Adsorbent, method for preparing same, and use thereof

Abstract

The application discloses an adsorbent and a preparation method and application thereof, and belongs to the technical field of environmental adsorption materials. The adsorbent comprises biogenic diatom and halloysite nanoparticles, and the biogenic diatom is in-situ loaded with the halloysite nanoparticles. The adsorbent is used for adsorbing tetracycline antibiotics. The biogenic diatom in the adsorbent has biological capture and adsorption effects on nanoclay minerals, can uniformly load the halloysite nanoparticles on surface organic active sites, and thus can in-situ load a halloysite nanoparticle film on the surface of the diatom. The adsorbent not only well retains the macroporous structure of the diatom, but also constructs mesoporous and microporous hierarchical pore structures, can effectively improve the adsorption capacity of the adsorbent on tetracycline antibiotics, and has a wide application prospect in the fields of adsorption and pollution treatment of tetracycline antibiotics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental adsorbent materials, and in particular, to an adsorbent and a preparation method and application thereof. BACKGROUND

[0002] Antibiotics are widely used in aquaculture, agriculture, veterinary and human medicine due to their important role in promoting growth and treating microbial infections. The mass production and consumption of antibiotics lead to their ubiquitous presence in the environment, becoming a global public environmental problem. Tetracycline antibiotics are an important broad-spectrum antibiotic, which are overused due to their low cost and high antibacterial activity. Due to the limited absorption of tetracycline antibiotics by humans and animals and partial metabolism, about 70% to 90% of tetracycline antibiotics and their metabolites are discharged into aquatic environments through urine or feces. In addition, long-term exposure to tetracycline antibiotic residues can lead to the development and spread of drug-resistant bacteria and drug-resistant genes, ultimately endangering human health.

[0003] Therefore, it is essential to develop an efficient and low-cost method for removing tetracycline antibiotics from wastewater to ensure human health and environmental safety.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The present application aims to provide an adsorbent and a preparation method and application thereof to solve or improve the above technical problems.

[0006] The present application can be achieved as follows:

[0007] In a first aspect, the present application provides an adsorbent, which comprises biogenic diatoms and halloysite nanoparticles, and the halloysite nanoparticles are in situ loaded on the surface of the biogenic diatoms;

[0008] The adsorbent is used for adsorbing tetracycline antibiotics.

[0009] In an optional embodiment, the adsorbent comprises at least one of the following features:

[0010] Feature 1: The halloysite nanoparticles form a film on the surface of the biogenic diatoms.

[0011] Feature 2: The adsorbent has a hierarchical pore structure including micropores, mesopores and macropores.

[0012] In a second aspect, the present application provides a preparation method of the adsorbent as in the preceding embodiments, comprising the following steps: mixing a halloysite suspension with a diatom suspension, aging, and drying.

[0013] In an optional embodiment, the mass ratio of the halloysite suspension to the diatom suspension is 0.2:1 to 5:1.

[0014] In an optional embodiment, the preparation of the allophane suspension comprises mixing the allophane with water.

[0015] In an optional embodiment, the solid-liquid ratio of the allophane and water is 1 g:10 mL to 1 g:100 mL.

[0016] In an optional embodiment, the mixing manner of the allophane and water is ultrasonic mixing.

[0017] In an optional embodiment, the mixing time of the allophane and water is 1 h to 5 h.

[0018] In an optional embodiment, the synthesis of the allophane comprises mixing an aluminum source and a silicon source to obtain a precursor, and performing a hydrothermal reaction on the precursor.

[0019] In an optional embodiment, the molar ratio of silicon in the silicon source to aluminum in the aluminum source is 0.5:1 to 1:1.

[0020] In an optional embodiment, the aluminum source comprises aluminum chloride, and the silicon source comprises sodium silicate.

[0021] In an optional embodiment, the aluminum source and the silicon source are mixed at 100 rpm to 1000 rpm for 1 h to 3 h.

[0022] In an optional embodiment, the hydrothermal reaction is performed at 80°C to 150°C for 24 h to 72 h.

[0023] In an optional embodiment, before the hydrothermal reaction, the precursor is further washed to remove by-products.

[0024] In an optional embodiment, the washing is performed at 3000 rpm to 5000 rpm for 5 min to 15 min.

[0025] In an optional embodiment, the preparation of the diatom suspension comprises mixing the biological diatom with water.

[0026] In an optional embodiment, the solid-liquid ratio of the biological diatom and water is 0.2 g:1 mL to 5 g:1 mL.

[0027] In an optional embodiment, the mixing manner of the biological diatom and water is stirring mixing.

