A rapid flocculant, its preparation method and application

Abstract

The application discloses a kind of quick flocculants and preparation method and application thereof, it is related to wastewater treatment technical field.The quick flocculants prepared by the application is sequentially carried out alkali extraction, acid extraction, first modification, secondary modification with fly ash as raw material;The first modification is that the secondary filter residue obtained by acid extraction is mixed with acetoacetic acid solution to obtain the first modified secondary filter residue;The secondary modification is that the secondary filter residue of first modification, sodium silicate, the filtrate obtained by filtering of acid extraction and alkali extraction, mixed solution of ferric chloride, zinc chloride and polyacrylamide are mixed and reacted to obtain the quick flocculants;The wastewater treatment efficiency of the quick flocculants prepared by the application is higher, and the removal effect of heavy metals and colority in water is obvious.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, in particular to a rapid flocculant and a preparation method and application thereof. BACKGROUND

[0002] Coal mine wastewater is wastewater generated in the process of coal mining and production, mainly including mine water, coal slurry water, coal mine domestic sewage, gangue field leaching wastewater, and wastewater discharged by hydraulic coal mining and water sand filling coal mining method. The mine water is wastewater generated by the contact between underground water and coal seam and rock layer in various operations of coal mining, and its water quality depends on the physical and chemical composition of minerals in the earth's crust; the coal slurry water is wastewater generated by wet coal separation; the coal mine domestic sewage is sewage formed by residents' life; the gangue field leaching wastewater and the wastewater discharged by hydraulic coal mining and water sand filling coal mining method are also wastewater generated in the process of coal production. According to the above description, it can be known that no matter which kind of coal mine wastewater, it may contain a high content of coal powder.

[0003] In traditional industry, the main method for treating coal mine wastewater is flocculant precipitation method, but the traditional flocculant precipitation method can only remove some suspended solids, has little effect on heavy metal ions and color, and has low COD removal rate.

[0004] Therefore, the present application solves these problems by preparing a rapid flocculant. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a rapid flocculant, which is obtained by sequentially performing alkali extraction, acid extraction, first modification and second modification on fly ash as raw material; the first modification is obtained by mixing and reacting the secondary filter residue obtained by acid extraction with an acetoacetic acid solution; and the second modification is obtained by mixing and reacting the secondary filter residue of the first modification, a mixed solution of sodium silicate, filtrate obtained by acid extraction and alkali extraction, ferric chloride, zinc chloride and polyacrylamide, and then aging.

[0006] The present application also provides a preparation method of the rapid flocculant, comprising the following preparation steps:

[0007] (1) Preparation of raw materials: crushing, grinding and sieving fly ash to obtain pretreated fly ash;

[0008] (2) Alkali extraction: adding an alkali solution with a mass of 2-6 times of the pretreated fly ash in step (1) at 1-6 MPa and 100-120℃, and stirring at 1200-1600 rpm for 2-3 h to obtain a first filtrate and a first filter residue, wherein the first filtrate is denoted as alkali extraction liquid;

[0009] (3) acid extraction: the acid solution with 2-6 times of the mass of the first filter residue obtained in step (2) is reacted at 1-6 MPa and 100-120 DEG C with stirring at 1200-1600 rpm for 2-3 h, and then filtered to obtain a second filtrate and a second filter residue, wherein the second filtrate is denoted as an acid extraction solution;

[0010] (4) first modification: the second filter residue obtained in step (3) is washed to be neutral, and an acetoacetic acid solution with 1-4 times of the mass of the second filter residue is added, and concentrated sulfuric acid with 0.3-0.5 times of the mass of the second filter residue is added at 60 DEG C, and then stirred at 400-600 rpm for 2-3 h, and then filtered, washed with deionized water for 2-4 times, and then placed in a blast drying oven, and dried at 50 DEG C to obtain a first modified second filter residue;

