Coalification wastewater membrane concentrated solution treating agent and preparation method thereof

Abstract

The invention belongs to the field of coalification wastewater membrane concentrated solution treatment, and discloses a coalification wastewater membrane concentrated solution treatment agent and a preparation method thereof. The coalification wastewater membrane concentrated solution treating agent is prepared from the following raw materials in parts by weight: 20 to 40 parts of sodium persulfate, 1 to 5 parts of polyacrylamide, 30 to 50 parts of modified diatomite and 10 to 30 parts of modified starch. Wherein the modified diatomite is obtained by carrying out ring-opening reaction on silanized modified diatomite and beta-cyclodextrin, and the modified starch is obtained by carrying out oxidation ring-opening reaction on starch after being pretreated by Na2S. Through dual modification and synergistic effect of the modified diatomite and the modified starch, efficient removal of organic matters and heavy metal ions in coalification wastewater is realized. Wherein hydroxyl and siloxane groups on the surface of the modified diatomite and beta-cyclodextrin have an inclusion effect, so that multiple types of organic pollutants can be adsorbed at the same time, carboxyl on the surface of the modified starch is used for complexing heavy metal ions, and the treatment efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of coal chemical wastewater membrane concentrated liquid treatment, and in particular to a coal chemical wastewater membrane concentrated liquid treatment agent and a preparation method thereof. Background Art

[0002] Coal chemical wastewater membrane concentrate is a high-concentration pollutant produced in the wastewater treatment process of the coal chemical industry. It is a byproduct of concentrating pollutants in the wastewater during the membrane treatment of coal chemical wastewater. Compared with the original coal chemical wastewater, membrane concentrate has higher pollutant concentration, more complex composition and more difficult to treat, which has become a major problem in the zero discharge process of coal chemical wastewater.

[0003] From the composition point of view, the membrane concentrate of coal chemical wastewater contains a large amount of refractory organic matter, such as phenols, polycyclic aromatic hydrocarbons, heterocyclic compounds, etc., and is also rich in inorganic salts, such as sodium salts, calcium salts, magnesium salts, etc. The complex combination of organic matter and inorganic salts makes the concentrate have the characteristics of high concentration of organic matter, high salinity, high chroma, and high toxicity. Among them, the biochemical oxygen demand concentration is usually between 10,000 and 50,000 mg / L, which is much higher than general industrial wastewater; the salt content can reach 30,000 to 80,000 mg / L, which is close to the concentration of seawater; the chroma is often above thousands of degrees. In addition, the concentrate may also contain a variety of heavy metal ions, such as chromium, nickel, zinc, etc. The synergistic effect of these pollutants makes the concentrate highly biologically toxic, posing a serious threat to the environment and ecosystem.

[0004] From the perspective of physical and chemical properties, the membrane concentrate of coal chemical wastewater is usually dark brown or black with a pungent odor. Due to the presence of high salt content, its conductivity is very high, reaching more than 20,000 μS / cm. The organic matter and inorganic salts in the concentrate make it have a high viscosity, which is not conducive to subsequent treatment. At the same time, the high concentration of organic matter and salt also causes the concentrate to have a strong tendency to scale, and it is easy to form difficult-to-remove deposits on the surface of the equipment.

[0005] It is precisely because of these characteristics of coal chemical wastewater membrane concentrate that its treatment technology faces many difficulties and challenges: First, the content of difficult-to-degrade organic matter in the concentrate is high, and the biochemical treatment effect is limited. Traditional biological treatment technologies such as activated sludge method are difficult to effectively degrade these complex organic matter, and the treatment efficiency is low. Even if specially domesticated microorganisms are used, it is difficult to cope with such high concentrations of organic pollution.

[0006] Secondly, high salt content has many adverse effects on the treatment process. On the one hand, high salt environment inhibits microbial activity and reduces the biochemical treatment effect; on the other hand, high salt content also interferes with many physical and chemical treatment processes, such as reducing the coagulation and sedimentation effect. In addition, removing high concentrations of salt is a technical problem in itself, and conventional processes such as ion exchange or electrodialysis are difficult to be economically applied to wastewater with such high salinity.

