CN112755982B - A kind of high-efficiency adsorption material of amphoteric cellulose silk and its preparation method and application - Google Patents

Abstract

The invention discloses an amphoteric cellulose fiber high-efficiency adsorption material, a preparation method and an application thereof. The material is based on carboxylated nanocellulose as a matrix, graphene oxide and polyethyleneimine as functional reagents, and is electrostatically combined by imitating spider spinning. method, and then obtained by glutaraldehyde micro-crosslinking. The material of the invention has good performance in the application of low concentration heavy metal adsorption field: for low concentration (1000ppb) anionic heavy metal ions Cr(VI) and cationic heavy metal ions Cd(II), Cu(II), Zn(II), Pb(II) can be removed efficiently at the same time, and the removal rate is greater than 99.99%. The concentration of heavy metal ions after removal reaches the national drinking water standard, and its regeneration stability is good. After 10 regenerations, the regeneration rate is still greater than 95%.

Description

A kind of high-efficiency adsorption material of amphoteric cellulose silk, preparation method and application thereof

technical field

The invention relates to the field of heavy metal ion adsorption, in particular to an amphoteric cellulose fiber high-efficiency adsorption material and a preparation method and application thereof.

Background technique

With the development of mining and metallurgical industries, heavy metal ions enter human and animal bodies through the water cycle and food chain, posing a great threat. Using chemical precipitation, biological treatment, membrane separation, ion exchange and adsorption of high concentration heavy metal ion wastewater can be effectively treated by chemical precipitation to achieve low concentration. However, to efficiently remove low-concentration heavy metal ions often requires greater human and financial resources. The adsorption method is considered as a promising method due to its strong operational adaptability and low processing cost, and the key to the adsorption technology is the adsorbent. Considering the economic benefits and removal efficiency, the currently used adsorbents mainly include carbonaceous materials, mineral materials, MOF materials, synthetic polymer materials and biomass materials. Adsorbent material. In particular, cellulose is not only cheap, easy to modify, but also can accelerate the adsorption rate of heavy metal ions, and is an excellent matrix for heavy metal adsorbents.

Amphoteric cellulose-based adsorbents refer to cellulose that contains both cationic and anionic groups on the molecular chain after modification. (L.Zheng, et al., J.Mater.Chem.A, 7(2019) 13714-13726.) obtained the amidoxime chelated cellulose with an amino concentration of 4.9 mmol/g by etherification and amination, The adsorption capacity of Cd(Ⅱ) was 34.13 mg/g, and the removal rate was maintained at about 80%. Martin et al. (M.d'Halluin, et al., ACS Sustainable Chem.Eng., 5(2017) 1965-1973) used ethylenediaminetetraacetic acid (EDTA) as a monomer to graft cellulose (cell-EDTA), The density of the generated functional groups was 6.2 mmol/g, and the removal rates of Ag(I), Pb(II), Cd(II), Ni(II), Zn(II), Sn(II) and Cu(II) were all 90%. Li et al. (Y.Li, et al., Cellulose., 25(2018) 4757-4769.) grafted PEI onto the cellulose surface to prepare a magnetic cellulose adsorbent with high amino density (7.85 mmol/g) ( Fe ₃ O ₄ /MCC-PEI), the adsorption capacity was 198.8 mg/g, and the removal rate was greater than 99.99%. Literature analysis shows that the removal rate of anionic and cationic heavy metal ions is higher for the adsorbents containing amino and carboxyl groups, and with the increase of the functional group density of the adsorbent, the removal rate and adsorption capacity increase. The functional group density of about 10.0 mmol/g is the guarantee for the efficient removal of low-concentration heavy metal ions. However, the currently reported methods cannot efficiently remove both anionic and cationic heavy metal ions from water due to the difficulty in preparing cellulose-based adsorbents with high amino and carboxyl densities. It can't make it meet the safe drinking standard required by the state.

In the traditional "step-by-step" grafting method, the hydroxyl groups of cellulose are covered by the graft layer, resulting in that some hydroxyl groups of cellulose cannot provide reaction sites for the next step of grafting, thus limiting the introduction of other functional groups. Therefore, designing and developing a simple, low-energy-consumption preparation route will help to improve the synthesis of cellulose-based adsorbents with high amino and carboxyl densities for simultaneous efficient removal of anionic and cationic heavy metal ions.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the above-mentioned problems in the prior art, and to provide an environment-friendly amphoteric cellulose fiber that can simultaneously efficiently remove low-concentration anionic heavy metal ions and cationic heavy metal ions, and can be recycled and regenerated at the same time. High-efficiency adsorption material.

The object of the present invention is to provide a kind of high-efficiency adsorption material of amphoteric cellulose silk;

Another object of the present invention is to provide a method for preparing the above-mentioned amphoteric cellulose filament high-efficiency adsorbent material.

