Green synthesize of fly ash-based zeolite X: A potential microwave absorbent

Green synthesize of fly ash-based zeolite X: A potential microwave absorbent | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Green synthesize of fly ash-based zeolite X: A potential microwave absorbent Bin Shi, Junjie Zhao, Qing Chang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-233778/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Zeolite X is a potential electromagnetic wave (EMW) absorption material owning to its advantages of good dielectric properties, light weight and large specific surface area. Herein, high-purity zeolite X was prepared from fly ash using a green synthesis approach, in which only trace water was used and achieved zero discharge of waste water. Physiochemical properties of fabricated zeolite X were comprehensively evaluated through XRD, PSD, SEM, TG-DSC and BET test. XRD pattern shows the successful preparation of zeolite X with good crystallinity and high purity, and the average particle size is ~2.45 μm, which conforms to Gaussian distributions. The fabricated zeolite X exhibits typical octahedral structure and good thermal stability. It is noteworthy that the specific surface area is up to 473.56 m 2 /g, representing porous structure, which is beneficial to EMW attenuation. What’s more, the abundant crystal water and adsorbed water existing in the sample is conductive to dipole polarization, which further consume EMW energy. This study provides an eco-friendly approach to change waste into valuables, and moreover the synthesized zeolite X is a potential EMW absorbing material. Electronic Materials and Devices Zeolite X Fly ash Green synthesis Dielectric absorber. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction With the wide use of electronic devices, electromagnetic wave (EMW) pollution is becoming more and more serious, and hence EMW absorbing materials have attracted wide attention [1-2]. So far, various materials have already been prepared for EMW adsorption [3-10]. As a kind of low-cost material, natural and synthetic zeolites have great application potential in EMW adsorption field owning to the advantages of unique dielectric properties, low density, high specific surface, and strong mechanical and chemical stability. Recently, Shang et al. reported a sepiolite-based EMW adsorption composites with superior EMW absorption performance, in which the minimum reflection loss of -50.23 dB and effective absorption bandwidth of 5.01 GHz [11]. Using low-cost light-weight and natural sepiolite as starting material, the synthesis procedure is facile, economic and commercially practical. What’s more, the large surface area of sepiolite is convenient for multiple reflections and scattering, which can increase the propagation path of incident EMW and promote EMW dissipation. As another kind of porous mineral material, the research of zeolite/zeolite-based materials as islanding or regional dielectric loss absorbers is of great significance in the research field of new EMW absorbing materials, while the relevant reports are still rare. Zeolite X is one of the most widely used zeolites due to its large specific surface area and high adsorption capacity [12-14]. As a kind of porous inorganic material, zeolite has the characteristics of crystal and open framework structure with many pores in it. These pores are connected with each other through channels, and the pore size distribution is highly uniform. The weak interaction between porous AlO 4 /SiO 4 structure and non-framework cations endows zeolite with unique dielectric properties. The characteristics above are beneficial to EMW loss. Fly ash, a solid waste with huge discharge, has been widely used for the synthesis of zeolite X owing to its high silicon and aluminum content [15-17]. Numerous studies have been established to synthesize zeolite X, such as one-step method [18-19], two-step method [20-21], microwave-assisted two-step method [22-23] and ultrasonic-assisted method [24]. Normally, a large amount of solvent involves water or organic solution is required in these processes, which inevitably results in wastewater pollution [25]. In light of this, a pioneering process of solvent-free (trace water system) approach is proposed to solve this problem [26]. As a green approach, solvent-free method possesses significant advantages as high yield, sufficient utilization of autoclaves, and reduction of pollutants and so on [27]. In this study, low-cost zeolite X was synthesized from fly ash using a solvent-free method. The prepared zeolite X possesses outstanding physical and chemical properties, and notably, the specific surface area is up to 473.56 m 2 /g, which represents porous structure and is beneficial to EMW attenuation. The work supplied a green and low-cost method to prepare zeolite X, which was expected to be an EMW absorbing material. 