Ozonation as a Scalable Method to Tune Biochar Cation Exchange Capacity and pH for Amending Alkaline Sandy Soils

Ozonation as a Scalable Method to Tune Biochar Cation Exchange Capacity and pH for Amending Alkaline Sandy Soils | 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 Ozonation as a Scalable Method to Tune Biochar Cation Exchange Capacity and pH for Amending Alkaline Sandy Soils Batool Albar, Nayara H. Musskopf, Andreia S.F. Farinha, George Harrison, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8691776/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 Biochar is increasingly being recognized as soil amendment that can enhance nutrient and water retention while sequestering carbon. However, biochars derived from locally available feedstocks in arid regions, e.g., date palm fronds, often exhibit high intrinsic alkalinity, which limits their application in sandy soils despite their high cation exchange capacity (CEC), the property governing nutrient retention in soil. Here, we investigate ozonation as a scalable post-treatment strategy to tune the CEC and pH of biochar produced from date palm fronds, a major organic waste stream in the Middle East. Ball-milled biochar was ozonated over a wide range of temperatures (25–190 ℃) and reaction durations (24–96 h), and changes in CEC, pH, surface area, functional groups, and mass were quantified. Ozonation increased CEC by up to 220 % and reduced biochar pH from 8.6 to as low as 3.9. Biochars ozonated at higher temperatures (≥110 ℃) exhibited significant mass loss, due to CO₂ evolution, and higher concentrations of adsorbed base cations, whereas lower-temperature ozonation (<80 ℃) resulted in net mass gain, associated with surface oxidation, and increased acidity. Although ozonation increased the O/C ratio, proximate analysis indicated that chemical stability was not compromised, and H/C org remained largely unchanged. A preliminary cost analysis further indicates that this approach is scalable. Therefore, these results establish ozonation as a sustainable method for tuning biochar properties for amending alkaline sandy soils, with implications for desert rehabilitation, urban greening, food production, and carbon sequestration. ozonation cation exchange capacity oxidation half-life O/C ratio H/C ratio pH Full Text Additional Declarations The authors declare potential competing interests as follows: BA, AGJ, and HM have filed a KAUST IP disclosure for biochar ozonation (KAUST IP#2023-073), and this IP is licensed exclusively Terraxy LLC (CR#4030502411) co-founded by AGJ and HM. 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. 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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-8691776","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":580025471,"identity":"08b960c3-d475-4206-896c-b84cf4c23942","order_by":0,"name":"Batool Albar","email":"","orcid":"","institution":"King Abdullah University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Batool","middleName":"","lastName":"Albar","suffix":""},{"id":580027847,"identity":"5ab4fffe-f399-4951-b490-1f9b3ac4074c","order_by":1,"name":"Nayara H. 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recognized as soil amendment that can enhance nutrient and water retention while sequestering carbon. However, biochars derived from locally available feedstocks in arid regions, e.g., date palm fronds, often exhibit high intrinsic alkalinity, which limits their application in sandy soils despite their high cation exchange capacity (CEC), the property governing nutrient retention in soil. Here, we investigate ozonation as a scalable post-treatment strategy to tune the CEC and pH of biochar produced from date palm fronds, a major organic waste stream in the Middle East. Ball-milled biochar was ozonated over a wide range of temperatures (25–190 ℃) and reaction durations (24–96 h), and changes in CEC, pH, surface area, functional groups, and mass were quantified. Ozonation increased CEC by up to 220 % and reduced biochar pH from 8.6 to as low as 3.9. Biochars ozonated at higher temperatures (≥110 ℃) exhibited significant mass loss, due to CO₂ evolution, and higher concentrations of adsorbed base cations, whereas lower-temperature ozonation (\u0026lt;80 ℃) resulted in net mass gain, associated with surface oxidation, and increased acidity. Although ozonation increased the O/C ratio, proximate analysis indicated that chemical stability was not compromised, and \u0026nbsp;H/C\u003csub\u003eorg\u003c/sub\u003e \u0026nbsp;remained largely unchanged. A preliminary cost analysis further indicates that this approach is scalable. Therefore, these results establish ozonation as a sustainable method for tuning biochar properties for amending alkaline sandy soils, with implications for desert rehabilitation, urban greening, food production, and carbon sequestration.\u003c/p\u003e","manuscriptTitle":"Ozonation as a Scalable Method to Tune Biochar Cation Exchange Capacity and pH for Amending Alkaline Sandy Soils","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-27 16:54:09","doi":"10.21203/rs.3.rs-8691776/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":"fb27295d-8c90-4cee-83ae-5d9ff352d6ef","owner":[],"postedDate":"January 27th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-27T16:54:10+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-27 16:54:09","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8691776","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8691776","identity":"rs-8691776","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}