Incineration bottom ash hollow fiber and method for fabricating the same

Abstract

The present invention provides an incineration bottom ash hollow fiber (BAHF) and a method for fabricating the same. The method includes: selecting incineration bottom ash in which the calcium element content is greater than the silicon element content; mixing the selected bottom ash with an organic solvent and a polymeric material to form a spinning solution; extruding the spinning solution through a spinning apparatus via a dry-wet spinning process to form a hollow fiber precursor; and sintering the hollow fiber precursor at a temperature ranging from 1100°C to 1200°C to produce hollow fibers composed of the incineration bottom ash. The resulting incineration bottom ash hollow fibers have a specific surface area S BETranging from 0.1 m 2 / g to 0.5 m 2 / g, and an average micropore diameter (Dp) ranging from 450 nm to 850 nm.

Description

Technical Field

[0001] This invention relates to a hollow fiber, particularly a hollow fiber from incineration bottom ash and its preparation method. Prior Technology

[0002] Human life generates a large amount of waste every day. According to statistics, Taiwan produces thousands of tons of waste daily that needs to be processed. After incineration, this waste produces a large amount of incinerator ash. Traditionally, this ash is mainly used in building materials, such as mixing with cement or tiles to build sidewalks. However, due to regional restrictions (such as soil and water conservation areas), the reuse of this ash is limited, leading to some of it needing to be landfilled or disposed of in other ways, increasing the environmental burden.

[0003] Furthermore, incineration ash has a complex composition, containing various metallic and non-metallic elements, such as silicon, aluminum, calcium, iron, and magnesium. Previous technologies have attempted to extract valuable metals, such as aluminum and silicon, from the ash, but these methods typically only recover a portion of the metals, and a large amount of waste remains after extraction, failing to completely solve the problem of ash disposal. Summary of the Invention

[0004] This invention discloses a hollow fiber from incineration bottom ash and its preparation method, mainly to improve the problems existing in the prior art and to find innovative ways to reuse and apply incineration bottom ash.

[0005] One embodiment of the present invention discloses a method for preparing hollow fibers from incineration bottom ash, comprising: a screening operation, comprising: screening incineration bottom ash with a calcium content greater than a silicon content in its elemental composition; a spinning solution preparation operation, comprising: mixing the screened incineration bottom ash with an organic solvent and a polymer to form a spinning solution; and a hollow fiber preparation operation, comprising: spinning the spinning solution through a spinning device using a dry-wet spinning method to form a hollow fiber precursor; and sintering the hollow fiber precursor at a sintering temperature between 1100°C and 1200°C to form hollow fibers composed of the incineration bottom ash.

[0006] Another embodiment of the present invention discloses a hollow fiber for incineration bottom ash, which is prepared by the method described above, wherein the calcium content in the elemental composition of the hollow fiber for incineration bottom ash is greater than the silicon content, the specific surface area SBET is 0.1 m 2 / g to 0.5 m 2 / g, and the average pore size Dp of the micropores is 450 nm to 850 nm.

[0007] In summary, the hollow fiber from incineration bottom ash and its preparation method provided by this invention can be prepared into hollow fibers with high economic value by "screening incineration bottom ash with a calcium content greater than a silicon content in its elemental composition", "mixing the screened incineration bottom ash with an organic solvent and a polymer to form a spinning solution", and "spinning the spinning solution through a spinning device using a dry-wet spinning method to form a hollow fiber precursor; and sintering the hollow fiber precursor at a sintering temperature between 1100°C and 1200°C".

[0008] Furthermore, this invention utilizes high-calcium-content incineration bottom ash to impart fluxing properties, enabling hollow fiber formation at lower sintering temperatures without the need for external fluxes, thus reducing energy consumption and costs. Compared to existing technologies that require purifying high-silica raw materials or adding multiple additives, this invention directly selects bottom ash with a specific composition, shortening the process and improving feasibility. The bottom ash powder is uniformly dispersed in an organic solvent and a polymer to prepare a spinning solution, which is then dry-wet sintered to form a hollow fiber precursor. The fiber is then stabilized and solidified at a lower sintering temperature, resulting in a uniform pore distribution and appropriate pore size. The final product maintains good structure and mechanical strength even under low-temperature sintering conditions, exhibits impurity adsorption properties, and is beneficial for water treatment and wastewater purification applications. It also facilitates aqueous phase separation, significantly enhancing economic benefits and practical value.

