Abstract:
Heavy metal contamination of water could occur anywhere at resources, course of distribution or consumption place. Precise knowledge on amount and type of water pollutants especially heavy metal are essential to protect the environment, and public health. This research aimed to evaluate concentration of heavy metal (Lead and Chromium) in drinking water of Jimma city and study means of removing the metals from the water. Accordingly, water samples were collected from five different sites which comprise raw and treated water, and the study showed that concentration of Pb {in Kochi [0.0196 ppm], Agaro ber [0.0195 ppm]}, and Cr (VI) {in Merkato [0.055 ppm]} drinking water of Jimma was higher than WHO standard limits among all samples. To this end, ways of mitigating heavy metal pollution should be investigated. Adsorption was found to be as one of the most widely used means. Varieties of precursor materials have been used for the preparation of activated carbons. In this study, activated carbon prepared from pine apple peel waste by KOH activation was investigated as adsorbent for the removal of Pb (II) and Cr (VI). Batch method was employed in this study to investigate the efficiency of the adsorbent. The optimum value for parameters influence adsorption:(adsorbent dose [0.25 g], [Pb (II)] and [Cr (VI)]: 0.02 & 0.05 mg/l, pH: 5 and 3 for Pb (II) and Cr (VI) respectively, contact time: 100 min and 70 min for both Pb (II) and Cr (VI), respectively and temperature 25oC) were obtained. To understand the adsorption isotherm, the Langmuir and Freundlich adsorption isotherm models were investigated. The results were found best fit to Freundlich adsorption isotherm which states that heterogeneity of the adsorbent surface. Kinetic studies of the data showed that the adsorption follows the pseudo-second-order kinetic model. Thermodynamic parameters for Pb (II) and Cr(VI) adsorption, enthalpy change (ΔH) {-0.149 and -0.081}, entropy change (ΔS){0.183 and 0.012}, and Gibbs free energy change (ΔG){-3.138 and -3.554 at 293 K, -3.191 and -3.615 at 298 k, -3.245 and -3.675 at 303 k}, respectively have also been calculated. The results of these parameters showed that adsorption was feasible, spontaneous in nature, and exothermic.
