Method for treating algal bloom based on chitosan quaternary ammonium salt and kaolin coupling

Abstract

The invention belongs to the technical field of algae-polluted water treatment, and particularly relates to a method for treating algae-polluted water by coupling chitosan quaternary ammonium salt and kaolin. The method comprises the following steps: (1) preparing a chitosan quaternary ammonium salt solution, namely dissolving chitosan quaternary ammonium salt in water to form the chitosan quaternary ammonium salt solution; and (2) adding the chitosan quaternary ammonium salt solution in the step (1) into kaolin, mixing to form slurry, standing, and then adding into the algae-polluted water body. According to the method, the algae removal and water purification effects are excellent, the algae cell removal effect in the logarithmic phase is optimal, and the turbidity, the algae density and the Chl-a removal rate reach 94.1%, 92.4% and 92.8% respectively.

Description

Technical Field

[0001] The invention belongs to the technical field of algae-polluted water treatment, and in particular relates to a method for treating algae-polluted water by coupling chitosan quaternary ammonium salt with kaolin. Background Art

[0002] Regarding the literature on algae removal by chitosan quaternary ammonium salt, Hu Yang et al. in the article "Study on the removal of Microcystis aeruginosa by modifying river sand with chitosan quaternary ammonium salt" quaternized chitosan and used chitosan and 2-3 epoxypropyltrimethylammonium chloride in isopropanol to prepare chitosan quaternary ammonium salt, which was used to remove Microcystis aeruginosa and form flocs. In order to accelerate the sedimentation rate of flocs, the gravity of river sand was used to promote floc coagulation and sedimentation. The above method has a certain effect on the removal of Microcystis aeruginosa, but the composition structure of river sand varies greatly and is complex. The accurate mechanism is difficult to explain clearly, the experimental reproducibility is poor, the quality control of large-scale products is difficult to guarantee, and standardized production is difficult.

[0003] Therefore, it is necessary to improve the above-mentioned deficiencies and invent a method for controlling algae blooms with good reproducibility, excellent treatment effect and strong continuous algae control ability. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for treating algae-contaminated water by coupling chitosan quaternary ammonium salt (HACC) and kaolin. The most prominent innovation of the method is that, on the one hand, chitosan quaternary ammonium salt and kaolin are combined in an optimal ratio to achieve an ideal effect of algae removal and water purification; on the other hand, the two are added to the algae-contaminated water in an optimal manner. The results show that the method of the present invention has excellent algae removal and water purification effect.

[0005] Specifically, the method of the present invention comprises the following steps:

[0006] (1) preparing a chitosan quaternary ammonium salt solution: dissolving chitosan quaternary ammonium salt in water at a solid-liquid ratio of 50 mg: (50-100) mL to form a chitosan quaternary ammonium salt solution;

[0007] (2) taking the chitosan quaternary ammonium salt solution in (1), adding kaolin, stirring to mix evenly to form a slurry, and standing for about 2 hours, and then adding the slurry to the algae-contaminated water body for 0.5 to 5 hours when the water temperature of the algae-contaminated water body is 20 to 45° C. and the pH is 6.5 to 10.5. The algae-contaminated water body includes but is not limited to the water body contaminated by Microcystis aeruginosa and the water body contaminated by Anabaena;

[0008] Wherein, the mass ratio of chitosan quaternary ammonium salt to kaolin is 1:10-20;

[0009] The mass volume ratio of the mud to the algae-polluted water body is 40-200 mg / L. Preferably, the added mud is 60 mg.

[0010] As one of the typical natural clay minerals, kaolin has a large output and low cost, and has broad application prospects in water treatment due to its unique structure and properties. However, natural kaolin generally contains a large amount of impurities, which leads to its unsatisfactory effect in practical applications. It needs to be modified to significantly enhance its adsorption performance. Natural kaolin has a negative charge, a large surface cation exchange capacity, and abundant active groups such as hydroxyl groups on the surface, making it easy to modify. Its layered structure and hydration allow water molecules to attach to the mineral surface by chemical adsorption, which can promote the catalytic reaction.

