An artificial pumice stone and its preparation method

Abstract

The present invention provides an artificial pumice stone and a preparation method thereof, belonging to the technical field of artificial pumice stones. In the present invention, foaming is carried out at 160-200 °C, and a large number of bubbles are generated by an organic foaming agent, an inorganic foaming agent and a foaming aid, forming a large number of pores and gaps inside the material; during the sintering process, the guiding agent guides the stacking and bridging between molecules through a biphenyl structure, and the quaternary ammonium group and the biphenyl center provide alkyl chains of sufficient length to guide capillary self-assembly in the gaps, so that the main material changes from a layered structure to a tubular structure, and open pores can be formed inside the material and there are capillary tubes connecting the internal pores of the material to the surface of the material, thereby improving the effective porosity and water permeability of the artificial pumice stone; by adopting a gas retention agent, the material can be wrapped to prevent the bubbles generated during foaming from quickly escaping, thereby improving the effective porosity; through activation, the micro-pores and capillary tubes of the artificial pumice stone can be further strengthened, and the effective porosity and water permeability can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of artificial pumice production, and particularly relates to an artificial pumice and a preparation method thereof. Background Art

[0002] In water treatment, biological aerated filters need to use filter media to treat organic matter in water bodies and store moisture. The two main functions of filter media are: one is the filtering and adsorption ability, and the other is high water permeability and non-blocking. These two properties are directly related to the effective porosity of the filter media itself. At present, the effective porosity of most filter media is not high, and the calculation method of mass ratio (Formula I) is used. Many filter media adopt the way of closed air holes, and their own specific gravity is very low, generally between 0.2 and 0.5. Theoretically, the porosity is very high, but the available porosity in water treatment is actually not high, which will cause the system to be blocked and collapse, such as pumice, ceramsite and glass light stone.

[0003] In actual water treatment, the volume calculation method (Formula II) is often used to obtain the effective porosity (volume ratio). The effective porosity represents: having the largest space liquid storage capacity and the smallest space volume loss, a larger specific surface area and better adsorption ability, and more surface tension and flow capacity.

[0004] The calculation formula of the mass ratio porosity of the filter media at normal temperature is shown in Formula 1,

[0005] The calculation formula of the effective porosity of the filter media at normal temperature is shown in Formula II:

[0006]

[0007] In the formula, m1 is the mass of the material when dry, and m2 is the mass of the material after being saturated with water;

[0008]

[0009] In the formula, m1 is the mass of the material when dry, m2 is the mass of the material after being saturated with water, and V1 is the volume of the material.

[0010] At present, the filter media are mainly various porous materials, usually pumice (or zeolite). Pumice is divided into natural pumice and artificial pumice. The performance of natural pumice varies greatly. Most of the mass water storage rates are 20% - 50%, and the effective porosities are 10% - 20%. The performance of artificial pumice is better. The artificial pumice commonly used in water treatment is similar to slag, and its interior is mainly closed air holes without through pipes as connections, so the actually available part is very small. Usually, the mass water storage rate is 20 - 80%, and the effective porosity is 10% - 30%. For ceramsite and glass light stone products, the data measured by mass ratio are usually very high, up to 200% at most, but the actually available porosity is very low, generally 10%.

[0011] The water storage clay is a patent previously applied by the applicant's technical team. It is a new material developed for storing rainwater in artificial wetlands in sponge cities and making it reusable. It is characterized by being a porous material with a large number of open pores inside. It is very light in weight, and the mass water storage rate can reach 80% - 110%. However, calculated by the tool volume ratio, the effective porosity is only 20% - 30%. The present invention is a new technology that adds honeycomb-shaped capillary pipes on the basis of this technology and increases the effective porosity.

[0012] Generally speaking, most of the filter materials in current water treatment are porous on the surface, and the specific surface area of the pores is used to absorb organic substances in the water body. The effective porosity is relatively low. At the same time, the liquid only flows in the gaps between the materials, and it is very easy to cause blockage due to poor water permeability or no water permeability. Therefore, how to improve the effective porosity of the filter material and its own water permeability has become an urgent technical problem in this field. Summary of the Invention

[0013] The purpose of the present invention is to provide an artificial pumice stone and a preparation method thereof.

[0014] The artificial pumice stone prepared by the preparation method provided by the present invention is improved on the basis of traditional porous materials to a connection structure composed of a honeycomb-shaped capillary pipe rich in penetration type and a large number of open pores inside. This structure creates a large number of pores inside the material while creating a large number of honeycomb-shaped capillary pipes that penetrate the entire material. These pipes connect the external space and the pores inside the material at the same time. This structure can not only greatly increase the effective porosity during water treatment, but also actively absorb liquid (siphon effect) using the surface tension of the liquid. At the same time, the structural parts connected to the pipes on each contacting artificial pumice stone can also conduct liquid, which makes the water permeability of the space formed by this material very high, greatly increasing the space inside the material that can absorb liquid, and at the same time greatly reducing the possibility of blockage, and also bringing good adsorption ability. It is the first time to appear in the common materials for water treatment currently.

