Artificial pumice stone and preparation method therefor

Abstract

The present invention relates to the technical field of artificial pumice stones, and provides an artificial pumice stone and a preparation method therefor. The present invention performs foaming at 160-200° C, with an organic blowing agent, an inorganic blowing agent, and a foaming aid generating a large volume of gas bubbles, which form a large number of pores and interstices in a material; during a sintering process, a structure-directing agent guides intermolecular packing and bridging by means of a biphenyl structure, and a quaternary ammonium group and a biphenyl center provide an alkyl linker of a sufficient length, guiding capillary self-assembly within the interstices, so that a primary material changes from a lamellar structure to a tubular structure, allowing for the formation of open pores inside the material and capillaries with through-channels connecting the pores inside the material to a surface of the material, thereby improving the effective porosity and water permeability of an artificial pumice stone. The use of an air-entraining agent allows for the material to be wrapped, so as to prevent gas bubbles generated during foaming from escaping quickly, thereby improving the effective porosity; and the micropores and the capillary channels of the artificial pumice stone are further strengthened by means of activation, thereby improving effective porosity and water permeability.

Description

Artificial pumice and method for preparing the same

[0001] This application claims priority to the Chinese patent application No. 202411317006.1, filed on September 20, 2024, and entitled "Artificial pumice and method for preparing the same", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of artificial pumice production, and in particular to an artificial pumice and a method for preparing the same. BACKGROUND

[0003] In water treatment, filter media is needed to be used to treat organic matter in water and store water. The two main functions of filter media are filtration and adsorption, and water permeability. Both of these properties are directly related to the effective porosity of the filter media itself. The effective porosity of most filter media is not high, and is calculated by the mass ratio (Formula I). The porosity of many filter media, such as pumice, ceramic and glass, is closed pore, which results in a very low specific gravity of the filter media, generally in the range of 0.2-0.5. Theoretically, the porosity is very high, but the available porosity in water treatment is not high, which can cause system clogging and collapse.

[0004] The formula for calculating the mass ratio porosity of filter media at room temperature is shown as Formula I,

[0005] In Formula I, m1 is the mass of the material when dried, and m2 is the mass of the material after being saturated with water.

[0006] In actual water treatment, the effective porosity (volume ratio) is often obtained by using the volume calculation method (Formula II). The effective porosity represents the maximum space liquid storage capacity and the minimum space volume loss, the larger specific surface area and better adsorption capacity, the more surface tension and flow capacity.

[0007] The formula for calculating the effective porosity of filter media at room temperature is shown as Formula II:

[0008] In Formula II, m1 is the mass of the material when dried, m2 is the mass of the material after being saturated with water, and V1 is the volume of the material.

[0009] Currently, the filter material is mainly various porous materials, usually including pumice (or zeolite). The pumice is divided into natural pumice and artificial pumice. The natural pumice has large performance difference, and most of the mass water storage rates are 20% to 50%, and the effective porosities are 10% to 20%. The artificial pumice has good performance, and the artificial pumice commonly used in water treatment is similar to slag, and the internal part is mainly closed pores without through pipes as a connection, so the actual available part is very small, and the mass water storage rate is usually 20 to 80%, and the effective porosity is 10% to 30%. The ceramic and glass pumice products have high mass ratio data, and the highest can reach 200%, but the actual available porosity is very low, generally 10%.

[0010] The water storage pottery clay is a patent previously applied by the technical team of the applicant, and is a new material developed for the artificial wetland for storing rainwater and recycling in the sponge city. The characteristic is that the internal part has a large number of open pores, the mass is very light, the mass water storage rate can reach 80% to 110%, but according to the volume ratio calculation, the effective porosity is only 20% to 30%.

