A flocculation complex for sewage treatment and its preparation method

Abstract

The present invention discloses a flocculation complex for sewage treatment. The present invention also discloses a preparation method of the above-mentioned flocculation complex for sewage treatment, which comprises the following steps: adding an emulsifier into an oily solvent and stirring evenly to obtain a premix a; adding acrylamide and fulvic acid into deionized water, adjusting the pH value of the system to 6.1 - 6.5, adding 2-acrylamido long-chain alkyl sulfonate and a hydrophilic monomer and stirring evenly, then adding them into the premix a and stirring until the system becomes a transparent emulsion to obtain a premix b; introducing nitrogen into the premix b, adding an initiator, stirring at 40 - 60 °C for 2 - 4 h, cooling to room temperature, and drying under vacuum to obtain the flocculation complex for sewage treatment. The operation of the present invention is simple, the reaction steps are simple and controllable, the polymerization process is easy to observe, and the reaction process is extremely easy to control. It neither requires additional addition of a coagulant aid nor makes the sedimentation effect of spherical precipitates extremely good.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment flocculants, and particularly to a flocculation complex for sewage treatment and a preparation method thereof. Background Art

[0002] Cadmium is a heavy metal with strong toxicity. Cadmium in the human body is mainly ingested through contaminated water. Cadmium-contaminated water is the main cause of cadmium poisoning due to its large accumulation in the human body. If this cadmium-containing water is used to irrigate farmland, the rice seedlings will grow poorly, and the produced rice will become "cadmium rice", seriously endangering human health. Cadmium entering the water body can be enriched and amplified through the food chain and can also be directly absorbed by plankton and higher organisms in elemental form. Therefore, finding a good way to solve cadmium pollution is very important for maintaining a good ecological environment, especially for the urban ecological environment in industrialized areas.

[0003] For treating heavy metal pollution in water bodies, traditional methods mainly include physical and chemical methods, such as chemical flocculation method, polymer collector method, natural zeolite adsorption method, membrane technology, activated carbon adsorption process, ion exchange method, etc. The research on the scientific theory and method of chemical flocculation has always been an important research field in the treatment of cadmium-polluted water and is also one of the essential unit operations in water treatment. For heavy metal sewage, certain methods can be used to convert it into colloidal substances first, and then the flocculation method can be used to remove it.

[0004] Polyacrylamide is a water-soluble high molecular polymer formed by homopolymerization of acrylamide monomers and copolymerization of other monomers with special groups. The structural unit of polyacrylamide contains amide groups, which are easy to form intramolecular and intermolecular hydrogen bonds, making it have good thickening, flocculation, and drag reduction effects and having a wide range of applications in the treatment of cadmium pollution. Currently, there are various methods for synthesizing polyacrylamide, such as aqueous solution polymerization method, bulk polymerization, suspension polymerization method, etc.

[0005] Currently, as the composition of heavy metal sewage becomes increasingly complex and the sewage discharge requirements gradually become stricter, the treatment with polyacrylamide can no longer meet the sewage discharge requirements. The main problems include that heavy metal sewage is generally acidic sewage, and a large amount of lime needs to be added to make the pH value of the system alkaline before treatment, thus increasing the treatment cost; at the same time, the sedimentation property of the precipitate is poor, and an additional coagulant aid needs to be added to achieve better removal of heavy metal cadmium, increasing the types and dosages of chemicals. Summary of the Invention

[0006] The purpose of the present invention is to solve the disadvantages existing in the prior art and to provide a flocculation complex for sewage treatment and a preparation method thereof.

[0007] A preparation method of a flocculation complex for sewage treatment includes the following steps:

[0008] S1. Add an emulsifier to an oily solvent and stir evenly to obtain a premix a;

[0009] S2. Add acrylamide and fulvic acid to deionized water, adjust the pH value of the system to 6.1 - 6.5, add 2-acrylamido long-chain alkyl sulfonate and a hydrophilic monomer, stir evenly, add to the premix a, and stir until the system becomes a transparent emulsion to obtain a premix b;

[0010] S3. Pass nitrogen into the premix b, add an initiator, stir at 40 - 60 °C for 2 - 4 h, cool to room temperature, and dry under vacuum to obtain a flocculation complex for sewage treatment.

