Preparation method and application of modified iron-based starch flocculant

Abstract

The invention provides a preparation method of a modified iron-based starch flocculant. The Fe / Mo / Gd composite flocculant is synthesized through material modification and used for treating biochemical effluent in the coal chemical industry, and after the Fe / Mo / Gd composite flocculant is subjected to starch grafting modification, the adsorption bridging and net capturing capacity can be effectively improved. In the electron beam irradiation process, the flocculating agent is hydrolyzed, the electron beam and the hydrolyzed polymer are ionized or excited, orbital electrons are released, free radicals are formed and the like, and the original molecular structure is changed. The free radicals or other activated-state groups can form a new molecular form, and the free radicals or other activated-state groups are used for destroying chemical bonds, generating new chemical reactions, decomposing organic matters and the like at the same time, so that the organic matters in the coal chemical tail water are finally removed.

Description

Technical Field

[0001] The invention belongs to the technical field of coal chemical industry, and particularly relates to a preparation method and application of a modified iron-based starch flocculant. Background Art

[0002] Coal chemical tailwater not only has a large volume, but also has a complex composition, including more than 300 chemical pollutants such as cyanide, phenolic substances, sulfide, ammonia nitrogen, etc. The concentration level of various pollutants is also high, and the color is also high. It is a kind of industrial tailwater that is difficult to treat. Because the composition of coal chemical tailwater is complex and contains highly toxic components such as cyanide, it is easy for microorganisms to be poisoned, activated sludge is easy to be inactivated, resulting in failure of biological treatment units, affecting the efficiency and effect of sewage treatment; coal chemical tailwater contains a large amount of ammonia nitrogen. If it cannot be treated and discharged in compliance with the standards, it is easy to cause eutrophication of water bodies, causing algae to proliferate and cause algal blooms; coal chemical tailwater contains a large amount of macromolecular organic matter that is difficult to biodegrade, and biochemical treatment is relatively difficult.

[0003] Commonly used advanced oxidation treatment processes for coal chemical tail water include Fenton process, ozone process, photocatalytic process, etc. When the water concentration is high and contains a lot of difficult-to-degrade organic matter, it is difficult to meet the effluent standards with a single process, and it needs to be treated in conjunction with catalytic oxidation and coagulation and sedimentation processes. Flocculants are particularly important in the coagulation and sedimentation process. At present, flocculants usually use PFS (polyferric sulfate), PAFC (polyaluminum ferric chloride) and PAC (polyaluminum chloride), but the coagulation precipitate formed by double layer action and chemical bridging action has limited ability to remove pollutants. It is planned to find an advanced oxidation process to enhance the removal of pollutants under catalysis.

[0004] As a new type of advanced oxidation process, electron beam treatment is applied to printing and dyeing wastewater, petrochemical wastewater, oil and gas field wastewater, coal chemical wastewater and other fields. On the one hand, electron beam irradiation technology directly acts on pollutants through high-energy electron beam irradiation to destroy the structure to achieve the purpose of removing pollutants. On the other hand, water molecules are stimulated by irradiation and ionized to produce oxidizing OH and H2O2 and reducing e aq - and ·H, can be assisted by catalysis to enhance the efficiency of ion binding in water, accelerate the rate of ·OH generation in advanced oxidation technology, and finally make pollutants degraded by addition, substitution and electron transfer reactions with active particles. However, the electron transfer rate of conventional catalysts under electron beam irradiation is not satisfactory, and the removal rate of pollutants is difficult to achieve the expected effect. Therefore, it is urgent to find a high-efficiency catalyst and provide a method to improve the removal effect of organic matter in coal chemical tail water. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a modified iron-based starch flocculant and a preparation method and application thereof. The modified iron-based starch flocculant prepared in the present invention can effectively coordinate the speeds of oxidation reaction, hydrolysis reaction and polymerization reaction under electron beam irradiation, and ultimately achieve effective removal of pollutants.

[0006] The present invention provides a method for preparing a modified iron-based starch flocculant, comprising the following steps:

[0007] A) mixing ferrous salt, aqueous sulfuric acid solution, oxidant, molybdenum source compound and gadolinium source compound to obtain an iron-based solution;

[0008] B) reacting the iron-based solution to obtain a modified iron-based flocculant solution;

[0009] C) mixing the modified grafted polypropylene sodium thickener with the modified iron-based flocculant solution to obtain a modified iron-based starch flocculant.

