### Adsorption Processes  
adsorption is a highly effective method for remediating various pollutants in water, including PFASs, owing to its environmentally friendly nature, cost-effectiveness, low energy requirement, high efficiency, simple design, and ease of operation [31; 34]. The mechanisms of adsorption encompass hydrophobic effects, self-aggregation (formation of micelles or hemmicelles), electrostatic interactions, hydrogen bonding, covalent bonding, ligand exchange, Van der Waals forces attraction, \(\pi\)-\(\pi\) bonding, and diffusion into adsorbent pores [9; 15; 22; 26; 31; 34; 35; 36]. A schematic illustration of the various mechanisms of PFAS adsorption is presented in Figure 2. Adsorption can also occur through an ion exchange process where target pollutant ions in a solution replace exchangeable charged co-ions (e.g., Cl\({}^{-}\) and Na\({}^{+}\)) on the surface of a polymeric resin. These ion exchange resins are classified as cation exchange resins and anion exchange resins, with positively charged pollutants and negatively charged pollutants being exchanged, leading to the removal of these pollutants on the resins. Since PFASs are anionic in the pH range of natural water [28], they are typically removed by anion exchangers. An advantage of this process is its reversibility, as the resin can be regenerated and reused after saturation with PFASs using organic solvents like methanol, inorganic salts such as sodium chloride, bases like sodium hydroxide, or a combination of these regenerants [8]. Various materials, including ion-exchange resins, carbonaceous materials (e.g., granular activated carbon, biochar, and graphene oxide), natural and modified clays and clay minerals, renewable polymeric materials (e.g., chitosan and alginate), and inorganic and synthesized materials (e.g., layered double hydroxides, metal-organic frameworks, and nanomaterials), have been extensively investigated for their ability to adsorb PFASs from wastewater. In the past five years, several review articles have been published, focusing on the use of these materials for the remediation of PFASs [1; 8; 9; 21; 22; 23; 25; 26; 31; 34; 35; 37]. Among various adsorbents and ion exchangers, activated carbon (AC) stands out as the most widely used for PFAS removal, owing to its exceptional adsorptive potential, primarily attributed to its unique porous structure [31]. Powdered activated carbon (PAC) exhibits higher adsorption capacity than granular activated carbon (GAC) due to its smaller pore size and larger surface area [37]. The reported adsorption capacity of GAC is in the range of 71.6-290 mg/g (for PFOS) and 41.3-120 mg/g (for PFOA), while PAC demonstrates a higher adsorption capacity of 560 mg/g (for PFOS) and 290-500 mg/g (for PFOA) [35]. However, PAC is not reusable, whereas GAC, despite being more expensive, can be regenerated and is better suited for column-based filtration in treatment plants. Considering the relatively long equilibrium time and limited adsorption capacities of AC, anion exchange resins have been employed, with adsorptive capacities ranging from 200 to 2390 mg PFOS/g and 525-1500 mg PFOA/g [33]. Anion exchange resins have been shown to be particularly effective for removing PFOA, which exists as an anion at the environmental pH. The hydrophobicity of the exchange functional group of the anion exchange resin also plays a significant role in its adsorptive capacity for PFASs [38]. Highly hydrophobic resins exhibited higher adsorptive capacity (52.3-260.5 mg/g) for PFASs than nonhydrophobic (19.1-186.2 mg/g) and fairly hydrophobic (29.5-210.4 mg/g) resins [38]. This is because the hydrophobic resins have an affinity to the hydrophobic C-F chain part of the PFAS [22]. Ion exchange resins have also demonstrated high adsorption capacity for PFOS (210-2575 mg/g) and PFOA (1206 mg/g) [37]. Anion exchange resins have shown potential for removing short-chain PFASs like PFBA and PFBS, making them a preferable choice over GAC in such cases [31].