[0015] The main components of the honeycomb-shaped capillary pipes inside the material are silicon oxide and alumina molecules.

[0016] The effective porosity of the artificial pumice stone provided by the present invention is reflected in the following points:

[0017] 1) Tested by the standard impregnation method, the porosity is 40% - 60% (volume ratio), 80% - 140% (mass ratio);

[0018] 2) In the test, each particle can saturatedly absorb 40% - 60% of its volume of liquid water;

[0019] 3) Specific surface area ≥ 60 cm 2 / g (BET method);

[0020] 4) High water permeability.

[0021] The high water permeability of the artificial pumice provided by the present invention is embodied in the following aspects:

[0022] 1) It can quickly reach saturation within one minute when immersed in water at room temperature.

[0023] 2) There is no head loss in the water permeability test (simulating an aerated biological filter).

[0024] 3) No clogging phenomenon is found after long-term use 200 times in the filtration test.

[0025] 4) In the test under the artificial wetland mode, in the environment of outdoor temperature of 35 - 40 °C in summer, it can remain without watering for a continuous month and still maintain the soil humidity of 23 - 30%.

[0026] At the same time, the increase in the effective porosity will also greatly increase the specific surface area, improve the organic matter adsorption capacity of the material and also enhance the liquid storage capacity in the space.

[0027] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0028] The present invention provides a preparation method of artificial pumice, comprising the following steps:

[0029] (1) Mix the main material, organic foaming agent, inorganic foaming agent, foaming aid, guiding agent, gas-retaining agent and water to obtain a slurry; the main material includes natural clay and / or silicon-aluminum ratio regulator; the guiding agent is dialkyl quaternary ammonium salt and biphenylacetic acid.

[0030] (2) Foam and dry the slurry obtained in step (1) in sequence to obtain a blank; the temperature of foaming is 160 - 200 °C.

[0031] (3) Granulate, sinter and activate the blank obtained in step (2) in sequence to obtain artificial pumice.

[0032] Preferably, the natural clay in step (1) is natural clay purified by water washing, and the particle size is 100 - 200 mesh.

[0033] Preferably, the silicon-aluminum ratio regulator in step (1) is Al4[Si4O 10 [OH]8, the purity of the silicon-aluminum ratio regulator is above 95%, and the particle size of the silicon-aluminum ratio regulator is 200 - 300 mesh.

[0034] Preferably, the organic foaming agent in step (1) is at least one of azodicarbonamide, DPT and peracetic acid, and the organic foaming agent is 0.5 - 1% of the mass of the main material.

[0035] Preferably, in the step (1), the inorganic foaming agent is at least one of sodium bicarbonate, ammonium bicarbonate, and calcium carbide, and the inorganic foaming agent accounts for 1-2.5% of the mass of the main material.

[0036] Preferably, in the step (1), the foaming aid is alum, and the foaming aid accounts for 0.25-1.5% of the mass of the main material.

[0037] Preferably, in the step (1), the gas retention agent is polyvinyl alcohol, and the gas retention agent accounts for 0.5-2% of the mass of the main material.

[0038] Preferably, in the step (3), the activator used for activation is an aqueous solution of at least one of citric acid, polylactic acid, and itaconic acid.

[0039] Preferably, the mass concentration of the activator is 3-5%.

[0040] The present invention also provides artificial pumice prepared by the preparation method described in the above technical solution.

[0041] The present invention provides a preparation method of artificial pumice, which includes the following steps: mixing the main material, organic foaming agent, inorganic foaming agent, foaming aid, guiding agent, gas retention agent, and water to obtain a slurry; the main material includes natural clay and / or silicon-aluminum ratio adjusting agent; the guiding agent is dialkyl quaternary ammonium salt and biphenylacetic acid; foaming and drying the slurry in sequence to obtain a blank; the temperature of foaming is 160-200°C; granulating, sintering, and activating the blank in sequence to obtain artificial pumice. In the present invention, foaming is carried out at 160-200°C, and a large number of bubbles will be generated by the organic foaming agent, inorganic foaming agent, and foaming aid, forming a large number of pores and gaps inside the material; during the sintering process, the guiding agent guides the stacking and bridging between molecules through the biphenyl structure, and the quaternary ammonium group and the biphenyl center provide long enough alkyl chains to guide capillary self-assembly in the gaps, so that the main material changes from a layered structure to a tubular structure, and open pores can be formed inside the material and there are capillary tubes connecting the internal pores of the material to the surface of the material, thereby improving the effective porosity and water permeability of the artificial pumice; by using a gas retention agent, the material can be wrapped to prevent the bubbles generated during foaming from quickly escaping, thereby further increasing the porosity of the artificial pumice and then increasing the effective porosity; sintering can achieve mullitization and improve the strength of the artificial pumice; activation can further strengthen the micropores and capillary tubes of the artificial pumice and improve the effective porosity and water permeability. The experimental results show that the mass water storage rate of the artificial pumice prepared by the present invention is 80%-140%, and the effective porosity is 40%-60%; the probability of space blockage formed by the artificial pumice is greatly reduced; the loss of liquid flowing inside is very small, almost no loss. Description of the Drawings

