An inorganic composite flocculant and its preparation method and application

Abstract

The present invention belongs to the field of wastewater treatment, specifically an inorganic composite flocculant and its preparation method and application. Using clay and mica powder as raw materials, sodium hydroxide is used for dissolution to obtain a solution containing a large amount of silicate, aluminate and a variety of metal ions with flocculation ability, and then microcrystalline cellulose is used as the nucleation center, ethylenediaminetetraacetic acid and sodium dodecylbenzene sulfonate are used to control the morphology, and a hydrothermal method is used for polycondensation to obtain a new type of nanoparticles, and then high-temperature calcination is performed to remove the microcrystalline cellulose to obtain nanoparticles with high adsorption. Then, the highly adsorbable nanoparticles are added to the polysilicate metal salt flocculant system to obtain an inorganic composite flocculant, which has high flocculation ability, extremely fast flocculation speed and excellent decolorization effect, and the residual rate in water is extremely low, which has very practical application value for the pretreatment of industrial wastewater and water supply and drainage.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment, and specifically relates to an inorganic composite flocculant and a preparation method and application thereof. Background Art

[0002] Flocculation technology plays a vital role in treating water pollution and protecting water resources. Flocculants have been widely used in the field of water treatment at home and abroad because of their irreplaceable advantages such as high cost performance and convenience of use. Common flocculants in water treatment at home and abroad are divided into three categories: organic flocculants, inorganic flocculants and microbial flocculants. Among them, inorganic flocculants occupy a large proportion in the research of flocculants due to their many advantages such as low price, low pollution to the environment and simple process. Among inorganic flocculants, inorganic polymer flocculants (IPF) are divided into three categories: cationic, anionic and composite. Because they have better water treatment performance and outstanding characteristics compared with other types of flocculants, they are also called the second generation of inorganic flocculants.

[0003] Organic flocculants mainly include organic high molecular polymers such as polyacrylamide. Organic flocculants have many advantages such as low dosage, strong flocculation ability, wide pH range, good precipitation effect, etc. However, the price of this substance is relatively high, and the residual monomers are biologically toxic, and some have "three-cause" effects (teratogenic, carcinogenic, and mutagenic). Therefore, the safety of the use of organic flocculants has always been a technical bottleneck. The development of non-toxic and efficient flocculants is the current research goal.

[0004] Inorganic polymer composite flocculants refer to inorganic polymer products that contain multiple ions with flocculation or coagulant effects, such as iron salts, aluminum salts and silicates, and are finally hydroxylated through a specific process. It can be a composite of several cationic flocculants, or a cationic inorganic polymer coagulant with negatively charged polysilicic acid, such as polyferric silicate sulfate (PFSS), polyferric silicate chloride (PFSC), polyferric silicate (PFSI) aluminum iron silicon copolymer (PAFSC), etc. They can be mixed after hydroxylation polymerization, or they can be mixed first and then hydroxylated polymerization to form a hydroxylated inorganic polymer form with a higher degree of polymerization. Since iron-based flocculants can form larger flocs and have good settling performance, they are highly corrosive, have low stability, and are prone to produce a large amount of sludge. Aluminum-based flocculants have poor settling performance and smaller flocs. The production process of some polyaluminum-based flocculants is complicated. Polysilicate flocculants have a large molecular weight and have a good net-catching and sweeping effect on suspended matter in water, but they are negatively charged and have poor electrical neutralization performance for colloids. The above three inorganic flocculants have their own characteristics. Therefore, the multifunctional and efficient flocculant that can combine the advantages of various flocculants and overcome their disadvantages has become the research direction.

[0005] The general direction of the current development of inorganic polymer flocculants is "polymerization, compounding, serialization, specialization, and multifunctionalization". In addition to the fact that the treatment effect of the commonly used aluminum-based coagulants is greatly affected by the temperature and alkalinity of the water, there is also the problem of biological toxicity of residual aluminum. With the increasing awareness of health and environmental protection, this problem has become more prominent. In recent years, there has been a trend of replacing aluminum salts with iron salts, but iron salts have some obvious disadvantages, especially in storage and application. They are highly hygroscopic and corrosive, have a large residual color after water treatment, and combine with humus to generate strong color.

