Preparation method of environment-friendly and efficient alga-removing organic quaternary ammonium salt modified clay
By hydroxyl activation treatment of clay mineral surfaces and the addition of silane-containing organic quaternary ammonium salt modifiers, the problem of poor stability of organic quaternary ammonium salt modified clay was solved, achieving efficient and safe control of harmful algal blooms.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF OCEANOLOGY - CHINESE ACAD OF SCI
- Filing Date
- 2024-11-12
- Publication Date
- 2026-07-14
AI Technical Summary
Existing organic quaternary ammonium salt modified clay has poor stability and unsatisfactory ecological safety, making it difficult to effectively remove harmful algal blooms.
By hydroxyl activation treatment of clay mineral surface and the addition of silane-containing organic quaternary ammonium salt modifier, the modifier is directionally anchored on clay surface by utilizing the valence bond reaction between silane and active sites on clay surface.
A class of organic quaternary ammonium salt modified clay with high stability and good ecological safety was obtained, which can effectively remove common harmful algal blooms.
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Figure CN119349673B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of harmful algal bloom control, specifically a method for preparing environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay. Background Technology
[0002] Harmful algal blooms (HABs), also known as red tides, are an abnormal ecological phenomenon caused by the explosive proliferation or aggregation of microorganisms in seawater. To protect nearshore ecological security, economic development, and human health, safe and efficient red tide control measures are urgently needed.
[0003] Modified clay (MC) technology for controlling red tides is currently the only large-scale emergency response method for red tides applied in the field both domestically and internationally. It has been successfully applied in more than 20 sea areas across my country, from south to north, becoming a crucial technical support for controlling harmful red tides during major events, in sensitive marine areas, and in important economic development zones. In 2017, this technology was first exported abroad, and subsequently exported to countries such as the United States and Chile, becoming a widely recognized method for controlling harmful algal blooms both domestically and internationally.
[0004] To date, various types of modified clay have been developed for different application scenarios, including inorganic modified clay, organic modified clay, microbial modified clay, and composite modified clay. Among them, organic quaternary ammonium salt modified clay (QAC-MC) is characterized by low dosage and high algae removal efficiency, demonstrating good applicability in the fine treatment of aquaculture water. However, the adsorption of ordinary organic quaternary ammonium salt modifiers (QAC) on clay surfaces mainly occurs through physical interactions such as electrostatics, van der Waals forces, and hydrophobicity. Its adsorption stability is poor, and it is prone to desorption from the clay surface, thus affecting the stability and ecological safety of QAC-MC. Therefore, there is an urgent need to develop a quantitatively controllable organic quaternary ammonium salt modification method that can stably bind to clay surfaces, providing a class of modified materials with higher stability and better ecological safety for the efficient treatment of harmful algal blooms. Summary of the Invention
[0005] To address the issues of poor stability and unsatisfactory ecological safety of existing organic quaternary ammonium salt modified clays, the purpose of this invention is to provide an environmentally friendly and efficient method for preparing organic quaternary ammonium salt modified clays for controlling harmful algal blooms.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] An environmentally friendly and efficient method for preparing organic quaternary ammonium salt modified clay for algae removal involves hydroxyl activation treatment of the surface of raw clay minerals, followed by the addition of a silane-containing organic quaternary ammonium salt modifier (Si-QAC). By regulating the valence bond reaction between the silane-containing molecules in the modifier and the active sites on the clay surface, organic quaternary ammonium salt modified clay is obtained.
[0008] The valence bond reaction between the silane-containing modifier molecule and the active sites on the clay surface is carried out by activating the clay mineral surface with hydroxyl groups, mixing the raw clay mineral with the silane-containing organic quaternary ammonium salt modifier (g: mmol) at a ratio of 5:(0.3~30), and reacting under heating conditions of 40~80℃ for 6~24h.
[0009] The silane-containing organic quaternary ammonium salt modifier (Si-QAC) contains silicon groups, aliphatic hydrocarbon groups, and nitrogen-containing groups.
[0010] The silane-containing organic quaternary ammonium salt modifier (Si-QAC) has the following structural formula as shown in general formula one.
