The absorption of toxic heavy metal by natural adsorbents from water were indicated by investigation the effect of nano sized (Delonix regia (DR)) and (CADR) citric acid Delonix regia chemically modified adsorbent for removing the Cd2+ ions. Different techniques were employed for characterizing the adsorbent (Delonix regia) such energy dispersive analysis of X-ray (EDAX), Fourier transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The effect of temperature, dosage of adsorbent, contact time, pH and Cd2+ ion concentration on adsorption process were studied. (qm) the maximum adsorption capacity of Cd2+ ions by Delonix regia was 37.2 mg g−1. The highest removal efficiency (R.E.) was 96.00 % at pH 4.0. FT-IR peaks indicated that the main functional groups are hydroxyl and carboxylic groups are responsible for Cd2+ ions binding in the adsorption. The adsorption process was endothermic. The adsorption process was best described by pseudo second order kinetics model. The Freundlich isotherm has a better fit with the experimental data compared to Langmuir isotherm. These results indicated that Delonix regia is environment friendly, available and low cost adsorbent for adsorbing the Cd2+ ions.