[0042] Figure 1 The physical diagram of the artificial pumice stone prepared in Example 3;

[0043] Figure 2 The SEM diagram of the artificial pumice stone prepared in Example 3 magnified 1000 times;

[0044] Figure 3 The SEM diagram of the artificial pumice stone prepared in Example 3 magnified 5000 times;

[0045] Figure 4 The SEM diagram of the artificial pumice stone prepared in Example 3 magnified 5000 times;

[0046] Figure 5 The test schematic diagram of the artificial pumice stone prepared in Example 3;

[0047] Figure 6 The water permeability data of the artificial pumice stone prepared in Example 3. Specific implementation manners

[0048] The present invention provides a preparation method of an artificial pumice stone, comprising the following steps:

[0049] (1) Mixing a main material, an organic foaming agent, an inorganic foaming agent, a foaming aid, a guiding agent, a gas-retaining agent and water to obtain a slurry; the main material includes natural clay and / or a silicon-aluminum ratio adjusting agent; the guiding agent is a dialkyl quaternary ammonium salt and biphenylacetic acid;

[0050] (2) Foaming and drying the slurry obtained in the step (1) in sequence to obtain a blank; the temperature of the foaming is 160-200 °C;

[0051] (3) Granulating, sintering and activating the blank obtained in the step (2) in sequence to obtain the artificial pumice stone.

[0052] The present invention has no special limitation on the sources of the raw materials, and commercially available products well-known to those skilled in the art can be used.

[0053] The present invention mixes a main material, an organic foaming agent, an inorganic foaming agent, a foaming aid, a guiding agent, a gas-retaining agent and water to obtain a slurry.

[0054] In the present invention, the main material includes natural clay and / or a silicon-aluminum ratio adjusting agent; the natural clay is preferably natural clay purified by water washing; the particle size of the natural clay is preferably 100-200 mesh; the silicon-aluminum ratio adjusting agent is preferably Al4[Si4O 10 [OH]8; the purity of the silicon-aluminum ratio adjusting agent is preferably above 95%; the particle size of the silicon-aluminum ratio adjusting agent is preferably 200-300 mesh.

[0055] In the present invention, when the main materials are natural clay and silica-alumina ratio modifier, the natural clay is preferably 40-60% by mass of the main materials, more preferably 45-55%, and the silica-alumina ratio modifier is preferably 40-60% by mass of the main materials, more preferably 45-55%. By controlling the mass of the natural clay and the silica-alumina ratio modifier, the present invention can further improve the effective porosity of the artificial pumice.

[0056] In the present invention, the organic blowing agent is preferably at least one of azodicarbonamide, DPT, and peracetic acid, more preferably azodicarbonamide; the organic blowing agent is preferably 0.5-1% by mass of the main materials, further preferably 0.2-0.8%, and more preferably 0.5-0.6%. Limiting the amount of the organic blowing agent within the above range can further improve the effective porosity of the artificial pumice.

[0057] In the present invention, when the organic blowing agent is azodicarbonamide, the azodicarbonamide is preferably 0.5-1% by mass of the main materials; when the organic blowing agent is DPT, the DPT is 0.5-1% by mass of the main materials; when the organic blowing agent is peracetic acid, the peracetic acid is 0.1-1% by mass of the main materials.

[0058] In the present invention, the inorganic blowing agent is preferably at least one of sodium bicarbonate, ammonium bicarbonate, hydrogen peroxide, and calcium carbide, more preferably ammonium bicarbonate; the inorganic blowing agent is preferably 1-2.5% by mass of the main materials, further preferably 1.2-2.3%, and more preferably 1.5-2.0%. Limiting the amount of the inorganic blowing agent within the above range can further improve the effective porosity of the artificial pumice.