[0011]
[0012] In the formula, R can be a C1-C20 alkoxy or a C1-C20 haloalkoxy; R1 can be a C1-C20 alkyl, C1-C20 alkoxy, C1-C20 haloalkoxy, C1-C20 acyl, or C1-C20 alkoxycarbonyl; R2 can be H, C1-C20 alkyl, or C1-C20 alkoxy, and X can be... - It is an anion.
[0013] Preferably, R is a C1-C4 alkoxy group; R1 and R2 are C1-C6 alkyl groups, and X... - For F - Cl - ,Br - I - Isohalogen anions.
[0014] The aforementioned hydroxyl activation treatment on clay surface refers to acid or alkali treatment of clay minerals, or the introduction of compounds containing active hydroxyl groups onto the clay surface.
[0015] The acid or alkali treatment refers to placing clay minerals in an acid or alkali solution, shaking and vibrating them for more than 1 hour at room temperature or under heating conditions, and then washing and drying them with ethanol by centrifugation.
[0016] The acid solution is composed of an inorganic acid; the alkaline solution is prepared from one or more of the hydroxides, oxides or salts of alkali metals or alkaline earth metals.
[0017] The acid or alkali treatment involves mixing the raw material kaolin with an acid or alkali solution at a mass ratio of 1:2 to 1:50 and then reacting the mixture.
[0018] The process of introducing a compound containing active hydroxyl groups onto the clay surface involves dispersing clay minerals in a mixture containing anhydrous ethanol, ammonia, and water, ultrasonicating to ensure uniform dispersion, and then slowly adding a silicon-based precursor capable of reacting to generate the active hydroxyl compound to the mixture under heating and stirring conditions at 40–80°C until the reaction is complete. The mass ratio of clay minerals to silicon-based precursors is 5:1 to 5:50. The silicon-based precursor is prepared from one or more of silanols, siloxanes, and silicates, preferably tetraethyl orthosilicate (TEOS).
[0019] The clay minerals mentioned are aluminosilicate minerals, such as kaolin, montmorillonite, illite, attapulgite, halloysite, and mixtures of two or more of them.
[0020] An environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay prepared by the method described above, wherein the organic quaternary ammonium salt modified clay with high stability and good ecological safety is obtained by the method described above.
[0021] An application of the aforementioned environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay, wherein the organic quaternary ammonium salt modified clay is used in the removal of harmful algal blooms in the environment.
[0022] An environmentally friendly and highly efficient method for preparing organic quaternary ammonium salt modified clay for algae removal involves adding a silane-containing organic quaternary ammonium salt modifier (Si-QAC) after hydroxyl activation treatment of the surface of aluminosilicate mineral clay. By regulating the valence bond reaction between the silane-containing molecules in the modifier and the active sites on the clay surface, the modifier is directionally anchored on the clay surface, thereby obtaining a type of quaternary ammonium salt modified clay material with high stability, good ecological safety, and highly efficient elimination ability against common harmful algal blooms.
[0023] The advantages and positive effects of this invention are as follows:
[0024] The advantage of this invention lies in the fact that by utilizing the molecular valence bond between the silane group in the Si-QAC molecule and the active sites on the clay surface, the grafting and modification of organic quaternary ammonium salt molecules on the clay surface can be precisely controlled and strongly bonded, resulting in a composite material that not only effectively removes algae but also has high stability. This provides a new method for the precise synthesis of ecologically safe organic quaternary ammonium salt modified clay. Attached Figure Description
[0025] Figure 1 This is a comparison chart showing the removal efficiency of red tide Heterobacterium erythrorhizon by silane-containing organic quaternary ammonium salt (Si-QAC) modified clay prepared by different surface hydroxyl activation methods provided in Example 1 of the present invention.
[0026] Figure 2 This is a comparison chart showing the removal efficiency of red tide Heterobacterium erythrorhizon by Si-QAC modified clay containing different nitrogen-containing head groups provided in Example 2 of the present invention.
[0027] Figure 3 This is a comparison chart showing the removal efficiency of Si-QAC modified clay containing different aliphatic hydrocarbon chain lengths on Heterosigma red tide, provided in Example 3 of the present invention.
[0028] Figure 4 This is a comparison chart showing the removal efficiency of modified clay against Heterosigma red tide under different tetraethyl orthosilicate (TEOS) addition ratios provided in Example 4 of the present invention.
