Preparation method of imprinting functionalized straw adsorbent

Abstract

The invention belongs to the technical field of material preparation and adsorption separation, and particularly relates to a preparation method of an imprinting functionalized straw adsorbent. The preparation method of the imprint functionalized straw adsorbent comprises the following steps: (1) preparing pretreated straw powder; (2) preparing amino-functionalized straw powder; and (3) dissolving the amino-functionalized straw powder in a first methanol-deionized water mixed solution, dissolving ethylenediamine tetraacetic anhydride in second methanol, then uniformly mixing the two solutions in a reaction container, then adding carboxylated carbon nanotubes, stirring and uniformly mixing, finally adding gadolinium chloride hexahydrate, continuously stirring, and after the reaction is finished, carrying out post-treatment to obtain the gadolinium-modified straw powder. And preparing to obtain the imprinting functionalized straw adsorbent. According to the preparation method disclosed by the invention, an ion imprinting technology is adopted, so that the gadolinium ions have a memory function, and the aim of selectively removing the gadolinium ions in a complex water environment is fulfilled.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation and adsorption separation, and specifically relates to a preparation method of an imprinted functionalized straw adsorbent. Background Art

[0002] The rare earth metal gadolinium has excellent optical and magnetic properties and is crucial in the production of medical imaging, magnetic refrigeration, nuclear reactions, and optical isolators. The rapid development of science and technology has forced people to excessively increase the demand for gadolinium. The active mining of rare earth mines and the improper disposal of gadolinium-containing wastes have caused the surrounding water environment to be polluted. Free gadolinium ions in water bodies are toxic and will seriously threaten the health and safety of living organisms in the long run. Therefore, efficient and selective removal of gadolinium ions in water bodies is of great practical significance for maintaining ecological security and improving the level of water purification technology.

[0003] At present, the main methods for treating gadolinium pollution in water bodies include chemical precipitation, solvent extraction and ion exchange. However, they also face many problems in practical applications, such as unpredictable secondary pollution to the environment, complex large-scale production procedures and relatively high costs. In recent years, straw adsorbents have gradually entered the public eye, and there are more and more studies on their removal of dyes and heavy metal ions in water bodies, but the remediation of rare earth metal gadolinium ions in water bodies has not been reported. One issue worthy of attention is that when using adsorbents to treat water environmental problems, other metal ions coexisting in the water body often compete with gadolinium ions for attachment to the same action site on the surface of the adsorbent, resulting in a reduction in the adsorbent's ability to remove gadolinium ions. Therefore, it is urgent to develop an adsorbent with selective adsorption function, economical, efficient and convenient.

[0004] In addition, since the straw adsorbent mainly chemically adsorbs metal ions, the functional groups carried by the adsorbent play a key role in the adsorption capacity of gadolinium ions. Therefore, how to make the straw adsorbent more effectively and specifically remove gadolinium ions from water is a technical problem that the present invention needs to focus on. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing an imprinted functionalized straw adsorbent. The preparation method adopts ion imprinting technology to make it have a memory function for gadolinium ions, thereby achieving the purpose of selectively removing gadolinium ions in a complex water environment.

[0006] The method for preparing the imprinted functionalized straw adsorbent of the present invention comprises the following steps: (1) grinding rice straw into powder, soaking it in a sodium hydroxide solution for a period of time, and then filtering, washing, and drying to prepare pretreated straw powder; (2) adding the pretreated straw powder prepared in step (1), potassium persulfate and water into a reaction container and mixing them evenly, then dropping an acrylamide solution to carry out an oil bath reaction, and finally filtering, washing with water and drying to prepare amino-functionalized straw powder; (3) The amino-functionalized straw powder prepared in step (2) is dissolved in a first methanol-deionized water mixed solution, ethylenediaminetetraacetic anhydride is dissolved in a second methanol, and then the two are placed in a reaction container and mixed, followed by adding carboxylated carbon nanotubes and stirring, and finally adding gadolinium trichloride hexahydrate and continuing to stir. After the reaction is completed, post-treatment is performed to prepare an imprinted functionalized straw adsorbent.

