<?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>P.A. Maurice</dc:contributor>
  <dc:contributor>G. R. Aiken</dc:contributor>
  <dc:contributor>S. Cabaniss</dc:contributor>
  <dc:contributor>Y.-P. Chin</dc:contributor>
  <dc:contributor>M.J. Pullin</dc:contributor>
  <dc:creator>K. Namjesnik-Dejanovic</dc:creator>
  <dc:date>2000</dc:date>
  <dc:description>&lt;p&gt;Molecular weight (MW) of humic materials is a key factor controlling proton and metal binding and organic pollutant partitioning. Several studies have suggested preferential&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ej-keyword" data-value="adsorption"&gt;adsorption&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;of higher MW, more aromatic moieties to mineral surfaces; quantification of such processes is fundamental to development of predictive models. We used high pressure size exclusion chromatography (HPSEC) to quantify MW changes upon&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ej-keyword" data-value="adsorption"&gt;adsorption&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;of a muck fulvic acid (MFA) extracted from a peat deposit to kaolinite and goethite, at pH 3.7, 6, and 8 at 22 °C, I = 0.01 (NaCl), 24-h reaction time. MFA&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ej-keyword" data-value="adsorption"&gt;adsorption&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;affinity was greater for goethite than for kaolinite. At concentrations less than the&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ej-keyword" data-value="adsorption"&gt;adsorption&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;maximum (A&lt;sub&gt;max&lt;/sub&gt;) for both adsorbents, the weight-average MW (M&lt;sub&gt;w&lt;/sub&gt;) of MFA remaining in solution decreased by as much as several hundred Daltons relative to control samples, indicating preferential&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ej-keyword" data-value="adsorption"&gt;adsorption&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;of the higher MW components. At concentrations more than A&lt;sub&gt;max&lt;/sub&gt;, M&lt;sub&gt;w&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;of MFA in solution did not change appreciably. Although total&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ej-keyword" data-value="adsorption"&gt;adsorption&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;decreased significantly as pH increased, fractionation as measured by change in M&lt;sub&gt;w&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;remained similar, perhaps indicating greater selectivity for higher MW components at higher pH.&lt;/p&gt;&lt;p&gt;Absorptivities at λ = 280 nm normalized to mg C L&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;(ε) suggested preferential&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ej-keyword" data-value="adsorption"&gt;adsorption&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;of more aromatic moieties to kaolinite. ε could not be used for goethite-reacted samples because high Fe concentrations in the aqueous phase brought about by goethite dissolution interfered with the spectroscopic analysis. Preliminary kinetic experiments suggested that smaller molecules adsorbed first and were replaced by larger molecules whose&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ej-keyword" data-value="adsorption"&gt;adsorption&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;was thermodynamically favored.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:language>en</dc:language>
  <dc:publisher>Wolters Kluwer</dc:publisher>
  <dc:title>Adsorption and fractionation of a muck fulvic acid on kaolinite and goethite at pH 3.7,6, and 8</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>