阅读说明：本技术 双层陶瓷膜及其制备方法 (Double-layer ceramic membrane and preparation method thereof ) 是由 唐圆圆 梁琨 刘云松 王子铱 王涛 于 2019-01-21 设计创作，主要内容包括：本发明提供了一种双层陶瓷膜,包括基层和置于基层一表面的覆盖层,所述基层包括配比为8-10:1的疏浚底泥和成孔剂；覆盖层包括配比为1:0.25-1的疏浚底泥和粘接剂。其制备方法包括步骤：将疏浚底泥原料烘干,筛分后与成孔剂混合、研磨均匀后再将混合物压成薄片,烧结形成基层陶瓷膜；然后先将粘接剂和无水乙醇按比例混合搅拌,再加入疏浚底泥搅拌,制得覆盖层旋涂液后涂覆于已制备的基层陶瓷膜表面,高温烧结后得到双层陶瓷膜。本发明以疏浚底泥为主要原料,辅以环境友好材料,既价格低廉,又达到了废物回收利用的目的,不会在成品膜中残存有害物质。其制备工艺过程简单、成本低廉,烧结温度低于现有技术的烧结温度,具有良好的应用前景。(The invention provides a double-layer ceramic membrane, which comprises a base layer and a covering layer arranged on one surface of the base layer, wherein the base layer comprises dredged sediment and a pore-forming agent in a ratio of 8-10: 1; the covering layer comprises dredged sediment and adhesive in a ratio of 1: 0.25-1. The preparation method comprises the following steps: drying the dredged sediment raw material, mixing the dredged sediment raw material with a pore-forming agent after screening, uniformly grinding, pressing the mixture into slices, and sintering to form a base ceramic membrane; and then, mixing and stirring the adhesive and absolute ethyl alcohol in proportion, adding the dredged sediment and stirring to prepare a covering layer spin-coating liquid, coating the covering layer spin-coating liquid on the surface of the prepared base ceramic membrane, and sintering at a high temperature to obtain the double-layer ceramic membrane. The invention takes the dredged sediment as the main raw material and is supplemented with environment-friendly materials, thereby not only having low price, but also achieving the purpose of recycling wastes, and avoiding harmful substances remaining in the finished film. The preparation process is simple, the cost is low, the sintering temperature is lower than that of the prior art, and the preparation method has a good application prospect.)

1. The double-layer ceramic membrane is characterized by comprising a base layer and a covering layer arranged on one surface of the base layer, wherein the base layer comprises dredged sediment and a pore-forming agent, and the ratio of the dredged sediment to the pore-forming agent is 8-10: 1; the covering layer comprises dredged sediment and adhesive, and the proportion of the dredged sediment to the adhesive is 1: 0.25-1.

2. The dual layer ceramic membrane of claim 1, wherein the pore former is CaCO₃or starch.

3. A double layer ceramic membrane according to claim 1 or 2, wherein the binder is selected from polyvinyl pyrrolidone or polyvinyl alcohol.

4. A method of producing a double layer ceramic membrane according to any one of claims 1 to 3, comprising the steps of:

Preparation of the base layer: drying the dredged sediment raw material, mixing the dredged sediment raw material with a pore-forming agent in proportion after screening, putting the mixture of the dredged sediment and the pore-forming agent into a tablet press to be pressed into a sheet after grinding the mixture evenly, and then sintering the sheet to form a base ceramic membrane;

Preparation of the covering layer: firstly, mixing and stirring the adhesive and absolute ethyl alcohol according to the proportion of 1:8-10, then adding dredged sediment and stirring again to prepare covering layer spin-coating liquid;

Preparation of a bilayer film: and coating the prepared coating layer spin coating liquid on the surface of the prepared base ceramic film, and sintering at high temperature to obtain the double-layer ceramic film.

5. The method for preparing a double-layer ceramic membrane according to claim 4, wherein in the step of preparing the base layer, the dredged sediment raw material is dried and then sieved by 350-500 mesh sieve to obtain fine dredged sediment particles.

6. The method of claim 4 or 5, wherein in the step of preparing the base layer, ethanol is added to the mixture of the dredged sediment and the pore-forming agent, and then the mixture is ground to be uniform.

7. The method for preparing a double-layered ceramic membrane according to claim 4, wherein the base layer is prepared by placing a mixture of dredged sediment and pore-forming agent in corresponding molds, and pressing the mixture into a sheet in a tablet press under a pressure of 20 to 30MPa for a dwell time of 1 to 3 min.

