TW201827358A - Method for preparing porous material - Google Patents

Abstract

The present invention provides a method for preparing a porous material, comprising: providing a dry sludge generated by chemical mechanical polishing in a semiconductor process; mixing and grinding the dry sludge, a clay mineral and a foaming agent to form a powder; mixing the powder and a binding agent to obtain a mixture; and then bloating the mixture at high temperature to obtain the porous material.

Description

 Method for preparing porous material  

The present invention relates to a method of producing a porous material, which is characterized in that a sludge produced by chemical mechanical polishing in a semiconductor process is converted into a porous material.

Lightweight aggregates originated in 1908. The United States used expansive clay and shale to be fired at high temperatures in a rotary kiln. In the selection of raw materials for burning lightweight aggregates, there are natural raw materials such as perlite, rosin rock, shale, slate and vermiculite. However, due to the acquisition of natural raw materials, mineral mining is required, and the damage to the environment is large. It is also not easy for countries with such mineral scarcity to develop lightweight aggregates. Since the 1970s, the development of raw materials for lightweight aggregates has selected industrial wastes such as expanded slag, coal gangue ceramsite, fly ash, sewage sludge, industrial sludge and fly ash; in Taiwan until the 1990s, The use of reservoir sludge as a lightweight aggregate to develop lightweight concrete.

Therefore, as the materials used to prepare the lightweight aggregates are different, the process will vary. The original method of making lightweight aggregates uses natural minerals as raw materials, such as shale or expanded clay. After mining, the minerals are crushed and sieved to the appropriate size and then enter the rotary kiln for sintering and expansion. Out of the product. Depending on the manufacturer, the pelletizing process is carried out during the process, so that the aggregate forms a circular granule of about 5 mm to 20 mm in size, which has different products depending on the size of the granule, circular granules. The main reason is that it can help the concrete to flow at high pressure, so the circular aggregate with low water absorption is more used by the industry. If the raw materials are used for industrial waste, in order to maintain the uniformity of the ingredients, the ingredients need to be added in the process to maintain the temperature conditions for subsequent firing and expansion. The German Dennert Poraver Company uses waste glass for the production of expanded aggregates. In addition to the production of lightweight aggregates from 5mm to 10mm, and successfully used spray granulation in 2003 to produce ultra-fine lightweight aggregates, the minimum particle size can reach 0.04mm. Due to the extension of the particle size range, the aggregates are used in production. Lightweight concrete can also be added to the coating, showing that lightweight aggregates are not limited to building materials.

In addition, when preparing lightweight aggregates, a firing process is required to cause expansion to form a porous structure. Previous studies have indicated that cerium oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ) and flux (sodium oxide (Na ₂ O), potassium oxide (K ₂ O), calcium oxide (CaO)) can be used as long as they meet a certain range of composition. , magnesium oxide (MgO), iron oxide (Fe ₂ O ₃ )), firing temperature of about 1100 ° C to 1300 ° C can achieve the effect of foaming, wherein SiO ₂ affects the viscosity of the glass phase, the higher the content, the The viscosity of the glass phase is also increased. The influence on the properties of the aggregate is to reduce the strength of the aggregate; the alumina affects the strength and density of the aggregate; the other flux affects the viscosity of the glass phase, and when the content increases, the glass The viscosity of the phase decreases. According to other studies, the manufacturing process of lightweight aggregates must meet two conditions: (1) When the raw material is heated to high temperature, it must be able to form a viscous glass phase to cover the fugitive gas; when the glass phase viscosity At higher levels, the resulting pores are finer, and when the viscosity is low, the pores generated inside are large; and (2) the surface must be formed to form a glass phase before the gas inside the raw material is generated.

Because the lightweight aggregate is a porous mineral material, it can be obtained by high-temperature firing, so it has fire-resistance properties, and because of its structural relationship, it has sound insulation, heat insulation and light weight effect, and is used according to physical properties. The use of structural concrete and non-structural concrete, such as road asphalt, structural beams of high-rise buildings or soundproof walls.

