Modified attapulgite adsorbent as well as preparation method and application thereof

Abstract

The invention provides a modified attapulgite adsorbent as well as a preparation method and application thereof, and relates to the technical field of adsorption materials. The preparation method of the modified attapulgite adsorbent comprises the following step: mixing chitosan, attapulgite, glutaraldehyde, lanthanum salt and water to prepare the modified attapulgite adsorbent. La ions are adopted to modify attapulgite, the La modified adsorbent with high adsorption capacity is prepared, the adsorbent is optimized on the basis, La metal is used for modification, the performance is improved, meanwhile, the material cost is reduced, and the preparation method is suitable for industrial production. The adsorbent which can effectively adsorb and treat phosphate in actual wastewater containing more humus and other ions is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorption materials, and particularly relates to a modified attapulgite adsorbent, a preparation method thereof, and an application thereof. Background Art

[0002] At present, water eutrophication has become an environmental problem that cannot be ignored worldwide. Approximately 40-50% of rivers, lakes, reservoirs and other water bodies around the world have shown varying degrees of water eutrophication, and phosphorus is one of the main factors leading to water eutrophication.

[0003] Phosphorus pollution in sewage is a common environmental problem, which has brought serious impacts on both the water ecosystem and human health. Phosphorus is an important plant nutrient, but excessive phosphorus can lead to eutrophication, promote the growth of algae and ultimately trigger algal blooms. In addition, phosphorus can also form sediments in water, affecting the water depth and the speed of water flow, and further affecting the living environment of aquatic organisms.

[0004] There are various sources of phosphorus pollution in water bodies. Among them, agricultural non-point source pollution caused by human activities is one of the main phosphorus pollution sources. The phosphorus pollution emissions caused by agricultural non-point source pollution are much larger than the point source pollution emissions caused by industrial wastewater and domestic sewage. The main factors of phosphorus pollution in agricultural non-point source pollution are phosphorus pollution in livestock and poultry breeding and phosphorus pollution in crop planting. The phosphorus non-point source pollution in crop planting is mainly caused by the unreasonable use of chemical fertilizers. Chemical fertilizers contain a large amount of phosphorus, and there are problems such as large application amounts, high intensities, and unreasonableness in the use of chemical fertilizers, resulting in phosphorus in chemical fertilizers flowing into water bodies through runoff without being absorbed by plants in farmland. The phosphorus non-point source pollution in livestock and poultry breeding mainly comes from livestock and poultry manure in livestock and poultry breeding. Due to the rapid development of the breeding industry, a large amount of phosphorus-containing livestock and poultry manure generated during the breeding process is not properly treated or directly discharged into the external environment, and phosphorus is brought into water bodies through soil erosion and water flow transportation. The non-point source pollution caused by human activities has further aggravated the phenomenon of water eutrophication.

[0005] At present, the common phosphorus removal methods in sewage include biological methods, chemical precipitation methods, adsorption methods, etc., but they all have certain disadvantages.

[0006] The biological method uses microorganisms to absorb phosphorus in water bodies. According to its principle, it can be divided into two adsorption methods. One is that microorganisms absorb phosphorus in water to meet the needs of their own growth, development and reproduction. The other is to use special microorganisms, polyphosphate-accumulating organisms (PAO), to absorb and convert phosphates in sewage into polyphosphates in cells and then release them again under anaerobic and aerobic conditions. At present, this method has been applied to many sewage treatment processes, such as the SBR process, the A2 / O process and the oxidation ditch process. Li Wei et al. used the A2 / O-SBR combined process to remove phosphorus from phosphorus-containing sewage, and the total phosphorus removal rate was stably maintained at 95%. The dominant phosphorus-removing bacteria DPAO in this process were screened out through high-throughput sequencing technology and 16S rRNA molecular biotechnology. The biological method has many advantages in treating phosphorus-containing sewage, with less environmental impact, low energy consumption, simple operation, easy long-term implementation and maintenance, and low cost. However, the biological method for treating phosphorus-containing sewage requires a long time, and microorganisms have high requirements for the surrounding environment. In order to maintain suitable living conditions for microorganisms, environmental conditions such as temperature, pH, and the concentration of organic matter in the water body need to be frequently controlled, and a large amount of sludge waste will be generated by this method.

[0007] The chemical precipitation method is to add relevant chemical reagents during the sewage treatment process. The chemical reagents react with phosphates in the sewage to form precipitates, and then operations such as filtration are used to remove phosphorus from the sewage (Li Qingqing et al., 2022). The basic principle of the chemical precipitation method is that the solubility product (Ksp) of the added chemical reagent and phosphate is small, and it is easy to form precipitates. Currently, the commonly used phosphorus-removing chemical agents are aluminum salts, iron salts and calcium salts. Phosphorus removal by precipitation is affected by multiple factors, such as the pH in actual sewage, various complex substances in the sewage, the phosphorus concentration in the sewage, and the dosage of the reagent (Meng Shunlong et al., 2012). Compared with the biological method, the chemical precipitation method has the advantages of simple operation, stable effect, and short reaction time. However, the chemical precipitation method has the disadvantages of high cost, high requirements for water quality, and high requirements for the surrounding environment. Moreover, the addition of a large amount of metal salts to the sewage will also cause secondary pollution and harm to the environment.

