The biosorption of Cd (II), Pb(II) and Fe(III) ions from dilute aqueous solution using unmodified and modified raphia palm fruit (Raphia hookeri) as an adsorbent was carried out through pH –dependent studies. The results from the pH study showed that the biosorption was pH dependent and optimum pH ranged from 8 to 11. The result of the pH study on the unmodified biomasses showed that adsorption increased with increase in pH up to a maximum for all the metal ions on all biomasses considered. The maximum adsorption capacities for Pb (II) in the unmodified biomasses were 99.66% for unmodified epicarp (UEP), 99.89% for unmodified endocarp (UEN) and 94.06% for unmodified mesocarp (UMS). The maximum adsorption capacities for Fe (III) were 99.8% for UEP at pH = 11, 99.5% for UEN at pH = 8 and 99.78% for UMS at pH =11.The maximum adsorption capacities for Cd (II) in the unmodified biomasses were 99.69% for UEN, 98.84% for UEP and 98.86% for UMS, all at the pH of 11. Adsorption expressed as percent adsorption showed that sorption of Pb (II) increased gradually to a maximum at pH = 8 for all hydroxylamine treated mercaptoacetic acid (NH2OH-MAA) modified raphia palm fruit biomasses. The maximum sorption capacities for Pb (II) were 97.17% for MMXY, 98.78% for MENXY and 99.76% for MEPXY. Percent sorption for Fe (III) showed that maximum adsorption for all NH2OH-MAA modified biomasses occurred at pH = 8. The maximum capacities for Fe (III) were 96.68% for MMXY, 99.34% for MENXY and 99.27% for MEPXY. For iron (III), adsorption increased very slightly to the maximum after the initial pH of adsorption. Sorption of Cd (II) on to the NH2OH-MAA modified biomasses followed a peculiar pattern for all the three biomasses considered except a single deviation for MENXY at pH = 8; all other maxima occurred at pH = 11 for Cd(II).
