Composite adsorbent material, method for preparing the same, and use thereof

Abstract

This invention provides a composite adsorbent material, its preparation method, and its application. The preparation method includes: preparing hydrogel pellets using montmorillonite minerals, agar, and sodium alginate as raw materials; culturing the hydrogel pellets and Bacillus cereus under oligotrophic conditions with inorganic salts; and performing solid-liquid separation after culturing to obtain the gel composite adsorbent material. The prepared microbial-mineral (micro-mineral) composite adsorbent material has high purity and can be applied to the treatment of uranium-containing wastewater (low concentration), for example, as a UO2 treatment. 2+ The adsorbent is applied to the treatment of radioactive wastewater. This invention has low preparation costs, helps alleviate the environmental pressure of radioactive wastewater, and has good environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of synergistic adsorption material preparation, and more specifically, to a composite adsorption material, its preparation method, and its application. Background Technology

[0002] With the depletion of fossil fuels, nuclear energy is playing an increasingly important role in energy utilization. As a fundamental raw material for nuclear energy, uranium ore is being mined extensively. However, the mining, enrichment, processing, and utilization of uranium inevitably result in radioactive wastewater entering surface runoff. This further diffusion through surface runoff will inevitably cause widespread radioactive contamination of soil and groundwater. In acidic (pH < 6.8) surface runoff systems, uranium primarily exists as uranyl (UO2). 2+ UO2 exists in the form of micro-minerals and migrates with water bodies, ultimately posing a serious potential threat to human health through bioaccumulation in the food chain. This invention specifically relates to the field of (micro-mineral) synergistic adsorption materials, which can alleviate UO2 in nuclear-related wastewater. 2+ Potential harm to the environment.

[0003] Montmorillonite is a layered crystalline mineral material with a repeating dioctahedral structure along both the b- and c-axis directions. Its basal and end faces are rich in various functional groups, which provide key sites for montmorillonite modification, making such modification possible. Naturally occurring montmorillonite-rich montmorillonite minerals, or their modified forms, can act as UO2 in aqueous systems. 2+ Preliminary studies have also confirmed the effectiveness of modified montmorillonite (montmorillonite) in adsorbing UO2. 2+ The adsorption capacity can be significantly improved. Furthermore, microorganisms are the most abundant biological group on Earth. They can utilize free organic compounds (carboxyl groups, amino acids, carbohydrates, etc.) in the terrestrial environment and produce low-molecular-weight organic functional groups, leading to reduction and oxidation of iron compounds in clay minerals, thus resulting in microbial mineralization. Metabolites can also react with UO2. 2+ Ions undergo adsorption, complexation, and valence change reactions to affect UO2. 2+ Ions play a role in both enrichment and removal. Therefore, microbial removal methods are currently widely used for removing low concentrations of UO2 in water. 2+ Ion removal. This study utilizes polymers as the main matrix to prepare composite adsorbent materials via cross-linking. Currently, there are no existing methods or applications for preparing similar composite adsorbent materials. Summary of the Invention

[0004] The purpose of this invention is to address at least one of the aforementioned shortcomings of the prior art. For example, one objective of this invention is to provide a composite adsorbent material with micro-mineral synergistic effect; a second objective of this invention is to provide a method for preparing a composite adsorbent material with low cost and high product purity; and a third objective of this invention is to provide a composite adsorbent material for UO2. 2+ Applications of highly efficient ion removal.

[0005] To achieve the above objectives, the present invention provides a method for preparing a composite adsorbent material.

[0006] The method may include the following steps: preparing hydrogel balls using montmorillonite minerals, agar, and sodium alginate as raw materials; culturing the hydrogel balls and Bacillus cereus under oligotrophic conditions with inorganic salts; and performing solid-liquid separation after culturing to obtain a gel composite adsorbent material.

[0007] Alternatively, the montmorillonite mineral may be obtained by pre-treating montmorillonite raw material. The pre-treating process may include crushing, washing, drying and grinding, or it may include crushing, washing and drying.

[0008] Alternatively, the montmorillonite raw material may have a specific surface area of ​​40–70 m². 2 ·g -1 For example, 45, 50, 56.37, 60, 65m 2 ·g -1 wait.

[0009] Alternatively, the cation exchange capacity of the montmorillonite raw material may be 70–90 mmol·100g. -1 For example, 75, 80, 84.8, 85, 89 mmol / 100g -1 wait.

[0010] Alternatively, the montmorillonite raw material can be modified to increase its cation exchange capacity.

[0011] Alternatively, the pulverized montmorillonite raw material can be completely passed through a 70-mesh sieve.