2. Experimental 2.1. Materials In this work, fly ash was obtained from Inner Mongolia, China. Analytical purity sodium aluminate, sodium hydroxide and sodium silicate were purchased from Aladdin reagent Co., Ltd. 2.2. Synthesis of zeolite X As we can see from XRF results (Table S1), Si/Al in fly ash is 1.70 which exhibits ideal raw materials for the synthesis of zeolite X, and no additional Si or Al source was necessary. The synthesis process was conducted in the following steps: Firstly, fly ash was homogeneously mixed with sodium hydroxide and the mixture was calcined in muffle furnace at 750℃ for 2h. After cooling, trace amounts of water and prepared seeds (5% wt) were added into the fused mixture to make a smooth paste. The final molar ratio of Na:Al:Si:H 2 O is 1:1:1.6:3.5 (in accordance with typical zeolite X (JCPDS card No. 12-0228): Na 2 Al 2 Si 3.3 O 10.6 ·7H 2 O). Then transferred the paste into autoclave, and heating in an oven at 120℃ for 12-72h. After that, filtered and washed with distilled water for three times. Finally, the solid was dried at 105℃ for 24 h, and Zeolite X powder was obtained. The scheme of the synthesis process was shown in Fig. 1 . 2.3. Characterization Elements of raw ore, synthesized zeolite X and residue were tested by X-ray fluorescence spectrometer (XRF, AXIOS Max , PANalytical). The phase structure of the samples were analyzed by X-ray Diffractionmeter (XRD, D8-FOCUS, Bruker). Morphological characteristics were performed by a Scanning Electron Microscope (SEM, SU8010, HITACHI). The particle size distribution (PSD) of samples were determined using laser particle size analyzer instrument (Mastersizer 2000, MALVERN). The Brunauer-Emmett-Teller (BET) surface area, pore volume and pore size distribution were performed by N 2 adsorption at 77 K with an ASAP2020 (TSI) Automatic Volumetric Sorption Analyzer. Thermogravimetry/Differential Scanning Calorimetry (TG-DSC) analyses were characterized by Netzsch STA 409 thermal analysis system. 3. Results And Discussion 3.1. XRD patterns and XRF analysis of synthesized zeolites To rapidly obtain pure zeolite X, synthesis time was controlled between 12h and 72h. When the reaction time is 12h, the product is completely amorphous. Then raising the reaction time to 24h, zeolite X (JCPDS card No. 12-0228 ) with low crystallinity and zeolite P (JCPDS card No. 39-0219) are obtained, and the content of zeolite X is higher than zeolite P. Thus, continuing to increase the reaction time to 48h, zeolite X with high crystallinity is prepared. Although there is still tiny amount of zeolite P, the purity and crystallinity are excellent enough. Further improving the reaction time to 72h, intensity of zeolite X weakens remarkably, however, intensity of zeolite P strengthens by contrast. In addition, peaks of sodalite (JCPDS card No. 73-1733) appear as well. It is obvious that high temperature is unfavorable to the crystallization of zeolite X. Therefore, zeolite X synthesized at 48h is taken for the further study, which is named SZX. X-ray fluorescence spectrometer (XRF) was used to conduct the chemical compositions of SZX. As is shown, apart from the structural components of zeolite X (Si, Al and Na), small amount of Ti, Fe, Mg, Ca, K are also concluded. The Si/Al ratio of SZX is 1.28, presents a typical zeolite X. ( Table 1 ). Table 1. Main compositions of SZX, LOI is loss on ignition. (mass fraction, %) Composition SiO 2 Al 2 O 3 Na 2 O TiO 2 TFe MgO CaO K 2 O LOI Wt.% 39.36 26.15 15.91 0.04 0.06 0.26 0.31 0.26 16.92 3.2. Morphology analysis of synthesized zeolites The SEM images and EDS result are shown in Fig. 3. When the reaction time is 24h (Fig.3(a)), it can be seen that the particle size of zeolite X is about 2.5μm, and the morphology is irregular. Thus, continuing to increase the reaction time to 48h (Fig.3(b)), the morphology of zeolite X is of regular octahedron and uniform particle size (about 2.5μm). Zeolite X synthesized at 72h presents regular octahedron as well (Fig.3(c)), but the particle size (about 2.6μm) is a little larger than that of 48h. The EDS result of SZX is exhibited in Fig. 2(d), and it shows that the Si/Al ratio is about 1.28, which fits the XRF result perfectly. 3.3. Particle size distribution of synthesized zeolites According to the data of PSD (Fig. 2(f)), the particle size distribution of SZX follows gaussian distributions, and the average particle size of SZX is about 2.45μm, which was in good agreement with the SEM results. The results above indicate that SZX was smaller and more uniform compared to that obtained by hydrothermal method [28-29] . 3.4. Thermal behavior analysis TG-DSC curves of SZX are shown in Fig. 5. Before 100℃, there is a weak endothermic peek, which shows adsorbing steam of air on SZX [30]. TG curve of the sample shows smooth mass loss and was devoid of any distinct kinks. And a significant endothermal valley appears at 136℃. Meanwhile, there is a dramatic weight loss on the TG curve. When it reaches to 246℃, the free water is removed completely. Obviously, the content of free water is high, which will produce dipole polarization and relaxation under the action of electromagnetic field so as to consume EMW energy. The strong exothermal peak at 246℃ may be caused by the combustion of organic impurities, which is another source of dipole polarization. After 600℃, mass loss is stable at about 20.61%. Although the TG-DSC analysis was conducted under 800℃, however, the tendency of DSC curve hints that there exists at least an exothermal peak after 800℃ which is caused by the phase transformation and the decomposition of zeolite structure [31]. Hence the heat treatment temperature of SZX should be controlled below 600℃. 