A novel flocculant and its preparation method and application

Abstract

The application belongs to the technical field of water treatment, and discloses a novel flocculant and a preparation method and application thereof, which comprises the following steps: S1, acid immersion: mixing red mud and HCl according to a proportion, water bath, and filtering and separating to obtain a first leaching solution and a first filter residue; mixing the red mud and lactic acid according to a proportion, water bath, and filtering and separating to obtain a second leaching solution and a second filter residue; S2, polysilicic acid preparation: adding NaOH solution into the first filter residue, water bath and stirring, adding HCl into the filtrate after filtering to adjust the pH to 3, and heating and stirring to prepare a polysilicic acid solution; S3, re-compounding and polymerization: re-compounding the first leaching solution and the second leaching solution according to a proportion, adjusting the pH to 2, adding the polysilicic acid solution, high-speed stirring, and aging to obtain a polysilicic acid metal salt solution; S4, after natural zeolite is ground, washed, dried, and sieved, the natural zeolite is immersed in the polysilicic acid metal salt solution, ultrasonic stirring is performed, the pH is adjusted, aging, filtering, washing, and low-temperature drying are performed until the constant weight is obtained. The application has the effects of realizing the resource utilization of red mud and good flocculation performance.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and specifically relates to a novel flocculant, its preparation method, and its application. Background Technology

[0002] As the proportion of large-scale and intensive pig farming in my country increases year by year, the discharge of wastewater from pig farms has caused serious environmental problems. Pig farm wastewater is characterized by high concentration of organic matter, large water quality variations, complex composition, high ammonia nitrogen content, and large discharge volume. Therefore, it is crucial to treat and utilize pig farm wastewater for resource purposes.

[0003] When treating wastewater from pig farms, flocculants are often used to coagulate the wastewater, thereby removing impurities in the wastewater by adsorption and charge neutralization, compression of the double electron layer, entrapment and adsorption bridging, and settling them to the bottom of the water. Currently, commonly used flocculants include inorganic flocculants and organic polymeric flocculants. However, due to the complex composition of livestock wastewater and its high content of ammonia nitrogen, phosphorus, and humic acid, the existing flocculants have low treatment efficiency and cannot meet the requirements.

[0004] Red mud is a highly alkaline waste residue produced during the production of alumina from bauxite (Bayer process or sintering process). Its main components are iron oxide, alumina, and silicon dioxide. my country has a high output of red mud, but it is currently mainly treated by stockpiling, landfilling, and physicochemical treatment. However, these methods are usually difficult to handle, pose high environmental risks, and have low resource recovery efficiency, resulting in serious environmental impact and resource waste.

[0005] Chinese invention patent CN109336236A discloses a method for preparing aluminum-iron flocculants from red mud. This method involves leaching and polymerizing red mud with organic acids such as tannic acid, citric acid, and malic acid to produce a highly efficient aluminum-iron flocculant. However, the citric acid and malic acid are strong acids, which not only affect the degree of polymerization of silicic acid, leading to instability in the resulting flocculant, but also, due to their strong complexing properties, interact with Al... 3+ and Fe 3+ The formation of stable chelates severely inhibits hydrolysis and polymerization, resulting in a reduction of effective flocculation components in the subsequently prepared flocculants and a decrease in flocculation efficiency. Furthermore, the polyphenolic structure of tannic acid easily complexes with metal ions, interfering with the effective components in subsequent flocculants and leading to poor flocculation performance. Summary of the Invention

[0006] The purpose of this invention is to provide a novel flocculant, its preparation method, and its application, which solves the above-mentioned technical problems and has good flocculation performance.

[0007] The above-mentioned technical objective of this invention is achieved through the following technical solution: a method for preparing a novel flocculant, comprising the following steps:

[0008] S1. Acid leaching: Red mud and hydrochloric acid are mixed in a certain mass ratio, and the mixture is kept in a constant temperature water bath for 2-3 hours. The mixture is then filtered to separate the primary leachate and primary filter residue. Red mud and lactic acid are mixed in a certain mass ratio, and the mixture is kept in a constant temperature water bath for 2-3 hours. The mixture is then filtered to separate the secondary leachate and secondary filter residue.