[0059] In the present invention, the blowing aid is preferably alum; the blowing aid is preferably 0.25-1.5% by mass of the main materials, further preferably 0.5-1.2%, and more preferably 0.8-1.0%. Limiting the amount of the blowing aid within the above range can further improve the effective porosity of the artificial pumice.

[0060] In the present invention, the guiding agent is a dialkyl quaternary ammonium salt and biphenylacetic acid, preferably didodecyldimethyl-γ-bisquaternary ammonium salt and biphenylacetic acid; the mass of the guiding agent is preferably 0.08-0.12% of the mass of the main material, more preferably 0.1%; the mass ratio of the dialkyl quaternary ammonium salt to biphenylacetic acid is preferably 1:1. By adding the guiding agent in the present invention, during the sintering process, the guiding agent guides the stacking and bridging between molecules through the biphenyl structure, and the quaternary ammonium group and the biphenyl center provide alkyl chains long enough to guide capillary self-assembly in the gaps, so that the main material changes from a layered structure to a tubular structure, and open pores can be formed inside the material, and there are capillaries connecting the internal pores of the material to the surface of the material, thereby improving the effective porosity and water permeability of the artificial pumice. After activation by the activator, the performance of the capillary bundle is further enhanced.

[0061] In the present invention, the gas-retaining agent is preferably polyvinyl alcohol; the gas-retaining agent is preferably 0.5-2% of the mass of the main material, further preferably 0.6-1.5%, and more preferably 0.8-1.2%. By using the gas-retaining agent in the present invention, the material can be wrapped to prevent the bubbles generated during foaming from quickly escaping, thereby further increasing the porosity of the artificial pumice and then increasing the effective porosity; limiting the dosage of the gas-retaining agent within the above range can further increase the effective porosity of the artificial pumice.

[0062] The present invention has no special limitation on the molecular weight of the polyvinyl alcohol, and commercially available products well-known to those skilled in the art can be used.

[0063] In the present invention, the water is preferably 30-70% of the mass of the main material, more preferably 50-60%.

[0064] In the present invention, the mixing of the main material, organic foaming agent, inorganic foaming agent, foaming aid, guiding agent, gas-retaining agent and water preferably includes the following steps:

[0065] 1) Mix the organic foaming agent and the foaming aid to obtain a first mixture;

[0066] 2) Mix the main material, the first mixture obtained in step 1), the inorganic foaming agent and the guiding agent to obtain a second mixture;

[0067] 3) Mix the gas-retaining agent and water to obtain a gas-retaining agent solution;

[0068] 4) Mix the second mixture obtained in step 2) and the gas-retaining agent solution obtained in step 3);

[0069] There is no order of priority for steps 1)-2) and step 3).

[0070] The present invention preferably mixes the organic foaming agent and the foaming aid to obtain a first mixture.

[0071] The present invention has no special limitation on the operation of mixing the organic foaming agent and the foaming aid, and the technical solutions for preparing the mixed material well-known to those skilled in the art can be adopted.

[0072] After obtaining the first mixed material, the present invention preferably mixes the main material, the first mixed material, the inorganic foaming agent and the guiding agent to obtain a second mixed material.

[0073] The present invention has no special limitation on the operation of mixing the main material, the first mixed material, the inorganic foaming agent and the guiding agent, and the technical solutions for preparing the mixed material well-known to those skilled in the art can be adopted.

[0074] The present invention preferably mixes the gas-retaining agent and water to obtain a gas-retaining agent solution.

[0075] The present invention has no special limitation on the operation of mixing the gas-retaining agent and water, and the technical solutions for preparing the mixed material well-known to those skilled in the art can be adopted.

[0076] After obtaining the second mixed material and the gas-retaining agent solution, the present invention preferably mixes the second mixed material and the gas-retaining agent solution.

[0077] The present invention has no special limitation on the operation of mixing the second mixed material and the gas-retaining agent solution, and the technical solutions for preparing the mixed material well-known to those skilled in the art can be adopted.

[0078] After mixing is completed, the present invention preferably ages the product obtained by mixing to obtain a slurry.

[0079] In the present invention, the temperature of the aging is preferably room temperature; the time of the aging is preferably 12 to 24 h, more preferably 15 to 24 h. The present invention can be fully infiltrated through aging.

[0080] After obtaining the slurry, the present invention foams and dries the slurry in sequence to obtain a blank. The present invention foams at 160 to 200 °C, and a large number of bubbles will be generated by the organic foaming agent, the inorganic foaming agent and the foaming aid, and a large number of pores and gaps will be formed inside the material.

