A modified mesoporous silica adsorbent and its preparation method and application

Abstract

The present invention discloses a modified mesoporous silica adsorbent and a preparation method and application thereof, and relates to the technical field of porous material preparation. The preparation method of the modified mesoporous silica adsorbent provided by the present invention comprises the following steps: firstly, a silicon source is hydrolyzed in a solution containing a template to form a preliminary framework of silica, and then a silane coupling agent containing at least one of a mercapto group, a sulfonic acid group, and an amino group is added, and a hydrothermal reaction is carried out at 60 to 120°C. After the template is removed, a modified mesoporous silica adsorbent capable of selectively adsorbing zirconium and hafnium can be obtained. The modified mesoporous silica adsorbent prepared by the present invention is used to adsorb and enrich zirconium and hafnium ions, and adsorption amounts of 6.23 mg / g and 5.95 mg / g or more can be obtained, respectively, with excellent adsorption capacity, and the adsorbent in the present invention can reach adsorption equilibrium within 10 minutes, with excellent adsorption rate.

Description

Technical Field

[0001] The invention relates to the technical field of porous material preparation, and in particular to a modified mesoporous silica adsorbent and a preparation method and application thereof. Background Art

[0002] Zirconium (Zr) and hafnium (Hf) are two metals with similar chemical properties, which are widely symbiotic in minerals. These two metals have important application value in high-tech fields such as nuclear energy, aerospace, and chemical industry. In particular, hafnium has a unique performance in nuclear reactor control materials, which has led to an increasing demand for it in various countries. However, the abundance of zirconium in the earth's crust is much higher than that of hafnium. How to effectively enrich zirconium and hafnium while maintaining the symbiotic state of the two has become a research hotspot in modern materials and resource development. After enriching zirconium and hafnium ions in the liquid phase, reducing the two metal ions to metal elements is a feasible way to enrich them while maintaining the symbiotic state of the two. However, how to modify the adsorbent so that it has the ability to selectively adsorb zirconium and hafnium ions and has excellent adsorption rate and adsorption capacity for zirconium and hafnium ions is still a problem that needs to be solved urgently. Summary of the invention

[0003] In order to solve the shortcomings of the prior art, the present invention provides a method for preparing a modified mesoporous silica adsorbent. First, a silicon source is hydrolyzed in a solution containing a template to form a preliminary framework of silica, and then a silane coupling agent containing a specific functional group is added, hydrothermally crystallized and the template is removed to obtain a modified mesoporous silica adsorbent capable of selectively adsorbing zirconium and hafnium. The obtained adsorbent has a high adsorption rate for zirconium and hafnium and an excellent adsorption capacity.

[0004] Another object of the present invention is to provide a modified mesoporous silica adsorbent.

[0005] Another object of the present invention is to provide an application of a modified mesoporous silica adsorbent.

[0006] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a modified mesoporous silica adsorbent comprises the following steps:

[0008] S1. hydrolyzing a silicon source in a solution containing a template to obtain a mixed solution A; the template comprises at least one of a triblock copolymer P123, a triblock copolymer F127, hexadecyltrimethylammonium bromide, and sodium dodecyl sulfate;

[0009] S2. Add a silane coupling agent to the mixed solution A obtained in step S1, perform a hydrothermal reaction at 60-120° C., remove the template agent, and obtain a modified mesoporous silica adsorbent; the silane coupling agent contains at least one group selected from the group consisting of a mercapto group, a sulfonic acid group, and an amino group.