[0028] In an optional embodiment, the mixing time of the biological diatom and water is 20 min to 60 min.

[0029] In an optional embodiment, the preparation of the biological diatom comprises inoculating an algal strain into a culture medium and performing light culture.

[0030] In an optional embodiment, the algal species comprises at least one of Melosira, Thalassiosira, Chaetoceros, Navicula, Phaeodactylum, Nitzschia, Coscinodiscus and Cyclotella.

[0031] In an optional embodiment, the inoculation density is 1×10 4 cells / mL to 1×10 5 cells / mL.

[0032] In an optional embodiment, the light intensity of the photobiological culture is 50 μmol E·m -2 s -1 to 70 μmol E·m -2 s -1 , the light cycle is 12 / 12 to 16 / 8 light / dark cycle, the light temperature is 20℃ to 25℃, and the culture cycle is 10 days to 20 days.

[0033] In an optional embodiment, the dropping speed of the allophane suspension is 0.5 mL / min to 2.5 mL / min.

[0034] In an optional embodiment, the allophane suspension is added into the diatom suspension with a stirring speed of 100 rpm to 500 rpm.

[0035] In an optional embodiment, after the dropping of the allophane suspension is completed, a mixed solution comprising the allophane suspension and the diatom suspension is obtained; the mixed solution is stirred at a speed of 100 rpm to 500 rpm for 20 min to 40 min, and then aged for 1 h to 3 h; the stirring and aging process is repeated for 3 to 5 times before drying.

[0036] In a third aspect, the present application provides an application of the adsorbent as described in the foregoing embodiments, which is used for adsorbing tetracycline antibiotics.

[0037] In an optional embodiment, the tetracycline antibiotics comprise at least one of terramycin, tetracycline and aureomycin.

[0038] The beneficial effects of the present application include:

[0039] The adsorbent provided by the present application has the following advantages: the surface of the biological diatom has abundant extracellular polymers, has unique affinity for allophane and biological capture and adsorption effect, and can load the allophane nanoparticles on the surface organic active sites through condensation of the organic functional groups contained in the biological diatom and the aluminum hydroxyl on the surface of the allophane, thereby loading the allophane nanoparticle film on the surface of the diatom in situ, avoiding the problem of reduction of the surface active sites due to agglomeration of the nanoparticles. The adsorbent not only retains the macroporous structure of the diatom, but also constructs the mesoporous and microporous hierarchical pore structure, has a large specific surface area and abundant surface active sites, can improve the contact area with the adsorbate, improve the mass transfer performance, accelerate the adsorption process and improve the adsorption efficiency. In addition, the adsorbent has a unique hierarchical organic-inorganic three-dimensional composite structure of nanoparticle film-organic matter-porous silicon, can effectively improve the adsorption capacity of the tetracycline antibiotics, and has a wide application prospect in the field of adsorption and pollution treatment of the tetracycline antibiotics.

[0040] The preparation method of the adsorbent does not add chemical reagents, avoids secondary pollution, and has the advantages of simple preparation method, mild conditions, short cycle, low energy consumption and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0042] Figure 1 The scanning diagram of the allophane / diatom composite adsorbent prepared in Example 1 is shown in the figure;

[0043] Figure 2 The X-ray diffraction diagram of the allophane / diatom composite adsorbent prepared in Example 2 is shown in the figure;

[0044] Figure 3 The nitrogen adsorption / desorption curve of the allophane / diatom composite adsorbent prepared in Example 3 is shown in the figure. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely. The specific conditions are not specified in the embodiments, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be purchased on the market.

[0046] The adsorbent provided by the present application and the preparation method and application thereof will be described in detail below.

[0047] The present application provides an adsorbent, which comprises biogenic diatoms and halloysite nanoparticles, and the surface of the biogenic diatoms in-situ loads the halloysite nanoparticles.

[0048] The adsorbent is used for adsorbing tetracycline antibiotics.

[0049] The halloysite (xSiO2·Al2O3·yH2O, wherein x = 1-2, y = 5-6) is a nanoscale hydrous aluminosilicate mineral, which has a unique hollow nanospherical structure (particle outer diameter of 3.5-5 nm), rich microporosity, high specific surface area, rich variable charge and sufficient aluminumol and silanol groups near the edge. However, the halloysite is prone to irreversible aggregation, thereby greatly reducing its porosity, specific surface area and effective active sites.

