Abstract:
This study was initiated to investigate the adsorption of cadmium from aqueous solution by two different rock types—Pumice (VPum) and Scoria (VSco), which are readily available in Ethiopia and other
countries. The influence of operational conditions, such as particle size, adsorbent/solution ratio, contact time, cadmium initial concentration, and pH was analyzed. The competition between metals was
also evaluated. The Cd(II) removal capacity was predominantly affected by the pH conditions, being
increased under alkaline conditions. For both adsorbents, when particle size was 0.075–0.425 mm, the
maximum Cd(II) adsorption was observed at pH 6.0 (contact time = 24 h, shaking speed = 200 rpm, adsorbent dose = 50 g L−1). Adsorption process revealed that the initial uptake was very fast during the first
1 h. The kinetics of the interactions follows pseudo second-order. Equilibrium assays confirm that VPum
has a larger capacity and affinity for Cd(II) adsorption than VSco. Both Langmuir and Freundlich models
described equally well the experimental data. VPum and VSco were found to be promising material for
the removal of cadmium from metal bearing water.
