Column versus batch methods for measuring PFOS and PFOA sorption to geomedia.

Area of Science:

• Environmental Chemistry
• Geochemistry
• Environmental Engineering

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants with significant environmental and health concerns.
• Understanding the sorption behavior of PFAS in porous media is crucial for predicting their fate and transport.
• Existing methods for measuring sorption coefficients and isotherms, such as batch and column experiments, require validation for PFAS.

Purpose of the Study:

• To compare the consistency of solid-phase sorption coefficients and isotherms for PFAS measured by column and batch experiment methods.
• To evaluate two column-based methods: multi-concentration (multi-C0) and elution-front integration.
• To assess the applicability of the Freundlich isotherm model for describing PFAS sorption.

Main Methods:

• Batch sorption experiments were conducted using natural porous media.
• Column experiments were performed using multiple input concentrations (multi-C0 method) to generate isotherms.
• Column experiments utilizing elution-front integration from a single breakthrough curve (BTC) were also employed.
• Sorption isotherms were analyzed using the Freundlich model.

Main Results:

• Column-derived isotherms from the multi-C0 method showed remarkable agreement with batch isotherms across a 3-4 order of magnitude aqueous concentration range.
• Isotherm variables from the multi-C0 method yielded statistically identical regressions compared to batch methods.
• Elution-front integration isotherms generally agreed with batch isotherms but showed some noise and deviation at lower concentrations.
• The Freundlich model effectively described all data sets, with N values consistent with literature.

Conclusions:

• Column and batch experiments can yield consistent sorption isotherms and coefficients for PFOS and PFOA.
• The multi-C0 column method is a reliable alternative to batch experiments for PFAS sorption assessment.
• Elution-front integration may require careful data analysis, especially at low concentrations.
• Robust experimental design and data analysis are key to obtaining consistent PFAS sorption data.