Apart from the Al 3+ center being a major MOF binding site, it is probable that the NH2, which will also exist in a protonated form as a NH3 + , contained in HPAM also attaches to the anionic carboxylate of PFOA via strong electrostatic adsorption forces. In addition, the van der Waals interaction between the carbon chain of PFOA (8 carbons on the PFOA) and the main skeleton (CH2-CH)n of HPAM may also contribute to the adsorption process. Altogether, these explanations for the incomplete desorption of PFOA from aminated adsorbents such as MIL-96-RHPAM2 are in line with the obtained result from batch desorption studies. Figure Although PFOA desorption efficiency from AC is inferior to MIL-96-RHPAM2 at lower ionic strengths, AC's desorption efficiency is improved at the highest ionic strength tested here. Similar to MOF, PFOA adsorption onto AC shares similar adsorption mechanisms, confirming the importance of surface chemistry on AC. There is a clear correlation with a marked increase in PFCs sorption with more availability of basic groups in the adsorbents. Thus, to enhance the adsorption process, an abundance of hydroxyl and carboxyl oxygen-containing functional groups on the AC surface will then interact with the PFOA anions via acid-base/electrostatic interactions. Along the same lines, the oxygen-containing basic and acidic surface groups on AC may form H-bond interactions with the amphoteric COOH functional groups within PFOA. An increase in the eluent ionic strength can potentially weaken these PFOA to AC H-bonding interactions by the Na + and the Cl -ions shielding the electrostatic interactions whilst also directly competing for the H-bonding sites. While these results show that NaCl was not an effective PFOA desorption facilitating agent, only catalytic degradation has so far offered superior performance.