[0009] S2. Preparation of polysilicic acid: Add NaOH solution to the primary filter residue, heat in a constant temperature water bath and stir for 2-3 hours. After filtration, add hydrochloric acid solution to the filtrate to adjust the pH to 3-3.5, and heat and stir continuously to obtain polysilicic acid solution.

[0010] S3, Compound polymerization: Mix the primary leaching solution and the secondary leaching solution in a certain proportion, adjust the pH to 2-5, add polysilicic acid solution to the mixture, stir at high speed, and mature to obtain polysilicic acid metal salt solution.

[0011] S4. Grind, wash, dry and sieve natural zeolite. Immerse the zeolite in a polysilicate metal salt solution, stir ultrasonically for 2-3 hours, and ensure the pH is between 3 and 6. After aging for a certain period of time, filter, wash and dry at low temperature to constant weight to obtain a new type of flocculant.

[0012] A further setting of the present invention is that, in step S1, the mass ratio of red mud to hydrochloric acid is 1–3:15, and the concentration of hydrochloric acid is 2–3 mol·L⁻¹. -1 The mass ratio of red mud to lactic acid is 1–3:15, and the lactic acid concentration is 3–5 mol·L⁻¹. -1 .

[0013] A further setting of the present invention is as follows: in step S2, the mass ratio of primary filter residue to NaOH solution is 1-3:20, and the heating temperature is 80-90℃.

[0014] A further setting of the present invention is as follows: in step S3, the volume ratio of the primary leachate to the secondary leachate is 3-5:2, the aging temperature is 60-70°C, and the aging time is 5 hours.

[0015] A further provision of the present invention is that, in step S4, the molar ratio of zeolite to polysilicate metal salt solution is 0.5 to 1.5.

[0016] A further setting of the present invention is that in step S4, the low-temperature drying temperature is 40-60°C.

[0017] A novel flocculant is prepared using the method described above.

[0018] The application of a novel flocculant is described, which is used to remediate aquaculture wastewater. The dosage ratio of the novel flocculant to the aquaculture wastewater is 20-80 mg / L. The dosage method is to directly add the novel flocculant to the aquaculture wastewater while stirring. After the reaction is complete, the wastewater is allowed to settle.

[0019] The beneficial effects of this invention are:

[0020] 1. This application uses hydrochloric acid and lactic acid to jointly acid leach red mud to remove Al from the red mud. 3+ and Fe 3+ The two acid leaching solutions are mixed and then reacted with the polysilicic acid solution obtained from the filter residue to form a polysilicic acid metal salt solution. Compared with the polysilicic acid metal salt solution obtained by a single acid leaching solution, the resulting polysilicic acid metal salt solution has more molecular surface wrinkles, a larger specific surface area, and a more compact and complex structure. This gives the prepared flocculant excellent adsorption bridging and precipitation trapping capabilities, resulting in excellent flocculation performance and efficient removal of pollutants from water. At the same time, the presence of lactic acid can inhibit the formation of polysilicic acid gel, ensuring the stability of the flocculant and further improving its flocculation performance.

[0021] 2. This application uses zeolite as a carrier to form a triple-action system of adsorption-flocculation-precipitation, resulting in more thorough pollutant removal. On the one hand, zeolite can adsorb and remove small molecule pollutants such as ammonia nitrogen in water and enrich the pollutants, thereby increasing the flocculation rate. On the other hand, it can also act as a carrier. The positive charge of polysilicate metal salt molecules and the negative charge on the zeolite surface attract each other electrostatically, making them stably connected. At the same time, polysilicate metal salt molecules can also be evenly distributed inside and on the surface of zeolite through surface encapsulation and hydrogen bonding, which can prevent molecular self-aggregation and improve stability and flocculation performance. In addition, after the polysilicate metal salt is released and takes effect, it forms a floc network that encapsulates the zeolite, quickly forming larger, denser composite flocs with better settling performance, further improving flocculation efficiency.

