A modified rapas-based flocculant, its preparation method and application

Abstract

This invention discloses a modified attapulgite-based flocculant, its preparation method, and its application, belonging to the field of water body treatment technology for harmful algal blooms. The modified attapulgite-based flocculant of this invention comprises attapulgite powder and chitosan, with chitosan loaded on the surface of the attapulgite powder. The mass ratio of chitosan to attapulgite powder is 1:(2-14). This invention rationally utilizes attapulgite minerals based on the principle of waste-to-waste conversion; the preparation method is simple, non-toxic, and low-cost; through the modification method of this invention on different clay minerals, it was found that compared with other minerals studied in this invention (attapulgite, montmorillonite, pyrite, and bentonite), chitosan-modified attapulgite has excellent removal effects; the flocculant can effectively settle harmful algae in wastewater containing *Microcystis aeruginosa* or *Anabaena globulus*, and is suitable for various complex environments.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology for harmful algal blooms, specifically relating to a modified attapulgite-based flocculant, its preparation method, and its application. Background Technology

[0002] With the increasing eutrophication of water bodies, the explosive proliferation of toxin-producing cyanobacteria such as Anabaena cinerea and Microcystis aeruginosa has become a global environmental problem. These algae not only release persistent toxins such as microcystin and geosmin, but also clog water treatment filters, threatening drinking water safety.

[0003] Currently, common methods for controlling cyanobacterial blooms are divided into three categories: physical, chemical, and biological methods, all of which have significant drawbacks. Among physical methods, ultrasonic technology has an inactivation rate of <40% for Microcystis aeruginosa and induces the release of 60% of intracellular toxins; membrane filtration technology suffers from a >80% decrease in membrane flux within 4 hours due to organic matter from algae. In chemical methods, oxidation techniques (such as ozone and sodium hypochlorite) destroy over 90% of algal cells and release 80-95% of intracellular toxins, while also generating carcinogens such as bromate or chloroform. Using chemical reagents to remove harmful algae, such as the long-chain alkylammonium leached from the quaternary ammonium salt modification method for preparing adsorbents, can generate N-nitrosodimethylamine exceeding the standard by 8 times. Traditional coagulant methods for algae removal (such as polyaluminum chloride) suffer from drawbacks such as high coagulant consumption, unstable floc morphology, and slow sedimentation; excessive polyaluminum chloride residues can also pose health risks. Biological methods (such as algicidal bacteria) are slow to take effect and have an inhibition rate of only 30% against Anabaena. Existing technologies cannot simultaneously meet the safety requirements of efficient algae removal, preservation of cell integrity, deep purification of toxins, and no secondary pollution.

[0004] In recent years, the technology of modifying and removing algae by comprehensively utilizing clay minerals has attracted more and more attention. Clay minerals are widely used for algae flocculation due to their layered structure and cation exchange capacity. However, clay minerals in their natural state have three major bottlenecks: narrow interlayer spacing, making it difficult to accommodate large molecular algal organic matter; excessively strong surface hydrophilicity, resulting in weak adsorption of hydrophobic toxins (such as MC-LR); and low mechanical strength, making them prone to disintegration and failure under water flow.

[0005] Therefore, there is a need for a flocculant that has a wide algae removal range, is easy and non-toxic to prepare, and can achieve highly efficient algae control in a very short time. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a modified pizosite-based flocculant, its preparation method and application. This invention follows the principle of making waste from waste to rationally utilize pizosite minerals; the preparation method is simple, non-toxic and low in cost; when the flocculant is added to wastewater containing Microcystis aeruginosa / Anabaena pyrenoidosa, it achieves excellent algae removal effects of 96.45% and 99.45% respectively after settling for 5 minutes.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a modified raptosite-based flocculant comprising raptosite powder and chitosan, wherein the chitosan is loaded on the surface of the raptosite powder.

[0009] Preferably, the mass ratio of chitosan to attapulgite powder is 1:(2-14).

[0010] Secondly, the present invention provides a method for preparing a modified raphe-based flocculant, comprising the following steps:

[0011] The modified attapulgite-based flocculant was obtained by mixing and stirring chitosan solution and attapulgite powder, centrifuging and drying, and grinding.