With the development of the semiconductor industry, the demand for wafer size has increased from 8吋 to 12吋. In order to accumulate more components on the wafer, wafer flattening has become a standardized process, chemical mechanical polishing ( The Chemical-Mechanical Polishing; CMP) method is currently the main method of flattening the wafer. In the CMP slurry, many nano-sized cerium oxide (SiO ₂ ) particles are mixed as abrasive granules. Suspended in waste water, in order to reduce environmental impact and meet wastewater discharge standards, CMP process wastewater has a number of sludges composed of nano particles and floes after a certain treatment process and filtration. The type of floc is white and brown.

At present, the treatment of CMP sludge is mostly buried. If the particles of extremely fine size are suspended in the water body, it is more likely to cause secondary pollution due to turbidity problems. The reason for choosing to bury is because there is no perfect recycling method to treat CMP. The sludge is recycled and reused.

Therefore, CMP sludge contains a high amount of cerium oxide (SiO ₂ ), so if it can be converted into a recycled material through a special process, it will contribute to environmental protection and resource reuse.

A main object of the present invention is to provide a regenerated aggregate using a business waste as a material and a method for regenerating the same, which is produced by a chemical-mechanical polishing (CMP) process when a wafer is manufactured by a semiconductor factory. Waste (such as sludge) can be converted into light aggregate by adding other substances to change its chemical composition and then sintering and expanding. The lightweight aggregate has the characteristics of heat insulation, light weight and water absorption, and can be used for concrete construction. Therefore, the product of the invention has the environmental protection benefits of waste reduction and resource reuse.

The articles "a" or "an" are used herein to describe the elements and compositions of the invention. This terminology is only for convenience of description and the basic idea of the invention. This description is to be construed as inclusive of the singular When used in conjunction with the word "comprising", the term "a" may mean one or more than one.

The term "or" in this document means "and/or".

In order to achieve the foregoing objects, the present invention provides a method of preparing a porous material comprising: (1) providing a sludge produced by chemical mechanical polishing in a dry semiconductor process; and (2) drying the semiconductor The sludge produced by the chemical mechanical polishing in the process is mixed with a clay mineral to obtain a first mixture, a foaming agent is added to the first mixture, and ground into a powder to obtain a second mixture; (3) The second mixture is mixed with a binder to obtain a third mixture; and (4) sintered to expand the third mixture to obtain a porous material.

Chemical mechanical polishing and wet pickling in the wafer manufacturing process of the semiconductor industry generate chemical mechanical polishing sludge (CMP sludge), which is a commercial waste, because the CMP sludge contains various The oxidizing agent, the additive, the dispersing agent, the organic and inorganic compound of the grinding buffer, and the like, and further contain a large amount of fine particles such as nanometer-sized cerium oxide (SiO ₂ ) or aluminum oxide (Al ₂ O ₃ ). At the same time, the CMP sludge will contain a large amount of water (water content of about 55 to 70%), so the CMP sludge needs to be dried (for example, hot air drying) so that the water content is less than 5%, and then the subsequent process is carried out. Therefore, the "sludge produced by chemical mechanical polishing in a dry semiconductor process" of the present invention is obtained by drying CMP sludge produced from a semiconductor wafer manufacturing plant. In one embodiment, the moisture produced by the chemical mechanical polishing in the dry semiconductor process has a moisture content of less than 5%. In a preferred embodiment, the moisture produced by the chemical mechanical polishing in the dry semiconductor process has a moisture content of less than 3%. In a more preferred embodiment, the moisture produced by the chemical mechanical polishing in the dry semiconductor process has a moisture content of less than 1%. In a specific embodiment, the method of the present invention further comprises a step (1'), which is performed prior to the step (1), comprising providing a sludge produced by chemical mechanical polishing in a semiconductor process, and drying the semiconductor process The sludge produced by the chemical mechanical grinding process is used to obtain the sludge produced by chemical mechanical polishing in a dry semiconductor process.

In another embodiment, the amount of cerium oxide in the sludge produced by chemical mechanical polishing in the dry semiconductor process is 60% or more. In a preferred embodiment, the amount of cerium oxide in the sludge produced by chemical mechanical polishing in the dry semiconductor process is 65% or more. In a more preferred embodiment, the amount of cerium oxide in the sludge produced by chemical mechanical polishing in the dry semiconductor process is 70% or more.

