Ultrahigh surface area nanoporous carbon for air and water purification: Pushing the boundaries and unveiling the key physicochemical features

Nanoporous carbons are widely employed in environmental remediation applications due to their high surface area, tunable porosity, and adaptable surface chemistry. In this study, three commercial activated carbons, MSC, CPL, and SXP, were intentionally and precisely selected to span a broad range of surface areas (∼1000–3000 m²/g) and surface pH values (5.3–7.5), enabling a comparative evaluation of their physicochemical properties and adsorptive performance. These materials and their oxidized counterparts were tested against hazardous vapors (blister agent mustard gas surrogate, CEES) and aqueous pollutants (radionuclides U-232 and Am-241). MSC exhibited an ultrahigh surface area and delivered the highest CEES uptake (1397 mg/g), the highest reported to date. However, oxidation significantly decreased porosity, resulting in diminished vapor-phase performance. In contrast, the same oxidation enriched the surfaces with acidic oxygen-containing functional groups, substantially enhancing radionuclide affinity, especially in neutral and saline media. The oxidized MSC outperformed all other materials in aqueous radionuclide removal, across a wide range of pH values (4–9) and more importantly, in seawater. These results reveal the dual role of oxidation: beneficial for liquid-phase adsorption through surface complexation, yet unfavorable for gas-phase purification where pore volume and accessibility maters the most. Overall, this work underscores the importance of tuning both surface area and surface chemistry for application-specific purification strategies and finally that activated nanoporous carbons can push even further the boundaries for efficient air and aqueous purification applications.