[0012] Preferably, the chitosan solution is prepared by dissolving chitosan in a 5% acetic acid solution.

[0013] Preferably, the concentration of the chitosan solution is 5-15 g / L.

[0014] Preferably, the mass ratio of chitosan to attapulgite powder is 1:(2-14).

[0015] Preferably, the mixing temperature is 20-25℃ and the mixing time is 5-16h.

[0016] Preferably, the modified tropane-based flocculant has a mesh size ≤ 100 mesh.

[0017] Thirdly, this invention provides the application of modified raphe-based flocculants in the removal of algae from water bodies.

[0018] Preferably, the aquatic algae include, but are not limited to, Microcystis aeruginosa and Anabaena pygmaea.

[0019] It contains at least the following beneficial technical effects:

[0020] This invention utilizes attapulgite minerals rationally based on the principle of "waste-to-waste"; the preparation method is simple, non-toxic, and low-cost; through the modification method of this invention, different clay minerals were modified, and it was found that attapulgite has excellent removal effect compared with other minerals studied in this invention (attapulgite, montmorillonite, pyrite, and bentonite); when the flocculant was added to wastewater containing Microcystis aeruginosa and settled for 5 minutes, the algal density, turbidity, and Chl-a removal rate were 96.45%, 94.32%, and 95.51%, respectively; after further settling for 30 minutes, the algal density, turbidity, and Chl-a removal rate reached 99.42%, 98.12%, and 99.21%, respectively. When the flocculant was added to wastewater containing Anabaena pyrenoidosa and settled for 5 minutes, the algal density, turbidity, and Chl-a removal rate reached 99.45%, 95.37%, and 95.51%, respectively, indicating that the chitosan-modified attapulgite material has rapid and excellent algae removal effect.

[0021] Moreover, it is suitable for a variety of complex environments and has good effects under different pH, temperature, coexisting ions, and humic acid influences. It is easier to adapt to complex environments such as natural water bodies and is suitable for widespread use. Attached Figure Description

[0022] Figure 1 This is a standard curve for the concentration of Microcystis aeruginosa cells.

[0023] Figure 2 This is a standard curve for the concentration of *Anabaena gracilis* cells.

[0024] Figure 3 The algae removal effect of CTS@REC at different dosages on Microcystis aeruginosa was investigated.

[0025] Figure 4 The algae removal effect of CTS@REC at different dosages on *Houttuynia cordata* was investigated.

[0026] Figure 5 The removal effect of Microcystis aeruginosa after different settling times.

[0027] Figure 6 The removal effect of gray false anemones on different settling times.

[0028] Figure 7 The effects of different materials on the removal of Microcystis aeruginosa.

[0029] Figure 8 The effects of different materials on the removal of *Houttuynia cordata*.

[0030] Figure 9 The effects of different ratios of chitosan and clay minerals on the removal of Microcystis aeruginosa were investigated.

[0031] Figure 10 The effect of different ratios of chitosan and clay minerals on the removal of gray algae.

[0032] Figure 11 The removal effect of different pH values ​​on two types of algae.

[0033] Figure 12 The effects of different temperatures on two types of algae.

[0034] Figure 13 The effects of different coexisting ions on two types of algae.

[0035] Figure 14 The algae removal effect of different dosages of CTS@REC under the condition of coexistence of 10 mg / L humic acid.

[0036] Figure 15 Effects of different dosages on the removal of Microcystis aeruginosa in actual water bodies.

[0037] Figure 16 Effects of different dosages on the removal of pseudo-fish algae in actual water bodies.

[0038] Figure 17 FTIR analysis plots of CTS and CTS@REC.

[0039] Figure 18 Zeta potential analysis diagrams under different pH conditions.

[0040] Figure 19 The images are different SEM images, where Figure a is the SEM image of REC; Figure b is the SEM image of CTS@REC; Figure c is the SEM image of M. aeruginosa; and Figure d is the SEM image of P. cinerea. Detailed Implementation

[0041] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0042] Example 1

[0043] Raw material selection:

[0044] Chitosan is a commercially available product, analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0045] The experiment used natural raptosite ore, which was naturally air-dried and then crushed using a crusher. Finally, the crushed material was collected through a 100-mesh sieve and stored in a dry place for later use.

