ, so as to obtain a hafnium phosphate / cerium nitride & clay mineral composite. DETAILED DESCRIPTION

[0031] The technical solutions of the present application are described below by means of specific examples. It should be understood that the one or more method steps mentioned in the present application do not exclude the presence of other method steps before and after the combination steps or the insertion of other method steps between the explicitly mentioned steps; it should also be understood that the examples are only used to illustrate the present application and do not limit the scope of the present application. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not a limitation on the arrangement order of each method step or a limitation on the range of implementation of the present application. Changes or adjustments of the relative relationship, without substantial changes in the technical content, are also considered as the implementation scope of the present application.

[0032] In order to better understand the above technical solutions, the exemplary embodiments of the present application are described in more detail below. Although exemplary embodiments of the present application are shown, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0033] The present application is further described below in conjunction with the following examples.

[0034] Example 1

[0035] A method for preparing a composite modified clay mineral adsorbent for adsorbing dioxins, comprising the following steps:

[0036] (1) According to the weight fraction, 20 parts of palygorskite, 20 parts of illite, 5 parts of montmorillonite and 10 parts of chlorite are taken, the taken clay minerals are mixed and crushed, then sieved through a 100 mesh sieve to obtain clay mineral powder, and then the powder is placed in a high temperature furnace at 220℃ and sintered for 3h, and then naturally cooled in the furnace to obtain sintered clay mineral powder;

[0037] (2) The sintered clay mineral powder and cerium trichloride are mixed into deionized water, the mass ratio of sintered clay mineral powder, cerium trichloride and deionized water is 1:0.2:15, and then uniformly dispersed at room temperature, to form a clay mineral mixture, then 15ω% citric acid solution is added dropwise, the mass ratio of citric acid solution to clay mineral mixture is 0.4:1, and stirring is continuously carried out during the process, after all the dropwise addition, stirring is continuously carried out at room temperature for 1.5h, and then vacuum drying is carried out to obtain cerium-treated clay minerals;

[0038] (3) The cerium-treated clay minerals, sodium azide and sodium element are mixed uniformly, the mass ratio of cerium-treated clay minerals, sodium azide and sodium element is 1:0.3:0.22, and then transferred to a graphite furnace, nitrogen gas is introduced to 0.5MPa pressure in the furnace, gradually heated to 600℃, and then kept for 36h, and then cooled to room temperature in the furnace, and then the solid product is collected, and then sequentially washed with alcohol and water for three times, and then vacuum dried to obtain cerium nitride & clay mineral composite;

[0039] (4) The cerium nitride & clay mineral composite is dispersed into a phosphate buffer aqueous solution (including: 0.24g / L of potassium dihydrogen phosphate, 1.42g / L of disodium hydrogen phosphate, 8.0g / L of sodium chloride, 0.2g / L of potassium chloride), under the protection of nitrogen, 6.1ω% hafnium oxychloride solution is added dropwise, the mass ratio of cerium nitride & clay mineral composite, hafnium oxychloride solution and phosphate buffer solution is 1:2.7:150, under the irradiation of 50W xenon lamp, stirring is carried out at a speed of 400r / min for 8h, in-situ photodeposition reaction is carried out, after the reaction is completed, filtration is carried out, and then sequentially washed with ethanol and deionized water for three times, and then vacuum dried to obtain hafnium phosphate / cerium nitride & clay mineral composite, that is, a composite modified clay mineral adsorbent.

