CN110746655A

CN110746655A - pH sensitive nanosphere based on cellulose nanowhisker and preparation and application thereof

Info

Publication number: CN110746655A
Application number: CN201911031151.2A
Authority: CN
Inventors: 柴飞; 王润锴; 饶品华; 严丽丽; 张文启
Original assignee: Shanghai University of Engineering Science
Current assignee: Shanghai University of Engineering Science
Priority date: 2019-10-28
Filing date: 2019-10-28
Publication date: 2020-02-04

Abstract

The invention relates to a pH sensitive nanosphere based on cellulose nanowhiskers and preparation and application thereof. Compared with the prior art, the method can effectively reduce the arsenic content in the acid wastewater, has simple preparation and no pollution to the environment, and can be widely applied to the treatment of heavy metal wastewater containing arsenic and the like. In addition, the invention recycles the kapok fiber, reduces the pollutant discharge, saves energy, accords with the sustainable development principle, accords with the national environmental protection strategy requirement, and has potential application prospect.

Description

pH sensitive nanosphere based on cellulose nanowhisker and preparation and application thereof

Technical Field

The invention belongs to the technical field of composite materials, and relates to a composite adsorbent and application thereof in the field of environmental protection. More specifically, the invention relates to rapid preparation of nanospheres based on cellulose nanowhiskers and application of nanospheres in adsorption of high-concentration acidic arsenic solution.

Background

Arsenic is a nonmetallic element widely distributed in the nature and is often added to herbicides, rodenticides, and the like. However, arsenic and its compounds have lethal toxicity, and are primarily referred to in the list of carcinogens published by the international cancer research institute of the world health organization, and arsenic and inorganic arsenic compounds are included in a list of carcinogens. As a big country in agriculture and industry, China also puts arsenic into a strict limit range. The flue gas generated in the industrial metal smelting process can generate a large amount of acidic waste water in the wet purification process when acid is prepared, the mass concentration of sulfuric acid in the waste acid is between 2 and 11 percent, and the waste acid contains one or more of copper, lead, mercury, antimony, zinc, arsenic, cadmium, indium, nickel, tin and manganese ions, sulfate radicals and hydrogen ions. In recent years, arsenic has been widely used in industry, which leads to the increasing concentration of arsenic in water environment, and in addition, arsenic damages the liver, lung and immune system of human, so how to remove as (v) from water has been a great concern of scholars in recent years.

Kapok (Ceiba pentandra) is mainly distributed in the south of China, is not cold-resistant and grows rapidly, and seeds of the Kapok (Ceiba pentandra) fall along with Kapok fibers after fruits of the Kapok (Ceiba pentandra) ripen and cracked. About 19 ten thousand tons of kapok fibers are naturally generated in China every year, but only a small number of kapok fibers can be collected to serve as filling materials of pillows and life jackets, and a large number of kapok fibers are scattered along with wind after being matured, so that the urban attractiveness is influenced, certain pollution is caused, meanwhile, the kapok fibers are wasted, and how to utilize the kapok fibers becomes one of the technical problems to be solved urgently at present.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the rapid preparation and application of the pH-sensitive nanosphere based on the cellulose nanowhisker. The novel arsenic removal adsorbent is prepared by mainly using carboxylated cellulose nanowhiskers as raw materials and crosslinking the nanowhiskers with glutaraldehyde and polyethyleneimine.

The purpose of the invention can be realized by the following technical scheme:

a rapid preparation method of pH sensitive nanospheres (PEI/GA-CNC) based on cellulose nanowhiskers comprises the following steps: preparation (CNC) of carboxylated cellulose nanowhiskers and rapid preparation of pH sensitive nanospheres (PEI/GA-CNC) formed on the basis of carboxylated Cellulose Nanowhiskers (CNC) cross-linked Glutaraldehyde (GA) and Polyethyleneimine (PEI).

In a first aspect, the invention provides a method for preparing carboxylated cellulose nanowhiskers, which comprises sequentially passing kapok fibers through sodium chlorite (NaClO)₂) Removing acid-soluble lignin, removing alkali-soluble lignin by potassium hydroxide (KOH), oxidizing by tetramethylpiperidine oxynitride (TEMPO), and adjusting the pH value to be strong alkali.