The term "clay mineral" as used herein includes, but is not limited to, layered citrate minerals. In one embodiment, the clay mineral comprises a kaolin, a bentonite, a mica, a pyrophyllite, a smectite, a vermiculite, and a talc. In a preferred embodiment, the clay mineral is a kaolin.

The term "foaming agent" as used herein includes, but is not limited to, a monocarbonate. In one embodiment, the blowing agent comprises sodium carbonate, sodium hydrogencarbonate, sodium percarbonate, monocalcium carbonate, and calcium carbonate. In a preferred embodiment, the blowing agent is sodium carbonate or calcium carbonate.

In one embodiment, the sludge produced by the chemical mechanical polishing in the dry semiconductor process comprises from 85% to 95% by weight of the first mixture. In another embodiment, the clay mineral comprises from 5% to 15% by weight of the first mixture. In one embodiment, the blowing agent is added in an amount from 0.5% to 8% by total weight of the first mixture.

After the first mixture and the foaming agent are mixed together, the first mixture is ground to obtain the powdery second mixture, and the "grinding" can be carried out by a conventional grinding method without limitation. Good for ball milling. The second mixture of the powder obtained after the grinding is sieved, and the purpose of the sieving is to obtain powder particles having a smaller average particle diameter, which will facilitate uniform mixing and mixing after the reaction with the binder. . The present invention uses a 100 to 200 mesh screen; preferably, a 200 mesh screen is used. Preferably, after the sieving step, the particle size of the powder particles to be screened is less than 150 μm; more preferably, the particle size of the powder particles to be screened is less than 75 μm. In a specific embodiment, the method of the present invention further comprises a step (2') between steps (2) and (3) comprising sieving the second mixture to make the powder of the second mixture The particle size of the bulk particles is less than 150 μm.

The term "adhesive" as used herein includes, but is not limited to, a solvent having the function of bonding powders (e.g., a second mixture of powders) to each other. In one embodiment, the binder comprises from 18% to 60% by weight of the third mixture.

In another embodiment, the binder comprises an alkali metal compound solution or an alkaline earth metal compound solution. The term "alkali metal compound solution" as used herein refers to a solution containing an alkali metal ion such as lithium ion, sodium ion or potassium ion. In one embodiment, the alkali metal compound solution is an alkali metal hydroxide solution or an alkali metal oxide solution. In a preferred embodiment, the alkali metal hydroxide solution is a sodium hydroxide solution. The term "alkaline earth metal compound solution" as used herein refers to a solution containing an alkaline earth metal ion such as barium ion, magnesium ion or calcium ion. In one embodiment, the alkaline earth metal compound solution is an alkaline earth metal hydroxide solution or an alkaline earth metal oxide solution. In a preferred embodiment, the alkaline earth metal hydroxide solution is a calcium hydroxide solution.

The second mixture of the present invention is mixed with a binder to form a paste (i.e., a third mixture). At this time, the user can granulate the paste according to the requirements of the product in the future, that is, cut into a desired size, for example, a particle having a particle size of 1 or 3 mm, and then perform a sintering expansion operation; or directly The paste is not granulated for sintering expansion. In a specific embodiment, the method of the present invention further comprises a step (3"), which is carried out in the middle of steps (3) and (4), comprising granulating the third mixture, ie cutting the third mixture Particles of a certain size. In one embodiment, the granulation cuts the third mixture into particles having a particle size of less than 5 mm. In a preferred embodiment, the granulation system is the third mixture. The granules are cut into particles having a particle size of less than 3 mm. In a more preferred embodiment, the granulation system cuts the third mixture into granules having a particle size of less than 1 mm.