[0011] However, the inventors have found through experiments that the algae removal effect of using kaolin alone is not very ideal. For example, the kaolin concentration gradient is set to 5, 10, 15, 30, 50, 70, 100, 150 and 200 mg / L, and added to the water body contaminated by Microcystis aeruginosa. The results show that with the continuous increase in the amount of kaolin added, the algae density and the removal rate of Chl-a have not increased significantly, and the turbidity has increased instead of decreased. The addition of kaolin alone has basically no algae reduction effect. The reason may be that the surface of kaolin in water is negatively charged, which makes it difficult for algae cells that are also negatively charged in water to aggregate due to the electrical repulsion, and kaolin added to water will directly increase the turbidity of the water, causing the turbidity to continue to decrease, so it is necessary to consider using kaolin in combination with other algaecides.

[0012] In addition, the addition method of chitosan quaternary ammonium salt and kaolin will also affect the effect of algae polluted water treatment. Regarding the addition method, the inventor conducted an experiment to investigate the relationship between 4 different addition methods and the algae water treatment effect, as shown in the data comparison in the embodiment.

[0013] The beneficial effects of the present invention are:

[0014] (1) The present invention compares different algae removal and water purification methods, such as the method of using kaolin alone to remove algae, the method of adding chitosan quaternary ammonium salt and kaolin in different proportions, and the effect of different addition amounts on the algae removal effect, and determines the optimal ratio of chitosan quaternary ammonium salt and kaolin. Under this ratio, the two can have a synergistic effect to achieve excellent algae removal and water purification effect;

[0015] (2) The present invention also provides different dosing methods, and the dosing method is also the key to the algae removal effect. For example, although HACC and kaolin are still used, if HACC is added first, stirred for 30 seconds, and then kaolin suspension is added, the algae removal effect is far less than that of adding HACC and kaolin into a slurry;

[0016] (3) The method of the present invention has excellent algae removal and water purification effects, and the best effect is achieved in removing algae cells in the logarithmic growth phase. The turbidity, algae density and Chl-a removal rates reach 94.1%, 92.4% and 92.8%, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The algae removal effect of different kaolin (used alone) dosages;

[0018] Figure 2 The algae removal effect of HACC coupled with kaolin was compared with that of HACC alone.

[0019] Figure 3 The effect of different dosage of mud on algae removal effect;

[0020] Figure 4 The influence of different ways of adding raw materials on the algae removal effect;

[0021] Figure 5 The effect of different growth stages of algae on algae removal effect;

[0022] Figure 6 is the Zeta potential value of algae removal at different ratios of HACC and kaolin;

[0023] Figure 7 The removal effect of HACC-coupled kaolin on algae blooms and the floccules formed. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in conjunction with specific implementation methods.

[0025] Chitosan quaternary ammonium salt is a common commercial product with a substitution degree of 98%, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0026] Kaolin: The kaolin used in the experiment was calcined at 800°C and had a particle size of 1250 mesh, and was purchased from Shanxi Xingle Kaolin Co., Ltd.

[0027] Algae source and cultivation:

[0028] The algae species selected in this experiment is the dominant algae species in the outbreak of cyanobacteria in my country, Microcystis aeruginosa, which is numbered FACHB-315 and purchased from the Freshwater Algae Species Bank of the Institute of Hydrobiology, Chinese Academy of Sciences.

[0029] Microcystis aeruginosa was cultured in BG-11 medium. Pour the prepared medium into a 5L conical bottle, seal the bottle mouth with a sealing film, and then sterilize it at 121℃ for 30min. After the medium cools to room temperature, inoculate Microcystis aeruginosa. The inoculation process is carried out in a clean bench. The inoculated medium is placed in a light incubator for culture, set the temperature to 25±1℃, the light intensity to 3000Lx, the light-dark ratio L:D=12h:12h, and shake once in the morning, noon, and evening every day.

[0030] Example 1

[0031] The algae removal effect of using kaolin alone is taken as an example to remove Microcystis aeruginosa; the water body polluted by this algae is used in the following examples;

[0032] The concentration gradient of kaolin is set to 5, 10, 15, 30, 50, 70, 100, 150 and 200 mg / L. The specific method of adding is: take kaolin, add water to form mud, add it to the algae polluted water body, and keep the kaolin in the added mud at 60-120 mg per liter of algae polluted water body. When the water temperature of the algae polluted water body is 25°C and the pH is 9.0, add the mud to the algae polluted water body for 0.5 hours.

[0033] The results are shown in Table 1 and Figure 1 shown.

