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    <title>Mark F. Roll on MillironX</title>
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    <description>Recent content in Mark F. Roll on MillironX</description>
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      <title>Investigation of Hydronium Diffusion in Poly(vinyl alcohol) Hydrogels: A Critical First Step to Describe Acid Transport for Encapsulated Bioremediation</title>
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      <pubDate>Fri, 02 Sep 2022 00:00:00 +0000</pubDate>
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      <description>&lt;p&gt;Bioremediation of chlorinated aliphatic hydrocarbon-contaminated aquifers can be&#xA;hindered by high contaminant concentrations and acids generated during&#xA;remediation. Encapsulating microbes in hydrogels may provide a protective,&#xA;tunable environment from inhibiting compounds; however, current approaches to&#xA;formulate successful encapsulated systems rely on trial and error rather than&#xA;engineering approaches because fundamental information on mass-transfer&#xA;coefficients is lacking. To address this knowledge gap, hydronium ion&#xA;mass-transfer rates through two commonly used hydrogel materials, poly(vinyl&#xA;alcohol) and alginic acid, under two solidification methods (chemical and&#xA;cryogenic) were measured. Variations in hydrogel crosslinking conditions,&#xA;polymer composition, and solvent ionic strength were investigated to understand&#xA;how each influenced hydronium ion diffusivity. A three-way ANOVA indicated that&#xA;the ionic strength, membrane type, and crosslinking method significantly (&lt;em&gt;p&lt;/em&gt; &amp;lt;&#xA;0.001) contributed to changes in hydronium ion mass transfer. Hydronium ion&#xA;diffusion increased with ionic strength, counter to what is observed in&#xA;aqueous-only (no polymer) solutions. Co-occurring mechanisms correlated to&#xA;increased hydronium ion diffusion with ionic strength included an increased&#xA;water fraction within hydrogel matrices and hydrogel contraction. Measured&#xA;diffusion rates determined in this study provide first principal design&#xA;information to further optimize encapsulating hydrogels for bioremediation.&lt;/p&gt;</description>
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      <title>Measuring Diffusion of Trichlorethylene Breakdown Products in Polyvinylalginate</title>
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      <pubDate>Mon, 29 Oct 2018 00:00:00 +0000</pubDate>
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      <description>&lt;p&gt;Trichloroethylene (TCE), a toxic and carcinogenic contaminant, presents unique&#xA;challenges for cleanup because of its water solubility, density, and volatility.&#xA;Bioremediation of TCE is a promising cleanup method; however, metabolism of TCE&#xA;results in acid generation that inhibits remediating microorganisms. Calcium&#xA;alginate(CA)-polyvinylalcohol (PVA) hydrogels show promise for protecting&#xA;remediating microbes, however diffusion of TCE or its byproducts through these&#xA;polymers is unknown. To measure the effective diffusion coefficient of TCE and&#xA;byproducts through hydrogel membranes, we used a modified diaphragm cell.&#xA;Measured effective diffusion coefficient of each species was (cm &lt;sup&gt;2&lt;/sup&gt;&#xA;/s&#xA;× 10&lt;sup&gt;6&lt;/sup&gt;&#xA;): 14.0 ± 1.91 for H&lt;sup&gt;&amp;#43;&lt;/sup&gt;&#xA; ions, 12.4 ± 1.64 for TCE,&#xA;7.83 ± 0.54 for cis-1,2-dichloroethylene (DCE), and 4.68 ± 4.14 for vinyl&#xA;chloride. These results aid in engineering biobeads and suggest that CA-PVA&#xA;hydrogel blends are effective in slowing diffusion of protons, buffering acids&#xA;produced by trichloroethylene metabolism, and remains suitable for encapsulation&#xA;of microorganisms involved in bioremediation.&lt;/p&gt;</description>
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