[0007] in: In step (1), the rice straw is ground into powder, and the powder is controlled to pass through a 60-mesh sieve.

[0008] In step (1), the concentration of the sodium hydroxide solution is 0.5 mol / L, the immersion temperature is 65° C., and the immersion time is 1 h.

[0009] In step (1), the drying temperature is 40° C. and the drying time is 12 h.

[0010] In step (2), the pretreated straw powder, potassium persulfate and water prepared in step (1) are added into a reaction container and mixed evenly at a mixing temperature of 80° C. for 30 min.

[0011] During the reaction of step (2), the stirring speed was controlled at 1700 r / min.

[0012] The temperature of the oil bath reaction in step (2) is 80° C., and the time of the oil bath reaction is 3 h.

[0013] The mass ratio of the pretreated straw powder, potassium persulfate and water in step (2) is 1:0.27:150.

[0014] In step (2), the mass ratio of potassium persulfate to acrylamide in the acrylamide solution is 0.27:7.1-21.3.

[0015] In step (2), the acrylamide solution uses water as solvent, and the mass concentration is 12.43%-29.87%.

[0016] In step (2), the washing time is 15 minutes, the drying temperature is 40°C, and the drying time is 8 hours.

[0017] In step (3), the mass ratio of amino-functionalized straw powder, ethylenediaminetetraacetic anhydride, carboxylated carbon nanotubes and gadolinium trichloride hexahydrate is 1:3-9:0.1:0.125-0.5.

[0018] In step (3), the volume ratio of the first methanol to the deionized water in the first methanol-deionized water mixed solution is 1:1.

[0019] In step (3), the mass volume ratio of the amino-functionalized straw powder to the first methanol-deionized water mixed solution is 1:20, expressed in g / mL.

[0020] In step (3), ethylenediaminetetraacetic anhydride is dissolved in the second methanol, and the mass volume ratio of ethylenediaminetetraacetic anhydride to the second methanol is 3-9:100, and the unit is g / mL.

[0021] In step (3), the stirring speed is controlled at 1700 r / min during the reaction, and finally gadolinium trichloride hexahydrate is added and stirring is continued for 24 hours.

[0022] The post-treatment in step (3) is to filter the product, add ethanol and continue stirring for 16 hours at a stirring speed of 1500 r / min, filter again, immerse in 1 mol / L HCl solution for 12 hours, filter the product again, wash with deionized water, wash with 0.1 mol / L NaOH solution, wash with deionized water, and dry to obtain an imprinted functionalized straw adsorbent; wherein the ratio of the volume of ethanol to the sum of the volumes of the first methanol and the second methanol is 15:11.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The method for preparing the imprinted functionalized straw adsorbent of the present invention uses rice straw, which is a natural, high-yield biomass. Using it as the base material of the adsorbent has the advantages of green economy and sustainable development. During the preparation, the pretreated straw is firstly amino-functionalized to provide binding sites that can interact with ethylenediaminetetraacetic anhydride, laying the foundation for the ion imprinting process. Ethylenediaminetetraacetic anhydride not only serves as a functional monomer for adsorbing gadolinium ions, but also serves as a cross-linking agent to polymerize the ion imprinting polymer in one step, greatly simplifying the ion imprinting process. Ethylenediaminetetraacetic anhydride reacts with amino groups to form an EDTA structure with hexadentate coordination ability. Gadolinium trichloride hexahydrate is used as the template ion. After elution with hydrochloric acid, pores matching the size of gadolinium ions are formed. The specific pores formed by the imprinting technology improve the selectivity for gadolinium ions. Carboxylated carbon nanotubes provide abundant oxygen-containing functional groups (-COOH), which enhance the coordination effect with gadolinium ions. The synergistic effect of the two ensures that the prepared imprinted functionalized straw adsorbent has excellent adsorption selectivity and adsorption capacity.