[0009] To further understand the features and technical content of this invention, please refer to the following detailed description and accompanying drawings. However, these descriptions and drawings are only for illustrating the invention and are not intended to limit the scope of protection of the invention in any way. Simple Explanation of the Diagram

[0010] Figure 1 is a flowchart of the method for preparing hollow fibers according to an embodiment of the present invention.

[0011] Figure 2 shows the spectrum of the incineration bottom ash selected in the embodiment of the present invention, analyzed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS).

[0012] Figure 3 is a schematic diagram of the spinning equipment according to an embodiment of the present invention.

[0013] Figure 4 is a schematic diagram of hollow fibers in the incineration bottom ash of an embodiment of the present invention.

[0014] Figure 5A is a scanning electron microscope (SEM) image (magnification 50x) of the cross section of the hollow fiber prepared by the spinning solution in Example 1 of the present invention without ball milling.

[0015] Figure 5B is a scanning electron microscope (SEM) image (magnification 200x) of the cross section of the hollow fiber prepared by the spinning solution in Example 1 of the present invention without ball milling.

[0016] Figure 6A is a scanning electron microscope (SEM) image (magnification 50x) of the cross section of hollow fiber prepared by ball milling in the spinning solution of Example 2 of the present invention.

[0017] Figure 6B is a scanning electron microscope (SEM) image (magnification 200x) of the cross section of hollow fiber prepared by ball milling in the spinning solution of Example 2 of the present invention.

[0018] Figure 7 is a scanning electron microscope (SEM) image (magnification 10,000x) of the hollow fiber prepared in Example 2 of the present invention at a sintering temperature of 1200℃.

[0019] Figure 8 is a scanning electron microscope (SEM) image (10,000x magnification) of the hollow fiber prepared in Example 3 of the present invention at a sintering temperature of 1150°C. Implementation

[0020] In the following description, if it is indicated that a specific diagram is referred to or as shown in a specific diagram, it is only to emphasize that most of the relevant content mentioned in the following description appears in that specific diagram, but does not limit the following description to refer only to that specific diagram.

[0021] It should be understood that while terms such as “first,” “second,” and “third” may be used in this document to describe various materials or properties, these materials or properties should not be limited by these terms. These terms are primarily used to distinguish one material from another, or one property from another. Furthermore, the term “or” used in this document should, as appropriate, include any combination of one or more of the related listed items.

[0022] It should be noted that, in this description, when a parameter's numerical range is mentioned as being between one value and another, it should be understood that the range includes both endpoints. In other words, the numerical range includes both the stated value and the other value, unless otherwise explicitly stated in the text or inferred from the context. This descriptive approach aims to clarify the technical scope and avoid unnecessary limitations arising from different interpretations.

[0023] [Method for preparing hollow fibers from incineration bottom ash]

[0024] As shown in Figure 1, this embodiment of the invention provides a method for preparing hollow fibers from incineration bottom ash, comprising steps S110, S120, S130, and S140. It should be noted that the order of the steps described in this embodiment and the actual operation method can be adjusted according to requirements, and this invention is not limited to what is described in this embodiment.

[0025] Step S110 is a screening operation, which includes: locating the source of incineration ash and screening incineration ash with a calcium content greater than a silicon content in its elemental composition. Incineration ash is generated after waste has undergone incineration.

[0026] In one embodiment of the present invention, the elemental composition of the screened incineration bottom ash, analyzed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), must meet the following conditions: (1) the weight percentage concentration of calcium is not less than 15 wt%, preferably not less than 20 wt%, and particularly preferably not less than 25 wt%; and (2) the weight ratio of calcium to silicon (Ca / Si) is not less than 2, preferably not less than 4, and particularly preferably not less than 8. The analytical parameters of the scanning electron microscope are as follows: a scanning electron microscope (SEM: Hitachi S-3400N) is used, the electron gun is a tungsten filament, and the accelerating voltage is 15.0 kV. The SEM-EDS analysis method can be, for example, according to ASTM E1508-12a, but is not limited thereto.

[0027] In addition, the elemental composition of the incineration bottom ash also includes a variety of other trace metal elements, such as aluminum, sodium, magnesium, molybdenum, or iron, and the weight percentage concentration of the above-mentioned calcium element is greater than the weight percentage concentration of any trace metal element, but the present invention is not limited thereto.