[0034] The equipment and methods for testing turbidity, algae density and Chl-a removal rate are as follows:

[0035] The turbidity of the water body was measured by the scattering method (turbidimeter, Leici, Shanghai); the algae density was measured by the hemocytometer (25×16) (inverted microscope, Olympus, Japan); the chlorophyll a content in the algae solution can be directly measured by the phytoplankton classification fluorescence instrument (PHYTO-PAM-II). Due to the high chlorophyll concentration, the sample was diluted to within the upper limit of the measurement of PHYTO-PAM-II (300μg / L) before the measurement. The sample was adjusted to zero with distilled water, dark-adapted for 30 minutes, and then the chlorophyll content of the algae was measured under the measurement light of 32 light frequencies.

[0036] Table 1 Statistical table of algae removal effect when using kaolin alone

[0037]

[0038]

[0039] As shown in Table 1 and Figure 1As shown in the figure, with the continuous increase of kaolin dosage, the algae density and Chl-a removal rate did not increase significantly, and the turbidity increased instead of decreasing. The addition of kaolin alone had basically no algae reduction effect. When the dosage was as high as 200 mg / L, the highest algae density removal rate was only 8.66%, and the highest Chl-a removal rate was only 8.94%. In addition, since the addition of kaolin, the turbidity removal rate has been negative, and the higher the dosage, the more negative the removal rate, indicating that the unmodified clay has a poor algae removal effect. Analyzing the reasons, the surface of unmodified kaolin is negatively charged in water, which makes it difficult for algae cells that are also negatively charged in water to aggregate due to electrical repulsion. In addition, the addition of kaolin into water will directly increase the turbidity of the water, resulting in a continuous decrease in turbidity, so it is necessary to consider modifying the kaolin.

[0040] Example 2

[0041] Dosage method 1: Investigate the effect of using HACC alone to remove algae and purify water, as follows:

[0042] HACC was added to the water body alone; the method was the same as in Example 1; the mass volume ratio of the amount of HACC added to the algae-contaminated water body was 60 mg / L.

[0043] Dosage method 2: Investigate the effect of the composite algae removal of kaolin and HACC, as follows:

[0044] Preparation of chitosan quaternary ammonium salt solution: first dissolve 50 mg of chitosan quaternary ammonium salt in 100 mL of distilled water to form a chitosan quaternary ammonium salt solution; then add kaolin to the chitosan quaternary ammonium salt solution, mix to form a slurry, let stand for 2 hours, and then add to the algae-contaminated water body;

[0045] The weight ratio of kaolin to HACC is 5:1, 10:1, 15:1, 20:1, 25:1, 30:1 and 40:1; the mass volume ratio of mud to algae polluted water is 60 mg / L. When the water temperature is 25°C and the pH is 9.0, the mud is added to the algae polluted water for 0.5 hours.

[0046] The experimental results are shown in Tables 2-1, 2-2 and Figure 2 :

[0047] Table 2-1 Statistical table of algae removal effect when HACC is used alone

[0048] HACC(mg / L) Turbidity removal rate (%) Algae density removal rate (%) Chl-a removal rate (%) 10 85.41 87.07 88.14 5.45 83.10 88.59 87.85 3.75 81.23 84.21 83.22 2.86 78.01 79.47 78.01 2.31 72.02 73.38 71.35 1.94 66.88 66.54 64.66 1.46 54.65 57.03 53.20

[0049] Table 2-2 Algae removal effect when kaolin and HACC are used together

[0050]

[0051] From Table 2 and Figure 2 It can be seen that the algae reduction effect of HACC alone is significantly lower than that of modified kaolin, and as the amount of HACC used decreases, its algae reduction effect decreases rapidly.

[0052] The kaolin and HACC composite group decreased relatively more slowly. In addition, the composite ratio had a certain influence on the flocculation algae removal effect of HACC modified clay. With the increase of the composite ratio, the removal rate of turbidity, algae density and Chl-a by modified kaolin first increased, then flattened and then decreased. The results showed that the removal effect was best when the composite ratio of kaolin and HACC was in the range of 10:1 to 15:1, and the removal rate was above 90%.