[0012] Alternatively, the washing may include washing with deionized water first, followed by further washing with an ethanol solution, with both washing processes performed under ultrasonic assistance.

[0013] Alternatively, the particle size of the montmorillonite mineral obtained after grinding is all less than 0.212 mm.

[0014] Optionally, the method may further include the cultivation of Bacillus cereus and the preparation of bacterial culture, wherein the culturing includes: inoculating Bacillus cereus into LB liquid medium and culturing it to the logarithmic growth phase, and then isolating the solid culture;

[0015] The preparation of the bacterial solution may include: removing the LB liquid culture medium remaining on the solid bacterial strain, then mixing the solid bacterial strain with inorganic salt culture medium and adjusting the OD600 value to 0.6-1.2 to obtain the bacterial solution.

[0016] Alternatively, the step of performing the combined culture may include: adding the hydrogel pellets to the above-mentioned bacterial solution and culturing for 6 to 24 hours, wherein the surface of the hydrogel pellets is free of moisture.

[0017] Alternatively, prior to the composite culture, the method may further include the step of drying the surface of the hydrogel pellets under aseptic conditions.

[0018] Optionally, the step of preparing hydrogel balls may include: dispersing the montmorillonite mineral and the agar in an aqueous solution at 60-100℃ at a liquid-to-solid ratio of 40-60 mL / g to obtain a first intermediate solution, wherein the mass ratio of the montmorillonite mineral to the agar is 3-1; adding the sodium alginate to the first intermediate solution and stirring to obtain a second intermediate solution, wherein the mass ratio of the sodium alginate to the montmorillonite mineral is 1.0-1.85; sterilizing the second intermediate solution, and then adding sterile CaCl2 solution dropwise to solidify and obtain the hydrogel balls.

[0019] Optionally, the stirring time can be 20-30 min, the concentration of the sterile CaCl2 solution can be 4-12%, and the curing time can be 9-15 h.

[0020] Another aspect of the present invention provides a composite adsorption material.

[0021] The composite adsorbent material can be prepared by the above preparation method.

[0022] In another aspect, the present invention provides the application of the above-mentioned composite adsorbent material.

[0023] The application may include the use of the composite adsorbent material in the treatment of uranium-containing wastewater.

[0024] Compared with the prior art, the beneficial effects of the present invention may include at least one of the following:

[0025] 1) Composite adsorption materials can remove UO2 from water systems. 2+ Adsorption, with a maximum adsorption capacity of 90 mg·g -1 It is an excellent adsorbent for treating uranium-containing wastewater.

[0026] 2) Low preparation cost.

[0027] 3) It helps alleviate the environmental pressure of radioactive wastewater.

[0028] 4) It has good environmental and economic benefits. Attached Figure Description

[0029] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0030] Figure 1 The X-ray diffraction pattern of the composite adsorption material in exemplary embodiment 1 of the present invention is shown;

[0031] Figure 2 A scanning electron microscope image of the composite adsorption material in exemplary embodiment 2 of the present invention is shown;

[0032] Figure 3 A scanning electron microscope image of the composite adsorbent material in Example 1 of the present invention is shown. Detailed Implementation

[0033] The present invention will be described in detail below with reference to exemplary embodiments and accompanying drawings.

[0034] Exemplary Example 1

[0035] This exemplary embodiment provides a method for preparing a composite adsorbent material, the method comprising the following steps:

[0036] S10: Hydrogel balls are prepared using montmorillonite minerals, agar, and sodium alginate as raw materials.

[0037] In this embodiment, montmorillonite mineral can be obtained by pre-treating montmorillonite raw material.

[0038] Montmorillonite raw materials have a specific surface area of ​​40–70 m². 2 ·g -1 For example, 41m 2 ·g -1 50m 2 ·g -1 52m 2 ·g -1 56.37m 2 ·g -1 58m 2 ·g -1 65m 2 ·g -1 69m 2 ·g -1 etc.; possessing a cation exchange capacity of 70–90 mmol·100g. -1 For example, 71 mmol / 100g -1 75mmol·100g -1 80mmol·100g -183mmol·100g -1 84.8 mmol / 100g -1 89mmol·100g -1 The cation exchange capacity of montmorillonite minerals can be further increased by inorganic modification, organic modification, or composite modification. The main chemical components of montmorillonite minerals may include: 53% SiO2, 18.74% Al2O3, 3.04% Fe2O3, and 2.06% MgO.