[0006] In order to enhance the flocculation ability of the flocculant, in the prior art, CN 108928874 B adopts a hydrothermal method to prepare a modified magnesium-aluminum inorganic composite flocculant, 2 mol / L of crystalline aluminum chloride solution and magnesium chloride solution are mixed evenly, 4 mol / L of NaOH solution is slowly added to the magnesium-aluminum mixed solution at a certain drop rate, and the reaction is fully reacted and mixed; a small amount of adsorbent powder is slowly added to the mixed solution, and the mixture is fully stirred and mixed for 40 minutes; the reaction product is transferred to a hydrothermal reactor, the reaction temperature and time are controlled, and the filtrate is cooled and filtered, and the filtrate obtained is the prepared modified magnesium-aluminum inorganic composite flocculant. It uses an adsorbent and a flocculant to enhance the flocculation ability and flocculation speed of the flocculant. The present invention believes that this is a new and effective way to enhance the flocculation ability of the flocculant, but the inorganic adsorbent is mostly nanoparticles, which are very easy to remain in the water, which is not conducive to human health. Therefore, it is necessary to develop a new inorganic composite flocculant with low residual rate, strong flocculation ability and fast flocculation speed. Summary of the invention

[0007] A method for preparing an inorganic composite flocculant comprises the following steps: preparing highly adsorbable nanoparticles, preparing a polysilicic acid solution, and mixing and stirring the highly adsorbable nanoparticles, FeCl2, aluminum chloride, and the polysilicic acid solution to obtain the inorganic composite flocculant.

[0008] Preferably, a method for preparing an inorganic composite flocculant comprises the following steps:

[0009] (1) Preparation of highly adsorbable nanoparticles;

[0010] (2) preparing a polysilicic acid solution;

[0011] (3) Add 5-10 parts by mass of the highly adsorbent nanoparticles obtained in step (1), 1-2 parts of FeCl2, and 1-2 parts of aluminum chloride to 100-120 parts of the polysilicic acid solution obtained in step (2), and stir at a speed of 100-200 r / min for 12-24 hours to obtain the inorganic composite flocculant.

[0012] The method for preparing highly adsorbable nanoparticles comprises the following steps: adding 5-10 parts of clay and 5-10 parts of mica powder to 100-120 parts of sodium hydroxide aqueous solution by weight, stirring at a speed of 100-200 r / min for 30-60 min, adding 3-5 parts of microcrystalline cellulose and 5-10 parts of surfactant thereto, and continuing to stir at a speed of 100-200 r / min for 20-40 min to obtain an emulsion; then adjusting the pH of the emulsion to 6-7 with 8-10wt% sulfuric acid under continuous stirring, stopping stirring to obtain a slightly acidic emulsion, transferring the obtained slightly acidic emulsion to a hydrothermal reaction kettle, reacting at 110-120°C for 12-24h, cooling to room temperature, centrifuging to obtain a precipitate, washing, drying, and then calcining at 700-900°C for 3-5h, and cooling to room temperature to obtain highly adsorbable nanoparticles;

[0013] The concentration of the sodium hydroxide aqueous solution is 30-50 wt %.

[0014] The surfactant is at least one of ethylenediaminetetraacetic acid and sodium dodecylbenzene sulfonate; preferably, the surfactant is a mixture of ethylenediaminetetraacetic acid and sodium dodecylbenzene sulfonate in a mass ratio of (1-2): (2-4).

[0015] The preparation method of the polysilicic acid solution comprises the following steps: adding 235-240 parts of sodium silicate into 760-770 parts of water by mass, stirring continuously at a speed of 100-200 r / min, adjusting the pH value to 1-3 with 8-10wt% sulfuric acid, stirring and polymerizing at room temperature for 3-4 hours, and then aging at room temperature for 5-7 hours to obtain the polysilicic acid solution.

[0016] Polysilicate metal salt flocculants are widely used in actual production processes due to their excellent properties and have good prospects. Polysilicate metal salt flocculants have both electrical neutralization and adsorption bridging effects, and are easy to prepare, cheap and have good flocculation effects. They have received great attention in the field of water treatment. However, a single polysilicate metal salt flocculant has the problems of poor decolorization effect and low flocculation ability.