[0011] Preferably, in S1, the mass ratio of the emulsifier to the oily solvent is 1 - 2:50 - 60.

[0012] Preferably, in S1, the HLB value of the emulsifier is 4 - 6, and the emulsifier is at least one of sorbitan monooleate, sorbitan monostearate, propylene glycol monolaurate, polyoxyethylene oleyl ether, methyl glucoside sesquistearate, and diethylene glycol fatty acid ester.

[0013] Preferably, in S1, the oily solvent is at least one of petrolatum, mineral oil, palm oil, coconut oil, corn oil, polydimethylsiloxane, and dioctyl carbonate.

[0014] Preferably, in S2, the mass ratio of acrylamide, fulvic acid, 2-acrylamido long-chain alkyl sulfonate, the hydrophilic monomer, and the premix a is 2 - 6:1 - 3:1 - 2:4 - 8:51 - 62.

[0015] Preferably, in S2, the hydrophilic monomer includes acrylic acid or methacrylic acid.

[0016] Preferably, in S3, the mass ratio of the premix b to the initiator is 78 - 100:0.1 - 1.

[0017] Preferably, in S3, the initiator is a persulfate, preferably ammonium persulfate.

[0018] Preferably, in S3, the average particle size of the flocculation complex for sewage treatment is 84.32 ± 1.47 nm, and the polydispersity index is 0.013 ± 0.002.

[0019] A flocculation complex for sewage treatment is prepared by the above preparation method of the flocculation complex for sewage treatment.

[0020] The technical effects of the present invention are as follows:

[0021] The present invention uses sodium 2-acrylamidotetradecanesulfonate as a hydrophobic monomer, which has both a short-chain hydrophilic segment and a long-chain hydrophobic segment in its molecular structure. When compounded with hydrophilic monomers acrylamide and acrylic acid, and under the emulsification of an emulsifier with an HLB value of 4-6, a water-in-oil emulsion is formed. Then, a polymer is synthesized under the action of an initiator. Since a hydrophobic group is introduced into the macromolecular chain, it promotes migration to the outer phase and has a strong association effect between molecular chains. At the same time, the mutual entanglement and association between molecular chains promote the formation of a complex network structure of the polymer in space, and the stability of the polymer in the outer phase structure is extremely good; while fulvic acid has good water solubility and dissolves in the inner phase of the emulsion. After the reaction, its molecular chain migrates to the inner phase, and finally a microsphere structure with a polyacrylamide shell layer structure and fulvic acid chain segments encapsulated inside is formed.

[0022] When the present invention is used for treating heavy metal sewage, even in an acidic environment, the coordination groups of heavy metal ions inside the microspheres can quickly chelate with heavy metal ions (especially cadmium). At the same time, the rapid flocculation of the outer microspheres is utilized for precipitation. Not only is the separation effect high and filtration is not required, but also the sedimentation speed is fast, making the treatment of heavy metal sewage simpler and easier.

[0023] The reaction of the present invention proceeds in the form of droplets in the organic phase component. Not only is the reaction heat relatively easy to dissipate during the polymerization process, the system will not show overheating or uneven heat distribution, the reaction proceeds smoothly, but also the polymerization rate is moderate, which is beneficial to the growth of the macromolecular chain of the product and is more conducive to the formation of hollow shell-shaped polymeric microspheres.

