Phase Equilibria of D2O Hydrates for Hydrate-Based Tritium Separation

Phase Equilibria of D2O Hydrates for Hydrate-Based Tritium Separation | 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 Phase Equilibria of D2O Hydrates for Hydrate-Based Tritium Separation Ryonosuke Kasai, Haruki Ito, Hitoshi Kiyokawa, Leo Kamiya, Saman Alavi, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7559542/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 18 Oct, 2025 Read the published version in International Journal of Thermophysics → Version 1 posted 9 You are reading this latest preprint version Abstract Clathrate-hydrate-based tritium separation from isotope water is a promising process for removing tritium that is not effectively separated by conventional methods. Clathrate hydrates (hereafter hydrates) are crystalline compounds composed of water and guest molecules. Hydrate-based tritium separation utilizes the property that heavy water (D 2 O) forms hydrates under milder temperatures than light water (H 2 O). Efficient industrial operation requires a guest compound that forms hydrates at high temperatures and low pressures and has a large difference in phase equilibrium temperature between H 2 O and D 2 O hydrates (Δ T DH ). In this study, we measured the phase equilibrium conditions of D 2 O hydrates formed with HFC-134a, HFC-32, and HFC-23. The formation of D 2 O hydrates with these guests can be a route to tritium separation through co-precipitation of T 2 O. HFC-134a formed hydrates under the mildest conditions, with Δ T DH values of 2.8 K, 1.8 K, and 2.4 K for HFC-134a, HFC-32, and HFC-23. In addition to the three investigated guests, the potentials of cyclopentane and cyclopentane + CO₂ hydrate systems for hydrogen isotope separations were also compared, suggesting that HFC-134a and cyclopentane may be suitable guests for tritium separation. Present and previous studies have also shown a strong positive correlation between the hydration number and Δ T DH (correlation coefficient = 0.76). This trend may be ascribed to the fact that a higher proportion of water molecules in the hydrate amplifies the effect of replacing H 2 O with D 2 O. These results indicate that the equilibrium conditions of D₂O hydrates may be approximately predicted to identify suitable guests for tritium separation. Clathrate hydrate Phase equilibrium Tritium separation Deuterium oxide Hydration number Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 18 Oct, 2025 Read the published version in International Journal of Thermophysics → Version 1 posted Editorial decision: Revision requested 28 Sep, 2025 Reviews received at journal 28 Sep, 2025 Reviews received at journal 25 Sep, 2025 Reviewers agreed at journal 12 Sep, 2025 Reviewers agreed at journal 11 Sep, 2025 Reviewers invited by journal 08 Sep, 2025 Editor assigned by journal 08 Sep, 2025 Submission checks completed at journal 08 Sep, 2025 First submitted to journal 07 Sep, 2025 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. 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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-7559542","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":514263764,"identity":"b0dbe867-0492-45ab-b44c-3cf8cc2be68d","order_by":0,"name":"Ryonosuke Kasai","email":"","orcid":"","institution":"Keio University","correspondingAuthor":false,"prefix":"","firstName":"Ryonosuke","middleName":"","lastName":"Kasai","suffix":""},{"id":514263765,"identity":"b4b259db-c9a4-48bd-bf55-abcbd783d5c3","order_by":1,"name":"Haruki Ito","email":"","orcid":"","institution":"Keio 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Separation","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-thermophysics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ijot","sideBox":"Learn more about [International Journal of Thermophysics](http://link.springer.com/journal/10765)","snPcode":"10765","submissionUrl":"https://submission.nature.com/new-submission/10765/3","title":"International Journal of Thermophysics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Clathrate hydrate, Phase equilibrium, Tritium separation, Deuterium oxide, Hydration number","lastPublishedDoi":"10.21203/rs.3.rs-7559542/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7559542/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eClathrate-hydrate-based tritium