[0017] In order to enhance the flocculation ability of the flocculant and reduce the residual inorganic nanoparticles in the flocculant, the present invention uses clay and mica powder as raw materials, adopts sodium hydroxide for dissolution, obtains a solution containing a large amount of silicate, aluminate and a variety of metal ions with flocculation ability, then uses microcrystalline cellulose as the nucleation center, uses ethylenediaminetetraacetic acid and sodium dodecylbenzene sulfonate to control the morphology, adopts hydrothermal polycondensation, obtains a new type of nanoparticles, and then high-temperature calcination removes the microcrystalline cellulose to obtain nanoparticles with high adsorption. The nanoparticles not only have high adsorption, but also have a high removal rate for dyeing factors in water, and can also be polycondensed with polysilicic acid to form a large flocculation group, which is removed after precipitation, and the residual amount in the water is extremely small.

[0018] The effect of microcrystalline cellulose treated with kaolin and mica powder is better than that of single kaolin or single mica powder. The present invention believes that this is due to the different ratios of aluminum oxide and silicon dioxide contained in kaolin and mica powder, and the different trace metal elements contained in them. The two are used in combination, dissolved in sodium hydroxide, and then subjected to hydrothermal reaction, which can form a structure with high porosity on the surface of microcrystalline cellulose, that is, it has extremely high adsorption and the ability to quickly release metal ions. Its high adsorption enables it to quickly remove insoluble substances in water, form flocculent precipitation, and has a good removal effect on phosphorus. Here, microcrystalline cellulose is mainly used as the nucleation center of the hydrothermal reaction of clay and mica powder solution. Its main component is a linear polysaccharide bonded by β-1,4-glucosidic bonds. It is a white, odorless, tasteless crystalline powder composed of extremely fine short rods or powdered porous particles that can flow freely after natural cellulose is hydrolyzed to the limit degree of polymerization (LODP) by dilute acid. It contains a large number of hydroxyl groups and has excellent adsorption and chelation effects on silicate and aluminate. It can make the silicate and aluminate in the clay and mica powder solution condense with microcrystalline cellulose as the nucleation center, which can ensure the uniformity of the morphology and structure of the generated product. It is supplemented by ethylenediaminetetraacetic acid and sodium dodecylbenzene sulfonate to regulate the morphology and structure, and generate microspheres with high porosity, which can greatly increase its surface area, thereby improving its adsorption capacity and metal ion release capacity. However, due to the good adsorption of metal ions by microcrystalline cellulose, it hinders the release of metal ions by highly adsorbable nanoparticles to a certain extent, which is not conducive to the decolorization of water bodies. Therefore, the present invention further adopts high-temperature calcination to carbonize the microcrystalline cellulose, which not only reduces the effect of the microcrystalline cellulose on the release of metal ions, but also forms a unique mesoporous structure, further enhancing the adsorption of the nanoparticles.

[0019] Beneficial effects of the present invention:

[0020] Using clay and mica powder as raw materials, sodium hydroxide was used for dissolution to obtain a solution containing a large amount of silicate, aluminate and a variety of metal ions with flocculation ability. Then, microcrystalline cellulose was used as the nucleation center, ethylenediaminetetraacetic acid and sodium dodecylbenzene sulfonate were used to control the morphology, and a new type of nanoparticles was obtained by hydrothermal polycondensation. The microcrystalline cellulose was then calcined at high temperature to remove the microcrystalline cellulose, and nanoparticles with high adsorption were obtained. Then, this highly adsorbable nanoparticle was added to the polysilicate metal salt flocculant system to obtain an inorganic composite flocculant with high flocculation ability, extremely fast flocculation speed and excellent decolorization effect, and the residual rate in water was extremely low, which has very practical application value for the pretreatment of industrial wastewater and water supply and drainage. DETAILED DESCRIPTION

[0021] The concentration of the sulfuric acid is 10 wt %.

[0022] White clay, product number: 1598536, Jinan Huiteng Chemical Co., Ltd.

[0023] Mica powder, model: 26520, Hubei Shiteng Chemical Technology Co., Ltd.

[0024] Microcrystalline cellulose, CAS: 9004-34-6, product number: HS91008, Shanghai Hushi Pharmaceutical Technology Co., Ltd.

