Date of Award

12-11-2025

Degree Type

Thesis

Degree Name

Master of Science (M.S.)

Department

Agricultural and Environmental Sciences

First Advisor

Sudipta Rakshit

Abstract

Emerging contaminants might pose serious threats to the soil and water environment. Metformin, an emerging micropollutant, is one of the most widely used drugs for type-2 diabetes treatment. However, its waste disposal through human excretion is causing environmental concern to the soil and water environment. Yet, knowledge about the interaction mechanism of metformin with soil remains very limited. In this study, we evaluated metformin adsorption mechanisms on model oxide minerals (gibbsite, hematite) and two Tennessee soils (Milan Loring soil and Cheatham County soil) and in the presence of soil micronutrient (molybdenum) using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and macroscopic adsorption experiments under environmentally relevant solution properties. The FTIR results suggested that metformin interacts with soil and gibbsite surfaces through the lone pair of electrons on N atoms (N5, N6 or N7 moieties) and the delocalized electrons in the N3-N5-N6 systems. For the soil, metformin may additionally bind via cation exchange mechanism in the inter-layer spaces of permanent charge minerals. From macroscopic experiments results, metformin adsorption was found to be increased higher in the Loring soil sample compared to the Cheatham County soil sample suggesting the influence of soil properties on the adsorption mechanism. From macroscopic competitive adsorption experiments, metformin adsorption was found to be decreased in the presence of molybdenum in Loring soil, suggesting that metformin and molybdenum may exhibit competitive adsorption affinity in soil.

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