[0040] Example 2

[0041] A preparation method of a composite modified clay mineral adsorbent for adsorbing dioxin, comprising the following steps:

[0042] (1) According to the weight fraction, 20 parts of palygorskite, 20 parts of illite, 5 parts of montmorillonite and 10 parts of chlorite are taken, the taken clay minerals are mixed and crushed, then sieved through a 100 mesh sieve to obtain clay mineral powder, and then the powder is placed in a high temperature furnace at 220℃ and sintered for 3h, and then naturally cooled in the furnace to obtain sintered clay mineral powder;

[0043] (2) The sintered clay mineral powder and cerium chloride are mixed into deionized water, and the mass ratio of the sintered clay mineral powder, cerium chloride and deionized water is 1:0.16:10. After being uniformly dispersed at room temperature by ultrasonic, a clay mineral mixture is formed. Then, 10ω% citric acid solution is added dropwise into the clay mineral mixture, and the mass ratio of the citric acid solution to the clay mineral mixture is 0.3:1. During the process, stirring is continuously performed until all the citric acid solution is added. Then, stirring is continuously performed at room temperature for 1h. After vacuum drying, a cerium-modified clay mineral is obtained.

[0044] (3) The cerium-modified clay mineral, sodium azide and sodium element are weighed and uniformly mixed, and the mass ratio of the cerium-modified clay mineral, sodium azide and sodium element is 1:0.24:0.15. The mixture is transferred into a graphite furnace, nitrogen is introduced into the furnace until the pressure in the furnace reaches 0.5MPa, and the temperature is gradually increased to 550℃. After being kept at 550℃ for 24h, the furnace is cooled to room temperature. The solid product is collected, and then is washed with alcohol and water three times in sequence. After vacuum drying, a cerium nitride & clay mineral composite is obtained.

[0045] (4) The cerium nitride & clay mineral composite is dispersed into a phosphate buffer aqueous solution (including: 0.24g / L of potassium dihydrogen phosphate, 1.42g / L of sodium phosphate dibasic, 8.0g / L of sodium chloride, and 0.2g / L of potassium chloride). Under the protection of nitrogen, 4.1%ω% hafnium oxychloride solution is added dropwise, and the mass ratio of the cerium nitride & clay mineral composite, hafnium oxychloride solution and phosphate buffer solution is 1:1.8:100. Under the irradiation of a 50W xenon lamp, stirring is performed at a speed of 300r / min for 5h to perform an in-situ photodeposition reaction. After the reaction is completed, the product is filtered and washed with ethanol and deionized water three times in sequence. After vacuum drying, a hafnium phosphate / cerium nitride & clay mineral composite, i.e., a composite modified clay mineral adsorbent, is obtained.

[0046] Example 3

[0047] A preparation method of a composite modified clay mineral adsorbent for adsorbing dioxins, comprising the following steps:

[0048] (1) The following components are weighed according to the weight fraction: 20 parts of palygorskite, 10 parts of illite, 2 parts of montmorillonite, and 15 parts of chlorite. The weighed clay minerals are mixed and crushed, and then are passed through a 100-mesh sieve to obtain clay mineral powder. Then, the powder is placed in a high-temperature furnace at 200℃ and sintered for 4h. After the furnace is naturally cooled, sintered clay mineral powder is obtained.

[0049] (2) The sintered clay mineral powder and cerium chloride are mixed into deionized water, and the mass ratio of the sintered clay mineral powder, cerium chloride and deionized water is 1:0.24:20. After being uniformly dispersed at room temperature by ultrasonic, a clay mineral mixture is formed. Then, 20ω% citric acid solution is added dropwise into the clay mineral mixture, and the mass ratio of the citric acid solution to the clay mineral mixture is 0.5:1. During the process, constant stirring is performed until all the citric acid solution is added. Then, the mixture is continuously stirred at room temperature for 2 hours. After vacuum drying, the cerium-treated clay mineral is obtained.

[0050] (3) The cerium-treated clay mineral, sodium azide and sodium element are uniformly mixed, and the mass ratio of the cerium-treated clay mineral, sodium azide and sodium element is 1:0.36:0.3. Then, the mixture is transferred into a graphite furnace, nitrogen is introduced into the furnace until the pressure in the furnace reaches 0.5 MPa, and the temperature is gradually increased to 600°C. After being kept at 600°C for 48 hours, the furnace is cooled to room temperature, and the solid product is collected. After being washed with alcohol and water three times in sequence, the nitrogenated cerium & clay mineral composite is obtained after vacuum drying.