[0022] 3. This application uses lactic acid and hydrochloric acid to modify zeolite. On the one hand, lactic acid and hydrochloric acid dissolve inorganic impurities in zeolite, loosen pores, increase the specific surface area of ​​zeolite, and improve the carrying efficiency of polysilicic acid metal salt molecules, thereby improving flocculation performance. On the other hand, lactic acid can also increase the molecular weight of flocculant, making it easier to settle and improving flocculation efficiency. In addition, lactic acid is a short-chain molecule, which can provide appropriate steric hindrance when adsorbed on the surface of polysilicic acid or metal hydroxide, preventing excessive aggregation, while not hindering the binding of active sites, which helps to form a loose and porous floc structure with a large specific surface area, strong adsorption bridging ability, and fast settling speed.

[0023] 4. This application uses red mud as raw material to recover Fe, Al and Si from it to prepare a new type of flocculant. All the raw materials used come from red mud, realizing the efficient resource utilization of red mud. The flocculant prepared can efficiently treat aquaculture wastewater. Detailed Implementation

[0024] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] A novel method for preparing flocculants

[0026] Example 1

[0027] S1. Acid leaching: Red mud and hydrochloric acid are mixed at a mass ratio of 1:15, and the mixture is heated in a constant temperature water bath for 2-3 hours. The mixture is then filtered to obtain a primary leachate and a primary filter residue. Red mud and lactic acid are mixed at a mass ratio of 1:15, and the mixture is heated in a constant temperature water bath for 2-3 hours. The mixture is then filtered to obtain a secondary leachate and a secondary filter residue. The hydrochloric acid concentration is 2 mol·L⁻¹. -1 The lactic acid concentration is 3 mol·L⁻¹ -1 ;

[0028] S2. Preparation of polysilicic acid: Add 20% NaOH solution to the primary filter residue, heat in an 80℃ constant temperature water bath and stir for 2-3 hours. After filtration, add hydrochloric acid solution to the filtrate to adjust the pH to 3-3.5, and heat and stir continuously to obtain polysilicic acid solution. The mass ratio of primary filter residue to NaOH solution is 1:20.

[0029] S3, Compound polymerization: Mix the primary leaching solution and the secondary leaching solution in a ratio of 5:2, adjust the pH to 2-5, add polysilicic acid solution to the mixture, stir at high speed, and mature at 70°C for 5 hours to obtain polysilicic acid metal salt solution.

[0030] S4. Grind, wash, and dry natural zeolite, then sieve it through a 20-30 mesh. Immerse the zeolite in a polysilicate metal salt solution with a molar ratio of zeolite to polysilicate metal salt solution of 0.5. Stir ultrasonically for 2-3 hours, ensuring the pH is between 3 and 6. After aging for a certain period of time, filter, wash, and dry at 40°C to constant weight to obtain a new type of flocculant, labeled as F1.

[0031] Example 2

[0032] S1. Acid leaching: Red mud and hydrochloric acid are mixed at a mass ratio of 3:15, and the mixture is heated in a constant temperature water bath for 2-3 hours. The mixture is then filtered to obtain a primary leachate and a primary filter residue. Red mud and lactic acid are mixed at a mass ratio of 3:15, and the mixture is heated in a constant temperature water bath for 2-3 hours. The mixture is then filtered to obtain a secondary leachate and a secondary filter residue. The hydrochloric acid concentration is 3 mol·L⁻¹. -1 The lactic acid concentration is 5 mol·L⁻¹ -1 ;

[0033] S2. Preparation of polysilicic acid: Add 20% NaOH solution to the primary filter residue, heat in a 90℃ constant temperature water bath and stir for 2-3 hours. After filtration, add hydrochloric acid solution to the filtrate to adjust the pH to 3-3.5, and heat and stir continuously to obtain polysilicic acid solution. The mass ratio of primary filter residue to NaOH solution is 3:20.

