Talc-loaded nano ZnO composite uvioresistant agent and preparation technology thereof
阅读说明：本技术 一种滑石负载纳米ZnO复合抗紫外剂及其制备技术 (Talc-loaded nano ZnO composite uvioresistant agent and preparation technology thereof ) 是由 汪灵 潘鹏飞 董秋冶 梁唯丛 于 2019-09-30 设计创作，主要内容包括：本发明涉及一种滑石负载纳米ZnO复合抗紫外剂及其制备技术,以天然片状矿物滑石为载体矿物原料,采用直接沉淀法,第1是按质量比4:1称取六水硝酸锌和滑石矿物原料粉末,在蒸馏水中搅拌混合得到六水硝酸锌-滑石混合液体；第2按六水硝酸锌和碳酸钠摩尔比1:1.5～3.5称取碳酸钠,溶于蒸馏水后加入前混合液体中,搅拌得到前驱体碳酸锌-滑石混合液体；第3是离心洗涤去除混合液体中杂质,得到前驱体碳酸锌-滑石混合物；第4是烘干混合物,温度105℃,时间3h～6h；第5是焙烧前烘干物料,升温速率10℃～15℃/min,焙烧温度350℃～550℃,保温1h～3h,即得到滑石负载纳米ZnO复合抗紫外剂。效果明显,安全性好,工艺简单,推广应用容易,用途广泛,社会经济效益显著。(The invention relates to a talc loaded nano ZnO composite uvioresistant agent and a preparation technology thereof, wherein natural flaky mineral talc is used as a carrier mineral raw material, a direct precipitation method is adopted, and step 1, zinc nitrate hexahydrate and talc mineral raw material powder are weighed according to the mass ratio of 4:1 and are stirred and mixed in distilled water to obtain zinc nitrate hexahydrate-talc mixed liquid; 2, weighing sodium carbonate according to the molar ratio of the zinc nitrate hexahydrate to the sodium carbonate of 1: 1.5-3.5, dissolving the sodium carbonate in distilled water, adding the solution into the mixed liquid, and stirring to obtain a precursor zinc carbonate-talc mixed liquid; 3, centrifugally washing to remove impurities in the mixed liquid to obtain a precursor zinc carbonate-talc mixture; 4, drying the mixture at 105 ℃ for 3-6 h; and 5, drying the material before roasting, wherein the heating rate is 10-15 ℃/min, the roasting temperature is 350-550 ℃, and the heat preservation is carried out for 1-3 h, so that the talc-loaded nano ZnO composite anti-ultraviolet agent is obtained. The method has the advantages of obvious effect, good safety, simple process, easy popularization and application, wide application and remarkable social and economic benefits.)
1. A talc loaded nano ZnO composite uvioresistant agent and a preparation technology thereof, which takes natural flaky mineral talc as a carrier mineral raw material and adopts a direct precipitation method to prepare the talc loaded nano ZnO composite uvioresistant agent, and is characterized in that:
(1) preparing zinc nitrate hexahydrate-talc mixed liquid: respectively weighing zinc nitrate hexahydrate (Zn (NO) with a certain mass ratio of 4:1 3) 2·6H 2O) and talc mineral raw material powder, dissolving zinc nitrate hexahydrate in a certain amount of distilled water, magnetically stirring for 10min, adding talc powder, and magnetically stirring for 30min to obtain zinc nitrate hexahydrate-talc mixed liquid;
(2) preparing a precursor zinc carbonate-talc mixed liquid:weighing a certain mass of sodium carbonate (Na) according to the molar ratio of zinc nitrate hexahydrate to sodium carbonate of 1: 1.5-3.5 2CO 3) Dissolving the mixture in a certain amount of distilled water, adding a sodium carbonate aqueous solution into a zinc nitrate hexahydrate-talc mixed liquid, and continuously magnetically stirring for 30-40 min to obtain a precursor zinc carbonate (ZnCO) 3) -a talc mixing fluid;
(3) washing to remove impurities: centrifugally washing a precursor zinc carbonate-talc mixed liquid by using a centrifugal washing device, washing with distilled water twice, washing with absolute ethyl alcohol twice, and removing impurities to obtain a precursor zinc carbonate-talc mixture;
(4) drying the materials: transferring the washed and impurity-removed precursor zinc carbonate-talc mixture into a drying device, wherein the drying temperature is 105 ℃, and the drying time is 3-6 h;
(5) roasting and loading: heating the dried precursor zinc carbonate-talc mixture to 350-550 ℃ by adopting a roasting device at the heating rate of 10-15 ℃/min in an air environment, and preserving the heat for 1-3 h to obtain the talc-loaded nano ZnO composite anti-ultraviolet agent.