[0011] In summary, most of the filter materials in the current water treatment are porous on the surface to absorb organic matter in the water body, and the effective porosity is low, and the liquid only flows in the gap between the materials, and the phenomenon of blockage caused by no or poor water permeability is prone to occur. Therefore, how to improve the effective porosity of the filter material and the water permeability of the filter material has become a technical problem to be solved in the field. SUMMARY

[0012] The application provides a preparation method of artificial pumice, and the method comprises the following steps:

[0013] (1) mixing main materials, an organic foaming agent, an inorganic foaming agent, a foaming aid, a directing agent, a gas retention agent and water to obtain a slurry; the main materials comprise natural clay and / or a silicon-aluminum ratio adjusting agent; the directing agent is a double alkyl quaternary ammonium salt and a biphenyl acetic acid;

[0014] (2) sequentially foaming and drying the slurry obtained in the step (1) to obtain a blank; the foaming temperature is 160 to 200 DEG C;

[0015] (3) sequentially granulating, sintering and activating the blank obtained in the step (2) to obtain the artificial pumice.

[0016] The application further provides the artificial pumice prepared by the preparation method. DRAWINGS

[0017] Fig. 1 is a real object diagram of the artificial pumice prepared in Example 3;

[0018] Figure 2 is a SEM image of the artificial pumice stone prepared in Example 3 at 1000 times magnification;

[0019] Figure 3 is a SEM image of the artificial pumice stone prepared in Example 3 at 5000 times magnification;

[0020] Figure 4 is a SEM image of the artificial pumice stone prepared in Example 3 at 5000 times magnification;

[0021] Figure 5 is a schematic diagram of the test method of the artificial pumice stone prepared in Example 3;

[0022] Figure 6 is the water permeability data of the artificial pumice stone prepared in Example 3. DETAILED DESCRIPTION

[0023] The present application provides a preparation method of artificial pumice stone, comprising the following steps:

[0024] (1) mixing a main material, an organic foaming agent, an inorganic foaming agent, a foaming aid, a directing agent, a gas retaining agent and water to obtain a slurry; the main material comprises natural clay and / or a silicon-aluminum ratio adjusting agent; the directing agent is a double alkyl quaternary ammonium salt and biphenyl acetic acid;

[0025] (2) sequentially foaming and drying the slurry obtained in step (1) to obtain a blank; the foaming temperature is 160-200℃;

[0026] (3) sequentially granulating, sintering and activating the blank obtained in step (2) to obtain the artificial pumice stone.

[0027] The present application does not have special limitations on the sources of each raw material, and commercially available products known to those skilled in the art can be used.

[0028] The present application mixes a main material, an organic foaming agent, an inorganic foaming agent, a foaming aid, a directing agent, a gas retaining agent and water to obtain a slurry.

[0029] In the present application, the main material comprises natural clay and / or a silicon-aluminum ratio adjusting agent; the natural clay is preferably water-washed and purified natural clay; 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 more than 95%; the particle size of the silicon-aluminum ratio adjusting agent is preferably 200-300 mesh.

[0030] In the present application, when the main material is natural clay and silicon-aluminum ratio adjusting agent, the natural clay is preferably 40-60% of the mass of the main material, more preferably 45-55%, and the silicon-aluminum ratio adjusting agent is preferably 40-60% of the mass of the main material, more preferably 45-55%. The present application can further improve the effective porosity of the artificial pumice by controlling the mass of the natural clay and the silicon-aluminum ratio adjusting agent.

[0031] In the present application, the organic foaming agent is preferably at least one of azodicarbonamide, DPT and peracetic acid, more preferably azodicarbonamide; and the mass of the organic foaming agent is preferably 0.5-1% of the mass of the main material, more preferably 0.5-0.6%. The present application can further improve the effective porosity of the artificial pumice by limiting the amount of the organic foaming agent to the above range.

[0032] In the present application, when the organic foaming agent is azodicarbonamide, the mass of the azodicarbonamide is preferably 0.5-1% of the mass of the main material; and when the organic foaming agent is DPT, the mass of the DPT is preferably 0.5-1% of the mass of the main material.

[0033] In the present application, the inorganic foaming agent is preferably at least one of sodium bicarbonate, ammonium bicarbonate, hydrogen peroxide and calcium carbide, more preferably ammonium bicarbonate; and the mass of the inorganic foaming agent is preferably 1-2.5% of the mass of the main material, further preferably 1.2-2.3%, more preferably 1.5-2.0%. The present application can further improve the effective porosity of the artificial pumice by limiting the amount of the inorganic foaming agent to the above range.