[0008] The adsorption method has the advantages of low cost, simple operation, fast reaction and high treatment efficiency, and is widely used in sewage treatment. The so-called adsorption is to use solid particles as adsorbents to fully contact with phosphates in the solution. The phosphates will quickly bind to the active sites on the adsorbent, thereby removing phosphorus from the water solution. The adsorbent as a solid particle can be reused multiple times after elution, and the concentrated phosphate solution eluted can be simply prepared into phosphate fertilizer for use in farmland. Therefore, the adsorption method can not only effectively alleviate water eutrophication, but also effectively recycle phosphates to make phosphorus further resourcefully utilized. How to disclose a solid adsorbent that is suitable for treating phosphorus pollutants in actual sewage is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0009] The object of the present invention is to provide a modified attapulgite adsorbent, a preparation method thereof and an application thereof, so as to solve the problems existing in the existing methods for treating phosphorus pollutants, such as high environmental requirements, high cost, complex operation, and easy secondary pollution to the environment.

[0010] In order to achieve the above object of the invention, the present invention provides the following technical solutions:

[0011] The present invention provides a preparation method of a modified attapulgite adsorbent, comprising the following steps: mixing chitosan, attapulgite, glutaraldehyde, lanthanum salt and water to prepare a modified attapulgite adsorbent.

[0012] Preferably, the preparation method of the modified attapulgite adsorbent further comprises the following steps:

[0013] 1) Mixing chitosan, acetic acid solution and attapulgite for reaction, and adding sodium hydroxide solution after the reaction is completed to obtain chitosan-attapulgite precipitate;

[0014] 2) Mixing the chitosan-attapulgite precipitate with glutaraldehyde solution for crosslinking reaction to obtain chitosan-attapulgite gel beads;

[0015] 3) Soaking the chitosan-attapulgite gel beads with lanthanum salt solution to obtain a modified attapulgite adsorbent.

[0016] Preferably, in step 1), the mass-volume ratio of chitosan, acetic acid solution and attapulgite is 1-10 g: 10-20 mL: 2 g, the concentration of the acetic acid solution is 1-4 wt%, and the mixing reaction time is 4-8 h.

[0017] Preferably, in step 2), the mass-volume ratio of the chitosan-attapulgite precipitate to the glutaraldehyde solution is 1-10 g: 10-20 mL, the concentration of the glutaraldehyde solution is 3-8 wt%, the crosslinking reaction temperature is 0-8 °C, and the crosslinking reaction time is 10-15 h.

[0018] Preferably, in step 3), the mass-volume ratio of the lanthanum salt solution to the chitosan-attapulgite gel beads is 1-10: 1-10, the lanthanum salt includes lanthanum chloride and / or lanthanum chloride heptahydrate, the concentration of the lanthanum salt is 6-8 wt%, and the soaking time is 20-38 h.

[0019] Preferably, the preparation method of the modified attapulgite adsorbent further comprises the following steps:

[0020] 1) Mixing chitosan, acetic acid solution, attapulgite and lanthanum salt to obtain a mixed solution, reacting each raw material, and adding NaOH solution after the reaction is completed to obtain lanthanum-modified attapulgite gel beads;

[0021] (2) Mix the lanthanum-modified attapulgite gel beads with glutaraldehyde solution for crosslinking reaction to obtain the modified attapulgite adsorbent.

[0022] Preferably, in step (1), the mass-volume ratio of chitosan, acetic acid solution to attapulgite is 2 g: 80 - 120 mL: 0.8 - 1.5 g;

[0023] The concentration of the acetic acid solution is 1.5 - 2.5 wt%;

[0024] The concentration of lanthanum salt in the mixed solution is 0.05 - 0.15 mol / L.

[0025] Preferably, in step (2), the mass-volume ratio of the lanthanum-modified attapulgite gel beads to glutaraldehyde solution is 1 - 10 g: 10 - 20 mL;

[0026] The time of the crosslinking reaction is 20 - 30 h; the temperature of the crosslinking reaction is 0 - 50 °C.

[0027] The present invention also provides a modified attapulgite adsorbent prepared by the above preparation method.

[0028] The present invention also provides an application of the modified attapulgite adsorbent in adsorbing phosphate pollutants.

[0029] The present invention has at least the following beneficial effects:

[0030] (1) Rapidly adsorb phosphate in water;

[0031] (2) Simple production, green production, no pollution generated;

[0032] (3) The price of attapulgite is relatively low and it can be produced in large quantities. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the adsorption performance diagram of LaATP / CS-0.1 for phosphate in actual wastewater, where Figure 1 (a) in it is the adsorption effect diagram under different dosages, Figure 1 (b) in it is the adsorption effect diagram under different durations. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The present invention provides a preparation method of a modified attapulgite adsorbent, which includes the following steps: Mix chitosan, attapulgite, glutaraldehyde, lanthanum salt and water to prepare the modified attapulgite adsorbent.