[0046] All other raw materials are sourced from commercially available sources.

[0047] Preparation steps of chitosan-modified tropite flocculant:

[0048] (1) Preparation of 10g / L chitosan solution: Weigh 1.5g of chitosan into a 100mL beaker, add 50mL of 5% acetic acid solution, and stir at room temperature until completely dissolved.

[0049] (2) Weigh out a certain amount of attapulgite and add it to a beaker containing a 10 g / L chitosan solution. Stir at room temperature for 12 h. The mass ratio of chitosan to attapulgite ore is 1:2, 1:4, 1:6, 1:8, 1:10, and 1:14, respectively. Centrifuge the mixed solutions with different mass ratios after stirring and wash the mixed material until neutral. Dry the resulting solid at 50 °C for 8 h, grind it, and pass it through a 100 mesh sieve.

[0050] Example 2

[0051] algae cultivation

[0052] The *Microcystis aeruginosa* and *Anabaena gracilis* used in the experiment were both obtained from the Freshwater Algae Culture Collection of the Chinese Academy of Sciences, with the numbers FACHB-315 and FACHB-1127, respectively. BG-11 medium was used for cultivation (the components of BG-11 medium are as follows).

[0053] (Table 1 and Table 2). After receiving the algal culture, shake the algal solution in the serum well and transfer it directly into a 2.5L glass Erlenmeyer flask under aseptic conditions. Seal the flask and place it in a light incubator under low light for 2-3 days. The incubation temperature is 25℃, the light conditions are 1000-2000 Lux, and the time is set to 12 hours day / 12 hours night. For algal culture transfer, take 500-800mL of algal solution and add it to 500mL-2L of fresh BG-11 medium. Incubate in a sterile Erlenmeyer flask for 20-30 days. If the algal culture is growing well and the biomass has increased significantly, it can be transferred again. When the algal solution is less than 500mL, shake the Erlenmeyer flask twice a day. When the algal solution is greater than 500mL, aerate or use a shaker to assist the culture. Shake once each in the morning, noon, and evening.

[0054] Table 1. Components of BG-11 culture medium

[0055]

[0056]

[0057] Table 2A5 (Trace mental solution)

[0058]

[0059] (4) Algae dilution:

[0060] Take 40 mL of *Microcystis aeruginosa* and *Anabaena granatum* in the logarithmic growth phase and in good culture condition, and pour them into a centrifuge tube. Centrifuge at 10000 rpm for 10 minutes. Slowly pour out the supernatant, being careful to avoid spilling the algal solution. Wash twice with ultrapure water to thoroughly remove the culture medium. Add an appropriate amount of ultrapure water and stir evenly on a magnetic stirrer. Measure the absorbance at 680 nm and adjust the absorbance to approximately 0.15 (at this point, the number of algal cells is close to 1.0*10^6). 6 (cells / L, which represents the algal cell concentration during an algal bloom). This algal solution is the one used in the experiment.

[0061] (5) Determination of algal density

[0062] The concentrations of *Microcystis aeruginosa* and *Anabaena glauca* were determined using absorbance, a method based on the absorption characteristics of algal cells or pigments at specific wavelengths of light. Absorbance measurement is based on Beer-Lambert's law, which states that the absorption of light by a substance is directly proportional to its concentration. When light passes through a solution containing algae, the algal cells or their pigments absorb light at specific wavelengths, resulting in a decrease in the intensity of transmitted light. By measuring the absorbance at this specific wavelength, the algal concentration can be calculated. In the experiment, the absorbance of the algal solution at 680 nm was measured to reflect the algal concentration. The standard curve of algal absorbance versus algal cell concentration obtained by the gravimetric method is shown below. Figure 1 and Figure 2 .

[0063] (6) Determination of Chl-a

[0064] The determination was performed strictly in accordance with the methods mentioned in the national standard HJ 897-2017 using a spectrophotometer.

[0065] (7) Turbidity measurement

[0066] Since the experimental algae strain was cultured in a sterile laboratory without other impurities, the turbidity value can also indirectly reflect the algae removal rate. In the experiment, a turbidity meter (Turb 550IR, WTW, Germany) was used for measurement.