[0028] In one embodiment of the present invention, the weight percentage concentration of calcium in the screened incineration bottom ash is between 25 wt% and 40 wt% (e.g., 30-33 wt%), and the weight percentage concentration of silicon is between 1 wt% and 10 wt% (e.g., 2-3 wt%), wherein the calcium (Ca) / silicon (Si) weight ratio is between 10 and 15, but the present invention is not limited thereto.

[0029] Please refer to Figure 2, which shows the spectrum of the incineration bottom ash selected in the embodiment of the present invention by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), which shows the characteristic energy peaks of the elements contained in the incineration bottom ash.

[0030] The Ca (calcium) peak is prominent, with a significant Ca energy peak at the high energy end (around 3.69 keV), indicating a high calcium content in the bottom ash. Calcium is one of the most characteristic and abundant elements in this bottom ash. A Si (silicon) peak is visible at approximately 1.74 keV, indicating the presence of silicate compounds in the bottom ash, but in a relatively low proportion compared to calcium. The peaks for Al (aluminum), Na (sodium), Mg (magnesium), and Mo (molybdenum) are smaller, indicating their relatively lower content compared to calcium and silicon. An O (oxygen) peak is also present in the spectrum, indicating that at least some metal elements exist in oxide form. In the elemental composition of this incineration bottom ash, the weight percentage concentration of calcium is 31.69 wt%, silicon is 2.57 wt%, and aluminum is 1.1 wt%.

[0031] Furthermore, the calcium in the incineration bottom ash comes from calcium compounds, such as calcium oxide (CaO) and calcium hydroxide (Ca(OH)2), while the silicon comes from silicon compounds, such as silicon dioxide (SiO2), and the aluminum comes from aluminum compounds, such as aluminum oxide (Al2O3).

[0032] In another embodiment of the present invention, the composition of the screened incineration bottom ash, analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES), needs to meet the following conditions: (1) the weight percentage concentration of calcium compounds (e.g., the sum of the weight percentage concentrations of calcium oxide and calcium hydroxide) is not less than 30 wt%, preferably not less than 40 wt%, and particularly preferably between 50 wt% and 75 wt%; and (2) the weight percentage concentration of calcium compounds is at least 1.2 times, preferably at least 1.5 times, and particularly preferably at least 1.8 times the weight percentage concentration of silicon compounds (e.g., silicon dioxide). An example of the analysis method in this embodiment is as follows: the characteristics of the incineration bottom ash used are obtained by microwave digestion to measure the metal ion concentration, which is then multiplied by the volume to obtain the weight of the metal ions. The microwave digestion assay is performed as follows: 1. Place 0.1g of sample (in this case, incineration bottom ash) in a 100℃ oven and dry for 2 hours; 2. Place 0.1g of the dried sample in a digestion flask, add 9 mL of 70% nitric acid, 3 mL of hydrofluoric acid, and 3 mL of 37% hydrochloric acid, and pre-digest for 30 minutes; 3. Heat at 180℃ for 25 minutes, then hold for 10 minutes; 4. After cooling, add 15 mL of boric acid and pre-digest for 30 minutes; 5. Repeat step 3; 6. Quantify the microwave-digested water sample and analyze the metal ion concentration using ICP-OES. 7. ICP-OES model: Inductively coupled plasma-optical emission spectrometry (ICP-OES, Avio 200, PerkinElmer). However, this invention is not limited to the above method.

[0033] Step S120 is a bottom ash pretreatment operation, which includes: sequentially passing the screened incineration bottom ash through drying treatment (S121), crushing treatment (S122), sieving treatment (S123), and calcination treatment (S124) to substantially remove residual moisture and organic matter in the incineration bottom ash, and to obtain incineration bottom ash powder with an average particle size of not more than 60 micrometers, preferably not more than 55 micrometers, and particularly preferably not more than 50 micrometers.

[0034] More specifically, the drying process (S121) includes placing the incineration bottom ash into a drying device (e.g., an oven) and drying it at a drying temperature of 50°C to 200°C, preferably 130°C to 170°C, to substantially remove residual moisture from the incineration bottom ash (e.g., reducing the moisture content to 1 wt%, preferably below 0.5 wt%). The drying duration can be, for example, from 0.5 hours to 36 hours (e.g., 24 hours), and can be adjusted according to actual operational needs.

