PAMPS PolyHIPEs : The Role of Shape, Porosity, and Sulfonate Group Density on Metal‐Ion Adsorption From Water

In this study, the adsorption performance of poly(2‐acrylamido‐2‐methylpropanesulfonic acid) (PAMPS)‐based polymerized high internal phase emulsion (polyHIPE) for the removal of Zn 2+ , Fe 3+ , and Al 3+ ions from water is investigated. The triple‐factor analysis includes the role of shape, porosity, and sulfonate group density. By systematically comparing different forms of PAMPS, that is, polyHIPE beads and monoliths (shape effect), PAMPS homopolymers and copolymers (SO 3 − group density effect), and porous polyHIPEs compared to commercially available gel‐type, non‐macroporous beads (porosity effect), we determine how structure–function relationships govern metal ion uptake. The results show ion‐specific effects: The high charge density of Fe 3+ and Al 3+ generates a strong electrostatic driving force for multipoint binding to SO 3 − groups, which leads to fast adsorption. In contrast, Zn 2+ adsorption is slower due to its lower charge density and the relatively stable hydration sphere. It therefore appears to be diffusion‐limited compared to Fe 3+ and Al 3+ . These results show how the polymer architecture can be tuned to optimize adsorption efficiency, selectivity, and robustness. Such a design principle of PAMPS‐based polyHIPEs demonstrates a strategy to customize adsorbents for advanced water treatment applications.