[0010] The preparation method of the modified mesoporous silica adsorbent provided by the present invention first hydrolyzes the silicon source in the presence of a template to form a preliminary mesoporous framework, and then introduces a silane coupling agent containing a specific functional group and performs a hydrothermal reaction to complete the crystallization of the framework, thereby obtaining mesoporous silica rich in functional groups such as mercapto, sulfonic acid, and amino groups inside the pores, and the preparation method provided by the present invention can make these functional groups evenly distributed inside the pores of the silica adsorbent. Based on this, the modified mesoporous silica adsorbent prepared by the present invention can enhance the selective adsorption capacity of zirconium and hafnium ions through the nano-confinement effect. Specifically, zirconium and hafnium ions usually exist in aqueous solution in the form of tetramers or larger sizes, and the structural size of the tetramer has reached about 0.7 nm. Compared with other metal ions, the size of the ion clusters formed by zirconium and hafnium ions in aqueous solution is significantly increased, which requires the adsorbent to have larger pores to achieve the adsorption of zirconium and hafnium. Therefore, mesoporous silica with a larger pore size (2~50 nm) is selected as the modified main body in the present invention; at the same time, it is also necessary to optimize the interaction between the internal structure of the mesoporous silica pores and the zirconium and hafnium ions, so as to achieve the selective adsorption of zirconium and hafnium and improve the adsorption efficiency of zirconium and hafnium ions. Therefore, the present invention uses a silane coupling agent containing at least one of mercapto, sulfonic acid and amino groups to modify silica, wherein the silane coupling agent can further adjust the pore structure of silica, and at the same time, the mercapto, sulfonic acid and amino functional groups can form stable complexes with zirconium and hafnium ions, thereby enhancing the selective adsorption effect of these two metal ions. The modified mesoporous silica adsorbent provided by the present invention is used to adsorb and separate zirconium and hafnium, and has high adsorption efficiency and excellent adsorption capacity.

[0011] It should be noted that in step S1 of the present invention, the silicon source needs to be initially hydrolyzed to form a rough framework of mesoporous silica, and then a silane coupling agent is added for modification, and finally crystallization is completed by hydrothermal treatment. The reason is that the present invention requires that the silane coupling agent containing different groups is stably and evenly distributed inside the silica pores. Whether the silicon source is directly hydrolyzed under the condition of the coexistence of the silane coupling agent and the template agent, or the silane coupling agent is first hydrothermally crystallized and then added for modification, it is difficult to achieve stable and uniform distribution of the silane coupling agent.

[0012] The template agent in step S1 includes at least one of triblock copolymer P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer), triblock copolymer F127 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, which differs from P123 in that the number of ethylene oxide and propylene oxide units in the block is different), hexadecyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). The above template agents are all common template agents used in the art for preparing mesoporous silica, among which P123 can generate mesoporous materials with moderate pore size (4~10 nm), F127 can generate mesoporous materials with moderate or even larger pore size (6~10 nm), CTAB can be used as a template to generate mesoporous materials with small pore size (2~5 nm), and SDS can generate mesoporous materials with pore size of 1~5 nm.

[0013] Preferably, the silicon source in step S1 includes at least one of tetraethoxysilane, sodium silicate, potassium silicate, silicic acid, methyl silicate and silica sol.

[0014] In a specific embodiment of the present invention, the step S1 of hydrolyzing the silicon source in a solution containing a template agent is specifically: hydrolyzing the silicon source in a solution containing a template agent at 30-60° C. More specifically, the hydrolysis is performed under stirring. More specifically, the time for hydrolyzing the silicon source in a solution containing a template agent in step S1 is 0.1-60 min.

[0015] More preferably, the silicon source in step S1 includes at least one of tetraethoxysilane and sodium silicate.

[0016] More preferably, the template in step S1 includes at least one of triblock copolymer P123 and triblock copolymer F127.

[0017] Preferably, the molar ratio of the silicon source to the template in step S1 is (10-70):1.

[0018] More preferably, the molar ratio of the silicon source to the template in step S1 is (30-60):1.

[0019] In a specific embodiment of the present invention, the concentration of the silicon source in step S1 is 3-7 mol / L, and the amount of the silicon source added is 0.1-100 mL.

[0020] In a specific embodiment of the present invention, the amount of the template added in step S1 is 0.1-100 g, more specifically, 1-10 g.

[0021] Preferably, the template-containing solution in step S1 further comprises an acid, wherein the acid comprises at least one of sulfuric acid, nitric acid, hydrochloric acid, acetic acid, ascorbic acid, malic acid, tartaric acid, and hydrofluoric acid solution, and the concentration of the acid is 1-6 mol / L.

