Carrier-mediated transport of uranium from phosphoric acid medium across TOPO/ n-dodecane-supported liquid membrane

Abstract

Present studies deals with the application of supported liquid membrane (SLM) technique for the separation of uranium (VI) from phosphoric acid medium. Tri- n-octyl phosphine oxide (TOPO)/ n-dodecane is used as a carrier and ammonium carbonate as a receiving phase for the separation of uranium (VI) from the phosphoric acid medium. Throughout the study PTFE membranes are used as a support. The studies involve the investigation of process controlling parameters like feed acidity of phosphoric acid, carrier concentration and stripping agents. The effect of nitric acid and sodium nitrate in feed is also studied. It is found that there is negligible transport of uranium (VI) from pure phosphoric acid medium but it increases to very significant amount if 2 M nitric acid is added to feed phase. More than 90% uranium (VI) is recovered in 360 min using 0.5 M TOPO/ n-dodecane as carrier and 1.89 M ammonium carbonate as stripping phase from the mixture of 0.001 M H 3PO 4 and 2 M of HNO 3 as a feed. The flux and permeability coefficient are found to be 9.21 × 10 − 6 mol/m 2 s and 18.26 × 10 − 5 m/s, respectively. Lower concentration of phosphoric acid with 2 M HNO 3 and higher concentration of carrier is found to be the most suitable condition for maximum transport of uranium (VI) from its low-level sources like commercial phosphoric acid.