The talc is a magnesium silicate mineral with a 2:1 type trioctahedral layered structure, and the chemical formula of the crystal is Mg 3[Si 4O 10](OH) 2The characteristic peak of the X-ray powder crystal diffraction analysis is
1. Field of the invention
The invention relates to a talc-loaded nano ZnO composite anti-ultraviolet agent and a preparation technology thereof.
2. Background of the invention
2.1 ultraviolet concept
Ultraviolet (UV) is an electromagnetic wave having a wavelength of 200nm to 400 nm. Ultraviolet rays in sunlight can be divided into three sections of long-wave ultraviolet ray UVA (320-400 nm), medium-wave ultraviolet ray UVB (280-320 nm) and short-wave ultraviolet ray UVC (200-280 nm) according to different wavelengths. Proper sunlight irradiation can increase oxygen content of body cells, reduce blood sugar and cholesterol content, and enhance human vitality. However, when the sun is excessively exposed for a long time, various skin diseases such as sunburn, freckle, acne and the like are easily induced and aggravated, and internal organs of the body are damaged in severe cases. The basic characteristics of the uv segments are now collated as shown in table 1.
TABLE 1 classification and characterization of UV
The short wave ultraviolet UVC is absorbed by the ozone layer, cannot reach the ground and has no effect on human bodies. The energy of the medium-wave ultraviolet UVB is highest, and the great part of the energy is absorbed by the skin dermis to cause the dermal blood vessels to expand and present the symptoms of red swelling, blisters and the like. If the skin is subjected to UVB irradiation for a long time, the skin can generate erythema, inflammation and skin aging, and skin cancer can be seriously caused. In daily life, 95% or more of ultraviolet rays which the skin comes into contact with are UVA, the penetration force is strong, the skin is photo-aged, skin cancer is caused, and UVA attracts people gradually in recent years.
Ultraviolet rays not only cause harm to human bodies, but also have certain damage and aging effects on coatings, plastics, printing ink and other high polymer materials, so that the high polymer materials have the phenomena of light loss, fading, yellowing, cracking, peeling, embrittlement, pulverization, strength reduction, delamination and the like. Even indoor light and sunlight transmitted through a glass window can degrade some materials.
Therefore, ultraviolet rays have considerable harm to human health, high polymer materials and the like, so that the research and application of the ultraviolet resistant agent or the ultraviolet shielding material have important practical significance.
2.2 research and State of the Art ultraviolet Shielding materials
Since the discovery of the hazards of ultraviolet light by humans, some means have been taken to shield ultraviolet light. Ultraviolet shielding materials for human skin protection are mainly of two types: one category is ultraviolet resistant textiles including sun protection clothing, sun protection hats, sun protection gloves, and sun protection umbrellas, among others. The ultraviolet resistant coating is a sunscreen skin care product or a cosmetic mainly used in daily life, and is prepared into a paste or liquid semi-liquid product by mutually matching ultraviolet resistant sunscreens (organic or inorganic) or compounding the ultraviolet resistant sunscreens with other components. The ultraviolet shielding material for protecting the high polymer material is mainly a filler with an ultraviolet shielding function, but the research on the aspect is relatively weak.
The anti-ultraviolet agent in skin care products or cosmetics means a substance which can effectively absorb or scatter solar radiation, can reduce damage to the skin, and can effectively absorb or scatter long-wave ultraviolet rays (UVA) and medium-wave ultraviolet rays (UVB) in sunlight. They can be divided into physical and chemical sunscreens by their protective mechanism of action, also commonly referred to as inorganic and organic sunscreens, respectively.