3.5. Specific surface area analysis The pore structure of SZX was evaluated by nitrogen adsorption measurements, and the results are shown in Fig.6. According to the IUPAC classification, the isotherm presents classical type IV with H3 hysteresis loop [32,33]. The pore size distribution for SZX was estimated by the BJH method as shown in the insert Fig. 6, which shows a pore radius below 3 nm. And the broad pore size distribution might be caused by the agglomeration of zeolite particles. The textural parameters of SZX are shown in Table 2. BET surface area is measured to be 473.56 m 2 /g, and the prepared zeolite is primarily microporous with average pore size of 1.914 nm. Large numbers of micropores and channels allows EMW transmit into the material easily, and extends the propagation channel of EMW. Thus, EMW adsorption is increased. According to the literatures, large specific surface area of porous material represents good EMW absorbing performance. Table 2. Textural Parameters of SZX S BET (m 2 /g) S mic (m 2 /g) V Total (cm 3 /g) V mic (cm 3 /g) Average pore size (nm) MSZX 473.56 428.32 0.265 0.240 1.914 3.6. Prospect as an EMW absorbent The zeolite X prepared in this work is of good prospect to be EMW absorbing materials. On one hand, the special porous structure and frame structure enable zeolite X good impedance matching, which make the incident EMW enter the material as much as possible; on the other hand, in addition to dipole polarization loss caused by adsorbed water and impurities, the vesicular cavity and the structure between vesicular in materials will also reflect and scatter EMWs, which dissipate EMW energy greatly. What’s more, Zeolite materials have the characteristics of light weight and thermal stability, which provides favorable conditions for it to become a new type of microwave absorbing material. Briefly, the zeolite X prepared in this work is of good prospect to be a EMW absorbing material. So zeolite and zeolite-based materials will be further studied in our following work. 4. Conclusions High purity zeolite X was synthesized by a green methed from fly ash in 48h. For SZX, the Si/Al ratio is 1.28; the average particle size is about 2.45μm; and the specific surface area is 473.56 m 2 /g. Besides, the SZX shows good phase, morphology and thermal stability as well. Besides, through theoretical analysis, zeolite X is a hopeful EMW absorbing material because of its good impedance matching, dipole polarization loss and reflecting and scattering EMWs caused by vesicular cavity. And the EMW adsorption capacity of zeolite X will be further studied in following research. Declarations The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgement This study was funded by the Research Program of Yan'an University (Grant No. YDY2019-25). References [1] A. Iqbal, F. Shahzad, K. Hantanasirisakul, Science 369 , 446 (2020) https://doi.org/10.1126/science.aba7977. [2] I. Abdalla, A. Elhassan, J.Y. 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Supplementary Files Supplementarymaterial.pdf Composition, phase analysis and SEM images of fly ash and residue. Preparation of seed and its role in synthesis of zeolite X. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-233778","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":11720608,"identity":"29762a0b-9739-4520-b544-b5d5fe8b6a19","order_by":0,"name":"Bin Shi","email":"","orcid":"","institution":"Yan'an University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Bin","middleName":"","lastName":"Shi","suffix":""},{"id":11720609,"identity":"303dc3fd-0579-49da-8a38-d7f4ceca0a2b","order_by":1,"name":"Junjie Zhao","email":"","orcid":"","institution":"Fujian Institute of Geological Survey","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Junjie","middleName":"","lastName":"Zhao","suffix":""},{"id":11720610,"identity":"9d956b98-efd4-4133-8388-0c66ade4af94","order_by":2,"name":"Qing Chang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4UlEQVRIiWNgGAWjYDACCSSS4YOBjRxpWhhnFKQZE6sFAph5PhxOJKiDf3bzs4dfyizy5COSn0nbGDAnMLAfProBryV3jpkby5yTKDa8kWYmnWPAlsfAk5Z2A58WA4kEM2nJNonEjTMSQFp4ihkkeMwIaEn/BtUCZFgYSCQ2ENaSYyb5EahlPpAhzWBgQFiLxI2cMmmGcxKJG3jeFFv2GCQYsxHyC/+M9G2SP8rqEue3p2+88ePPfzl+9sPH8GoBAWYeNqALLyRAeGyElIMA4w+gMvn+A8SoHQWjYBSMgpEIAPSgRlmdXQ7tAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-9153-2509","institution":"Yan'an University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Qing","middleName":"","lastName":"Chang","suffix":""}],"badges":[],"createdAt":"2021-02-11 11:44:51","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-233778/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-233778/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":6324907,"identity":"c4d7bb97-4f1d-497b-be84-c2626bfeade5","added_by":"auto","created_at":"2021-02-24 20:10:03","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":28100,"visible":true,"origin":"","legend":"The scheme of synthesize zeolite X.","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-233778/v1/1c275ba33f439de7ca846554.jpg"},{"id":6324908,"identity":"6b35f0bf-67ea-4fe4-bbf4-364e2a120cfc","added_by":"auto","created_at":"2021-02-24 20:10:03","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":30661,"visible":true,"origin":"","legend":"XRD patterns of products synthesized at different crystallization time.","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-233778/v1/04bd76aa4f531400cb4213b1.jpg"},{"id":6324909,"identity":"48a8dc6b-db1c-4de3-846a-e6bb8b5dcad6","added_by":"auto","created_at":"2021-02-24 