Valorization of Adenanthera pavonina seeds as a potential biosorbent for lead and cadmium removal from single and binary contaminated system

Abstract

This study investigated the biosorption of Pb (II) and Cd (II) on powdered seeds of Adenanthera pavonina from single and binary heavy metal solutions. The adsorption capacity of the metal ions was studied as a function of pH, adsorbent dose, initial metal ion concentration, and contact time. In the single heavy metal system, maximum removal of Pb (II) and Cd (II) were achieved at pH 4 and 6, respectively, while the equilibrium was attained at a contact duration of 35 min at a constant dose of 5 g L−1 was maintained for both Pb (II) and Cd (II). Further, the kinetic study revealed that the biosorption process was best described by the second-order kinetic model. In the competitive biosorption of binary mixtures of Pb (II) and Cd (II) were studied in terms of percentage removal of metal ions, adsorption capacity and equilibrium sorption isotherm. The percentage removal of metal ions in binary solutions was suppressed in presence of the other competitive metal ion. Field emission scanning electron microscopy integrated with energy dispersive X-ray spectroscopy of the biomass before (control) and after (metal loaded biomass) the biosoption process, confirmed the presence of respective heavy metal on to the biomass. Fourier transmission infrared spectroscopy spectra supported the activity of hydroxyl, amines, amides, and carboxyl groups in uptake of both heavy metal ions.