Oxalate enhanced photochemical decomplexation of Cu(II)-EDTA in a Cu-Fenton system

Oxalate enhanced photochemical decomplexation of Cu(II)-EDTA in a Cu-Fenton system | 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 Oxalate enhanced photochemical decomplexation of Cu(II)-EDTA in a Cu-Fenton system Chengyu Wang, yuhang Zhang, Zhijun Luo, Lingling Qu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8413039/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract The removal of recalcitrant copper complexes necessitates an initial decomplexation step to free the copper ions, enabling their subsequent removal by alkaline precipitation. The conventional Cu-Fenton processes suffer from slow kinetics due to the rate-limiting reduction of Cu(II). This study introduces a novel oxalate-enhanced, visible-light-driven Cu-Fenton process (H₂O₂/Cu(II)/OA/VL) that overcomes this bottleneck through a targeted photochemical mechanism. The synergistic use of oxalic acid (OA) and visible light (VL) dramatically enhanced Cu(II)-EDTA decomplexation, increasing copper removal efficiency from 22.78% to 94.37% and accelerating the reaction rate by 14.42-fold (rate constant: 0.0217 vs. 0.0019 min⁻¹). Mechanistic investigations confirm that OA coordinates with Cu(II) to form photoactive Cu(II)-oxalate complexes. Under VL irradiation, these complexes undergo a ligand-to-metal charge transfer (LMCT) process, which efficiently accelerates the rate-limiting reduction of Cu(II) to Cu(I). This sustains an active Cu(I)/Cu(II) redox cycle, enabling continuous H₂O₂ activation to generate a suite of reactive species (•OH, O₂•⁻, and Cu(III)). These species collectively drive the complete degradation of EDTA via stepwise decarboxylation, yielding low-molecular-weight acids, CO₂, and inorganic ions. The environmental viability of the process is demonstrated by a significant reduction in phytotoxicity, as evidenced by improved lettuce growth. This work provides an efficient, iron-free advanced oxidation process hinged on a well-defined photochemical Cu(I)/Cu(II) redox cycle, offering a sustainable strategy for treating recalcitrant metal-complexed wastewater. Photo-Fenton advanced oxidation processes decomplexation Cu complexes visible light Full Text Additional Declarations No competing interests reported. Supplementary Files SI.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 23 Mar, 2026 Reviewers agreed at journal 27 Feb, 2026 Reviews received at journal 29 Jan, 2026 Reviewers agreed at journal 25 Jan, 2026 Reviewers agreed at journal 19 Jan, 2026 Reviewers invited by journal 06 Jan, 2026 Editor assigned by journal 06 Jan, 2026 Submission checks completed at journal 20 Dec, 2025 First submitted to journal 20 Dec, 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-8413039","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":570332379,"identity":"71699bf0-f3f5-449a-bdd8-bc65a985af0c","order_by":0,"name":"Chengyu Wang","email":"","orcid":"","institution":"Jiangsu University","correspondingAuthor":false,"prefix":"","firstName":"Chengyu","middleName":"","lastName":"Wang","suffix":""},{"id":570332380,"identity":"4803d5c8-2103-4aec-b732-7ffc1f52a4b3","order_by":1,"name":"yuhang Zhang","email":"","orcid":"","institution":"Jiangsu 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system","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":"photochemical-and-photobiological-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ppss","sideBox":"Learn more about [Photochemical \u0026 Photobiological Sciences](https://link.springer.com/journal/43630)","snPcode":"43630","submissionUrl":"https://www.editorialmanager.com/ppss/","title":"Photochemical \u0026 Photobiological Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Photo-Fenton, advanced oxidation processes, decomplexation, Cu complexes, visible light","lastPublishedDoi":"10.21203/rs.3.rs-8413039/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8413039/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe removal of recalcitrant copper complexes necessitates an initial decomplexation step to free the copper ions, enabling their subsequent removal by alkaline precipitation. The conventional Cu-Fenton processes suffer from slow kinetics due to the rate-limiting reduction of Cu(II). This study introduces a novel oxalate-enhanced, visible-light-driven Cu-Fenton process (H₂O₂/Cu(II)/OA/VL) that overcomes this bottleneck through a targeted photochemical mechanism. The synergistic use of oxalic acid (OA) and visible light (VL) dramatically enhanced Cu(II)-EDTA decomplexation, increasing copper removal efficiency from 22.78% to 94.37% and accelerating the reaction rate by 14.42-fold (rate constant: 0.0217 vs. 0.0019 min⁻¹). Mechanistic investigations confirm that OA coordinates with Cu(II) to form photoactive Cu(II)-oxalate complexes. Under VL irradiation, these complexes undergo a ligand-to-metal charge transfer (LMCT) process, which efficiently accelerates the rate-limiting reduction of Cu(II) to Cu(I). This sustains an active Cu(I)/Cu(II) redox cycle, enabling continuous H₂O₂ activation to generate a suite of reactive species (•OH, O₂•⁻, and Cu(III)). These species collectively drive the complete degradation of EDTA via stepwise decarboxylation, yielding low-molecular-weight acids, CO₂, and inorganic ions. The environmental viability of the process is demonstrated by a significant reduction in phytotoxicity, as evidenced by improved lettuce growth. This work provides an efficient, iron-free advanced oxidation process hinged on a well-defined photochemical Cu(I)/Cu(II) redox cycle, offering a sustainable strategy for treating recalcitrant metal-complexed wastewater.\u003c/p\u003e","manuscriptTitle":"Oxalate enhanced photochemical decomplexation of Cu(II)-EDTA in a Cu-Fenton system","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-12 10:32:08","doi":"10.21203/rs.3.rs-8413039/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-23T17:26:33+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"184129176798966254631480862109630406532","date":"2026-02-27T14:09:40+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-29T11:53:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"329290016166894696009852302038087434905","date":"2026-01-25T06:05:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"152691806102813545517199188400099852537","date":"2026-01-19T12:09:37+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-06T16:06:05+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-06T15:09:59+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-20T17:49:43+00:00","index":"","fulltext":""},{"type":"submitted","content":"Photochemical \u0026 Photobiological Sciences","date":"2025-12-20T15:06:35+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"photochemical-and-photobiological-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ppss","sideBox":"Learn more about [Photochemical \u0026 Photobiological Sciences](https://link.springer.com/journal/43630)","snPcode":"43630","submissionUrl":"https://www.editorialmanager.com/ppss/","title":"Photochemical \u0026 Photobiological Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"b4421392-3448-4cca-b5b9-3ad6073fcfc8","owner":[],"postedDate":"January 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-14T06:26:26+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-12 10:32:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8413039","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8413039","identity":"rs-8413039","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}