Preferably, the kapok fiber is obtained by washing, removing impurities and drying kapok fiber; the wet fiber was 10 g.

Preferably, the kapok fibers are passed through sodium chlorite (NaClO)₂) The method for removing acid soluble lignin is as follows: dissolving kapok fiber in 700mL sodium chlorite (NaClO)₂) The solution is stirred evenly. Then placed in a water bath to heat, and 1mL of glacial acetic acid was added every one hour to remove acid-soluble lignin in cellulose. Washing with water to neutrality.

Preferably, the sodium chlorite (NaClO)₂) The mass fraction of (A) is 0.8%; the temperature of the water bath kettle is 70 ℃; the glacial acetic acid was added every other hour, repeated three times.

Preferably, the method for removing alkali-soluble lignin by potassium hydroxide (KOH) is as follows: the fiber after washing was put into 700mL of potassium hydroxide (KOH) and stirred well. Standing at room temperature, and heating in water bath to remove alkali soluble lignin. Washing with water to neutrality.

Preferably, the mass fraction of the potassium hydroxide (KOH) is 6%; the standing time at room temperature is 8 hours; the temperature of the water bath kettle is 80 ℃; the heating time is 2 hours;

preferably, the method of oxidation of tetramethylpiperidine nitroxide (TEMPO) is as follows: the wet fiber was added to a stoppered 100mL sodium hydroxide (NaOH) solution, allowed to stand, and washed with water to neutrality. Mixing tetramethylpiperidine oxynitride (TEMPO), sodium hypochlorite (NaClO) and sodium bromide (NaBr), continuously stirring, and adjusting the pH value to be strong alkali. Adding ethanol (C)₂H₆O) in a reaction vessel. Standing, and performing suction filtration to obtain filtrate, namely the carboxylated Cellulose Nanowhisker (CNC).

Preferably, the mass fraction of sodium hydroxide (NaOH) is 25%; the standing time is 30 min;

preferably, the volume ratio of TEMPO to NaBr is 1: 10; the NaClO and the C₂H₆The volume ratio of O is 2: 1; the stirring time is 24 hours and the room temperature is kept; the pH is adjusted by adopting a sodium hydroxide (NaOH) solution, and the sodium hydroxide (NaOH) solution is selected as an acid-base regulator, because the preparation system needs to be completed under an alkaline condition, the prepared cellulose nanowhiskers are uniform, stable and high in yield; the strong basicity, preferably the pH, is 12.

In a second aspect, the present invention provides a rapid preparation of pH sensitive nanospheres (PEI/GA-CNC) based on carboxylated cellulose nanowhiskers cross-linked Glutaraldehyde (GA) and Polyethyleneimine (PEI).

Preferably, the preparation of the said PEI/GA-CNC is as follows: crosslinking CNC and GA in a water bath; adding PEI, stirring and carrying out suction filtration to obtain the product.

Preferably, the volume ratio of the CNC, the GA and the PEI is 1:1: 1; the GA concentration is 0.5% -2%; the concentration of the PEI is 20 mg/mL-30 mg/mL; the temperature of the water bath kettle is 40 ℃; the crosslinking time is 30 min; the stirring time is 20 min;

in a third aspect, the present invention provides a use of carboxylated cellulose nanowhiskers crosslinked with Glutaraldehyde (GA) and Polyethyleneimine (PEI) to form pH-sensitive nanospheres (PEI/GA-CNC) at initially varying pH as arsenic solutions, comprising: and putting the obtained nanospheres into arsenic solutions with different initial pH values, sampling to detect the arsenic concentration after constant-temperature oscillation, and calculating the adsorption quantity.

Preferably, the pH values differ by 3, 4, 6 and 8; the constant temperature oscillation temperature is 25 ℃; the constant-temperature oscillation time is 2 hours; the concentration detecting instrument is inductively coupled plasma (ICP-OES).

