Isotherm Studies of Equilibrium Sorption of Cu2+ and Cd2+ from Aqueous Solutions by Modified and Unmodified Breadfruit Seed Hull

The ability of an economically cheap adsorbent material of natural origin, African breadfruit seed hull, was assessed for Cu(II) and Cd(II) ions' adsorption from aqueous solutions. The effects of adsorbent dose, particle size and initial metal ion concentrations were investigated in a batch adsorption process. The experimental data were analyzed using five two-parameter isotherm equations (i.e., Langmuir, Freundlich, Temkin, Harkins-Jura and Halsey isotherm models). Freundlich and Halsey models provided the best description for the adsorption data while the other three models gave fairly good interpretation to the experimental adsorption data. The maximum adsorption capacity corresponding to saturation of sites (q(max)), obtained from the Langmuir plots, were 7.76 and 8.06 mg g(-1) for Cu(II) and Cd(II) onto the unmodified breadfruit seed hull (UBSH) and 12.67 and 13.97 mg g(-1), respectively for Cu(II) and Cd(II) adsorption onto the modified breadfruit seed hull (MBSH). The experimental results showed that there was an enhancement in the removal of the metal ions by the mercaptoacetic acid-modified breadfruit seed hull.