[0053] After analysis, it was found that the algae removal effect of adding HACC alone was poor in comparison, which may be because the density of algae flocs was close to that of water, and the algae were not completely destabilized and could not form dense flocs. In addition, there are a certain number of binding sites on the surface of clay minerals. When the composite ratio of kaolin and HACC is small, the molecular weight of HACC exceeds the number of binding sites of kaolin. Excessive HACC increases the positive charge in the water, and the repulsion between the charges hinders the further flocculation of algae, affecting the algae removal effect. When the composite ratio is large, the surface of the modified kaolin carries less positive charge, and the synergistic effect of flocculation and algae removal cannot be achieved. Therefore, when using HACC to modify kaolin, the appropriate ratio of the two must be controlled to effectively improve its algae removal effect.

[0054] Example 3

[0055] Investigate the effect of the dosage of HACC and kaolin slurry on algae removal

[0056] Preparation of chitosan quaternary ammonium salt solution: first dissolve 50 mg of chitosan quaternary ammonium salt in 100 mL of distilled water to form a chitosan quaternary ammonium salt solution; then add 750 mg of kaolin to the chitosan quaternary ammonium salt solution, mix to form a slurry, let stand for 2 hours, and then add to the algae-contaminated water body;

[0057] The mass volume ratio of mud to algae-contaminated water was set to 5, 10, 20, 40, 60, 80, 100, 120, 150 and 200 mg / L, and the removal rates of turbidity, algae density and Chl-a were tested respectively. When the water temperature was 25°C and the pH was 9.0, the mud was added to the algae-contaminated water for 0.5 hours.

[0058] The experimental results are shown in Table 3 and Figure 3 :

[0059] Table 3 Effect of the dosage of HACC and kaolin slurry on algae removal effect

[0060] Mud (mg / L) Turbidity removal rate (%) Algae density removal rate (%) Chl-a removal rate (%) 5 21.03 12.78 15.71 10 39.84 31.31 34.75 20 82.86 74.76 66.92 40 93.96 86.90 89.49 60 94.48 92.65 90.15 80 94.69 93.73 93.66 100 94.63 94.65 93.91 120 94.66 95.83 94.90 150 89.64 96.01 95.27 200 84.50 96.90 96.44

[0061] When the dosage is less than 60 mg / L, with the increase of the amount of modified kaolin used, the removal rates of turbidity, algae density and Chl-a increase sharply. When the dosage is between 60 and 120 mg / L, the removal rates of these three indicators are all above 90%. When the dosage increases from 120 mg / L to 200 mg / L, there is no significant change in the removal rates of algae density and Chl-a, while the removal rate of turbidity begins to show a downward trend. The experiment found that the algae removal efficiency of kaolin modified by HACC is greatly enhanced. Analysis shows that HACC organic polymer flocculant has an electrical neutralization and coagulation effect on algae suspension. Its synergy with the bonding and bridging of clay is more conducive to the removal of algae cells in the water body during the coagulation process, saving flocculants while improving the flocculation and algae removal effect of kaolin. The experiment also found that the more modified kaolin was added, the better the algae reduction effect was. The optimal dosage of modified kaolin was between 60 and 120 mg / L. When the dosage exceeded 120 mg / L, the turbidity removal rate began to decrease. This was because the excess positively charged modified kaolin was electrostatically repelled and could not precipitate, resulting in the turbidity in the water beginning to rise.

[0062] Example 4

[0063] Study on the effect of adding method on algae removal when HACC and kaolin are used in combination

[0064] When implementing the specific adding method, when the water temperature is 25°C and the pH is 9.0, the slurry is added to the algae-contaminated water body for treatment for 0.5 hours.

[0065] The kaolin:HACC ratio is 15:1 (weight ratio), the ratio of mud to water to be de-algae is 60 mg / L, and the algae cell density in the logarithmic phase is about 4.86×10 6 cells / mL, four dosing methods were set to treat the effects of logarithmic algae-containing water. The four dosing methods are represented by ①, ②, ③ and ④ respectively.

