Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a waste cotton fabric modified microfiber and a preparation method and application thereof. The raw materials of the method provided by the invention are derived from waste cotton fabrics, the resources are rich, and the waste utilization is realized. The method has the advantages of simple process, environmental protection and low production cost.
The technical scheme provided by the invention is as follows:
a preparation method of waste cotton fabric modified microfiber comprises the following steps:
1) crushing the waste pure cotton fabric dried to constant weight into chips, and crushing the chips into powder by using a crusher to obtain waste cotton fabric fiber powder;
2) mixing the waste cotton fabric fiber powder obtained in the step 1) with a sodium hydroxide solution, performing alkali treatment, and performing suction filtration and washing to obtain alkali-treated waste cotton fabric fibers;
3) mixing the alkali-treated waste cotton fabric fibers obtained in the step 2) with deionized water, and then performing high-speed homogenization to obtain waste cotton fabric microfiber suspension;
4) treating the waste cotton fabric microfiber suspension obtained in the step 3) with polyethyleneimine, cooling to room temperature, then treating with glutaraldehyde, performing solid-liquid separation on the obtained system to obtain a solid material, washing the solid material with deionized water, and then performing freeze drying to obtain the waste cotton fabric modified microfiber.
In the above technical scheme:
stripping the waste cotton fabric fiber powder into waste cotton fabric fibers with smaller sizes through the alkali treatment in the step 2). Furthermore, the waste cotton fabric fibers are homogenized at a high speed through high-speed homogenization to obtain a waste cotton fabric microfiber suspension, wherein the microfibers have a loose net structure and the specific surface area is remarkably improved, so that more amino groups can be exposed on the surface of the modified waste cotton fabric fibers, and the modified waste cotton fabric microfiber suspension has a better dye adsorption effect.
In the modification process of the step 4), interchain crosslinking is formed between polyethyleneimine and cotton fiber molecules through hydrogen bonds. After being added, glutaraldehyde reacts with polyethyleneimine and cotton fibers to generate chemical bonds respectively, and reacts with-OH groups of the cotton fibers to remove water molecules, and meanwhile, glutaraldehyde and polyethyleneimine molecules are crosslinked together through generating C ═ N double bonds. The surface of the cotton fiber is modified by polyethyleneimine through the bridging action of glutaraldehyde molecules, and the cotton fiber is rich in chargedGroup (-NH)2). The principle is as follows:
specifically, in the step 1), the particle size of the waste cotton fabric fiber powder is 0.05-0.2 mm.
Specifically, in the step 2):
the concentration of the sodium hydroxide solution is 5-8 wt.%, and the dosage ratio of the solid material to the sodium hydroxide solution in the system during alkali treatment is 1g: 20-30 mL;
the temperature of the alkali treatment is 80-100 ℃, the time of the alkali treatment is 2-4 h, the stirring speed during the alkali treatment is 150-350 rpm, and the filtrate is washed after suction filtration until the pH value of the filtrate is 7-8.
Specifically, in the step 3), the number of times of medium-high speed homogenization treatment is 8-10.
Specifically, the method comprises the following steps:
the solid content of the system is 2-3 wt% during high-speed homogenization treatment;
the rotating speed of the high-speed homogenizing treatment is 15000-20000 rpm, and the time of single high-speed homogenizing treatment is 5-8 min.
Specifically, in the step 4):
the concentration of the polyethyleneimine solution is 1-1.5 wt.%, the dosage ratio of the solid material to the polyethyleneimine solution in the polyethyleneimine modification system is 1g (3-5) mL, the treatment time is 4-6 h, the treatment temperature is 45-55 ℃, and the stirring speed is 150-350 rpm;
the dosage ratio of the solid material to the glutaraldehyde in the glutaraldehyde treatment system is 1g (0.3-0.5) mL, the treatment time is 1.5-2.5 h, and the stirring speed is 150-350 rpm;
washing for 3-5 times by using deionized water after solid-liquid separation, wherein the using amount ratio of the deionized water to the solid material is (80-100) mL:1 g;
the temperature of the freeze drying is-50 ℃ to-60 ℃, and the freezing time is 36-48 h.
The invention also provides the waste cotton fabric modified microfiber prepared by the preparation method.
The modified microfiber based on waste cotton fabric provided by the invention has a large specific surface area and a loose reticular structure, and a large amount of amino groups are arranged on the fiber surface, so that the modified microfiber has strong adsorption capacity on dyes.
The invention also provides the modified microfiber based on the waste cotton fabric as an adsorbent for treating printing and dyeing wastewater.
The invention has the advantages that:
1) the high-speed homogenate is used for replacing the traditional acid hydrolysis, so that the problem of environmental pollution caused by the traditional chemical treatment is greatly relieved;
2) the high-speed homogenate can enable the fibers to be stripped into microfibrillated cellulose with a loose net-shaped structure, so that the specific surface area of the microfibrillated cellulose is greatly increased;
3) polyethyleneimine and glutaraldehyde are used for modifying waste cotton fabric microfiber, and the surface of the microfiber has a large number of amino groups, so that the microfiber has strong adsorption capacity on dyes.
4) The invention has simple production process, high efficiency and low production cost.
Detailed Description
The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.