[0024] The present invention is simple to operate, the reaction steps are simple and controllable, the polymerization process is easy to observe, and the reaction process is extremely easy to control. It neither requires additional addition of a coagulant aid nor has excellent sedimentation effect for spherical precipitates. Only by adding a certain amount of the product of the present invention to the sewage and fully stirring, insoluble flocculent precipitates can be quickly generated. It is widely applicable to the treatment of sewage containing heavy metal cadmium such as electroplating sewage, smelting sewage, non-ferrous metal processing sewage, and ore dressing sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Comparison chart of the removal rates of Cd in cadmium-containing sewage by the flocculation complex obtained in Example 7 and the polyacrylamide-based heavy metal flocculant used in the comparative example at different pH values 2+

[0026] Figure 2 Comparison chart of the removal rates of Cd in cadmium-containing sewage with different initial concentrations by the flocculation complex obtained in Example 7 and the polyacrylamide-based heavy metal flocculant used in the comparative example 2+ DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will be further illustrated below with specific examples.

[0028] Example 1

[0029] A preparation method of a flocculation complex for sewage treatment, comprising the following steps:

[0030] S1. Add 1 kg of emulsifier with an HLB value of 4 to 50 kg of palm oil and stir evenly to obtain premix a;

[0031] S2. Add 2 kg of acrylamide and 1 kg of fulvic acid to 20 kg of deionized water, adjust the pH value of the system to 6.1 - 6.5 with 0.1 mol / L sodium hydroxide, add 1 kg of 2-acrylamido long-chain alkyl sulfonate and 4 kg of acrylic acid, stir evenly, add to 51 kg of premix a, and stir at a speed of 1000 r / min until the system becomes a transparent emulsion to obtain premix b;

[0032] S3. Pass nitrogen into 78 kg of premix b to remove oxygen in the system, add 0.1 kg of sodium persulfate, stir at 40 °C for 2 h, cool to room temperature, and vacuum dry to obtain the flocculation complex for sewage treatment.

[0033] Example 2

[0034] A preparation method of a flocculation complex for sewage treatment, comprising the following steps:

[0035] S1. Add 2 kg of emulsifier with an HLB value of 6 to 60 kg of polydimethylsiloxane and stir evenly to obtain premix a;

[0036] S2. Add 6 kg of acrylamide and 3 kg of fulvic acid to 30 kg of deionized water, adjust the pH value of the system to 6.1 - 6.5 with 1 mol / L sodium hydroxide, add 2 kg of 2-acrylamido long-chain alkyl sulfonate and 8 kg of methacrylic acid, stir evenly, add to 62 kg of premix a, and stir at a speed of 2000 r / min until the system becomes a transparent emulsion to obtain premix b;

[0037] S3. Pass nitrogen into 100 kg of premix b to remove oxygen in the system, add 1 kg of potassium persulfate, stir at 60 °C for 4 h, cool to room temperature, and vacuum dry to obtain the flocculation complex for sewage treatment.

[0038] Example 3

[0039] A preparation method of a flocculation complex for sewage treatment, comprising the following steps:

[0040] S1. Add 1.2 kg of sorbitan monooleate to 53 kg of mineral oil and stir evenly to obtain premix a;

[0041] S2. Add 5 kg of acrylamide and 1.5 kg of fulvic acid to 28 kg of deionized water, adjust the pH value of the system to 6.1 - 6.5 with 0.2 mol / L sodium hydroxide, add 1.7 kg of 2-acrylamido long-chain alkyl sulfonate, 2 kg of acrylic acid, and 3 kg of methacrylic acid, stir evenly, add to 60 kg of premix a, and stir at a speed of 1200 r / min until the system becomes a transparent emulsion to obtain premix b;

[0042] S3. Pass nitrogen into 96 kg of premix b to remove oxygen in the system, add 0.3 kg of ammonium persulfate, stir at 55 °C for 2.5 h, cool to room temperature, and dry under vacuum to obtain the flocculation complex for sewage treatment.