[0007] Third, the synergistic effect of multiple pollutants in the concentrate makes it difficult for a single treatment process to achieve ideal results. For example, the presence of organic matter will interfere with salt removal, and the presence of salt will affect the degradation of organic matter, forming a mutual constraint. This requires the use of a combination of multiple processes to achieve effective treatment, which greatly increases the process complexity and treatment cost.

[0008] Fourth, the presence of heavy metal ions in the concentrate not only increases the difficulty of treatment, but may also cause secondary pollution to equipment and the environment. Removal of these heavy metal ions usually requires a special pretreatment step, further increasing the cost of treatment.

[0009] Fifth, the strong scaling tendency of the concentrate poses a challenge to the operation and maintenance of the treatment equipment. Difficult-to-remove deposits are easily formed on the surface of the equipment, affecting the mass transfer effect, reducing the treatment efficiency, and also shortening the service life of the equipment.

[0010] Faced with these difficulties, traditional single treatment technology is often difficult to work. Therefore, in recent years, researchers have begun to try to use various treatment agents to enhance the treatment effect. Summary of the invention

[0011] The object of the present invention is to provide a coal chemical wastewater membrane concentrate treating agent and a preparation method thereof, so as to solve the problem that high concentration of refractory organic matter and high salt content in the coal chemical wastewater membrane concentrate are difficult to be effectively removed.

[0012] To achieve the above object, on the one hand, the present invention provides a coal chemical wastewater membrane concentrate treatment agent, comprising the following raw materials in parts by weight: 20-40 parts of sodium sulfate, 1-5 parts of polyacrylamide, 30-50 parts of modified diatomaceous earth, and 10-30 parts of modified starch; The modified diatomaceous earth is obtained by a ring-opening reaction between silanized modified diatomaceous earth and β-cyclodextrin, and the modified starch is obtained by an oxidative ring-opening reaction after starch is pretreated with Na2S.

[0013] Preferably, the starch comprises any one of corn starch, tapioca starch, wheat starch and potato starch.

[0014] Preferably, the mass ratio of silanized modified diatomaceous earth to β-cyclodextrin is (0.05-0.2):1.

[0015] Preferably, the silanized modified diatomaceous earth is pretreated diatomaceous earth modified by silanization with γ-glycidyloxypropyltrimethoxysilane.

[0016] Preferably, the mass ratio of γ-glycidyloxypropyltrimethoxysilane to pretreated diatomaceous earth is (0.01-0.05:):1.

[0017] Preferably, the modified diatomite preparation method is: dispersing the silanized modified diatomite in N,N-dimethylformamide, reacting with β-cyclodextrin and p-toluenesulfonic acid at 70-80°C for 12-24h; cooling to room temperature after the reaction, filtering the product, washing and drying.

[0018] Preferably, the mass ratio of toluenesulfonic acid to β-cyclodextrin is (0.01-0.05):1.

[0019] Preferably, when starch is pretreated with Na2S, the reaction temperature is 45-50°C and the pH is 8-9; the oxidative ring-opening reaction is carried out at a stirring speed of 150-200 rpm and a temperature of 37±2°C for 1-2 hours.

[0020] Preferably, the mass ratio of starch to Na2S is (0.05-0.2):1.

[0021] On the other hand, based on the same inventive concept, the present invention also provides a method for preparing a coal chemical wastewater membrane concentrate liquid treatment agent, which is applied to the aforementioned coal chemical wastewater membrane concentrate liquid treatment agent, comprising: mixing the raw materials evenly and then screening them.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. Through the dual modification and synergistic effect of modified diatomite and modified starch, the efficient removal of organic matter and heavy metal ions in coal chemical wastewater is achieved. Among them, the hydroxyl group, siloxane group and β-cyclodextrin inclusion complex on the surface of modified diatomite can simultaneously adsorb various types of organic pollutants, and the carboxyl group on the surface of modified starch is used to complex heavy metal ions, thereby improving the treatment efficiency.

