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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>Carol J. Lind</dc:contributor>
  <dc:creator>J.D. Hem</dc:creator>
  <dc:date>1983</dc:date>
  <dc:description>&lt;p&gt;Manganese oxides precipitated by bubbling air through 0.01 molar solutions of MnCl&lt;sub&gt;2&lt;/sub&gt;, Mn(NO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;, MnSO&lt;sub&gt;4&lt;/sub&gt;, or Mn(ClO&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;at a constantly maintained pH of 8.5 to 9.5 at temperatures of 25°C or higher consisted mainly of hausmannite, Mn&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;. At temperatures near 0°C, but with other conditions the same, the product is feitknechtite, βMnOOH, except that if the initial solution is MnSO&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and the temperature is near 0°C the product is a mixture of manganite, γMnOOH and groutite, αMnOOH.&lt;/p&gt;&lt;p&gt;All these oxides are metastable in aerated solution and alter by irreversible processes to more highly oxidized species during aging. A two-step nonequilibrium thermodynamic model predicts that the least stable species, βMnOOH, should be most readily converted to MnO&lt;sub&gt;2&lt;/sub&gt;. Some preparations of βMnOOH aged in their native solution at 5°C attained a manganese oxidation state of +3.3 or more after 7 months. Hausmannite aged at 25°C altered to γMnOOH. The latter is more stable than a or βMnOOH, and manganese oxidation states above 3.0 were not reached in hausmannite precipitates during 4 months of aging. Initial precipitation of MnCO&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;rather than a form of oxide is likely only where oxygen availability is very low.&lt;/p&gt;&lt;p&gt;Composition of solutions and oxidation state and morphology of solids were determined during the aging process by chemical analyses, X-ray and electron diffraction and transmission electron micrographs.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/0016-7037(83)90219-3</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Elsevier</dc:publisher>
  <dc:title>Nonequilibrium models for predicting forms of precipitated manganese oxides</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>