A Microwave-Assisted Method for the Rapid Removal of K From Phlogopite

Abstract

AbstractThe ability to remove K rapidly with a solution containing sodium tetraphenylborate (NaTPB) from the interlayers of naturally-occurring phlogopite using a microwave-assisted technique has been examined. Samples were equilibrated with a 1.0 N sodium chloride (NaCl) – 0.2 N NaTPB – 0.01 M disodium ethylenediaminetetraacetic acid (EDTA) solution at 60, 80 and 100°C under both conventional and microwave-assisted heating methods and for periods of time ranging from 1 to 3 h. The samples also underwent treatments of either continuous time periods or for successive treatments of 1 h with a washing step between each treatment.Following sample treatment, the expansion of the c-axis value (d001) from 10.0 to 12.2 Å indicated the presence of hydrated Na ions in the phlogopite structure. Under most treatment conditions the 10.0 Å peak remained even after treatment due to incomplete K removal. Chemical analysis and X-ray diffraction (XRD) revealed that samples heated using microwave radiation exchanged their interlayer K for Na much more rapidly than under conventional heating for all treatment times and temperatures. The successive treatments also degraded the mica more rapidly than the continuous treatments. The greatest amount of K (95%) was removed when the mica was treated three times for 1 h at 60°C. The results suggest that successive treatments of phlogopite mica heated under microwave radiation will rapidly remove K from the mica. Decreasing the amount of time required to prepare K-depleted phlogopite micas will make these materials more appealing as ion exchangers for separation of Cs from nuclear wastes.