[0025] Example 1

[0026] A method for preparing an inorganic composite flocculant comprises the following steps:

[0027] (1) By weight, 20 parts of clay were added to 120 parts of sodium hydroxide aqueous solution, stirred at 200 r / min for 40 min, then 5 parts of microcrystalline cellulose and 10 parts of surfactant were added thereto, and stirred at 200 r / min for 30 min to obtain an emulsion; then, the pH of the emulsion was adjusted to 7 with sulfuric acid under continuous stirring, and stirring was stopped to obtain a slightly acidic emulsion. The obtained slightly acidic emulsion was transferred to a hydrothermal reactor, reacted at 120° C. for 24 h, cooled to room temperature, centrifuged to obtain a precipitate, washed, dried, and then calcined at 800° C. for 4 h. After cooling to room temperature, highly adsorbable nanoparticles were obtained;

[0028] (2) adding 236.50 parts of sodium silicate to 763.5 parts of water, stirring at 200 r / min, adjusting the pH value to 2 with sulfuric acid, stirring and polymerizing at room temperature for 3 hours, and then aging at room temperature for 6 hours to obtain a polysilicic acid solution;

[0029] (3) By mass, 7 parts of the highly adsorbent nanoparticles obtained in step (1), 1.6 parts of FeCl2 and 1.4 parts of aluminum chloride were added to 110 parts of the polysilicic acid solution obtained in step (2), and stirred at a speed of 200 r / min for 12 hours to obtain the inorganic composite flocculant.

[0030] The concentration of the sodium hydroxide aqueous solution in step (1) is 50wt%.

[0031] The surfactant in step (1) is prepared by mixing ethylenediaminetetraacetic acid and sodium dodecylbenzenesulfonate in a mass ratio of 2:3.

[0032] Example 2

[0033] A method for preparing an inorganic composite flocculant comprises the following steps:

[0034] (1) Add 20 parts of mica powder to 120 parts of sodium hydroxide aqueous solution by mass, stir at 200 r / min for 40 min, then add 5 parts of microcrystalline cellulose and 10 parts of surfactant, continue to stir at 200 r / min for 30 min to obtain an emulsion; then adjust the pH of the emulsion to 7 with sulfuric acid under continuous stirring, stop stirring to obtain a slightly acidic emulsion, transfer the obtained slightly acidic emulsion to a hydrothermal reactor, place it at 120° C. for reaction for 24 h, cool it to room temperature, centrifuge to obtain a precipitate, wash it, dry it, and then place it at 800° C. for calcination for 4 h, cool it to room temperature, and obtain highly adsorbable nanoparticles;

[0035] (2) adding 236.50 parts of sodium silicate to 763.5 parts of water, stirring at 200 r / min, adjusting the pH value to 2 with sulfuric acid, stirring and polymerizing at room temperature for 3 hours, and then aging at room temperature for 6 hours to obtain a polysilicic acid solution;

[0036] (3) By mass, 7 parts of the highly adsorbent nanoparticles obtained in step (1), 1.6 parts of FeCl2 and 1.4 parts of aluminum chloride were added to 110 parts of the polysilicic acid solution obtained in step (2), and stirred at a speed of 200 r / min for 12 hours to obtain the inorganic composite flocculant.

[0037] The concentration of the sodium hydroxide aqueous solution in step (1) is 50wt%.

[0038] The surfactant in step (1) is prepared by mixing ethylenediaminetetraacetic acid and sodium dodecylbenzenesulfonate in a mass ratio of 2:3.

[0039] Example 3

[0040] A method for preparing an inorganic composite flocculant comprises the following steps:

[0041] (1) By weight, 10 parts of clay and 10 parts of mica powder were added to 120 parts of sodium hydroxide aqueous solution, stirred at 200 r / min for 40 min, and then 5 parts of microcrystalline cellulose and 10 parts of surfactant were added thereto, and the mixture was stirred at 200 r / min for 30 min to obtain an emulsion; then, the pH of the emulsion was adjusted to 7 with sulfuric acid under continuous stirring, and the stirring was stopped to obtain a slightly acidic emulsion. The obtained slightly acidic emulsion was transferred to a hydrothermal reactor, reacted at 120° C. for 24 h, cooled to room temperature, centrifuged to obtain a precipitate, washed, dried, and then calcined at 800° C. for 4 h, and cooled to room temperature to obtain highly adsorbable nanoparticles;

[0042] (2) adding 236.50 parts of sodium silicate to 763.5 parts of water, stirring at 200 r / min, adjusting the pH value to 2 with sulfuric acid, stirring and polymerizing at room temperature for 3 hours, and then aging at room temperature for 6 hours to obtain a polysilicic acid solution;

[0043] (3) By mass, 7 parts of the highly adsorbent nanoparticles obtained in step (1), 1.6 parts of FeCl2 and 1.4 parts of aluminum chloride were added to 110 parts of the polysilicic acid solution obtained in step (2), and stirred at a speed of 200 r / min for 12 hours to obtain the inorganic composite flocculant.