20:10:03","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":64811,"visible":true,"origin":"","legend":"SEM images of zeolites synthesized at (a) 24h, (b) 48h and (c) 72h respectively; (d): EDS result of zeolite (b);","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-233778/v1/3b41c265a1e383e9c968df6b.jpg"},{"id":6324696,"identity":"595ff842-d874-4733-95a7-c82240d45f43","added_by":"auto","created_at":"2021-02-24 20:07:03","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":22428,"visible":true,"origin":"","legend":"Particle size distribution of zeolite synthesized at 48h.","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-233778/v1/c63d396a14b94b37a213047b.jpg"},{"id":6324990,"identity":"d2dd97d9-ef1f-4419-bb98-ffe2f9d6a024","added_by":"auto","created_at":"2021-02-24 20:13:03","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":27266,"visible":true,"origin":"","legend":"TG-DSC curves of SZX.","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-233778/v1/03c07963b19d2d0a4161f838.jpg"},{"id":6324701,"identity":"d85231c6-9f4a-4b70-bc35-45d98723e69e","added_by":"auto","created_at":"2021-02-24 20:07:04","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":22549,"visible":true,"origin":"","legend":"Nitrogen adsorption–desorption isotherms of SZX; Insert is BJH pore size distribution curve.","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-233778/v1/4beaccdbfc26244685105d96.jpg"},{"id":13670913,"identity":"21f7fdec-032b-4a63-b7cf-f1b6c1e9cbe4","added_by":"auto","created_at":"2021-09-17 11:07:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":445962,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-233778/v1/6f3c21f0-97f3-4a38-9334-f6040fae5e06.pdf"},{"id":6324700,"identity":"b0824008-995e-4575-93e3-2f648bce9157","added_by":"auto","created_at":"2021-02-24 20:07:03","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":253374,"visible":true,"origin":"","legend":"Composition, phase analysis and SEM images of fly ash and residue. Preparation of seed and its role in synthesis of zeolite X.","description":"","filename":"Supplementarymaterial.pdf","url":"https://assets-eu.researchsquare.com/files/rs-233778/v1/1772867a227f0d79a8f02282.pdf"}],"financialInterests":"","formattedTitle":"Green synthesize of fly ash-based zeolite X: A potential microwave absorbent","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eWith the wide use of electronic devices, electromagnetic wave (EMW) pollution is becoming more and more serious, and hence EMW absorbing materials have attracted wide attention [1-2]. So far, various materials have already been prepared for EMW adsorption [3-10]. As a kind of low-cost material, natural and synthetic zeolites have great application potential in EMW adsorption field owning to the advantages of unique dielectric properties, low density, high specific surface, and strong mechanical and chemical stability. Recently, Shang et al. reported a sepiolite-based EMW adsorption composites with superior EMW absorption performance, in which the minimum reflection loss of -50.23 dB and effective absorption bandwidth of 5.01 GHz [11]. Using low-cost light-weight and natural sepiolite as starting material, the synthesis procedure is facile, economic and commercially practical. What\u0026rsquo;s more, the large surface area of sepiolite is convenient for multiple reflections and scattering, which can increase the propagation path of incident EMW and promote EMW dissipation. As another kind of porous mineral material, the research of zeolite/zeolite-based materials as islanding or regional dielectric loss absorbers is of great significance in the research field of new EMW absorbing materials, while the relevant reports are still rare.\u003c/p\u003e\n\u003cp\u003eZeolite X is one of the most widely used zeolites due to its large specific surface area and high adsorption capacity [12-14]. As a kind of porous inorganic material, zeolite has the characteristics of crystal and open framework structure with many pores in it. These pores are connected with each other through channels, and the pore size distribution is highly uniform. The weak interaction between porous AlO\u003csub\u003e4\u003c/sub\u003e/SiO\u003csub\u003e4\u003c/sub\u003e structure and non-framework cations endows zeolite with unique dielectric properties. The characteristics above are beneficial to EMW loss. Fly ash, a solid waste with huge discharge, has been widely used for the synthesis of zeolite X owing to its high silicon and aluminum content [15-17]. Numerous studies have been established to synthesize zeolite X, such as one-step method [18-19], two-step method [20-21], microwave-assisted two-step method [22-23] and ultrasonic-assisted method [24]. Normally, a large amount of solvent involves water or organic solution is required in these processes, which inevitably results in wastewater pollution [25]. In light of this, a pioneering process of solvent-free (trace water system) approach is proposed to solve this problem [26]. As a green approach, solvent-free method possesses significant advantages as high yield, sufficient utilization of autoclaves, and reduction of pollutants and so on [27].