8. The method for preparing a double-layer ceramic membrane according to claim 4, wherein in the step of preparing the base layer, the sheet is sintered in a muffle furnace at a heating rate of 4-6 ℃/min for 2-4 hours at 700 ℃ -900 ℃.

9. the method for preparing a double-layer ceramic film according to claim 4, wherein in the step of preparing the capping layer, the coating time of the spin coating solution for the capping layer is 1-2min, the rotation speed of a spin coater is 900-1000rpm, and the acceleration during spin coating is 80-150 rpm/s.

10. the method for preparing a double-layered ceramic membrane according to claim 4 or 9, wherein in the double-layered membrane preparation step, the base ceramic membrane coated with the covering layer is sintered in a muffle furnace at a temperature rise rate of 4-6 ℃/min at 700 ℃ -900 ℃ for 2-4 hours, and then cooled to room temperature at a temperature drop rate of 4-6 ℃/min to prepare the double-layered ceramic membrane.

Technical Field

The invention belongs to the technical field of materials, and particularly relates to a ceramic membrane for separation and filtration treatment and a preparation method thereof.

background

Currently, membranes for sewage treatment are widely used, wherein the membranes are classified into organic membranes and ceramic membranes from materials. Compared with organic films, ceramic films have the advantages of long service life, high mechanical strength, strong corrosion resistance and the like. However, the ceramic film has a disadvantage in that the raw material is mainly Al₂O₃，SiO₂，TiO₂And ZrO₂the pure phase inorganic compound is expensive; and the ceramic film is prepared by high-temperature sintering (generally above 1300 ℃) in the preparation process, so that the preparation cost of the ceramic film is high. The existing research focuses on replacing the original oxide material with cheap minerals and industrial waste fly ash, kaolin, mullite, sludge and the like as raw materials to reduce the preparation cost.

The ceramic membrane has a three-layer structure, namely a supporting layer, a transition layer and a separating layer. The supporting layer is a ceramic membrane matrix and is used for enhancing the mechanical property of the ceramic membrane and providing mechanical strength for the separation layer in the using process; the transition layer prevents particles of the separation layer and pollutants from directly rushing into the support layer, and the main component of the transition layer is inorganic oxide; the separation layer serves as a screen to separate the contaminating materials and is typically prepared using nanoscale particles. In the process, the preparation flow is complex, and two or three times of sintering is needed, so that the preparation cost of the ceramic membrane is high. In addition, the amount of the dredged sediment generated by the dredging engineering adopted for treating the river channels and landscape water bodies in China is increasing day by day, and as the dredged sediment has the characteristics of large sediment amount, higher water content, complex composition and the like, the sediment disposal mode generally adopts sanitary landfill or is used as building materials or roadbed materials to replace clay, but most of the sediment is mainly discarded, but enough land or space storage is lacked, and secondary pollution is easy to generate, and if the sediment is improperly disposed, the environment is seriously adversely affected, so that the disposal and disposal of the dredged sediment become a problem which is generally concerned by people.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a double-layer ceramic membrane which takes dredged sediment as a main raw material, has simple preparation process, low cost, good mechanical strength and good separation and filtration performance.

The invention provides a double-layer ceramic membrane which comprises a base layer and a covering layer arranged on one surface of the base layer, wherein the base layer comprises dredged sediment and a pore-forming agent, and the ratio of the dredged sediment to the pore-forming agent is 8-10: 1; the covering layer comprises dredged sediment and adhesive, and the proportion of the dredged sediment to the adhesive is 1: 0.25-1.

in the components of the double-layer ceramic membrane, the pore-forming agent can be CaCO₃Or starch.

in the components of the double-layer ceramic membrane, the adhesive is selected from polyvinylpyrrolidone or polyvinyl alcohol.

according to the double-layer ceramic membrane provided by the invention, dredged sediment is selected as a main raw material, so that the price is low, the purpose of recycling waste is achieved, and the manufacturing cost of the ceramic membrane can be greatly saved; the proper proportion of the adhesive and the pore-forming agent in the components is assisted, so that the ceramic membrane processing and forming are facilitated, the covering layer can be completely combined with the surface of the base layer, the separation in future use is guaranteed, and the performance requirements and the service life of the ceramic membrane during use can be met. Meanwhile, the two adjuvants are introduced and used as compounds which are very cheap and easy to obtain, other impurities cannot be introduced into the ceramic membrane, the preparation cost can be further reduced on the basis of waste recycling to the maximum extent, and the two adjuvants are environment-friendly materials, cannot remain harmful substances in a finished membrane and meet the requirement of environmental protection.