[0010] Preferably, the ferrous salt is selected from one or more of ferrous sulfate heptahydrate and ferrous chloride;

[0011] The molybdenum source compound is selected from one or more of sodium molybdate and ammonium molybdate;

[0012] The gadolinium source compound is selected from one or more of gadolinium nitrate, gadolinium sulfate and gadolinium chloride;

[0013] The oxidant is selected from one or more of potassium chlorate, hydrogen peroxide, ammonium persulfate and sodium hypochlorite;

[0014] The mass concentration of the sulfuric acid aqueous solution is 15% to 30%;

[0015] In the modified iron-based flocculant solution, Fe 3+ The mass fraction is 25% to 30%, the mass fraction of Mo is 2 to 3%, the mass fraction of Gd is 0.5 to 1%, and the basicity is 10% to 15%.

[0016] Preferably, in step A), the reaction is carried out under ultrasonic conditions, and the reaction time is 30 to 60 minutes;

[0017] In step B), the reaction is carried out under the following conditions:

[0018] The iron-based solution is reacted at 60-70° C. for 2-4 hours, and finally at room temperature for 24-48 hours.

[0019] Preferably, the mass ratio of the modified grafted polypropylene sodium thickener to the modified iron-based flocculant solution is 1:(10-15).

[0020] Preferably, the preparation method of the modified grafted polypropylene sodium thickener comprises the following steps:

[0021] The gelatinized starch, acrylic acid monomer and cross-linking agent are mixed and reacted to obtain a modified grafted polypropylene sodium thickener.

[0022] Preferably, the starch is selected from one or more of cassava starch, potato starch and corn starch;

[0023] The cross-linking agent is selected from N,N-methylenebisacrylamide.

[0024] The present invention also provides a modified iron-based starch flocculant prepared by the above preparation method, characterized in that the modified iron-based starch flocculant comprises:

[0025] ≥11% iron content, 0-0.5% molybdenum content, 0-0.5% gadolinium content;

[0026] Basicity ≥12%.

[0027] The present invention also provides an application of the modified iron-based starch flocculant in the treatment of coal chemical biochemical tail water.

[0028] The present invention also provides a method for treating coal chemical biochemical tail water, comprising the following steps:

[0029] The coal chemical biochemical tail water to be treated is mixed with a modified iron-based starch flocculant and then irradiated, and then mixed with anionic polyacrylamide for reaction to obtain the treated coal chemical biochemical tail water.

[0030] Preferably, the added amount of the modified iron-based starch flocculant is 1 to 3‰ by volume of the coal chemical biochemical tail water to be treated;

[0031] The electron accelerator for the irradiation treatment is selected to be 0.5-2.0 MeV, the beam current is 20-66 mA, the cumulative irradiation time is 0.005-0.1 s, and the water curtain thickness is 1-5 mm.

[0032] Compared with the prior art, the present invention provides a method for preparing a modified iron-based starch flocculant, comprising the following steps: A) mixing ferrous salt, sulfuric acid aqueous solution, oxidant, molybdenum source compound, and gadolinium source compound to obtain an iron-based solution; B) reacting the iron-based solution to obtain a modified iron-based flocculant solution; C) mixing a modified grafted polypropylene sodium thickener with the modified iron-based flocculant solution to obtain a modified iron-based starch flocculant. The present invention synthesizes a Fe / Mo / Gd composite flocculant for treating biochemical effluent from coal chemical industry through material modification. After the Fe / Mo / Gd composite flocculant is modified by starch grafting, it can effectively improve the adsorption bridging and net capturing capabilities. During the electron beam irradiation process, the flocculant is hydrolyzed, and the electron beam ionizes or excites the hydrolyzed polymer, releasing orbital electrons, forming free radicals, etc. to change the original molecular structure. Free radicals or other activated groups can form new molecular forms, which can destroy chemical bonds and generate new chemical reactions, decompose organic matter, etc., and finally remove organic matter from coal chemical tail water. In the present invention, without adding any additives, a certain amount of Fe / Mo / Gd modified flocculant is fully mixed with coal chemical biochemical effluent for electron beam irradiation, which can effectively coordinate the speed of oxidation reaction, hydrolysis reaction and polymerization reaction, and ensure the total iron content of the product, and improve the basicity of the product. The H2O2, ·OH and H generated during the reaction are + It acts on the organic matter in the tail water and eventually decomposes it into CO2 and H2O. DETAILED DESCRIPTION