[0011] (5) second modification: the first modified second filter residue obtained in step (4) is placed in deionized water with 2-6 times of the mass of the first modified second filter residue, and then stirred in a water bath at 35-45 DEG C at 1200-1600 rpm for 10-20 min, and then sodium silicate with 1.5-2.5 times of the mass of the first modified second filter residue is added, and then the stirring is continued until the sodium silicate is dissolved, and then the acid extraction solution and the alkali extraction solution are added to adjust the pH to 2.5-3.5, and then stirred in a water bath at 400-600 rpm at 35-45 DEG C for 1.8-2.2 h, and then allowed to stand for 1.8-2.2 h, and then ferric chloride and zinc chloride are added, and then stirred in a water bath at 400-600 rpm at 35-45 DEG C for 1.8-2.2 h, and then a mixed solution of polyacrylamide with 0.3-0.5 times of the mass of the first modified second filter residue is added, and then heated to 90 DEG C, and then the stirring is continued for 1.8-2.2 h, and then cooled to 35-45 DEG C, and then placed in an ultrasonic cleaning machine, and then vibrated at 40 kHz for 25-35 min, and then allowed to stand for 17.5-18.5 h to obtain a rapid flocculant.

[0012] Further, the particle size of the pretreated fly ash in step (2) is 80-120 mesh.

[0013] Further, the alkali solution in step (2) is a sodium hydroxide solution with a mass fraction of 10-30%.

[0014] Further, the mixed acid solution in step (3) is a mixed acid solution of hydrochloric acid solution, sulfuric acid solution and phosphoric acid solution with a mass fraction of 30%, and the mass ratio of the hydrochloric acid solution, the sulfuric acid solution and the phosphoric acid solution is 0.2-0.4:0.5-0.7:0.8-1.

[0015] Further, the acetoacetic acid solution in step (4) has a mass fraction of 5-15%.

[0016] Further, the mass of the ferric chloride in step (5) is 0.6-0.62 times the mass of the secondary filter residue of the first modification; and the mass of the zinc chloride is 0.046-0.048 times the mass of the secondary filter residue of the first modification.

[0017] Further, the preparation method of the mixed solution of polyacrylamide in step (5) comprises the following steps: mixing polyacrylamide with a molecular weight of 1.5 million, o-aminobenzyl alcohol and ethylene glycol according to a mass ratio of 1:0.2-0.3:5-7, stirring at 400-600 rpm for 15-25 min to obtain the mixed solution of polyacrylamide.

[0018] The application further provides an application method of the rapid flocculant.

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] The rapid flocculant disclosed by the application is obtained by sequentially performing alkali extraction, acid extraction, first modification and second modification on fly ash as raw material; the first modification is obtained by mixing and reacting the secondary filter residue obtained by acid extraction with an acetoacetic acid solution; and the second modification is obtained by mixing and reacting the secondary filter residue of the first modification, a sodium silicate solution, a filtrate obtained by filtering the filtrate of the acid extraction and the alkali extraction, ferric chloride, zinc chloride and a mixed solution of polyacrylamide.

[0021] The fly ash collected from coal mines is used as raw material to perform alkali extraction, and there is a large amount of active silicon oxide and aluminum oxide in the fly ash; after the alkali extraction, the active silicon oxide and aluminum oxide react with the alkali, so that the structure is further changed; not only the specific surface area is significantly increased, the adsorption capacity is increased, but also the interlayer spacing is increased, the intercalation reaction potential barrier is reduced, the intercalation polymerization is more easily occurred, the polymerization degree is increased, and the polymerization time is shortened; therefore, the flocculation capacity of the flocculant can be obviously improved, the flocculation effect is good, the dosage is small, the formed flocculation is coarse, the COD removal rate is high, the wastewater treatment cost is reduced, and the economic benefit is high.

[0022] Then, acid extraction, first modification, a large number of hydroxyl groups are formed on the surface of the secondary filter residue, acetyl acetic acid is grafted onto the surface of the secondary filter residue by the reaction of carboxyl and hydroxyl groups, then sodium silicate, acid extraction liquid, alkali extraction liquid, ferric chloride and zinc chloride are introduced, the acid extraction liquid and the alkali extraction liquid are recycled, at the same time, the phosphoric acid in the acid extraction liquid is mixed with polysilicic acid, ferric chloride and zinc chloride to form a mixed solution of polysilicon iron and zinc with hyperbranched structure on the surface of the secondary filter residue, the mixed solution of polyacrylamide is quickly immersed into the secondary filter residue through the cavity of the mixed solution of polysilicon iron and zinc, the o-aminobenzyl alcohol in the mixed solution of polyacrylamide is cyclized with acetyl acetic acid in the secondary filter residue under the catalysis of part of ferric chloride to form quinoline, the quinoline quickly captures heavy metal ions to form quinoline metal complexes, and the adsorption and net capture of the flocculant are further enhanced after ultrasonic treatment, the removal of COD and heavy metals by the flocculant is enhanced, and the colority of the coal mine wastewater is obviously reduced. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0024] In order to more clearly illustrate the method provided by the present application, the following embodiments are described in detail. The test methods of various indexes of the rapid flocculant prepared in the following embodiments are as follows:

[0025] Heavy metal content: the same mass of the rapid flocculant prepared in the embodiments and the comparative examples is used for flocculation treatment of the same mass of coal mine wastewater with total iron of 10.8 mg / L, total manganese of 5.2 mg / L, colority of 45 and COD of 295 mg / L, to obtain treated coal mine wastewater, and the total iron content and the manganese content of the treated coal mine wastewater are tested by ICP-OES.

[0026] Colority: the same mass of the rapid flocculant prepared in the embodiments and the comparative examples is used for flocculation treatment of the same mass of coal mine wastewater with total iron of 10.8 mg / L, total manganese of 5.2 mg / L, colority of 45 and COD of 295 mg / L, to obtain treated coal mine wastewater, and the treated coal mine wastewater is tested by the standard GB11903-1989.

[0027] COD value: the same quality of the prepared rapid flocculant of the example and the comparative example, the total iron 10.8 mg / L, the total manganese 5.2 mg / L, the colority 45, the COD of the coal mine wastewater with the same quality 295 mg / L was flocculated, the treated coal mine wastewater was obtained, the COD content was tested by coulometric titration method, and the chemical oxygen demand tester used for testing met the standard of GB / T32208-2015.

[0028] Example 1

[0029] A preparation method of a rapid flocculant, comprising the following preparation steps:

[0030] (1) material preparation: the fly ash was crushed, ground and sieved through an 80-mesh sieve to obtain pretreated fly ash;

[0031] (2) alkali extraction: 2 times the mass of the pretreated fly ash in step (1) was added with a 10% sodium hydroxide solution, and the mixture was stirred at 1200 rpm under 1 MPa and 100°C for 2 h, and then filtered to obtain a first filtrate and a first residue, wherein the first filtrate was denoted as an alkali extraction solution;

[0032] (3) acid extraction: 2 times the mass of the first residue obtained in step (2) was added with a 10% acid solution, and the mixture was stirred at 1200 rpm under 1 MPa and 100°C for 2 h, and then filtered to obtain a second filtrate and a second residue, wherein the second filtrate was denoted as an acid extraction solution;

[0033] (4) first modification: the second residue obtained in step (3) was washed to neutral, 1 times the mass of the second residue was added with a 5% acetoacetic acid solution, 0.3 times the mass of the second residue was added with concentrated sulfuric acid, and the mixture was stirred at 400 rpm under 60°C for 2 h, and then filtered, washed with deionized water for 2 times, and then placed in a blast drying oven, dried at 50°C to obtain a first modified second residue;

[0034] (5) Secondary modification: the secondary filter residue of the first modified obtained in step (4) is put into deionized water with 2 times of the mass of the secondary filter residue, stirred at 35℃ for 10 min at 1200 rpm in a water bath, then sodium silicate with 1.5 times of the mass of the secondary filter residue is added, and the stirring is continued until the sodium silicate is dissolved, and then the acid extraction liquid and the alkali extraction liquid are added to adjust the pH to 2.5, and the stirring is continued at 35℃ for 1.8 h in a water bath at 400 rpm, then it is left to stand for 1.8 h, then ferric chloride with 0.6 times of the mass of the secondary filter residue and zinc chloride with 0.046 times of the mass of the secondary filter residue are added, and the stirring is continued at 35℃ for 1.8 h in a water bath at 400 rpm, then a mixed solution of polyacrylamide with 0.3 times of the mass of the secondary filter residue is added, the temperature is increased to 90℃, and the stirring is continued for 1.8 h, then the temperature is decreased to 35℃, and it is put into an ultrasonic cleaning machine for 25 min under the condition of 40 kHz, and then it is left to stand for 17.5 h to obtain the rapid flocculant.