[0023] 2. The sodium persulfate and polyacrylamide used in the present invention form a complete treatment system with the modified components. The oxidizing effect of sodium persulfate makes it easier to remove the difficult-to-degrade organic matter, and the flocculation effect of polyacrylamide promotes the separation of pollutants, ultimately forming a stable three-dimensional network structure, effectively preventing the secondary release of pollutants. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The first embodiment of the present invention provides a coal chemical wastewater membrane concentrate treatment agent, comprising the following raw materials in parts by weight: 20 to 40 parts of sodium sulfate, 1 to 5 parts of polyacrylamide, 30 to 50 parts of modified diatomaceous earth, and 10 to 30 parts of modified starch; wherein the modified diatomaceous earth is obtained by a ring-opening reaction of silanized modified diatomaceous earth and β-cyclodextrin, and the modified starch is obtained by an oxidative ring-opening reaction of starch after pre-treatment with Na2S.

[0026] The coal chemical wastewater membrane concentrate treatment agent provided in the embodiment of the present invention achieves efficient removal of multiple pollutants in coal chemical wastewater through the synergistic effect of multiple components. Among them, modified diatomaceous earth and modified starch are core components, which play a key role through special structures and functional groups.

[0027] Specifically, the modified diatomite is double-modified with γ-glycidyloxypropyltrimethoxysilane and β-cyclodextrin, and hydroxyl and siloxane groups are formed on its surface, which has excellent adsorption properties. The porous structure of diatomite itself provides a large number of adsorption sites, and the hydroxyl groups on the surface enhance the hydrophilicity of the material, which is conducive to full contact with pollutants in water; at the same time, the hydrophobic area formed by the siloxane group can adsorb hydrophobic organic pollutants in water; through the selective inclusion complex of β-cyclodextrin, it can specifically capture specific organic pollutants such as aromatic compounds and phenols in coal wastewater; in addition, the hydroxyl groups on the surface can form a coordination effect with metal ions in water, while the siloxane groups provide a stable supporting skeleton.

[0028] Modified starch is prepared by pretreating starch with Na2S and oxidizing it with H2O2. A large number of carboxyl groups are formed on its surface, which has unique functions: the carboxyl groups give the material a strong negative charge, which can adsorb positive ion pollutants in water through electrostatic action, and at the same time have strong complexing ability and can form stable complexes with heavy metal ions; in addition, modified starch can form a synergistic flocculation effect with polyacrylamide, connecting fine pollutant particles into large molecular flocs through bridging flocculation.

[0029] The hydroxyl groups (-OH) on the surface of modified diatomite and the carboxyl groups (-COOH) on the surface of modified starch form a stable spatial network structure through intermolecular hydrogen bonds. In this network structure, the diatomite particles are connected and wrapped by starch molecular chains, forming a mutually supporting spatial framework. This hydrogen bond network not only enhances the structural stability of the composite material, improves the floc strength, prevents the floc from breaking under hydraulic shear, enhances the ability to fix pollutants, and prevents the desorption of adsorbed pollutants, but also provides more active sites for the adsorption of organic pollutants and heavy metal ions; in addition, the regularly arranged carboxyl groups on the modified starch molecular chains can effectively prevent the modified diatomite particles from approaching and agglomerating through electrostatic repulsion and steric hindrance effects, thereby improving the dispersion stability of the modified diatomite in high-concentration wastewater, preventing it from agglomerating and failing due to excessive pollutant concentrations, ensuring the continuity and stability of the treatment process, and ultimately achieving efficient removal of pollutants in coal chemical wastewater membrane concentrate.

[0030] In the process of treating coal chemical wastewater membrane concentrate, sodium persulfate first releases active free radicals to oxidize some of the difficult-to-degrade organic matter, making it easier to be adsorbed or complexed; then the modified diatomaceous earth removes organic pollutants through surface adsorption and selective inclusion, the modified starch removes metal ions through carboxyl complexation, and polyacrylamide promotes the separation of pollutants through flocculation; the flocs finally formed have a three-dimensional network structure, which can effectively intercept and encapsulate various pollutants to prevent them from being released again. This multi-component synergistic treatment mechanism based on modified diatomaceous earth and modified starch provides a technical idea for the efficient treatment of coal chemical wastewater membrane concentrate.

[0031] In some preferred embodiments, the modified diatomite preparation method is: dispersing the silanized modified diatomite in N,N-dimethylformamide, reacting with β-cyclodextrin and p-toluenesulfonic acid at 70-80°C for 12-24h; after the reaction is completed, cooling to room temperature, filtering the product, washing and drying.