[0034] In the present application, the foaming aid is preferably alum; and the mass of the foaming aid is preferably 0.25-1.5% of the mass of the main material, further preferably 0.5-1.2%, more preferably 0.8-1.0%. The present application can further improve the effective porosity of the artificial pumice by limiting the amount of the foaming aid to the above range.

[0035] In the present application, the directing agent is bisalkyl quaternary ammonium salt and biphenyl acetic acid, preferably bisdodecyl dimethyl-γ-bis quaternary ammonium salt and biphenyl acetic acid; the mass of the directing agent is preferably 0.08-0.12% of the mass of the main material, more preferably 0.1%; and the mass ratio of the bisalkyl quaternary ammonium salt to the biphenyl acetic acid is preferably 1:1. The present application adds the directing agent, which guides the accumulation and bridging between molecules through the biphenyl structure in the sintering process, and the quaternary ammonium group and the biphenyl center provide a long enough alkyl link to guide the capillary self-assembly in the gap, so that the main material changes from a layered structure to a tubular structure, can form open pores in the material and capillary tubes that connect the internal pores of the material to the surface of the material, thereby improving the effective porosity and water permeability of the artificial pumice, and further enhancing the performance of the capillary bundle through the activation of the activator.

[0036] In the present application, the air-retaining agent is preferably polyvinyl alcohol; the air-retaining agent is preferably 0.5-2% of the main material, further preferably 0.6-1.5%, and more preferably 0.8-1.2%. By using the air-retaining agent, the material can be wrapped to prevent the bubbles generated during foaming from escaping quickly, thereby further improving the porosity of the artificial pumice and further improving the effective porosity; limiting the amount of air-retaining agent to the above range can further improve the effective porosity of the artificial pumice.

[0037] The present application does not have special limitations on the molecular weight of the polyvinyl alcohol, and commercially available products known to those skilled in the art can be used.

[0038] In the present application, the water is preferably 30-70% of the main material, and more preferably 50-60%.

[0039] In the present application, the mixing of the main material, organic foaming agent, inorganic foaming agent, foaming aid, directing agent, air-retaining agent and water preferably includes the following steps:

[0040] 1) Mix the organic foaming agent and the foaming aid to obtain a first mixture;

[0041] 2) Mix the main material, the first mixture obtained in step 1), the inorganic foaming agent and the directing agent to obtain a second mixture;

[0042] 3) Mix the air-retaining agent and the water to obtain an air-retaining agent solution;

[0043] 4) Mix the second mixture obtained in step 2) and the air-retaining agent solution obtained in step 3);

[0044] Steps 1)-2) and step 3) have no sequence.

[0045] The present application preferably mixes the organic foaming agent and the foaming aid to obtain a first mixture.

[0046] The present application does not have special limitations on the mixing of the organic foaming agent and the foaming aid, and the technical solution for preparing the mixed material known to those skilled in the art can be used.

[0047] After obtaining the first mixture, the present application preferably mixes the main material, the first mixture, the inorganic foaming agent and the directing agent to obtain a second mixture.

[0048] The present application does not have special limitations on the mixing of the main material, the first mixture, the inorganic foaming agent and the directing agent, and the technical solution for preparing the mixed material known to those skilled in the art can be used.

[0049] The present application preferably mixes the air-retaining agent and the water to obtain an air-retaining agent solution.

[0050] The present application does not have special limitation on the operation of mixing the gas preservative and water, and the preparation of mixed materials can be achieved by using the technical solution known by those skilled in the art.

[0051] After obtaining the second mixed material and the gas preservative solution, the present application preferably mixes the second mixed material and the gas preservative solution.

[0052] The present application does not have special limitation on the operation of mixing the second mixed material and the gas preservative solution, and the preparation of mixed materials can be achieved by using the technical solution known by those skilled in the art.

