Attenuation Kinetics and Desorption Performance of artocarpus altilis Seed Husk for Co (II), Pb (II) and Zn (II) Ions

The potential of Bread Fruit (artocarpus altilis) Seed Husk (BFSH) as low-cost biosorbent for the removal of Pb (II), Zn (II) and Co (II) ions from aqueous solution was investigated. The adsorbent was characterized by the Fourier Transform InfraRed (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The batch methodology was utilized to determine the effect of pH, metal ion concentration, adsorbent dose, contact time and temperature on biosorption. Data generated were fitted into appropriate isotherm, kinetic and thermodynamic models. The effect of pH showed an increase in adsorption of metals with an increase in pH and an optimum pH of 5.0 was obtained for Pb (II), while 6.0 were obtained for Co (II) and Zn (II) ions biosorption. An equilibrium sorption contact time of 30, 40 and 60 min was obtained for Co (II), Zn (II) and Pb (II) ions respectively. The biosorption of metal ions was in the order Co (II) > Pb (II) > Zn (II). In general, the Freundlich model provided a better fit than the Langmuir, Tempkin, and Dubinin-Radushkevich isotherm models with R2 values greater than 0.9. The pseudo-firstorder kinetic model was applicable in the adsorption of Pb (II) and Zn (II) ions while the pseudo-second-order model provided the best fit for Co (II) ion adsorption. The adsorption mechanism was found to be controlled by the liquid film diffusion model (R2>0.9) rather than the intraparticle diffusion model (R2<0.9). Thermodynamics revealed a spontaneous, feasible, exothermic physisorption process and over 60% of the metal ions were desorbed using 0.1M HCl and 0.1M NaOH as eluent. The results showed that BFSH could be utilized as low-cost adsorbent for the removal of toxic heavy metals from solution.