Yet another object of the present invention is to provide the application of the above-mentioned amphoteric cellulose filament high-efficiency adsorbent material.

Above-mentioned purpose of the present invention is achieved through the following technical solutions:

An efficient adsorption material for amphoteric cellulose silk, which is based on carboxylated nanocellulose as a matrix, graphene oxide and polyethyleneimine as functional reagents, and blends carboxylated nanocellulose and polyethyleneimine, and then adopts a spider imitation. In the spinning method, the blend and graphene oxide are drawn into filamentous fibers, which are combined into filaments by electrostatic action, and then prepared by micro-crosslinking.

Preferably, the crosslinking agent used in the micro-crosslinking is glutaraldehyde.

The preparation method of the above-mentioned amphoteric cellulose fiber high-efficiency adsorption material, comprising the following steps:

S1. The carboxylated nanocellulose is blended with polyethyleneimine, and then the blend and graphene oxide are drawn into filamentous fibers by means of imitating spider spinning, and the two are combined into filaments by electrostatic action;

S2. The surface of the filamentation product obtained in step S1 is sprayed with a cross-linking agent glutaraldehyde, and after drying, solid filaments are formed, that is, the amphoteric cellulose filament high-efficiency adsorption material is obtained.

The specific operation of the step S1 is as follows: adding carboxylated nanocellulose into the polyethyleneimine solution with a mass fraction of 2-20%, and the mass ratio of carboxylated nanocellulose and polyethyleneimine is 1:5-10, Stir until the carboxylated nanocellulose is completely dispersed and uniform to obtain a blend of carboxylated nanocellulose and polyethyleneimine; disperse the graphene oxide in water, and perform ultrasonic activation treatment; mix the carboxylated nanocellulose and polyethyleneimine with The amine blend and the ultrasonically activated graphene oxide dispersion are respectively dropped on the drawing bottom plate. When the interface of the two droplets is in contact, the blend and graphene oxide are drawn into filamentous fibers. They are combined into filaments by electrostatic action.

Preferably, the ultrasonic power is 100W-1000W, the ultrasonic time is 60-120min, and the concentration of the graphene oxide dispersion liquid is 2.5-10mg/L.

Preferably, the material of the wire drawing bottom plate is polystyrene, polytetrafluoroethylene or TiO ₂ .

Preferably, the mass ratio of the silk-forming product in the step S2 to glutaraldehyde is 1:0.01-1:0.03.

The high-efficiency adsorption material of amphoteric cellulose silk prepared by the invention can be applied to the adsorption of heavy metals, and the material of the invention has good performance in the application of the field of low-concentration heavy metal adsorption: for low-concentration (1000ppb) anionic heavy metal ions Cr(VI) and Cationic heavy metal ions Cd(II), Cu(II), Zn(II), Pb(II) can be removed efficiently at the same time, and the removal rate is more than 99.99%. The concentration of heavy metal ions after removal reaches the national drinking water standard, and its regeneration is stable. Good performance, after 10 regenerations, the regeneration rate is still greater than 95%. The application of the material of the present invention in heavy metal adsorption is also within the protection scope of the present invention.

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

(1) The present invention uses carboxylated nanocellulose as a matrix, graphene oxide and polyethyleneimine as functional reagents, adopts the method of imitating spider spinning to form fibrils through the action of electrostatic binding force, and then adopts the mode of micro-crosslinking The high-efficiency adsorption material of amphoteric cellulose fibers with high content of anionic (carboxyl) and cationic (amino) functional groups at the same time is prepared, and the complete utilization of carboxylated nanocellulose, polyethyleneimine, and graphene oxide is realized. The material can efficiently remove low concentration (1000ppb) anionic heavy metal ions Cr(VI) and cationic heavy metal ions Cd(II), Cu(II), Zn(II), Pb(II) at the same time, and the removal rates are all greater than 99.99% . The invention overcomes the need to introduce intermediate active groups and then introduce anionic and cationic functional groups respectively when the functional materials are prepared by introducing functional groups on plant fibers through grafting modification in the traditional method. As a result, the amount of functional groups introduced is less, which affects its performance, and there are many preparation steps and severe reaction conditions.

(2) The traditional cellulose-based heavy metal ion adsorbents are mostly realized by the method of surface step-by-step polymerization, which has many preparation steps and severe reaction conditions. performance. In the invention, the fiber structure of carboxylated nanocellulose is ensured by the method of imitating spider spinning, the carboxylated nanocellulose acts as a skeleton support in the interior of the fibril, and meanwhile, the good swelling property of nanocellulose promotes diffusion and transmission. improve the adsorption rate of heavy metal ions. Compared with the traditional blending method, the method of imitating spider spinning of the present invention blends carboxylated nanocellulose and polyethyleneimine into filamentous fibers with graphene oxide, and the two are combined by electrostatic action to form filamentous fibers. Silk, while maintaining the filamentous structure, improves the utilization rate of functional groups, and efficiently utilizes the high-density carboxyl groups of graphene oxide and a large number of amino groups on polyethyleneimine, so that the material has high amino and carboxyl density at the same time. It ensures the rapid and efficient removal of a variety of low-concentration heavy metal ions.

