Study on the Competitive Removal of Heavy Metals (Cr+6 and Pb+2) from Wastewater By Using Activated Coffee Husk

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Addis Ababa University


Due to the release of toxic heavy metals from various industries, water pollution has been a major challenge to environmental engineers today. Among various heavy metals, Pb(II) and Cr(VI) are considered as highly toxic due to their carcinogenicity and various health disorders. This study aimed was to investigate the competitive removal of heavy metal ions (cr+6 and pb+2) from aqueous solutions by using activated carbon prepared from the coffee husk. The initial work involves the optimization of process parameters involved in the preparation of activated carbon by chemical activation using H3PO4. The effects of activation temperature and concentration of H3PO4 at 2h contact times on the yield and MBN of prepared activated carbon were investigated. The highest yield (73%) of activated carbon was obtained at 400 0C temperatures and 30% H3PO4 concentrations while the highest removal efficiency (52%) was observed at 600 0C temperatures and 30% H3PO4 concentration. The prepared activated carbons were characterized for different physicochemical properties. The surface and structural properties of the adsorbent were studied using FTIR spectrometer and X- XRD analysis. The characterization result showed that the coffee husk-activated carbon has good properties and is compared favorably with other reference activated carbons. A series of batch adsorption of Cr(VI), as a single component, on ACs were carried out and the effect of experimental parameters on the removal efficiency were studied. The maximum removal efficiency of Cr(VI) was 98.1%. The competition of ions to active sites was studied and the result showed that the removal efficiency of Cr(VI) from binary solution was decreased to 94.77% compared to the removal efficiency (98.1% ) of Cr(VI) as a single component at the same conditions. The linear form of Langmuire and Freudlich models were applied to analyze adsorption data and the equilibrium data of Cr(VI) were well fitted to Langmuir isotherm model with R2 of 0.98. Two kinetic models were used to determine the adsorption mechanism and the kinetic data were correlated (R2 =0.998) well with the pseudo second order kinetic model for the adsorption study of Cr(VI) which implies that adsorption follows second order kinetics.



Wastewater, Heavy Metals, Coffee Husk, Activated Carbon, Adsorption Isotherms, Adsorption Kinetics