Impact of Variable Water Chemistry on PFOS-Goethite Interactions: Experimental Evidence and Surface Complexation...

Area of Science:

• Environmental Chemistry
• Geochemistry
• Surface Chemistry

Background:

• Perfluorooctanesulfonate (PFOS) is a persistent environmental contaminant with significant toxic effects.
• Understanding PFOS interactions with mineral surfaces is crucial for predicting its environmental behavior.

Purpose of the Study:

• To investigate the sorption mechanisms of PFOS on goethite surfaces.
• To determine the impact of varying water chemistry (pH, ionic strength) on PFOS sorption.

Main Methods:

• Sorption experiments with controlled pH, ionic strength, and PFOS concentration.
• Infrared (IR) spectroscopy for surface analysis.
• Surface complexation modeling to elucidate binding mechanisms.

Main Results:

• PFOS binds to goethite through strong hydrogen-bonded (HB) complexes and weaker outer-sphere complexes (OS-Na+).
• Acidic conditions and low ionic strength favor HB complex formation.
• Higher electrolyte concentrations and pH promote ternary PFOS-Na+-goethite outer-sphere complex formation.

Conclusions:

• Solution chemistry critically controls PFOS adsorption onto mineral surfaces.
• Accurate prediction of PFOS mobility requires surface complexation models incorporating mechanistic details.