Adsorption of Perfluoroalkyl Substances with Activated Carbon: Characterizing Non-hazardous Simulants
Citation:
Hensley, J., K. Eckhoff, W. Harper, AND M. Magnuson. Adsorption of Perfluoroalkyl Substances with Activated Carbon: Characterizing Non-hazardous Simulants. 2023 EPA International Decontamination Research and Development Conference, Charleston, SC, December 05 - 07, 2023.
Impact/Purpose:
Simulants could facilitate treatment studies of PFAS, reducing cost, timeline, and safety concerns. This study used powdered activated carbon batch experiments and artificial neural networks (ANN) to access allura red, tartrazine, and indigo carmine as simulants for PFOA, PFOS, and other PFAS species. These 3 non-hazardous food dyes have similar functional groups and anionic charges, to that of PFOA and PFOS, two of the most well-known toxic PFAS chemicals. Powdered Activated Carbon (PAC) is among the most cost effective and time efficient treatment processes available for PFAS remediation. Artificial neural networks are a tool that can be utilized to help predict which chemicals can serve as simulants for PFAS species.
Description:
This work investigated the suitability of three non-hazardous food dyes as PFAS simulants during wastewater treatment with powdered activated carbon (PAC). Data from batch experiments with PAC revealed equilibrium constants (Log Kd) and pseudo first-order adsorption rate constants (k) for allura red, tartrazine, indigo carmine, PFOA, PFOS, and several other PFAS species commonly found in aqueous film-forming foam. The food dyes were found to have k values comparable to PFOA, PFOS, and other PFAS species. An Artificial Neural Network (ANN) was developed to predict the surrogacy of the food dyes by correlating sixteen molecular descriptors with publicly-available Log Kd values. Based on experimental observations and ANN predictions, all three food dyes were found to be conservative simulants for PFBA, PFBS, and PFHpA (food dyes Log Kd > PFAS Log Kd), but poor simulants for PFOA, PFOS, and other PFAS species (food dyes Log Kd < PFAS Log Kd). The PAC was analyzed using Scanning Electron Microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to reveal fluorine and PFAS functional groups attached to the surface. These results are expected to inform future efforts to identify non-hazardous simulants that could be tested in place of toxic PFAS species.