Removal of HFPO-DA (GenX) from aqueous solutions: A mini-review

Hexafluoropropylene oxide dimer acid (HFPO-DA) and its ammonium salt (GenX) are anthropogenic substances widely used in the industry. They belong to the class of perfluoroalkyl substances, possessing properties such as high chemical stability, high mobility, high water solubility, extraordinary persistence in the environment, bioaccumulability in living tissues, and toxicity. Because of such properties, HFPO-DA and GenX are ubiquitously found in the environment, where they can remain almost unmutated for an extremely long time, so that such chemicals, together with the other perfluoroalkyl substances, are being named "forever chemicals". Due to their adverse effects on human health and the environment, growing regulatory attention is paid to these pollutants. Parallelly, new technologies for their removal are highly necessary because conventional ones are almost ineffective. However, there is limited available information regarding the effectiveness of HFPO-DA and GenX treatment methods. The present article reviews the characteristics and occurrence of these emerging chemicals in the environment. Also, the removability of HFPO-DA and GenX by novel treatment approaches (membranes, adsorption, and degradation techniques) and conventional wastewater treatment are discussed. Studies reported in the literature indicate that these chemicals are not efficaciously eliminated by conventional technologies currently used in wastewater treatment plants. Early observations suggest that adsorption and high-pressure membranes could be considered the most promising removal technologies available on the market.