[0043] Example 4

[0044] A preparation method of a flocculation complex for sewage treatment, comprising the following steps:

[0045] S1. Add 1.4 kg of sorbitan monostearate to 54 kg of mineral oil and stir evenly to obtain premix a;

[0046] S2. Add 3.5 kg of acrylamide and 1.8 kg of fulvic acid to 24 kg of deionized water, adjust the pH value of the system to 6.1 - 6.5 with 0.3 mol / L sodium hydroxide, add 1.4 kg of 2-acrylamido long-chain alkyl sulfonate, 5.5 kg of acrylic acid, stir evenly, add to 55 kg of premix a, and stir at a speed of 1400 r / min until the system becomes a transparent emulsion to obtain premix b;

[0047] S3. Pass nitrogen into 86 kg of premix b to remove oxygen in the system, add 0.4 kg of ammonium persulfate, stir at 47 °C for 2.8 h, cool to room temperature, and dry under vacuum to obtain the flocculation complex for sewage treatment.

[0048] Example 5

[0049] A preparation method of a flocculation complex for sewage treatment, comprising the following steps:

[0050] S1. Add 1.8 kg of propylene glycol monolaurate to 57 kg of coconut oil and stir evenly to obtain premix a;

[0051] S2. Add 3 kg of acrylamide and 2.5 kg of fulvic acid to 22 kg of deionized water, adjust the pH value of the system to 6.1 - 6.5 with 0.8 mol / L sodium hydroxide, add 1.3 kg of 2-acrylamido long-chain alkyl sulfonate, 5 kg of acrylic acid, 2 kg of methacrylic acid, stir evenly, add to 53 kg of premix a, and stir at a speed of 1800 r / min until the system becomes a transparent emulsion to obtain premix b;

[0052] S3. Nitrogen is introduced into 82 kg of premix b to expel oxygen in the system, 0.8 kg of ammonium persulfate is added, and the mixture is stirred at 45 °C for 3.5 h, cooled to room temperature, and dried under vacuum to obtain the flocculation complex for sewage treatment.

[0053] Example 6

[0054] A preparation method of a flocculation complex for sewage treatment includes the following steps:

[0055] S1. 1 kg of propylene glycol monolaurate and 0.6 kg of diethylene glycol fatty acid ester are added to 56 kg of corn oil and stirred evenly to obtain premix a;

[0056] S2. 4.5 kg of acrylamide and 2.2 kg of fulvic acid are added to 26 kg of deionized water, the pH value of the system is adjusted to 6.1 - 6.5 with 0.7 mol / L sodium hydroxide, 1.6 kg of 2-acrylamido long-chain alkyl sulfonate and 6.5 kg of methacrylic acid are added and stirred evenly, then added to 58 kg of premix a, and stirred at a speed of 1600 r / min until the system becomes a transparent emulsion to obtain premix b;

[0057] S3. Nitrogen is introduced into 92 kg of premix b to expel oxygen in the system, 0.7 kg of ammonium persulfate is added, and the mixture is stirred at 53 °C for 3.2 h, cooled to room temperature, and dried under vacuum to obtain the flocculation complex for sewage treatment.

[0058] Example 7

[0059] A preparation method of a flocculation complex for sewage treatment includes the following steps:

[0060] S1. 1.5 kg of polyoxyethylene oleyl ether is added to 55 kg of palm oil and stirred evenly to obtain premix a;

[0061] S2. 4 kg of acrylamide and 2 kg of fulvic acid are added to 25 kg of deionized water, the pH value of the system is adjusted to 6.1 - 6.5 with 0.5 mol / L sodium hydroxide, 1.5 kg of 2-acrylamido long-chain alkyl sulfonate and 6 kg of acrylic acid are added and stirred evenly, then added to 56.5 kg of premix a, and stirred at a speed of 1500 r / min until the system becomes a transparent emulsion to obtain premix b;

[0062] S3. Nitrogen is introduced into 90 kg of premix b to expel oxygen in the system, 0.5 kg of ammonium persulfate is added, and the mixture is stirred at 50 °C for 3 h, cooled to room temperature, dried to constant weight under vacuum with a vacuum degree of 50 Pa, and pulverized to obtain the flocculation complex for sewage treatment.

