A highly efficient supported liquid membrane system for selective strontium separation leading to radioactive waste remediation

The present paper deals with the selective separation of radio-strontium from acidic feeds using a highly efficient novel supported liquid membrane method suggesting possible applications in radioactive waste remediation. This method is a first ever report on near quantitative (∼99%) Sr transport with crown ether carrier from acidic feeds (∼3 M HNO3) using a supported liquid membrane method. The supported liquid membrane consists of a solution of di-tert-butyl-dicyclohexano-18-crown-6 (DTBCH18C6) dissolved in a mixture of 2-nitrophenyl ether and n-dodecane absorbed into a microporous polytetrafluoroethylene film. A mixture of 80% 2-nitrophenyl ether and 20% n-dodecane was found to be the most suitable diluent system and was evaluated in the present studies. The transport rates were correlated with the carrier extractant concentration, strontium concentration as well as the feed acid concentration. Transport of Sr from Pressurized Heavy Water Reactor Simulated High Level Waste (SHLW) was also studied with encouraging results. Selective transport of Sr(II) was observed from a feed solution constituting a mixture of fission products spiked individually. Radiation stability of the carrier solvent with respect to the efficiency and selectivity was also investigated. The stability of the membrane was remarkably good when tested over 20 days of continuous operation.