(3) The present invention adopts the mode of blending carboxylated nanocellulose and polyethyleneimine. Since polyethyleneimine has good water solubility, carboxylated nanocellulose can be uniformly distributed in polyethyleneimine. Carboxylated nanocellulose can not only play a good supporting role in the material, but also adjust its swelling property inside the material and accelerate the adsorption rate of the material.

(4) The present invention simultaneously introduces functional groups of anionic (carboxyl) and cationic (amino), which can be negative in aqueous solution (such as Cr(VI) (exist in the form of CrO ₄ ^2- in aqueous solution)) It can efficiently remove low-concentration heavy metal ions that are positive (Cd(II), Cu(II), Zn(II), Pb(II)) at the same time.

(5) The removal rate of low-concentration heavy metal ions by the material prepared by the present invention is greater than 99.99%.

(6) Due to the stable chemical bond connection of the cross-linking agent after wire drawing, the regeneration stability of the material is good. After 10 regenerations, the regeneration rate is still greater than 95%.

Detailed ways

The present invention is further illustrated below in conjunction with the examples, but should not be construed as a limitation of the present invention. Simple modifications or substitutions made to the methods, steps or conditions of the present invention without departing from the spirit and essence of the present invention all belong to the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

Example 1: Preparation of Amphoteric Cellulose Filament High-efficiency Adsorbent Material

(1) Add carboxylated nanocellulose to the polyethyleneimine solution with a molecular weight of 75000 and a mass fraction of 10%, the mass ratio of carboxylated nanocellulose and polyethyleneimine is 1:5, and stir until the carboxylated nanofibers are The carboxylated nanocellulose and polyethylenimine are obtained by dispersing completely and uniformly. The graphene oxide was dispersed in water, and the ultrasonic activation treatment was carried out. The ultrasonic power was 100 W, the ultrasonic time was 60 min, and the concentration of the graphene oxide dispersion liquid was 2.5 mg/L. The blend of carboxylated nanocellulose and polyethyleneimine and the graphene oxide dispersion treated by ultrasonic activation were dropped on the polystyrene plate respectively. When the interface of the two droplets was in contact, the blend was added It is drawn into filamentous fibers with graphene oxide, and the two are combined into filaments through electrostatic interaction.

(2) by spraying, spray the cross-linking agent glutaraldehyde on the surface of the silk-forming product obtained in step (1), the mass ratio of the silk-forming product and glutaraldehyde is 1:0.01, and a solid is formed after drying filament, that is, the high-efficiency adsorption material of the amphoteric cellulose filament is obtained.

Example 2: Preparation of Amphoteric Cellulose Filament High-efficiency Adsorbent Material

(1) Add carboxylated nanocellulose to the polyethyleneimine solution with a molecular weight of 75,000 and a mass fraction of 2%, the mass ratio of carboxylated nanocellulose and polyethyleneimine is 1:7.5, and stir until the carboxylated nanofibers are The carboxylated nanocellulose and polyethylenimine are obtained by dispersing completely and uniformly. The graphene oxide was dispersed in water, and the ultrasonic activation treatment was carried out. The ultrasonic power was 500 W, the ultrasonic time was 90 min, and the concentration of the graphene oxide dispersion was 7.5 mg/L. The blend of carboxylated nanocellulose and polyethyleneimine and the graphene oxide dispersion were dropped on the polystyrene plate respectively. When the interface of the two droplets was in contact, the blend and the graphene oxide were pulled together. Filamentous fibers, the two are combined into filaments by electrostatic interaction.

(2) by spraying, spray cross-linking agent glutaraldehyde on the surface of the silk product obtained in step (1), the mass ratio of the silk product to glutaraldehyde is 1:0.02, and after drying, a solid is formed filament, that is, the high-efficiency adsorption material of the amphoteric cellulose filament is obtained.