In a fourth aspect, the present invention provides a use of a carboxylated cellulose nanowhisker based cross-linked Glutaraldehyde (GA) and Polyethyleneimine (PEI) to form a pH sensitive nanosphere (PEI/GA-CNC) in a high concentration arsenic solution, comprising: and (3) putting the obtained nanospheres into a high-concentration arsenic solution, sampling to detect the arsenic concentration after constant-temperature oscillation, and calculating the adsorption quantity.

Preferably, the mass of the nanospheres is 20 mg; the volume of the arsenic solution is 50 mL; the high-concentration arsenic solution is 50mg/L, 150mg/L, 200mg/L and 300 mg/L; the constant-temperature oscillation time is 2 hours; the concentration detecting instrument is inductively coupled plasma (ICP-OES).

The adsorption capacity of the pH sensitive nanosphere prepared by the invention reaches 255.19mg/g under the condition of strong acid.

The cellulose nano-whisker is obtained by extracting acid or alkaline hydrolysis kapok fiber, and the surface of the cellulose nano-whisker contains a large number of hydroxyl (-OH) functional groups. In recent years, a number of techniques have been applied to modify cellulose nanowhiskers, including grafting, copolymerization and carboxylation. The carboxylated cellulose nanowhiskers treated in combination with tetramethylpiperidine nitroxide (TEMPO) have carboxylic acid functionality, large specific surface area, high crystallinity and high specific strength, while maintaining the basic cellulose structure comparable to natural cellulose.

Compared with the prior art, the invention has the following advantages:

(1) the method mainly utilizes the cellulose nanowhiskers extracted from the kapok fibers as the main raw material of the adsorbent, effectively improves the repeated utilization rate of the material, reduces the emission of pollutants, saves energy, meets the sustainable development principle, and meets the requirements of the national environmental protection strategy.

(2) The preparation of nanosphere (PEI/GA-CNC) adsorbents of the present invention is very sensitive to the initial pH of the arsenic solution.

(3) The pH-sensitive nanosphere adsorbent obtained by crosslinking Glutaraldehyde (GA) and Polyethyleneimine (PEI) through the carboxylated cellulose nanowhiskers has obvious effect in arsenic removal experiments, relatively high adsorption amount to As (V), and high adsorption rate.

(4) The pH sensitive nanosphere (PEI/GA-CNC) adsorbent disclosed by the invention is simple in preparation method, simple in required equipment and simple in operation, and is beneficial to industrial production and practical application.

(5) The nanosphere takes the cellulose nanowhisker as the substrate, thereby reducing the secondary pollution to the environment.

Drawings

Fig. 1 is a flow chart of a preparation process of a pH sensitive nanosphere based on cellulose nanowhiskers.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

The preparation method of the pH sensitive nanosphere based on the cellulose nanowhisker has the process flow as shown in figure 1, and can adopt the following steps:

(1) uniformly stirring the kapok fiber in a sodium chlorite solution with the mass concentration of 0.8-1%, heating in a water bath at 70-80 ℃, adding glacial acetic acid every 1h, repeatedly removing acid-soluble lignin in cellulose for several times, and washing to be neutral;

(2) putting the kapok fiber obtained by the treatment in the step (1) into a potassium hydroxide solution with the mass concentration of 6-10%, uniformly stirring, standing at room temperature, heating in a water bath at 70-80 ℃ to remove alkaline soluble lignin, and washing to be neutral;

(3) adding the kapok fiber obtained by the treatment in the step (2) into a sodium hydroxide solution with the mass concentration of 25% -30%, standing for 30-120 min, washing with water to be neutral, mixing the tetramethylpiperidine nitrogen oxide, sodium hypochlorite and sodium bromide, continuing stirring, adjusting the pH value to 12 by using sodium hydroxide, adding the mixture into ethanol for reaction, wherein the volume ratio of the tetramethylpiperidine nitrogen oxide to the sodium bromide is 1: 7-1: 10, the volume ratio of the sodium hypochlorite to the ethanol is 2: 1-2: 3, standing, and performing suction filtration to obtain a filtrate, namely the carboxylated cellulose nanowhisker, with the concentration of 0.4 g/L.