[0053] After the mixing is completed, the present application preferably ages the product obtained by mixing to obtain a slurry.

[0054] In the present application, the temperature of the aging is preferably room temperature, and the time of the aging is preferably 12-24h, more preferably 15-24h. The present application can be fully infiltrated by aging.

[0055] After obtaining the slurry, the present application sequentially foams and dries the slurry to obtain a blank. The present application foams at 160-200℃, and the organic foaming agent, the inorganic foaming agent and the foaming aid can generate a large amount of bubbles to form a large number of pores and gaps in the material.

[0056] In the present application, the temperature of the foaming is 160-200℃, more preferably 170-180℃, and the time of the foaming is preferably 50-120min, more preferably 60-100min. The present application can rapidly increase the temperature of the mud by foaming at high temperature, so that the foaming agent can fully react in a short time to generate a large amount of bubbles, and the effective porosity of the artificial floating stone can be further improved by controlling the temperature and time of the foaming.

[0057] The present application does not have special limitation on the operation of drying, as long as the water content of the blank is controlled to be below 10%.

[0058] After obtaining the blank, the present application sequentially granulates, sintering and activates the blank to obtain an artificial floating stone.

[0059] In the present application, the blank preferably further includes cutting before granulation. The present application does not have special limitation on the operation of cutting, and the operation can be achieved by using the operation known by those skilled in the art. The present application is beneficial to the subsequent granulation by cutting.

[0060] The present application does not have special limitation on the operation of granulation, and the operation can be achieved by using the operation known by those skilled in the art.

[0061] In the present application, the particle size obtained by the granulation is preferably 0.5-1.5cm, more preferably 0.5-1cm or 1-1.5cm.

[0062] In the present application, the sintering temperature is preferably 800-1000℃, more preferably 850-900℃; the sintering time is preferably 60-90min, more preferably 60-70min. The present application can realize mullitization through sintering, thereby improving the strength of artificial pumice; in the sintering process, the directing agent guides the molecular stacking and bridging through the biphenyl structure, the quaternary ammonium group and the biphenyl center provide long enough alkyl link, and the capillary self-assembly is guided in the gap, so that the main material changes from a layered structure to a tubular structure, and open pores can be formed in the material, and the capillary can connect the internal pores of the material to the surface of the material, thereby improving the effective porosity and water permeability of the artificial pumice.

[0063] In the present application, the activation agent used in the activation is preferably an aqueous solution of at least one of citric acid, polylactic acid and glycolic acid; the mass concentration of the activation agent is preferably 3-5%, more preferably 3.5-4.0%. The present application does not have special limitations on the amount of the activation agent, as long as the product obtained by sintering is completely soaked in the activation agent.

[0064] In the present application, the activation temperature is preferably room temperature; the activation time is preferably >10min, further preferably 12-20min, more preferably 15min. The present application can precipitate impurities in the material through activation to obtain pure material, thereby further strengthening the micro-pores and capillary pipes of the artificial pumice and improving the effective porosity.

[0065] After the activation is completed, the present application preferably performs water washing on the product obtained by the activation to obtain artificial pumice.

[0066] The present application does not have special limitations on the operation of the water washing, and the operation well known to those skilled in the art can be used.

[0067] The artificial pumice prepared by the preparation method provided by the present application is improved on the basis of traditional porous materials to be a connected structure rich in penetrating honeycomb capillary pipes and a large number of open pores. This structure can produce a large number of pores in the material while producing a large number of honeycomb capillary pipes penetrating through the entire material. These pipes simultaneously connect the external space and the pores in the material. This structure not only greatly increases the effective porosity of the material in the water treatment process, but also actively absorbs liquid (siphon effect) by using the surface tension of the liquid. At the same time, the structure connected with the pipes on each particle of the artificial pumice can also conduct liquid, which makes the water permeability of the space formed by the material very high, greatly increases the space for absorbing liquid in the material, greatly reduces the possibility of blockage, and also brings good adsorption capacity. At present, it is first appeared in the common materials for water treatment.