[0051] (4) The nitrogenated cerium & clay mineral composite is dispersed into a phosphate buffer aqueous solution (including 0.24 g / L of potassium dihydrogen phosphate, 1.42 g / L of sodium phosphate dibasic, 8.0 g / L of sodium chloride and 0.2 g / L of potassium chloride). Under the protection of nitrogen, 8.2ω% hafnium oxychloride solution is added dropwise into the phosphate buffer aqueous solution, and the mass ratio of the nitrogenated cerium & clay mineral composite, hafnium oxychloride solution and phosphate buffer solution is 1:3.6:200. The in-situ photodeposition reaction is performed under the irradiation of a 50W xenon lamp at a stirring speed of 500 r / min for 10 hours. After the reaction is completed, the product is filtered and washed with ethanol and deionized water three times in sequence, and vacuum drying is performed to obtain the hafnium phosphate / nitrogenated cerium & clay mineral composite, i.e., the composite modified clay mineral adsorbent.

[0052] Comparative Example 1

[0053] A method for preparing a dioxin adsorbent, which is different from Example 1 in that the adsorbent is a traditional clay mineral, i.e., 20 parts of palygorskite, 20 parts of illite, 5 parts of montmorillonite and 10 parts of chlorite are weighed according to the weight fraction.

[0054] Comparative Example 2

[0055] A method for preparing a dioxin adsorbent, which is different from Example 1 in that the adsorbent is not subjected to in-situ treatment of hafnium phosphate, i.e., the nitrogenated cerium & clay mineral composite prepared in Example 1 is used as the dioxin adsorbent in this comparative example.

[0056] Comparative Example 3

[0057] A method for preparing a dioxin adsorbent, which is different from Example 1 in that the adsorbent is not subjected to in-situ treatment of nitrogenated cerium, and the preparation process includes:

[0058] (1) The sintered clay mineral powder was prepared in the same manner as in Example 1.

[0059] (2) The sintered clay mineral powder was dispersed in a phosphate buffer aqueous solution (containing 0.24 g / L of potassium dihydrogen phosphate, 1.42 g / L of sodium dihydrogen phosphate, 8.0 g / L of sodium chloride, and 0.2 g / L of potassium chloride) under nitrogen protection, and 6.1 ω% hafnium oxychloride solution was added dropwise. The mass ratio of the sintered clay mineral powder, the hafnium oxychloride solution, and the phosphate buffer solution was 1:2.7:150. The in-situ photodeposition reaction was carried out under the irradiation of a 50 W xenon lamp at a stirring speed of 400 r / min for 8 h. After the reaction, the product was filtered and washed with ethanol and deionized water three times in sequence, and vacuum dried to obtain a hafnium phosphate / clay mineral composite, i.e., a dioxin adsorbent.

[0060] Experimental Example

[0061] The adsorbents prepared in Example 1 and Comparative Examples 1-3 were used for the adsorption detection of dioxin.

[0062] The specific steps include:

[0063] In a plurality of identical vessels capable of producing gas exchange and resistant to high temperature, 5 g of the composite clay mineral prepared in Example 1 and Comparative Examples 1-3 was respectively placed in each vessel, and then 10 ng TEQ / m 3 of dioxin was simultaneously introduced into the inlet of the vessels at a flow rate of 500 Nm 3 / h, the same temperature was maintained in the vessels, and a 300 W xenon lamp was irradiated, and the temperature in the vessels was set to 200°C. Then, the concentration of dioxin was detected at the outlet after 1 h.

[0064] Data detection:

[0065] (1) The removal rate of dioxin was calculated by the concentration at the inlet and the outlet.