[0024] (2) The preparation method of the imprinted functionalized straw adsorbent described in the present invention not only simplifies the ion imprinting procedure and provides more gadolinium ion adsorption sites, but also can solve the problem of removing gadolinium ions from water in a targeted and effective one-step manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a scanning electron microscope comparison of the pretreated straw powder prepared in Example 2, the amino-functionalized straw prepared in Example 2, the imprinted functionalized straw adsorbent prepared in Example 2, the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3, and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes prepared in Comparative Example 4; Figure 1 In the figure: Figure a is a scanning electron microscope image of the pretreated straw powder prepared in Example 2 at a magnification of 2000, Figure b is a scanning electron microscope image of the amino-functionalized straw prepared in Example 2 at a magnification of 2000, Figure c is a scanning electron microscope image of the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes prepared in Comparative Example 4 at a magnification of 2000, Figure d is a scanning electron microscope image of the imprinted functionalized straw adsorbent prepared in Example 2 at a magnification of 2000, Figure e is a scanning electron microscope image of the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3 at a magnification of 2000, and Figure f is a scanning electron microscope image of the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3 at a magnification of 5000; Figure 2 It is an infrared spectra of the pretreated straw powder prepared in Example 2, the amino-functionalized straw prepared in Example 2, the imprinted functionalized straw adsorbent prepared in Example 2, the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3, and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes prepared in Comparative Example 4; Figure 2 In: PS represents the pretreated straw powder in Example 2, AMS represents the amino-functionalized straw in Example 2, CEAMS-IIM represents the imprinted functionalized straw adsorbent prepared in Example 2, CEAMS-NIIM represents the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3, and EAMS-IIM represents the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes prepared in Comparative Example 4; Figure 3 The nitrogen adsorption / desorption isotherms of the pretreated straw powder prepared in step (1) of Example 2, the imprinted functionalized straw adsorbent prepared in step (3) of Example 2, the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3, and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes prepared in Comparative Example 4; Figure 3 In: PS represents the pretreated straw powder in Example 2, CEAMS-IIM represents the imprinted functionalized straw adsorbent prepared in Example 2, CEAMS-NIIM represents the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3, and EAMS-IIM represents the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes prepared in Comparative Example 4; Figure 4 The adsorption isotherm data and model diagram of gadolinium ions of the imprinted functionalized straw adsorbent prepared in step (3) of Example 2, the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3, and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes prepared in Comparative Example 4; Figure 4 In: CEAMS-IIM represents the imprinted functionalized straw adsorbent prepared in Example 2, CEAMS-NIIM represents the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3, and EAMS-IIM represents the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes prepared in Comparative Example 4; LangmuirFit is the Langmuir fitting model; FreundlichFit is the Freundlich fitting model; Figure 5 The adsorption kinetic data and model diagram of gadolinium ions by the imprinted functionalized straw adsorbent prepared in step (3) of Example 2, the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3, and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes prepared in Comparative Example 4; Figure 5 In: CEAMS-IIM represents the imprinted functionalized straw adsorbent prepared in Example 2, CEAMS-NIIM represents the non-imprinted functionalized straw adsorbent prepared in Comparative Example 3, EAMS-IIM represents the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes prepared in Comparative Example 4; PFOKMFit is a pseudo-first-order kinetic model fitting curve for the adsorption kinetics data; PSOKMFit is a pseudo-second-order kinetic model fitting curve for the adsorption kinetics data. DETAILED DESCRIPTION

[0026] The present invention is further described below with reference to the embodiments.

[0027] The manufacturer of carboxylated carbon nanotubes is McLean Chemical Reagent Co., Ltd. The purity is >95%, the inner diameter is about 2-5nm, the outer diameter is <8nm, the length is about 10-30μm, and the carboxyl functional group content is about 3.9wt%.

[0028] Example 1 The preparation method of the imprinted functionalized straw adsorbent described in Example 1 is composed of the following steps: (1) The washed and dried rice straw was cut into 5 cm long segments, then put into a grinder and ground into powder, and the powder was sieved through a 60-mesh sieve. The powder was soaked in a 0.5 mol / L NaOH solution at 65°C for 1 h, and finally filtered, washed with water, and dried (drying temperature was 40°C, drying time was 12 h) to prepare pretreated straw powder.

