Structural Evolution and Sorption Performance of Fly Ash-Based Geopolymers for Trivalent Actinide Sequestration

Structural Evolution and Sorption Performance of Fly Ash-Based Geopolymers for Trivalent Actinide Sequestration | 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 Structural Evolution and Sorption Performance of Fly Ash-Based Geopolymers for Trivalent Actinide Sequestration ATANU DAS, Aishwarya S. Kar, Vaishali Arunachalam, Deepak Tyagi, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8981614/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 This study investigates the structural evolution and sorption performance of fly ash-based GPs (FA-GP) and GP modified with γ-Al 2 ​O 3 ​ (FA-Al-GP) for the sequestration of trivalent actinides, using 241 Am(III). Comprehensive characterization via XRD, FTIR, and SEM-EDS confirmed that geopolymerization leads to the consumption of the amorphous FA phase, while 27 Al MAS NMR revealed the successful integration of γ-Al 2 O 3 ​ into the aluminosilicate framework. Although BET analysis showed a reduction in surface area from 41 m 2 /g (FA-GP) to 16 m 2 /g (FA-Al-GP), the alumina-modified matrix exhibited superior densification and a more refined polymeric network. Sorption experiments demonstrated that both GPs achieve high uptake efficiencies (> 97%) across a wide pH range (4–8). Kinetic data obeyed the pseudo-second-order model, indicating a chemisorption-controlled process. Equilibrium sorption data were well fitted by the Langmuir isotherm, confirming monolayer adsorption on energetically favorable sites. FA-Al-GP exhibited significantly enhanced sorption capacities compared to FA-GP, reaching a maximum capacity of ~ 66 mg.g − 1 at 328 K, suggesting that γ -Al 2 ​O 3 modification introduces highly accessible, thermally stable active sites. Mechanistic insights were provided by Time-Resolved Fluorescence Spectroscopy (TRFS) and X-ray Photoelectron Spectroscopy (XPS). TRFS of sorbed Eu(III) revealed inner-sphere complexation with aluminol and silanol groups present in the GPs. XPS analysis further evidenced the interaction between trivalent ions and oxygen-donor groups (Si-O- and Al-O-) through distinct binding energy shifts in O 1s. These findings underscore that γ-Al 2 ​O 3 ​ modification not only enhances the structural integrity of FA-Al-GP but also significantly improves its capacity for radioactive waste remediation. Full Text Additional Declarations No competing interests reported. Supplementary Files supportinginformation.docx 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-8981614","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":600806451,"identity":"f04ac928-e24f-4ac2-a2ef-c862cd9b3209","order_by":0,"name":"ATANU DAS","email":"","orcid":"","institution":"Bhabha Atomic Research Centre","correspondingAuthor":false,"prefix":"","firstName":"ATANU","middleName":"","lastName":"DAS","suffix":""},{"id":600806452,"identity":"e36f24a8-5bc1-488d-8563-a11463147dc8","order_by":1,"name":"Aishwarya S. 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Comprehensive characterization via XRD, FTIR, and SEM-EDS confirmed that geopolymerization leads to the consumption of the amorphous FA phase, while \u003csup\u003e27\u003c/sup\u003eAl MAS NMR revealed the successful integration of γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e​ into the aluminosilicate framework. Although BET analysis showed a reduction in surface area from 41 m\u003csup\u003e2\u003c/sup\u003e/g (FA-GP) to 16 m\u003csup\u003e2\u003c/sup\u003e/g (FA-Al-GP), the alumina-modified matrix exhibited superior densification and a more refined polymeric network. Sorption experiments demonstrated that both GPs achieve high uptake efficiencies (\u0026gt;\u0026thinsp;97%) across a wide pH range (4\u0026ndash;8). Kinetic data obeyed the pseudo-second-order model, indicating a chemisorption-controlled process. Equilibrium sorption data were well fitted by the Langmuir isotherm, confirming monolayer adsorption on energetically favorable sites. FA-Al-GP exhibited significantly enhanced sorption capacities compared to FA-GP, reaching a maximum capacity of ~\u0026thinsp;66 mg.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 328 K, suggesting that γ -Al\u003csub\u003e2\u003c/sub\u003e​O\u003csub\u003e3\u003c/sub\u003e modification introduces highly accessible, thermally stable active sites. Mechanistic insights were provided by Time-Resolved Fluorescence Spectroscopy (TRFS) and X-ray Photoelectron Spectroscopy (XPS). TRFS of sorbed Eu(III) revealed inner-sphere complexation with aluminol and silanol groups present in the GPs. XPS analysis further evidenced the interaction between trivalent ions and oxygen-donor groups (Si-O- and Al-O-) through distinct binding energy shifts in O 1s. 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