[0081] In the present invention, the temperature of the foaming is 160 to 200 °C, more preferably 170 to 180 °C; the time of the foaming is preferably 50 to 120 min, more preferably 60 to 100 min. Foaming at a high temperature in the present invention can rapidly increase the temperature of the mud material, enabling the foaming agent to fully react within a short time to generate a large number of bubbles; by controlling the temperature and time of the foaming, the effective porosity of the artificial pumice can be further improved.

[0082] The present invention has no special limitation on the operation of the drying, as long as the water content of the blank is controlled below 10%.

[0083] After obtaining the blank, the present invention granulates, sinters and activates the blank in sequence to obtain artificial pumice.

[0084] In the present invention, cutting is preferably further included before granulating the blank. The present invention has no special limitation on the operation of the cutting, and the operation well-known to those skilled in the art can be adopted. The present invention adopts cutting, which is beneficial to subsequent granulation.

[0085] The present invention has no special limitation on the operation of the granulation, and the operation well-known to those skilled in the art can be adopted.

[0086] In the present invention, the particle size obtained by granulation is preferably 0.5 - 1.5 cm, more preferably 0.5 - 1 cm or 1 - 1.5 cm.

[0087] In the present invention, the sintering temperature is preferably 800 - 1000 °C, more preferably 850 - 900 °C; the sintering time is preferably 60 - 90 min, more preferably 60 - 70 min. The present invention can achieve mullitization through sintering, thereby improving the strength of artificial pumice; during the sintering process, the guiding agent guides the stacking and bridging between molecules through the biphenyl structure, and the quaternary ammonium group and the biphenyl center provide long enough alkyl chains to guide capillary self-assembly in the gaps, so that the main material changes from a layered structure to a tubular structure, and open pores can be formed inside the material and capillaries connecting the internal pores of the material to the surface of the material can be formed, thereby improving the effective porosity and water permeability of artificial pumice.

[0088] In the present invention, the activator used for activation is preferably an aqueous solution of at least one of citric acid, polylactic acid and itaconic acid; the mass concentration of the activator is preferably 3 - 5%, more preferably 3.5 - 4.0%. The present invention has no special limitation on the dosage of the activator, as long as the product obtained by roasting is completely immersed in the activator.

[0089] In the present invention, the activation temperature is preferably room temperature; the activation time is preferably > 10 min, further preferably 12 - 20 min, more preferably 15 min. The present invention can precipitate impurities in the material through activation to obtain a pure material, thereby further strengthening the micropores and capillary ducts of artificial pumice and improving the effective porosity.

[0090] After the activation is completed, the present invention preferably washes the product obtained by activation with water to obtain artificial pumice.

[0091] The present invention has no special limitation on the operation of the water washing, and the operation well-known to those skilled in the art can be adopted.

[0092] The present invention also provides artificial pumice prepared by the preparation method described in the above technical solution.

[0093] In the present invention, the interior of the artificial pumice has a structure combining micro pores and through-type pipes.

[0094] The artificial pumice of the present invention is a porous material combining silicon and carbon elements. Its exterior is similar to that of a conventional porous material, and its interior has a structure combining micro pores and through-type pipes. Through this structure, a considerable number of voids can be formed inside the material. In a liquid, these voids combine with the surface tension of the liquid, allowing the liquid to flow freely inside the material, similar to the siphon effect, thereby improving the water permeability inside the material.

[0095] In the present invention, the shape of the artificial pumice is preferably porous block, angular gravel, cobblestone, spherical, columnar or powdery.

[0096] In the present invention, the physical parameters of the artificial pumice are as follows:

[0097] Bulk density: 0.33 - 0.67 tons per cubic meter;

[0098] Specific surface area: ≥60 cm 2 / g;

[0099] Porosity: 40 - 60%;

[0100] Mass water storage rate: 80% - 140%;

[0101] Effective porosity: 40% - 60%;

[0102] Cylinder compressive strength: 0.5 - 2 MPa

[0103] Appearance: white, earthy yellow, reddish brown or grayish white; spherical or ellipsoidal grains;

[0104] Particle size: 5 - 15 mm;

[0105] Composition: silicon oxide, aluminum oxide or iron oxide.

[0106] The present invention simulates the formation principle of volcanic rock to produce an artificial pumice containing a large number of micro pores and capillaries. It can not only store a large amount of flowable liquid, but also utilize the siphon effect of the capillaries to maintain the fluidity of the liquid therein, preventing it from being blocked. This greatly improves the performance of the artificial pumice while significantly reducing its manufacturing cost. This characteristic enables it to be used in water purification, constructed wetlands, soil improvement and agricultural production in arid areas.

