Abstract:
There are many techniques to adsorb heavy metals from waste water. Adsorption is one of the
aqueous solution treatment technologies with low cost compared to the other technologies.
Different adsorbents have been used for the removal of heavy metals from wastewater. This study
was carried out to investigate the adsorption efficiency of the Ambo sandstone sorbent for Cr(VI)
and Cd(II) ions from an aqueous solution. The parameters investigated in this study included the
pH, the dose of adsorbent, agitation speed, contact time and initial metal ions concentration of
commercially available aqueous solution. Batch adsorption studies demonstrated that the Ambo
sandstone has a significant capacity for the adsorption of Cr(VI) and Cd(II) from aqueous solution.
The adsorption efficiency of Cr(VI) and Cd(II) are determined using general formula: Removal
%=(
𝐶𝑜−𝐶𝑓
𝐶𝑜
) 𝑥100. The results indicate that optimum conditions for Cr(VI) and Cd(II) adsorption
were at pH 5 an d 8 respectively. The Ambo sandstone powder sorbent was dosed at 5g Cr(VI)
and 7 g Cd (II), with a contact time of 60 minutes for Cr(II) and 30 minutes for Cd (II), an agitation
speed of 120 rpm, and an initial concentration of 20 mg/L of each metal ion. The residual metallic
ion concentrations were determined using Atomic Absorption Spectrometer(AAS). The equilibrium
data obtained in the present study fitted well with Freundlich isotherms for Cd(II) and Cr(VI) and
the maximum adsorption capacity (qmax) of Ambo sandstone was found to be 16.4 for chromium(VI)
ions and 10.224 mg/g for cadmium (II) ions. In case of adsorption kinetics, both Cd(II) and Cr(VI)
fitted Pseudo-second order and the maximum adsorption capacity (qm) of Ambo sandstone was
found to be 1.88 for chromium (VI) ions and 2.02 mg/g for cadmium (II) ions. The results indicated
that the adsorbent was effective for removal of Cr(VI) and Cd(II) ions from aqueous solutions
containing these metal ions