[0029] (2) 1 g of the pretreated straw powder prepared in step (1), 0.27 g of potassium persulfate and 150 mL of deionized water were placed in a round-bottom flask and placed in an oil bath at 80°C for 30 min. Subsequently, 7.1 g of acrylamide was dissolved in 50 mL of deionized water to prepare an acrylamide solution, and the acrylamide solution was added dropwise to the round-bottom flask and continued to react in an oil bath at 80°C for 3 h. During the reaction, the stirring speed was controlled to be 1700 r / min. The product was filtered, soaked in deionized water for 15 min, and then dried at 40°C for 8 h to obtain amino-functionalized straw.

[0030] (3) Disperse 1g of amino-functionalized straw powder obtained in step (2) in a mixture of first methanol and deionized water (the volume ratio of first methanol to deionized water is 10mL:10mL), disperse 3g of ethylenediaminetetraacetic anhydride in 100mL of second methanol, place the two in a round-bottom flask and stir to mix evenly, then add 0.1g of carboxylated carbon nanotubes and continue stirring until uniform. Add 0.125g of gadolinium trichloride hexahydrate to the round-bottom flask and continue stirring for 24h, control the stirring speed during the reaction to be 1700r / min, filter the product, add 150mL of ethanol and continue stirring for 16h, filter the product, immerse it in 1mol / L HCl solution for 12h, filter the product, wash it with deionized water, wash it with 0.1mol / LNaOH solution, wash it with deionized water, and dry it to obtain an imprinted functionalized straw adsorbent.

[0031] Comparative Example 1 The preparation method of the straw adsorbent described in this comparative example 1 is the same as that of Example 1, the only difference being that gadolinium trichloride hexahydrate is not added in step (3), and a non-imprinted functionalized straw adsorbent is prepared.

[0032] Comparative Example 2 The preparation method of the straw adsorbent described in this comparative example 2 is the same as that of Example 1, the only difference being that no carboxylated carbon nanotubes are added in step (3), and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes is prepared.

[0033] Example 2 The preparation method of the imprinted functionalized straw adsorbent described in Example 2 is composed of the following steps: (1) The washed and dried rice straw was cut into 5 cm long segments, then put into a grinder and ground into powder. The powder was sieved through a 60-mesh sieve. The powder was soaked in a 0.5 mol / L NaOH solution at 65 °C for 1 h, and finally filtered, washed with water, and dried (drying temperature was 40 °C, drying time was 12 h) to prepare pretreated straw powder (named PS).

[0034] (2) 1 g of the pretreated straw powder prepared in step (1), 0.27 g of potassium persulfate and 150 mL of deionized water were placed in a round-bottom flask and placed in an oil bath at 80°C for 30 min. Subsequently, 14.2 g of acrylamide was dissolved in 50 mL of deionized water to prepare an acrylamide solution, and the acrylamide solution was added dropwise to the round-bottom flask and continued to react in an oil bath at 80°C for 3 h. During the reaction, the stirring speed was controlled to be 1700 r / min. The product was filtered, soaked in deionized water for 15 min, and then dried at 40°C for 8 h to obtain amino-functionalized straw (named AMS).

[0035] (3) Disperse 1 g of amino-functionalized straw powder obtained in step (2) in a mixture of first methanol and deionized water (the volume ratio of the first methanol to deionized water is 10 mL:10 mL), disperse 6 g of ethylenediaminetetraacetic anhydride in 100 mL of the second methanol, place the two in a round-bottom flask and stir to mix evenly, then add 0.1 g of carboxylated carbon nanotubes and continue stirring until uniform. Add 0.25 g of gadolinium trichloride hexahydrate to the round-bottom flask and continue stirring for 24 h. Control the stirring speed during the reaction at 1700 r / min. Filter the product and add 150 mL of ethanol to continue stirring for 16 h. Filter the product and immerse it in 1 mol / L HCl solution for 12 h. Filter the product and wash it with deionized water, wash it with 0.1 mol / L NaOH solution, wash it with deionized water, and dry it to obtain an imprinted functionalized straw adsorbent (named CEAMS-IIM).