[0067] Example 3

[0068] The effect of chitosan-modified attapulgite (chitosan to attapulgite ore mass ratio of 1:6, denoted as CTS@REC-(1:6)) on the removal of Microcystis aeruginosa and Anabaena aeruginosa was investigated by analyzing three indicators: algal density, turbidity, and Chl-a removal rate under different dosage conditions.

[0069] Take 100mL OD 680A 0.15 concentration of *Microcystis aeruginosa* solution / *Anabaena globulus* solution was poured into several 150 mL beakers. 10, 20, 50, 75, 100, and 125 mg / L of CTS@REC-(1:6) were added to the *Microcystis aeruginosa* solution; 10, 20, 40, 60, 80, and 100 mg / L of CTS@REC-(1:6) were added to the *Anabaena globulus* solution. The solutions were then placed in a six-unit stirrer and stirred in a rotary motion. The basic hydraulic conditions were set to 200 rpm for 5 min, 40 rpm for 20 min, pH 7, and water temperature 25℃. After standing for 30 min, the floc morphology was observed, and samples were taken 2 cm below the liquid surface to determine algal density, turbidity, and Chl-a.

[0070] The results are as follows Figure 3 and Figure 4 As shown, Figure 3 To assess the sedimentation effect of the Microcystis aeruginosa solution, Figure 4 The sedimentation effect of the *Houttuynia cordata* solution is shown, indicating that CTS@REC-(1:6) has a significant sedimentation effect on algae.

[0071] Example 4

[0072] To investigate the algae-removing effects of CTS@REC on Microcystis aeruginosa and Anabaena gracilis under different dosages and different settling times.

[0073] As can be seen from Example 3 above, the three indicators of algal density, turbidity and Chl-a show the same trend and the difference in the amount of change is not significant. Therefore, subsequent experiments will only measure algal density.

[0074] Take 100mL OD 680 Pour a 0.15 concentration of *Microcystis aeruginosa* / *Anabaena glauca* solution into several 150 mL beakers. Add 10, 20, 50, 75, 100, and 125 mg / L of CTS@REC-(1:6) to the *Microcystis aeruginosa* solution; add 10, 20, 40, 60, 80, and 100 mg / L of CTS@REC-(1:6) to the *Anabaena glauca* solution. Place the beakers in a six-unit stirrer and stir in a rotary motion. Set the basic hydraulic conditions to 200 rpm for 5 min and 40 rpm for 20 min. Set the pH of the algal solution to 7 and the water temperature to 25℃. Let the beakers stand for 0, 5, 10, 20, 30, 60, and 90 min, observe the floc morphology, and take samples 2 cm below the liquid surface.

[0075] The results are as follows Figure 5 and Figure 6 As shown, Figure 5 The sedimentation effect of different dosages of Microcystis aeruginosa solution and different standing times was observed. Figure 6 The sedimentation effect of different dosages of *Houttuynia cordata* solution and different standing times was observed.

[0076] Example 5

[0077] To investigate the algae-removing effects of different materials on Microcystis aeruginosa and Anabaena gracilis under different dosage conditions.

[0078] The preparation methods for different materials are the same as those in Example 1. The attapulgite of the supporting matrix is ​​replaced with ATP, MMT, Fe2S, and BE respectively, and the mass ratio of chitosan to the supporting matrix is ​​1:6.

[0079] Take 100mL OD 680 Pour a 0.15 concentration of *Microcystis aeruginosa* / *Houttuynia cordata* solution into several 150 mL beakers. Add 10, 20, 50, 75, 100, and 125 mg / L of REC, CTS, CTS@REC, CTS@APT (chitosan-modified attapulgite), CTS@MMT (chitosan-modified montmorillonite), CTS@Fe2S (chitosan-modified pyrite), and CTS@BE (chitosan-modified bentonite) to the *Microcystis aeruginosa* solution, respectively. Add the following to the *Houttuynia cordata* solution in sequence: Add 10, 20, 40, 60, 80 and 100 mg / L of REC, CTS, CTS@REC, CTS@ATP, CTS@MMT, CTS@Fe2S and CTS@BE; place in a six-unit stirrer for rotary stirring, set the basic hydraulic conditions to 200 r / min for 5 min and 40 r / min for 20 min, set the pH of the algal solution to 7, the water temperature to 25℃, let stand for 30 min, observe the floc morphology, and take samples 2 cm below the liquid surface.

