Preparation method of low-temperature plasma modified chitosan flocculant

Abstract

The present invention discloses a method for preparing a low-temperature plasma-modified chitosan flocculant, comprising the following steps: placing chitosan in a low-temperature plasma modification device, introducing air and performing low-temperature plasma modification; then placing the low-temperature plasma-modified chitosan in an acrylamide solution, adding an inorganic initiator, and subsequently placing the mixed solution in a water bath and stirring to obtain a gel material, and cooling, washing, centrifuging, and drying the obtained gel material to obtain a modified chitosan flocculant. The flocculant of the present invention uses the natural polysaccharide flocculant chitosan as a base material and is prepared using a low-temperature plasma-induced modification method; it has the advantages of good stability, environmental friendliness, and reduced risk of secondary pollution. The flocculant is prepared by combining only two steps, low-temperature plasma modification and grafting, and has the advantages of a simple process and low comprehensive processing cost.

Description

Technical Field

[0001] The present invention relates to the technical field of flocculant preparation, and in particular to a method for preparing a low-temperature plasma modified chitosan flocculant. Background Art

[0002] Chitosan is made from chitin, which is commonly found in the shells of arthropods (shrimp, crabs, and insects). Chitosan, obtained by deacetylation of chitin, possesses unique physical and chemical properties and bioactivation capabilities, making it absorbable by the human body. The interaction of internal and external hydrogen bonds within chitin molecules forms an ordered macromolecular structure. This poor solubility results in poor water solubility and mechanical strength, limiting its application in many areas. Most organic matter, inorganic suspended particles, and pathogenic microorganisms in wastewater have negative surface charges. The positively charged chitosan chains under acidic conditions are highly conducive to flocculation and removal of these pollutants. In recent years, many researchers have used chitosan as a flocculant for wastewater treatment, but its poor water solubility and other drawbacks have limited its effectiveness in water treatment. Chitosan structure contains a large number of active groups such as amino groups and hydroxyl groups, so it is easy to introduce different functional groups into the skeleton for modification; modification can improve the water solubility and molecular conformation of chitosan, thereby enhancing its flocculation properties and expanding its application range in water treatment.

[0003] The preparation of modified chitosan typically involves various modification methods, which trigger free radical polymerization between monomers and initiators to produce the desired product. Modification methods include hydrothermal, ultraviolet light, microwave, and irradiation. However, these methods suffer from low reaction efficiency and secondary pollution, necessitating the continued exploration and development of efficient and environmentally friendly preparation methods.

[0004] Low-temperature plasma-induced modification technology is an environmentally friendly polymerization technology that uses plasma as energy. Compared with other polymerization methods, it is a cleaner and more environmentally friendly technology, and the reaction conditions are mild and the reaction is controllable. It is a green and sustainable development method. For example, CN108585145A discloses a process for preparing chitosan-based flocculants using a low-temperature plasma method. The preparation steps include: low-temperature plasma treatment, microwave treatment, micronization, chemical modification, and flocculant preparation. This method can effectively reduce the COD value and metal ion content in sewage, thereby reducing the difficulty of subsequent sewage treatment. However, this process is too cumbersome and costly, which is not conducive to promotion and application. It requires vacuuming and then passing nitrogen to the vacuum chamber pressure to reach 10Pa before low-temperature plasma treatment can be achieved, and the reaction conditions are relatively harsh. In addition, whether this process is suitable for the treatment of micro-nano particle suspensions in sewage needs further study. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing a low-temperature plasma modified chitosan flocculant, so as to solve the problems of the existing modified chitosan flocculant preparation method, such as low reaction efficiency, easy to cause secondary pollution, complicated process and high cost.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a low-temperature plasma-modified chitosan flocculant comprises the following steps:

[0008] (1) Chitosan treatment: Place chitosan in a low-temperature plasma modification device, introduce air, turn on the power supply and adjust the discharge power before performing low-temperature plasma modification;

[0009] (2) Chitosan-acrylamide graft polymerization: Chitosan modified by low-temperature plasma is placed in an acrylamide solution, an inorganic initiator is added, and the mixed solution is then stirred in a water bath to produce a gel material;

[0010] (3) Cleaning and drying of chitosan flocculant: The obtained gel material is cooled, washed, centrifuged and dried to obtain the modified chitosan flocculant.

[0011] Furthermore, the low-temperature plasma modification device is a dielectric barrier discharge device, and the discharge is powered by a high-frequency AC power supply, a microsecond pulse power supply, or a nanosecond pulse power supply.

[0012] Furthermore, in step (1), the discharge power is 50-70W, and the discharge time is 1-10min. Preferably, in step (1), the discharge power is 60-70W, and the discharge time is 3-5min.

[0013] Furthermore, the mass ratio of chitosan to acrylamide in step (2) is 1:1.5 to 1:4. Preferably, the mass ratio of chitosan to acrylamide in step (2) is 1:2 to 3.