[0044] The concentration of the sodium hydroxide aqueous solution in step (1) is 50wt%.

[0045] The surfactant in step (1) is prepared by mixing ethylenediaminetetraacetic acid and sodium dodecylbenzenesulfonate in a mass ratio of 2:3.

[0046] Example 4

[0047] A method for preparing an inorganic composite flocculant comprises the following steps:

[0048] (1) By weight, 10 parts of clay and 10 parts of mica powder were added to 120 parts of sodium hydroxide aqueous solution, stirred at 200 r / min for 40 min, and then 10 parts of surfactant were added thereto, and the mixture was stirred at 200 r / min for 30 min to obtain an emulsion; then, the pH of the emulsion was adjusted to 7 with sulfuric acid under continuous stirring, and stirring was stopped to obtain a slightly acidic emulsion. The obtained slightly acidic emulsion was transferred to a hydrothermal reactor, reacted at 120° C. for 24 h, cooled to room temperature, centrifuged to obtain a precipitate, washed, dried, and then calcined at 800° C. for 4 h, and cooled to room temperature to obtain highly adsorbable nanoparticles;

[0049] (2) adding 236.50 parts of sodium silicate to 763.5 parts of water, stirring at 200 r / min, adjusting the pH value to 2 with sulfuric acid, stirring and polymerizing at room temperature for 3 hours, and then aging at room temperature for 6 hours to obtain a polysilicic acid solution;

[0050] (3) By mass, 7 parts of the highly adsorbent nanoparticles obtained in step (1), 1.6 parts of FeCl2 and 1.4 parts of aluminum chloride were added to 110 parts of the polysilicic acid solution obtained in step (2), and stirred at a speed of 200 r / min for 12 hours to obtain the inorganic composite flocculant.

[0051] The concentration of the sodium hydroxide aqueous solution in step (1) is 50wt%.

[0052] The surfactant in step (1) is prepared by mixing ethylenediaminetetraacetic acid and sodium dodecylbenzenesulfonate in a mass ratio of 2:3.

[0053] Example 5

[0054] A method for preparing an inorganic composite flocculant comprises the following steps:

[0055] (1) By weight, 10 parts of clay and 10 parts of mica powder were added to 120 parts of sodium hydroxide aqueous solution, stirred at 200 r / min for 40 minutes, and then 5 parts of microcrystalline cellulose were added thereto, and the mixture was stirred at 200 r / min for 30 minutes to obtain an emulsion; then, the pH of the emulsion was adjusted to 7 with sulfuric acid under continuous stirring, and the stirring was stopped to obtain a slightly acidic emulsion. The obtained slightly acidic emulsion was transferred to a hydrothermal reactor, reacted at 120° C. for 24 hours, cooled to room temperature, centrifuged to obtain a precipitate, washed, dried, and then calcined at 800° C. for 4 hours. After cooling to room temperature, highly adsorbable nanoparticles were obtained;

[0056] (2) adding 236.50 parts of sodium silicate to 763.5 parts of water, stirring at 200 r / min, adjusting the pH value to 2 with sulfuric acid, stirring and polymerizing at room temperature for 3 hours, and then aging at room temperature for 6 hours to obtain a polysilicic acid solution;

[0057] (3) By mass, 7 parts of the highly adsorbent nanoparticles obtained in step (1), 1.6 parts of FeCl2 and 1.4 parts of aluminum chloride were added to 110 parts of the polysilicic acid solution obtained in step (2), and stirred at a speed of 200 r / min for 12 hours to obtain the inorganic composite flocculant.

[0058] The concentration of the sodium hydroxide aqueous solution in step (1) is 50wt%.