[0068] The application further provides the artificial pumice prepared by the preparation method.

[0069] In the application, the inside of the artificial pumice is a structure combined with micro-pores and through-pipe.

[0070] The artificial pumice of the application is a porous material combined with silicon and carbon, the outside of which is similar to conventional porous materials, and the inside of which is a structure combined with micro-pores and through-pipe, through which a considerable number of voids can be formed inside the material, and in the liquid, the voids and the liquid surface tension can combine the liquid to flow freely inside the material, similar to siphon effect, so as to improve the water permeability of the material inside.

[0071] The main composition of the honeycomb-shaped capillary pipe inside the artificial pumice material of the application is silicon oxide and aluminum oxide molecules.

[0072] The effective porosity of the artificial pumice provided by the application is embodied in the following points:

[0073] 1) The porosity is 40% to 60% (volume ratio) and 80% to 140% (mass ratio) by using standard immersion method test;

[0074] 2) Each particle can saturate and absorb 40% to 60% of the volume of liquid water in the test;

[0075] 3) The specific surface area is greater than or equal to 60 cm 2 / g (BET method);

[0076] 4) High water permeability.

[0077] The high water permeability of the artificial pumice provided by the application is embodied in the following points:

[0078] 1) In normal temperature, it can quickly reach saturation in one minute of soaking in water;

[0079] 2) In the water permeability test, there is no water head loss (simulating aeration biological filter);

[0080] 3) In the filtration test, no clogging phenomenon is found after long-term use of 200 times;

[0081] 4) In the artificial wetland mode test, in the summer outdoor temperature of 35 to 40℃ environment, it can continuously maintain soil humidity of 23 to 30% without watering for one month.

[0082] At the same time, the increase of effective porosity also increases the specific surface area, which improves the organic matter adsorption capacity of the material and also improves the liquid storage capacity in the space.

[0083] In the application, the shape of the artificial pumice is preferably porous block, angular gravel, cobblestone, spherical, columnar or powder.

[0084] In the present application, the physical parameters of the artificial pumice are as follows:

[0085] Bulk density: 0.33-0.67 tons per cubic meter;

[0086] Specific surface area: > 60 cm 2 / g;

[0087] Porosity: 40-60%; (volume ratio)

[0088] Mass water storage rate: 80-140%;

[0089] Effective porosity: 40-60%;

[0090] Cylinder pressure strength: 0.5-2 MPa

[0091] Appearance: white, yellowish-brown, red-brown or grayish-white; spherical or ellipsoidal;

[0092] Particle size: 5-15 mm;

[0093] Composition: silicon oxide, aluminum oxide or iron oxide.

[0094] The present application simulates the formation principle of volcanic rocks to produce a kind of artificial pumice containing a large number of micro-pores and capillary tubes, which not only can store a large amount of flowable liquid, but also can use the capillary siphon effect to maintain the flowability of the liquid therein, so that it will not be blocked, greatly improving the performance of the artificial pumice while greatly reducing the manufacturing cost of the artificial pumice. This feature allows it to be used for water purification, constructed wetlands, soil improvement and agricultural production in arid areas.

[0095] The artificial pumice provided by the present application increases a large number of honeycomb tube structure capillary pipes on the basis of the original water storage pottery, which are connected with the pores and the outside of the material, ensuring the maximum liquid storage capacity and water permeability of the material inside, improving the water treatment effect and efficiency and saving cost. The mass water storage rate is 80-140%, and the effective porosity is 40-60%. It is the porous material with the highest liquid storage capacity, and the space water storage rate after stacking can reach 70%, of which 30-40% is inter-particle water storage, and 40-50% is internal water storage of the material.

[0096] The artificial pumice provided by the present application has open pores inside and through pipes connecting the pores inside the material to the surface of the material, so that the material has very strong liquid absorption capacity and can absorb water to saturation state within one minute. It also can output internal water to the surface under appropriate conditions. It has more external and internal specific surface area, which improves its ability to absorb organic matter in water.

[0097] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Apparently, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application.