[0036] Comparative Example 3 The preparation method of the straw adsorbent described in this comparative example 3 is the same as that of Example 2, the only difference being that gadolinium trichloride hexahydrate is not added in step (3), and a non-imprinted functionalized straw adsorbent (named CEAMS-NIIM) is prepared.

[0037] Comparative Example 4 The preparation method of the straw adsorbent described in this comparative example 4 is the same as that of Example 2, the only difference being that no carboxylated carbon nanotubes are added in step (3), and an imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes (named EAMS-IIM) is prepared.

[0038] Example 3 The preparation method of the imprinted functionalized straw adsorbent described in Example 3 is composed of the following steps: (1) The washed and dried rice straw was cut into 5 cm long segments, then put into a grinder and ground into powder, and the powder was sieved through a 60-mesh sieve. The powder was soaked in a 0.5 mol / L NaOH solution at 65°C for 1 h, and finally filtered, washed with water, and dried (drying temperature was 40°C, drying time was 12 h) to prepare pretreated straw powder.

[0039] (2) 1 g of the pretreated straw powder prepared in step (1), 0.27 g of potassium persulfate and 150 mL of deionized water were placed in a round-bottom flask and placed in an oil bath at 80°C for 30 min. Subsequently, 21.3 g of acrylamide was dissolved in 50 mL of deionized water to prepare an acrylamide solution, and the acrylamide solution was added dropwise to the round-bottom flask and continued to react in an oil bath at 80°C for 3 h. During the reaction, the stirring speed was controlled to be 1700 r / min. The product was filtered, soaked in deionized water for 15 min, and then dried at 40°C for 8 h to obtain amino-functionalized straw.

[0040] (3) Disperse 1g of amino-functionalized straw powder obtained in step (2) in a mixture of first methanol and deionized water (the volume ratio of first methanol to deionized water is 10mL:10mL), disperse 9g of ethylenediaminetetraacetic anhydride in 100mL of second methanol, place the two in a round-bottom flask and stir to mix evenly, then add 0.1g of carboxylated carbon nanotubes and continue stirring until uniform. Add 0.5g of gadolinium trichloride hexahydrate to the round-bottom flask and continue stirring for 24h, control the stirring speed during the reaction to be 1700r / min, filter the product, add 150mL of ethanol and continue stirring for 16h, filter the product, immerse it in 1mol / L HCl solution for 12h, filter the product, wash it with deionized water, wash it with 0.1mol / LNaOH solution, wash it with deionized water, and dry it to obtain an imprinted functionalized straw adsorbent.

[0041] Comparative Example 5 The preparation method of the straw adsorbent described in this comparative example 5 is the same as that of Example 3, the only difference being that gadolinium trichloride hexahydrate is not added in step (3), and a non-imprinted functionalized straw adsorbent is prepared.

[0042] Comparative Example 6 The preparation method of the straw adsorbent described in this comparative example 6 is the same as that of Example 3, the only difference being that no carboxylated carbon nanotubes are added in step (3), and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes is prepared.

[0043] The pretreated straw powder (named PS) prepared in step (1) of Example 2, the amino-functionalized straw (named AMS) prepared in step (2) of Example 2, the imprinted functionalized straw adsorbent (named CEAMS-IIM) prepared in step (3) of Example 2, the non-imprinted functionalized straw adsorbent (named CEAMS-NIIM) prepared in comparative example 3, and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes (named EAMS-IIM) prepared in comparative example 4 were tested by scanning electron microscopy to obtain the adsorbent. Figure 1 The SEM images are shown in Figure 2. Figure 1 It can be seen that the surface morphologies of PS and AMS are similar. Compared with AMS, EAMS-IIM has a wrinkled surface structure, indicating that the introduction of EDTA will change the surface morphology of AMS. Compared with EAMS-IIM, there are several clusters scattered on the layered structure surface of CEAMS-IIM, which may be caused by the aggregation of COOH-CNTs. The surface morphology of CEAMS-NIIM is similar to that of CEAMS-IIM, but the surface of CEAMS-NIIM is smoother, which may be due to the presence of imprinted cavities on the surface of CEAMS-IIM. In summary, the influence of the grafting effect of functional groups and the imprinting effect on the surface morphology of different materials helps to evaluate whether the material is successfully prepared and whether the imprinting site is successfully constructed.