[0035] In the present invention, the preparation method of the modified attapulgite adsorbent further includes the following steps:

[0036] 1) Mix chitosan, acetic acid solution and attapulgite clay and react. After the reaction is completed, add sodium hydroxide solution to obtain chitosan-attapulgite clay precipitate;

[0037] 2) Mix the chitosan-attapulgite clay precipitate with glutaraldehyde solution for cross-linking reaction to obtain chitosan-attapulgite clay gel beads;

[0038] 3) Soak the chitosan-attapulgite clay gel beads with lanthanum salt solution to obtain a modified attapulgite adsorbent.

[0039] In the present invention, in step 1), the mass-volume ratio of chitosan, acetic acid solution and attapulgite clay is 1-10 g: 10-20 mL: 2 g, preferably 2-9 g: 12-18 mL: 2 g, more preferably 4-7 g: 14-16 mL: 2 g, and still more preferably 5-6 g: 15 mL: 2 g; the concentration of the acetic acid solution is 1-4 wt%, preferably 2-3 wt%; the mixing reaction time is 4-8 h, preferably 5-7 h, more preferably 6 h.

[0040] In the present invention, in step 2), the mass-volume ratio of the chitosan-attapulgite clay precipitate to the glutaraldehyde solution is 1-10 g: 10-20 mL, preferably 2-8 g: 12-18 mL, more preferably 4-6 g: 14-16 mL, and still more preferably 5 g: 15 mL; the concentration of the glutaraldehyde solution is 3-8 wt%, preferably 4-7 wt%, more preferably 5-6 wt%; the cross-linking reaction temperature is 0-8 °C, preferably 2-6 °C, more preferably 4-5 °C; the cross-linking reaction time is 10-15 h, preferably 11-14 h, more preferably 12-13 h.

[0041] In the present invention, in step 2), the concentration of the sodium hydroxide solution is preferably 0.05-0.3 mol / L, more preferably 0.07-0.2 mol / L, and still more preferably 0.1-0.12 mol / L.

[0042] In the present invention, in step 3), the mass-volume ratio of the lanthanum salt solution to the chitosan-attapulgite clay gel beads is 1-10: 1-10, preferably 2-8: 2-8, more preferably 4-6: 4-6, and still more preferably 5: 5; the lanthanum salt includes lanthanum chloride and / or lanthanum chloride heptahydrate; the concentration of the lanthanum salt is 6-8 wt%, preferably 6-8 wt%, more preferably 6.5-7.5 wt%, and still more preferably 7 wt%; the soaking time is 20-38 h, preferably 24-34 h, more preferably 28-30 h.

[0043] In the present invention, after the soaking in step 3), the steps of filtering, washing, and drying the modified attapulgite adsorbent are further included; the drying temperature is 50-80°C, preferably 55-75°C, and more preferably 60-70°C; the drying time is 4-10 h, preferably 5-8 h, and more preferably 6-7 h.

[0044] In the present invention, the method for preparing the modified attapulgite adsorbent further includes the following steps:

[0045] 1) Mix chitosan, acetic acid solution, attapulgite, and lanthanum salt to obtain a mixed solution, and react the raw materials. After the reaction is completed, add NaOH solution to obtain lanthanum-modified attapulgite gel beads;

[0046] 2) Mix the lanthanum-modified attapulgite gel beads with glutaraldehyde solution for cross-linking reaction to obtain the modified attapulgite adsorbent.

[0047] In the present invention, in step 1), the mass-volume ratio of chitosan, acetic acid solution, and attapulgite is 2 g: 80-120 mL: 0.8-1.5 g, preferably 2 g: 90-110 mL: 1.0-1.3 g, and more preferably 2 g: 100 mL: 1.2 g;

[0048] The concentration of the acetic acid solution is 1.5-2.5 wt%, preferably 1.7-2.3 wt%, more preferably 1.9-2.1 wt%, and still more preferably 2.0 wt%;

[0049] The concentration of lanthanum salt in the mixed solution is 0.05-0.15 mol / L, preferably 0.07-0.13 mol / L, more preferably 0.09-0.11 mol / L, and still more preferably 0.10 mol / L.

[0050] In the present invention, in step 1), the preferred mixing order of chitosan, acetic acid solution, attapulgite, and lanthanum salt is to first mix chitosan, glacial acetic acid, and attapulgite and stir for 1 h, and then add lanthanum salt for reaction.

[0051] In the present invention, in step 1), the concentration of the sodium hydroxide solution is preferably 0.05-0.3 mol / L, more preferably 0.07-0.2 mol / L, and still more preferably 0.1-0.12 mol / L.

[0052] In the present invention, after adding the sodium hydroxide solution in step 1), a aging process is further included, and the aging time is preferably 12-48 h, more preferably 12-36 h, and still more preferably 12-24 h.

[0053] In the present invention, in step 2), the mass-volume ratio of the lanthanum-modified attapulgite gel beads to the glutaraldehyde solution is 1-10 g: 10-20 mL, preferably 2-8 g: 12-18 mL, more preferably 4-6 g: 14-16 mL, and still more preferably 5 g: 15 mL.