[0098] The natural clay used in the embodiments is a river water-washed natural clay in Guangdong.

[0099] Embodiment 1

[0100] A preparation method of the artificial pumice stone comprises the following steps:

[0101] (1) 100-mesh water-washed natural clay is mixed with Al4[Si4O 10 ][OH]8 with a purity of more than 95% and a particle size of 300 meshes to obtain a raw material 1; wherein the water-washed natural clay accounts for 40% of the total mass of the water-washed natural clay and Al4[Si4O 10 ][OH]8, and the Al4[Si4O 10 ][OH]8 accounts for 60% of the total mass of the water-washed natural clay and Al4[Si4O 10 ][OH]8;

[0102] (2) 1% of azodicarbonamide by mass of the raw material 1 is mixed with 1.5% of alum by mass of the raw material 1 to obtain a first mixture;

[0103] (3) 2.5% of ammonium bicarbonate by mass of the raw material 1, 0.05% of didodecyldimethyl-γ-bis quaternary ammonium salt by mass of the raw material 1, and 0.05% of biphenyl acetic acid by mass of the raw material 1 are mixed with the raw material 1 and the first mixture in a dry powder mixer for 15 min to obtain a second mixture;

[0104] (4) 60% of water by mass of the raw material 1 is selected, and 2% of polypropylene glycol-2000 by mass of the raw material 1 is added into a liquid mixer to obtain a gas preservative solution;

[0105] (5) the second mixture and the gas preservative solution are placed into a mud stirrer for stirring for 15 min to obtain a slurry;

[0106] (6) the slurry is aged for 24 h, and then foamed at 200°C for 60 min, and then dried to a water content of less than 10% to obtain a blank;

[0107] (7) the blank is cut into small pieces with a diameter of 1 cm*1 cm*1 cm, and then placed into a disc granulator to obtain spheres with a diameter of 1 cm;

[0108] (8) Put the ball into 850℃ sintering furnace for 60min, then soak in 3.5% citric acid solution for 15min, and then get the artificial pumice after washing.

[0109] Example 2

[0110] A method for preparing artificial pumice is as follows:

[0111] (1) Mix 0.5% azodicarbonamide and 0.5% alum in the water-washed natural clay to obtain the first mixture;

[0112] (2) Mix 1.0% ammonium bicarbonate, 0.05% didodecyldimethyl-γ-bis quaternary ammonium salt, 0.05% biphenyl acetic acid in the water-washed natural clay in the dry powder mixer for 15min to obtain the second mixture; wherein the particle size of the water-washed natural clay is 100 mesh;

[0113] (3) Select 30% water in the water-washed natural clay, and add 0.5% polypropylene glycol-2000 into the liquid mixer to obtain the air-retaining agent solution;

[0114] (4) Put the second mixture and the air-retaining agent solution into the mud mixer and stir for 15min to obtain the slurry;

[0115] (5) Age the slurry for 24h, then foam at 200℃ for 120min, and then dry to less than 10% moisture content to obtain the blank;

[0116] (6) Cut the blank into small pieces with a diameter of 1cm*1cm*1cm, and then put them into the disc granulator to obtain the balls with a diameter of 1cm;

[0117] (7) Put the balls into 1000℃ sintering furnace for 90min, then soak in 3% citric acid solution for 15min, and then get the artificial pumice after washing.

[0118] Example 3

[0119] A method for preparing artificial pumice is as follows:

[0120] (1) Mix 100 mesh water-washed natural clay and 95% or more pure Al4[Si4O 10 ][OH]8 with a particle size of 200 mesh to obtain the ingredient 1; wherein the water-washed natural clay is 45% of the total mass of the water-washed natural clay and Al4[Si4O 10 ][OH]8, and Al4[Si4O 10][OH] is water-washed natural clay and Al4[Si4O 10 ]8total mass of 55%;

[0121] (2) 1% of the mass of the ingredients 1 azodicarbonamide mixed with 1% of the mass of the ingredients 1 alum, to get the first mixture;

