Preparation method of polyaluminum chloride-based composite sewage treatment agent

Abstract

The invention discloses a preparation method of a polyaluminum chloride-based composite sewage treatment agent, and the polyaluminum chloride-based composite sewage treatment agent is prepared from the following raw materials in parts by weight: 20-35 parts of polyaluminum chloride, 5-12 parts of slow-release microbial bacteria, 3-6 parts of modified activated carbon, 4-8 parts of modified attapulgite, 0.5-1.2 parts of cocamidopropyl betaine and 2-5 parts of polyacrylamide. The preparation method comprises the following steps: uniformly mixing polyaluminum chloride and cocamidopropyl betaine, then adding the modified activated carbon, the modified attapulgite and the polyacrylamide, uniformly stirring again, then adding the slow-release microbial flora, and finally stirring and drying to obtain the water-retaining agent. The polyaluminum chloride-based composite sewage treatment agent prepared by the preparation method disclosed by the invention is good in effect of efficiently removing nitrogen, phosphorus and heavy metals in a short time, good in slow-release effect and good in performance.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage material preparation, and particularly relates to a method for preparing a polyaluminum chloride-based composite sewage treatment agent. Background Art

[0002] With the acceleration of global industrialization and urbanization, wastewater discharge has surged, posing a serious challenge to human health, disrupting ecological balance, and hindering sustainable development. Excessive levels of nitrogen and phosphorus in industrial and domestic wastewater remain major concerns, and heavy metal pollution, due to its hidden nature, also poses a potential risk. Consequently, abnormal nitrogen and phosphorus levels can easily lead to eutrophication and algae blooms, while heavy metal pollution poses a direct threat to human health. Therefore, water management remains a critical and arduous task.

[0003] In existing research, there have been many reports on water treatment agents, which can be divided into biological treatment technology, chemical oxidation treatment technology and physical treatment technology according to the type of technology. Among them, biological treatment technology mainly relies on the metabolism of microorganisms in aerobic or anoxic, anaerobic environment to biodegrade and assimilate organic pollutants in water, effectively removing biodegradable organic matter, ammonia nitrogen, total phosphorus, nitrite and iron and manganese and other pollutants in the contaminated water; chemical oxidation technology uses the oxidizing property of chemical oxidants to oxidize pollutants in contaminated water and lose electrons, thereby reducing the stability of organic matter and the interaction between them, and then oxidizing and decomposing them (such as potassium permanganate, chlorine, etc.), and aggregating them into colloidal particles through the Tyndall effect, so as to achieve the purpose of degrading and removing pollutants; physical treatment technologies include membrane separation technology, adsorption method, etc. In the prior art, there have been many application reports. For example, patent document CN108017129A provides a composite sewage treatment agent, which is made from the following raw materials in percentage by weight: polyaluminum chloride 20-35wt%, polyferric chloride 15-20wt%, modified bentonite 10-20wt%, silica gel 10-15wt%, acrylate adhesive 3-5wt%, and the balance is modified zero-valent iron; it combines multiple functions such as decolorization, flocculation, COD and BOD removal, and has an extremely high decolorization rate. However, the treatment of nitrogen, phosphorus and heavy metals needs to be improved, and the treatment is not long-lasting.

[0004] For example, patent document CN102409035A provides a microecological sustained-release bacterial agent, which is a Bacillus subtilis microcapsule product, which mainly relies on microbial treatment and has a single effect.

[0005] For another example, patent document CN115286063A provides a sewage treatment agent based on polyaluminum chloride, which is made of the following raw material components in parts by weight: 40-70 parts of polyaluminum chloride, 5-15 parts of mineral powder, 3-8 parts of dispersant, 3-6 parts of absorbent, 5-10 parts of shell ash, 3-5 parts of cross-linking agent, and 3-5 parts of fungicide; the mineral powder is a mixed mineral powder of sepiolite powder and lycra stone powder in a mass ratio of 1:1; the shell ash is a mixture of rice husk ash and millet husk ash in a mass ratio of 1:1. In the above scheme, polyaluminum chloride is used as the main active ingredient, and a mixed mineral powder of sepiolite powder and lycra stone powder in a mass ratio of 1:1 is added, which significantly reduces the COD of sewage, and a mixture of rice husk ash and millet husk ash in a mass ratio of 1:1 is added, which significantly reduces the SS in sewage. However, its treatment effect also needs to be further improved.

[0006] Therefore, the present invention hopes to provide a method for preparing a polyaluminum chloride-based composite sewage treatment agent. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for preparing a polyaluminum chloride-based composite sewage treatment agent, which has good effects of removing nitrogen, phosphorus and heavy metals in a short time and high efficiency, and has good slow-release effect and excellent performance.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] First, the present invention provides a polyaluminum chloride-based composite sewage treatment agent, which is prepared from the following raw materials, in parts by weight: 20 to 35 parts of polyaluminum chloride, 5 to 12 parts of slow-release microorganisms, 3 to 6 parts of modified activated carbon, 4 to 8 parts of modified attapulgite, 0.5 to 1.2 parts of cocamidopropyl betaine, and 2 to 5 parts of polyacrylamide.

[0010] As a preferred embodiment of the technical solution of the present invention, the preparation of the modified activated carbon comprises the following steps:

[0011] S11, adding activated carbon to nitric acid, performing ultrasonic treatment under heating conditions, and after the treatment is completed, washing and drying to obtain pre-modified activated carbon;

[0012] S12, adding the pre-modified activated carbon obtained in step S11 to water, then adding urea, stirring evenly and then heating. After the treatment is completed, drying and high-temperature treatment are performed to obtain primary modified activated carbon;

[0013] S13, adding the primary modified activated carbon obtained in step S12 to the ferric nitrate solution, stirring evenly, filtering, drying, and then calcining under nitrogen protection to obtain modified activated carbon.

[0014] As a preferred embodiment of the technical solution of the present invention, in step S11, the concentration of nitric acid is 4-6 mol / L, the heating temperature is 35-45°C, the ultrasonic treatment power is 50-100 W, and the ultrasonic treatment time is 1-4 h; the usage ratio of activated carbon to nitric acid is 1 g: 8-15 mL;

[0015] In step S12, the mass ratio of pre-modified activated carbon, water, and urea is 1:10-20:0.8-1.2; the heating treatment temperature is 35-55°C, and the treatment time is 12-36 hours; the high-temperature treatment is carried out under nitrogen protection, the treatment temperature is 550-650°C, and the treatment time is 1-4 hours;

[0016] In step S13, the concentration of the ferric nitrate solution is 5-10 wt %, the usage ratio of the primary modified activated carbon to the ferric nitrate solution is 1 g:15-30 mL, the calcination treatment temperature is 500-580° C., and the treatment time is 1-4 h.

