CN104324720A - Water purification film and preparation method thereof - Google Patents

Abstract

The invention discloses a water purification film, which is composed of a silicate glass fiber non-woven film and photocatalytic nano crystals attached to the surface of the silicate glass fiber; the diameter of the silicate glass fiber is in the nanoscale; the The photocatalytic nano crystals are at least one of Bi ₂ WO ₆ nano crystals, TiO ₂ nano crystals, ZnO nano crystals, CaWO ₃ nano crystals, SnO ₂ , and BiOI nano crystals. The invention also discloses a preparation method of the water purification film. The water purification film of the invention not only has good flexibility, huge specific surface area and extremely high chemical and thermal stability, but also has the function of visible light catalytic degradation of organic pollutants.

Description

Water purification film and preparation method thereof

technical field

The invention relates to the field of water purification films, in particular to a water purification film material with the function of catalytically degrading organic pollutants with visible light and reusable performance.

Background technique

Environmental pollution is a major crisis facing the world today, especially in developing countries. Environmental pollution mainly includes air pollution, soil pollution and water pollution. Water is the source of life and the most important raw material for human production and life. Water pollution control is a common and severe challenge facing mankind today. China is one of the countries with the most serious water pollution in the world. According to the data in 2005, 59% of the river sections of the seven major water systems in the country are not suitable for drinking water sources, 72% of the lakes and reservoirs are not suitable for drinking water sources, 43% of the lakes and reservoirs have even lost their function, and 25% of the country 35% of groundwater sources are unqualified, about 54% of groundwater in plain areas does not meet domestic water quality standards, and groundwater in more than half of urban areas is seriously polluted. China's Ministry of Environmental Protection, together with relevant departments, is preparing the "Water Pollution Prevention and Control Action Plan". In the future, China will invest huge sums of money in water pollution control.

Electrospinning is recognized as the only technology that can achieve industrial batch preparation of ultra-long continuous nanofiber materials. Electrospinning can prepare many kinds of fibers, and can flexibly control the morphology and structure of fibers, and it is easy to realize the assembly and arrangement of fibers in the process of fiber collection. The film formed by stacking fibers in the electrospun fiber collection process has a huge specific surface area and a three-dimensional interconnected porous structure, and the pore size of the porous structure can also be flexibly adjusted by changing the spinning process. Such nanofibrous nonwoven membranes have important applications in water purification. Many research institutes in the world have conducted a lot of research on the development of electrospun membranes for water purification, and applied for a series of patents with potential application value. At present, research and patents on electrospun fiber membranes for water purification mainly focus on organic polymer materials. This type of material has good flexibility, is convenient for design and processing, and has a wide variety, so there is a large selection of water purification membranes designed with specific functions. However, organic polymer materials have poor chemical and thermal stability, and it is difficult to restore their water purification function through simple methods such as incineration after being contaminated (especially organic contamination).

On the other hand, using semiconductor photocatalysis to degrade pollutants to achieve water purification is an important research direction in the field of water purification in the future. In particular, using a photocatalyst that can respond well to light (the main part of sunlight) for water purification treatment can effectively reduce water treatment energy consumption, and is not easy to cause other pollution. Combining photocatalytic materials with electrospun fiber water purification filter membrane will endow the filter membrane with the function of photocatalytic degradation of organic matter. However, the large difference in inorganic-organic chemical properties between photocatalysts and organic electrospun fiber materials makes it difficult to attach photocatalysts to the surface of organic electrospun fibers.

Contents of the invention

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a water purification film, which not only has good flexibility, huge specific surface area and high chemical and thermal stability, but also has the ability to catalytically degrade organic compounds under visible light. function of pollutants.

Another object of the present invention is to provide a method for preparing the above-mentioned water purification membrane.

The object of the present invention is achieved through the following technical solutions:

A water purification film is composed of a silicate glass fiber non-woven film and photocatalytic nanocrystals attached to the surface of the silicate glass fiber;

The diameter of the silicate glass fiber is in the nanoscale;

The photocatalytic nanocrystals are more than one of Bi ₂ WO ₆ nanocrystals, TiO ₂ nanocrystals, ZnO nanocrystals, CaWO ₃ nanocrystals, SnO ₂ , and BiOI nanocrystals.

The composition of the silicate glass fiber includes more than one of SiO ₂ , Al ₂ O ₃ , ZrO ₂ , CaO, and P ₂ O ₅ .