[0033] The present invention provides a method for preparing a modified iron-based starch flocculant, comprising the following steps:

[0034] A) mixing ferrous salt, aqueous sulfuric acid solution, oxidant, molybdenum source compound and gadolinium source compound to obtain an iron-based solution;

[0035] B) reacting the iron-based solution to obtain a modified iron-based flocculant solution;

[0036] C) mixing the modified grafted polypropylene sodium thickener with the modified iron-based flocculant solution to obtain a modified iron-based starch flocculant.

[0037] The present invention firstly mixes ferrous salt with aqueous sulfuric acid solution to obtain a sulfuric acid solution of ferrous salt, wherein the ferrous salt is selected from one or more of ferrous sulfate heptahydrate and ferrous chloride;

[0038] The mass concentration of the aqueous sulfuric acid solution is 15% to 30%, which can be 15%, 20%, 25%, 30%, or any value between 15% and 30%;

[0039] The molar volume ratio of the ferrous salt to the aqueous sulfuric acid solution is 0.15 to 0.3 mol:30 mL, and can be 0.15 mol:30 mL, 0.2 mol:30 mL, 0.25 mol:30 mL, 0.3 mol:30 mL, or any value between 0.15 and 0.3 mol:30 mL.

[0040] Then, the sulfuric acid solution of the ferrous salt is heated. The present invention has no particular limitation on the heating method, and preferably adopts water bath heating. The heating temperature is 50-70°C, and can be 50, 55, 60, 65, 70, or any value between 50-70°C.

[0041] Next, an oxidant is added to the sulfuric acid solution of the ferrous salt for mixed reaction, wherein the oxidant is selected from one or more of potassium chlorate, hydrogen peroxide, ammonium persulfate and sodium hypochlorite; the molar volume ratio of the oxidant to sulfuric acid is 0.03-0.05 mol:30 mL, which can be 0.03 mol:30 mL, 0.04 mol:30 mL, 0.05 mol:30 mL, or any value between 0.03-0.05 mol:30 mL. The mixed reaction time is 20-40 min.

[0042] Then, a molybdenum source compound and a gadolinium source compound are added and mixed to react to obtain an iron-based solution. The molybdenum source compound is selected from one or more of sodium molybdate and ammonium molybdate; the gadolinium source compound is selected from one or more of gadolinium nitrate, gadolinium sulfate and gadolinium chloride. The molar volume ratio of the molybdenum source compound to sulfuric acid is 0.02 to 0.04 mol:30 mL, which can be 0.02 mol:30 mL, 0.03 mol:30 mL, 0.04 mol:30 mL, or any value between 0.02 and 0.04 mol:30 mL; the molar volume ratio of the gadolinium source compound to sulfuric acid is 0.01 to 0.03 mol:30 mL, which can be 0.01 mol:30 mL, 0.02 mol:30 mL, 0.03 mol:30 mL, or any value between 0.01 and 0.03 mol:30 mL.

[0043] In the present invention, the molar ratio of the ferrous salt, the molybdenum source compound and the gadolinium source compound is (0.15-0.3): (0.02-0.04): (0.01-0.03).

[0044] The oxidation reaction is preferably carried out under ultrasonic conditions, and the reaction time is 30 to 60 minutes, which can be 30, 40, 50, 60, or any value between 30 and 60 minutes.

[0045] Then, the iron-based solution is subjected to a complexation reaction, and the reaction is carried out under the following conditions:

[0046] The iron-based solution is reacted at 60-70° C. for 2-4 hours, which can be 2, 3, 4, or any value between 2-4 hours, and finally reacted at room temperature for 24-48 hours, which can be 24, 36, 48, or any value between 24-48 hours.

[0047] Wherein, the present invention defines the room temperature condition as 25±5°C.

[0048] In the modified iron-based flocculant solution, Fe 3+ The mass fraction is 25% to 30%, and can be 25%, 26%, 27%, 28%, 29%, 30%, or any value between 25% and 30%; the mass fraction of Mo is 2 to 3%, and can be 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or any value between 2% and 3%; the mass fraction of Gd is 0.5 to 1%, and can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any value between 0.5% and 1%, and the basicity is 10% to 15%, and can be 10%, 11%, 12%, 13%, 14%, 15%, or any value between 10% and 15%.

