CN112642406A

CN112642406A - Wood fiber based composite sponge and preparation method thereof

Info

Publication number: CN112642406A
Application number: CN202011386190.7A
Authority: CN
Inventors: 杨进; 宋浩杰; 宋飞; 贾晓华; 李永; 王思哲
Original assignee: Shaanxi University of Science and Technology
Current assignee: Shaanxi University of Science and Technology
Priority date: 2020-12-02
Filing date: 2020-12-02
Publication date: 2021-04-13

Abstract

The invention relates to a wood fiber-based composite sponge and a preparation method thereof.A white wood fiber is prepared by using wood as a raw material, removing lignin by using sodium hydroxide and sodium sulfite, combining sodium chlorite, hydrogen peroxide oxidation and other methods, dissolving the wood fiber in deionized water, adding bismuth nitrate pentahydrate, dispersing a potassium bromide solution in the solution, and then freeze-drying to obtain a fiber sponge; the composite sponge shows super-hydrophilicity and super-oleophobicity under water, selectively separates layered oil/water mixtures, can also be used for separating oil-in-water emulsions, and simultaneously adsorbs water-soluble organic pollutants, and has high separation efficiency and adsorption efficiency; the regenerated composite sponge still has excellent reusability and high-efficiency performance of separating emulsion and adsorbing dye.

Description

Wood fiber based composite sponge and preparation method thereof

Technical Field

The invention belongs to the technical field of material preparation, relates to the field of green fiber materials and environment-friendly materials, and particularly relates to a wood fiber-based composite sponge and a preparation method thereof.

Background

Water is an indispensable resource and plays an important role in human life. However, with the rapid development of global industrialization, serious water pollution has posed a great threat to human beings and the environment. The treatment of waste water with complex contaminants, especially emulsified oils and organic dyes, is urgent and challenging. What is troublesome is that emulsified oil/water mixtures containing complex ingredients are more difficult to solve because surfactants have an amphiphilic nature between water and oil molecules, resulting in multi-molecular interactions. On the other hand, organic dyes such as rhodamine b (rhb) and Methyl Orange (MO) resist aerobic digestion and stabilize the structure of oxidant dyes due to complex organic molecules. In this respect, separation, extraction, flotation, centrifugation and coalescence agents have been developed, but these methods have the disadvantage of energy consumption and secondary pollution. Furthermore, and equally important, a process can generally relocate one of the two contaminants due to different physical and chemical properties between the organic dye and some of the oil. Therefore, a great challenge is how to design a multifunctional material to simultaneously relocate both types of contaminants, thereby increasing the purity of water to achieve efficient cleaning and collection.

Sponges are a potential type of three-dimensional porous material with many advantageous physicochemical properties including their low density, required biosafety, ease of handling and surface-tunable chemistry. The use of sponges is highly appreciated to enhance sustainability development, which is more effective than conventional techniques for adsorption of the two types of contaminants. Due to the current development of sponge synthesis technology and the improvement of a series of methods, various sponges appeared, including silica sponge, melamine/graphene oxide sponge, phenol-formaldehyde sponge and cellulose fiber sponge. Pure silica gel sponges are prone to deterioration of mechanical properties. Graphene oxide sponge has good corrosion resistance, but is complex to operate and expensive to consume. Compared with phenolic sponge with higher toxicity, the cellulose fiber sponge is easier to obtain, can be continuously used, has stable chemical performance, is environmentally friendly and biodegradable, and is beneficial to treating two types of pollutants. Unfortunately, these cellulosic fibers are easily contaminated with adsorbed organic dyes, resulting in their rapid flux reduction and removal efficiency. Other disadvantages include low recyclability and relatively difficult disposal capability, which may lead to secondary contamination. With the rapid increase of the discharge amount of waste water, the design of the regenerated cellulose fiber sponge is very necessary.

In recent years, due to the continuous reduction of the reserves of non-renewable resources, the expansion of the high added value utilization of renewable raw materials is the need of the development strategy of national renewable resources, and is one of the hot areas of energy and new material development. At present, most of the development and utilization of the wood are processed on a macroscopic scale, but the potential value of the wood is not excavated deeper. Wood, as a renewable resource, is composed primarily of parallel hollow tubes, in which the woody cell walls are composed of nanocomposite layers composed of oriented cellulose microfibrils in a hydrated matrix of lignin and hemicellulose. The cellulose has the advantages of wide source, no toxicity, good biocompatibility, biodegradability and the like, and the surface of the cellulose contains a large amount of hydroxyl groups, so the cellulose is easy to modify and can be used for preparing multifunctional materials. Cellulose can replace expensive and non-biodegradable synthetic materials (such as polyurethane), and is called a new generation material with great potential. The existing wood expanding use mainly aims at lignin or hemicellulose or cellulose, and if the substances can be further purified, the use value of the wood on a microscopic scale can be greatly increased.