A method for preparing a water purification film, comprising the following steps:

(1) Synthesis of silicate glass precursor spinning sol by sol-gel technology;

(2) using the sol synthesized in step (1) as a spinning solution, preparing a silicate glass nanofiber non-woven membrane by electrospinning technology;

(3) growing photocatalytic nanocrystals on the surface of the silicate glass nanofiber nonwoven membrane obtained in step (2) by hydrothermal method, said photocatalytic nanocrystals being Bi ₂ WO ₆ nanocrystals, TiO ₂ nanocrystals, ZnO One or more of nanocrystals, CaWO ₃ nanocrystals, SnO ₂ , and BiOI nanocrystals.

In step (1), the silicate glass precursor spinning sol synthesized by sol-gel technology is specifically:

Mix TEOS, EtOH, water and HCl solution with a concentration of 30wt% at a volume ratio of 10:(10-50):(1-3):(0.03-0.2), and then heat, hydrolyze and age to obtain a spinnable Precursor spinning sol.

In the step (2), the sol synthesized in the step (1) is used as the spinning liquid, and the silicate glass nanofiber non-woven membrane is prepared by electrospinning technology, specifically:

Put the precursor spinning sol obtained in step (1) into the liquid supply device, connect a high-voltage DC power supply, prepare continuous silicate glass nanofibers by electrospinning, and use a high-speed rotating electric control motor to drive a stainless steel roller to collect silicate nanofibers. After spinning, the fiber non-woven film is peeled off from the stainless steel drum.

The preparation method of the Bi ₂ WO ₆ nanocrystals described in step (3) is as follows:

Dissolve Bi(NO ₃ ) ₃ ·5H ₂ O and Na ₂ WO ₄ ·2H ₂ O in distilled water at a molar ratio of 2:1, then add ethylene glycol to control the concentration of Bi ₂ WO ₆ precursor at 0.5-7.5 millimole/liter, then immerse the _SiO2 electrospun fiber film into the above solution, and transfer it to a high-pressure reactor with a polytetrafluoroethylene liner for hydrothermal reaction. The reaction temperature and time are 120-160 °C and 8-8 15 hours.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The water purification film of the present invention is composed of silicate glass fibers and photocatalytic nanocrystals loaded thereon. The silicate glass nanofibers are prepared by sol-gel and electrospinning techniques, and have good flexibility And extremely high chemical and thermal stability, its inorganic material characteristics make this fiber very easy to grow various photocatalytic nanomaterials on the surface of the fiber by a simple hydrothermal method. The silicate glass-photocatalyst composite fiber film of the invention can be used as water purification to realize continuous filtration treatment of water purification and decompose organic pollutants by visible light irradiation. Due to the pure inorganic material properties of the membrane, this filter membrane is also easy to restore the water purification function through subsequent treatment, such as simple incineration.

(2) Since the water purification filter membrane of the present invention is mainly formed by stacking silicate glass fibers with diameters in the nanometer scale, and is coated with nanocrystals such as photocatalyst Bi2WO6 on the fiber surface through subsequent treatment, the water purification disclosed by the present invention The filter membrane has the function of degrading organic pollutants with visible light. This kind of fiber film is made of pure inorganic material, which can withstand high temperature above 600°C without deformation and combustion. When contaminated by some organic pollutants, the water purification function of the film can be restored by simple incineration treatment, so it has good performance. reusable performance. Since the diameter of the fiber is in the nanometer scale, and the fiber matrix is dense, it has good flexibility and high mechanical strength, so it is very convenient to process in practical applications, and realizes continuous filtration and purification of sewage. This water purification filter membrane has good chemical stability, moisture resistance, and chemical corrosion resistance, and this filter membrane material also has good environmental performance, non-toxic and tasteless, and is not easy to produce secondary pollution. In addition, this fiber filter membrane is mainly prepared based on electrospinning technology, which can completely realize large-scale large-scale production. Therefore, the nanofiber filter membrane disclosed by the present invention is very suitable for industrial water purification applications, and has high economic and environmental values.

Description of drawings

Fig. 1 is a scanning electron micrograph of SiO ₂ glass nanofibers prepared by electrospinning in Example 1 of the present invention.

Fig. 2 is a scanning electron micrograph of the water purification filter membrane of Example 1 of the present invention.

Fig. 3 is a transmission electron micrograph of the water purification filter membrane of Example 1 of the present invention.

Fig. 4 is the tensile stress-strain curve of the SiO ₂ electrospun film, the water purification filter membrane prepared in Example 1 of the present invention and the water purification filter membrane after thermal shock experiment.