[0017] As a preferred embodiment of the technical solution of the present invention, the preparation of the slow-release microorganisms comprises the following steps:

[0018] S21, adding titanium dioxide to anhydrous ethanol, stirring and dispersing it uniformly, adding KH550, and then reflux reaction under heating conditions; then filtering, washing, and drying to obtain a pretreated support;

[0019] S22, dissolving caffeic acid in PBS buffer, then adding 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, and activating under stirring, then adding the pretreated support obtained in step S21, and reacting under heating and stirring; after the reaction is completed, filtering, washing, and drying to obtain a modified support;

[0020] S23, adding the mixed bacteria to the modified carrier obtained in step S22, stirring, then adding sodium alginate solution, stirring evenly again, then slowly adding calcium chloride solution, and then freeze-drying to obtain slow-release microorganisms.

[0021] As a preferred embodiment of the technical solution of the present invention, in step S21, the usage ratio of titanium dioxide, anhydrous ethanol, and KH550 is 1 g: 5-10 mL: 1-3 mL;

[0022] The reflux reaction temperature is 80~85℃, and the reaction time is 8~16h.

[0023] As a preferred embodiment of the technical solution of the present invention, in step S22, the dosage ratio of caffeic acid to PBS buffer is 1 mg: 0.5-1 mL;

[0024] The mass ratio of caffeic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide, and pretreated carrier is 1:0.8~1.2:0.3~0.5:1.5~2.5;

[0025] The activation temperature is 4°C and the activation time is 20~50min;

[0026] The heating and stirring temperature is 40~55℃, and the reaction time under heating and stirring is 3~6h.

[0027] As a preferred embodiment of the technical solution of the present invention, in step S23, the total viable count of the mixed bacteria is not less than 1×10 10 CFU / g; the mixed bacteria were obtained by mixing Nitrobacter, Pseudomonas mendocina, and Bacillus subtilis at a ratio of 1:1:1.2;

[0028] The mass concentration of sodium alginate solution is 1.5~3%, and the mass concentration of calcium chloride solution is 5~10%;

[0029] The mass ratio of the modified carrier to sodium alginate is 1:0.45~0.65.

[0030] As a preferred embodiment of the technical solution of the present invention, the preparation of modified attapulgite includes the following steps:

[0031] S31, adding attapulgite to a hydrochloric acid solution, stirring under heating conditions, filtering, washing, and drying to obtain pretreated attapulgite;

[0032] S32. Add boric acid to anhydrous ethanol and stir to obtain a boric acid ethanol solution for later use; add the pretreated attapulgite obtained in step S31 to the boric acid ethanol solution and stir under heating conditions. After the treatment is completed, filter, wash and dry to obtain modified attapulgite.

[0033] As a preferred embodiment of the technical solution of the present invention, in step S31, the concentration of the hydrochloric acid solution is 5-10wt%, the dosage ratio of attapulgite to hydrochloric acid solution is 1g:5-10mL; the heating temperature is 40-55°C, and the stirring treatment time is 1-4h;

[0034] In step S32, the concentration of the boric acid ethanol solution is 0.05-0.1 g / mL; the usage ratio of the pretreated attapulgite and the boric acid ethanol solution is 1 g:10-15 mL; the heating temperature is 55-70° C., and the stirring treatment time is 5-20 min.

[0035] Secondly, the present invention also provides a preparation method of the above-mentioned polyaluminum chloride-based composite sewage treatment agent, comprising the following steps: mixing polyaluminum chloride and cocamidopropyl betaine evenly, then adding modified activated carbon, modified attapulgite, and polyacrylamide, stirring evenly again, then adding slow-release microorganisms, and finally stirring and drying to obtain the product.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention provides a polyaluminum chloride-based composite sewage treatment agent, which uses polyaluminum chloride as the main raw material and is combined with modified activated carbon, modified attapulgite and slow-release microorganisms to prepare a water treatment agent that has good effects in removing nitrogen, phosphorus and heavy metals and has a good slow-release effect.

[0038] The present invention provides a kind of polyaluminum chloride-based composite sewage treatment agent, and the activated carbon used is itself a kind of better water treatment agent, and the present invention modifies it to further improve its treatment effect. Specifically, in the present invention, the activated carbon is first subjected to ultrasonic acid treatment, which is beneficial to further increase its specific surface area while increasing its active groups, which is beneficial to the subsequent modification of urea and the loading of ferric nitrate; further urea modification is beneficial to improve the hydrophilicity of the activated carbon and improve the sewage treatment effect of the activated carbon. At the same time, the introduction of nitrogen is beneficial to further improve the subsequent adsorption of iron and improve the loading effect of iron; ferric nitrate modified activated carbon itself is a more common modified substance, based on the ultrasonic acid treatment and nitrogen modification of the aforementioned activated carbon, which can effectively improve the sewage treatment effect of the activated carbon after iron modification. The various modification steps of the activated carbon in the present invention cooperate with each other, so that the sewage treatment capacity of the modified activated carbon is greatly improved.

[0039] The present invention provides a polyaluminum chloride-based composite sewage treatment agent, in which the slow-release microorganisms used are in a microcapsule structure, ensuring the long-term effectiveness of sewage treatment. Specifically, in order to improve the use effect of the microorganisms, the present invention first uses a modified carrier to adsorb and fix them, and then uses calcium chloride to solidify sodium alginate to form a wall material; the carrier is mainly titanium dioxide, which has a certain flora adsorption property. The present invention uses KH550 and caffeic acid for treatment, thereby further improving the adhesion effect of the composite flora. The use of KH550 is conducive to the introduction of amino groups, which can react with the carboxyl groups in caffeic acid under the activation of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide; in addition, the introduced phenolic hydroxyl groups (bionic adhesion interface) can improve the adsorption effect of the microorganisms, and the antioxidant property of caffeic acid itself can reduce the oxidative stress of the microorganisms on the external system, thereby improving its adsorption strength, activity and action time.