[0014] Furthermore, the water bath temperature in step (2) is 30-80° C. Preferably, the water bath temperature in step (2) is 60-70° C.

[0015] Furthermore, in step (2), the inorganic initiator is one or both of potassium persulfate and ammonium persulfate, and the dosage is 10-60 mg.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The flocculant of the present invention uses chitosan, a natural polysaccharide flocculant, as its base material and is prepared using a low-temperature plasma-induced modification method. The modified chitosan flocculant structure contains a large number of active groups such as amino and hydroxyl groups, resulting in a flocculation effect superior to that of chitosan alone. It has the advantages of good stability, environmental friendliness, and reduced risk of secondary pollution. Furthermore, the flocculant is prepared through a combination of low-temperature plasma modification and grafting in just two steps, resulting in a simple process and low overall treatment costs. It is particularly suitable for treating micro-nanoparticle suspensions in wastewater and exhibits excellent treatment results, with a turbidity removal rate exceeding 90%.

[0018] 2. The plasma initiation of the present invention adopts dielectric barrier discharge at normal temperature and pressure. Dielectric barrier discharge can prevent the formation of sparks or arcs between electrodes, and will not cause local overheating. It can achieve stable and uniform discharge effect at normal pressure without vacuuming, and there will be no electrode corrosion affecting the treatment effect and contamination of the treated material.

[0019] 3. This invention bridges the gap between chitosan, which is only soluble in acidic solutions, and graft polymerizes acrylamide after plasma discharge modification. Low-temperature plasma modification is a normal temperature and pressure reaction process, resulting in a fast reaction rate and no environmental pollution. The resulting flocculant has a wide range of applications, is biodegradable in the natural environment, requires little energy, and requires minimal equipment. DETAILED DESCRIPTION

[0020] The specific implementation methods of the present invention are further described in detail below with reference to specific examples.

[0021] The numerical ranges herein are understood to specifically disclose every intervening value between the upper and lower limits of the range. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in that stated range is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0022] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. Although the present invention has only described preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail. As used herein, "comprising", "including", "having", "containing", etc. are all open-ended terms, meaning including but not limited to.

[0023] Unless otherwise specified, the experimental methods used in the present invention are all conventional methods.

[0024] Unless otherwise specified, the materials, reagents, etc. used in the present invention can be purchased or synthesized by known methods.

[0025] The quantitative tests in the present invention were repeated three times and the results were averaged.

[0026] Example 1

[0027] A method for preparing a low-temperature plasma-modified chitosan flocculant comprises the following steps:

[0028] (1) Chitosan treatment: Chitosan was placed in a low-temperature plasma modification device (dielectric barrier discharge device). After air was introduced, the plasma generator was turned on and the discharge power was adjusted to 60 W for 5 minutes. After the reaction was completed, the plasma generator was turned off.

[0029] (2) Chitosan-acrylamide graft polymerization: The treated chitosan was placed in an acrylamide solution, where the mass ratio of chitosan to acrylamide was 1:2 and the total monomer concentration was 80 g / L; then 20 mg of ammonium persulfate initiator was added, and the mixed solution was placed in a water bath at 70 °C and stirred for 4 h to obtain a polymer of chitosan and acrylamide.

[0030] (3) The polymer of chitosan and acrylamide is cooled at room temperature to form a gel, and the gel is washed with anhydrous ethanol. The gel is then placed in a centrifuge tube and centrifuged in a centrifuge. After the centrifugation, the gel is dried at 80°C to obtain a modified chitosan flocculant.

[0031] Wastewater treatment: Add the modified chitosan flocculant to 100 mL of a 1 g / L kaolin suspension to a modified chitosan concentration of 5 mg / L. Stir the suspension at a pH of 7 at 250 rad / min for 1 minute, then at 100 rad / min for 19 minutes. After settling for 30 minutes, the supernatant was collected and the kaolin suspension concentration before and after flocculation was measured using a UV spectrophotometer. The turbidity of the kaolin suspension before and after flocculation was measured using a turbidimeter. The kaolin removal rate and turbidity removal rate reached 95.8% and 96.9%, respectively.

[0032] Example 2

[0033] A method for preparing a low-temperature plasma-modified chitosan flocculant comprises the following steps:

[0034] The discharge power is 70 W, the discharge time is 3 minutes, and other conditions are the same as in Example 1.

[0035] In the sewage treatment test, the kaolin removal rate and turbidity removal rate reached 93.7% and 95.2% respectively after treatment.

[0036] Example 3

[0037] A method for preparing a low-temperature plasma-modified chitosan flocculant comprises the following steps:

[0038] The discharge power is 50 W, the discharge time is 3 minutes, and other conditions are the same as in Example 1.

[0039] In the sewage treatment test, the kaolin removal rate and turbidity removal rate reached 78.5% and 83.7% respectively.

