<?xml version='1.0' encoding='utf-8'?>
<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>J.A. Davis</dc:contributor>
  <dc:contributor>G. W. Luther III</dc:contributor>
  <dc:creator>P.M. Fox</dc:creator>
  <dc:date>2009</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;The kinetics of iodide (I&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;) and molecular iodine (I&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;) oxidation by the manganese oxide mineral birnessite (δ-MnO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;) was investigated over the pH range 4.5–6.25. I&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;oxidation to iodate&amp;nbsp;&lt;/span&gt;&lt;span class="math"&gt;&lt;span id="MathJax-Element-1-Frame" class="MathJax_SVG" data-mathml="&lt;math xmlns=&amp;quot;http://www.w3.org/1998/Math/MathML&amp;quot;&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mo stretchy=&amp;quot;false&amp;quot; is=&amp;quot;true&amp;quot;&gt;(&lt;/mo&gt;&lt;mmultiscripts is=&amp;quot;true&amp;quot;&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mtext is=&amp;quot;true&amp;quot;&gt;IO&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mn is=&amp;quot;true&amp;quot;&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mo is=&amp;quot;true&amp;quot;&gt;-&lt;/mo&gt;&lt;/mrow&gt;&lt;/mmultiscripts&gt;&lt;mo stretchy=&amp;quot;false&amp;quot; is=&amp;quot;true&amp;quot;&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;"&gt;&lt;span class="MJX_Assistive_MathML"&gt;(IO3-)&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&amp;nbsp;proceeded as a two-step reaction through an I&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;intermediate. The rate of the reaction varied with both pH and birnessite concentration, with faster oxidation occurring at lower pH and higher birnessite concentration. The disappearance of I&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;from solution was first order with respect to I&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;concentration, pH, and birnessite concentration, such that −&lt;/span&gt;&lt;i&gt;d&lt;/i&gt;&lt;span&gt;[I&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;]/&lt;/span&gt;&lt;i&gt;dt&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span&gt;=&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;k&lt;/i&gt;&lt;span&gt;[I&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;][H&lt;/span&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;][MnO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;], where&amp;nbsp;&lt;/span&gt;&lt;i&gt;k&lt;/i&gt;&lt;span&gt;, the third order rate constant, is equal to 1.08&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span&gt;±&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span&gt;0.06&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span&gt;×&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span&gt;10&lt;/span&gt;&lt;sup&gt;7&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span&gt;M&lt;/span&gt;&lt;sup&gt;−2&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span&gt;h&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;. The data are consistent with the formation of an inner sphere I&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;surface complex as the first step of the reaction, and the adsorption of I&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;exhibited significant pH dependence. Both I&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;, and to a lesser extent,&amp;nbsp;&lt;/span&gt;&lt;span class="math"&gt;&lt;span id="MathJax-Element-2-Frame" class="MathJax_SVG" data-mathml="&lt;math xmlns=&amp;quot;http://www.w3.org/1998/Math/MathML&amp;quot;&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mmultiscripts is=&amp;quot;true&amp;quot;&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mtext is=&amp;quot;true&amp;quot;&gt;IO&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mn is=&amp;quot;true&amp;quot;&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mo is=&amp;quot;true&amp;quot;&gt;-&lt;/mo&gt;&lt;/mrow&gt;&lt;/mmultiscripts&gt;&lt;/mrow&gt;&lt;/math&gt;"&gt;&lt;span class="MJX_Assistive_MathML"&gt;IO3-&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&amp;nbsp;sorbed to birnessite. The results indicate that iodine transport in mildly acidic groundwater systems may not be conservative. Because of the higher adsorption of the oxidized I species I&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;and&amp;nbsp;&lt;/span&gt;&lt;span class="math"&gt;&lt;span id="MathJax-Element-3-Frame" class="MathJax_SVG" data-mathml="&lt;math xmlns=&amp;quot;http://www.w3.org/1998/Math/MathML&amp;quot;&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mmultiscripts is=&amp;quot;true&amp;quot;&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mtext is=&amp;quot;true&amp;quot;&gt;IO&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mn is=&amp;quot;true&amp;quot;&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow is=&amp;quot;true&amp;quot;&gt;&lt;mo is=&amp;quot;true&amp;quot;&gt;-&lt;/mo&gt;&lt;/mrow&gt;&lt;/mmultiscripts&gt;&lt;/mrow&gt;&lt;/math&gt;"&gt;&lt;span class="MJX_Assistive_MathML"&gt;IO3-&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;span&gt;, as well as the biophilic nature of I&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;, redox transformations of iodine must be taken into account when predicting I transport in aquifers and watersheds.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/j.gca.2009.02.016</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Elsevier</dc:publisher>
  <dc:title>The kinetics of iodide oxidation by the manganese oxide mineral birnessite</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>