[0122] (3) 1.5% of the mass of the ingredients 1 ammonium bicarbonate, 0.05% of the mass of the ingredients 1 didodecyl dimethyl-γ-bis quaternary ammonium salt, 0.05% of the mass of the ingredients 1 biphenyl acetic acid and ingredients 1 with the first mixture placed in a dry powder mixer mixing and stirring for 15 min, to get the second mixture;

[0123] (4) select 40% of the mass of the ingredients 1 water, 1.5% of the mass of the ingredients 1 polypropylene glycol-2000 into the liquid mixer to get the gas retention agent solution;

[0124] (5) the second mixture and the gas retention agent solution into the mud mixer, stirring for 15 min, to get the slurry;

[0125] (6) the slurry placed 24 h for aging, then at 200 ℃ foaming 60 min, and then dried to a moisture content of 10% or less, to get the blank;

[0126] (7) the blank cut into 1 cm * 1 cm * 1 cm small block, and then put into the disc granulator to get the 1 cm diameter sphere;

[0127] (8) the sphere into the 900 ℃ sintering furnace for 90 min, then soaked in a 3% mass concentration of citric acid aqueous solution for 15 min, and then washed to get the artificial pumice.

[0128] The artificial pumice prepared in Example 3 is shown in Figure 1.

[0129] As can be seen from Figure 1, the artificial pumice prepared is ellipsoidal.

[0130] The SEM images of the artificial pumice prepared in Example 3 are shown in Figures 2-4; Figure 2 is a SEM image of the artificial pumice prepared in Example 3 at 1000 times magnification; Figures 3 and 4 are both SEM images of the artificial pumice prepared in Example 3 at 5000 times magnification.

[0131] As can be seen from Figures 2-4, there are a large number of capillary channels and pores mixed together in the artificial pumice prepared in Example, forming a structure of through-type channels and pores connected.

[0132] Comparative Example 1

[0133] Industrial production of artificial pumice (6000 yuan / ton)

[0134] Comparative Example 2

[0135] Water storage clay (CN1218904C)

[0136] The performance tests of the artificial pumice stones prepared in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1, wherein the mass water storage rate and effective porosity (volume water storage rate) are tested by using the standard immersion method (using water at normal temperature and pressure for measurement); the cylinder compressive strength is tested by using the national standard method GB2842-81 "Lightweight aggregate test method", and the following are all average values.

[0137] Table 1 Performance data of the artificial pumice stones prepared in Examples 1-3 and Comparative Examples 1-2

[0138] As can be seen from Table 1, the artificial pumice stones prepared in the present application have good effective porosity and mass water storage rate; in addition, the artificial pumice stones prepared in the present application have excellent cylinder compressive strength.

[0139] Water permeability test

[0140] 1. The saturated adsorption time (water adsorption) of the artificial pumice stones prepared in Examples 1-3 and Comparative Examples 1-2 is tested, and the results are shown in Table 2.

[0141] Table 2 Saturated adsorption time data of the artificial pumice stones prepared in Examples 1-3 and Comparative Examples 1-2

[0142] As can be seen from Table 2, the artificial pumice stones prepared in the present application can actively absorb liquid (siphon effect) by using the surface tension of the liquid, so that saturated adsorption can be carried out in a short time.

[0143] 2. Strong flowability test (simulating BAF biological aerated filter)

[0144] The strong flowability of the artificial pumice stones prepared in Example 3 (in the structure of a large number of open pores + through-type capillary channels, liquid will quickly flow in the channels and pores due to surface tension, so the liquid in the space composed of the material is actually flowing continuously) is tested. In the mode of simulating BAF, a water pump is used to inject water at the same power through the pipe inserted into the bottom to the bottom of the container at a fixed height position. The total amount of water flow and the time when the water level reaches four standard positions of the container are measured by using a weigher and a timer to calculate the flow rate of water flow in the space filled with different particles. The three modes of this test are: no material filling, 5-10 mm particles filling, and 10-15 mm particles filling. In the mode of no filler filling, 4.15 m takes 1 h, and the water amount test is 302 kg. The test method is shown in Figure 5.