[0040] The present invention provides a polyaluminum chloride-based composite sewage treatment agent, in which the attapulgite used is subjected to simple acid treatment and boric acid modification. The boric acid modification can, on the one hand, form acidic sites to improve the adsorption effect of pollutants in water, and on the other hand, can also reduce the surface energy of the attapulgite, improve its compatibility with other substances, and promote the efficient compounding of the sewage treatment agent system.

[0041] The present invention provides a polyaluminum chloride-based composite sewage treatment agent, which uses modified activated carbon, modified attapulgite and slow-release microorganisms to work together to achieve the best sewage treatment effect. Specifically, the nitrogen substances adsorbed by attapulgite are oxidized to nitrate by Nitrobacter, and reduced to nitrogen gas by Pseudomonas Mendocina after adsorption by activated carbon; titanium dioxide can decompose macromolecules into small molecules based on photolysis, and Bacillus subtilis can directly degrade and metabolize them to avoid product accumulation; nitrogen-modified activated carbon can serve as an electron intermediary, and the added Fe transfers electrons between microorganisms to promote nitrification and denitrification; and the caffeic acid introduced by titanium dioxide can effectively shield the inhibitory effect of heavy metals in sewage on microorganisms and improve the timeliness of bacterial flora. In short, the above substances work together to achieve a very good sewage treatment effect.

[0042] In summary, the present invention can achieve an excellent treatment effect within 5 minutes through the coordinated use of various substances, and can efficiently treat ammonium ions, phosphate ions and heavy metals at the same time; at the same time, due to the use of slow-release microorganisms, it can achieve a long-term treatment effect. Therefore, it is suitable for both the rapid treatment of sewage and the long-term treatment of flowing water bodies. DETAILED DESCRIPTION

[0043] The embodiments of the present invention are described in detail below. All embodiments are exemplary and intended to be used to explain the present invention, but are not to be construed as limiting the present invention.

[0044] In the embodiment of the present invention, the activated carbon was purchased from Chengde Tianyuan Activated Carbon Co., Ltd., and the particle size was about 150 μm;

[0045] Polyaluminium chloride was purchased from Shenzhen Qingyuan Water Purification Equipment Co., Ltd.

[0046] Attapulgite was purchased from Junda Attapulgite Company;

[0047] Polyacrylamide was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0048] Nitrobacter was Nitrobacter welchii, purchased from Beijing Biobowei Biotechnology Co., Ltd.;

[0049] Pseudomonas mendocina was purchased from Beijing Biobowei Biotechnology Co., Ltd.;

[0050] Bacillus subtilis was purchased from Beijing Biobowei Biotechnology Co., Ltd.;

[0051] 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide, CAS number 1892-57-5, abbreviated as EDC;

[0052] N-hydroxysuccinimide, CAS number 6066-82-6, abbreviated as NHS.

[0053] It should be noted that the parts mentioned in the following embodiments are parts by weight unless otherwise specified, and the specific weights mentioned are only examples, which can be increased proportionally as needed in actual production.

[0054] Example 1

[0055] A polyaluminum chloride-based composite sewage treatment agent is prepared from the following raw materials, measured by mass: 30g of polyaluminum chloride, 8g of slow-release microorganisms, 4g of modified activated carbon, 5.5g of modified attapulgite, 0.65g of cocamidopropyl betaine, and 2.5g of polyacrylamide.

[0056] The preparation of the modified activated carbon comprises the following steps:

[0057] S11. Add activated carbon to 5 mol / L nitric acid at a ratio of 1 g:10 mL, and perform ultrasonic treatment (80 W, 2 h) under heating conditions (40°C). After the treatment, wash and dry to obtain pre-modified activated carbon.

[0058] S12, adding the pre-modified activated carbon obtained in step S11 to water, then adding urea, stirring evenly and heating (40°C, 16 hours), drying and high-temperature treatment (nitrogen protection, 600°C, 1.5 hours) to obtain primary modified activated carbon; wherein the mass ratio of pre-modified activated carbon, water, and urea is 1:15:1;

[0059] S13. Add the primary modified activated carbon obtained in step S12 to 8 wt% ferric nitrate solution at a dosage ratio of 1 g:20 mL, stir evenly, filter, dry, and then calcine under nitrogen protection (520°C, 2h). After the treatment is completed, the modified activated carbon is obtained.

[0060] The preparation of the slow-release microorganisms comprises the following steps:

[0061] S21. Add titanium dioxide to anhydrous ethanol, stir and disperse evenly, then add KH550, and then reflux under heating conditions (85°C, 10 hours); then filter, wash, and dry to obtain a pretreated support; wherein the amount ratio of titanium dioxide, anhydrous ethanol, and KH550 is 1g:6mL:2mL;

[0062] S22. Dissolve caffeic acid in PBS buffer at a ratio of 1 mg:0.8 mL, then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, and activate under stirring (4°C, 30 min). Then add the pretreated carrier obtained in step S21, and react under heating and stirring (45°C, 4 h). After the reaction, filter, wash, and dry to obtain a modified carrier. The mass ratio of caffeic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide, and pretreated carrier is 1:1:0.4:2.

[0063] S23, the mixed bacteria (total viable count of 1 × 10 10 CFU / g, obtained by mixing Nitrobacter, Pseudomonas mendocina, and Bacillus subtilis in a ratio of 1:1:1.2 in terms of viable cell count, was added to the modified carrier obtained in step S22, and then a 2 wt % sodium alginate solution was added after stirring. After stirring again, an 8 wt % calcium chloride solution was slowly added, and then freeze-dried to obtain a slow-release microbial bacteria; wherein the mass ratio of the modified carrier to sodium alginate was 1:0.55.

[0064] The preparation of modified attapulgite comprises the following steps:

[0065] S31, adding attapulgite to 8 wt% hydrochloric acid solution at a dosage ratio of 1 g:8 mL, stirring under heating conditions (45° C., 3 h), filtering, washing, and drying to obtain pretreated attapulgite;

[0066] S32. Add boric acid to anhydrous ethanol and stir to obtain a boric acid ethanol solution (concentration of 0.08m / mL) for later use; add the pretreated attapulgite obtained in step S31 to the boric acid ethanol solution in a dosage ratio of 1g:12mL, and stir under heating conditions (60°C, 15min). After the treatment is completed, filter, wash, and dry to obtain modified attapulgite.