[0050] The diatom is a unique microalgae, and the shell mainly consists of amorphous hydrated silicon dioxide (SiO2·nH2O), which is called diatom opal or diatom biogenic silica, and widely exists in seawater and freshwater ecosystems. The diatom opal has developed macropores and mesopores, strong chemical stability and high mechanical strength. Moreover, the living diatom outer surface is wrapped with extracellular polymeric substances (EPS), which has various functional groups such as amino, amide, carboxyl and the like, so that it can react with the aluminum hydroxyl groups on the surface of the halloysite without chemical modification.

[0051] In some embodiments, the halloysite nanoparticles form a film on the surface of the biogenic diatoms, achieving uniform loading.

[0052] In some embodiments, the adsorbent has a hierarchical pore structure including micropores, mesopores and macropores, and a unique hierarchical organic-inorganic three-dimensional composite structure of nanoparticle film-organic matter-porous silicon.

[0053] In the adsorbent, the biological diatom surface has abundant extracellular polymers, unique affinity for halloysite, and biological capture and adsorption effect. The halloysite nanoparticles can be uniformly loaded on the surface organic active sites through condensation of the organic functional groups contained in the halloysite and the aluminum hydroxyl on the surface of the halloysite, so that the halloysite nanoparticle film can be in-situ loaded on the diatom surface, thereby avoiding the problem of reducing the surface active sites due to the agglomeration of the nanoparticles. The adsorbent not only retains the large pore structure of the diatom, but also constructs the mesoporous and microporous multi-level pore structure, has a large specific surface area and abundant surface active sites, can improve the contact area with the adsorbate, improve the mass transfer performance, accelerate the adsorption process and improve the adsorption efficiency. In addition, the adsorbent also has a unique multi-level organic-inorganic three-dimensional composite structure of nanoparticle film-organic matter-porous silicon, which can effectively improve the adsorption capacity of tetracycline antibiotics, and has a wide application prospect in the field of adsorption and pollution control of tetracycline antibiotics.

[0054] Correspondingly, the application also provides a preparation method of the above adsorbent, comprising the following steps: mixing halloysite suspension and diatom suspension, aging, and drying.

[0055] It should be noted that if diatomite is added to an aluminum solution to prepare a suspension, and then a silicon solution is added to the above suspension and subjected to hydrothermal reaction, a diatomite-halloysite composite material with multi-level pores can also be obtained. However, the above preparation process involves organic reagent pretreatment and complex operation steps, which not only has certain environmental potential threat, but also is difficult to obtain a surface halloysite film and form an organic-inorganic composite.

[0056] However, the application can achieve uniform loading of halloysite on the diatom surface to form a film and form a multi-level organic-inorganic three-dimensional composite structure of nanoparticle film-organic matter-porous silicon by creatively obtaining halloysite suspension and diatom suspension respectively, and then adding the halloysite suspension to the diatom suspension.

[0057] In some embodiments, the mass ratio of the halloysite suspension to the diatom suspension can be 0.2:1 to 5:1, such as 0.2:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, or 5:1, etc., or other values within the range of 0.2:1 to 5:1.

[0058] If the mass ratio of the halloysite suspension to the diatom suspension is less than 0.2:1 (such as 0.1:1), it is not conducive to the construction of the pore structure and the increase of the surface adsorption sites; if the mass ratio of the halloysite suspension to the diatom suspension is greater than 5:1 (such as 6:1), it is not conducive to the dispersion of the halloysite.

[0059] In some embodiments, the dropping speed of the allophane suspension can be 0.5 mL / min to 2.5 mL / min (e.g., 0.5 mL / min, 1 mL / min, 1.5 mL / min, 2 mL / min, or 2.5 mL / min, etc.). Specifically, the allophane suspension is added to the diatom suspension at a stirring speed of 100 rpm to 500 rpm (e.g., 100 rpm, 200 rpm, 300 rpm, 400 rpm, or 500 rpm, etc.).

[0060] After the dropping of the allophane suspension is completed, a mixed solution including the allophane suspension and the diatom suspension is obtained; the mixed solution is stirred at a speed of 100 rpm to 500 rpm (e.g., 100 rpm, 200 rpm, 300 rpm, 400 rpm, or 500 rpm, etc.) for 20 min to 40 min (e.g., 20 min, 25 min, 30 min, 35 min, or 40 min, etc.), and then aged for 1 h to 3 h (e.g., 1 h, 1.5 h, 2 h, 2.5 h, or 3 h, etc.), and the stirring and aging process is repeated 3 to 5 times (e.g., 3 times, 4 times, or 5 times) before drying.

[0061] In some specific embodiments, after the repeated stirring, the un-loaded allophane is removed by centrifugation, and then freeze-dried.

[0062] In some embodiments, the preparation of the above-mentioned allophane suspension can include mixing the allophane with water.