[0029] Figure 5 This is a comparison chart showing the removal efficiency of modified clay against Heterosigma red tide under different addition ratios of trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPTAC) provided in Example 5 of the present invention.
[0030] Figure 6 This is a comparison chart showing the effects of the optimized modified clay provided in Example 6 of the present invention on the removal of different typical red tide algae.
[0031] Figure 7 This is a comparison chart of the surface potential and removal efficiency of Heterosigma red tide after multiple washings of the optimized modified clay and ordinary quaternary ammonium salt modified clay provided in Example 6 of the present invention. Detailed Implementation
[0032] The following specific embodiments further illustrate the preparation method of the environmentally friendly and efficient algae-removing organic quaternary ammonium salt modified clay of the present invention, which helps those skilled in the art to more fully understand the present invention, but does not limit the present invention in any way.
[0033] The present invention modifies clay by adding a silane-containing organic quaternary ammonium salt modifier (Si-QAC) after hydroxyl activation treatment of the surface of aluminosilicate mineral clay. By regulating the valence bond reaction between the silane-containing molecules in the modifier and the active sites on the clay surface, the modifier is directionally anchored on the clay surface, thereby obtaining a type of quaternary ammonium salt modified clay material with high stability, good ecological safety, and efficient elimination ability against common harmful algal blooms.
[0034] This invention involves adding a silane-containing organic quaternary ammonium salt modifier (Si-QAC) after hydroxyl activation treatment of the clay surface. By regulating the valence bond reaction between the silane group in the Si-QAC molecule and the active sites on the clay surface, the modifier is directionally anchored on the clay surface, resulting in a class of organic quaternary ammonium salt modified clay materials with high stability, good ecological safety, and efficient elimination ability against common harmful algal blooms. The advantage of this invention lies in utilizing the valence bond between the silane group in the organosilicon quaternary ammonium salt molecule and the active sites on the clay surface to achieve precise control and strong bonding of the organic quaternary ammonium salt molecule onto the clay surface, obtaining a highly efficient and stable algae-removing composite material. This provides a new method for the precise synthesis of ecologically safe organic quaternary ammonium salt modified clay.
[0035] Example 1
[0036] The mineral raw material used in this invention is commercially available washed kaolin. The clay is treated with different surface hydroxylation activation methods, followed by the addition of a silicon-containing organic quaternary ammonium salt modifier (Si-QAC). By regulating the valence bond reaction between the silane groups in the Si-QAC molecule and the active sites on the clay surface, the modifier is directionally anchored on the clay surface, resulting in organic quaternary ammonium salt modified clay. The specific preparation method is as follows:
[0037] Step 1: Activate the kaolin surface with acid, alkali, and covalently grafted active hydroxyl compounds respectively:
[0038] (1) Acid-activated clay: Weigh 10g of raw kaolin and place it in 200ml of a 4mol / dm³ solution. 3 The mixture was reacted with a shaker in a hydrochloric acid solution at room temperature for 6 days. After that, it was washed three times by centrifugation with a 1:1 volume ratio of ethanol and aqueous solution, dried and pulverized for later use.
[0039] (2) Alkali-activated clay: Weigh 10g of raw kaolin and place it in 200ml of a 2mol / dm³ solution. 3 In a sodium hydroxide solution, the mixture was shaken and reacted on a shaker for 6 days at room temperature. After that, it was washed three times by centrifugation with a 1:1 volume ratio of ethanol and aqueous solution, dried and pulverized for later use.
[0040] (3) Covalent grafting of hydroxyl compounds: Weigh 5g of raw kaolin and place it in a 250ml three-necked flask. Add 80ml of anhydrous ethanol, 4.6ml of ammonia, and 1.5ml of pure water, and sonicate for 30min to mix thoroughly. Then add tetraethyl silicate (TEOS) to a partial pressure funnel at a Kaolin:TEOS mass ratio of 5:12. Then add it to the three-necked flask containing the activated kaolin mixture at a rate of 1 drop / s. Stir continuously for 6h at 60℃.