[0066] The details are as follows:

[0067] ①HACC solution (50 mg in 100 mL of water) and kaolin (750 mg) were mixed into a slurry and allowed to stand for 1 hour before adding;

[0068] ②Add kaolin suspension (750 mg in 100 mL of water) and HACC solution (50 mg in 100 mL of water) respectively;

[0069] ③ First add HACC (50 mg in 100 mL of water), stir for 30 seconds and then add kaolin suspension (750 mg in 100 mL of water);

[0070] ④ First add kaolin suspension (750 mg in 100 mL of water), stir for 30 seconds and then add HACC solution (50 mg in 100 mL of water);

[0071] The dosing method is shown in the following table:

[0072] Table 4-1 Different dosing methods for the combination of HACC and kaolin

[0073]

[0074] Table 4-2 Effects of algae removal and water purification by different dosing methods

[0075] Dosing method Turbidity removal rate (%) Algae density removal rate (%) Chl-a removal rate (%) ① 91.56 93.16 90.70 ② 86.39 86.57 87.35 ③ 79.88 81.32 81.78 ④ 76.61 80.05 75.64

[0076] From the above table and attached Figure 4 It can be seen that the removal rate of each indicator of algae solution under the four addition methods is ranked as follows: ①>②>③>④. The average removal rates of turbidity, algae density and Chl-a in methods ①~④ are 91.8%, 86.8%, 81.0% and 77.4% respectively. Method ① is 5.0%, 10.8% and 14.4% higher than methods ②~④ respectively. It can be concluded that the flocculation algae removal effect of method ① is the best. By comparing and analyzing the flocculation algae removal effects of methods ① and ② with those of methods ③ and ④, it is found that HACC and kaolin need to be added at the same time to ensure the best flocculation and algae sinking effect. In addition, from the algae removal effect method ①>②, it can be inferred that the structure or properties of the surface of kaolin will change after 1h of static reaction after HACC encapsulated modified kaolin, so that the flocculation algae effect after mixing and static is stronger than that of directly adding HACC solution and kaolin.

[0077] Therefore, in this application, method ① is selected as the dosing method, that is, the HACC solution and kaolin are mixed into a suspension and then added after standing for 1 hour. It can be seen that even if the raw materials are the same, different treatment methods (dosing methods) have a greater impact on the removal effect of algae.

[0078] Example 5

[0079] Study on the flocculation ability of HACC coupled with kaolin on Microcystis aeruginosa cells at different algae growth stages

[0080] The algae liquids in the delayed phase, logarithmic phase, stable phase, decay phase and late decay phase were used for flocculation and algae removal experiments. The results are shown in Table 5 and Figure 5 As shown:

[0081] Table 5 Effect of algae at different growth stages on algae removal effect

[0082] Dosing period Turbidity removal rate (%) Algae density removal rate (%) Chl-a removal rate (%) Delayed period 93.28 92.11 91.45 Logarithmic period 94.07 92.42 92.76 Stable period 88.97 86.57 87.39 Decline 30.12 48.79 52.27 Late Decline 31.41 46.04 48.29

[0083] Depend on Figure 5 It can be seen that, except for the decay and late stages of algae liquid, HACC coupled with kaolin can effectively remove turbidity, algae density and Chl-a in water. Turbidity, algae cell density and Chl-a removal rate showed a trend of first slightly increasing and then gradually decreasing with the growth of algae cells.

[0084] The algae cell removal effect is best in the logarithmic growth period, and the turbidity, algae density and Chl-a removal rates reach 94.1%, 92.4% and 92.8% respectively. With the further growth and reproduction of algae cells, the removal rates of the three are reduced. When the algae cells are in the late stage of decay, the removal rates drop sharply, and the removal rates of the three are reduced to 31.4%, 46.0% and 48.3% respectively. Analysis of the reasons shows that as the algae cells grow, the algae cells will continuously release extracellular organic matter (EOM) into the water. A small amount of EOM has a certain promoting effect on the flocculation and algae removal of modified kaolin, but with the increase of EOM concentration in the algae solution, its hindering effect on flocculation is gradually enhanced. Therefore, when the algae cells grow to the logarithmic growth period, it is the best time for algae removal.

[0085] Example 6

[0086] Investigating the effect of the mass ratio of kaolin and HACC on the flocculation algae removal effect

[0087] The specific method of adding only kaolin is shown in the method in Example 1;

[0088] The methods in other groups are shown in the addition method 2 in Example 2.

[0089] The Zeta potential values ​​of HACC coupled kaolin under different composite ratios (mass ratios) were analyzed. The Zeta potential values ​​of HACC coupled kaolin when the composite ratios of HACC and kaolin were set to 0, 1:40, 1:30, 1:20, 1:15, 1:10, and 1:5 were measured. The results are shown in Table 6 and Figure 6 The dosage of each material is 60 mg per liter of polluted water.