[0044] The pretreated straw powder (named PS) prepared in step (1) of Example 2, the amino-functionalized straw (named AMS) prepared in step (2) of Example 2, the imprinted functionalized straw adsorbent (named CEAMS-IIM) prepared in step (3) of Example 2, the non-imprinted functionalized straw adsorbent (named CEAMS-NIIM) prepared in comparative example 3, and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes (named EAMS-IIM) prepared in comparative example 4 were subjected to infrared spectroscopy test to obtain the adsorbent. Figure 2 Infrared spectrum shown.

[0045] Figure 2 The infrared spectra of PS, AMS, EAMS-IIM, CEAMS-IIM and CEAMS-NIIM are shown in Figure 2. Figure 2 It can be seen that all materials have a wavelength of 3434cm -1 There is a broad adsorption peak at 2933 and 2852 cm-1, which corresponds to the stretching vibration of OH and NH. -1 Compared with PS, AMS has the stretching vibration of CH at 891, 1388 and 1626 cm -1Several characteristic adsorption peaks appeared at 891, 1388 and 3434 cm-1 after EDTA was grafted onto AMS. -1 The peak intensity at 1741cm -1 A new characteristic absorption peak appeared at , which is the C=O stretching vibration peak of the free carboxyl group, indicating that they were successfully grafted with EDTA. There was no significant difference between CEAMS-IIM and CEAMS-NIM, indicating that imprinting had little effect on the change of functional groups.

[0046] The pretreated straw powder (named PS) prepared in step (1) of Example 2, the imprinted functionalized straw adsorbent (named CEAMS-IIM) prepared in step (3) of Example 2, the non-imprinted functionalized straw adsorbent (named CEAMS-NIIM) prepared in comparative example 3, and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes (named EAMS-IIM) prepared in comparative example 4 were subjected to adsorption-desorption tests to obtain the adsorbent. Figure 3 Nitrogen adsorption / desorption isotherms are shown.

[0047] from Figure 3 It can be seen that the adsorption isotherm models of PS and EAMS-IIM are similar, characterized by a higher relative pressure (P / P 0 >0.8), the adsorption capacity increased significantly. In contrast, the adsorption of CEAMS-IIM and CEAMS-NIIM began to increase at a relative pressure of about 0.4, and obvious H3-type isotherm hysteresis loops appeared, indicating that both have abundant slit-like mesopores, while PS and EAMS-IIM have smaller or no hysteresis loops, indicating that their pores are mainly macropores or non-rigid pores (such as interparticle stacking gaps). The BET surface area and pore volume of CEAMS-IIM and CEAMS-NIIM are much larger than those of PS and EAMS-IIM, and the pore size is much smaller, which is due to the introduction of COOH-CNTs. The BET surface area and pore size of CEAMS-IIM were 56.24m² / g and 7.256nm, respectively, that of CEAMS-NIIM were 43.45m² / g and 8.070nm, that of PS were 7.379m² / g and 21.50nm, and that of EAMS-IIM were 7.725m² / g and 28.30nm. These results indicate that there are imprinted sites in CEAMS-IIM, which are beneficial to the adsorption of gadolinium ions in water.

[0048] Figure 4 The adsorption isotherm data and model diagram of gadolinium ions of the imprinted functionalized straw adsorbent (named CEAMS-IIM) prepared in step (3) of Example 2, the non-imprinted functionalized straw adsorbent (named CEAMS-NIIM) prepared in Comparative Example 3, and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes (named EAMS-IIM) prepared in Comparative Example 4.