[0041] Step 2: Weigh 5g each of kaolin, alkali-activated kaolin, and acid-activated kaolin, and place them in a 250ml three-necked flask. Then add 80ml of anhydrous ethanol and 1.5ml of pure water, and sonicate for 30min to mix thoroughly. Next, add trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPTAC) to the flask at a ratio of 5:1 (kaolin to TPTAC g: mmol), and heat at 60℃ for 12h with stirring. After the reaction is complete, wash the resulting mixture three times with anhydrous ethanol at a centrifugation speed of 5000r / min for 5min to obtain modified clay materials, designated as Modified Clay-I, II, and III of this invention (see [link to relevant documentation]). Figure 1 );
[0042] Step 3: Add a certain amount of trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPTAC) to the product obtained in steps 1-(3) above, and then stir and heat at 60°C for 12 hours; wherein, the proportion of TPTAC added is based on the raw material kaolin, and the ratio of kaolin to TPTAC (g: mmol) is 5:1. After the reaction is completed, wash the mixture three times with anhydrous ethanol at a centrifugation speed of 5000 r / min and a centrifugation time of 5 min to obtain the modified clay material, which is designated as the modified clay-IV of this invention.
[0043] Example 2
[0044] The modified clay-IV of the present invention was prepared according to the same steps and conditions as in Example 1, except that the type of nitrogen-containing group of Si-QAC added in step 3 was changed. The specific implementation method is as follows:
[0045] Step 1: Weigh out 4 portions of 5g each of raw kaolin and place them in 250ml three-necked flasks. Then add 80ml of anhydrous ethanol, 4.6ml of ammonia and 1.5ml of pure water respectively, and sonicate for 30 minutes to mix them evenly. Then place them in a 60℃ water bath for heating and stirring.
[0046] Step 2: Weigh the raw materials kaolin and tetraethyl silicate (TEOS) at a mass ratio of 5:12. Place the weighed TEOS in a partial pressure funnel and add it to the three-necked flask containing the kaolin mixture from Step 1 at a rate of 1 drop / s. Maintain the mixture at 60°C and stir and heat for 6 hours.
[0047] Step 3: Select Si-QACs (primary, secondary, tertiary amines and quaternary ammonium) containing different nitrogen-containing head groups, namely 3-aminopropyltrimethoxysilane (APTES), N-methyl-3-aminopropyltrimethoxysilane (MAPTES), [3-(N,N-dimethylamino)propyl]trimethoxysilane (DAPTES) and trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPTAC);
[0048] The product obtained in step 2 was mixed with the different Si-QACs mentioned above, and then stirred and heated at 60°C for 12 hours. The Si-QAC addition ratio was based on the raw material kaolin, and the ratio of kaolin to the different Si-QACs mentioned above (g: mmol) was 5:1.
[0049] Step 4: The mixture obtained in Step 3 is centrifuged at 5000 r / min for 5 min and then washed three times with anhydrous ethanol to obtain organic quaternary ammonium salt modified clay containing different nitrogen-containing head groups.
[0050] Example 3
[0051] The same steps and conditions as in Example 2 were followed, except that the chain length of the aliphatic hydrocarbon group to which Si-QAC was added in step 3 was changed. The specific implementation method is as follows:
[0052] Step 1: Weigh out 5 portions of raw kaolin clay, each weighing 5g, and place them in a 250ml three-necked flask. Then add 80ml of anhydrous ethanol, 4.6ml of ammonia, and 1.5ml of pure water to each flask. Sonicate the mixture for 30 minutes to ensure it is well mixed. Then place the flask in a 60℃ water bath for heating and stirring.
[0053] Step 2: Weigh the raw materials kaolin and tetraethyl silicate (TEOS) at a mass ratio of 5:12. Place the weighed TEOS in a partial pressure funnel and add it to the three-necked flask containing the kaolin mixture from Step 1 at a rate of 1 drop / s. Maintain the mixture at 60°C and stir and heat for 6 hours.
[0054] Step 3: Select Si-QAC with different aliphatic hydrocarbon chain lengths, i.e., the two R2 substituents in the Si-QAC structure are both C1, and the other R2 substituent is C1, C6, C12, C14, or C18, respectively, which are trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPTAC), hexaalkyldimethyl(3-trimethoxysilylpropyl)ammonium chloride (TPHDAC), dodecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride (TPDDAC), tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride (TPTDAC), and dimethyloctadecyl[3-trimethoxysilylpropyl]ammonium chloride (TPODAC);
[0055] The product obtained in step 2 was mixed with the different Si-QACs mentioned above, and then stirred and heated at 60°C for 12 hours. The Si-QAC addition ratio was based on the raw material kaolin, and the ratio of kaolin to the different Si-QACs mentioned above (g: mmol) was 5:1.