[0107] The artificial pumice provided by the present invention is based on the original water-storing clay, and a large number of capillary pipes with a honeycomb tube structure are added, connecting the continuous pores to the outside of the material, ensuring the maximum liquid storage capacity and water permeability inside the material, which can improve the effect and efficiency of water treatment and save costs. The mass water storage rate is 80-140%, the effective porosity is 40-60%, it is a porous material with the highest liquid storage capacity, and the space water storage rate after stacking can reach 70%, among which 30-40% is intergranular water storage and 40-50% is internal water storage of the material.

[0108] The internal part of the artificial pumice provided by the present invention is open pores and there are through pipes connecting the internal pores of the material to the surface of the material, making the material have a very strong liquid absorption capacity. It can absorb water to reach the saturation state within one minute, and can also output the internal water to the surface under appropriate circumstances; it has a larger external and internal specific surface area, which improves its ability to absorb organic substances in the water body.

[0109] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts belong to the protection scope of the present invention.

[0110] The natural clay used in the embodiment is the river-washed natural clay in Guangdong region.

[0111] Embodiment 1

[0112] A preparation method of artificial pumice is as follows:

[0113] (1) Mix 100-mesh washed natural clay with Al4[Si4O 10 [OH]8 with a purity of more than 95% and a particle size of 300 meshes to obtain a first mixture; among them, the washed natural clay is 40% of the total mass of the washed natural clay and Al4[Si4O 10 [OH]8, and Al4[Si4O 10 [OH]8 is 60% of the total mass of the washed natural clay and Al4[Si4O 10 [OH]8;

[0114] (2) Mix 1% of azodicarbonamide by mass of the first mixture with 1.5% of alum by mass of the first mixture to obtain a first blended material;

[0115] (3) Mix 2.5% of ammonium bicarbonate by mass of the first mixture, 0.05% of ditetradecyldimethyl-γ-bisquaternary ammonium salt by mass of the first mixture, 0.05% of biphenylacetic acid by mass of the first mixture with the first mixture and the first blended material in a dry powder mixer and stir for 15 minutes to obtain a second blended material;

[0116] (4) Select water that is 60% of the mass of ingredient 1, add polyvinyl alcohol - 2000 that is 2% of the mass of ingredient 1, and mix them in a liquid blender to obtain a gas - retaining agent solution;

[0117] (5) Put the second mixture and the gas - retaining agent solution into a slurry blender and stir for 15 min to obtain a slurry;

[0118] (6) Let the slurry age for 24 h, then foam it at 200 °C for 60 min, and then dry it until the moisture content is below 10% to obtain a blank;

[0119] (7) Cut the blank into small pieces with a size of 1 cm×1 cm×1 cm, and then granulate them in a disk granulator to obtain spheres with a diameter of 1 cm;

[0120] (8) Send the spheres into a sintering furnace at 850 °C for solid - forming for 60 min, then soak them in a citric acid aqueous solution with a mass concentration of 3.5% for activation for 15 min, and wash them with water to obtain artificial pumice.

[0121] Example 2

[0122] A preparation method of artificial pumice, which comprises the following steps:

[0123] (1) Mix azodicarbonamide that is 0.5% of the mass of washed natural clay and alum that is 0.5% of the mass of washed natural clay to obtain a first mixture;

[0124] (2) Put ammonium bicarbonate that is 1.0% of the mass of washed natural clay, didodecyldimethyl - γ - bisquaternary ammonium salt that is 0.05% of the mass of washed natural clay, biphenylacetic acid that is 0.05% of the mass of washed natural clay, and the washed natural clay and the first mixture into a dry powder blender and mix and stir for 15 min to obtain a second mixture; wherein, the particle size of the washed natural clay is 100 mesh;

[0125] (3) Select water that is 30% of the mass of washed natural clay, add polyvinyl alcohol - 2000 that is 0.5% of the mass of washed natural clay, and mix them in a liquid blender to obtain a gas - retaining agent solution;

[0126] (4) Put the second mixture and the gas - retaining agent solution into a slurry blender and stir for 15 min to obtain a slurry;

[0127] (5) Let the slurry age for 24 h, then foam it at 200 °C for 120 min, and then dry it until the moisture content is below 10% to obtain a blank;

[0128] (6) Cut the blank into small pieces with a size of 1 cm×1 cm×1 cm, and then granulate them in a disk granulator to obtain spheres with a diameter of 1 cm;

[0129] (7) The spheres are sent into a sintering furnace at 1000 °C for solidification for 90 min, and then soaked in a citric acid aqueous solution with a mass concentration of 3% for activation for 15 min. After washing with water, artificial pumice is obtained.

