Thin extractive membrane for monitoring actinides in aqueous streams

Highlights: • Thin polymer inclusion membrane has been developed for selective actinide sorption. • Actinide sorption in membrane is dependent on acidity and oxidation states. • A scheme for selective preconcentration of target actinide has been developed. • Quantification of actinide in membrane is possible by SSNTD or α-spectrometry. • This membrane was used for assay of Pu in acidic waste and urine -- Abstract: Alpha spectrometry and solid state nuclear track detectors (SSNTDs) are used for monitoring ultra-trace amount of alpha emitting actinides in different aqueous streams. However, these techniques have limitations i.e. alpha spectrometry requires a preconcentration step and SSNTDs are not chemically selective. Therefore, a thin polymer inclusion membrane (PIM) supported on silanized glass was developed for preconcentraion and determination of ultra-trace concentration of actinides by α-spectrometry and SSNTDs. PIMs were formed by spin coating on hydrophobic glass slide or solvent casting to form thin and self-supported membranes, respectively. Sorption experiments indicated that uptakes of actinides in the PIM were highly dependent on acidity of solution i.e. Am(III) sorbed up to 0.1 mol L−1 HNO3, U(VI) up to 0.5 mol L−1 HNO3 and Pu(IV) from HNO3 concentration as high as 4 mol L−1. A scheme was developed for selective sorption of target actinide in the PIM by adjusting acidity and oxidation state of actinide. The actinides sorbed in PIMs were quantified by alpha spectrometry and SSNTDs. For SSNTDs, neutron induced fission-fragment tracks and α-particle tracks were registered in Garware polyester and CR-39 for quantifications of natural uranium and α-emitting actinides (241Am/239Pu/233U), respectively. Finally, the membranes were tested to quantify Pu in 4 mol L−1 HNO3 solutions and synthetic urine samples