Green and Low-Energy Preparation Method for Cellulose Nanofibers Based on Cold Plasma

Abstract

Disclosed is a green and low-energy preparation method for cellulose nanofibers based on cold plasma. The preparation method comprises the following steps: (1) uniformly mixing cellulose with a FeSO.sub.4 solution, so that FeSO.sub.4 is immersed into cellulose, and then performing cold plasma treatment under atmospheric-pressure air to obtain oxidized cellulose, the water in the FeSO.sub.4 solution being subjected to cold plasma treatment; and (2) washing and suction filtering the oxidized cellulose obtained in step (1), and then carrying out mechanical fibrillation treatment to obtain the cellulose nanofibers (CNF). According to the invention, the cold plasma and the FeSO.sub.4 catalyst are compounded to construct a highly oxidizing environment that oxidizes cellulose and obtain CNFs by means of mild mechanical dispersion treatment. The whole process is carried out at normal temperature. The method is simple and mild, and does not require other non-environment-friendly chemicals. Meanwhile, the energy consumption of the nanocrystallization process is significantly reduced, the obtained CNF is uniformly dispersed, and the yield is higher.

Claims

1: A green and low-energy preparation method for cellulose nanofibers (CNFs) based on cold plasma, comprising the following steps: (1) uniformly mixing cellulose with a FeSO.sub.4 solution, so that FeSO.sub.4 is immersed into the cellulose, and then performing cold plasma treatment under atmospheric-pressure air to obtain oxidized cellulose; and (2) washing the oxidized cellulose obtained in step (1), and carrying out suction filtration and mechanical fibrillation treatment to obtain the CNFs.

2: The method according to claim 1, wherein water in the FeSO.sub.4 solution in step (1) is subjected to cold plasma treatment.

3: The method according to claim 2, wherein the preparation of the FeSO.sub.4 solution in step (1) comprises the following steps: treating deionized water with the cold plasma under the atmospheric-pressure air, and then dissolving a FeSO.sub.4 catalyst into the deionized water to obtain the FeSO.sub.4 solution.

4: The preparation method according to claim 3, wherein the cold plasma treats the deionized water at an operating voltage of 120-160 kV for 1-5 min.

5: The preparation method according to claim 1, wherein in step (1), the cold plasma treats the cellulose at an operating voltage of 120-160 kV for 45-90 min.

6: The preparation method according to claim 1, wherein a mass ratio of FeSO.sub.4 to the cellulose in step (1) is 1-4:100.

7: The preparation method according to claim 1, wherein in step (1), the cold plasma treats the cellulose at an operating voltage of 120-140 kV for 60-90 min; and a mass ratio of FeSO.sub.4 to the cellulose is 3-4:100.

8: The preparation method according to claim 1, wherein a concentration of FeSO.sub.4 in the FeSO.sub.4 solution in step (1) is 0.1 wt %-0.4 wt %.

9: The preparation method according to claim 1, wherein a mixing time in step (1) is 10-20 min.

10: The preparation method according to claim 1, wherein in step (2), the oxidized cellulose is treated under an ultrasonic condition of 600 W at a concentration of 0.5 wt %-2 wt % for 90 min to obtain the CNFs.

11: The preparation method according to claim 2, wherein in step (1), the cold plasma treats the cellulose at an operating voltage of 120-160 kV for 45-90 min.

12: The preparation method according to claim 3, wherein in step (1), the cold plasma treats the cellulose at an operating voltage of 120-160 kV for 45-90 min.

13: The preparation method according to claim 4, wherein in step (1), the cold plasma treats the cellulose at an operating voltage of 120-160 kV for 45-90 min.

14: The preparation method according to claim 2, wherein a mass ratio of FeSO.sub.4 to the cellulose in step (1) is 1-4:100.

15: The preparation method according to claim 3, wherein a mass ratio of FeSO.sub.4 to the cellulose in step (1) is 1-4:100.

16: The preparation method according to claim 4, wherein a mass ratio of FeSO.sub.4 to the cellulose in step (1) is 1-4:100.

17: The preparation method according to claim 2, wherein in step (1), the cold plasma treats the cellulose at an operating voltage of 120-140 kV for 60-90 min; and a mass ratio of FeSO.sub.4 to the cellulose is 3-4:100.

18: The preparation method according to claim 3, wherein in step (1), the cold plasma treats the cellulose at an operating voltage of 120-140 kV for 60-90 min; and a mass ratio of FeSO.sub.4 to the cellulose is 3-4:100.

19: The preparation method according to claim 4, wherein in step (1), the cold plasma treats the cellulose at an operating voltage of 120-140 kV for 60-90 min; and a mass ratio of FeSO.sub.4 to the cellulose is 3-4:100.

20: The preparation method according to claim 4, wherein in step (2), the oxidized cellulose is treated under an ultrasonic condition of 600 W at a concentration of 0.5 wt %-2 wt % for 90 min to obtain the CNFs.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a flowchart for preparing CNFs according to the present disclosure;

[0029] FIG. 2 is a scanning electron microscope graph of CNFs prepared according to example 1 of the present disclosure;

[0030] FIG. 3 is a scanning electron microscope graph of CNFs prepared according to example 2 of the present disclosure;

[0031] FIG. 4 is a scanning electron microscope graph of CNFs prepared according to example 3 of the present disclosure;

[0032] FIG. 5 is a graph showing carboxyl contents of oxidized cellulose prepared according to examples 1-3 of the present disclosure; and

[0033] FIG. 6 is a graph showing a polymerization degree of oxidized cellulose prepared according to examples 1-3 of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Specific embodiments of the present disclosure are further described below in conjunction with examples and accompanying drawings, but the embodiments of the present disclosure are not limited thereto.