[0145] The water permeability data of the artificial pumice prepared in Example 3 is shown in Figure 6.

[0146] As can be seen from Figure 6, the probability of space blockage of the artificial pumice prepared by the present application is greatly reduced; the loss of liquid flowing inside is very small, almost no loss.

[0147] 3. Long-acting

[0148] No blockage phenomenon was found in the long-term use of 200 times in the filtration test of the artificial pumice prepared in Example 3.

[0149] In summary, the artificial pumice prepared by the present application has excellent water permeability.

[0150] The carbon element content of the artificial pumice prepared in Example 3 was detected, and the results are shown in Table 3.

[0151] Table 3 Carbon element content of the artificial pumice prepared in Example 3

[0152] As can be seen from Table 3, the carbon element content of the artificial pumice is relatively low.

[0153] The artificial pumice prepared in Example 3 was subjected to component analysis test; wherein, the instrument model is X-ray fluorescence spectrometer ARL Perform'X, instrument number is 21003415; the test is based on JY / T 0569-2020 wavelength dispersion X-ray fluorescence spectrometry general method; the test method is to add artificial pumice and boric acid into a tablet press, and press into a circular block with a diameter of 40 mm, a thickness of 3 mm and a smooth surface, then put the circular block into a sample holder, put it into the instrument sample site, fill in the sample information on the instrument software, start the test, and 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.

[0154] As can be seen from the above examples and comparative examples, the artificial pumice prepared by the preparation method provided by the present application has high effective porosity and high water permeability.

[0155] The above description of the embodiments is only for the purpose of helping to understand the method of the present application and its core idea. It should be noted that, for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application. Various modifications to the embodiments are apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Accordingly, the present application is not to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing artificial pumice, comprising the following steps: (1) mixing a main material, an organic foaming agent, an inorganic foaming agent, a foaming aid, a directing agent, a gas retaining agent and water to obtain a slurry; the main material comprises natural clay and / or a silicon-aluminum ratio adjusting agent; the directing agent is a bis-alkyl quaternary ammonium salt and a biphenyl acetic acid; (2) sequentially foaming and drying the slurry obtained in step (1) to obtain a blank; the foaming temperature is 160-200℃; (3) sequentially granulating, sintering and activating the blank obtained in step (2) to obtain artificial pumice. The natural clay in step (1) is water-washed and purified natural clay with a particle size of 100-200 mesh. 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. The inorganic foaming agent in step (1) is at least one of sodium bicarbonate, ammonium bicarbonate, hydrogen peroxide and calcium carbide, and the inorganic foaming agent is 1-2.5% of the mass of the main material.

2. The production method according to claim 1, characterized by, The foaming aid in step (1) is alum, and the foaming aid is 0.25-1.5% of the mass of the main material.

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

4. The method of claim 1, wherein, The mass of the directing agent in step (1) is 0.08-0.12% of the mass of the main material.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the bis-alkyl quaternary ammonium salt to the biphenyl acetic acid in step (1) is 1:

1.

6. The method of claim 1, wherein, The gas retaining agent in step (1) is polypropylene glycol, and the gas retaining agent is 0.5-2% of the mass of the main material.

7. The preparation method according to claim 1, characterized in that, The foaming time in step (2) is 50-120 min.

8. The method of claim 1, wherein, The sintering temperature in step (3) is 800-1000℃, and the sintering time is 60-90 min.

9. The method of claim 1, wherein, The activating agent used in step (3) is an aqueous solution of at least one of citric acid, polylactic acid and cumic acid.

10. The method of claim 1, wherein, The mass concentration of the activating agent is 3-5%.

11. The method of claim 1, wherein, The activation temperature in step (3) is room temperature, and the activation time is >10 min.

12. The method of claim 1, wherein, 15. Artificial pumice prepared by the method of any one of claims 1-14.

13. The method of claim 12, wherein, The artificial pumice has a structure in which micro-pores and through-pipes are combined.

14. The method of claim 1, wherein, ​ ​ 16. The artificial pumice of claim 15, wherein, ​

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