[0090] Table 6 Zeta potential values ​​at different ratios when HACC is coupled with kaolin

[0091] Add raw materials Parallel sample 1(mV) Parallel sample 2 (mV) Parallel sample 3 (mV) Kaolin -16.0 -16.4 -17.5 HACC: Kaolin = 1:40 36.6 34.7 34.6 HACC: Kaolin = 1:30 37.5 36.8 37.4 HACC: Kaolin = 1:20 38.3 39.6 40.2 HACC: Kaolin = 1:15 43.3 44.6 45.4 HACC: Kaolin = 1:10 51.4 50.2 49.9 HACC: Kaolin = 1:5 56.2 55.7 54.6

[0092] From Table 6 and Figure 6It can be seen that the Zeta potential of kaolin itself is negatively charged. After using HACC to couple kaolin, when the ratio of HACC to kaolin is 1:40, the Zeta potential changes from negative to positive, and increases sharply from -16.63mV to 35.30mV. As the proportion of HACC in the coupled kaolin increases, the Zeta potential of HACC coupled kaolin gradually increases. When the ratio of HACC to kaolin is 1:15, the Zeta potential value changes to 44.43mV. Comprehensive analysis shows that when the proportion of HACC in the coupled kaolin is too small, the surface positive charge of kaolin is low, and it is difficult to neutralize the charge with algae cells, resulting in low algae removal efficiency; when the proportion of HACC in the coupled kaolin is too large, the excess HACC makes the flocs carry positive charges. Since the flocs repel each other due to the same charge, they cannot aggregate into larger flocs, which hinders further flocculation and thus affects the algae removal effect. Therefore, the greater the proportion of flocculant in the modified clay, the better the flocculation and algae removal effect is not necessarily the case; HACC is coupled with kaolin, which makes the surface of kaolin positively charged and added to the algae solution. Kaolin and algae cells are equivalent to two kinds of colloids, and HACC is equivalent to electrolyte, which compresses the diffusion layer between them, reduces the distance between the colloids, forces the Zeta potential to drop, and destabilizes the particles and causes coagulation, indicating that adsorption charge neutralization is one of the main mechanisms of HACC coupled with kaolin flocculation and algae removal.

[0093] Application Example 1

[0094] The algae used in the application experiment were collected from the bay and near the shore of Bali Lake in Jiujiang, Jiangxi. The collected algae were mixed algae, containing four types of algae, mainly Microcystis, accounting for 80.67%, Anabaena accounting for 12.91%, Cryptomonadales accounting for 5.11%, and Nostoc accounting for 1.31%. At the same time, the lake water from Bali Lake in Jiujiang, Jiangxi was filtered through a 0.45μm mixed fiber filter membrane, then sterilized at 121℃ for 30min, and added with BG-11 culture solution (specific formula see Table 2-3) for algae cultivation after cooling. The culture temperature was 25 (±1)℃, the light intensity was 3000lx, and the light-dark ratio was 12h:12h. The algae growth was monitored by counting the algae every day under a microscope using a plankton counting frame, and the algae solution in the exponential growth period was selected for the experiment. The above method was used to simulate the water body polluted by algae.

[0095] The kaolin used in the application experiment was calcined at 800°C and had a particle size of 300 mesh. Its cation exchange capacity was 3.01 mg / 100 g and was purchased from Yangzhou Dilan Chemical Raw Materials Co., Ltd. Accurately weigh 1 g of kaolin and dissolve it in 100 mL of distilled water, then weigh 50 mg of HACC and add it to the kaolin suspension, ultrasonicate for 20 min, and stir at room temperature for 3 h to prepare the HACC-coupled kaolin material.

[0096] A certain amount of algae solution in the logarithmic growth period was transferred to a 250mL triangular flask and diluted with lake water from Bali Lake to an algae solution with a chlorophyll a concentration of 5000μg / L for algae flocculation experiments. Each batch of experiments was divided into 6 groups: experimental group (5 groups) and control group (1 group), with 3 parallels in each group. The experimental groups were added with 20mg / L, 30mg / L, 40mg / L, 50mg / L and 60mg / L of HACC-coupled kaolin materials respectively; the control group was not treated. After adding HACC-coupled kaolin materials to the experimental group and flocculating for 5h, the remaining algae solution containing no flocculation was taken at 3cm below the liquid surface to determine its chlorophyll content; and the upper layer of water bloom algae (residual water bloom algae) that was not flocculated was separated for culture, and its chlorophyll content was determined. At the same time, according to the concentration of residual water bloom algae in each experimental group, the original algae solution was diluted to the above algae concentration and then cultured. All flocculation experiments were carried out in a light incubator at a temperature of 25 (±1) °C and a light intensity of 3000 lx.