Disclosure of Invention

The invention aims to provide a wood fiber-based composite sponge and a preparation method thereof, the preparation method is simple, and the prepared composite sponge has excellent reusability and high-efficiency emulsion and dye separation adsorption performance.

In order to achieve the above object, the present invention adopts the following technical solutions.

A preparation method of a wood fiber-based composite sponge comprises the following steps:

(1) cleaning a certain volume of wood with deionized water, and ultrasonically treating the wood to remove impurities for later use; respectively taking sodium sulfite, sodium hydroxide and deionized water according to the mass ratio of (1) - (4) to (50-200) to obtain a solution, placing the cleaned wood in the solution, heating and boiling the wood in a water bath to remove most of lignin, taking out the wood, and cleaning surface residues with the deionized water;

(2) adding the wood obtained in the step (1), sodium chlorite and hydrogen peroxide into deionized water, wherein the mass ratio of the hydrogen peroxide to the sodium chlorite to the deionized water is 1 (1-4) to (100-400), dropwise adding acetic acid to adjust the pH value to be 4, heating in a water bath, magnetically stirring, washing with the deionized water to be neutral, filtering, and finally performing freeze drying to obtain white wood fibers;

(3) adding the white wood fiber obtained in the step (2) into deionized water, and adding bismuth nitrate pentahydrate, wherein the mass ratio of the bismuth nitrate pentahydrate to the deionized water is 1 (1-100); then the mixed solution is shaded and magnetically stirred to obtain white suspension;

(4) and (3) slowly dropwise adding a potassium bromide solution into the white suspension, wherein the mass ratio of the dropwise added potassium bromide to the deionized water in the step (3) is 1 (1-50), stirring at room temperature to obtain a precipitate, repeatedly washing the precipitate with deionized water, then placing the cleaned sample into a refrigerator for precooling, and finally performing vacuum freeze drying to obtain the wood fiber-based composite sponge.

Further, the wood in the step (1) is balsa wood, white wood or pinus sylvestris.

Further, the heating and boiling temperature in the step (1) is 60-90 ℃, and the heating time is 1-4 hours.

Further, the temperature of the water bath heating in the step (2) is 60-90 ℃, the heating time is 2-6 h, and the magnetic stirring speed is 1000-3000 rpm.

Further, the time for freeze drying in the step (2) is 48 h.

Further, the magnetic stirring time in the step (3) is 0.5 h.

Further, the stirring time in the step (4) is 12h, and the stirring speed is 1000-3000 rpm.

Furthermore, the precooling time in the step (4) is 24 hours, and the freeze-drying time is 36 hours.

The invention has the beneficial effects that:

(1) the raw material adopted by the invention is wood, and is a renewable natural resource. The utilization of the wood is expanded from the macroscopic scale to the microscopic scale, and the high value-added utilization of the wood is realized.

(2) The method has the advantages of simple and convenient operation and effective removal of lignin by treating the sodium hydroxide and the sodium sulfite.

(3) The method combines sodium chlorite, hydrogen peroxide and acetic acid to perform acid oxidation, so as to oxidize wood into micro-scale white fiber, and the wood has good quality and high use value.

(4) The method uses bismuth nitrate pentahydrate and then adds the potassium bromide solution, thereby being beneficial to the growth of bismuth oxybromide on wood fibers.

The invention takes wood as raw material, removes lignin by sodium hydroxide and sodium sulfite, prepares a white wood fiber by combining sodium chlorite, hydrogen peroxide oxidation and other methods, dissolves the wood fiber in deionized water, adds bismuth nitrate pentahydrate, disperses potassium bromide solution in the solution, and then freezes and dries to obtain the fiber sponge.

The method obtains wood fiber by using wood as a raw material through oxidation and freeze drying, and the irregular flaky bismuth oxybromide is tightly grown on the fiber through an in-situ method. By virtue of the unique functions, the composite sponge shows super-hydrophilicity and super-oleophobicity under water, selectively separates layered oil/water mixtures, and can also be used for separating oil-in-water emulsions and adsorbing water-soluble organic pollutants. The separation efficiency and the adsorption efficiency are high.

