KINETIC STUDIES ON BIOSORPTION OF Pb(II), Cd(II) AND Ni(II) IONS FROM AQUEOUS SOLUTION BY ACTIVATED CEASAR WEED (Urena lobata) BARK

O.K. Amadi, F.K. Ekuma, C. M. Ngwu, C. H. Nwankwo

Abstract


In this research work, Urena Lobata bark, an agricultural product, available in large quantity in Southern region of  Nigeria was  used as low-cost adsorbent for  the removal  of  the following metal  ions: Pb(II), Cd(II) and Ni(II ) from aqueous solution. Batch adsorption technique was used to study the effects of solution pH and contact time for the sorption process. The kinetics of the process was investigated using Pseudo first-order, Pseudo second-order, Elovich model, Weber and Morris, Macky and Poot and liquid film diffusivity models. Results showed that the adsorption process was fast and that equilibrium was achieved within 120 min. Results further showed that the optimum pH for sorption of the metal ions occurred at pH 6.0 with maximum percentage removals recorded as 94.0 %, 96.78 % and 94.26 % for Pb(II), Cd(II) and Ni(II) ions respectively. The adsorption process was found to follow Pseudo second-order kinetics as observed by the high correlation coefficient (R2) values obtained when compared to the other kinetic models. The calculated equilibrium adsorption capacities, qe(cal) values (in mg/g) of 52.63, 50.00 and 47.67 for (Pb(II), Cd(II) and Ni(II) ions respectively were close to experimental equilibrium qe(exp) values of 49.26, 47.25 and 49.71 for Pb(II), Cd(II) and Ni(II) ions respectively. The transport mechanism for the process involved both intra-particle and liquid film diffusivities. The trend of the sorption process also follows: Cd(ll) > Pb(ll) > Ni(ll) indicating that the adsorbent showed strong affinity for Cd(ll) ions. The results of this study will serve as design parameter for wastewater treatment plant for Pb(II), Cd(II) and Ni(II) ions detoxification using Urena Lobata bark.

Key Words: Adsorption kinetics, biosorption, kinetic models, metal ions, Urena Lobata


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Chemical Society of Nigeria