[0056] Step 4: The mixture obtained in Step 3 is centrifuged at 5000 r / min for 5 min and then washed three times with anhydrous ethanol to obtain organic quaternary ammonium salt modified clay containing different aliphatic hydrocarbon chain lengths.
[0057] Example 4
[0058] The procedure was carried out under the same steps and conditions as in Example 3, except that the type of Si-QAC was kept constant as trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPTAC), and the addition ratio of tetraethyl silicate (TEOS) in step 2 was changed. The specific implementation method is as follows:
[0059] Step 1: Weigh out 6 portions of raw kaolin clay, each weighing 5g, and place them in a 250ml three-necked flask. Then add 80ml of anhydrous ethanol, 4.6ml of ammonia, and 1.5ml of pure water to each flask. Sonicate the mixture for 30 minutes to ensure it is well mixed. Then place the flask in a 60℃ water bath for heating and stirring.
[0060] Step 2: Weigh the raw materials kaolin and tetraethyl orthosilicate (TEOS) at mass ratios of 5:3, 5:6, 5:12, 5:24, 5:36, and 5:48 respectively. Place the weighed TEOS in a partial pressure funnel and add it to the three-necked flask containing the kaolin mixture at a rate of 1 drop / s. Keep the mixture at 60°C and stir and heat for 6 hours.
[0061] Step 3: Mix the different products obtained in Step 2 with a certain proportion of trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPTAC), and then keep stirring and heating at 60°C for 12 hours; wherein, the proportion of TPTAC added is based on the raw material kaolin, and the ratio of kaolin to TPTAC (g: mmol) is 5:2.
[0062] Step 4: The mixture obtained in Step 3 is centrifuged at 5000 r / min for 5 min and then washed three times with anhydrous ethanol to obtain modified clays prepared under different tetraethyl silicate addition ratios.
[0063] Example 5
[0064] The procedure was carried out under the same steps and conditions as in Example 4, except that the mass ratio of kaolin to tetraethyl silicate (TEOS) was changed to 5:12 in step 2, and the addition ratio of Si-QAC was altered. The specific implementation method is as follows:
[0065] Step 1: Weigh out 6 portions of 5g kaolin and place them in 250ml three-necked flasks. Then add 80ml anhydrous ethanol, 4.6ml ammonia and 1.5ml pure water respectively, and sonicate for 30min to mix them evenly. Then place them in a 60℃ water bath for heating and stirring.
[0066] Step 2: Weigh the raw materials kaolin and tetraethyl silicate (TEOS) at a mass ratio of 5:12. Place the weighed TEOS in a partial pressure funnel and add it to the three-necked flask containing the kaolin mixture at a rate of 1 drop / s. Maintain the temperature at 60°C and stir and heat for 6 hours.
[0067] Step 3: Mix the product obtained in Step 2 with trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPTAC) in different proportions, and then keep stirring and heating at 60°C for 12 hours; wherein, the proportion of TPTAC added is based on the raw material kaolin, and the ratio of kaolin to TPTAC (g: mmol) is 5:0.3, 5:0.6, 5:1, 5:2, 5:6, and 5:30.
[0068] Step 4: The mixture obtained in Step 3 is centrifuged at 5000 r / min for 5 min and then washed three times with anhydrous ethanol to obtain modified clay prepared under different TPTAC addition ratios.
[0069] Example 6
[0070] The procedure was carried out under the same conditions as in Example 5, except that the Kaolin:TPTAC (g:mmol) ratio was kept constant at 5:2, and the number of centrifugation and washing cycles was varied. The specific implementation method is as follows:
[0071] Step 1: Weigh out 6 portions of 5g kaolin and place them in 250ml three-necked flasks. Then add 80ml anhydrous ethanol, 4.6ml ammonia and 1.5ml pure water respectively, and sonicate for 30min to mix them evenly. Then place them in a 60℃ water bath for heating and stirring.