The combination of the wood fiber and the bismuth oxybromide nano particles can enhance the photocatalytic activity, and the composite sponge has the capability of realizing the degradation of dye pollutants under a xenon lamp. Furthermore, the regenerated composite sponge still has excellent reusability and high-efficiency performance of separating emulsion and adsorbing dye. In view of the low material cost and excellent performance, the environment-friendly composite sponge has great prospect and competitiveness in the aspect of wastewater treatment.

Drawings

FIG. 1a is a digital photograph of an underwater superoleophobic (chloroform) wood fiber sponge of example 5

FIG. 1b is a graph showing the change in the underwater contact angle of the wood fiber sponge of example 5

FIG. 1c is a schematic view of the oil-water separation process of the wood fiber sponge in example 5

FIG. 2a is a photograph of a purification of a water-in-kerosene emulsion for RhB coloring (5ppm) using the wood fiber sponge of example 5

FIG. 2b is a photograph of a kerosene water-in-oil emulsion observed under a microscope

FIG. 2c is a photograph of the separated filtrate observed under a microscope

FIG. 2d is a graph showing the particle size distribution of the filtrate before emulsion separation using the wood fiber sponge of example 5

FIG. 2e is a graph showing the particle size distribution of the filtrate after emulsion separation using the wood fiber sponge of example 5

FIG. 3a is a photograph of the UV-VIS spectrum of RhB in water before and after separation and the corresponding filtrate

FIG. 3b is FTIR before and after adsorption of dye (RhB) by wood fiber sponge in example 5

FIG. 3c is a photograph of RhB after degradation, i, ii, iii respectively show the degradation time of xenon lamp is 5min, the sunlight is 15min, the fluorescent lamp is 180min, and the infrared spectrum;

FIG. 3d is a graph of water flux and separation efficiency of a water-in-kerosene emulsion after each cycle;

FIG. 3e is a graph of the removal efficiency of organic dye versus cycle number

FIG. 3f is a UV-Vis spectrum of a wood fiber sponge separation mixed emulsion of example 5.

Detailed Description

The present invention will be described in further detail with reference to the following examples, which are not intended to limit the invention thereto.

Example 1:

(1) cleaning a certain volume of wood with deionized water, and ultrasonically treating the wood to remove impurities for later use; dissolving sodium sulfite and sodium hydroxide in a mass ratio of 1:1 in 50ml of deionized water, placing the cleaned wood in a water bath for heating at 60 ℃ for 1h to remove most of lignin, taking out the wood, and cleaning surface residues with deionized water;

(2) adding the cleaned wood, hydrogen peroxide and sodium chlorite with the mass ratio of 1:2 into 200ml of deionized water, dropwise adding acetic acid to adjust the pH value of the solution to be 4, heating in a water bath for 60 ℃, heating for 2h, magnetically stirring for 1000rpm, washing with the deionized water to be neutral, filtering, and finally freeze-drying for 48 h.

(3) Adding the obtained wood-derived fibers into deionized water, adding bismuth nitrate pentahydrate and deionized water in a mass ratio of 1:100, and then stirring the mixed solution in a shading magnetic manner for 0.5 h.

(4) A white suspension was obtained, and then potassium bromide and deionized water solution in a mass ratio of 1:50 were slowly added dropwise to the white suspension, stirring at room temperature. The pale yellow suspensions were observed to mix and the resulting precipitate was washed repeatedly with deionized water, after which the washed sample was placed in a refrigerator for pre-cooling for 24h and finally vacuum freeze-dried for 36 h.

Example 2:

(1) cleaning a certain volume of wood with deionized water, and ultrasonically treating the wood to remove impurities for later use; dissolving sodium sulfite and sodium hydroxide in a mass ratio of 1:2 in 100ml of deionized water, placing the cleaned wood in a water bath for heating at 70 ℃ for 2 hours to remove most of lignin, taking out the wood, and cleaning surface residues with the deionized water;

(2) adding the cleaned wood, hydrogen peroxide and sodium chlorite with the mass ratio of 1:2 into 200ml of deionized water, dropwise adding acetic acid to adjust the pH value of the solution to be 4, heating in a water bath at 70 ℃, heating for 4h, magnetically stirring at 1500rpm, washing with the deionized water to be neutral, filtering, and finally freeze-drying for 48 h.