[0035] Crushing (S122) includes crushing the dried incineration bottom ash by passing it through a crushing device (e.g., a crusher) or a crushing means (e.g., a hammer crusher) to break larger particles or clumps in the incineration bottom ash into smaller particles or powder.

[0036] The sieving process (S123) includes: sieving the crushed incineration bottom ash through a particle size screening device (e.g., a 200-mesh to 1000-mesh screen) to obtain incineration bottom ash with an average particle size D50 of not more than 60 micrometers, preferably not more than 55 micrometers, and especially preferably not more than 50 micrometers.

[0037] The calcination treatment (S124) includes: placing the sieved incineration bottom ash into a high-temperature device (e.g., a high-temperature furnace) and calcining it at a calcination temperature between 300°C and 800°C, preferably between 500°C and 800°C (e.g., 750°C), to substantially remove residual organic matter in the incineration bottom ash (e.g., reducing the organic matter content to below 1 wt%, preferably below 0.5 wt%). The calcination duration can be, for example, between 0.5 hours and 12 hours (e.g., 3 hours), and can be adjusted according to actual operational needs.

[0038] It is worth mentioning that the incineration bottom ash can remove residual moisture and organic matter through the above-mentioned bottom ash pretreatment process, and can have a finer and more uniform particle size, which is beneficial to subsequent spinning operations and hollow fiber preparation.

[0039] However, the present invention is not limited to the above embodiments. In another embodiment of the present invention, the incineration bottom ash may be used directly for the preparation of subsequent spinning solution and hollow fibers without undergoing the above-mentioned bottom ash pretreatment operation.

[0040] Step S130 is a spinning solution preparation operation, which includes: further mixing the screened and treated incineration bottom ash with organic solvent and polymer to form a spinning solution.

[0041] The organic solvent may be selected, for example, from at least one of the group consisting of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and dimethyl sulfoxide (DMSO). In one embodiment of the invention, the organic solvent is selected from N-methylpyrrolidone (NMP).

[0042] The polymer may be selected from, for example, at least one of the group consisting of polyvinylpyrrolidone (PVP), polyethersulfone (PESf), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyetherimide (PEI), polyether ether ketone (PEEK), polyvinyl alcohol (PVA), and polyethylene glycol (PEG).

[0043] In the composition of the spinning solution, based on a total weight of 100% for the spinning solution, the content of incineration bottom ash is 35 to 65% by weight, preferably 40 to 60% by weight, and particularly preferably 45 to 55% by weight. The content of organic solvent is 25 to 60% by weight, preferably 30 to 55% by weight, and particularly preferably 40 to 50% by weight. The content of polymer is 0.1 to 15% by weight, preferably 0.5 to 10% by weight, and particularly preferably 1 to 8% by weight.

[0044] In one embodiment of the present invention, the polymer contains both polyvinylpyrrolidone (PVP) and polyether sulfide (PESf), and the content of polyvinylpyrrolidone (PVP) is 0.5 to 2% by weight, while the content of polyether sulfide (PESf) is 4 to 6% by weight, but the present invention is not limited thereto.

[0045] Polyvinylpyrrolidone (PVP) is hydrophilic, which helps to form a porous structure on hollow fibers, and polyether sulfide (PESf) can be used as an adhesive to help the hollow fibers bind the incineration bottom ash together during spinning.

[0046] Based on the above configuration, a hollow fiber spinning solution with moderate viscosity and uniform dispersion of incineration bottom ash can be obtained, which is beneficial for subsequent spinning and hollow fiber preparation.

[0047] In one embodiment of the present invention, the spinning solution preparation process selectively includes: grinding the spinning solution with a grinding device to uniformly mix all components (including incineration bottom ash, organic solvent and polymer) in the spinning solution and to further reduce the particle size of the incineration bottom ash.

[0048] The grinding equipment can be, for example, a ball mill, a grinding mill, or a bead mill. Preferably, the grinding equipment is a planetary ball mill, and the revolution speed of the ball mill can be, for example, between 120 and 240 rpm, preferably between 160 and 200 rpm, and the grinding time can be, for example, at least 3 hours, and preferably at least 12 hours, but the present invention is not limited thereto.