Chemical sunscreens (organic sunscreens), also known as uv absorbers, are primarily organic compounds which absorb harmful uv radiation. Among them, tert-butyl methoxydibenzoylmethane is the most representative UVA segment ultraviolet absorbent in the current sunscreen cosmetics, and isooctyl methoxycinnamate is the most widely used UVB segment ultraviolet absorbent in the current sunscreen cosmetics. However, organic sunscreens often require strict precautions with respect to heat resistance, stability, ultraviolet absorption range, toxicity, etc., which act only in a single wavelength band (UVA or UVB), and which may also decompose and lose the sunscreen effect under the action of light, with a short duration of action. In contrast, inorganic sunscreens (physical sunscreens) are more stable and safer, and they achieve the goal of sunscreening by primarily scattering ultraviolet light while absorbing ultraviolet light in small amounts. Inorganic sunscreens are increasingly widely used due to their advantages of high efficiency, safety, durability, etc.
Current inorganic sunscreens (physical sunscreens) are predominantly TiO 2And ZnO, both of which are semiconductor materials, TiO 2Mainly aiming at UVB protection, ZnO mainly shields UVA. But the sun-screening and ultraviolet screening effects of the two are closely related to the particle size or nanometer effect of the two. The results of the previous study show that when both are nanoparticles, i.e. TiO 2When the particle size is 30-50 nm (grandma et al, 1998) and the particle size of ZnO is 10-35 nm, the nano effect is prominent, and the sunscreen ultraviolet shielding effect is excellent (YaoOer et al, 2003).
Nanometer ZnO is used as a widely used physical sun-screening agent, the principle of shielding ultraviolet rays is to absorb and scatter the ultraviolet rays, and the nanometer ZnO has the characteristics of small particle size, large specific surface area, good stability, small irritation and the like; in addition to good ultraviolet shielding performance, the antibacterial ultraviolet shielding material also has the advantages of safety, stability, heat resistance, certain antibacterial property and the like, so the antibacterial ultraviolet shielding material is widely applied to the field of sunscreen skin care products or cosmetics in recent years.
However, as the nano ZnO has the characteristics of weak polarity and tiny nano particles and high surface energy, the nano particles are in a thermodynamic unstable state and tend to agglomerate, thereby limiting the exertion of the nano effect and the ultraviolet shielding effect. In addition, in the process of manufacturing skin care products or cosmetics, nano ZnO particles are difficult to disperse to the original particle size, the ultraviolet absorption effect in the UVA, UVB, and UVC bands is reduced, the transparency and ultraviolet shielding performance thereof cannot be sufficiently exhibited, and the effect as a sunscreen agent in practical use is not good. In summary, as an inorganic sunscreen agent, the nano ZnO has the following main problems:
(1) agglomeration problem: the nano ZnO has high surface energy, and the particles tend to agglomerate.
(2) The problem of delamination: the density of the emulsifier in the sunscreen product is about 0.96-1.1g/cm 3And the density of the nano ZnO is about 5.6g/cm 3Therefore, when the nano ZnO with high density is mixed into the emulsifier, the nano ZnO is easy to precipitate, and the delamination phenomenon is generated. The layering phenomenon greatly limits the use efficiency of the nano ZnO material, and the nano ZnO material cannot be directly mixed with common cosmetics for use. If the dispersion is used alone, the dispersion and the dispersion can be separated into layers, and the dispersion must be shaken well before being used. This not only causes inconvenience to the user but also increases the use cost.
(3) Health problems are as follows: the nanometer ZnO in the sunscreen product is easy to gather at the horny layer of the skin of a human body, the opening of hair follicle sebaceous glands and wrinkles, and the size of facial pores of the human body is generally 20 mu m, so that the skin pores are easy to block by excessive use, the secretion of sweat is not facilitated, and skin infection is easy to cause. Furthermore, trace amounts of zinc may also be absorbed through the skin into the blood, which is very detrimental to human health, especially in sunburn and skin-damaged patients.
(4) The aesthetic problem is that: due to the aggregation of the nano ZnO, the phenomenon of unnatural whitening can be generated when the nano ZnO is smeared on the skin, and the aesthetic effect is influenced.
(5) Environmental problems: zn 2+The dissolution and the generation of active oxygen may have certain influence on the environment and the ecosystem and are not easy to recycle.
(6) The price problem is as follows: because the nano ZnO can not be directly mixed with common cosmetics for use, in order to overcome the layering phenomenon of dispersion liquid when the nano ZnO is used alone, a small-sized special container and a device are needed in actual use, the production and use cost of physical sun-proof products is greatly increased, the market condition of the products is generally higher, and the using amount of the products is limited.