[0059] Comparative Example 1

[0060] A method for preparing an inorganic composite flocculant comprises the following steps:

[0061] (1) By weight, 10 parts of clay and 10 parts of mica powder were added to 120 parts of sodium hydroxide aqueous solution, stirred at 200 r / min for 40 min, and continued to stir at 200 r / min for 30 min to obtain an emulsion; then, the pH of the emulsion was adjusted to 7 with sulfuric acid under continuous stirring, and stirring was stopped to obtain a slightly acidic emulsion. The obtained slightly acidic emulsion was transferred to a hydrothermal reactor, placed at 120° C. for reaction for 24 h, cooled to room temperature, centrifuged to obtain a precipitate, washed, dried, and then placed at 800° C. for calcination for 4 h. After cooling to room temperature, highly adsorbent nanoparticles were obtained;

[0062] (2) adding 236.50 parts of sodium silicate to 763.5 parts of water, stirring at 200 r / min, adjusting the pH value to 2 with sulfuric acid, stirring and polymerizing at room temperature for 3 hours, and then aging at room temperature for 6 hours to obtain a polysilicic acid solution;

[0063] (3) By mass, 7 parts of the highly adsorbent nanoparticles obtained in step (1), 1.6 parts of FeCl2 and 1.4 parts of aluminum chloride were added to 110 parts of the polysilicic acid solution obtained in step (2), and stirred at a speed of 200 r / min for 12 hours to obtain the inorganic composite flocculant.

[0064] The concentration of the sodium hydroxide aqueous solution in step (1) is 50wt%.

[0065] Comparative Example 2

[0066] A method for preparing an inorganic composite flocculant comprises the following steps:

[0067] (1) adding 236.50 parts of sodium silicate to 763.5 parts of water, stirring at 200 r / min, adjusting the pH value to 2 with sulfuric acid, stirring and polymerizing at room temperature for 3 hours, and then aging at room temperature for 6 hours to obtain a polysilicic acid solution;

[0068] (2) By mass, 1.6 parts of FeCl2 and 1.4 parts of aluminum chloride were added to 110 parts of the polysilicic acid solution obtained in step (1), and stirred at a speed of 200 r / min for 12 hours to obtain the inorganic composite flocculant.

[0069] Test Example 1

[0070] The water sample used in the test was: phosphorus-containing wastewater with a turbidity of 40NTU and a concentration of 25mg / L prepared in the laboratory.

[0071] Flocculation test process

[0072] Take 400 mL of water sample and put it in a 500 mL beaker, add 40 mg of the inorganic composite flocculant prepared by the present invention into the beaker, use an automatic stirrer to quickly stir at 180 r / min for 2 minutes, then slowly stir at 30 r / min for 10 minutes. After the stirring is completed, take it off and let it stand for 20 minutes, take the supernatant about 3 cm below the liquid surface to measure the residual turbidity and residual phosphorus content, and obtain the turbidity removal rate and phosphorus removal rate.

[0073] In this test, turbidity and phosphorus were determined by spectrophotometry and ammonium molybdate spectrophotometry, respectively.

[0074] Table 1: Flocculation test results

[0075]

[0076]

[0077] Test Example 2

[0078] Flocculation decolorization experiment

[0079] Water sample for the test: Direct blended orange D-GGL was selected for dyeing according to conventional prescription and process. Then the dyeing residual liquid was collected to obtain the water sample for the test.

[0080] Flocculation test process

[0081] Take 400 mL of water sample in a 500 mL beaker, add 40 mg of the inorganic composite flocculant prepared by the present invention into the beaker, use an automatic stirrer to quickly stir at 180 r / min for 5 minutes, then slowly stir at 30 r / min for 10 minutes. After the stirring is completed, take it off and let it stand for 20 minutes, take the COD content and chromaticity of the supernatant about 3 cm below the liquid surface, and obtain the COD removal rate and decolorization rate.

[0082] In this test, the COD content and decolorization rate were determined by spectrophotometry.

[0083] Table 2: Flocculation decolorization test results

[0084] COD removal rate / % Decolorization rate / % Example 1 86.7 89.2 Example 2 86.9 88.3 Example 3 93.8 94.8 Example 4 91.4 92.7 Example 5 90.2 91.6 Comparative Example 1 81.4 83.1 Comparative Example 2 72.1 73.6

