Removel of Uranium from Aqueous Solutions by Spirodela Punctata as the Mechanism of Biomineralization

Abstract

Click This study evaluates the feasibility of biosorption of uranium from aqueous solutions using living and dried S. punctata. The uranium maximum removal efficiency for the plant cultivar occurrs in the soluation at pH 4-5 and the uranium removal efficiency exceeds 90%. In the kinetics studies, the dried powder of duckweed can reach nearly 80% adsorption within 5min, and the batch adsorption equilibrium can be reached within 24h for the living and dried powder of duckweed. Both for the living and dried powder of duckweed, the experimental data were fitted by the pseudo-second-order rate model with the degree of fitting (R2) higher than 0.99. The uranium was deposited onto the root surface of living S. punctata as 100-500 nanometer size schistose structures that consist of primarily U (82.5%,wt%) and P(8.76%,wt %), and no carbon; while no similar uranium phosphate minerals were found on the dried powder of S. punctata, as revealed by scanning electron microscope and energy dispersive spectrometer analysis. The results suggest that there is one particularly promising biosportion processes, namely, biomineralization. And the root surface of the living S. punctata plays an important role in the uranium phosphate precipitate processes, not only play as a carrier of the functional groups but also as a substrate inducing the nucleation of uranium-phosphate nanoparticles. The dried powder of S. punctata adsorption of U is mainly through the effect of electrostatic attraction, ion exchange, and complexation coordination.