Abstract
High efficient removal and recovery of uranium and thorium from nuclear waste solution are essential for environmental preservation and fuel recycle. A new polymer fiber adsorbent (UHMEPE-g-PAO fiber), prepared by amidoximation of grafted polyacrylonitrile onto Ultra High Molecular Weight Polyethylene (UHMWPE) fiber, was used to remove the uranyl and thorium ions from acid aqueous solutions and its performance was carefully investigated. It was found that uranyl ion can penetrate the fiber through the connected pore structures, forming (UO2) (R-C(NH2)-NO)2 chelates with the amidoxime groups within the fiber. Two amidoxime groups (U-N and U-Oeq) and two water molecules (U-Oeq2) are bound to uranyl ion in the fiber. On the contrary, thorium ions are adsorbed mainly on the fiber surface in the form of Th(OH)4 precipitate that blocks the entrance of Th4+ ion into fiber pores. The maximum included other two capacities of uranyl and thorium ions were estimated to be 262.01 mg/g and 160 mg/g at room temperature with pH 3.0, respectively. The results also indicate that the UHMWPE-g-PAO fiber has higher adsorption selectivity for uranyl ion than thorium ion. Uranium and thorium oxide particles were obtained as the ultimate product after sintering of the fiber adsorbent. This novel and environmentally friendly adsorption process is feasible to extract uranium or thorium from acidic aqueous solution.
Highlights
Thorium ions are adsorbed mainly on the fiber surface in the form of Th(OH)4 precipitate that blocks the entrance of Th4+ ion into fiber pores
The results indicate that the Ultra High Molecular Weight Polyethylene (UHMWPE)-g-PAO fiber has higher adsorption selectivity for uranyl ion than thorium ion
Uranium and thorium oxide particles were obtained as the ultimate product after sintering of the fiber adsorbent
Summary
Nuclear energy is considered as one of the best sources of clean energy without pollut-. C. Jin et al 46 ing the environment by ejecting carbon dioxide. One major challenge is the disposal of nuclear waste [1] [2] [3] including the removal and recovery of radionuclides with minimum impact on the environment. From the point view of uranium resources and environmental protection [4] [5], separation and recovery of the essential uranium element in nuclear waste solution are of great significance. Solid phase extraction [6] [7] (SPE) has been considered to be one of the most effective methods for recovery of materials because of its simplicity, low cost and wide adaptability [8]
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