[0072] Step 2: According to the mass ratio of Kaolin:TEOS 5:12, place a certain amount of TEOS in a partial pressure funnel and add it to the three-necked flask containing the kaolin mixture at a rate of 1 drop / s, and keep stirring and heating at 60°C for 6 hours.
[0073] Step 3: Mix the product obtained in Step 2 with a certain proportion of trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPTAC), and then keep it at 60°C and stir and heat for 12 hours; wherein, the proportion of TPTAC added is based on the raw material kaolin, and the ratio of kaolin to TPTAC (g: mmol) is 5:2.
[0074] Step 4: The mixture obtained in Step 3 is centrifuged at 5000 r / min for 5 min and then washed with anhydrous ethanol 3, 4, 5, 6, 7, 8 and 9 times respectively to obtain the modified clay, which is recorded as the optimized modified clay prepared in this invention.
[0075] Comparative Example 1
[0076] 2.5g of kaolin and 0.025g of hexadecyltrimethylammonium chloride were weighed and placed in 80ml of deionized water. After mixing, the mixture was aged at 60℃ for 3h. Then, the mixture was washed with anhydrous ethanol 3, 4, 5, 6, 7, 8 and 9 times at a centrifugation speed of 5000r / min for 5min to obtain the modified clay material, which was denoted as ordinary quaternary ammonium salt modified clay.
[0077] Application examples
[0078] The selection and cultivation process of the experimental organisms are as follows: Common harmful algal blooms in the coastal waters of my country were selected as the experimental organisms. Based on their different cell structures and cell sizes, the selected algal species were *H. akashiwo*, *P. donghaiense*, and *A. anophagefferens*. All common algal species were preserved in the Key Laboratory of Marine Ecology and Environmental Science, Institute of Oceanology, Chinese Academy of Sciences. The seawater used for culturing the algal species was taken from the coastal waters of Huangdao District, Qingdao, China. The seawater was filtered through a 0.45 μm mixed fiber membrane during collection. Afterwards, the seawater was sterilized by high-temperature steam in an autoclave, and L1-type medium was added for algal culture. The culture conditions were: temperature (20±1)℃, light-dark ratio L:D = 12h:12h.
[0079] The specific preparation method of L1 type culture medium used for algal culture is as follows: Add 1 ml of 75 g / L NaNO3, 1 ml of 5 g / L NaH2PO4·H2O, 1 mL of 30 g / L Na2SiO3·9H2O, 1 mL of trace element solution, and 0.5 mL of f / 2 vitamin solution to 950 ml of filtered and sterilized seawater.
[0080] The algae removal experiment steps are as follows: Seawater was added to the obtained modified clay material to prepare a 50 g / L modified clay suspension. Then, red tide algae in the late stage of exponential growth (algal cell density approximately 1–2 × 10⁻⁶) were collected.6 Using cells / L as the removal target, the algae were placed in a 25 mL colorimetric tube. Then, according to the modified clay concentration used, a quantitative amount of the modified clay suspension was added to the colorimetric tube containing the algae solution, and the mixture was inverted and incubated for 3 hours. Afterwards, the fluorescence value of the algae solution at a depth of 5 cm below the surface was measured. The formula for calculating the algae removal efficiency of the modified clay is as follows:
[0081] Algae removal efficiency (%) = [1 - (experimental group live fluorescence value / control group live fluorescence value)] × 100%
[0082] 1) The organic quaternary ammonium salt modified clay prepared by different surface hydroxyl activation methods provided in Example 1 was used to remove Heterosigma erythrorhizon from red tides. The results are as follows: Figure 1 As shown, at a concentration of 0.1 g / L, the algae removal efficiency of kaolin alone was poor, only 5.1%. Direct Si-QAC modification of the kaolin surface resulted in a 9.7% algae removal efficiency for the synthesized modified clay-I. Acid or alkali activation of the kaolin surface followed by Si-QAC modification resulted in algae removal efficiencies of 14.6% and 21.8% for the synthesized modified clay-II and III, respectively. Covalent grafting of silanol compounds onto the kaolin surface followed by Si-QAC modification resulted in an 84.1% algae removal efficiency for the synthesized modified clay-IV. This demonstrates that introducing active silanol compounds onto the clay surface significantly improves the algae removal efficiency of the modified clay prepared according to this invention. Therefore, the treatment of introducing active silanol compounds onto the clay surface is considered the optimal surface activation method in this invention.
