Uranium adsorbent fibers prepared by atom-transfer radical polymerization from chlorinated polypropylene and polyethylene trunk fibers

Seawater contains a large amount of uranium (~4.5 billion tons) which can serve as a nearly limitless supply for an energy source. However, to make the recovery of uranium from seawater economically feasible, lower manufacturing and deployment costs are desirable, and good solid adsorbents must have high uranium uptake, reusability, and high selectivity toward uranium. In this study, atom-transfer radical polymerization (ATRP), without the high-cost radiation-induced graft polymerization, was used for grafting acrylonitrile and tert-butyl acrylate from a new class of trunk fibers, forming adsorbents in a readily deployable form. The new class of trunk fibers was prepared by the chlorination of polypropylene (PP) round fiber, hollow-gear PP fiber, and hollow-gear polyethylene fiber. During ATRP, degrees of grafting (d.g.) varied according to the structure of active chlorine sites on trunk fibers and ATRP conditions, and the d.g. as high as 2570% was obtained. Resulting adsorbent fibers were evaluated in U-spiked simulated seawater, and the maximum adsorption capacity of 146.6 g U/kg, much higher than that of a standard adsorbent Japan Atomic Energy Agency fiber (75.1 g/kg), was obtained. This new type of trunk fiber can be used for grafting a variety of uranium-interacting ligands, including designed ligands that are highly selective toward uranium.