[0040] Example 4

[0041] A method for preparing a low-temperature plasma-modified chitosan flocculant comprises the following steps:

[0042] The mass ratio of chitosan to acrylamide was 1:3, and other conditions were the same as in Example 1.

[0043] In the sewage treatment test, the kaolin removal rate and turbidity removal rate reached 91.1% and 92.0% respectively.

[0044] Example 5

[0045] A method for preparing a low-temperature plasma-modified chitosan flocculant comprises the following steps:

[0046] The mass ratio of chitosan to acrylamide was 1:4, and other conditions were the same as in Example 1.

[0047] In the sewage treatment test, the kaolin removal rate and turbidity removal rate reached 89.5% and 91.0% respectively.

[0048] Example 6

[0049] A method for preparing a low-temperature plasma-modified chitosan flocculant comprises the following steps:

[0050] The mass ratio of chitosan to acrylamide was 1:1.5, and other conditions were the same as in Example 1.

[0051] In the sewage treatment test, the kaolin removal rate and turbidity removal rate reached 85.5% and 87.0% respectively.

[0052] Example 7

[0053] A method for preparing a low-temperature plasma-modified chitosan flocculant comprises the following steps:

[0054] The water bath temperature was 60°C, and other conditions were the same as in Example 1.

[0055] In the sewage treatment test, the kaolin removal rate and turbidity removal rate reached 95.6% and 96.7% respectively.

[0056] Example 8

[0057] A method for preparing a low-temperature plasma-modified chitosan flocculant comprises the following steps:

[0058] The water bath temperature was 80°C, and other conditions were the same as in Example 1.

[0059] In the sewage treatment test, the kaolin removal rate and turbidity removal rate reached 81.0% and 84.8% respectively.

[0060] Example 9

[0061] A method for preparing a low-temperature plasma-modified chitosan flocculant comprises the following steps:

[0062] The water bath temperature was 50°C, and other conditions were the same as in Example 1.

[0063] In the sewage treatment test, the kaolin removal rate and turbidity removal rate reached 74.2% and 78.5% respectively.

[0064] Example 10

[0065] When the flocculant obtained in Example 1 was used to treat sewage: the modified chitosan was added to 100 mL of a 1 g / L carbon nanotube nanoparticle suspension, the modified chitosan dosage was 8 mg / L, the pH of the suspension was 5, stirring was carried out at 250 rad / min for 2 min, stirring was carried out at 75 rad / min for 18 min, and the suspension was allowed to settle for 30 min. The supernatant was taken and the concentration of the carbon nanotube nanoparticle suspension before and after the flocculation reaction was measured using an ultraviolet spectrophotometer. The turbidity of the carbon nanotube nanoparticle suspension before and after the flocculation reaction was measured using a turbidity meter. The carbon nanotube nanoparticle removal rate and the turbidity removal rate reached 91.7% and 90.4%, respectively.

[0066] The flocculant obtained in Example 1 was used to treat sewage with a COD of 160 mg / L. Modified chitosan was added to a concentration of 30 mg / L, the pH was 7.5, and the mixture was stirred at 250 rad / min for 1 min, 150 rad / min for 5 min, and 50 rad / min for 14 min. The mixture was allowed to settle for 30 min, and the supernatant was taken and the COD was measured using a COD meter. The COD removal rate was 90.3%.

[0067] The flocculant obtained in Example 1 was used to treat metal-containing wastewater. Modified chitosan was added to the wastewater to a concentration of 100 mg / L. After measurement, the removal rate of Cr was 94.7%, and the removal rate of Ni was 99.3%.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention that do not depart from the purpose and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a low-temperature plasma modified chitosan flocculant, characterized in that: The following steps are involved: (1) Chitosan treatment: Place chitosan in a low-temperature plasma modification device, introduce air, turn on the power supply and adjust the discharge power before performing low-temperature plasma modification; (2) Chitosan-acrylamide graft polymerization: Chitosan modified by low-temperature plasma is placed in an acrylamide solution, an inorganic initiator is added, and the mixed solution is then stirred in a water bath to produce a gel material; (3) Cleaning and drying of chitosan flocculant: The obtained gel material is cooled, washed, centrifuged and dried to obtain the modified chitosan flocculant; In step (1), the discharge power is 60-70W and the discharge time is 3-5min; In step (2), the mass ratio of chitosan to acrylamide is 1:2-3; The water bath temperature in step (2) is 60-70°C.

2. The method for preparing the low-temperature plasma modified chitosan flocculant according to claim 1, characterized in that: The low-temperature plasma modification device is a dielectric barrier discharge device.

3. The method for preparing the low-temperature plasma modified chitosan flocculant according to claim 1, characterized in that: In step (2), the inorganic initiator is one or both of potassium persulfate and ammonium persulfate, and the dosage is 10-60 mg.