[0083] 2) The removal experiment of Heterosigma red tide using Si-QAC modified clay containing different nitrogen-containing head groups provided in Example 2 was conducted, and the results are as follows: Figure 2 As shown, the algae removal efficiencies of organic quaternary ammonium salt modified clays containing different nitrogen-containing groups vary significantly, with the order of algae removal efficiency being: TPTAC (quaternary ammonium) > APTES (primary amine) > MAPTES (secondary amine) > DAPTES (tertiary amine). Therefore, the optimal nitrogen-containing head group for preparing organic quaternary ammonium salt modified clay by the method of this invention is quaternary ammonium.
[0084] 3) The Si-QAC modified clay containing different aliphatic hydrocarbon chain lengths provided in Example 3 was used in the removal experiment of Heterosigma red tide. The results are as follows: Figure 3As shown, when both R2 substituents in the Si-QAC structure are C1, and the other R2 substituent is C1, C6, C12, C14, or C18, the algae removal efficiency of the synthesized organic quaternary ammonium salt modified clay gradually decreases with the increase of the aliphatic hydrocarbon chain length. When all three R2 substituents in the Si-QAC molecular structure are C1, the algae removal efficiency of the synthesized modified clay is the highest, at 84.1%. Therefore, trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPTAC), which contains quaternary ammonium groups and has three R2 substituents of C1, is considered the optimal Si-QAC of this invention.
[0085] 4) The modified clay obtained under different tetraethyl orthosilicate (TEOS) addition ratios provided in Example 4 was used in the removal experiment of Heterosigma rubrum red tide. The results are as follows: Figure 4 As shown, the algae removal efficiency of the organic quaternary ammonium salt modified clay synthesized by the method of this invention first increases and then decreases with the increase of the TEOS addition ratio. When the mass ratio of Kaolin to TEOS is controlled at 5:12, an organic quaternary ammonium salt modified clay with excellent algae removal performance can be obtained. Under this ratio condition, when the modified clay concentration is 0.1 g / L, a removal efficiency of 97% can be achieved against Heterosigma rubrum red tide.
[0086] 5) The modified clay materials obtained under different TPTAC addition ratios provided in Example 5 were used in the removal experiment of Heterosigma rubrum red tide. The results are as follows: Figure 5 As shown, the algae removal efficiency of the synthetic modified clay initially increases and then decreases with increasing TPTAC addition ratio. When the Kaolin:TPTAC ratio is controlled between 5:1 and 5:6 (g:mmol), an organic quaternary ammonium salt modified clay with excellent algae removal performance can be obtained. Within this ratio range, a modified clay concentration of 0.1 g / L can achieve a removal efficiency of over 90% against Heterosigma rubrum.
[0087] 6) The modified clay provided in Example 6 (taking three washes as an example) was used at different concentrations (i.e., 0.05, 0.1, 0.15, and 0.2 g / L) to conduct removal experiments on *Heterosigma rubrum*, *Prorocentrum donghaiense*, and *Aureobasidium globosum*. The results are as follows: Figure 6 As shown. The organic quaternary ammonium salt modified clay prepared by this invention can achieve a removal efficiency of over 90% for Heterosigma rubrum at a usage concentration of 0.1 g / L; and for Prorocentrum thomsoniae and Aureobasidium globosum, the organic quaternary ammonium salt modified clay prepared by this invention can also achieve a removal efficiency of over 90% at a usage concentration of 0.15 g / L.