2.3 Current State of the Art for the preparation of Nano ZnO
The preparation method of nano ZnO mainly comprises three types, namely a liquid phase method, a solid phase method and a gas phase method according to different states of raw materials and preparation processes. Among them, the gas phase method is not suitable for wide application due to the disadvantages of harsh reaction conditions, high production cost, low product purity, etc. At present, the liquid phase method and the solid phase method are mainly adopted for preparing the nano ZnO, and the main advantages and disadvantages are shown in the table 2.
TABLE 2 advantages and disadvantages of the main preparation method of nano ZnO
2.4 research technical status of mineral-loaded nano ZnO composite uvioresistant agent
The problems of nano ZnO agglomeration, delamination and the like are solved, and the method can be started from two aspects: firstly, a certain preparation method is adopted to modify nano ZnO, regulate and control the shape of the nano ZnO and the like; firstly, the mineral is used as a carrier to load nano ZnO. The leading research progress of the predecessors was as follows:
US 6086666 discloses a method for preparing a flaky mineral loaded nano ZnO anti-ultraviolet material by a hydrolysis precipitation method, which is characterized in that a zinc source and a precipitator are added into an aqueous solution of minerals at a certain reaction temperature for reaction, and after a certain time, the mixture is filtered, dried and calcined to obtain the anti-ultraviolet composite material, wherein the flaky material can be muscovite, sericite, talc and kaolinite.
CN 104017393a discloses a method for preparing nano ZnO-coated sericite powder composite material by direct precipitation, which is characterized in that in an aqueous solution system, calcium hydroxide or calcium oxide is added into a mixed system of sericite powder and zinc sulfate solution to directly obtain the nano ZnO-coated sericite powder composite material. The obtained composite material has good dispersibility in an organic solvent, and has excellent uvioresistant performance and antibacterial and deodorant performance.
Gongmegang, Zhengshuihu et al (2017) mention that the hydrolysis precipitation method is adopted to coat nano ZnO on the surface of talc to prepare the nano ZnO/calcined kaolin composite anti-ultraviolet powder material, and the composite powder material has good anti-ultraviolet performance under the appropriate preparation conditions, namely, the coating amount is 8%, the reaction temperature is 90 ℃, the modification time is 10min, the pulp concentration is 10:1, and the calcination temperature is 400 ℃.
From the above descriptions, the preparation method adopted for the mineral-loaded nano ZnO uvioresistant agent at present is mainly a hydrolysis precipitation method in a liquid phase method, and the nano ZnO-coated sericite powder composite material is prepared by a direct precipitation method in the methods of Wanbin et al (2014). However, according to the search of the inventor, no technical result report of preparing the talc-supported nano ZnO composite uvioresistant agent by adopting a direct precipitation method exists at present.
3. Technical scheme
The invention aims to prepare a composite uvioresistant agent or an ultraviolet shielding material by taking natural flaky mineral talc with a layered structure as a raw material and loading nano ZnO, so as to overcome the problems of easy agglomeration, easy delamination, poor dispersibility and the like of the existing nano ZnO, improve the sun-proof and ultraviolet shielding performances, improve the aesthetic effect, prevent the whitening phenomenon, improve the use efficiency and reduce the use cost. To achieve the above object, the following technical problems must be solved:
(1) selection of carrier mineral raw materials: the layered structure silicate minerals are of various types, and the selection conditions are as follows: has a layered structure and two-dimensional habit crystals, and mineral crystals are mainly in a fine scale shape, are non-toxic and harmless, and have rich mineral raw materials.
(2) Selecting a preparation method of nano ZnO: as shown in Table 2, several methods of the present invention have advantages and disadvantages, and the selection conditions of the preparation method of the present invention are: no toxicity and harm, convenience and feasibility and good effect.
(3) The preparation process of the nano ZnO by the direct precipitation method comprises the following steps: and (3) further determining the process conditions for preparing the nano ZnO by the direct precipitation method through experiments on the basis of the work in the step (2).
(4) The preparation process of the talc-loaded nano ZnO composite uvioresistant agent comprises the following steps: on the basis of the work in the step (3), the process conditions for preparing the talc-loaded nano ZnO composite uvioresistant agent by adopting a direct precipitation method are further determined through experiments.