[0034] S3, Compound polymerization: Mix the primary leaching solution and the secondary leaching solution in a ratio of 3:2, adjust the pH to 2-5, add polysilicic acid solution to the mixture, stir at high speed, and mature at 60°C for 5 hours to obtain polysilicic acid metal salt solution.

[0035] S4. Grind, wash, and dry natural zeolite, then sieve it through a 20-30 mesh. Immerse the zeolite in a polysilicate metal salt solution with a molar ratio of 1:1. Stir ultrasonically for 2-3 hours, ensuring the pH is between 3 and 6. After aging for a certain period, filter, wash, and dry at 60°C to constant weight to obtain a new type of flocculant, labeled as F2.

[0036] Example 3

[0037] S1. Acid leaching: Red mud and hydrochloric acid are mixed at a mass ratio of 2:15, and the mixture is heated in a constant temperature water bath for 2–3 hours. The mixture is then filtered to obtain a primary leachate and a primary filter residue. Red mud and lactic acid are also mixed at a mass ratio of 2:15, and the mixture is heated in a constant temperature water bath for 2–3 hours. The mixture is then filtered to obtain a secondary leachate and a secondary filter residue. The hydrochloric acid concentration is 2.5 mol·L⁻¹. -1 The lactic acid concentration is 4 mol·L⁻¹ -1 ;

[0038] S2. Preparation of polysilicic acid: Add 20% NaOH solution to the primary filter residue, heat in a constant temperature water bath at 85℃ and stir for 2-3 hours. After filtration, add hydrochloric acid solution to the filtrate to adjust the pH to 3-3.5, and heat and stir continuously to obtain polysilicic acid solution. The mass ratio of primary filter residue to NaOH solution is 2:20.

[0039] S3, Compound polymerization: Mix the primary leaching solution and the secondary leaching solution in a ratio of 4:2, adjust the pH to 2-5, add polysilicic acid solution to the mixture, stir at high speed, and mature at 65°C for 5 hours to obtain polysilicic acid metal salt solution.

[0040] S4. Grind, wash, and dry natural zeolite, then sieve it through a 20-30 mesh. Immerse the zeolite in a polysilicate metal salt solution with a molar ratio of zeolite to polysilicate metal salt solution of 1.5. Stir ultrasonically for 2-3 hours, ensuring the pH is between 3 and 6. After aging for a certain period of time, filter, wash, and dry at 50°C to constant weight to obtain a new type of flocculant, labeled as F3.

[0041] Comparative Example 1

[0042] S1. Acid leaching: Acid leaching is performed using red mud with a concentration of 2 mol·L⁻¹. -1 Hydrochloric acid was mixed at a mass ratio of 1:15, and the mixture was placed in a constant temperature water bath for 2–3 hours. The mixture was then filtered to separate the primary leachate and the primary filter residue. Red mud and a solution with a concentration of 3 mol·L⁻¹ were then added. -1 Hydrochloric acid was mixed at a mass ratio of 1:15, and the mixture was placed in a constant temperature water bath for 2-3 hours. The secondary leachate and secondary filter residue were then separated by filtration.

[0043] S2. Preparation of polysilicic acid: Add 20% NaOH solution to the primary filter residue, heat in an 80℃ constant temperature water bath and stir for 2-3 hours. After filtration, add hydrochloric acid solution to the filtrate to adjust the pH to 3-3.5, and heat and stir continuously to obtain polysilicic acid solution. The mass ratio of primary filter residue to NaOH solution is 1:20.

[0044] S3, Compound polymerization: Mix the primary leaching solution and the secondary leaching solution in a ratio of 5:2, adjust the pH to 2-5, add polysilicic acid solution to the mixture, stir at high speed, and mature at 70°C for 5 hours to obtain polysilicic acid metal salt solution.