[0097] Depend on Figure 7 It can be seen that HACC coupled kaolin material flocculated algae for 0.5h. When the concentration of HACC coupled kaolin material was 20 and 30 mg / L, the chlorophyll content was significantly reduced (P < 0.01); when the concentration of HACC coupled kaolin material was 40, 50 and 60 mg / L, the chlorophyll content increased (addition amount was 40 mg / L, P > 0.05; addition amount was 50 mg / L, P < 0.01; addition amount was 60 mg / L, P > 0.05). As time went by, the chlorophyll content of each experimental group began to decrease. The chlorophyll content of the experimental group with HACC coupled kaolin material of 40, 50, and 60 mg / L was higher than that of the experimental group with HACC coupled kaolin material of 20 and 30 mg / L (P < 0.01), and this trend was maintained until the end of the experiment (lasting 5 hours). After 5h treatment, the chlorophyll a removal rate of the 20 and 30 mg / L experimental groups was over 95%.

[0098] The reason why the present application can achieve excellent algae removal effect is that the formation of mud by kaolin and HACC is actually a process of modifying them at room temperature, and the electrostatic attraction between the modified kaolin and the negatively charged algae cells is enhanced, which can adsorb and condense tiny algae blooms to form large floccules, and then settle to the bottom under the action of gravity to achieve the purpose of controlling the bloom. This is also one of the important reasons why HACC coupled with kaolin can flocculate and remove algae. If HACC and kaolin are only added to algae-contaminated water bodies according to different processes, the effect is far inferior to the former. This is because kaolin fails to improve its charging capacity and fails to achieve the effect of 1+1>2, indicating that the addition process is significantly different. At the same time, through a large number of experiments in the present application, it is verified that the mud formed by HACC modified kaolin has excellent algae removal ability and good reproducibility. When examining various influencing factors, the algae removal rate is relatively stable. Therefore, the present application has achieved unexpected technical effects.

Claims

1. A method for treating algae blooms based on coupling chitosan quaternary ammonium salt and kaolin, characterized in that: The following steps are involved: (1) preparing chitosan quaternary ammonium salt solution: dissolving chitosan quaternary ammonium salt in water at a solid-liquid ratio of 50 mg: (50-100) mL to form a chitosan quaternary ammonium salt solution; (2) Take the chitosan quaternary ammonium salt solution in (1), add kaolin, stir to mix evenly to form a slurry, let it stand, and then add it to the algae-contaminated water body; Among them, the mass ratio of chitosan quaternary ammonium salt to kaolin is 1:10~20; The mass volume ratio of mud to algae-contaminated water is 40~200 mg / L.

2. The method for treating algae bloom based on coupling of chitosan quaternary ammonium salt and kaolin as claimed in claim 1, characterized in that: (2) Let stand for 2 hours.

3. The method for treating algae bloom based on coupling of chitosan quaternary ammonium salt and kaolin as claimed in claim 1, characterized in that: (2) Water bodies polluted by algae include water bodies polluted by Microcystis.

4. The method for treating algae bloom based on coupling of chitosan quaternary ammonium salt and kaolin as claimed in claim 1, characterized in that: (2) Water bodies polluted by medium algae include water bodies polluted by Microcystis aeruginosa and water bodies polluted by Anabaena.

5. The method for treating algae bloom based on coupling of chitosan quaternary ammonium salt and kaolin as claimed in claim 1, characterized in that: When the water temperature of the algae-contaminated water body is 20-45°C and the pH is 6.5-10.5, the slurry is added into the algae-contaminated water body for treatment for 0.5-5 hours.

6. The method for treating algae bloom based on coupling of chitosan quaternary ammonium salt and kaolin as claimed in claim 1, characterized in that: For every liter of algae-contaminated water, the amount of mud added is 60~120mg.

7. The method for treating algae bloom based on coupling of chitosan quaternary ammonium salt and kaolin as claimed in claim 1, characterized in that: The slurry is added during the lag phase, logarithmic phase and stable phase of algae growth.

Images