[0054] In the present invention, the time of the crosslinking reaction is 20-28 h, preferably 22-26 h, more preferably 24 h; the temperature of the crosslinking reaction is 0-45 °C, preferably 0-30 °C, more preferably 0-20 °C, and still more preferably 0-10 °C.

[0055] In the present invention, after the crosslinking reaction, the steps of washing, pre-treating, and freeze-drying the modified attapulgite adsorbent are further included; the temperature of the pre-treatment is preferably -25 to -15 °C, more preferably -22 to -18 °C, and still more preferably -20 °C, and the time of the pre-treatment is preferably 8-36 h, more preferably 8-24 h, and still more preferably 8-12 h; the temperature of the freeze-drying is preferably -60 to -50 °C, more preferably -18 to -5 °C, and still more preferably -15 to -10 °C; the time of the freeze-drying is preferably 8-36 h, more preferably 12-30 h, and still more preferably 18-24 h.

[0056] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0057] Example 1

[0058] (1) 2 g of chitosan was uniformly dispersed and dissolved in 10 mL of acetic acid solution with a concentration of 2 wt%, and then 2 g of attapulgite treated at 500 °C for 6 h was added. After stirring for 6 h, 100 mL of 0.1 mol / L sodium hydroxide solution was added dropwise to obtain a light brown chitosan-attapulgite precipitate.

[0059] (2) The 4 g of chitosan-attapulgite precipitate was washed with ultrapure water until the pH was neutral, and then a glutaraldehyde solution with a concentration of 5 wt% (the mass-volume ratio of the glutaraldehyde solution to the chitosan-attapulgite precipitate was 10 mL: 4 g) was added, and a crosslinking reaction was carried out at 4 °C for 12 h to obtain chitosan-attapulgite gel beads.

[0060] (3) The 4 g of chitosan-attapulgite gel beads were washed with ultrapure water until neutral, and 10 mL of LaCl 3 ·7H 2 O solution (LaCl 3 ·7H 2The addition ratio of the O solution to the chitosan attapulgite gel beads was 20 mL: 4 g. After soaking for 24 h, the gel beads were washed twice with ultrapure water and dried in a hot air oven at 60 °C for 6 h to obtain the modified attapulgite adsorbent, denoted as La-CTS-APT.

[0061] Example 2

[0062] (1) 4 g of chitosan was uniformly dispersed and dissolved in 15 mL of acetic acid solution with a concentration of 1 wt%, and then 2 g of attapulgite treated at 700 °C for 6 h was added. After stirring for 6 h, 100 mL of 0.2 mol / L sodium hydroxide solution was added dropwise to obtain a light brown chitosan attapulgite precipitate.

[0063] (2) The 4 g of chitosan attapulgite precipitate was washed with ultrapure water until the pH was neutral, and then a glutaraldehyde solution with a concentration of 8 wt% (the mass-volume ratio of the glutaraldehyde solution to the chitosan attapulgite precipitate was 20 mL: 4 g) was added, and a cross-linking reaction was carried out at 8 °C for 10 h to obtain chitosan attapulgite gel beads.

[0064] (3) The 4 g of chitosan attapulgite gel beads were washed with ultrapure water until neutral, and a LaCl 3 ·7H 2 O solution (the addition ratio of the LaCl 3 ·7H 2 O solution to the chitosan attapulgite gel beads was 4 mL: 4 g) was added. After soaking for 20 h, the gel beads were washed twice with ultrapure water and dried in a hot air oven at 60 °C for 6 h to obtain the modified attapulgite adsorbent, denoted as La-CTS-APT.

[0065] Example 3

[0066] (1) 4 g of chitosan was uniformly dispersed and dissolved in 15 mL of acetic acid solution with a concentration of 4 wt%, and then 2 g of attapulgite treated at 700 °C for 6 h was added. After stirring for 6 h, 100 mL of 0.1 mol / L sodium hydroxide solution was added dropwise to obtain a light brown chitosan attapulgite precipitate.

[0067] (2) The 4 g of chitosan attapulgite precipitate was washed with ultrapure water until the pH was neutral, and then a glutaraldehyde solution with a concentration of 3 wt% (the mass-volume ratio of the glutaraldehyde solution to the chitosan attapulgite precipitate was 15 mL: 4 g) was added, and a cross-linking reaction was carried out at 0 °C for 15 h to obtain chitosan attapulgite gel beads.

[0068] (3) The 4 g of chitosan attapulgite gel beads were washed with ultrapure water until neutral, and a LaCl 3 ·7H 2 O solution (LaCl3 ·7H 2 The addition ratio of the LaCl₃·7H₂O solution to the chitosan attapulgite gel beads was 8 mL:4 g). After soaking for 38 h, the gel beads were washed twice with ultrapure water and dried in a hot air oven at 60 °C for 6 h to obtain the modified attapulgite adsorbent, denoted as La-CTS-APT.

