The world’s oceans contain a relatively uniform uranium concentration of about 3 µg/L. While this appears to be an exceedingly small concentration, the total quantity of uranium throughout the world’s oceans is on the order of 1000 times higher than presently known in terrestrial deposits. In order to take advantage of this immense resource to support the nuclear energy industry for years to come, a co-polymer system produced by attaching a monomer capable of extracting uranium from seawater to a durable polymer substrate has been developed. A class of azo monomers were chosen for extraction experiments due to their high affinity for uranium. This was shown in preliminary testing through the use of activated charcoal loaded with said compounds where they were shown to remove more than 90 wt. % of the total uranium in a 0.2 mg U/L solution. The fabrics were irradiated using an electron beam, wherein radicals were generated on the surface of the substrate to initiate radical polymerization. By themselves, the azo compounds could not be grafted using radiation directly; they had to be chemically attached to the surface of the fabrics after a chemical precursor, vinylbenzyl chloride (VBC), had been grafted. The fabrics were characterized with attenuated total reflectance Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy in order to verify the attachment. These fabrics were then exposed to uranium-doped seawater solutions for a set period of time, after which the remaining solution was tested for the quantity of uranium left in solution using a spectrophotometric method and inductively coupled plasma mass spectrometry. Initially, the azo grafted fabrics extracted about 10 wt. % of uranium in solution. This was likely due to the hydrophobic nature of the azo groups, which prevented access of the uranium-carrying seawater to the azo binding sites. To correct for this, acidic monomers were co-grafted with the VBC precursor and then the co-grafted fabrics were chemically treated to attach the azo groups. The acid-azo functionalized fabrics were able to extract more than 70 wt. % of uranium in 0.2 mg U/L seawater solution after being rotated in the solution for nine days. This extraction efficiency is still lower than that achieved by the charcoal experiments, indicating that the fabrication of the adsorbents can be further optimized.

Azo functionalized, hydrophilic fabrics for the extraction of uranium from seawater

254th National Meeting (2017)

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