Chemical Studies on Uranium Biosorption by using Non-Living Water Hyacinth Roots

Natural non-living water hyacinth roots (WHR) and the treated either with nitric acid (WHR-HNO3) or sodium hydroxide (WHR-NaOH) are effectively adsorbed uranyl ions from its aqueous solution. At various pH values, adsorption equilibrium was reached within 10 min. and the adsorption isotherms were interpreted according to Langmuir and Freundlich models. Also, experimental adsorption data was analyzed by two kinetic models, namely; pseudo first order and pseudo second order. Among these models, pseudo second order model fits better with the experimental data of the treated non-living water hyacinth roots while pseudo first order model fits better with the data of the natural non-living water hyacinth roots. On the other hand, treatment of non-living water hyacinth roots by either nitric acid or sodium hydroxide was found to improve their interaction properties with uranium ions in adsorption process. The adsorption mechanism was investigated by Fourier transform infrared spectroscopy (FTIR), Scan electron microscope (SEM) and effect of pH. These analyses suggested that the adsorption mainly involved the ion exchange of UO22+ with cations and complex formation with functional groups on the surface of the roots. All the results showed that water hyacinth roots are an alternative low-cost adsorbent for the removal of uranium from aqueous media.