Adsorbents of natural origin are widely used for industrial wastewater treatment in order to replace currently costly methods of heavy metals removal from solutions. For that purpose, the potential of an agricultural waste, Piliostigma thonningii pod as an adsorbent in the removal of Cr(III), Cd(II) and Pb(II) ions from aqueous solution was investigated. The removal of these metal ions by the biosorbent has been found to be dependent on contact time and adsorbent dose. Results showed that the

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... sorption process was fast and that equilibrium was achieved within 70 min. Results further showed that increase in adsorbent dose caused enhancement in the removal efficiencies for the metal ions by the adsorbent. The applicability of the pseudo first-order, pseudo second-order and intraparticle diffusivity models was also investigated. Results showed that the experimental data were better correlated by the pseudo second-order model. The transport mechanism of the process was found to follow intra-particle diffusion.