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Denatonium Benzoate (DB), commercially known as Bitrex, is a denaturant added to many common commercial products, such as laundry detergent and antifreeze (in some states) to deter ingestion by humans and animals. The intensely bitter taste of DB is detectable by humans at aqueous concentrations as low as 50 ng/L while 10 - 30 mg/L concentrations can render drinking water unpalatable. Given the push by US lawmakers to mandate that DB be added to some commercial antifreeze formulations, it is imperative that potential environmental consequences associated with accidental releases of this material be investigated. Knowing if, and understanding how, sorption to soils and clays occurs can provide important information that can be used to (a) assess the potential of transport through the soil environment and (b) determine treatment strategies for bodies of water impacted by DB. Accordingly, the main objective of this study was to evaluate the kinetic parameters associated with denatonium sorption to clay minerals. Batch sorption experiments using 200 mg/L DB in 0.01M calcium chloride were run for three types of 2:1 layered aluminosilicates. High pressure liquid chromatography analyses were used to quantify absorption, the sorption kinetic rate constant, and the activation energy. The results suggest that denatonium sorption is a pseudo-second order process for each clay. Additionally, the activation energy (energy barrier to sorption) was determined for Syn-1 to be 25.89 kJ/mol from which we concluded that a physisorption process occurred. Finally, upon comparing the surface-area normalized sorption capacities (Qs) we determined that sorption was greatest for SWy-2 and least for Syn-1 based on calculated capacities of 1.54 x 10^-2 g DB/m^2 and 3.08 x 10^-4 g DB/m^2, respectively. Thus, a possible treatment method for water-impacted by DB could include SWy-2 clay as an absorbent.
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Stander Symposium poster
Sandmann, Emily J., "Sorption Kinetics of Denatonium Benzoate to 2:1 Layered Aluminosilicates" (2012). Stander Symposium Posters. 144.