The term "sintering expansion" as used herein encompasses the use of a high temperature furnace for sintering expansion, wherein the high temperature furnace comprises an electric kiln, a gas kiln and a kiln. The present invention does not directly perform the sintering expansion of the third mixture or the third mixture after granulation, and the sintering expansion temperature ranges from 400 ° C to 800 ° C; preferably, the sintering expansion temperature ranges from 500 ° C To 700 ° C; more preferably, the sintering expands at a temperature in the range of 500 ° C to 600 ° C. The third mixture or the third mixture after granulation is directly sintered and expanded without drying, and is obtained as a highly water-absorptive porous material. Therefore, in one embodiment, the water absorption of the porous material is 70% by weight or more; preferably, the water absorption is 80% by weight or more; more preferably, the water absorption is 90% by weight or more.

Further, the present invention may further dry the third mixture or the third mixture after granulation, wherein the "drying" may be carried out by a conventional drying method without limitation, and is preferably hot air drying. The method of the present invention further comprises a step (3') in the middle of the steps (3) and (4), the step (3') comprising drying the third mixture. Further, if the third mixture is to be granulated (i.e., step (3")), the drying operation of the step (3') is carried out after the granulation operation of the step (3"). In one embodiment, the drying temperature ranges from 40 °C to 60 °C. In another embodiment, the third mixture after drying has a moisture content of less than 20%. In a preferred embodiment, the third mixture after drying has a moisture content of less than 15%. In a more preferred embodiment, the third mixture after drying has a moisture content of less than 10%.

The present invention performs the sintering expansion operation of the third mixture after drying, and the sintering expansion temperature ranges from 600 ° C to 800 ° C; preferably, the sintering expansion temperature ranges from 600 ° C to 750 ° C; more preferably The sintering expands at a temperature ranging from 650 ° C to 700 ° C. The third mixture after drying or the third mixture after granulation and drying is sintered and expanded to obtain a low water absorbing porous material. In a specific embodiment, the water absorbing material has a water absorption ratio of 35 wt% or less; preferably, the water absorption ratio is 25 wt% or less; more preferably, the water absorption ratio is 15 wt% or less. Therefore, the present invention can change the water absorption rate of the porous material which is sintered and expanded after the third mixture is dried. Therefore, the present invention can produce a porous material having a high or low water absorption rate in accordance with the demand for product utilization.

The term "porous material" as used herein is not limited to a ceramic material having pores (or porous). Because porous ceramic materials have the advantages of high temperature resistance, high stability, low thermal conductivity, high flushing resistance, high specific surface area, porous holes, closed or through holes, and material specificity, lightweight bones for construction can be developed. Materials, heat-insulating aggregates, gardening moisturizing materials, soil care materials or water filtration materials. In one embodiment, the porous material is an aggregate. Since the porous material of the present invention has a pore structure, it is light in weight and has a density of less than 1 g/cm ³ ; preferably, the density is less than 0.5 g/cm ³ . In a preferred embodiment, the porous material is a lightweight aggregate.

The present invention provides a lightweight aggregate having a spherical body, wherein the spherical body has a plurality of holes.

In a specific embodiment, the spherical body is made of a ceramic material. In a preferred embodiment, the ceramic material is a chalk.

In another embodiment, the spherical body has a diameter of less than 5 mm. In a preferred embodiment, the spherical body has a diameter of less than 3 mm. In a more preferred embodiment, the spherical body has a diameter of less than 1 mm.

The method for preparing a porous material provided by the present invention has the following advantages when compared with other conventional techniques:

(1) The present invention expands a waste sludge (CMP sludge) into a porous material (such as a lightweight aggregate) by a special process, so that the regenerated porous material can be used for various purposes such as construction, civil engineering, agriculture, and the like. The most important application of lightweight aggregates is as a graded component of lightweight concrete, mainly providing light, sound insulation and heat insulation effects, while the high water content of the aggregate is applied to horticultural materials as soil water retention material. There are also a small number of high-permeability aggregates that are used as water purification sediment filters. The porous structure of lightweight aggregates should develop higher value-added functional materials in the future, or combined with surface treatment methods to make the surface have special properties, not just as building materials, thereby improving lightweight bone. The applicability and economic output value of the material, whether its porous nature can develop gas storage carriers, special gas adsorption materials, special liquid loading containers and soil nutrient preservation materials. Therefore, the process of the present invention can achieve the effects of "zero waste", "reuse of resources" and "additional value of reused products", so the present invention has practical value.

