###### Abstract  
Poly- and perfluoroalkyl substances (PFASs) encompass a diverse group of engineered chemicals extensively manufactured and utilized in various facets of human life. They exhibit widespread distribution in aquatic environments due to their prevalent usage and resistance to degradation. Recognized for their toxicity to both humans and animals and a major public health concern, various techniques have been employed to eliminate them from water sources. However, these methods have shown limitations in efficiently and cost-effectively removing PFASs, particularly in the presence of other water contaminants, which are often present at much higher concentrations than PFASs. This review critically discusses these methods, presenting their respective advantages and limitations. This review illustrates that, rather than solely depending on individual methods as often presented in previous reviews, a combination of techniques has shown greater effectiveness in PFAS removal, owing to their synergistic effects. Hybrid methods capable of practical integration for efficient PFAS removal include adsorption coupled with oxidation, membrane separation combined with oxidation, and the integration of adsorption with membrane separation and incineration. In these hybrid approaches, one technique extracts PFASs from contaminated water and concentrates them, while the other degrades the extracted PFASs. The review presents strategies to enhance the performance of these hybrid methods. PFASs; treatment; adsorption; membrane separation; oxidation +
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long biological half-lives and a high potential for accumulation [3]. Consequently, these compounds are widely distributed in the environment due to their extensive use and resistance to degradation [4]. They have been extensively detected in various aquatic systems, including wastewater, surface water, groundwater, and drinking water. Their concentrations typically range from several picograms per litre (pg/L) to micrograms per litre (ug/L), with concentrations in the low nanograms per litre (ng/L) range being the most commonly observed [1]. They have been associated with significant human health risks, including cancer, infertility, low birth weight, and delayed puberty [2; 3; 5]. Recognizing these concerns, the US Environmental Protection Agency (EPA) established a lifetime health advisory level for combined perfluorooctanoic acid (PFOA) and perfluorooctane-sulfonic acid (PFOS) in drinking water at 70 parts per trillion (70 ng/L or 70 ppt) [1; 4; 5]. In March 2023, the US EPA proposed Federal Maximum Contaminant Levels (MCLs) for six PFASs in drinking water. The proposed MCLs for PFOA and PFOS are 4 ppt. Additionally, a Hazard Index MCL was proposed for the combined concentration of four other PFAS compounds (perfluorononanoic acid (PFNA), GenX chemicals, perfluorohexane sulfonic acid (PEhxS), and perfluoro-butane sulfonic acid (PFBS)), reflecting their differing relative health risks [6; 7]. PFAS compounds represent a diverse group of engineered chemicals, with the number of known compounds exceeding several thousand [1]. They can be classified into three categories: perfluoroalkyl acids (PFAAs), PFAA precursors, and other compounds such as fluoropolymers and perfluoropolyethers (PFPEs). Among the PFAAs, PFOA and PFOS are the most commonly encountered species in the environment that have been extensively studied [1]. Their structures are shown in Figure 1. These substances were previously produced in significant quantities worldwide but have since undergone a voluntary and gradual phase-out in the United States since 2000, driven by ecological and health concerns [1]. However, despite these efforts, PFOA and PFOS persist in the environment due to their inherent stability and ongoing imports from other countries [1]. Since the 1940s, PFASs have been extensively manufactured and utilized in various aspects of our lives [1].