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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:contributor>C. E. Roberson</dc:contributor>
  <dc:creator>J.D. Hem</dc:creator>
  <dc:date>1989</dc:date>
  <dc:description>&lt;div id="abstracts" class="Abstracts u-font-serif"&gt;&lt;div id="aep-abstract-id5" class="abstract author"&gt;&lt;div id="aep-abstract-sec-id6"&gt;&lt;p&gt;Open-system, continuous-titration experiments have been done in which a slow flux of ∼0.02 molar solution of Mn&lt;sup&gt;2+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;chloride, nitrate, or perchlorate with Cu&lt;sup&gt;2+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;or Ni&lt;sup&gt;2+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in lesser concentrations was introduced into an aerated reactor solution held at constant temperature and at constant pH by a pH-stat titrator that added dilute NaOH. The resulting mixtures of metal oxyhydroxides and their native solutions were aged for periods as long as 2 1/2 years. Fresh and aged precipitates were characterized by chemical analysis, oxidation state determinations, X-ray and electron diffraction, and electron microscopy. The precipitates can be described as mixtures of oxide and oxyhydroxide species, using concepts of equilibrium and nonequilibrium chemical thermodynamics. The metal-ion content of the aged precipitates in systems that contained copper is distributed among three principal components. One of these is a mixed oxide Cu&lt;sub&gt;2&lt;/sub&gt;Mn&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;8&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in which all Mn is in the 4+ oxidation state. A major component in all precipitates is feitknechtite, βMnOOH. These forms are supplemented by CuO or by birnessite or ramsdellite forms of MnO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;where stoichiometry and thermodynamic calculations predict them. In systems that contained nickel and manganese, identifiable components included βMnOOH, Ni(OH)&lt;sub&gt;2&lt;/sub&gt;, and the same two forms of MnO&lt;sub&gt;2&lt;/sub&gt;. The oxidation number of the precipitated manganese increased during aging, and the pH of the supernatant solution decreased. The maximum Mn oxidation number observed was 3.55 in an Mn + Cu precipitate aged for 18 months. Concentrations of Cu&lt;sup&gt;2+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and Ni&lt;sup&gt;2+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;generally decreased to values substantially below those predicted by oxide or hydroxide equilibrium. Scavenging effects of this type are common in natural aqueous systems.&lt;/p&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/0016-7037(89)90159-2</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Elsevier</dc:publisher>
  <dc:title>Coprecipitation and redox reactions of manganese oxides with copper and nickel</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>