Continuous-flow separation of cesium ion by ammonium molybdophosphate immobilized in a silica microhoneycomb (AMP-SMH)

Monolithic cesium ion (Cs+) adsorbents were synthesized via the directional freezing of a silica hydrogel containing ammonium molybdophosphate (AMP) particles, followed by freeze-drying. The adsorbents have a honeycomb-like structure with nearly straight microchannels (approximately 21 µm in diameter) running through them and with AMP particles partially embedded intact within the channel walls. Because of its honeycomb-like structure, the adsorbent, denoted as AMP silica microhoneycomb (AMP-SMH), achieves a significantly lower pressure drop than a typical column packed with spherical particles with similar diffusion path lengths for Cs+ when water was passed through it (about 35-times lower). Comparison of breakthrough curves between the AMP-SMH and columns packed with particles by numerical simulation also indicates that AMP-SMH shows shorter length of unused bed values. These results demonstrate that the AMP-SMH shows a high performance in the continuous separation of Cs+ due to their unique microhoneycomb structure.