© 2020 Elsevier B.V. Groundwater, one of the significant potable water resources of the geological epoch is certainly contaminated with class I human carcinogenic metalloid of pnictogen family which delimiting its usability for human consumption. Hence, this study concerns with the elimination of arsenate (As(V)) from groundwater using bilayer–oleic coated iron–oxide nanoparticles (bilayer–OA@FeO NPs). The functionalized (with high–affinity carboxyl groups) adsorbent was characterized using the state–of–the–art techniques in order to understand the structural arrangement. The major emphasis was to examine the effects of pH (5.0–13), contact times (0–120 min), initial concentrations (10–150 μg L–1), adsorbent dosages (0.1–3 g L–1), and co–existing anions in order to understand the optimal experimental conditions for the effective removal process. The adsorbent had better adsorption efficiency (∼ 32.8 μg g–1, after 2 h) for As(V) at neutral pH. Adsorption process mainly followed pseudo–second–order kinetics and Freundlich isotherm models (R2∼0.90) and was facilitated by coulombic, charge–dipole and surface complexation interactions. The regeneration (upto five cycles with 0.1 M NaOH) and competition studies (with binary and cocktail mixture of co–anions) supported the potential field application of the proposed adsorbent.