Adsorption of Rare-Earth Metal Ions on Natural Banana Fiber

The adsorption properties of banana fibers for rare-earth metal ions (La, Gd, Tm, Pr, Tb, Yb, Nd, Dy, Lu, Sm, Ho, Eu, and Er) were investigated, and the concentrations of metal ions were measured by using an inductively coupled plasma optical emission spectrometer. The pH value of the aqueous phase was measured using a pH meter equipped with glass electrodes. Over 70% of all the metal ions were adsorbed on non-treated banana fiber at pH values ranging from 2.0 to 6.0. On the other hand, using alkali-treated banana fiber, the adsorption ratio for rare-earth metal ions increased with pH. The reaction equation for the alkali-treated banana fiber system was investigated by the slope analysis between logarithmic distribution ratio and pH. The results suggest that not only the hydroxy groups originated from the interaction between cellulose and metal ions but also other negative ions might be involved in the ionexchange reaction in the alkali-treated banana fiber. Such distinct behavior raises the possibility of the utilization of banana fibers in the separation and adsorption of metal ions.