[0032] It should be noted that the amount of silanized modified diatomite, β-cyclodextrin and toluenesulfonic acid used in the preparation process of modified diatomite can be selected by those skilled in the art according to the desired effect. In some preferred embodiments, the mass ratio of silanized modified diatomite to β-cyclodextrin can be (0.05-0.2):1; the mass ratio of toluenesulfonic acid to β-cyclodextrin can be (0.01-0.05):1.

[0033] There is no need to specifically limit the source of starch, and starch from various sources can be used, such as corn starch, cassava starch, wheat starch, potato starch, etc. During the pretreatment process, the amount of starch and Na2S can be determined by those skilled in the art according to the desired effect, for example, the mass ratio of starch to Na2S can be (0.05-0.2):1.

[0034] It should also be noted that the silanized modified diatomite is silanized modified pretreated diatomite by γ-glycidyloxypropyltrimethoxysilane, and the specific preparation method is the modification method of diatomite by silane coupling agent commonly used in the art, and there is no need for special limitation. The method of silanized modified diatomite in the following embodiment is only exemplary. For example, the mass ratio of γ-glycidyloxypropyltrimethoxysilane to pretreated diatomite can be (0.01-0.05:):1.

[0035] The second embodiment of the present invention provides a method for preparing a coal chemical wastewater membrane concentrated liquid treatment agent, which is applied to the aforementioned coal chemical wastewater membrane concentrated liquid treatment agent, comprising: mixing the raw materials uniformly and then sieving.

[0036] In order to make the technical solution of the present invention clearer, the coal chemical wastewater membrane concentrate treatment agent and its effects are described in detail through a number of specific embodiments below.

[0037] The test equipment and preparations of the examples described below are as follows: Electronic balance (Sartorius, Germany), electric blast constant temperature dryer (Shanghai Fomar Experimental Equipment), stainless steel reactor (Shanghai Laibei), electric constant temperature water bath (Jiangsu Kedao), rotary evaporator (Shanghai Darlow Scientific Instruments), pulverizer (Shandong Tianfang Machinery), magnetic stirrer (Shanghai Meiyingpu), Soxhelt extractor (Qingdao Juchuang); chemicals and reagents were purchased from Sigma-Aldrich.

[0038] In the following examples, "parts" are all "parts by weight".

[0039] Example 1 Coal chemical wastewater membrane concentrate treatment agent, the raw materials are: 31 parts of sodium persulfate, 3 parts of polyacrylamide, 42 parts of modified diatomaceous earth, and 26 parts of modified starch.

[0040] Wherein, the preparation method of modified diatomite is: S11. The diatomaceous earth is treated with dilute hydrochloric acid, washed with deionized water until neutral, dried, and calcined at 400-500°C for 3-4h to obtain pretreated diatomaceous earth; S12. The pretreated diatomite is dispersed in anhydrous toluene, γ-glycidyloxypropyltrimethoxysilane is added, the temperature is controlled at 80-85°C, and the reaction is refluxed for 6-8h; cooled to room temperature, the product is filtered, washed, and dried to obtain silanized modified diatomite; wherein the mass ratio of γ-glycidyloxypropyltrimethoxysilane to pretreated diatomite is 0.038:1; S13. Disperse the silanized modified diatomaceous earth in N,N-dimethylformamide, add β-cyclodextrin, add a small amount of p-toluenesulfonic acid, control the temperature at 70-80°C, and stir the reaction for 12-24 hours; after the reaction is completed, cool to room temperature, filter, wash and dry the product to obtain modified diatomaceous earth; the mass ratio of p-toluenesulfonic acid, silanized modified diatomaceous earth and β-cyclodextrin is 0.03:0.16:1.

[0041] The preparation method of modified starch is: S21. Mix corn starch and distilled water evenly to form a starch slurry; slowly add Na2S solution to the starch slurry, and keep the mixture at 45-50°C, pH 8-9 for 2-3 hours while stirring to obtain a pretreated starch slurry; wherein the mass ratio of corn starch to Na2S is 0.1; S22. After the pretreated starch slurry is cooled, the pH value is adjusted to 5-6, and H2O2 and FeSO4 solutions are slowly added dropwise. The mixture is reacted at 37±2°C for 1-2 hours with a stirring speed of 150-200 rpm. Anhydrous ethanol is added to the reaction solution for precipitation, the mixture is allowed to stand, centrifuged, the supernatant is discarded, the precipitate is collected, washed, dried, and crushed through a 100-mesh sieve.

