Disposal of Heavy Transition Cd2+ Ions from Aqueous Solution Utilizing Nanosized Flamboyant Pod (Delonix regia)

The absorption of toxic heavy metal by natural adsorbents from water was indicated by investigating the effect of nanosized Delonix regia (D. regia) and the chemically modified adsorbent citric acid D. regia (CA-D. regia) for removing the Cd2+ ions. Different techniques were employed for characterizing the adsorbent D. regia such as energy-dispersive X-ray (EDX) analysis, 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 the adsorption process was studied. The maximum adsorption capacity of Cd2+ ions by D. regia, (qm), was 37.2 mg.g−1. The highest removal efficiency (RE) was 96.00% at pH 4.0. FT-IR peaks indicated that the main functional groups (hydroxyl and carboxylic groups) are responsible for Cd2+ ions binding in the adsorption. The adsorption process was endothermic and was best described by a pseudo-second-order kinetics model. The Freundlich isotherm has a better fit with the experimental data compared to the Langmuir isotherm. These results indicated that D. regia is an environment-friendly, available, and low cost adsorbent for adsorbing the Cd2+ ions.