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Electron Paramagnetic Resonance Stopped‐Flow Kinetic Study of Manganese(II) Sorption‐Desorption on Birnessite
Author(s) -
Fendorf S. E.,
Sparks D. L.,
Franz J. A.,
Camaioni D. M.
Publication year - 1993
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1993.03615995005700010011x
Subject(s) - sorption , reaction rate constant , electron paramagnetic resonance , birnessite , chemistry , desorption , manganese , analytical chemistry (journal) , kinetics , reaction rate , paramagnetism , kinetic energy , nuclear magnetic resonance , adsorption , catalysis , chromatography , organic chemistry , physics , quantum mechanics , manganese oxide
Many important reactions involving colloidal suspensions are rapid. Here, we introduce the application of a technique capable of rapidly measuring a reactant species (within 20 ms after the reaction initiation) in situ: an electron paramagnetic resonance spectroscopically monitored stopped‐flow method (EPR‐SF). The utility of this technique is demonstrated by investigating the sorption of Mn 2+ on δ‐MnO 2 . The sorption reaction was complete in <1 s, with >80% of the Mn 2+ being sorbed within 200 ms. A first‐order rate dependence on Mn 2+ was observed. Measurement of the initial reaction rate allowed the forward (sorption) rate constant to be determined ( k f = 3.74 × 10 −3 s −1 ), and the reverse (desorption) rate constant was determined using an integrated reversible first‐order rate expression ( k r = 3.08 × 10 −4 s −1 ). Using these rate constants, the predicted time dependence of Mn 2+ sorption was in good agreement with the measured sorption rate. The results indicate that chemical kinetics are being measured that allow determination of precise reaction rates and mechanisms.