[0069] Example 4

[0070] (1) 4 g of chitosan was uniformly dispersed and dissolved in 13 mL of acetic acid solution with a concentration of 3 wt%, and then 2 g of attapulgite treated at 500 °C for 6 h was added. After stirring for 6 h, 100 mL of 0.05 mol / L sodium hydroxide solution was added dropwise to obtain a light brown chitosan attapulgite precipitate.

[0071] (2) The 4 g of chitosan attapulgite precipitate was washed with ultrapure water until the pH was neutral, and then a 5 wt% glutaraldehyde solution (the mass-volume ratio of the glutaraldehyde solution to the chitosan attapulgite precipitate was 12 mL:4 g) was added, and a cross-linking reaction was carried out at 4 °C for 12 h to obtain chitosan attapulgite gel beads.

[0072] (3) The 4 g of chitosan attapulgite gel beads were washed with ultrapure water until neutral, and a 6 wt% LaCl₃ 3 ·7H 2 ₃ solution (the addition ratio of the LaCl₃ 3 ·7H 2 ₃ solution to the chitosan attapulgite gel beads was 15 mL:4 g) was added. After soaking for 24 h, the gel beads were washed twice with ultrapure water and dried in a hot air oven at 60 °C for 6 h to obtain the modified attapulgite adsorbent, denoted as La-CTS-APT.

[0073] Example 5

[0074] (1) 6 g of chitosan was uniformly dispersed and dissolved in 10 mL of acetic acid solution with a concentration of 3 wt%, and then 2 g of attapulgite treated at 500 °C for 6 h was added. After stirring for 6 h, 100 mL of 0.1 mol / L sodium hydroxide solution was added dropwise to obtain a light brown chitosan attapulgite precipitate.

[0075] (2) The 4 g of chitosan attapulgite precipitate was washed with ultrapure water until the pH was neutral, and then a 5 wt% glutaraldehyde solution (the mass-volume ratio of the glutaraldehyde solution to the chitosan attapulgite precipitate was 18 mL:4 g) was added, and a cross-linking reaction was carried out at 8 °C for 10 h to obtain chitosan attapulgite gel beads.

[0076] (3) The 4 g of chitosan attapulgite gel beads were washed with ultrapure water until neutral, and a 6.5 wt% LaCl₃ 3·7H 2 O solution (LaCl 3 ·7H 2 The addition ratio of the O solution to the chitosan attapulgite gel beads was 5 mL: 4 g). After soaking for 24 h, the gel beads were washed twice with ultrapure water and dried in a hot air oven at 60 °C for 6 h to obtain the modified attapulgite adsorbent, denoted as La-CTS-APT.

[0077] Example 6

[0078] (1) Dissolve 6 g of chitosan uniformly in 10 mL of acetic acid solution with a concentration of 2 wt%, then add 2 g of attapulgite treated at 700 °C for 6 h, stir for 6 h, and then gradually add 100 mL of 0.1 mol / L sodium hydroxide solution to obtain a light brown chitosan attapulgite precipitate.

[0079] (2) Wash 2 g of the chitosan attapulgite precipitate with ultrapure water until the pH is neutral, then add a 5 wt% glutaraldehyde solution (the mass-volume ratio of the glutaraldehyde solution to the chitosan attapulgite precipitate is 15 mL: 4 g), and carry out a cross-linking reaction at 4 °C for 14 h to obtain chitosan attapulgite gel beads.

[0080] (3) Wash 4 g of the chitosan attapulgite gel beads with ultrapure water until neutral, add a 7 wt% LaCl 3 ·7H 2 O solution (LaCl 3 ·7H 2 The addition ratio of the O solution to the chitosan attapulgite gel beads was 12 mL: 4 g). After soaking for 28 h, the gel beads were washed twice with ultrapure water and dried in a hot air oven at 60 °C for 6 h to obtain the modified attapulgite adsorbent, denoted as La-CTS-APT.

[0081] Example 7

[0082] (1) Dissolve 2 g of chitosan uniformly in 10 mL of acetic acid solution with a concentration of 4 wt%, then add 2 g of attapulgite treated at 500 °C for 6 h, stir for 6 h, and then gradually add 100 mL of 0.1 mol / L sodium hydroxide solution to obtain a light brown chitosan attapulgite precipitate.

[0083] (2) Wash 4 g of the chitosan attapulgite precipitate with ultrapure water until the pH is neutral, then add a 5 wt% glutaraldehyde solution (the mass-volume ratio of the glutaraldehyde solution to the chitosan attapulgite precipitate is 12 mL: 4 g), and carry out a cross-linking reaction at 4 °C for 12 h to obtain chitosan attapulgite gel beads.

[0084] (3) Wash 4 g of chitosan attapulgite gel beads with ultrapure water until neutral, add an LaCl 3 ·7H 2 O solution (the addition ratio of the LaCl 3 ·7H 2 O solution to the chitosan attapulgite gel beads is 20 mL: 4 g), after soaking for 24 h, wash the gel beads twice with ultrapure water, and dry them in a hot air oven at 60 °C for 6 h to obtain a modified attapulgite adsorbent, denoted as La-CTS-APT.

