Degradation and Removal Methods for Perfluoroalkyl and Polyfluoroalkyl Substances in Water

Several perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been identified as chemicals of concern in the environment due to their persistence, global ubiquity, and classification as reproductive and developmental toxicants, endocrine disrupters, and possible carcinogens. Multiple PFASs are often found together in the environment due to product manufacturing methods and abiotic and biotic transformations. Treatment methods are needed to effectively sequester or destroy a variety of PFASs from groundwater, drinking water, and wastewater. This review presents a comprehensive summary of several categories of treatment approaches: (1) sorption using activated carbon, ion exchange, or other sorbents, (2) advanced oxidation processes, including electrochemical oxidation, photolysis, and photocatalysis, (3) advanced reduction processes using aqueous iodide or dithionite and sulfite, (4) thermal and nonthermal destruction, including incineration, sonochemical degradation, sub- or supercritical treatment, microwave-hydrothermal treatment, and high-voltage electric discharge, (5) microbial treatment, and (6) other treatment processes, including ozonation under alkaline conditions, permanganate oxidation, vitamin-B12 and Ti(III) citrate reductive defluorination, and ball milling. Discussion of each treatment technology, including background, mechanisms, advances, and effectiveness, will inform the development of cost-effective PFAS remediation strategies based on environmental parameters and applicable methodologies. Further optimization of current technologies to analyze and remove or destroy PFASs below regulatory guidelines is needed. Due to the stability of PFASs, a combination of multiple treatment technologies will likely be required to effectively address real-world complexities of PFAS mixtures and cocontaminants present in environmental matrices.