[0045] S4. Grind, wash, and dry natural zeolite, then sieve it through a 20-30 mesh. Immerse the zeolite in a polysilicate metal salt solution with a molar ratio of 0.5. Stir ultrasonically for 2-3 hours, ensuring the pH is between 3 and 6. After aging for a certain period, filter, wash, and dry at 40°C to constant weight to obtain the flocculant, labeled as D1.

[0046] Comparative Example 2

[0047] S1. Acid leaching: Acid leaching is performed using red mud with a concentration of 2 mol·L⁻¹. -1 Lactic acid was mixed at a mass ratio of 1:15, and the mixture was placed in a constant temperature water bath for 2–3 hours. The mixture was then filtered to separate the primary leachate and the primary filter residue. Red mud and a solution with a concentration of 3 mol·L⁻¹ were then added. -1 Lactic acid was mixed at a mass ratio of 1:15, and the mixture was placed in a constant temperature water bath for 2-3 hours. The mixture was then filtered to separate the secondary leachate and secondary filter residue.

[0048] S2. Preparation of polysilicic acid: Add 20% NaOH solution to the primary filter residue, heat in an 80℃ constant temperature water bath and stir for 2-3 hours. After filtration, add hydrochloric acid solution to the filtrate to adjust the pH to 3-3.5, and heat and stir continuously to obtain polysilicic acid solution. The mass ratio of primary filter residue to NaOH solution is 1:20.

[0049] S3, Compound polymerization: Mix the primary leaching solution and the secondary leaching solution in a ratio of 5:2, adjust the pH to 2-5, add polysilicic acid solution to the mixture, stir at high speed, and mature at 70°C for 5 hours to obtain polysilicic acid metal salt solution.

[0050] S4. Grind, wash, and dry natural zeolite, then sieve it through a 20-30 mesh. Immerse the zeolite in a polysilicate metal salt solution with a molar ratio of 0.5. Stir ultrasonically for 2-3 hours, ensuring the pH is between 3 and 6. After aging for a certain period, filter, wash, and dry at 40°C to constant weight to obtain the flocculant, labeled as D2.

[0051] Comparative Example 3

[0052] S1. Acid leaching: Red mud and hydrochloric acid are mixed at a mass ratio of 1:15, and the mixture is heated in a constant temperature water bath for 2-3 hours. The mixture is then filtered to obtain a primary leachate and a primary filter residue. Red mud and lactic acid are mixed at a mass ratio of 1:15, and the mixture is heated in a constant temperature water bath for 2-3 hours. The mixture is then filtered to obtain a secondary leachate and a secondary filter residue. The hydrochloric acid concentration is 2 mol·L⁻¹. -1 The lactic acid concentration is 3 mol·L⁻¹ -1 ;

[0053] S2. Preparation of polysilicic acid: Add 20% NaOH solution to the primary filter residue, heat in an 80℃ constant temperature water bath and stir for 2-3 hours. After filtration, add hydrochloric acid solution to the filtrate to adjust the pH to 3-3.5, and heat and stir continuously to obtain polysilicic acid solution. The mass ratio of primary filter residue to NaOH solution is 1:20.

[0054] S3, Compound polymerization: Mix the primary leaching solution and the secondary leaching solution in a ratio of 5:2, adjust the pH to 2-5, add polysilicic acid solution to the mixture, stir at high speed, and mature at 70°C for 5 hours to obtain polysilicic acid metal salt solution.

[0055] S4. Take a polysilicate metal salt solution and ultrasonically stir for 2-3 hours, ensuring the pH is between 3 and 6. After aging for a certain period of time, filter, wash, and dry at 40℃ to constant weight to obtain the flocculant, labeled as D3.

[0056] Experimental method: F1-F3 and D1-D3 prepared according to the preparation methods of Examples 1-3 and Comparative Examples 1-3 were added to pig farming wastewater. The addition ratio of flocculant to farm wastewater was 80 mg / L. The addition method was to directly add the new flocculant to the farm wastewater while stirring. After the reaction was completed, the mixture was allowed to settle.