[0130] Example 3

[0131] A preparation method of artificial pumice comprises the following steps:

[0132] (1) 100-mesh water-washed natural clay is mixed with dry Al4[Si4O 10 [OH]8 with a purity of more than 95% and a particle size of 200 mesh to obtain mixture 1; wherein, the water-washed natural clay accounts for 45% of the total mass of the water-washed natural clay and Al4[Si4O 10 [OH]8, and Al4[Si4O 10 [OH] accounts for 55% of the total mass of the water-washed natural clay and Al4[Si4O 10 [OH]8;

[0133] (2) Azodicarbonamide accounting for 1% of the mass of mixture 1 is mixed with alum accounting for 1% of the mass of mixture 1 to obtain the first mixture;

[0134] (3) Ammonium bicarbonate accounting for 1.5% of the mass of mixture 1, didodecyldimethyl-γ-bisquaternary ammonium salt accounting for 0.05% of the mass of mixture 1, biphenylacetic acid accounting for 0.05% of the mass of mixture 1, mixture 1 and the first mixture are placed in a dry powder mixer and mixed and stirred for 15 min to obtain the second mixture;

[0135] (4) 40% of the mass of water of mixture 1 is selected, and polyvinyl alcohol-2000 accounting for 1.5% of the mass of mixture 1 is added and mixed in a liquid mixer to obtain a gas-retaining agent solution;

[0136] (5) The second mixture and the gas-retaining agent solution are put into a slurry mixer and stirred for 15 min to obtain a slurry;

[0137] (6) The slurry is left for 24 h for aging, then foamed at 200 °C for 60 min, and then dried to a water content of less than 10% to obtain a blank;

[0138] (7) The blank is cut into small pieces with a diameter of 1 cm * 1 cm * 1 cm, and then granulated in a disk granulator to obtain spheres with a diameter of 1 cm;

[0139] (8) The spheres are sent into a sintering furnace at 900 °C for solidification for 90 min, and then soaked in a citric acid aqueous solution with a mass concentration of 3% for activation for 15 min. After washing with water, artificial pumice is obtained.

[0140] The physical picture of the artificial pumice prepared in Example 3 is as Figure 1 shown.

[0141] From Figure 1 it can be seen that the prepared artificial pumice is ellipsoidal in shape.

[0142] The SEM images of the artificial pumice prepared in Example 3 are as shown in Figures 2 - 4 ; among them, Figure 2 is the SEM image of the artificial pumice prepared in Example 3 magnified 1000 times; Figure 3 and 4 are both the SEM images of the artificial pumice prepared in Example 3 magnified 5000 times.

[0143] From Figures 2 - 4 it can be seen that there is a structure in the artificial pumice prepared in the examples, in which a large number of capillary ducts and pores are mixed together to form through-type ducts and pore connections.

[0144] Comparative Example 1

[0145] Artificial pumice produced industrially (6000 yuan / ton)

[0146] Comparative Example 2

[0147] Water storage clay (CN1218904C)

[0148] The performance tests of the artificial pumice prepared in Examples 1 to 3 and Comparative Examples 1 to 2 are shown in Table 1. Among them, the mass water storage rate and the effective porosity (volume water storage rate) are tested by the standard impregnation method (measured with clear water at normal temperature and pressure); the cylinder compressive strength is tested by the national standard method GB2842-81 "Test Methods for Lightweight Aggregates", and the following are all average values.

[0149] Table 1 Performance data of the artificial pumice prepared in Examples 1 to 3 and Comparative Examples 1 to 2

[0150] Item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Quality water storage rate / % 140 80 120 30～80 80～100 Effective porosity / % 60 40 53 10～30 20～30 Cylinder compressive strength / MPa 0.5 2 1 2～3 0.3～0.5

[0151] As can be seen from Table 1, the artificial pumice prepared by the present invention has good effective porosity and mass water storage rate; in addition, the artificial pumice prepared by the present invention has excellent cylinder compressive strength.

[0152] Water permeability test

[0153] 1. The saturated adsorption duration (adsorbed water) of the artificial pumice prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested, and the results are shown in Table 2.

[0154] Table 2 Saturated adsorption duration data of the artificial pumice prepared in Examples 1 to 3 and Comparative Examples 1 to 2

[0155] Item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Saturated adsorption duration 30s 200s 60s 30 - 60 min 200～300s

[0156] As can be seen from Table 2, the artificial pumice prepared by the present invention can actively absorb liquid by the surface tension of the liquid (siphon effect), so that it can be saturatedly adsorbed in a relatively short time.