\u003c/p\u003e\n\u003cp\u003eIn this study, low-cost zeolite X was synthesized from fly ash using a solvent-free method. The prepared zeolite X possesses outstanding physical and chemical properties, and notably, the specific surface area is up to 473.56 m\u003csup\u003e2\u003c/sup\u003e/g, which represents porous structure and is beneficial to EMW attenuation. The work supplied a green and low-cost method to prepare zeolite X, which was expected to be an EMW absorbing material.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cp\u003e\u003cstrong\u003e2.1. Materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn this work, fly ash was obtained from Inner Mongolia, China. Analytical purity sodium aluminate, sodium hydroxide and sodium silicate were purchased from Aladdin reagent Co., Ltd.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.2. Synthesis of zeolite X \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAs we can see from XRF results (Table S1), Si/Al in fly ash is 1.70 which exhibits ideal raw materials for the synthesis of zeolite X, and no additional Si or Al source was necessary. The synthesis process was conducted in the following steps: Firstly, fly ash was homogeneously mixed with sodium hydroxide and the mixture was calcined in muffle furnace at 750℃ for 2h. After cooling, trace amounts of water and prepared seeds (5% wt) were added into the fused mixture to make a smooth paste. The final molar ratio of Na:Al:Si:H\u003csub\u003e2\u003c/sub\u003eO is 1:1:1.6:3.5 (in accordance with typical zeolite X (JCPDS card No. 12-0228): Na\u003csub\u003e2\u003c/sub\u003eAl\u003csub\u003e2\u003c/sub\u003eSi\u003csub\u003e3.3\u003c/sub\u003eO\u003csub\u003e10.6\u003c/sub\u003e\u0026middot;7H\u003csub\u003e2\u003c/sub\u003eO). Then transferred the paste into autoclave, and heating in an oven at 120℃ for 12-72h. After that, filtered and washed with distilled water for three times. Finally, the solid was dried at 105℃ for 24 h, and Zeolite X powder was obtained. The scheme of the synthesis process was shown in \u003cstrong\u003eFig. 1\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.3. Characterization\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eElements of raw ore, synthesized zeolite X and residue were tested by X-ray fluorescence spectrometer (XRF, AXIOS\u003csup\u003eMax\u003c/sup\u003e, PANalytical). The phase structure of the samples were analyzed by X-ray Diffractionmeter (XRD, D8-FOCUS, Bruker). Morphological characteristics were performed by a Scanning Electron Microscope (SEM, SU8010, HITACHI). The particle size distribution (PSD) of samples were determined using laser particle size analyzer instrument (Mastersizer 2000, MALVERN). The Brunauer-Emmett-Teller (BET) surface area, pore volume and pore size distribution were performed by N\u003csub\u003e2\u003c/sub\u003e adsorption at 77 K with an ASAP2020 (TSI) Automatic Volumetric Sorption Analyzer. Thermogravimetry/Differential Scanning Calorimetry (TG-DSC) analyses were characterized by Netzsch STA 409 thermal analysis system.\u003c/p\u003e"},{"header":"3. Results And Discussion","content":"\u003cp\u003e\u003cstrong\u003e3.1. XRD patterns and XRF analysis of synthesized zeolites\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo rapidly obtain pure zeolite X, synthesis time was controlled between 12h and 72h. When the reaction time is 12h, the product is completely amorphous. Then raising the reaction time to 24h, zeolite X (JCPDS card No. 12-0228 ) with low crystallinity and zeolite P (JCPDS card No. 39-0219) are obtained, and the content of zeolite X is higher than zeolite P. Thus, continuing to increase the reaction time to 48h, zeolite X with high crystallinity is prepared. Although there is still tiny amount of zeolite P, the purity and crystallinity are excellent enough. Further improving the reaction time to 72h, intensity of zeolite X weakens remarkably, however, intensity of zeolite P strengthens by contrast. In addition, peaks of sodalite (JCPDS card No. 73-1733) appear as well. It is obvious that high temperature is unfavorable to the crystallization of zeolite X. Therefore, zeolite X synthesized at 48h is taken for the further study, which is named SZX.\u003c/p\u003e\n\u003cp\u003eX-ray fluorescence spectrometer (XRF) was used to conduct the chemical compositions of SZX. As is shown, apart from the structural components of zeolite X (Si, Al and Na), small amount of Ti, Fe, Mg, Ca, K are also concluded. The Si/Al ratio of SZX is 1.28, presents a typical zeolite X. (\u003cstrong\u003eTable 1\u003c/strong\u003e).\u003c/p\u003e\u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;text-indent:24.0pt;line-height:200%;'\u003e\u003cspan style=\"font-size: 15px; line-height: 200%; font-family: Calibri, sans-serif; color: black;\"\u003eTable 1. Main compositions of SZX, \u003cspan style=\"color: black; font-weight: normal; font-style: italic;\"\u003eLOI is loss on ignition.