Towards optimizing short-chained PFCA esterification in water

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies

Background:

• Short-chained perfluorocarboxylic acids (PFCAs) are persistent and mobile contaminants in aqueous environments.
• Effective treatment technologies are needed to mitigate rising PFCA emissions from industrial sources.

Purpose of the Study:

• To expand the esterification-based removal of per- and polyfluoroalkyl substances (PFAS) to short-chained PFCAs.
• To develop and utilize a quantitative 19F NMR method for in-situ measurement of PFAS partitioning and transformation.
• To systematically evaluate influencing factors for optimizing PFCA removal.

Main Methods:

• Esterification reaction with decanol within spontaneously formed emulsions.
• Development of a quantitative 19F NMR method for in-situ PFAS analysis.
• Systematic evaluation of water constituents (e.g., NaCl) and reaction additives (e.g., alcohol chain length).

Main Results:

• PFCA removal is driven by both chemical transformation (esterification) and emulsion formation/stabilization.
• Higher ionic strengths (NaCl, Na2SO4) hinder PFCA partitioning and esterification, while humic acid shows minimal inhibition.
• PFCA mixtures showed improved removal (11-15%) compared to single solutes.
• Optimized conditions achieved ≥70% total removal yields for perfluorohexanoic acid (PFHxA) and perfluorobutanoic acid (PFBA).

Conclusions:

• The esterification-based approach, coupled with emulsion stabilization, is effective for removing short-chained PFCAs.
• Optimizing reactant concentrations and temperature is crucial for maximizing removal efficiency.
• This method offers a promising strategy for treating industrial wastewater contaminated with short-chained PFCAs.