[0066] (2) After the adsorbent was continuously used for 100 h according to the above experimental standard, the removal rate of dioxin was detected again to determine the reusability of the adsorbent.

[0067]

[0068] The results are shown in Table 1:

[0069] Table 1 Comparison of the removal rates of different adsorbents for dioxin

[0070]

[0071] From the detection results in Table 1, the adsorbent prepared in Example 1 of the present application has a higher removal efficiency for dioxins, reaching 98.2%, and after 100 h of continuous use, it can still reach 91.2%, indicating that it also has better reusability. Example 1 of the present application not only combines the advantages of high removal efficiency of Comparative Example 2 and high removal stability of Comparative Example 3, but also has better performance than Comparative Examples 2 and 3 in the final detection results.

[0072] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and integrate different embodiments or examples described in the present specification.

[0073] Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for preparing a composite modified clay mineral adsorbent for adsorbing dioxins, characterized by, The method comprises the following steps: (1) crushing and sieving clay minerals to obtain clay mineral powder, and then sintering the powder in a high-temperature furnace at 200-250 DEG C for 2-4 hours to obtain sintered clay mineral powder; (2) mixing the sintered clay mineral powder and cerium chloride into deionized water, uniformly dispersing at room temperature, and then adding citric acid solution drop by drop to form a clay mineral mixture, stirring at room temperature for 1-2 hours, and drying to obtain cerium-treated clay minerals; (3) mixing the cerium-treated clay minerals, sodium azide and alkali metal elements, transferring them into a graphite furnace, introducing nitrogen as a protective gas, and then washing and drying to obtain cerium nitride & clay mineral composite; (4) dispersing the cerium nitride & clay mineral composite into a phosphate buffer solution, adding hafnium oxychloride solution drop by drop under the protection of nitrogen, and reacting under the conditions of in-situ photodeposition to obtain a composite modified clay mineral after filtration, washing and drying. In step (2), the mass ratio of sintered clay mineral powder, cerium chloride and deionized water is 1:0.16-0.24:10-20; In step (3), the alkali metal element includes one of lithium, sodium and potassium, and the mass ratio of cerium-treated clay minerals, sodium azide and alkali metal elements is 1:0.24-0.36:0.15-0.3; In step (4), the mass fraction of hafnium oxychloride solution is 4.1%-8.2%, and the mass ratio of cerium nitride & clay mineral composite, hafnium oxychloride solution and phosphate buffer solution is 1:1.8-3.6:100-200.

2. The method of claim 1, wherein the method is characterized by: In step (1), the clay minerals are crushed to pass through a 100-200 mesh sieve, and the clay minerals include, by weight fraction, 10-20 parts of palygorskite, 10-20 parts of illite, 2-6 parts of montmorillonite and 5-15 parts of chlorite.

3. The method of claim 1, wherein the method is characterized by: In step (2), the mass fraction of citric acid solution is 10%-20%, and the mass ratio of citric acid solution to clay mineral mixture is 0.3-0.5:

1.

4. The method of claim 1, wherein the method is characterized by: In step (3), the nitrogen gas is introduced into the furnace to a pressure of 0.5 MPa, the furnace is heated to 550-600 DEG C, and the treatment time is 24-48 hours.

5. The method of claim 1, wherein the method is characterized by: In step (4), the components of the phosphate buffer solution include 0.24 g / L of potassium dihydrogen phosphate, 1.42 g / L of disodium hydrogen phosphate, 8.0 g / L of sodium chloride and 0.2 g / L of potassium chloride.

6. The method of claim 1, wherein the method is characterized by: In step (4), the conditions of in-situ photodeposition include 50 W of xenon lamp irradiation, a stirring speed of 300-500 r / min and a reaction time of 5-10 hours.

7. Use of the composite modified clay mineral adsorbent produced by the method of claim 1, characterized in that, The composite modified clay mineral adsorbent is used for adsorbing dioxins generated in the garbage incineration process.

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