Fig. 5 is the decomposition kinetics curve of rhodamine B solution under simulated sunlight irradiation, _SiO2 thin film and the water purification membrane filtration of the embodiment 1 of the present invention.

Fig. 6 is the result of repeated purification of Rhodamine B solution by the water purification filter membrane of Example 1 of the present invention.

Fig. 7 shows the changes in the photocatalytic degradation effect of the water purification filter membrane of Example 1 of the present invention on rhodamine B solution before and after being polluted by green algae and after burning out the green algae.

Detailed ways

The present invention will be described in further detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto.

Example 1

In this embodiment, nanofibers prepared by electrospinning of _SiO2 sol are used as the main material of the filter membrane to further illustrate the present invention through examples, but this should not limit the scope of protection of this patent. All other inorganic glass precursors that can be used for spinning Sol and photocatalytic semiconductor materials such as TiO ₂ , ZnO, CaWO ₃ , SnO ₂ , BiOI and their mixtures that can grow on the surface of silicate electrospun fibers by hydrothermal method are all suitable for the water purification film disclosed in the present invention.

The preparation process of the water purification membrane of the present embodiment is as follows:

Step 1. With tetraethyl orthosilicate (TEOS), absolute ethanol (EtOH), water (H ₂ O), acid (including hydrochloric acid (HCl), nitric acid (HNO ₃ ), sulfuric acid (H ₂ SO ₄ ), acetic acid ) as raw material, SiO ₂ spinnable sol was synthesized by sol-gel technique. In this embodiment, the preparation of SiO ₂ sol is taken as an example. The acid used was hydrochloric acid (HCl) at a concentration of 30 wt%. TEOS, EtOH, water and HCl in a volume ratio of 10:10:1:0.03 (can also be 10:10:1.5:0.03 or 10:10:2:0.03 or 10:10:1:0.02 or 10:10: 1:0.04 or 10:10:1.5:0.02 or 10:10:1.5:0.03 or 10:10:1.5:0.04 or 10:10:2:0.02 or 10:10:2:0.04) mix well, and then heat Hydrolysis and aging yielded a spinnable _SiO2 precursor spinning sol. The typical temperature of heating hydrolysis is 70-90°C, and the typical time is 2-3 hours; the typical temperature of aging is 40°C, and the typical time is 5-8 hours.

Step 2. The sol synthesized in the above step 1 is used as a spinning solution, and _SiO2 glass nanofiber film is prepared by electrospinning technology. In the electrospinning process, a high-speed rotating electric drum is used to collect electrospun nanofibers, and the collected fibers are peeled off the drum to obtain a silicate glass nanofiber film with good flexibility. The process of electrospinning is as follows: the sol is loaded into the liquid supply device, connected to a high-voltage DC power supply, and ultra-long continuous _SiO2 glass nanofibers are prepared by electrospinning. The SiO ₂ glass nanofibers prepared in this example are shown in FIG. 1 by scanning electron microscope.

Step 3. Attachment of Bi ₂ WO ₆ nanocrystals. First, prepare the hydrothermal reaction precursor solution of the water purification film of the present invention: add sodium tungstate to ethylene glycol, fully stir until it is completely dissolved to obtain solution A, then slowly add bismuth nitrate in a stoichiometric ratio to obtain a uniform solution b. The silicate glass electrospun fiber film is placed in the solution B for hydrothermal reaction, and Bi ₂ WO ₆ nanocrystals are grown on the surface of the fiber to obtain a water purification filter membrane. Specifically, Bi(NO ₃ ) ₃ ·5H ₂ O and Na ₂ WO ₄ ·2H ₂ O were dissolved in distilled water at a molar ratio of 2:1 (the amount of distilled water used was based on the ability to completely immerse the glass fiber film), and then Add a certain amount of ethylene glycol. Control the concentration of Bi ₂ WO ₆ precursor at 0.5 mmol/L to regulate the growth density of Bi ₂ WO ₆ on the fiber surface. Then the _SiO2 electrospun fiber film was immersed in the above solution and transferred to a polytetrafluoroethylene-lined autoclave for hydrothermal reaction at 120 °C and 8 h, respectively. The reaction temperature and time can be changed to adjust the growth of Bi ₂ WO ₆ on the fiber surface. After the hydrothermal reaction is finished, the fiber membrane is taken out, rinsed with water to obtain the final water purification filter membrane. In this embodiment, the water purification filter membrane is called SBWO membrane, and its scanning electron microscope photo is shown in FIG. 2 , and its transmission electron microscope photo is shown in FIG. 3 .