[0063] Dissolve the flocculation complex for sewage treatment obtained in this example in deionized water, and perform a 3-minute pretreatment using a 40 kHz 500 W ultrasonic instrument. Then, place the uniformly dispersed nanoparticles in a Malvern nanoparticle size potentiometer (Zetasizer Nano ZSE) to analyze the size distribution, average particle size, and polydispersity index (PDI) of the nanoparticles.

[0064] Use a pipette to aspirate 700 μL of the above-mentioned uniformly dispersed nanoparticles, slowly push them into the sample cell, avoid generating bubbles, insert the sample slot, cover the outer cover of the instrument, and start measuring the Zeta potential of each group of samples.

[0065] The average particle size of the flocculation complex for sewage treatment obtained in this example is 84.32 ± 1.47 nm, the polydispersity coefficient is 0.013 ± 0.002, and the Zeta potential is 30.03 ± 0.37 mV. It is confirmed that the flocculation complex for sewage treatment obtained in this example has a uniform particle size and good stability.

[0066] Comparative example

[0067] Use the polyacrylamide-based heavy metal flocculant disclosed in CN 105753128A (application number 201610241883.4, application date April 19, 2016, publication date July 13, 2016) as a control.

[0068] Use the flocculation complex obtained in Example 7 and the polyacrylamide-based heavy metal flocculant used in the comparative example to treat cadmium-containing sewage under different conditions, specifically as follows:

[0069] I. Removal effect of Cd 2+ under different pH values

[0070] Take a simulated water sample containing Cd 2+ with a concentration of 100 mg / L, adjust its pH value to 4.0, 5.0, 6.0, and 7.0 respectively, add each group of samples (the addition amount is 2 mg / L), stir rapidly at a speed of 120 r / min for 2 min, then stir slowly at a speed of 40 r / min for 10 min, and then settle for 10 min. Take the clear liquid 2 cm below the liquid surface and measure the residual Cd 2+ concentration using an atomic absorption spectrophotometer, and calculate the Cd 2+ removal rate.

[0071] As Figure 1 shown, by horizontal comparison, it can be found that the flocculation complex obtained in Example 7 has a better removal effect on Cd 2+ under different pH values than the comparative example; by vertical comparison, it can be found that the flocculation complex obtained in the example has a good removal effect on Cd 2+The removal rate can also reach over 95%, and as the pH increases, the Cd 2+ removal rate is also gradually increasing.

[0072] II. Removal effect of Cd 2+ at different initial concentrations

[0073] Take simulated water samples with initial concentrations of 10, 50, 100, 150, and 200 mg / L of Cd 2+ respectively, adjust their pH values to 5.0, add each group of samples (the addition amount is 2 mg / L), stir rapidly at a speed of 120 r / min for 2 min, then stir slowly at a speed of 40 r / min for 10 min, and then settle for 10 min. Take the clear liquid 2 cm below the liquid surface and measure the residual Cd 2+ concentration, and calculate the Cd 2+ removal rate.

[0074] As Figure 2 shown, by comparing vertically, it can be found that as the initial concentration increases, the Cd 2+ removal rate is decreasing; and by comparing horizontally, it can be found that the flocculation complex obtained in Example 7 has a better removal effect on Cd 2+ under different initial concentration conditions than the comparative example, and the greater the difference between the two when the initial concentration is higher.