[0067] In this embodiment, a preparation method of the above-mentioned polyaluminum chloride-based composite sewage treatment agent is also provided, comprising the following steps: mixing polyaluminum chloride and cocamidopropyl betaine evenly, adding modified activated carbon, modified attapulgite, and polyacrylamide, stirring evenly again, and then adding slow-release microorganisms, and finally stirring and drying to obtain the product.

[0068] Example 2

[0069] A polyaluminum chloride-based composite sewage treatment agent is prepared from the following raw materials, measured by mass: 30g of polyaluminum chloride, 7.5g of slow-release microorganisms, 4.5g of modified activated carbon, 5g of modified attapulgite, 0.6g of cocamidopropyl betaine, and 2.2g of polyacrylamide.

[0070] The preparation of the modified activated carbon comprises the following steps:

[0071] S11. Add activated carbon to 5 mol / L nitric acid at a ratio of 1 g:10 mL, and perform ultrasonic treatment (80 W, 1.5 h) under heating conditions (40°C). After the treatment, wash and dry to obtain pre-modified activated carbon.

[0072] S12, adding the pre-modified activated carbon obtained in step S11 to water, then adding urea, stirring evenly and heating (45°C, 12h), drying and high-temperature treatment (nitrogen protection, 600°C, 1h) to obtain primary modified activated carbon; wherein the mass ratio of pre-modified activated carbon, water, and urea is 1:12:1;

[0073] S13. Add the primary modified activated carbon obtained in step S12 to 8 wt% ferric nitrate solution at a dosage ratio of 1 g:20 mL, stir evenly, filter, dry, and then calcine under nitrogen protection (530°C, 1.5 h). After the treatment is completed, the modified activated carbon is obtained.

[0074] The preparation of the slow-release microorganisms comprises the following steps:

[0075] S21. Add titanium dioxide to anhydrous ethanol, stir and disperse uniformly, then add KH550, and then reflux under heating conditions (85°C, 10 hours); then filter, wash, and dry to obtain a pretreated support; wherein the amount ratio of titanium dioxide, anhydrous ethanol, and KH550 is 1g:7mL:2mL;

[0076] S22. Dissolve caffeic acid in PBS buffer at a ratio of 1 mg:0.75 mL, then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, and activate under stirring (4°C, 25 min). Then add the pretreated carrier obtained in step S21, and react under heating and stirring (45°C, 4 h). After the reaction, filter, wash, and dry to obtain a modified carrier. The mass ratio of caffeic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide, and pretreated carrier is 1:1:0.4:2.

[0077] S23, the mixed bacteria (total viable count of 1 × 10 10CFU / g, obtained by mixing Nitrobacter, Pseudomonas mendocina, and Bacillus subtilis in a ratio of 1:1:1.2 in terms of viable bacteria count, was added to the modified carrier obtained in step S22, and then a 2 wt % sodium alginate solution was added after stirring. After stirring again, an 8 wt % calcium chloride solution was slowly added, and then freeze-dried to obtain a slow-release microorganism; wherein the mass ratio of the modified carrier to sodium alginate was 1:0.6.

[0078] The preparation of modified attapulgite comprises the following steps:

[0079] S31, adding attapulgite to a 7 wt % hydrochloric acid solution at a dosage ratio of 1 g:8 mL, stirring under heating conditions (45° C., 3 h), filtering, washing, and drying to obtain pretreated attapulgite;

[0080] S32. Add boric acid to anhydrous ethanol and stir to obtain a boric acid ethanol solution (concentration of 0.08m / mL) for later use; add the pretreated attapulgite obtained in step S31 to the boric acid ethanol solution in a dosage ratio of 1g:12mL, and stir under heating conditions (60°C, 10min). After the treatment is completed, filter, wash, and dry to obtain modified attapulgite.

[0081] In this embodiment, a preparation method of the above-mentioned polyaluminum chloride-based composite sewage treatment agent is also provided, comprising the following steps: mixing polyaluminum chloride and cocamidopropyl betaine evenly, adding modified activated carbon, modified attapulgite, and polyacrylamide, stirring evenly again, and then adding slow-release microorganisms, and finally stirring and drying to obtain the product.

[0082] Example 3

[0083] A polyaluminum chloride-based composite sewage treatment agent is prepared from the following raw materials, measured by mass: 30g of polyaluminum chloride, 8.5g of slow-release microorganisms, 3.5g of modified activated carbon, 6g of modified attapulgite, 0.6g of cocamidopropyl betaine, and 2g of polyacrylamide.

[0084] The preparation of the modified activated carbon comprises the following steps:

[0085] S11. Add activated carbon to 5.5 mol / L nitric acid at a ratio of 1 g:12 mL, and perform ultrasonic treatment (100 W, 1 h) under heating conditions (40°C). After the treatment, wash and dry to obtain pre-modified activated carbon.

[0086] S12, adding the pre-modified activated carbon obtained in step S11 to water, then adding urea, stirring evenly and heating (45°C, 12h), drying and high-temperature treatment (nitrogen protection, 600°C, 1.5h) to obtain primary modified activated carbon; wherein the mass ratio of pre-modified activated carbon, water, and urea is 1:15:1;

[0087] S13. Add the primary modified activated carbon obtained in step S12 to 9 wt% ferric nitrate solution at a dosage ratio of 1 g:18 mL, stir evenly, filter, dry, and then calcine under nitrogen protection (520°C, 2h). After the treatment is completed, the modified activated carbon is obtained.

[0088] The preparation of the slow-release microorganisms comprises the following steps:

[0089] S21. Add titanium dioxide to anhydrous ethanol, stir and disperse evenly, then add KH550, and then reflux under heating conditions (85°C, 10 hours); then filter, wash, and dry to obtain a pretreated support; wherein the amount ratio of titanium dioxide, anhydrous ethanol, and KH550 is 1g:6mL:2mL;

[0090] S22. Dissolve caffeic acid in PBS buffer at a ratio of 1 mg:0.8 mL, then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, and activate under stirring (4°C, 30 min). Then add the pretreated carrier obtained in step S21, and react under heating and stirring (45°C, 4 h). After the reaction, filter, wash, and dry to obtain a modified carrier. The mass ratio of caffeic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide, and pretreated carrier is 1:1:0.4:2.