\u003c/span\u003e (mass fraction, %)\u003c/span\u003e\u003c/p\u003e\n\u003ctable style=\"width:100.0%;margin-left:5.4pt;border-collapse:collapse;border:none;\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 18.44%;border-top: 1.5pt solid windowtext;border-left: none;border-bottom: 1.5pt solid windowtext;border-right: none;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eComposition\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.4%;border-top: 1.5pt solid windowtext;border-left: none;border-bottom: 1.5pt solid windowtext;border-right: none;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.92%;border-top: 1.5pt solid windowtext;border-left: none;border-bottom: 1.5pt solid windowtext;border-right: none;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.62%;border-top: 1.5pt solid windowtext;border-left: none;border-bottom: 1.5pt solid windowtext;border-right: none;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eNa\u003csub\u003e2\u003c/sub\u003eO\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8.84%;border-top: 1.5pt solid windowtext;border-left: none;border-bottom: 1.5pt solid windowtext;border-right: none;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eTiO\u003csub\u003e2\u003c/sub\u003e\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;border-top: 1.5pt solid windowtext;border-left: none;border-bottom: 1.5pt solid windowtext;border-right: none;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eTFe\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.34%;border-top: 1.5pt solid windowtext;border-left: none;border-bottom: 1.5pt solid windowtext;border-right: none;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eMgO\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8.7%;border-top: 1.5pt solid windowtext;border-left: none;border-bottom: 1.5pt solid windowtext;border-right: none;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eCaO\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8.38%;border-top: 1.5pt solid windowtext;border-left: none;border-bottom: 1.5pt solid windowtext;border-right: none;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eK\u003csub\u003e2\u003c/sub\u003eO\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.4%;border-top: 1.5pt solid windowtext;border-left: none;border-bottom: 1.5pt solid windowtext;border-right: none;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eLOI\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 18.44%;border-top: none;border-right: none;border-left: none;border-image: initial;border-bottom: 1.5pt solid windowtext;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eWt.%\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.4%;border-top: none;border-right: none;border-left: none;border-image: initial;border-bottom: 1.5pt solid windowtext;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e39.36\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.92%;border-top: none;border-right: none;border-left: none;border-image: initial;border-bottom: 1.5pt solid windowtext;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e26.15\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.62%;border-top: none;border-right: none;border-left: none;border-image: initial;border-bottom: 1.5pt solid windowtext;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e15.91\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8.84%;border-top: none;border-right: none;border-left: none;border-image: initial;border-bottom: 1.5pt solid windowtext;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e0.04\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;border-top: none;border-right: none;border-left: none;border-image: initial;border-bottom: 1.5pt solid windowtext;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e0.06\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.34%;border-top: none;border-right: none;border-left: none;border-image: initial;border-bottom: 1.5pt solid windowtext;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e0.26\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8.7%;border-top: none;border-right: none;border-left: none;border-image: initial;border-bottom: 1.5pt solid windowtext;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e0.31\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8.38%;border-top: none;border-right: none;border-left: none;border-image: initial;border-bottom: 1.5pt solid windowtext;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e0.26\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.4%;border-top: none;border-right: none;border-left: none;border-image: initial;border-bottom: 1.5pt solid windowtext;padding: 0in 5.4pt;height: 16.5pt;vertical-align: top;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-family: Calibri, sans-serif; font-size: 15px;\"\u003e\u003cspan style=\"color: black;\"\u003e16.92\u0026nbsp;\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\u003cbr\u003e\u003cp\u003e\u003cstrong\u003e3.2. Morphology analysis of synthesized zeolites\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe SEM images and EDS result are shown in Fig. 3. When the reaction time is 24h (Fig.3(a)), it can be seen that the particle size of zeolite X is about 2.5\u0026mu;m, and the morphology is irregular. Thus, continuing to increase the reaction time to 48h (Fig.3(b)), the morphology of zeolite X is of regular octahedron and uniform particle size (about 2.5\u0026mu;m). Zeolite X synthesized at 72h presents regular octahedron as well (Fig.3(c)), but the particle size (about 2.6\u0026mu;m) is a little larger than that of 48h. The EDS result of SZX is exhibited in Fig. 2(d), and it shows that the Si/Al ratio is about 1.28, which fits the XRF result perfectly.