Two conformations were obtained for adsorbed pentavalent methylarsenicals according to their speciation at neutral pH (Fig. ): (i) lying-down or (ii) seated conformations, where deprotonated oxygen of methylarsenicals is oriented toward the adsorbent surface, while the arsenic atom is placed at intermolecular distances of 3.0-3.7 Å from the adsorbent surface. In comparison, neutral pentavalent methylarsenicals reach adsorption energies of 0.42-0.68 eV onto intrinsic phosphorene. In the case of pentavalent methylarsenicals adsorbed onto phosphorene oxide, a slight shortening of intermolecular length (dPhosO-As) is accompanied to an increase of stabilization compared to the intrinsic phosphorene; that is, neutral pentavalent methylarsenicals display Eads of 0.77-0.91 eV showing a substantial increment of up to 115% (+0.49 eV) in the adsorption process for MMA V (Fig. ). Concerning the adsorption of anionic pentavalent methylarsenicals, the adsorption process is substantially more robust using phosphorene oxides as nanoadsorbents.