[0022] The silicon source can be hydrolyzed under both acidic and alkaline conditions. In the present invention, the silicon source is hydrolyzed under acidic conditions to obtain a mesoporous silica adsorbent with a more regular structure and conducive to adsorption.

[0023] Preferably, the acid comprises hydrochloric acid.

[0024] More preferably, the concentration of the acid is 1-3 mol / L.

[0025] In a specific embodiment of the present invention, the volume of the solution containing the template in step S1 is 100-300 mL.

[0026] Preferably, when the silane coupling agent in step S2 contains a mercapto group, the silane coupling agent includes at least one of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane and 3-mercaptopropylmethyldimethoxysilane.

[0027] Preferably, when the silane coupling agent in step S2 contains an amino group, the silane coupling agent includes at least one of 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane.

[0028] Preferably, when the silane coupling agent in step S2 contains a sulfonic acid group, the silane coupling agent is prepared by an oxidation reaction of a silane coupling agent containing a mercapto group. In a specific embodiment of the present invention, hydrogen peroxide is used to oxidize the silane coupling agent containing a mercapto group into a silane coupling agent containing a sulfonic acid group.

[0029] More preferably, the silane coupling agent includes at least one of 3-mercaptopropyltrimethoxysilane and 3-aminopropyltrimethoxysilane.

[0030] In a specific embodiment of the present invention, the concentration of the silane coupling agent in step S2 is 3-7 mol / L, and the amount added is 0.1-10 mL.

[0031] Preferably, the molar ratio of the silane coupling agent in step S2 to the silicon source in step S1 is 1:(1-6).

[0032] In a specific embodiment of the present invention, after adding the silane coupling agent to the mixed solution A obtained in step S1 in step S2, a mixing step is also included. More specifically, the mixing is stirring at 20-60° C. for 18-22 h.

[0033] Preferably, the time for the hydrothermal reaction at 60-120° C. in step S2 is 10-28 h.

[0034] More preferably, the temperature of the hydrothermal reaction is 100-120°C.

[0035] Preferably, the removal of the template in step S2 comprises at least one of dissolving the template with an organic solvent and removing the template by calcination;

[0036] The method of dissolving the template agent by using an organic solvent is: dissolving the template agent by using at least one organic solvent selected from methanol, ethanol, n-heptane and kerosene at 60-120° C.; the method of removing the template agent by calcination is: removing the template agent by calcination at 500-600° C.

[0037] More preferably, the organic solvent is at least one of ethanol and methanol.

[0038] More preferably, the time for dissolving the template with an organic solvent is 1 to 30 hours.

[0039] In a specific embodiment of the present invention, the dissolving of the template agent with an organic solvent is carried out under the condition of ethanol reflux.

[0040] More preferably, the calcination time for removing the template is 1 to 30 hours.

[0041] In a specific embodiment of the present invention, step S2 further includes a drying step after removing the template.

[0042] The present invention also protects the modified mesoporous silica adsorbent prepared by the above preparation method.

[0043] The present invention also protects the use of the modified mesoporous silica adsorbent in adsorbing and enriching metal ions.

[0044] Preferably, the metal ions include at least one of zirconium ions and hafnium ions.

[0045] The modified mesoporous silica adsorbent provided by the present invention is used to adsorb and enrich zirconium and hafnium, and the enrichment process can be carried out under mild conditions, reducing the use of a large amount of chemical reagents, significantly reducing environmental impact, conforming to the innovative concept of green development, and providing technical support for the sustainable development and utilization of zirconium and hafnium resources.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The modified mesoporous silica adsorbent prepared by the present invention is used to adsorb and enrich zirconium and hafnium ions, and the adsorption amounts of 6.23~49.85mg / g and 5.95~50.02mg / g can be obtained respectively, indicating that the modified mesoporous silica adsorbent prepared by the present invention has adsorption selectivity for zirconium and hafnium ions and excellent adsorption capacity. In addition, the adsorbent in the present invention can reach adsorption equilibrium in 10 minutes and has excellent adsorption rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The pore size distribution diagram of the mesoporous silica prepared in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0049] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents. Among them, the raw material information used in each embodiment and comparative example is as follows:

[0050] 3-Mercaptopropyltrimethoxysilane: CAS No. 4420-74-0.