Example 3: Preparation of Amphoteric Cellulose Filament High-efficiency Adsorbent Material

(1) Add carboxylated nanocellulose to the polyethyleneimine solution with a molecular weight of 75000 and a mass fraction of 20%, the mass ratio of carboxylated nanocellulose and polyethyleneimine is 1:10, and stir until the carboxylated nanofibers are The carboxylated nanocellulose and polyethylenimine are obtained by dispersing completely and uniformly. The graphene oxide was dispersed in water, and the ultrasonic activation treatment was carried out. The ultrasonic power was 1000 W, the ultrasonic time was 120 min, and the concentration of the graphene oxide dispersion liquid was 10 mg/L. The blend of carboxylated nanocellulose and polyethyleneimine and the graphene oxide dispersion were dropped on the polystyrene plate respectively. When the interface of the two droplets was in contact, the blend was combined with graphene oxide and pulled into a Filamentous fibers, the two are combined into filaments by electrostatic interaction.

(2) by spraying, spray the cross-linking agent glutaraldehyde on the surface of the silk-forming product obtained in step (1), the mass ratio of the silk-forming product and glutaraldehyde is 1:0.03, and a solid is formed after drying filament, that is, the high-efficiency adsorption material of the amphoteric cellulose filament is obtained.

Comparative Example 1

The difference from Example 1 is that the blend of carboxylated nanocellulose and polyethyleneimine is directly mixed with the graphene oxide dispersion after ultrasonic activation treatment, and then glutaraldehyde is added in a mass ratio of 1:0.01, and then Stir for 30 min, and the stirring speed is 800 rpm. After the stirred solid is ground and crushed, it is washed with deionized water at 60° C. and dried to constant weight.

Comparative Example 2

The difference from Example 1 is that no carboxylated nanocellulose is added in step (1), and other steps and process conditions are the same as those in Example 1.

Comparative Example 3

The difference from Example 1 is that no ultrasonic activation treatment is performed in step (1), and other steps and process conditions are the same as in Example 1.

Performance Testing:

(1) The materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to a heavy metal ion removal rate test, and the results are shown in Table 1.

Table 1 Test results of removal rate of heavy metal ions by materials

From the experimental results in Table 1, it can be concluded that the introduction of polyethyleneimine with high amino density and graphene oxide with high carboxyl density, the prepared material has a higher content of functional groups. The material contains anionic (carboxyl) and cationic (amino) functional groups, which greatly improves the removal rate of low-concentration anionic and cationic heavy metal ions, and the removal rate is close to 100%.

(2) The materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to a heavy metal ion adsorption rate test, and the results are shown in Table 2.

Table 2 Test results of adsorption rate of heavy metal ions on materials

From the test results in Table 2, it can be concluded that the material of the present invention has a faster adsorption rate to heavy metal ions, and the adsorption rate of the carboxylated nanocellulose to the material is significantly improved.

(3) The materials obtained in Examples 1 to 3 were subjected to a regeneration test, and the results are shown in Table 3.

Table 3 Regeneration test results of materials

From the test results in Table 3, it can be concluded that due to the chemical bond of the crosslinking agent strengthening the connection between graphene oxide and polyethyleneimine, the regeneration stability of the material is good. After 10 regenerations, the regeneration rate is still greater than 95%.

Claims (3)

1. a preparation method of an amphoteric cellulose silk high-efficiency adsorption material, is characterized in that, comprises the following steps: S1. The carboxylated nanocellulose is blended with polyethyleneimine, and then the blend and graphene oxide are drawn into filamentous fibers by means of imitating spider spinning, and the two are combined into filaments by electrostatic action; S2. Spray the cross-linking agent glutaraldehyde on the surface of the filamentation product obtained in step S1, and form solid filaments after drying, that is, to obtain the amphoteric cellulose filament high-efficiency adsorption material; The specific operation of the step S1 is as follows: adding carboxylated nanocellulose into the polyethyleneimine solution with a mass fraction of 2-20%, and the mass ratio of carboxylated nanocellulose and polyethyleneimine is 1:5-10, Stir until the carboxylated nanocellulose is completely dispersed and uniform to obtain a blend of carboxylated nanocellulose and polyethyleneimine; disperse the graphene oxide in water, and carry out ultrasonic activation treatment, the ultrasonic power is 100W ~ 1000W, and the ultrasonic time is 5～120min, the concentration of graphene oxide dispersion liquid is 2.5～10mg/L; the blend of carboxylated nanocellulose and polyethyleneimine and the graphene oxide dispersion liquid after ultrasonic activation treatment are respectively dropped on the drawing bottom plate When the interface of the two droplets is in contact, the blend and graphene oxide are drawn into filamentous fibers, and the two are combined into filaments through electrostatic interaction; The mass ratio of the silk-forming product in the step S2 to glutaraldehyde is 1:0.01-1:0.03. 2 . The preparation method according to claim 1 , wherein the material of the wire drawing bottom plate is polystyrene, polytetrafluoroethylene or TiO ₂ . 3 . 3. The application of the high-efficiency amphoteric cellulose filament adsorption material prepared by the preparation method of the amphoteric cellulose filament high-efficiency adsorption material according to claim 1 or 2 in heavy metal adsorption.