[0088] To further analyze the stability of the organic quaternary ammonium salt modified clay prepared by this invention, the red tide Heterosigma removal efficiency and surface potential of the modified clay prepared by this invention in Example 6 (after multiple washings, i.e., washing with anhydrous ethanol 3, 4, 5, 6, 7, 8, and 9 times respectively) were compared with those of ordinary quaternary ammonium salt modified clay (Comparative Example 1). The results are as follows: Figure 7 As shown, at a concentration of 0.1 g / L, the algae removal efficiency of ordinary quaternary ammonium salt modified clay after three centrifugal washes was 38%, and the surface potential was -3.2 mV. Furthermore, with increasing centrifugal wash cycles, both the algae removal efficiency and surface potential of ordinary quaternary ammonium salt modified clay gradually decreased. After nine centrifugal washes, the algae removal efficiency dropped to 10%, and the surface potential decreased to -10.8 mV. In contrast, the algae removal efficiency and surface potential of the modified clay prepared according to the present invention did not change significantly with increasing centrifugal wash cycles; its algae removal efficiency remained at 90% ± 2%, and its surface potential remained at 9.15 mV ± 0.15 mV.
[0089] This indicates that ordinary quaternary ammonium salts have poor adsorption stability on clay surfaces and are prone to desorption. However, the present invention utilizes the valence bond between the silane group in the organosilicon quaternary ammonium salt molecule and the active sites on the clay surface to achieve a strong bond between the organosilicon quaternary ammonium salt molecule and the clay surface, thereby obtaining a class of organosilicon quaternary ammonium salt modified clay materials with high stability, good ecological safety, and efficient elimination ability against common harmful algal blooms.
Claims
1. A method for preparing an environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay, characterized in that: The surface of the raw clay mineral is subjected to hydroxyl activation treatment. After treatment, a silane-containing organic quaternary ammonium salt modifier (Si-QAC) is added. By regulating the valence bond reaction between the silane-containing molecules in the modifier and the active sites on the clay surface, organic quaternary ammonium salt modified clay is obtained. The silane-containing organic quaternary ammonium salt modifier (Si-QAC) has the following structural formula as shown in general formula one. Formula 1 In the formula, R is a C1-C20 alkoxy or a C1-C20 haloalkoxy; R1 is a C1-C20 alkyl, C1-C20 alkoxy, C1-C20 haloalkoxy, C1-C20 acyl, or C1-C20 alkoxycarbonyl; R2 is H, a C1-C20 alkyl, or a C1-C20 alkoxy; X - It is an anion.
2. The method for preparing environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay according to claim 1, characterized in that: The valence bond reaction between the silane-containing modifier molecule and the active sites on the clay surface is carried out by activating the clay mineral surface with hydroxyl groups, mixing the raw clay mineral with the silane-containing organic quaternary ammonium salt modifier (g: mmol) at a ratio of 5:(0.3~30), and reacting under heating conditions of 40~80℃ for 6~24h.
3. The method for preparing environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay according to claim 1 or 2, characterized in that: The aforementioned hydroxyl activation treatment of clay mineral surface refers to acid or alkali treatment of clay minerals, or the introduction of compounds containing active hydroxyl groups onto the clay surface.
4. The preparation method of the environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay according to claim 3, characterized in that: The acid or alkali treatment refers to placing clay minerals in an acid or alkali solution, shaking and vibrating them for more than 1 hour at room temperature or under heating conditions, and then washing and drying them with ethanol by centrifugation. The acid solution is an inorganic acid solution; the alkaline solution is prepared from one or more of the hydroxides, oxides or salts of alkali metals or alkaline earth metals.
5. The method for preparing environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay according to claim 3, characterized in that: The process of introducing a compound containing active hydroxyl groups onto the clay surface involves dispersing clay minerals in a mixture containing anhydrous ethanol, ammonia, and water, ultrasonicating to ensure uniform dispersion, and then slowly adding a silicon-based precursor capable of generating the active hydroxyl compound dropwise to the mixture under heating and stirring conditions at 40-80°C until the reaction is complete. The mass ratio of clay minerals to silicon-based precursors is 5:1 to 5:
50. The silicon-based precursor is prepared from one or more of silanols, siloxanes, and silicates.
6. The method for preparing environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay according to claim 3, characterized in that: The clay mineral is an aluminosilicate mineral.
7. An environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay prepared by the method of claim 1, characterized in that: Organic quaternary ammonium salt modified clay with high stability and good ecological safety was prepared according to the method described in claim 1.
8. The application of the environmentally friendly and highly efficient algae-removing organic quaternary ammonium salt modified clay according to claim 7, characterized in that: The organic quaternary ammonium salt modified clay is used in the removal of harmful algal blooms in the environment.