CN104874298A - Method for preparing nanometer ZnS/cellulose complex film with photocatalytic activity - Google Patents

Abstract

The invention discloses a method for preparing a nano-ZnS/cellulose composite membrane with photocatalytic activity. Firstly, a pure cotton pulp cellulose membrane is prepared by using an NMMO process, and then a nano-ZnS/cellulose composite membrane is prepared by a liquid impregnation method. Abundant, safe, non-toxic and low-cost renewable resources are used as raw materials to prepare cellulose-based composite materials; the process is simple, the preparation process is green and pollution-free, and the obtained nano-ZnS/cellulose composite film has good UV absorption Photocatalytic degradation of water pollutants; while retaining the characteristics of pure cellulose film, such as good chemical resistance and thermal stability; also has good photoelectric and photocatalytic properties, widely used in optoelectronic devices, luminescent materials, sewage treatment materials and biomedical materials.

Description

A method for preparing nano-ZnS/cellulose composite film with photocatalytic activity

technical field

The invention relates to the combination of inorganic nano-semiconductor ZnS particles and natural organic polymer cellulose film to prepare a nano-ZnS/cellulose composite film with photocatalytic function, which can effectively photocatalyze and degrade organic dyes in sewage, and can be widely used in chemical industry, Biomedical and environmental protection and other fields.

Background technique

Inorganic nano-ZnS particles are an important metal chalcogenide semiconductor material, which has unique properties such as quantum size effect, volume effect, surface effect and quantum tunneling effect. Excellent performance, has broad application prospects.

Inorganic nano-ZnS is safe and non-toxic, has a wide bandgap between 3.6 and 3.8eV, strong absorption and excellent photoelectric catalytic performance, and is widely used as a luminescent material, nonlinear optical material and photocatalytic material. However, due to the small particle size and large surface energy of nano-ZnS, it is easy to cause agglomeration; in addition, due to its poor water solubility, it is difficult to disperse uniformly in aqueous solution; at the same time, there are still great problems in the separation and recycling of nano-particle photocatalyst materials. . Therefore, the practical application of ZnS nano-semiconductor materials in the field of photocatalysis is greatly limited. In order to solve the above problems, it is necessary to prepare an efficient, economical and environmentally friendly photocatalytic material. For example, Zhang Guanghui et al. used eggshell membrane (ESM) as the matrix material of ZnS, and successfully prepared ZnS/eggshell membrane composite materials with photocatalytic activity by liquid impregnation method. As we all know, cellulose is one of the most abundant renewable resources in nature. It has the advantages of safety, non-toxicity, low cost, good film-forming property, good chemical stability and thermal stability, etc. It is widely used in packaging, chemical industry, water treatment and It is an ideal green environmental protection material for biomedicine and other aspects, and can be used as an effective organic polymer base material.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, including aspects such as cost reduction, limited technical support and environmental protection requirements, and provide a nano-ZnS/cellulose composite membrane material with photocatalytic activity and a preparation method thereof. The technological process of the present invention is simple, environmental protection and pollution-free, easy to operate, low in price, does not need to use expensive instruments and complicated operation steps, and is easy to popularize; at the same time, the prepared nano-ZnS/cellulose composite membrane material has good ultraviolet photocatalytic degradation The nature of organic pollutants.

The invention combines inorganic nano ZnS particles and natural plant cellulose regenerated membrane for the first time, and prepares a ZnS/cellulose composite membrane material with photocatalytic activity. Selecting the organic polymer cellulose membrane as the carrier material for inorganic nanomaterials is beneficial to improve the poor stability and easy aggregation of inorganic nano ZnS particles, improve the catalytic activity of the catalyst, and facilitate the separation and recovery of the catalyst.

To achieve the above object, the present invention adopts the following technical solutions:

A method for preparing a nano-ZnS/cellulose composite film with photocatalytic activity, characterized in that the nano-ZnS/cellulose composite film is prepared by using the NMMO process to prepare a pure cellulose film, and then using a liquid immersion method to synthesize ZnS particles in situ materials, including the following steps:

Step (1): Preparation of pure cellulose membrane

The cellulose in the cellulose film is one or a mixture of wood pulp cellulose, cotton pulp cellulose or straw pulp cellulose, and the pulverized raw material cellulose is added to the concentrated water content of about 13.3%. The NMMO solvent and the antioxidant whose quality is 0.5-1.5% of the cellulose mass are prepared into a cellulose casting liquid, and the fiber content of the obtained cotton pulp is 5-11% of the mass of the casting liquid; stir evenly, and swell 0.5-3.0 After 1 hour, put it in a vacuum drying oven at 100-120°C to dissolve completely. When the solution is amber, uniform and transparent, degas it in vacuum at 60-80°C for 2-5 hours, and scrape the film; then, pass through a coagulation bath and Water bath treatment to obtain a wet pure cellulose film, wherein the coagulation bath and water bath are carried out in deionized water at 20-40°C;

