Continuous adsorption and advanced oxidative degradation of pharmaceuticals pollutants using iron-modified MWCNT–Bentonite pellets

In this study, extrusion-molded composite pellets based on iron-modified multi-walled carbon nanotubes (Fe-MWCNTs) and bentonite were developed as a macroscopic material platform for the removal of pharmaceutical contaminants from water. The pellets were designed to overcome typical limitations of powdered carbon nanotubes in continuous systems, enabling practical handling and application in fixed-bed configurations. The structured composites were evaluated as bifunctional materials, independently applied as adsorbents in continuous fixed-bed columns and as catalysts in advanced oxidation processes. In continuous adsorption assays, the removal of diclofenac (DCF) and losartan (LS) was investigated under different flow rates and inlet concentrations, with breakthrough behavior successfully described by the Modified Dose–Response model and mass transfer alternating between external and intraparticle diffusion. Regeneration experiments demonstrated sustained adsorption performance over multiple cycles, indicating adequate structural integrity for repeated use. In separate catalytic tests, the pellets were applied in advanced oxidation processes, including heterogeneous Fenton, catalytic ozonation, and UV-assisted photocatalysis. Among the evaluated routes, the Fenton-like process showed the highest degradation efficiency for both pharmaceuticals, with quenching experiments indicating hydroxyl radicals as the predominant reactive species and a relevant contribution of superoxide, particularly for losartan degradation. Overall, the results demonstrate that macroscopic engineering of CNT-based composites enables continuous-flow operation while preserving adsorption and catalytic functionalities. By integrating material shaping, fixed-bed adsorption performance, and catalytic oxidation within a single structured architecture, this study provides practical and mechanistic insights for the design of multifunctional carbon-based materials for water treatment applications.