[0085] Example 8

[0086] (1) Uniformly disperse and dissolve 2 g of chitosan in 10 mL of a 2 wt% acetic acid solution, then add 2 g of attapulgite treated at 500 °C for 6 h, stir for 6 h, and then gradually add 100 mL of 0.1 mol / L sodium hydroxide solution to obtain a light brown chitosan attapulgite precipitate.

[0087] (2) Wash 4 g of the chitosan attapulgite precipitate with ultrapure water until the pH is neutral, then add a 5 wt% glutaraldehyde solution (the mass-volume ratio of the glutaraldehyde solution to the chitosan attapulgite precipitate is 20 mL: 4 g), and carry out a cross-linking reaction at 4 °C for 12 h to obtain chitosan attapulgite gel beads.

[0088] (3) Wash 4 g of the chitosan attapulgite gel beads with ultrapure water until neutral, add an LaCl 3 ·7H 2 O solution (the addition ratio of the LaCl 3 ·7H 2 O solution to the chitosan attapulgite gel beads is 20 mL: 4 g), after soaking for 24 h, wash the gel beads twice with ultrapure water, and dry them in a hot air oven at 60 °C for 6 h to obtain a modified attapulgite adsorbent, denoted as La-CTS-APT.

[0089] Example 9

[0090] (1) Dissolve 2 g of chitosan fully in 100 mL of a 2 wt% acetic acid solution, then add 1 g of attapulgite treated at 500 °C for 6 h, stir for 1 h, then add LaCl 3 ·7H 2 O to make the concentration of lanthanum ions in the solution 0.05 mol / L, stir for 2 h, and then use a peristaltic pump to drop 100 mL of 1 mol / L sodium hydroxide solution to obtain lanthanum-modified attapulgite gel beads. After aging for 24 h, wash the gel beads with distilled water until neutral.

[0091] (2) Crosslink the gel beads with a 5 wt% glutaraldehyde solution (the mass-volume ratio of the glutaraldehyde solution to the gel beads is 20 mL:5 g). After 24 h of crosslinking reaction, wash with distilled water to remove the residual glutaraldehyde solution on the surface. Treat the washed gel beads at -20 °C for 0.1 h and then perform freeze-drying. The temperature of freeze-drying is -50 °C and the time of freeze-drying is 10 h. Obtain the modified attapulgite adsorbent, denoted as LaATP / CS-0.05.

[0092] Example 10

[0093] (1) Dissolve 2 g of chitosan fully in 80 mL of 1.5 wt% acetic acid solution, then add 0.8 g of attapulgite treated at 500 °C for 6 h, stir for 1 h, and then add LaCl 3 ·7H 2 O to make the concentration of lanthanum ions in the solution 0.1 mol / L. After stirring for 2 h, drop 100 mL of 1 mol / L sodium hydroxide solution using a peristaltic pump to obtain lanthanum-modified attapulgite gel beads. After aging for 36 h, wash the gel beads with distilled water until neutral.

[0094] (2) Crosslink the gel beads with a 5 wt% glutaraldehyde solution (the mass-volume ratio of the glutaraldehyde solution to the gel beads is 15 mL:5 g). After 24 h of crosslinking reaction, wash with distilled water to remove the residual glutaraldehyde solution on the surface. Treat the washed gel beads at -20 °C for 0.1 h and then perform freeze-drying. The temperature of freeze-drying is -50 °C and the time of freeze-drying is 8 h. Obtain the modified attapulgite adsorbent, denoted as LaATP / CS-0.1.

[0095] Example 11

[0096] (1) Dissolve 2 g of chitosan fully in 100 mL of 2 wt% acetic acid solution, then add 1 g of attapulgite treated at 500 °C for 6 h, stir for 1 h, and then add LaCl 3 ·7H 2 O to make the concentration of lanthanum ions in the solution 0.15 mol / L. After stirring for 2 h, drop 100 mL of 1 mol / L sodium hydroxide solution using a peristaltic pump to obtain lanthanum-modified attapulgite gel beads. After aging for 24 h, wash the gel beads with distilled water until neutral.

[0097] (2) The gel beads were crosslinked with a 5 wt% glutaraldehyde solution (the mass-volume ratio of the glutaraldehyde solution to the chitosan attapulgite precipitate was 15 mL: 6.5 g). After 24 h of crosslinking reaction, they were washed with distilled water to remove the residual glutaraldehyde solution on the surface. The washed gel beads were treated at -20 °C for 0.1 h and then freeze-dried. The temperature of freeze-drying was -55 °C, and the time of freeze-drying was 6 h. The modified attapulgite adsorbent was obtained and denoted as LaATP / CS-0.15.

[0098] Comparative Example 1

[0099] (1) 2 g of chitosan was evenly dispersed and dissolved in 10 mL of a 2 wt% acetic acid solution, and then untreated attapulgite was added. After stirring for 6 h, 100 mL of 0.1 mol / L sodium hydroxide solution was added dropwise to obtain a light brown chitosan attapulgite precipitate.