[0049] More specifically, the spinning solution preparation process can be achieved, for example, by mixing incineration bottom ash, an organic solvent (such as NMP), and polyvinylpyrrolidone (PVP), and then ball-milling the mixture in a planetary ball mill at a revolution speed of 160 to 200 rpm for 12 to 48 hours to form a mixed liquid. Then, polyether sulfate (PESf) is added to the mixed liquid, and the mixture is further ball-milled in a planetary ball mill at a revolution speed of 160 to 200 rpm for 12 to 48 hours to form the spinning solution.

[0050] Therefore, all components in the spinning solution can be mixed more evenly, achieving homogeneity.

[0051] Please refer to Figures 3 and 4. Step S140 is a hollow fiber preparation operation, which includes: spinning the spinning solution L1 through a spinning device 100 (e.g., a spinning machine) using a dry-wet spinning method to form a hollow fiber precursor P' with a hollow structure; then, sintering the hollow fiber precursor P' at a sintering temperature between 1100°C and 1200°C to remove the organic solvent and polymer, and to form a hollow fiber P mainly composed of incineration bottom ash.

[0052] Specifically, the spinning nozzle 1 of the spinning equipment 100 has a coaxial double-tube structure consisting of an outer tube 11 and an inner tube 12. The outer tube 11 is through which spinning solution L1 flows, and the inner tube 12 is through which a mesoporous liquid L2 (e.g., deionized water) flows. After the spinning solution L1 is ejected from the outer tube 11 of the spinning nozzle 1, it undergoes phase separation and solidification in the coagulation bath T to form the outer wall of the hollow fiber precursor P'. After the mesoporous liquid L2 is ejected from the inner tube 12 of the spinning nozzle 1, it leaves a hollow inner cavity during solidification, giving the fiber a hollow structure after solidification. The coagulation bath T can, for example, use the same liquid composition as the mesoporous liquid, such as deionized water, and the temperature can be room temperature, allowing the spinning solution L1 to undergo phase separation and solidification in the coagulation bath T.

[0053] In some embodiments of the present invention, the diameter of the outer tube 11 of the spinning nozzle 1 is between 1.5 mm and 4 mm, and preferably between 2 mm and 3 mm. The diameter of the inner tube 12 of the spinning nozzle 1 is between 0.8 mm and 1.35 mm, and preferably between 0.9 mm and 1.3 mm. Furthermore, the difference between the diameter of the outer tube 11 and the diameter of the inner tube 12 is between 0.5 mm and 2.5 mm, and preferably between 0.7 mm and 2.1 mm.

[0054] Furthermore, the flow rate of the spinning nozzle 1 is between 5 ml / min and 12 ml / min, and preferably between 7 ml / min and 10 ml / min. Here, the flow rate of the spinning solution L1 and the medium-hole solution L2 refer to the flow rates of the spinning solution L1 and the medium-hole solution L2 respectively (e.g., the flow rate of the spinning solution L1 in the outer tube 11 is 5~12 ml / min, and the flow rate of the medium-hole solution L2 in the inner tube 12 is 5~12 ml / min).

[0055] In some embodiments of the present invention, after the hollow fiber precursor P' is formed, the hollow fiber preparation process further includes removing the hollow fiber precursor P' from the coagulation bath, washing and drying it, and finally heat treating it to form hollow fiber P composed of incineration bottom ash.

[0056] The drying process can be, for example, by naturally drying the wet hollow fiber precursor at room temperature, or by drying it in a drying device (such as an oven) at a temperature of 50°C to 200°C, until the moisture and organic solvents in the fiber are completely evaporated.

[0057] Heat treatment can be performed, for example, by placing the dried hollow fiber precursor into a high-temperature furnace and following the heat treatment procedure below. The calcination stage involves heating at 1-5°C / min to 300°C-800°C and holding for 0.5-12 hours (e.g., 1 hour) to remove polymers (e.g., PVP and PESf). The sintering stage involves further heating to a sintering temperature between 1100°C and 1200°C and holding for 0.5-12 hours (e.g., 3 hours) to sinter the inorganic metal components in the incineration ash, forming a stable hollow fiber structure (with a diameter shrinkage of approximately 5% to 30% after sintering). Finally, the fiber is allowed to cool naturally to room temperature to complete the preparation of the hollow fiber.