(4) Crosslinking the carboxylated cellulose nanowhiskers with a glutaraldehyde solution with a concentration of 0.5-2 wt% at 40-60 ℃ for 30-60 min,

(5) and adding a polyethyleneimine solution with the concentration of 20-30mg/mL, wherein the volume ratio of the carboxylated cellulose nanowhisker to the glutaraldehyde solution to the polyethyleneimine solution is 1:1: 1-1: 3:3, stirring and reacting for 20-60 min, then carrying out suction filtration, drying and grinding, and thus obtaining the cellulose nanowhisker-based pH sensitive nanospheres.

The following are more detailed embodiments, and the technical solutions and the technical effects obtained by the present invention will be further described by the following embodiments.

Example 1

The embodiment provides a preparation method of a pH-sensitive nanosphere (PEI/GA-CNC), which comprises the following steps:

and (3) crosslinking CNC and 0.5% GA in a water bath kettle at 40 ℃ for 30min, then adding PEI with the concentration of 20mg/mL, wherein the volume ratio of the CNC to the GA to the PEI is 1:1:1, and stirring for 20min to obtain the PEI/GA-CNC composite adsorbent.

Example 2

Example 2 is a variation of example 1, varying only: the concentration of PEI was 25 mg/mL.

And (3) crosslinking CNC and 0.5% GA in a water bath kettle at 40 ℃ for 30min, then adding 25mg/mL PEI, wherein the volume ratio of the CNC to the GA to the PEI is 1:1:1, and stirring for 20min to obtain the PEI/GA-CNC composite adsorbent.

Example 3

Example 3 is a variation of example 1, varying only: the concentration of PEI was 30 mg/mL.

And (3) crosslinking CNC and 0.5% GA in a water bath kettle at 40 ℃ for 30min, then adding 30mg/mL PEI, wherein the volume ratio of the CNC to the GA to the PEI is 1:1:1, and stirring for 20min to obtain the PEI/GA-CNC composite adsorbent.

Example 4

Example 4 is a variation of example 1, varying only: the GA concentration was 1%.

And (3) crosslinking CNC and 1% GA in a water bath kettle at 40 ℃ for 30min, then adding the CNC, the GA and the PEI into the water bath kettle at a concentration of 20mg/mLPEI, wherein the volume ratio of the CNC, the GA and the PEI is 1:1:1, and stirring the mixture for 20min to obtain the PEI/GA-CNC composite adsorbent.

Example 5

Example 5 is a variation of example 4, varying only: the concentration of PEI was 25 mg/mL.

And (3) crosslinking CNC and 1% GA in a water bath kettle at 40 ℃ for 30min, then adding PEI with the concentration of 25mg/mL, wherein the volume ratio of the CNC to the GA to the PEI is 1:1:1, and stirring for 20min to obtain the PEI/GA-CNC composite adsorbent.

Example 6

Example 6 is a variation of example 4, varying only: the concentration of PEI was 30 mg/mL. And (3) crosslinking CNC and 1% GA in a water bath kettle at 40 ℃ for 30min, then adding 30mg/mL PEI, wherein the volume ratio of the CNC to the GA to the PEI is 1:1:1, and stirring for 20min to obtain the PEI/GA-CNC composite adsorbent.

Example 7

Example 7 is a variation of example 1, varying only: the GA concentration was 2%.

And (3) crosslinking CNC and 2% GA in a water bath kettle at 40 ℃ for 30min, then adding PEI with the concentration of 20mg/mL, wherein the volume ratio of the CNC to the GA to the PEI is 1:1:1, and stirring for 20min to obtain the PEI/GA-CNC composite adsorbent.

Example 8

Example 8 is a variation of example 7, varying only: the concentration of PEI was 25 mg/mL.

And (3) crosslinking CNC and 2% GA in a water bath kettle at 40 ℃ for 30min, then adding 25mg/mL PEI, wherein the volume ratio of the CNC to the GA to the PEI is 1:1:1, and stirring for 20min to obtain the PEI/GA-CNC composite adsorbent.