Step (2): Preparation of nano ZnS/cellulose composite membrane material

Cut the wet film obtained in step (1) into a film of a certain size, soak it in the Zn precursor solution, react for 3 to 6 hours, take it out and rinse it with deionized water; then immerse it in the S-containing precursor solution, react After 3 to 6 hours, take it out and rinse it with deionized water; the above process is a cycle. After the impregnation is completed, the sample is placed at room temperature to dry naturally, and a nano-ZnS/cellulose composite membrane material with photocatalytic activity is obtained once impregnated.

The raw material cellulose in the step (1) is agricultural waste or plant cellulose.

The agricultural wastes described in the step (1) are reeds, straws, wheat straws, straw, bagasse, rice husks, and peanut husks.

The purification process of the solvent NMMO in the described step (1) is as follows: take a certain amount of commercially available NMMO with a water content of 50-60% and put it into a rotary evaporator, and the vacuum degree is -0.08--0.1MPa, the temperature Under the condition of 90-95°C, a certain amount of water was evaporated by rotary evaporation until the water content of NMMO was 13.3%, and NMMO·H2O solvent for dissolving cellulose was obtained.

In the described step (1), the antioxidant is ascorbic acid or gallic acid.

The Zn precursor solution used in the step (2) is a water-soluble zinc source, and the S precursor solution is a water-soluble sulfur source.

The water-soluble zinc source is one of zinc sulfate solution, zinc chloride solution, and zinc acetate solution; the water-soluble sulfur source is one of sodium sulfide solution, sodium thiosulfate solution, and thioacetamide solution. kind.

The molar concentration ratio of the Zn precursor solution to the S precursor solution is 1:1.

The antioxidant used in the present invention is the most commonly used antioxidant - ascorbic acid, also known as vitamin C.

The method prepared by the invention is a nanometer ZnS/cellulose composite film material with photocatalytic activity.

The photocatalytically active nano ZnS/cellulose composite membrane material prepared by the above method can be used to degrade organic dyes in wastewater under the irradiation of ultraviolet light.

Compared with prior art, the present invention has following advantage:

1. The raw material used is renewable natural high-molecular cellulose. This polyhydroxy high-molecular polymer has good physical and chemical modification activity, and the cellulose has a wide range of sources and low price;

2. The preparation process of cellulose film adopts a new green production process - NMMO process. The solvent of this process is NMMO. The solvent is non-toxic, non-polluting and recyclable; Low, it is a green production process of pure physical process;

3. Nano-ZnS particles are synthesized in situ on the cellulose film, the reaction is carried out at room temperature, the conditions are mild, and the operation is convenient;

4. Nano-ZnS/cellulose composite membrane material with photocatalytic activity is easy to separate and recycle when used as a photocatalyst;

5. The nano-ZnS/cellulose composite membrane material with photocatalytic activity in the present invention has a simple preparation process, easy operation, simple equipment, low cost and easy popularization.

Description of drawings

Fig. 1 is a diagram of the absorption change of the ultraviolet photocatalytic degradation methyl orange of the nano-ZnS/cellulose composite film dipped 4 times in the present invention as a function of the contact time.

Fig. 2 is a diagram of the degradation rate of the nano-ZnS/cellulose composite film obtained by the present invention for the ultraviolet photocatalytic degradation of methyl orange.

In the figure: a~h represent different sampling times in the photocatalytic experiment, namely: 0min, 20min, 40min, 60min, 80min, 100min, 120min, 150min; C1 represents the membrane sample impregnated once; C2 represents the impregnated twice C3 represents the membrane sample dipped 3 times; C4 represents the membrane sample dipped 4 times.

Detailed ways

In the present invention, the NMMO solvent is nitrogen methylmorpholine oxide solvent.

Example 1:

1. Preparation of Cellulose Membrane

One of the 2g cotton pulp cellulose, wood pulp cellulose or straw pulp cellulose after pulverization is added to the NMMO solvent and 0.02g ascorbic acid (mass approx. 1% of the element weight) in a beaker, prepare a casting solution with a cellulose content of about 6%, and stir evenly; after swelling for 2 hours, put it in a vacuum drying oven at 110°C to dissolve completely, and wait until the solution is amber and uniform When the solution is transparent, place it at 80°C for vacuum defoaming for 4 hours, and scrape the film; then, treat it with a coagulation bath (about 25°C deionized water) and a water bath (about 25°C deionized water) to obtain wet pure cotton pulp fibers plain film.