[0091] S23, the mixed bacteria (total viable count of 1 × 10 10 CFU / g, obtained by mixing Nitrobacter, Pseudomonas mendocina, and Bacillus subtilis in a ratio of 1:1:1.2 in terms of viable cell count, was added to the modified carrier obtained in step S22, and then a 2 wt % sodium alginate solution was added after stirring. After stirring again, an 8 wt % calcium chloride solution was slowly added, and then freeze-dried to obtain a slow-release microbial bacteria; wherein the mass ratio of the modified carrier to sodium alginate was 1:0.55.

[0092] The preparation of modified attapulgite comprises the following steps:

[0093] S31, adding attapulgite to 8 wt% hydrochloric acid solution at a dosage ratio of 1 g:8 mL, stirring under heating conditions (45° C., 3 h), filtering, washing, and drying to obtain pretreated attapulgite;

[0094] S32. Add boric acid to anhydrous ethanol and stir to obtain a boric acid ethanol solution (concentration of 0.07m / mL) for later use; add the pretreated attapulgite obtained in step S31 to the boric acid ethanol solution in a dosage ratio of 1g:10mL, and stir under heating conditions (65°C, 12min). After the treatment is completed, filter, wash, and dry to obtain modified attapulgite.

[0095] In this embodiment, a preparation method of the above-mentioned polyaluminum chloride-based composite sewage treatment agent is also provided, comprising the following steps: mixing polyaluminum chloride and cocamidopropyl betaine evenly, adding modified activated carbon, modified attapulgite, and polyacrylamide, stirring evenly again, and then adding slow-release microorganisms, and finally stirring and drying to obtain the product.

[0096] Comparative Example 1

[0097] Compared with Example 1, step S12 is omitted in Comparative Example 1, and all other steps are the same. Specifically, in this comparative example, a polyaluminum chloride-based composite sewage treatment agent is provided, which is prepared from the following raw materials by mass: 30g polyaluminum chloride, 8g slow-release microorganisms, 4g modified activated carbon, 5.5g modified attapulgite, 0.65g cocamidopropyl betaine, and 2.5g polyacrylamide.

[0098] The preparation of the modified activated carbon comprises the following steps:

[0099] S11. Add activated carbon to 5 mol / L nitric acid at a ratio of 1 g:10 mL, and perform ultrasonic treatment (80 W, 2 h) under heating conditions (40°C). After the treatment, wash and dry to obtain pre-modified activated carbon.

[0100] S12. Add the pre-modified activated carbon obtained in step S12 to 8 wt% ferric nitrate solution in a dosage ratio of 1 g:20 mL, stir evenly, filter, dry, and then calcine under nitrogen protection (520°C, 2h). After the treatment is completed, the modified activated carbon is obtained.

[0101] The preparation of the slow-release microorganisms comprises the following steps:

[0102] S21. Add titanium dioxide to anhydrous ethanol, stir and disperse evenly, then add KH550, and then reflux under heating conditions (85°C, 10 hours); then filter, wash, and dry to obtain a pretreated support; wherein the amount ratio of titanium dioxide, anhydrous ethanol, and KH550 is 1g:6mL:2mL;

[0103] S22. Dissolve caffeic acid in PBS buffer at a ratio of 1 mg:0.8 mL, then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, and activate under stirring (4°C, 30 min). Then add the pretreated carrier obtained in step S21, and react under heating and stirring (45°C, 4 h). After the reaction, filter, wash, and dry to obtain a modified carrier. The mass ratio of caffeic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide, and pretreated carrier is 1:1:0.4:2.

[0104] S23, the mixed bacteria (total viable count of 1 × 10 10 CFU / g, obtained by mixing Nitrobacter, Pseudomonas mendocina, and Bacillus subtilis in a ratio of 1:1:1.2 in terms of viable cell count, was added to the modified carrier obtained in step S22, and then a 2 wt % sodium alginate solution was added after stirring. After stirring again, an 8 wt % calcium chloride solution was slowly added, and then freeze-dried to obtain a slow-release microbial bacteria; wherein the mass ratio of the modified carrier to sodium alginate was 1:0.55.

[0105] The preparation of modified attapulgite comprises the following steps:

[0106] S31, adding attapulgite to 8 wt% hydrochloric acid solution at a dosage ratio of 1 g:8 mL, stirring under heating conditions (45° C., 3 h), filtering, washing, and drying to obtain pretreated attapulgite;

[0107] S32. Add boric acid to anhydrous ethanol and stir to obtain a boric acid ethanol solution (concentration of 0.08m / mL) for later use; add the pretreated attapulgite obtained in step S31 to the boric acid ethanol solution in a dosage ratio of 1g:12mL, and stir under heating conditions (60°C, 15min). After the treatment is completed, filter, wash, and dry to obtain modified attapulgite.

[0108] In this comparative example, a preparation method of the above-mentioned polyaluminum chloride-based composite sewage treatment agent is also provided, comprising the following steps: mixing polyaluminum chloride and cocamidopropyl betaine evenly, adding modified activated carbon, modified attapulgite, and polyacrylamide, stirring evenly again, and then adding slow-release microorganisms, and finally stirring and drying to obtain the product.

[0109] Comparative Example 2

[0110] Compared with Example 1, step S22 is omitted in Comparative Example 2, and the rest are the same. Specifically, in this comparative example, a polyaluminum chloride-based composite sewage treatment agent is provided, which is prepared from the following raw materials by mass: 30g polyaluminum chloride, 8g slow-release microorganisms, 4g modified activated carbon, 5.5g modified attapulgite, 0.65g cocamidopropyl betaine, and 2.5g polyacrylamide.

[0111] The preparation of the modified activated carbon comprises the following steps:

[0112] S11. Add activated carbon to 5 mol / L nitric acid at a ratio of 1 g:10 mL, and perform ultrasonic treatment (80 W, 2 h) under heating conditions (40°C). After the treatment, wash and dry to obtain pre-modified activated carbon.

[0113] S12, adding the pre-modified activated carbon obtained in step S11 to water, then adding urea, stirring evenly and heating (40°C, 16 hours), drying and high-temperature treatment (nitrogen protection, 600°C, 1.5 hours) to obtain primary modified activated carbon; wherein the mass ratio of pre-modified activated carbon, water, and urea is 1:15:1;

[0114] S13. Add the primary modified activated carbon obtained in step S12 to 8 wt% ferric nitrate solution at a dosage ratio of 1 g:20 mL, stir evenly, filter, dry, and then calcine under nitrogen protection (520°C, 2h). After the treatment is completed, the modified activated carbon is obtained.