[0049] After the modified iron-based flocculant solution is obtained, the modified grafted polypropylene sodium thickener is mixed with the modified iron-based flocculant solution to react and obtain the modified iron-based starch flocculant.

[0050] Wherein, the mass ratio of the modified grafted polypropylene sodium thickener to the modified iron-based flocculant solution is 1:(10-15), and can be 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, or any value between 1:(10-15).

[0051] The preparation method of the modified grafted polypropylene sodium thickener comprises the following steps:

[0052] The gelatinized starch, acrylic acid monomer and cross-linking agent are mixed and reacted to obtain a modified grafted polypropylene sodium thickener.

[0053] Specifically, gelatinized starch is first prepared, and the preparation method preferably includes the following steps:

[0054] Under protective atmosphere conditions, starch is mixed with deionized water, stirred and heated to obtain gelatinized starch.

[0055] Wherein, the protective atmosphere condition is preferably a nitrogen atmosphere;

[0056] The starch is preferably one or more of tapioca starch, potato starch and corn starch;

[0057] The mass volume ratio of the starch to deionized water is 2-5g:60mL, and can be 2g:60mL, 2.5g:60mL, 3g:60mL, 3.5g:60mL, 4g:60mL, 4.5g:60mL, 5g:60mL, or any value between 2-5g:60mL.

[0058] The stirring and heating temperature is 80-90°C, which can be 80, 85, 90, or any value between 80 and 90°C; the stirring and heating time is 20-40min, which can be 20, 30, 40, or any value between 20 and 40min; the stirring speed of the stirring and heating is 200-300rpm, which can be 200, 250, 300, or any value between 200 and 300rpm.

[0059] After gelatinization is complete, the gelatinized starch is cooled to room temperature.

[0060] The acrylic acid monomer was neutralized with NaOH aqueous solution in an ice-water bath and then added dropwise to the gelatinized starch. After stirring for a period of time, the crosslinking agent aqueous solution was added, mixed and stirred, and N2 was continuously filled to remove all air and then sealed.

[0061] Wherein, the mass concentration of the NaOH aqueous solution is 10%;

[0062] The cross-linking agent is preferably N,N-methylenebisacrylamide.

[0063] The invention mixes and reacts the modified grafted polypropylene sodium thickener with the modified iron-based flocculant solution to obtain the modified iron-based starch flocculant.

[0064] The stirring speed of the reaction is 200-300 rpm, which can be 200, 250, 300, or any value between 200-300 rpm. The temperature of the reaction is 60-80°C, which can be 60, 65, 70, 75, 80, or any value between 60-80°C. During the reaction, the modified grafted sodium polyacrylate thickener is added slowly and dropwise, and the reaction is continued for 50-70 minutes after the addition is complete, which can be 50, 60, 70, or any value between 50-70 minutes. The modified iron-based starch flocculant is obtained by standing at room temperature for 24-48 hours, and the standing time can be 24, 36, 48, or any value between 24-48 hours.

[0065] The present invention also provides a modified iron-based starch flocculant prepared by the above preparation method, wherein the modified iron-based starch flocculant comprises:

[0066] ≥11% iron content, 0-0.5% molybdenum content, 0-0.5% gadolinium content;

[0067] Basicity ≥12%.

[0068] In the modified iron-based starch flocculant, the iron content is ≥11%, and can be 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or any content ≥11%;

[0069] The molybdenum content may be 0.001, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, or any value between 0 and 0.5%;

[0070] The gadolinium content may be 0.001, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, or any value between 0 and 0.5%.

[0071] The basicity is ≥12%, and can be 12%, 12.1%, 12.2%, 12.3%, 12.4%, 12.5%, 12.6%, 12.7%, 12.8%, 12.9%, 13%, or any content ≥12%.

[0072] The present invention also provides an application of the modified iron-based starch flocculant in the treatment of coal chemical biochemical tail water.

[0073] The present invention also provides a method for treating coal chemical biochemical tail water, comprising the following steps:

[0074] The coal chemical biochemical tail water to be treated is mixed with a modified iron-based starch flocculant and then irradiated, and then mixed with anionic polyacrylamide APAM for reaction to obtain the treated coal chemical biochemical tail water.