[0080] The results are as follows Figure 7 and Figure 8 As shown, Figure 7 The sedimentation effect of different materials in Microcystis aeruginosa solution at different dosages and times was investigated. Figure 8 The sedimentation effect of different materials in the *Houttuynia cordata* solution at different dosages was studied.

[0081] Example 6

[0082] To investigate the algae-removing effects of different materials on Microcystis aeruginosa and Anabaena gracilis under different mass ratios of chitosan and clay minerals.

[0083] Take 100mL OD 680A solution of 0.15 μL of Microcystis aeruginosa / Anabaena globulus was poured into several 150 mL beakers. Different materials, namely CTS@REC, CTS@ATP, CTS@MMT, CTS@Fe2S and CTS@BE, were added to the algal solution at concentrations of 75 mg / L and 60 mg / L, respectively. The mixture was then placed in a six-unit stirrer and stirred in a rotary motion. The basic hydraulic conditions were set as follows: stirring at 200 rpm for 5 min and stirring at 40 rpm for 20 min. The pH of the algal solution was set to 7 and the water temperature to 25 °C. The mixture was allowed to stand for 30 min, and the morphology of the flocs was observed. Samples were taken at a depth of 2 cm below the liquid surface.

[0084] The results are as follows Figure 9 and Figure 10 As shown, Figure 9 The sedimentation effects of different materials in Microcystis aeruginosa solution on chitosan and clay minerals at different mass ratios were investigated. Figure 10 The sedimentation effects of different materials in *Houttuynia cordata* solution with chitosan and clay minerals at different mass ratios were investigated.

[0085] Example 7

[0086] To investigate the algae removal effect of CTS@REC on Microcystis aeruginosa and Anabaena gracilis under different pH conditions.

[0087] Take 100mL OD 680 A 0.15 solution of *Microcystis aeruginosa* / *Anabaena granatum* was poured into several 150 mL beakers. 75 mg / L and 60 mg / L of CTS@REC-(1:6) were added to the two solutions, respectively. The pH values ​​of the solutions were controlled at 4, 6, 7, 8, 9, and 10. The solutions were then stirred in a six-unit vortex mixer with the basic hydraulic conditions set at 200 rpm for 5 min and 40 rpm for 20 min, at a water temperature of 25℃. After standing for 30 min, the floc morphology was observed, and samples were taken 2 cm below the liquid surface. The results are as follows: Figure 11 As shown.

[0088] Example 8

[0089] To investigate the algae removal effect of CTS@REC on Microcystis aeruginosa and Anabaena globulus under different temperature conditions.

[0090] Take 100mL OD 680A solution of 0.15% *Microcystis aeruginosa* / *Anabaena globulus* was poured into several 150mL beakers. 75mg / L and 60mg / L of CTS@REC-(1:6) were added to the two solutions, respectively. The solutions were kept at temperatures of 16, 26, and 36℃ and stirred in a six-unit vortex mixer. The basic hydraulic conditions were set to 200 rpm for 5 min, 40 rpm for 20 min, and pH = 7. After standing for 30 min, the floc morphology was observed, and samples were taken 2 cm below the liquid surface. The results are as follows: Figure 12 As shown.

[0091] Example 9

[0092] To investigate the algae-removing effect of CTS@REC on Microcystis aeruginosa and Anabaena gracilis under different ion coexistence conditions.

[0093] Take 100mL OD 680 Pour a 0.15 concentration of Microcystis aeruginosa / Anabaena globulus solution into several 150 mL beakers, and then add 50 mg / L SO4 to each beaker sequentially. 2- Cl - HCO3 - NO3 - Then, 75 mg / L and 60 mg / L LCTS@REC-(1:6) were added to the two algal solutions respectively, and the solutions were placed in a six-unit stirrer for rotary stirring. The basic hydraulic conditions were set as follows: stirring at 200 r / min for 5 min and 40 r / min for 20 min. The pH was set to 7, and the temperature was controlled at 25℃. After standing for 30 min, the morphology of the flocs was observed, and samples were taken at 2 cm below the liquid surface. The results are as follows. Figure 13 As shown.