[0115] The preparation of the slow-release microorganisms comprises the following steps:

[0116] S21. Add titanium dioxide to anhydrous ethanol, stir and disperse evenly, then add KH550, and then reflux under heating conditions (85°C, 10 hours); then filter, wash, and dry to obtain a pretreated support; wherein the amount ratio of titanium dioxide, anhydrous ethanol, and KH550 is 1g:6mL:2mL;

[0117] S22, the mixed bacteria (total viable count of 1 × 10 10 CFU / g, obtained by mixing Nitrobacter, Pseudomonas mendocina, and Bacillus subtilis in a ratio of 1:1:1.2 in viable cell count, was added to the pretreated carrier obtained in step S21, and then a 2 wt % sodium alginate solution was added after stirring. After stirring again, an 8 wt % calcium chloride solution was slowly added, and then freeze-dried to obtain slow-release microorganisms; wherein the mass ratio of the pretreated carrier to sodium alginate was 1:0.55.

[0118] The preparation of modified attapulgite comprises the following steps:

[0119] S31, adding attapulgite to 8 wt% hydrochloric acid solution at a dosage ratio of 1 g:8 mL, stirring under heating conditions (45° C., 3 h), filtering, washing, and drying to obtain pretreated attapulgite;

[0120] S32. Add boric acid to anhydrous ethanol and stir to obtain a boric acid ethanol solution (concentration of 0.08m / mL) for later use; add the pretreated attapulgite obtained in step S31 to the boric acid ethanol solution in a dosage ratio of 1g:12mL, and stir under heating conditions (60°C, 15min). After the treatment is completed, filter, wash, and dry to obtain modified attapulgite.

[0121] In this comparative example, a preparation method of the above-mentioned polyaluminum chloride-based composite sewage treatment agent is also provided, comprising the following steps: mixing polyaluminum chloride and cocamidopropyl betaine evenly, adding modified activated carbon, modified attapulgite, and polyacrylamide, stirring evenly again, and then adding slow-release microorganisms, and finally stirring and drying to obtain the product.

[0122] Comparative Example 3

[0123] Compared with Example 1, step S32 is omitted in Comparative Example 3, and the rest are the same. Specifically, in this comparative example, a polyaluminum chloride-based composite sewage treatment agent is provided, which is prepared from the following raw materials by mass: 30g polyaluminum chloride, 8g slow-release microorganisms, 4g modified activated carbon, 5.5g modified attapulgite, 0.65g cocamidopropyl betaine, and 2.5g polyacrylamide.

[0124] The preparation of the modified activated carbon comprises the following steps:

[0125] S11. Add activated carbon to 5 mol / L nitric acid at a ratio of 1 g:10 mL, and perform ultrasonic treatment (80 W, 2 h) under heating conditions (40°C). After the treatment, wash and dry to obtain pre-modified activated carbon.

[0126] S12, adding the pre-modified activated carbon obtained in step S11 to water, then adding urea, stirring evenly and heating (40°C, 16 hours), drying and high-temperature treatment (nitrogen protection, 600°C, 1.5 hours) to obtain primary modified activated carbon; wherein the mass ratio of pre-modified activated carbon, water, and urea is 1:15:1;

[0127] S13. Add the primary modified activated carbon obtained in step S12 to 8 wt% ferric nitrate solution at a dosage ratio of 1 g:20 mL, stir evenly, filter, dry, and then calcine under nitrogen protection (520°C, 2h). After the treatment is completed, the modified activated carbon is obtained.

[0128] The preparation of the slow-release microorganisms comprises the following steps:

[0129] S21. Add titanium dioxide to anhydrous ethanol, stir and disperse evenly, then add KH550, and then reflux under heating conditions (85°C, 10 hours); then filter, wash, and dry to obtain a pretreated support; wherein the amount ratio of titanium dioxide, anhydrous ethanol, and KH550 is 1g:6mL:2mL;

[0130] S22. Dissolve caffeic acid in PBS buffer at a ratio of 1 mg:0.8 mL, then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, and activate under stirring (4°C, 30 min). Then add the pretreated carrier obtained in step S21, and react under heating and stirring (45°C, 4 h). After the reaction, filter, wash, and dry to obtain a modified carrier. The mass ratio of caffeic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide, and pretreated carrier is 1:1:0.4:2.

[0131] S23, the mixed bacteria (total viable count of 1 × 10 10 CFU / g, obtained by mixing Nitrobacter, Pseudomonas mendocina, and Bacillus subtilis in a ratio of 1:1:1.2 in terms of viable cell count, was added to the modified carrier obtained in step S22, and then a 2 wt % sodium alginate solution was added after stirring. After stirring again, an 8 wt % calcium chloride solution was slowly added, and then freeze-dried to obtain a slow-release microbial bacteria; wherein the mass ratio of the modified carrier to sodium alginate was 1:0.55.

[0132] The preparation of modified attapulgite comprises the following steps:

[0133] S31, adding attapulgite to 8 wt% hydrochloric acid solution at a dosage ratio of 1 g:8 mL, stirring under heating conditions (45° C., 3 h), filtering, washing, and drying to obtain modified attapulgite;

[0134] In this comparative example, a preparation method of the above-mentioned polyaluminum chloride-based composite sewage treatment agent is also provided, comprising the following steps: mixing polyaluminum chloride and cocamidopropyl betaine evenly, adding modified activated carbon, modified attapulgite, and polyacrylamide, stirring evenly again, and then adding slow-release microorganisms, and finally stirring and drying to obtain the product.

[0135] Comparative Example 4

[0136] Compared with Example 1, the use of modified activated carbon was directly omitted in Comparative Example 4, and all other conditions were the same. Specifically, this comparative example provides a polyaluminum chloride-based composite sewage treatment agent, which is prepared from the following raw materials by mass: 30g polyaluminum chloride, 8g slow-release microorganisms, 5.5g modified attapulgite, 0.65g cocamidopropyl betaine, and 2.5g polyacrylamide.