[0035] The acid solution in step (3) is a mixed acid solution of hydrochloric acid solution, sulfuric acid solution and phosphoric acid solution with a mass fraction of 30%, and the mass ratio of the hydrochloric acid solution, the sulfuric acid solution and the phosphoric acid solution is 0.2:0.5:0.8.

[0036] The preparation method of the mixed solution of polyacrylamide in step (5) comprises the following steps: polyacrylamide with a molecular weight of 1.5 million, o-aminobenzyl alcohol and ethylene glycol are mixed in a mass ratio of 1:0.2:5, and stirred at 400 rpm for 15 min to obtain the mixed solution of polyacrylamide.

[0037] Example 2

[0038] A preparation method of a rapid flocculant comprises the following preparation steps:

[0039] (1) Preparation: the fly ash is crushed, ground and sieved through a 100-mesh screen to obtain pretreated fly ash;

[0040] (2) Alkali extraction: the pretreated fly ash obtained in step (1) is added with sodium hydroxide solution with a mass fraction of 20% and 4 times of the mass of the pretreated fly ash, and stirred at 1400 rpm at 3 MPa and 110℃ for 2.5 h to obtain a first filter liquid and a first filter residue, wherein the first filter liquid is denoted as an alkali extraction liquid;

[0041] (3) Acid extraction: the first filter residue obtained in step (2) is added with acid solution with a mass fraction of 20% and 4 times of the mass of the first filter residue, and stirred at 1400 rpm at 3 MPa and 110℃ for 2.5 h to obtain a second filter liquid and a second filter residue, wherein the second filter liquid is denoted as an acid extraction liquid;

[0042] (4) First modification: the secondary filter residue obtained in step (3) is washed to neutral, 3 times the mass of the secondary filter residue of 10% acetyl acetic acid solution is added, 0.4 times the mass of the secondary filter residue of concentrated sulfuric acid is added at 60℃, stirring at 500 rpm for 2.5h, filtering, washing with deionized water for 3 times, then placing in a blast drying oven, drying at 50℃, obtaining the first modified secondary filter residue;

[0043] (5) Second modification: the first modified secondary filter residue obtained in step (4) is put into 4 times the mass of deionized water, stirring at 1400 rpm in a water bath at 40℃ for 15 min, then adding 2 times the mass of the first modified secondary filter residue of sodium silicate, continuing to stir until the sodium silicate is dissolved, then adding the acid extraction liquid and the alkali extraction liquid to adjust the pH to 3, stirring at 500 rpm in a water bath at 40℃ for 2h, then standing for 2h, then adding 0.61 times the mass of the first modified secondary filter residue of ferric chloride, and 0.047 times the mass of the first modified secondary filter residue of zinc chloride, stirring at 500 rpm in a water bath at 40℃ for 2h, adding 0.4 times the mass of the first modified secondary filter residue of polyacrylamide mixed solution, warming to 90℃, continuing to stir for 4h, then cooling to 40℃, placing in an ultrasonic cleaner under the condition of 40kHz for 30 min, then standing for 18h, obtaining the rapid flocculant.

[0044] The acid solution in step (3) is a mixed acid solution of hydrochloric acid solution, sulfuric acid solution and phosphoric acid solution, each with a mass fraction of 30%, and the mass ratio of the hydrochloric acid solution, the sulfuric acid solution and the phosphoric acid solution is 0.3:0.6:0.9.

[0045] The preparation method of the polyacrylamide mixed solution in step (5) comprises: mixing polyacrylamide with a molecular weight of 1.5 million, o-aminobenzyl alcohol and ethylene glycol at a mass ratio of 1:0.25:6, stirring at 500 rpm for 20 min, obtaining the polyacrylamide mixed solution.

[0046] Example 3

[0047] A preparation method of a rapid flocculant, comprising the following preparation steps:

[0048] (1) Preparation: crushing, grinding and sieving the fly ash through a 120 mesh sieve to obtain pretreated fly ash;

[0049] (2) Alkali extraction: adding 6 times the mass of the pretreated fly ash in step (1) of 30% sodium hydroxide solution, stirring at 1600 rpm at 6MPa and 120℃ for 3h, filtering, obtaining a first filtrate and a first filter residue, wherein the first filtrate is denoted as an alkali extraction liquid;