The invention also provides a preparation method of the double-layer ceramic membrane, which comprises the following steps:

Preparation of the base layer: drying the dredged sediment raw material, mixing the dredged sediment raw material with a pore-forming agent in proportion after screening, putting the mixed powder into a tablet press to be pressed into slices after grinding the mixture evenly, and forming a base ceramic membrane by sintering the slices;

Preparation of the covering layer: firstly, mixing and stirring the adhesive and absolute ethyl alcohol according to the proportion of 1:8-10, then adding dredged sediment and stirring again to prepare covering layer spin-coating liquid;

preparation of a bilayer film: and coating the prepared coating layer spin coating liquid on the surface of the prepared base ceramic film, and sintering at high temperature to obtain the double-layer ceramic film.

In the preparation steps of the double-layer ceramic membrane, in the preparation process of the base layer, the dredged sediment raw material is dried and then sieved by 350-mesh and 500-mesh sieves, so that fine dredged sediment particles can be obtained.

In the preparation steps of the double-layer ceramic membrane, in the preparation process of the base layer, ethanol can be added into the mixture of the dredged sediment and the pore-forming agent, and then the mixture is ground to be uniform.

in the preparation steps of the double-layer ceramic membrane, in the preparation process of the base layer, the mixture of the dredged sediment and the pore-forming agent can be placed in a corresponding mould, and then the mixture is pressed into a sheet by a tablet press, wherein the pressure is 20-30MPa, and the pressure maintaining time is 1-3 min.

In the preparation steps of the double-layer ceramic membrane, in the preparation process of the base layer, the thin slice is sintered for 2-4 hours in a muffle furnace at the temperature rise rate of 4-6 ℃/min and at the temperature of 700-900 ℃.

In the preparation steps of the double-layer ceramic membrane, in the preparation process of the covering layer, the coating time of the covering layer spin coating liquid is 1-2min, the rotating speed of a spin coater is 900-1000rpm, and the acceleration during spin coating is 80-150 rpm/s.

in the preparation steps of the double-layer ceramic membrane, after the spin coating is finished, the base layer ceramic membrane coated with the covering layer is sintered for 2-4 hours in a muffle furnace at the temperature rising rate of 4-6 ℃/min and the temperature of 700-900 ℃, and then the temperature is reduced to the room temperature at the temperature falling rate of 4-6 ℃/min to prepare the double-layer ceramic membrane.

the preparation method of the double-layer ceramic membrane provided by the invention has the advantages that the process steps are very simple, the sintering temperature is lower than the sintering temperature in the prior art, the cost is low, the implementation is easy, the mechanical strength of the prepared double-layer ceramic membrane is 27.33MPa, the average pore diameter is 73.5nm, the aperture ratio is 39.8638%, compared with the average pore diameter of 381.0nm of a single-layer membrane, the double-layer ceramic membrane prepared by the method has better separation and filtration performances, the double-layer ceramic membrane is made of waste materials and environment-friendly materials, the better effect can be achieved with lower cost, a very good approach is provided for the resource utilization of dredged sediment, and the method has a good application prospect in the fields of petroleum, chemistry and food industry.

drawings

FIG. 1 is an SEM photograph of a single-layer ceramic film prepared in example 1 of the present invention;

Fig. 2 is an SEM photograph of the double-layered ceramic membrane prepared in example 1 of the present invention.

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention provides a double-layer ceramic membrane, which comprises a base layer and a covering layer arranged on one surface of the base layer, wherein the base layer comprises dredged sediment and a pore-forming agent, and the ratio of the dredged sediment to the pore-forming agent is 8-10: 1; the covering layer comprises dredged sediment and adhesive, and the proportion of the dredged sediment to the adhesive is 1: 0.25-1.

The invention provides the double-layer ceramic membrane component, wherein the dredged sediment mainly contains SiO (about 70 percent)₂And Al₂O₃They are made ofpreparation of ceramic membranes from the main material, in which Al₂O₃Is a high-hardness compound, has better reinforcing and toughening effects, can improve the integral mechanical strength of the ceramic membrane and provide better support for the ceramic membrane on the one hand, and Al is used₂O₃The ceramic membrane has better dispersibility, can ensure that the prepared ceramic membrane has even thickness and lower cost; on the other hand, Al₂O₃The ceramic membrane is a porous inorganic substance, can increase the permeation flux of the ceramic membrane, has better dispersity, high hardness, good dimensional stability and very good reinforcing and toughening effects in an inorganic system of the ceramic membrane, and can also improve the compactness, the smoothness, the cold and hot fatigue properties, the fracture toughness, the creep resistance and the wear resistance of the ceramic membrane; SiO 2₂The ceramic film has fusion film-forming property, and can improve the wear resistance and corrosion resistance of the ceramic film.