2. Preparation of nano-ZnS/cellulose composite membrane material with photocatalytic activity

Cut the above wet film into a film with a size of 10cm×15cm, soak it in 0.1M zinc sulfate precursor solution, react for 5h, take it out and rinse it with deionized water; then immerse it in 0.1M sodium sulfide precursor solution After reacting for 5 hours, it was taken out and rinsed with deionized water. The above process is a cycle. After the impregnation is completed, the sample is placed at room temperature and dried naturally to obtain a photocatalytically active nano-ZnS/cellulose composite membrane material impregnated once.

Example 2:

1. Preparation of Cellulose Membrane

The preparation of the cellulose film was the same as in Example 1.

2. Preparation of nano-ZnS/cellulose composite membrane material with photocatalytic activity

Cut the above wet film into a film with a size of 10cm×15cm, soak it in 0.1M zinc sulfate precursor solution, react for 5h, take it out and rinse it with deionized water; then put it into 0.1M sodium sulfide After reacting for 5 hours in the precursor solution, take it out and rinse it with deionized water. The above process is a cycle, and then the second cycle of impregnation experiment is carried out. After the impregnation is completed, the sample film is naturally dried at room temperature to obtain a nano-ZnS/cellulose composite membrane material with photocatalytic activity that is impregnated twice.

Example 3:

1. Preparation of Cellulose Membrane

The preparation method of the cellulose film is the same as that of Example 1.

2. Preparation of nano-ZnS/cellulose composite membrane material with photocatalytic activity

Cut the above wet film into a film with a size of 10cm×15cm, soak it in 0.1M zinc sulfate precursor solution, react for 5h, take it out and rinse it with deionized water; then put it into 0.1M sodium sulfide After reacting for 5 hours in the precursor solution, take it out and rinse it with deionized water. The above process is a cycle, and then repeat the impregnation experiment twice. After the impregnation is completed, the sample film is naturally dried at room temperature to obtain a nano-ZnS/cellulose composite membrane material with photocatalytic activity that has been impregnated three times.

Example 4:

1. Preparation of Cellulose Membrane

The preparation of the cellulose film was the same as in Example 1.

2. Preparation of nano-ZnS/cellulose composite membrane material with photocatalytic activity

Cut the above wet film into a film with a size of 10cm×15cm, soak it in 0.1M zinc sulfate precursor solution, react for 5h, take it out and rinse it with deionized water; then put it into 0.1M sodium sulfide After reacting for 5 hours in the precursor solution, take it out and rinse it with deionized water. The above process is a cyclical period, and then repeat the impregnation experiment 3 times. After the impregnation is completed, the sample film is dried naturally at room temperature to obtain a nano-ZnS/cellulose composite membrane material with photocatalytic activity impregnated 4 times.

3. The detection of the photocatalytic property of nano-ZnS/cellulose composite film material: the present invention takes methyl orange (MO) as organic pollutant, takes nano-ZnS/cellulose composite film material as photocatalyst, carries out under the irradiation of ultraviolet light Photocatalytic experiment to characterize the photocatalytic activity of the sample film. The specific experimental process is as follows: Weigh the same amount of 2g of nano-ZnS/cellulose composite membrane materials prepared in the above-mentioned 4 embodiments and 1 pure cellulose membrane with a balance, and measure 40ml in parallel with a 50ml graduated cylinder. ㎎/L MO solution 5 parts, add both into the quartz test tube; then put the magneton, put the test tubes into the BL-GHX-V photochemical reaction apparatus, stir and place in the dark room for 20min, wait for adsorption After equilibration, turn on the 300W mercury lamp to irradiate, react for 150min, take a sample every 20min, label the samples taken as 1-7, and mark the original MO solution as sample 0. After each degraded sample is centrifuged, take the supernatant and measure the absorbance value of the solution at λ=464nm with a UV-visible spectrophotometer, so as to obtain the concentration of the MO solution before and after the photocatalytic reaction, and calculate the degradation rate, the formula as follows:

Degradation rate D=(A ₀ -A)/A ₀ ×100%=(C ₀ -C)/C ₀ ×100%

In the formula: D represents the degradation rate of catalyst membrane sample degradation MO;

A ₀ -absorbance of the initial methyl orange MO solution at the same wavelength λ=464nm;

The absorbance of the MO solution in the solution at λ=464nm after a period of time after the A-reaction;

C ₀ -the concentration of the MO solution under the same wavelength λ=464nm of the initial methyl orange MO solution;

The concentration of the MO solution at λ=464nm of the MO solution in the solution after C-reaction for a period of time.

As can be seen from accompanying drawing 1: take the nanometer ZnS/cellulose composite membrane that impregnates repeatedly 4 times as photocatalyst, under the irradiation of 300W mercury lamp, the concentration of the organic dye methyl orange (MO) in the solution increases with the increase of illumination time After 150min of light irradiation, the concentration of methyl orange in the solution is very low, indicating that the photocatalyst prepared by the present invention has a better photocatalytic effect on methyl orange.

