Arsenic species-adaptive removal from groundwater by carbon foam-supported Mn-doped FeOOH with precisely regulated Fe/Mn ratios.

at As(Ⅲ)/As(V) ratios of 1 and 2, respectively, with corresponding total As removal efficiencies of 87.50 % and 90.00 %, which are in close agreement with model predictions. Systematic characterization combined with density functional theory (DFT) calculations unveiled a redox-coupled mechanism in which Mn sites selectively oxidize As(Ⅲ) to As(V), followed by efficient capture of the generated As(V) by Fe sites. DFT results quantitatively confirmed that Mn doping significantly enhances the adsorption energy of As(Ⅲ), increasing it from -2.02 eV to -5.30 eV. This work provides not only a highly efficient adsorbent but also a predictive framework for the rational design of customizable materials tailored to address complex As speciation in groundwater.