The test result of this embodiment is as follows:

The SBWO film prepared in this embodiment has good flexibility. After testing, the tear strength of this fiber filter membrane is 5.29 N (film size is: length * width * thickness = 50mm * 10mm * 0.41mm), elastic modulus It is 164 N/m2. The tensile stress-strain curve of the above-mentioned water purification filter membrane is shown in the red curve in Fig. 2 . At the same time, the results of the high-temperature thermal shock test show that this film has good thermal shock resistance. After repeated five times of rapid cooling and rapid heating at 600°C (each time placed in a muffle furnace at 600°C for 10 minutes, take it out, and wait until it drops to room temperature) Repeat the previous step, repeating 5 times), the film can still maintain good flexibility, and its elastic modulus decreases slightly, becoming about 110 N/m 2 . Its stress-strain curve is shown in Fig. 4. As shown in the scanning electron microscope photo of the water purification filter membrane in Figure 2, the diameter range of the water purification filter membrane fiber of the present embodiment is 200-1000nm, and the average diameter and thickness of the _{Bi2WO 6} nanosheets are about 300nm and 40nm, three-dimensional The average pore size of the pore structure is about 2 microns, which can effectively filter suspended particles and microorganisms in water. The realization of photocatalytic degradation shows that this film can effectively remove organic dye molecules (rhodamine B) in water by filtering and adding light (simulating sunlight), as shown in Figure 5. And the film can be repeatedly subjected to photodegradation of Rhodamine B without significant photocatalytic activity decline, as shown in Figure 6. After being polluted by organic matter, its photocatalytic ability will decrease, and its photocatalytic function can be easily restored by heat treatment, as shown in Figure 7. This kind of water purification filter membrane raw material is common and cheap, and the manufacturing process is simple, efficient, safe, environmentally friendly, energy-saving, and it is easy to realize large-scale production. The main equipment (electrospinning machine) needed is also very simple, easy to operate, and the price is relatively low. There are already electrospinning machines for industrial production on the market. Therefore, this water purification filter membrane has the feasibility of industrialized mass production.

Example 2-25

The silicate electrospun nanofibers involved in the present invention have _SiO2 as the main component, and Al2O3, ZrO2 and other components can also be added to improve the mechanical and thermal properties of the fiber. Illustrate below through embodiment 2-25. The main feature of embodiment 2-25 is to adjust the molar ratio of each added raw material in the spinning sol, as shown in table 1:

The mass ratio of each raw material in the spinning sol of embodiment 2-25 of table 1

The specific operation steps of embodiment 2-25 are:

Step 1. Use tetraethyl orthosilicate (TEOS), aluminum nitrate pentahydrate (Al(NO ₃ ) ₃ 5H ₂ O), zirconium nitrate pentahydrate (Zr(NO ₃ ) ₂ 5H ₂ O), absolute ethanol (EtOH), water (H ₂ O), and hydrochloric acid (HCl), as raw materials, the spinnable sol was synthesized by sol-gel technology. The above raw materials were uniformly mixed according to the proportion listed in Table 1, and then a spinnable silicate precursor spinning sol was obtained by heating, hydrolysis and aging. Typical sol hydrolysis and aging temperature and time are the same as in Example 1.

Step 2. Using the sol synthesized in the above step 1 as a spinning solution, prepare a silicate glass nanofiber film by electrospinning technology. In the electrospinning process, a high-speed rotating electric drum is used to collect electrospun nanofibers, and the collected fibers are peeled off the drum to obtain a silicate glass nanofiber film with good flexibility. The process of electrospinning is as follows: the sol is loaded into the liquid supply device, connected to a high-voltage DC power supply, and ultra-long continuous silicate nanofibers are prepared by electrospinning.

Step 3. Attachment of Bi ₂ WO ₆ nanocrystals. First, prepare the hydrothermal reaction precursor solution of the water purification film of the present invention: add sodium tungstate to ethylene glycol, fully stir until it is completely dissolved to obtain solution A, then slowly add bismuth nitrate in a stoichiometric ratio to obtain a uniform solution b. The silicate glass electrospun fiber film is placed in the solution B for hydrothermal reaction, and Bi ₂ WO ₆ nanocrystals are grown on the surface of the fiber to obtain a water purification filter membrane. Specifically, Bi(NO ₃ ) ₃ ·5H ₂ O and Na ₂ WO ₄ ·2H ₂ O were dissolved in distilled water at a molar ratio of 2:1 (the amount of distilled water used was based on the ability to completely immerse the glass fiber film), and then Add a certain amount of ethylene glycol. The concentration of the Bi ₂ WO ₆ precursor was controlled at 7.5 mmol/L to regulate the growth density of Bi ₂ WO ₆ on the fiber surface. Then the _SiO2 electrospun fiber film was immersed in the above solution, transferred to a polytetrafluoroethylene-lined autoclave for hydrothermal reaction, and the reaction temperature and time were 160 °C and 15 h, respectively. The reaction temperature and time can be changed to adjust the growth of Bi ₂ WO ₆ on the fiber surface. After the hydrothermal reaction is finished, the fiber membrane is taken out and rinsed with water to obtain the final water purification filter membrane. In this implementation, the water purification filter membrane is called SBWO membrane.