[0049] from Figure 4 It can be seen that the equilibrium adsorption capacity of CEAMS-IIM ( q e ) is the highest, significantly better than EAMS-IIM and CEAMS-NIM, indicating that the introduction of carboxylated carbon nanotubes and imprinting technology synergistically improve the adsorption capacity of gadolinium ions. The Langmuir model fitting effect is better ( R 2 The results are close to 1), indicating that the adsorption behavior of the three materials is more consistent with monolayer chemical adsorption, and the surface adsorption sites are evenly distributed. The Freundlich model has a lower fit, indicating that the adsorption process is less affected by surface heterogeneity and multilayer adsorption, further supporting the monolayer-dominated adsorption mechanism.

[0050] The adsorption capacities of the imprinted functionalized straw adsorbent in Example 2, the non-imprinted functionalized straw adsorbent in Comparative Example 3, and the imprinted functionalized straw adsorbent without carboxylation carbon nanotubes in Comparative Example 4 for gadolinium ions were 59.82 mg / g, 45.02 mg / g, and 39.54 mg / g, respectively. Among them, the imprinted functionalized straw adsorbent in Example 2 has the best adsorption performance for gadolinium ions, which is mainly due to the chemical complexation of the carboxyl functional groups in the imprinted sites on gadolinium ions, and the specific selectivity effect of steric hindrance, indicating that the abundant imprinted active sites can enhance the adsorption performance of the adsorbent for gadolinium ions.

[0051] At the same time, the adsorption capacity of the materials prepared in Example 1, Example 3, Comparative Examples 1-2 and Comparative Examples 5-6 was tested, and the results are as follows: the adsorption capacity of the imprinted functionalized straw adsorbent in Example 1, the non-imprinted functionalized straw adsorbent in Comparative Example 1 and the imprinted functionalized straw adsorbent without carboxylation carbon nanotubes in Comparative Example 2 for gadolinium ions are 50.66 mg / g, 41.88 mg / g and 30.65 mg / g, respectively; the adsorption capacity of the imprinted functionalized straw adsorbent in Example 3, the non-imprinted functionalized straw adsorbent in Comparative Example 5 and the imprinted functionalized straw adsorbent without carboxylation carbon nanotubes in Comparative Example 6 for gadolinium ions are 51.07 mg / g, 42.94 mg / g and 31.32 mg / g, respectively.

[0052] Figure 5The adsorption kinetic data and model diagram of gadolinium ions by the imprinted functionalized straw adsorbent (named CEAMS-IIM) prepared in step (3) of Example 2, the non-imprinted functionalized straw adsorbent (named CEAMS-NIIM) prepared in Comparative Example 3, and the imprinted functionalized straw adsorbent lacking carboxylated carbon nanotubes (named EAMS-IIM) prepared in Comparative Example 4. PSOKMFit is a pseudo-second-order kinetic model, and PFOKMFit is a pseudo-first-order kinetic model.

[0053] from Figure 5 It can be seen that CEAMS-IIM has the fastest adsorption rate and reaches adsorption equilibrium in a short time (about 300 minutes), while EAMS-IIM and CEAMS-NIM need longer time (about 600 minutes), indicating that carboxylated carbon nanotubes and imprinting technology synergistically improve mass transfer efficiency. The pseudo-second-order kinetic model fits better (R² is close to 1), indicating that the adsorption process is mainly chemical adsorption, involving ion exchange, coordination or covalent bonding; the pseudo-first-order kinetic model has a lower fit, indicating that physical adsorption contributes less.

[0054] By comparing Example 2 with Comparative Examples 3-4, it can be seen that the specific pores formed by the imprinting technology improve the selectivity for gadolinium ions; the carboxylated carbon nanotubes provide abundant oxygen-containing functional groups (-COOH), which enhance the coordination effect with gadolinium ions; the two work synergistically to ensure that the prepared imprinted functionalized straw adsorbent has excellent adsorption selectivity and adsorption capacity.

