Biochar Surface Oxygenation by Ozonization for Super High Cation Exchange Capacity

dc.contributor.authorKharel, Gyanendraen
dc.contributor.authorSacko, Oumaren
dc.contributor.authorFeng, Xuen
dc.contributor.authorMorris, John R.en
dc.contributor.authorPhillips, Claire L.en
dc.contributor.authorTrippe, Kristinen
dc.contributor.authorKumar, Sandeepen
dc.contributor.authorLee, James W.en
dc.description.abstractBiochar cation exchange capacity (CEC) is a key property central to better retention of soil nutrients and reduction of fertilizer runoff. This paper reports a breakthrough process to improve biochar CEC value by a factor of nearly 10 through biochar surface oxygenation by ozonization. The CEC value of the untreated biochar was measured to be anywhere between 14 and 17 cmol/kg. A 90 min dry ozonization treatment resulted in an increased biochar CEC value of 109-152 cmol/kg. Simultaneously, the biochar ozonization process resulted in a reduction of biochar pH from 9.82 to as low as 3.07, indicating the formation of oxygen-functional groups including carboxylic acids on biochar surfaces. Using the technique of X-ray photoelectron spectroscopy (XPS), the formation of oxygen-functional groups including carboxylic acids on biochar surfaces have been observed at a nanometer molecular scale following the ozonization treatment. The molar O/C ratio (0.31:1) on ozonized biochar surface as analyzed by XPS was indeed significantly higher than that (0.16:1) of the control biochar surface. The molar O/C ratio from the elemental analysis data also showed an increase from the nonozonized sample (0.077:1) to the dry-ozonized sample (0.193:1). Fourier-transform infrared (FTIR) spectroscopy analysis also showed an increase in the content of oxygen-functional groups in the form of carbonyl groups on biochar surfaces upon ozonization, which can also produce certain amount of oxygenated biochar molecular fragments that may be solubilized by liquid water, potentially leading to greater effects upon application of biochar in soil.en
dc.description.adminPublic domain – authored by a U.S. government employeeen
dc.description.notesWe thank Kameron Adams and Ashani Samaratunga for their assistance in BET, elemental analysis, and dissolved organic carbon concentration measurements, Thomas Wanzek for his technical support in biochar cation exchange capacity measurement at the USDA/ARS laboratory, and the summer students of the REU projects (NSF Award number: 1560194 and CHE-1659476) at ODU for their participation in technical support for this research. We thank our summer REU undergraduate students Jorge Morales, Ryan Gunter, and James Dawe for their help in preparing some of the biochar materials. We thank Drs. Jim Ippolito and Kurt Spokas for their stimulating discussions on biochar research and Mr. Grant Scheve of Oregon Biochar Solutions for generously sending the Rogue biochar samples and associated biochar characterization data used in this study. This research was supported, in part, by the Old Dominion University Multidisciplinary Seed Funding Program and by Dr. Lee's start-up research funds provided by the Department of Chemistry and Biochemistry, the College of Sciences, the Office of Research at ODU, and the ODU Research Foundation. XPS analysis at Virginia Tech was supported by the National Science Foundation under Grant No. CHE-1531834.en
dc.description.sponsorshipNSF AwardNational Science Foundation (NSF) [1560194, CHE-1659476]; Old Dominion University Multidisciplinary Seed Funding Program; Department of Chemistry and Biochemistry, the College of Sciences, the Office of Research at ODU; ODU Research Foundation; National Science FoundationNational Science Foundation (NSF) [CHE-1531834]en
dc.rightsCreative Commons CC0 1.0 Universal Public Domain Dedicationen
dc.subjectBiochar surface oxygenationen
dc.subjectCation exchange capacityen
dc.subjectBiochar ozonizationen
dc.subjectX-ray photoelectron spectroscopyen
dc.subjectOxygen functional groups on biochar surfaceen
dc.titleBiochar Surface Oxygenation by Ozonization for Super High Cation Exchange Capacityen
dc.title.serialACS Sustainable Chemistry & Engineeringen
dc.typeArticle - Refereeden


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