Transport of cesium using hollow fiber supported liquid membrane containing calix[4]arene-bis(2,3-naphtho)crown-6 as the carrier extractant: Part II. Recovery from simulated high level waste and mass transfer modeling

Transport studies for the recovery of cesium from pressurized heavy water reactor (PHWR) simulated high level waste (SHLW) were attempted by hollow fiber supported liquid membrane (HFSLM) technique using calix[4]arene-bis-2,3-naphthocrown-6 as the carrier ligand. Aqueous mass transfer coefficient of cesium in the feed solution was determined experimentally, which was found to be in good agreement with the theoretically predicted value obtained from assumed mass transfer models. The aqueous mass transfer coefficient increased continuously with the flow rate. The membrane mass transfer coefficient was found to be the rate controlling step in the transport process of cesium. The transport rate of cesium increased with increased ligand concentration. Quantitative (>99.9%) transport of cesium was obtained at tracer concentration in feed solution in 6 h. However, only about 88% transport of cesium was possible in 12 h from SHLW which contained ∼0.3 g/L Cs, due to increased strip phase acidity with time. Nevertheless, the complete recovery of cesium from SHLW was possible after neutralization of strip phase acidity with NaOH. Mathematical modeling of the transport data was also carried out for SHLW feeds.