[0042] Preparation method of coal chemical wastewater membrane concentrate treatment agent: Mix all the raw materials evenly and pass through a 40-60 mesh sieve.

[0043] Example 2 Coal chemical wastewater membrane concentrate treatment agent, the raw materials are: 20 parts of sodium persulfate, 1 part of polyacrylamide, 30 parts of modified diatomaceous earth (the mass ratio of silanized modified diatomaceous earth to β-cyclodextrin is 0.05:1), and 10 parts of modified starch.

[0044] The preparation methods of modified diatomaceous earth, modified starch and coal chemical wastewater membrane concentrate treatment agent refer to Example 1.

[0045] Example 3 Coal chemical wastewater membrane concentrate treatment agent, the raw materials are: 40 parts of sodium persulfate, 5 parts of polyacrylamide, 50 parts of modified diatomaceous earth (the mass ratio of silanized modified diatomaceous earth to β-cyclodextrin is 0.2:1), and 30 parts of modified starch.

[0046] The preparation methods of modified diatomaceous earth, modified starch and coal chemical wastewater membrane concentrate treatment agent refer to Example 1.

[0047] Example 4 Coal chemical wastewater membrane concentrate treatment agent, the raw materials are: 30 parts of sodium persulfate, 3 parts of polyacrylamide, 40 parts of modified diatomaceous earth (the mass ratio of silanized modified diatomaceous earth to β-cyclodextrin is 0.125:1), and 20 parts of modified starch.

[0048] The preparation methods of modified diatomaceous earth, modified starch and coal chemical wastewater membrane concentrate treatment agent refer to Example 1.

[0049] Example 5 Coal chemical wastewater membrane concentrate treatment agent, the raw materials are: 22 parts of sodium persulfate, 2 parts of polyacrylamide, 38 parts of modified diatomaceous earth (the mass ratio of silanized modified diatomaceous earth to β-cyclodextrin is 0.08:1), and 16 parts of modified starch.

[0050] The preparation methods of modified diatomaceous earth, modified starch and coal chemical wastewater membrane concentrate treatment agent refer to Example 1.

[0051] Comparative Example 1 Compared with Example 1, the only difference is that modified diatomaceous earth is not used in the raw materials of the coal chemical wastewater membrane concentrate treatment agent, and the other raw materials and preparation methods are the same as those in Example 1.

[0052] Comparative Example 2 Compared with Example 1, the only difference is that modified starch is not used in the raw materials of the coal chemical wastewater membrane concentrate treatment agent, and the other raw materials and preparation methods are the same as those in Example 1.

[0053] Comparative Example 3 Compared with the embodiment, the only difference is that modified diatomaceous earth and modified starch are not used in the raw materials of the coal chemical wastewater membrane concentrate treatment agent, and the other raw materials and preparation methods are the same as those in embodiment 1.

[0054] Comparative Example 4 Compared with Example 1, the only difference is that the modified diatomaceous earth in the raw material of the coal chemical wastewater membrane concentrate treatment agent is replaced by an equal amount of γ-glycidyloxypropyltrimethoxysilane modified diatomaceous earth, and the other raw materials and preparation method are the same as those in Example 1.

[0055] Test example The coal chemical wastewater membrane concentrate treatment agent prepared in the above embodiments and comparative examples was subjected to a variety of performance tests. The physical and chemical properties of the coal chemical wastewater membrane concentrate used below are: pH value: 7.5-9.0; COD: 1000-3000 mg / L; heavy metal concentration: chromium: 10-50 mg / L, nickel: 5-30 mg / L; zinc: 15-60 mg / L; conductivity: 2000-5000 μS / cm; the test results are shown in Tables 1-3, and the specific test methods are as follows: 1. Floc strength test: 3 g / L of the coal chemical wastewater membrane concentrate treatment agent of each embodiment and comparative example was added to 1 L of coal chemical wastewater membrane concentrate, stirred at 200 rpm for 2 min, then reduced the stirring speed to 80 rpm and continued stirring for 15 min. After flocs were formed, the stirring speed gradient was set to 50, 100, 150, 200, 250, and 300 rpm, and each speed was maintained for 5 min. The d of each sample was measured using a particle size analyzer. 50 value.