[0157] 2. Strong fluidity test (simulating BAF aerated biological filter)

[0158] The strong fluidity of the artificial pumice prepared in Example 3 (in the structure of a large number of open pores + through capillary pipes, the liquid will flow rapidly in the pipes and pores due to surface tension, so the liquid is actually flowing continuously in the space composed of this material) was tested. The BAF simulation mode was adopted. A water pump was used to inject water into the bottom of the container through a pipe inserted into the bottom at a fixed height position with the same power. The total water flow and time when the water level reached 4 standard positions of the container were measured by a weighing scale and a timer to calculate the flow rate of the water in the space when different particles were filled; the three modes of this test were no material filling, filling with 5 - 10 mm particles, and filling with 10 - 15 mm particles; in the mode of no filler filling, it took 1 h for 4.15 m, and the water volume test was 302 kg. The test method is as Figure 5 shown.

[0159] The water permeability data of the artificial pumice prepared in Example 3 are as Figure 6 shown.

[0160] From Figure 6 it can be seen that the probability of blockage in the space formed by the artificial pumice prepared by the present invention is greatly reduced; the loss of liquid flowing inside is very small, almost no loss.

[0161] 3. Long - term effectiveness

[0162] The artificial pumice prepared in Example 3 was used in the filtration test for 200 times without any blockage found.

[0163] In summary, the artificial pumice prepared by the present invention has excellent water permeability.

[0164] The carbon element content of the artificial pumice prepared in Example 3 was detected, and the results are shown in Table 3.

[0165] Table 3 Carbon element content of the artificial pumice prepared in Example 3

[0166] Item Method C(％) Artificial pumice 5 mg standard sample method 0.14

[0167] As can be seen from Table 3, the carbon element content of the artificial pumice is relatively low.

[0168] The artificial pumice prepared in Example 3 was subjected to component analysis and testing; among them, the instrument model was the X-ray fluorescence spectrometer ARL Perform’X, and the instrument number was 21003415; the test was based on the General Rules for Wavelength Dispersive X-ray Fluorescence Spectral Analysis Method JY / T0569-2020; the test method was to add artificial pumice and boric acid to a tablet press, press them into a round block with a diameter of 40 mm and a thickness of 3 mm and a smooth surface, then put the round block into the sample holder, place it in the instrument injection position, fill in the sample information on the instrument software, start the test, export the test data after the test is completed. The XRF component analysis results show that the main components are SiO2, Al2O3, K2O, and Fe2O3, and the contents are 52.11%, 39.09%, 3.07%, and 2.70% respectively.

[0169] As can be seen from the above examples and comparative examples, the artificial pumice prepared by the preparation method provided by the present invention has high effective porosity and high water permeability.

[0170] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an artificial pumice stone comprises the following steps: (1) mixing a main material, an organic foaming agent, an inorganic foaming agent, a foaming aid, a directing agent, an air retaining agent and water to obtain a slurry; the main material comprises natural clay and / or a silicon-aluminum ratio blending agent; the directing agent comprises didodecyl dimethyl-γ-diquaternary ammonium salt and felbinac; (2) foaming and drying the slurry obtained in step (1) in sequence to obtain a blank; the foaming temperature is 160-200° C.; (3) The blank obtained in step (2) is granulated, sintered and activated in sequence to obtain artificial pumice.

2. The preparation method according to claim 1, characterized in that: The natural clay in step (1) is water-washed and purified natural clay with a particle size of 100-200 meshes.

3. The preparation method according to claim 1, characterized in that: The silicon-aluminum ratio adjusting agent in step (1) is Al4[Si4O 10 ][OH]8, the purity of the silicon-aluminum ratio adjusting agent is above 95%, and the particle size of the silicon-aluminum ratio adjusting agent is 200~300 mesh.

4. The preparation method according to claim 1, characterized in that: In the step (1), the organic foaming agent is at least one of azodicarbonamide, DPT and peracetic acid, and the organic foaming agent accounts for 0.5-1% of the mass of the main material.

5. The preparation method according to claim 1, characterized in that: In the step (1), the inorganic foaming agent is at least one of sodium bicarbonate, ammonium bicarbonate, hydrogen peroxide and calcium carbide, and the inorganic foaming agent accounts for 1-2.5% of the mass of the main material.

6. The preparation method according to claim 1, characterized in that: In the step (1), the foaming aid is alum, and the foaming aid accounts for 0.25-1.5% of the mass of the main material.

7. The preparation method according to claim 1, characterized in that: In the step (1), the air retaining agent is polypropylene alcohol, and the air retaining agent accounts for 0.5-2% of the mass of the main material.

8. The preparation method according to claim 1, characterized in that: The activator used for activation in step (3) is an aqueous solution of at least one of citric acid, polylactic acid and itaconic acid.

9. The preparation method according to claim 8, characterized in that: The mass concentration of the activator is 3-5%.

10. The artificial pumice prepared by the preparation method according to any one of claims 1 to 9.

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