[0039] The pretreatment of montmorillonite raw materials may include crushing, washing, drying, and grinding. For example, after processing the montmorillonite raw materials with a magnetic pulverizer, all of them are passed through a 70-mesh sieve. They are then washed with deionized water under ultrasonic assistance, followed by further washing with an ethanol solution (e.g., a 20% ethanol solution). The entire washing process is carried out under ultrasonic irradiation at a frequency of 25kHz to 50kHz, such as 26kHz, 36kHz, 40kHz, 45kHz, and 49kHz. The vibration frequency should not be lower than the lower limit of the frequency range, as a low vibration frequency will hinder the dispersion of the raw materials. The pretreated samples are then separated into solid and liquid components using a vacuum filter. The solid is dried in a vacuum drying oven at 40–60℃ for 12–18 hours, for example, drying temperatures such as 41℃, 43℃, 48℃, 55℃, and 59℃, and drying times such as 13h, 16h, and 17h. Excessively high drying temperatures are detrimental to subsequent crosslinking. After drying, the samples are stored in a desiccator for later use, or ground and passed through a 70-mesh sieve after drying.

[0040] In this embodiment, the specific steps for preparing hydrogel balls may include:

[0041] S11: The mass ratio of montmorillonite mineral to agar can be 3.0–1 g·g. -1 The montmorillonite mineral is dispersed in an aqueous solution at 60–100°C, with a liquid-to-solid ratio of 40–60 mL / g during dispersion. After thorough dispersion, a first intermediate solution is obtained. For example, the mass ratio of montmorillonite mineral to agar can be 2.9 g / g. -1 2.5g·g -1 1.6g·g -1 1.1 g·g -1 The temperature of the aqueous solution used for dispersion can be 61℃, 68℃, 76℃, 85℃, 99℃, etc., and the liquid-to-solid ratio of the dispersion process can be 41mL / g, 43mL / g, 50mL / g, 55mL / g, 59mL / g, etc.

[0042] S12: Add sodium alginate to the first intermediate solution, with a sodium alginate to mineral mass ratio of 1–1.85 g / g. -1 For example, 1.01 g·g -1 1.55g·g -11.84 g·g -1 The system temperature is controlled at 40–70°C, and stirring is continued for 20–30 minutes, for example, the stirring temperature can be 21 minutes, 27 minutes, 29 minutes, etc., to obtain the second intermediate solution.

[0043] S13: The second intermediate solution is sterilized in an autoclave, and after cooling, 4%–12% sterile CaCl2 solution is dripped into it using a sterile syringe and solidified for 9–15 hours to prepare hydrogel balls. The concentration of the sterile CaCl2 solution can be 5%, 7%, 8%, 11%, etc., and the solidification time can be 10 hours, 11 hours, 12 hours, 14 hours, etc.

[0044] S20: Hydrogel balls and Bacillus cereus are cultured together under inorganic salt oligotrophic conditions, and then solid-liquid separation is performed to obtain gel composite adsorbent material.

[0045] In this embodiment, step S20 may specifically include:

[0046] S21: Inoculate the Bacillus cereus strain into LB liquid medium using an Erlenmeyer flask and incubate in a constant temperature incubator at 25-35℃ for 48-72 hours until the logarithmic phase of the strain. For example, the incubation time can be 49 hours, 52 hours, 65 hours, 70 hours, 71 hours, etc. Strictly control the incubation environment to prevent contamination by other microorganisms.

[0047] S22: After the bacterial strain grows to the logarithmic phase, centrifuge at 3000-5000 rpm for 7-12 minutes; for example, the centrifugation speed can be 3100 rpm, 3500 rpm, 4000 rpm, 4500 rpm, 4900 rpm, etc., and the centrifugation time can be 8 minutes, 9 minutes, 10 minutes, 11 minutes, etc.

[0048] S23: The solid bacterial culture obtained after isolation is washed 3 to 7 times with 0.9% sterile physiological saline to remove LB liquid culture medium.

[0049] S24: Adjust the washed bacterial culture to OD using inorganic salt culture medium. 600 A value of 0.6 to 1.2 yields the OD. 600 The Bacillus cereus bacterial suspension was prepared on an inorganic salt oligotrophic substrate with a pH of 0.6–1.2 and then stored in a refrigerator (3℃–8℃) for later use. The number of times the sample was washed with physiological saline could be 4, 5, or 6 times, etc., to determine the OD value. 600 Values ​​can be 0.7, 0.8, 0.9, 1.1, etc., and refrigerator storage temperatures can be 4℃, 6℃, 7℃, etc. Inorganic salt culture medium can contain: sodium lactate 10 mmol·L⁻¹ -1 NaHCO3 2g·L -1 0.1 g·L -1The pH value can be adjusted to 7.0±0.1 using 1M hydrochloric acid, for example, the pH value can be 6.9, 7.0 or 7.1.