(2) The drying of the mixture before sintering of the present invention can affect the degree of water absorption of the resulting porous material. Therefore, a different step in the same process can obtain different products, which is beneficial to the efficiency of the process and the manufacture of the product.

(3) The present invention uses a high by-product industrial by-product (CMP sludge) to produce a lightweight aggregate under a sintering expansion procedure of less than 800 ° C, and to produce a lightweight aggregate compared to other existing sludges. The process has a sintering expansion temperature higher than 900 ° C. The process of the invention uses a lower sintering temperature (less than 800 ° C) to produce a lightweight aggregate, so the invention can effectively reduce heat energy consumption and reduce high temperature. Environmental impact.

10‧‧‧Light aggregate

100‧‧‧ spherical body

200‧‧‧ holes

Figure 1 shows the process of making lightweight aggregates using Chemical-Mechanical Polishing (CMP) sludge.

Figure 2 shows the shape of the granules by extrusion granulation.

Fig. 3 is a low-water ratio porous lightweight aggregate obtained by CMP sludge sample 1.

Figure 4 is a high water rate porous lightweight aggregate obtained from CMP sludge sample 2.

Fig. 5 is a low-water ratio porous lightweight aggregate obtained by using CMP sludge sample 3.

Figure 6 is a view showing the porous structure of the lightweight aggregate of the present invention.

Figure 7 is a view showing the structure of the lightweight aggregate of the present invention.

The invention includes, but is not limited to, the description above and below. The embodiment is shown in the following example.

A. Production process of recycled lightweight aggregate

1. Identification of the components of sludge produced by chemical mechanical polishing in a semiconductor process

When a semiconductor factory applies Chemical-Mechanical Polishing (CMP) to a wafer fabrication process, it produces a large amount of CMP sludge. The three CMP sludge samples are subjected to X-ray Fluorescence Spectrometer (XRF) detection, and the component analysis and detection data are shown in Table 1. From the results of Table 1, the CMP sludge samples are known. The content of cerium oxide (SiO ₂ ) is over 70%, so subsequent processes can be carried out.

2. Preparation process

The process of making lightweight aggregates from CMP sludge is shown in Figure 1. The sequence of steps is as follows:

(1) Drying: CMP sludge will contain a large amount of water (water content of about 55 to 70%) due to the CMP process. Therefore, the CMP sludge can be dried by a hot air drying rotary kiln or a hot air dryer to dry it. The moisture removal of the CMP sludge becomes a CMP sludge block or CMP sludge cake having a moisture content of less than 1%.

(2) Mixing and grinding: a clay mineral (such as kaolin) and a foaming agent (such as sodium carbonate or calcium carbonate) are added to the dried CMP sludge block or CMP sludge cake to adjust its chemistry. Composition, and ball milled to form a powder mixture; and mixing, firstly, 85% to 95% by weight of CMP sludge is mixed with 5% to 15% by weight of clay minerals to obtain a mixture, and then added A blowing agent is added in an amount of from 0.5 to 8% by weight based on the total weight of the mixture.

(3) Stirring: The powder mixture is mixed with a binder which binds the powder mixture into a piece which, when stirred, forms a paste, such as a dough. The binder comprises an alkali metal or alkaline earth metal compound solution; in the case of an alkali metal compound solution, when mixed, the powder mixture is mixed with the alkali metal compound solution in a weight percentage ratio of an alkali metal compound solution of 18% to 60%. %. In the present invention, the alkali metal compound solution is selected from a sodium hydroxide solution.

(4) Granulation: The paste is extruded through an extrusion molding machine and granulated into a target size for granulation to obtain a granulated aggregate. Therefore, the user can granulate according to the size requirement of the final product, for example, dicing into particles having a particle diameter of less than 3 to 5 mm.

(5) Sintering expansion: (i) The granulated aggregates of the pellets are directly subjected to a sintering expansion process in a rotary kiln without drying, and the sintering expansion temperature is 400 to 700 ° C, thereby forming a high water absorption. a porous lightweight aggregate having a rate (water absorption of 70% by weight or more); or (ii) drying the granulated aggregate of the granules again, such as drying under hot air (40 to 60 ° C) to moisture content Less than 15% of the granule aggregate, dried and then sintered and expanded in a rotary kiln, and the sintering expansion temperature is 600 to 800 ° C, thereby obtaining a porous lightweight aggregate having a low water absorption rate (water absorption ratio of 35 wt% or less) .