[0075] Specifically, the coal chemical biochemical tail water to be treated and the modified iron-based starch flocculant are mixed, wherein the volume percentage of the modified iron-based starch flocculant added to the coal chemical biochemical tail water to be treated is 1 to 3‰, which can be 1‰, 1.5‰, 2‰, 2.5‰, 3‰, or any value between 1 and 3‰.

[0076] The electron accelerator for the irradiation treatment is selected to be 0.5-2.0 MeV, which can be 0.5, 1, 1.5, 2, or any value between 0.5 and 2.0 MeV; the beam current is 20-66 mA, which can be 20, 30, 40, 50, 60, 66, or any value between 20 and 66 mA; the cumulative irradiation time is 0.005-0.1 s, which can be 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any value between 0.005 and 0.1 s; the water curtain thickness is 1-5 mm, which can be 1, 2, 3, 4, 5, or any value between 1 and 5 mm.

[0077] After the irradiation is completed, it is mixed with anionic polyacrylamide to react to obtain the treated coal chemical biochemical tail water.

[0078] Among them, the volume percentage of the anionic polyacrylamide added to the coal chemical biochemical tail water to be treated is 1-4‰, which can be 1‰, 1.5‰, 2‰, 2.5‰, 3‰, 3.5‰, 4‰, or any value between 1 and 4‰.

[0079] The stirring speed of the reaction is 100-200 r / min, the stirring temperature is 25±5° C., the reaction time is 5-10 min, and after the reaction is completed, the mixture is allowed to stand and settle for 30±10 min.

[0080] The present invention synthesizes a Fe / Mo / Gd composite flocculant for treating coal chemical biochemical effluent through material modification. After the Fe / Mo / Gd composite flocculant is modified by starch grafting, the adsorption bridging and net capturing capabilities can be effectively improved. During the electron beam irradiation process, the flocculant is hydrolyzed, and the electron beam and the hydrolyzed polymer are ionized or excited, releasing orbital electrons, forming free radicals, etc., which change the original molecular structure. Free radicals or other activated groups can form new molecular forms, and their function is to destroy chemical bonds while generating new chemical reactions, decomposing organic matter, etc., and finally achieving the removal of organic matter in coal chemical tail water. In the present invention, without adding any additives, a certain amount of Fe / Mo / Gd modified flocculant is fully mixed with coal chemical biochemical effluent for electron beam irradiation, which can effectively coordinate the speed of oxidation reaction, hydrolysis reaction and polymerization reaction, which not only ensures the total iron content of the product, but also improves the basicity of the product. The H2O2, ·OH and H generated during the reaction are + It acts on the organic matter in the tail water and eventually decomposes it into CO2 and H2O.

[0081] In order to further understand the present invention, the modified iron-based starch flocculant provided by the present invention, its preparation method and application are described below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0082] Example 1

[0083] Preparation of modified iron-based flocculant solution: weigh 0.2 mol of ferrous sulfate heptahydrate, add 30 mL (20%) sulfuric acid aqueous solution, dissolve it completely under stirring, heat the water bath to 50°C, slowly add 0.03 mol of potassium chlorate, mix and stir for 30 minutes, then add 0.03 mol of sodium molybdate and 0.02 mol of gadolinium nitrate hexahydrate, and react with ultrasound for 30 minutes. After the ultrasonic reaction, the temperature is 60-70°C, continue to stir and react for 2 hours, then take it out and fully react at room temperature for 24 hours to obtain the modified iron-based flocculant solution. The performance indicators of the obtained modified iron-based flocculant solution are: Fe 3+ The mass fraction is 25%, the mass fraction of Mo is 2%, the mass fraction of Gd is 0.5%, and the basicity is 10%.

[0084] Preparation of modified grafted sodium polyacrylate thickener: Under N2 protection, 2g of cassava starch was placed in a 250mL three-necked flask, 60mL of deionized water was added, and the temperature was stirred and raised to 85°C. The temperature was maintained for 30min to fully gelatinize the cassava starch. The stirring speed was 200rpm. After gelatinization was completed, the temperature was lowered to room temperature. A certain amount of acrylic acid monomer was neutralized with 10% NaOH aqueous solution in an ice-water bath and then added dropwise to the gelatinized starch. After stirring for 10min, the pre-prepared N,N-methylenebisacrylamide aqueous solution was added and stirred for 10min. N2 was continuously filled to remove all air and then sealed.

