Facile structuring of amine-rich covalent organic polymer on melamine sponge for rapid removal of per- and polyfluoroalkyl substances

The monolithic three-dimensional (3D) melamine sponge-supported amine-rich porous covalent organic polymer (MS@ACOP), composed of melamine and aldehyde, was synthesized via a one-pot Schiff-base reaction without additional surface modification. This immobilization strategy facilitated the recovery of the adsorbent after use and promoted a uniform particle distribution to ensure available adsorption-active sites. The adsorption performance of MS@ACOP was evaluated for the removal of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) from water. According to the Langmuir isotherm model, the maximum adsorption capacity ( Q _m ) for PFOS was approximately 2.94 times higher than that for PFOA. Recyclability tests revealed that MS@ACOP could be effectively regenerated through sequential washing with methanol and deionized water, maintaining adsorption capacities over five consecutive cycles. Additionally, continuous-flow column experiments demonstrated that MS@ACOP exhibited enhanced adsorption capacities, which were approximately 29.7 times higher for PFOA and 11.6 times higher for PFOS compared to pure MS under dynamic flow conditions. The proposed adsorption mechanism suggested that negatively charged PFOA and PFOS were captured by MS@ACOP due to the abundant amine functionalities and porous structure of ACOP. Overall, these findings highlight the potential of MS@ACOP as an efficient, regenerable, and practical adsorbent for the removal of PFOA and PFOS from drinking water sources.