The removal of zinc and nickel ions from aqueous solutions by adsorption on maize cobs was investigated. The amount of the metal ions increased with time. The highest sorption rates of the metal ions were obtained in the first ten minutes, in the next fifty minutes the uptake rate gradually decreases progressive and practically is zero after sixty minutes. The sorption rates were 72% for Zn2+, and 82% for Ni2+. This study showed that the sorption of zinc and nickel ions on maize cobs is particle diffusion controlled. The rate coefficients for particle diffusion were 0.053 min-1 for Zn2+ and 0.076min-1 for Ni2+.