[0085] Preparation of modified flocculant: Mix the modified grafted sodium polypropylene thickener and the modified iron-based flocculant solution in a mass ratio of 1:10, stir at 200 rpm, heat the water bath to 60°C, add the modified grafted sodium polyacrylate thickener slowly, drop by drop, and continue to react for 60 minutes after complete addition. Let stand at room temperature for 24 hours to obtain the Fe / Mo / Gd-starch composite flocculant.

[0086] The quality analysis of the prepared Fe / Mo / Gd-starch composite flocculant was performed, and the results are shown in Table 1.

[0087] Table 1 Quality analysis results of Fe / Mo / Gd-starch composite flocculants

[0088]

[0089]

[0090] Example 2

[0091] On the basis of Example 1, the oxidant was changed to 0.03 mol hydrogen peroxide, the ferrous salt was selected from 0.2 mol ferrous chloride, the molybdenum source compound was selected from 0.03 mol ammonium molybdate, and other conditions remained unchanged to prepare a Fe / Mo / Gd-starch composite flocculant.

[0092] Example 3

[0093] On the basis of Example 1, the oxidant was changed to 0.03 mol sodium hypochlorite, the ferrous salt was selected from 0.2 mol ferrous chloride, the gadolinium source compound was selected from 0.02 mol gadolinium sulfate, and other conditions remained unchanged to prepare a Fe / Mo / Gd-starch composite flocculant.

[0094] Example 4

[0095] On the basis of Example 1, the modified grafted polypropylene sodium thickener and the iron-based flocculant solution were mixed in a mass ratio of 1:15, the stirring speed was 300 rpm, the water bath was heated to 70° C., and other conditions remained unchanged to prepare a Fe / Mo / Gd-starch composite flocculant.

[0096] Example 5

[0097] Tailwater treatment:

[0098] Scenario 1:

[0099] Take 500 mL of coal chemical biochemical effluent, add the Fe / Mo / Gd-starch composite flocculant prepared in Example 1 at a volume ratio of 1‰, stir quickly and evenly, the stirring speed is 300 r / min, the stirring temperature is 25°C, after mixing evenly, add APAM (mass concentration is 1‰) at a volume ratio of 2‰, stir slowly, the stirring speed is 100-200 r / min, the stirring temperature is 25°C, let it stand for 30 minutes and take samples for detection.

[0100] Scenario 2:

[0101] Take 500mL of coal chemical biochemical effluent and irradiate the water sample. The electron accelerator is selected as 1.0MeV, the beam current is 50mA, the cumulative irradiation time is 0.005s, and the water curtain thickness is 5mm. After irradiation treatment, add the Fe / Mo / Gd-starch composite flocculant prepared in Example 1 to the water at a volume ratio of 1‰, stir quickly and evenly, the stirring speed is 300r / min, and the stirring temperature is 25°C. After mixing evenly, add APAM at a volume ratio of 2‰, stir slowly, the stirring speed is 100r / min, and the stirring temperature is 25°C. After reacting for 5min, let it settle for 30min and take samples for detection.

[0102] Scenario 3:

[0103] Take 500mL of coal chemical biochemical effluent, add the Fe / Mo / Gd-starch composite flocculant prepared in Example 1 at a volume ratio of 1‰, stir quickly and evenly, the stirring speed is 300r / min, the stirring temperature is 25°C, and the water sample is irradiated. The electron accelerator is selected as 1.0MeV, the beam current is 50mA, the cumulative irradiation time is 0.005s, and the water curtain thickness is 5mm. After mixing evenly, add APAM at a volume ratio of 2‰, stir slowly, the stirring speed is 100r / min, the stirring temperature is 25°C, react for 5min, let it settle for 30min, and take samples for detection.

[0104] Solution 4

[0105] On the basis of Scheme 3, Fe / Mo / Gd-starch composite flocculant was added at a volume ratio of 2‰, and other conditions remained unchanged.

[0106] Solution 5

[0107] On the basis of Scheme 3, Fe / Mo / Gd-starch composite flocculant was added at a volume ratio of 3‰, and other conditions remained unchanged.