[0094] Example 10

[0095] To investigate the algae-removing effect of CTS@REC on Microcystis aeruginosa and Anabaena gracilis in the presence of humic acid.

[0096] Take 100mL OD 680 A solution of *Microcystis aeruginosa* / *Anabaena granatum* with a concentration of 0.15 was poured into several 150 mL beakers. 10 mg / L humic acid was added to each beaker sequentially. Then, 50, 75, 100, 200, and 300 mg / L CTS@REC-(1:6) were added to each of the two algal solutions respectively. The mixtures were placed in a six-unit stirrer and stirred using a rotary mixer. The basic hydraulic conditions were set to 200 rpm for 5 min, 40 rpm for 20 min, pH = 7, and temperature controlled at 25℃. The mixtures were allowed to stand for 30 min, and the floc morphology was observed. Samples were taken 2 cm below the liquid surface. The results are as follows: Figure 14 As shown.

[0097] Example 10

[0098] To investigate the algae removal effect of CTS@REC on Microcystis aeruginosa and Anabaena gracilis in actual water bodies.

[0099] Take 100mL OD 680 Water samples from tap water, reservoir, and Nanhu Lake (0.15 concentration) were poured into several 150mL beakers. Then, 50, 75, 100, 200, and 300 mg / L CTS@REC-(1:6) were added sequentially to the two algal solutions. The solutions were then placed in a six-unit stirrer with rotary stirring. The basic hydraulic conditions were set to 200 rpm for 5 minutes, 40 rpm for 20 minutes, pH = 7, and temperature controlled at 25℃. After standing for 30 minutes, the floc morphology was observed, and samples were taken 2 cm below the liquid surface. The results are as follows: Figure 15 and Figure 16 As shown.

[0100] Example 11

[0101] The flocculant effect of chitosan-modified attapulgite CTS@REC-(1:6) on the flocculation and harvesting of two algal blooms, Microcystis aeruginosa and Anabaena gracilis, was investigated by preparing chitosan-modified attapulgite CTS@REC-(1:6).

[0102] The physicochemical properties of rettosite (REC) and CTS@REC were characterized by Fourier transform infrared spectroscopy (FTIR), zeta potential, and scanning electron microscopy (SEM).

[0103] The results are as follows Figure 17-19 As shown; the characteristic functional groups of CTS (chitosan) and CTS@REC (chitosan-modified attapulgite) powder samples were characterized by Fourier transform infrared spectroscopy, and the analytical results are as follows. Figure 17 As shown. Figure 17 The main absorption peaks of CTS in the middle are at 3382.58 cm⁻¹. -1 1662.37cm -1 1083.82cm -1 and 848.54cm -1 Among them, CMRB is at 3382.58cm. -1 The absorption peak that appears is caused by the stretching vibration of the OH group in the hydroxyl group; at 1662.37 cm⁻¹ -1 The absorption peak that appears is due to the stretching vibration of the NH peak in the amino groups on the surface of CTS; at 1083.82 cm⁻¹ -1 The absorption peaks that appear are attributed to the C-C stretching vibration absorption peak in the aromatic ring; at 840.82 cm⁻¹ -1 The absorption peak that appears is caused by the CH stretching vibration. From... Figure 17 As can be seen from this, CTS@REC, except for 956.53cm -1 and 721.26cm -1Aside from the appearance of a new characteristic absorption peak at 956.53 cm⁻¹, the other absorption peaks remain consistent with those of CTS. -1 The peak is attributed to the stretching vibration absorption peak of Si-O; 721.26 cm⁻¹ -1 The peak corresponds to the octahedral tensile vibration peak of Al-O. 1662.37 cm⁻¹ -1 The peak is due to the stretching vibration of the NH peak on the CTS surface. Compared to CTS, the NH peak in CTS@REC is weakened, indicating an interaction between the negative charge on REC and the protonated amino group on CTS; 3382.58 cm⁻¹ -1 The relatively broad peak belongs to the -OH stretching vibration peak. Compared with CTS, CTS@REC shows a weakening peak intensity, which may be due to the hydrogen bonding between the -NH2 of chitosan and the REC surface, leading to the weakening of the -OH vibration peak. FTIR analysis revealed the presence of both the Al-O and Si-O peaks of REC and the NH, CC, and CH peaks of CTS, with a weakening of the NH and -OH vibration peaks, indicating the successful preparation of CTS@REC.

