Surface Properties of Hydrous Manganite (γ-MnOOH) : A Potentiometric, Electroacoustic, and X-ray Photoelectron Spectroscopy Study

• The acid-base characteristics of the manganite (-MnOOH) surface have been studied at pH above 6, where dissolution is negligible. Synthetic microcrystalline particles of manganite were used in the experiments. From potentiometric titrations, electrophoretic mobility measurements, and X-ray photoelectron spectroscopy (XPS), a one pKa model was constructed that describes the observed behavior. The data show no ionic strength effect at pH < 8.2, which is the pH at the isoelectric point (pHiep), but ionic strength effects were visible above this pH. To explain these observations, Na+ ions were suggested to form a surface complex. The following equilibria were established: =MnOH2+1/2 =MnOH-1/2 + H+, log 0 (intr.) = -8.20; =MnOH2+1/2 + Na+ =MnOHNa+1/2 + H+, log 0 (intr.) = -9.64. The excess of Na+ at the surface was supported by XPS measurements of manganite suspensions containing 10 mM NaCl. The dielectric constant of synthetic manganite powder was also determined in this study.

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NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

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