While the other component Fe in the dredged sediment raw material₂O₃、CaO、MgO、K₂Oxides of O and the like, capable of reacting with SiO during high-temperature sintering₂And Al₂O₃The reaction generates various minerals which are retained in the ceramic membrane, so that the mechanical strength of the ceramic membrane can be enhanced. For example, CaO, has the reaction formula:

Al₂O₃+2SiO₂+CaO→CaO·Al₂O₃·2SiO₂

In addition, the dredged sediment contains a small amount of organic matters which can be decomposed into steam and other gases to be volatilized in high-temperature sintering.

in the double-layer ceramic membrane component provided by the invention, the base layer and the covering layer both contain dredged sediment raw materials, wherein the dredged sediment proportion of the base layer is relatively high and is used as a substrate of the ceramic membrane to provide mechanical strength for the ceramic membrane in the using process, and meanwhile, the prepared ceramic membrane has small and uniform pores by being matched with a pore-forming agent, so that the screening effect is provided for the ceramic membrane to separate pollutants. The proportion of the adhesive to the dredged sediment in the covering layer can ensure that the covering layer has certain pores, film-forming property and mechanical property, and can ensure that the covering layer can be completely combined with the surface of the base layer so as to ensure that the covering layer cannot be separated in future use and meet the requirement of service life of the covering layer.

CaCO (CaCO) capable of being selected as double-layer ceramic membrane pore-forming agent₃Or starch, preferably CaCO₃. The pore-forming agent is selected to enhance the permeability of the prepared ceramic membrane, so that the prepared ceramic membrane can obtain uniform pores with small size and better separation and filtration performance. Preferred CaCO among these₃The inorganic ceramic membrane is an inorganic substance, and in an inorganic system of the ceramic membrane, the prepared ceramic membrane can be ensured to have a hole structure with very uniform shape and size, the surface of the ceramic membrane can be ensured to be compact and smooth, the separation and filtration performance is better, and the quality of the ceramic membrane can be further improved. Further, CaCO is selected as pore-forming agent₃Or starch, belongs toEnvironmental friendly Good tasteThe addition of the material does not bring secondary pollution.

In the double-layer ceramic membrane component provided by the invention, the adhesive can uniformly disperse dredged sediment particles and enable the base layer and the covering layer to be mutually and tightly adhered into a whole, and various performance requirements of a finished membrane can be met. The adhesive of the invention is selected from polyvinylpyrrolidone or polyvinyl alcohol, preferably polyvinylpyrrolidone. The polyvinylpyrrolidone is a non-ionic high molecular compound, has good complexation and dispersibility with other compounds, excellent solubility, physiological compatibility and safety, can be used as an adhesive, and has film-forming property, cohesiveness or coacervation effect. Furthermore, the polyvinyl pyrrolidone or polyvinyl alcohol is used as an additive, belongs to a safe and non-toxic material, and cannot cause secondary pollution when added.

Therefore, in the selection of the component raw materials of the double-layer ceramic membrane provided by the invention, the dredged sediment is selected as a main raw material which contains main components for preparing the ceramic membrane, particles can be bonded together by high-temperature sintering during preparation, the dredged sediment has the characteristic of looseness and porosity, the permeability flux of the ceramic membrane can be increased by utilizing the characteristic, the dredged sediment is used as waste, the raw materials have wide sources and very low cost, the dredged sediment is used for manufacturing the ceramic membrane, the production cost of the ceramic membrane is reduced, a good path is provided for the treatment and disposal of the dredged sediment, the sintering temperature during preparation can be lower than that for preparing the ceramic membrane in the prior art, other materials in the components are safe and nontoxic environment-friendly materials, the finished product after the ceramic membrane is prepared has no harmful element residues, and the raw materials have very low price, therefore, the ceramic membrane can achieve better effect with lower cost, and greatly saves the manufacturing cost of the ceramic membrane.