[0075] The applicant believes that: This is because the present invention uses 2-acrylamidotetradecanesulfonic acid sodium as the hydrophobic monomer, which has both a short-chain hydrophilic segment and a long-chain hydrophobic segment in its molecular structure. When compounded with the hydrophilic monomers acrylamide and acrylic acid, an oil-in-water emulsion is formed under the emulsification of an emulsifier with an HLB value of 4-6, and then a polymer is synthesized under the action of an initiator. Since a hydrophobic group is introduced into the macromolecular chain, it promotes migration to the outer phase and has a strong association effect between molecular chains. At the same time, the mutual entanglement and association of molecular chains promote the formation of a complex network structure of the polymer in space, and the stability of the polymer in the outer phase structure is extremely good; while fulvic acid has good water solubility and dissolves in the inner phase of the emulsion. After the reaction, its molecular chain migrates to the inner phase, and finally forms a microsphere structure with a polyacrylamide shell layer structure and fulvic acid chain segments encapsulated inside.

[0076] When the present invention is used for treating heavy metal sewage, even in an acidic environment, the coordination groups of heavy metal ions inside the microspheres can quickly chelate with heavy metal ions (especially cadmium), and at the same time, the rapid flocculation and precipitation of the outer microspheres are utilized. Not only is the separation effect high and filtration is not required, but also the sedimentation speed is fast, making the treatment of heavy metal sewage simpler and easier.

[0077] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

Claims

1. A preparation method of a flocculation composite for sewage treatment, characterized in that, It includes the following steps: S1. Add an emulsifier to an oily solvent and stir evenly to obtain a premix a; S2. Add acrylamide and fulvic acid to deionized water, adjust the pH value of the system to 6.1 - 6.5, add 2-acrylamido long-chain alkyl sulfonate and a hydrophilic monomer, stir evenly, add to the premix a, and stir until the system becomes a transparent emulsion to obtain a premix b; S3. Pass nitrogen into the premix b, add an initiator, stir at 40 - 60 °C for 2 - 4 h, cool to room temperature, and dry under vacuum to obtain a flocculation complex for sewage treatment.

2. The preparation method of the flocculation composite for sewage treatment according to claim 1, characterized in that, In S1, the mass ratio of the emulsifier to the oily solvent is 1 - 2:50 - 60.

3. The preparation method of the flocculation composite for sewage treatment according to claim 1, characterized in that, In S1, the HLB value of the emulsifier is 4 - 6, and the emulsifier is at least one of sorbitan monooleate, sorbitan monostearate, propylene glycol monolaurate, polyoxyethylene oleyl ether, methyl glucoside sesquistearate, and diethylene glycol fatty acid ester.

4. The preparation method of the flocculation composite for sewage treatment according to claim 1, characterized in that, In S1, the oily solvent is at least one of petrolatum, mineral oil, palm oil, coconut oil, corn oil, polydimethylsiloxane, and dioctyl carbonate.

5. The preparation method of the flocculation composite for sewage treatment according to claim 1, characterized in that, In S2, the mass ratio of acrylamide, fulvic acid, 2-acrylamido long-chain alkyl sulfonate, the hydrophilic monomer, and the premix a is 2 - 6:1 - 3:1 - 2:4 - 8:51 - 62.

6. The preparation method of the flocculation composite for sewage treatment according to claim 1, characterized in that, In S2, the hydrophilic monomer includes acrylic acid or methacrylic acid.

7. The preparation method of the flocculation composite for sewage treatment according to claim 1, characterized in that, In S3, the mass ratio of the premix b to the initiator is 78 - 100:0.1 - 1.

8. The preparation method of the flocculation composite for sewage treatment according to claim 1, characterized in that, In S3, the initiator is a persulfate.

9. The preparation method of the flocculation composite for sewage treatment according to claim 1, characterized in that, In S3, the initiator is ammonium persulfate.

10. The preparation method of the flocculation composite for sewage treatment according to claim 1, characterized in that, In S3, the average particle size of the flocculation complex for sewage treatment is 84.32 ± 1.47 nm, and the polydispersity index is 0.013 ± 0.

002.

11. A flocculation composite for sewage treatment, characterized in that, It is prepared by the preparation method of the flocculation complex for sewage treatment according to any one of claims 1 - 10.

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