The specific technical scheme is as follows:
3.1 selection of Carrier mineral raw materials
TalcIs a magnesium silicate mineral with a 2:1 type trioctahedral lamellar structure and a crystal chemical formula of Mg 3[Si 4O 10](OH) 2The theoretical chemical composition is MgO 31.72%, SiO 263.52% and H 2And 4.76 percent of oxygen. Talc is monoclinic system, and its crystal structure is composed of two layers of SiO 4]Tetrahedron and a layer of [ MgO 6]Octahedron structure with typical 2:1 layer structure; the glass is glossy, smooth, non-toxic, harmless and stable in chemical property, and meets the requirements of serving as a nano ZnO carrier mineral.
FIG. 1 is an X-ray powder diffraction pattern (XRD) of a talc sample used in the present invention, and it can be seen that the diffraction peak of the talc is relatively sharp, which indicates that the raw material talc has a complete crystal structure and a good crystalline state, and is substantially consistent with talc standard card (PDF: 29-1493), and the characteristic peaks are:
Table 3 shows the results of X-ray fluorescence spectrum (XRF) measurements of the chemical components of the talc sample used in the present invention, and it can be seen that the weight percentage (%) of the chemical components of the talc sample is closer to the theoretical components, and the contents of other impurities are very low, and the talc sample does not contain toxic and harmful impurities to human body. And the XRD analysis result is combined, so that the experimental sample is relatively pure, belongs to the talc single mineral aggregate and meets the selection condition of the carrier mineral raw material.
TABLE 3X-ray fluorescence Spectroscopy (XRF) measurements of the chemical composition of talc samples (in weight percent,%)
Name (R)
SiO
2
Al
2O
3
Fe
2O
3
TiO
2
CaO
MgO
K
2O
Na
2O
MnO
P
2O
5
SO
3
H
2O
Content (wt.)
56.70
3.89
1.85
0.26
2.45
30.33
0.01
0.04
0.02
0.11
0.01
4.33
3.2 selection of preparation method of Nano ZnO
According to related documents, the invention adopts five methods shown in Table 2, prepares nano ZnO under optimized conditions, and further detects and analyzes the ultraviolet shielding performance of the nano ZnO by adopting an ultraviolet-visible light spectrophotometer, and the result is shown in figure 2.
According to the purpose and requirement of the invention, the ultraviolet resistant agent or the ultraviolet shielding material not only ensures higher absorbance of the ultraviolet region, but also ensures high transmittance of the visible region. As can be seen from fig. 2, the industrial ZnO has coarse particles and poor uv shielding performance, and thus is not satisfactory. The standard for distinguishing the ultraviolet resistance of domestic products at present is divided into the following parts according to the ultraviolet shielding rate: class a, the ultraviolet shielding rate is more than 90 percent; b level, ultraviolet shielding rate is 80-90%; c level, and the ultraviolet shielding rate is 50-80%. The ultraviolet resistant agent or ultraviolet shielding material should be selected from a class a as appropriate. As shown in FIG. 2, the ultraviolet screening rate of the nano ZnO prepared by the direct precipitation method is more than 90%, belongs to a grade, and meets the requirements of the invention.
Direct precipitation process for preparing 3.3 nm ZnO
The invention further experimentally determines the technological conditions for preparing the nano ZnO by the direct precipitation method, and the technological conditions are as follows:
(1) preparing a precursor zinc carbonate liquid: weighing a certain mass of zinc nitrate hexahydrate (Zn (NO) according to the molar ratio of the zinc nitrate hexahydrate to sodium carbonate of 1: 1.5-3.5 3) 2·6H 2O) and sodium carbonate (Na) 2CO 3) Respectively dissolving the zinc nitrate hexahydrate and the sodium carbonate in a certain amount of distilled water, magnetically stirring the zinc nitrate hexahydrate and the sodium carbonate aqueous solution for 10min, and continuously magnetically stirring for 30-40 min to obtain a precursor zinc carbonate liquid;
(2) washing to remove impurities: carrying out centrifugal washing on a precursor zinc carbonate liquid by adopting a centrifugal washing device, carrying out two times of distilled water washing, and carrying out two times of absolute ethyl alcohol washing to remove impurities so as to obtain a precursor zinc carbonate material;
(3) drying the materials: transferring the washed and impurity-removed precursor zinc carbonate material into a drying device, wherein the drying temperature is 105 ℃, and the drying time is 3-6 h;
(4) roasting synthesis: heating the dried precursor zinc carbonate material to 350-550 ℃ by adopting a roasting device in an air environment at the heating rate of 10-15 ℃/min, and preserving the heat for 1-3 h to obtain the nano ZnO powder.