In the double-layer ceramic membrane structure provided by the invention, the base layer is formed by combining dredged sediment and a pore-forming agent, so that the prepared finished ceramic membrane has better mechanical strength and pore-forming performance. The covering layer is made of the combination of the adhesive and the dredged sediment, so that dredged sediment particles in the covering layer can be combined with each other, the covering layer is favorable for covering the surface of the base layer during preparation, the base layer and the covering layer are bonded with each other, a double-layer membrane structure is formed, the mechanical strength and the wear resistance of the ceramic membrane can be improved, the aperture of the ceramic membrane and the porosity after membrane forming can be reduced, the uniform porosity and the high permeation flux are achieved, and the use requirement of the ceramic membrane can be completely met.

the mechanical strength of the double-layer ceramic membrane prepared by the invention is generally between 25MPa and 30MPa, the average pore diameter is 70-75nm, the aperture ratio is 35-40%, compared with a single-layer ceramic membrane, the double-layer ceramic membrane has better performance, meets the requirements of the current industry, and has very wide application prospect.

the invention also provides a preparation method of the double-layer ceramic membrane, which comprises the following steps:

Preparation of S1 base layer: grinding and screening dredged sediment, mixing the dredged sediment with a pore-forming agent in proportion, putting the mixed powder into a tablet press, pressing the mixture into slices, and sintering the slices to form a base ceramic membrane;

In the step, the dredged sediment is water-containing sludge discharged in the course of dredging the river, and the water-containing sludge is dried, ground and screened to obtain 350-mesh and 500-mesh fine sediment particles.

In the step, the dredged sediment is dried and screened to obtain fine particles, then the fine particles are mixed with a pore-forming agent, and a proper amount of ethanol is added to make the mixture powder into a paste, so that the mixture of the dredged sediment and the pore-forming agent is more uniform in the subsequent grinding process, and the quality of a finished film can be improved.

After the ethanol is volatilized, the mixed powder can be placed in a corresponding die and pressed in a tablet press, the pressure is 20-30MPa, and the pressure maintaining time is 1-3 min.

After being made into thin slices, the thin slices can be sintered for 2 to 4 hours in a muffle furnace at the high temperature of 700 to 900 ℃ at the heating rate of 4 to 6 ℃/min, so that certain impurities in the mixture can be decomposed into H after being calcined₂O、CO₂And volatilizing the gaseous organic matters to form a single-layer ceramic film with a plurality of pore structures.

Preparation of S2 coating layer: firstly, mixing and stirring the adhesive and absolute ethyl alcohol according to the proportion of 1:8-10, then adding dredged sediment and stirring, and mixing to form the covering layer spin-coating liquid.

In the step, the adhesive and the absolute ethyl alcohol are prepared according to the proportion of 1:8-10, the mixture is stirred for 3-5 hours at normal temperature, the adhesive can be uniformly dispersed into solution, and dredged sediment is added after the solution is uniform, so that the proportion of the adhesive to the absolute ethyl alcohol is as follows: and (3) dredging sediment is 1:8-10: 0.25-1. And stirring the mixed solution for 3-5 hours to ensure that the adhesive and the dredged sediment are fully fused and dispersed so as to ensure that uniform covering layer spin-coating solution is obtained.

Preparation of S3 bilayer films: and coating the coating layer spin-coating liquid on the surface of the prepared base ceramic film through a spin coater, and sintering at a high temperature to obtain the double-layer ceramic film.

In the step, the base ceramic membrane can be fixed inside a spin coating instrument, after vacuumizing, prepared coating layer spin coating liquid is added on the base ceramic membrane, spin coating is carried out for 1-2min, so that the base ceramic membrane is coated with the coating layer, and double-layer ceramic membranes are formed after mutual adhesion. During spin coating, the spin speed of the spin coater is 900-.

After coating, the double-layer ceramic membrane is placed in a muffle furnace, sintered for 2-4 hours at the temperature of 700-900 ℃ at the heating rate of 4-6 ℃/min, and then cooled to room temperature at the cooling rate of 4-6 ℃/min.

In the preparation method, the ethanol is adopted in the preparation of the base layer and the covering layer, so that the grinding of raw materials and the dispersion of a mixture are facilitated, the prepared ceramic membrane can be ensured to have uniform thickness, the uniformity of pores of the ceramic membrane is facilitated, the preparation quality of the ceramic membrane can be improved, and a better separation and filtration effect can be achieved during use.

in the preparation method, the base ceramic membrane is sintered for the second time, so that the first sintering temperature of the base ceramic membrane can be reduced, the pore-forming performance of the base ceramic membrane can be further improved, meanwhile, the covering layer can form a pore structure through high-temperature sintering, the viscosity of the adhesive can be improved, and the covering layer can be ensured to be uniformly and tightly attached to the surface of the base ceramic membrane so as to meet the performance requirement of the finished double-layer ceramic membrane.

The present invention will be described in further detail with reference to examples.