We have theoretically elucidated the sorption properties of phosphorene oxide nanoadsorbents for the simultaneous removal of inorganic As(III) and As(V) pollutants from water. It is found that phosphorene oxide forms stable inner-sphere surface complexes with arsenicals even under aqueous environments, and it shows a strong affinity with highly mobile As(III). Electrostatic driving forces govern the adsorption of neutral arsenicals, while the interplay between electrostatic and polarization phenomena drives the uptake of anionic arsenicals. Furthermore, the optimum adsorption efficiency is reached with a 25% in the content of oxidizing groups, which also turns the phosphorene oxide nanoadsorbents convenient to be recycled via simple alkaline treatment. Moreover, the adsorption process is allowed in a wide range of ambient temperatures.