Example 1
The waste cotton fabric modified microfiber can be obtained according to the following method:
10g of waste white pure cotton T-shirt is taken and dried in an oven at 60 ℃ to constant weight. Cutting into pieces with scissors, and pulverizing into powder with particle size of 0.05-0.2mm with pulverizer. And (3) mixing fiber powder according to the solid-liquid ratio of 1: 20 was added to a 7% aqueous solution of NaOH. Stirring at 80 deg.C for 2 hr, vacuum filtering, and washing the filter residue with deionized water until the pH of the filtrate is neutral. Taking the cotton fiber treated by the alkali, preparing a 2 wt% cellulose suspension by water, homogenizing at a high speed (15000rpm) for 5min, and circularly homogenizing for 10 times to obtain a waste cotton fabric microfiber suspension (see figure 1). To this suspension was added dropwise 30mL of a 1 wt% polyethyleneimine solution, and the mixture was stirred (rotation speed: 350rpm) at 55 ℃ for 4 hours. After naturally cooling to room temperature, 5mL of glutaraldehyde was added and stirred (rotation speed 350rpm) for 1.5 hours. After the reaction was complete, it was filtered and the filter residue was washed 3 times with water. And (3) freeze-drying the washed sample (drying at the temperature of-50 ℃ for 48 hours) to obtain the waste cotton fabric modified microfiber product (see figure 2).
The SEM test result of the waste cotton fabric modified microfiber is shown in figure 3. As can be seen from fig. 3, after the waste cotton fabric is subjected to alkali treatment, high-speed homogenization and crosslinking treatment, the microfibers are peeled off, and a loose mesh structure is formed, and the surface of the waste cotton fabric is coated with a large amount of polyethyleneimine. FIG. 4 is an FTIR absorption spectrum of the waste cotton fabric microfiber before and after modification prepared in example 1, and it can be seen from FIG. 4 that the positions of peaks appeared in the microfiber before and after modification are substantially the same, but the microfiber after modification is 1650cm-1The obvious characteristic absorption peak of C ═ N proves that PEI is successfully crosslinked with cellulose. Fig. 5 shows thermogravimetric analysis results of the waste cotton fabric micro-fibers before and after modification, and it can be seen from fig. 5 that the maximum decomposition temperature of the modified waste cotton fabric micro-fibers is increased to 481 ℃ compared with that before modification, and the thermal stability of the modified waste cotton fabric micro-fibers is increased probably due to intermolecular cross-linking caused by glutaraldehyde.
Example 2
The waste cotton fabric modified microfiber can be obtained according to the following method:
10g of waste white pure cotton T-shirt is taken and dried in an oven at 60 ℃ to constant weight. Cutting into pieces with scissors, and pulverizing into powder with particle size of 0.05-0.2mm with pulverizer. And (3) mixing fiber powder according to the solid-liquid ratio of 1: 30, adding 5 percent NaOH aqueous solution, stirring (150rpm) at 100 ℃ for 4 hours, filtering, and fully washing filter residues with deionized water until the filtrate is neutral. Taking the cotton fiber treated by the alkali, preparing a 3 wt% cellulose suspension by water, homogenizing at a high speed (20000rpm) for 8min, and circularly homogenizing for 8 times to obtain the waste cotton fabric microfiber suspension. To this suspension was added dropwise 50mL of a 1.5 wt% Polyethyleneimine (PEI) solution and the mixture was stirred (rotation speed 350rpm) at 45 ℃ for 6 hours. After cooling to room temperature, 3mL of glutaraldehyde were added and stirred (350 rpm) for 2.5 h. Filter and wash the residue 5 times with water. And (4) freeze-drying the washed sample at (-60 ℃ for 36 hours) to obtain the waste cotton fabric modified microfiber product. The characterization results of the waste cotton fabric modified microfiber prepared in example 2 are similar to the sample prepared in example 1, and are all loose net structures.
Example 3
Adsorption of the waste cotton fabric modified microfiber on dye:
50mg of the waste cotton fabric modified microfiber prepared in example 1 was added to 100mL of a methyl blue solution with a concentration of 50mg/L, and the mixture was stirred and adsorbed at room temperature and 100rpm for 30min (see FIG. 5), and the dye removal rate was calculated to be 98.4%. Adding 50mg of waste cotton fabric modified microfiber into 100mL of methyl blue solution with the concentration of 150mg/L, stirring and adsorbing for 120min at room temperature and 100rpm, calculating the adsorption capacity to be 279.26mg/g, and soaking the microfiber after dye adsorption in 40mL of methanol solution containing 1N KSCN for analysis. After filtration, the filter residue is soaked in 60mL deionized water solution for 30 minutes, the filter residue is filtered to obtain the resolved microfiber, and the microfiber is added into 100mL methyl blue solution with the concentration of 150mg/L again to be adsorbed at room temperature for 120 min. The adsorption and analysis process was repeated 5 times, and the adsorption rate of the dye is shown in Table 1. The results show that the adsorption rate of the dye after 5 times of repetition is still as high as 84.6%.
TABLE 1 repeated adsorption rate of waste cotton fabric modified microfiber to methyl blue solution
The adsorption performance of the waste cotton fabric modified microfiber prepared in example 2 is tested according to the method, and the result shows that the adsorption capacity of the waste cotton fabric modified microfiber prepared in example 2 to a methyl blue solution of 150mg/L is 278.35 mg/g.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.