[0051] 3-Mercaptopropyltriethoxysilane: CAS No. 14814-09-6.

[0052] 3-Mercaptopropylmethyldimethoxysilane: CAS No. 31001-77-1.

[0053] 3-Aminopropyltriethoxysilane: CAS No. 919-30-2.

[0054] 3-Aminopropyltrimethoxysilane: CAS No. 13822-56-5.

[0055] Example 1

[0056] A method for preparing a modified mesoporous silica adsorbent comprises the following steps:

[0057] S1. Weigh 4.0 g of P123 and dissolve it in a hydrochloric acid solution (concentration: 1.9 mol / L, volume: 125 mL) to obtain a solution containing a template, heat it to 40°C, add 4.39 mol / L tetraethoxysilane (7.5 mL, molar ratio of tetraethoxysilane: P123 = 47.74:1), and hydrolyze for 45 min under stirring to obtain a mixed solution A;

[0058] S2. Add 2 mL, 5.22 mol / L 3-mercaptopropyltrimethoxysilane to the mixed solution A obtained in step S1 (tetraethoxysilane: 3-mercaptopropyltrimethoxysilane = 1:3.1), continue stirring at 40°C for 20 h, perform hydrothermal reaction at 100°C for 24 h, perform ethanol reflux treatment at 70°C for 24 h to remove the template, and dry to obtain the modified mesoporous silica adsorbent.

[0059] Example 2

[0060] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0061] The hydrochloric acid solution in step S1 has a concentration of 1.5 mol / L and a volume of 125 mL, and the silicon source is tetramethoxysilane.

[0062] Example 3

[0063] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0064] The hydrochloric acid solution in step S1 has a concentration of 1.0 mol / L and a volume of 125 mL, and the silicon source is tetramethoxysilane;

[0065] In step S2, 2 mL of 3.22 mol / L 3-mercaptopropyltrimethoxysilane is added to the mixed solution A obtained in step S1 (tetramethoxysilane: 3-mercaptopropyltrimethoxysilane = 1:5.11).

[0066] Example 4

[0067] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0068] The temperature of the hydrothermal reaction in step S2 is 80°C.

[0069] Example 5

[0070] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0071] The temperature of the hydrothermal reaction in step S2 is 120°C.

[0072] Example 6

[0073] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0074] The hydrothermal reaction time in step S2 is 12 h.

[0075] Example 7

[0076] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0077] In step S2, the template is removed by calcination at 350°C.

[0078] Example 8

[0079] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0080] In step S2, the template is removed by calcination at 400°C.

[0081] Example 9

[0082] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0083] In step S2, the template is removed by calcination at 500°C.

[0084] Example 10

[0085] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0086] In step S2, 3-mercaptopropyltrimethoxysilane is replaced with an equal molar amount of 3-aminopropyltrimethoxysilane, that is, the molar ratio of tetraethoxysilane:3-aminopropyltrimethoxysilane=1:3.1.

[0087] Embodiment 11

[0088] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0089] After adding 3-mercaptopropyltrimethoxysilane in step S2, 7.56 mL of hydrogen peroxide with a concentration of 9.79 mol / L was added to oxidize the thiol group to a sulfonic acid group.

[0090] Example 12

[0091] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0092] The hydrolysis time in step S1 is 20 h 45 min, and in step S2, 3-mercaptopropyltrimethoxysilane is added and stirred evenly before carrying out a hydrothermal reaction.

[0093] Example 13

[0094] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0095] The template in step S1 was replaced with an equal molar amount of CTAB, that is, the molar ratio of tetraethoxysilane:CTAB = 47.74:1 (0.25 g of CTAB was weighed and dissolved in a hydrochloric acid solution in step S1).