[0050] S25: Dry the surface moisture of the prepared montmorillonite hydrogel balls under sterile conditions, and then add OD. 600 The *Bacillus cereus* bacterial culture was incubated in an inorganic salt oligotrophic substrate with a pH of 0.6–1.2 for 6–24 hours (e.g., 7 h, 12 h, 18 h, 20 h, 23 h, etc.). After incubation, vacuum filtration was used to separate the solid and liquid phases, and the resulting solid-based material was the composite adsorbent. XRD analysis was used to analyze the phase composition of the prepared solid-based composite adsorbent material. Figure 1 As shown, the main phases of the adsorbent material are montmorillonite and sodium alginate. Figure 1 In this text, Montmorillonite represents montmorillonite, and SA represents sodium alginate. Phase analysis shows that no other phases are generated during the crosslinking process of montmorillonite and sodium alginate, indicating a good crosslinking effect.

[0051] Exemplary Example 2

[0052] This exemplary embodiment provides a composite adsorbent material. The composite adsorbent material is prepared by the method described in Exemplary Embodiment 1. A scanning electron microscope (SEM) image of the obtained composite adsorbent material is shown below. Figure 2 As shown in the figure, Mt represents montmorillonite, and SA represents sodium alginate (the area marked by the lighter-colored lines). Montmorillonite is adsorbed on the surface and in the crevices of sodium alginate, increasing the specific surface area of ​​the adsorbent material. Additionally, it also represents UO2. 2+ It provides abundant active sites, which is conducive to the adsorption process.

[0053] Exemplary Example 3

[0054] This exemplary embodiment provides the application of the composite adsorption material in Exemplary Embodiment 2.

[0055] The applications may include the use of the composite adsorbent material in the treatment of uranium-containing wastewater, for example, using the composite adsorbent material as UO2. 2+ The adsorbent is used in the treatment of radioactive wastewater.

[0056] To better understand the present invention, the exemplary embodiment 1 described above will be further described below in conjunction with specific embodiments.

[0057] Example 1

[0058] S10: The mass ratio is 1g·g -1 Montmorillonite mineral and agar (at a mass ratio of 1:1) were thoroughly dispersed in an aqueous solution at 60°C, with a liquid-to-solid ratio of 40 mL·g during the dispersion process. -1After dispersion, sodium alginate is added, with a mass ratio of sodium alginate to mineral of 1 g / g. -1 The system temperature was controlled and stirred continuously for 20–30 minutes. It was then sterilized in an autoclave. After cooling, 4% sterile CaCl2 solution was immediately added dropwise using a sterile syringe and solidified for 12 hours to prepare hydrogel balls, which were then stored at 5°C.

[0059] S20: Dry the surface moisture of the hydrogel balls prepared in the previous step under sterile conditions, and then add them to OD. 600 The *Bacillus cereus* bacterial culture was cultured for 12 hours in an inorganic salt oligotrophic substrate with a pH of 0.6. 50 mL of the bacterial culture was added, and the solid-liquid mixture was separated by vacuum filtration to obtain a solid-based composite adsorbent material.

[0060] The solid-based composite adsorbent material obtained above was examined by scanning electron microscopy, and the results are as follows: Figure 3 As shown, the surface of the adsorbent material exhibits numerous irregular depressions, with fine montmorillonite particles filling the pores of sodium alginate. This results in a large specific surface area for the adsorbent material. Furthermore, the surface of sodium alginate is rich in UO2 functional groups. 2+ Ions provide a large number of active sites, which is beneficial to improving adsorption capacity.

[0061] Example 2

[0062] S10: The mass ratio is 1g·g -1 Montmorillonite mineral and agar were thoroughly dispersed in an aqueous solution at 80°C, with a liquid-to-solid ratio of 40 mL / g during the dispersion process. -1 After dispersion, sodium alginate is added, with a sodium alginate to mineral mass ratio of 1.5 g / g. -1 The system temperature was controlled and stirred continuously for 20–30 minutes. It was then sterilized in an autoclave. After cooling, 4% sterile CaCl2 solution was immediately added dropwise using a sterile syringe and solidified for 12 hours to prepare hydrogel balls, which were then stored at 5°C.

[0063] S20: Dry the surface moisture of the hydrogel balls prepared in the previous step under sterile conditions, and then add them to OD. 600 Bacillus cereus culture was incubated for 12 hours in an inorganic salt oligotrophic substrate with a pH of 0.8. 50 mL of the culture was added, and solid-liquid separation was achieved by vacuum filtration to obtain a solid-based composite adsorbent. The specific surface area of ​​the adsorbent was determined to be 29.5 m² using a BET surface area analyzer. 2 ·g -1 The increase in specific surface area is beneficial to the increase in adsorption effect. In addition, the functional groups on the surface of the material are further enriched after composite processing, which can further improve the adsorption capacity of the material for UO2. 2+ Adsorption effect.