[0035] A flowchart for preparing CNFs according to the present disclosure is shown in FIG. 1.

Example 1

[0036] 1000 mL of deionized water was treated with cold plasma under atmospheric-pressure air (with treatment time of 3 min, and operating voltage of 150 kV), and then 1 g of FeSO.sub.4 catalyst was added to obtain a FeSO.sub.4 solution. 100 g of cellulose and the FeSO.sub.4 solution were magnetically stirred and mixed for 20 min, so that FeSO.sub.4 was immersed into the cellulose, and then cold plasma treatment was continued under atmospheric-pressure air (with treatment time of 45 min, and operating voltage of 160 kV). Obtained oxidized cellulose was washed with deionized water, and suction filtration was carried out (with a carboxyl content and a polymerization degree of the oxidized cellulose shown in FIG. 5 and FIG. 6). Finally, mechanical fibrillation treatment was performed on the oxidized cellulose at a mass fraction of 1% (w/w) by an ultrasonic biomixer (600 W, 90 min) to obtain CNFs (FIG. 2) with a yield of 70.7%. The whole process did not involve use of any non-environment-friendly chemicals, and was simple, efficient, green, and non-polluting.

Example 2

[0037] 1000 mL of deionized water was treated with cold plasma under atmospheric-pressure air (with treatment time of 5 min, and operating voltage of 120 kV), and then 3 g of FeSO.sub.4 catalyst was added to obtain a FeSO.sub.4 solution. 100 g of cellulose and the FeSO.sub.4 solution were magnetically stirred and mixed for 15 min, so that FeSO.sub.4 was immersed into the cellulose, and then cold plasma treatment was continued under atmospheric-pressure air (with treatment time of 60 min, and operating voltage of 140 kV). Obtained oxidized cellulose was washed with deionized water, and suction filtration was carried out (with a carboxyl content and a polymerization degree of the oxidized cellulose shown in FIG. 5 and FIG. 6). Finally, mechanical fibrillation treatment was performed on the oxidized cellulose at a mass fraction of 1% (w/w) by an ultrasonic biomixer (600 W, 90 min) to obtain CNFs (FIG. 3) with a yield of 90.1%. The whole process did not involve use of any non-environment-friendly chemicals, and was simple, efficient, green, and non-polluting.

Example 3

[0038] 1000 mL of deionized water was treated with cold plasma under atmospheric-pressure air (with treatment time of 1 min, and operating voltage of 160 kV), and then 4 g of FeSO.sub.4 catalyst was added to obtain a FeSO.sub.4 solution. 100 g of cellulose was mixed with the FeSO.sub.4 solution for 10 min, so that FeSO.sub.4 was immersed into the cellulose, and then cold plasma treatment was continued under atmospheric-pressure air (with treatment time of 90 min, and operating voltage of 120 kV). Obtained oxidized cellulose was washed with deionized water, and suction filtration was carried out (with a carboxyl content and a polymerization degree of the oxidized cellulose shown in FIG. 5 and FIG. 6). Finally, mechanical fibrillation treatment was performed on the oxidized cellulose at a mass fraction of 1% (w/w) by an ultrasonic biomixer (600 W, 90 min) to obtain CNFs (FIG. 4) with a yield of 95.2%. The whole process did not involve use of any non-environment-friendly chemicals, and was simple, efficient, green, and non-polluting.

Comparative Example 1

[0039] 100 g of cellulose was mixed with 1000 mL of deionized water, and then cold plasma treatment was performed under atmospheric-pressure air (with treatment time of 60 min, and operating voltage of 140 kV). Obtained oxidized cellulose was washed with deionized water, and suction filtration was carried out. Finally, mechanical fibrillation treatment was performed on the oxidized cellulose at a mass fraction of 1% (w/w) by an ultrasonic biomixer (600 W, 90 min) to obtain CNFs with a yield of 55.9%.

Comparative Example 2

[0040] 3 g of FeSO.sub.4 catalyst was dissolved in 1000 mL of deionized water to obtain a FeSO.sub.4 solution, and 100 g of cellulose was mixed with the FeSO.sub.4 solution for 15 min, so that FeSO.sub.4 was immersed into the cellulose, and then cold plasma treatment was performed under atmospheric-pressure air (with treatment time of 60 min, and operating voltage of 140 kV). Obtained oxidized cellulose was washed with deionized water, and suction filtration was carried out. Finally, mechanical fibrillation treatment was performed on the oxidized cellulose at a mass fraction of 1% (w/w) by an ultrasonic biomixer (600 W, 90 min) to obtain CNFs with a yield of 62.1%.

[0041] The above-mentioned examples are preferred embodiments of the present disclosure, but the embodiments of the present disclosure are not limited to the above-mentioned examples. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present disclosure are intended to be equivalent substitution modes and are intended to be within the scope of protection of the present disclosure.