Experimental study of humic acid adsorption onto bacterial and Al-mineral surfaces; a chemical equilibrium approach

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Authors:Fein, Jeremy B.; Guclu, Kubilay; Kaulbach, Emily; McCoy, Kaycee
Author Affiliations:Primary:
University of Notre Dame, Department of Civil Engineering and Geological Sciences, Notre Dame, IN, United States
Volume Title:Geological Society of America, 1998 annual meeting
Source:Abstracts with Programs - Geological Society of America, 30(7), p.205; Geological Society of America, 1998 annual meeting, Toronto, ON, Canada, Oct. 26-29, 1998. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592
Publication Date:1998
Note:In English
Summary:Aqueous metal and organic contaminant transport can be strongly influenced by the behavior of humic acids and bacteria in groundwater systems. Both humic acids and bacterial surfaces can adsorb contaminant metals and organic molecules, tying the mobility of the contaminants to that of the sorbents. Enhanced contaminant transport is possible when humic acids and/or bacteria are mobile in the subsurface. Therefore, in order to quantitatively model the effects of humic acid and bacteria on contaminant transport, it is crucial to understand the controls on the mobilities of each in water-rock systems.In this study, we measured the adsorption and desorption behavior of humic acid in mineral-only, bacteria-only, and mineral-bacteria systems. The experiments were conducted at constant ionic strength, and the adsorption behavior was determined as a function of pH and sorbent:humic ratio. In order to isolate specific adsorption reactions, we used corundum (Al2O3) as representative of Al mineral surface sites, and the Gram-positive species Bacillus subtilis as representative of a common type of subsurface bacteria. Aldrich humic acid was used in all experiments, and the extent of adsorption of the humic acid onto each sorbent was determined using a uv-vis spectrophotometric technique. The experimental results indicate that both Al mineral surface sites and bacterial cell walls efficiently adsorb humic acid. Adsorption of humic acid onto each type of site is highest under low pH conditions, and decreases with increasing pH. The decrease in adsorption is likely due to increased electronegativity of each type of surface with increasing pH. Adsorption is completely reversible in the systems studied, and we use a chemical equilibrium approach to model the data. The accuracy of the approach was tested by estimating the extent of adsorption that occurs in a humic-bacteria-mineral system, based solely on independently-obtained measurements of humic-bacteria and humic-mineral adsorption. The estimated adsorption behavior is in excellent agreement with that observed in the complex ternary system, suggesting that the chemical equilibrium approach can adequately quantify the distribution of humic acid in realistic bacteria-water-rock systems.
Subjects:Adsorption; Aluminum; Controls; Corundum; Desorption; Experimental studies; Ground water; Humic acids; Humic substances; Metals; Organic acids; Organic compounds; Oxides; PH; Pollutants; Pollution; Quantitative analysis; Transport; Water-rock interaction; Bacteria
Record ID:1999017343
Copyright Information:GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
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