[0063] In the above-mentioned method, the solid-liquid ratio of the allophane to water can be 1 g:10 mL to 1 g:100 mL (e.g., 1 g:10 mL, 1 g:20 mL, 1 g:30 mL, 1 g:40 mL, 1 g:50 mL, 1 g:60 mL, 1 g:70 mL, 1 g:80 mL, 1 g:90 mL, or 1 g:100 mL, etc.), or other values within the range of 1 g:10 mL to 1 g:100 mL.

[0064] The mixing of the allophane and water can be performed by ultrasonic mixing, for example, but is not limited thereto. The mixing time of the allophane and water can be 1 h to 5 h (e.g., 1 h, 2 h, 3 h, 4 h, or 5 h, etc.), or other values within the range of 1 h to 5 h.

[0065] In the present application, the allophane can be a laboratory-synthesized allophane or a natural allophane collected from an allophane deposit.

[0066] In some embodiments, the synthesis of the allophane can include mixing an aluminum source and a silicon source to obtain a precursor, and performing a hydrothermal reaction on the precursor.

[0067] The molar ratio of silicon in the silicon source to aluminum in the aluminum source can be 0.5:1 to 1:1, such as 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, or 1:1, among others, or any other value within the range of 0.5:1 to 1:1.

[0068] The aluminum source can illustratively but non-limitingly include aluminum chloride, and the silicon source can illustratively but non-limitingly include sodium silicate. The concentration of the aluminum source can be 0.01 mol / L to 1 mol / L (such as 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, or 1 mol / L, among others), and the concentration of the silicon source can also be 0.01 mol / L to 1 mol / L (such as 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, or 1 mol / L, among others).

[0069] The aluminum source and the silicon source can be mixed at 100 rpm to 1000 rpm (such as 100 rpm, 200 rpm, 500 rpm, 800 rpm, or 1000 rpm, among others) for 1 h to 3 h (such as 1 h, 1.5 h, 2 h, 2.5 h, or 3 h, among others).

[0070] The hydrothermal reaction can be performed at 80°C to 150°C (such as 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C, among others) for 24 h to 72 h (such as 24 h, 48 h, or 72 h, among others).

[0071] In some embodiments, the hydrothermal reaction can be performed at 100°C for 48 h.

[0072] In some embodiments, before the hydrothermal reaction, the precursor is further washed to remove by-products (such as NaCl).

[0073] The washing can be performed at 3000 rpm to 5000 rpm (such as 3000 rpm, 4000 rpm, or 5000 rpm, among others) for 5 min to 15 min (such as 5 min, 10 min, or 15 min, among others).

[0074] In some embodiments, the preparation of the diatom suspension can include mixing the biological diatom with water.

[0075] The solid-liquid ratio of the biological diatom to water can be 0.2 g:1 mL to 5 g:1 mL, such as 0.2 g:1 mL, 0.5 g:1 mL, 1 g:1 mL, 2 g:1 mL, 3 g:1 mL, 4 g:1 mL, or 5 g:1 mL, among others, or any other value within the range of 0.2 g:1 mL to 5 g:1 mL.

[0076] If the solid-liquid ratio of the biological diatom to water is less than 0.2 g:1 mL (such as 0.05 g:1 mL), the carrier effect of the diatom is not good; if the solid-liquid ratio of the biological diatom to water is more than 5 g:1 mL (such as 10 g:1 mL), the dispersion of the diatom in water is not good.

[0077] The mixing mode of the biological diatom and water can exemplarily but not limitatively adopt a stirring mixing mode. The mixing time of the biological diatom and water can be 20 min to 60 min, such as 20 min, 30 min, 40 min, 50 min or 60 min, etc.

[0078] In the present application, the biological diatom can be a diatom artificially cultured in a laboratory or a diatom caught in a natural water area.

[0079] In some embodiments, the preparation of the biological diatom can include inoculating an algal strain into a culture medium and performing light culture.

[0080] The algal strain can exemplarily but not limitatively include at least one of Melosira, Corethron, Chaetoceros, Navicula, Phaeodactylum, Nitzschia, Coscinodiscus and Cyclotella.

[0081] The inoculation density can be 1×10 4 cells / mL to 1×10 5 cells / mL.