B. Nature test method

The water absorption rate and density measurement method of the product obtained through the above process is as follows: the product is first measured in the air (Wa), and after being placed in water for 24 hours, the weight (Ww) in the water is measured, and the product is taken out. The surface is wiped to a clean surface and its weight (Wb) is weighed. Therefore, the algorithm for water absorption is (in weight percent): water absorption: [(Wb-Wa)/Wa] x 100%

The algorithm for density is (in g/cm ³ ): density: Wa / [(Wb - Ww) / 1 (density of water)]

Since the measurement medium is water and its density is 1 (g/cm ³ ), its volume and density are pushed back by weight.

Further, the present invention utilizes a pressure cylinder to measure the average relative compressive strength index of the particles as an evaluation of the quality of the coarse particles. The coarse particle barrel compressive strength test method comprises the steps of: (1) screening 5 L of a sample having a particle size of 3 to 5 mm; (2) loading a sample with a pressure tube (with a bottom), and measuring the loose bulk weight three times, respectively. Take the arithmetic mean; (3) Weigh the sample according to the above sample volume, and put it into the pressure cylinder 3 times, each time to be evenly tamped on the surface with a mast for 25 times, and use a wooden hammer to divide the wall around the wall. Tap three to five times at four points, then install the guiding cylinder and the stamping die to check whether the lower scale of the stamping die coincides with the upper edge of the guiding cylinder. If it does not overlap, tap the wall around the cylinder until it is completely coincident; And (4) placing the pressure cylinder on the lower pressure plate of the press, and loading at a uniform speed of about 30 to 50 kgf per second. When the press mold is pressed to a depth of 20 mm, the pressure value is recorded. The calculation of the compressive strength of the pellet is: R = P / F

R: the cylinder strength (kg/cm ² ) of the lightweight aggregate, calculated to the accuracy of 1 kg/cm ² ; P: the pressure value (kg) when the penetration depth is 20 mm; and F: the pressure-bearing area (ie, the stamping die) Area F = 100 cm ² ).

C. Product manufacturing

Product 1 (low water absorption type)

After drying, about 60% of the moisture in the CMP sludge sample 1 was removed, and then 5 wt% of kaolin was added to the 95 wt% dried CMP sludge sample 1 and 0.5 wt% of sodium percarbonate was additionally added, followed by uniform grinding by a ball mill. An aggregate of bone material is formed, wherein the aggregate powder system refers to a powder that can pass through a No. 100 sieve. Further, 5 N molar concentration (about 20% by weight) of sodium hydroxide was mixed with the aggregate powder until the viscosity was suitable, and extrusion granulation was carried out, and the granule size was 3 to 5 mm (Fig. 2). After granulation, the granules are dried again (for example, drying at 40 to 60 ° C under hot air to reduce the water content of the granules to less than 15%), and then performing a sintering expansion process at 680 ° C in a rotary kiln to obtain a porous lightweight material. The aggregate (Fig. 3) has a bulk density of 0.62 g/cm ³ , a bulk density of 0.36 g/cm ³ , a water absorption of 12 wt%, and a compressive strength of 5.34 MPa (about 54.5 kg/cm). ² ).

Product 2 (high water absorption type)

After drying, the CMP sludge sample 2 is removed by about 60% moisture, and 92% by weight of the dried CMP sludge sample 2 is added to 8 wt% of kaolin and an additional 2 wt% of calcium carbonate is added, and then uniformly ground by a ball mill to form an aggregate powder. Body, wherein the aggregate powder system refers to a powder that can pass through a No. 100 sieve. Further, 5 N molar concentration (about 20% by weight) of sodium hydroxide was mixed with the aggregate powder until the viscosity was suitable, and extrusion granulation was carried out, and the granule size was 3 to 5 mm. The granulated granules were directly subjected to a 550 ° C sintering expansion procedure in a rotary kiln to obtain a porous lightweight aggregate (Fig. 4) having a bulk density of 0.37 g/cm ³ and a water absorption of 92 wt%. The compressive strength was 1.23 MPa (about 12.5 kg/cm ² ).

