Selective and Fast Separation of Cesium Ions by In Situ Synthesized Ammonium Molybdophosphate-Like Moieties in a Polymer Gel

The objective of the present study is to develop a selective and fast separation media for cesium ions for nuclear fission studies. Here, ammonium molybdophosphate (AMP)-like moieties have been synthesized in situ in a polymer gel with bis[2-(methacryloyloxy)ethyl] phosphate as the monomer. Two types of AMP-modified gels, poly(bis[2-(methacryloyloxy)ethyl] phosphate) and poly(bis[2-(methacryloyloxy)ethyl] phosphate-co-acrylic acid), have been prepared using in situ UV polymerization and characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopy. The successful formation of the Keggin structure of [PMo12O40]3– in the modified gels has been confirmed by the presence of its distinctive spectral signatures. The AMP-modified gels have been shown to extract Cs+ at all of the studied acid concentrations (0.5–8 mol L–1) and are found to be selective for Cs+ in the presence of other fission products (Ba2+, Eu3+, Ce3+) and even in the presence of bulk lead nitrate. A selectivity ratio as high as ∼47 for cesium ion with respect to other fission products has been obtained. The kinetics of Cs+ ion uptake has been observed to be fast with >90% uptake in ∼8 s, which is almost two orders of magnitude faster than the Cs+ adsorbents/extraction methods reported so far to the best of our knowledge. This fast kinetics can be attributed to the hydrophilic and porous nature of the synthesized polymer gel. The AMP-modified gels were successfully tested for the selective and fast separation of short-lived cesium isotopes produced in neutron-induced fission of 235U and allowed us to experimentally determine the half-life of one of the short-lived isotope of cesium, i.e., 140Cs, which was found to be in excellent agreement with the literature-reported value (t1/2 = 63.7 s). This is a significant improvement over previous studies and can have a variety of interesting applications not only in nuclear physics studies but also for the separation processes where Cs+ needs to be separated in a minimum time scale.