[0082] The light culture can have a light intensity of 50 μmol E·m -2 s -1 to 70 μmol E·m -2 s -1 (such as 50 μmol E·m -2 s -1 , 55 μmol E·m -2 s -1 , 60 μmol E·m -2 s -1 , 65 μmol E·m -2 s -1 or 70 μmol E·m -2 s -1 ), a light cycle of 12 / 12 to 16 / 8 light-dark cycle (wherein "12 / 12" can be understood as 12 hours of light and 12 hours of darkness; "16 / 8" can be understood as 16 hours of light and 8 hours of darkness), a light temperature of 20℃ to 25℃ (such as 20℃, 21℃, 22℃, 23℃, 24℃ or 25℃, etc.), and a culture cycle of 10 days to 20 days (such as 10 days, 15 days or 20 days, etc.).

[0083] According to the above, the preparation method of the adsorbent provided by the present application does not add chemical reagents, avoids secondary pollution, and has the advantages of simple preparation method, mild conditions, short cycle, low energy consumption, and low cost.

[0084] In addition, the present application also provides an application of the above adsorbent, which is used for adsorbing tetracycline antibiotics and has good adsorption performance.

[0085] In some embodiments, the tetracycline antibiotics may include at least one of terramycin, tetracycline, and aureomycin, for example.

[0086] The features and performances of the present application are further described in detail below in combination with examples.

[0087] Example 1

[0088] The present example provides a halloysite / nitzschia complex adsorbent with high terramycin adsorption capacity, and a preparation method thereof includes:

[0089] 1) According to the solid-liquid ratio of 1g:20mL, 1.0g of synthetic halloysite is weighed into 20mL of ultrapure water, and ultrasonic treatment is performed for 2h to obtain a halloysite suspension.

[0090] The synthetic halloysite is prepared as follows: the steps of synthesizing halloysite are as follows: 0.5mol / L of AlCl3·6H2O and 0.5mol / L of Na4SiO4 are used as Al source and Si source solutions, and the Si / Al ratio is 1:1 for rapid mixing, and the precursor is obtained by stirring at 500rpm for 2h; the precursor is washed with ultrapure water at 4000rpm for 10min to remove the byproduct NaCl; hydrothermal treatment is performed at 100℃ for 48h; and the product obtained is the synthetic halloysite.

[0091] 2) According to the solid-liquid ratio of 1g:40mL, 1.0g of cultured nitzschia is weighed and dispersed into 40mL of ultrapure water as biological diatom, and after stirring and mixing for 30min, stirring is performed for 10min to obtain a diatom suspension.

[0092] The cultured nitzschia includes the following steps: an artificial seawater culture medium is configured and sterilized, and the algal strain is transferred to the culture medium at a density of 1x10 4 cells / mL; it is placed in a light incubator to control the light intensity of 60μmolE·m -2 s -1 , the light cycle is 12 / 12 light and dark cycle, the temperature is 25℃, and the culture is performed; the culture period is 15 days; after the culture is completed, the sample is centrifuged and washed with ultrapure water for 3 times to obtain the biological diatom.

[0093] 3) The above said halloysite suspension was added dropwise into the above said diatom suspension at a rate of 1.2 mL / min with the diatom suspension stirring at a rate of 500 rpm; after the addition of halloysite was completed, the mixture was continued to stir at a rate of 300 rpm for 30 min and then aged for 2 h, and the stirring and aging process was repeated for 5 times; the un-loaded halloysite was removed by centrifugation, and the halloysite / diatom composite adsorbent was obtained after freeze-drying, and the scanning graph thereof is shown in Figure 1

[0094] The above said halloysite / diatom composite adsorbent was subjected to the following adsorption test:

[0095] At room temperature, 5 mg of the halloysite / diatom composite adsorbent was added into a solution of oxytetracycline (10 mL) with a concentration of 100 mg / L, and after oscillation at a rate of 200 rpm for 24 h, centrifugation was performed, and the filtrate was filtered by using a 0.22 μm filter membrane, and the content of oxytetracycline in the filtrate was measured by using a UV-visible spectrophotometer. Analysis showed that the adsorption capacity of the composite adsorbent for oxytetracycline was 132.44 mg / g.

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 1 is that steps 1) and 3) are cancelled, and no halloysite is added, and the types and amounts of other raw materials remain unchanged.

[0098] The adsorption test was the same as that in Example 1. Analysis showed that the adsorption capacity of the diatom adsorbent for oxytetracycline was 13.31 mg / g.

[0099] Example 2

[0100] This example provides a halloysite / ceratium composite adsorbent with high adsorption capacity for tetracycline, and the preparation method thereof comprises:

[0101] 1) According to a solid-liquid ratio of 1 g:30 mL, 1.25 g of synthetic halloysite was weighed into 37.5 mL of ultrapure water, and ultrasonic treatment was performed for 3 h to obtain a halloysite suspension.