[0058] It is worth mentioning that the incineration bottom ash screened through the above screening process has a specific proportion of calcium compounds (such as calcium oxide and calcium hydroxide) and a calcium / silicon weight ratio, which can help reduce the sintering temperature during the subsequent preparation of hollow fibers from the bottom ash, and can eliminate the need to add other catalysts (such as AlF3) or metal fluxes.

[0059] If the incineration bottom ash is not screened and does not have the specific composition mentioned above, it may be detrimental to the preparation of hollow fibers (e.g., the required sintering temperature may be too high or the hollow fibers may not be able to be formed).

[0060] Please refer to Figures 5A and 5B, which show scanning electron microscope (SEM) images of the cross-section of hollow fibers prepared by the spinning solution of Example 1 of the present invention without ball milling.

[0061] In Example 1, the incineration bottom ash used was the composition shown in Figure 2, and the incineration bottom ash underwent pretreatment. The pretreatment included placing the incineration bottom ash in a 150°C oven to remove moisture, followed by crushing. The crushed incineration bottom ash was then sieved through a 45 μm screen, and subsequently placed in a 750°C high-temperature furnace for 3 hours to remove organic matter, yielding incineration bottom ash powder. Then, 50 parts by weight of the incineration bottom ash powder, 44 parts by weight of N-methylpyrrolidone (NMP), 1 part by weight of polyvinylpyrrolidone (PVP), and 5 parts by weight of polyethersulfone (PESf) were mixed to form a spinning solution (without ball milling). Hollow fiber spinning was then performed using a wet-dry spinning method, wherein the flow rate of the spinning solution in the outer tube of the spinning nozzle was 7 ml / min, and the flow rate of the mesoporous solution (deionized water) in the inner tube was 7 ml / min. The sintering temperature of hollow fibers is 1,200℃.

[0062] As shown in Figures 5A and 5B, the hollow fiber of Example 1 has been roughly formed, but the pores are large, the structure is loose, and it is more brittle, but it is still within the scope of application.

[0063] Please refer to Figures 6A and 6B, which show scanning electron microscope (SEM) images of the cross-section of hollow fibers prepared under ball milling conditions in the spinning solution of Example 2 of the present invention.

[0064] The hollow fiber preparation conditions in Example 2 are roughly the same as those in Example 1. The main difference is that the spinning solution in Example 2 is further ball-milled for 48 hours using a planetary ball mill at a revolution speed of 180 rpm to ensure that the incineration bottom ash is uniformly dispersed and homogeneous.

[0065] As shown in Figures 6A and 6B, the hollow fiber in Example 2 has smooth inner and outer walls, and at least a certain thickness of the inner wall has a finger-like pore structure, which is beneficial for supporting the shape of the hollow fiber and making it less brittle. The middle part of the cross-section of the hollow fiber in Example 2 exhibits a dense sponge-like structure (as shown in Figure 7). Compared with Example 1, the hollow fiber of Example 2 has more stable performance and reliability.

[0066] Please refer to Figure 8, which shows a scanning electron microscope (SEM) image of the hollow fiber of Example 3 of the present invention. The preparation method of the hollow fiber of Example 3 is largely the same as that of Example 2, the main difference being that the sintering temperature of the hollow fiber of Example 3 is reduced to 1150°C. As can be seen from the SEM image, the hollow fiber can still be formed at a lower sintering temperature, and the micropores increase, which is beneficial for impurity adsorption.

[0067] In terms of dimensions, the hollow fibers in the incineration bottom ash of the embodiments of the present invention have a length of 3 cm to 15 cm, an outer diameter of 1.0 mm to 2.5 mm, an inner diameter of 0.6 mm to 1.8 mm, and a wall thickness of 0.1 mm to 0.4 mm, but the present invention is not limited thereto.

[0068] Furthermore, the specific surface area (SBET) of the hollow fiber is 0.1 m2 / g to 0.5 m2 / g, and preferably 0.25 m2 / g to 0.45 m2 / g, and the average pore size (Dp) of the micropores is 450 nm to 850 nm, and preferably 550 nm to 750 nm. It is worth noting that micropores with an average pore size greater than 50 nm are classified as macroporous materials, with larger pores suitable for adsorbing larger molecules or colloidal substances, and also facilitating fluid passage.