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.3. Particle size distribution of synthesized zeolites\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAccording to the data of PSD (Fig. 2(f)), the particle size distribution of SZX follows gaussian distributions, and the average particle size of SZX is about 2.45\u0026mu;m, which was in good agreement with the SEM results. The results above indicate that SZX was smaller and more uniform compared to that obtained by hydrothermal method [28-29]\u003cstrong\u003e.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.4. Thermal behavior analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTG-DSC curves of SZX are shown in Fig. 5. Before 100℃, there is a weak endothermic peek, which shows adsorbing steam of air on SZX [30]. TG curve of the sample shows smooth mass loss and was devoid of any distinct kinks. And a significant endothermal valley appears at 136℃. Meanwhile, there is a dramatic weight loss on the TG curve. When it reaches to 246℃, the free water is removed completely. Obviously, the content of free water is high, which will produce dipole polarization and relaxation under the action of electromagnetic field so as to consume EMW energy. The strong exothermal peak at 246℃ may be caused by the combustion of organic impurities, which is another source of dipole polarization. After 600℃, mass loss is stable at about 20.61%. Although the TG-DSC analysis was conducted under 800℃, however, the tendency of DSC curve hints that there exists at least an exothermal peak after 800℃ which is caused by the phase transformation and the decomposition of zeolite structure [31]. Hence the heat treatment temperature of SZX should be controlled below 600℃.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.5. Specific surface area analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe pore structure of SZX was evaluated by nitrogen adsorption measurements, and the results are shown in Fig.6. According to the IUPAC classification, the isotherm presents classical type IV with H3 hysteresis loop [32,33]. The pore size distribution for SZX was estimated by the BJH method as shown in the insert Fig. 6, which shows a pore radius below 3 nm. And the broad pore size distribution might be caused by the agglomeration of zeolite particles. The textural parameters of SZX are shown in Table 2. BET surface area is measured to be 473.56 m\u003csup\u003e2\u003c/sup\u003e/g, and the prepared zeolite is primarily microporous with average pore size of 1.914 nm. Large numbers of micropores and channels allows EMW transmit into the material easily, and extends the propagation channel of EMW. Thus, EMW adsorption is increased. According to the literatures, large specific surface area of porous material represents good EMW absorbing performance.\u003c/p\u003e\u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px; font-family: Calibri, sans-serif; color: black;\"\u003eTable 2.\u0026nbsp;\u003c/span\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003eTextural Parameters of SZX\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n\u003ctable style=\"width:100.0%;margin-left:5.4pt;border-collapse:collapse;border:none;\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:8.88%;border-top:solid black 1.5pt;border-left: none;border-bottom:solid black 1.5pt;border-right:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003e\u0026nbsp;\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:14.92%;border-top:solid black 1.5pt;border-left: none;border-bottom:solid black 1.5pt;border-right:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eS\u003csub\u003eBET\u003c/sub\u003e (m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:14.3%;border-top:solid black 1.5pt;border-left: none;border-bottom:solid black 1.5pt;border-right:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eS\u003csub\u003emic\u003c/sub\u003e (m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:16.96%;border-top:solid black 1.5pt;border-left: none;border-bottom:solid black 1.5pt;border-right:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eV\u003csub\u003eTotal\u003c/sub\u003e (cm\u003csup\u003e3\u003c/sup\u003e/g)\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:16.04%;border-top:solid black 1.5pt;border-left: none;border-bottom:solid black 1.5pt;border-right:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eV\u003csub\u003emic\u003c/sub\u003e (cm\u003csup\u003e3\u003c/sup\u003e/g)\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:28.9%;border-top:solid black 1.5pt;border-left: none;border-bottom:solid black 1.5pt;border-right:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eAverage pore size (nm)\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:8.88%;border:none;border-bottom:solid black 1.5pt;padding:0in 5.4pt 0in 5.4pt;height:20.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: black;\"\u003eMSZX\u003c/span\u003e\u003c/strong\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:14.92%;border:none;border-bottom:solid black 1.5pt;padding:0in 5.4pt 0in 5.4pt;height:20.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e473.56\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:14.3%;border:none;border-bottom:solid black 1.5pt;padding:0in 5.4pt 0in 5.4pt;height:20.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e428.32\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:16.96%;border:none;border-bottom:solid black 1.5pt;padding:0in 5.4pt 0in 5.4pt;height:20.