To search for new uptake platforms for the removal of highly toxic and mobile arsenite [or trivalent arsenic, As(OH)3], we theoretically investigate the adsorption properties of intrinsic and metal-doped phosphorene nanoadsorbents. The doping of phosphorene with Ni or Cu atoms remarkably increases the uptake stability of arsenite at water environments compared to intrinsic phosphorene, with a weak competition of H2O molecules by the adsorption sites, where the adatom doping of phosphorene allows obtaining better uptake performance compared to the substitutional doping. The uptake is explained by a strong inner-sphere surface complexation, which is dominated by permanent electrostatic physical effects. Hydroxide anions show strong competitive adsorption compared to H2O and arsenite; thus, the straightforward recovery of the nanoadsorbents could be reached after removal by treatment at high pH solutions. Therefore, metal-doped phosphorene hybrids could serve as superior nanoadsorbents for arsenic separation from water by adsorption in solid phases.