[0102] In the preparation of the synthetic halloysite, the following steps were performed: 0.01 mol / L of AlCl3·6H2O and 0.01 mol / L of Na4SiO4 were used as Al source and Si source solutions, and rapid mixing was performed at a Si / Al ratio of 0.5:1, and stirring was performed at a rate of 100 rpm for 3 h to obtain a precursor; the precursor was washed with ultrapure water at a rate of 3000 rpm for 15 min to remove by-products NaCl; and hydrothermal treatment was performed at 120°C for 36 h; and the product obtained was the synthetic halloysite.

[0103] ​2) According to the proportion of solid-liquid ratio 1 g:30 mL, 1.0 g of cultured Chaetoceros culture was dispersed into 30 mL of ultrapure water, stirred and mixed for 20 min, and then stirred for 5 min to obtain a diatom suspension.

[0104] The culture of Chaetoceros includes: configuring an artificial seawater medium and sterilizing the algae seeds to be transferred to the medium at a density of 1×10 5 cells / mL; placed in a light incubator to control the light intensity of 50 μmol E·m -2 s -1 , the light cycle is 16 / 8 light-dark cycle, the temperature is 20℃, and the culture is carried out; the culture period is 20 days; after the culture is completed, the sample is centrifuged and washed with ultrapure water for 3 times to obtain biological diatom.

[0105] 3) According to the proportion of 1.25:1, the above halloysite suspension is added dropwise into the above diatom suspension at a speed of 1.0 mL / min, and the diatom suspension is stirred at a speed of 300 rpm at the same time; after the addition of halloysite is completed, the mixture is continuously stirred at a speed of 200 rpm for 20 min and then aged for 3 h, and the stirring and aging process is repeated 4 times; the unloaded halloysite is removed by centrifugation, and the halloysite / Chaetoceros composite adsorbent is obtained after freeze-drying, and the X-ray diffraction pattern thereof is shown in Figure 2 .

[0106] The halloysite / Chaetoceros composite adsorbent is subjected to the following adsorption test:

[0107] At room temperature, 5 mg of halloysite / Chaetoceros composite adsorbent is added to 150 mg / L of tetracycline (10 mL), shaken for 24 h, centrifuged (200 rpm), filtered with a 0.22 μm filter membrane, and the tetracycline content in the filtrate is measured using a UV-visible spectrophotometer. Analysis shows that the adsorption capacity of the composite adsorbent for tetracycline is 207.15 mg / g.

[0108] Comparative Example 2

[0109] The difference between this comparative example and Example 2 is that steps 2) and 3) are cancelled, and biological diatom is no longer added, and the types and amounts of other raw materials remain unchanged.

[0110] The adsorption test is the same as that of Example 2. Analysis shows that the adsorption capacity of the halloysite adsorbent for oxytetracycline is 26.88 mg / g.

[0111] Example 3

[0112] This example provides a halloysite / chaetoceros composite adsorbent with high adsorption capacity for chlortetracycline, and the preparation method thereof includes:

[0113] 1) According to the ratio of solid to liquid 1 g: 50 mL, 0.5 g of natural allophane was weighed into 25 mL of ultrapure water, and ultrasonic treatment was performed for 3 h to obtain an allophane suspension.

[0114] The synthetic allophane was prepared as follows: the step of synthesizing the allophane: 1 mol / L of AlCl3·6H2O and 1 mol / L of Na4SiO4 were used as Al source and Si source solution, and the precursor was obtained by rapid mixing at a Si / Al ratio of 0.75:1 and stirring at 1000 rpm for 1 h; the precursor was washed with ultrapure water at 5000 rpm for 5 min to remove the byproduct NaCl; hydrothermal treatment was performed at 90℃ for 60 h; and the product obtained was the synthetic allophane.

[0115] 2) According to the ratio of solid to liquid 1 g: 25 mL, 0.67 g of cultured Skeletonema costatum was dispersed into 16.75 mL of ultrapure water, and after stirring and mixing for 25 min, stirring was performed for 7 min to obtain a diatom suspension.

[0116] The cultured Skeletonema costatum includes the following steps: an artificial seawater culture medium was prepared and sterilized, and the algal strain was transferred to the culture medium at a density of 5×10 4 cells / mL; and the culture was placed in a light incubator to control the light intensity at 70 μmol E·m -2 s -1 , the light cycle was 12 / 12 light and dark cycles, the temperature was 22℃, and the culture was performed; the culture period was 10 days; after the culture was completed, the sample was centrifuged and washed with ultrapure water 3 times to obtain the biological diatom.

