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Colloid-chemical properties of manganese dioxide

Morgan, James J. and Stumm, Werner (1964) Colloid-chemical properties of manganese dioxide. Journal of Colloid Science, 19 (4). pp. 347-359. ISSN 0095-8522. doi:10.1016/0095-8522(64)90036-4.

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A synthetic, poorly ordered manganese dioxide (Mn_(01.90)-MnO_(1.95)) has been studied with respect to colloidal stability and the ability to sorb or exchange Mn⁺², with concomitant release of H⁺ ions. MnO₂ suspensions of concentrations 10⁻⁵ to 10⁻³M were observed to exist as colloidal dispersions at neutral and alkaline pH values for periods of several months or more. Deductions based upon acid-base titrations of MnO₂ suspensions indicate that the zero point of charge with respect to net OH⁻ and H⁺ ions bound is somewhat below pH 3 and that H⁺ and OH⁻ function as potential-determining ions. Colloidal MnO₂ is destabilized by relatively small concentrations of Mn⁺² ions; H⁺ ions are released in the process. At pH 7.5 the capacity of the oxide for Mn⁺² sorption is 0.5 mole of Mn⁺² per mole of MnO₂; capacities of ca. 2 moles per mole are realized at pH values near 9. The uptake of Mn⁺² and release of H⁺ occurs rather rapidly, times of the order of 5 minutes or less being required for 50 % exchange. The observed nonstoichiometric products of oxidation of dilute Mn⁺² would seem to be interpreted satisfactorily as resulting from the uptake of Mn⁺² ions in varying proportions by hydrous manganese dioxide. The characteristics of colloidal MnO₂ appear to provide an instructive model for interpreting the behavior of a number of other colloidal hydrous metal oxides.

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Additional Information:© 1964 Published by Elsevier. Received 7 August 1963, Revised 16 September 1963. This work was supported by the U. S. Public Health Service, Research Grants WP-13 and WP-98. The authors wish to thank Jessie Lee for excellent technical assistance and O. P. Bricker, Division of Geological Sciences, Harvard University, for his kindness in running a number of X-ray powder patterns.
Funding AgencyGrant Number
U.S. Public Health Service (USPHS)WP-13
U.S. Public Health Service (USPHS)WP-98
Issue or Number:4
Record Number:CaltechAUTHORS:20201202-154044074
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Official Citation:James J Morgan, Werner Stumm, Colloid-chemical properties of manganese dioxide, Journal of Colloid Science, Volume 19, Issue 4, 1964, Pages 347-359, ISSN 0095-8522,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106887
Deposited By: George Porter
Deposited On:03 Dec 2020 16:18
Last Modified:16 Nov 2021 18:57

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