[0050] (3) acid extraction: 6 times the mass of the residue obtained in step (2) is added into a 30% acid solution, and the mixture is stirred at 1600 rpm under 6 MPa and 120°C for 3 h, and then filtered to obtain a secondary filtrate and a secondary residue, wherein the secondary filtrate is denoted as an acid extraction solution;

[0051] (4) first modification: the secondary residue obtained in step (3) is washed to neutral, and 4 times the mass of the secondary residue is added into a 15% acetylacetic acid solution, and the mixture is stirred at 600 rpm under 60°C for 3 h, and then filtered, washed with deionized water for 4 times, and then placed in a blast drying oven for drying at 50°C to obtain a first modified secondary residue;

[0052] (5) second modification: the first modified secondary residue obtained in step (4) is placed in 6 times the mass of deionized water, and the mixture is stirred at 1600 rpm under 45°C for 20 min, and then 2.5 times the mass of the first modified secondary residue is added into sodium silicate, and the mixture is continuously stirred until the sodium silicate is dissolved, and then the acid extraction solution and the alkali extraction solution are added to adjust the pH to 3.5, and the mixture is stirred at 600 rpm under 45°C for 2.2 h, and then the mixture is allowed to stand for 2.2 h, and then 0.62 times the mass of the first modified secondary residue is added into ferric chloride, and 0.048 times the mass of the first modified secondary residue is added into zinc chloride, and the mixture is stirred at 600 rpm under 45°C for 2.2 h, and then 0.5 times the mass of the first modified secondary residue is added into a mixed solution of polyacrylamide, and the mixture is heated to 90°C, and then the mixture is continuously stirred for 2.2 h, and then the mixture is cooled to 45°C, and then the mixture is placed in an ultrasonic cleaning machine for 35 min under the condition of 40 kHz, and then the mixture is allowed to stand for 18.5 h to obtain a rapid flocculant.

[0053] The acid solution in step (3) is a mixed acid solution of hydrochloric acid solution, sulfuric acid solution and phosphoric acid solution, each having a mass fraction of 30%, and the mass ratio of the hydrochloric acid solution, the sulfuric acid solution and the phosphoric acid solution is 0.4:0.7:1.

[0054] The preparation method of the mixed solution of polyacrylamide in step (5) comprises the following steps: 1 million molecular weight polyacrylamide, o-aminobenzyl alcohol and ethylene glycol are mixed in a mass ratio of 1:0.3:7, and the mixture is stirred at 600 rpm for 25 min to obtain a mixed solution of polyacrylamide.

[0055] Comparative Example 1

[0056] The difference between Comparative Example 1 and Example 2 is that only the fly ash is subjected to acid extraction, first modification and second modification, and the other components and steps are the same as those in Example 2.

[0057] Comparative Example 2

[0058] The difference between Comparative Example 2 and Example 2 is that only the fly ash is subjected to alkali extraction, acid extraction and secondary modification, and the rest of the components and steps are the same as those of Example 2.

[0059] Comparative Example 3

[0060] The difference between Comparative Example 3 and Example 2 is that step (5) of Comparative Example 3 specifically comprises: placing the secondary filter residue of the first modified obtained in step (4) into deionized water with a mass of 4 times that of the secondary filter residue of the first modified, stirring in a water bath at 40°C at 1400 rpm for 15 min, then adding sodium silicate with a mass of 2 times that of the secondary filter residue of the first modified, continuing to stir until the sodium silicate is dissolved, then adding acid extract and alkali extract to adjust the pH to 3, stirring in a water bath at 40°C at 500 rpm for 2 h, then standing for 2 h, then adding zinc chloride with a mass of 0.047 times that of the secondary filter residue of the first modified, stirring in a water bath at 40°C at 500 rpm for 2 h, adding a mixed solution of polyacrylamide with a mass of 0.4 times that of the secondary filter residue of the first modified, increasing the temperature to 90°C, continuing to stir for 4 h, then decreasing the temperature to 40°C, placing it in an ultrasonic cleaning machine and oscillating at 40 kHz for 30 min, and then standing for 18 h to obtain a rapid flocculant; the rest of the steps and components are the same as those of Example 2.