[0096] Embodiment 14

[0097] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0098] The template in step S1 was replaced with an equimolar amount of SDS, that is, the molar ratio of tetraethoxysilane:SDS=47.74:1 (0.2 g SDS was weighed and dissolved in a hydrochloric acid solution in step S1).

[0099] Embodiment 15

[0100] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0101] The template in step S1 was replaced with an equimolar amount of F127, that is, the molar ratio of tetraethoxysilane: F127 = 47.74:1 (8.7 g of F127 was weighed and dissolved in a hydrochloric acid solution in step S1).

[0102] Example 16

[0103] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0104] In step S1, 19.1 g of P123 was weighed and dissolved in a hydrochloric acid solution, and then tetraethoxysilane (7.5 mL, molar ratio of tetraethoxysilane: P123 = 10:1) with a concentration of 4.39 mol / L was added after heating to 40°C.

[0105] Embodiment 17

[0106] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0107] In step S1, 2.73 g of P123 was weighed and dissolved in a hydrochloric acid solution, and then tetraethoxysilane (7.5 mL, molar ratio of tetraethoxysilane: P123 = 70:1) with a concentration of 4.39 mol / L was added after heating to 40°C.

[0108] Embodiment 18

[0109] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0110] The molar ratio of the silane coupling agent in step S2 to the silicon source in step S1 is 1:0.5.

[0111] Embodiment 19

[0112] A method for preparing a modified mesoporous silica adsorbent, which differs from Example 1 only in that:

[0113] The molar ratio of the silane coupling agent in step S2 to the silicon source in step S1 is 1:8.

[0114] Comparative Example 1

[0115] A method for preparing a mesoporous silica adsorbent, which differs from Example 1 only in that:

[0116] In step S2, 3-mercaptopropyltrimethoxysilane is not added.

[0117] The pore size test was performed on the mesoporous silica adsorbent obtained in this comparative example and Example 1. The results are shown in Tables 1 and Figure 1 As shown:

[0118] Table 1. Pore structure data of mesoporous silica adsorbent obtained in Example 1 and Comparative Example 1

[0119]

[0120] As shown in Table 1 and Figure 1 As shown, in step S2, the silane coupling agent is introduced to modify the pores of the mesoporous silica, which can reduce the pore size and specific surface area of ​​the silica, proving that the silane coupling agent is successfully used to modify the inside of the pores of the mesoporous silica in the present invention, and the modification of the silane coupling agent can adjust the pore structure of the silica.

[0121] Comparative Example 2

[0122] A method for preparing a mesoporous silica adsorbent, which differs from Example 1 only in that:

[0123] No template is added in step S1, and no 3-mercaptopropyltrimethoxysilane is added in step S2.

[0124] Comparative Example 3

[0125] A method for preparing a mesoporous silica adsorbent, which differs from Example 1 only in that:

[0126] In step S2, ethanol reflux treatment at 70° C. for 24 h is not performed to remove the template.

[0127] Comparative Example 4

[0128] A method for preparing a mesoporous silica adsorbent comprises the following steps:

[0129] S1. Weigh 4.0 g of P123 and dissolve it in a hydrochloric acid solution (concentration: 1.9 mol / L, volume: 125 mL), heat to 40°C, add tetraethoxysilane (7.5 mL) with a concentration of 4.39 mol / L, and perform a hydrothermal reaction at 100°C for 24 h;

[0130] S2. Add 5.22 mol / L (3-mercaptopropyl)trimethoxysilane (2 mL), stir the reaction system at 40°C for 20 h, reflux the obtained product with ethanol at 70°C for 24 h, and dry it to obtain a mesoporous silica adsorbent.

[0131] Comparative Example 5

[0132] A method for preparing a mesoporous silica adsorbent comprises the following steps:

[0133] S1. Tetraethoxysilane (7.5 mL, 4.39 mol / L) was hydrolyzed in a hydrochloric acid solution (1.9 mol / L, 125 mL) in which 3-mercaptopropyltrimethoxysilane (2 mL, 5.22 mol / L) and P123 (4.0 g) were co-existing. The hydrolysis was carried out under stirring at 40°C for 20 h 45 min. After the hydrolysis, a hydrothermal reaction was carried out at 100°C.