[0069] The hollow fiber can be analyzed for specific surface area S BET and average pore size D p using a gas adsorption analyzer (such as N₂ adsorption / desorption method), but the present invention is not limited thereto.

[0070] Furthermore, the hollow fiber in the incineration bottom ash of the present invention is suitable for wastewater treatment, such as dye adsorption in wastewater.

[0071] In one embodiment, the hollow fiber from Example 3 was used to conduct dye adsorption tests in wastewater. The following describes the test method and results of the adsorption experiment on Methyl Blue (MyB) dye solution using incineration bottom ash hollow fiber (BAHF) as the adsorbent material in this case.

[0072] The experimental method involved using a 50 mL solution of methylene blue dye and 2 g of BAHF (battery bottom ash) hollow fiber adsorbent. The solution was continuously stirred at 100 rpm in a reciprocating shaking water bath. Different contact times (e.g., 10, 30, 60, 120, and 180 minutes) were set to observe the adsorption kinetics. The initial concentration of methylene blue was 200 mg / L to assess its effect on adsorption capacity. The temperature was 25 °C. After the adsorption experiment, the solution was filtered through 0.22 µm filter paper, and the residual dye content was measured using spectrophotometry.

[0073] Regarding dye adsorption, the hollow fiber incinerator bottom ash (BAHF) significantly removed the blue color of MyB dye within approximately 10 minutes, causing the solution color to fade. This demonstrates that BAHF exhibits a rapid initial adsorption reaction for MyB dye. Experimental results show that the adsorption capacity (qe) of MyB by the hollow fiber incinerator bottom ash (BAHF) is approximately 1–3 mg / g (e.g., 2 mg / g).

[0074] Overall, under the conditions of an initial methylene blue concentration of 200 mg / L and a solution temperature of 25°C, adding 2 g of hollow fiber to 50 mL of methylene blue solution and stirring at 100 rpm can reduce the concentration of methylene blue in the solution by at least 90% within 10 minutes, and the adsorption capacity is 1~3 mg / g.

[0075] [Beneficial Effects of the Embodiments of the Invention]

[0076] In summary, the method for preparing hollow fibers from incineration bottom ash and the hollow fibers from incineration bottom ash provided by this invention can be achieved by "screening incineration bottom ash with a calcium content greater than a silicon content in its elemental composition", "mixing the screened incineration bottom ash with an organic solvent and a polymer to form a spinning solution", and "spinning the spinning solution through a spinning device using a dry-wet spinning method to form a hollow fiber precursor; and sintering the hollow fiber precursor at a sintering temperature between 1100°C and 1200°C to form hollow fibers composed of the incineration bottom ash". This allows incineration bottom ash to be prepared into hollow fibers with high economic value.

[0077] Furthermore, this invention utilizes high-calcium-content incineration bottom ash to impart fluxing properties, enabling hollow fiber formation at lower sintering temperatures without the need for external fluxes, thus reducing energy consumption and costs. Compared to existing technologies that require purifying high-silica raw materials or adding multiple additives, this invention directly selects bottom ash with a specific composition, shortening the process and improving feasibility. The bottom ash powder is uniformly dispersed in an organic solvent and a polymer to prepare a spinning solution, which is then dry-wet sintered to form a hollow fiber precursor. The fiber is then stabilized and solidified at a lower sintering temperature, resulting in a uniform pore distribution and appropriate pore size. The final product maintains good structure and mechanical strength even under low-temperature sintering conditions, exhibits impurity adsorption properties, and is beneficial for water treatment and wastewater purification applications. It is also easily separated from the aqueous phase, significantly enhancing economic benefits and practical value.

[0078] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Therefore, all equivalent technical changes made based on the description and drawings of the present invention are included within the protection scope of the present invention.