Example 9

Example 9 is a variation of example 7, varying only: the concentration of PEI was 30 mg/mL.

And (3) crosslinking CNC and 2% GA in a water bath kettle at 40 ℃ for 30min, then adding 30mg/mL PEI, wherein the volume ratio of the CNC to the GA to the PEI is 1:1:1, and stirring for 20min to obtain the PEI/GA-CNC composite adsorbent.

Example 10

In this embodiment, the application of the optimal PEI/GA-CNC composite adsorbent in different pH values of arsenic solutions is specifically as follows:

(i) an aqueous solution of As (V) ions at a concentration of 20mg/L was prepared and placed in a 250ml Erlenmeyer flask. Regulating the pH value of the aqueous solution to 3 by using 1mol/L hydrochloric acid solution and 1mol/L sodium hydroxide solution;

(ii) adding the PEI/GA-CNC composite adsorbent into the aqueous solution obtained in the step (i), enabling the mass-volume ratio of the adsorbent to the aqueous solution to be 0.4g/L, simultaneously placing an erlenmeyer flask into a constant-temperature oscillator to be fully oscillated (at 25 ℃ and at 120rpm for 2h), reducing the As (V) ion concentration in the aqueous environment through the adsorption effect of the PEI/GA-CNC composite adsorbent, taking a supernatant by using a 5mL syringe after the oscillation is finished, and testing the As (V) ion concentration in the supernatant.

Example 11

Example 11 is a variation of example 10, varying only: the pH of the aqueous solution was 4.

(i) An aqueous solution of As (V) ions at a concentration of 20mg/L was prepared and placed in a 250ml Erlenmeyer flask. Regulating the pH value of the aqueous solution to be 4 by utilizing 1mol/L hydrochloric acid solution and 1mol/L sodium hydroxide solution;

Example 12

Example 12 is a variation of example 11, varying only: the pH of the aqueous solution was 6.

(i) An aqueous solution of As (V) ions at a concentration of 20mg/L was prepared and placed in a 250ml Erlenmeyer flask. Regulating the pH value of the aqueous solution to be 6 by utilizing 1mol/L hydrochloric acid solution and 1mol/L sodium hydroxide solution;

Example 13

Example 11 is a variation of example 10, varying only: the pH of the aqueous solution was 8.

(i) An aqueous solution of As (V) ions at a concentration of 20mg/L was prepared and placed in a 250ml Erlenmeyer flask. Regulating the pH value of the aqueous solution to be 8 by utilizing 1mol/L hydrochloric acid solution and 1mol/L sodium hydroxide solution;

Example 14

In this embodiment, the application of the optimal PEI/GA-CNC composite adsorbent in different high-concentration arsenic solutions is specifically as follows:

Example 15

Example 15 is a variation of example 14, varying only: as (V) concentration of the ionic water solution was 100 mg/mL.

(i) An aqueous solution of As (V) ions at a concentration of 100mg/L was prepared and placed in a 250ml Erlenmeyer flask. Regulating the pH value of the aqueous solution to 3 by using 1mol/L hydrochloric acid solution and 1mol/L sodium hydroxide solution;

Example 16

Example 16 is a variation of example 14, varying only: as (V) concentration of the ionic water solution was 200 mg/mL.

(i) An aqueous solution of As (V) ions was prepared at a concentration of 200mg/L and placed in a 250ml Erlenmeyer flask. Regulating the pH value of the aqueous solution to 3 by using 1mol/L hydrochloric acid solution and 1mol/L sodium hydroxide solution;

Example 17

Example 17 is a variation of example 14, varying only: as (V) concentration of the ionic water solution was 300 mg/mL.