[0064] Example 3

[0065] S10: The mass ratio is 2g·g -1 The mass ratio of montmorillonite mineral to agar is 2 g·g -1 It is fully dispersed in an aqueous solution at 80℃, with a liquid-to-solid ratio of 60 mL·g during the dispersion process. -1 After dispersion, sodium alginate is added, with a sodium alginate to mineral mass ratio of 1.5 g / g. -1 The system temperature was controlled and stirred continuously for 20–30 minutes. It was then sterilized in an autoclave. After cooling, 4% sterile CaCl2 solution was immediately added dropwise using a sterile syringe and solidified for 12 hours to prepare hydrogel balls, which were then stored at 5°C.

[0066] S20: Dry the surface moisture of the hydrogel balls prepared in the previous step under sterile conditions, and then add them to OD. 600 Bacillus cereus culture was incubated for 12 h in an inorganic salt oligotrophic substrate with a pH of 0.8. 50 mL of the culture was added, and solid-liquid separation was achieved by vacuum filtration to obtain a solid-based composite adsorbent. The prepared composite adsorbent was then subjected to UO2 testing. 2+ Ion cycling adsorption experiments showed that, under the synergistic mechanism of microorganisms and minerals, UO2... 2+ The maximum adsorption capacity can exceed 90 mg·g -1 After three cycles, the composite adsorbent still maintains a concentration of 78.5 mg / g. -1 The maximum adsorption capacity.

[0067] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for preparing a composite adsorbent material, characterized in that, Composite adsorbent materials for UO2 2+ Adsorption, the method comprising the following steps: Hydrogel balls were prepared using montmorillonite minerals, agar, and sodium alginate as raw materials. Hydrogel balls and Bacillus cereus were co-cultured under inorganic salt oligonutrient conditions, and solid-liquid separation was performed after culture to obtain gel composite adsorbent material. The montmorillonite mineral can pass through a 70-mesh sieve; the montmorillonite mineral is obtained by pre-treating montmorillonite raw material, the pre-treatment including crushing, washing and drying; the montmorillonite raw material has a specific surface area and cation exchange capacity of 40-70 m². 2 ·g -1 and 70–90 mmol / 100g -1 And / or the montmorillonite raw material has been modified to increase its cation exchange capacity; The steps for preparing hydrogel balls include: dispersing the montmorillonite mineral and the agar in an aqueous solution at 60-100℃ at a liquid-to-solid ratio of 40-60 mL / g to obtain a first intermediate solution, wherein the mass ratio of the montmorillonite mineral to the agar is 3-1; adding the sodium alginate to the first intermediate solution and stirring to obtain a second intermediate solution, wherein the mass ratio of the sodium alginate to the montmorillonite mineral is 1.0-1.85; sterilizing the second intermediate solution, then adding sterile CaCl2 solution dropwise and solidifying to obtain the hydrogel balls; The step of performing the composite culture includes: adding the hydrogel balls to the Bacillus cereus bacterial solution and culturing for 6 to 24 hours, wherein the surface of the hydrogel balls is free of moisture; The method further includes the cultivation of Bacillus cereus and the preparation of bacterial solution, wherein: the cultivation includes: inoculating Bacillus cereus into LB liquid medium and culturing it to the logarithmic growth phase, and then isolating the solid strain; the preparation of bacterial solution includes: removing the LB liquid medium remaining on the solid strain, and then mixing the solid strain with inorganic salt culture medium and adjusting it to an OD600 value of 0.6-1.2 to obtain the bacterial solution.

2. The method for preparing the composite adsorbent material according to claim 1, characterized in that, The crushed montmorillonite raw material can all pass through a 70-mesh sieve; The washing process includes first washing with deionized water, followed by further washing with an ethanol solution, all under ultrasonic assistance.

3. The method for preparing the composite adsorbent material according to claim 1, characterized in that, The pretreatment includes crushing, washing, drying and grinding; The particle size of the montmorillonite mineral obtained after grinding is less than 0.212 mm.

4. The method for preparing the composite adsorbent material according to claim 1, characterized in that, Prior to the composite culture, the method further includes the step of drying the surface of the hydrogel pellets under aseptic conditions.

5. A composite adsorbent material, characterized in that, The adsorbent material is prepared by the method according to any one of claims 1 to 4.

6. The application of the composite adsorbent material according to claim 5 in the treatment of uranium-containing wastewater.

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