[0134] S2. The product was treated with ethanol reflux at 70°C for 24 hours and dried to obtain a mesoporous silica adsorbent.

[0135] Performance Testing

[0136] 1. Test of zirconium and hafnium ion adsorption

[0137] Next, the amount and rate of adsorption of zirconium and hafnium ions on the silica adsorbents obtained in the examples and comparative examples were tested to characterize their adsorption capacity for zirconium and hafnium. The specific test steps are as follows: 0.1 g of the mesoporous silica adsorbents obtained in the examples and comparative examples were weighed and placed in 100 ml of a zirconium and hafnium mixed solution (the concentrations of zirconium and hafnium ions were both 50 mg / L) for adsorption, and samples were taken at regular intervals. When the concentrations of zirconium and hafnium in the sample remained unchanged, it was considered that the adsorption had reached equilibrium (for example, sampling was performed every 10 minutes, and when the concentrations of zirconium and hafnium ions in the sample at the 20th minute were not much different from those at the 10th minute, it was considered that the adsorption equilibrium had been reached at the 10th minute). The time for the adsorption to reach equilibrium was used to characterize the adsorption rate. The shorter the time for the adsorption to reach equilibrium, the higher the adsorption rate. The sample was filtered through a filter membrane to obtain an adsorbed sample, and the adsorption concentrations of zirconium and hafnium ions in the adsorbent were collected using an ICP-OES instrument.

[0138] Calculation of adsorption amount: Calculate the adsorption amount of the adsorbent based on the ion concentration in the initial solution and the ion concentration in the filtrate:

[0139]

[0140] Where q is the adsorption amount (mg / g), C 0 is the initial concentration (mg / L), C e is the equilibrium concentration (mg / L), V is the volume of the solution (L), and m is the mass of the adsorbent (g).

[0141] The specific test data are shown in Tables 2 and 3 below:

[0142] Table 2. Adsorption of zirconium and hafnium by adsorbents in Examples and Comparative Examples

[0143]

[0144] Table 3. Time for adsorbents to reach adsorption equilibrium in Examples and Comparative Examples

[0145]

[0146] Note: “ / ” in Table 3 above means no test was performed.

[0147] It can be seen from Table 3 above that the zirconium and hafnium ion concentrations in the samples measured by the adsorbent provided in the embodiment of the present invention at 20 minutes of adsorption are consistent with those at 10 minutes of adsorption. Therefore, it can be considered that the adsorbent in the embodiment of the present invention can reach adsorption equilibrium at 10 minutes of adsorption. Comparative Examples 1 to 5 were not tested at 20 minutes of adsorption, but the ion concentrations in the samples tested at 730 minutes of adsorption were consistent with those at 720 minutes of adsorption. It is considered that the adsorbent in the comparative example has reached adsorption equilibrium at 720 minutes of adsorption.

[0148] According to the data of the embodiments in Tables 2 and 3, it can be seen that the modified mesoporous silica adsorbent prepared by the present invention is used to adsorb and enrich zirconium and hafnium ions, and the adsorption amounts of 6.23-49.85 mg / g and 5.95-50.02 mg / g can be obtained respectively, indicating that the modified mesoporous silica adsorbent prepared by the present invention has adsorption selectivity for zirconium and hafnium ions and excellent adsorption capacity, and the adsorbent in the present invention can reach adsorption equilibrium in 10 min, and the adsorption rate is excellent.

[0149] From the comparison between Example 1 and Examples 4 to 6, it can be seen that the hydrothermal reaction temperature of Example 4 is lower than the preferred range of 100 to 120°C, and the probability of the hydrolyzed silicon source re-condensing is reduced, resulting in a decrease in the integrity of the pore structure of the modified mesoporous silica adsorbent, so the zirconium and hafnium enrichment is reduced; the hydrothermal temperature of Example 5 is increased, and the pore structure of the modified mesoporous silica adsorbent obtained is complete, but it does not change much compared with Example 1. Considering the energy consumption and adsorption effect, the preferred hydrothermal temperature of the present invention is 100 to 120°C; the hydrothermal time of Example 6 is shortened, the condensation of the silicon source has not yet reacted completely, and the pore structure integrity of the modified mesoporous silica adsorbent obtained is reduced, so the zirconium and hafnium enrichment is also reduced.