[0057] Water quality parameter determination methods: Ammonia nitrogen was determined according to Nessler's reagent spectrophotometric method (HJ 535-2009) for the determination of ammonia nitrogen in water quality; total phosphorus was determined according to ammonium molybdate spectrophotometric method (GB 11893-89) for the determination of total phosphorus in water quality; and humic acid (UV absorbance method) was determined according to UV absorbance method. 254 ).

[0058] Measurements were performed on raw water before addition and the supernatant after settling to determine ammonia nitrogen, total phosphorus, and humic acid. For humic acid measurement, both raw water and supernatant were first filtered through a 0.45 μm nylon membrane before UV measurement. 254 The removal rates of each indicator parameter were calculated, and the results are shown in Table 1:

[0059] Table 1

[0060]

[0061] In summary, as shown in Examples 1, 1, and 2, the flocculant obtained by combining hydrochloric acid and lactic acid in the acid leaching of red mud exhibits superior adsorption bridging and sedimentation trapping capabilities compared to the flocculant obtained by using a single acid leaching solution. It also demonstrates excellent flocculation performance and can efficiently remove pollutants from water. Furthermore, as shown in Examples 1 and 3, using zeolite as a carrier results in more thorough pollutant removal.

Claims

1. A method for preparing a novel flocculant, characterized in that: Includes the following steps: S1. Acid leaching: Mix red mud and hydrochloric acid in a certain mass ratio, bathe in a constant temperature water bath for 2-3 hours, and filter to separate the primary leachate and primary filter residue; mix red mud and lactic acid in a certain mass ratio, bathe in a constant temperature water bath for 2-3 hours, and filter to separate the secondary leachate and secondary filter residue. S2. Preparation of polysilicic acid: Add NaOH solution to the primary filter residue, heat in a constant temperature water bath and stir for 2-3 hours. After filtration, add hydrochloric acid solution to the filtrate to adjust the pH to 3-3.5, and heat and stir continuously to obtain polysilicic acid solution. S3, Compound polymerization: Mix the primary leaching solution and the secondary leaching solution in a certain proportion, adjust the pH to 2~5, add polysilicic acid solution to the mixture, stir at high speed, and mature to obtain polysilicic acid metal salt solution. S4. Grind, wash, dry and sieve natural zeolite. Immerse the zeolite in a polysilicate metal salt solution, stir ultrasonically for 2-3 hours, and ensure the pH is between 3 and 6. After aging for a certain period of time, filter, wash and dry at low temperature to constant weight to obtain a new type of flocculant.

2. The method for preparing a novel flocculant according to claim 1, characterized in that: In step S1, the mass ratio of red mud to hydrochloric acid is 1~3:15, and the concentration of hydrochloric acid is 2~3 mol·m·kJ. The mass ratio of red mud to lactic acid is 1~3:15, and the lactic acid concentration is 3~5 mol·m·kJ ... .

3. The method for preparing a novel flocculant according to claim 1, characterized in that: In step S2, the mass ratio of primary filter residue to NaOH solution is 1~3:20, and the heating temperature is 80~90℃.

4. The method for preparing a novel flocculant according to claim 1, characterized in that: In step S3, the volume ratio of the primary leachate to the secondary leachate is 3~5:2, the aging temperature is 60~70℃, and the aging time is 5h.

5. The method for preparing a novel flocculant according to claim 1, characterized in that: In step S4, the molar ratio of zeolite to polysilicate metal salt solution is 0.5~1.

5.

6. The method for preparing a novel flocculant according to claim 1, characterized in that: In step S4, the low-temperature drying temperature is 40~60℃.

7. A novel flocculant, characterized in that: It is prepared by any one of the preparation methods described in claims 1 to 5.

8. The application of the novel flocculant according to claim 7, characterized in that: This novel flocculant was used to remediate aquaculture wastewater. The dosage ratio of the novel flocculant to the aquaculture wastewater was 20~80 mg / L. The addition method was to directly add the novel flocculant to the aquaculture wastewater while stirring. After the reaction was complete, the mixture was allowed to settle.

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