Research and Regulatory Advancements on Remediation and Degradation of Fluorinated Polymer Compounds

PFOA-contaminated soil remediation: a comprehensive review

Soil and groundwater contamination has been raised as a concern due to the capability of posing a risk to human health and ecology, especially in facing highly toxic and emerging pollutants. Because of the prevalent usage of perfluorooctanoic acid (PFOA), in industrial and production processes, and subsequently the extent of sites contaminated with these pollutants, cleaning up PFOA polluted sites is paramount. This research provides a review of remediation approaches that have been used, and nine remediation techniques were reviewed under physical, chemical, and biological approaches categorization. As the pollutant specifications, environmental implications, and adverse ecological effects of remediation procedures should be considered in the analysis and evaluation of remediation approaches, unlike previous research that considered a couple of PFAS pollutants and generally dealt with technical issues, in this study, the benefits, drawbacks, and possible environmental and ecological adverse effects of PFOA-contaminated site remediation also were discussed. In the end, in addition to providing sufficient and applicable understanding by comprehensively considering all aspects and field-scale challenges and obstacles, knowledge gaps have been found and discussed.

Per-and polyfluoroalkyl (PFAS) eternal pollutants: Sources, environmental impacts and treatment processes

Per- and polyfluoroalkyl substances (PFAS) have become a growing environmental concern due to their tangible impacts on human health. However, due to the large number of PFAS compounds and the analytical difficulty to identify all of them, there are still some knowledge gaps not only on their impact on human health, but also on how to manage them and achieve their effective degradation. PFAS compounds originate from man-made chemicals that are resistant to degradation because of the presence of the strong carbon-fluorine bonds in their chemical structure. This review consists of two parts. In the first part, the environmental effects of fluorinated compound contamination in water are covered with the objective to highlight how their presence in the environment adversely impacts the human health. In the second part, the focus is put on the different techniques available for the degradation and/or separation of PFAS compounds in different types of waters. Examples of removal/treatment of PFAS present in either surface or ground water are presented.

Emergence of per- and poly-fluoroalkyl substances (PFAS) and advances in the remediation strategies

A group of fluorinated organic molecules known as per- and poly-fluoroalkyl substances (PFAS) have been commonly produced and circulated in the environment. PFAS, owing to multiple strong CF bonds, exhibit exceptional stability and possess a high level of resistance against biological or chemical degradation. Recently, PFAS have been identified to cause numerous hazardous effects on the biotic ecosystem. As a result, extensive efforts have been made in recent years to develop effective methods to remove PFAS. Adsorption, filtration, heat treatment, chemical oxidation/reduction, and soil washing are a few of the physicochemical techniques that have shown their ability to remove PFAS from contaminated matrixes. However these methods also carry significant drawbacks, including the fact that they are expensive, energy-intensive, unsuitable for in-situ treatment, and requirement to be carried under dormant conditions. The metabolic products released upon PFAS degradation are largely unknown, despite the fact that thermal disintegration methods are widely used. In contrast to physical and chemical methods, biological degradation of PFAS has been regarded as efficient method. However, PFAS are difficult to instantly and completely metabolize through biological methods due to the limitations of biocatalytic mechanisms. Nevertheless, cost, easy-to-operate and environmentally safe are some of the advantages over its counterpart. The present review comprehensively discusses the occurrence of PFAS, the state-of-the science of remediation technologies and approaches applied, and the remediation challenges. The article also focuses on the future research directions toward the development of effective methods for PFAS-contaminated site in-situ treatment.

Fluoropolymers as Unique and Irreplaceable Materials: Challenges and Future Trends in These Specific Per or Poly-Fluoroalkyl Substances

In contrast to some low-molar-mass per- and polyfluoroalkyl substances (PFASs), which are well established to be toxic, persistent, bioaccumulative, and mobile, fluoropolymers (FPs) are water-insoluble, safe, bioinert, and durable. These niche high-performance polymers fulfil the 13 polymer-of-low-concern (PLC) criteria in their recommended conditions of use. In addition, more recent innovations (e.g., the use of non-fluorinated surfactants in aqueous radical (co)polymerization of fluoroalkenes) from industrial manufacturers of FPs are highlighted. This review also aims to show how these specialty polymers endowed with outstanding properties are essential (even irreplaceable, since hydrocarbon polymer alternatives used in similar conditions fail) for our daily life (electronics, energy, optics, internet of things, transportation, etc.) and constitute a special family separate from other "conventional" C1-C10 PFASs found everywhere on Earth and its oceans. Furthermore, some information reports on their recycling (e.g., the unzipping depolymerization of polytetrafluoroethylene, PTFE, into TFE), end-of-life FPs, and their risk assessment, circular economy, and regulations. Various studies are devoted to environments involving FPs, though they present a niche volume (with a yearly production of 330,300 t) compared to all plastics (with 460 million t). Complementary to other reviews on PFASs, which lack of such above data, this review presents both fundamental and applied strategies as evidenced by major FP producers.