[0108] Table 2 Composite flocculant tail water verification experiment

[0109]

[0110] As can be seen from Table 2, when Fe / Mo / Gd-starch is used alone for coagulation and sedimentation, the COD content is reduced from 803 mg / L to 667 mg / L, and the removal rate is 16.9%; when the electron beam irradiation technology is added, the same amount of Fe / Mo / Gd-starch is added, and the COD content is reduced from 803 mg / L to 407 mg / L when the flocculant is added first and then irradiated, and the removal rate is 49.3%. With the increase of modified flocculants, the COD content in the solution first increases and then decreases, indicating that there is a certain relationship between the modified flocculant and the irradiation dose, and the coupling effect of flocculants and electron beam irradiation can only be reflected under the optimal conditions. According to the data in Table 3, it can be concluded that the fully mixed Fe / Mo / Gd modified flocculant and the coal chemical biochemical effluent for electron beam irradiation can effectively coordinate the speed of oxidation reaction, hydrolysis reaction and polymerization reaction, and the H2O2, ·OH and H generated during the reaction process can be effectively coordinated. + It acts on the organic matter in the wastewater, eventually reducing the COD content in the solution and achieving the purpose of pollutant removal.

[0111] Comparative Example 1:

[0112] The experimental method was the same as the tailwater treatment scheme, wherein Fe / Mo / Gd-starch was replaced with PFS (10 wt% polyferric sulfate, purchased from Binzhou Shengyuan Chemical Technology Co., Ltd.) conventional flocculant, and the dosage and experimental conditions remained unchanged.

[0113] Table 3 Conventional flocculant tail water verification experiment

[0114]

[0115] It can be seen from Table 3 that under the same conditions of coagulant addition, the COD content in the solution is 701 mg / L when conventional flocculants are used and electron beam irradiation process is added. However, when the conventional flocculant is changed to Fe / Mo / Gd-starch flocculant, the COD content in the solution is 407 mg / L, and the COD removal rate is increased by 36.6%. Therefore, it is further verified that there is a synergistic effect between the modified flocculant and the electron beam irradiation reaction, which can effectively improve the removal effect of coagulation and sedimentation on organic matter.

[0116] Comparative Example 2:

[0117] The experimental method is the same as the tail water treatment scheme of Example 5, wherein Mo / Gd is doped alone or replaced with other metal doping, such as cobalt and nickel, and the dosage and experimental conditions remain unchanged.

[0118] See Table 4 for specific flocculant types and quality analysis results.

[0119] Table 4 Flocculant quality analysis results

[0120]

[0121]

[0122] In Table 4, the Fe-starch composite flocculant was prepared according to the following method:

[0123] Based on Example 1, sodium molybdate and gadolinium nitrate hexahydrate were not added, and the other contents remained unchanged.

[0124] The Fe / Mo-starch composite flocculant was prepared as follows:

[0125] On the basis of Example 1, gadolinium nitrate hexahydrate was not added, the amount of sodium molybdate used was 0.05 mol, and the other conditions remained unchanged.

[0126] The Fe / Gd-starch composite flocculant was prepared as follows:

[0127] On the basis of Example 1, sodium molybdate was not added, the usage amount of gadolinium nitrate hexahydrate was 0.05 mol, and the other conditions remained unchanged.

[0128] The Fe / Co-starch composite flocculant was prepared as follows:

[0129] On the basis of Example 1, sodium molybdate and gadolinium nitrate hexahydrate are not added, but cobalt salt is used instead, and the cobalt salt is cobalt nitrate hexahydrate, and the usage amount is 0.05 mol, and other conditions remain unchanged.

[0130] The Fe / Ni-starch composite flocculant was prepared as follows:

[0131] On the basis of Example 1, sodium molybdate and gadolinium nitrate hexahydrate are not added, but are replaced by nickel salt, the nickel salt is nickel nitrate hexahydrate, and the usage amount is 0.05 mol, and the other contents remain unchanged.

[0132] Table 5 Validation experiment of flocculant tail water with different metal doping

[0133]

[0134]

[0135] Table 4 shows the quality analysis results of flocculants doped with different metals, among which different metal ion doping has basically no effect on the density of the flocculants, and has basically no effect on the total iron content and appearance. Tail water verification experiments were carried out on flocculants doped with different metals, as shown in Table 5.