separation from isotope water is a promising process for removing tritium that is not effectively separated by conventional methods. Clathrate hydrates (hereafter hydrates) are crystalline compounds composed of water and guest molecules. Hydrate-based tritium separation utilizes the property that heavy water (D\u003csub\u003e2\u003c/sub\u003eO) forms hydrates under milder temperatures than light water (H\u003csub\u003e2\u003c/sub\u003eO). Efficient industrial operation requires a guest compound that forms hydrates at high temperatures and low pressures and has a large difference in phase equilibrium temperature between H\u003csub\u003e2\u003c/sub\u003eO and D\u003csub\u003e2\u003c/sub\u003eO hydrates (Δ\u003cem\u003eT\u003c/em\u003e\u003csub\u003eDH\u003c/sub\u003e). In this study, we measured the phase equilibrium conditions of D\u003csub\u003e2\u003c/sub\u003eO hydrates formed with HFC-134a, HFC-32, and HFC-23. The formation of D\u003csub\u003e2\u003c/sub\u003eO hydrates with these guests can be a route to tritium separation through co-precipitation of T\u003csub\u003e2\u003c/sub\u003eO. HFC-134a formed hydrates under the mildest conditions, with Δ\u003cem\u003eT\u003c/em\u003e\u003csub\u003eDH\u003c/sub\u003e values of 2.8 K, 1.8 K, and 2.4 K for HFC-134a, HFC-32, and HFC-23. In addition to the three investigated guests, the potentials of cyclopentane and cyclopentane\u0026thinsp;+\u0026thinsp;CO₂ hydrate systems for hydrogen isotope separations were also compared, suggesting that HFC-134a and cyclopentane may be suitable guests for tritium separation. Present and previous studies have also shown a strong positive correlation between the hydration number and Δ\u003cem\u003eT\u003c/em\u003e\u003csub\u003eDH\u003c/sub\u003e (correlation coefficient\u0026thinsp;=\u0026thinsp;0.76). This trend may be ascribed to the fact that a higher proportion of water molecules in the hydrate amplifies the effect of replacing H\u003csub\u003e2\u003c/sub\u003eO with D\u003csub\u003e2\u003c/sub\u003eO. These results indicate that the equilibrium conditions of D₂O hydrates may be approximately predicted to identify suitable guests for tritium separation.\u003c/p\u003e","manuscriptTitle":"Phase Equilibria of D2O Hydrates for Hydrate-Based Tritium Separation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-15 18:58:16","doi":"10.21203/rs.3.rs-7559542/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-28T16:31:38+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-28T16:08:14+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-25T14:37:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"80477634356028860528143188813640791779","date":"2025-09-12T14:20:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"102885353907608346355091104359749216192","date":"2025-09-11T07:31:39+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-08T10:17:43+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-08T04:33:22+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-08T04:32:59+00:00","index":"","fulltext":""},{"type":"submitted","content":"International Journal of Thermophysics","date":"2025-09-08T03:13:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-thermophysics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ijot","sideBox":"Learn more about [International Journal of Thermophysics](http://link.springer.com/journal/10765)","snPcode":"10765","submissionUrl":"https://submission.nature.com/new-submission/10765/3","title":"International Journal of Thermophysics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"36e92b7c-913d-4878-a033-54242bebe21e","owner":[],"postedDate":"September 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-10-20T16:02:52+00:00","versionOfRecord":{"articleIdentity":"rs-7559542","link":"https://doi.org/10.1007/s10765-025-03666-7","journal":{"identity":"international-journal-of-thermophysics","isVorOnly":false,"title":"International Journal of Thermophysics"},"publishedOn":"2025-10-18 15:57:09","publishedOnDateReadable":"October 18th, 2025"},"versionCreatedAt":"2025-09-15 18:58:16","video":"","vorDoi":"10.1007/s10765-025-03666-7","vorDoiUrl":"https://doi.org/10.1007/s10765-025-03666-7","workflowStages":[]},"version":"v1","identity":"rs-7559542","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7559542","identity":"rs-7559542","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}