[0061] Comparative Example 4

[0062] The difference between Comparative Example 4 and Example 2 is that step (5) of Comparative Example 4 specifically comprises: placing the secondary filter residue of the first modified obtained in step (4) into deionized water with a mass of 4 times that of the secondary filter residue of the first modified, stirring in a water bath at 40°C at 1400 rpm for 15 min, then adding sodium silicate with a mass of 2 times that of the secondary filter residue of the first modified, continuing to stir until the sodium silicate is dissolved, then adding acid extract and alkali extract to adjust the pH to 3, stirring in a water bath at 40°C at 500 rpm for 2 h, then standing for 2 h, then adding ferric chloride with a mass of 0.61 times that of the secondary filter residue of the first modified, stirring in a water bath at 40°C at 500 rpm for 2 h, adding a mixed solution of polyacrylamide with a mass of 0.4 times that of the secondary filter residue of the first modified, increasing the temperature to 90°C, continuing to stir for 4 h, then decreasing the temperature to 40°C, placing it in an ultrasonic cleaning machine and oscillating at 40 kHz for 30 min, and then standing for 18 h to obtain a rapid flocculant; the rest of the steps and components are the same as those of Example 2.

[0063] Comparative Example 5

[0064] The difference between Comparative Example 5 and Example 2 is in step (5), and step (5) of Comparative Example 5 specifically comprises: placing the secondary filtration residue of the first modified product obtained in step (4) into deionized water with 4 times the mass of the secondary filtration residue of the first modified product, stirring in a water bath at 1400 rpm at 40℃ for 15 min, then adding sodium silicate with 2 times the mass of the secondary filtration residue of the first modified product, continuing to stir until the sodium silicate is dissolved, then adding the acid extract and the alkali extract to adjust the pH to 3, stirring in a water bath at 500 rpm at 40℃ for 2 h, then standing for 2 h for maturation, then adding ferric chloride with 0.61 times the mass of the secondary filtration residue of the first modified product, and zinc chloride with 0.047 times the mass of the secondary filtration residue of the first modified product, stirring in a water bath at 500 rpm at 40℃ for 2 h, adding polyacrylamide aqueous solution with 20% mass fraction and with 0.4 times the mass of the secondary filtration residue of the first modified product, increasing the temperature to 90℃, continuing to stir for 4 h, then decreasing the temperature to 40℃, placing in an ultrasonic cleaner to oscillate at 40 kHz for 30 min, and then standing for 18 h for maturation, to obtain the rapid flocculant; the remaining steps and components are the same as in Example 2.

[0065] Effect Example

[0066] The following Table 1 shows the analysis results of total iron content, total manganese content, colority, and COD value of the rapid flocculants prepared using the rapid flocculants prepared in Examples 1 to 3 and Comparative Examples 1 to 5.

[0067] Table 1

[0068] Total iron content (mg / L) Total manganese content (mg / L) Colour COD value (mg / L) Example 1 0.8 0.4 17 20 Example 2 0.3 0.1 13 18 Example 3 0.5 0.3 16 22 Comparative Example 1 0.4 0.3 28 118 Comparative Example 2 6.2 4.1 22 106 Comparative Example 3 5.8 3.6 19 65 Comparative Example 4 0.6 0.5 25 109 Comparative Example 5 6.1 3.9 18 74

[0069] It can be found from Table 1 that the rapid flocculants prepared in Examples 1, 2, and 3 have better removal effects on heavy metal ions iron and manganese and COD of coal mine wastewater, and the colority decreases more obviously; it can be found from the experimental data of Examples 1, 2, 3, and Comparative Example 1 that the rapid flocculants prepared by alkali extraction of fly ash have better removal effects on COD of coal mine wastewater, and the colority decreases more obviously; it can be found from the experimental data of Examples 1, 2, 3, and Comparative Example 2 that the rapid flocculants prepared by first modification of fly ash have better removal effects on heavy metal ions iron and manganese and COD of coal mine wastewater, and the colority decreases more obviously; it can be found from the experimental data of Examples 1, 2, 3, and Comparative Example 3 that the rapid flocculants prepared by secondary modification using ferric chloride have better removal effects on heavy metal ions iron and manganese and COD of coal mine wastewater, and the colority decreases more obviously; it can be found from the experimental data of Examples 1, 2, 3, and Comparative Example 4 that the rapid flocculants prepared by secondary modification using zinc chloride have better removal effects on COD of coal mine wastewater, and the colority decreases more obviously; it can be found from the experimental data of Examples 1, 2, 3, and Comparative Example 5 that the rapid flocculants prepared by secondary modification using a mixed solution of polyacrylamide have better removal effects on heavy metal ions iron and manganese and COD of coal mine wastewater, and the colority decreases more obviously.