According to the test results of Examples 2-25, the high-temperature mechanical properties of the fiber can be improved by adding Al ₂ O ₃ and ZrO ₂ , which is beneficial to improve the reusability of the water purification membrane. Other properties of the products prepared in Examples 2-25 are similar to those in Example 1, and will not be repeated here.

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, such as, photocatalytic nanocrystals can also be Bi ₂ WO ₆ nanocrystals, TiO ₂ nanocrystals, ZnO One or more of nanocrystals, CaWO ₃ nanocrystals, SnO ₂ , BiOI nanocrystals; the composition of the silicate glass fiber can also include SiO ₂ , Al ₂ O ₃ , ZrO ₂ , CaO, P ₂ O ₅ More than one; any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included within the protection scope of the present invention.

Claims (6)

1. a Water warfare film, is characterized in that, is made up of at the photocatalytic nanometer crystal on silicate glass fiber surface silicate glass fiber nonwoven film and appendix;

The diameter of described silicate glass fiber is at nanoscale;

Described photocatalytic nanometer crystal is Bi ₂wO ₆nanocrystal, TiO ₂nanocrystal, ZnO nano crystal, CaWO ₃nanocrystal, SnO ₂, more than one in BiOI nanocrystal.

2. Water warfare film according to claim 1, is characterized in that, the composition of described silicate glass fiber comprises SiO ₂, Al ₂o ₃, ZrO ₂, CaO, P ₂o ₅in more than one.

3. a preparation method for Water warfare film, is characterized in that, comprises the following steps:

(1) by sol-gel technique synthetic silicate glass precursor spinning colloidal sols;

(2) colloidal sol synthesized with step (1), for spinning solution, prepares silicate glass nano fiber non-woven film by electrostatic spinning technique;

(3) by the silicate glass nano fiber non-woven film superficial growth photocatalytic nanometer crystal that hydro-thermal method obtains in step (2), described photocatalytic nanometer crystal is Bi ₂wO ₆nanocrystal, TiO ₂nanocrystal, ZnO nano crystal, CaWO ₃nanocrystal, SnO ₂, more than one in BiOI nanocrystal.

4. the preparation method of Water warfare film according to claim 3, is characterized in that, step (1) is described by sol-gel technique synthetic silicate glass precursor spinning colloidal sols, is specially:

Be that the HCl solution of 30wt% is with volume ratio 10:(10 ~ 50 by TEOS, EtOH, water and concentration): (1 ~ 3): (0.03 ~ 0.2) mixes, then obtains spinnable precursor spinning colloidal sols by heating hydrolysis and ageing.

5. the preparation method of Water warfare film according to claim 3, it is characterized in that, the described colloidal sol synthesized with step (1) of step (2), for spinning solution, is prepared silicate glass nano fiber non-woven film by electrostatic spinning technique, is specially:

Step (1) gained precursor spinning colloidal sols is loaded liquid feed device, connect high-voltage DC power supply, continuous print silicate glass nanofiber is prepared by electrostatic spinning, adopt High Rotation Speed electronically controlled motor drive stainless steel drum collect silicate nano-fiber, after spinning terminates by fiber non-woven film from stainless steel drum peel.

6. the preparation method of Water warfare film according to claim 3, is characterized in that, step (3) described Bi ₂wO ₆the preparation method of nanocrystal is as follows:

By Bi (NO ₃) ₃5H ₂o and Na ₂wO ₄2H ₂o is dissolved in distilled water with mol ratio 2:1, then adds ethylene glycol, control Bi ₂wO ₆the concentration of presoma at 0.5 ~ 7.5 mM/l, then by SiO ₂electricity spinning fibre film immerses above-mentioned solution, and transfer in band teflon-lined autoclave and carry out hydro-thermal reaction, reaction temperature and time are respectively 120 ~ 160 DEG C and 8 ~ 15 hours.