[0150] From the comparison of Examples 7 to 9, it can be seen that the template in silica can also be removed by calcination, but the calcination temperature needs to be adjusted. The calcination temperature of Examples 7 to 8 is relatively low, and the removal rate of the template is also reduced. The pores of the modified mesoporous silica adsorbent are filled with a certain amount of template, so the zirconium and hafnium enrichment is reduced; the calcination temperature of Example 9 is relatively high, and the template is effectively removed, but the temperature affects the number of functional groups in the pores. Although the pore structure of the modified mesoporous silica adsorbent is intact, the enrichment of zirconium and hafnium is also affected.

[0151] From the comparison between Example 1 and Examples 10 to 11, it can be seen that the silane coupling agent used in the present invention may contain at least one group of mercapto, sulfonic acid, and amino.

[0152] Comparison of the data of Example 1 and Example 12 shows that stirring after adding the silane coupling agent in step S2 can make it fully dispersed in the preliminary framework of silica, which is more conducive to the uniform distribution of functional groups such as mercapto groups inside the pores of the final adsorbent, so the adsorption amount of zirconium and hafnium is higher.

[0153] From the data of Examples 1, 13 to 15, it can be seen that the template agents commonly used in the art for achieving pore formation of mesoporous silica can be applied to prepare the modified mesoporous silica adsorbent of the present invention. Among them, when the template agent is the preferred F127 or P123 of the present invention, the adsorption effect of the obtained mesoporous silica adsorbent is better.

[0154] According to the data of Examples 1, 16-17, when the ratio of silicon source to template is 47.74:1 (Example 1), the mesoporous silica has the best zirconium and hafnium enrichment effect; whether this ratio is increased or decreased (Examples 16-17), the adsorption effect of the obtained mesoporous silica will decrease. In order to ensure that the mesoporous silica adsorbent has a certain adsorption and enrichment capacity for zirconium and hafnium, the present invention preferably has a ratio of silicon source to template of (10-70):1, and more preferably (30-60):1.

[0155] According to the data of Examples 1 and 18 to 19, when the amount of silane coupling agent added in step S2 is not appropriate, the degree of modification of the silica pores is insufficient, which also leads to a decrease in the adsorption effect.

[0156] From the data in Tables 1 to 3, it can be seen that when comparing Example 1 with Comparative Example 1, Comparative Example 1 is not modified, has fewer adsorption points in the pores, and the pore size structure of the prepared mesoporous silica adsorbent is not suitable. Therefore, the interaction effect with zirconium and hafnium ions is reduced, and the enrichment of zirconium and hafnium is low.

[0157] From the comparison of Example 1 and Comparative Examples 2-3 in Tables 2-3, it can be seen that in Comparative Example 2, no template agent was introduced and no silane coupling agent was added for modification when preparing the silica adsorbent, so the pore structure could not be generated and it was difficult to obtain regular mesoporous silica; in Comparative Example 3, the template agent was not removed, which affected the pore structure of the adsorbent, and the pore structure of the modified mesoporous silica adsorbent was blocked, so the zirconium and hafnium enrichment amount also decreased.

[0158] From the comparison between Example 1 and Comparative Examples 4 to 5, it can be seen that in Comparative Example 4, since the silicon source has been crystallized, the subsequent addition of (3-mercaptopropyl)trimethoxysilane is difficult to react, so that almost no functional groups are generated on the pores of the obtained mesoporous silica, affecting the adsorption of zirconium and hafnium metal ions; in Comparative Example 5, the degree of acid hydrolysis of the silicon source is insufficient, and it is difficult to react with (3-mercaptopropyl)trimethoxysilane, the degree of crystallization is low, and the product structure is incomplete, which also affects the adsorption of zirconium and hafnium metal ions.