[0137] The preparation of the slow-release microorganisms comprises the following steps:

[0138] S21. Add titanium dioxide to anhydrous ethanol, stir and disperse evenly, then add KH550, and then reflux under heating conditions (85°C, 10 hours); then filter, wash, and dry to obtain a pretreated support; wherein the amount ratio of titanium dioxide, anhydrous ethanol, and KH550 is 1g:6mL:2mL;

[0139] S22. Dissolve caffeic acid in PBS buffer at a ratio of 1 mg:0.8 mL, then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, and activate under stirring (4°C, 30 min). Then add the pretreated carrier obtained in step S21, and react under heating and stirring (45°C, 4 h). After the reaction, filter, wash, and dry to obtain a modified carrier. The mass ratio of caffeic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide, and pretreated carrier is 1:1:0.4:2.

[0140] S23, the mixed bacteria (total viable count of 1 × 10 10 CFU / g, obtained by mixing Nitrobacter, Pseudomonas mendocina, and Bacillus subtilis in a ratio of 1:1:1.2 in terms of viable cell count, was added to the modified carrier obtained in step S22, and then a 2 wt % sodium alginate solution was added after stirring. After stirring again, an 8 wt % calcium chloride solution was slowly added, and then freeze-dried to obtain a slow-release microbial bacteria; wherein the mass ratio of the modified carrier to sodium alginate was 1:0.55.

[0141] The preparation of modified attapulgite comprises the following steps:

[0142] S31, adding attapulgite to 8 wt% hydrochloric acid solution at a dosage ratio of 1 g:8 mL, stirring under heating conditions (45° C., 3 h), filtering, washing, and drying to obtain pretreated attapulgite;

[0143] S32. Add boric acid to anhydrous ethanol and stir to obtain a boric acid ethanol solution (concentration of 0.08m / mL) for later use; add the pretreated attapulgite obtained in step S31 to the boric acid ethanol solution in a dosage ratio of 1g:12mL, and stir under heating conditions (60°C, 15min). After the treatment is completed, filter, wash, and dry to obtain modified attapulgite.

[0144] In this comparative example, a preparation method of the above-mentioned polyaluminum chloride-based composite sewage treatment agent is also provided, comprising the following steps: mixing polyaluminum chloride and cocamidopropyl betaine evenly, then adding modified attapulgite and polyacrylamide, stirring evenly again, then adding slow-release microorganisms, and finally stirring and drying to obtain the product.

[0145] Comparative Example 5

[0146] Compared with Example 1, the use of modified attapulgite was directly omitted in Comparative Example 5, and all other conditions were the same. Specifically, this comparative example provides a polyaluminum chloride-based composite sewage treatment agent, which is prepared from the following raw materials by mass: 30g polyaluminum chloride, 8g slow-release microorganisms, 4g modified activated carbon, 0.65g cocamidopropyl betaine, and 2.5g polyacrylamide.

[0147] The preparation of the modified activated carbon comprises the following steps:

[0148] S11. Add activated carbon to 5 mol / L nitric acid at a ratio of 1 g:10 mL, and perform ultrasonic treatment (80 W, 2 h) under heating conditions (40°C). After the treatment, wash and dry to obtain pre-modified activated carbon.

[0149] S12, adding the pre-modified activated carbon obtained in step S11 to water, then adding urea, stirring evenly and heating (40°C, 16 hours), drying and high-temperature treatment (nitrogen protection, 600°C, 1.5 hours) to obtain primary modified activated carbon; wherein the mass ratio of pre-modified activated carbon, water, and urea is 1:15:1;

[0150] S13. Add the primary modified activated carbon obtained in step S12 to 8 wt% ferric nitrate solution at a dosage ratio of 1 g:20 mL, stir evenly, filter, dry, and then calcine under nitrogen protection (520°C, 2h). After the treatment is completed, the modified activated carbon is obtained.

[0151] The preparation of the slow-release microorganisms comprises the following steps:

[0152] S21. Add titanium dioxide to anhydrous ethanol, stir and disperse evenly, then add KH550, and then reflux under heating conditions (85°C, 10 hours); then filter, wash, and dry to obtain a pretreated support; wherein the amount ratio of titanium dioxide, anhydrous ethanol, and KH550 is 1g:6mL:2mL;

[0153] S22. Dissolve caffeic acid in PBS buffer at a ratio of 1 mg:0.8 mL, then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, and activate under stirring (4°C, 30 min). Then add the pretreated carrier obtained in step S21, and react under heating and stirring (45°C, 4 h). After the reaction, filter, wash, and dry to obtain a modified carrier. The mass ratio of caffeic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide, and pretreated carrier is 1:1:0.4:2.

[0154] S23, the mixed bacteria (total viable count of 1 × 10 10 CFU / g, obtained by mixing Nitrobacter, Pseudomonas mendocina, and Bacillus subtilis in a ratio of 1:1:1.2 in terms of viable cell count, was added to the modified carrier obtained in step S22, and then a 2 wt % sodium alginate solution was added after stirring. After stirring again, an 8 wt % calcium chloride solution was slowly added, and then freeze-dried to obtain a slow-release microbial bacteria; wherein the mass ratio of the modified carrier to sodium alginate was 1:0.55.

[0155] In this comparative example, a preparation method of the above-mentioned polyaluminum chloride-based composite sewage treatment agent is also provided, comprising the following steps: mixing polyaluminum chloride and cocamidopropyl betaine evenly, then adding modified activated carbon and polyacrylamide, stirring evenly again, then adding slow-release microorganisms, and finally stirring and drying to obtain the product.

[0156] The performance of the polyaluminium chloride-based composite sewage treatment agent prepared in Example 1 and Comparative Examples 1 to 5 was tested. The specific method is as follows: K2Cr2O7 was added to pure tap water so that Cr 6+The concentration of the wastewater was 100 mg / L; ammonium chloride was added to make the concentration of ammonium ions 40 mg / L; potassium dihydrogen phosphate was added to make the concentration of phosphate ions 40 mg / L, and after stirring evenly, simulated wastewater was prepared. Then, an equal amount of the above-mentioned simulated wastewater was taken, and the polyaluminum chloride-based composite sewage treatment agent prepared in Example 1 and Comparative Examples 1 to 5 was added at 0.15 g / L, and stirred at 40 rpm for 5 minutes. The test groups maintained the same conditions. Then, samples were immediately taken to measure the phosphate ions, ammonium ions and Cr 6+ The removal rate of the above substances was calculated; after stopping the stirring, the mixture was allowed to stand for 12 hours, and the content of the above substances was tested again. 6+ The spectrophotometer was used for detection. The detection method is relatively common and can be performed using existing general methods. This will not be described in detail here. The test results are shown in Table 1.