[0056] 2. Isothermal adsorption experiment: Take 3g / L of the coal chemical wastewater membrane concentrate treatment agent of each embodiment and comparative example, add them into 1L of coal chemical wastewater membrane concentrate respectively, oscillate at a constant temperature until adsorption equilibrium is reached, centrifuge and separate, use the supernatant and untreated coal chemical wastewater membrane concentrate as test samples, and measure the concentrations of organic pollutants and heavy metals in the coal chemical wastewater membrane concentrate treated with the treatment agent and the untreated coal chemical wastewater membrane concentrate respectively.

[0057] (1) Determination of COD concentration: Take 10.0 mL of the water sample to be tested and place it in a conical flask. Add mercuric sulfate solution, 5.00 ml of potassium dichromate standard solution and several explosion-proof glass beads in turn and shake well. Add mercuric sulfate solution at a mass ratio of m[HgSO4]:m[C1]>20:1, and the maximum addition amount is 2 ml. Slowly add 15 ml of silver sulfate-sulfuric acid solution from the upper end of the condenser. Heat the mixed water sample under reflux for 2 hours. After cooling, add ferrochlore indicator and titrate with ammonium ferrous sulfate standard solution until the color of the solution changes to reddish brown. Calculate the COD value based on the volume of ammonium ferrous sulfate standard solution consumed in the titration. The COD removal rate calculation formula is: COD removal rate (%) = (COD of untreated coal chemical wastewater membrane concentrate - COD of coal chemical wastewater membrane concentrate treated with treatment agent) / COD of untreated coal chemical wastewater membrane concentrate × 100%.

[0058] (2) Determination of heavy metal concentration (chromium, nickel, zinc): prepare a series of multi-element standard solutions (national standard samples) of known concentrations for establishing a standard curve; take 5 ml of the water sample to be tested, add 5 ml of hydrogen peroxide and 5 ml of nitric acid, digest to <5 ml, then adjust the volume to 25 ml, and then filter with a 0.45 μm membrane to complete pretreatment; inject the pretreated sample solution into the ICP-OES instrument, and determine the heavy metal concentration in the sample through instrumental analysis. The heavy metal removal rate calculation formula is: heavy metal removal rate (%) = (untreated coal chemical wastewater membrane concentrate heavy metal concentration - coal chemical wastewater membrane concentrate heavy metal concentration after treatment agent) / untreated coal chemical wastewater membrane concentrate heavy metal concentration × 100%; the comprehensive removal rate calculation formula is: comprehensive removal rate (%) = (COD removal rate + chromium removal rate + nickel removal rate + zinc removal rate) / 4.

[0059] 3. Zeta potential test: Take 3g / L of the coal chemical wastewater membrane concentrate treatment agent of each embodiment and comparative example, add it to 1L of coal chemical wastewater membrane concentrate, stir at 200rpm for 2min, then reduce the stirring speed to 80rpm, continue stirring for 15min, and after flocs are formed, measure the Zeta potential; and determine the time required to reach adsorption equilibrium, i.e., adsorption equilibrium time; determine the maximum adsorption capacity by measuring the difference between the remaining pollutant concentration in the solution at adsorption equilibrium and the initial concentration. The maximum adsorption capacity is an important parameter for evaluating the performance of the adsorbent, which reflects the adsorption capacity of the adsorbent for specific pollutants.

[0060] Table 1 Floc strength test results .

[0061] Table 2 Pollutant removal effect .

[0062] Table 3 Zeta potential and adsorption kinetic parameters .

[0063] Based on the experimental data analysis of Tables 1-3, it can be seen that the coal chemical wastewater membrane concentrate treatment agent of the present invention shows excellent performance in Examples 1-5, especially the various indicators of Example 1 are the most excellent.

[0064] From the floc strength test results, the floc d of Example 1-5 under high shear conditions (300 rpm) 50 The values ​​are 348, 298, 320, 335 and 312 μm, respectively, which are significantly higher than 168, 205, 130 and 248 μm of Comparative Examples 1 to 4. At the same time, from the trend of floc particle size change from 50 rpm to 300 rpm, the floc particle size of Examples 1 to 5 decreases less, indicating that a floc structure with significant shear resistance is formed by compounding modified diatomaceous earth and modified starch.