[0085] It can be seen from Table 1 and Table 2 that the inorganic composite flocculant prepared by the present invention has an excellent turbidity removal rate and phosphorus removal rate. Among them, Example 3 has the best effect, while the effects of Example 1 and Example 2 are slightly worse than Example 3, which shows that the effect of microcrystalline cellulose treated with kaolin and mica powder is better than that of single kaolin or single mica powder. The present invention believes that this is due to the different proportions of aluminum oxide and silicon dioxide contained in kaolin and mica powder, and the different trace metal elements contained in them. The two are used in combination, dissolved in sodium hydroxide, and then subjected to hydrothermal reaction, which can form a structure with high porosity on the surface of microcrystalline cellulose, that is, it has extremely high adsorption and the ability to quickly release metal ions. Its high adsorption enables it to quickly remove insoluble substances in water, form flocculent precipitation, and has a good removal effect on phosphorus. Here, microcrystalline cellulose is mainly used as the nucleation center of the hydrothermal reaction of clay and mica powder solution. Its main component is a linear polysaccharide bonded by β-1,4-glucosidic bonds. It is a white, odorless, tasteless crystalline powder composed of extremely fine short rods or powdered porous particles that can flow freely after natural cellulose is hydrolyzed to the limit degree of polymerization (LODP) by dilute acid. It contains a large number of hydroxyl groups and has excellent adsorption and chelation effects on silicate and aluminate. It can make the silicate and aluminate in the clay and mica powder solution condense with microcrystalline cellulose as the nucleation center, which can ensure the uniformity of the morphology and structure of the generated product. It is supplemented by ethylenediaminetetraacetic acid and sodium dodecylbenzene sulfonate to regulate the morphology and structure, and generate microspheres with high porosity, which can greatly increase its surface area, thereby improving its adsorption capacity and metal ion release capacity. However, due to the good adsorption of metal ions by microcrystalline cellulose, it hinders the release of metal ions by highly adsorbable nanoparticles to a certain extent, which is not conducive to the decolorization of water bodies. Therefore, the present invention further adopts high temperature calcination to carbonize the microcrystalline cellulose, which not only reduces the effect of the microcrystalline cellulose on the release of metal ions, but also forms a unique mesoporous structure, further enhancing the adsorption of the nanoparticles. Therefore, the turbidity removal rate, phosphorus removal rate and decolorization rate of Example 3 are better than those of Example 4, Example 5 and Comparative Example 1 and Comparative Example 2.

Claims

1. A method for preparing an inorganic composite flocculant, characterized in that: The following steps are involved: preparing highly adsorbent nanoparticles, preparing a polysilicic acid solution, mixing and stirring the highly adsorbent nanoparticles, FeCl2, aluminum chloride, and the polysilicic acid solution to obtain an inorganic composite flocculant; The preparation method of the highly adsorbable nanoparticles, The method comprises the following steps: adding 5-10 parts of clay and 5-10 parts of mica powder to 100-120 parts of sodium hydroxide aqueous solution by weight, stirring at a speed of 100-200 r / min for 30-60 min, adding 3-5 parts of microcrystalline cellulose and 5-10 parts of a surfactant thereto, and continuing to stir at a speed of 100-200 r / min for 20-40 min to obtain an emulsion; Then, under continuous stirring, the pH of the emulsion is adjusted to 6-7 with sulfuric acid, and the stirring is stopped to obtain a slightly acidic emulsion. The slightly acidic emulsion is transferred to a hydrothermal reactor, placed at 110-120°C for reaction for 12-24 hours, cooled to room temperature, centrifuged to obtain a precipitate, washed, dried, calcined, and cooled to room temperature to obtain highly adsorbable nanoparticles.

2. The method for preparing the inorganic composite flocculant according to claim 1, characterized in that: The concentration of the sodium hydroxide aqueous solution is 30-50 wt %.

3. The method for preparing the inorganic composite flocculant according to claim 1, characterized in that: The surfactant is at least one of ethylenediaminetetraacetic acid and sodium dodecylbenzene sulfonate.

4. The method for preparing the inorganic composite flocculant according to claim 1, characterized in that: The concentration of the sulfuric acid is 8-10 wt %.

5. The method for preparing the inorganic composite flocculant according to claim 1, characterized in that: The calcination temperature is 700-900° C. and the calcination time is 3-5 hours.

6. The method for preparing the inorganic composite flocculant according to claim 1, characterized in that: The preparation method of the polysilicic acid solution, The method comprises the following steps: adding 235-240 parts of sodium silicate into 760-770 parts of water by mass, stirring continuously at a speed of 100-200 r / min, adjusting the pH value to 1-3 with sulfuric acid, stirring and polymerizing at room temperature for 3-4 hours, and then aging at room temperature for 5-7 hours to obtain a polysilicic acid solution.

7. An inorganic composite flocculant, characterized in that: The inorganic composite flocculant is prepared by the preparation method of any one of claims 1 to 6.

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