Claims

1. A method for preparing an imprinted functionalized straw adsorbent, characterized in that: It consists of the following steps: (1) grinding rice straw into powder, soaking it in a sodium hydroxide solution for a period of time, and then filtering, washing, and drying to prepare pretreated straw powder; (2) adding the pretreated straw powder prepared in step (1), potassium persulfate and water into a reaction container and mixing them evenly, then dropping an acrylamide solution to carry out an oil bath reaction, and finally filtering, washing with water and drying to prepare amino-functionalized straw powder; (3) The amino-functionalized straw powder prepared in step (2) is dissolved in a first methanol-deionized water mixed solution, ethylenediaminetetraacetic anhydride is dissolved in a second methanol, and then the two are placed in a reaction container and mixed, followed by adding carboxylated carbon nanotubes and stirring, and finally adding gadolinium trichloride hexahydrate and continuing to stir. After the reaction is completed, post-treatment is performed to prepare an imprinted functionalized straw adsorbent.

2. The method for preparing the imprinted functionalized straw adsorbent according to claim 1, characterized in that: In step (1), the rice straw is ground into powder, and the powder is controlled to pass through a 60-mesh sieve; In step (1), the concentration of the sodium hydroxide solution is 0.5 mol / L, the immersion temperature is 65° C., and the immersion time is 1 h; In step (1), the drying temperature is 40° C. and the drying time is 12 h.

3. The method for preparing the imprinted functionalized straw adsorbent according to claim 1, characterized in that: In step (2), the pretreated straw powder, potassium persulfate and water prepared in step (1) are added into a reaction container and mixed evenly at a mixing temperature of 80° C. for 30 min. During the reaction of step (2), the stirring speed is controlled to be 1700 r / min; The temperature of the oil bath reaction in step (2) is 80° C., and the time of the oil bath reaction is 3 h.

4. The method for preparing the imprinted functionalized straw adsorbent according to claim 1, characterized in that: The mass ratio of the pretreated straw powder, potassium persulfate and water in step (2) is 1:0.27:150; In step (2), the mass ratio of potassium persulfate to acrylamide in the acrylamide solution is 0.27:7.1-21.

3.

5. The method for preparing the imprinted functionalized straw adsorbent according to claim 1, characterized in that: In step (2), the acrylamide solution uses water as solvent and has a mass concentration of 12.43%-29.87%; In step (2), the washing time is 15 minutes, the drying temperature is 40°C, and the drying time is 8 hours.

6. The method for preparing the imprinted functionalized straw adsorbent according to claim 1, characterized in that: In step (3), the mass ratio of amino-functionalized straw powder, ethylenediaminetetraacetic anhydride, carboxylated carbon nanotubes, and gadolinium trichloride hexahydrate is 1:3-9:0.1:0.125-0.5; In step (3), the volume ratio of the first methanol to the deionized water in the first methanol-deionized water mixed solution is 1:

1.

7. The method for preparing the imprinted functionalized straw adsorbent according to claim 1, characterized in that: In step (3), the mass volume ratio of the amino-functionalized straw powder to the first methanol-deionized water mixed solution is 1:20, expressed in g / mL.

8. The method for preparing the imprinted functionalized straw adsorbent according to claim 1, characterized in that: In step (3), ethylenediaminetetraacetic anhydride is dissolved in the second methanol, and the mass volume ratio of ethylenediaminetetraacetic anhydride to the second methanol is 3-9:100, and the unit is g / mL.

9. The method for preparing the imprinted functionalized straw adsorbent according to claim 1, characterized in that: In step (3), the stirring speed is controlled at 1700 r / min during the reaction, and finally gadolinium trichloride hexahydrate is added and stirring is continued for 24 hours.

10. The method for preparing the imprinted functionalized straw adsorbent according to claim 1, characterized in that: The post-treatment in step (3) is to filter the product, add ethanol and continue stirring for 16 hours at a stirring speed of 1500 r / min, filter again, immerse in 1 mol / L HCl solution for 12 hours, filter the product again, wash with deionized water, wash with 0.1 mol / L NaOH solution, wash with deionized water, and dry to obtain an imprinted functionalized straw adsorbent; wherein the ratio of the volume of ethanol to the sum of the volumes of the first methanol and the second methanol is 15:11.

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