(3) Adding the obtained wood-derived fibers into deionized water, adding bismuth nitrate pentahydrate and deionized water in a mass ratio of 1:75, and then stirring the mixed solution in a shading magnetic manner for 0.5 h.

(4) A white suspension was obtained, and then potassium bromide and deionized water solution in a mass ratio of 1:25 were slowly added dropwise to the white suspension, stirring at room temperature. The pale yellow suspensions were observed to mix and the resulting precipitate was washed repeatedly with deionized water, after which the washed sample was placed in a refrigerator for pre-cooling for 24h and finally vacuum freeze-dried for 36 h.

Example 3:

(1) cleaning a certain volume of wood with deionized water, and ultrasonically treating the wood to remove impurities for later use; dissolving sodium sulfite and sodium hydroxide in a mass ratio of 1:3 in 150ml of deionized water, placing the cleaned wood in a water bath for heating at 80 ℃ for 3 hours to remove most of lignin, taking out the wood, and cleaning surface residues with deionized water;

(2) adding the cleaned wood, hydrogen peroxide and sodium chlorite with the mass ratio of 1:3 into 300ml of deionized water, dropwise adding acetic acid to adjust the pH value of the solution to be 4, heating in a water bath at 80 ℃, heating for 5h, magnetically stirring at 2000rpm, washing with the deionized water to be neutral, filtering, and finally freeze-drying for 48 h.

(3) Adding the obtained wood-derived fibers into deionized water, adding bismuth nitrate pentahydrate and deionized water in a mass ratio of 1:25, and then stirring the mixed solution in a shading magnetic manner for 0.5 h.

(4) A white suspension was obtained, and then potassium bromide and deionized water solution in a mass ratio of 1:1 were slowly added dropwise and dispersed in the white suspension, and stirred at room temperature. The pale yellow suspensions were observed to mix and the resulting precipitate was washed repeatedly with deionized water, after which the washed sample was placed in a refrigerator for pre-cooling for 24h and finally vacuum freeze-dried for 36 h.

Example 4:

(1) cleaning a certain volume of wood with deionized water, and ultrasonically treating the wood to remove impurities for later use; dissolving sodium sulfite and sodium hydroxide in a mass ratio of 1:4 in 200ml of deionized water, placing the cleaned wood in a water bath for heating at 90 ℃ for 4 hours to remove most of lignin, taking out the wood, and cleaning surface residues with deionized water;

(2) adding the cleaned wood, hydrogen peroxide and sodium chlorite with the mass ratio of 1:1 into 400ml of deionized water, dropwise adding acetic acid to adjust the pH value of the solution to be 4, heating in a water bath for 90 ℃, heating for 6h, magnetically stirring at 3000rpm, washing with the deionized water to be neutral, filtering, and finally freeze-drying for 48 h.

(3) Adding the obtained wood-derived fibers into deionized water, adding bismuth nitrate pentahydrate and deionized water in a mass ratio of 1:1, and then stirring the mixed solution in a shading magnetic manner for 0.5 h.

Example 5:

(1) cleaning a certain volume of wood with deionized water, wherein the wood is balsawood, white wood or pinus sylvestris, and ultrasonically treating the wood to remove impurities for later use; dissolving sodium sulfite and sodium hydroxide in a mass ratio of 1:2 in 100ml of deionized water, placing the cleaned wood in a water bath for heating at 90 ℃ for 4 hours to remove most of lignin, taking out the wood, and cleaning surface residues with the deionized water;

(2) adding the cleaned wood, hydrogen peroxide and sodium chlorite with the mass ratio of 1:4 into 100ml of deionized water, dropwise adding acetic acid to adjust the pH value of the solution to be 4, heating in a water bath for 90 ℃, heating for 6h, magnetically stirring at 3000rpm, washing with the deionized water to be neutral, filtering, and finally freeze-drying for 48 h.

(3) Adding the obtained wood-derived fibers into deionized water, adding bismuth nitrate pentahydrate and deionized water in a mass ratio of 1:50, and then stirring the mixed solution in a shading magnetic manner for 0.5 h.

(4) A white suspension was obtained, followed by slowly dropwise addition of potassium bromide and its ionic aqueous solution in a mass ratio of 1:25 to the white suspension, stirring at room temperature. The pale yellow suspensions were observed to mix and the resulting precipitate was washed repeatedly with deionized water, after which the washed sample was placed in a refrigerator for pre-cooling for 24h and finally vacuum freeze-dried for 36 h.

