Flotation of Uranium from Seawater with Phosphate Esters of C-Undecylcalix[4]resorcinarene

Table-type chelating surfactants ([4]ArmX-R12, mX means the number of phosphates (P), carboxylic acid (Ac), and hydroxamic acid (Hx), respectively) have been derived from the calix[4]resorcinarene bearing tetradodecyl side chains ([4]Ar-R12), and applied to a collector of uranium flotation. The surface tension of the aqueous solution was 35 mN m−1 for [4]Ar5.6P-R6 (Rn means the alkyl chain length), 52 mN m−1 for [4]Ar5.9P-R12, 42 mN m−1 for [4]Ar8.0Ac-R12, and 48 mN m−1 for [4]Ar5.1Hx-R12. They formed UO2 complexes and floated the UO22+ from an aqueous solution by air-bubbling. Furthermore, [4]Ar5.9P-R12 and [4]Ar6.3P-R12 had competence to float the uranium from seawater. A trace amount of uranium in 450 cm3 of seawater was floated at 68—94% using 1—10 mg of [4]Ar5.9P-R12 or [4]Ar6.3P-R12. On the other hand, [4]Ar5.1Hx-R12 and [4]Ar8.0Ac-R12 brought about lower floatabilities. [4]ArmP-R12 could be recycled several times by dissolving the scum (uranium complex) in 5 mol dm−3 H2SO4.