Selective Recovery of Am(III) over Eu(III) by Hollow Fiber Supported Liquid Membrane Using Cyanex 301 in the Presence of Synergists as the Carrier

Abstract

Lanthanide/actinide separation was investigated on 0.5 L scale (both feed and receiver phase volumes) with Cyanex-301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid) as the carrier using the Hollow Fiber Supported Liquid Membrane (HFSLM) technique under varying feed pH conditions. At pH 3.4, the quantitative transport of Am(III) was achieved within 15 minutes with 0.5 M Cyanex 301 as the carrier with separation factor of >100 over Eu(III). The transport rate of Am(III) decreased significantly with increasing feed acidity, and was independent of the feed nitrate concentration. The effect of neutral auxiliary donor ligands as synergists, viz. tri-n-butyl phosphate (TBP), N,N,-dihexyl octanamide (DHOA) and 2,2′-bipyridyl (Bipy) on the selective recovery of Am(III) over lanthanides was also investigated. The presence of synergists led to the possibility of Am(III) recovery at lower pH values with improved separation factors (SF). It was particularly beneficial as the use of buffer for feed pH adjustment could be avoided. In the presence of synergists, >85% transport of Am(III) was achieved in 30 minutes of operation at pH 2.0. The SF value at pH 2.0 for different synergists followed the order: bipyridyl (350) >DHOA (50) >TBP (8). The transport rate of Am(III) by HFSLM system was found to be satisfactory for 25 hours of continuous operation. However, the SF values deteriorated significantly with the time of operation.