(i) An aqueous As (V) ion solution was prepared at a concentration of 300mg/L and placed in a 250ml Erlenmeyer flask. Regulating the pH value of the aqueous solution to 3 by using 1mol/L hydrochloric acid solution and 1mol/L sodium hydroxide solution;

Comparative examples 1 to 3

Comparative examples 1 to 3 are comparative examples of example 1, and the comparative points and effects are shown in Table 1-1, and the parameters of As (V) adsorption of each material of examples 1 to 3 are shown in Table 1-2:

TABLE 1-1

	Comparative example 1	Comparative example 2	Comparative example 3
				Comparison of	The PEI concentration was 20mg/mL	The PEI concentration was 25mg/mL	The PEI concentration was 30mg/mL
Contrast effect	12.00mg/g	19.00mg/g	13.00mg/g

Tables 1 to 2

	Example 1	Example 2	Example 3
				Sample input amount	0.4g/L	0.4g/L	0.4g/L
Temperature of	25℃	25℃	25℃
				Stirring speed	120rpm	120rpm	120rpm
Time of stirring	24h	24h	24h
				As(V)	20mg/L	20mg/L	20mg/L
pH(As)	7.80	7.80	7.80

Comparative examples 4 to 6

Comparative examples 4 to 6 are comparative examples of example 4, and the comparative points and effects are shown in Table 2-1, and the parameters of As (V) adsorption of each material of examples 4 to 6 are shown in Table 2-2:

TABLE 2-1

	Comparative example 4	Comparative example 5	Comparative example 6
				Comparison of	The PEI concentration was 20mg/mL	The PEI concentration was 25mg/mL	The PEI concentration was 30mg/mL
Contrast effect	9.50mg/g	11.00mg/g	12.00mg/g

Tables 2 to 2

	Example 4	Example 5	Example 6
				Sample input amount	0.4g/L	0.4g/L	0.4g/L
Temperature of	25℃	25℃	25℃
				Stirring speed	120rpm	120rpm	120rpm
Time of stirring	24h	24h	24h
				As(V)	20mg/L	20mg/L	20mg/L
pH(As)	7.80	7.80	7.80

Comparative examples 7 to 9

Comparative examples 7 to 9 are comparative examples of example 7, and the comparative points and effects are shown in Table 3-1, and the parameters of As (V) adsorption of each material of examples 7 to 9 are shown in Table 3-2:

TABLE 3-1

	Comparative example 7	Comparative example 8	Comparative example 9
				Comparison of	The PEI concentration was 20mg/mL	The PEI concentration was 25mg/mL	The PEI concentration was 30mg/mL
Contrast effect	5.00mg/g	7.00mg/g	6.00mg/g

TABLE 3-2

Comparative examples 10 to 13

Comparative examples 10 to 13 are comparative examples of example 10, and the comparative points and effects are shown in Table 4-1, and the parameters of As (V) adsorption of the respective materials of examples 10 to 13 are shown in Table 4-2:

TABLE 4-1

TABLE 4-2

Comparative examples 14 to 17

Comparative examples 14 to 17 are comparative examples of example 14, and the comparative points and effects are shown in Table 5-1, and the parameters of As (V) adsorption of each material of examples 14 to 17 are shown in Table 5-2:

TABLE 5-1

TABLE 5-2

As can be seen from the above comparison, in the embodiment of the present invention, a pH sensitive nanosphere (PEI/GA-CNC) synthesized by crosslinking GA and PEI based on carboxylated cellulose nanowhisker realizes removal of as (v); the principle of the PEI/GA-CNC composite adsorbent is that the surface of the carboxylated cellulose nanowhisker has a large number of carboxyl functional groups, the specific surface area is high, and the PEI/GA-CNC composite adsorbent is easy to be combined with amine ions. PEI has a large amount of amine ions, and the amine functional groups have good adsorption capacity for acid radical anions, and have good potential for preparing high-efficiency adsorption purified water. Therefore, the PEI/GA-CNC composite nanosphere can become a novel and efficient adsorbent, and the effect of changing waste into valuable is achieved.