[0117] 3) According to the ratio of 0.75:1, the above allophane suspension was added dropwise to the above diatom suspension at a rate of 1.5 mL / min, and the diatom suspension was stirred at a speed of 350 rpm; after the addition of the allophane was completed, the mixture was continuously stirred at a speed of 250 rpm for 25 min, then aged for 2.5 h, and the stirring and aging process was repeated 3 times; the un-loaded allophane was removed by centrifugation, and after freeze-drying, the allophane / Skeletonema costatum composite adsorbent was obtained, and the nitrogen adsorption-desorption curve thereof is shown in Figure 3 .

[0118] The allophane / Skeletonema costatum composite adsorbent was subjected to the following adsorption test:

[0119] At room temperature, 5 mg of the allophane / Skeletonema costatum composite adsorbent was added to a 150 mg / L chlortetracycline solution (10 mL), and after oscillation for 24 h, centrifugation (200 rpm) was performed, and the filtrate was filtered using a 0.22 μm filter membrane, and the content of chlortetracycline in the filtrate was measured using an inductively coupled atomic emission spectrometer. Analysis showed that the adsorption capacity of the composite adsorbent for chlortetracycline was 171.14 mg / g.

[0120] Comparative Example 3

[0121] This example differs from Example 3 in that in step 3), the diatom suspension was added dropwise to the halloysite suspension at a rate of 1.5 mL / min.

[0122] The adsorption test was the same as in Example 3. Analysis showed that the adsorption capacity of the composite adsorbent for aureomycin was 153.62 mg / g.

[0123] Comparative Example 4

[0124] This example differs from Example 3 in that in step 3), the mass ratio of the halloysite suspension to the diatom suspension was 0.1:1.

[0125] The adsorption test was the same as in Example 3. Analysis showed that the adsorption capacity of the composite adsorbent for aureomycin was 17.39 mg / g.

[0126] Comparative Example 5

[0127] This example differs from Example 3 in that in step 3), the mass ratio of the halloysite suspension to the diatom suspension was 6:1.

[0128] The adsorption test was the same as in Example 3. Analysis showed that the adsorption capacity of the composite adsorbent for aureomycin was 37.45 mg / g.

[0129] Comparative Example 6

[0130] This example differs from Example 3 in that in step 1), the solid-liquid ratio of halloysite to water was 1 g:5 mL.

[0131] The adsorption test was the same as in Example 3. Analysis showed that the adsorption capacity of the composite adsorbent for aureomycin was 126.89 mg / g.

[0132] Comparative Example 7

[0133] This example differs from Example 3 in that in step 1), the solid-liquid ratio of halloysite to water was 1 g:150 mL.

[0134] The adsorption test was the same as in Example 3. Analysis showed that the adsorption capacity of the composite adsorbent for aureomycin was 157.26 mg / g.

[0135] Comparative Example 8

[0136] This example differs from Example 3 in that in step 2), the solid-liquid ratio of biological diatom to water was 0.05 g:1 mL.

[0137] The adsorption test was the same as in Example 3. Analysis showed that the adsorption capacity of the composite adsorbent for aureomycin was 114.61 mg / g.

[0138] Comparative Example 9

[0139] The difference between the present comparative example and Example 3 is that in step 2), the solid-liquid ratio of the biosilica and water is 10 g: 1 mL.

[0140] The adsorption test is the same as that of Example 3. Analysis shows that the adsorption capacity of the composite adsorbent for chlortetracycline is 87.33 mg / g.

[0141] In summary, the adsorbent provided by the present application has abundant extracellular polymers on the surface of the biosilica, unique affinity for halloysite, and biological capture and adsorption effect. The condensation between the various organic functional groups contained therein and the aluminum hydroxyl groups on the surface of the halloysite can uniformly load halloysite nanoparticles on the surface of the organic active sites, thereby enabling in-situ loading of a halloysite nanoparticle film on the surface of the diatom, avoiding the problem of reduced surface active sites due to nanoparticle agglomeration. The adsorbent not only better retains the macroporous structure of the diatom, but also constructs a mesoporous and microporous hierarchical pore structure, has a large specific surface area and abundant surface active sites, can improve the contact area with the adsorbate, improve the mass transfer performance, accelerate the adsorption process, and improve the adsorption efficiency. In addition, the adsorbent also has a unique hierarchical organic-inorganic three-dimensional composite structure of nanoparticle film-organic matter-porous silicon, which can effectively improve the adsorption capacity for tetracycline antibiotics, and has a broad application prospect in the field of adsorption and pollution control of tetracycline antibiotics.

