Partitioning of Humic Acids between Aqueous Solution and Hydrogel: Concentration Profiling of Humic Acids in Hydrogel Phases

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• 作者：Katarzyna Zieli艅ska ; Raewyn M. Town ; Kamuran Yasadi ; Herman P. van Leeuwen
• 刊名：Langmuir
• 出版年：2014
• 出版时间：March 4, 2014
• 年：2014
• 卷：30
• 期：8
• 页码：2084-2092
• 全文大小：340K
• 年卷期：v.30,no.8(March 4, 2014)
• ISSN：1520-5827

文摘

The partitioning of the natural polyelectrolyte humic acid (HA) from an aqueous dispersion into a model biomimetic gel (alginate) and a synthetic polyacrylamide gel (PAAm) is explored. In both gels, the spatial distribution of HA in the gel body, as measured by confocal laser scanning microscopy, is markedly nonhomogeneous. A striking feature is the enhanced accumulation of HA in a thin film of thickness ca. 15 渭m at the surface of the gel body, resulting in average local concentrations that are, for PAAm and alginate respectively, a factor of 10 and 4 greater than that in the bulk solution. The time dependence of accumulation in the surface film is predominantly controlled by the diffusive supply of HA from the aqueous medium, with a time constant on the order of 10³ s for both gels. The concentration of HA within the bulk gel body differs significantly from that in the bulk aqueous medium: substantially higher for PAAm but much lower for alginate. The results are significant for understanding the nature and rate of sink/source functioning at permeable phases in contact with aqueous media, e.g., biofilms and gel-like layers at biological interfaces or employed in chemical speciation sensors.