Example 18

The preparation method of the pH sensitive nanosphere based on the cellulose nanowhisker comprises the following steps:

(1) uniformly stirring the kapok fiber in a sodium chlorite solution with the mass concentration of 0.8%, heating in a water bath at 70 ℃, adding glacial acetic acid every 1h, repeatedly removing acid-soluble lignin in the cellulose for several times, and washing with water until the cellulose is neutral;

(2) putting the kapok fiber obtained by the treatment in the step (1) into a potassium hydroxide solution with the mass concentration of 6%, uniformly stirring, standing at room temperature, heating in a water bath at 70 ℃ to remove alkaline soluble lignin, and washing with water to be neutral;

(3) adding the kapok fiber obtained by the treatment in the step (2) into a sodium hydroxide solution with the mass concentration of 25%, standing for 30min, washing with water to be neutral, mixing the tetramethylpiperidine nitrogen oxide, sodium hypochlorite and sodium bromide, continuing stirring, adjusting the pH value to 12 by using sodium hydroxide, adding into ethanol for reaction, standing, performing suction filtration, and obtaining a filtrate, namely the carboxylated cellulose nanowhisker, with the concentration of 0.4g/L, wherein the volume ratio of the tetramethylpiperidine nitrogen oxide to the sodium bromide is 1:7, and the volume ratio of the sodium hypochlorite to the ethanol is 2: 1.

(4) Crosslinking the carboxylated cellulose nanowhiskers with a glutaraldehyde solution with a concentration of 0.5 wt% at 40 ℃ for 30min,

(5) and adding a polyethyleneimine solution with the concentration of 20mg/mL, wherein the volume ratio of the carboxylated cellulose nanowhisker to the glutaraldehyde solution to the polyethyleneimine solution is 1:1:1, stirring for reaction for 20min, then carrying out suction filtration, drying and grinding to prepare the pH sensitive nanosphere based on the cellulose nanowhisker.

Example 19

(1) uniformly stirring kapok fibers in a sodium chlorite solution with the mass concentration of 1%, heating in a water bath at the temperature of 80 ℃, adding glacial acetic acid every 1h, repeatedly removing acid-soluble lignin in the cellulose for several times, and washing with water until the cellulose is neutral;

(2) putting the kapok fiber obtained by the treatment in the step (1) into a potassium hydroxide solution with the mass concentration of 10%, uniformly stirring, standing at room temperature, heating in a water bath at 80 ℃ to remove alkaline soluble lignin, and washing with water to be neutral;

(3) adding the kapok fiber obtained by the treatment in the step (2) into a sodium hydroxide solution with the mass concentration of 30%, standing for 120min, washing with water to be neutral, mixing the tetramethylpiperidine nitrogen oxide, sodium hypochlorite and sodium bromide, continuing stirring, adjusting the pH value to 12 by using sodium hydroxide, adding into ethanol for reaction, standing, performing suction filtration, and obtaining a filtrate, namely the carboxylated cellulose nanowhisker, with the concentration of 0.4g/L, wherein the volume ratio of the tetramethylpiperidine nitrogen oxide to the sodium bromide is 1:10, and the volume ratio of the sodium hypochlorite to the ethanol is 2: 3.

(4) Crosslinking the carboxylated cellulose nanowhiskers with a glutaraldehyde solution with a concentration of 2 wt% at 60 ℃ for 60min,

(5) adding 20-30mg/mL polyethyleneimine solution, wherein the volume ratio of the carboxylated cellulose nanowhisker, the glutaraldehyde solution and the polyethyleneimine solution is 1:3:3, stirring and reacting for 60min, then carrying out suction filtration, drying and grinding to prepare the pH sensitive nanosphere based on the cellulose nanowhisker.

The invention provides a pH sensitive nanosphere (PEI/GA-CNC) and a preparation method and application thereof, in particular to a method for removing As (V) in a water body by using a nanosphere synthesized based on carboxylated cellulose nanowhiskers, and the material is easy to prepare, simple to operate, free of pollution to the environment, easy to separate from the water body, capable of rapidly and efficiently removing arsenic, and has the outstanding characteristics of high efficiency, environmental protection, simplicity in operation and the like.

