Sorption of ammonium and nitrate to biochars is electrostatic and pH-dependent
AffiliationUniv Arizona, Dept Soil Water & Environm Sci
MetadataShow full item record
PublisherNATURE PUBLISHING GROUP
CitationFidel, R. B., Laird, D. A., & Spokas, K. A. (2018). Sorption of ammonium and nitrate to biochars is electrostatic and pH-dependent. Scientific reports, 8(1), 17627.
Rights© The Author(s) 2018. This article is licensed under a Creative Commons Attribution 4.0 International License.
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AbstractBiochars are potentially effective sorbents for NH4+ and NO3- in water treatment and soil applications. Here we compare NH4+ and NO3- sorption rates to acid-washed biochars produced from red oak (Quercus rubra) and corn stover (Zea mays) at three pyrolysis temperatures (400, 500 and 600 °C) and a range of solution pHs (3.5-7.5). Additionally, we examined sorption mechanisms by quantification of NH4+ and NO3- sorption, as well as Ca2+ and Cl- displacement for corn stover biochars. Solution pH curves showed that NH4+ sorption was maximized (0.7-0.8 mg N g-1) with low pyrolysis temperature (400 °C) biochar at near neutral pH (7.0-7.5), whereas NO3- sorption was maximized (1.4-1.5 mg N g-1) with high pyrolysis temperatures (600 °C) and low pH (3.5-4). The Langmuir (r2 = 0.90-1.00) and Freundlich (r2 = 0.81-0.97) models were good predictors for both NH4+ (pH 7) and NO3- (pH 3.7) sorption isotherms. Lastly, NH4+ and NO3- displaced Ca2+ and Cl-, respectively, from previously CaCl2-saturated corn stover biochars. Results from the pH curves, Langmuir isotherms, and cation displacement curves all support the predominance of ion exchange mechanisms. Our results demonstrate the importance of solution pH and chemical composition in influencing NH4+ and NO3- sorption capacities of biochar.
NoteOpen access journal.
VersionFinal published version
SponsorsGlobal Climate and Energy Project [640 60413992-112883-A]
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