[0065] In terms of pollutant removal effect, the removal rate of COD in Example 1 is 92.5%, and the removal rates of heavy metals chromium, nickel and zinc are 95.8%, 94.2% and 96.3% respectively, with a comprehensive removal rate of up to 94.7%. The comprehensive removal rates of Comparative Examples 1-4 are only 66.0%, 74.0%, 47.4% and 81.3%, which fully confirms that the synergistic effect of modified diatomaceous earth and modified starch significantly improves the pollutant removal ability of the treatment agent.

[0066] In addition, it can be seen from the Zeta potential and adsorption kinetic parameters that Example 1 has the most suitable Zeta potential (-32.5mV), the shortest adsorption equilibrium time (45min) and the largest adsorption capacity (385mg / g), which is significantly superior to the comparative examples, in which the adsorption equilibrium time of comparative examples 1-4 is extended to 95min, 85min, 120min and 75min, respectively, and the maximum adsorption capacity is only 225mg / g, 245mg / g, 168mg / g and 282mg / g.

[0067] This series of data shows that the spatial network structure formed by the hydroxyl groups on the surface of modified diatomaceous earth and the carboxyl groups on the surface of modified starch through intermolecular hydrogen bonds not only improves the mechanical strength of the flocs, but also significantly enhances the removal effect of organic matter and heavy metal ions through synergistic effects. At the same time, the regularly arranged carboxyl groups on the modified starch molecular chain effectively prevent the agglomeration of modified diatomaceous earth through electrostatic repulsion and steric hindrance effects, so that the treatment agent maintains good dispersion stability in high-concentration coal chemical wastewater membrane concentrate.

[0068] Finally, it should be noted that: Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A coal chemical wastewater membrane concentrate treatment agent, characterized in that: The invention comprises the following raw materials in parts by weight: 20-40 parts of sodium persulfate, 1-5 parts of polyacrylamide, 30-50 parts of modified diatomaceous earth, and 10-30 parts of modified starch; The modified diatomaceous earth is obtained by a ring-opening reaction between silanized modified diatomaceous earth and β-cyclodextrin, and the modified starch is obtained by an oxidative ring-opening reaction after starch is pretreated with Na2S.

2. The coal chemical wastewater membrane concentrate treating agent according to claim 1, characterized in that: The starch comprises any one of corn starch, tapioca starch, wheat starch and potato starch.

3. The coal chemical wastewater membrane concentrate treating agent according to claim 1, characterized in that: The mass ratio of silanized modified diatomaceous earth to β-cyclodextrin is (0.05-0.2):

1.

4. The coal chemical wastewater membrane concentrate treating agent according to claim 1, characterized in that: The silanized modified diatomaceous earth is prepared by silanizing the pretreated diatomaceous earth with γ-glycidyloxypropyltrimethoxysilane.

5. The coal chemical wastewater membrane concentrate treating agent according to claim 4, characterized in that: The mass ratio of γ-glycidyloxypropyltrimethoxysilane to pretreated diatomaceous earth is (0.01-0.05):

1.

6. The coal chemical wastewater membrane concentrate treating agent according to claim 1, characterized in that: The preparation method of modified diatomite is as follows: dispersing silanized modified diatomite in N,N-dimethylformamide, reacting with β-cyclodextrin and p-toluenesulfonic acid at 70-80°C for 12-24h; cooling to room temperature after the reaction, filtering the product, washing and drying.

7. The coal chemical wastewater membrane concentrate treating agent according to claim 6, characterized in that: The mass ratio of toluenesulfonic acid to β-cyclodextrin is (0.01-0.05):

1.

8. The coal chemical wastewater membrane concentrate treating agent according to claim 1, characterized in that: When starch is pretreated with Na2S, the reaction temperature is 45~50°C and the pH is 8~9; the oxidative ring-opening reaction is carried out at a stirring speed of 150~200rpm and a temperature of 37±2°C for 1~2h.

9. The coal chemical wastewater membrane concentrate treating agent according to claim 1 or 8, characterized in that: The mass ratio of starch to Na2S is (0.05-0.2):

1.

10. The method for preparing a treatment agent for coal chemical wastewater membrane concentrate according to any one of claims 1 to 9, characterized in that: Including: Mix all the raw materials evenly and sieve them.