Perfluoroalkyl sulfonic and carboxylic acids: A critical review of physicochemical properties, levels and patterns in waters and wastewaters, and treatment methods

Abstract

Perfluorinated acids (PFAs) are an emerging class of environmental contaminants present in various environmental and biological matrices. Two major PFA subclasses are the perfluorinated sulfonic acids (PFSAs) and carboxylic acids (PFCAs). The physicochemical properties and partitioning behavior for the linear PFA members are poorly understood and widely debated. Even less is known about the numerous branched congeners with varying perfluoroalkyl chain lengths, leading to confounding issues around attempts to constrain the properties of PFAs. Current computational methods are not adequate for reliable multimedia modeling efforts and risk assessments. These compounds are widely present in surface, ground, marine, and drinking waters at concentrations that vary from pg L^{− 1} to μg L^{− 1}. Concentration gradients of up to several orders of magnitude are observed in all types of aquatic systems and reflect proximity to known industrial sources concentrated near populated regions. Some wastewaters contain PFAs at mg L^{− 1} to low g L^{− 1} levels, or up to 10 orders of magnitude higher than present in more pristine receiving waters. With the exception of trifluoroacetic acid, which is thought to have both significant natural and anthropogenic sources, all PFSAs and PFCAs are believed to arise from human activities. Filtration and sorption technologies offer the most promising existing removal methods for PFAs in aqueous waste streams, although sonochemical approaches hold promise. Additional studies need to be conducted to better define opportunities from evaporative, extractive, thermal, advanced oxidative, direct and catalyzed photochemical, reductive, and biodegradation methods. Most PFA treatment methods exhibit slow kinetic profiles, hindering their direct application in conventional low hydraulic residence time systems.

Keywords:

• Perfluorinated acids
• perfluoroalkyl sulfonic acids
• perfluoroalkyl carboxylic acids
• review
• physicochemical properties
• partitioning behavior
• water and wastewater
• treatment methods

Acknowledgments

S.R. thanks the Natural Sciences and Engineering Research Council (NSERC) of Canada for partial financial support of this work.

Notes

^aLog₁₀ P from ref.^{[ 24 ]}

^bFrom ref.^{[ 5 ]}

^cFrom ref.^{[ 200 ]}

^dCalculated with SPARC (August 2007 release w4.0.1219-s4.0.1219; http://ibmlc2.chem.uga.edu/sparc/).^{[ 87 , 204 , 205 ]} using SMILES molecular notation^{[ 94 , 95 ]} as inputs.

^elog₁₀ D from ref.^{[ 52 ]}

^flog₁₀ P from ref.^{[ 80 ]}

^aCalculated with SPARC (August 2007 release w4.0.1219–s4.0.1219; http://ibmlc2.chem.uga.edu/sparc)^{[ 87 , 204 , 205 ]} using SMILES molecular notation^{[ 94 , 95 ]} as inputs.

^bCalculated with EPI Suite EPIWEB v.4.0 (http://www.epa.gov/oppt/exposure/pubs/episuite.htm) using SMILES molecular notation as inputs with the following modules: KOWWIN v1.67, MPBPVP v1.43, WSKOW v1.41, HENRYWIN v3.20, KOAWIN v1.10, BIOWIN v4.10, BioHCwin v1.01, AEROWIN v1.00, AopWin v1.92, KOCWIN v2.00, and BCFBAF v3.00.

^cCalculated using ALOGPS 2.1 (http://www.vcclab.org/lablogps/).^{[ 88 , 89 , 212 ]}

^dFrom ref.^{[ 12 ]}

^eSaturated subcooled liquid vapor pressure.

^fDimensionless air-water partitioning constant.

^gOctanol-water partitioning constant.

^hOctanol-air partitioning constant.

^aCalculated with SPARC (August 2007 release w4.0.1219–s4.0.1219; http://ibmlc2.chem.uga.edu/sparc/)^{[ 87 , 204 , 205 ]} using SMILES molecular notation^{[ 94 , 95 ]} as inputs.

^bCalculated with EPI Suite EPIWEB v.4.0 (http://www.epa.gov/oppt/exposure/pubs/episuite.htm) using SMILES molecular notation as inputs with the following modules: KOWWIN v1.67, MPBPVP v1.43, WSKOW v1.41, HENRYWIN v3.20, KOAWIN v1.10, BIOWIN v4.10, BioHCwin v1.01, AEROWIN v1.00, AopWin v1.92, KOCWIN v2.00, and BCFBAF v3.00.

^cCalculated using ALOGPS 2.1 (http://www.vcclab.org/lablogps/).^{[ 88 , 89 , 212 ]}

^dFrom ref.^{[ 12 ]}

^eSaturated subcooled liquid vapor pressure.

^fDimensionless air-water partitioning constant.

^gOctanol-water partitioning constant.

^hOctanol-air partitioning constant.

^aFrom ref.^{[ 52 ]}

^bFrom ref.^{[ 97 ]}

^cFrom ref.^{[ 12 ]}

^aFrom ref.^{[ 52 ]}

^b From ref.^{[ 12 ]}