[0070] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the present application. The presently disclosed embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No feature of the application is considered critical unless it is expressly stated in the claims.

Claims

1. A method for preparing a rapid flocculant, characterized in that, The preparation steps include the following: (1) Material preparation: crush, grind and sieve the fly ash to obtain pretreated fly ash; (2) Alkali extraction: Add 2 to 6 times the mass of the alkaline solution to the fly ash pretreated in step (1), stir and react at 1200 to 1600 rpm for 2 to 3 hours at 1 to 6 MPa and 100 to 120℃, filter, and obtain primary filtrate and primary filter residue, wherein the primary filtrate is referred to as alkaline extraction solution; (3) Acid extraction: Add 2 to 6 times the mass of the acid solution to the primary filter residue obtained in step (2), stir and react at 1200 to 1600 rpm for 2 to 3 hours at 1 to 6 MPa and 100 to 120°C, filter, and obtain secondary filtrate and secondary filter residue. The secondary filtrate is referred to as acid extraction solution. (4) First modification: Wash the secondary filter residue obtained in step (3) until neutral, add acetoacetic acid solution with a mass of 1 to 4 times that of the secondary filter residue, add concentrated sulfuric acid with a mass of 0.3 to 0.5 times that of the secondary filter residue at 60°C, stir and react at 400 to 600 rpm for 2 to 3 hours, filter, wash with deionized water 2 to 4 times, and then place in a forced-air drying oven and dry at 50°C to obtain the first modified secondary filter residue; (5) Secondary modification: The secondary filter residue obtained from the first modification in step (4) is placed in 2-6 times its mass of deionized water and stirred in a water bath at 1200-1600 rpm for 10-20 min at 35-45℃. Then, sodium silicate with a mass of 1.5-2.5 times its mass of the secondary filter residue is added and stirred until the sodium silicate dissolves. Then, acid extraction solution and alkaline extraction solution are added to adjust the pH to 2.5-3.

5. The mixture is stirred in a water bath at 400-600 rpm for 1.8-2.2 h at 35-45℃. Then, it is allowed to stand for 1.8-2.2 h. Then, ferric chloride and zinc chloride are added and stirred in a water bath at 400-600 rpm for 1.8 h at 35-45℃. ~2.2h, add a mixed solution of polyacrylamide at 0.3~0.5 times the mass of the first modified secondary filter residue, heat to 90℃, continue stirring for 1.8~2.2h, then cool to 35~45℃, place in an ultrasonic cleaner and vibrate at 40kHz for 25~35min, then let stand and mature for 17.5~18.5h to obtain a rapid flocculant; the preparation method of the polyacrylamide mixed solution includes: mixing polyacrylamide with a molecular weight of 1.5 million, o-aminobenzyl alcohol, and ethylene glycol at a mass ratio of 1:0.2~0.3:5~7, stirring at 400~600rpm for 15~25min to obtain the polyacrylamide mixed solution.

2. The method for preparing the rapid flocculant according to claim 1, characterized in that, The particle size of the pretreated fly ash in step (2) is 80~120 mesh.

3. The method for preparing the rapid flocculant according to claim 1, characterized in that, The alkaline solution mentioned in step (2) is a sodium hydroxide solution with a mass fraction of 10-30%.

4. The method for preparing the rapid flocculant according to claim 1, characterized in that, The acid solution mentioned in step (3) is a mixed acid solution of hydrochloric acid solution, sulfuric acid solution and phosphoric acid solution, each with a mass fraction of 30%, wherein the mass ratio of hydrochloric acid solution, sulfuric acid solution and phosphoric acid solution is 0.2~0.4:0.5~0.7:0.8~1.

5. The method for preparing the rapid flocculant according to claim 1, characterized in that, The mass fraction of the acetoacetic acid solution in step (4) is 5-15%.

6. The method for preparing the rapid flocculant according to claim 1, characterized in that, In step (5), the mass of ferric chloride is 0.6 to 0.62 times the mass of the secondary filter residue after the first modification; the mass of zinc chloride is 0.046 to 0.048 times the mass of the secondary filter residue after the first modification.