[0157] Table 1 Removal rate results of various substances

[0158]

[0159] As can be seen from Table 1, the polyaluminum chloride-based composite sewage treatment agent prepared in the embodiment of the present invention can achieve very good treatment effect within 5 minutes, and can simultaneously and efficiently remove ammonium ions, phosphate ions and Cr 6+ , meeting the high-level sewage treatment discharge requirements; at the same time, from the comparison of the treatment results of 12h and 5min, as the treatment time increases, the slow-release bacteria gradually play a role and can also achieve better treatment effects, which is suitable for the long-term treatment needs of flowing water bodies.

[0160] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A polyaluminium chloride-based composite sewage treatment agent, characterized in that: The invention is prepared from the following raw materials in parts by weight: 20-35 parts of polyaluminium chloride, 5-12 parts of slow-release microorganisms, 3-6 parts of modified activated carbon, 4-8 parts of modified attapulgite, 0.5-1.2 parts of cocamidopropyl betaine and 2-5 parts of polyacrylamide.

2. A polyaluminum chloride-based composite sewage treatment agent according to claim 1, characterized in that: The preparation of the modified activated carbon comprises the following steps: S11, adding activated carbon to nitric acid, performing ultrasonic treatment under heating conditions, and after the treatment is completed, washing and drying to obtain pre-modified activated carbon; S12, adding the pre-modified activated carbon obtained in step S11 to water, then adding urea, stirring evenly and then heating. After the treatment is completed, drying and high-temperature treatment are performed to obtain primary modified activated carbon; S13, adding the primary modified activated carbon obtained in step S12 to the ferric nitrate solution, stirring evenly, filtering, drying, and then calcining under nitrogen protection to obtain modified activated carbon.

3. A polyaluminium chloride-based composite sewage treatment agent according to claim 2, characterized in that: In step S11, the concentration of nitric acid is 4-6 mol / L, the heating temperature is 35-45°C, the ultrasonic treatment power is 50-100 W, and the ultrasonic treatment time is 1-4 h; the usage ratio of activated carbon to nitric acid is 1 g:8-15 mL; In step S12, the mass ratio of pre-modified activated carbon, water, and urea is 1:10-20:0.8-1.2; the heating treatment temperature is 35-55°C, and the treatment time is 12-36 hours; the high-temperature treatment is carried out under nitrogen protection, the treatment temperature is 550-650°C, and the treatment time is 1-4 hours; In step S13, the concentration of the ferric nitrate solution is 5-10 wt %, the usage ratio of the primary modified activated carbon to the ferric nitrate solution is 1 g:15-30 mL, the calcination treatment temperature is 500-580° C., and the treatment time is 1-4 h.

4. A polyaluminium chloride-based composite sewage treatment agent according to claim 1, characterized in that: The preparation of the slow-release microorganism comprises the following steps: S21, adding titanium dioxide to anhydrous ethanol, stirring and dispersing it uniformly, adding KH550, and then reflux reaction under heating conditions; then filtering, washing, and drying to obtain a pretreated support; S22, dissolving caffeic acid in PBS buffer, then adding 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, and activating under stirring, then adding the pretreated support obtained in step S21, and reacting under heating and stirring; after the reaction is completed, filtering, washing, and drying to obtain a modified support; S23, adding the mixed bacteria to the modified carrier obtained in step S22, stirring, then adding sodium alginate solution, stirring evenly again, then slowly adding calcium chloride solution, and then freeze-drying to obtain slow-release microorganisms.

5. A polyaluminium chloride-based composite sewage treatment agent according to claim 4, characterized in that: In step S21, the ratio of titanium dioxide, anhydrous ethanol, and KH550 is 1 g: 5-10 mL: 1-3 mL; The reflux reaction temperature is 80~85℃, and the reaction time is 8~16h.

6. A polyaluminium chloride-based composite sewage treatment agent according to claim 4, characterized in that: In step S22, the ratio of caffeic acid to PBS buffer is 1 mg: 0.5-1 mL; The mass ratio of caffeic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide, and pretreated carrier is 1:0.8~1.2:0.3~0.5:1.5~2.5; The activation temperature is 4°C and the activation time is 20~50min; The heating and stirring temperature is 40~55℃, and the reaction time under heating and stirring is 3~6h.

7. A polyaluminium chloride-based composite sewage treatment agent according to claim 4, characterized in that: In step S23, the total viable count of the mixed bacteria is not less than 1×10 10 CFU / g; the mixed bacteria were obtained by mixing Nitrobacter, Pseudomonas mendocina, and Bacillus subtilis at a ratio of 1:1:1.2; The mass concentration of sodium alginate solution is 1.5~3%, and the mass concentration of calcium chloride solution is 5~10%; The mass ratio of the modified carrier to sodium alginate is 1:0.45~0.

65.

8. A polyaluminum chloride-based composite sewage treatment agent according to claim 1, characterized in that: The preparation of modified attapulgite comprises the following steps: S31, adding attapulgite to a hydrochloric acid solution, stirring under heating conditions, filtering, washing, and drying to obtain pretreated attapulgite; S32. Add boric acid to anhydrous ethanol and stir to obtain a boric acid ethanol solution for later use; add the pretreated attapulgite obtained in step S31 to the boric acid ethanol solution and stir under heating conditions. After the treatment is completed, filter, wash and dry to obtain modified attapulgite.

9. A polyaluminium chloride-based composite sewage treatment agent according to claim 8, characterized in that: In step S31, the concentration of the hydrochloric acid solution is 5-10 wt %, the ratio of attapulgite to hydrochloric acid solution is 1 g: 5-10 mL; the heating temperature is 40-55° C., and the stirring treatment time is 1-4 h; In step S32, the concentration of the boric acid ethanol solution is 0.05-0.1 g / mL; the usage ratio of the pretreated attapulgite and the boric acid ethanol solution is 1 g:10-15 mL; the heating temperature is 55-70° C., and the stirring treatment time is 5-20 min.

10. A method for preparing the polyaluminum chloride-based composite sewage treatment agent according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: uniformly mixing polyaluminum chloride and cocamidopropyl betaine, then adding modified activated carbon, modified attapulgite and polyacrylamide, stirring evenly again, then adding slow-release microorganisms, and finally stirring and drying to obtain the product.

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