[0100] (2) The chitosan attapulgite precipitate was washed with ultrapure water until the pH was neutral, and then a 5 wt% glutaraldehyde solution (the mass-volume ratio of the glutaraldehyde solution to the chitosan attapulgite precipitate was 18 mL: 10 g) was added, and a crosslinking reaction was carried out at 4 °C for 12 h to obtain chitosan attapulgite gel beads.

[0101] (3) The chitosan attapulgite gel beads were washed with ultrapure water until neutral, and a 6 wt% LaCl 3 ·7H 2 O solution (the addition ratio of the LaCl 3 ·7H 2 O solution to the chitosan attapulgite gel beads was 15 mL: 5 g) was added. After soaking for 24 h, the gel beads were washed twice with ultrapure water and dried in a hot air oven at 60 °C for 6 h to obtain the modified attapulgite adsorbent, denoted as La-CTS-APT.

[0102] Comparative Example 2

[0103] (1) 4 g of chitosan was evenly dispersed and dissolved in 20 mL of a 2 wt% acetic acid solution, and then untreated attapulgite was added. After stirring for 6 h, 100 mL of 0.1 mol / L sodium hydroxide solution was added dropwise to obtain a light brown chitosan attapulgite precipitate.

[0104] (2) The chitosan attapulgite precipitate was washed with ultrapure water until the pH was neutral, and then a 5 wt% glutaraldehyde solution (the mass-volume ratio of the glutaraldehyde solution to the chitosan attapulgite precipitate was 15 mL: 8 g) was added, and a crosslinking reaction was carried out at 4 °C for 12 h to obtain chitosan attapulgite gel beads.

[0105] (3) Wash the chitosan attapulgite gel beads with ultrapure water until neutral, and add a LaCl 3 ·7H 2 O solution (the addition ratio of the LaCl 3 ·7H 2 O solution to the chitosan attapulgite gel beads is 20 mL: 8 g), soak for 24 h, then wash the gel beads twice with ultrapure water, and dry in a hot air oven at 60 °C for 6 h to obtain the modified attapulgite adsorbent, denoted as La-CTS-APT.

[0106] Comparative Example 3

[0107] (1) Dissolve 2 g of chitosan fully in 100 mL of acetic acid solution with a concentration of 2 wt%, then add 1 g of attapulgite treated at 500 °C for 6 h, stir for 3 h, and then drop 100 mL of sodium hydroxide solution with a concentration of 1 mol / L using a peristaltic pump to obtain lanthanum-modified attapulgite gel beads. After aging for 24 h, wash the gel beads with distilled water until neutral.

[0108] (2) Crosslink the gel beads with a glutaraldehyde solution with a concentration of 5 wt% (the mass-volume ratio of the glutaraldehyde solution to the gel beads is 15 mL: 5 g). After crosslinking for 24 h, wash with distilled water to wash away the residual glutaraldehyde solution on the surface. Treat the washed gel beads at -20 °C for 0.1 h and then perform freeze-drying. The temperature of freeze-drying is -60 °C and the time of freeze-drying is 8 h. Obtain the ATP-CS composite adsorbent.

[0109] To further evaluate the application ability of La-CTS-ATP, the adsorption performance of the modified attapulgite prepared in Example 1 in actual sewage was studied. Two kinds of actual wastewater (breeding wastewater and domestic sewage) were selected for adsorption experiments. Their initial phosphate concentrations were 47.70 mg / L and 14.47 mg / L respectively. The specific adsorption capacities are shown in Table 1. After adsorption, the phosphate concentration in the breeding wastewater decreased to 12.71 mg / L, the removal rate was 73.37%, and the adsorption capacity was 34.99 mg / g; the phosphate concentration in the domestic sewage decreased to 0.45 mg / L, the removal rate was 96.75%, and the adsorption capacity was 14.02 mg / g. Therefore, when the adsorbent dosage is 1 g / L, the P concentration in the treated domestic sewage is 0.45 mg / L, meeting the phosphate discharge standard (0.5 mg / L). However, the breeding wastewater with a high phosphate concentration (47.7 mg / L) requires a larger adsorbent dosage for treatment.

[0110] Table 1 Adsorption performance of the modified attapulgite prepared in Example 1 for phosphate in actual sewage

[0111]

[0112] Existing experiments all use laboratory-synthesized phosphate-concentrated sewage. However, the components in actual sewage are complex and there are many influencing factors. Therefore, it is necessary to use real water bodies to evaluate the adsorption performance of the modified attapulgite adsorbent. The actual sewage used in this experiment comes from aquaculture sewage with a high concentration of phosphate in Ninghe District, Tianjin, and the phosphorus concentration is 75.65 mg / g. When treated with LaATP / CS-0.1 at a dosage of 2 g / L, the phosphorus concentration in the treated actual sewage is 0.032 mg / L, which is lower than 0.05 mg / L and meets the sewage TP discharge standard.