As can be seen from accompanying drawing 2: when using pure cellulose film as photocatalyst, the concentration change of the methyl orange in the solution is little, promptly degradation effect is bad, less than 10%, this shows that pure cellulose film does not have photocatalytic performance , and the reason for the change in the concentration of methyl orange in the solution at this time is caused by the microscopic physical adsorption of the pure cellulose membrane; as the number of repeated dipping of the membrane increases from 1 to 4, the nano-ZnS/cellulose composite membrane The degradation rate of methyl orange in the solution increased from 60% to 90%, which shows that the nano-ZnS/cellulose composite film has photocatalytic properties, and with the increase of the number of repeated immersion, the ZnS nanoparticles loaded on the cellulose film The amount of particles increases, so the effect of photocatalytic degradation of organic dyes of the nano-ZnS/cellulose composite film increases.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the embodiment, and any other changes, modifications, substitutions and combinations made without departing from the spirit and principle of the present invention , simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present invention.

Claims (8)

1. A method for preparing a nano ZnS/cellulose composite film with photocatalytic activity, characterized in that by adopting NMMO process to prepare pure cellulose film, then adopting liquid immersion method to synthesize ZnS particles in situ to prepare nano ZnS/cellulose Composite membrane material, comprises the following steps: Step (1): Preparation of pure cellulose membrane The cellulose in the cellulose film is one or a mixture of wood pulp cellulose, cotton pulp cellulose or straw pulp cellulose, and the pulverized raw material cellulose is added to the concentrated water content of about 13.3%. The NMMO solvent and the antioxidant whose quality is 0.5-1.5% of the cellulose mass are prepared into a cellulose casting liquid, and the fiber content of the obtained cotton pulp is 5-11% of the mass of the casting liquid; stir evenly, and swell 0.5-3.0 After 1 hour, put it in a vacuum drying oven at 100-120°C to dissolve completely. When the solution is amber, uniform and transparent, degas it in vacuum at 60-80°C for 2-5 hours, and scrape the film; then, pass through a coagulation bath and Water bath treatment to obtain a wet pure cellulose film, wherein the coagulation bath and water bath are carried out in deionized water at 20-40°C; Step (2): Preparation of nano ZnS/cellulose composite membrane material Cut the wet film obtained in step (1) into a film of a certain size, soak it in the Zn precursor solution, react for 3 to 6 hours, take it out and rinse it with deionized water; then immerse it in the S-containing precursor solution, react After 3 to 6 hours, take it out and rinse it with deionized water; the above process is a cycle. After the impregnation is completed, the sample is placed at room temperature to dry naturally, and a nano-ZnS/cellulose composite membrane material with photocatalytic activity is obtained once impregnated. 2. The method for preparing a nano-ZnS/cellulose composite film with photocatalytic activity according to claim 1, characterized in that: the raw material cellulose in step (1) is agricultural waste or plant cellulose. 3. the method for preparing the nano ZnS/cellulose composite film with photocatalytic activity according to claim 2, is characterized in that: the agricultural waste described in step (1) is reed, straw, wheat straw, rice straw, Bagasse, rice husk, peanut husk. 4. the preparation according to claim 1 has the method for the nanometer ZnS/cellulose composite membrane of photocatalytic activity, it is characterized in that: the purification treatment process of solvent NMMO is as follows in the step (1): get a certain amount of commercially available water content Put 50-60% NMMO into a rotary evaporator, and under the conditions of vacuum degree of -0.08-0.1MPa and temperature of 90-95°C, a certain amount of water is evaporated until the water content of NMMO is 13.3%. So far, NMMO·H2O solvent for dissolving cellulose is obtained. 5. The method for preparing a nano-ZnS/cellulose composite film with photocatalytic activity according to claim 1, characterized in that: in the step (1), the antioxidant is ascorbic acid or gallic acid. 6. the method for preparing the nanometer ZnS/cellulose composite film with photocatalytic activity according to claim 1, is characterized in that: the Zn precursor solution that step (2) uses is water-soluble zinc source, and S precursor solution It is a water-soluble sulfur source. 7. the method for preparing the nanometer ZnS/cellulose composite film with photocatalytic activity according to claim 6 is characterized in that: the water-soluble zinc source is one of zinc sulfate solution, zinc chloride solution, zinc acetate solution species; the water-soluble sulfur source is one of sodium sulfide solution, sodium thiosulfate solution, and thioacetamide solution. 8. The method for preparing a photocatalytically active nano-ZnS/cellulose composite film according to claim 5, wherein the ratio of the molar concentration of the Zn precursor solution to the S precursor solution is 1:1.