[0136] Table 5 shows the flocculants modified by different metal doping experiments, in which Mo, Gd, Co and Ni metal elements were doped. The metal modified flocculants doped at the same molar number were used for tail water verification experiments. The experimental results show that the COD content in the solution is the lowest when the Mo / Gd co-doped flocculant is combined with electron beam irradiation technology, and the COD removal rate reaches 49.3%. Studies have shown that Mo, Gd, Co and Ni are often used as catalysts for surface termination structure regulation, surface interface electron migration mechanism and reaction mechanism theoretical research due to their high electrochemical activity and good conductivity. In conventional doping, due to different binding efficiencies, the transfer efficiency of electrons is different. Molybdenum forms a composite cementite with iron and carbon, which plays a role in transferring electrons in redox reactions. Gadolinium, as a rare earth element, exists in a chelated state during the doping process, which increases the electron transfer efficiency of the modified material. High-energy electron beam irradiation directly acts on pollutants, destroys their structure, and finally removes pollutants.

[0137] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a modified iron-based starch flocculant, characterized in that: The following steps are involved: A) mixing a ferrous salt, an aqueous sulfuric acid solution, an oxidant, a molybdenum source compound, and a gadolinium source compound to obtain an iron-based solution; B) reacting the iron-based solution to obtain a modified iron-based flocculant solution; C) mixing the modified grafted polypropylene sodium thickener with the modified iron-based flocculant solution to react to obtain a modified iron-based starch flocculant.

2. The preparation method according to claim 1, characterized in that The ferrous salt is selected from one or more of ferrous sulfate heptahydrate and ferrous chloride; The molybdenum source compound is selected from one or more of sodium molybdate and ammonium molybdate; The gadolinium source compound is selected from one or more of gadolinium nitrate, gadolinium sulfate and gadolinium chloride; The oxidant is selected from one or more of potassium chlorate, hydrogen peroxide, ammonium persulfate and sodium hypochlorite; The mass concentration of the sulfuric acid aqueous solution is 15% to 30%; In the modified iron-based flocculant solution, Fe 3+ The mass fraction is 25% to 30%, the mass fraction of Mo is 2 to 3%, the mass fraction of Gd is 0.5 to 1%, and the basicity is 10% to 15%.

3. The preparation method according to claim 1, characterized in that In step A), the reaction is carried out under ultrasonic conditions for 30 to 60 minutes; In step B), the reaction is carried out under the following conditions: The iron-based solution is reacted at 60-70° C. for 2-4 hours, and finally at room temperature for 24-48 hours.

4. The preparation method according to claim 1, characterized in that The mass ratio of the modified grafted polypropylene sodium thickener to the modified iron-based flocculant solution is 1:(10-15).

5. The preparation method according to claim 1, characterized in that The preparation method of the modified grafted polypropylene sodium thickener comprises the following steps: The gelatinized starch, acrylic acid monomer and cross-linking agent are mixed and reacted to obtain a modified grafted polypropylene sodium thickener.

6. The preparation method according to claim 5, characterized in that The starch is selected from one or more of tapioca starch, potato starch, and corn starch; The cross-linking agent is selected from N,N-methylenebisacrylamide.

7. A modified iron-based starch flocculant prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The modified iron-based starch flocculant comprises: ≥11% iron content, 0-0.5% molybdenum content, 0-0.5% gadolinium content; Basicity ≥12%.

8. Use of the modified iron-based starch flocculant according to claim 7 in the treatment of coal chemical biochemical tail water.

9. A method for treating coal chemical biochemical tail water, characterized in that: The following steps are involved: The coal chemical biochemical tail water to be treated is mixed with a modified iron-based starch flocculant and then irradiated, and then mixed with anionic polyacrylamide for reaction to obtain the treated coal chemical biochemical tail water.

10. The method according to claim 9, characterized in that The added amount of the modified iron-based starch flocculant accounts for 1 to 3‰ of the volume of the coal chemical and biochemical tail water to be treated; The electron accelerator for the irradiation treatment is selected to be 0.5-2.0 MeV, the beam current is 20-66 mA, the cumulative irradiation time is 0.005-0.1 s, and the water curtain thickness is 1-5 mm.

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