Product 3 (low water absorption type)

When using CMP sludge sample 3 as a raw material, after drying and removing about 60% of water, adding 10 wt% of kaolin in 90 wt% of dried CMP sludge sample 3 and additionally adding 2 wt% of sodium hydrogencarbonate, and then using a ball mill The aggregate is uniformly ground to form an aggregate powder, wherein the aggregate powder system refers to a powder that can pass through a No. 100 sieve. Further, 14 N molar concentration (about 55 wt%) of sodium hydroxide was mixed with the aggregate powder until the viscosity was suitable, and extrusion granulation was carried out, and the granule size was 3 to 5 mm. After granulation, the granules are dried again (for example, drying at 40 to 60 ° C under hot air to reduce the water content of the granules to less than 15%), and then performing a 680 ° C sintering expansion procedure in a rotary kiln to obtain a porous light. The material (Fig. 5) has a bulk density of 0.43 g/cm ³ and a water absorption of 10 wt%.

Fig. 6 is a view showing the porous structure of the product of the above porous lightweight aggregate, which has a porous structure and is light in energy, and has a density of less than 1 g/cm ³ .

Table 2 compares the properties of porous lightweight aggregates made from three CMP sludge samples.

7 is a structure of a lightweight aggregate of the present invention, the lightweight aggregate 10 having a spherical body 100, wherein the spherical body has a plurality of holes 200. The material of the spherical body is a ceramic material, and further, the composition of the ceramic material is a chalk mineral. Further, the spherical body has a diameter of less than 5 mm.

Suitable descriptions of the invention may be implemented in elements or limitations not specifically disclosed herein. The terminology that has been used for description is not limiting. There is no difference in the expression and description of the use of these terms and any equivalents, but it is to be understood that the scope of the invention may be modified. Therefore, the present invention has been described with reference to the embodiments and other aspects, and the modifications and variations of the present invention are considered to be within the scope of the present invention.

Claims (15)

 A method for preparing a porous material, comprising: (1) providing sludge produced by chemical mechanical polishing in a dry semiconductor process; (2) sludge produced by chemical mechanical polishing in the dried semiconductor process and Mixing the clay mineral to obtain a first mixture, adding a blowing agent to the first mixture, and grinding into a powder to obtain a second mixture; (3) mixing the second mixture with a binder to obtain a third mixture; and (4) sintering to expand the third mixture to obtain a porous material.    The method of claim 1, wherein the sludge produced by the chemical mechanical polishing in the dry semiconductor process has a moisture content of less than 1%.    The method of claim 1, wherein the chemical mechanical grinding in the dry semiconductor process comprises from 85% to 95% by weight of the first mixture.    The method of claim 1, wherein the clay mineral comprises from 5% to 15% by weight of the first mixture.    The method of claim 1, wherein the blowing agent is added in an amount of from 0.5% to 8% by weight based on the total weight of the first mixture.    The method of claim 1, wherein the binder accounts for 18% to 60% by weight of the third mixture.    The method of claim 1, wherein the binder comprises an alkali metal compound solution or an alkaline earth metal compound solution.    The method of claim 7, wherein the alkali metal compound solution is an alkali metal hydroxide solution.    The method of claim 8, wherein the alkali metal hydroxide solution is a sodium hydroxide solution.    The method of claim 1, wherein the sintering expands at a temperature in the range of 400 ° C to 800 ° C.    The method of claim 1, wherein the porous material has a water absorption of 70% by weight or more.    The method of claim 1, wherein the step (3) and (4) further comprises a step (3'), the step (3') comprising drying the third mixture.    The method of claim 12, wherein the third mixture after drying has a moisture content of less than 15%.    The method of claim 12, wherein the sintering temperature ranges from 600 ° C to 800 ° C.    The method of claim 12, wherein the porous material has a water absorption of 35 wt% or less.