FIGS. 1 a-1 c are schematic drawings of the underwater superoleophobic property of the wood fiber sponge of example 5. Wherein FIG. 1a is a digital photograph of an underwater superoleophobic (chloroform) composite sponge with hydrophilic groups imparting a particular wettability capability to the composite sponge; FIG. 1b is a change in contact angle ranging from 151.8 to 161.2, which illustrates the underwater superoleophobic property of the composite sponge; FIG. 1c shows the oil-water separation process using a composite sponge, in which a water film is formed to have super-hydrophilicity, thereby effectively reducing the contact area.

Fig. 2 a-2 e show the emulsion separation performance and photocatalytic performance of the wood fiber sponge of example 5. Wherein figure 2a is a photograph of a purification of a water-in-kerosene emulsion colored with RhB (5ppm), both contaminants were successfully removed under the action of gravity. Fig. 2b shows that the micro-scale droplets are closely packed in the initial water-in-kerosene emulsion as observed under a microscope, while fig. 2c shows that no oil droplets are found in the filtrate. FIG. 2d shows the results of separating a kerosene-in-water emulsion having a particle size range of 190-3000nm, which is significantly distributed at about 850nm, and FIG. 2e shows the particle size distribution of the filtrate at 23-66nm, based on which the oil droplets in the kerosene-in-water emulsion were successfully removed using a composite sponge.

FIGS. 3a to 3f are UV spectrums and the like of the wood fiber sponge of example 5. Wherein fig. 3a is the uv-vis spectrum of RhB in water and the corresponding filtrate, a characteristic peak at a wavelength of 550nm was observed confirming the presence of RhB in the initial emulsion, which peak disappears sharply in the permeate after the first filtration, since the composite sponge can selectively adsorb dye contaminants; FIG. 3b is FTIR before and after adsorption of the dye (RhB) to the complex sponge, the difference in these spectra depicting the presence of electrostatic interactions and hydrogen bonding between the complex sponge and the dye molecules; FIG. 3c is a photograph of the RhB after degradation, wherein i, ii, and iii respectively show that the degradation time of xenon lamp is 5min, the sunlight is 15min, and the fluorescent lamp is 180 min. After photodegradation, these peaks disappeared under irradiation, while the other peaks diminished, indicating that almost all contaminants were degraded; FIG. 3d shows the water flux and the oil discard amount of the kerosene water emulsion after each cycle, after 5 times of permeation treatment, the one-time waste oil rate of the filtrate is 99.91%, and the waste oil rate is still stable and reaches more than 98.23%; FIG. 3e is a graph showing the relationship between the removal efficiency of organic dye and the number of cycles, wherein the removal rate of RhB in the filtrate is maintained at 99.90% or more in the whole cycle; FIG. 3f is a UV-Vis spectrum, which can confirm that the composite sponge can absorb other organic pollutants.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims

1. The preparation method of the wood fiber-based composite sponge is characterized by comprising the following steps of:

2. The method for preparing a wood fiber-based composite sponge according to claim 1, wherein: the wood in the step (1) is balsawood, white wood or pinus sylvestris.

3. The method for preparing a wood fiber-based composite sponge according to claim 1, wherein: the heating and boiling temperature in the step (1) is 60-90 ℃, and the heating time is 1-4 h.

4. The method for preparing a wood fiber-based composite sponge according to claim 1, wherein: the temperature of the water bath heating in the step (2) is 60-90 ℃, the heating time is 2-6 h, and the magnetic stirring speed is 1000-3000 rpm.

5. The method for preparing a wood fiber-based composite sponge according to claim 1, wherein: the freeze drying time in the step (2) is 48 h.

6. The method for preparing a wood fiber-based composite sponge according to claim 1, wherein: and (4) the magnetic stirring time in the step (3) is 0.5 h.

7. The method for preparing a wood fiber-based composite sponge according to claim 1, wherein: the stirring time in the step (4) is 12h, and the stirring speed is 1000-3000 rpm.

8. The method for preparing a wood fiber-based composite sponge according to claim 1, wherein: the precooling time in the step (4) is 24 hours, and the freeze-drying time is 36 hours.

9. A wood fiber-based composite sponge prepared according to the method of any one of claims 1 to 8.