Per- and polyfluoroalkyl substances (PFAS) exposure through munitions in the Russia-Ukraine conflict

Considered contaminants of emerging concern, per- and polyfluoroalkyl substances (PFAS) are a class of toxic, manufactured chemicals found in commercial and consumer products such as nonstick cookware, food packaging, and firefighting foams. Human exposure to PFAS through inhalation and ingestion can cause a variety of harmful effects and negative health outcomes. Per- and polyfluoroalkyl substances possess high polarity and chemical stability, enabling them to resist degradation in most environmental conditions. These characteristics allow PFAS to be mobile in soil, air, and water, and bioaccumulate in living organisms. Due to their thermally resistant chemical properties, PFAS are used as binders in polymer-bonded explosives (PBX) and in various components of munitions. Thus, when munitions are detonated, PFAS are released into the environment as aerosols and can deposit in the soil, surface water, or biota. Air emission modeling suggests that ground-level and airborne detonation of munitions can increase PFAS deposition both locally and long range. Further, if industrial facilities with PFAS are damaged or destroyed, there is greater potential for environmental degradation from increased release of PFAS into the environment. As a consequence of their persistent nature, PFAS can remain in an environment long after armed conflict, indirectly affecting ecosystems, food sources, and human health. The toxic contamination from munitions could present a greater hazard to a larger population over time than acute detonation events. This article discusses methods for estimating war-related damage from PFAS by exploring predictive modeling approaches and postwar ground validation techniques. Integr Environ Assess Manag 2023;19:376-381. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Review of influence of critical operation conditions on by-product/intermediate formation during thermal destruction of PFAS in solid/biosolids

Poly- and perfluoroalkyl substances (PFAS) are a large group of synthetic organofluorine compounds. Over 4700 PFAS compounds have been produced and used in our daily life since the 1940s. PFAS have received considerable interest because of their toxicity, environmental persistence, bioaccumulation and wide existence in the environment. Various treatment methods have been developed to overcome these issues. Thermal treatment such as combustion and pyrolysis/gasification have been employed to treat PFAS contaminated solids and soils. However, short-chain PFAS and/or volatile organic fluorine is produced and emitted via exhaust gas during the thermal treatment. Combustion can achieve complete mineralisation of PFAS at large scale operation using temperatures >1000 °C. Pyrolysis has been used in treatment of biosolids and has demonstrated that it could remove PFAS completely from the generated biochar by evaporation and degradation. Although pyrolysis partially degrades PFAS to short-chain fluorine containing organics in the syngas, it could not efficiently mineralise PFAS. Combustion of PFAS containing syngas at 1000 °C can achieve complete mineralisation of PFAS. Furthermore, the by-product of mineralisation, HF, should also be monitored due to its low regulated atmospheric discharge values. Alkali scrubbing is normally required to lower the HF concentration in the exhaust gas to acceptable discharge concentrations.

PFAS fate and destruction mechanisms during thermal treatment: a comprehensive review

Per- and polyfluoroalkyl substances (PFAS) are persistent chemicals and have been detected throughout the environment. Thermal treatment is the most common remediation approach for PFAS-contaminated solid wastes. Although various thermal treatment techniques have demonstrated the potential to destruct PFAS, the fate of PFAS, removal efficacy, potential emissions, and the formation of incomplete combustion products during thermal treatment are little known. This study provides a critical review on the behavior of PFAS based on different types of thermal treatment technologies with various PFAS-impacted environmental medias that include water, soil, sewage sludge, pure PFAS materials, and other PFAS-containing wastes. Different extents of PFAS thermal destruction are observed across various thermal treatment techniques and operating conditions. PFAS removal and destruction efficiencies rely heavily on PFAS structures, the complex combustion chemistry, the presence or absence of oxygen, temperature, and other operational conditions. This review also covers proposed PFAS thermal destruction mechanisms. Different thermal destruction mechanisms for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), and other PFAS are reviewed and compared. The majority of studies about PFAS thermal destruction mechanisms were focused on a specific list of PFAS and based mostly on the pyrolysis treatment. The basic pathway for PFAS destruction during pyrolysis is hydrodefluorination, which could be largely influenced by the alkaline condition. Future field-scale research that involves the characterization of PFAS destruction products and incomplete combustion products is needed to address public concerns and better emission control.