FIG. 3 is an X-ray powder diffraction pattern of nano ZnO prepared by direct precipitation method, and it can be seen that three standard strong peaks with sharp peak shape and high intensity appear in the range of 30-40 degree diffraction angle, i.e. three standard strong peaks with sharp peak shape and high intensity
FIG. 4 is a scanning electron microscope analysis photo of nano ZnO prepared by direct precipitation method, which shows that the nano ZnO powder crystal grain is spherical or quasi-spherical, has the characteristics of nano particles, the particle size is 30 nm-50 nm, but the agglomeration phenomenon is more obvious.
Preparation process of 3.4 talc-loaded nano ZnO composite anti-ultraviolet agent
On the basis of the work, the process conditions for preparing the talc-loaded nano ZnO composite anti-ultraviolet agent by adopting a direct precipitation method are determined by further experiments, and specifically comprise the following steps:
(1) preparing zinc nitrate hexahydrate-talc mixed liquid: respectively weighing zinc nitrate hexahydrate (Zn (NO) with a certain mass ratio of 4:1 3) 2·6H 2O) and talc mineral raw material powder, dissolving zinc nitrate hexahydrate in a certain amount of distilled water, magnetically stirring for 10min, adding talc powder, and magnetically stirring for 30min to obtain zinc nitrate hexahydrate-talc mixed liquid;
(2) preparing a precursor zinc carbonate-talc mixed liquid: weighing a certain mass of sodium carbonate (Na) according to the molar ratio of zinc nitrate hexahydrate to sodium carbonate of 1: 1.5-3.5 2CO 3) Dissolving the sodium carbonate into a certain amount of distilled water, adding a sodium carbonate aqueous solution into a zinc nitrate hexahydrate-talc mixed liquid, and continuously magnetically stirring for 30-40 min to obtain a precursor zinc carbonate (ZnCO) 3) -talc mixed liquids;
(3) washing to remove impurities: centrifugally washing a precursor zinc carbonate-talc mixed liquid by using a centrifugal washing device, washing with distilled water twice, washing with absolute ethyl alcohol twice, and removing impurities to obtain a precursor zinc carbonate-talc mixture;
(4) drying the materials: transferring the washed and impurity-removed precursor zinc carbonate-talc mixture into a drying device, wherein the drying temperature is 105 ℃, and the drying time is 3-6 h;
(5) roasting and loading: heating the dried precursor zinc carbonate-talc mixture to 350-550 ℃ by adopting a roasting device at the heating rate of 10-15 ℃/min in an air environment, and preserving heat for 1-3 h to obtain the talc-loaded nano ZnO composite uvioresistant agent.
4. Technical advantages
(1) The effect is obvious. The talc-loaded nano ZnO composite uvioresistant agent is prepared by taking talc as a carrier and adopting a direct precipitation method, and compared with nano ZnO prepared independently, the talc-loaded nano ZnO composite uvioresistant agent has better uvioresistant performance or ultraviolet shielding performance, better dispersibility in a solvent and higher transmittance for visible light, and solves the problems of agglomeration, layering, attractiveness and the like of nano ZnO.
(2) The safety is good. The talc used in the invention is natural mineral, and is nontoxic and pollution-free. The raw material reagents used in the process of preparing the nano ZnO are nontoxic, safe and reliable.
(3) The process is simple. The direct precipitation method used in the invention has simple operation and convenient work.
(4) Easy popularization and application. The invention has simple process, convenient operation and easy learning, mastering, popularization and application.
(5) Has wide application and remarkable economic and social benefits. With the recognition of the harm of ultraviolet rays to human bodies, ultraviolet-resistant materials are receiving more and more attention, and especially, compared with chemical ultraviolet-resistant agents, physical ultraviolet-resistant agents are safer and more stable. The talc-loaded nano ZnO composite uvioresistant agent prepared by the invention better solves the technical problems of agglomeration of the current nano ZnO and the like, has important significance for the development of the uvioresistant material industry, and has wide application prospect and remarkable economic and social benefits.