[0079] S110: Step S110 S120: Step S120 S130: Step S130 S140: Step S140 100: Spinning equipment 1: Spinning nozzle 11: Outer pipe 12: Inner tube L1: Spinning solution L2: Mesoporous liquid T: Coagulation bath P': Hollow fiber precursor P: Hollow fiber

Claims

1. A method for preparing hollow fibers from incineration bottom ash, comprising: a screening operation, comprising: screening incineration bottom ash in which the calcium content is greater than the silicon content in the elemental composition; wherein, In the screening operation, the screened incineration bottom ash is analyzed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and must meet the following conditions: (1) the weight percentage concentration of calcium is not less than 15 wt%; and (2) the weight ratio of calcium to silicon is not less than 2. A bottom ash pretreatment operation includes: sequentially passing the screened incineration bottom ash through a drying process, a crushing process, a sieving process and a calcination process to remove residual moisture and organic matter in the incineration bottom ash and obtain the incineration bottom ash with an average particle size of not more than 60 micrometers. A spinning solution preparation operation includes: mixing the screened incineration bottom ash with an organic solvent and a polymer to form a spinning solution; and a hollow fiber preparation operation includes: spinning the spinning solution through a spinning device using a dry-wet spinning method to form a hollow fiber precursor; and sintering the hollow fiber precursor at a sintering temperature between 1100°C and 1200°C to form hollow fibers composed of the incineration bottom ash.

2. The method for preparing hollow fibers from incineration bottom ash as described in claim 1, wherein, In the incineration bottom ash, the calcium element is a calcium-derived compound, which includes calcium oxide and calcium hydroxide; the silicon element is derived from a silicon compound, which includes silicon dioxide; wherein, in the screening operation, the screened incineration bottom ash, analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES), needs to meet the following conditions: (1) the weight percentage concentration of the calcium compound is not less than 30 wt%; and (2) the weight percentage concentration of the calcium compound is more than 1.2 times the weight percentage concentration of the silicon compound.

3. The method for preparing hollow fibers from incineration bottom ash as described in claim 1, wherein, The drying process includes: placing the screened incineration bottom ash into a drying device and drying it at a drying temperature of 50°C to 200°C to remove residual moisture; the crushing process includes: crushing the dried incineration bottom ash using a crushing device or a crushing method; the sieving process includes: sieving the crushed incineration bottom ash through a particle size screening device to obtain incineration bottom ash with an average particle size of not more than 60 micrometers; and the calcination process includes: placing the sieved incineration bottom ash into a high-temperature device and calcining it at a calcination temperature between 300°C and 800°C to remove residual organic matter.

4. The method for preparing hollow fibers from incineration bottom ash as described in claim 1, wherein, The organic solvent is selected from at least one of the group consisting of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and dimethyl sulfoxide (DMSO), and the polymer is selected from at least one of the group consisting of polyvinylpyrrolidone (PVP), polyether sulfide (PESf), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyetherimide (PEI), polyether ether ketone (PEEK), polyvinyl alcohol (PVA), and polyethylene glycol (PEG).

5. The method for preparing hollow fibers from incineration bottom ash as described in claim 4, wherein, Based on the total weight of the spinning solution being 100% by weight, the content of the incineration bottom ash being 35 to 65% by weight, the content of the organic solvent being 25 to 60% by weight, and the content of the polymer being 0.1 to 15% by weight.

6. The method for preparing hollow fibers from incineration bottom ash as described in claim 5, wherein, The organic solvent is selected from N-methylpyrrolidone (NMP), and the polymer contains both polyvinylpyrrolidone (PVP) and polyether sulfide (PESf), with the content of PVP being 0.5 to 2% by weight and the content of PESf being 4 to 6% by weight.

7. The method for preparing hollow fibers from incineration bottom ash as described in claim 1, wherein, The spinning solution preparation process includes grinding the spinning solution with a grinding device; wherein the grinding device is a planetary ball mill with a revolution speed between 120 and 240 rpm and a grinding time of not less than 3 hours.

8. A hollow fiber for incineration bottom ash, formed by the method of any one of claims 1 to 7, wherein the elemental composition of the hollow fiber for incineration bottom ash contains more calcium than silicon, has a specific surface area SBET of 0.1 m² / g to 0.5 m² / g, and has an average pore size Dp of 450 nm to 850 nm.

9. Hollow fiber incineration bottom ash as described in claim 8, wherein, Under the conditions of an initial methylene blue concentration of 200 mg / L and a solution temperature of 25°C, the hollow fiber of the incineration bottom ash, when 2 g of hollow fiber is added to 50 mL of methylene blue solution and stirred at 100 rpm, can reduce the concentration of methylene blue in the solution by at least 90% within 10 minutes, and the adsorption capacity is 1~3 mg / g.