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Sorption of Anionic Organic Contaminants to Goethite

Patterson, Andrea
http://rave.ohiolink.edu/etdc/view?acc_num=osu1543427642730863

Abstract Details

2018, Master of Science, Ohio State University, Civil Engineering.
Contaminant environmental fate, exposure, and risk assessment are dependent on quantifying the extent of compound sorption to environmental solids. Many emerging contaminants, including pharmaceutical, pesticide, and personal care products, possess anionic functional groups that largely sorb to solids via electrostatic interactions. Iron oxides, like goethite, are a main source of positive charge that influence the fate of anionic compounds in the environment. Predictive fate models currently lack the capability to account for these electrostatic interactions, so a new mechanistic approach was proposed by Mackay and Vasudevan (2012) that utilizes probe compounds to capture these interactions and how changes in structure change the extent of sorption. The influence of structural effects on sorption are evaluated on the basis of isotherms collected on lab-synthesized goethite using a column chromatography method in which HPLC columns are manually packed with a known amount of goethite. This method was optimized for use with anionic contaminants with a fixed pH (6-7) and ionic strength (5 mM CaCl2); however, some variability issues in the column may suggest that batch techniques are more appropriate for future determination of Kd values. Isotherms were collected for 21 compounds with varying structural substituents. One group of compounds was analyzed based on hydratropic acid as the probe molecule and the other based on salicylic acid. The hydratropic acid group produces linear isotherms (R2 > 0.99), whereas the salicylic acid group was more suited for a Langmuir fit, suggesting that the latter compounds may have filled surface sites or formed stronger complexes with the goethite surface. No significant trends in sorption with physiochemical properties were seen other than for pKa of the monocarboxylic acids (p < 0.005). Functional groups were also evaluated with bonding in the meta position on the monocarboxylic acids, where the bond strength followed: aliphatic chain > additional ring > methyl group > chlorine group > nitro group substitution. Addition of an ether group between the ring structure and the carboxylic acid group produced 1.12x less sorption than the phenylacetic acid counterpart. On the salicylic acid set, the trend was different for functional groups where the trend followed: nitro group > chlorine group > additional ring > methyl group. The salicylic acid derivatives also had much greater sorption coefficients than the carboxylic acid set. As more emerging contaminants are released into the environment, more datasets like this need to be evaluated in order to advance modeling approaches for anionic organic compounds.
Allison MacKay (Advisor)
John Lenhart (Committee Member)
Nicholas Basta (Committee Member)
73 p.
Engineering; Environmental Engineering; Organic Chemistry
emerging contaminants; goethite; sorption; column chromatography

Recommended Citations

Citations

  • Patterson, A. (2018). Sorption of Anionic Organic Contaminants to Goethite [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543427642730863

    APA Style (7th edition)

  • Patterson, Andrea. Sorption of Anionic Organic Contaminants to Goethite. 2018. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1543427642730863.

    MLA Style (8th edition)

  • Patterson, Andrea. "Sorption of Anionic Organic Contaminants to Goethite." Master's thesis, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543427642730863

    Chicago Manual of Style (17th edition)

osu1543427642730863
276
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This open access ETD is published by The Ohio State University and OhioLINK.