ABSTRACT:The contamination of water by potentially toxic elements is considered a global problem. It calls for a safe, economic and technological approach in order to curb and prevent the devastating effect of the menace on both human and the aquatic life. In the light of this background, the adsorption potential of flamboyant pod activated carbon (FPAC) for the removal of chromium and lead from aqueous solution was studied. The effect of contact time, pH, initial concentration as well as adsorbent dosage on the removal efficiency of both metal ions was investigated via batch adsorption. Characterization of the FPAC adsorbent was done using Brunaur Emmett Teller and Fourier transform infrared spectroscopy. The maximum adsorption capacity Q e was found to be 34.48 and 16.13 mg/g for Pb (II) and Cr (VI), respectively. The Langmuir isotherm model showed a better fit to the equilibrium data than the Freundlich isotherm model. The mechanism of adsorption for both metal ions onto the FPAC agrees well with pseudo second order kinetic model. The results showed that FPAC has excellent adsorption properties and thus can be used as an effective low-cost adsorbent for the removal of lead and chromium ions from aqueous solution.

A central composite design (CCD) under the response surface methodology (RSM)was used to study the effect of three adsorption variables (pH, initial concentration, and adsorbent dosage) in order to determine the optimum process conditions for the adsorptions of Ni (II) and Cr (III) onto sulphuric acid modified sorghum bicolor activated carbon (SBAC).This study yielded removal efficiency of 98.89 % for Ni (II) and 94.27 % for Cr (III) ion under optimal conditions of pH (8), initial metal ion concentration (25 mg/L), adsorbent dosage (10 mg) and pH (7), initial metal ion concentration (5 mg/L), dosage (15 mg);respectively. Statistical analysis of variance results showed a good correlation existed between the experimental and predicted data with R2 values of 0.99 for Ni and 0.98 for Cr. The equilibrium data for Ni (II) adsorption was best described using Freundlich model while Langmuir model best fit Cr (III) adsorption. The mechanism of adsorption for both Ni and Cr adsorptions on SBAC followed Pseudo second order kinetic model.  http://dx.doi.org/10.4314/njt.v36i3.41

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