[0104] The effect of pH on the flocculation process was analyzed from the perspective of surface electrophoresis by measuring the Zeta potentials of CTS@REC (chitosan-modified attapulgite), REC (attapulgite), M. aeruginosa (Microcystis aeruginosa), and P. cinerea (Pseudo-anabaena) at different pH values. Figure 18 It is known that when the pH varies within the range of 4-10, both types of algal cells and the surface of REC carry a negative charge. Therefore, using REC alone for algae removal will result in mutual repulsion due to the negative surface charge, leading to poor algae removal efficiency. After modifying REC with CTS, CTS@REC carries a positive charge within the pH range of 4-10. The Zeta potential is lowest at pH=10 (3.198mV), while under this pH condition, M. aeruginosa and P. cinerea have -18.987mV and -16.034mV, respectively. Based on the principle of charge neutralization, this can be explained... Figure 11A significant decrease in the removal efficiency of CTS@REC against both algae was observed at pH 10. Similarly, at pH 4, the removal efficiency of CTS@REC against P. cinerea did not show a significant improvement. This is because, under these pH conditions, the potentials of CTS@REC, M. aeruginosa, and P. cinerea were 27.983 mV, -14.097 mV, and -22.876 mV, respectively. Under strongly acidic conditions, the negative charge of P. cinerea increases, leading to a weakening of the neutralizing ability of the positive charge carried by CTS@REC. When the pH ranges from 6 to 9, the potentials of CTS@REC, M. aeruginosa, and P. cinerea are 17.46–20.531 mV, -8.34–-3.792 mV, and -10.534–-7.860 mV, respectively. The positive charge of CTS@REC is much greater than the negative charge of the two algae, therefore, it exhibits good algae removal efficiency within this pH range. The Zeta potential analysis also illustrates that after CTS modification, REC introduces a large number of positively charged cationic groups onto the surface of clay minerals. Simultaneously, the presence of surface carboxyl (-COOH) and amino (-NH2) groups ensures that the algal surface maintains a consistently negative charge. When CTS@REC is introduced into algae-containing water, the charge density is significantly increased, playing a major role in flocculation and algae removal.

[0105] The surface morphology of REC, CTS@REC, Microcystis aeruginosa flocculentum, and Anabaena glomeratus flocculentum were observed using scanning electron microscopy. Figure 19 As shown in -a, REC is sheet-like with a smooth surface, layered structure, and wrinkled edges. Figure 19 -b represents CTS@REC material modified with CTS, which has a rough and irregular surface with a distinct porous network structure. This unique structure provides more adsorption sites for algal cells to contact CTS@REC, enhancing the trapping function and gravity sedimentation effect of CTS@REC for algal cells, and improving the flocculation and algae removal efficiency. Figure 19 -c and 19-d are SEM images of algal flocs removed by CTS@REC from Microcystis aeruginosa and Anabaena pygmaea, respectively. It can be seen that the cells of the two algae still have complete spherical structures, are tightly attached to the surface of CTS@REC and have not broken. A clear network structure can be seen between the flocs. This indicates that CTS@REC does not destroy the cell structure of the two algae after being added to algae-containing wastewater.

[0106] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of a modified tropane-based flocculant in the removal of algae from water bodies, characterized in that, The modified raptosite-based flocculant comprises raptosite powder and chitosan, wherein the chitosan is loaded on the surface of the raptosite powder. The preparation method of the modified raptosite-based flocculant includes the following steps: mixing and stirring chitosan solution and raptosite powder, centrifuging and drying, and grinding to obtain the modified raptosite-based flocculant; The chitosan solution was prepared by dissolving chitosan in a 5% acetic acid solution; The concentration of the chitosan solution is 5-15 g / L; The mass ratio of chitosan to palladium powder is 1:(2-14); The mixing temperature is 20-25℃; the mixing time is 5-16 hours. The modified raphe-based flocculant has a mesh size ≤ 100 mesh.

2. The application according to claim 1, characterized in that, The aquatic algae include, but are not limited to, Microcystis aeruginosa and Anabaena gracilis.

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