[0142] The above only describes preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An adsorbent, characterized by, The adsorbent comprises biological diatom and halloysite nanoparticles, and the halloysite nanoparticles are in-situ loaded on the surface of the biological diatom; The preparation of the adsorbent comprises the following steps: mixing a halloysite suspension into a diatom suspension, aging, and drying; the mass ratio of the halloysite suspension to the diatom suspension is 0.2:1 to 5:1; The preparation of the halloysite suspension comprises: mixing halloysite and water; the solid-liquid ratio of the halloysite to water is 1g:10mL to 1g:100mL; The preparation of the diatom suspension comprises: mixing biological diatom and water; the solid-liquid ratio of the biological diatom to water is 1g:40mL, 1g:30mL or 1g:25mL.

2. The adsorbent according to claim 1, characterized in that The adsorbent comprises at least one of the following features: Feature 1: the halloysite nanoparticles form a film on the surface of the biological diatom; Feature 2: the adsorbent has a hierarchical pore structure comprising micropores, mesopores and macropores.

3. A method for producing the adsorbent according to claim 1 or 2, characterized by, The preparation of the adsorbent comprises the following steps: mixing a halloysite suspension into a diatom suspension, aging, and drying; The mass ratio of the halloysite suspension to the diatom suspension is 0.2:1 to 5:1; The preparation of the halloysite suspension comprises: mixing halloysite and water; the solid-liquid ratio of the halloysite to water is 1g:10mL to 1g:100mL; The preparation of the diatom suspension comprises: mixing biological diatom and water; the solid-liquid ratio of the biological diatom to water is 1g:40mL, 1g:30mL or 1g:25mL.

4. The production method according to claim 3, characterized by, The mixing of the halloysite and water is ultrasonic mixing.

5. The production method according to claim 4, characterized by, The mixing time of the halloysite and water is 1h~5h.

6. The preparation method according to claim 3, characterized in that The synthesis of the halloysite comprises: mixing an aluminum source and a silicon source to obtain a precursor; and performing hydrothermal reaction on the precursor.

7. The preparation method according to claim 6, characterized in that The molar ratio of silicon in the silicon source to aluminum in the aluminum source is 0.5:1 to 1:

1.

8. The preparation method according to claim 6, characterized in that The aluminum source comprises aluminum chloride, and the silicon source comprises sodium silicate.

9. The preparation method according to claim 6, characterized in that The aluminum source and the silicon source are mixed at 100rpm~1000rpm for 1h~3h.

10. The method of claim 6, wherein, The hydrothermal reaction is performed at 80℃~150℃ for 24h~72h.

11. The method of claim 10, wherein, Before the hydrothermal reaction, the precursor is washed to remove by-products.

12. The method of claim 11, wherein, The washing is performed at 3000rpm~5000rpm for 5min~15min.

13. The preparation method according to claim 3, characterized in that The mixing of the biological diatom and water is stirring.

14. The method of claim 13, wherein, The mixing time of the biological diatom and water is 20min~60min.

15. The preparation method according to claim 3, characterized in that The preparation of the biological diatom comprises: inoculating an algal strain into a culture medium and performing light culture.

16. The method of claim 15, wherein, The algal strain comprises at least one of the following: Melosira, Corethron, Chaetoceros, Navicula, Phaeodactylum, Nitzschia, Cyclotella and Chroococcus.

17. The preparation method according to claim 15, characterized in that Inoculation density was 1 x 10 4 cells / mL ~ 1 x 10 5 cells / mL.

18. The method of claim 15, wherein, The light intensity of the light culture is 50 μmol E·m -2 s -1 The light intensity of the light culture is 50 μmol E·m -2 s -1 The light intensity of the light culture is 50 μmol E·m 19. The preparation method according to claim 3, characterized in that: The dropping speed of the halloysite suspension is 0.5mL / min~2.5mL / min.

20. The method of claim 3, wherein, The halloysite suspension is added into the diatom suspension at a stirring speed of 100rpm~500rpm.

21. The method of claim 3, wherein, After the dropping of the halloysite suspension ends, a mixed solution including the halloysite suspension and the diatom suspension is obtained; the mixed solution is stirred at a speed of 100 rpm to 500 rpm for 20 min to 40 min, and then aged for 1 h to 3 h; the stirring and aging process is repeated for 3 to 5 times, and then dried.

22. Use of the adsorbent according to claim 1 or 2, characterized in that, The adsorbent is used for adsorbing tetracycline antibiotics.

23. The use according to claim 22, characterized in that, The tetracycline antibiotics include at least one of terramycin, tetracycline, and aureomycin.

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