[0159] 2. Metal ion adsorption selectivity test

[0160] Next, the modified mesoporous silica adsorbent in Example 1 is used to adsorb other metal ions to explore the selectivity of the adsorbent in the present invention for zirconium and hafnium. The specific test steps are as follows: Weigh 0.1g of the mesoporous silica adsorbent prepared in Example 1 and place it in 100ml of metal ion solution (metal ion concentration is 50mg / L) for adsorption, take samples at regular intervals, and when the metal ion concentration in the sample remains unchanged, it is considered that the adsorption has reached equilibrium, and the sample is filtered through a filter membrane to obtain an adsorbed sample, and the metal ion adsorption concentration in the adsorbent is collected using an ICP-OES instrument. According to the ion concentration in the initial solution and the ion concentration in the filtrate, the adsorption amount of the adsorbent is calculated:

[0161]

[0162] Where q is the adsorption amount (mg / g), C 0 is the initial concentration (mg / L), C e is the equilibrium concentration (mg / L), V is the volume of the solution (L), and m is the mass of the adsorbent (g).

[0163] The specific performance test data is shown in Table 3 below:

[0164] Table 3. Adsorption performance of the adsorbent in Example 1 for other ions

[0165]

[0166] It can be seen from Table 3 above that the adsorbent provided by the present invention has excellent adsorption selectivity for zirconium and hafnium ions.

[0167] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. Application of a modified mesoporous silica adsorbent in adsorption and enrichment of metal ions, characterized in that: The metal ion is at least one of a zirconium ion and a hafnium ion; The preparation method of the modified mesoporous silica adsorbent comprises the following steps: S1. hydrolyzing a silicon source in a solution containing a template to obtain a mixed solution A; the template comprises a triblock copolymer P123; the molar ratio of the silicon source to the template in step S1 is (30-60):1; S2. Add a silane coupling agent to the mixed solution A obtained in step S1, perform a hydrothermal reaction at 60-120° C., remove the template agent, and obtain a modified mesoporous silica adsorbent; the silane coupling agent contains at least one of a mercapto group, a sulfonic acid group, and an amino group; the molar ratio of the silane coupling agent to the silicon source in step S1 is 1:(1-6).

2. The use according to claim 1, characterized in that: In the preparation method of the modified mesoporous silica adsorbent, the silicon source in step S1 includes at least one of tetraethoxysilane, sodium silicate, potassium silicate, silicic acid, methyl silicate, and silica sol.

3. The use according to claim 1, characterized in that: In the preparation method of the modified mesoporous silica adsorbent, the template-containing solution in step S1 also includes an acid, and the acid includes at least one of sulfuric acid, nitric acid, hydrochloric acid, acetic acid, ascorbic acid, malic acid, tartaric acid, and hydrofluoric acid solution, and the concentration of the acid is 1-6 mol / L.

4. The use according to claim 1, characterized in that: Include at least one of the following (a) to (c): (a) In the method for preparing the modified mesoporous silica adsorbent, when the silane coupling agent in step S2 contains a mercapto group, the silane coupling agent includes at least one of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropylmethyldimethoxysilane; (b) In the method for preparing the modified mesoporous silica adsorbent, when the silane coupling agent in step S2 contains an amino group, the silane coupling agent includes at least one of 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; (c) In the method for preparing the modified mesoporous silica adsorbent, when the silane coupling agent in step S2 contains a sulfonic acid group, the silane coupling agent is prepared by an oxidation reaction of a silane coupling agent containing a mercapto group.

5. The use according to claim 1, characterized in that: In the preparation method of the modified mesoporous silica adsorbent, the removal of the template agent in step S2 includes at least one of dissolving the template agent with an organic solvent and removing the template agent by calcination; The method of using an organic solvent to dissolve the template agent comprises: using at least one organic solvent selected from methanol, ethanol, n-heptane and kerosene to dissolve the template agent at 60-120° C.; The calcination to remove the template agent comprises: calcining to remove the template agent at 500-600°C.

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