In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The embodiments described above are intended to facilitate the understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. The preparation method of the pH sensitive nanosphere based on the cellulose nanowhiskers is characterized in that the method comprises the steps of crosslinking carboxylated cellulose nanowhiskers with a glutaraldehyde solution, then adding a polyethyleneimine solution, stirring for reaction, and then carrying out suction filtration, drying and grinding to prepare the pH sensitive nanosphere based on the cellulose nanowhiskers.

2. The method for preparing pH-sensitive nanospheres based on cellulose nanowhiskers according to claim 1, wherein the carboxylated cellulose nanowhiskers are prepared by the following method:

removing acidic lignin in the kapok fiber by using sodium chlorite and acetic acid, then removing alkaline lignin in the kapok fiber by using potassium hydroxide, mixing the obtained product with tetramethyl piperidine nitrogen oxide, sodium hypochlorite and sodium bromide, regulating the pH value to be strong alkalinity, and stirring to react to obtain the carboxylated cellulose nanowhisker.

3. The method for preparing pH-sensitive nanospheres based on cellulose nanowhiskers as claimed in claim 2, wherein the carboxylated cellulose nanowhiskers are prepared by the following method:

(1) uniformly stirring kapok fibers in a sodium chlorite solution, heating in a water bath, adding glacial acetic acid every 1h, repeatedly removing acid-soluble lignin in cellulose for several times, and washing to be neutral;

(2) putting the kapok fiber obtained by the treatment in the step (1) into a potassium hydroxide solution, uniformly stirring, standing at room temperature, heating in a water bath to remove alkaline soluble lignin, and washing to be neutral;

(3) adding the kapok fiber obtained by the treatment in the step (2) into a sodium hydroxide solution, standing, washing with water to be neutral, mixing tetramethylpiperidine nitrogen oxide, sodium hypochlorite and sodium bromide, continuously stirring, adjusting the pH value to be strong alkalinity, adding into ethanol for reaction, standing, and performing suction filtration to obtain a filtrate, namely the carboxylated cellulose nanowhisker.

4. The method for preparing pH-sensitive nanospheres based on cellulose nanowhiskers according to claim 3,

in the step (1), the mass concentration of the sodium chlorite solution is 0.8-1 percent, the water bath heating temperature is 70-80 ℃,

in the step (2), the mass concentration of the potassium hydroxide solution is 6-10%, the water bath heating temperature is 70-80 ℃,

in the step (3), the mass concentration of the sodium hydroxide solution is 25-30%, the standing time is 30-120 min, the volume ratio of the tetramethylpiperidine oxynitride to the sodium bromide is 1: 7-1: 10, the volume ratio of the sodium hypochlorite to the ethanol is 2: 1-2: 3, and the pH value is adjusted to 12 by adopting sodium hydroxide.

5. The method for preparing pH-sensitive nanospheres based on cellulose nanowhiskers according to claim 1, wherein the concentration of carboxylated cellulose nanowhiskers is 0.4g/L, the concentration of glutaraldehyde solution is 0.5-2 wt%, and the concentration of polyethyleneimine solution is 20-30 mg/mL.

6. The preparation method of the pH-sensitive nanosphere based on the cellulose nanowhisker according to claim 1 or 5, wherein the volume ratio of the carboxylated cellulose nanowhisker, the glutaraldehyde solution and the polyethyleneimine solution is 1:1: 1-1: 3: 3.

7. The method for preparing pH-sensitive nanospheres based on cellulose nanowhiskers according to claim 1, wherein the temperature for crosslinking the carboxylated cellulose nanowhiskers with the glutaraldehyde solution is 40-60 ℃ for 30-60 min, and the reaction time after adding the polyethyleneimine solution is 20-60 min.

8. Cellulose nanowhiskers based on cellulose produced by a method according to any one of claims 1 to 7.

9. Use of cellulose-based nanowhiskers prepared according to any one of claims 1 to 7 for the removal of as (v) ions from acidic wastewater.

10. Use of cellulose nanowhisker based pH sensitive nanospheres according to claim 9, wherein the cellulose nanowhisker based pH sensitive nanospheres are added to wastewater containing as (v) ions, and shaken under room temperature conditions to adsorb as (v) ions therein.