[0113] To further study the adsorption performance of LaATP / CS-0.1 for phosphate in actual wastewater, it is necessary to consider the effects of various anions, cations, and humus in actual wastewater on the adsorption capacity of LaATP / CS-0.1. Therefore, it is necessary to study the adsorption performance of the material in actual wastewater. The actual sewage is domestic sewage with a low phosphorus concentration from a three-room septic tank of a farmer in Jinnan District, Tianjin, China. The adsorption experiment considered the adsorbent dosage and adsorption duration. Figure 1 Shows the influence of adsorbent dosage and kinetic process of LaATP / CS-0.1 in removing phosphate from actual wastewater. As Figure 1 (a) in shows the adsorption effect diagrams at different adsorbent dosages. Figure 1 As shown in (a), the initial phosphate concentration of domestic wastewater is 18.95 mg / L. After treatment with LaATP / CS-0.1, the remaining phosphate concentration decreases sharply. When the adsorbent dosage is 0.5 g / L, the remaining phosphate concentration drops to 3.5699 mg / L. As the dosage increases, the removal efficiency of phosphate also improves. When the adsorbent dosage exceeds 1.0 g / L, the treated concentration reaches the phosphate discharge standard of 0.5 mg / L. It can be seen from Figure 1 (a) that the adsorbent has the best effect at a dosage of 1 g / L and can quickly adsorb phosphate in the water body.

[0114] Figure 1 (b) in shows the effect diagrams at different adsorption durations, demonstrating the kinetic process of removing phosphate from actual wastewater. Figure 1 As shown in (b), similar to the previous trend in synthetic wastewater, the entire adsorption process is divided into two stages, namely the rapid rise period and the equilibrium period. Compared with the equilibrium time (400 minutes) in synthetic wastewater, the equilibrium time (300 minutes) in actual wastewater is shorter, which can be attributed to the high phosphate concentration in synthetic wastewater. In actual wastewater with a low concentration, phosphate is quickly and completely adsorbed by LaATP / CS-0.1. At the same time, there are still unused active sites on the material.

[0115] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a modified attapulgite adsorbent, characterized in that: The following steps are involved: The modified attapulgite adsorbent is prepared by mixing chitosan, attapulgite, glutaraldehyde, lanthanum salt and water.

2. The method for preparing a modified attapulgite adsorbent according to claim 1, characterized in that: The following steps are also included: 1) mixing chitosan, acetic acid solution and attapulgite for reaction, and after the reaction is completed, adding sodium hydroxide solution to obtain chitosan attapulgite precipitation; 2) mixing the chitosan attapulgite precipitate with a glutaraldehyde solution to perform a cross-linking reaction to obtain chitosan attapulgite gel beads; 3) The chitosan attapulgite gel beads were soaked in a lanthanum salt solution to obtain a modified attapulgite adsorbent.

3. The method for preparing a modified attapulgite adsorbent according to claim 2, characterized in that: In step 1), the mass volume ratio of chitosan, acetic acid solution and attapulgite is 1-10 g: 10-20 mL: 2 g, the concentration of acetic acid solution is 1-4 wt %, and the mixing reaction time is 4-8 h.

4. The method for preparing a modified attapulgite adsorbent according to claim 3, characterized in that: In step 2), the mass volume ratio of chitosan attapulgite precipitate to glutaraldehyde solution is 1-10 g: 10-20 mL, the concentration of glutaraldehyde solution is 3-8 wt %, the temperature of cross-linking reaction is 0-8° C., and the time of cross-linking reaction is 10-15 h.

5. The method for preparing a modified attapulgite adsorbent according to any one of claims 2 to 4, characterized in that: In step 3), the mass volume ratio of the lanthanum salt solution to the chitosan attapulgite gel beads is 1-10:1-10, the lanthanum salt includes lanthanum chloride and / or lanthanum chloride heptahydrate, the concentration of the lanthanum salt is 6-8wt%, and the soaking time is 20-38h.

6. The method for preparing a modified attapulgite adsorbent according to claim 1, characterized in that: The following steps are also included: 1) chitosan, acetic acid solution, attapulgite and lanthanum salt are mixed to obtain a mixed solution, each raw material is reacted, and after the reaction is completed, NaOH solution is added to obtain lanthanum-modified attapulgite gel beads; 2) The lanthanum-modified attapulgite gel beads are mixed with a glutaraldehyde solution to undergo a cross-linking reaction to obtain a modified attapulgite adsorbent.

7. The method for preparing a modified attapulgite adsorbent according to claim 6, characterized in that: In step 1), the mass volume ratio of chitosan, acetic acid solution and attapulgite is 2 g: 80-120 mL: 0.8-1.5 g; The concentration of the acetic acid solution is 1.5-2.5wt%; The concentration of the lanthanum salt in the mixed solution is 0.05-0.15 mol / L.

8. The method for preparing a modified attapulgite adsorbent according to claim 7, characterized in that: In step 2), the mass volume ratio of the lanthanum modified attapulgite gel beads to the glutaraldehyde solution is 1-10 g: 10-20 mL; The cross-linking reaction time is 20 to 30 hours; the cross-linking reaction temperature is 0 to 50°C.

9. The modified attapulgite adsorbent prepared by the method for preparing the modified attapulgite adsorbent according to any one of claims 1 to 8.

10. Use of the modified attapulgite adsorbent according to claim 9 in adsorbing phosphate pollutants.

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