Phosphorylated cellulose nanofibers exhibit exceptional capacity for uranium capture

Janika Lehtonen,Thalappil Pradeep,Olli Ikkala,Avula Anil Kumar,Jukka Hassinen,Leena-Sisko Johansson,Nikolaos Pahimanolis,Roni Mäenpää,Orlando J Rojas

doi:10.1007/s10570-020-02971-8

Janika Lehtonen, Thalappil Pradeep + Show 7 more

Open Access

https://doi.org/10.1007/s10570-020-02971-8

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Abstract

We investigate the adsorption of hexavalent uranium, U(VI), on phosphorylated cellulose nanofibers (PHO-CNF) and compare the results with those for native and TEMPO-oxidized nanocelluloses. Batch adsorption experiments in aqueous media show that PHO-CNF is highly efficient in removing U(VI) in the pH range between 3 and 6. Gelling of nanofiber hydrogels is observed at U(VI) concentration of 500 mg/L. Structural changes in the nanofiber network (scanning and transmission electron microscopies) and the surface chemical composition (X-ray photoelectron spectroscopy) gave insights on the mechanism of adsorption. The results from batch adsorption experiments are fitted to Langmuir, Freundlich, and Sips isotherm models, which indicate a maximum adsorption capacity of 1550 mg/g, the highest value reported so far for any bioadsorbent. Compared to other metals (Zn, Mn, and Cu) and typical ions present in natural aqueous matrices the phosphorylated nanofibers are shown to be remarkably selective to U(VI). The results suggest a solution for the capture of uranium, which is of interest given its health and toxic impacts when present in aqueous matrices.

Highlights

Cellulose has been considered in the development of eco-friendly materials
Fourier transform infrared spectroscopy (FT-IR) was used to confirm the functional groups on the TO-cellulose nanofibers (CNF) and phosphorylated cellulose nanofibers (PHO-CNF) (Fig. 1a)
The zeta potentials of the native CNF indicate that it is negatively charged owing to the residual hemicelluloses and other impurities originating from the fibers used to prepare the material

Summary

Introduction

Cellulose has been considered in the development of eco-friendly materials. cellulose nanofibers (CNF) have raised interest for their suitability for water purification and heavy metal removal (Voisin et al 2017). We study the removal of uranium with PHO-CNF using several batch adsorption approaches. Samples for XPS were prepared by vacuum filtration of PHO-CNF1.00 onto 0.1 lm filters after adsorption of U(VI) from the initial concentrations of 0, 100 mg/L, and 500 mg/L.

Results

Conclusion