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e0.265\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:16.04%;border:none;border-bottom:solid black 1.5pt;padding:0in 5.4pt 0in 5.4pt;height:20.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-size: 15px;\"\u003e\u003cspan style=\"font-family: Calibri, sans-serif;\"\u003e\u003cspan style=\"color: black;\"\u003e0.240\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:28.9%;border:none;border-bottom:solid black 1.5pt;padding:0in 5.4pt 0in 5.4pt;height:20.5pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;'\u003e\u003cspan style=\"font-family: Calibri, sans-serif; font-size: 15px;\"\u003e\u003cspan style=\"color: black;\"\u003e1.914\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\u003cbr\u003e\u003cp\u003e\u003cstrong\u003e3.6. Prospect as an EMW absorbent\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe zeolite X prepared in this work is of good prospect to be EMW absorbing materials. On one hand, the special porous structure and frame structure enable zeolite X good impedance matching, which make the incident EMW enter the material as much as possible; on the other hand, in addition to dipole polarization loss caused by adsorbed water and impurities, the vesicular cavity and the structure between vesicular in materials will also reflect and scatter EMWs, which dissipate EMW energy greatly. What\u0026rsquo;s more, Zeolite materials have the characteristics of light weight and thermal stability, which provides favorable conditions for it to become a new type of microwave absorbing material. Briefly, the zeolite X prepared in this work is of good prospect to be a EMW absorbing material. So zeolite and zeolite-based materials will be further studied in our following work.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eHigh purity zeolite X was synthesized by a green methed from fly ash in 48h. For SZX, the Si/Al ratio is 1.28; the average particle size is about 2.45\u0026mu;m; and the specific surface area is 473.56 m\u003csup\u003e2\u003c/sup\u003e/g. Besides, the SZX shows good phase, morphology and thermal stability as well. Besides, through theoretical analysis, zeolite X is a hopeful EMW absorbing material because of its good impedance matching, dipole polarization loss and reflecting and scattering EMWs caused by vesicular cavity. And the EMW adsorption capacity of zeolite X will be further studied in following research.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was funded by the Research Program of Yan'an University (Grant No. YDY2019-25).\u003c/p\u003e"},{"header":"References","content":"\u003cp\u003e[1] A. Iqbal, F. Shahzad, K. Hantanasirisakul, Science \u003cstrong\u003e369\u003c/strong\u003e, 446 (2020) https://doi.org/10.1126/science.aba7977.\u003c/p\u003e\n\u003cp\u003e[2] I. Abdalla, A. Elhassan, J.Y. Yu, Carbon \u003cstrong\u003e157,\u003c/strong\u003e 703-713 (2020) https://doi.org/10.1016/j.carbon.2019.11.004.\u003c/p\u003e\n\u003cp\u003e[3] H.J. Wu, L.D. Wang, S.L. Guo, Appl. Phys. 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Mater. \u003cstrong\u003e11, \u003c/strong\u003e60-67 (2019) https://doi.org/10.1166/sam.2019.3387.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Zeolite X, Fly ash, Green synthesis, Dielectric absorber.","lastPublishedDoi":"10.21203/rs.3.rs-233778/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-233778/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Zeolite X is a potential electromagnetic wave (EMW) absorption material owning to its advantages of good dielectric properties, light weight and large specific surface area. Herein, high-purity zeolite X was prepared from fly ash using a green synthesis approach, in which only trace water was used and achieved zero discharge of waste water. Physiochemical properties of fabricated zeolite X were comprehensively evaluated through XRD, PSD, SEM, TG-DSC and BET test. XRD pattern shows the successful preparation of zeolite X with good crystallinity and high purity, and the average particle size is ~2.45 μm, which conforms to Gaussian distributions. The fabricated zeolite X exhibits typical octahedral structure and good thermal stability. It is noteworthy that the specific surface area is up to 473.56 m 2 /g, representing porous structure, which is beneficial to EMW attenuation. What’s more, the abundant crystal water and adsorbed water existing in the sample is conductive to dipole polarization, which further consume EMW energy. This study provides an eco-friendly approach to change waste into valuables, and moreover the synthesized zeolite X is a potential EMW absorbing material.","manuscriptTitle":"Green synthesize of fly ash-based zeolite X: A potential microwave absorbent","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-02-24 20:07:01","doi":"10.21203/rs.3.rs-233778/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e615d12c-f1e7-4240-8b03-65977cdb7d5e","owner":[],"postedDate":"February 24th, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":2611897,"name":"Electronic Materials and Devices"}],"tags":[],"updatedAt":"2021-05-10T08:35:38+00:00","versionOfRecord":[],"versionCreatedAt":"2021-02-24 20:07:01","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-233778","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-233778","identity":"rs-233778","version":["v1"]},"buildId":"-HB7Z8yhvgn0wM9Nzuekk","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}